3-Rollen-Schubbiegen zur flexiblen Herstellung freiformgebogener Rohrleitungen - Merklein, Marion; Geiger, Manfred; Hagenah, Hinnerk; Cojutti, Massimo (Zukunftstechnologien in Bayern, 2008)
LFT Import::2019-07-29 (257)

4.0 in metal forming - Questions and challenges - Hagenah, Hinnerk; Schulte, Robert Karl; Vogel, Manfred; Hermann, Jennifer; Scharrer, Hannes; Lechner, Michael; Merklein, Marion (Procedia CIRP, 2019)
The paper gives a view on perspectives for metal forming processes rising due to the industry 4.0 discussion and its consequences. The discussion starts with a view at aims pursued by introducing 4.0 into metal forming. From the results of this the needed data and required sensors are discussed as well as the potential of their introduction into current processes. At this point the processes in metal forming and their respective demands have to be taken into account as well. From here the step to the specific challenges, e.g. originating from the machine tools at hand, can be elaborated on.
CRIS-Team Scopus Importer:2019-05-17
Keywords: Digital manufacturing system; Lifecycle; Metal forming

Accumulative Roll Bonding: Forming Behavior, Tailored Properties and Upscaling Approach - Merklein, Marion; Böhm, Wolfgang (Advanced Materials Research, 2014)
The Accumulative Roll Bonding (ARB) process enables the manufacturing of high strength sheet metals with outstanding mechanical properties by repeated rolling. However, the significant increase in strength leads to loss in ductility, especially regarding aluminum alloys of the 6000 series. The low formability obviously limits the implementation of these sheet products for formed components in automotive applications. To enhance formability, a local short term heat treatment according to the Tailored Heat Treated Blanks technology is used. For the finite element based design of forming operations accurate information about the plastic behavior of these tailored materials is required. Therefore, different stress - strain paths are considered using the tensile test and the layer compression test. In this context, heat treated and non-heat treated specimens out of ARB processed AA6016 were tested at room temperature. With the experimental results true stress – strain curves and yield loci determined from different criteria and represented in a principal stress state were established. Regarding the experimental setup of the ARB process, an upscaling is essential for the production of sufficiently large strips to cut out blanks for the forming of components such as B-pillars. However, this requires the adaptation of the different process steps of the ARB process. In this context, the surface treatment before rolling of such large sheets is investigated, since it is particularly relevant for obtaining a strong bonding between the sheets. Another aspect is the investigation of the rolling process using the finite element analysis. In this regard, a thermalmechanical coupled simulation model of the roll bonding operation will be developed for the evaluation of different material combinations, different process temperatures and varying roller geometries. These investigations will enable the production of lightweight automotive components made of ARB processed high strength aluminum sheet metal with tailored properties.
EAM Import::2019-03-13

Accumulative Roll Bonding of precipitation-hardenable aluminum alloys of the 6000 series in a warm rolling process - Merklein, Marion; Herrmann, Jürgen (Proc. ROLLING Conference, 2016)
In several industrial fields there is a persistent trend to lightweight construction. An auspicious possibility to cope with this challenge is the application of high strength aluminum, produced by accumulative roll bonding (ARB). Key idea of the ARB approach, which was originally invented by Saito et al. (1998), is the subsequent stacking and rolling of sheet material in order to gain an ultrafine-grained microstructure. The grain refinement results from the high deformations and shear stresses during each cycle of ARB. At the moment aluminum alloys of the 6000 series are pre-heated and rolled at room temperature. Within this contribution sheets of an AA6014 alloy are manufactured in a warm rolling process for the first time. The aluminum sheets are characterized regarding their mechanical properties and in particular their flow behavior. Furthermore, the bond strength of the respectively last bonded layer is examined using T-peel tests. Both testing methods are carried out after two and four rolling cycles. Based on these investigations a process strategy for the production of multilayered sheets in a warm rolling process is derived.
EAM Import::2019-03-13

Accuracy of conventional FE-Models in Bulk-Forming of Micropins from Sheet Metal - Kraus, Martin; Hufnagel, Thomas; Merklein, Marion (Journal of Micro and Nano-Manufacturing, 2019)
LFT Import::2019-07-29 (2357)

Accuracy of Conventional Finite Element Models in Bulk-Forming of Micropins from Sheet Metal - Kraus, Martin; Hufnagel, Thomas; Merklein, Marion (Journal of Micro and Nano-Manufacturing, 2019)
The ongoing miniaturization trend in combination with increasing production and functional volume leads to a rising demand for metallic microparts. Bulk forming of microparts from sheet metal provides the potential for mass production of those components by an extensive simplification of the handling. The advantage of a high production rate contrasts with the disadvantage of a low utilization of material. In this context, it is necessary to investigate suitable measures to increase the material utilization. To save cost intensive trial and error tests, numerical analysis could be an appropriate method for a basic process investigation. In this work, a validation with experimental results in the macro- and microscale was used to investigate the eligibility of the finite element method (FEM) for a basic process analysis. For a high transferability, the finite element (FE) models were validated for various tribological conditions and material states. The results reveal that there is a high agreement of the experimental and numerical results in the macroscale. In microscale, conventional FEM shows inaccuracies due to the negligence of size effects in the discretization of the process. This fact limits the application of conventional FE-programs. Furthermore, the results show that lubricated and dry formed blanks lead to the same friction force and process result in the microscale. In addition, the basic formability of the prestrengthened pins in further forming stages was experimentally demonstrated.
CRIS-Team Scopus Importer:2019-05-02
Keywords: bulk microforming; friction; Microforming; micropart; size effects; validation

A concept for process-oriented interdisciplinary tolerance management considering production-specific deviations - Heling, Björn; Oberleiter, Thomas; Rohrmoser, Andreas; Kiener, Christoph; Schleich, Benjamin; Hagenah, Hinnerk; Merklein, Marion; Willner, Kai; Wartzack, Sandro (Proceedings of the 22nd International Conference on Engineering Design (ICED19), 2019)

A Contribution to the Optimisation of a Simple Shear Test - Merklein, Marion; Biasutti, Manfredi (Key Engineering Materials, 2009)
The finite element method is a widely used tool in sheet metal forming. The quality of the results of such an analysis depends largely on the applied constitutive model and its material parameters, which have to be determined experimentally. These data are relevant on the choice of the yield criterion among the wide range of options available in the commercial applications implementing the finite element method. Since the accuracy of material parameters estimation is therefore crucial, investigations were performed with an Al-Mg sheet alloy and a mild steel sheet to optimize a Miyauchi-based simple shear test. This method is one of the basic ways to investigate the plastic properties of a sheet metal up to large strains, which is very important for numerical analysis of sheet metal forming processes. Aim of the test is to determine the shear stress-strain correlation. In order to enhance the quality of the experimental results the detection of the deformation's field, trough an optical measurement system, and the methodology for its evaluation are focus of the present study.
LFT Import::2019-07-29 (195)
Keywords: Material testing; Simple shear

Adapted mechanical properties for improved formability of aluminium blanks by local induction heating - Kerausch, Michael; Merklein, Marion; Geiger, Manfred (Adapted mechanical properties for improved formability of aluminium blanks by local induction heating. Proceedings of the International Body Engineering Conference 2003 in Chiba, Japan, 2003)
In this paper a novel process sequence consisting of local induction heating followed by deep drawing of a precipitation hardenable aluminum alloy is presented and compared with conventional processing. Using an induction heating system, it is possible to change the mechanical properties of the 6xxx-series in a restricted area by influencing the precipitation structure. Hardness measurements and tensile tests characterize the conversion from the stable naturally aged condition T4 to reversible solution heat-treated conditions of AA6016 as function of temperature and time. This effect leads to a reduction of flow stress, which is used to design an initial material property distribution adapted for the subsequent deep drawing process. A process characterization study provides detailed information concerning induction heating parameters, to improve the deep drawing of cylindrical cups, which results in a decisive increase of the limiting drawing ratio. Accompanying the experimental investigations, a finite element analysis approach is realized as a process design and optimization tool. Copyright © 2003 SAE International.
LFT Import::2019-08-05 (997)

Adapted tool design for the cold forging of gears from non-ferrous and light metals - Rohrmoser, Andreas; Hagenah, Hinnerk; Merklein, Marion (International Journal of Advanced Manufacturing Technology, 2021)
Due to growing competitive pressure within the manufacturing sector, there have been increasing attempts to establish resource saving production methods in gear manufacturing within recent years. Cold forging offers the potential—in addition to a high material and energy efficiency—to produce gears with an excellent surface quality, increased hardness as well as a load adapted fiber orientation. With regard to the wide range of applications there is a broad demand for gear materials, ranging from high-strength steels to non-ferrous and light metals. The flow behavior of the material has a significant influence on the cold forging process. Therefore, no consistent process result is achieved when forming different materials. Challenges exist due to deficient die filling and poor resulting geometrical accuracy. In this contribution, material-specific challenges during the full forward extrusion of gears from non-ferrous and light metals have been identified and suitable tool-sided measures were derived. A validated numerical process model was used to determine the underlying mechanisms of action and to verify the derived measures. A reduced yield stress leads to inflow formation, insufficient die filling, and low achievable strain hardening, as well as gearing accuracy. The tool-sided measures achieved a significant increase of resulting die filling and gearing accuracy as well as the mechanical properties. That provides the basis for the production of ready-to-use gears from various metal materials.
CRIS-Team Scopus Importer:2021-02-05
Keywords: Cold forging; Gears; Light metals; Simulation; Tool design

Adaption des Ringstauchversuchs für die Untersuchung der tribologischen Bedingungen beim Fügen warmumgeformter Stähle mittels Schneidclinchen - Müller, Martin; Vierzigmann, Ulrich; Hörhold, R.; Meschut, G.; Merklein, Marion (9. Erlanger Workshop Warmblechumformung, 2014)
LFT Import::2019-08-05 (2054)

Adaption of tool surface for sheet-bulk metal forming by means of pressurized air wet abrasive jet machining - Freiburg, Dennis; Assmuth, R.; Carballo, R. Garcia; Biermann, D.; Henneberg, Johannes; Merklein, Marion (Production Engineering, 2019)
Surface structures are used for several applications in industry to enhance the characteristics of surfaces and therefore processes. One example is the Sheet-bulk metal forming process which combines the advantages of bulk and sheet metal forming. Due to the complex material flow and load, the tool surfaces do need adapted tribological properties. High feed milled surface structures have been used in the past to control the material flow of the sheets. But due the high stresses appearing, the surfaces show a running-in behavior which altereds the tribological conditions. Within this study, a pressurized air wet abrasive jet machining (PAWAJM) process is used for adapting the high feed milled surface in order to manipulate the tribological conditions. Therefore, the surfaces characteristics, residual stresses as well as the tribological effects were investigated. It is shown that the PAWAJM process can be used to modify the surface characteristics and thus the friction of the surface. In addition, it can be seen that residual compressive stresses are applied during the PAWAJM.
CRIS-Team WoS Importer:2019-02-21

Adaption of tribological behavior of a-C:H coatings for application in dry deep drawing - Häfner, Tom; Rothammer, Benedict; Tenner, Jennifer; Krachenfels, Kim; Merklein, Marion; Tremmel, Stephan; Schmidt, Michael; Schmidt, Michael (MATEC Web of Conferences, 2018)
Nowadays the sheet metal forming industry faces challenges regarding efficient usage of resources and sustainability. One strategy to increase the environmental friendliness is to abandon the application of lubricants. The direct contact between tool and workpiece leads to an intensive interaction which increases friction. Especially for deep drawing processes with long sliding distances, this causes distinctive wear. The tool sided application of carbon based coatings is a well-known approach to reduce friction and wear. Former studies have shown a beneficial behavior of hydrogenated amorphous carbon based coatings (a-C:H) to improve the tribological conditions in contact with steel sheets and aluminium alloys under dry conditions. Within this study the coating process and the resulting coating properties will be analyzed. Afterwards mechanical and laser based surface treatment processes prior and after the deposition process will be investigated to reduce the coating roughness. Different roughness values were achieved by varying the surface treatment processes. The laser based finishing enables a reduction of the Spk values by removing single roughness asperities. In order to identify the necessary process parameters for the laser treatment, an analytical model of the material removal was applied. The laser surface treatment achieved similar roughness characteristics compared to mechanical treatment. In this study the tribological behavior of a-C:H coated tools was analyzed under dry conditions within strip drawing tests. The tribological investigations revealed that for dry deep drawing of zinc coated DC04 a broader range of Spk values leads to acceptable tribological conditions whereas for AA5182 a smoother tool surface has to be ensured to prevent adhesion and utilize the full potential of a-C:H coatings.<br
Keywords: Tribology; Surface Modification; Dry Deep Drawing

Adaptive Design of Aluminium Sheets for Deep Drawing Processes - Geiger, Manfred; Merklein, Marion (Production Engineering, 2002)
LFT Import::2019-07-16 (1721)

Additive Fertigung eines hybriden Planetenträgers - Papke, Thomas; Bartels, Dominic; Hofmann, Harald; Mys, Ruslana; Schmidt, Michael; Merklein, Marion (Zeitschrift für wirtschaftlichen Fabrikbetrieb, 2021)
Additive Manufacturing of a Hybrid Planet Carrier. The opportunity of freedom in design of additive manufacturing is applied to a planet carrier. Additive manufacturing starts on a conventionally manufactured base body, which is part of the planet carrier. This enables increased stiffness compared to the conventional design. Torsion tests show that stiffness can be doubled. Compared to singular additive manufacturing, costs decrease due to the hybrid design by 6 % for higher lot sizes.
Created from Fastlane, Scopus look-up
Keywords: Additive manufacturing; Assembly; Hybrid parts; Innovative technologies; Lightweight design

Additive Fertigung für industrielle Anwendungen - Entwicklung einer Auswahlsystematik für Bauteile zur Generierung funktionalen Mehrwerts mittels additiver Fertigung - Papke, Thomas; Bartels, Dominic; Schmidt, Michael; Merklein, Marion; Gerhard, Daniel; Baumann, Jonas; Pitz, Indra (Industrie 4.0 Management : Gegenwart und Zukunft industrieller Geschäftsprozesse, 2020)
Durch hohe Gestaltungsfreiheit und den Entfall produktspezifischer Werkzeuge gewinnen additive Fertigungsprozesse im industriellen Umfeld immer stärker an Bedeutung. Mit der Ausnutzung der verfahrensspezifischen Vorteile gegenüber konventionellen Fertigungsverfahren kann ein Mehrwert für Bauteile und Produkte generiert werden. Allerdings stellt die Auswahl potenzieller Bauteile, die durch die additive Fertigung einen Mehrwert erhalten können, eine Herausforderung dar. Zu diesem Zweck wurde eine Auswahlsystematik erarbeitet, um das Potenzial zu quantifizieren. Darauf aufbauend wird ein Ansatz vorgestellt, mit welchem beginnend mit der Bauteilauswahl über die Bauteil- und Prozesskettengestaltung eine Bewertung des Mehrwerts möglich ist. Dieser wird abschließend auf ein Strukturbauteil eines Fahrzeugs angewendet.<br

Additive Manufacturing of Functional Elements on Sheet Metal - Schaub, Adam; Ahuja, Bhrigu; Butzhammer, Lorenz; Osterziel, Johannes; Schmidt, Michael; Merklein, Marion (Physics Procedia, 2016)
Laser Beam Melting (LBM) process with its advantages of high design flexibility and free form manufacturing methodology is often applied limitedly due to its low productivity and unsuitability for mass production compared to conventional manufacturing processes. In order to overcome these limitations, a hybrid manufacturing methodology is developed combining the additive manufacturing process of laser beam melting with sheet forming processes. With an interest towards aerospace and medical industry, the material in focus is Ti-6Al-4V. Although Ti-6Al-4V is a commercially established material and its application for LBM process has been extensively investigated, the combination of LBM of Ti-6Al-4V with sheet metal still needs to be researched. Process dynamics such as high temperature gradients and thermally induced stresses lead to complex stress states at the interaction zone between the sheet and LBM structure. Within the presented paper mechanical characterization of hybrid parts will be performed by shear testing. The association of shear strength with process parameters is further investigated by analyzing the internal structure of the hybrid geometry at varying energy inputs during the LBM process. In order to compare the hybrid manufacturing methodology with conventional fabrication, the conventional methodologies subtractive machining and state of the art Laser Beam Melting is evaluated within this work. These processes will be analyzed for their mechanical characteristics and productivity by determining the build time and raw material consumption for each case. The paper is concluded by presenting the characteristics of the hybrid manufacturing methodology compared to alternative manufacturing technologies.
Keywords: Laser Beam Melting; Additive Manufacturing; Titanium alloy

Additive Manufacturing of Tailored Blank for Sheet-Bulk Metal Forming Processes - Schulte, Robert Karl; Papke, Thomas; Lechner, Michael; Merklein, Marion (2020)

Additive und umformtechnische Fertigung hybrider Bauteile mit lokal angepassten Eigenschaften - Hafenecker, Jan; Rothfelder, Richard; Merklein, Marion; Schmidt, Michael (Abschlusskolloquium des SFB 814, 2023)
Das Teilprojekt B5 hat zum Ziel, die Kombination aus additiver Fertigung und Umformtechnik zur Herstellung von maßgeschneiderten, funktionalisierten und individualisierten Titan-Hybridbauteilen eingehend zu erforschen. Neben dem Blechgrundkörper werden die additiv gefertigten Elemente der Hybridbauteile umgeformt, um den Werkstoff gezielt zu verfestigen und lokale Unterschiede in den Eigenschaften einzustellen. Zusätzlich wird angestrebt, eine lokale Werkstoffmodifikation in den additiv gefertigten Elementen zu erreichen. Dies wird durch den ortsselektiven Eintrag von Zusatzstoffen in Kombination mit in situ Legierungsbildung während des Laserstrahlschmelzprozesses (LSS-M) ermöglicht. Diese Modifikation soll sowohl den Anforderungen der Umformung als auch den Anforderungen des Einsatzes der Bauteile gerecht werden und individuell angepasst werden könne

Adjusting Optimized Material Properties for Tailored Heat Treated Blanks - Merklein, Marion; Hung Nguyen, (Key Engineering Materials, 2011)
Aluminum alloys have great potential for lightweight construction. In order to achieve an optimized properties distribution for the forming operation and to enhance the formability of aluminum alloys, so called Tailored Heat Treated Blanks (THTB) are developed. In this context, this paper is about the local precipitation hardening of sheet metals for the application of THTB. By using a specific, short-term heat treatment via conductive heating plates the thermal induced hardening of the fast hardenable alloy AA6181PX is quantified and qualified. Considering the processibility of the local precipitation hardening for THTB, a process window for the heat treatment parameters is presented allowing a precise setting of the mechanical material properties.
EAM Import::2019-03-13

Advanced laser heat treatment with respect to the application for Tailored Heat Treated Blanks - Nguyen, Manh Hung; Merklein, Marion (Physics Procedia, 2010)
LFT Import::2019-07-29 (1769)
Keywords: Aluminum alloy; Laser heat treatment; Tailored Heat Treated Blanks

