Gezielte Beeinflussung der einsatzrelevanten Bauteileigenschaften kaltfließgepresster Zahnräder - Rohrmoser, Andreas; Kiener, Christoph; Schubert, Dirk W.; Hagenah, Hinnerk; Drummer, Dietmar; Merklein, Marion (Konstruktion, 2019)
LFT Import::2019-07-29 (2385)

Grundlagenuntersuchungen zum Presshärten höchstfester Vergütungsstähle - Merklein, Marion; Hoff, Cornelia; Lechler, Jürgen (6. Stahl-Symposium 2006 - Werkstoffe, Anwendung, Forschung, 06. April, 2006)
LFT Import::2019-08-05 (1304)

Grundlegende Untersuchungen zur Verbindung von pressgehärtetem Stahl und Aluminium mittels Schneidclinchen - Merklein, Marion; Meschut, G.; Müller, Martin; Hörhold, R. (Tagungsband - 20. Sächsiche Fachtagung Umformtechnik, 2013)
LFT Import::2019-08-05 (1928)

Heating effect on the forming behaviour of high nitrogen steel in bulk forming - Kuball, Clara-Maria; Merklein, Marion (AIP Conference Proceedings, 2019)
As a result of the ongoing trend towards lightweight design in various industrial sectors like the automotive industry, mechanical joining methods become increasingly important. These methods make multi-material design possible, while thermic joining techniques reach their limits. Semitubular self-piercing riveting is a mechanical joining technology which allows joining dissimilar materials by using rivets as fasteners. The manufacturing of the rivets, however, is costly and time-consuming, as the rivets conventionally have to be hardened, tempered and coated after forming, in order to achieve adequate strength and corrosion resistance. By using high nitrogen steel for the rivets, these additional process steps are not necessary anymore. Hence, the rivet production becomes more efficient. Because of the strengthening, caused by strain hardening, high-strength parts can be produced by cold bulk forming of high-strength steels. Nevertheless, pressure-nitrided steels are still rarely used in cold bulk forming due to high tool loads, which is a major challenge for the manufacturing process. Under those circumstances, there is a need for new approaches to manufacturing with the aim of reducing the tool loads and realising the production of rivets made of pressure-nitrided steel. One possibility is forming at elevated temperatures below recrystallisation temperature. For this purpose, the influence of the temperature on the forming behaviour of high nitrogen steel is investigated. In this context, possible changes in nitrogen content caused by heating of the material and thereby induced negative effects on the material properties have to be evaluated. The results of compression tests at different temperatures demonstrate the distinct reduction of yield strength at elevated temperatures. Moreover, further investigations show that the heat treatment tends to result in a change of the nitrogen content determined using energy dispersive X-ray spectroscopy. However, the changing nitrogen content does not affect the strength of the heat treated material after cooling.
CRIS-Team Scopus Importer:2019-07-23

Herstellung funktionaler Blechkomponenten - Merklein, Marion; Opel, Simon; Schneider, Thomas (wt Werkstattstechnik - Online, 2010)
LFT Import::2019-07-29 (723)

Herstellung hochfester Aluminiumblechwerkstoffe mittels Accumulative Roll Bonding - Böhm, Wolfgang; Merklein, Marion (Internationale Konferenz "Neuere Entwicklungen in der Blechumformung", 2014)
Ein entscheidender Aspekt bei der Produktentwicklung nachhaltiger Erzeugnisse ist die Berücksichtigung der Energieaufwendungen während des Herstellungsprozesses, der gesamten Nutzungsdauer und für das Recycling. Um den Treibstoffverbrauch und damit den Schadstoffausstoß während der Nutzung von PKWs zu minimieren, ist der Leichtbau im Karosseriebereich eine vielversprechende Strategie. Das Ziel dabei ist die Reduktion der Wanddicke der Komponenten bei gleichzeitiger Sicherstellung der Crashanforderungen. Dies erfordert den Einsatz hochfester Leichtbauwerkstoffe. Ein innovativer Fertigungsprozess zur Herstellung von Aluminiumblechen mit gesteigerter Festigkeit ist das Accumulative Roll Bonding (ARB). Hierbei werden mehrlagige Bleche hergestellt, die ein nanokristallines Gefüge aufweisen. Neben einer signifikant gesteigerten Festigkeit und einer erhöhten Dehnratensensitivität weisen diese Blechwerkstoffe in der Regel eine reduzierte Duktilität auf. Im Sinne einer wirtschaftlichen Weiterverarbeitung dieser Werkstoffe zu Karosseriekomponenten müssen jedoch effiziente Umformtechnologien zum Einsatz kommen. Um das Formgebungsvermögen zu erhöhen, wird die Technologie der Tailored Heat Treated Blanks (THTB) eingesetzt. Dabei wird vor der Umformung durch eine Kurzzeitwärmebehandlung in bestimmten Platinenbereichen die Festigkeit definiert reduziert. Über die geeignete Positionierung der Wärmebehandlungszonen kann die Umformbarkeit der gesamten Platine gesteigert und der Einsatz dieser hochfesten, mehrlagigen Aluminiumblechwerkstoffe im Bereich der Karosseriefertigung ermöglicht werden. Darüber hinaus bietet der ARB-Prozess ein großes Potential für die Verarbeitung großflächiger Recycling-Blechwerkstoffe, die beispielsweise aus Dachelementen oder Motorhauben entnommen wurden. Dies ermöglicht die Herstellung von Aluminiumhalbzeugen mit gesteigerter Festigkeit, die dann für tragende Komponenten außerhalb des Sichtbereichs im PKW eingesetzt werden können. Zudem sind im ARB-Prozess energetisch effiziente und kostengünstige Materialverbunde durch die angewandte Prozessstrategie realisierbar. Hierbei können beispielsweise zur Einsparung von Primärwerkstoff bzw. zur Realisierung bestimmter Materialeigenschaften an der Außenseite aufbereitete Recyclingwerkstoffe und die gewünschten Aluminiumgüten miteinander durch Walzplattieren gefügt werden. Vorab ist jeweils durch eine gewisse Anzahl an ARB-Zyklen eine Verbesserung der mechanischen Eigenschaften denkbar.
EAM Import::2019-03-13

Herstellung maßgeschneiderter Aluminiumwerkstoffe - Lechner, Michael; Böhm, Wolfgang; Nguyen, Manh Hung; Merklein, Marion (Konstruktion, 2013)
LFT Import::2019-07-29 (1913)

Herstellung und Umformeigenschaften hochfester mehrlagiger Aluminiumlegierungen der 6000er-Serie - Herrmann, Jürgen; Merklein, Marion (Energie / Effiziente Verarbeitung zukunftsweisender Leichtbauwerkstoffe, 2017)
LFT Import::2019-08-05 (2224)

Herstellung von funktionsoptimierten Bauteilen im Presshärtprozess - Merklein, Marion; Lechler, Jürgen; Stöhr, Thomas; Svec, Thomas (Stahl und Eisen, 2010)
LFT Import::2019-07-29 (225)

High-Feed Milling of Tailored Surfaces for Sheet-Bulk Metal Forming Tools - Hense, Rouven; Wels, Christoph; Kersting, Petra; Vierzigmann, Ulrich; Löffler, Maria; Biermann, Dirk; Merklein, Marion (Production Engineering, 2015)
The increasingly investigated and applied production process sheet-bulk metal forming (SBMF) has novel requirements for the forming tools, e.g., the need of an adaptive material flow at different areas of the tool for an adequate form filling. One new method to realize different, defined tribological conditions are tailored surfaces (TS). During the design of forming tools, it is imperative to have profound knowledge about the tribology between the tool and the workpiece. This article introduces structuring with high-feed milling tools as one possibility for influencing the material flow during forming processes and presents a ring-compression test for the quantification of the tribological conditions, which is adapted for SBMF. On the basis of various machined structures, surface parameters are analyzed to identify a correlation with the friction coefficient to gain knowledge about the mechanisms of TS and to be able to choose structures according to the needs of SBMF processes.
LFT Import::2019-07-29 (2062)
Keywords: High-feed milling; Sheet-bulk metal forming; Tribology

High Power Laser Beam Melting of Ti-6Al-4V on Formed Sheet Metal to achieve Hybrid structures - Ahuja, Bhrigu; Schaub, Adam; Karg, Michael; Schmidt, Roman; Merklein, Marion; Schmidt, Michael (Proc. of SPIE Vol. 9353, 93530X, 2015)
Motivated by the desire to combine the advantages of two manufacturing concepts, namely Additive Manufacturing and sheet metal forming, the concept of hybrid processes emerged. Laser Beam Melting process with its characteristic layer by layer fabrication methodology has already been proved to be successful in fabricating fully dense 3D structures with micro sized Ti6Al4V powder. The presented research focuses on direct fabrication of Ti6 Al4V Additive Structures on a thin pre-formed Ti6 Al4V sheet metal substrate. In the state of the art Laser Beam Melting process, fabrication of solid structures is done on a support structure attached to a thick conventionally manufactured base plate. The state of the art process also uses a 200°C pre-heating of the fabrication platform in order to reduce the effect of heat induced stresses on the fabricated structures. Within the hybrid fabrication concept, 3D structures are directly fabricated on a thin sheet metal and the thermodynamic conditions are significantly different in comparison to the conventional process. The research aims at understanding the fundamental aspects of the interaction between the formed sheet metal and additive structure determines the corresponding mechanical characteristics. The interaction process during the fabrication exposes the alloy locally to non-optimum thermal cycles and the research therefore aims to understand the various influencing factors involved during the fabrication process. The system technology modifications required to achieve the aimed fabrication are also discussed in the presented research. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use onl
Keywords: Additive Manufacturing; Hybrid Fabrication; Ti-6Al-4V; Sheet Metal Forming

High-precision blanking of thin copper foils using uncoated and coated monocrystalline silicon punches - Hildering, Sven; Becsi, L.; Engel, Ulf; Merklein, Marion; Mescheder, U. (Proc. 8th Int. Conf. Multi-Material Micro Manufacture, 2011)
LFT Import::2019-08-05 (1655)

Hochleistungsbauteile durch Kaltmassivumformung hochfester, druckaufgestickter Stähle - Noneder, Johannes; Merklein, Marion; Engel, Ulf; Frank, M.; Frank, J.; Ritzenhoff, R.; Egerer, E. (UTF-Science, 2012)
LFT Import::2019-07-29 (1866)

Hot Stamping – Manufacturing functional optimized components - Merklein, Marion; Svec, Thomas (Production Engineering, 2013)
LFT Import::2019-07-29 (1842)

Hot Stamping of Boron Steel Sheets with Tailored Properties: a Review - Merklein, Marion; Wieland, Michael; Lechner, Michael; Bruschi, Stefania; Ghiotti, Andrea (Journal of Materials Processing Technology, 2016)
The paper gives a review of the main research activities recently carried out in the framework of hot stamping of boron steel sheets with tailored properties. The focus is on the process variants developed to locally adjust the mechanical properties of the hot stamped component as well as on the testing and modeling techniques needed to calibrate the numerical models of the tailored tempering processes and to evaluate the post-forming properties of the stamped products.
LFT Import::2019-07-29 (2121)
Keywords: Hot stamping; Tailored properties; Tailored tempering

Hot stamping of ultra-high strength steel parts - Mori, Ken-Ichiro; Bariani, P. F.; Behrens, B. -A.; Brosius, Alexander; Bruschi, Stefania; Maeno, Tomoyoshi; Merklein, Marion; Yanagimoto, J. (CIRP Annals - Manufacturing Technology, 2017)
The demand for new processes to produce high strength parts, under appropriate cost and productivity, has grown with weight reduction and crash safety improvements in automobile design. The hot stamping processes of quenchable steel sheets potentially offer not only small forming load and high formability, but also high strength and no springback by die quenching. This paper aims to provide an overview of the state-of-the-art in such hot stamping processes, including quenchability, formability, heating and cooling approaches and lubrication. The paper also includes a description of the mechanism of formability and quenching, tailoring, analysis of hot stamping processes and applicability.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Forming; Hot stamping; Sheet metal

Hot stamping of ultra high strength steels as a key technology for lightweight construction - Lechler, Jürgen; Merklein, Marion (Tagungsband Material Science & Technology Conference MS&T’08, 2008)
Due to increased usage of high strength steels in scope of lightweight construction design in this context thermal assistant forming technologies like hot stamping of boron-manganese steels of the type 22MnB5 obtained more and more industrial relevance in the last five years. For a reliable process design the knowledge of the material properties in dependency of the process influencing characteristics and hereby mainly the temperature displays a base requirement. In the following publication an overview will be given about different experimental methodologies developed at the Chair of Manufacturing technology for being capable to investigate the material behavior according to the typical time-temperature profile of hot stamping. Furthermore, main experimental results acquired regarding the thermal, the mechanical and the tribological properties of 22MnB5 will be exemplarily shown as well. © 2008 MS&T'08 ®.
LFT Import::2019-08-05 (1550)
Keywords: 22MnB5; Hot stamping; Material properties; Modeling

Hot Stamping - Process Window for the Austenitization of a Dualphase Steel - Svec, Thomas; Merklein, Marion (4th International Conference Hot Sheet Metal Forming of High-Performance Steel, 2013)
LFT Import::2019-08-05 (1900)

Hybrid Additive Manufacturing Technologies - An Analysis regarding Potentials and Applications - Merklein, Marion; Junker, Daniel; Schaub, Adam; Neubauer, Franziska (Physics Procedia, 2016)
Imposing the trend of mass customization of lightweight construction in industry, conventional manufacturing processes like forming technology and chipping production are pushed to their limits for economical manufacturing. More flexible processes are needed which were developed by the additive manufacturing technology. This toolless production principle offers a high geometrical freedom and an optimized utilization of the used material. Thus load adjusted lightweight components can be produced in small lot sizes in an economical way. To compensate disadvantages like inadequate accuracy and surface roughness hybrid machines combining additive and subtractive manufacturing are developed. Within this paper the principles of mainly used additive manufacturing processes of metals and their possibility to be integrated into a hybrid production machine are summarized. It is pointed out that in particular the integration of deposition processes into a CNC milling center supposes high potential for manufacturing larger parts with high accuracy. Furthermore the combination of additive and subtractive manufacturing allows the production of ready to use products within one single machine. Additionally actual research for the integration of additive manufacturing processes into the production chain will be analyzed. For the long manufacturing time of additive production processes the combination with conventional manufacturing processes like sheet or bulk metal forming seems an effective solution. Especially large volumes can be produced by conventional processes. In an additional production step active elements can be applied by additive manufacturing. This principle is also investigated for tool production to reduce chipping of the high strength material used for forming tools. The aim is the addition of active elements onto a geometrical simple basis by using Laser Metal Deposition. That process allows the utilization of several powder materials during one process what enables the tailoring of the tools materials mechanical properties. Another aspect is the possibility of Laser Alloying of the tools surface to reduce abrasive and adhesive wear. This technique is especially interesting for tools used in hot stamping production.
LFT Import::2019-07-29 (2265)
Keywords: additive manufacturing; hybrid processes; process combination

Hybride Bauteile, Werkzeuge und Prozessketten – Anwendungen der Kombination aus Additiver Fertigung und Umformtechnik - Papke, Thomas; Huber, Florian; Hafenecker, Jan; Schmidt, Michael; Merklein, Marion (7. Industriekolloquium des Sonderforschungsbereichs 814 - Additive Fertigung, 2019)

Hybrid process chains combining metal additive manufacturing and forming – A review - Hafenecker, Jan; Bartels, Dominic; Kuball, Clara-Maria; Kreß, Maximilian; Rothfelder, Richard; Schmidt, Michael; Merklein, Marion (CIRP Journal of Manufacturing Science and Technology, 2023)
Mass production of customized parts using conventional manufacturing technologies is challenging. The increasing use of hybrid approaches is a promising way to address mass customization. Due to the widespread use of the term hybrid in manufacturing technologies, the amount of literature is increasing dramatically. Therefore, this paper aims to provide an overview of the current state of the art on the combination of additive manufacturing (AM) and metal forming. First, the term hybrid is classified, followed by examples of hybrid AM. The focus of this paper is on the combination of either sheet metal forming or bulk metal forming with either powder bed fusion or directed energy deposition. Examples of both sequences - AM before or after forming - are presented and analyzed for their potential use in hybrid parts. From the selected literature, the possibilities of this approach are derived as well as the ongoing need for future research. AM offers great potential for adjusting the microstructure and resulting material properties to improve formability. Furthermore, forming operations need to be adapted to the different material properties found in hybrid part
Keywords: Hybrid manufacturing Hybrid processes Hybrid parts Additive manufacturing Sheet metal forming Bulk metal forming Review paper

Hydroforming in Patchwork Blanks - Numerical Modeling and Experimental Validation - Lamprecht, Klaus; Merklein, Marion; Geiger, Manfred (Proceedings of the 6th International Conference and Workshop on Numerical Simulation of 3D Sheet forming Processes (NumiSheet), 15.-19.08., Detroit, USA, 2005)
LFT Import::2019-08-05 (1139)

Hydroforming of High-Strength Aluminum Tubes with Thermo-Mechanical Manufacturing Processes - Trân, Ricardo; Reblitz, Jonas; Haase, Rico; Psyk, Verena; Kräusel, Verena; Merklein, Marion (Engineering Proceedings, 2022)
The amount of complex profile components in car bodies increases due to the emerging electromobility. High-strength aluminum alloys are ideally suited as material for automotive applications due to their extraordinary lightweight construction potential. The presented study focuses on the transfer of established thermo-mechanical manufacturing processes for sheet metal components to hydroforming of tube material. Demonstrator components are produced from EN AW-7020 using W-temper-forming and hot forming and compared numerically and experimentally. The results show that the determined material properties are sufficiently accurate to numerically represent the temperature-supported processes with excellent precision. The formed components can be used to demonstrate the potential of hydroforming for high-strength aluminum tubes using W-temper-forming and hot forming.
Created from Fastlane, Scopus look-up
Keywords: aluminum; finite element method (FEM); heat treatment; hydroforming; metal forming

Hydroforming of Inhomogeneous Sheet Pairs with Counterpressure - Geiger, Manfred; Merklein, Marion; Cojutti, Massimo (Production Engineering Research and Development, 2008)
LFT Import::2019-07-29 (1544)

Identification of a process window for tailored carburization of sheet metals in hot stamping - Horn, Alexander; Merklein, Marion (AIP Conference Proceedings, 2018)
LFT Import::2019-07-29 (2299)

Identification of Process-Based Limit Stress States Applying a Stretch-Bending-Test - Hezler, Christian; Merklein, Marion; Hecht, Joachim; Griesbach, Bernd (Key Engineering Materials, 2012)
The evaluation of forming simulation by using the forming limit curve has only limited validity if it is applied on car body components with non-linear strain paths. If modern high strength materials are used, the forming limit criteria can also provide invalid predictions. Especially high strength multiphase steels show a specific behaviour in forming, necking and crack initiation. If bending loads are applied to these materials, the onset of cracking occurs partially not within the range of the forming limit curve (FLC). The stress limit indicates the failure beginning more accurate. It is independent of the forming history and should be less sensitive to the behaviour of high strength steels. In the post processing of a simulation it could be used similar to the forming limit. A limit curve applied on the in-plane-stress-diagram of an analysed component defines areas that are more vulnerable for cracking. The required stress limit curve will be obtained in this research by applying a stretch-bending-test. It is selected in order to reach loads, which are comparable to the forming process in the components' production. The forming state that is affecting the specimen is a combination of bending and stretching load. Different load conditions can be applied at the test by altering the stamp-radius and the specimen geometry. Since stresses cannot be measured directly in the experiment, the test is modelled in the simulation where the stresses can be calculated for a given material model. Finally the stress limit criterion was applied on the test parts' stress distribution diagram. Occurring stresses above the stress limit curve are displayed on the simulation. Thereby it is possible to show a good correlation in critical areas between the failure prediction in the simulation and occurring rupture on the test component. © (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1786)
Keywords: High strength steels; Process-orientated characterisation; Stress limit criteria; Stretchbending- test

Identification of tribological mechanisms of shot peened steel surfaces for an application in sheet-bulk metal forming - Löffler, Maria; Engel, Ulf; Andreas, Kolja; Merklein, Marion (Proceedings of the 13th International Conference on Shot Peening, 2017)
LFT Import::2019-08-05 (2254)

Identifikation von Modellparametern zur Bestimmung des Fließ- und Verfestigungsverhaltens unter Berücksichtigung einer Belastungsumkehr - Kaupper, Markus; Merklein, Marion (Bauteile der Zukunft - Methoden und Prozesse - Tagungsband T31 des 30. EFB-Kolloquiums Blechverarbeitung am 2. und 3. März 2010 in Bad Boll, 2010)
LFT Import::2019-08-05 (211)

Impact of Coating Systems on the Tribological and Wear Behavior of Hot Stamping Tools - Merklein, Marion; Wieland, Michael (Proc. 4th Int. Conf. on Tribology in Manufacturing Processes (ICTMP), 2010)
LFT Import::2019-08-05 (307)

