Definition and validation of a customized classification system for sheet metal bending parts - Schmid, Daniel; Merklein, Marion (Materials Research Proceedings, 2023)
The industry demands an increasing individualization, which leads to a rising variety of sheet metal parts. The consequence for sheet metal manufacturers are larger amounts of product data, smaller batch sizes and a larger quantity of different parts per year. The challenge for an efficient company is the availability and use of the corporate product data. Classification is a suitable tool for organizing corporate product data sets. In order to better reflect the individualization of customer demands and the resulting flexible manufacturing processes in a classification system, a method is needed to adapt the classification system based on the frequently used feature list. In the context of this paper, features are defined and parts are classified that are manufactured with the technology of air bending. It is a contribution to the creation of more precise approaches to the sheet metal part classification with simultaneous validation by a measurable characteristic. Focus is placed on the validation of the system with empirical measurement data. This allows every company to optimize and validate their own classification system.
CRIS-Team Scopus Importer:2023-04-28
Keywords: Bending; Optimization; Sheet Metal

Designing, manufacturing and processing of Tailored Blanks in a sheet-bulk metal forming process - Schulte, Robert Karl; Hildenbrand, Philipp; Lechner, Michael; Merklein, Marion (45th SME North American Manufacturing Research Conference, NAMRC 45, LA, USA, 2017)
Sheet-bulk metal forming is an innovative method for the manufacturing of functional components by applying bulk metal forming processes or combined sheet and bulk metal forming processes to sheet metal. The investigated process combines deep drawing and upsetting. Occurring 2D and 3D stress and strain states lead to challenges regarding the material flow control during the forming process to ensure a high die filling and accurate part geometry. Regarding these challenges, the application of conventional semi-finished products is not expedient wherefore Tailored Blanks with a process adapted sheet thickness distribution are applied to the forming process. The Tailored Blank geometry is designed by a numerical analysis and manufactured by an orbital forming process considering the resulting geometric part properties during deep drawing and upsetting. Therefore, the whole process chain from the conventional circular blank to the finished functional component is linked and modelled. This enables a realistic description of the part properties as the effective plastic strain caused in the manufacturing of semi-finished products is taken into account in the processing of the material. Subsequently the results are verified by experimental tests.
LFT Import::2019-08-05 (2231)
Keywords: Deep drawing; Finite element method (FEM); Forming; Sheet metal

Design, Manufacturing and Tribological Performance of Microtextured Bucket Tappets for Friction Reduction in the Valve Train - Marian, Max; Zahner, Michael; Tremmel, Stephan; Andreas, Kolja; Merklein, Marion; Wartzack, Sandro (6th World Tribology Congress, 2017)
In order to improve lubricating conditions as well as friction and wear behavior, the surfaces of contacting bodies in lubricated tribological contacts can be microtextured. While this approach has already reached industrial application for lower loaded contacts, the effects for higher loaded contacts, where elastic deformation plays a significant role, are still topic of basic research. For this reason, microtextures are adapted to the conditions of the tribological system of the bucket tappet/camshaft contact in the valve train as a demonstrator and major contributor to combustion engine losses. The tribological performance of various microtexture geometries and arrangements is analyzed on a one bucket tappet/one cam test-rig using series production valve train parts. A resistive measurement system is first applied to the highly dynamic tappet/camshaft contact and allows the investigation of the correlation between lubricating conditions and friction force. In the tests, a significant friction force reduction using microtextured surfaces compared to polished surfaces is achieved. Additionally, quantitative ex-situ wear characterization is carried out for long-run test cycles, using Laser Scanning Microscopy. Thus, wear mechanisms and rates are compared with the measurements of lubricating conditions and friction force. Besides the identification of advantageous microtexture geometries and arrangements regarding the tribological performance, possibilities and limitations of the manufacturing technology are examined. In order to realize high-volume production, a micro coining process was studied. In this regard the manufacturing of the coining punch using µEDM and the coining process itself were analyzed with respect to accuracy and reproducibility. Additionally, the durability of the pins was investigated for the micro coining process. The limitations of the manufacturing process and of the micro coining process are summarized in a process windo
Keywords: Microtextures; Micro Coining; EHL Contact

Design Principles of Tailored Heat Treated Blanks for the manufacturing of complex car body parts - Merklein, Marion; Vogt, Uwe (Proceedings of the IDDRG 2008, 2008)
LFT Import::2019-08-05 (1528)

Determination of contact stresses in the boundary area considering elastomere-pad bending as example - Geiger, Manfred; Merklein, Marion; Trägler, Horst; Nock, Marco (Production Engineering - Annals of the WGP, 2005)
LFT Import::2019-08-05 (1218)

Determination of Data for the Hot Stamping Process - Geiger, Manfred; Merklein, Marion; Hoff, Cornelia (Production Engineering. Annals of the German Academic Society for Production Engineering, 2006)
LFT Import::2019-08-05 (1344)

Determination of Forming Limit Curves - Strain Path and Failure Analysis - Kohl, Doris; Merklein, Marion (Key Engineering Materials, 2022)
With the goal to define a cost-effective and efficient process to identify adequate materials for sheet metal forming processes, it is crucial to evaluate the formability of materials. Forming limit curves (FLC) are used to analyze the forming and failure limits of sheet metals and dependence of the major (ε1) and minor strain (ε 2) from the uniaxial stress-strain area through the plane-strain point to the biaxial strain area. According to ISO 12004-2, the FLC is performed by Nakajima or Marciniak tests. Due to the experimental setup and the preconditions, pre-stretching occurs in the specimens and bending and friction effect are the result. The determination of the onset of necking (FLC) results mathematically from a “best-fit inverse parabola” on section lines. In addition, the failure point, i.e. the maximum strain value one frame before failure, is also analyzed. In contrast, tensile, notched tensile and hydraulic bulge tests, which are known in the literature as basic tests for the determination of the FLC, exhibit a linear strain path evaluation. These tests are used in this investigation as an alternative for the determination of the FLC. The behavior of the various strain paths of Nakajima and the alternative methods are examined for necking and cracking. Furthermore, the fracture surfaces are investigated by confocal laser scanning microscopy to identify influences of the different FLC methods on the fracture mechanics. FLCs were conducted with the Nakajima and the alternative FLC characterization method for a ductile steel (DX54D). To ensure transferability, the tensile tests are also performed with a high-strength steel (DP800). The FLC of the ductile steel, generated through the alternative method, exhibits a similar shape to the Nakajima generated FLC with the advantage of a constant strain rate leading to linear strain paths and a lower number of tests. The same results are achieved for the uniaxial strain tests with DP800.<br

Determination of forming limit diagrams? a new analysis method for characterization of materials' formability - Geiger, Manfred; Merklein, Marion (CIRP Annals - Manufacturing Technology, 2003)
LFT Import::2019-07-16 (1007)

Determination of forming limit diagrams at elevated temperatures for failure prediction within hot stamping of quenchenable ultra high strength steels - Lechler, Jürgen; Merklein, Marion (Tagungsband International Conference on Plasticity, 2008)
LFT Import::2019-08-05 (1552)

Determination of Forming Limits in Sheet Metal Forming Using Deep Learning - Jaremenko, Christian; Ravikumar, Nishant; Affronti, Emanuela; Merklein, Marion; Maier, Andreas (Materials, 2019)
The forming limit curve (FLC) is used to model the onset of sheet metal instability during forming processes e.g., in the area of finite element analysis, and is usually determined by evaluation of strain distributions, derived with optical measurement systems during Nakajima tests. Current methods comprise of the standardized DIN EN ISO 12004-2 or time-dependent approaches that heuristically limit the evaluation area to a fraction of the available information and show weaknesses in the context of brittle materials without a pronounced necking phase. To address these limitations, supervised and unsupervised pattern recognition methods were introduced recently. However, these approaches are still dependent on prior knowledge, time, and localization information. This study overcomes these limitations by adopting a Siamese convolutional neural network (CNN), as a feature extractor. Suitable features are automatically learned using the extreme cases of the homogeneous and inhomogeneous forming phase in a supervised setup. Using robust Student's t mixture models, the learned features are clustered into three distributions in an unsupervised manner that cover the complete forming process. Due to the location and time independency of the method, the knowledge learned from formed specimen up until fracture can be transferred on to other forming processes that were prematurely stopped and assessed using metallographic examinations, enabling probabilistic cluster membership assignments for each frame of the forming sequence. The generalization of the method to unseen materials is evaluated in multiple experiments, and additionally tested on an aluminum alloy AA5182, which is characterized by Portevin-LE Chatlier effects.
CRIS-Team WoS Importer:2019-05-07

Determination of frictional and thermal characteristics for hot stamping with respect to a numerical process design - Stöhr, Thomas; Merklein, Marion; Lechler, Jürgen (Proceedings 1st International Conference Hot Sheet Metal Forming of High-Performance Steel - CHS2, 2008)
LFT Import::2019-08-05 (213)

Determination of Friction Coefficients for the FE Analysis of Sheet Forming of Tailored Welded Blanks - Tolazzi, Massimo; Merklein, Marion (Sheet Metal 2005, Proceedings of the 11th International Conference on Sheet Metal; Advanced Materials Research, 2005)
The finite element analysis of sheet forming processes needs precise and reproducible data of the tribological conditions, which influence the material flow during the process. In this work the friction coefficient and its dependency on the hardness and surface topography of the blank are investigated. The selected materials are four steels with different surface qualities and coatings, FeP04, ZStE340, DP450 and TRIP800, which are joined by laser welding. Moreover, each material both with and without weld seam, was tested at three different values of normal contact pressure in a strip drawing test. The topography of both the base material and the weld line was obtained by measuring the surface roughness and implementing the data in a surface analysis software. Micro-hardness profiles along the tailored welded blanks were also determined. The strip drawing test was used to measure the friction coefficient between sheet metal and tool both in the case of tailored welded blanks and base material. The comparison between the results obtained for base materials and tailored welded blanks shows that the presence of the weld seam causes a clear increase of the friction between blank and tool.
LFT Import::2019-08-05 (1128)
Keywords: Sheet metal; Tailored blank; Tribology

Determination of friction coefficients in deep drawing by modification of Siebel's formula for calculation of ideal drawing force - Grüner, Martin; Merklein, Marion (Production Engineering, 2014)
LFT Import::2019-07-29 (2031)

Determination of Influencing Parameters of the Hot Stamping Process - Merklein, Marion; Lechler, Jürgen (Tagungsband AsiaSteel 06 conference, Fukuoba, Japan, 2006)
LFT Import::2019-08-05 (1267)

Determination of Material and Process Characteristics for Hot Stamping Processes of Quenchenable Ultra High Strength Steels with Respect of a Numerical Process Design - Merklein, Marion; Lechler, Jürgen (Sae World Congress 2008, 2008)
LFT Import::2019-08-05 (1554)