Alloy design and adaptation for additive manufacture - Clare, A. T.; Mishra, R. S.; Merklein, Marion; Tan, H.; Todd, I.; Chechik, L.; Li, J.; Bambach, M. (Journal of Materials Processing Technology, 2022)
In this review the authors provide a comprehensive insight into additive manufacturing process mechanics which explore how thermodynamics give rise to characteristic microstructure and property. Discussion is then given over to how solidification microstructure is modified using processing conditions and utilisation of traditional casting methods which give rise to grain refinement and some cases ‘texture by design’. The review then makes observation and provides analysis on the typical material types reported in powder bed fusion and directed energy deposition. These are organised to efficiently highlight the key observations in terms of alloy creation and adaption with a specific focus on the relevant additive manufacturing technique. The emergent alloy families are also explored alongside the rapidly expanding topic of functionally graded alloys produced by the breadth of additive manufacturing techniques. The review concludes with a detailed critique of the state-of-the-art and an examination of where opportunities exist to advance the interdependency between process and emergent alloys exhibiting superior properties. The authors propose several areas worthy of consideration and attempt to provide inspiration for our community in the pursuit of new alloys and accompanying process designs for additive manufacturing.
CRIS-Team Scopus Importer:2021-10-08
Keywords: Additive manufacture; Alloy development; Directed energy deposition; Powder bed fabrication

Alternating Additive Manufacturing and Forming - An Innovative Manufacturing Approach - Papke, Thomas; Hafenecker, Jan; Römisch, David; März, Raphaela; Hentschel, Oliver; Bartels, Dominic; Schmidt, Michael; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2023)
In this work, an innovative manufacturing approach that includes a fully linked and integrated manufacturing system consisting of a laser-based directed energy deposition (DED-LB/M) module and a forming press is presented. The alternating additive manufacturing (AM) process is based on a combination of a DED-LB/M process using a laser power of 600 W and a feed rate of 400 mm/min and a subsequent forming process, in which the structure is upset with a hydraulic press using a constant forming force of 500 kN in order to smooth the surface and influence the accuracy of the components. For the generation of a fundamental process understanding, a cuboid, basic shape was chosen as geometry for the investigations. The aim is to improve part properties by applying the process steps to generate part properties, which are superior to solely additive manufactured material. It is shown that the geometry of additive manufactured structures can be adapted, and the top surface can be smoothed due to the forming operation. The mean roughness value Rz decreases up to 50% after the forming operation. The hardness can be increased by work hardening. Of special interest is that the higher hardness can be kept up even though a further DED-LB/M process step and forming operation are applied to the additively manufactured and formed structure again. Finally, an analysis of the new manufacturing approach regarding its potential is give
Keywords: forming; additive manufacturing; DED-LB/M; process combination

Alternative characterization method for the failure behavior of sheet metals derived from Nakajima test - Kohl, Doris; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
CRIS-Team WoS Importer:2021-11-05

Aluminiumlösungen aus maßgeschneidert wärmebehandelten Halbzeugen - Graser, Matthias; Degner, Julia; Böhm, Wolfgang; Merklein, Marion (Konstruktion, 2017)
LFT Import::2019-07-29 (2271)

Aluminium Tailored Heat Treated Blanks - Geiger, Manfred; Merklein, Marion; Vogt, Uwe (Annals of the German Academic Society for Production Engineering WGP, 2009)
LFT Import::2019-08-05 (1567)

Aluminum tailored heat treated blanks - Geiger, Manfred; Merklein, Marion; Vogt, Uwe (Production Engineering, 2009)
Tailored Heat Treated Blanks (THTB) are blanks, which exhibit locally different material properties optimized for the succeeding sheet metal forming process. The distribution of the material properties is obtained by a local, short-term heat treatment. As a result of the optimized property gradients in the sheet metal's plain, THTB allow enhancing the forming limits significantly. The research work covered in this paper focuses on THTB made out of aluminum alloys. The article presents the microstructural mechanisms due to a short-term heat treatment as well as design principles for the heat treatment layout for THTB made out of AlMgSi alloys and ultra-fine grained (UFG) aluminum alloys produced by the Accumulative Roll Bonding process.
EAM Import::2019-03-13

A Method for the Layer Compression Test Considering the Anisotropic Material Behavior - Merklein, Marion; Kuppert, Andreas (International Journal of Material Forming, 2009)
The layer compression test is used in the field of material characterization to determine the onset of yielding and the hardening behavior of a sheet metal within uniaxial compression loading. For testing anisotropic materials the experimental setup has to be adjusted and the evaluation has to be adapted. This could be achieved with the installation of a second optical strain measurement system to get data of both symmetry axes. In the following paper the experimental procedure with two strain measurement systems and the evaluation methodology regarding the two sets of data will be presented and validated with experimental results. The advantage of the layer compression test is discussed in comparison with the results of a standard tensile test. © Springer/ESAFORM 2009.
LFT Import::2019-08-05 (292)
Keywords: Anisotropy; Layer compression test; Material characterization

A methodology for the application of virtual evaluation methods within the design process of cold forged steel pinions - Rohrmoser, Andreas; Heling, Björn; Schleich, Benjamin; Kiener, Christoph; Hagenah, Hinnerk; Wartzack, Sandro; Merklein, Marion (Proceedings of the 22nd International Conference on Engineering Design (ICED19), 2019)

Analyse der Abbildbarkeit des dehnungsabhängigen Bauschinger-Effekts mithilfe istrop-kinematischer Modelle - Rosenschon, Martin; Merklein, Marion (Tagungsband XXXV. Verformungskundliches Kolloquium, 2016)
LFT Import::2019-08-05 (2164)

Analyse des Einflusses der tribologischen Eigenschaften auf die Tiefziehbarkeit metallischer Blechwerkstoffe nach dem Durchlauf einer Ziehsicke - Merklein, Marion; Schmid, Harald (2021)

Analyse des tribologischen Einsatzverhaltens von modifizierten Werkzeugoberflächen - Wild, Thomas; Merklein, Marion (Aktuelle Entwicklungen im Bereich der Umformtechnik, 2020)

Analysing resistance element welding with upset auxiliary joining steel-elements under shear load - Meinhardt, Mario; Endres, Martin; Graf, Marcel; Lechner, Michael; Merklein, Marion (Procedia Manufacturing, 2019)
The multi-material-design, as one common lightweight design strategy, has to be intensified in order to reach climate-goals and to comply with exhaust gas emission limits. For joining sheet metal parts of different materials, enhanced joining technologies are used, which are specific for each application case. Within this paper, resistance element welding joints of sheet metals in shear load tests are investigated. The resistance element welding process with upset auxiliary joining steel-elements is a possibility for joining multi-material sheet metal parts, using the standard process of resistance spot welding. In order to assess the potential of this joining process, it is necessary to determine the load-bearing behaviour under shear load by shear tensile tests. The objective of this paper is to analyse the maximum shear strength for resistance element welding specimen with upset steel-elements in aluminium carrier sheets of different thicknesses. The geometry of the test specimen is adapted to resistance element welding process conditions. Failure behaviour under shear load is analysed and related to the applied upset elements. Finally, the maximum shear load strength of resistance element welding joints are presented and compared to similar joining technologies.
CRIS-Team Scopus Importer:2019-12-20
Keywords: Joining Technology; Lightweight; Multi-Material; Resistance Element Welding; Shear Tensile Test

Analysis of combined extrusion micro coining process to manufacture microstructured tappets - Zahner, Michael; Merklein, Marion (Procedia Manufacturing, 2018)
In times of enhanced functional integration of machine elements the combination of forming processes offers an opportunity to increase the efficiency of the manufacturing process. Due to mutual interactions combining different forming operations a comprehensive analysis of the processes is necessary especially regarding micro forming processes. Within this study a combined extrusion micro coining process to manufacture microstructured tappets was investigated. The results reveal that the achieved homogeneity on tappet surface is mainly influenced by the microstructure layout applied on the tool components, due to locally widely varying material flow in the coining region.
LFT Import::2019-07-29 (2334)
Keywords: Combined forming process; Geometrical accuracy; Micro Coining; Microstructures; Tribology

Analysis of Distributed-Ledger-Technology for the Exchange of Design, Production and Simulation Data in Roll Forming - Kohl, B.; Krueger, M.; Dietl, T.; Lechner, Michael; Trunzer, E.; Merklein, Marion; Sedlmaier, A.; Vogel-Heuser, B. (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2022), 2022)
CRIS-Team WoS Importer:2023-01-20

Analysis of Effectiveness of Locally Adapted Tribological Conditions for Improving Product Quality in Sheet-Bulk Metal Forming - Löffler, Maria; Gröbel, Daniel; Engel, Ulf; Andreas, Kolja; Merklein, Marion (Applied Mechanics and Materials, 2015)
LFT Import::2019-07-29 (2099)

Analysis of Forming Limits in Sheet Metal Forming with Pattern Recognition Methods. Part 1: Characterization of Onset of Necking and Expert Evaluation - Affronti, Emanuela; Jaremenko, Christian; Merklein, Marion; Maier, Andreas (Materials, 2018)
In automotive manufacturing, high strength materials, and aluminum alloys are widely used to address the requirement of ensuring a lightweight car body and correspondingly, reducing pollution. In this context of complexity of materials and structures, an optimized process design with finite element analyses (FEA) is mandatory, as well as a correct definition of the material forming limits. For this purpose, in sheet metal forming, the forming limit curve (FLC) is used. The FLC is defined by the onset of necking. The standard evaluation method according to DIN EN ISO 12004-2 is based on the cross-section method and assumes that the failure occurs due to a clear localized necking. However, this approach has its limitations, specifically in the case of brittle materials that do not exhibit a distinct necking phase. To overcome this challenge, a pattern recognition-based evaluation is proposed. Although pattern recognition and machine learning techniques have been widely employed in the medical field, few studies have investigated them in the context of analyzing metal sheet forming limits. The application of pattern recognition in metal forming is subject to the exact definition of the forming behaviors. Thereby, it is challenging to relate patterns on the strain distribution during Nakajima tests with the onset of necking for the FLC determination. Thus, the first approach was based on the crack evaluation, since this class is well-defined. However, of substantial interest is the evaluation of the general material instabilities that precede failure. Therefore, in the present study, the analysis of the material behavior during stretching is conducted in order to characterize instability classes. The results of Nakajima tests are investigated using an optical measurement system. A conventional pattern recognition approach based on texture features, considering the outcomes of expert interviews for the definition of classes is used for the FLC determination. Moreover, an analysis of the validity of the supervised learning is conducted. The results show a good prediction of the onset of necking, even for high strength materials with a recall of up to 92%. Some deviations are observed in the determination of the diffuse necking. The discrepancies of the different experts' prognoses highlight the user-dependency of the FLC, suggesting further investigations with an data-driven approach, could be beneficial.
LFT Import::2019-07-29 (2319)
Keywords: Forming limit curve; Machine learning; Pattern recognition; Sheet metal forming

Analysis of Forming Limits in Sheet Metal Forming with Pattern Recognition Methods. Part 2: Unsupervised Methodology and Application - Jaremenko, Christian; Affronti, Emanuela; Maier, Andreas; Merklein, Marion (Materials, 2018)
The forming limit curve (FLC) is used in finite element analysis (FEA) for the modeling of onset of sheet metal instability during forming. The FLC is usually evaluated by achieving forming measurements with optical measurement system during Nakajima tests. Current evaluation methods such as the standard method according to DIN EN ISO 12004-2 and time-dependent methods limit the evaluation range to a fraction of the available information and show weaknesses in the context of brittle materials that do not have a pronounced constriction phase. In order to meet these challenges, a supervised pattern recognition method was proposed, whose results depend on the quality of the expert annotations. In order to alleviate this dependence on experts, this study proposes an unsupervised classification approach that does not require expert annotations and allows a probabilistic evaluation of the onset of localized necking. For this purpose, the results of the Nakajima tests are examined with an optical measuring system and evaluated using an unsupervised classification method. In order to assess the quality of the results, a comparison is made with the time-dependent method proposed by Volk and Hora, as well as expert annotations, while validated with metallographic investigations. Two evaluation methods are presented, the deterministic FLC, which provides a lower and upper limit for the onset of necking, and a probabilistic FLC, which allows definition of failure quantiles. Both methods provide a necking range that shows good correlation with the expert opinion as well as the results of the time-dependent method and metallographic examinations.
LFT Import::2019-07-29 (2327)
Keywords: Forming limit curve; Machine learning; Pattern recognition; Sheet metal forming

Analysis of fundamental dependencies between manufacturing and processing Tailored Blanks in sheet-bulk metal forming processes - Schulte, Robert Karl; Hildenbrand, Philipp; Vogel, Manfred; Lechner, Michael; Merklein, Marion (International Conference on the Technology of Plasticity, ICTP 2017, 17-22 September 2017, Cambridge, United Kingdom, 2017)
LFT Import::2019-08-05 (2232)
Keywords: Cold forming; Deep drawing; Tailored Blank

Analysis of material behaviour in experimental and simulative setup of joining by forming of aluminium alloy and high strength steel with shear-clinching technology - Müller, Martin; Hörhold, Réjane; Merklein, Marion; Meschut, Gerson (Advanced Materials Research, 2014)
LFT Import::2019-07-29 (2020)
Keywords: Clinching; FEM; Joining by forming; Lightweight design; Multi-material mix

Analysis of microbending of CuZn37 brass foils based on strain gradient hardening models - Li, He-Zong; Dong, Xiang-Huai; Shen, Yu; Zhou, Rui; Diehl, Alexander; Hagenah, Hinnerk; Engel, Ulf; Merklein, Marion; Cao, Jian (Journal of Materials Processing Technology, 2012)
Microbending experiments of brass foils were conducted and demonstrated clear size effects, i.e., the normalized bending moment increased with the reduction of foil thickness. The experiments were modeled using the classical plasticity model and three strain-gradient plasticity models. A modified Nix-Gao model was proposed to consider the number of twins across the thickness direction in strain hardening. It was found that the proposed model could better predict the normalized bending moment for both fine-grain and coarse-grain foils and the proposed equation for material intrinsic length could better capture the physics of material deformation. Furthermore, micro-hardness distributions in the bending area were measured and obvious lower-hardness region was found in the middle layer of fine-grain foils instead of coarse-grain foils. This indicates that the modified Nix-Gao model and the assumption of fully plastic bending worked better for coarse-grain foils than for fine-grain foils. © 2011 Elsevier B.V. All rights reserved.
LFT Import::2019-07-29 (1779)
Keywords: Bending moment; CuZn37 brass; Material intrinsic length; Microbending; Strain gradient

Analysis of Production Limits in Manufacturing of Micro Coined Structures - Zahner, Michael; Andreas, Kolja; Engel, Ulf; Merklein, Marion (ASPEN/ASPE 2017 Spring Topical Meeting - Manufacture and Metrology of Structured and Freeform Surfaces for Functional Applications, 2017)
LFT Import::2019-08-05 (2225)

Analysis of stress pins for the local prestressing of cold forging tools - Killmann, Martin; Merklein, Marion (Production Engineering, 2021)
The trend towards lightweight design leads to an increasing demand for sophisticated part geometries with high functional integration. In order to use the advantages of cold forging regarding the time- and resource-efficient production of high-quality parts, high local stresses causing fatigue failure in geometrically complex tools have to be controlled. The objective of this manuscript is to analyse the use of stress pins for a local influence on the stress state within forging, especially in non-circular symmetrical cold forging dies. For this purpose, a closed-die forging process for elliptical parts is designed and analysed regarding the die stresses. Distinct areas with local compressive and tensile stresses occur in the process. To counteract the tensile stresses critical for fatigue failure, the effect of stress pins pressed into the die creating a local prestress is analysed. Around the pins, compressive radial and tensile tangential stresses occur. While large pin diameters, interferences and close positioning to the tensile area lead to an increasing prestressing effect, too high values of these parameters cause a detrimental superposition of tensile process and pin stresses. If used correctly, there is high potential to improve the stress state and tool life especially for locally stressed complex tools.<br
Keywords: Cold forging; Die design; Tool load; Local prestressing; Stress pins

Analysis of the bending effects and the biaxial pre-straining in sheet metal stretch forming processes for the determination of the forming limits - Affronti, Emanuela; Merklein, Marion (International Journal of Mechanical Sciences, 2018)
LFT Import::2019-07-29 (2291)
Keywords: Bending effect; Biaxial pre-straining; Forming limit curve; Sheet metal forming

Analysis of the deformation behavior of Ti-6Al-4V at elevated temperatures - Merklein, Marion; Hagenah, Hinnerk; Kaupper, Markus; Schaub, Adam (Key Engineering Materials, 2013)
Titanium alloys, such as Ti-6Al-4V, offer favorable characteristics as significant strength, biocompatibility and metallurgical stability at elevated temperatures. These advantages afford the application of parts out of Ti-6Al-4V in a wide field within aerospace, astronautic and medical technologies. Most applied shaping operations for parts out of titanium alloys are forging, casting, forming and machining. In order to develop and improve forming operations numerical simulations are applied during preprocessing. For that purpose mechanical properties of the material such as yield stress and Lankford parameter have to be determined. Due to the two-phase (α + β) microstructure of Ti-6Al-4V, forming operations have to be carried out at elevated temperatures to reduce the required forming force and extend forming limits. Taking the temperature and stress state dependency of the material into consideration, uniaxial tensile and compression tests are accomplished at elevated temperatures, ranging from 400 to 600 °C. Furthermore, the experimenttally determined yield stress and Lankford parameter are approximated with the yield loci model proposed by Barlat 2000. The model predicts the flow response of the material, thus provides input data for the finite element analysis of forming processes at different temperature levels. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1876)
Keywords: Compression test; Temperature effects; Tensile test; Ti-6AL-4V alloy; Yield loci

Analysis of the evolution of the Lankford coefficient in uniaxial tensile tests and validation with grain structure analysis - Lenzen, Matthias; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2022)
Modern materials mostly exhibit a low formability or a complex material behavior. For example, the common mild steel DC06 exhibits a strain state dependency in the yield stress and a strain dependency of the Lankford coefficients. Thus it is necessary to characterize the material properties from the onset of plastic deformation up to fracture. For example in the uniaxial tensile test, the flow stress and the r-values can be determined. According to the standards, the characterization is only applicable up to uniform elongation. In the case of DC06, the uniform elongation is with 24% comparatively low in contrast to the ultimate elongation with 60%. Research has proven, that the true stress can be characterized up to high strain in the uniaxial tensile test. For the strain dependent Lankford coefficient, this validation is missing. The aim in this investigation is the analysis of the strain dependent anisotropy up to high strain levels in uniaxial tensile tests and the validation. This is done with a comparison of optically measured r-values with the grain structure evolution of the pre stretched parts. These results prove the applicability of the standardized evaluation of Lankford coefficients out of DIC data above the uniform elongation.
CRIS-Team WoS Importer:2022-09-16

Analysis of the formation of gap-based leakages in polymer-metal electronic systems with labyrinth seals - Kleffel, Tobias; Frey, Philipp; Merklein, Marion; Drummer, Dietmar (Journal of Polymer Engineering, 2019)