Impact of optical strain rate controlling on the determination of mechanical sheet metal properties - Naumann, David; Merklein, Marion (6th MATFEM Conference, 2024)
A key aspect of state of the art part, tool and process development is the prediction quality of numerical simu- lations. Costs and time in the design process can be reduced only with sufficiently reliable results. To obtain meaningful results, precise material data is an important input variable. In the state of the art material characteri- zation with universal testing machines, material beha- vior is either determined at constant crosshead speed or at constant strain rates, only in the elastic region, accor- ding to ISO 6892-1 for tensile tests. Due to the fact, that commercial simulation software expects strain hardening data at constant strain rates, an error is made with current characterization tests at non-constant strain rates, due to the strain rate sensitivity that most metals exhibit. To obtain constant strain rate material data, optical controlled characterization tests can be conducted. In the scope of this research, an optical strain rate con- trolled tensile testing method was developed for and ap- plied to uniaxial tensile tests to investigate its influence on the measurement of mechanical properties of typical drawing grade steels. Therefore, displacement strain rate controlled (DSRC) and optical strain rate controlled (OSRC) tensile tests at room temperature with a nomi- nal strain rate of 0.004 1/s were conducted and evalua- ted. Flat specimens according to ISO 6892-1 with a gauge length of 80 mm were used. The tests were per- formed with a universal testing machine (ZwickRoell GmbH & Co. KG.) and the strain was measured and controlled with a 3D DIC System (GOM ARAMIS 12M SRX). The both commercial common steels DP600 (CR330Y590T-DH) and DC05 (CR4) at a nominal thickness of 1.2 mm were analyzed regarding strain rate evolution during tensile testing and how OSRC influences the strain rate development. The OSRC-method shows the potential to obtain materi- al data in material testing at constant strain rates over the complete tensile testing trial from the elastic area to ✻ the failure of the specimen. For both investigated steels DP600 and DC05, the influence of the testing method is negligibly small. The root mean squared error of the av- eraged strain rates for DP600 and DC05 was decreased from 0.011 respectively 0.012 to 2.4·10-5 respectively 5.6·10-5 with the OSRC-method. In future work, an adaptive strain rate controlling will be developed, to obtain material data to higher strains in the area of dif- fuse necking. This can be applied to testing at elevated temperatures with e.g. electrically conductive specimen heating, where necking starts at an early stage due to inhomogeneous specimen tempera
Keywords: strain rate controll; DIC; material characterization

Improved Deep Drawability of Aluminium Blanks by Local Laser Heat Treatment - Kerausch, Michael; Merklein, Marion; Geiger, Manfred (Laser Assisted Net shape Engineering 4. Proceedings ot the 4th LANE, 2004)
LFT Import::2019-08-05 (1066)

Improved Formability of Aluminum Alloys using Laser Induced Hardening of Tailored Heat Treated Blanks - Nguyen Hung,; Merklein, Marion (Physics Procedia, 2012)
LFT Import::2019-07-29 (1861)
Keywords: Forming limit; Laser hardening; Laser radiation; Layout design; Tailored Heat Treated Blanks

Improved material flow for deep drawing of aluminium blanks by local laser heat treatment - Kerausch, Michael; Merklein, Marion; Geiger, Manfred (Proceedings of the 10th International Conference on Sheet Metal, She Met, 2003)
LFT Import::2019-08-05 (952)

Improved Roller Hemming System for High Volume Part Production - Zubeil, Martin; Roll, Karl; Merklein, Marion (Key Engineering Materials, 2011)
Roller hemming is usually applied for hang-on-parts such as hoods, doors or trunk-lids which all have complex non-linear geometries. The flange is often hemmed along both surfaces and edges which have 3D curvilinear shapes. Minimization of hemming defects and the requirement to improve cycle time of the roller hemming process are essential for roller hemmed hang-on-parts in the automotive industry. Different systems such as the driven roller hemming provide the possibility to increase the strain rate without loosing surface quality and dimensional stability. Investigating the influence of friction during roller hemming, results will give an understanding of the advantage for mentioned roller hemming systems. © (2011) Trans Tech Publications.
LFT Import::2019-07-29 (1749)
Keywords: Design of experiments method; Driven roller hemming system; Finite element method; Friction; Roller hemming; Tandem roller hemming system

Improved Sheet Bulk Metal Forming Processes by Local Adjustment of Tribological Properties - Hetzner, Harald; Koch, Johannes Peter Karl; Tremmel, Stephan; Wartzack, Sandro; Merklein, Marion (Journal of Manufacturing Science and Engineering, 2011)
This paper is focused on a combined deep drawing and extrusion process dedicated to the new process class of sheet bulk metal forming (SBMF). Exemplified by the forming of gearings, combined sheet and bulk forming operations are applied to sheet metal in order to form local functional features through an intended and controlled change of the sheet thickness. For investigations on the form filling and the identification of significant influencing factors on the material flow, a FE simulation model has been built. The FE model is validated by the results of manufacturing experiments using DC04 with a thickness of 2.0 mm as blank material. Due to the fact that the workpiece is in extensive contact to the tool surface and that the pressure reaches locally up to 2500 MPa, the tribological conditions are a determining factor of the process. Thus, their influence is discussed in detail in this paper. In the first instance, different frictional zones having a distinct effect on the resulting material flow are identified and their effect on improved form filling is demonstrated. Subsequently, a more comprehensive methodology is developed to define tribological zones of forming tools. For this, a system analysis of the digital mock-up of the forming process is performed. Besides friction, other relevant aspects of forming tool tribology like contact pressure, sliding velocity, and surface magnification are considered. The gathered information is employed to partition the tools into tribological zones. This is done by systematically intersecting and re-merging zones identified for each of the criterion. The so-called load-scanning test allows the investigation of the friction coefficient in dependence of the contact pressure and possible loading limits of tribological pairings. It provides an appropriate tribological model test to evaluate tribological measures like coatings, surface textures and lubricants with respect to their targeted application in particular zones. The obtained results can be employed in the layout of further forming processes to reach the desired process behavior. This can be, for example, an improved form filling, less abrasive wear and adhesive damage or lower forming forces, respectively tool load for an improved durability of the die.
UnivIS-Import:2015-03-09:Pub.2011.tech.FT.FT-KLMEFK.improv
Keywords: load-scanning test; material flow; sheet bulk metal forming; tribology

Improved Tool Performance in Microblanking of Thin Metal Foils Through Defined Cutting Edge Modification of Silicon Punches - Hildering, Sven; Engel, Ulf; Merklein, Marion (Proc. 4M/ICOMM2015 Conf., 2015)
LFT Import::2019-08-05 (2087)

Improvement of a rivet geometry for the self-piercing riveting of high-strength steel and multi-material joints - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Production Engineering, 2020)
As a result of lightweight design, increased use is being made of high-strength steel and aluminium in car bodies. Self-piercing riveting is an established technique for joining these materials. The dissimilar properties of the two materials have led to a number of different rivet geometries in the past. Each rivet geometry fulfils the requirements of the materials within a limited range. In the present investigation, an improved rivet geometry is developed, which permits the reliable joining of two material combinations that could only be joined by two different rivet geometries up until now. Material combination 1 consists of high-strength steel on both sides, while material combination 2 comprises aluminium on the punch side and high-strength steel on the die side. The material flow and the stress and strain conditions prevailing during the joining process are analysed by means of numerical simulation. The rivet geometry is then improved step-by-step on the basis of this analysis. Finally, the improved rivet geometry is manufactured and the findings of the investigation are verified in experimental joining tests.
CRIS-Team Scopus Importer:2020-08-07
Keywords: Aluminium; High-strength steel; Joining technology; Multi-material design; Rivet geometry; Self-piercing riveting

Improvement of deep drawability of ultra-fine grained 6000 series aluminum alloy by tailored heat treatment - Herrmann, Jürgen; Merklein, Marion (Procedia Manufacturing, 2018)
Among other approaches like alloying, it is possible to increase the strength of aluminum sheet material by the application of processing techniques like Accumulative Roll Bonding. However, the ductility will be reduced, which results in a limited formability in deep drawing operations. In this context, the Tailor Heat Treated Blanks technology is a well-known approach to enhance the forming limits of conventional precipitation hardenable aluminum alloys. The local softening of a blank can be achieved by a short-term heat treatment, which causes a dissolution of the MgSi-clusters in the heat treated zones. In a subsequent deep drawing operation, the material flow can be improved from the softened towards crack-critical areas. Within this investigation, the method of Tailor Heat Treated Blanks is transferred to a multi-layered, ultra-fine grained sheet material of the aluminum alloy AA6014 in order to investigate the effect of a local short-term heat treatment on the forming limits in deep drawing. In a first step, a material characterization in dependency of different heat treatment temperatures is carried out. The strength and ductility, as well as the bond strength of the multi-layered sheets, are investigated. Concluding, the effect on the formability is examined by deep drawing experiments on cylindrical cups in combination with a local heat treatment of the outer flange area prior to the forming step. The results regarding the limiting drawing ratio are compared with a conventional sheet material in the T4 temper condition and a multi-layered sheet material without heat treatment. The investigations indicate that the drawability can be enhanced significantly by the combination of both methods.
LFT Import::2019-07-29 (2318)
Keywords: Accumulative roll bonding; Aluminum alloy; Deep drawing; Laser; Sheet metal; Tailor heat treated blanks

Improvement of numerical modelling considering plane strain material characterization with an elliptic hydraulic bulge test - Lenzen, Matthias; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2018)
LFT Import::2019-07-29 (2288)

Improvement of process control in sheet metal forming by considering the gradual properties of the initial sheet metal - Zettl, Bastian; Schmid, Harald; Pulvermacher, Samuel; Dyck, Alexander; Böhlke, Thomas; Gibmeier, Jens; Merklein, Marion (SAGE Open, 2023)
In scientific studies, sheet metal is usually considered as a two-dimensional body. Thus, it is accepted that material properties are in most cases regarded homogeneous in thickness direction. However, a gradation of certain properties becomes apparent when going beyond the standard characterization methods for sheet metals, which can for example, influence the springback behavior and the thinning of the sheet after forming. Thus, the aim of this work is to further improve the prediction accuracy of springback after forming in simulations, by implementing several inhomogeneous properties over the sheet thickness in an existing material model. For this purpose, the entire procedure from the identification of the inhomogeneous properties for describing the gradation to the implementation in a numerical model and its validation by comparing experimental and simulated bending operations is carried out on a DC04 cold-forming steel in order to prove its influence on the springback behavior. It is shown that including graded material properties in simulations does indeed have an impact on the prediction quality of springback and that the information about inhomogeneous properties can be provided by existing characterization methods with a high local resolution like electron backscatter diffraction or X-ray stress analysis. In a further step, it was possible to validate the improvement in numerical accuracy by comparing the prediction of the springback angle from both the existing and the extended model with experimental bending results. Both the initial model as well as the model supplemented with the 3D properties provide a good prediction accuracy in the solution heat treated material state. For the predeformed material, however, the initial numerical model predicts a springback angle of about 13°, which deviates remarkably from the experimentally obtained mean value of about 17°. The extended model delivers a significantly improved accuracy in springback prediction in relation to the initial prediction (deviation of 4°) with a minor deviation of only about 0.8°, which proves the importance of considering the gradation of material properties in thickness direction for an overall higher dimensional accuracy of sheet metal product
Keywords: sheet metal; forming; springback; simulation; microstructural modelling; strain; residual stress; characterization

Improvement of surface integrity of cold forging tools by adaption of tool making process - Andreas, Kolja; Merklein, Marion (Production Engineering, 2014)
Cold forging enables mass production of steel based components. High loads within cold forging presuppose high loadable tool materials. This is why apart from tool steels cemented carbides are mainly used as tool materials. Due to brittleness of these materials, fatigue is one of the major limits of tool life. Tool manufacturing requires a combination of hard machining and subsequent machining steps. For hard machining of complex tool geometries electrical discharge machining (EDM) represents the industrial standard. The thermal influenced surface layer has to be removed by post and fine machining steps. The resulting surface integrity has a major influence on the internal strength of a tool. Correlations between tool manufacturing, surface properties and tool behavior will gain knowledge for an optimized tool production. In this context, scope of the present paper are the investigation and description of the interactions between tool manufacturing and resulting surface properties for tools made of cemented carbide and tool steel. Within the article, the surface properties caused by a conventional process chain consisting of EDM and polishing are quantified. In addition, these results are compared to an adapted process chain with an integrated peening process. The results reveal that the conventional and the adapted process chain lead to similar surface topographies and roughness values. However, the integration of a peening process shifts the residual stress level towards higher compressive stresses. © 2013 German Academic Society for Production Engineering (WGP).
LFT Import::2019-07-29 (1929)
Keywords: Machining; Surface analysis; Surface integrity; Tool

Improvement of the drawing ratio of the anisotropic material behaviour under near plane strain conditions for DP600 characterized in elliptic hydraulic bulge test - Lenzen, Matthias; Merklein, Marion (Institute of Physics Publishing, 2018)
The plane strain condition is one of the most frequent reasons for failure in a deep drawing process. State of the art material models do not consider this strain state in FE simulations. Since there is only the notched tensile test to determine the first principal stress, an improved testing setup is needed to characterize the first and second principal stresses up to high deformations to determine the material behaviour under plane strain conditions. Within this contribution, an innovative testing setup is used, which induces a near plane strain regime in the specimen with an elliptical hydraulic bulge test. Experiments are carried out in rolling and transversal direction for DP600. Based on the experiments, stress and stain based material characteristics are evaluated. For validation of the setup, square cups are deep drawn, which have a plane strain area at the drawing radius which causes cracking under this strain state. Due to the highly directional dependent material behaviour, the drawing ratio can be increased by considering the anisotropic material behaviour by cutting the blank in an optimized position according to the rolling direction.
LFT Import::2019-08-05 (2315)

Improvement of the Formability of Aluminum Extrusion Profiles by a Tailored, Local Short-Term Heat Treatment - Merklein, Marion; Lechner, Michael; Graser, Matthias (Proceedings COMA16, 2016)
LFT Import::2019-08-05 (2156)

Increased Sustainability in Fastener Production with the Example of Self-Piercing Rivets - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Journal of Manufacturing and Materials Processing, 2023)

Increasing the Adhesive Wear Resistance of Hot Stamping Tools By Modifiying the Surfaces - Neubauer, Franziska; Reil, T.; Hofmann, K.; Merklein, Marion (Key Engineering Material, 767, 2018)
LFT Import::2019-08-05 (2320)

Induction heat treatment of sheet-bulk metal-formed parts assisted by water-air spray cooling - Besserer, Hans-Bernward; Dalinger, Andrej; Rodman, Dmytro; Nuernberger, Florian; Hildenbrand, Philipp; Merklein, Marion; Maier, Hans Juergen (Steel Research International, 2016)
In order to produce components with massive secondary functional elements from sheet metal bulk forming operations, termed sheet-bulk metal forming, can be applied. Owing to high, three-dimensional stress and strain states present during sheet-bulk metal forming, ductile damage occurs in the form of micro-voids. Depending on the material flow properties, tensile residual stresses can also be present in the components' formed functional elements. During service, the components are subjected to cyclic loading via these functional elements, and tensile residual stresses exert an unfavorable influence on crack initiation and crack growth, and therefore on the fatigue life. Following the forming process, temperature and microstructurally related compressive residual stresses can be induced by local heat treating of the surface. These residual stresses can counteract potential crack initiation on the surface or in the subsurface regions. In the present study, the adjustability of the residual stress state is investigated using a workpiece manufactured by orbital cold-forming, which possesses an accumulation of material in its edge region. Based on residual stress measurements in the workpiece's edge region using x-ray diffractometry, it is possible to verify the compressive residual stresses adjusted by varying the cooling conditions.
LFT Import::2019-07-29 (2150)
Keywords: DP600; induction heat treatment; orbital forming; residual stress; water–air spray cooling

Influence of a bending operation on the bonding strength for hybrid parts made of Ti-6Al-4V - Papke, Thomas; Dubjella, Patrick; Butzhammer, Lorenz; Huber, Florian; Petrunenko, Oleksandra; Klose, Dominik; Schmidt, Michael; Merklein, Marion (Procedia CIRP, 2018)

Influence of a drawbead passage in deep drawing processes on surface values and the tribological system - Schmid, Harald; Merklein, Marion (International Deep-Drawing Research Group (IDDRG 2020), 2020)

Influence of a local laser heat treatment on the bending properties of aluminium extrusion profiles - Graser, Matthias; Pflaum, Nico; Merklein, Marion (Procedia CIRP, 2018)
Driven by ecological and economical demands, lightweight design and in this context, the substitution of steel by aluminium has become a major trend in the automotive industry. However, design possibilities are limited by the low formability of aluminium alloys. One approach to overcome these limitations is the usage of tailor heat treated semi-finished products. By a local short-term heat treatment, distinct areas are softened, which can be used to improve the material flow into critical forming zones. Within this work, the influence of local short-term heat treatment on the formability of aluminium extrusion profiles is analysed by experimental bending tests. Aims are the enhancement of maximum reachable bending angles as well as the reduction of cross section deformations. Therefore, different heat treatment layouts are applied by laser irradiation. Finally, the bending results are evaluated and promising heat treatment strategies are derived.
LFT Import::2019-07-29 (2336)
Keywords: Aluminium; Bending; Extrusion profiles; Heat treatment

Influence of a local short-term heat treatment on the formability of orbital formed functional components - Hetzel, Andreas; Merklein, Marion; Lechner, Michael (Procedia Manufacturing, 2021)
Conventional processes like shearing dispose a lack in efficiency and formability to manufacture functional components with a high geometric variety. A possibility to allow the efficient and sustainable manufacturing is the application of innovative forming operations like orbital forming. Thus, a strain-hardened component with a load-adapted thickness profile can be manufactured in a single-stage process. Thereby, the control of the material flow could be identified as major challenge due to the three-dimensional stress and strain state. In order to reduce the parts weight and simultaneously guarantee the same level of performance, conventional steel is substituted by lightweight materials such as precipitation hardenable aluminum alloys. However, new challenges arise due to the reduced formability of aluminum compared to conventional steel. In recent research, the potential of a short-term heat treatment to enlarge the formability could be shown. The presented process locally reduces the materials strength, thus allowing a control of the material flow by the interaction between softened areas and areas, which offer the initial conditions. In this contribution, the influence on the formability of orbital formed components manufactured out of the precipitation hardenable aluminum alloy EN AW 6016 by a local short-term heat treatment is investigated. Different geometry-based heat treatment layouts are applied in order to maximize the thickening on different radial positions. The potential to enhance the formability is evaluated by comparing geometrical and mechanical properties of the components manufactured in the conventional process route and with a previous heat treatment. The analysis of radial cross-sections and the hardness distribution reveals the positive influence of the heat treatment but also points out the geometrical dependency of the effect due to the characteristic material flow in orbital forming.<br
CRIS-Team Scopus Importer:2021-11-05
Keywords: Sheet-Bulk Metal Forming; Orbital Forming; Local Short-term Heat Treatment; EN AW 6016; Material Flow Control; Lightweight Design

Influence of an optical strain rate controlled tensile testing method on mechanical properties of sheet metals - Naumann, David; Merklein, Marion (Material Forming The 27th International ESAFORM Conference -On Material Forming, 2024)
Abstract. Precise material characterization is a key factor not only for representative finite-element-analysis (FEA) in production technology, but also for product development in general. Hereby, the tensile test is of particular importance, as it can be used to determine the most relevant material parameters. These are used to ensure a better process and tool design but therefore material behavior has to be determined to a high level of precision [1]. Especially in the field of metal forming, strain rate sensitive material properties like work hardening, yield point or tensile strength need to be measured at constant strain rate to provide coherent data for material models in numerical forming simulations [2]. Current testing procedures control the strain rate with a feedback control, in which various measuring systems can be used. From this comes the necessity to investigate the influence of a strain rate controlled tensile testing procedure compared to a conventional crosshead-displacement controlled one. Thus, in the scope of this study, an optical strain rate controlled (OSRC) tensile test procedure with a digital image correlation (DIC) system, and a universal testing machine (UTM) was developed. The resulting mechanical properties and the evolution of the strain rate during the test of the steel DP600 (CR330Y590T-DH) and DC05 (CR4) were analyzed at a nominal strain rate of 0.4 %/s. In addition, the results obtained from displacement strain rate controlled (DSRC) tensile tests were compared. The results demonstrate that OSRC testing method enables the measurement of mechanical material properties at a higher level of precision in terms of constant strain rate compared to DSRC procedure.<br

Influence of a short-term heat treatment on the formability and ageing characteristics of aluminum profiles - Merklein, Marion; Lechner, Michael; Graser, Matthias (Lasers in Manufacturing Conference, 2015)
LFT Import::2019-08-05 (2113)