Determination of material intrinsic length and strain gradient hardening in microbending process - Li Hezong,; Dong Xianghuai,; Wang Qian,; Shen Yu,; Diehl, Alexander; Hagenah, Hinnerk; Engel, Ulf; Merklein, Marion (International Journal of Solids and Structures, 2011)
Microbending experiments of pure aluminum show that the springback angles increase with the decrease of foil thickness, which indicates obvious size effects and attributes to plastic strain gradient hardening. Then a constitutive model, taking into accounts both plastic strain and plastic strain gradient hardening, is proposed to analyze the microbending process of thin foil. The model is based on the relationship between shear yield stress and dislocation density, in which the material intrinsic length is related to material properties and average grain numbers along the characteristic scale direction of part. It is adopted in analytical model to calculate the non-dimensional bending moment and predict the springback angle after microbending. It is confirmed that the predictions by the proposed hardening model agree well with the experimental data, while those predicted by the classical plasticity model cannot capture such size effects. The contribution of plastic strain gradient increases with the decrease of foil thickness and is independent on the bending angle. © 2010 Elsevier Ltd. All rights reserved.
LFT Import::2019-07-29 (720)
Keywords: Gradient of effective plastic strain; Material intrinsic length; Microbending; Springback

Determination of strain dependent anisotropy in layer compression tests and resulting influence on the yield locus modelling - Lenzen, Matthias; Merklein, Marion (2019)
LFT Import::2019-08-05 (2361)

Determination of the biaxial anisotropy coefficient using a single layer sheet metal compression test - Hetz, Peter; Lenzen, Matthias; Kraus, Martin; Merklein, Marion (19th International Conference on Sheet Metal, SheMet 2021, 2021)
Keywords: Anisotropy; Metal forming; Material characterization

Determination of the heat transfer during hot stamping - Geiger, Manfred; Merklein, Marion; Hoff, Cornelia (Steel-Future for the Automotive Industry, 2005)
LFT Import::2019-08-05 (1179)

Determination of the mechanical properties of hot stamped parts from numerical simulations - Hagenah, Hinnerk; Merklein, Marion; Lechner, Michael; Schaub, Adam; Lutz, Stefan (Procedia CIRP, 2015)
Hot stamping is a well-established process in car manufacturing today. However, the resulting mechanical properties of a hot stamped part and its behaviour during a crash are still open questions. The usual procedure includes destructive experiments to determine the mechanical properties resulting from the forming and quenching process. The gained information is then used for crash simulation. Using images from micrographs to determine the proportion of bainite and martensite resulting from the hot stamping process has proved to be difficult, as these structures are fairly similar and hard to distinguish. Sophisticated numerical simulations of the hot stamping process are available. The hardness resulting from the hot stamping process can be predicted fairly well from these process simulations. However, information like the tensile strength that is more relevant for the crash behaviour cannot be predicted that easily. It is not yet state of the art to map the results from the hot stamping simulation directly into the crash simulation. The approach to be presented in detail in this contribution uses the forming speed and the quenching velocity to predict the relevant mechanical properties of the hot stamped parts. Both input parameters, the forming speed and the quenching velocity, can be derived from the numerical hot stamping simulation. By means of experiments using a thermomechanical test system Gleeble well defined process parameters were used. Micro tensile test specimens were manufactured out of the Gleeble specimens to eliminate the effect of the Gaussian temperature profile created during the Gleeble experiments. Afterwards, tensile tests were carried out to derive a response surface for 22MnB5. The validated results allow the determination of the tensile strength of hot stamped parts from the numerical simulation of the hot stamping process with good accuracy.
LFT Import::2019-07-29 (2013)
Keywords: Hot stamping; Simulation

Determination of the properties of semi-finished parts in blanking processes - Wiesenmayer, Sebastian; Frey, Philipp; Lechner, Michael; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2020)

Determination of thermal and mechanical material properties if ultra high strength steels for hot stamping - Lechler, Jürgen; Merklein, Marion; Geiger, Manfred (Steel Research International, 2008)
Direct and indirect hot stamping presently constitutes one of the most innovative forming technologies in the automotive industry through the combination of forming and hardening in one process step or line. Thus, structural components with strength up to 1600 MPa can be accomplished with the quench hardenable ultra-high strength steel 22MnB5. With respect to the numerical investigation of the feasibility of different parts the knowledge of various thermal and mechanical material characteristics determined under process relevant conditions are required. Within the scope of this paper different experimental methods will be introduced for the determination of material properties according to the typical time-temperature characteristics of the hot stamping process, as well as the modelling of it as input data for the FE analysis.
LFT Import::2019-07-29 (1561)
Keywords: 22MnB5; Flow behaviour; Heat transfer; Hot stamping; Modelling

Determination of tribological conditions within hot stamping - Geiger, Manfred; Merklein, Marion; Lechler, Jürgen (Production Engineering, 2008)
Innovative hot sheet metal forming technologies are gaining an increasing significance in the scope of application of more and more innovative high and ultra high strength steels in the automotive industry. With respect to a numerical process design beside the mechanical and the thermal material characteristics the friction coefficient represents an important input parameter for finite element (FE) simulation. Within the scope of this paper an evaluation method for the determination of the friction coefficient μ for the direct hot stamping process of boron-manganese steels will be presented. Therefore cup deep drawing tests at elevated temperatures following the time-temperature-characteristic of the hot stamping process are carried out. For the calculation of the friction coefficient the approach according to Siebel for the modeling of the maximum drawing force is used. © German Academic Society for Production Engineering (WGP) 2008.
LFT Import::2019-07-29 (1553)
Keywords: Friction coefficient; Hot stamping; Production process

Determination of Yield Loci of Sheet Metal at Elevated Temperatures by the Integration of a Diode Laser Source - Hußnätter, Wolfgang; Merklein, Marion; Geiger, Manfred (Proceedings of AMPT 2006, 2006)
LFT Import::2019-08-05 (1264)

Developing LBM process parameters for Ti-6Al-4V thin wall structures and determining the corresponding mechanical characteristics - Ahuja, Bhrigu; Schaub, Adam; Karg, Michael; Lechner, Michael; Merklein, Marion; Schmidt, Michael (Physics Procedia, 2014)
The Laser Beam Melting (LBM) process technology within the family of Additive Manufacturing technology is characterized by its ability to fabricate fully dense 3D structures directly from micro-sized metal powder. With the current state of the art, Ti-6Al-4V has been processed using LBM machine systems constituting a laser with a beam diameter of about 100 μm. In order to fabricate structures with smaller wall thicknesses, processing of Ti-6Al-4V is attempted on the LBM machine system, Realizer SLM 50 consisting of a laser with a beam diameter 10 μm. The proposed paper presents the development of process parameters for fabricating fully dense Ti-6Al-4V 3D structures using the LBM machine system, Realizer SLM 50. Further experiments are carried out to determine the wall thickness and mechanical properties achievable using the selected process parameters. Analysis and scientific arguments are presented to explain the influence of building direction and heat treatment on mechanical propertie
Keywords: Laser Beam Melting; titanium alloy; mechanical characterization

Development and Evaluation of Tool Sided Surface Modifications for Dry Deep Drawing of Steel and Aluminum Alloys - Merklein, Marion; Schmidt, Michael; Wartzack, Sandro; Tremmel, Stephan; Andreas, Kolja; Häfner, Tom; Zhao, Rong; Steiner, Jennifer (Dry Metal Forming Open Access Journal, 2015)

Development and launching of an application-oriented test rig for wear investigations in sheet-bulk metal forming - Merklein, Marion; Andreas, Kolja; Kraus, Martin; Löffler, Maria; Pilz, Florian (THE"A" Coatings, 2017)
LFT Import::2019-08-05 (2256)

Development of a Biaxial Tensile Machine for Characterization of Sheet Metals - Merklein, Marion; Biasutti, Manfredi (Journal of Materials Processing Technology, 2013)
A new stand-alone biaxial testing machine with out-of-plane loading system has been developed to study the anisotropic plastic behavior of metal sheets on cruciform specimens. In this apparatus a single screw driven actuator is used and the variation of the load ratio along the two main directions is achieved by adjusting the geometry of a link mechanism. This design firstly combines the advantages of biaxial displacement devices, typically mounted in a universal tensile tester, with stand-alone machines and by at the same time providing a solution to the limitations associated with each of these types. The used specimen is discussed and compared through numerical simulations to a prominent geometry proposed in the literature. Experiments are presented and the results are implemented in identifying classical and advanced yield criteria and though represented as yield surfaces. © 2012 Elsevier B.V.
LFT Import::2019-07-29 (1862)
Keywords: Biaxial tensile machine; Cruciform specimen; Sheet metal

Development of a damage prediction system for bending and cutting of high strength steels - Vatter, Peter; Hildering, Sven; Tsoupis, Ioannis; Merklein, Marion (Key Engineering Materials, 2013)
The application of modern high-strength low-alloy steels (HSLA) and advanced high strength steels (AHSS) for structural and safety relevant components in the automotive industry offers the advantage of combining low specific weight with high material strength. Typical manufacturing processes for these steel grades are bending and cutting operations. However, the forming and cutting potential of these innovative steel grades is different to conventional steels as the process and the damage behaviour is changing. In bending operations cracks occur at the outer bending edge, whereas in cutting operations delamination can appear at the sheared edge, which can initiate component failure. In the scope of this work a method is presented to describe the damage behaviour of both, bending and cutting operations, by theoretical meta models. In order to generate a database experiments were carried out using a typical HSLA. The main influencing factors have been varied experimentally, such as the rolling direction, normalised bending radius and punch to die clearance. To calculate further sampling points a finite element model has been developed and validated against the experimental data. The damage criterion of LemaÎtre has been applied. The necessary parameters were determined by reverse numerical identification by means of the major strain for the bending operation and by the punch force-punch stroke curve for the cutting operation. To build up a system for the prediction of the damage the gained data basis was approximated by mathematical functions. An error analysis was carried out showing good accordance. In doing so, a meta model for the evaluation of the damage rate could be established. The functions were implemented in a software tool which allows the user to determine the failure probability for a given parameter set. This software tool is exemplarily validated against experimental air bending tests using a higher normalised bending radius. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1853)
Keywords: Bending; Cutting; Damage prediction; High strength steel

Development of a feature adapted measurement evaluation strategy - Loderer, Andreas; Hausotte, Tino; Steinmann, Paul; Merklein, Marion; Landkammer, Philipp; Hildenbrand, Philipp; Schneider, Thomas (MacroScale 2014 - Recent developments in traceable dimensional measurements, 2015)
This article describes a methodical approach for developing a feature adapted measurement evaluation strategy using the example of a multi-scale multi-sensor fringe projection system. In a first step calibrated standard features were selected and measured in the next step by different fringe projection sensors with varying measuring range and resolution. For selecting which sensor is most appropriate for which feature the standard deviation as well as the deviation between calibrated values and measured values were considered. Finally the results were summarized in a decision matrix, which helps to select a feature adapted measurement strategy.