Analysis of the influence of a cold leveling process on the properties of multi-layered aluminum sheets - Zettl, Bastian; Merklein, Marion (XLI. Verformungskundliches Kolloquium, 2023)
One approach for reducing emissions in the transportation and traffic sector is offered by lightweight material construction. In the automotive and aircraft industry, materials with a high specific strength are used, such as aluminum alloys of the 5xxx, 6xxx and 7xxx series. The strength of these alloys can be further increased by mechanical forming processes and the associated work hardening. The mechanical process group includes the so-called severe plastic deformation processes, which, by introducing very high degrees of plastic deformation, also induce the mechanism of fine-grain hardening in addition to work hardening. Accumulative roll bonding (ARB) is a process variant in which large-area semi-finished sheet products with a multilayered structure can be produced. It has already been identified that the layer interfaces and the intermediate bond strengths have a significant influence on the subsequent product properties, since delamination effects lead to premature material failure. For improving the dimensional accuracy and flatness of large-scaled sheets, straightening processes can be used. In this work, the influence of sheet leveling at room temperature on the feasibility and interface properties of ARB-products is investigated. In detail, the investigations include the analysis of the interface as well as the distribution of the sheet thickness as a function of the number of ARB process cycles in the initial state and after straightening at room temperature.<br
Keywords: accumulative roll bonding; cold leveling; multi-layered sheets

Analysis of the Influence of Surface Modifications on the Fatigue Behavior of Hot Work Tool Steel Components - Wild, Thomas; Platt, Timo; Biermann, Dirk; Merklein, Marion (Materials, 2021)
Hot work tool steels (HWS) are widely used for high performance components as dies and molds in hot forging processes, where extreme process-related mechanical and thermal loads limit tool life. With the functionalizing and modification of tool surfaces with tailored surfaces, a promising approach is given to provide material flow control resulting in the efficient die filling of cavities while reducing the process forces. In terms of fatigue properties, the influence of surface modifications on surface integrity is insufficiently studied. Therefore, the potential of the machining processes of high-feed milling, micromilling and grinding with regard to the implications on the fatigue strength of components made of HWS (AISI H11) hardened to 50 ± 1 HRC was investigated. For this purpose, the machined surfaces were characterized in terms of surface topography and residual stress state to determine the surface integrity. In order to analyze the resulting fatigue behavior as a result of the machining processes, a rotating bending test was performed. The fracture surfaces were investigated using fractographic analysis to define the initiation area and to identify the source of failure. The investigations showed a significant influence of the machining-induced surface integrity and, in particular, the induced residual stress state on the fatigue properties of components made of HWS.
Keywords: fatigue; surface modification; micromilling; high-feed milling; grinding; residual stresses; AISI H11

Analysis of the Lankford Coefficient Evolution at Different Strain Rates for AA6016-T4, DP800 and DC06 - Lenzen, Matthias; Merklein, Marion (AIP Conference Proceedings 1896(2017)160001, 2017)
None
LFT Import::2019-08-05 (2248)

Analysis of the modification of tool surfaces by abrasive blasting and laser polishing - Wild, Thomas; Bestenlehrer, Marcel; Merklein, Marion (Defect and Diffusion Forum, 2020)
The surface treatment of tools plays an important role for the operational behaviour of forming processes. Up to now, industrial standard is the manual finishing of tool surfaces, which can lead to a varying quality of the surface finish and therefore influence the tool service life and the forming results. One method to perform the polishing operation automatically is to remelt the top layer of materials by laser polishing. This is accompanied by a considerable change in the material properties in this zone. Therefore, the effect of laser polishing with respect to the local modification of the tool surface is investigated in this study. The results of the investigations reveal that a precise adjustment of the laser parameters is required in order to reduce the roughness of the surface. The heat input also leads to a significant influence on the microstructure of the material. In this study laser polishing remelts the material up to a depth of approximately 20 µm. Furthermore, it can be observed that the heat input during the process results in a heat affected zone of up to a depth of 30 µm. As a contrast to laser polishing, abrasive blasting is investigated as a roughness increasing surface modification.
CRIS-Team Scopus Importer:2020-12-04
Keywords: Laser; Polishing; Surface Modification

Analysis of the Part Quality and Process Stability when Producing Metallic Micro Parts by Multi-Stage Bulk Forming from Sheet Metal - Kraus, Martin; Merklein, Marion (Key Engineering Materials, 2022)
Miniaturization of parts for technical products is an ongoing trend across all industries over the past decades. Due to the large number of possible applications, several billion micro parts are produced every year. In mass production, cold forming offers technological, economical and ecological benefits in comparison to other manufacturing methods. Unfortunately, due to size effects that negatively influence the part geometry, the process stability, the handling and the tool stress, this manufacturing technology is currently barely used. Previous research results have shown that bulk microforming from sheet metal has the potential to reduce the aforementioned restrictions decisively. Within this paper, a three-stage bulk microforming process from sheet metal is experimentally analysed to form a demonstrator geometry with dimensions in the sub-millimetre range in all spatial directions. In the first stage, material is provided in form of a pin for subsequent forming stages. During the second stage, a cup geometry is formed on the pin. Finally, the micro part is separated from the sheet metal by shear cutting. To ensure a wide range of applications, the investigations are carried out with copper, steel and aluminium material. This study is focused on the evaluation of the achievable part quality and the process stability. For the evaluation of the geometry and the surface quality, the micro parts are optically measured with a three-dimensional surface measuring system. The standard deviation of the part dimensions and the process forces are used to investigate the influence of size effects in relation to the material and the grain structure.
CRIS-Team Scopus Importer:2022-11-04
Keywords: Bulk microforming; Metallic micro parts; Pin extrusion; Sheet metal; Size effects

Analysis of the stress and directional dependent Bauschinger-effect of sheet metals - Rosenschon, Martin; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2018)
The increasing application of lightweight metals in combination with a growth in the complexity of components provides new challenges to the numerical modeling of sheet materials. The choice of the material model and the associated mapping of the hardening behavior are of substantial importance for a realistic process prediction and the following spring back calculation in particular. The implementation of the Bauschinger-effect via isotropic-kinematic hardening laws can lead to a substantial improvement of the prediction quality. It is commonly known, that an accurate prognosis of sheet metal forming processes requires the consideration of the semi-finished products anisotropy. However, the identification of the Bauschinger-effect, which describes the reduction of the yield stress after a load reversal, and corresponding numerical models, is usually done under a specific stress state and in one direction of the sheet. Considering the vast variety of stress states and loading directions occurring in a forming operation, the anisotropic behavior of the Bauschinger-effect under uniaxial stress and its evolution during shearing is analyzed. Using a miniaturized tension-compression test, the cyclic hardening of the mild steel DX56 and the high strength steel DP600 and the aluminum alloy AA6016 is characterized in 0°, 45° and 90° to the rolling direction. By the identification of an isotropic-kinematic hardening law in combination with the anisotropic flow criterion Yld2000-2d the model's ability to extrapolate the hardening behavior is evaluated. In the last step, the transferability of parameters from the uniaxial stress state to results from a modified shear test is analyzed.
CRIS-Team Scopus Importer:2023-03-29

Analysis of the stress state in non-axially symmetrical cold forging dies - Killmann, Martin; Merklein, Marion (Procedia Manufacturing, 2020)
Conventionally, reinforcement systems are used to decrease tensile stresses in axially symmetrical cold forging dies. The increasing complexity of parts due to lightweight design leading to higher functional integration causes the necessity of producing non-axially symmetrical parts, for which there is insufficient knowledge about the adequate application of reinforcement systems. To gain understanding about the stress distribution for non-axially symmetrical dies, a cold forging process for producing elliptical parts is introduced and numerically described. The simulation model is validated in a test set up with strain gauges, which are used to measure the strains on the die and reinforcement ring. Subsequently, the process is analysed regarding the location, direction and magnitude of the resulting prestresses and maximum stresses. Based on the findings, a classification of areas for non-circular symmetrical cold forging tools is introduced. The compressive area is subjected to increasingly high contact pressures by the workpiece. This leads to compressive radial stresses and radial displacements. The high displacements induce a bending effect, which causes tangential stresses in the tensile area. The gained process understanding is used to propose measures for improving the stress state in cold forging dies for asymmetrical parts by locally strengthening the reinforcement syste
Keywords: Cold Forming; Forging; Die Load; Asymmetrical Tools; Reinforcement Systems

Analysis of the thermomechanical flow behavior of carburized sheet metal in hot stamping - Horn, Alexander; Merklein, Marion (Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity, 2021)
The reduction of fuel consumption due to restrictions regarding CO2 emissions is one of the major driving forces for lightweight design in the automotive industry. In this context, hot stamping of ultra-high-strength steels has developed to a state of the art process for manufacturing safety-relevant components. With regard to passenger safety and weight reduction, further potential lies in the functional optimization of the parts. Prior local carburization followed by hot-stamping is a new process variant for tailored properties, which overcomes the limitations of established processes. Due to the varying carbon content after carburization, the sheets have graded mechanical properties. Within this contribution, the influence of temperature, strain rate and carburization on the flow behavior will be investigated. For this purpose, tensile tests at elevated temperatures are carried out in a physical simulator of type Gleeble. The resulting flow curves of the carburized complex phase steel are modeled with a modified Norton-Hoff hardening law and the influence of the carburization process is analyzed by means of the initial yield stress. Furthermore, the results from tensile tests are correlated with the phase transformation behavior obtained by a laser ultrasonic sensor.
CRIS-Team Scopus Importer:2021-09-03
Keywords: Carburization; Hot stamping; Quenching

Analysis of the Young’s modulus reduction and cyclic hardening of HCT780X - Rosenschon, Martin; Merklein, Marion (Proc. of MATFEM Conference 2017, 2017)
LFT Import::2019-08-05 (2272)

Analysis of tool-sided surface modifications for dry deep drawing of deep drawing steel and aluminum alloys in a model process - Steiner, Jennifer; Häfner, Tom; Zhao, Rong; Andreas, Kolja; Schmidt, Michael; Tremmel, Stephan; Merklein, Marion (Dry Metal Forming Open Access Journal, 2017)
The concept of sustainability motivates the development of energy-saving and low-polluting production processes. A sheet metal forming process without usage of lubricants is considered as one of these green production technologies. Forming processes without the need for traditional lubricants save process steps and additional costs to remove the remaining lubrication from the workpiece after forming. In order to realize such a dry forming process and to adjust the material flow effectively, tool surfaces were modified by amorphous carbon coatings and different surface finishing processes for roughness adjustment. To verify the general feasibility of the lubricant-free metal forming process, deep drawing of rectangular cups with and without lubrication with conventional forming tools was investigated. The dry deep drawing process was modelled numerically to analyze process parameters and identify critical contact conditions. By strip drawing tests, the tribological behavior of ta-C and a-C:H coated tools with different surface treatments was investigated. The deposition process and resulting properties of a-C:H coatings were further analyzed to improve their tribological performance. The effects of the process parameters – deposition temperature and bias voltage in the deposition chamber – were investigated using the one-factor-at-a-time method. The strip drawing tests revealed a high influence of the surface roughness of coated tools on the tribological behavior. Therefore, laser based smoothing was further investigated in this study. Laser radiation at 355 nm wavelength was applied as an effective and minimum heat-generating technique to remove the roughness asperities on ta-C coatings which are built during its growth. Finally, ta-C and a-C:H coatings were applied on tool surfaces and tested in a drawing process of strip profiles. As reference the same forming process with a conventional forming tool was carried out.<br
Keywords: Dry Deep Drawing; Tribology; Carbon Based Coatings; Laser Based Modification

Analysis of tribological behavior of surface modifications for a dry deep drawing process - Henneberg, Johannes; Rothammer, Benedict; Zhao, Rong; Vorndran, Martin; Tenner, Jennifer; Krachenfels, Kim; Häfner, Tom; Tremmel, Stephan; Schmidt, Michael; Merklein, Marion (Dry Metal Forming Open Access Journal, 2019)
The global trend towards more environment-friendly and sustainable production motivates the development of efficient manufacturing processes. Forming technology has great potential regarding that due to its high material efficiency. Research is necessary to improve the sustainability of established forming processes such as deep drawing. One possibility to improve the environmental friendliness of deep drawing is the realization of lubricant-free processes. This avoids the usage of harmful lubricants. Additionally, it has the potential to shorten process chains by eliminating cleaning steps. However, dry deep drawing is associated with challenges. Due to the lack of a lubricant between tool and workpiece, friction and wear increase. An approach to overcome these challenges is the usage of modified tool surfaces. In this context, the aim of this research is to investigate dry deep drawing operations under application-oriented conditions. Firstly, the cause-effect relationships between the properties and tribological performance for a-C:H and ta-C coating systems as well as laserbased micro-textures are investigated in strip drawing tests using the workpiece materials DC04 and AA5182. Therefore, different amorphous carbon coating approaches for DC04 and AA5182 are evaluated. Beside of coatings, diverse laser micro-texturings are investigated and applied on forming tools. Key parameters are identified, which result in low friction and adhesion. Based on these findings, the different modifications are evaluated. Promising modifications are selected and applied in a novel test rig under application-oriented conditions to analyze their durability. The test rig enables the time- and material-efficient forming of a great number of parts. In this regard, in addition to the occurring process forces, the tool and component topographies are determined at periodic intervals in order to derive the cause-effect relationships between friction, wear and component quality as well as to demonstrate the feasibility of dry deep drawing operations under application-oriented forming conditions.<br
Keywords: Dry Deep Drawing; Tribology; Carbon Based Coatings; Laser Based Modification

Analysis of Varying Properties of Semi-finished Products in Sheet-bulk Metal Forming of Functional Components - Schneider, Thomas; Vierzigmann, Ulrich; Merklein, Marion (AIP Conference Proceedings, 2014)
LFT Import::2019-07-29 (1915)

Analysis of Work Hardening and Tribological Changes After a Gap Controlled Drawbead Passage - Schmid, Harald; Merklein, Marion (The Minerals, Metals & Materials Series. Springer, Cham., 2021)

Analytical and numerical approaches to predict the flow characteristics of a magnetorheological fluid in rotational symmetric cross sections - Rösel, Sebastian; Merklein, Marion; Grüner, Martin (Key Engineering Materials, 2012)
For a better understanding of the hydroforming process using magnetorheological fluids as a medium it is necessary to gain basic information for an analytical and numerical description of the fluid behaviour under process relevant conditions. Therefore an experimental setup is build up, which consists of a pressure chamber and a rotational symmetric outlet. Different parameters like feed rate and magnetic flux density are varied. Afterwards an analytical approach and a numerical model are developed. To get the relevant material input data for the fluid description an additional numerical simulation of the created magnetic flux density with flux lines perpendicular to the symmetry line of the outlet is performed. The leakage rates, which are observed for the experiments, are compared to the analytically calculated ones and to the results of the numerical simulation. © (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1803)
Keywords: Active fluid media; Hydroforming; Magnetorheological fluid (MR-Fluid); Sheet metal forming

Analytical friction force compensation of flow curves out of layer compression tests with the pin extrusion test - Lenzen, Matthias; Kraus, Martin; Merklein, Marion (International Journal of Material Forming, 2020)
For conventional material models like Yld2000-2d or BBC05 the equi-biaxial yield strength is required for the parameter identification. In this context, a commonly used test setup is the hydraulic bulge test. However, an inaccuracy in the characterization of the initial yield strength is present in the hydraulic bulge test. Due to the evaluation of the resulting curvature of the specimen, that is nearly infinite at the onset of yielding, the calculated stress can significant vary. Another proposed test setup for the characterization of the equi-biaxial stress state is the layer compression test. Here, the onset of yielding can be characterized with sufficient accuracy. The disadvantage in this test is the friction between stack and tool that leads to an overestimation of the flow curve. Thus, robust and experimental based friction compensation should be used, to gain a comparable hardening behaviour as in the hydraulic bulge test. In this contribution, the friction in the layer compression test is compensated by characterization of the tribological conditions. Thus, the tribological system consisting of workpiece surface, tool surface and lubricant is characterized using pin extrusion tests. The friction is analysed for the two steel grades DC06 and DP600 and the aluminium AA5182. With the identified friction factors, the measured testing force in the layer compression test is reduced by the portion of friction. For verification, hydraulic bulge tests, which are approximately friction free, are performed and compared with the resulting flow curves of the layer compression tests. Results confirm, that a friction compensation of the layer compression tests lead to a significant improvement of the resulting material parameters in comparison to the hydraulic bulge tests. Additional, a new method for the friction factor characterization is presented that uses in the stress difference of flow curves characterized in hydraulic bulge tests and layer compression tests.
CRIS-Team Scopus Importer:2020-05-12
Keywords: Friction compensation; Layer compression test; Material characterization; Pin extrusion test

Analytic Methods for the Calculation of the Heat Transfer Coefficient - Merklein, Marion; Wieland, Michael; Stöhr, Thomas; Lechler, Jürgen; Grüner, Martin (International Review of Mechanical Engineering, 2010)
In the product development cycle numerical simulations are commonly used for the process layout. In case of hot stamping the process layout gets quite complex because material's thermal and mechanical properties have to be taken into account. Hot stamping can be explained as forming and quenching in one process step and therefore the knowledge of thermal properties is indispensable to fulfill the opposing requirements of a good heat flux with respect to a good energy balance of the tool. A description of this energy exchange between the hot blank and the tool is given by the heat transfer coefficient. The determination of the heat flux under process relevant conditions for hot stamping is influenced by several variables. Within the scope of this work, these different variables are compared using two analytical methods to calculate the heat transfer coefficient based on the same measurement data. Furthermore the advantage of these analytical methods and the possibility of improvement is shown up. At least a validation of the calculated heat transfer coefficients by simulation is presented. Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved.
LFT Import::2019-07-29 (224)
Keywords: Heat transfer coefficient; Hot stamping

A new approach for the determination of the linear elastic modulus from uniaxial tensile tests of sheet metals - Suttner, Sebastian; Merklein, Marion (Journal of Materials Processing Technology, 2017)
The determination of the linear elastic modulus is important for the numerical process design of forming operations. Test setups for the identification of the linear elastic modulus can be divided into dynamic methods like ultrasonic measurement and static methods like indentation tests or uniaxial tensile tests. Relevant standards recommend the determination of the linear elastic modulus via linear regression from stress vs. strain curves, while no information for an upper boundary exists. In this contribution, a new approach is presented, which uses the deformation work to identify a material-dependent upper boundary for the determination of the linear elastic modulus. The method is applied to two aluminum alloys AA5182-O and AA6016-T4, a deep drawing steel DX54, two advanced high strength steels HCT600X and HCT980X and a magnesium alloy AZ31B. The results confirmed a robust determination of the linear elastic modulus from the linear elastic behavior and a good reproducibility with a deviation below 5%. Moreover, with exception of AA5182-O, all investigated materials exhibit a quasi-elastic-plastic (QPE) transition between elastic and plastic material behavior.
LFT Import::2019-07-29 (2200)
Keywords: Elasticity; Material characterization; Young's modulus

A new approach to the evaluation of forming limits in sheet metal forming - Merklein, Marion; Maier, Andreas; Kinnstätter, Daniel; Jaremenko, Christian; Affronti, Emanuela (Key Engineering Materials, 2015)
UnivIS-Import:2015-04-14:Pub.2015.tech.IMMD.IMMD5.anewap

A new process chain for joining sheet metal to fibre composite sheets - Plettke, Raoul; Schaub, Adam; Gröschel, Christian; Scheitler, Christian Josef; Heinle, Martina; Ranft, Florian; Merklein, Marion; Schmidt, Michael; Drummer, Dietmar (Key Engineering Materials (Volumes 611 - 612), 2014)
Mixed-Materials parts have great light-weight potential for the automotive application to reduce the carbon footprint. But the joining of fibre composite plastic sheets to metal sheets is in practical application limited to adhesive bonding or mechanical joining with additional fastener elements due to the large differences in physical properties. A new process chain based on plastic joining without fastener elements is proposed and first results on the mechanism and on the achievable strength of the new joints are shown. The process chain consists of three steps: First joining pins are added to the sheet metal by an additive manufacturing process. In a second step these pins are pierced through the fibre composite sheet with a local heating of the thermoplastic in an overlap setup. In the third and last step the joint is created by forming the pins with the upsetting process to create a shape lock. The shear strength of the joined specimens was tested in a tensile testing machine. The paper shows that even with a non-optimized initial setup joints can be realised and that the new process chain is a possible alternative to adhesive bonding. © 2014 Trans Tech Publications, Switzerland.
UnivIS-Import:2018-09-06:Pub.2014.tech.FT.FT-KT.anewpr
Keywords: Aluminium; Endless-fibre reinforced plastics; Joining; Joining by forming; Mixed materials; Titanium