Influence of Combined Hard and Fine Machining on the Surface Properties of Cemented Carbides - Andreas, Kolja; Merklein, Marion; Engel, Ulf (Tribology in Industry, 2012)
As a result of recent developments in cold forging cemented carbides are increasingly used as tool materials. Due to their high hardness only electrical discharge machining (EDM) and grinding are suitable for tool machining. The structure of tool surface has significant influence on dominating failure mechanisms wear and fatigue. For improvement of tribological conditions the surface is polished in a finale processing step. The result of hard and fine machining is a specific combination of coarse and fine structure which is determined by processing parameters. The different surface structures lead to a particular tool behavior in forming process. This paper aims to show the influence of combined hard and fine machining on the surface properties of cemented carbides. © 2012 Published by Faculty of Engineering.
LFT Import::2019-07-29 (1859)
Keywords: Cemented carbide; Cold forging; Surface machining

Influence of component design on extrusion processes in sheet-bulk metal forming - Pilz, Florian; Merklein, Marion (International Journal of Material Forming, 2019)
Nowadays, the functional integration of workpieces challenges existing forming processes. The combination of established forming processes – like sheet metal and bulk forming – offers the possibility to counter this issue. The application of bulk forming operations on sheet metal semi-finished products, also called sheet-bulk metal forming (SBMF), is an innovative approach. The potential of SBMF cannot be fully exploited, as there are no recommendations in terms of workpiece design and layout influence on the process result. Therefore, this paper focuses on the analysis of semi-finished products and component design parameters on resulting part and process properties in two extrusion processes in SBMF. The investigation is based on a combined numerical and experimental approach. It is shown that the investigated design parameters, in addition to the achievable dimensional accuracy, substantially influence the occurring tool loads as well as the required process forces.
CRIS-Team Scopus Importer:2019-11-29
Keywords: Component design; Extrusion; Sheet forming; Sheet-bulk metal forming; Simulation

Influence of Cutting Processes on Edge Cracking Sensitivity of Bright Finishing Alloys - Merklein, Marion; Gnibl, Tobias; Tsoupis, Ioannis; Friedrichsen, Martin; Beck, Johannes (Key Engineering Materials, 2016)
LFT Import::2019-07-29 (2189)
Keywords: Aluminum; Cutting Edge; Sheet Metal Forming

Influence of dry ice blasting process properties on surface roughness and residual stresses of machined and additive manufactured workpieces - Amon, Sven; Jobst, Andreas; Merklein, Marion; Hanenkamp, Nico (Procedia CIRP, 2022)
Dry ice blasting has shown the potential to remove metallic burrs after machining processes and support structures after additive manufacturing. During blasting, process parameters need to be chosen depending on the material and the geometric properties of the burr. However, dry ice blasting affects the local material properties on a micro level and improper blasting parameters may lead to changes in the part surface. In this article, correlations and interactions between dry ice blasting parameters and resulting specimen roughness and residual stresses are identified for machined and additive manufactured metallic materials.<br
Keywords: dry ice blasting; metallic edge zone; deburring; post-processing; residual stresses

Influence of Grinding on the Surface Properties of Cemented Carbides - Andreas, Kolja; Engel, Ulf; Merklein, Marion (Key Engineering Materials, 2012)
The increased demand for manifold industrial goods requires superior manufacturing techniques. In the field of steel products, cold forging has gained importance for the last sixty years. Within cold forging the tool takes a key role as it determines both accuracy and efficiency of forming process. For forming processes with high demands regarding wear resistance WC-Co cemented carbides are increasingly used as tool materials. The manufacturing process of the tool requires a combination of hard and fine machining. In order to reduce the effort of subsequent fine machining process, surfaces with low roughness are preferred. As grinding leads to high surface qualities, it is a common method in tool machining. Grinding is accompanied by compressive residual stresses in the surface which have a positive influence on the tool life. The absolute value of residual stresses is determined by the machining parameters. The present study investigates the influence of feed and in-feed on the topography and the near surface residual stresses. While the surface roughness is correlated with both parameters, the feed has a major influence on the residual stresses in the surface of cemented carbides.© (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1780)
Keywords: Cemented Carbides; Grinding; Residual Stresses

Influence of laser generated micro textured coated tool surfaces on dry deep drawing processes - Tenner, Jennifer; Häfner, Tom; Rothammer, Benedict; Krachenfels, Kim; Zhao, Rong; Schmidt, Michael; Tremmel, Stephan; Merklein, Marion (Dry Metal Forming Open Access Journal, 2018)
The idea of sustainability and resource conservation promotes the development of energy-efficient and low-emission production processes. A lubricant-free sheet metal forming process is considered as one of these environmentally friendly production technologies. Metal forming processes without conventional lubricants shorten process steps and reduce additional costs, such as removal of residual lubrication from the workpiece after forming. In order to realize such a dry forming process and effectively control the material flow, amorphous carbon coatings were applied to the tool surfaces and a brushing process was carried out as a surface finishing process for roughness adjustment. Laser generated micro features on the surface should make an effective contribution to local friction adaptation. The transferability of strip drawing test to strip bending rotation test was successfully demonstrated by dry and oiled blank reference tests. The first modification of the tool sided surface was achieved by applying ta-C and a-C:H layers. The influence of the coatings on the tribological behaviour was determined in strip drawing tests for DC04 and AA5182. Additional friction adaptation is made possible by the fine and flexible laser based micro texturing of the coated tool surface. Experiments were carried out with different coverage and depth of the laser generated features in order to analyze the tribological influence. Flat and deep features with a degree of coverage of 20 %, 35 % and 50 % are considered in order to analyze the factors influencing their tribological behavior. Compared to ta-C coated references, it can be seen that micro features on the ta-C coated tool surface causes a friction reduction for DC04, independent of the features depth. However, deep laser generated features in particular lead to an increase in friction for AA5182, so that this could potentially lead to a selective local increase in friction in the flange area. For the transferability of the tribological system from the flat application case to a curved tool surface, the basics for laser based texturing of cylinder surfaces are illustrated. The limits of the holographic beam shaping technology used for this are demonstrated.
Keywords: Dry Deep Drawing; Tribology; Carbon Based Coatings; Laser Based Texturing

Influence of machining process on residual stresses in the surface of cemented carbides - Merklein, Marion; Andreas, Kolja; Engel, Ulf (Procedia Engineering, 2011)
LFT Import::2019-07-29 (1766)
Keywords: Cemented carbide; Residual stress; Tool

Influence of Material Delivery Condition on Residual Stresses and Part Properties During Forward Rod Extrusion - Jobst, Andreas; Merklein, Marion (13th International Conference on the Technology of Plasticity, 2021)
During the manufacturing of semi-finished products, the material is subjected to various forming steps to achieve the final geometry. In order to reduce the work hardening introduced and to ensure a good formability, it is annealed before component manufacturing. Forming technologies like forward rod extrusion are well-established methods for the efficient production of resilient components. In this process, however, an inhomogeneous pre-strengthening of the material influences the stress distribution during forming and therefore the mechanical properties and the residual stresses in the component. Since they affect the parts’ operating behaviour, knowledge of the influence of the delivery condition of the material is necessary. The aim of this paper is to derive dependencies between material properties and the resulting residual stresses and work hardening in the component. Due to the increasing application, ferritic stainless steel X6Cr17 in the skin passed (+LC) and soft annealed (+A) states are used. Residual stresses, microstructure, and microhardness distribution of both material states are compared regarding the rods and extruded parts. The effects of the delivery condition are evaluated by comparing process and component properties.
Keywords: Forward extrusion; Material condition; Stainless steel; Residual stress; Work hardening

Influence of Materials and Its Conditions on Pin-Extrusion from Sheet Metal - Kraus, Martin; Merklein, Marion (Lecture Notes in Mechanical Engineering, 2024)
Pin structures extruded from the sheet metal plane have numerous industrial applications. For instance, they can be used in bulk microforming to solve handling difficulties or in joining technology to connect dissimilar materials. Due to the absence of material flow restrictions in the direction of the sheet metal plane, pin extrusion is affected by numerous process-, workpiece- and tool-related parameters, which have a huge impact on the material utilization and the obtainable pin geometry. Within the scope of this study, a combined numerical-experimental research approach is used to analyze the influence of the material and its condition on the achievable pin height and the occurrence of the mostly undesired funnel formation at high punch penetration depths. For this purpose, elastic-ideal plastic and elastic-real hardening model materials are first investigated numerically, which are subsequently validated and verified in experiments by using the materials Cu-OFE, AA6016, DC04 on a laboratory scale. Based on the results, recommendations for the material selection and its properties are derived in order to maximize the material utilization.
Created from Fastlane, Scopus look-up
Keywords: extrusion; material flow; pin-extrusion; sheet metal

Influence of Media on Process Stability in Sheet Metal Hydroforming - Geiger, Manfred; Merklein, Marion; Blankl, Andreas (International Journal of Materials & Product Technology, 2008)
The difference between sheet metal hydroforming and deep drawing is elementary: one half of the tool is substituted by hydraulic pressure. In order to guarantee an optimised forming result a tight cavity in the tool has to be created, since as soon as a leakage occurs, the forming pressure decreases rapidly and the forming operation is interrupted. The separation plane of the tool is the critical area for an occurring leakage because here a metallic sealing is often realised. Therefore, the objective of this paper is to present theoretical consideration on the leakage problematic in hydroforming. For illustration of the problem an existing process chain is presented in the beginning of this paper. Subsequently theoretical considerations are made. In the end a new strategy for defusing the leakage problem by changing the hydroforming media is presented in the outlook. Copyright © 2008 Inderscience Enterprises Ltd.
LFT Import::2019-07-29 (1505)
Keywords: Hydroforming; Process stability; Sheet metal

Influence of Metal Flank Hardness of Machined and Cold Forged Gears on Wear within a Metal-Polyamide Gear Pair and Targeted Process Adaptation - Rohrmoser, Andreas; Merklein, Marion (Journal of Materials Engineering and Performance, 2022)
Metal-polyamide gear pairs provide advantages but their application is limited due to wear. The properties of the metallic gearing significantly affect the wear behavior. However, the influence of varying metallic materials as well as flank hardness is not known. Within this contribution, the occurring wear mechanisms when applying steel, brass and aluminum with varying hardness resulting from manufacturing by machining and cold forging were identified. Depending on the hardness of the metallic tooth flank, the release of metallic particles (3-body abrasion) or surface roughening (2-body abrasion) results. The formation of a wear-reducing transfer film is only possible with sufficient strength of the metallic tooth flank and tribological compatibility. Maximum wear occurs at a metal hardness of about 120 HV due to 3-body abrasion with high abrasive effect of the metallic particles. The adaptation of the cold forging process enables a local increase in the plastic strain of the tooth flank by 84% resulting in an elevated tooth flank hardness (+ 53%) for aluminum and significantly reduced wear. Furthermore, the formation of a wear-reducing transfer film results. Aluminum pinions produced in the adapted cold forging process achieve performance level of steel within the investigated load case.
CRIS-Team WoS Importer:2022-09-09

Influence of metal gear tooth geometry on load and wear within metal-polymer gear pairs - Rohrmoser, Andreas; Bode, Christoph; Schleich, Benjamin; Hagenah, Hinnerk; Wartzack, Sandro; Merklein, Marion (Applied Sciences, 2022)
Gear pairs made of the material pairing metal-polymer provide advantages, such as a reduced weight, beneficial damping properties and the possibility to be operated in dry running conditions. However, the service life of the pairing is limited due to wear. The properties of the metallic gearing have a significant influence on the wear behavior of the material pairing. From previous investigations, the influence of the surface topography and the flank hardness of the metal pinion is known. With regard to resource saving and efficient manufacturing of the metal pinion, cold forging offers benefits. Through cold forging, metallic gears for the material pairing can be produced ready-to-use in a process suitable for serial production. In order to enable manufacturing by extrusion, the application of gear radii is necessary. The gear radii significantly affect the extrusion process and the achievable gear properties. However, the influence of gear radii on wear within the metal-polymer material pairing has not yet been investigated. Within this contribution, the influence of the gear radii on the contact behavior as well as the resulting local load and wear of the tooth flank is determined. For this purpose, wear tests with aluminum (AlMgSi1) and steel (16MnCr5) gears with different gear radii within the pairing with polyamide (PA66) gears were performed. It has been shown that the local wear of the tooth flank can be attributed to the local load and that adjusted gear radii lead to a varying load and wear of the metal and polymer gears. Based on the findings, functional relationships regarding the choice of gear radii and the wear behavior are derived which can be applied in the design of cold forged gears.
Created from Fastlane, Scopus look-up
Keywords: Gear; Metal; Polymer; Tooth contact; Tooth geometry; Wear

Influence of metal inserts with microformed edges on subsequent injection assembly moulding for media tight electronic systems - Frey, Philipp; Heinle, Martina; Drummer, Dietmar; Merklein, Marion (4th International Conference on New Forming Technology, ICNFT 2015, 2015)

Influence of predeformation on the formability of aluminium alloys - Merklein, Marion; Beccari, S. (Proceedings of the 8th International Conference on Technology of Plasticity (ICTP), 09.-13.10., Verona, Italy, 2005)
LFT Import::2019-08-05 (1221)

Influence of Pre-forming on the Forming Limit Diagram - Tolazzi, Massimo; Merklein, Marion (Key Engineering Materials, 2007)
LFT Import::2019-07-16 (1468)

Influence of Pre-forming on the Forming Limit Diagram of Aluminium and Steel Sheets - Tolazzi, Massimo; Merklein, Marion (Sheet Metal 2007, Proceedings of the 12th International Conference on Sheet Metal; Advanced Materials Research, 2007)
This paper presents a method for the experimental determination of forming limit diagrams under non linear strain paths. The method consists in pre-forming the sheets under two different strain conditions: uniaxial and biaxial, and then stretching the samples, cut out of the preformed sheets, using a Nakajima testing setup. The optical deformation measurement system used for the process analysis (ARAMIS, Company GOM) allows to record and to analyze the strain distribution very precisely with respect to both time and space. As a reference also the FLDs of the investigated grades (the deep drawing steel DC04, the dual phase steel DP450 and the aluminum alloy AA5754) in as-received conditions were determined. The results show as expected an influence of the pre-forming conditions on the forming limit of the materials, with an increased formability in the case of biaxial stretching after uniaxial pre-forming and a reduced formability for uniaxial load after biaxial stretching if compared to the case of linear strain paths. These effects can be observed for all the investigated materials and can be also described in terms of a shifting of the FLD, which is related to the art and magnitude of the pre-deformation.
LFT Import::2019-08-05 (1387)
Keywords: Forming limit diagram; Sheet metal forming; Strain path

Influence of Pre-Strain and Simulated Paint-Bake on Mechanical Properties of High Strength Aluminium Alloy AA7020 - Merklein, Marion; Degner, Julia (Applied Mechanics and Materials, 2015)
LFT Import::2019-07-29 (2122)

Influence of Pre-straining and Heat Treatment on the Yield Surface of Precipitation Hardenable Aluminum Alloys - Lechner, Michael; Johannes, Maren; Kuppert, Andreas; Merklein, Marion (Physics Procedia, 2014)
LFT Import::2019-07-29 (2045)
Keywords: Aluminum; Intermediate heat treatment; Yield surface

Influence of Process Errors on the Tool Load in Microblanking of Thin Metal Foils with Silicon Punches - Hildering, Sven; Engel, Ulf; Merklein, Marion (9th International Conference on MicroManufacturing (ICOMM 2014), 2014)
Influence of Process Errors on the Tool Load in Microblanking of Thin Metal Foils with Silicon Punches.
LFT Import::2019-07-29 (2011)

Influence of production process-induced surface topologies at varying roughness depths on the tribological properties of polyamide steel contact - Schubert, Dominik; Rohrmoser, Andreas; Herzog, Christoph; Wolf, Michael; Hagenah, Hinnerk; Merklein, Marion; Drummer, Dietmar (Journal of Polymer Engineering, 2022)
Friction and wear in a tribological system are directly dependent on the surface structure and roughness of the friction partners involved. In this article, a clear interaction between surface topologies and their roughness depth was identified for the material pairing polyamide 66 - steel. The typical correlation between roughness and wear, initially decreasing and increasing after a wear minimizing roughness, was found for all surface topologies, albeit at different levels. The effect of the surface topology is negligible at low roughness (S z < 2.0 μm) with adhesive wear processes determining the wear behaviour. At higher roughness depths (S z > 2.0 μm), the ability of the surface topology to form a stable transfer film determines the tribological behaviour by limiting the effect of abrasive wear processes. A stable transfer film is formed with sufficient roughness and undercuts in the direction of motion, which can be characterised by the average roughness depth, R z , in the direction of motion. Based on these empirical results, an explanatory model for the observed behaviour is presented.
Created from Fastlane, Scopus look-up
Keywords: polymer metal contact; surface structure; transfer film; tribology; wear

Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW 6060 T4 extrusion profiles - Part A - Fröck, H.; Graser, Matthias; Reich, M.; Lechner, Michael; Merklein, Marion; Keßler, O. (Production Engineering, 2016)
LFT Import::2019-08-07 (2180)

Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW‑6060 T4 extrusion profiles – Part B - Graser, Matthias; Fröck, H.; Lechner, Michael; Reich, M.; Keßler, O.; Merklein, Marion (Production Engineering, 2016)
LFT Import::2019-07-29 (2179)

Influence of specimen geometry and strain rate on elongation in tensile testing of packaging steel - Knieps, Fabian; Köhl, Manuel; Merklein, Marion (ESAFORM 2021 - 24th International Conference on Material Forming, 2021)
Packaging steel is characterized by low thickness (0.1 mm - 0.5 mm) and ferritic microstructure resulting from low carbon contents. In combination with continuous annealing processes and temper rolling, this results in only little elongation observed in tensile tests. However, as in real forming processes much higher deformation occurs, it is important to receive true stress-true strain data up to a highest possible level e.g. to characterize material for finite element analysis. Therefore, tensile tests with three different measuring lengths (80 mm, 50 mm, 20 mm) were conducted for the packaging steel TH415. Likewise, the testing speed was reduced to investigate the possibility to receive more elongation under the condition of a constant stress level. The results revealed a significant increase in elongation when using smaller tensile test geometries. As well, the reduction in testing speed leads to much higher elongation while showing only little strain rate influence. While for the 80 mm geometry and standard speed no homogenous forming condition could be reached due to early failure before Lüders strain, this could be improved by using smaller testing specimens and a lower strain rate. Combining the influence of strain rate and geometry a significant increase of more than ten percentage points in elongation was reached.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Material characterization; Packaging steel; Tensile test

Influence of specimen size and sheet thickness on the material behavior of AZ31B under uniaxial tension - Suttner, Sebastian; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2016)
Concerning a low specific density, magnesium alloys offer a great potential to reduce the part weight. Due to the conditional formability of magnesium alloys at room temperature, forming processes are mostly realized at elevated temperatures. Within this contribution, uniaxial tensile tests for two different specimen geometries with a gauge length of 50 mm and 2 mm and a cross section of 12.5×1 mm2 and 2×1 mm2 are carried out for the magnesium alloy AZ31B at an elevated temperature of 200 °C. Since the specimen size is reduced, the influence of the sheet thickness needs to be analyzed. The analysis of the sheet thickness results in a change of the determined flow curve above a strain level of 0.1 and a much earlier failure of specimen with an initial sheet thickness of 1.5 mm. The changed material behavior can be explained by a different microstructure, e.g. the influence of the grain size. In summary, a characterization of the magnesium alloy AZ31B at elevated temperatures can be realized with a miniaturized test setup.
LFT Import::2019-07-29 (2212)

Influence of stress relaxation after uniaxial pre-straining on subsequent plastic yielding in the uniaxial tensile test of sheet metal - Suttner, Sebastian; Merklein, Marion (Key Engineering Materials, 2015)
Resource efficiency, design oriented accuracy and lightweight properties are demands on modern sheet metal forming parts in the automotive sector. The use of new materials leads to additional challenges on the numerical design of forming processes. During these forming processes the material undergoes different strain states that cause non-linear strain paths. Since the numerical prediction highly depends on the identified characteristic values of the material, an exact characterisation of the material behaviour is essential. Especially obtuse angles of the stress vector trigger a recovery of the material by returning stress. Besides, a relaxation of the material is investigated during holding a constant strain level. The effect of relaxation lead to an altered material behaviour that appears in a reduction of the beginning of plastic yielding. In addition, a kinematic hardening behaviour as under cyclic loading and load reversal, known as the Bauschinger effect, occurs after the relaxation of the stress and results in a reduced beginning of plastic yielding by loading in the same direction as the introduced pre-strain. Within this research work the effect of relaxation is investigated for two materials, AA5182 and DP600, with an initial sheet thickness of 1.0 mm. These materials are typically used for internal and accordingly functional parts in the automotive sector. The relaxation of the material is analysed with different holding times of a constant pre-strain at different levels of straining. The release of the material is studied by subsequent uniaxial tensile tests after pre-straining with the same load condition. Moreover, the influence of the named effects is shown by comparison of the translation of the yield loci.
LFT Import::2019-07-29 (2093)
Keywords: Metal forming; Modelling; Relaxation