Development of a New Method for Producing Plane Expanded Metal by Laser Cutting and Forming of Metal Plates under Uniaxial Tension - Merklein, Marion; Junker, Daniel; Schaub, Adam; Kretschmer, Anne; Lechner, Michael (Key Engineering Materials, 2015)
The on-going trend to lightweight construction leads to a special focus on plane lattice structures as an alternative for solid metal plates. They demonstrate similar mechanical properties while taking up only a fraction of the normal material input and are thus economically favourable. Additionally, they fulfil functional and design aspects and therefore are used by several industries like the automobile. Nevertheless, the two most common types of lattice structures-perforated metal plates and expended metal plates-Are either waste intensive or uneven and hence require additional rolling of the metal plate. Therefore, within this contribution a new and innovative approach for the production of plane lattice structures will be presented. The manufacturing process thereby consists of two steps. At first, a specially designed pattern is cut into metal plates via a laser. Subsequently, the plates are formed under uniaxial tension to realize the lattice structures. Based on the cutting length, cutting space and the row space different blanks with tailored lattice structures can be produced. From the experimental results first guidelines for the design of suitable patterns are derived. The investigations will be performed with precipitation hardenable aluminium AA6014.
LFT Import::2019-07-29 (2118)
Keywords: Design method; Lattice structure; Metal forming

Development of a novel in-situ measurement method for thermo-mechanically coupled material characterization of high-strength aluminum alloys - Rigas, Nikolaos; Garcin, Thomas; Kuball, Clara-Maria; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2023)
High-strength aluminum alloys are more and more used for safety and crash-relevant components due to their advantageous density-to-strength ratio. By using thermal-supported forming strategies, failure-free deep drawing is possible for these materials. In this context, the hot form quench process (HFQ®) has shown to be a promising thermally-assisted forming strategy. By using locally tempered forming tools, the production of tailored components with different mechanical properties is possible. However, material characterization and process design with conventional characterization methods are quite challenging in this context. A new approach is the use of ultrasound-assisted material characterization in combination with a thermo-mechanical simulator. Thereby it is possible to perform an in-situ material characterization. So far, this technology is mainly used for steel materials. In this contribution, the potential of an adapted measurement strategy for high-strength aluminum alloys is presented. For this purpose, the influence of different measurement parameters on modified samples and the resulting measurement signal is investigated. With the help of this study, new standards are set for time-bound material characterization under thermo-mechanical stress. As a result, thermally-assisted forming methods can be designed more efficiently and faster in the futur

Development of a testing method for the identification of friction coefficients for numerical modeling of the shear-clinching process - Müller, Martin; Vierzigmann, Ulrich; Hörhold, Réjane; Meschut, Gerson; Merklein, Marion (Key Engineering Materials, 2015)
LFT Import::2019-07-29 (2108)
Keywords: Joining; Sheet Metal; Tribology

Dickblechumformen und Formhärten - Potentiale und Grenzen bei der Herstellung hochbelasteter Funktionsbauteile - Wieland, Michael; Merklein, Marion (6. Erlanger Workshop Warmblechumformung, 2011)
LFT Import::2019-08-05 (1775)

Diesseits und jenseits der Umformtechnik - Geiger, Manfred; Merklein, Marion; Nock, Marco (Lange währt die Umformtechnik, 2004)
LFT Import::2019-07-16 (1097)

Discontinuous laser dispersing of titanium nitride based hard ceramic particles for improving the tribological behavior of hot stamping tools - Schirdewahn, Stephan; Carstensen, Niels; Spranger, Felix; Hilgenberg, Kai; Merklein, Marion (Hot Sheet Metal Forming of High-Performance Steel, 2022)
Over the last decades, the application of ultra-high strength steel (UHSS) has constantly increased within the automotive industry due to its favorable strength-to-weight ratio. For manufacturing such steel grades to complex-shaped body-in-white parts, temperature-assisted forming operations are required. In this regard, hot stamping has been established as a suitable technology to generate geometrical complex car body components with high shape accuracy. During the forming operation, however, high thermo-mechanically tool stresses appear, which in turn promote the occurrence of severe wear and high friction values at the blank-die interface. Within short production periods, the quality of the parts as well as the operating time of the tool are negatively affected. For this purpose, an innovative surface engineering technology named laser implantation has been applied, in order to improve the tribological performance of hot stamping tools. The implantation technique is based on manufacturing highly wear-resistant, separated and elevated microfeatures onto the tool surface by embedding hard ceramic particles via pulsed laser radiation. To qualify the resulting tribological behavior, modified pin-on-disk tests have been performed under hot stamping conditions. Afterwards, optical and tactile measurements of the blank surface as well as Energy-dispersive X-ray spectroscopy (EDS) analysis on the worn tool topography have been carried out to clarify the cause-effect relations. The results have been compared to unmodified tooling systems, in order to evaluate the tribological impact of the laser implantation process. <

Distributed Ledgers für den Materialdatenaustausch - Lechner, Michael; Frey, Philipp; Kreß, Maximilian; Christ, Tassilo; Charlet, Christoph; Merklein, Marion (wt Werkstattstechnik - Online, 2021)
Moderne industrielle Fertigungsprozesse müssen stetig wachsende Anforderungen an Material- und Ressourceneffizienz, Qualität und Variantenvielfalt erfüllen. Die unternehmensübergreifende Zusammenführung integritätsgesicherter Daten ist hierbei Voraussetzung für die retrospektive Identifikation von Qualitätsproblemen, die Dokumentation der Einhaltung von Standards und die Allokation von Ressourcenverbräuchen entlang der Wertschöpfungskette. In diesem Beitrag wird am Beispiel eines Materialcharakterisierungsverfahrens für den hybriden Leichtbau diskutiert, wie mit der Blockchain- Technologie ein manipulationssicheres Speicherkonzept umgesetzt werden kann.<br
Keywords: Werkstoffe; Digitalisierung; Industrie 4.0

Drawing Capability of High Formable Packaging Steel: Comparison of Limiting Drawing Ratio and Forming Limit Curve - Knieps, Fabian; Köhl, Manuel; Merklein, Marion (Key Engineering Materials, 2022)
To assess the suitability of different packaging steels for complex deep drawing applications, nowadays, the total elongation and the Lankford coefficients in simple tensile tests are used. However, the simple use of uniaxial tensile tests is not supposed to predict the limiting drawing ratio precisely and thus the suitability for deep drawing applications. At the same time, the conduction of limiting drawing ratio experiments is extensive and requires a high testing effort. Therefore, in this work, the correlation between the forming limit curve results were compared to the results of limiting drawing ratio experiments to predict the formability of packaging steel by a much simpler criterion. At the same time, different approaches to calculate the plane strain forming limit by tensile test data were used to assess the drawing capability of packaging steel. Results revealed a strong correlation between the measured plane strain forming limit and the limiting drawing ratio at a fixed blank holder force. However, calculation methods based on tensile test data were not able to predict the drawing capability sufficiently.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Deep Drawing; Forming Limit Curve; Packaging Steel

Druckversuch bei erhöhten Temperaturen - Schaub, Adam; Lechner, Michael; Merklein, Marion (Tagungsband Werkstoffprüfung DGM, 2013)
LFT Import::2019-08-05 (1919)

Dry Film Lubricants in Aluminium Sheet Metal Forming - Geiger, Manfred; Meiler, M.; Pfestorf, Markus; Merklein, Marion (Proceedings of the 3rd International Conference THE Coatings in Manufacturing Engineering, 2002)
LFT Import::2019-08-05 (1720)

Dual beam Nd:YAG laser welding: Influence of lubricants to lap joint welding of steel sheets - Geiger, Manfred; Merklein, Marion; Otto, Andreas; Blankl, Andreas (Proceedings of the XVI. International Symposium on Gas Flow and Chemical Lasers & High Power Laser Conference, Gmunden, Austria, 2006)
LFT Import::2019-08-05 (1313)

Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes - Besserer, Hans-Bernward; Hildenbrand, Philipp; Gerstein, Gregory; Rodman, Dmytro; Nuernberger, Florian; Merklein, Marion; Maier, Hans Juergen (Journal of Materials Engineering and Performance, 2016)
To produce parts from sheet metal with thickened functional elements, bulk forming operations can be employed. For this new process class, the term sheet-bulk metal forming has been established recently. Since sheet-bulk metal forming processes such as orbital forming generates triaxial stress and strain states, ductile damage is induced in the form of voids in the microstructure. Typical parts will experience cyclic loads during service, and thus, the influence of ductile damage on the fatigue life of parts manufactured by orbital forming is of interest. Both the formation and growth of voids were characterized following this forming process and then compared to the as-received condition of the ferritic deep drawing steel DC04 chosen for this study. Subsequent to the forming operation, the specimens were fatigued and the evolution of ductile damage and the rearrangement of the dislocation networks occurring during cyclic loading were determined. It was shown, that despite an increased ductile damage due to the forming process, the induced strain hardening has a positive effect on the fatigue life of the material. However, by analyzing the fatigued specimens a development of the ductile damage by an increasing number of voids and a change in the void shape were detected.
LFT Import::2019-07-29 (2149)
Keywords: DC04; ductile damage; orbital forming; sheet-bulk metal forming

Dynamic correction of oscillatory forces during ultrasonic-assisted metal forming - Michalski, Markus; Leicht, Uwe; Heath, Andrew; Merklein, Marion (Production Engineering, 2017)
Numerous investigations in the past decades reported that the forces required for forming processes can be reduced by superimposing high frequency oscillation. Even though many studies have been carried out identifying and assessing the complex cause of this reduction, cause-effect relationships are generally not yet established in detail. Since the measurement of dynamic forces plays a key role in clarifying the causes, a precise measurement of the forming forces oscillating with high frequency is necessary. Although dynamic force measurement is a well-known field of research, this study focuses on its utilisation for ultrasonic-assisted forming processes. Since dynamic effects distort original measurements in this frequency range, adjustment is required. Based on measurement instruments with high temporal resolution the present study introduces an approach for creating and employing a frequency dependent force correction in the high dynamic range. The experimental procedure for creating a transfer function up to a limiting frequency of 40 kHz is later analysed and verified by numerical modal and transient simulations. The results indicate that the highly location dependent dynamic force detection has major influence on peak forces. Observed deviations can be precisely corrected using the generated frequency dependent transfer function.
LFT Import::2019-07-29 (2239)
Keywords: Finite element method (FEM); Force; Measurement; Metal forming; Transfer function; Ultrasonic

Edge crack sensitivity of lightweight materials under different load conditions - Tsoupis, Ioannis; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2016)
This study addresses the analysis of edge crack sensitivity of DP800 steel and AA5182 aluminum alloy in dependency of punching and machining operation as well as load case of subsequent forming. The inserting of a round hole by punching with defined punch-to- die-clearance, milling and drilling is compared. Subsequent forming is performed by standardized hole expansion test and by Nakajima-tests with three different specimen geometries. Local strain distribution at the surface for Nakajima-tests is measured by optical strain measurement technique and investigated in order to evaluate local deformation before failure. Additionally, resulting hole expansion ratio λ is determined. Significant higher X as well as local strain values ϵ max are achieved by machined holes. This is directly coupled to higher local formability and stretchability for both materials. Furthermore, the load condition has a strong impact on the edge crack sensitivity of the material. Prior failure is observed with changing stress conditions using different specimen geometries also influencing the reachable maximum failure strain. Higher edge crack sensitivity is observed for DP800, which is in good accordance to the material properties in terms of ductility and strength. These data in dependency of the process parameter can be used for the design of automotive components.
LFT Import::2019-07-29 (2172)