A new process chain for joining sheet metal to fibre composite sheets - Plettke, Raoul; Schaub, Adam; Gröschel, Christian; Scheitler, Christian Josef; Vetter, Martina; Hentschel, Oliver; Ranft, Florian; Merklein, Marion; Schmidt, Michael; Drummer, Dietmar (Key Engineering Materials, 2014)
Keywords: Aluminium; Endless-fibre reinforced plastics; Joining; Joining by forming; Mixed materials; Titanium

A new strategy for manufacturing tailored blanks by a flexible rolling process - Hildenbrand, Philipp; Lechner, Michael; Merklein, Marion (Materials Science Forum, 2016)
LFT Import::2019-07-29 (2143)
Keywords: Forming; Rolling; Sheet metal

A New Way for the Adaption of Inverse Identified GTN-Parameters to Bending Processes - Tsoupis, Ioannis; Merklein, Marion (13th International LS-DYNA Users Conference 2014, 2014)
LFT Import::2019-08-05 (2023)

An experimental and numerical investigation of different shear test configurations for sheet metal characterization - Yin, Qing; Zillmann, Benjamin; Suttner, Sebastian; Gerstein, Gregory; Biasutti, Manfredi; Tekkaya, A. Erman; Wagner, Martin F. -X.; Merklein, Marion; Schaper, Mirko; Halle, Thorsten; Brosius, Alexander (International Journal of Solids and Structures, 2014)
Simple shear tests are widely used for material characterization especially for sheet metals to achieve large deformations without plastic instability. This work describes three different shear tests for sheet metals in order to enhance the knowledge of the material behavior under shear conditions. The test setups are different in terms of the specimen geometry and the fixtures. A shear test setup as proposed by Miyauchi, according to the ASTM standard sample, as well as an in-plane torsion test are compared in this study. A detailed analysis of the experimental strain distribution measured by digital image correlation is discussed for each test. Finite element simulations are carried out to evaluate the effect of specimen geometries on the stress distributions in the shear zones. The experimental macroscopic flow stress vs. strain behavior shows no significant influence of the specimen geometry when similar strain measurements and evaluation schemes are used. Minor differences in terms of the stress distribution in the shear zone can be detected in the numerical results. This work attempts to give a unique overview and a detailed study of the most commonly used shear tests for sheet metal characterization. It also provides information on the applicability of each test for the observation of the material behavior under shear stress with a view to material modeling for finite element simulations. © 2013 Elsevier Ltd. All rights reserved.
LFT Import::2019-07-29 (1932)
Keywords: Heterogeneity; Sheet metal; Simple shear

An improvement of the time dependent method based on the coefficient of correlation for the determination of the forming limit curve - Merklein, Marion; Kuppert, Andreas; Affronti, Emanuela (Advanced Materials Research, 2014)
Due to the global energy policy according to the aims of economic efficiency and environmental compatibility the production of lightweight constructions is nowadays a need in many fields of mechanical engineering, especially in automotive and aerospace sectors. The substitution of conventional deep drawing steels with modern sheet metals, i.e. aluminium or high strength steel, provides a positive contribution towards this trend. Prerequisite for an efficient application of these resources is a comprehensive material characterization including the analysis of the formability as well as the failure behaviour. Regarding the accurate prediction of forming behaviour, a robust failure criterion is necessary in order to perform the numerical simulation designs by using finite element method (FEM). The leading criterion used for sheet metal forming is the forming limit diagram (FLD). The FLD gives a graphical description of material formability by plotting the major strain values related to the minor strain values to failure in a curve called forming limit curve (FLC). With the improvement of the digital image correlation (DIC) techniques, which provide very accurate strain measurement, new methods relied on the strain history of the specimen during the test are proposed to determine the FLC. Within this paper, the time dependent method based on the coefficient of correlation is investigated. In particular an improvement dependent on experimental parameter is presented in order to increase its sensibility and reliability for different materials.
LFT Import::2019-08-05 (2037)
Keywords: Forming limit curve (FLC); Metal forming; Sheet metal

An incremental analysis of a deep drawing steel’s material behaviour undergoing the predeformation using drawbeads - Schmid, Harald; Suttner, Sebastian; Merklein, Marion (IOP Conf. Series: Journal of Physics: Conf. Series 896 (2017) 011001, 2017)
LFT Import::2019-08-05 (2237)

An innovative approach for the process design for three-roll bending of plain tubular components - Cojutti, Massimo; Vipavc, Daniel; Hagenah, Hinnerk; Merklein, Marion (Proc. 1st Int. Congress on Roll Forming, 2009)
LFT Import::2019-08-05 (134)

An Innovative Process Combination of Additive Manufacturing and Sheet Bulk Metal Forming for Manufacturing a Functional Hybrid Part - Merklein, Marion; Schulte, Robert Karl; Papke, Thomas (Journal of Materials Processing Technology, 2020)
The combination of additive manufacturing (AM) and forming offers new opportunities in part and process chain design. To show the potential of this process combination, a gear component with discrete tooth geometry is manufactured by powder bed fusion of metal using a laser beam (PBF-LB/M) and forming. Such gear components are manufactured conventionally in a process chain of several sheet bulk metal forming operations like orbital forming, deep drawing and upsetting. Orbital forming is used to manufacture a tailored blank to increase form filling in the subsequent forming operations. However, challenges are form filling and control of material flow. These severely affect whether the target geometry can be realized. To overcome these limitations, in this work PBF-LB/M is used to manufacture the tooth geometry close to the target on a flat sheet. Subsequently, the three-dimensional part geometry is realized by forming. The advantage is that the orbital forming step is not necessary. With that, the tooth geometry does not depend on material flow. A further benefit is geometric flexibility of additive manufacturing processes. Hence, diversity of variations can be increased over a wide range without additional cost intensive forming tools for each single part geometry. Besides, the potentials and challenges of the approach are discussed. The investigations include characterization of formability of sheet metal and AM material, metallographic analysis and hardness measurement. A process chain for manufacturing hybrid parts is presented and the final part geometry is evaluated by topography measurement. The major finding is that the tooth geometry manufactured by additive manufacturing and forming is closer to the target than for the conventional process chain. Additionally, a comparison of technological and economic advantages is drawn. Finally, an extension of the approach is presented by hybrid parts with additively manufactured structures on both sides of the sheet metal.<br
Keywords: Forming; Additive manufacturing; Process combination; Hybrid part

An inverse approach to the numerical design of the process sequence of tailored heat treated blanks - Geiger, Manfred; Merklein, Marion; Staud, Detlev; Kaupper, Markus (Production Engineering, 2008)
While in industries lightweight construction gain an increasingly significant role and as weight reduction is often done with aluminum sheets, advanced production technologies have to be developed to be competitive for this evolution. Since steel sheet metal parts cannot be substituted directly with aluminum due to its minor formability, the usage of so called tailored heat treated blanks (THTB) is presented in this work. THTB are locally heat treated aluminum blanks from the 6,000-series alloy which exhibit a specific strength pattern optimized to the forming operation leading to a significantly improved formability for the manufacturing of complex aluminum car body parts. The enhancement of the formability is reached by a local heat treatment before the forming process. Due to the strong interdependency of heat treatment and forming operation, a numerical investigation of the process sequence is a prerequisite for a cost-effective usage of the THTB. An inverse approach on basis of a finite element simulation enables the determination of process parameters for an optimized THTB, thus having an effective and efficient engineering method for this technology. © German Academic Society for Production Engineering (WGP) 2007.
LFT Import::2019-07-29 (204)
Keywords: Aluminum; Production process; Simulation

A non-invasive form finding approach with application to metal forming - Landkammer, Philipp; Schneider, Thomas; Schulte, Robert Karl; Steinmann, Paul; Merklein, Marion (Production Engineering, 2016)
Inverse form finding aims in determining the optimal material configuration of a workpiece for a specific forming process. A gradient- and parameter-free (nodal-based) form finding approach has recently been developed, which can be coupled non-invasively as a black box to arbitrary finite element software. Additionally the algorithm is independent from the constitutive behavior. Consequently, the user has not to struggle with the underlying optimization theory behind. Benchmark tests showed already that the approach works robustly and efficiently. This contribution demonstrates that the optimization algorithm is also applicable to more sophisticated forming processes including orthotropic large strain plasticity, combined hardening and frictional contact. A cup deep drawing process with solid-shell elements and a combined deep drawing and upsetting process to form a functional component with external teeth are investigated.
LFT Import::2019-08-07 (2148)
Keywords: Inverse form finding; Shape optimization; Cup deep drawing; Sheet-bulk Metal Forming

A novel ultrasonic-assisted staking process for mechanical fasteners - Jäckisch, Manuel; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2022)
Increasing material variety in car body engineering causes new challenges regarding the joining processes and therefore, leads to an enhanced usage of mechanical joining technologies. Mechanical fasteners, as self-piercing nuts, can be staked cost-efficiently without a pre-punching operation to create detachable joints. Nevertheless, elevated workpiece strengths lead to high forming forces and a limited application range. One promising approach to reduce tool and workpiece loads in forming operations is superimposing a high-frequency oscillation to the tool movement. The so-called ultrasonic assistance enables an immediate and considerable reduction of the material’s flow stress. This beneficial softening effect has been confirmed for several materials and processes. Since the process management and monitoring are highly affected by the frequency-dependent dynamic behavior of the whole test setup, the application of ultrasonic assistance is already challenging for basic forming operations. Hence, only a few studies have been investigating ultrasonic-assisted joining processes. In particular, joining processes with auxiliary elements have been hardly considered. Within the scope of this work, a novel ultrasonic-assisted staking process for mechanical fasteners is proposed. Therefore, the punch movement for the installation of a self-piercing nut into an aluminum sheet is superimposed with a 20 kHz oscillation of 10 μm, 15 μm, and 20 μm amplitude. Ultrasonic assistance in the initial staking phase, characterized by moderate loads, causes irregular tool–specimen contact. Since the effect is promoted by increasing amplitudes, a correlation with the elastic tool deflection is presumed. Additionally, the transferability of the ultrasonic-based force reduction to mechanical joining with auxiliary element is confirmed and a beneficial influence on the joint formation is identified. Thus, ultrasonic assistance is proven as a promising approach for the extension of existing process limits.<br
Keywords: ultrasonic; joining; aluminum; measurement

Anwendungsorientiertes Laserstrahlumformen - Merklein, Marion; Hennige, Thomas (Idee-Vision-Innovation, 2001)
LFT Import::2019-07-15 (897)

Applicability of blasted blanks for adaption of tribological conditions in sheet-bulk metal forming - Löffler, Maria; Andreas, Kolja; Engel, Ulf; Merklein, Marion (Procedia CIRP, 2016)
LFT Import::2019-07-29 (2159)
Keywords: Sheet-bulk metal forming; Surface modification; Tribology

Applicability of Solid Lubricant Coatings in Cold Rod Extrusion of Stainless Steels - Jobst, Andreas; Merklein, Marion (Defect and Diffusion Forum, 2020)
Cold extrusion is an established technology for the production of dimensionally accurate components in large series. Due to the high material and energy efficiency, a resource-saving manufacturing of high-performance parts is possible. Forming at room temperature leads to an advantageous grain structure and work hardening of the material, resulting in components with favorable operating characteristics. Nevertheless, a challenge is the generation of residual stresses during forming, which are influencing the fatigue behavior. The modification of the tribological conditions is one method for influencing the parts’ residual stress state. However, the high strength and work hardening of the materials formed at room temperature leads to high tribological loads between billet and die. These challenges are intensified by the increasing use of stainless steels due to growing demands for corrosion resistant components. The aim followed within this paper is therefore to investigate the applicability of typical lubricant coatings in the forward rod extrusion of stainless steels. For this purpose, the ferritic stainless steel X6Cr17 (DIN 1.4016) and the ferritic-austenitic stainless steel X2CrNiMoN22-5-3 (DIN 1.4462) are extruded with an equivalent plastic strain of ε̅ ≈ 1. The research is performed with a molybdenum disulfide (MoS2), a soap and a polymer-based lubricant coating. For reproducing different contact conditions, the die geometry is varied with die opening angles of 60°, 90° and 120°. The suitability of the lubricants is evaluated using the integrity of the lubricant coating after forming. From the correlations between process forces, temperatures and surface integrity, recommendations for the application of the researched lubricants are derived.

Application based PVD-coatings for cold forging tools - Schrader, Tobias; Merklein, Marion; Engel, Ulf (Proc. 6th Int. Conf. and Exhibition on Design and Production of Machines and Dies / Molds, 2011)
LFT Import::2019-08-05 (1637)

Application of cemented carbide based forming tools in cold forging - Andreas, Kolja; Noneder, Johannes; Engel, Ulf; Merklein, Marion (Proc. 10th Int. Conf. THE "A" Coatings in Manufacturing Engineering, 2013)
LFT Import::2019-08-05 (1863)

Application of Process adapted semi-finished Parts for the Production of Thin-walled Components via Sheet-Bulk Forming - Merklein, Marion; Hildenbrand, Philipp; Schneider, Thomas (AutoMetForm / SFU 2014, 2014)
LFT Import::2019-08-05 (2038)

Application of Tailored Heat Treated Blanks under quasi series conditions - Merklein, Marion; Vogt, Uwe (Proceedings of the 12th International Conference on Sheet Metal (SheMet), 2007)
Tailored Heat Treated Blanks (THTB) are blanks that exhibit locally different strength specifically optimized for the succeeding forming process. The strength distribution is set by a local, short-term heat treatment modifying the mechanical properties of the material. Hence, THTB allow enhancing forming limits significantly leading to shorter and more robust manufacture process chains. In order to qualify the use of THTB under quasi series conditions, the interdependencies of the blank's local heat treatment and the entire process chain of the car body manufacture have to be analyzed. In this respect, the impact of a short-term heat treatment on the mechanical properties of AA6181PX, a commonly used aluminum alloy in today's car bodies, was studied. Also the influence of a short-term heat treatment on the coil lubricant, usually already applied by the material supplier, was given a closer look. Based on these experiments process restrictions for the application of THTB in an industrial automotive environment were derived and a process window for the THTB design was set up. In conclusion, strategies were defined how to enhance the found process boundaries leading to a more robust process window.
LFT Import::2019-08-05 (1388)
Keywords: AA6181PX; Coil lubricant; Process window; Tailored heat treated blanks

Application of Tailor Heat Treated Blanks technology in a joining by forming process - Graser, Matthias; Wiesenmayer, Sebastian; Müller, Martin; Merklein, Marion (Journal of Materials Processing Technology, 2019)
The usage of modern materials in the automotive industry for the body in white construction leads to increasing requirements for the manufacturing process. Due to the limited formability of high-strength aluminium alloys and steels, joining by forming of these dissimilar materials is still a big challenge, which requires suitable and innovative manufacturing technologies. In sheet forming processes the Tailor Heat Treated Blank (THTB) technology allows enhancing the formability of high-strength aluminium alloys. Therefore, the applicability of the THTB technology for the shear-clinching technology is investigated in this paper. Up till now, this innovative joining by forming technology is only qualified to join ductile aluminium alloys and high-strength steels, but the combination of high-strength aluminium and high-strength steel has not been realized yet. In this research work, the limits of the shear-clinching process have been extended to successfully join the material combinations of AA7075 on the punch side and HCT780X, as well as press hardened 22MnB5 on the die side by using aluminium specimens with different heat treatment layouts. Further, this paper shows the possibility to adjust the material flow of the shear-clinching process by local and short-term heat treatment.
CRIS-Team WoS Importer:2019-02-21

Application of the Finite element methods on the staking process of staking fasteners - Tofall, Miriam; Merklein, Marion; Plettke, Raoul (Key Engineering Materials, 2011)
The increasing use of new materials with varying thicknesses within the automotive industry creates high demands on joining elements such as staking fasteners. Simultaneously statements about the feasibility of the design with joining elements already in the early stage of the development are necessary. The challenge is to define suitable element geometry, tool geometry and process parameters. To meet those requirements, a good understanding of the staking process is inevitable. According to the state of the art the examinations regarding the performance of staking fasteners under different conditions are totally conducted experimentally. This trial-and-error procedure leads to an extensive financial effort and to long development times for new elements. It is furthermore not possible to observe all influences of different process parameters. In the field of mechanical engineering the use of numerical simulation for complex constructions is a common technique. This paper deals with the applicability of the finite element method (FEM) on the joining of sheet metals with staking fasteners. In this matter the FEM is used to get scientific insights in the staking process and is also used to identify influencing variables and their interactions. © (2011) Trans Tech Publications.
LFT Import::2019-07-29 (1645)
Keywords: FEM; Mechanical joining; Self-piercing fastener

Approach for a sustainable process chain in manufacturing of fasteners for mechanical joining - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Materials Research Proceedings, 2023)

A Review on Tailored Blanks - Production, Applications and Evaluation - Merklein, Marion; Johannes, Maren; Lechner, Michael; Kuppert, Andreas (Journal of Materials Processing Technology, 2014)
Tailored Blanks is the collective for semi-finished sheet products which are characterised by a local variation of the sheet thickness, sheet material, coating or material properties. With these adaptions the tailored blanks are optimised for a subsequent forming process or the final application. In principle four different approaches can be distinguished to realise tailored blanks: joining materials with different grade, thickness or coating by a welding process (tailor welded blanks), locally reinforcing the blank by adding a second blank (Patchwork blanks), creating a continuous variation of the sheet thickness via a rolling process (tailor rolled blanks) and adapting the material properties by a local heat treatment (tailor heat treated blanks). The major advantage of products made from tailored blanks in comparison to conventional products is a weight reduction. This paper covers the state of the art in scientific research concerning tailored blanks. The review presents the potentials of the technology and chances for further scientific investigations. © 2013 Elsevier B.V.
LFT Import::2019-07-29 (1911)
Keywords: Forming; Patchwork blanks; Tailor heat treated blanks; Tailor rolled blanks; Tailor welded blanks; Tailored blanks

A ROUND ROBIN STUDY FOR LASER BEAM MELTING IN METAL POWDER BED - Ahuja, Bhrigu; Schaub, Adam; Junker, Daniel; Karg, Michael; Tenner, Felix; Plettke, Raoul; Merklein, Marion; Schmidt, Michael (South African Journal of Industrial Engineering, 2016)
With its ability to fabricate fully dense 3-dimensional structures by selectively melting micro-sized metal powder, the Additive Manufacturing process of Laser Beam Melting (LBM) is being considered by many as a significant complimentary technology to the conventional forming and subtractive manufacturing processes. Even with its industrial acceptance, the LBM process still lacks a high degree of repeatability for the quality of the fabricated structures. This issue is often related to the variation in system technology, process or user influence. In order to fully understand the potential and limitations of the LBM process, the presented paper discusses the design, methodology and results of a round robin test conducted within the Collaborative Working Group (CWG) Lasers in Production at the International Academy of Production Engineering (CIRP). Observed mechanical characteristics for samples from each of the participant are presented. The experiments are designed to obtain data related to mechanical characteristics for different build orientations and processing conditions in addition to the inherent system technology variations. The paper further discusses the observed process phenomena and their association to the induced mechanical characteristics.
Keywords: Additive Manufacturing; Laser Beam Melting; Stainless Steel 15-5 PH; Round Robin; CIRP