Influence of Stress States on Forming Hybrid Parts with Sheet Metal and Additively Manufactured Element - Hafenecker, Jan; Papke, Thomas; Merklein, Marion (Journal of Materials Engineering and Performance, 2021)
Hybrid parts with additively manufactured elements (AME) combine the advantages of two or more manufacturing processes, e.g., forming and additive manufacturing (AM), and thus offer a solution to the increasing demands of industrial trends such as personalized mass production. Despite their advantageous properties, research in this field still lacks in clear classification and process interactions. Due to the strong influence of the AME on the formability of hybrid parts, the combination of laser-based powder bed fusion (PBF-LB) with subsequent sheet metal forming is examined in this paper. Therefore, cylindrical functional elements are built up on sheet metal and the resulting hybrid components are subsequently formed. Common forming processes such as bending, stretch forming and deep drawing are compared in regard to the different stress states. The results show a reduction in formability for hybrid components compared to conventional sheet metal materials. Reasons found are geometrical properties, gradients of mechanical properties and induced stresses. Consequently, requirements for the additive manufacturing process regarding a subsequent forming process are outlined. Namely, the gradient of mechanical properties should be smoothened, residual stresses kept low and the design of AMEs should avoid stress concentration.<br
Keywords: additive manufacturing; hybrid material; modelling and simulation; sheet metal formability; titanium

Influence of surface integrity on the tribological performance of cold forging tools - Andreas, Kolja; Merklein, Marion (Procedia CIRP, 2014)
LFT Import::2019-07-29 (1946)
Keywords: Cold forming; Finishing; Surface integrity; Tribology

Influence of tailored blanks on forming of cold forged functional elements in a sheet bulk metal forming process - Gröbel, Daniel; Hildenbrand, Philipp; Engel, Ulf; Merklein, Marion (Proceedings METEC & 2nd ESTAT, 2015)
LFT Import::2019-08-05 (2080)

Influence of Tailored Surfaces on the Surface Properties of Sheet-Bulk Metal Formed Parts - Wild, Thomas; Merklein, Marion (Proceedings of the Steel in Cars and Trucks (SCT), 2022)
In order to address the increasing challenges on manufacturing of components, including lightweight design and rising geometric complexity, the challenge emerges to further improve existing fabrication processes. In particular, drive train applications include filigree part geometries and functional elements, which is demanding for forming technology. Sheet-Bulk metal forming (SBMF) provides an option for addressing these issues in the production of planar and functional integrated parts. This approach uses bulk forming operations on sheet metals and leads to complex three dimensional strain and stress states during forming and thus incomplete die filling of functional elements as a consequence of unintended material flow. As a result of this central challenge of SBMF, locally modified tool surfaces, so called Tailored Surfaces, are used to control the material flow and improve the process results. In order to analyze the impact of Tailored Surfaces on the functional component properties, 1.0338 (DC04) and 1.0480 (HC260LA) are used in a SBMF forward extrusion process. Thereby, a locking tooth as a model geometry is formed. In the area of the functional elements, the active tool parts are in a laser polished condition, whereas the remaining tool areas are abrasive blasted to reduce the unintended material flow. Based on a parameter study varying the counterholder pressures during the forming process, the effect of the tool surfaces and the process parameters on the components surface properties are investigated by means of a confocal laserscanning microscope and tactile roughness measurements. In addition, measurements with an X-Ray diffractometer are carried out in order to analyze residual stress state of the formed parts.<br

Influence of the coating process on the tribological conditions during cold forging with a MoS2 based lubricant - Lorenz, Robby; Hagenah, Hinnerk; Merklein, Marion (AIP Conference Proceedings, 2018)
Cold forging processes such as forward rod extrusion can be used to produce high quality components like connection rods, shafts and gears. The main advantages of these extruded components are sufficient surface quality, work hardening, compressive residual stresses and fatigue strength. Since one technical disadvantage of extruded components lies in the achievable tolerance classes, the improvement of these should be of crucial importance. For instance, the attainable workpiece accuracy and component quality can be influenced by adapting the tribological system in such a way that the resulting friction is specifically controlled in order to improve component forming. Lubricant modification is one practical way of adapting the tribological system to the requirements of the forming process. An industrial established and highly efficient lubricant system is the application of a zinc-phosphate conversion layer with a molybdenum disulfide-based lubricant. While offering many advantages, its tribological conditions seem to depend strongly on the layer weight and the application strategy. These parameters and the respective interdependencies have not been sufficiently investigated yet. In order to examine this, the tribological conditions depending on the layer weight are analyzed in greater detail using the Ring-Compression-Test (RCT). This tribometer provides a comparative representation of the forming conditions during cold forging. Furthermore, a potential dependency between the tribological conditions and two different coating techniques is analyzed. The latter are represented by the industrial standards dipping and dip-drumming.<br

Influence of the Cutting Edge Geometry on the Tool Stress Distribution in Monocrystalline Silicon Punches for Microblanking of Thin Metal Foils - Hildering, Sven; Engel, Ulf; Merklein, Marion (Proc. 10th Int. Conf. Multi-Material Micro Manufacture, 2013)
LFT Import::2019-08-05 (1908)

Influence of the forming induced hardening on the wear behavior of aluminum gears within a metal-plastic material pairing and targeted adaption - Rohrmoser, Andreas; Hagenah, Hinnerk; Merklein, Marion (Procedia Manufacturing, 2021)
The material pairing metal-plastic offers advantages such as a reduced weight and the ability to be operated in dry conditions, but the application is limited due to the occurring wear. The properties of the metallic gearing have a significant influence on the wear behavior. From previous investigations on the application of steel within the material pairing, the influence of the surface topography and the load case is known. With regard to further weight reduction, the application of light metals such as aluminum is promising. However, the low strength of aluminum poses a challenge due to the low wear resistance. The properties of the metallic gearing are not only determined by the choice of material but also by the manufacturing process. In this context, cold extrusion offers potential for the production of ready-to-use gears. Sufficient geometrical properties and a substantial increase in tooth flank hardness are achieved. In this contribution, the influence of the forming induced hardening on the wear behavior of aluminum gears was investigated. Wire eroded aluminum and steel gears were used for comparison. The low hardness of conventionally manufactured aluminum gears was identified as a major challenge. Subsequently, gears with significantly higher tooth flank hardness were manufactured in an adapted full-forward extrusion process and the improved wear behavior was verified. Finally, functional correlations regarding the hardness of the metal pinion and the resulting wear behavior were derived.
CRIS-Team Scopus Importer:2021-11-05
Keywords: Aluminum; Cold-forging; Gears; Metal-plastic; Polymer; Wear

Influence of the forming process on springback - Durmaz, U.; Heibel, S.; Schweiker, T.; Prabhakar, A.; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2022), 2022)
CRIS-Team WoS Importer:2023-01-20

Influence of the Material Combination on the Load-bearing Capacity of Shear-clinched Joints - Wiesenmayer, Sebastian; Graser, Matthias; Merklein, Marion (1st International Conference on Advanced Joining Processes AJP 2019, 2019)

Influence of the mechanical fatigue progress on the magnetic properties of electrical steel sheets - Karthaus, Jan; Steentjes, Simon; Gröbel, Daniel; Andreas, Kolja; Merklein, Marion; Hameyer, Kay (Archives of Electrical Engineering, 2017)
The purpose of this paper is to study the variation of the magnetic properties of non-oriented electrical steel sheets with the fatigue state during cyclic mechanical loading. The obtained results are central to the design of variable drives such as traction drives in electric vehicles in which varying mechanical loads, e.g. in the rotor core (centrifugal forces), alter the magnetic properties. Specimens of non-oriented electrical steel are subject to a cyclically varying mechanical tensile stress with different stress amplitudes and number of cycles. The specimens are characterised magnetically at different fatigue states for different magnetic flux densities and magnetising frequencies. The measurements show a variation in magnetic properties depending on the number of cycles and stress magnitude which can be explained by changes in the material structure due to a beginning mechanical fatigue process. The studied effect is critical for the estimation of the impact of mechanical material fatigue on the operational behaviour of electrical machines. Particularly in electrical machines with a higher speed where the rotor is stressed by high centrifugal forces, material fatigue occurs and can lead to deterioration of the rotor's stack lamination.
LFT Import::2019-07-29 (2242)
Keywords: Cyclic mechanical stress; electrical machines; electrical steel sheets; magnetic properties; material fatigue

Influence of the plasticity strain gradient on springback in micro-bending process of metal foils - Li, H. Z.; Dong, X. H.; Shen, Y.; Diehl, Alexander; Hagenah, Hinnerk; Engel, Ulf; Merklein, Marion (Proceedings of The 2nd Asia Conference on micro/nano sized technology (AWMFT-2009), 2009)
LFT Import::2019-08-05 (133)

Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel - Kuball, Clara-Maria; Jung, Robert; Uhe, Benedikt; Meschut, Gerson; Merklein, Marion (Journal of Advanced Joining Processes, 2020)

Influence of the process temperature on the tribological behaviour during bulk forming of high nitrogen steel - Kuball, Clara-Maria; Jung, Robert; Uhe, Benedikt; Meschut, Gerson; Merklein, Marion (1st International Conference on Advanced Joining Processes AJP 2019, 2019)

Influence of the properties of the joining partners on the load-bearing capacity of shear-clinched joints - Wiesenmayer, Sebastian; Graser, Matthias; Merklein, Marion (Journal of Materials Processing Technology, 2020)
Shear-clinching requires a minimum ductility for the punch-sided sheet material. A promising approach to overcome this limitation is a local short-term heat treatment of the upper joining partner in the joining zone. However, the design of heat treatment layouts for high-strength aluminum alloys necessitates fundamental knowledge on the mechanisms in shear-clinching processes in dependence of the properties of both joining partners. Therefore, within the paper, the mechanisms in shear-clinching were analyzed for a common aluminum magnesium alloy of the 5000 series, an alloy of the 6000 series with higher strength and a high-strength alloy of the 7000 series. On the die-side, hot stamped 22MnB5 and the dual phase steel HCT780X was utilized. For upper sheet materials with higher strength, the radial material extrusion of the upper joining partner decreases, which leads to the increase of the material volume in the joining zone and therefore to a larger bottom thickness and interlock. In addition, the decreased penetration of the outer punch results in a larger upper neck thickness. Due to the larger load-bearing cross section and the higher tensile strength, higher forces can be transmitted for high-strength materials. However, the low ductility of high-strength materials results in a failure of the joint at lower displacements and therefore in a decreased energy absorption. The found mechanisms provide the theoretical basis for the design of heat treatment layouts for high-strength aluminum alloys.
CRIS-Team Scopus Importer:2020-04-24
Keywords: Heat treatment; High-strength aluminum; High-strength steel; Joining; Multi-material design

Influence of the rivet coating on the friction during self-piercing riveting - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Key Engineering Materials, 2021)

Influence of the strain dependent material behaviour under plane strain on the yield locus modelling - Lenzen, Matthias; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
CRIS-Team WoS Importer:2021-11-05

Influence of the Variation of Material Properties on the Risk of Failure in Dependency of the Materials Flow Condition during Forming Processes - Sturm, Vera; Merklein, Marion; Bernhard, Oberpriller (International Journal of Material Forming, 2010)
LFT Import::2019-07-29 (314)
Keywords: Failure risk; Sheet metal forming; Variation of materials properties

Influence of Tool Surface on Tribological Conditions in Conventional and Dry Sheet Metal Forming - Merklein, Marion; Andreas, Kolja; Steiner, Jennifer (International Journal of Precision Engineering and Manufacturing - Green Technology, 2015)
LFT Import::2019-07-29 (2086)
Keywords: Dry forming; Sheet metal forming; Tribology

Influence of tool wear on the load-bearing capacity of shear-clinched joints - Wiesenmayer, Sebastian; Merklein, Marion (Defect and Diffusion Forum, 2020)
Shear-clinching allows the joining by forming of dissimilar materials with high differences between their mechanical properties without additional fasteners. Since the lower joining partner is indirectly shear cut during the process, even ultra-high strength materials can be joined. However, the cutting of the high-strength materials as well as the extrusion of the upper joining partner leads to high process forces and therefore to high tool loads. This applies in particular for the die, which is highly stressed during the cutting phase and therefore plastically deformed. Within the scope of this work, the influence of the occurring wear on the formation of the joint and its load-bearing capacity is analyzed for a scope of 500 strokes. For this purpose, press hardened 22MnB5 is used as lower joining partner. Its high strength leads to the plastic deformation of the cutting edge, which increases within the first 200 strokes. Afterwards only minor changes occur. Yet, no effect of the occurring wear on the joint formation and the joint strength, which was tested under shear and tensile load, could be determined. Functioning joints could still be produced for more than 500 strokes as the load-bearing capacity remained on a comparable level.
CRIS-Team Scopus Importer:2020-12-04
Keywords: High-strength steel; Joining; Wear

Influence of tribological conditions on application relevant component properties of cold forged gears - Rohrmoser, Andreas; Kiener, Christoph; Hagenah, Hinnerk; Merklein, Marion (Production Engineering, 2019)

Influence of tribological conditions on cold forging of gears - Kiener, Christoph; Neher, R.; Merklein, Marion (Production Engineering, 2018)
Gears are integral and vital machine elements in the field of drive and transmission technology. With regard to economic and ecological aspects, cold forging represents a promising approach compared to conventional cutting processes for producing highly-loadable gears. A possible extrusion process for manufacturing helical gears is the so-called “Samanta”-process. In comparison to conventional extrusion processes, an additional ejector system is avoidable. Thus, in particular for helical gears, a negative impact on the gear quality by the ejector operation is prevented. Furthermore, the process chain during the component production cycle is shortened which leads to a more efficient production. The achievable gear accuracy as well as insufficient tool life are major challenges while establishing the “Samanta”-process in industry. To enable an industrial application, basic process understanding as well as knowledge about the influences on the process results is required. For influencing component and process properties within cold forging, approaches from the tribological system can be generally used. The aim of this study is to analyze the influence of the friction conditions on selected component and process properties within cold forging of gears by the “Samanta”-process. For adjusting the occurring friction, various lubrication systems were applied, which have been qualified using a double cup extrusion test (DCE-test). The results reveal that the lubrication system determines the friction conditions during forming. Within cold forging of helical gears by the “Samanta”-process, the friction influences the resulting strain hardening of the components and the required maximum forming force as well as the energy amount.
LFT Import::2019-07-29 (2285)
Keywords: Cold forging; Friction; Gears; Tool technology

Influence of tribological conditions on cold forging processes - Kiener, Christoph; Dohmstreich, J.; Andreas, Kolja; Merklein, Marion (Proceedings THE"A" Coatings, 2017)
LFT Import::2019-08-07 (2262)

Influence of Ultrasonic Assistance on the Forming Limits of Steel - Jäckisch, Manuel; Merklein, Marion (Minerals, Metals and Materials Series, 2021)
Since Blaha discovered the beneficial effect of superimposing high-frequency oscillations to the metal forming process, the occurring force and stress reduction are well-known phenomena. Leading to an immediate flow stress reduction, the so-called ultrasonic assistance is a promising approach to enable forming with reduced process forces. While the achievable force reduction has been investigated intensively, only a few analyses have been conducted in the context of the impact of ultrasonic superposition on the forming limits. The latest investigations state earlier material failure due to localized forming with recurrent high strain rates. Within this paper, the influence of superimposed vibrations on the forming limits of C35E is investigated with regard to distinct oscillation amplitudes and press velocities. It was found that superimposed 20 kHz oscillations of 10 and 20 µm cause considerable earlier material failure. In comparison to conventional testing, the crack initiation, as well as the shear zone formation, is alternated due to the ultrasonic assistance.
CRIS-Team Scopus Importer:2021-09-03
Keywords: Failure; Forming; Steel; Ultrasonic

Influence of ultrasonic vibration on the shear formability of metallic materials - Michalski, Markus; Lechner, Michael; Gruber, Micha; Merklein, Marion (CIRP Annals - Manufacturing Technology, 2018)
The flow stress reduction of metallic materials due to superimposed ultrasonic vibration is an intensively researched phenomenon. So far, however, only a few studies have analysed the vibrational influence on forming limits. Existing findings are inconsistent, suggesting both a formability extension and a decrease. Ultrasonic-assisted shear tests constitute a novel experimental approach for the fundamental investigation of predominant cause–effect–relationships. The test results reveal a distinct correlation between the application of ultrasonic vibration and earlier material failure. This effect is attributed to enhanced crack initiation and propagation caused by localised stress and strain concentration as well as intermittent high strain rates.
LFT Import::2019-07-29 (2298)
Keywords: Failure; Forming; Ultrasonic

Influence of upscaling accumulative roll bonding on the homogeneity and mechanical properties of AA1050A - Ruppert, Mathis; Böhm, Wolfgang; Nguyen, H.; Höppel, Heinz Werner; Merklein, Marion; Göken, Mathias (Journal of Materials Science, 2013)
Accumulative roll bonding (ARB), as a method for production of ultrafine grained materials, is frequently supposed to be easily transferable to established industrial production lines. In literature, however, common sheet dimensions used for ARB in a laboratory scale are between 20 and 100 mm in width. In order to quantify the potential of upscaling the ARB process to a technological relevant level, sheets of AA1050A with an initial sheet width of 100–450 mm were accumulative roll bonded up to 8 cycles. In this regard, three different rolling mills of distinct dimensions were used for processing of the sheet material. The influence of process parameters and the reproducibility of the process, in terms of mechanical properties and homogeneity of the sheets, were studied by means of mechanical and microstructural characterization. Both appear to be largely independent on the sheet size and the rolling mill utilized for production. Only small deviations after the first cycles could be detected, vanishing in subsequent cycles due to the features of microstructural evolution. The finally obtained results indicate a high potential for industrial application of ARB and illustrate the possibility to upscale the process to a level necessary for that purpose.
WW1::970

Influence of varying sheet material properties on dry deep drawing process - Krachenfels, Kim; Rothammer, Benedict; Zhao, Rong; Tremmel, Stephan; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2019)
Deep drawing is one of the most important processes in sheet metal forming. Conventionally, lubricants are used to reduce friction and wear. Demands for increased sustainability, environmental protection and resource efficiency motivate the realization of lubricant-free forming processes. The direct contact between tool and workpiece during dry deep drawing results in changed tribological conditions, which cause an increase in friction and wear. Friction-reducing surface modifications of the tool such as carbon based coatings are being developed for the adaptation of the tribological conditions. The aim of this work is the simulation-based analysis of the stress spectrum for varying sheet properties for the qualification of wear-reducing surface modifications for a wide range of applications. By a simulation model for a rectangular cup, the influence of different batches of steel and aluminum materials with varying friction coefficients and mechanical properties is investigated within the framework of variant simulations. The tribological conditions in the simulation are described on the basis of friction coefficients from the strip drawing test. From the simulation results, the applicability of surface modifications for dry deep drawing is being evaluated depending on the sheet specific properties.<br

Influence of Warm Bending on the Surface Topography of Titanium Alloy Ti-6Al-4V - Dubjella, Patrick; Merklein, Marion (Procedia Engineering, 2017)
More frequently industry reverts to titanium alloys such as Ti-6Al-4V for several applications. This is due to its wide range of positive material characteristics like high biocompatibility, good corrosion resistance and high specific strength. Hence, Ti-6Al-4V is utilized for applications in medicine technique, marine and aerospace. However, forming of Ti-6Al-4V at room temperature is limited, which is caused by its hexagonal closed packed (hcp) grain structure. To overcome these limitations it is necessary to form Ti-6Al-4V at elevated temperatures. Thus, further gliding planes are activated and large scaled parts can be formed at low cycle times. Another promising process to generate Ti-6Al-4V structures is additive manufacturing. Via Laser Beam Melting (LBM) geometrical limitations of the forming process can be overcome. Nearly every conceivable geometry like undercuts is possible to generate. However, the process takes comparatively long time and the costs for large batch sizes are high. In order to merge the advantages of forming and LBM a combination of both processes is favorable. The sequence of forming and a subsequent additive process to produce a hybrid part leads to several challenges. Besides forming induced residual stresses in the sheet metal, the topography of the sheet has effect on the bonding quality of sheet metal and additive structure. Especially peaks in roughness may serve as crack initiators. In order to provide suitable parts for the subsequent additive process it is necessary to have a sound knowledge of the impact of the forming operation on the surface topography. For this reason this paper focuses on the investigation of the influence of warm bending on the surface topography of Ti-6Al-4V. Therefore bending tests with varying temperatures, punch radii and different bending angles are conducted and the topography is analyzed with confocal microscopy.
LFT Import::2019-07-29 (2260)
Keywords: Additive Manufacturing; Bending; Titanium

Influences of indentation forming on surface characteristics and metallographic properties of bright finishing alloys - Beck, Johannes; Friedrichsen, M.; Merklein, Marion (7. WGP-Jahreskongress Aachen, 5.-6. Oktober 2017, 2017)
LFT Import::2019-08-05 (2257)