Effect of a Local Laser Heat Treatment on the Formability of Multi-layered 6000 Series Aluminum Alloys - Merklein, Marion; Herrmann, Jürgen (Physics Procedia, 2016)
The production of multi-layered aluminum alloys using the Accumulative Roll Bonding Process (ARB) is an auspicious possibility to fabricate nanostructured sheet material with enhanced mechanical properties. The increased strength qualifies these semi-finished products for lightweight applications in automotive industry. However, the ARB process also leads to a reduced ductility of the ultra-fine grained material. Furthermore, failure mechanisms like delamination can occur during forming operations. A local short term laser heat treatment according to the Tailor Heat Treated Blanks technology can be applied in order to enhance the formability and prevent failure. Multi-layered sheets of the aluminum alloy AA6014 were produced in a warm rolling process. The mechanical properties as well as the bond strength are investigated within this contribution using tensile tests and T-peel tests. The material characterization is carried out in dependency of the heat treatment temperature. Air bending tests in combination with a local laser heat treatment are used in order to investigate the formability of the multi-layered aluminum sheets.
EAM Import::2019-03-14

Effect of a strain rate dependent material modeling of a steel on the prediction accuracy of a numerical deep drawing process - Vallaster, Eva; Wiesenmayer, Sebastian; Merklein, Marion (Production Engineering, 2023)
In the production of sheet metal components, batch and process fluctuations cause deviations in the resulting component properties, which often lead to production rejects. To counteract this inline, the computing time for predicting the process result and optimizing the process parameters must be very short, which is why analytical models are advantageous. A large database is usually required for modeling, and numerical simulations are well suited for generating it. The stamping velocity is a process parameter possibly varying, but strain rate dependency of the material often is neglected in numerical simulations. The objective of this study is to analyze the effects of strain rate dependent material modeling on the simulation accuracy of a sheet metal forming process. Therefore, uniaxial tensile tests and layer compression tests at different strain rates are conducted on the steel HC340LA. Based on this, the material behavior is captured in a strain rate dependent material card, which is used for the numerical simulation of a deep drawing process of a geometry with complex shape. For the validation of the model, experiments are carried out and being compared with the computational results in terms of force–displacement curves and part geometry. Furthermore, numerical investigations are used to analyze if drawbead height and blankholder force have an influence on the strain rate distribution and whether this affects the process forc

Effect of elevated tool temperatures on the properties of high-strength aluminum alloys during tailor quench forming (TQF) - Rigas, Nikolaos; Jäckisch, Manuel; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2022)
High-strength aluminum alloys have a great lightweight potential due to their high specific strength-to-weight ratio. However, industrial use of this material is limited due to the low formability at room temperature. In recent years, the so-called hot forming quench (HFQ®) process has proven, to be an effective forming method for manufacturing high-strength aluminum alloys. During deep drawing, the high cooling rate generates the potential for a subsequent aging operation and thereby the formation of strength-increasing precipitations. As a result, complex-shaped components with high strength can be produced. In the future, tailored components with both ductile and high-strength areas are increasingly needed to fulfill the growing lightweight and safety requirements of the government. One method to influence the mechanical properties is the use of a tailor quench forming (TQF) process. In this regard, a simultaneous component production and adjustment of the final mechanical properties is possible. However, it has not been investigated so far, how the tool temperature and the subsequent aging parameters influence the thermal interactions and thus the mechanical characteristics of the parts. In addition, the crash performance of these components has not been investigated. For this reason, a high-strength aluminum alloy is quenched under different thermal conditions and is then artificially aged. To determine the resulting thermo-mechanical properties, temperature analysis, hardness tests and tensile tests, as well as high-speed tests have been performe
Keywords: AA7075; Tailor quench forming; Mechanical properties; Crash performance

Effect of picosecond laser based modifications of amorphous carbon coatings on lubricant-free tribological systems - Häfner, Tom; Heberle, Johannes; Hautmann, Hubert; Zhao, Rong; Tenner, Jennifer; Tremmel, Stephan; Merklein, Marion; Schmidt, Michael (Journal of Laser Micro Nanoengineering, 2017)

Effect of process conditions on mechanical behavior of aluminium wrought alloy EN AW-2618 additively manufactured by Laser Beam Melting in powder bed - Karg, Michael; Ahuja, Bhrigu; Schaub, Adam; Schmidt, Jochen; Sachs, Marius; Mahr, Alexander; Wiesenmayer, Sebastian; Wigner, Leon; Wirth, Karl-Ernst; Peukert, Wolfgang; Merklein, Marion; Schmidt, Michael (Proceedings of Laser in Manfacturing Conference 2015, 2015)
Additive Manufacturing offers geometric freedom excellently suited for topology optimized light weight designs. Ideally these should be built from materials of high strength to weight ratio and high plastic formability- such as aluminium-copper wrought alloys. Al-Cu wrought alloys are considered much less suitable for welding without cracks, so processing them in Laser Beam Melting of Metals in powder bed (LBM) can be considered challenging. Today, the only class of aluminium alloys widely processed by LBM is that of aluminium-silicon cast alloys which are easily weldable. In this contribution, mechanical characteristics of LBM samples are presented and discussed. Tensile tests were conducted under variation of load direction relative to build-up direction and heat treatment. Pronounced anisotropy was observed. Remarkably, elongation at break of T6 heat treated samples pulled in build-up direction exceeds values from literature for conventionally manufactured EN AW-2618A. The chemical constitutions of both the powder and the LBM samples were analyzed and shown to be similar to the expected EN AW-2618A. For further interpretation, boundary conditions of sample production, metallographic microsections and fracture surfaces were considere
Keywords: Additive Manufacturing; high-strength Aluminium Copper Wrought Alloy EN AW-2618A; AlCuMgNi; 3.1924; Selective Laser Melting™; LaserCUSING™; Direct Metal-Laser-Sintering™

Effect of Residual Stress on the Distortion of Microembossed Metal Inserts for Assembly Injection Moulding - Frey, Philipp; Höhler, C.; Merklein, Marion (4M/IWMF2016 Conference: Proceedings of 11th International Conference on Multi-Material Micro Manufacture, 2016)
LFT Import::2019-08-05 (2214)

Effect of Surface Structure on Run-in Wear in Steel-Polyamide Gear Sets - Schubert, Dominik; Rohrmoser, Andreas; Merklein, Marion; Drummer, Dietmar (Zeitschrift Kunststofftechnik, 2019)

Effect of temperature and punch speed on forming limit strains of AA5182 alloy in warm forming and improvement in failure prediction in finite element analysis - Satish, D. Raja; Kumar, D. Ravi; Merklein, Marion (Journal of Strain Analysis For Engineering Design, 2017)
Formability of AA5182-O aluminum alloy sheets in the warm working temperature range has been studied. Forming limit strains of sheets of two different thicknesses have been determined experimentally in different modes of deformation (biaxial tension, plane strain and tension-compression) by varying temperature and punch speed. A correlation has been established for plane strain intercept of the forming limit diagram (FLD0) with temperature, punch speed and thickness from the experimental results. This correlation has been used to plot the forming limit diagrams for failure prediction in the finite element analysis of warm deep drawing of cylindrical cups. The effect of strain and strain rate on material flow behavior has been incorporated using a strain rate-sensitive power hardening law in which the strain hardening exponent and strain rate sensitivity index have been experimentally determined. The predictions from simulations have been validated by warm deep drawing experiments. Large improvement in accuracy of failure prediction has been observed using the FLDs plotted based on the developed correlation when compared to the existing method of calculating FLD0 using only strain hardening coefficient and thickness. The results clearly indicate the importance of incorporating temperature and punch speed in failure prediction of Al alloys using FLDs in the warm working temperature range.
CRIS-Team Scopus Importer:2023-03-29
Keywords: aluminum alloy; failure prediction; finite element simulation; forming limit diagram; warm deep drawing; Warm forming

Effect on the mechanical properties of sheet metals after the use of drawbeads in deep drawing - Schmid, Harald; Merklein, Marion (5th International Conference on New Forming Technology ICNFT Bremen 2018, 2018)
The use of modern and more complex materials leads to a need for detailed knowledge and controlling of the material flow. Next to the blank holder force or the lubrication system, drawbeads are nowadays one common way to bring serial forming processes under control. Although drawbeads are already well investigated regarding their retention forces, the effect on the resulting mechanical properties after a drawbead passage is not analysed in detail yet. This work will show the influence of a common drawbead geometry used in forming processes on typical mechanical properties of sheet metal. Therefore, two different sheet metal materials are preloaded in a modified strip drawing test with industrial used drawbead geometry. In testing, three different pressure levels between 2.5 MPa and 7.5 MPa and three levels of drawing speed between 10 mm/s and 50 mm/s are combined to nine variations which will be examined. Afterwards, specimens are cut out by a laser cutting machine of the drawn strips. Those already preloaded and deformed specimens are then tested under standard conditions with the use of an optical measurement system. The results like tensile strength or elongation at fracture are compared to the initial state and each other and discussed with consideration of pressure and speed levels to work out the main effects. Those results are a contribution for the optimization of deep drawing simulations of parts including drawbeads or to evaluate the influence of drawbeads on forming processes to specify or even expand process limitations.
LFT Import::2019-08-05 (2317)
Keywords: Deep drawing; Hardening; Sheet metal

Efficient Aluminium - Anwendung hochfester Aluminiumlegierungen im modernen Karosseriebau - Degner, Julia; Merklein, Marion (Tagungsband des 37. EFB-Kolloquiums Blechverarbeitung 2017, 2017)
LFT Import::2019-08-05 (2223)

Efficient Aluminum - Qualifizierung des Einsatzes höchstfester Aluminiumlegierungen im Karosseriebau - Lechner, Michael; Zimmermann, Andrea; Graser, Matthias; Merklein, Marion (Tagungsband zum 1. Green Factory Bavaria Kolloquium 2014 - Engergieeffiziente Produktion, 2014)
LFT Import::2019-08-05 (2044)

Effiziente Bewertung von Blechumformprozessen durch die Reduzierung kritischer Einflussgrößen in der stochastischen Simulation - Merklein, Marion; Sturm, Vera; Wahl, M. (Bauteile der Zukunft - Methoden und Prozesse - Tagungsband T31 des 30. EFB-Kolloquiums Blechverarbeitung am 2. und 3. März 2010 in Bad Boll, 2010)
LFT Import::2019-08-05 (311)

Effiziente maßgeschneiderte Wärmebehandlung von Blechhalbzeugen in der Serienfertigung - Kahrimanidis, Alexander; Lechner, Michael; Wortberg, D.; Merklein, Marion (wt Werkstattstechnik - Online, 2015)
LFT Import::2019-07-29 (2119)

Effiziente maßgeschneiderte Wärmebehandlung von Blechhalbzeugen in der Serienfertigung - Kahrimanidis, A.; Lechner, Michael; Wortberg, D.; Merklein, Marion (wt Werkstattstechnik - Online, 2015)
By using aluminium alloys in the automotive industry, the mass of cars can be reduced and their environmental compatibility increased. However, the formability of aluminium alloy is limited in comparison to conventional steel material. Therefore, the Institute of Manufacturing Technology has cooperated with the Daimler AG to develop a new approach for enhancing formability by local heat treatment before the forming operation. The technology is known as Tailor Heat Treated Blanks (THTB). This paper presents the efficient integration of the approach in the press shop with respect to technological restrictions. Also, the suitability of different heat treatment methods in dependency of production quantity and the number of variants will be discussed and a recommendation is derived.
CRIS-Team Scopus Importer:2024-02-29