A round robin study for Laser Beam Melting in Metal Powder Bed: Comparing mechanical characteristics with system technology variation - Ahuja, B.; Schaub, Adam; Junker, Daniel; Karg, M.; Tenner, F.; Plettke, Raoul; Merklein, Marion; Schmidt, M. (Proc. 15th Annual Conference of RAPDASA 2014, 2014)
LFT Import::2019-08-05 (2095)

A Round Robin study for Selective Laser Sintering of polyamide 12: Microstructural origin of the mechanical properties - Stichel, Thomas; Frick, Thomas; Laumer, Tobias; Tenner, Felix; Hausotte, Tino; Merklein, Marion; Schmidt, Michael (Optics and Laser Technology, 2017)
The mechanical and microstructural investigation of polymer parts (polyamide 12) fabricated by Selective Laser Sintering as part of a Round Robin initiative is presented. The paper focuses on the microstructural analysis of the Round Robin samples and their evaluation regarding their effect on mechanical properties with respect to each other. Therefore optical microscopy on microtomed samples, X-ray computed tomography and Differential Scanning Calorimetry is used to determine the morphology of residual particle cores and of internal pores.The mechanical tensile testing revealed a high variability of the ductility of the samples among the used machines and a distinctive anisotropic mechanical response. Especially the quite brittle characteristic along the building direction has shown to be still a crucial challenge for the process. However, one machine delivered samples with outstanding ductility with total elongation values of about 21% along the building direction and of about 32% planar to the layer. This result was back traced to a distinctive pore and residual particle morphology which is characterized by low pore concentration, the absence of coplanar pore or residual particle arrangements and the highest degree of particle melting measured. Furthermore, the analysis depicts that both features, pores and residual particles, contribute to the mechanical properties significantly and that they are not necessarily linked since they can vary independently in a certain range depending on the machine configuration.
Keywords: Additive manufacturing; Polymers; Polyamide-12; Selective Laser Sintering; Round Robin

A Round Robin study for selective laser sintering of polymers: Back tracing of the pore morphology to the process parameters - Stichel, Thomas; Frick, Thomas; Laumer, Tobias; Tenner, Felix; Hausotte, Tino; Merklein, Marion; Schmidt, Michael (Journal of Materials Processing Technology, 2018)
The mechanical properties of polymer parts built by Selective Laser Sintering are strongly related to the internal microstructure which differs with the applied production parameters. The paper focuses on the back tracing of the pore morphology of laser sintered polyamide-12 samples to the process parameters. Therefore, a data base is used which is supplied by a Round Robin initiative and includes mechanical tensile tests and the microstructural analysis of the pore morphology of several different sample charges built with different machines. The pore morphologies (porosity, pore density, pore shape and pore arrangement) measured by X-ray computed tomography are compared and discussed regarding the employed parameters and the resulting mechanical properties.The investigations point out that pore density is a superior indicator than porosity for mechanical issues. This is especially valid along the build direction since pore morphology has shown to be strongly anisotropic. Moreover, the analysis revealed that pore density is strongly affected by the process temperature, which is proved to be essential for the fabrication of mechanical robust parts using Selective Laser Sintering.
Keywords: Additive manufacturing; Polymers; Polyamide-12; Selective laser sintering; Round Robin; Porosity; Pore density; X-ray computed tomography

Assessment of springback behaviour of 800-1200 mpa dual-phase steel grades - Durmaz, Ulas; Heibel, Sebastian; Schweiker, Thomas; Merklein, Marion (Key Engineering Materials, 2021)
Springback occurs in sheet metal forming due to elastic strain recovery after removal of process forces respectively after opening of the tool. For this reason, a precise description of springback requires the elastic stress-strain relationship described by the Young’s modulus as well as the internal stress distribution of the part before unloading. In this context, the Bauschinger effect influences the stress state before springback due to premature plastification during load reversal or load path change. As is well known, the stress-strain curve of a material during unloading is nonlinear because of additional microplastic strain, which is reflected in a decrease of the Young’s modulus. The aim of this work is to characterize the aforementioned phenomena and their effect on springback for three dual-phase steels namely DH800, DH1000 and DP1200LY. For this purpose, cyclic tensile-compression tests as well as loading and unloading loops within uniaxial tensile tests are performed at different plastic strains. To evaluate the springback behaviour of the investigated materials, two different hat-profiles geometries are investigated. By comparing the springback of dual-phase steels on part level, the significance of different material influences with regard to springback is evaluated. The results show that the investigated dual-phase steels exhibit a pronounced Bauschinger effect and a considerable amount of microplastic strain with increasing total strain. However, the comparison between the springback of the hat-profiles and the determined material parameters proves a significant influence of the elastic strain on springback, while microplastic strain and the Bauschinger effect have a minor influence.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Cold forming; Dual-phase steels; Springback

Augmented Reality for Forming Technology - Visualisation of Simulation Results and Component Measurement - Lechner, Michael; Schulte, Robert Karl; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2019)
In sheet and bulk forming, numerical simulation has become established over the last 20 years as an indispensable tool for research and industrial practice. The numerical calculation of forming processes supports a time- and cost-efficient development in the context of a virtual product evaluation. Currently, simulation and measurement results are mainly displayed on conventional screens. However, this approach has several disadvantages. On the one hand, only cut-outs can be displayed, especially in the case of large components. A visualisation of entire components in real size is often not possible. On the other hand, no direct comparison with the real components is possible. Augmented Reality is a promising approach to solve the challenges outlined above. As part of the contribution, an innovative approach for component validation based on Augmented Reality technology will be introduced. Thereby, the visualisation using different Augmented Reality devices and the feasibility of a measurement task with Augmented Reality devices will be presented.
CRIS-Team Scopus Importer:2020-02-21

Augmented Reality Technology for the Purpose of Sheet Metal Forming Simulation Evaluation - Lechner, Michael; Schulte, Robert Karl; Meckler, S.; Merklein, Marion (10th Forming Technology Forum 2017 - Model Based Control for Smart Forming Processes, 2017)
LFT Import::2019-08-05 (2276)

A unified model for isothermal and non-isothermal phase transformation in hot stamping of 22MnB5 steel - Hart-Rawung, Thawin; Buhl, Johannes; Horn, Alexander; Bambach, Markus; Merklein, Marion (Journal of Materials Processing Technology, 2023)
The hot stamping of tailored properties is widely established in the automotive industry. However, unlike conventional press hardening, this technique is designed to generate varying mechanical properties by controlling the cooling rate locally. Current material models cannot accurately represent the locally very different thermomechanical paths. This research aims to address this problem by developing a new phase transformation model capable of handling complicated thermal histories and the effects of deformation. A ’unified JMAK‘ model is proposed to capture various thermal-mechanical loading conditions. These conditions include the deformation effect and cooling paths where isothermal conditions range from 450° to 725°C and non-isothermal conditions range from 5° to 40°C/s. Furthermore, for the extension to linear and non-linear cooling paths, correction factors for the phase transformations are introduced into the model. Finally, the model's performance is compared to well-known transformation models, such as the non-isothermal JMAK and the K-V (Kirkaldy and Venugopalan), by comparing the results obtained from isothermal and non-isothermal dilatometer tests and a scaled-down b-pillar experiment. The results from the comparison are classified into 3 cases, isothermal, continuous cooling and non-linear cooling (b-pillar). Case 1 shows that the non-isothermal and K-V models provide low accuracy, while the proposed model yields an error below 2 %. For Case 2, the proposed models and non-iso JMAK are agreeable with the experiment, and the K-V model shows a maximum error of 15 %. Finally, in the b-pillar case study mean absolute errors of hardness predictions are 33.06 HV (mean relative error is 9 %), 43.92 HV (13 %), and 67.70 HV (20 %) for the unified JMAK, non-iso JMAK, and K-V model, respectively.
CRIS-Team Scopus Importer:2023-02-03
Keywords: 22MnB5; Austenite decomposition model; Hot stamping process; Johnson-Mehl-Avrami-Kolmogorov

Ausgewählte Einflussgrößen auf die erzielbaren Verzahnungstoleranzen beim Kaltfließpressen. - Rohrmoser, Andreas; Heling, Björn; Schleich, Benjamin; Hagenah, Hinnerk; Merklein, Marion (Summer School Toleranzmanagement - Beiträge zur 4. Summer School - September 2020, 2020)

Auswirkungen spezifischer Abkühlbedingungen auf den Wärmeübergang bei Presshärtprozessen - Svec, Thomas; Merklein, Marion (5. Erlanger Workshop Warmblechumformung, 2010)
LFT Import::2019-08-05 (769)

Basic experimental and numerical investigations on chip pressing - Grüner, Martin; Merklein, Marion (Key Engineering Materials, 2013)
Aluminium alloys show a great potential for lightweight constructions due to their high strength and low density but the production of this material is very energy consuming. Also the recycling of aluminium alloys, e.g. chips from the milling process, shows different challenges. Beside contamination by cooling lubricant and oxidation of the surface of the chips the melting and rolling process for new semi finish products needs a high amount of energy. TEKKAYA shows a new approach for recycling of aluminium alloy chips by an extrusion process at elevated temperatures producing different kinds of profiles. A new idea is the production of components directly out of chips using severe plastic deformation for joining of the chips similar to the accumulative roll bonding process in sheet metal forming. In a first approach aluminium alloy chips out of a milling process were uniaxial compressed with different loads inside an axisymmetric tool installed in a universal testing machine. The compressed chip disks subsequently were tested with two experiments to gain information on their stability. First experiment is a disk compression test with the disk standing on its cylindrical surface, giving information on the stability perpendicular to the compression direction. Second experiment is a stacked disk compression test with three disks to investigate the stability parallel to compression direction. During all three tests force and displacement values are recorded by the universal testing machine. These data are also processed to calculate or identify input parameters for the numerical investigations. For numerical simulation ABAQUS in conjunction with the Drucker-Prager-Cap material model, which is often used for sintering processes, seems to be a good choice. By numerical simulation of the experiments and comparison with the experiments input parameters for the material model can be identified showing good accordance. This material model will be used in future numerical investigations of an extrusion process to identify tool geometries leading to high strains inside the material and by this to an increased stability of the parts. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1890)
Keywords: Aluminum alloys; Chip pressing; Drucker-prager-cap; Recycling

Basic Investigations of Non-Pre-Punched Joining by Forming of Aluminium Alloy and High Strength Steel with Shear-Clinching Technology - Merklein, Marion; Meschut, Gerson; Müller, Martin; Hoerhold, Rejane (Key Engineering Materials, 2014)
LFT Import::2019-07-29 (2017)
Keywords: Clinching; FEM; Joining by forming; Lightweight design; Multi-material mix

Basic investigations on boundary lubrication in metla forming processes by in situ observation of the real contact area - Weidel, Stephan; Engel, Ulf; Merklein, Marion; Geiger, Manfred (Production Engineering, 2009)
LFT Import::2019-07-29 (1576)

Basic investigations on hot sheet metal forming of quenchable high strength steels - Geiger, Manfred; Merklein, Marion; Lechler, Jürgen; Bach, F.W.; Springer, R.; Kleiner, M.; Tekkaya, A.E.; Homberg, W.; Brosius, A.; Karbasian, H.; et al. (2nd International Conference on New Forming Technology, 2007)
LFT Import::2019-08-05 (1460)

Basic Investigations on Hot Stamping of Tailor Welded Blanks Regarding the Manufacturing of Lightweight Components with Functionally Optimized Mechanical Properties - Lechler, Jürgen; Stöhr, Thomas; Kuppert, Andreas; Merklein, Marion (Transactions of the North American Manufacturing Research Institute of SME, 2010)
The combination of two innovative technologies, the application of tailored products on the one hand and hot sheet metal forming on the other, allows to achieve final component properties, that could not be realized so far. Within this work major research activities are described concerning material engineering, which have been carried out within the scope of component and process development of hot stamping of tailor welded blanks (TWB). This includes basic analyses related to the selection of an appropriate steel grade. For the finally selected and with an aluminum-silicon layer pre-coated steel grade HX340 LAD+AS150 investigations have been performed to determine the thermo-mechanical properties of the material subject to the most important process parameters during hot stamping. In addition special emphasis is placed on the description of the weld seam properties and the forming and failure behavior of hot stamping TWBs under process relevant conditions.
LFT Import::2019-07-29 (1161)
Keywords: 22MnB5; Hot stamping; HX340 LAD+AS150; Mechanical properties; Tailor welded blanks

Basic investigations on the hot stamping steel 22MnB5 - Geiger, Manfred; Merklein, Marion; Hoff, Cornelia (Sheet Metal 2005, Proceedings of the 11th International Conference on Sheet Metal, 2005)
Basic research concerning the material properties of the hot stamping steel 22MnB5 has been carried out. A survey is given about the as-delivered conditions with hardness tests, micrographs and flow curves. The process window of the austenitization time, before hot stamping can take place, is defined by austenitization tests. Also a new experimental set-up to detect the cooling rate in dependency on the contact pressure is presented. In addition to that the cooling experiments were simulated with ABAQUS and the heat transfer coefficient for each contact pressure is determined by inverse modeling.
LFT Import::2019-08-05 (1130)
Keywords: Heat treatment; Hot stamping; Sheet metal

Basic numerical analysis of a “Samanta” based forward extrusion process - Kiener, Christoph; Andreas, Kolja; Merklein, Marion (Advanced Materials Research, 2016)
LFT Import::2019-07-29 (2181)

Basics for inline measurement of tribological conditions in series production of car body parts - Hansen, B.; Hoebler, M.; Purr, S.; Meinhardt, J.; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2019)
The quality of car body parts in series production is strongly dependent on the tribological behavior. Fluctuating material properties such as the sheet roughness and the amount of lubricant have an influence on the forming process. On the basis of large amounts of data it is possible to investigate the friction behavior in series production and to make process adjustments if required. Therefore, inline measurement systems have a great potential to detect the sheet roughness during the cutting process of blanks in the coil line. Furthermore, contactless systems are advantageous as they do not damage the surface. Nevertheless, the optical measuring is influenced by the lubricant layer on top of the surface. Therefore, the previously unknown impact of the lubricant on the measuring result is investigated. Within this study, stationary optical roughness measurements have been conducted using different amounts of lubricant on hot-dip galvanized EDT steel. The results demonstrate the influence of different amounts of lubricant on the sheet roughness measurement. Hence, it is possible to correct the inline measuring results and gain knowledge of fluctuating surface roughness. In addition, strip drawing test has been carried out to investigate the effect of fluctuating tribological conditions.
CRIS-Team Scopus Importer:2020-02-21

Bendability of advanced high strength steels - A new evaluation procedure - Kaupper, Markus; Merklein, Marion (CIRP ANNALS - Manufacturing Technology, 2013)
The significant lightweight engineering potential of advanced high strength steels (AHSS) is limited by its moderate formability and altered failure behavior compared to mild steel grades. Especially bendability is crucial in automotive applications. The failure phenomena and underlying damage mechanisms in small curvature bending of AHSS are revealed in this work. A new characterization approach based on optical strain measurement is presented to comprehensively identify the failure stages, critical strains and bending angles in a user-independent manner. The novel approach is generalized and broadly applicable. Thus it gives a prerequisite for improved and material specific industrial process design in future. © 2013 CIRP.
LFT Import::2019-08-05 (1891)
Keywords: Bending; Forming; High strength steel

Bending behavior of a hot stamped complex phase steel with tailored properties by local carburization - Horn, Alexander; Merklein, Marion (IOP Conference Series: Materials Science and Engineering 1157, 2021)
CRIS-Team WoS Importer:2021-11-05

Bending of high-strength low-alloyed steel with respect to edge crack sensitivity caused by shearing operations - Tsoupis, Ioannis; Hildering, Sven; Merklein, Marion (Procedia Engineering, 2014)
LFT Import::2019-07-29 (2036)
Keywords: Bending; Blanking; Fracture analysis

Berücksichtigung funktionsrelevanter Gestaltabweichungen bei der Auslegung von Umformprozessen zur Herstellung von Stirnrädern mit Sonderverzahung durch Fließpressen - Rohrmoser, Andreas; Hagenah, Hinnerk; Merklein, Marion (Industriekolloquium der Forschungsgruppe FOR 2271, 2019)
LFT Import::2019-08-05 (2355)

Berücksichtigung von produktionsspezifischen Abweichungen im interdisziplinären Toleranzmanagement - Heling, Björn; Oberleiter, Thomas; Rohrmoser, Andreas; Kiener, Christoph; Schleich, Benjamin; Hagenah, Hinnerk; Merklein, Marion; Willner, Kai; Wartzack, Sandro (Industriekolloquium der Forschergruppe FOR 2271, 2019)
LFT Import::2019-08-05 (2353)

Beschichtungssysteme auf AlCrN-Basis für das Presshärten - thermische Kennwertermittlung für Werkzeug und Werkstoff - Wieland, Michael; Merklein, Marion (4. Erlanger Workshop Warmblechumformung, 2009)
LFT Import::2019-08-05 (308)

Beschreibung des mechanischen Werkstoffverhaltens beim Warmumformen höchstfester Stähle - Stöhr, Thomas; Merklein, Marion (Tagungsband 5. Erlanger Workshop Warmblechumformung, 2010)
LFT Import::2019-08-05 (744)

Beschreibung des mechanischen Werkstoffverhaltens beim Warumumformen höchstfester Vergütungsstähle - Geiger, Manfred; Merklein, Marion; Lechler, Jürgen (1. Erlanger Workshop Warmblechumformung, Tagungsband zum Berichts- und Industriekolloquium der FOR552, Erlangen, 7. November 2006, 2006)
LFT Import::2019-08-05 (1340)

Blank hydroforming using granular material as medium - investigations on leakage - Grüner, Martin; Gnibl, Tobias; Merklein, Marion (Procedia Engineering, 2014)
LFT Import::2019-07-29 (2032)
Keywords: Granular material; Hydroforming; Leakage

Blechmassivumformung - Stand der Technik und Ausblick - Merklein, Marion; Hagenah, Hinnerk; Schneider, Thomas (2. Workshop Blechmassivumformung, 2013)
LFT Import::2019-08-05 (1925)

Blechmassivumformung – vom Halbzeug zum Funktionsbauteil - Merklein, Marion; Schneider, Thomas; Gröbel, Daniel; Nürnberger, F. (21. Umformtechnisches Kolloquium Hannover, Industrie und Wissenschaft – Gemeinsam die Zukunft gestalten, 2014)
LFT Import::2019-08-05 (2010)