Influences on the Molding in Hydroforming Using Granular Material as a Medium - Grüner, Martin; Merklein, Marion (AIP Conference Proceedings Volume 1383 - The 8th International Conference and Workshop on Numerical Simulation of 3D Sheet Metal Forming Processes (NUMISHEET 2011), 2011)
The need of lightweight construction for the body in white of modern cars increases due to legal restrictions of CO2 emissions and the passenger s wishes of safety and low fuel consumption. On e approach of lightweight construction is the use of high and ultra high strength steel, to reduce the weight of the single parts, another approach is the use of modern forming technologies, e.g. hydroforming with the possibility to create undercuts, to produce complex parts and thus to reduce the number of parts, the number of joining operations and the weight. The mentioned ultra high strength steels show a poor formability at room temperature and the necessary process forces are high compared to standard deep drawings teels. Warmforming operations can help to reduce the process forces and to increase formability [1]. To combine the benefits of warm forming and hydroforming new forming media are necessary to overcome the problem of temperature stability of fluids, which is limited to about 350 °C [2]. Beside gases, which tend to leakage and which are highly compressible, granular material like small ceramic beads can be used as a forming medium. First results of forming operations using this medium were presented in [3]. The experimental tool used for those tests pressurizes the medium by a punch. To divide the effects caused by temperature and steel grade from the other effects experiments were carried out at room temperature using the well know n deep drawing steel DC04. Influences of the ceramic beads diameter, the number of repetitions, the punch geometry as the punch position, determining the volume of media, on the forming are presented. © 2011 American Institute of Physics.
LFT Import::2019-08-05 (1757)
Keywords: Elevated temperatures; Granular material; Hydroforming

Influences on wear load in cup extrusion processes - Schrader, Tobias; Engel, Ulf; Merklein, Marion (7th ICFG Workshop on Process Simulation in Metalforming, 2012)
LFT Import::2019-08-05 (1843)

In-Line strategies and methods to reduce balancing efforts within rotor production for electric drives - Hofmann, Benjamin; Masuch, Michael; Frey, Philipp; Franke, Jörg; Merklein, Marion (6th International Electric Drives Production Conference (EDPC), 2016)
Within a research project focussing the optimization of the entire process chain of rotor production, balancing is identified as one of the processes with a high potential for innovation. As most research efforts concentrate on the additive or subtractive process itself, the presented paper follows a different approach concentrating on the impact of process steps prior to rotor assembly and the actual balancing operation. Within current production processes, weighing is almost exclusively performed as an end-of–line process to take the entire rotor assembly into account. However, concerning the production of drives with permanent magnets, particularly those with magnets integrated into the lamination stack (IPM-Drives), production steps leading to the rotor assembly already deliver prefabricated lamination modules that can be evaluated regarding their imbalance. By determining the imbalance of those modules and a varying rotational combination of a number of modules being needed to form a complete rotor assembly, balancing efforts are considered to be reduced significantly; resulting in a lighter rotor assembly due to thinner end caps on the rotor. The presented Paper describes methods and strategies to evaluate the imbalance of single lamination stacks and their preferred orientation prior to their assembly onto the rotor shaft. Depending on the rotor topology (pole number, magnet count), restrictions regarding free rotation have to be considered. Additionally, known methods for balancing in single and double layers have to be practically analysed and compared for the balancing operation in focus. Using pre-stacked laminations, the balancing operation is validated in practice to determine actual effects on the imbalance of a complete lamination stack. Using different combinations for aggregating single packages, the imbalance can be reduced by up to 30%.<br
Keywords: balancing; rotor; electric drives

Innenhochdruck-Umformen von Doppelblechen - Geiger, Manfred; Neugebauer, Stephan; Merklein, Marion; Lamprecht, Klaus; Tolazzi, Massimo; Bahn, V. (Wirkmedienbasierte Fertigungstechniken zur Blechumformung, Abschlussbereicht zum DFG-Schwerpunktprogramm SPP 1098, 28.-29.09., Dortmund, 2006)
LFT Import::2019-08-05 (1298)

Innenhochdruck-Umformen von Magnesiumblechen - Merklein, Marion; Hecht, Joachim; Hußnätter, Wolfgang; Geiger, Manfred (Karosserie II, 2006)
LFT Import::2019-07-16 (1312)

Innovative Aluminium Lightweight Design by the Combination of Accumulative Roll Bonding and Local Intermediate Heat Treatment - Böhm, Wolfgang; Merklein, Marion; Lechner, Michael (Materials Today, 2015)
The intensifying regulations for CO2 emissions of passenger cars lead to increased efforts in the field of lightweight construction. In this context, the application of aluminium is a promising strategy. Another approach is the implementation of high strength materials to enable the reduction of the wall thickness of components and to ensure the crash performance. The manufacturing of multi-layered aluminium sheet metal with enhanced strength and nanocrystalline grain structure can be performed using the Accumulative Roll Bonding process (ARB). However, the formability of ARB processed aluminium is relatively poor. Therefore, within this paper an innovative approach to enhance the formability is presented. Key idea of the local short term intermediate heat treatment is the tailoring of the mechanical properties between two forming operations. In order to identify suitable process parameters for beneficial heat treatment, the interaction of pre-straining and heat treatment is evaluated.
EAM Import::2019-03-13

Innovative approaches for controlling the material flow in sheet-bulk metal forming processes - Merklein, Marion; Lechner, Michael; Gröbel, Daniel; Löffler, Maria; Schneider, Thomas; Schulte, Robert Karl; Hildenbrand, Philipp (Manufacturing Review, 2016)
Using sheet-bulk metal forming processes the application of bulk forming operations on sheet metals enables the manufacturing of functional components with local wall thickness variations. As these processes come along with a two- and three-dimensional material flow, the control of the material flow is crucial for ensuring a proper filling of functional elements and thus ensuring the components quality. Controlling the material flow can be achieved by different solutions: the local adaption of tribological conditions and the application of process adapted semi-finished parts. In this paper, both solutions as well as their general qualification in two sheet-bulk metal forming processes are presented.
LFT Import::2019-07-29 (2144)
Keywords: Forming; Material flow; Processes

Innovative Manufactring Chain for Complex Hydroforming Parts - Special Solutions for Process and Systems Technology - Geiger, Manfred; Merklein, Marion; Blankl, Andreas (Proceedings of the 22nd International Manufacturing Conference (IMC), 2005)
LFT Import::2019-08-05 (1198)

Innovative manufacturing solutions for the efficient production of car bodies - Merklein, Marion; Tsoupis, Ioannis; Gnibl, Tobias; Lechner, Michael (Forming in Car Body Engineering 2015, 2015)
LFT Import::2019-08-05 (2123)

Innovative Methoden zur Charakterisierung des Fließverhaltens und des Werkstoffversagens von Blechwerkstoffen - Merklein, Marion; Kuppert, Andreas; Biasutti, Manfredi; Lupino, Roberto (testXpo - 18. Fachmesse für Prüftechnik, 2009)
LFT Import::2019-08-05 (199)

Innovative Process Strategies in Powder-Based Multi-Material Additive Manufacturing - Setter, Robert; Hafenecker, Jan; Rothfelder, Richard; Kopp, Sebastian-Paul; Roth, Stephan; Schmidt, Michael; Merklein, Marion; Wudy, Katrin (Journal of Manufacturing and Materials Processing, 2023)
Multi-material additive manufacturing (AM) attempts to utilize the full benefits of complex part production with a comprehensive and complementary material spectrum. In this context, this research article presents new processing strategies in the field of polymer- and metal-based multi-material AM. The investigation highlights the current progress in powder-based multi-material AM based on three successfully utilized technological approaches: additive and formative manufacturing of hybrid metal parts with locally adapted and tailored properties, material-efficient AM of multi-material polymer parts through electrophotography, and the implementation of UV-curable thermosets within the laser-based powder bed fusion of plastics. Owing to the complex requirements for the mechanical testing of multi-material parts with an emphasis on the transition area, this research targets an experimental shear testing set-up as a universal method for both metal- and polymer-based processes. The method was selected based on the common need of all technologies for the sufficient characterization of the bonding behavior between the individual materials.<br
Keywords: additive manufacturing; multi-material additive manufacturing; polymers; metals; shear testing; mechanical testing; powder bed fusion; binder jetting; electrophotography; vibration dispenser

Innovative Prozesskette für Strukturleichtbauteile - Verarbeitung von Aluminium Tailored Blanks bei erhöhten Temperaturen - Gnibl, Tobias; Merklein, Marion (wt Werkstattstechnik - Online, 2014)
LFT Import::2019-07-29 (2035)

Innovative Sitzbauteile durch Umformen von Mehrphasenstählen - Kaupper, Markus; Merklein, Marion; Weidinger, Peter (Maschinenmarkt, 2011)
LFT Import::2019-07-29 (1659)

Innovatives Konstruktions- und Fertigungskonzept für Straßenbahn-Rohbau - Celeghini, Martino; Pohl, Thomas; Geiger, Manfred; Merklein, Marion; Hecht, Joachim; Meerkamm, H.; Stockinger, A. (8. Fachtagung Fügen und Konstruieren im Schnienfahrzeugbau, 2009)
LFT Import::2019-08-05 (1584)

Innovative Tribological Systems in Sheet Metal Forming - Revolution in the Press Shop? - Andreas, Kolja; Tenner, Jennifer; Vierzigmann, Ulrich; Merklein, Marion; Tremmel, Stephan; Zhao, R. (Proc. 11th Int. Conf. THE "A" Coatings in Manufacturing Engineering, 2014)
LFT Import::2019-08-05 (2048)

In Situ Formation of a Metastable β-Ti Alloy by Laser Powder Bed Fusion (L-PBF) of Vanadium and Iron Modified Ti-6Al-4V - Huber, Florian; Papke, Thomas; Scheitler, Christian Josef; Hanrieder, Lukas; Merklein, Marion; Schmidt, Michael (Metals, 2018)

Integrated manufacturing by hydroforming, laser welding and cutting - Kreis, Oliver; Celeghini, Martino; Merklein, Marion (Proceedings of the 11th International Conference on Sheet Metal, 2005)
The shortening of process chains and the combination of innovative manufacturing technologies offer the possibility to enhance the complexity of technical products. The presented work describes the development of a process chain for the manufacturing of complex hollow parts out of double sheets and tubes with a big variation of the cross section, e.g. for A-pillars in the automotive sector. Two blanks and a tube are inserted in a hydroforming tool by a handling robot. The processes forming of blanks and tubes as well as joining by clinching are integrated in this tool. After these steps, the handling robot places the part in a laser station, where integrated laser welding and cutting processes take place. This paper focuses on special solutions developed both in the hydroforming and in the laser processing. In particular, the connection between blanks and tube is extremely problematic with regard to the sealing in the hydroforming process and the welding operations due to an existing gap. The requested tightness is reached by reinforcing the tube in the connection area with a ring insert, by placing sealing profiles on the outer surface of the tube and particularly by adding a sealing medium to the hydroforming fluid. In laser operations, special challenges result from complex welding and cutting paths, contaminations of the blanks with hydroforming media and lubricants, gaps between the blanks that occur due to residual stresses after forming and burr formatio
LFT Import::2019-08-05 (1166)
Keywords: Hydroforming; Laser; Process

Integrated manufacturing by hydroforming, laser welding and cutting of complex hollow parts - Kreis, Oliver; Celeghini, Martino; Geiger, Manfred; Merklein, Marion (LANE 2004, Proceedings of the 4th International Conference on Laser Assisted Net Shape Engineering, 21.-24.09.2004, Erlangen, Germany, 2004)
LFT Import::2019-08-05 (1084)

Integrated Tube and Double Sheet Hydroforming Technology - Optimised Process for the Production of a Complex Part - Geiger, Manfred; Merklein, Marion; Cojutti, Massimo (Key Engineering Materials, 2007)
LFT Import::2019-07-16 (1399)
Keywords: Double sheet hydroforming; Process optimisation; Tube hydroforming

Integrierte Fertigung durch Umformen, Fügen und Trennen - Merklein, Marion; Blankl, Andreas; Cojutti, Massimo (Arbeits- und Ergebnisbericht des DFG SFB 396, 2007)
LFT Import::2019-07-16 (1498)

Integrierte Fertigung von tiefgezogenen Blechbauteilen mit Verzahnungselementen unter Einsatz von prozessangepassten Halbzeugen - Merklein, Marion; Behrens, B.-A.; Plettke, Raoul; Krimm, R.; Opel, Simon; Schneider, Thomas; Matthias, T.; Salfeld, V. (Tagungsband zum 1. Erlanger Workshop Blechmassivumformung 2011, 2011)
LFT Import::2019-08-05 (1765)

Interaction analysis of a notching and cyclic bending process - Biallas, Alina; Merklein, Marion (Manufacturing Letters, 2022)
The economic and ecological efficient production of steel wire fibers for reinforcing concrete is essential for exploiting their potential to reduce the required amount of building material. An innovative production process bases on the process chain notch rolling and cyclic bending. A sheet metal is notched on both sides and subsequently bent under undulated motion for causing a cyclic bending load in the formed notches. Due to damage effects during the cyclic bending, cracks initiate. The damage procedure and crack growth is influenced by the previous notched sheet called wire strip and the characteristics of the bending process. To analyze these effects, an influence and interaction study of the notches on the cyclic bending process is aspired. Based on a two-staged experimental design, the notching parameters notch tip radius and web height, which correlate with the amount of strain hardening, as well as the bending parameter bending angle, for identifying the interdependency of both processes, are evaluated. For study execution, an experimental model test for applying a cyclic bending load on a notched specimen is introduced.
Keywords: Metal forming; Cyclic bending; Damage

Interaction of Additive Manufacturing and Forming - Merklein, Marion; Dubjella, Patrick; Schaub, Adam; Butzhammer, Lorenz; Schmidt, Michael (Proceedings of 6th International Conference on Additive Technologies, 2016)
Titanium alloys such as Ti-6Al-4V are utilized for a wide range of industrial approaches. This is primarily due to their positive material characteristics such as high biocompatibility, good corrosion resistance and outstanding specific strength. As a result of the hexagonal close packed (hcp) grain structure the achievable plastic deformation of these alloys at room temperature is limited. To overcome these limitations, forming at elevated temperatures is a promising process. A further promising manufacturing method for titanium is laser beam melting (LBM). LBM functions at melted material condition and thereby neglects most manufacturing challenges. It enables to produce individual parts by overcoming geometrical design restrictions compared to conventional manufacturing techniques. Within this work a process chain combining sheet metal forming and laser beam melting is presented and discussed. The main benefit of this combined process is a merge of the positive  characteristics of both manufacturing methods. In former researches deep drawing was used as forming process. Due to inducing a more complex stress level, which is more application oriented, bending will be investigated as a forming strategy for a combination with LBM. Therefore a tool was developed and manufactured. In this study the function of this tool will be described in detail and its qualification for bending flat sheets of Ti-6Al-4V as well as hybrid parts will be researched.
Keywords: Additive Manufacturing; Forming; Bending; Titanium alloys

Interaction of various functional elements in thin-walled cups formed by a sheet-bulk metal forming process - Schulte, Robert Karl; Schneider, Thomas; Lechner, Michael; Merklein, Marion (NUMIFORM 2016: The 12th International Conference on Numerical Methods in Industrial Forming Processes, 2016)
Sheet-bulk metal forming allows the manufacturing of sheet metal parts with integrated functional elements. The investigated process combines deep drawing and upsetting. The occurring 2D and 3D stress and strain states lead to challenges regarding material flow control due to different geometries of functional elements. The numerical analysis shows the transferability for the results of the different functional elements for their combination and the interaction between those functional elements regarding the material flow. The results are validated by experimental tests.
LFT Import::2019-08-05 (2202)

Interlaboratory comparison for heat transfer coefficient identification in hot stamping of high strength steels - Bosetti, Paolo; Bruschi, S.; Stöhr, Thomas; Lechler, Jürgen; Merklein, Marion (Proceedings of Esaform 2010, 2010)
The topic of the paper is the identification of the heat transfer coefficient (HTC) in hot stamping of boron steel sheets under conditions very close to the industrial ones. Two approaches followed by one lab in Germany and one lab in Italy are presented for HTC identification, showing the two experimental apparatuses that were set-up to conduct the tests, the procedures developed and applied to identify the HTC. The obtained results are compared in terms of dependence of HTC from the applied contact pressure, the similarities and the differences of the two approaches are outlined and commented. © 2010 Springer-Verlag France.
LFT Import::2019-08-05 (223)
Keywords: Heat transfer coefficient; Hot stamping; Inverse analysis

Interlaboratory Comparison of Forming Limit Curves for Hot Stamping of High Strength Steels - Pellegrini, D.; Lechler, Jürgen; Ghiotti, Andrea; Bruschi, S.; Merklein, Marion (SheMet'09, Proceedings of the 13th International Conference on Sheet Metal, 2009)
The paper presents the approaches followed by two labs - LFT at the University of Erlangen-Nuremberg (Germany) and DIMEG at University of Padua (Italy) - in evaluating formability limits of 22MnB5 sheets when processed under hot stamping conditions. Details about the two testing apparatuses and the testing procedures are outlined, and the results in terms of Forming Limit Curves FLC compared and critically commented. © (2009) Trans Tech Publications, Switzerland.
LFT Import::2019-08-05 (1565)
Keywords: Forming limit curve; High strength steel; Hot stamping

Interlaboratory Comparison of Friction Conditions in Hot Stamping Operations - Borsetto, F.; Ghiotti, Andrea; Bruschi, S.; Stöhr, Thomas; Lechler, Jürgen; Merklein, Marion (Key Engineering Materials, 2010)
The paper presents results obtained at two labs, on in Germany and one in Italy, in terms of friction coefficient as function of hot stamping process parameters. Even if the testing procedures and analysis tools to evaluate tribological conditions are different for the two labs, both the approaches show a similar trend as regards the friction coefficient dependence from the process parameters. © (2010) Trans Tech Publications.
LFT Import::2019-07-29 (1160)
Keywords: High strength steel; Hot stamping; Tribology

Intermediate Heat Treatment - A New Proceeding for Aluminium Alloys Using Forming Limit Diagrams - Siefert, Kathleen; Merklein, Marion; Töpperwien, Almut; Nester, Winfried; Gruenbaum, Martin (Key Engineering 473, 2011)
This paper presents a new procedure for a heat treatment embedded between two cold forming steps. A first cold forming step induces a defined strain hardening in the material. The following step is the heat treatment which takes place in a furnace at various temperatures and for certain durations. The application of such an intermediate heat treatment reduces the strain hardening of the material and enhances the elongation. This allows a higher degree of deformation in the second cold forming operation. The achievable properties of the aluminum alloy AlMg4.5Mn (AA5182) were discussed in detail. Further investigations using Nakajima test setup revealed an increased formability of the material. First the Nakajima samples were pre-strained along different linear strain paths to a predefined strain value. Afterwards the samples were heat treated without allowing the aluminum alloy to recrystallize. After cooling down the samples to room temperature, the tests are continued until the material's fracture. As a result heat treatment dependent forming limit curves (FLC) are obtained. In comparison with a measured FLC at room temperature the support of the intermediate heat treatment on enhanced formability were shown. Furthermore the method is not restricted to AA5182 aluminum alloys. © (2011) Trans Tech Publications.
LFT Import::2019-08-05 (1745)
Keywords: Aluminum alloys; Aluminum sheet forming; Forming limit diagram; Heat treatment

Introduction to sheet-bulk metal forming - Merklein, Marion; Hagenah, Hinnerk (Production Engineering, 2016)
Sheet-bulk metal forming as a new class of manufacturing processes is one of the possible answers production processes provide to the increasing demands on functional integration into light weight parts made of high strength steel. Research in this field is carried out in several places. The special issue was initiated by the Transregional Collaborative Research Centre 73. It contains newest results from this research initiative as well as international results in the field of sheet-bulk metal forming.
LFT Import::2019-07-29 (2155)
Keywords: Metal forming; Plate forging; Sheet metal; Sheet-bulk metal forming; TCRC 73

Inverse Approach to the Forming Simulation of Tailored Heat Treated Blanks - Staud, Detlev; Merklein, Marion (International Journal of Material Forming, 2008)
While climate protection and environmental conservation gain an increasingly significant role, the weight reduction of car body parts is a consequence of the need for efficient fuel consumption and for reduced CO2-emissions. Therefore advanced material and production methods have to be developed to meet this requirement. Since steel sheet metal parts cannot be substituted directly with lightweight aluminium parts, due to its minor formability, so called Tailored Heat Treated Blanks (THTB) are presented in this work. THTB are locally heat treated aluminium blanks from the 6000-series alloy, leading to a significantly improved formability for the manufacturing of complex aluminium car body parts. The enhancement of formability is reached by a local laser heat treatment before the forming operation. Since there is a strong influence of the heating on the forming process, a finite-element simulation of the process sequence is a prerequisite for the cost-effective usage of the THTB. The presented inverse approach considers first the desired forming result and enables the precise determination of heat treatment areas including the specific heat treatment temperatures. In conclusion the numerical solved appropriate strength pattern is verified with experimental test results of THTB. © Springer/ESAFORM 2008.
LFT Import::2019-07-29 (1558)
Keywords: Aluminium; Finite element simulation; Parameter identification