Eigenschaften reibrührgeschweißter Aluminium-Stahl-Verbindungen - Geiger, Manfred; Merklein, Marion; Giera, Artur; Staud, Detlev (Berichtskolloquium der DFG-Forschergruppe 505, 2005)
LFT Import::2019-08-05 (1242)

Einfluss anisotropen Materialverhaltens von Aluminium-Glänzwerkstoffen auf die Rissausbildung beim Lochaufweitversuch - Beck, Johannes; Merklein, Marion; Friedrichsen, M. (Tagung Werkstoffprüfung 2016, 2016)
LFT Import::2019-08-05 (2198)

Einfluss der Auflösung des Dehnungsfeldes auf die Kennwertermittlung im Scherzugversuch von Aluminium- und Magnesiumlegierungen - Lenzen, Matthias; Suttner, Sebastian; Merklein, Marion (Tagung Werkstoffprüfung 2016, 2016)
LFT Import::2019-08-05 (2194)

Einfluss der Auswertestrategie auf die Grenzformänderungskurve - Kuppert, Andreas; Friebe, H.; Hotz, W.; Merklein, Marion; Möller, T.; Volk, W. (Tagungsband Werkstoffprüfung 2012, 2012)
LFT Import::2019-08-05 (1850)

Einfluss der Auswertestrategie auf die Grenzformänderungskurve - Kuppert, Andreas; Merklein, Marion; Friebe, H.; Möller, T.; Hotz, W.; Volk, W. (MP Materials Testing, 2013)
LFT Import::2019-07-29 (1914)

Einfluss der fertigungsbedingten Gestalt und Struktur auf das Einlaufverhalten von Stahl-Kunststoff-Getriebepaarungen - Schubert, Dominik; Rohrmoser, Andreas; Hagenah, Hinnerk; Merklein, Marion; Drummer, Dietmar (Industriekolloquium der Forschergruppe FOR 2271, 2019)

Einfluss der Fließkurve auf den Rohrbiegeradius - Merklein, Marion; Vatter, Peter; Plettke, Raoul; Grüner, Martin (wt Werkstattstechnik - Online, 2012)
LFT Import::2019-07-29 (1816)

Einfluss der Werkzeugeigenschaften auf die tribologischen Bedingungen beim Presshärten - Schwingenschlögl, Patrik; Merklein, Marion (XXXVII. Verformungskundliches Kolloquium, 2018)
LFT Import::2019-08-05 (2311)

Einfluss der Werkzeugtemperatur auf die tribologischen Bedingungen beim Presshärten - Schwingenschlögl, Patrik; Tenner, Jennifer; Gauglitz, S.; Merklein, Marion (11. Erlanger Workshop Warmblechumformung, 2016)
LFT Import::2019-08-05 (2217)

Einflussgrößen im Presshärtprozess - Merklein, Marion; Hoff, Cornelia; Lechler, Jürgen (Car Body Colloquium, 2005)
LFT Import::2019-08-05 (1202)

Einfluss mikrogeformter Kanten an Metalleinlegern auf die Temperaturwechselbeständigkeit mediendichter Kunststoff-Metall-Hybriden - Heinle, Martina; Frey, Philipp; Merklein, Marion; Drummer, Dietmar (Zeitschrift Kunststofftechnik, 2018)
The increasing number of electronics in several industrial sectors leads to a rising demand for flexible and adaptable electronic systems with high functional density and resilience. An efficient method for producing such parts is the encapsulation of metal inserts, for example lead frames, by means of assembly injection molding. Here one major challenge is to provide electronics with durable media tightness in a severe environment. The research work covered in this paper focuses on the influence of micro formed edges of metal inserts on the durability of tightness during temperature cycling.
LFT Import::2019-07-29 (2339)
Keywords: Assembly injection molding; Edge rounding; Embossing; Polymer-metal-hybrids; Temperature-shock-test; Tightness

Einfluss thermomechanischer Prozessparameter auf die tribologischen Eigenschaften beim Presshärten - Wieland, Michael; Merklein, Marion (8. Erlanger Workshop Warmblechumformung, 2013)
LFT Import::2019-08-05 (1922)

Einfluß unterschiedlicher Wärmebehandlungsrouten auf die Robustheit und Höhe der mechanischen Eigenschaften des Stahls 22MnB5 - Glatzer, M.; Stöhr, Thomas; Merklein, Marion; Sikora, S. (Tagungsband 4. Erlanger Workshop Warmblechumformung, 2009)
LFT Import::2019-08-05 (218)

Einsatz numerischer Analysetools bei der Auslegung und Herstellung kaltfließgepresster Stahlzahnräder - Rohrmoser, Andreas; Kiener, Christoph; Hagenah, Hinnerk; Merklein, Marion (Konstruktion, 2019)
In the drivetrain and transmission technology gears are used in large quantities, which is why an efficient and sustainable production is gaining importance. At the same time the application of new material combinations leads to a demand for adjustable component properties in order to positively influence the operational behavior. Cold forging provides the potential of manufacturing geared components with beneficial mechanical and geometrical properties in a highly productive process. However the industrial application of cold forging faces challenges regarding limited tool life and the achievable gear quality. To face these challenges the development of targeted approaches within the component and process design is necessary. In this context the application of numerical analyses offers a promising approach, which enables the investigation of the resulting operational behavior of the forming tool and gear.
LFT Import::2019-07-29 (2372)

Einsatz prozessangepasster Aluminiumplatinen für die Herstellung von Karosserieziehteilen - Merklein, Marion; Vogt, Uwe (Arbeits- und Ergebnisbericht des DFG SFB 396, 2007)
LFT Import::2019-08-05 (1472)

Einsatz prozessangepasster Aluminiumplatinen in der Blechumformung - Merklein, Marion; Kerausch, Michael (Viertes Industriekolloquium, SFB 362 Fertigen in Feinblech, Multi-Material-Design, 2004)
LFT Import::2019-08-05 (1056)

Embossing of Metal Inserts for Subsequent Assembly Injection Moulding of Media Tight - Frey, Philipp; Heinle, Martina; Leisen, Christoph; Drummer, Dietmar; Merklein, Marion (Key Engineering Materials, 2015)
UnivIS-Import:2017-12-18:Pub.2015.tech.FT.FT-KT.emboss

Embossing of metal inserts for subsequent assembly injection moulding of media tight electronic systems - Frey, Philipp; Heinle, Martina; Leisen, Christoph; Drummer, Dietmar; Merklein, Marion (Key Engineering Materials, 2015)
Keywords: Metal forming; Microforming; Moulding

Enhanced formability of aluminium blanks by local laser heat treatment - Merklein, Marion; Geiger, Manfred; Vogt, Uwe (Proceedings of the 5th LANE Conference, 2007)
LFT Import::2019-08-05 (1471)

Enhanced Formability of Ultrafine-Grained Aluminum Blanks by Local Heat Treatments - Merklein, Marion; Vogt, Uwe (Key Engineering Materials, 2009)
High strength aluminum blanks can be obtained by grain-refinement due to an Accumulativ Roll Bonding (ARB) process, in which two sheets are iteratively brushed, stacked on top of each other and subsequently rolled together. The high shear stresses during the rolling cycles result in an ultrafine-grained microstructure with an average grain size ranging between 200 to 1000 nm. Whereas the grain-refinement causes a drastically increased strength of the aluminum material, the formability of the ARB-blanks made of industrially used aluminum alloys such as the AA6016 deteriorates to the same degree as the strength rises. In this context, a local heat treatment of the ARB-blank reducing the material's strength and increasing its ductility in specific zones will allow to recover the blank's formability again. The research work presented in this paper studies the microstructural effects of a short-term heat treatment on the mechanical properties of ARB-blanks made of AA6016. Experimental investigations including hardness measurements, tensile tests as well as microscopic analyses show that heat treatments of only several seconds already result in significant increases of the material's ductility and decreases of the material's strength. By applying these microstructural mechanisms in terms of a specific heat treatment layout, functional gradients of strength and ductility adapted to the succeeding forming operation can be setup significantly enhancing the ARB-blank's formability.
EAM Import::2019-03-14

Enhanced Investigation of Flow and Necking Behavior of Sheet Metal within Layer Compression and Tensile Tests - Kuppert, Andreas; Merklein, Marion (Proc. of COMA 10, 2010)
LFT Import::2019-08-05 (295)

Enhanced numerical results on friction stir welded aluminium butt joints - Staud, Detlev; Giera, Artur; Merklein, Marion; Geiger, Manfred (Proceedings of the 12th International Conference on Sheet Metal (SheMet), 2007)
Friction stir welding is a newer technology to join materials in the solid phase. Therefore plenty of problems which appear by melting phase welding technologies for aluminium alloys are avoided by this process. This is the main chance for friction stir welding to be accepted and integrated in forthcoming applications, especially for uses out of aluminium alloys. Starting from former results for friction stir welding of aluminium this article deals with the determination of the constitutive material properties of friction stir welded aluminium tailored blanks with regard to the finite-element (FE) simulation of sheet metal forming. The FE simulation of the formability of welded sheet metal demands the knowledge of the precise mechanical properties of the base material as well as the characteristic zones of the weld seam, which are affected by friction stir welding. While ordinary tensile tests can only determine the constitutive behaviour of a simple tensile specimen, an optical strain measurement can be used to determine flow stresses of the base and of the welded material with an adapted tensile specimen, respectively. By the usage of the so called rule of mixture the advantages of this new approach is demonstrated with a comparison of the tensile forces within FE simulations and experimental validations. For this purpose specimen with the weld seam oriented perpendicular and parallel to the uniaxial loading direction are utilized.
LFT Import::2019-08-05 (1395)
Keywords: Friction stir welding; Mechanical properties; Simulation; Tensile test

Enhancement of a Constitutive Friction Law by Considering Plastic Smoothing of Rough Surfaces in Dependency on the Bulk Stresses - Beyer, Florian; Löffler, Maria; Willner, Kai; Engel, Ulf; Merklein, Marion (Tribology in Industry, 2016)
The aim of this work is the improvement of a constitutive friction law which has been identified for the specific demands of sheet-bulk metal-forming. The constitutive friction law determines the friction shear stress in dependency on the plastic smoothing of the surface roughness, which also affects the real contact area. An experimental setup is introduced to determine the change of the surface roughness, which is influenced by the tensile bulk stress in the workpiece. In order to model the experimental results, a well-established half-space model is presented and improved to consider strain hardening. The half-space model is used to determine the change of the contact area as a function of the tensile bulk stress. This interdependency is also reflected by the proposed constitutive friction law.
Keywords: friction; constitutive friction law; half-space model; elasto-plastic contact; strain hardening; bulk stresses; sheet-bulk metal forming