Blockchain for forming technology - Tamper-proof exchange of production data - Frey, Philipp; Lechner, Michael; Bauer, T.; Shubina, Tatyana; Yassin, Antonia; Wituschek, Simon; Virkus, Maximilian; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2019)
An increasingly connected production in the sense of Industry 4.0 allows completely new possibilities in regard to improved and more efficient production and higher product quality. But a key factor to Industry 4.0 is a consistent data flow along the production chain. However, the exchange of data, especially between companies, still is a major obstacle to overcome in order to achieve the aforementioned advantages. Currently, there are increasing efforts to record and analyse data. But there is a lack of a holistic system to handle data, therefore commonly company databases or other inefficient methods are used. These solutions are limited with regard to data exchange since the ownership of data cannot be proven, production data has no unforgeable timestamp, which in turn hinders the generation of complete production history from the final product (e.g., car door) back to the semi-finished product (e.g., steel sheet). As a result, there is insufficient to no data exchange along the production chain. In order to solve these problems blockchain is a promising approach. At the Institute of Manufacturing Technology, an operational blockchain system was developed and implemented using standard production machines. With the combination of a quarto rolling mill and a 400t - press, representing the sheet metal supplier and a forming company, respectively, the typical process chain of sheet metal processing is represented, which allows the detailed investigation of the established blockchain in this field of application. Within this contribution, the conceptual approach of a blockchain system for forming technology will be presented. The nature and the classification of occurring data throughout the production chain will be addressed.
CRIS-Team Scopus Importer:2020-02-21

Blockchain in sheet metal processing. - Lechner, Michael; Christ, T.; Frey, Philipp; Wituschek, Simon; Arzhanov, A.; Petrov, F.; Merklein, Marion (wt Werkstattstechnik - Online, 2020)
The ability to both track physical products and to gather a production data record are important elements of modern manufacturing processes and crucial requirements for an end-to-end digital production. This work presents a solution for both challenges based on the combination of two systems: While a blockchain-based data exchange platform ensures that the requirements towards networked processes are met, an optical technology for marker-free identification of component parts is used.
CRIS-Team Scopus Importer:2021-04-19

Blockchain-Systeme für den manipulationssicheren Datenaustausch in der industriellen Fertigung: Distributed Ledgers für den Materialdatenaustausch - Lechner, Michael; Frey, Philipp; Kreß, Maximilian; Christ, T.; Charlet, C.; Merklein, Marion (wt Werkstattstechnik - Online, 2021)
Modern industrial manufacturing processes have to meet ever-increasing requirements in terms of material and resource efficiency, quality and product variety. The cross-company consolidation of integrity-secured data is a prerequisite for the retrospective identification of quality problems, the documentation of compliance with standards and the allocation of resource consumption along the value chain. This paper uses the example of a material characterization process for hybrid lightweight construction processes to discuss how blockchain technology can be used to implement a tamper-proof storage concept.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Digitalisierung; Industrie 4.0; Werkstoffe

Bulk forming of sheet metal - Merklein, Marion; Allwood, Julian; Behrens, Bernd-Arno; Brosius, Alexander; Hagenah, Hinnerk; Kuzman, Karl; Mori, Ken-ichiro; Tekkaya, A. Erman; Weckenmann, Albert (CIRP Annals - Manufacturing Technology, 2012)
Ever increasing demands on functional integration of high strength light weight products leads to the development of a new class of manufacturing processes. The application of bulk forming processes to sheet or plate semi-finished products, sometimes in combination with conventional sheet forming processes creates new products with the requested properties. The paper defines this new class of sheet-bulk metal forming processes, gives an overview of the existing processes belonging to this class, highlights the tooling aspects as well as the resulting product properties and presents a short summary of the relevant work that has been done towards modeling and simulation. © 2012 CIRP.
UnivIS-Import:2015-03-09:Pub.2012.tech.FT.FT-QMFMT.bulkfo
Keywords: Forming; Processes; Sheet-bulk

Bulk Metal Forming of Additively Manufactured Elements - Papke, Thomas; Junker, Daniel; Schmidt, Michael; Kolb, Tobias; Merklein, Marion (190, 2018)
Current trends in the industry go towards individualised parts in high volume production. Facing the high amount of different parts, efficient processes with a high flexibility are necessary. Within this context, laser-based additive manufacturing of metal parts become more important. These processes enable the production of individual geometries using a variety of metal materials. However, main challenges of this technology are rough surfaces, limited geometric precision and varying material properties. Therefore machining after the additive manufacturing process is a common approach for improving surface quality and geometric accuracy. However, the machining process affects the grain structure at the edges of the part. Using forming instead leads to a deformation of the grains but does not create new interfaces. Furthermore, the material properties can be improved due to work hardening and fibre flow. Within this work, a bulk metal forming process of an additively manufactured element of stainless steel 316L will be analysed. The aim of the investigation is a fundamental understanding of the forming behaviour and the material flow of an additively built metal part compared to the conventionally manufactured material. Therefore mechanical properties of both materials will be identified by upsetting tests. Additionally, fibre flow and Vickers hardness before and after the forming operation are analysed. It is detected that the forming behaviour of the additively manufactured material is strongly influenced by the layer-wise building process.<br

Bulk Microforming from Sheet Metal—A Promising Approach for the Mass Production of Cold-Formed Metallic Micro Parts - Kraus, Martin; Merklein, Marion (Minerals, Metals and Materials Series, 2021)
Every year billions of micro parts are produced. In mass production, cold bulk forming offers considerable technological, economical, and ecological potentials compared to alternative production methods. Due to the occurrence of scale effects, high tool stresses, and handling problems, cold bulk forming is not used for the mass production of multi-stage formed metallic micro parts. Within this paper, multi-stage bulk microforming from sheet metal is investigated on the laboratory scale with the material Cu-OFE. Throughout this process, the sheet metal strip serves both as a semi-finished product and as a handling aid. In the first forming stage, a pin is extruded from sheet metal, which is then extruded in a cup during the second stage. For the identification of size effects and the evaluation of such effects on the part quality, the tests are carried out on macro- and micro-scale. In the first step, the process-influencing variable of the blank holder pressure is investigated in the first forming stage in order to derive measures for the highest possible material utilization. The two-stage forming of the pin with cup is compared with a single-stage process to assess the part quality and material utilization depending on the process strategy. Using the correct geometric scaling, size effects are identified and their effects on the forming process are evaluated. The experimental results reveal that it is possible to fabricate micro parts with a diameter of 470 µm and a minimum wall thickness of 36 µm reproducible by using the presented cold bulk microforming process strategy.
CRIS-Team Scopus Importer:2021-09-03
Keywords: Bulk microforming; Material flow; Metallic micro parts; Pin extrusion; Sheet metal; Size effects

Bulk Microforming from Sheet Metal—A Promising Approach for the Mass Production of Cold-Formed Metallic Micro Parts - Kraus, Martin; Merklein, Marion (Proceedings of the 13th International Conference on the Technology of Plasticity, 2021)

Carburization behavior at elevated temperatures and mechanical properties of a hot stamped complex phase steel - Risse, Jan Henning; Sippel, Frank; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2023)
As a lightweight construction strategy, hot stamped parts of ultra-high-strength steels with tailored properties are increasingly used for crash relevant components in car bodies, e.g., as B-pillars. With the process of tailored carburization, parts can be reinforced locally without increasing the sheet metal thickness. Thus, this process has the potential to be applied to lightweight components for no deformation zones, e.g., in the battery housings. Standardly, carburization is performed at 950 °C, with the highest strengths achieved at long times of up to 6 h, which prolongs the total process time. By raising the temperature, the carbon diffusion increases, which enables a reduced heat treatment time and, consequently, a shorter process time. Therefore, the objective of this study is to investigate the influence of elevated carburization temperatures on the mechanical properties of a carburized and hardened complex phase steel, CP-W® 800. A single carburization step at the enhanced temperatures leads to an embrittlement of the samples. Hence, an additional diffusion-annealing step is implemented to homogenize the carbon content, without enlarging the total heat treatment time. Depending on the time allocation of carburization and diffusion, the application of the diffusion annealing step results in higher strengths and ductility compared to only carburized samples.

Characterisation of kinematic hardening and yield surface evolution from uniaxial to biaxial tension with continuous strain path change - Merklein, Marion; Suttner, Sebastian; Brosius, Alexander (CIRP Annals - Manufacturing Technology, 2014)
With respect to multistage forming processes the material behaviour and the history of the strain path during the process is of special interest for the improvement of the numerical prediction of forming processes. While different researchers investigated the Bauschinger effect during a load reversal and biaxial loading with pre-strained specimens, in this paper the yield locus evolution in the first quadrant of the principles stress space under biaxial loading of a modified cruciform specimen without test interruption is presented. The movement of the yield surface centre caused by kinematic hardening is approximated by an alternative approach based on experimental results. © 2014 CIRP.
LFT Import::2019-07-29 (2026)
Keywords: Kinematic hardening; Sheet metal; Stress

Characterisation of mechanical properties of laser welded tailored and patchwork blanks - Lamprecht, Klaus; Merklein, Marion (Proceedings of the 4th International Conference on Laser Assisted Net Shape Engineering, 2004)
LFT Import::2019-07-16 (1061)

Characterisation of new lubrication systems for hot forming of high strength aluminum alloys - Rigas, Nikolaos; Degner, Julia; Berendt, E.; Junker, F.; Merklein, Marion (OP Conference Series, Materials Science and Engineering, 2019)
LFT Import::2019-08-05 (2381)

Characterisation of strain rate dependency of sheet metals under biaxial loading with a strain rate controlled hydraulic bulge test - Lenzen, Matthias; Suttner, Sebastian; Merklein, Marion (7. WGP-Jahreskongress Aachen, 5.-6. Oktober 2017, 2017)
LFT Import::2019-08-05 (2247)

Characterisation of the flow behavior of deep drawing steel grades in dependency of the stress state and its impact on FEA - Merklein, Marion; Sturm, Vera (International Journal of Material Forming, 2009)
In numerical simulation the flow behavior of the material is described by the flow curve under uniaxial stress condition. As within the tensile test experimental values can only be determined up to low strains, further experiments are applied in order to obtain higher strains. The alternative experiments are generally carried out under different stress conditions in comparison to the stress condition of the tensile test. Within this paper the differences in flow behavior under the respective stress conditions are figured out. Apart from the optical strain analysis of the tensile test after the onset of necking, the bulge test and the layer compression test are applied. Furthermore the work hardening of materials under different test conditions is compared. © Springer/ESAFORM 2009.
LFT Import::2019-07-29 (310)
Keywords: Deep drawing steel grades; Flow behavior; Stress condition

Characterisation of the flow properties of the quenchable ultra high strength steel 22MnB5 - Merklein, Marion; Lechler, Jürgen; Geiger, Manfred (Annals of the CIRP, 2006)
LFT Import::2019-08-05 (1268)

Characterisation of the Tensile Bonding Strength of Ti-6Al-4V Hybrid Parts Made by Sheet Metal Forming and Laser Beam Melting - Papke, Thomas; Huber, Florian; Geyer, Georg; Schmidt, Michael; Merklein, Marion (8th Congress of the German Academic Association for Production Technology (WGP), 2019)

Characterisation of the transition area at partial hot stamped car body components by the 3-point bending test - Hezler, Christian; Kopp, C.; Bader, M.; Griesbach, B.; Merklein, Marion; Russ, F. (Proceedings SCT2011, 2011)
LFT Import::2019-08-05 (1649)

Characterisation of Yielding BEhvior of Sheet Metal under Biaxial Stress Condition at Elevated Temperatures - Merklein, Marion; Hußnätter, Wolfgang; Geiger, Manfred (Annals of the CIRP, 2008)
LFT Import::2019-08-05 (1512)

Characterization and Description of Friction Conditions for Hot Stamping and Partial Hot Stamping of Ultra High Strength Steel - Schwingenschlögl, Patrik; Hildering, Sven; Merklein, Marion (Proceedings METEC & 2nd ESTAD, 2015)
LFT Import::2019-08-05 (2104)

Characterization and Modelling of Sheet Material with Graded Strength for More Accurate Finite Element Analysis - Lenzen, Matthias; Kraus, Martin; Merklein, Marion (Key Engineering Materials, 2022)
Many sheet materials do not exhibit constant properties over the sheet thickness. On the one hand, this can be caused by a rolling process with a pass reduction of 1-2%, the so-called skin pass rolling. This is mainly used for deep drawing steel grades to eliminate the pronounced yield strength of the base material. Another possibility is abrasive blasting or shot peening of sheet metal. This causes plastic deformation of the sheet surface and material strengthening. The grading can be used to locally strengthen components or locally adapt the roughness. Since many production processes today are designed numerically, the mapping of such a grading is necessary but currently not implemented in FE code. The aim of this research is, to correlate the material hardness to a plastic pre-strain with a newly developed characterization method. For this purpose, graded material properties are generated by means of abrasive blasting as an example process. The resulting locally varying work hardening over the sheet thickness is further integrated in finite element analysis by the assignment of a starting condition of a 2d-shell element formulation. With this approach, it is possible to map the graded material properties easily in FE simulations with a very good accuracy.
CRIS-Team Scopus Importer:2022-11-04
Keywords: abrasive blasting; Graded material properties; material modelling; sheet metal forming

Characterization of a magnetorheological fluid and simulative design of a magnetic field with respect to its suitability for hydroforming - Rösel, Sebastian; Merklein, Marion (Proceedings of the 5th International Conference on ADVANCES IN PRODUCTION ENGINEERING, 2010)
LFT Import::2019-08-05 (140)

Characterization of a Magnetorheological Fluid with Respect to its Suitability for Hydroforming - Rösel, Sebastian; Merklein, Marion (International Journal of Material Forming, 2010)
Nowadays the global warming and the shortage of resources represent big challenges. To cope with these deviances it is the duty of the automotive industry, to build up light weight constructions for high efficient vehicles. For example forming parts as components of exhaust systems or chassis components could be realized by hydroforming, a new flexible technology, which enables the realisation of undercuts and increases the forming limits. Thereby comparatively complex part geometries can be produced. Using this process the blank is deformed by gases or fluids as pressure media. In this case a magnetorheological fluid could be used. The key property of magnetorheological media is an increasing viscosity under magnetic fields. Thus they can not only serve as a pressure medium, but also act as a sealing in the flange area to prevent leakage. For a better understanding of the process a basic characterisation has to be done. Therefore an experimental setup is built up. Different parameters like feed rate and magnetic flux density are varied to get information about the behaviour of the tested fluid. The achievable cavity pressure is perhaps the most important parameter, because it determines the geometry of the part at the end of the forming step, especially at the small radii of the component. Another result of these tests is the fundamental potential of magnetorheological fluids for the process of hydroforming of blanks. © 2010 Springer-Verlag France.
LFT Import::2019-07-29 (137)
Keywords: Forming technology; Hydroforming; Magnetorheological fluid

Characterization of damage and fracture of high strength steels within air bending - Kaupper, Markus; Tsoupis, Ioannis; Merklein, Marion; Weidinger, P. (Proc. 6th Int. Conf. and Exhibition on Design and Production of Machines and Dies/Molds, 2011)
LFT Import::2019-08-05 (1638)

Characterization of friction stir consolidated recycled billet by uniaxial compression tests with miniaturized cylindrical specimen - Latif, Abdul; Ingarao, Giuseppe; Fratini, Livan; Hetz, Peter; Merklein, Marion (Materials Research Proceedings, 2023)
Friction stir consolidation (FSC) is a solid-state recycling method that directly converts machining scraps into semifinished billets. This process has been proven to be a more energy efficient and environmentally friendly technique compared to remelting based conventional recycling methods. During FSC, machining chips are transformed into a solid billet by the stirring action and friction heat of the rotating tool. Due to process mechanics, especially temperature gradient and strain rate, billets have shown different hardness values and grain size distribution across their sections. Therefore, in this research, miniaturized upsetting samples are extracted from the FSC billet. The purpose of minimizing the sample size is to get the local properties of a particular position. The intensive characterization was performed with future goals to find a more accurate numerical modelling and ultimately assign FSC billet to a potential industrial application.
CRIS-Team Scopus Importer:2023-08-04
Keywords: Aluminum Alloys; Compression Test; Friction Stir Consolidation; Recycling

Characterization of Heat Transfer Coefficients of Tool Materials and Tool Coatings for Hot Stamping of Boron-Manganese Steels - Wieland, Michael; Merklein, Marion (Key Engineering Materials, 2010)
LFT Import::2019-07-29 (1017)
Keywords: Heat transfer coefficient; Hot stamping; Tool coating

Characterization of hybrid components consisting of SEBM additive structures and sheet metal of alloy Ti-6Al-4V - Schaub, Adam; Jüchter, Vera; Singer, Robert; Merklein, Marion (Key Engineering Materials, 2014)
Within this paper the characterization of hybrid components consisting of selective electron beam melting (SEBM) additive structures and sheet metal of alloy Ti-6Al-4V will be presented. Key idea of the new production approach is the combination of the advantages of two different manufacturing processes. On the one hand the very high flexibility of the additive manufacturing process and on the other hand the economic production of conventional geometries by deep drawing operations. Main challenge within this new and innovative process is the identification and quality of the properties of the new hybrid components after the manufacturing process. The necessary evaluation consists of three parts: the analysis of the deep drawing blanks, the additive manufactured structure and finally the connection between both. Whereas standardized testing methods are available for the testing of the blanks and the additive structure, there are hardly scientific publication which deals with the investigation of the connection between them. Therefore, a new testing methods and consequently a new tool design was developed in order analyze the specimens in dependency of different strain- and stress conditions. At the end microstructural investigations were performed to identify the fundamental mechanisms which lead to the different properties on macroscopic scale. The result proofed that in particular the electron beam power has a high influence on the production process and thereby the connection quality. © 2014 Trans Tech Publications, Switzerland.
Keywords: Additive manufacturing; Selective electron beam melting; Sheet metal; Ti-6Al-4V

Characterization of kinematic hardening with a hydraulic bulge test - Lenzen, Matthias; Schmid, Harald; Merklein, Marion (Procedia Manufacturing, Special Issue, 2020)

Characterization of material behaviour under pure shear condition - Hußnätter, Wolfgang; Merklein, Marion (Proceedings of ESAFORM 2008, 2008)
In the last decades the design of sheet metal manufacturing processes and products has been mainly influenced by modern tools, e. g. the large field of numerical simulations based on the finite element (FE-) method. Since the modeling of the material behavior is essential for the quality of the calculated results both the determination of characteristic material data and the transformation of these into material models are of high relevance for the whole process-chain. New materials, e. g. light weight sheet metals often show anisotropic and sometimes also some special forming behavior like the twinning effect of magnesium alloys. Furthermore, car body components become more and more complex concerning the geometry and that leads to a mixture of different stress conditions during forming, e. g. deep drawing, stretching and shearing. As a consequence of these reasons also the material models have to be enhanced and therefore especially the yield locus diagram and the real stress-strain curve must include the relevant material characteristics and data. Nevertheless, the forming behavior of sheet metal under pure shearing condition is not sufficient described. In 1984 Miyauchi proposed a new kind of shear test that is characterized by a symmetrical loading of the specimen and homogenous areas of shearing. In this paper a new tool and a new specimen's geometry are introduced with which shear tests have been done in the style of Miyauchi for different materials. The forming behavior is analyzed using an optical strain measurement system, in order to obtain detailed information on the onset of plastification as well as the homogeneity of the plastification itself. It can be shown that the two shear zones are constant and homogenous during the forming process. Basing on the experimental investigations the real stress-strain curves and the yield loci under pure shear conditions are obtained. © Springer/ESAFORM 2008.
LFT Import::2019-08-05 (1511)
Keywords: Anisotropy; Material characterization; Shear Test; Yield Loci; Yielding