Inverse Identification of Kinematic Hardening Parameters with Bending Tests - Doig, M.; Kaupper, Markus; Kraska, M.; Eßer, G.; Merklein, Marion; Roll, K.; Keßler, L. (Proc. 50th Conference of IDDRG 2010, 2010)
LFT Import::2019-08-05 (212)

Inverse Parameteridentifikation mittels Biegeversuchen - Doig, M.; Kraska, M.; Eßer, G.; Kaupper, Markus; Merklein, Marion; Keßler, L.; Gerlach, J. (Tagungsband Werkstoffprüfung 2009, 2009)
LFT Import::2019-08-05 (210)

Inverse Parameteridentifikation mittels Wechselbiegeversuch zur Ermittlung der nicht isotropen Verfestigung von Blechwerkstoffen - Wieland, Michael; Biasutti, Manfredi; Kaupper, Markus; Merklein, Marion (LS-DYNA Forum 2012, 2012)
LFT Import::2019-08-05 (1828)

Investigation and modeling of austenite grain growth of conventional hot stamping steel and its influence on microhardness - Horn, Alexander; Merklein, Marion (Hot Sheet Metal Forming of High-Performance Steel, 2022)

Investigation of a novel ultrasonic-assisted staking process for mechanical fasteners - Jäckisch, Manuel; Merklein, Marion (2nd International Conference on Advanced Joining Processes AJP 2021, 2021)

Investigation of a process simulation method for flexible clamping of sheet metal parts - Bauer, Felix; Werber, Alexandra; Merklein, Marion (Procedia Engineering, 2017)
Flexibility in the body-in-white shop can be increased with the use of a running clamping technology, which enables clamping with a welding robot during laser welding. Unlike common clamping fixtures, the running clamping technology is operated force controlled. A closed gap between flanges is necessary to achieve a proper weld seam. The objective of the presented FE-simulation method is to predict required clamping forces to close the gap between sheet metal part flanges with geometrical inaccuracies. For calibration of the simulation model, clamping experiments with simple geometry are used. Steel and aluminum L-specimens are manufactured using air bending and clamped with the running clamping technology. Clamping forces are measured precisely using a load cell, which has been integrated into the running clamping technology. In this contribution a FE-simulation method for process analysis of the flexible clamping process with the running clamping technology is investigated. For clamping simulation, specimens are generated by air bending simulation, as well as by optical measurement of experimentally manufactured specimens. Since specimens are bent during clamping process in the opposite direction of the previous bending process, influences of residual stresses and kinematic hardening on the required clamping forces are expected. Thus, in FE-simulation an elastic-plastic material model with kinematic hardening parameters is used. A mapping method with springback compensation is applied to obtain specimens with optically measured geometry including forming history data of bending simulation. Simulation setups are investigated regarding results of clamping forces. Simulation results are verified using the obtained experimental data.
CRIS-Team Scopus Importer:2023-03-29
Keywords: clamping simulation; finite element method; forming history

Investigation of Different Joining by Forming Strategies when Connecting Different Metals without Auxiliary Elements - Römisch, David; Kraus, Martin; Merklein, Marion (Sheet Metal 2021, 2021)
Lightweight constructions become more and more important, especially in the mobility sector. In this industry, the increasingly strict regulations regarding the emissions of carbon dioxide can be achieved to a certain extent by reducing the vehicle weight. Thus, multi-material systems are used. Conventional joining techniques reach their limits when joining different materials due to different thermal expansion, unequal stiffness or chemical incompatibilities. This is why additional joining elements or adhesives are used. These must be viewed critically regarding a lightweight and resource-efficient production, since they add weight or complicate the recycling process of these components. Consequently, there is a great and growing need for new versatile joining technologies in order to overcome these challenges and to be able to react to changing process parameters and boundary conditions. Joining without an auxiliary element using pin structures formed directly from the sheet metal plane is one approach to meet these challenges. These pin structures are then joined by direct pressing into the joining partner. This is possible with a variety of material combinations, but is advantageous with regard to continuous fibre-reinforced thermoplastic composites (CFRTP), as the fibres do not have to be cut when joining CFRTP using pin structures. In this paper, the formability of pin structures made of a dual-phase steel DP600 (HCT590X + Z) is investigated. The extruded pin structures are joined by direct pin pressing with an EN AW-6014 to form tensile shear specimens. Different joining strategies are investigated to compare their influence on the joint strength. The results have shown that it is feasible to form suitable pins from a DP600 dual-phase steel to produce reliable connections with an aluminium sheet joined by direct pin pressin
Keywords: joining by forming; multi-metal-systems; pin forming; pin joining

Investigation of different surface treatment parameters in the context of roll bonding processes - Schödel, Sandra; Herrmann, Jürgen; Merklein, Marion (18th International Conference on Sheet Metal, SHEMET 2019, 2019)
LFT Import::2019-08-05 (2367)

Investigation of diffusion behavior of carburized sheet metal in hot stamping - Horn, Alexander; Merklein, Marion (Manufacturing Review, 2019)
Today, manufacturing of structural car body parts faces several challenges, like forming accuracy, passenger safety and lightweight design. One possibility to fulfill these partially rivalling demands is the application of hot stamped components. The combination of hot forming and in-die quenching reduces not only springback, but also results in tensile strengths of more than 1500 MPa. Besides conventional hot stamping, the process can be adapted to manufacture parts with tailored properties. One of the biggest issues of these state-ofthe-art processes is the formation of extensive transition zones due to heat transfer. A promising approach to adjust the mechanical properties with a minimized transition zone is tailored carburization of sheet metal. Therefore, the parts are locally coated with graphite, heat treated and subsequently quenched. In this work, the time variant process of carbon diffusion is investigated. Sheets with two different thicknesses are carburized and quenched. The resulting mechanical properties are analyzed using uniaxial tensile tests and microhardness measurements. On this basis, a process window is identified. Furthermore, the applicability of EDX and WDX analysis for the measurement of carbon concentration is investigated within this work.
CRIS-Team WoS Importer:2019-07-12

Investigation of diffusion behavior of carburized sheet metal in hot stamping - Horn, Alexander; Merklein, Marion (MATEC Web Conf, 2018)
Today’s manufacturing of structural car body parts faces several challenges, like forming accuracy and passenger safety. Besides these two requirements, lightweight design plays an important role. One possibility to fulfill these partially rivalling demands is the application of hot stamped parts. The combination of hot forming and in die quenching reduces not only springback, but also results in tensile strengths of up to 1500 MPa. This makes a simultaneous reduction of sheet thickness and therefore weight reduction possible. Further development enabled a tailored adjustment of mechanical properties, for example by applying different cooling conditions along the parts. One of the biggest issues of these state of the art processes is the formation of a transition zone due to heat transfer. A promising approach to adjust the mechanical properties with a minimized transition zone is the carburization of sheet metal. Therefore, the parts are coated with graphite, heat treated and subsequently quenched. In this work, the time variant process of carbon diffusion is investigated. Sheets with two different thicknesses are carburized and quenched. The resulting mechanical properties are analyzed using uniaxial tensile tests and microhardness measurements. The results are correlated with the carbon content measured by EDX-analysis. <
Keywords: Hot stamping; Heat treatment; Carburization

Investigation of dry lubrication systems for lightweight materials in hot forming processes. - Rigas, Nikolaos; Junker, Freidhelm; Berendt, Erik; Merklein, Marion (Produktion im Grenzbereich – Vorsprung halten, Zukunft sichern, 2019)
In the automotive industry, growing demands for lightweight solutions lead to new materials and forming methods. Because of the high specific strength and low density, high-strength aluminum alloys like 7xxx series have a big potential for safety-relevant components, in the future. With the help of thermal supported forming operations like hot forming and quenching, complex part geometries are realizable. The high formability compared with the lower forming forces and reduced springback, as well as a subsequent hardening step enables the production of complex parts. Currently, this forming process is reaching its limits because of high adhesive wear during forming. Therefore industrial use is not suitable at the moment. New developed dry lubrication systems enable hot forming operations without the generation of toxic emissions and a reduction of the adhesive wear. Therefore, different dry lubricants with varying particle size have been analyzed for deep drawing operations under quenching conditions. The influence of the particle size on the applicable lubrication thickness and the necessary consumption has not been analyzed before. Aim of this research is the characterization of different dry lubricant particle size distributions for hot forming and quenching of high-strength aluminum allo
Keywords: Hot forming and quenching; High formability; Lubricant particle size

Investigation of failure under shear-tension conditions with optical metrology - Merklein, Marion; Kuppert, Andreas; Biasutti, Manfredi (Proc. of GOM Conference, 2009)
LFT Import::2019-08-05 (198)

Investigation of Fatigue Strength of Tool Steels in Sheet-Bulk Metal Forming - Pilz, Florian; Gröbel, Daniel; Merklein, Marion (AIP Conference Proceedings 1960:1, 2018)
LFT Import::2019-08-05 (2316)
Keywords: Fatigue; Sheet-Bulk metal forming; Steel; Tailored Surface; Tool

Investigation of Friction Conditions at Elevated Temperatures for Hot Stamping - Schwingenschlögl, Patrik; Hildering, Sven; Merklein, Marion (Proceedings 7th International Conference on Tribology in Manufacturing Processes, 2016)
LFT Import::2019-08-05 (2162)

Investigation of Geometrical and Microstructural Influences on the Mechanical Properties of an Extruded AA7020 Tube - Reblitz, Jonas; Wiesenmayer, Sebastian; Trân, Ricardo; Merklein, Marion (Lecture Notes in Production Engineering, 2023)
In the automotive sector, an important strategy for reducing CO2- emissions is lightweight construction. In this regard, body-in-white parts offer a high potential for weight reductions by substituting conventional steel parts with tubular, aluminum-based components. Due to their high strength-to-weightratio and high crashworthiness, tube profiles are often used as safety-relevant car body components. Therefore, an exact determination of the material properties is necessary, in order to achieve a high prediction accuracy of FE-simulations. In contrast to the testing of flat semi-finished parts, there are only few standardized methods for the material characterization of tubular components. Furthermore, a profound knowledge regarding the influences of geometry and manufacturing process of the tube profiles on the material properties has to be gained. Thus, AA7020 tubes are analyzed in this research work. Tensile specimens are cut out of a tube by a laser-cutting machine. As a result, the cross-section of the samples is curved as well. To ensure a proper material testing, the clamping jaws for the tensile test are adjusted to the curvature of the samples. For the characterization of the tube properties, caused by the manufacturing process, optical measurements are performed. The mechanical properties of the different grain structures are determined by the thermo-mechanical simulator Gleeble 3500 in T6 condition. Therefore, tensile specimens with a reduced wall thickness are prepared. Afterwards the curved tensile samples are tested in T6 and W-temper condition. To validate the comparability of the determined material properties, a comparison is conducted with flat specimens prepared from the semi-finished tube profiles.<br
Keywords: Material characterization; W-temper condition; Tubes

Investigation of Geometrical and Microstructural Influences on the Mechanical Properties of an Extruded AA7020 Tube - Reblitz, Jonas; Wiesenmayer, Sebastian; Trân, Ricardo; Merklein, Marion (Production at the Leading Edge of Technology, 2023)
In the automotive sector, an important strategy for reducing CO2-emissions is lightweight construction. In this regard, body-in-white parts offer a high potential for weight reductions by substituting conventional steel parts with tubular, aluminum-based components. Due to their high strength-to-weight-ratio and high crashworthiness, tube profiles are often used as safety-relevant car body components. Therefore, an exact determination of the material properties is necessary, in order to achieve a high prediction accuracy of FE-simulations. In contrast to the testing of flat semi-finished parts, there are only few standardized methods for the material characterization of tubular components. Furthermore, a profound knowledge regarding the influences of geometry and manufacturing process of the tube profiles on the material properties has to be gained. Thus, AA7020 tubes are analyzed in this research work. Tensile specimens are cut out of a tube by a laser-cutting machine. As a result, the cross-section of the samples is curved as well. To ensure a proper material testing, the clamping jaws for the tensile test are adjusted to the curvature of the samples. For the characterization of the tube properties, caused by the manufacturing process, optical measurements are performed. The mechanical properties of the different grain structures are determined by the thermo-mechanical simulator Gleeble 3500 in T6 condition. Therefore, tensile specimens with a reduced wall thickness are prepared. Afterwards the curved tensile samples are tested in T6 and W-temper condition. To validate the comparability of the determined material properties, a comparison is conducted with flat specimens prepared from the semi-finished tube profiles.<br
Keywords: Material characterization; W-temper condition; Tubes

Investigation of heat treatment strategies for additively-manufactured tools of X37CrMoV5-1 - Junker, Daniel; Hentschel, Oliver; Schmidt, Michael; Merklein, Marion (Metals, 2018)
For cost-intensive products like automobiles, clients often with to personalize their product; this forces the industry to create a large diversity of combinable parts. Additionally, the life cycles of many components become shorter. For highly-stressable parts, which are commonly manufactured by forging, the short changeover cycles result in expensive products, as the costs of tools must be offset by the sale of only a few parts. To reduce the tool cost, new, flexible processes have to be established in tool manufacturing. Laser-based additive manufacturing is noted for its high flexibility; notably, Laser Metal Deposition (LMD) is gaining increasing relevance in research, as it is already used for coating and repairing forming tools; this technology makes it possible to add material onto free-formed surfaces. Therefore, investigations are being conducted to qualify this process to produce forging tools. Due to the thermal processes which are required during additive manufacturing, the microstructure of the material differs from that of wrought material. This, in turn, affects the strategy of post heat treatment in order that the required mechanical properties for tools be attained. Within this manuscript, the influence of additive manufacturing on performance characteristics of hot work tool steel X37CrMoV5-1 (1.2343) is analyzed. To investigate the behavior of additive manufactured material during the process chain of tool manufacturing, properties for different states of a heat treatment are characterized by hardness and strength. It was shown that the strength of the additive manufactured material could be increased compared to wrought material by using a tailored heat treatment. The effects that cause this behavior are investigated by comparing the microstructure at different states of heat treatment.
CRIS-Team Scopus Importer:2022-06-05
Keywords: Directed energy deposition; Heat treatment; Microstructure

Investigation of Influencing Parameters for Tribological Conditions in Dry Forming Processes - Tenner, Jennifer; Merklein, Marion (Acta Metallurgica Sinica (English Letters), 2015)
LFT Import::2019-07-29 (2140)

Investigation of influencing parameters on the joint formation of the self-piercing riveting process - Kappe, Fabian; Wituschek, Simon; Lechner, Michael; Bobbert, Mathias; Meschut, Gerson; Merklein, Marion (Material Science and Engineering Congress - MSE 2020, 2020)

Investigation of influencing parameters on the shape of experimentally determined stress limit curves - Hezler, Christian; Kaupper, Markus; Merklein, Marion; Kasparbauer, M. (Proceedings IDDRG2012, 2012)
LFT Import::2019-08-05 (1815)

Investigation of Measures for Material Flow Control for a Backward Extrusion of Geared Components from Coil - Leicht, Miriam; Henneberg, Johannes; Merklein, Marion (Lecture Notes in Mechanical Engineering, 2024)
Increasing ecological and economic demands are setting new requirements for industrial manufacturing processes and components. The use of functional integration as a strategy of lightweight design offers the possibility to meet these requirements. However, a high functional integration implies an increasing component complexity, which challenges conventional forming processes to their limits regarding formability and efficiency. The novel process class of sheet-bulk metal forming (SBMF) offers the opportunity to combine the advantages of sheet metal and bulk forming by applying bulk forming operations to sheet metal semi-finished products. SBMF from coil offers further economic and ecological benefits through high output rates, short process times by eliminating costly handling tasks and a greater material efficiency. However, forming from coil also poses coil-specific challenges such as anisotropic material flow and reduced geometric part accuracy. Against this background, in this study, a backward extrusion process from coil for forming geared functional components is investigated on a high-speed press. The objective of this study is to analyze measures for a targeted material flow control in order to avoid unequal material flow and to improve part accuracy. Therefore, the mild deep drawing steel DC04 with an initial sheet thickness of 2.0 mm is analyzed in a combined numerical-experimental approach. Within these investigations, the influences of coil width, friction and feed width are analyzed and evaluated based on component and process parameters. Finally, measures for a purposive material flow are derived.
CRIS-Team Scopus Importer:2023-10-20
Keywords: Cold forming; Extrusion; Sheet-bulk metal forming

Investigation of process induced changes of material behaviour using a drawbead in forming operations - Schmid, Harald; Suttner, Sebastian; Merklein, Marion (7. WGP-Jahreskongress Aachen, 5.-6. Oktober 2017, 2017)
LFT Import::2019-08-05 (2249)

Investigation of Production Limits in Manufacturing Microstructured Surfaces Using Micro Coining - Zahner, Michael; Lentz, Lukas; Steinlein, Felix; Merklein, Marion (Micromachines, 2017)
The application of microstructured surfaces is one possible method to reduce friction in lubricated contacts between components with relative movement. Due to this, the energy efficiency and the occurring wear during the operating time of the final products could be decreased. To manufacture structured surfaces economically, a micro coining process was analyzed within this study. This process offers the potential for integration into the established manufacturing processes of different final products, such as tappets used in a valve train. Thus, large-scale production is enabled. To detect the manufacturing limits of the micro coining process, the manufacturing of the coining tools as well as the coining process needs to be investigated. Within this study, the achievable accuracy and the failure of cuboid and cylindrical microstructure elements with selected dimensions were analyzed. For both types of microstructures, the minimal lateral dimensions were detected. Besides the achievable accuracy, correlations between different geometrical dimensions of the micro elements are presented. Additionally, the aspect ratio is detected as the main cause of failure for the micro coining process. In general, the suitability of a coining process for manufacturing microstructured surfaces is proven.
LFT Import::2019-07-29 (2277)
Keywords: Geometrical accuracy; Microstructures; Tribology

Investigation of Size Effects in Multi-Stage Cold Forming of Metallic Micro Parts from Sheet Metal - Kraus, Martin; Merklein, Marion (Micromachines, 2021)
Product miniaturisation and functional integration are currently global trends to save weight, space, materials and costs. This leads to an increasing demand for metallic micro components. Thus, the development of appropriate production technologies is in the focus of current research activities. Due to its efficiency, accuracy and short cycle times, microforming at room temperature offers the potential to meet the steadily increasing demand. During microforming, size effects occur which negatively affect the part quality, process stability, tool life and handling. Within this contribution, a multi-stage bulk microforming process from sheet metal is investigated for the materials Cu-OFE and AA6014 with regard to the basic feasibility and the occurrence of size effects. The results reveal that the process chain is basically suitable to produce metallic micro parts with a high repeatability. Size effects are identified during the process. Since several studies postulate that size effects can be minimised by scaling down the metallic grain structure, the grain size of the aluminium material AA6014-W is scaled down to less than one micrometre by using an accumulative roll bonding process (ARB). Subsequently, the effects of the ultrafine grain (UFG) structure on the forming process are analysed. It could be shown that a strengthened material state increases the material utilization. Furthermore, too soft materials can cause damage on the part during ejection. The occurring size effects cannot be eliminated by reducing the grain size.
CRIS-Team WoS Importer:2022-01-07

Investigation of surface finishing of carbon based coated tools for dry deep drawing of aluminium alloys - Steiner, Jennifer; Andreas, Kolja; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2016)
Global trends like growing environmental awareness and demand for resource efficiency motivate an abandonment of lubricants in metal forming. However, dry forming evokes increased friction and wear. Especially, dry deep drawing of aluminum alloys leads to intensive interaction between tool and workpiece due to its high adhesion tendency. One approach to improve the tribological behavior is the application of carbon based coatings. These coatings are characterized by high wear resistance. In order to investigate the potential of carbon based coatings for dry deep drawing, friction and wear behavior of different coating compositions are evaluated in strip drawing tests. This setup is used to model the tribological conditions in the flange area of deep drawing operations. The tribological behavior of tetrahedral amorphous (ta-C) and hydrogenated amorphous carbon coatings with and without tungsten modification (a-C:H:W, a-C:H) is investigated. The influence of tool topography is analyzed by applying different surface finishing. The results show reduced friction with decreased roughness for coated tools. Besides tool topography the coating type determines the tribological conditions. Smooth tools with ta-C and a-C:H coatings reveal low friction and prevent adhesive wear. In contrast, smooth a-C:H:W coated tools only lead to slight improvement compared to rough, uncoated specimen.
LFT Import::2019-07-29 (2211)