Enhancement of formability of aluminum alloys in multi-stage forming operations by a local intermediate heat treatment - Merklein, Marion; Lechner, Michael; Kuppert, Andreas (Production Engineering, 2012)
Within this paper a new approach to enhance the formability of aluminum alloys in multi-stage forming processes will be presented. The technology's key idea is the local adaption of the mechanical properties after a first forming step and their optimization for the subsequent forming operation. The partial change of the mechanical properties is obtained by a short term heat treatment between two forming steps. Based on the new property distribution the material flow during the second forming is improved and the formability of the material can be enhanced. The presented work covers all necessary steps for a successful application of the technology. After a material characterization in dependency of the pre-straining and the heat treatment, the heat affected zone, which is a result of the high heat conductivity of aluminum alloys was analyzed. In the end appropriate heat treatment layouts were designed via numerical simulation and the enhancement of formability was demonstrated with a real multi-stage forming process. © 2012 German Academic Society for Production Engineering (WGP).
LFT Import::2019-07-29 (1823)
Keywords: Enhancement of formability; Hardenable aluminum alloys; Local intermediate heat treatment; Multi-stage forming-process

Enhancement of springback prediction of AHSS parts by advanced friction modelling - Durmaz, U.; Heibel, S.; Schweiker, T.; Merklein, Marion; Berahmani, S.; Hol, J.; Naegele, P. (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
CRIS-Team WoS Importer:2021-11-05

Enhancement of the Forming Limits for Orbital Formed Tailored Blanks by Local Short-term Heat Treatment - Hetzel, Andreas; Merklein, Marion; Lechner, Michael (Procedia Manufacturing, 2020)
Nowadays, the manufacturing industry faces opposing challenges like a reduction of carbon dioxide on the one hand and on the other hand an increasing weight due to higher safety standards and additional functions. Concepts like lightweight design and functional integration are essential to ensure a sustainable and individual mobility. Gear systems consist of multi-functional parts with a varying sheet thickness and different geometric elements. Since conventional manufacturing processes like shearing are reaching their limits due to complexity and a lack in efficiency, the application of Tailored Blanks is a promising approach to meet these requirements. Manufactured by orbital forming, these process-adapted blanks dispose a high material efficiency. A tumbling motion of the upper punch enables the material distribution, realizing functional components with different material thickenings. The substitution of steel by aluminum is a common approach to meet the demands of lightweight construction. However, the use of aluminum results in a decreased formability at a constant level of strength. In order to enhance the local forming limits, a short-term heat treatment can be applied, reducing the materials' strength, whereas the untreated areas still offer the initial properties. To transfer the results of fundamental research in Sheet-Bulk Metal Forming with conventional steel to the use of lightweight material, the precipitation hardenable aluminum alloy EN AW 6016 is investigated in an orbital forming process. Since the formability of aluminum is limited and the material flow during the process is three-dimensional, different heat treatment strategies are applied to a rotational-symmetric Tailored Blank and the resulting components are investigated regarding their geometry and mechanical properties. To increase the geometric complexity with regard to an industrial application, the transferability to a cyclic-symmetric layout is analyzed. To evaluate the potential of the heat treatment, the treated components are compared to Tailored Blanks manufactured without heat treatment.
CRIS-Team Scopus Importer:2020-06-05
Keywords: Aluminum EN AW 6016; Heat Treatment; Lightweight Design; Orbital Forming; Tailored Blanks

Enhancing Forming Limits by Using a Magnetorheological Fluid as Active Fluid Medium for Hydroforming - Rösel, Sebastian; Merklein, Marion (Steel research international: Special Edition: 10th International Conference on Technology of Plasticity, 2011)
The automobile industry has to preserve commodities by light weight constructions. It is to the forming technology to overcome the challenges of forming high complex part geometries, by offering more flexible forming technologies e.g. hydroforming, which are cost efficient and can utilize the whole formability of the used materials. One active deviance, which has prevented the application of hydroforming of blanks In serial production, is the sealing of the cavity In the flange area. To Insure a complete sealing, it Is necessary to remain below a defined ratio between cavity pressure and contact pressure In the flange area, which Is restricting the process window. This experimental work focuses on the Influence of the magnetorheological fluid Basonetic 5030 on the sealing ratio compared to mineral oil shell tellus 100. Experiments are carried out at different cavity and contact pressures with the media mentioned above. Additionally a defined magnetic flux density Is applied to the magnetorheological fluid In the flange area to Increase its viscosity. Afterwards cups are drawn with DC04 of a sheet thickness of 1 mm and the resulting cup geometries are measured. Various geometric parameters are compared to each other to identify the process latitudes and the possible process parameters. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
LFT Import::2019-08-05 (1650)
Keywords: Forming processes; Hydroforming; Magnetorheological fluid (MRF); Sheet metal

Enhancing Process Limits of Blank Hydroforming - Merklein, Marion; Grüner, Martin; Rösel, Sebastian (Internationale Konferenz „Hydroumformung von Blechen, Rohren und Profilen“, 2012)
LFT Import::2019-08-05 (1813)

Enlargement of deep drawability of aluminium blanks - Merklein, Marion; Kerausch, Michael; Hußnätter, Wolfgang; Geiger, Manfred (Advanced Technology of Plasticity, Proceedings of the 7th ICTP, 2002)
LFT Import::2019-08-05 (1697)

Entwicklung von Ansätzen zur Erweiterung der Prozessgrenzen in industrienahen Laborversuchen anhand einer Streifenzuganlage - He, Franz; Merklein, Marion; Dechant, Stefanie (Warmumformung von höchstfesten Vergütungsstählen: Tagungsband zum 17. Erlanger Workshop Warmblechumformung, 2022)
Zur Umsetzung der immer weiter steigenden Anforderungen an die passive Sicherheit bei gleichzeitiger Verringerung des Bauteilgewichts spielt die Warmumformung ein wesentliche Rolle. Die Technologie des Presshärtens bietet dabei die Möglichkeit zur Herstellung höchstfester Strukturbauteile bei gleichzeitig reduzierter Wandstärke. Um Verzunderung zu unterbinden und Korrosionsschutz im Prozess zu gewährleisten, wird auf die verwendeten Blechhalbzeuge eine Aluminisum-Silizium(AlSi)-Beschichtung aufgebracht. Die Werkstück-beschichtung wurde als Hauptursache für die adhäsive Verschleißbildung identifiziert und hat somit einen entscheidenden Einfluss auf die Werkzeugstandzeit und die Qualität von pressgehärteten Bauteilen. Die Entwicklung effektiver Maßnahmen zur Verringerung von Reibung und Verschleiß setzt ein grundlegendes Prozessverständnis in Bezug auf das tribologische System voraus. Vor diesem Hintergrund werden die industriellen Presshärtebedingungen im Labormaßstab anhand von Streifenzuganlagen abgebildet. Ein limitierender Faktor im Flachbahnzugversuch in bisherigen Untersuchungen ist die erreichbare Flächenpressung. Während die existierende Anlage eine theoretische maximale Flächenpressung von 130 MPa umsetzen kann, können bereits Anpressdrücke von 7,5 MPa zur Ausbildung von Kaltverschweißungen durch Abscherung der Beschichtung und Reibzahlabbrüchen führen. Vor diesem Hintergrund werden Störfaktoren im Versuch identifiziert, um die vorhandene Warmstreifenziehanlage zu modifizieren und Versuche unter industrierelevanten Parametern durchzuführen. <
Keywords: Streifenzugversuch; Reibkoeffizient; Verschleiß; 22MnB5

Environmentally benign tribo-systems for metal forming - Bay, Niels Oluf; Azushima, A.; Groche, P.; Ishibashi, I.; Merklein, Marion; Morishita, M.; Nakamura, T.; Schmid, S.; Yoshida, M. (CIRP ANNALS - Manufacturing Technology, 2010)
The growing awareness of environmental issues and the requirements to establish solutions diminishing the impact on working environment as well as external environment has initiated ever increasing efforts to develop new, environmentally benign tribological systems for metal forming. The present paper gives an overview of these efforts substituting environmentally hazardous lubricants in cold, warm and hot forging as well as sheet forming and punching/blanking by new, less harmful lubricants and furthermore describes other measures directed towards the same goal such as development of anti-seizure tool materials and coatings and application of structured workpiece and tool surfaces. © 2010 CIRP.
LFT Import::2019-08-05 (1897)
Keywords: Environmental impact; Lubricants; Metal forming tribology; Structured tool surfaces; Structured workpiece surfaces; Tool coatings; Tool materials

Erfassung von Kontaktspannungen im Flansch während wirkmedienbasierter Blechumformprozesse - Merklein, Marion; Trägler, Horst; Blankl, Andreas (Automobiltechnik in Bayern, 2009)
LFT Import::2019-07-29 (1583)

Ermittlung des Reibverhaltens von Tailor Welded Blanks im Näpfchenziehversuch - Tolazzi, Massimo; Lamprecht, Klaus; Merklein, Marion (Tagungsband zum XXV. Verformungskundlichen Kolloquium 04.-07.03., 2006)
LFT Import::2019-08-05 (1259)

Ermittlung prozessrelevanter Werkstoffkenngrößen für die Blechumformung bei erhöhten Temperaturen - Merklein, Marion; Hußnätter, Wolfgang; Hecht, Joachim (Tagungsband Werkstoffprüfung 2006, 2006)
LFT Import::2019-08-05 (1319)

Ermittlung temperaturabhängiger Werkstoffkennwerte für die Auslegung von Halbwarm- und Warmumformprozessen - Kuppert, Andreas; Merklein, Marion (Metall, 2008)
LFT Import::2019-07-29 (290)

Ermittlung vin thermischen und mechanischen Werkstoffeigenschaften höchstfester Vergütungsstähle für das Presshärten - Merklein, Marion; Geiger, Manfred; Lechler, Jürgen (Tagungsband VDEh-Workshop: Moderne thermomechanische Prozessstrategien in der Stahlumformung, 2007)
LFT Import::2019-08-05 (1459)

Erratum: “Potential of joining dissimilar materials by cold formed pin-structures” (Journal of Materials Processing Tech. (2020) 283, (S0924013620301114), (10.1016/j.jmatprotec.2020.116697)) - Kraus, Martin; Merklein, Marion (Journal of Materials Processing Technology, 2021)
The publisher regrets that the below images appear incorrectly in the original article. Figure 3 should appear as follows:
CRIS-Team Scopus Importer:2021-05-14

Erweiterung des Prozessfensters für das lokale Aufkohlen bei erhöhten Temperaturen eines pressgehärteten Komplexphasenstahls - Risse, Jan Henning; Merklein, Marion (Warmumformung von höchstfesten Vergütungsstählen: Tagungsband zum 18. Erlanger Workshop Warmblechumformung, 2023)
Als Leichtbaustrategie werden in der Automobilkarosserie, z. B. als B-Säulen, höchstfeste Stähle mit maßgeschneiderten Eigenschaften zunehmend für crashrelevante Bauteile eingesetzt. Mit dem Verfahren Tailored Carburization können Bauteile lokal verstärkt werden, ohne die Blechdicke zu erhöhen und ohne die Notwendigkeit von komplexer Werkzeugtechnik. Damit hat dieses Verfahren das Potenzial, bei Leichtbauteilen mit verformungsfreien Zonen, z.B. bei Batteriegehäusen, oder in Kleinserien Verwendung zu finden. Normalerweise wird die Aufkohlung bei 950 °C durchgeführt, wobei die höchsten Festigkeiten bei langen Zeiten von bis zu 6 Stunden erreicht werden, was die Gesamtprozesszeit verlängert. Durch die Erhöhung der Temperatur nimmt die Kohlenstoffdiffusion zu, was eine kürzere Wärmebehandlungszeit und folglich eine kürzere Prozessdauer ermöglicht, wie bereits grundlegend gezeigt wurde. Ziel dieser Untersuchung ist es daher, den Einfluss der einzelnen Aufkohlungsparameter beim Diffusionshärten auf die mechanischen Eigenschaften des aufgekohlten und gehärteten Komplexphasenstahls CP-W® 800 zu identifizieren sowie das Prozessfensters zu erweitern.<br
Keywords: Presshärten; Maßgeschneiderte Eigenschaften; Aufkohlung