Characterization of mechanical properties in processed friction stir welded high-strength aluminum alloy blanks - Gnibl, Tobias; Merklein, Marion (Procedia Engineering, 2014)
LFT Import::2019-07-29 (2034)
Keywords: Material characterization; Recrystallization; Rolling

Characterization of sheet metal components by using an upsetting test with miniaturized cylindrical specimen - Hetz, Peter; Kraus, Martin; Merklein, Marion (CIRP Annals - Manufacturing Technology, 2022)
Especially for safety-relevant components local characterization of the mechanical properties is necessary for product testing. For sheet metal parts with a complicated geometry conventional specimens for standardized tests cannot be extracted due to size limitations. Thus, a novel extraction procedure of miniaturized upsetting specimens is investigated. Taking a miniaturized upsetting specimen out of the sheet component allows for the first time the characterization of sheet metals in a standardized upsetting test under uniaxial compression stresses. Furthermore, this enables the analysis of strain hardening behavior of components and a direct validation of finite element simulations based on the true stress.
CRIS-Team Scopus Importer:2022-08-12
Keywords: Material characterization; Metal forming; Wire EDM

Characterization of temperature-dependent tension-compression asymmetry for high-strength aluminium alloys - Hetz, Peter; Merklein, Marion (Production at the leading edge of technology. Proceedings of the 9th Congress of the German Academic Association for Production Technology (WGP), 2019)
In the course of lightweight construction, modern materials with high strength and low density are essential. High-strength aluminium alloys such as 7000 series aluminium alloys meet these requirements but are only limited formable at room temperature. Thus, different heat assisted sheet metal forming processes are used to increase the formability. First investigations on the highstrength aluminium alloy AA7075 show a temperature-dependent and tensilecompressive asymmetric material behaviour. Since both tensile and compressive forces occur in sheet metal forming processes, an understanding of temperaturedependent tension-compression asymmetry is vital to set up material models for process design. Until now, the tension-compression asymmetry has barely been investigated for high-strength aluminium alloys at different temperatures. Therefore, further experimental studies are necessary. Within this contribution, the material behaviour of AA7020-T6 and AA7075-T6 is hence examined under uniaxial tensile and compressive load at different temperatures. For this purpose, both tensile and compressive tests are carried out on flat specimens between room temperature and 200 °C.<br
Keywords: Tension-compression asymmetry; High-strength aluminium alloy; Warm forming

Characterization of the Bauschinger effect and identification of the kinematic Chaboche model by tension-compression tests and cyclic shear tests - Suttner, Sebastian; Merklein, Marion (Proc. International Deep Drawing Research Group Conf. IDDRG 2014, 2014)
LFT Import::2019-08-05 (2025)

Characterization of the shear stress state under non-proportional strain paths realized by biaxial stretching in the Marciniak Test - Suttner, Sebastian; Merklein, Marion (Materials Today: Proceedings, 2015)
Complex parts with sharp corners are on the rise to satisfy increasing customer demands on the design. To realize these parts in single or multistage forming processes the information of the material behavior under linear and non-linear strain paths is essential. As Bauschinger already showed for the material behavior under cyclic loading, a reduction of the subsequent beginning of plastic yielding can be observed. Different research works studied the Bauschinger effect under cyclic proportional loading or non-proportional strain paths mostly with uniaxial pre-straining of the material. In this paper the material behavior under shearing after previous biaxial stretching in the Marciniak test is analyzed for the aluminum alloy AA5182 and the advanced high strength steel DP600. The Marciniak test is suited for biaxial pre-straining due to an almost almost equibiaxial strain state and a homogeneous strain distribution in-plane on the bottom of the specimen up to higher strains than in a biaxial tensile test. The subsequent shear test is realized with a modified shear test specimen according to the ASTM standard. Finally, the influence of biaxal pre-straining on the beginning of plastic yielding under shear condition, the hardening behavior and the maximum reachable shear strain is investigated for a better understanding of the material behavior under non-proportional loading paths.
LFT Import::2019-07-29 (2101)
Keywords: Bauschinger effect; Material characterization; Non-linear strain paths

Characterization of the Tribological Behavior of Different Tool Coatings and Dry Lubricant for High-Strength Aluminum Alloys at Elevated Temperatures - Rigas, Nikolaos; Merklein, Marion (Advanced Engineering Materials, 2023)
Keywords: high-strength aluminum; wear; tool coatings; hot form quench

Characterization of tribological and thermal properties of metallic coatings for hot stamping boron-manganese steels - Merklein, Marion; Lechler, Jürgen; Stöhr, Thomas (Tagungsband The Coatings, 2008)
LFT Import::2019-08-05 (194)

Characterization of tribological conditions within direct hot stamping - Schwingenschlögl, Patrik; Merklein, Marion (Journal of Materials Processing Technology, 2020)
The aim of this study is to create a detailed process understanding regarding the tribological conditions within direct hot stamping. Hot stamping has established as a common technology for manufacturing safety-relevant components in modern car bodies. However, due to the high forming temperatures within hot stamping applications, no suitable lubricants have been developed yet. As a consequence, high friction and severe wear occur during the forming. This affects the tool wear as well as the resulting part quality. For improving the robustness and the efficiency of industrial hot stamping processes, future measures to reduce the tribological loads have to be found. The key to the development of such measures is a detailed process understanding of the tribological conditions. Within this study, friction and wear are analyzed for different workpiece and tool temperatures, relative velocities and contact pressures. Based on the experimental results, detailed knowledge of the critical cause-effect relations between process parameters and tribological behavior is acquired. The friction behavior is analyzed via strip drawing experiments under hot stamping conditions. The amount of wear is determined via confocal microscopy measurements before and after the experiments. 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 wear.
CRIS-Team Scopus Importer:2019-12-17
Keywords: 22MnB5; AlSi; Friction; Hot stamping; Strip drawing test; Wear

Characterization of Work Hardening Behavior of Additively Manufactured Stainless Steel 316L (1.4404) Using Bulk Metal Forming at Elevated Temperature. - Papke, Thomas; Merklein, Marion (Lasers in Manufacturing Conference 2019, 2019)

Characterization of yielding and hardening of AA6016 - Hußnätter, Wolfgang; Merklein, Marion (Proceedings of IDDRG Conference, 2006)
LFT Import::2019-08-05 (1276)

Characterization of Yielding Magnesium Alloy AZ31 with BBC2005 - Hußnätter, Wolfgang; Banabic, D.; Merklein, Marion; Geiger, Manfred (Proceedings of ICTP2008, 2008)
The finite element analysis (FEA) is getting more and more important in fields of sheet metal forming for process design and parts' dimensioning. But the reliability and the quality of the numerical results strongly depend on the model that has to be built for the calculations. Especially the modelling of the elastic-plastic material behaviour is of main importance, since it shows a wide impact on the numerically calculated stresses and strains in sheet metal parts. Therefore, the material data have to be determined using experiments and have to be modelled basing on the experimental results. Most of semi-finished products are characterized by anisotropic material properties which can be approximated by yield criteria like those of Hill'48 for common steels or Barlat'89 and various BBC-models for some aluminium alloys. The diversity of new materials, in particular light weight materials like magnesium sheet metals may cause the necessity of new yield criteria, but in some cases the material behaviour can also be modelled by existing ones. In this paper the material behaviour of the magnesium alloy AZ31 under plane tensile stress conditions is investigated. The experimental investigations have been done at the Chair of Manufacturing Technology (LFT) of the University of Erlangen using a novel experimental setup. The yielding behaviour is determined basing exclusively on real material data out of experiments so that no FE-calculations are necessary to detect strains and stresses. Using these data different yield criteria are applied to model the real material characteristics, whereas the criterion of BBC2005 gives to the best approximation for uniaxial yield stresses, the anisotropy coefficients and also the yield locus diagram.
LFT Import::2019-08-05 (1514)

Characterization of yielding of sheet metal at elevated temperatures - Hußnätter, Wolfgang; Merklein, Marion; Geiger, Manfred (Journal of Materials Processing Technology, 2007)
In times of highest significance of process modeling and numerical simulation characterization of material properties is of special importance for components' and tools' dimensioning. Especially in fields of sheet metal forming the mechanical behavior of components highly differ according to real stress condition. In particular yield loci combine the information of beginning of yielding with biaxial stress conditions. Although these data are essential, they are unknown for many different sheet metals, mainly new materials used for light-weight constructions, e.g. aluminum and magnesium alloys. In this paper investigations done on a novel concept of experimental setup, which has been developed at the Chair of Manufacturing Technology (LFT) and which enables the determination of yield loci at elevated temperatures, are presented. The strategy for local heating is based on FE-calculations and verified afterwards. A 210 W-diode laser is used for the local heating of the specimens up to temperatures in the range of 300 °C. During forming process a constant temperature is guaranteed by a closed-loop temperature-control (CLTC), the homogeneous distribution of temperature in the forming zone is realized using a special optical system. © 2007 Elsevier B.V. All rights reserved.
LFT Import::2019-07-16 (1381)
Keywords: Diode laser; FE-simulation; Materials' characterization; Yield locus

Charakterisierung der Fließeigenschaften von Aluminium- und Magnesiumblechwerkstoffen - Geiger, Manfred; Merklein, Marion; Hußnätter, Wolfgang (Tagungsband 12. Sächsische Fachtagung Umformtechnik (SFU) - Leichtbau durch Umformtechnik, 2005)
LFT Import::2019-08-05 (1192)

Charakterisierung der Umformbarkeit und mechanischen Eigenschaften von additiv gefertigtem Ti6Al4V - Papke, Thomas; Huber, F.; Heimes, M.; Schmidt, M.; Merklein, Marion (XXXVIII. Verformungskundliches Kolloquium, 2019)
LFT Import::2019-08-05 (2359)

Charakterisierung der Umformeigenschaften von Blechwerkstoffen - Trends und Möglichkeiten der Prüftechnik - Merklein, Marion; Hußnätter, Wolfgang; Staud, Detlev; Kuppert, Andreas (Tagungsband Werkstoffprüfung 2007, 2007)
LFT Import::2019-08-05 (289)

Charakterisierung des Formänderungsvermögens von hoch- und höchstfesten Karosseriestählen mit dem 3-Punkt Biegeversuch - Einfluss der Probenpräparation - Kopp C.; Schaller L.; Jessen, B.; Merklein, Marion; Hezler, Christian (Tagungsband Werkstoffprüfung 2009, 2009)
LFT Import::2019-08-05 (253)

Charakterisierung des Umformverhaltens von Magnesiumblechen bei erhöhter Temperatur - Hecht, Joachim; Merklein, Marion (Tagungsband XXIV. Verformungskundliches Kolloquium, 2005)
LFT Import::2019-08-05 (1252)

Charakterisierung des Verfestigungsverhaltens der Magnesiumlegierung AZ31 im Scherspannungszustand bei erhöhter Temperatur - Suttner, Sebastian; Merklein, Marion (Tagung Werkstoffprüfung 2015, 2015)
LFT Import::2019-08-05 (2124)

Charakterisierung des Versagens von hochfesten, mehrphasigen Stahlwerkstoffen in Abhängigkeit der Dehnungshistorie - Merklein, Marion; Lechler, Jürgen; Lupino, Roberto (Tagungsband Werkstoffprüfung, 2009)
LFT Import::2019-08-05 (717)

Charakterisierung und Modellierung des Fließverhaltens höchstfester Vergütungsstähle bei erhöhten Temperaturen - Merklein, Marion; Lechler, Jürgen; Geiger, Manfred (Umformtechnik im Spannungsfeld zwischen Plastomechanik und Werkstofftechnik, 2008)
LFT Import::2019-07-29 (1560)

Cold forging of closely-tolerated functional components out of blanks – possibilities of the new process class sheet-bulk metal forming - Koch, Johannes Peter Karl; Merklein, Marion (Proc. 6th JSTP Int. Seminar Precision Forging, 2013)
LFT Import::2019-08-05 (1903)

Combined tube and double sheet hydroforming for the manufacturing of complex parts - Merklein, Marion; Geiger, Manfred; Celeghini, Martino (Annals of the CIRP 2005, 2005)
LFT Import::2019-08-05 (1222)
Keywords: Hydroforming; Sheet metal; Tube

Comparative study of two different laser forming mechanisms regarding the mechanical properties of aluminium alloys - Merklein, Marion; Geiger, Manfred (Laser Assisted Net shape Engineering (LANE), 2001)
LFT Import::2019-07-15 (872)

Comparison of different forming methods on deep drawing and springback behavior of high-strength aluminum alloys - Rigas, Nikolaos; Schmid, Harald; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
High-strength aluminum alloys of the 7XXX series have a high potential for safety and crash-relevant components due to their advantageous density-to-strength ratio. Currently, the use of these alloys is limited because of the low formability at room temperature. By using thermal supported forming strategies, failure-free deep drawing is possible for these materials. At present, several thermal-assisted forming processes exist, but so far there is no comparison between these forming operations. For this purpose, this study compares the deep drawing behavior of the alloy AA7075 by using different thermally-assisted forming operations. Aim of this work is to enhance the understanding and comparability between different thermally-assisted forming processes for high-strength aluminum alloys. First, a thermal simulator is used to investigate the mechanical material behavior according to different temperature-time curves by using uniaxial tensile tests. Subsequently, the formability and springback behavior is determined numerically and experimentally in a model test. Finally, for one thermally assisted forming method, the experiments are scaled up to a real size process with drawbeads to validate the transferability. This study can help to improve the scientific knowledge for the use of these materials in future.<br
CRIS-Team WoS Importer:2021-11-05
Keywords: High Strength Aluminum; Drawbead; Springback; Finite Element Simulation

Comparison of extrusion processes in sheet-bulk metal forming for production of filigree functional elements - Pilz, Florian; Merklein, Marion (CIRP Journal of Manufacturing Science and Technology, 2019)
Increasing demands on forming processes with regard to the functional integration of components and lightweight construction pose a challenge to conventional processes. The application of bulk forming operations on sheet metal semi-finished products, also called sheet-bulk metal forming (SBMF), is a suitable approach to meet these challenges. Insufficient die filling and high tool loads are limiting factors in SBMF processes. In order to overcome these limitations in the future, it is necessary to provide appropriate measures. The basis for this is a comprehensive understanding of the manufacturing process for lock and gear toothing by extrusion on sheet metal. This paper identifies requirements for extrusion processes and establishes two corresponding processes. In addition to carrying out experimental investigations, numerical models are developed and validated with the aid of forming tests. In combination with experimental analysis, the simulation models are then used to investigate similarities and differences between both processes. During the processing of the steel 1.0338 (DC04), the investigations showcase a process class specific material flow, demanding tool loads and challenges in the production of filigree functional elements.
CRIS-Team Scopus Importer:2019-07-19
Keywords: Extrusion; Process design; Sheet forming; Sheet-bulk metal forming; Simulation; Tool load

Comparison of forming processes for micro textured cups - Reck, Manuel; Merklein, Marion (51st SME North American Manufacturing Research Conference, 2023)

Comparison of forming processes for micro textured cups - Reck, Manuel; Merklein, Marion (Manufacturing Letters, 2023)
Friction losses are present in all kinds of technical systems. This is always associated with additional energy consumption, which can be partly avoided as it arises. Energy savings can be achieved by a wide range of approaches. The application of friction reducing coatings on bodies in relative motion is widespread. The coating of parts is however only suitable to a limited extent for the production in large batches. Therefore, research approaches consider alternative methods to achieve friction reductions. A promising approach is the integration of miniaturized pockets on the surface of the component. In lubricated contacts, the lubricant can then accumulate in these indentations. The relative motion between two bodies thus builds up a hydrodynamic pressure and consequently reduces friction. Forming technology is suitable for the efficient production of metallic components in large quantities. The aim of this study is therefore to identify challenges in the integration of micro coining in established forming processes. Two processes from sheet metal forming and bulk metal forming are investigated. In a combined experimental and numerical approach, process-specific challenges are derived regarding the texturing process and the numerical process modelling for combined micro coining. The analysis is carried out on a cup geometry, as used in the automotive sector as tappets in the valve train. The case hardening steel 16MnCr5 (1.7131) is used as workpiece material.
CRIS-Team Scopus Importer:2023-10-20
Keywords: Extrusion; Modelling; Sheet metal; Texture

Comparison of numerical simulation and measurement of shear test and uniaxial compression test to verify material model for granular material used as medium for hydroforming - Grüner, Martin; Merklein, Marion (Proc. 5th International Conference on Advances in Production Engineering, 2010)
LFT Import::2019-08-05 (494)

Comparison of process characteristics and resulting microstructures of maraging steel 1.2709 in Additive Manufacturing via Laser Metal Deposition and Laser Beam Melting in Powder Bed - Karg, Michael; Hentschel, Oliver; Ahuja, Bhrigu; Junker, Daniel; Haßler, Ulf; Schäperkötter, Claus; Haimerl, Andreas; Arnet, Horst; Merklein, Marion; Schmidt, Michael (6th International Conference on Additive Technologies, 2016)
Laser Metal Deposition (LMD) with Blown Powder and Laser Beam Melting (LBM) in Powder Bed are two Additive Manufacturing technologies that can produce high-quality metal parts in principle. Both technologies are based on melting of fine metal powders employing highintensity laser radiation. Apart from the obvious differences defined by system technology, LMD and LBM differ largely in fundamental boundary conditions of laser-materialinteraction. Process conditions in LMD and LBM and corresponding microstructures were compared on the example of martensitic aging steel 1.2709. This material has been one of the most popular ones in industrial use with LBM for about a decade, typically processed with laser powers below 400 W in continuous wave (cw) mode. With LMD, 1.2709 has not been commonly used so far. LMD typically engages higher cw laser powers of around 1000 W, larger laser spot diameters and smaller feed rates than LBM. Increased laser power kindles hopes for increased productivity, which is a key factor for economic viability. For a more comprehensive comparison, 1.2709 processed by LBM with 1000 W was also considered. Samples were analyzed metallographically, by computed x-ray tomography, hardness testing before and after heat treatment. Chemical compositions of powder and built samples were compared.
Keywords: Maraging Steel; 1.2709; microstructure; Laser Beam Melting; Laser Metal Deposition

Comparison of Strain-path Indicators for Analysis of Processes in Sheet-bulk Metal Forming - Gutknecht, Florian; Vogel, Manfred; Schulte, Robert Karl; Merklein, Marion; Rosenbusch, Daniel; Koch, Sergej; Hübner, Sven; Behrens, Bernd Arno; Tekkaya, Erman; Clausmeyer, Till (The 13th International Conference on Numerical Methods in Industrial Forming Processes, 2019)

Component residual stress control in forward rod extrusion by material flow and tribology—experiments and modeling - Jobst, Andreas; Floros, Dimosthenis; Steinmann, Paul; Merklein, Marion (Forschung Im Ingenieurwesen-Engineering Research, 2021)
The forward rod extrusion of ferritic stainless steel X6Cr17 (DIN 1.4016) is here investigated with the objectives to experimentally identify and numerically verify the effect of the lubrication system and die opening angle on residual stresses. Three lubricants – MoS2, soap and polymer – are considered whose tribological properties are characterized via double cup extrusion tests. The effect of material flow is also studied by forming in conical dies featuring three different opening angles. The extrusion experiments revealed a decrease in the near-surface tensile stresses with decreasing friction for all the considered opening angles. An opening angle of 2α = 90° led to the highest tensile residual stresses. Both an increase to 2α = 120° and a decrease to 60° resulted in reduced tensile stresses and even a shift to compressive stresses. Furthermore, a previously developed numerical model of forward rod extrusion is optimized and validated against the experimentally measured residual stresses. The effect of the spatial and temporal discretizations of the model on the predicted residual stresses is investigated. Based on the experimental and numerically verified results, the recommendation to reduce friction in forward rod extrusion is derived as a means to obtain a less detrimental to the lifecycle of extruded parts residual stress state.