Investigation of Tailored Blank Production by the Process Class Sheet-Bulk Metal Forming - Merklein, Marion; Opel, Simon (International Conference on Advances in Materials and Processing Technologies (AMPT2010), 2010)
Nowadays efforts are made to improve sheet metal manufacturing processes and forming capability. Functional sheet metal components, for example toothed synchronizer rings, show closely-tolerated complex geometric features, especially in the automotive industry. Unfortunately sheet metal forming operations do not offer the possibility for complex shapes as do for example cutting technologies [1]. To avoid this restriction, the usage of semi-finished products with a material pre-distribution in the blank is investigated. So-called tailored blanks are usually made of different materials or sheet thicknesses. A common way of joining diverse blanks is welding [2]. In most cases the joining has a significant influence on the consecutively forming process due to varying local mechanical properties [3]. Hence the manufacturing of tailored blanks with a defined sheet thickness characteristic by the process class "sheet-bulk metal forming" is investigated. Subsequent the tailored blanks are provided for forming operations such as deep-drawing and the direct forming of complex functional shape elements. Aim of the project is the manufacturing of circular blanks with a sheet thickening in the exterior area by an upsetting operation. At the beginning, FE-based studies and physical experiments using blanks of DC04 are carried out, to create a fundamental knowledge base of the forming process. A comparatively large contact area between blank and forming tool, a three-dimensional material flow and the low sheet thickness cause high process forces. Building up a multi-stage upsetting process with different sequenced tool geometries is one approach to meet this challenge. The material flow out of the sheet center is realized step-by-step to lower the actual contact area and sequential the appearing forces. © 2010 American Institute of Physics.
LFT Import::2019-08-05 (887)
Keywords: FE-Simulation; Sheet-Bulk Metal Forming; Tailored Blanks

Investigation of tailored tool surfaces for improving the component quality of sheet-bulk metal forming parts produced by a combined deep-drawing and upsetting process - Henneberg, Johannes; Schulte, Robert Karl; Merklein, Marion (SCT Conference Proceedings, 2022)
Nowadays the automotive industry is confronted with increasing demands for lightweight components with integrated functional elements, as they are for instance used as synchronizers in gearboxes. Established manufacturing processes like sheet metal forming are limited producing such parts. Therefore, the innovative manufacturing technology sheet-bulk metal forming is investigated. By the application of bulk forming operations to sheet metals, functionally integrated parts can be produced in an efficient way. In this research, a combined deep-drawing and upsetting process is analyzed to form components with involute external gears. The reduced die filling of the gears is identified as a major challenge. Consequently, this research aims to increase the die filling of the gears through tool-sided adaptions. For analyzing the cause of the reduced die filling, a numerical process model is built up and validated. By analyzing this model, an undesired material flow from the functional elements to the center of the part is identified. In a next step, the potential of material flow control by global and local adaptation of the friction is numerically investigated. For this, the friction factor is varied between 0.1 and 0.5 in different areas. The numerical results indicate that by locally adjusting the friction, the material flow can be controlled and thus the shape of the gearing can be improved. Based on the numerical findings, tailored friction systems are implemented in an experimental setup. The tool surfaces are locally modified by an abrasive blasting process. Hereby, the friction is tailored according to the numerically determined requirements. Concluding, the applicability of tailored tool surfaces for material flow control and improvement of component quality is experimentally show
Keywords: Cold forming; Tribology; Surface modification; Material flow control; Numerical simulation; Lightweight design; Steel

Investigation of the Adhesive Wear Behavior of Alloyed and Not Alloyed Hot Stamping Tools in Contact with 22MnB5 - Neubauer, Franziska; Tenner, Jennifer; Andreas, Kolja; Merklein, Marion (Hot Sheet Metal Forming of high-Performance Steel - CHS2, Wissenschaftliche Skripten, 2017, 2017)
LFT Import::2019-08-05 (2250)

Investigation of the Anisotropic Strain Rate Dependency of AA5182-O and DC04 for Different Stress States - Lenzen, Matthias; Affronti, Emanuela; Rosenschon, Martin; Merklein, Marion (Advanced Materials Research, 2016)
LFT Import::2019-07-29 (2184)

Investigation of the direct recyclability of chip waste by cold cup extrusion and identification of its potential in continuous processes - Zettl, Bastian; Kraus, Martin; Böhm, Wolfgang; Zippert, Patrick; Merklein, Marion (Forming Technology Forum 2022, 2022)
Environmental protection and the responsible use of natural resources are currently the main challenges facing our society. When machining metallic materials, the formation of chips is unavoidable caused by technological reasons. This leads to a large proportion of chip waste. This waste needs to be subsequently recycled in energy-intensive cleaning and melting processes. To face these, this work is dealing with a novel direct recyclability method of chips from technically pure aluminum EN AW-1050A and pure copper CW004A by cold cup extrusion. The cups are characterized in regard to their bonding quality by light microscopy and X-ray analysis in order to prove the feasibility of the method. The objective is to demonstrate the suitability of cold cup drawing for creating cohesive bonds even under varying chip properties. Additionally, the usage of chip waste for recycling without melting in a continuous forming process is analyzed. For this, the so called Temconex® method is introduced, which enables the production of semi-finished profiles by a combination of friction and severe plastic deformation in an extrusion process.<br
Keywords: recycling; chips; cyclic economy; extrusion; sustainability; aluminum; copper

Investigation of the impact of heat treatment on the layer formation of AlSi-coated boron-manganese steel - He, Franz; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
Hot stamping is a well-established technology for producing safety relevant car components. The usage of hot stamping allows for reduced sheet thicknesses and weight of formed parts due to an increase in strength because of martensitic phase transformations. To prevent surface carburization and the formation of oxide layers AlSi coatings are applied to the workpiece surface. Due to a lack of suitable lubricants at process temperatures of over 800 °C, severe friction and wear affect the final part quality. Furthermore, process temperatures influence the layer formation and surface roughness due to diffusion processes. Consequently, a deeper process understanding is needed to acquire detailed knowledge of the impact on the tribological behavior to increase part quality and reduce tool wear. To this end the influence of heat treatment parameters on the coating layer and the subsequent layer formation is analyzed by comparing the resulting material composition and surface roughness. This is achieved by analyzing the impact of the furnace temperature and holding time on an AS150 coating and determining the effect of the parameters via metallographic investigation and tactile measuremen
CRIS-Team WoS Importer:2021-11-05

Investigation of the impact of process parameters on the layer formation of AlSi coated boron-manganese steel - He, Franz; Merklein, Marion (International Deep-Drawing Research Group Conference (IDDRG 2022), 2022)
Hot stamping has established itself as a technology for manufacturing safety-relevant car body components. Its usage has found increased importance due to rising political and social pressure e.g. for improved fuel conservation. Due to reduced sheet thickness, hot stamping parts offer lightweight solutions while at the same time providing improved crash performance due to their high strength. Boron-manganese steel is commonly used in hot stamping processes. Due to hot scale formation during heat treatment and the subsequent forming process, additional coatings, typically AlSi-coatings, are applied. Since hot stamped parts are formed at temperatures of 600 °C to 800 °C no suitable lubricants have yet been found. This leads to increased friction and severe wear in the process, which negatively affect tool lifetime and overall part quality. Additionally, process temperatures influence the layer formation and surface roughness due to diffusion processes. A deeper process understanding is needed to acquire detailed knowledge of the resulting impact on tribological behavior. Within this study, the effect of coating thickness on the resulting layer is analyzed by comparing the resulting material composition and surface roughness. To this end, the layer formation and surface roughness are analyzed for two different layer thicknesses (AS150 and AS80) in relation to furnace temperature, holding time and heat up rate. Both are characterized by means of heating experiments conducted on an annealing furnace. The change in layer composition and surface roughness are determined via metallographic investigation and tactile measurement. The results of this study help to improve the process understanding of the tribological conditions within the hot stamping process and to develop future measures for reducing tool we
Keywords: Hot Stamping; 22MnB5; Coating

Investigation of the impact of the layer formation of AlSi coated boron-manganese steel in regard to friction and wear - He, Franz; Merklein, Marion (International Conference on Hot Sheet Metal Forming of High Performance Steel, 2022)
With the increase in electric vehicles, factors for limiting reach due to finite battery capacity have found increased significance. Lightweight solutions are needed, amongst which the construction with ultra-high strength steels have been established as the industrial standard. These materials are able to bridge the gap between providing reduced part weight while improving mechanical properties. While cold forming faces various challenges such as high forming resistance and spring-back behavior, hot stamping of boron manganese steels allow for reduced forming forces and increased dimensional accuracy. The sheet is austenized at temperatures above 850 °C which leads to a phase change in the material and decrease in tensile strength. Since uncoated material suffers from decarburization and scale formation, which negatively inform the forming process and final part quality, aluminum silicon coatings (Al-Si) are applied. Additionally, lubricants lose their properties at higher process temperatures, leading to increased friction and severe wear in the process. Previous investigations have shown that furnace holding times influence the layer formation of AlSi-based coatings due to diffusion processes. Within this study, the influence of furnace holding times and subsequent layer formation on the friction and wear behavior as well as interdependencies with other relevant process parameters is investigated. To this end single sided strip drawing tests are performed with an industrial standard coating AS150 and analyzed in regard to the friction coefficient. Additionally, the tool sided wear is investigated through contactless 3D measurement. The results of this study help to improve the process understanding of the tribological conditions within the hot stamping process and to develop tailored measures for reducing tool wear.
Keywords: Friction; wear; hot stamping; 22MnB5

Investigation of the Influence by Size Effects on the Material Characterization of the Uniaxial Compression Stress State - Hetz, Peter; Kraus, Martin; Merklein, Marion (Key Engineering Materials, 2022)
For the evaluation of final component properties under consideration of production-induced material characteristics, it is necessary to determine the mechanical parameters of parts and structures. Thus, there is a need of new test methods for the material characterization and quality control of produced goods. The miniaturization of the test specimens offers the potential for the local testing of the material properties at almost any position on the component. However, due to the reduction in size of the test specimens, size effects can occur which may affect the material behavior. For this reason, this contribution analyses the influence of size effects on the derived material parameters in dependence of the specimen size and material by using upsetting tests according to DIN 50106:2016 standard. The materials Cu-OFE (copper), X5CrNi18-10 (stainless steel) and AA7075-T6 (aluminum) are investigated to ensure a broad transferability of the findings. The specimens are cut from a bar stock by using a high precision 3D micro electrical discharge milling machining. Due to the small size, every specimen is measured with an optical 3D coordinate measuring system to determine the exact size. Through these investigations, the reproducibility and scatter in the determination of material properties for scaled cylindrical upsetting specimens are evaluated. Furthermore, limits of geometric dimensions at constant aspect ratios are derived. The results of this investigation enable an estimation of the geometrical influence of the specimen size in regard to the mechanical properties.
CRIS-Team Scopus Importer:2022-11-04
Keywords: Compression test; Material characterization; Miniaturization; Size effects

Investigation of the influence of formed, non-rotationally symmetrical pin geometries and their effect on the joint quality of steel and aluminium sheets by direct pin pressing - Römisch, David; Kraus, Martin; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2022)
Resource-saving and sustainable production is becoming increasingly important regarding social, political and economic aspects, thus making the use of lightweight-construction technologies a current trend. For this reason, multi-material-systems made of high-strength steel and aluminium as well as metal and fibre-reinforced plastics gain in importance. However, different material properties, e.g. stiffness, thermal expansion coefficients or chemical incompatibilities, are challenging for conventional joining technologies. Joining by cold formed pin structures has shown to have high potential for joining multi-material-systems. These pins can be joined either by direct pin pressing into an unperforated joining partner or by caulking, where the pins are inserted through a pre-punched joining partner and the pin head is upset, resulting in a form-fit joint. Usually, cylindrical pins are used for joining. However, non-rotationally symmetrical pin geometries offer the possibility of introducing a predetermined breaking point or reinforcing a connection in the principal force direction. In this work, cylindrical pins as well as non-rotationally symmetrical pin geometries, such as polygonal and oval pin structures, are cold extruded from the sheet metal plane of an HCT590X+Z dual phase steel and joined in the next step with an EN AW-6014 aluminium using direct pin pressing. Since the formation of an undercut has an crucial influence on the joint strength, the investigations will be focused on the resulting joint geometry. In addition, the effect of different pin heights will be examined to analyse the joint formation at different levels of compression of the pin structures. Finally, the joints are evaluated regarding their joint strength in tensile shear tests and cross tension tests. Here the flow resistance of the geometry used as well as the pin height and thus the strain hardening of the pin base during the extrusion of the pins play a decisive role for the shear strengt
Keywords: pin-joining; alternative pin geometries; joining by forming; versatile joining process

Investigation of the Influence of Formed, Non-rotationally Symmetrical Pin Geometries and their Effect on the Joint Quality of Steel and Aluminum Sheets by Direct Pin Pressing - Römisch, David; Kraus, Martin; Merklein, Marion (AJP2021, 2021)
Resource-saving and sustainable production is becoming increasingly important regarding social, political and economic aspects, thus making the use of lightweight construction technologies a current trend. For this reason, multi-material systems made of high-strength steel and aluminium as well as metal and fibre-reinforced plastics gain in importance. However, different material properties, e.g. stiffness, thermal expansion coefficients or chemical incompatibilities, are challenging for conventional joining technologies. Joining by using cold formed pin structures has shown to be a process with high potential for joining multi-material systems. These pin structures can be joined either by direct pin pressing into an unperforated joining partner or by caulking, where the pin structures are inserted through a pre-punched joining partner and the pin head is upset, resulting in a form fit joint. Usually, cylindrical pin structures are used for joining. However, non-rotationally symmetrical pin geometries offer the possibility of introducing a predetermined breaking point or reinforcing a connection in the principal force direction. In this work, cylindrical pin structures as well as non-rotationally symmetrical pin geometries, such as polygonal and oval pin structures, are cold extruded from the sheet metal plane of an HCT590X + Z dual phase steel and joined in the next step with an EN AW-6014 aluminium using direct pin pressing. Since the formation of an undercut is a crucial influence on the joint strength [1], the investigations will be focused on the resulting joint geometry. In addition, the effect of different pin heights will be examined in order to analyze the joint formation at different levels of compression of the pin structures. Finally, the joints are evaluated regarding their joint strength in tensile shear tests and cross tension test
Keywords: pin joining; mechanical joining; joining by forming

Investigation of the influence of material and sheet thickness on a three-stage process chain for cold forming of micro gears with a module of 0.1 mm - Leicht, Miriam; Rohrmoser, Andreas; Kraus, Martin; Merklein, Marion (The 19th International Conference on Metal Forming (MF 2022), 2022)
In many industries, there is a trend towards miniaturization of technical components, such as drive systems, which enable the solution of high-precision positioning tasks because of their low volume and high dynamics. Geared micro parts are currently mainly produced by cutting and LIGA processes, but in mass production cold forming offers ecological and economic benefits. However, the cold forming of micro gears is restricted to a lower module limit of m = 0.2 mm due to high tool stresses, size effects and handling difficulties. To solve these challenges, in this contribution a three-stage forming process chain for the manufacturing micro gears (m = 0.1 mm) is investigated. In the first stage, a pin as wheel blank is extruded from sheet metal, which is geared subsequently by lateral extrusion. Finally, the micro gear is separated from sheet by shear cutting. The aim of this study is to demonstrate the applicability of the process chain for the materials Cu-OFE and CuZn30. In addition, the influence of the sheet thickness, which has a major impact on the forming process and the material efficiency, is analyzed. The geometrical and mechanical component properties as well as the machine data are evaluated to assess the variable

Investigation of the influence of process parameters on adhesive wear under hot stamping conditions - Schwingenschlögl, Patrik; Weldi, Maraike; Merklein, Marion (Journal of Physics: Conference Series, 2017)
LFT Import::2019-08-05 (2236)

Investigation of the Influence of Slightly Increased Process Temperatures on the Extrusion of Functional Aluminum Components in Sheet-Bulk Metal Forming - Wild, Thomas; Merklein, Marion (Production at the Leading Edge of Technology, 2023)
By using high-strength aluminum, weight savings can be achieved. However, limited formability of these alloys at room temperature is a challenging aspect regarding the manufacturing of components with filigree functional elements within sheet-bulk metal forming. So as to derive detailed process knowledge and to improve the achievable process results, forward extrusion of geared components made of EN AW 6082 sheets at room temperature is investigated within this work. Furthermore, robust large-scale industrial cold forming is a demanding task, as tool temperatures increase over time due to forming and frictional heat, leading to varying material and process properties. In order to determine measures for the compensation of these fluctuations, additional experiments are carried out with slightly increased tool temperatures. By analyzing workpiece and process related parameters for both sets of experiments, potential approaches to control the outcome of forming operations under variable conditions are discussed.<br
Keywords: Sheet-Bulk Metal Forming; Extrusion; Aluminum

Investigation of the Influence of Tool Geometry on Effective Strain Distribution in Full Forward Extrusion - Merklein, Marion; Ndzomssi, Franck; Engel, Ulf (AIP Conference Proceedings, 2011)
Due to strain hardening of the material, the hardness of cold forged parts is considerably improved. It is well known that the hardness of cold forged parts is closely related to its deformation, and that this relation is not dependent on the deformation process. The effective strain defines the local deformation, and can be determined in simulation of the cold forming process. In order to reach the required or to set specific hardness distribution with cold forging without any heat treatment processes, it is necessary to find out which manufacturing parameters influence the effective strain, and determine the effects of these parameters. The research work covered in this paper investigates the influence of the die geometry (as manufacturing parameter) on the effective strain. For that, a full forward extrusion process was modeled using the FE-software Simufact. Forming and three parameters of the die geometry, namely the deformation ratio, the shoulder radius and the opening angle were varied. The maximum effective strain from each combination is determined, and the effects of each considered parameter as well as the effects of interactions between these factors are checked. © 2011 American Institute of Physics.
LFT Import::2019-07-29 (1692)
Keywords: deformation ratio; Design of Experiments; effective strain; Finite Elements Method; full forward extrusion

Investigation of the influence of tool-sided parameters on deformation and occurring tool loads in shear-clinching processes - Han, Daxin; Hörhold, Réjane; Wiesenmayer, Sebastian; Merklein, Marion; Meschut, Gerson (Procedia Manufacturing, 2018)
Shear-clinching is a method for joining of dissimilar materials without auxiliary element. The technology combines shear-cutting and clinching in one process. Challenges of the process are the deformation of the specimens and the high process forces, which lead to high tool loads. Thus, the influence of the punch-sided tool geometry on the deformation of multi-element specimens was tested experimentally within this study. The effect of the geometrical changes on the occurring tool loads was analysed with a numerical model in order to evaluate the benefit of the adapted design with regard of the lifetime of the toolset.
LFT Import::2019-07-29 (2321)
Keywords: Clinching; Deformation of specimen; Joining by forming; Lightweight; Multi-material design; Tool load

Investigation of the influence of workpiece-side parameters on the layer formation of zinc-coated boron-manganese steel - He, Franz; Merklein, Marion (Materials Research Proceedings, 2023)
The hot stamping process has been established as a technology for the production of ultrahigh-strength steel parts for safety-relevant components in lightweight construction for the automotive sector. Thanks to the reduced overall thickness combined with high tensile strength, it is possible to realize lightweight design concepts with improved crash behavior. Boron-manganese steels are usually used for this purpose. Due to initial process temperatures above 800 °C, hot stamping is considered a lubricant-free process. In addition to high friction and wear in the process, surface scaling and the need for tool repairs are the result. In light of these phenomena, hot stamping materials are coated to protect them from corrosion. Until now, aluminum-silicon-based coatings have been primarily used for the direct hot stamping route. While zinc-based coatings have so far mainly found usage in the indirect process route, they are now also become a valid alternative for the direct process route. In previous investigations, a significant influence of workpiece-side parameters on the formation of the coating during the austenitization process was found for aluminum-silicon (AlSi) coatings. In light of this, a similarly significant influence is suspected for zinc-based coatings. The parameters heating rate, furnace temperature and dwell time in the furnace and the effect on the coating formation of zinc-coated 20MnB8 during austenitization will be investigated. The resulting findings will form the basis for further experiments to investigate the influence of the parameters on friction and wear in the industry near strip drawing tests.
CRIS-Team Scopus Importer:2023-04-28
Keywords: 20MnB8; Coating; Hot Stamping

Investigation of the joinability of single- and multi-layered AA6014 sheets produced by accumulative roll bonding in the shear-clinching process - Zettl, Bastian; Wiesenmayer, Sebastian; Kraus, Martin; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2022)
Accumulative roll bonding belongs to the severe plastic deformation processes and is suitable for producing multi-layered as well as high-strength sheets through repeated rolling. After four accumulative roll bonding-cycles, the strength of the investigated AA6014-T4 alloy is elevated due to strain and fine grain hardening by 170% in yield strength and by 37% in ultimate tensile strength. This is accompanied by a significant decrease in material ductility which is disadvantageous for joining processes based on forming operations. Shear-clinching, however, can be used to join high-strength and low-ductile materials on the die side. Thus, it is a promising method for the mechanical joining of accumulative roll bonding components. The multi-layered and more brittle material is located on the die side whereas the single-layered base material with higher ductility is positioned on the punch side. At present, there is no scientific knowledge how the multi-layered material behaves in the shear-clinching process. Since the material is cut in the process, delamination effects could occur at the interfaces produced via accumulative roll bonding. Additionally, the investigation aims at the influence of the accumulative roll bonding process on the properties of the joints. They are expected to depend on the number of process cycles and thus on the change of mechanical properties of the multi-layered material. The bond strength of the shear-clinched joints is determined by shear and tensile tests. The areas of material failure are analysed via metallographic methods. From the failure behaviour and load-bearing capacity it is determined which number of accumulative roll bonding cycles is ideal for joining multi-layered sheets via shear-clinching.
CRIS-Team Scopus Importer:2022-02-04
Keywords: accumulative roll bonding; Joining; multi-layered materials; shear-clinching