Evaluation of Crack Propagation During Cyclic Bending of Wire Strip - Biallas, Alina; Merklein, Marion (Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, 2024)
Steel fibers applied as concrete reinforcement like in Ultra High Performance Concrete reduce the wall thickness and thus the amount of concrete [1]. The process chain notch rolling and cyclic bending presents the foundation of an ecologically and economically efficient approach for production of steel wire fibers. For fundamental perception of the characteristics and interdependencies of the innovative production method, analysis by experimental model processes is required. Previous research determined influence of various process parameters on crack propagation [2], which is further analyzed in this study. As testing material, a DP600 sheet metal (t0 = 0.8 mm) is applied. Cyclic bending tests of wire strip with staggered amounts of cycles and varying bending angles are performed and evaluated based on load curves and micrographs. The analysis supplies identification of stages of crack propagation, which allows recommendations for process design regarding controllability and geometry of fracture. For supporting the analysis, stamping and cyclic bending is numerically implemented in the simulation software LS DYNA to picture the present strain stage applied during bending. The process evaluation together with the built simulation model can later be used as reference for a suitable numerical modeling of crack propagation that will enable a more flexible analysis of the process chain and parameter effects by simulation.<br
Created from Fastlane, Scopus look-up
Keywords: Bending; Damage; Crack propagation

Evaluation of kinematic hardening models for multiple stress reversals under continuous cyclic shearing and multi - step bending - Rosenschon, Martin; Suttner, Sebastian; Merklein, Marion (LS-DYNA Forum 2015, 2015)
LFT Import::2019-08-05 (2125)

Evaluation of Material Behavior for Wire Strip under Cyclic Bending Load and Preparation of an Experimental Test Method - Biallas, Alina; Merklein, Marion (Paper presented at ESAFORM 2021, 2021)
Steel fibers as concrete reinforcement improve the building material’s mechanical properties and enlarges its field of application. The production of steel fibers by the process chain notch rolling and cyclic bending promises energetic improvement compared to the conventional manufacturing process wire drawing. The innovative procedure is not yet researched extensively and modelling of the material behavior brings with it many challenges. Different stress states of both process steps require various material models and material failure must be considered. The study brings an appropriate modelling of the test sheet metal DP600 with a thickness of t0 = 0.8 mm for the second process step into focus. The wire strip’s notches are exposed to a cyclic tension-compression load for which high strength steel exhibits early yielding and a distinct transient region of the stress-strain curve after load reversal. For this reason, the isotropic-kinematic hardening model by Chaboche and Rousselier determined in tension-compression tests is validated by cyclic bending tests. For considering crack initiation, an appropriate ductile damage model for depicting material fatigue is identified. To allow practical realization of the process and validation of the material model, an experimental test method for manufacturing wire strip samples by notch stamping is introduc
Keywords: Kinematic hardening; Damage; Steel fibers

Evaluation of testing methods for the characterization of material properties under plane strain - Lenzen, Matthias; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2022), 2022)
CRIS-Team WoS Importer:2023-01-20

Evaluation of the properties of AA7020 tubes generated by a heat treatment based hydroforming process - Reblitz, Jonas; Trân, Ricardo; Kräusel, Verena; Merklein, Marion (SheMet2023, 2023)
Energy efficiency and sustainability are getting more and more relevant in society and industry. Especially energy-intensive sectors offer a high potential for power savings. Thus, different lightweight strategies are applied in the automotive sector. In this context, high strength profile components are used as crash structures. As an example, these profiles are deployed to protect the battery of electrically powered vehicles. Therefore, high strength aluminum alloys of the 7xxx series are suitable for compensating the high battery weight partly. Compared to steel, this material is characterized by a high strength-to-weight ratio as well as an increased thermal conductivity. However, one challenge in forming high strength aluminum alloys is the limited formability at room temperature. For this purpose, heat treatment based process routes for tube hydroforming are investigated within this research work. By the combination of W-temper forming and hydroforming complex part geometries can be generated. A subsequent artificial ageing process realizes the required high strength of the profiles. Using AA7020 tubes, the properties of a demonstrator geometry are compared to the initial state T6 of the semi-finished parts. For this purpose, the wall thickness distribution and the grain structure are evaluated. Thereby, the influence of forming and heat treatment on the geometrical and microstructural properties is to be analyzed. For the evaluation of the achievable hardening of the aluminum alloy, the mechanical properties are investigated by tensile tests. This investigations provide an assessment of the process route under industry-related conditions.<br
Keywords: Heat Treatment; Hydroforming; Tubes

Evaluierung von Modellen zur Beschreibung der Umwandlungsplastizität durch experimentelle Untersuchungen an einem Wälzlagerstahl - Lutz, Stefan; Weninger, J.; Helldörfer, B.; Merklein, Marion (9. Erlanger Workshop Warmblechumformung, 2014)
LFT Import::2019-08-05 (2064)

Evolution of yield loci for aluminum alloy AA6016 and deep drawing steel DC06 under the influence of non-linear strain paths - Merklein, Marion; Suttner, Sebastian (Key Engineering Materials, 2013)
The application of modern materials plays an important role directly under the aspect of lightweight potential. To exploit these options effectively a numerical accurate reproduction of the material behavior is indispensable. Especially in the case of large deformations a directional and strain rate dependent hardening behavior can be observed. By disregarding this effect significant failure in the computed stress state can arise, which can conduct to a corruption of the spring-back forecast. Within this contribution a new test method for analyzing the evolution of subsequent yield loci under strain path changes for the aluminum alloy AA6016 and the deep drawing steel DC06 is presented. In the first stage of the experimental investigations, yield loci with linear strain paths were considered to characterize the material behavior for the initial condition. On further experiments with several stress states the strain path dependent hardening behavior of the material is determined. The non-linear strain paths are realized through uniaxial prestrained primary specimens with following extraction of secondary samples for following stress states, e.g. a modified ASTM simple shear test specimen. Subsequent yield loci are investigated and compared to the yield surfaces Hill'48 and Barlat 2000 (Yld2000-2d) with an isotropic hardening behavior. With this study the evolution of the yield locus for prestrained specimens is evaluated. The research of the subsequent yield loci for strain path changes serves as basis for further scientific investigations with a view to assess different approaches of isotropic-kinematic hardening models in consideration of the analyzed steel and aluminum sheet metals. © (2013) Trans Tech Publications.
LFT Import::2019-07-29 (1852)
Keywords: Hardening behavior; Simple shear test; Strain path changes; Yield locus evolution

Examination of controlled thermal radiation exchange for the production of tailored properties on press-hardened components - Reihani, Alborz; Heibel, Sebastian; Schweiker, Thomas; Merklein, Marion (Materials Research Proceedings, 2023)
Through the development of furnace technologies and tool concepts, partial press hardening has become an established process in the automotive industry for setting tailored properties on press-hardened components. Tailored properties on press-hardened components offer the potential to improve crash performance as well as to facilitate downstream joining processes and mechanical treatments. One approach to adjust these properties through local pre-cooling is based on a special oven chamber with an integrated masking technology, called TemperBox®. The integrated mask protects the blank locally from incident heat radiation and simultaneously absorbs the blank's own radiation. An important parameter during this process is the pre-cooling time in the TemperBox®. The pre-cooling time can influence the phase transformation and the component properties. Therefore, blanks made of the conventional press hardening steel 22MnB5 AS150 are partially precooled in the TemperBox® for different periods of time and the component properties are investigated on the basis of formed hat profiles. In addition, a simulation approach for calculating the heat radiation exchange with the finite element software LS-Dyna® is shown. Based on the simulative and experimental investigations, it is demonstrated that there is a dependency between pre-cooling time and the components properties.
CRIS-Team Scopus Importer:2023-04-28
Keywords: Heat Treatment; Hot Stamping; Tailored Properties

Examining Hot Crack Susceptibility of Aluminium Laser Welds with Help of FE Simulation - Komlodi, Attila; Merklein, Marion; Otto, Andreas (Proceedings of Modelling and Simulation Workshop, 20.-24.01, Igls, österreich, 2003)
LFT Import::2019-08-05 (972)

Experimental analysis of the forming behavior of ash wood veneer with nonwoven backings - Zerbst, David; Affronti, Emanuela; Gereke, Thomas; Buchelt, Beate; Clauß, Sebastian; Merklein, Marion; Cherif, Chokri (European Journal of Wood and Wood Products, 2020)
In the present study, the forming behavior of veneer with nonwoven backings was analyzed. The paper contributes to the lack of data on numerical predictions of the formability of veneers for the manufacturing of automotive trim parts. Tensile and shear tests were carried out at normal climate conditions and after water immersion to obtain material parameters for a transverse isotropic material description. The Tsai Wu failure criterion was applied to the estimation of strength under different stress combinations. Analysis of the directional deep drawing capacity of the veneer laminate was done by the Nakajima test. Stress states from biaxial to uniaxial were induced into the material depending on the geometry of the sample. Strains were evaluated locally until material failure using the digital image correlation method. Major strain was defined in the direction perpendicular to the grain. Increasing major strain was found from biaxial to uniaxial stress states. Highest strain limits were found for wet veneers tested with heated forming tools. Cracks occurred in the early wood zone for all geometries and propagated in the direction parallel to the grain. Generally, the Nakajima test is suitable for the evaluation of the formability of veneer laminate sheets. The presented data and, in general, the suggested experimental program can be used for the development and validation of veneer laminate material models for forming simulations.
CRIS-Team Scopus Importer:2020-02-28

Experimental analysis of the influence of the embossing and upsetting process on joint strength in resistance element welding with upset auxiliary joining elements - Meinhardt, M.; Lechner, Michael; Merklein, Marion (INTERNATIONAL DEEP-DRAWING RESEARCH GROUP CONFERENCE (IDDRG 2021), 2021)
CRIS-Team WoS Importer:2021-11-05

Experimental and analytical investigations on friction stir welding of steel aluminium tailored hybrids - Geiger, Manfred; Merklein, Marion; Giera, Artur; Staud, Detlev (Production Engineering, 2006)
LFT Import::2019-07-16 (1254)

Experimental and Analytic Determination of Forming Limit Curves Applied to a Bainitic Steel - Kuppert, Andreas; Merklein, Marion; Mütze, S. (Proc. of MATFEM Conference 2010, 2010)
LFT Import::2019-08-05 (890)