Comprehensive approach for process modeling and optimization in cold forging considering interactions between process, tool and press - Kroiss, Thomas; Engel, Ulf; Merklein, Marion (Journal of Materials Processing Technology, 2012)
LFT Import::2019-07-29 (1847)

Comprehensive material characterization for an intermediate heat treatment - Lechner, Michael; Kuppert, Andreas; Merklein, Marion (Key Engineering Materials, 2013)
Encouraged by increasing climate regulations there is a trend to lightweight constructions in the transportation sector, particularly in the automotive industry. An auspicious possibility to reduce the weight of the vehicle is the substitution of conventional steel by aluminum alloys. However, aluminum has a low formability and therefore new technologies have to be found in order to enhance the materials spectrum of application. A new strategy to extend the process limit is the short-term aluminum intermediate heat treatment between two forming operations. Key idea is the partial adaption of the mechanical properties with a short term heat treatment. By the interaction of soft and hard areas the material flow during the forming operation can be improved and the formability can be enhanced. Prerequisite for a successful application of the technology and the numerical simulation is a comprehensive knowledge about the interaction of pre-straining and a subsequent short term heat treatment. Within this paper the mechanical properties in dependency of the two parameters will be presented and a process window for the heat treatment after first forming operations will be derived. Moreover, the influence of batch fluctuations and the impact of ageing will be demonstrated. © (2013) Trans Tech Publications.
LFT Import::2019-07-29 (1855)
Keywords: Intermediate heat treatment; Material characterization; Precipitation hardenable aluminum alloy

Compression testing of martensitic stainless steel with superimposed ultrasonic vibration - Michalski, Markus; Piott, Florian; Merklein, Marion (Procedia Engineering, 2017)
LFT Import::2019-07-29 (2233)
Keywords: Finite element method (FEM); high strength steel; metal forming; ultrasonic

Connection strength of additive manufactured tool elements to the substrate - Junker, Daniel; Fedorov, Aleksandr; Hentschel, Oliver; Schmidt, Michael; Merklein, Marion (Trans Tech Publications Ltd, 2016)
In industry the increasing variety of products leads to shorter product life cycles. For parts made by forging processes this trend results in very high prizes, as the tool costs have to be assimilated with only few parts. To reduce the tool costs new, flexible processes have to be investigated and established in tool manufacturing. Laser based additive manufacturing is noted for its high flexibility and especially laser metal deposition (LMD) gets in the focus of the research as it allows adding material on free formed surfaces. Therefore it is already used for coating and repairing of forming tools. New investigations are made to qualify this process for the production of forging tools. The aim is to generate active elements onto a geometrical simple base unit. Within first investigations the manufacturing of high carbon hot work tool steel 1.2343 was analysed. The measured mechanical properties were similar to those of conventional manufactured material. The focus of this paper is the connection strength of the additively built structures to the substrate. Therefore cylindrical specimens for tensile tests are manufactured with the linkage zone in the parallel area, in which the highest tension will be achieved. To assess the strength of the connection a comparison with conventional manufactured steel will be made. Furthermore specimens produced with various settings will be tested to analyse the influence of the LMD process. Additionally post heat treated samples will be analysed to recognize the effect of the hardening on the strength of the specimens.
LFT Import::2019-08-05 (2264)
Keywords: Additive Manufacturing; Tool Manufacturing; Tool Steel Welding

Consideration of elastic tool deformation in numerical simulation of hydrofroming with granular material used as a medium - Grüner, Martin; Merklein, Marion (Key Engineering Materials, 2011)
LFT Import::2019-07-29 (1653)

Consideration of the manufacturing history of sheet metal components for the adaptation of a clinching process - Heyser, Per; Wiesenmayer, Sebastian; Frey, Philipp; Nehls, Thomas; Scharr, C; Flügge, Wilko; Merklein, Marion; Meschut, Gerson (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2022)
The process chain for the manufacturing of sheet metal components in mass production includes various cutting and forming operations, which influence the resulting properties of the parts and therefore subsequent manufacturing steps, such as clamping and joining. It is shown that clamping of the components leads to superimposed residual stresses and geometry changes. Therefore, the part properties differ from the initial state of the semifinished products, which has to be considered in the design of clinched joints. This paper presents an approach for coupled determination of the properties of semifinished and finished parts during deep drawing and clamping as well as their effects on the joint quality during clinching. One method for the effective and efficient determination of the properties of semifinished products and components during production is using process data from the preceding manufacturing processes, which is concretely presented in this work. In addition to the interconnection of the entire production chain, it is necessary to define relevant process data for each individual manufacturing step and to correlate the data with the material properties reliably. Therefore, the cross-process interactions of different steps of the process chain for the manufacturing of sheet metal components and the effect of process variations on subsequent manufacturing steps are investigated. Consequently, the boundary conditions for a mechanical joining process based on data from preceding process steps can be predicted.<br
Keywords: Deep drawing; clamping; joining; process chain; manufacturing history

Constitutive Friction Law for the Description and Optimization of Tailored Surfaces - Henneberg, Johannes; Beyer, Florian; Löffler, Maria; Willner, Kai; Merklein, Marion (Sheet Bulk Metal Forming, 2021)

Contact pressure-dependent friction characterization by using a single sheet metal compression test - Kraus, Martin; Lenzen, Matthias; Merklein, Marion (Wear, 2021)
Tribology has a major impact on process stability, product quality and tool life in metal forming processes. Today, the complex system of friction is simplified by the Coulomb friction coefficient or friction factor model for analytical and numerical process analysis. These friction values are determined in laboratory tests and assumed to be constant. Due to smoothing of the surface, displacement of lubricant from the active joint and locally different relative velocities, the friction state changes while forming. To achieve a high accuracy of finite element analysis, it is essential to consider these changing boundary conditions. Identifying strain-dependent friction coefficient or friction factor models by conventional characterization tests, such as the pin extrusion test or ring compression test, require a high number of experiments. Besides that, these tests are not suitable for low plastic strains due to their poor sensitivity. The sheet metal compression test, analyzed in this contribution, enables the description of the strain and contact pressure dependent progression of the friction values in one simple experimental setup. To determine the friction coefficients, the experimentally measured force-displacement curves will be assigned to friction coefficients in a numerically determined nomogram. The calibration of the nomogram is done analytically for the friction-free condition by using the flow curve determined in the uniaxial tensile test. The sheet metal compression test reacts sensitive to changes of the tribological system due to the high ratio of surface to specimen volume and the direct measuring of the press force as an evaluation quantity. The characterization of friction value progression is done for the materials DP600, DC06, Cu-OFE and CuZn30 with different tribological conditions. The results confirm that the friction values and thus the friction condition is changing during the forming process. Additionally, the validity limit of the friction coefficient model can be easily identified by analysing the friction coefficient progression.
CRIS-Team Scopus Importer:2021-03-05
Keywords: Contact mechanics; Contact pressure dependent friction model; Friction progression; Tribology; Tribophysics

Contact pressure-dependent friction compensation in upsetting tests with miniaturized specimens - Hetz, Peter; Rentz, Marcel; Merklein, Marion (Materials Research Proceedings, 2023)
Components produced by sheet metal forming can so far only be characterized locally to a limited extent using conventional tests, such as the tensile test or the hydraulic cupping test, due to the size of the specimen. A new approach based on miniaturized upsetting specimens taken from the sheet plane allows to determine the material properties of semi-finished products locally, for example in radii. However, in addition to this specific advantage, challenges such as friction between the specimen and the tool also appear with this testing method. For an accurate determination of the material parameters, it is therefore necessary to correct the test force by the friction coefficient. According to the state of the art, a variety of tests for friction coefficient characterization exist. By using a novel numerical method, friction coefficients for upsetting tests can be calculated contact pressure-dependent by means of an experimental single layer upsetting test. Therefore, in this paper, this method will be used for the first time to compensate the friction part in an upsetting test with miniaturized specimens as a function the contact pressure. This can improve the experimental mapping of the material behavior in the uniaxial compression stress state with increasing strain and hardening, since share of friction force increases with a higher deformation in the upsetting test. In contrast, a friction coefficient compensation based on an average value is provided in order to analyze, whether or in which case a contact pressure-dependent friction compensation is appropriate. In particular, for upsetting tests with miniaturized specimens, these results are relevant, since a major advantage of this test compared to conventional tests besides the local component characterization is the determination of material properties at high strains.
CRIS-Team Scopus Importer:2023-04-28
Keywords: Friction; Metal Forming; Upsetting Test

Controlled Rivet Deformation During Self-piercing Riveting Through a Tailored Strength Distribution Within the Rivet Material - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity. ICTP 2023. Lecture Notes in Mechanical Engineering., 2023)

Control of the material flow in sheet-bulk metal forming using modifications of the tool surface - Löffler, Maria; Schulte, Robert Karl; Freiburg, D.; Biermann, Dirk; Stangier, D.; Tillmann, W.; Merklein, Marion (International Journal of Material Forming, 2019)
Sheet-bulk metal forming (SBMF) processes are characterized by a successive and/or simultaneous occurrence of different load conditions such as the stress and strain states. These conditions influence the material flow and often lead to a reduced geometrical accuracy of the produced components. To improve the product quality, a control of the material flow is required. One suitable approach, the local adaption of tribological conditions by means of surface modifications of tool or workpiece, so-called tailored surfaces. To control the material flow and thus to improve the component accuracy, methods to reduce and to increase friction are needed. The aim of this study is to determine requirements for necessary adaptions of the friction, the identification of tribological mechanisms for different types of tool-sided tailored surfaces as well as the verification of the effectiveness of these surface modifications to improve the results of a specific SBMF process. The numerical analysis of a combined deep drawing and upsetting process revealed that this process is characterized by two areas of varying tribological load conditions. Using a numerical analysis, the friction factor gradient between these two areas was identified as a main influencing factor on the material flow. Based on this finding, Chromium-based hard coatings for the reduction of the friction and high-feed milled surfaces for an increase of the friction were investigated regarding their frictional behaviour. The results of the ring-compression tests revealed that the carbon content and the post treatment of coated tool surfaces are relevant to reduce the friction. The increased profile depth of the milled surfaces was identified as the main influencing factor on the tribological behaviour of this kind of tailored surfaces. The effectiveness of both types of tailored surfaces was verified for the combined deep drawing and upsetting process.
CRIS-Team Scopus Importer:2019-05-28
Keywords: Coating; Milling; Sheet-Bulk Metal Forming; Surface Modification; Tribology

Corrosion behaviour of self-piercing riveted joints with uncoated rivets in high nitrogen steel - Uhe, Benedikt; Kuball, Clara-Maria; Merklein, Marion; Meschut, Gerson (Production Engineering, 2024)

Crash behviour of various modern steels exposed to high deformation - Laumann, T.; Pfestorf, Markus; Beil, A.; Geiger, Manfred; Merklein, Marion (Key Engineering Materials, 2007)
LFT Import::2019-07-16 (1466)

Cross-profile deep drawing of magnesium alloy AZ31 sheet metal for springback analysis under various temperatures - Suttner, Sebastian; Schmid, Harald; Merklein, Marion (18th International Conference on Sheet Metal, SHEMET 2019, 2019)
LFT Import::2019-08-05 (2363)

Customized Exposure Strategies for Manufacturing Hybrid Parts by Combining Laser Beam Melting and Sheet Metal Forming - Huber, Florian; Papke, Thomas; Kerkien, Melanie; Tost, Florian; Geyer, Georg; Merklein, Marion; Schmidt, Michael (2018)

Customized exposure strategies for manufacturing hybrid parts by combining laser beam melting and sheet metal forming - Huber, Florian; Papke, Thomas; Kerkien, Melanie; Tost, Florian; Geyer, Georg; Merklein, Marion; Schmidt, Michael (Journal of Laser Applications, 2019)

Cyber-Physical Systems in the Context of Industry 4.0: A Review, Categorization and Outlook - Oks, Sascha Julian; Jalowski, Max; Lechner, Michael; Mirschberger, Stefan; Merklein, Marion; Vogel-Heuser, Birgit; Möslein, Kathrin (Information Systems Frontiers, 2022)
Cyber-physical systems (CPS) offer great potential for the digital transformation of industrial value creation in the context of Industry 4.0. They unify and integrate several technological approaches, including big data analysis and artificial intelligence, enhancing real-time monitoring and control of manufacturing processes. An extensive knowledge base formed by various disciplines, including information systems, engineering, and computer science, already exists for CPS. However, this knowledge has not been holistically captured and structured to date. To address this research gap, this study conducts a large-scale literature review of 2365 papers representing the current state of the research and then develops a novel categorization on industrial CPS with 10 sections, 32 areas, and 246 fields. The categorization is presented in hierarchical graphical form and can also be utilized as a web tool. To conclude, a perspective on future research needs and potentials to enhance Industry 4.0 in both research and practice are offere
Keywords: Cyber-physical systems; Industry 4.0; State of research; Categorization

Cyclic tension test of AZ31 magnesium alloy at elevated temperature realized in a miniaturized uniaxial tensile test setup - Suttner, Sebastian; Merklein, Marion (Materials Science Forum, 2016)
The use of new materials, e.g. aluminum and magnesium alloys, in the automotive and aviation sector is becoming increasingly important to reach the global aim of reduced emissions. Especially magnesium alloys with their low density offer great potential for lightweight design. However, magnesium alloys are almost exclusively formable at elevated temperatures. Therefore, material characterization methods need to be developed for determining the mechanical properties at elevated temperatures. In particular, cyclic tests at elevated temperatures are required to identify the isotropic-kinematic hardening behavior, which is important for numerically modeling the springback behavior. In this contribution, a characterization method for determining the cyclic behavior of the magnesium alloy AZ31B at an elevated temperature of 200 °C is presented. The setup consists of a miniaturized tensile specimen and stabilization plates to prevent buckling under compressive load. The temperature in the relevant area is introduced with the help of conductive heating. Moreover, the complex kinematic model according to Chaboche and Rousselier is identified, to map the transient hardening behavior of AZ31B after load reversal, which cannot be modeled with a single Bauschinger coefficient.
LFT Import::2019-07-29 (2186)
Keywords: Bauschinger effect; Characterization; Cyclic testing; Magnesium alloy

Data acquisition and control at the edge: a hardware/software-reconfigurable approach - Streit, Franz-Josef; Wituschek, Simon; Pschyklenk, Michael; Becher, Andreas; Lechner, Michael; Wildermann, Stefan; Pitz, Indra; Merklein, Marion; Teich, Jürgen (Production Engineering, 2020)
Today’s manufacturing facilities and processes offer the potential to collect data on an unprecedented scale. However, conventional Programmable Logic Controllers are often proprietary systems with closed-source hardware and software and not designed to also take over the seamless acquisition and processing of enormous amounts of data. Furthermore, their major focus on simple control tasks and a rigid number of static built-in I/O connectors make them not well suited for the big data challenge and an industrial environment that is changing at a high pace. This paper, advocates emerging hardware- and I/O reconfigurable Programmable System-on-Chip (PSoC) solutions based on Field-Programmable Gate Arrays to provide flexible and adaptable capabilities for both data acquisition and control right at the edge. Still, the design and implementation of applications on such heterogeneous PSoC platforms demands a comprehensive expertise in hardware/software co-design. To bridge this gap, a model-based design automation approach is presented to generate automatically optimized HW/SW configurations for a given PSoC. As a case study, a metal forming process is considered and the design automation of an industrial closed-loop control algorithm with the design objectives performance and resource costs is investigated to show the benefits of the approac
Keywords: FPGA; PSoC; Hardware/software co-design; Model-based engineering; Industrial automation; Manufacturing technology; Forming process; Motor control

Data-Based Control of A Multi-Step Forming Process - Schulte, Robert Karl; Frey, Philipp; Hildenbrand, Philipp; Vogel, Manfred; Betz, C.; Lechner, Michael; Merklein, Marion (Proc. International Deep Drawing Research Group Conf. IDDRG 2017, 2017)
LFT Import::2019-08-05 (2253)

Data-driven analysis of cold-formed pin structure characteristics in the context of versatile joining processes - Römisch, David; Zirngibl, Christoph; Schleich, Benjamin; Wartzack, Sandro; Merklein, Marion (IOP Conference Series, 2021)
Due to increasingly strict emission targets and regulatory requirements, especially for companies in the transport industry, the demand for multi-material-systems is continuously rising in order to lower energy consumption. In this context, mechanical joining processes offer an environmentally friendly and flexible alternative to established joining methods, especially in the field of lightweight design. For example, cold-formed cylindrical pin structures show high potentials in joining multi-material-systems without auxiliary elements. The pin structures are joined either by pressing them directly into the joining partner or by caulking with a pre-punched part. However, to evaluate the strength of the joint and to ensure the joining reliability for versatile processes, such as changing joining partners or batch variations, engineering designers currently have only limited design principles available compared to thermal joining processes. Consequently, the design of an optimal pin joint requires cost- and time-intensive experimental investigations and adjustments to design or process parameters. As a solution, data-driven methods offer procedures for structuring data and identifying dependencies between varying process parameters and resulting pin structure characteristics. Motivated by this, the paper presents an approach for the data-driven analysis of cold-formed pin structures and offers a deeper understanding of how versatile processes affect the pin characteristics. Therefore, the application of an intelligent design of experiment in combination with several machine learning methods enable the setup of a best-fitting meta-model. Resulting, the determination of a mathematical model provides the opportunity to accurately estimate the pin height considering only relevant geometrical and process parameters with a prediction quality of 95

Data-driven inline optimization of the manufacturing process of car body parts - Purr, S.; Wendt, A.; Meinhardt, J.; Moelzl, K.; Werner, A.; Hagenah, Hinnerk; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2016)
LFT Import::2019-07-29 (2213)

Data-driven Model Development for Quality Prediction in Forming Technology - Kirchen, Iris; Vogel-Heuser, Birgit; Hildenbrand, Philipp; Schulte, Robert Karl; Vogel, Manfred; Lechner, Michael; Merklein, Marion (15th IEEE International Conference on Industrial Informatics (INDIN), 2017)
this investigation data recorded from a flexible rolling process is processed by data driven methods to develop a quality prediction model for manufactured blanks. A concept for an incremental prediction method is proposed, which takes into account the specific character of the discrete manufacturing process. The method is evaluated based on a data set of process and quality data provided by a test rig. By the example of a specific quality parameter the effectiveness of the proposed method is confirmed. A precise quality prediction model is developed, which predicts the quality value with a high accuracy.
LFT Import::2019-08-05 (2252)
Keywords: automated Production Systems; data analytics; quality prediction

Deep Drawing of Friction Stir Welded Aluminium Tailored Blanks - Geiger, Manfred; Merklein, Marion; Giera, Artur (Proceedings of IDDRG, 24.-26.05., 2001)
LFT Import::2019-08-05 (1064)

Deep drawing of friction stir welded thin sheet aluminium-steel tailored hybrids - Merklein, Marion; Giera, Artur; Geiger, Manfred (Steel Research International, 2005)
LFT Import::2019-07-16 (1223)
Keywords: Aluminium steel tailored hybrids; Deep drawing; Forming behaviour; Friction stir welding