Investigation of the joinability of the high-strength aluminum alloy AA7075 in shear-clinching processes - Wiesenmayer, Sebastian; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2021)
Shear-clinching has proven to be a suitable technology for joining of high-strength materials. However, the mechanical properties of the upper joining partner are limited due to the high strains, which occur during the process. Therefore, shear-clinching of the high-strength aluminum alloy AA7075 in the T6 temper is not possible. Yet, the mechanical properties of hardenable alloys of the 7000 series can be influenced by a heat treatment. Thus, within the scope of this work, the joinability of the high-strength alloy AA7075 in shear-clinching processes in dependance of its temper is investigated. The as fabricated state F, the artificially aged T6 temper, a paint baked state and the naturally aged T4 temper are compared to the fully solution annealed W temper as well as to a retrogression heat-treated state. For retrogression heat treatment, a laser is used as heat source, heating up the alloy for a short term in order to only partially dissolve precipitations. The resulting mechanical properties are determined with uniaxial tensile tests. Moreover, the influence of the mechanical properties of AA7075 on the shear-clinching process, the joint formation and the resulting joint strength is analyzed.
CRIS-Team WoS Importer:2022-01-14

Investigation of the mechanical behaviour of advanced high strength steels under various loading conditions - Geiger, Manfred; Merklein, Marion; Kaupper, Markus (International Journal of Material Forming, 2008)
Nowadays advanced high strength steel sheets and related forming technologies play a vital role in light weight construction in the transportation sector. Within this paper the mechanical behaviour of the multi phase steels DP600, DP800 and CP800 is investigated, being focussed on the influence of various loading conditions in particular. Uniaxial tensile tests, layer compression tests and bulge tests are carried out, to characterize plastic material properties like anisotropy and work hardening. The forming behaviour is evaluated utilizing optical strain measurement, to obtain detailed information on the deformation behaviour. True stress strain curves are obtained, clearly quantifying the properties described above. The results are discussed and evaluated with regard to numerical simulation of sheet metal forming processes. © Springer/ESAFORM 2008.
LFT Import::2019-07-29 (207)
Keywords: Loading condition; Material characterization; Work hardening; Yielding

Investigation of the Microstructural Evolution during Hot Stamping of a Carburized Complex Phase Steel by Laser-Ultrasonics - Horn, Alexander; Merklein, Marion (Materials, 2021)
Prior carburization of semi-finished steel sheets is a new process variant in hot stamping to manufacture parts with tailored properties. Compared to conventional hot stamping processes, a complex phase typed steel alloy is used instead of 22MnB5. Yet recent investigations focused on final mechanical properties rather than microstructural mechanisms cause an increase in strength. Thus, the influence of additional carburization on the microstructural evolution during hot stamping of a complex phase steel CP-W(R)800 is investigated within this work. The phase transformation behavior, as well as the grain growth during austenitization, is evaluated by in-situ measurements employing a laser-ultrasound sensor. The results are correlated with additional hardness measurements in as-quenched condition and supplementary micrographs. The experiments reveal that the carburization process significantly improves the hardenability of the CP-W(R)800. However, even at quenching rates of 70 K/s no fully martensitic microstructure was achievable. Still, the resulting hardness of the carburized samples might exceed the fully martensitic hardness of 22MnB5 derived from literature. Furthermore, the carburization process has no adverse effect on the fine grain stability of the complex phase steel. This makes it more robust in terms of grain size than the conventional hot stamping steel 22MnB5.
CRIS-Team WoS Importer:2021-05-07
Keywords: hot stamping; phase transformation; quenching; grain growth; carburization

Investigation of the Phase Transformation in Hot Stamping Processes with Regard to the Testing Facility - Horn, Alexander; Hart-Rawung, T.; Buhl, J.; Bambach, Markus; Merklein, Marion (Congress of the German Academic Association for Production Technology WGP 2021, 2020)
Hot stamping of boron manganese steel is a state of the art process for manufacturing safety-relevant automotive components with regard to lightweight design. In terms of the mechanical properties, the microstructural evolution is of particular interest. Besides conventional hot stamping processes, this is especially apparent for the manufacture of hot stamped parts with tailored properties. To reduce costs and scrap parts, numerical process design requires appropriate material models considering transformation kinetics during in-die quenching. The phase transformation behavior can be characterized through experiments on various testing facilities, which can lead to discrepancies in the results and therefore in the predicted mechanical properties. In this paper, the results from two testing facilities are compared to each other through dilatometry experiments on the boron-manganese steel 22MnB5. For further characterization of the differences, secondary samples are taken to analyze the hardness as well as the microstructure by optical microscopy.
Keywords: Hot stamping; Dilatometry test; Phase transformation

Investigation of the Potential for the Fabrication and Forming of Adaptronic Semi-finished Parts Joined by Cold Formed Pin Structures - Kraus, Martin; Suttner, Sebastian; Merklein, Marion (2ND INTERNATIONAL CONFERENCE ON ADVANCED JOINING PROCESSES (AJP 2021), 2021)

Investigation of the Quenching Behavior of Carburized Sheet Metal in Hot Stamping - Horn, Alexander; Merklein, Marion (Proceedings of the 7th International Conference on Hot Sheet Metal Forming of high-performance steel - CHS2, 2019)

Investigation of thermal effects during ultrasonic-assisted upsetting - Jäckisch, Manuel; Merklein, Marion (Procedia Manufacturing, 2020)
Minimizing tool wear is a crucial goal in metal forming to increase the tool durability and thus reduce costs. One approach is to superimpose the tool movement with a high frequency oscillation. The so-called ultrasonic assistance enables an immediate process force reduction and lowers the workpiece and tool loads significantly. This phenomenon has been discovered by Langenecker and Blaha in 1955 and since then been confirmed for several forming applications like wire drawing, deep drawing and forging. Nevertheless, the underlying softening mechanisms are still subject of current research. Explaining theories may be attributed to the principle of stress superposition, surface and volume effects. The latter includes the thermal softening due to ultrasonic vibration. Moreover, interactions as well as the proportional force reduction of these effects vary with the process parameters and the investigated material. Therefore, this paper aims for the separation and quantification of thermal softening with respect to the process parameters. Ultrasonic-assisted compression testing with the steel C35E is carried out with an oscillation frequency of 20 kHz. Process forces as well as specimen heating are measured with regard to the tested amplitudes and deformation rates. Based on these measurements, hot compression tests are conducted with identical temperature slopes. This way, thermal softening is determined and can be separated from acoustic softening effects. Besides, material hardening is determined for ultrasonic-assisted and temperature controlled compression. Using a shortened oscillation interval the influence of both, the superimposed oscillations as well as the specimen heating is proven.<br
Keywords: ultrasonic; steel; thermal effects; measurement; cold forming

Investigation of the Springback Behaviour of High-strength Aluminium Alloys Based on Cross Profile Deep Drawing Tests - Hetz, Peter; Suttner, Sebastian; Merklein, Marion (Procedia Manufacturing, 2020)
The prediction of springback of sheet metal parts is still a challenge in metal forming processes. To meet the requirements for dimensional accuracy of a sheet metal part, the springback must be compensated and the production process has to be designed accordingly. During forming, elastic energy is stored in the semi-finished product. When removing a part from the deep-drawing tool, the resulting residual stresses with an elastic component cause unwanted changes of the part`s geometry in forming. Especially sheet materials with low elastic modulus and high yield strength tend to an increased springback. Among others, these materials include aluminium alloys of the 7000 series. For this reason, a fundamental understanding of the material behaviour of these materials is relevant for designing a sheet metal forming process. This contribution uses a novel approach to investigate the springback behaviour of AA7020-T6 and AA7075-T6. For this purpose, cross profiles are deep-drawn with various parameter settings and subsequently digitised with a three-dimensional optical measurement system. By analysing the digitised profiles, the springback behaviour is quantified depending on the experimental parameters. Due to the right-angled structure of the cross profile, the influence of anisotropy in 0 and 90 degree to rolling direction is investigated within one forming operation.
CRIS-Team Scopus Importer:2020-06-05
Keywords: Cross profile; Deep drawing; High-strength aluminium alloys; Springback compensation

Investigation of the tensile response and the microstructural evolution during hot drawing of multi-layered, ultrafine-grained AA6014 sheets by thermomechanical analyzes - Zettl, Bastian; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2022)
Mechanical strengthening of sheet material can be realized by accumulative roll bonding, which belongs to the severe plastic deformation processes. Beside fine-grain hardening also work and precipitation hardening is responsible for the rise of material strength. However, this is also accompanied by a significant decrease in ductility. Thus, the need for an enhancement of ductility is essential for a sufficient formability in later applications and was already introduced by tailored heat treatments. The challenge, however, is to realize a process temperature that leads to a degradation of dislocations and dissolution of MgSi-precipitations, without a recrystallization of the fine-grained microstructure to coarse grain sizes. In order to identify a suitable temperature range to avoid recrystallization, hot forming experiments are carried out at successive temperatures from 20 to 300 °C. Tensile specimens are drawn with the thermomechanical simulator Gleeble 3500 (Dynamic Systems Inc.) aided by the strain measurement system Aramis (GOM GmbH). The aim is to investigate the dependence of the mechanical properties from the forming temperature in order to identify a temperature range, in which high strength with simultaneous enhanced ductility is maintaine

Investigation of the thermal and tribological performance of localized laser dispersed tool surfaces under hot stamping conditions - Schirdewahn, Stephan; Spranger, Felix; Hilgenberg, Kai; Merklein, Marion (Wear, 2021)
In the automotive industry, hot stamping has been established as a key technology for manufacturing safety-relevant car body components with high strength-to-weight ratio. However, hot stamping tools are stressed by cyclic thermo-mechanical loads, which leads to severe wear and high friction during the forming operation. Consequently, the quality of the parts, the durability of the tools and the efficiency of the process are negatively affected. Within the scope of this work, a promising approach named laser implantation process has been investigated for improving the tribological behavior of hot stamping tools. This technique enables the fabrication of highly wear resistant, separated and elevated micro-features by embedding hard ceramic particles into the tool via pulsed laser radiation. Hence, highly stressed tool areas can be modified, which influences the thermal and tribological interactions at the blank-die interface. To clarify these cause-effect relations, numerical simulations, quenching tests as well as tribological investigations have been conducted. In this context, laser-implanted tools reveal a significantly improved tribological performance while offering the possibility to adjust the thermal properties within hot stamping. Based on these results, a tailored tool modification can be pursued in future research work, in order to enhance the effectiveness of hot stamping tooling systems.
CRIS-Team Scopus Importer:2021-03-05
Keywords: Friction; Hot stamping; Laser implantation; Surface structuring; Wear

Investigation of the Thermomechanical Properties During Hot Stamping of a Complex Phase Steel Carburized at Elevated Temperatures - Risse, Jan Henning; Merklein, Marion (Hot Sheet Metal Forming of High-Performance Steel, 2024)
In order to reduce greenhouse gas emissions or to increase the range of electrically powered vehicles, several lightweighting strategies are applied in the manufacturing of the latest cars. The hot stamping of ultrahigh-strength steels, which is becoming an increasingly common strategy, can be used to produce lighter components with reduced sheet thickness. In particular, parts with tailored properties that are already in use for B pillars for example, increase the crashworthiness and the lightweight potential at the same time. In contrast to existing processes, tailored carburization does not require complex tooling or intricate furnace technologies, material thickening, or welding processes to locally adjust the mechanical properties. The to-be-reinforced areas are geometrically flexible, which makes this process especially suitable for small batch series of lightweight components. At standardly 950 °C, the carburization takes up to 6 h to achieve the highest combination of strength and ductility. Thus, strategies are needed to shorten the total process time. Diffusion hardening at elevated temperatures seems promising to achieve a similar level of mechanical properties but in a significantly reduced time. So, this contribution aims to investigate the dependence of the thermomechanical behavior on the carburization above 950 °C, forming temperature, and strain rate of a tailored carburized material. Therefore, thermal tensile tests were performed with the complex phase steel CP-W® 800 in two different carburized states as well as in the not-carburized state. In the physical simulator Gleeble 3500 GTC the specimens pass through a simulated hot stamping process and are tested at different forming temperatures with varying strain rates. In addition to the dependency analysis, the obtained flow curves can also be used to partially generate a thermo-mechanically coupled simulation. This model is intended to replicate the hot stamping of components with customized properties induced by tailored carburization.<br

Investigation of the thermo-mechanical properties of hot stamping steels - Merklein, Marion; Lechler, Jürgen (Tagungsband Metal Forming Conference 2006, Birmingham, England, 2006)
Within the innovative hot forming process for sheet metals, called hot stamping, it is possible to combine forming and quenching in one process step. This affords the opportunity to manufacture components with complex geometric shapes, high strength and a minimum of springback which currently find applications as crash relevant components in the automotive industry. As standard material for hot stamping the quenchenable high strength steel 22MnB5 is commonly used. With regard to the numerical modeling of the process, the knowledge of thermal and thermo-mechanical properties of the material is required. To determine the thermo-mechanical material characteristics, the flow behavior of the steel 22MnB5 in the austenitic state has been investigated by conductive, hot tensile tests with a Gleeble 1500 system dependent on the time-temperature characteristic of the hot stamping process. © 2006 Elsevier B.V. All rights reserved.
LFT Import::2019-08-05 (1269)
Keywords: 22mnB5; Flow behavior; High strength steels; Hot stamping; Thermo-mechanical properties

Investigation of the tool wear behaviour in shear-clinching processes during the running-in phase - Wiesenmayer, Sebastian; Han, Daxin; Meschut, Gerson; Merklein, Marion (AIP Conference Proceedings, 2019)
The multi-material design of modern cars is a challenge for common joining technologies. Joining by welding is often not possible, due to different melting temperatures of the joining partners. Indeed, the usage of fasteners allows the joining by forming of high-strength steels with aluminium, but increases the weight and the costs. Common joining by forming technologies without additional fasteners are limited by the mechanical properties of the joining partners. Thus, clinching of ultra-high strength steels with low ductility, like press-hardened manganese-boron steels, is not possible. However, the innovative shear-clinching technology enables the joining by forming of ultra-high strength steels and aluminium without fasteners. In one combined process, the die-sided steel sheet is cut and the punch-sided aluminium is pressed into the cut out hole, resulting in a form and force fitting joint. Nevertheless, the cutting of the high-strength steel and the subsequent upsetting of the aluminium both lead to high tool loads, especially for the die. Thus, it is necessary to analyse the wear behaviour of the shear-clinching tool. Within the scope of this work, the tool wear behaviour in shear-clinching and the influence of wear on the process will be investigated experimentally. The focus will be on the die and the running-in phase, since there are no references for the wear behaviour in shear-clinching yet.
CRIS-Team Scopus Importer:2019-07-23

Investigation of the tribological behavior of car body parts in series production - Hansen, B.; Purr, S.; Meinhardt, J.; Merklein, Marion (6th ICAFT – International Conference on Accuracy in Forming Technology 25th SFU – Saxon Conference on Forming Technology 6th AutoMetForm – International Lower Silesia – Saxony Conference on Advanced Metal Forming Processes in the Automotive Industry, 2019)
CRIS-Team WoS Importer:2020-09-25

Investigation of the tribological behaviour of alloyed hot stamping tools in contact with AlSi coated 22MnB5 - Neubauer, Franziska; Rupprecht, P.; Hofmann, K.; Andreas, Kolja; Merklein, Marion (2017)
LFT Import::2019-08-05 (2270)

Investigation of the tribological behaviour of microstructures for controlling the material flow in sheet-bulk metal forming - Löffler, Maria; Engel, Ulf; Willner, Kai; Beyer, Florian; Merklein, Marion (CIRP Journal of Manufacturing Science and Technology, 2018)
Sheet-bulk metal forming (SBMF) processes are characterized by a successive and/or simultaneous occurrence of different load conditions with regard to stress and strain states. These conditions significantly influence the material flow and thus the geometrical accuracy of the produced components. To improve the product quality a control of the material flow is required. A suitable approach is given by a local modification of the tribological conditions using surface modifications of tool or workpiece. To control the material flow, methods to adjust the friction are needed. Within the present study, microstructured workpiece surfaces to reduce the friction are investigated. The aim of the study is the determination of the tribological mechanisms of this kind of surface modifications. To identify the mechanisms a combined experimental and numerical approach was used. The use of such a combined approach revealed that the structure volume and the interaction between different types of structures significantly influence the friction reducing potential of microstructured workpiece surfaces.<br
Keywords: Sheet-bulk metal forming; Tribology; Surface modification; Surface analysis; Modelling

Investigation of the tribological performance of a-C:H coating systems by modifying adhesive layer for application in dry deep drawing - Rothammer, Benedict; Zhao, Rong; Krachenfels, Kim; Merklein, Marion; Tremmel, Stephan (International Tribology Conference Sendai 2019, 2019)
Lubricants are essential in conventional deep drawing processes to improve the tribological behavior and product quality. Requirements for increasing sustainability and resource efficiency motivate the realization of lubricant-free deep drawing processes. However, the direct contact between tool and workpiece during dry deep drawing leads to increased adhesive wear and surface damage on the sheet metal. A promising approach to face these challenges due to dry deep drawing is the application of amorphous carbon coating systems on tool surfaces. The roughness peaks on the coating surface caused by deposition have to be kept as low as possible, in order to reduce the risk of abrasive wear caused by interlocking into the ductile metal sheet and thus the initial adhesive wear can be avoided. In this study, the influence of adhesive layer on the topography of a‑C:H functional layer is investigated and its tribological performance verified. The modified deposited a‑C:H coating system exhibits similar adhesion to the substrate as the standard a‑C:H coating system. In addition, it shows a more homogeneous surface topography without formation of droplets. Due to the modified adhesion layer, the Rpk value in as-deposited state is 10 times lower by changing the deposition technique of the chromium adhesive layer. As a result, the extremely low roughness peaks of the coating penetrate only slightly into the rough sheet surface with EDT texturing. The standard and modified a‑C:H coated tool surfaces against two common used aluminum alloys (AA6014, AA5182) are applied for the tribological evaluation by the flat strip drawing test. The analysis of the resulting coefficients of friction shows that the tribological behavior is directly influenced by the roughness. The roughness of the functional layer and thus the tribological behavior can be changed by the application of different adhesive layers. Furthermore, the tool and workpiece surfaces are characterized before and after the test in order to investigate wear mechanisms on tool
Keywords: Tribology; Dry Sheet Metal Forming; Diamond-like Carbon (DLC) Coating; Roughness

Investigation of the Unloading Yield Effect in Aluminum and Magnesium Sheet Metal Alloys at Room Temperature - Degner, Julia; Suttner, Sebastian; Merklein, Marion (Key Engineering Materials, 2016)
LFT Import::2019-07-29 (2178)
Keywords: Advanced Lightweight Materials; Material Characterization; Unloading Yield

Investigation of the wear behavior for not alloyed and alloyed hot forming tools - Neubauer, Franziska; Hofmann, K.; Andreas, Kolja; Merklein, Marion (WGP Congress 2016, 2016)
LFT Import::2019-08-05 (2201)

Investigation of Tribological Behavior of Carbon Coatings in Dry Sheet Metal Forming - Steiner, Jennifer; Zhao, Rong; Tremmel, Stephan; Merklein, Marion (Proceedings 12th International Conference THE "A" Coatings 2016, 2016)
Keywords: Dry Sheet Metal Forming; Carbon Coating; Tribology; Friction

Investigation of Tribological Behaviour of a-C:H Coatings for Dry Deep Drawing of Aluminium Alloys - Zhao, Rong; Steiner, Jennifer; Andreas, Kolja; Merklein, Marion; Tremmel, Stephan (Abstracts Programme, 2016)
Keywords: Dry metal forming; DLC; aluminium; adhesive wear

Investigation of tribological behaviour of a-C:H coatings for dry deep drawing of aluminium alloys - Zhao, Rong; Steiner, Jennifer; Andreas, Kolja; Merklein, Marion; Tremmel, Stephan (Tribology International, 2017)
Lubricant‑free sheet metal forming increases resource efficiency and contributes to environmental protection. One approach to reducing friction and wear in dry forming is the tool-sided application of carbon-based coatings. In this work, amorphous hydrogenated carbon (a‑C:H) coatings were prepared by plasma‑enhanced chemical vapour deposition (PECVD). The coating samples were deposited under different amounts and ratios of acetylene (C2H2) and argon (Ar) gas atmospheres. The coating samples were characterized regarding their thickness, roughness and mechanical as well as chemical bond structures. The tribological behaviour against aluminium alloys was investigated under lubricant‑free conditions with a ring‑on‑disc tribometer. The relationships between chemical bond composition and coating properties were clarified. Finally, one a-C:H coating variant with promising tribological performance against aluminium alloys was exemplarily tested in a flat strip drawing test, which models the tribological conditions in the flange area of a deep drawing process.
Keywords: Dry sheet metal forming; DLC; aluminium; adhesive wear