Experimental and Numerical Analysis of Cold Formed Multi Pin Structures Using a Multi-Acting Tool Design - Römisch, David; Merklein, Marion (12th Tooling Conference and Exhibition Tooling 2022, 2022)
Intelligent material combinations for the production of multi-material systems as well as lightweight construction to save weight are becoming increasingly important in industrial applications. However, the joining process of dissimilar materials poses challenges to established joining processes due to different mechanical properties and chemical incompatibilities and lead to a need for new, versatile joining technologies. The use of cold extruded pins made from the sheet metal plane is the subject of current research due to the added potential for weight saving and the advantage of process-induced work hardening. To produce these pins and especially multi-pin structures, however, new tool concepts are needed. In the present work, a multi-acting tooling design is presented to produce a multi-pin array consisting of a 3x4 matrix by extrusion from the sheet metal plane. The tool allows the punches, the blank holder and the ejector to be controlled independently. The individual pins can be formed both simultaneously in one stroke and sequentially to control the formation of each pin individually. The numerical model utilised for designing the active parts of the tool is used to analyse the complex, resulting material flow and to gain insights into the pin forming. Furthermore, first experimental results of cold extruded multi-pin arrays are presented to obtain a basic scientific understanding of the influence of the tool on the process in combination with the numerical result
Keywords: Multi pin extrusion; Multi pin tool; Joining by forming; Mechanical joining

Experimental and numerical analysis of tribological effective surfaces for forming tools in Sheet-Bulk Metal Forming - Kersting, Petra; Gröbel, Daniel; Merklein, Marion; Peter, Sieczkarek; Wernicke, Sebastian; Tekkaya, A. Erman; Krebs, Eugen; Freiburg, Dennis; Biermann, Dirk; Weikert, Tim; Tremmel, Stephan; Stangier, Dominic; et al. (Production Engineering, 2016)
Sheet-Bulk Metal Forming (SBMF) allows the manufacture of complex parts with integrated functional form elements, such as teeth and thickened areas. Therefore, bulk forming operations are applied to sheets with initial thicknesses of 2 or 3 mm. The design and functionality of the tools are as important as the process itself. Therefore, the working group “Tools” of the Transregional Collaborative Research Centre on Sheet-Bulk Metal Forming (CRC/TR73) focuses on the optimization of the technical tool design. By varying topographies or applying tailored coatings, the friction behavior is changed to achieve a better form filling and to reduce process forces during the forming operations. In this paper, the potential of different tailored surfaces is validated by simulations and experimental studies. The tribological behavior of 14 surface microstructures is evaluated using a half-space model in order to select structures suitable for application. Those were characterized experimentally by ring-compression and pin-extrusion tests. The determined friction factors were used in a forming simulation to predict the form filling of small cavities in a flow forming operation. Furthermore, special attention is paid to the utilization of the anisotropic behavior of specific structures. The results were validated by an incremental gear forming process.
Keywords: Sheet-Bulk Metal Forming; Tailored surfaces; Milling technologies; Coating technologies; Forming simulations; Tribology simulation

Experimental and numerical investigation of a strain rate controlled hydraulic bulge test of sheet metal - Suttner, Sebastian; Merklein, Marion (Journal of Materials Processing Technology, 2016)
LFT Import::2019-07-29 (2185)
Keywords: Constant strain rate; Hydraulic bulge test; Material characterization; Metal forming

Experimental and Numerical Investigation on a Full Forward Extrusion Process from Metal Strip - Stellin, Tommaso; Merklein, Marion; Engel, Ulf (Proc. 9th Int. Conf. Multi-Material Micro Manufacture, 2012)
LFT Import::2019-08-05 (1844)

Experimental and numerical investigations of the tribological conditions in a cup drawing process - Merklein, Marion; Zöller, Fabian; Sturm, V. (Proc. Int. Deep Drawing Research Group Conf. 2014 (IDDRG 2014), 2014)
LFT Import::2019-08-05 (2012)

Experimental and numerical investigations on a pressure dependent friction model - Zöller, Fabian; Vera, Sturm; Merklein, Marion (Key Engineering Materials, 2015)
The objective of this paper is the investigation of the implemented pressure dependent friction model in the FE simulation program AutoForm. Since the values for the required parameters of this approach are not defined in the actual FE simulation program, this paper contributes to a first definition of these parameters. Therefore, experimental investigations with the cup drawing tests are carried out. With the support of the experimental results regarding the maximum stamping force, the model is calibrated and subsequently validated by the comparison of the sheet thicknesses of the experimental and numerical investigations. The results of this validation reveal a good accordance of simulation and reality in nearly all areas. However there are also areas in which the prediction accuracy decreases in comparison to the basic simulation. Therefore, additional investigations have to be carried out which concentrate on the modification of this pressure dependent approach towards a better universal prediction accuracy of the simulation.
LFT Import::2019-08-05 (2084)
Keywords: Friction; Simulation; Tribology

Experimental and numerical investigations on frictional behaviour under consideration of varying tribological conditions - Merklein, Marion; Zöller, Fabian; Sturm, Vera (Advanced Materials Research, 2014)
In present time the FE-simulation of body parts in sheet metal drawing processes has to be continuously improved to increase the prediction accuracy. The objective of this paper is to describe a methodology to improve the simulation by mapping the complex tribological conditions of the process in the simulation. This methodology focuses on the dependency of influencing parameters on the friction coefficient. The influence respectively the dependency of these factors has been investigated, both in an experiment of a plane strip drawing test and in a FE-simulation of this test. With the sensitivity analysis in the numerical simulation it is possible to compare the implemented COULOMB-friction-model against the experimental results. The results of the experimental and numerical investigation show the need of further investigations on a more geometrical complex test to prove if it is possible to transfer the knowledge and dependencies that has been found in the experiment with the strip drawing test to a more geometrical complex test. © (2014) Trans Tech Publications, Switzerland.
LFT Import::2019-08-05 (1979)
Keywords: Numerical Simulation; Sheet Metal Forming; Tribology

Experimental and Numerical Studies on the Forming Behavior of High Strain Al-Mg-Si(-Cu) Sheet Alloys - Klos, Artur; Kahrimanidis, Alexander; Wortberg, Daniel; Merklein, Marion (Procedia Engineering, 2017)
Al-Mg-Si(-Cu) heat-treatable alloys are characterized by a significant increase in hardness upon ageing compared to 6xxx series alloys with a copper content of Cu<0.15 wt.%. With a higher amount of copper, the formability and ductility of the alloy are typically decreased compared to 6xxx alloys with a low content of Cu. The purpose of this paper is to discuss recent developments of high-strain 6xxx alloys for future automotive applications. The influence of copper content on the forming behavior of Al-Mg-Si(-Cu) sheet alloys was investigated. The examination was confined to four different alloys in total: Three of type AA6111 with varying Cu contents and a reference alloy type AA6016. All alloys were pre-aged at > 80 °C after quenching and had a solute content of Si/Mg ratio in balance (wt.%). The forming behavior was characterized by tensile tests, bending tests, cup drawing tests and Nakajima tests. The experimental results are supplemented by numerical simulation. Hocket-Sherby's hardening law and Hill 90 yield criterion were used for the material modeling behavior. The Marciniak-Kuczynski model (M-K-model) approach was chosen to construct forming limit diagrams for all alloys. The study showed that forming behavior is strongly dependent on the type of alloy, the thickness, and natural aging, which is in turn influenced by the storage period and the quenching rate in sheet production. Up to a Cu content of 0.8 wt.% the limiting drawing ratio is approximately equal to the reference alloy. With contents greater than 0.8wt%, an exponential drop of the formability is observed. Furthermore, the results of the cup drawing tests are compared to the numerical simulations in order to validate the simulation of parts with higher complexity. The results of this work contribute to the application of high strain 6xxx alloys in automotive applications.
CRIS-Team Scopus Importer:2023-03-29
Keywords: AA6016; AA6111; Aluminum; formability

Experimental determination of stress limit curves - comparison of applied technological tests and stamped components by fractographic examinations - Hezler, Christian; Tsoupis, Ioannis; Merklein, Marion; Kasparbauer, M. (Proc. 5th Forming Technology Forum, 2012)
LFT Import::2019-08-05 (1807)

Experimental Determination of Yielding of the Aluminium Wrought Alloy AA6016 for Biaxial Loading - Hußnätter, Wolfgang; Merklein, Marion; Geiger, Manfred (Proceedings of COMA 2007, 2007)
LFT Import::2019-08-05 (1385)

Experimental Determination of Yield Loci for Magnesium Alloy AZ31 under Biaxial Tensile Stress Conditions at Elevated Temperatures - Geiger, Manfred; Merklein, Marion; Hußnätter, Wolfgang; Grüner, Martin (Production Engineering, 2008)
The finite element analysis (FEA) has become one of the most relevant and most important tools in fields of sheet metal forming for designing processes and dimensioning parts. However, reliability and quality of the numerical results strongly depend on the whole FE-model and especially on the modeling of the material behavior, which shows wide impact on calculated stresses and strains of sheet metal parts. Therefore, the experimental determination of characteristic material data concerning anisotropic and temperature-effects is essential. In this paper the influence of temperature on the yielding and the hardening behavior of the magnesium sheet metal alloy AZ31 are investigated for different uniaxial and biaxial stress conditions. For that purpose an experimental setup has been developed at the Chair of Manufacturing Technology (LFT) which enables biaxial tensile testing of sheet metal. Yield loci of AZ31 are determined as a function of temperature and they are based on solely measurement data of the forming process itself. © German Academic Society for Production Engineering (WGP) 2008.
LFT Import::2019-07-29 (294)
Keywords: Computer aided engineering; Material characterization; Yield locus diagram

Experimental Evaluation of Cold Forging Lubricants Using Double-Cup-Extrusion-Tests - Lorenz, Robby; Hagenah, Hinnerk; Merklein, Marion (Materials Science Forum, 2018)
Cold forging processes enable the economical production of high quality components like joints, shafts and gears. The manufactured parts are characterized by improved properties such as hardness, surface quality and fatigue strength. For manufacturing components using cold forging, a comprehensive knowledge regarding the cold forging procedure and its process parameters is needed. One important influencing factor, which needs to be analyzed to use the potential of this kind of processes, is the tribological system, especially the used lubricant. The tribological conditions significantly influence the material flow and thus the workpiece quality. Furthermore, resource efficient and environmentally benign metal forming processes became very important within the last decade. The present study evaluates the resulting tribological conditions and their differences for various cold forging lubricants with and without a zinc phosphate based lubricant carrier. The lubricants are based on molybdenum disulphide, polymers, or both inorganic salts and waxes. The tribological conditions of the different lubricants are investigated using the Double-Cup-Extrusion-Test (DCET) as a laboratory friction test.<br
LFT Import::2019-08-07 (2295)
Keywords: Cold forming; Gear; Lubrication; Steel; Tribology

Experimental Evaluation of the Feasibility and Reproducibility of a Novel Multi-step Forming Process for Cu-OFE Micro Gear Manufacturing Compared to Macro-scale Forming - Rohrmoser, Andreas; Kraus, Martin; Leicht, Miriam; Merklein, Marion (Manufacturing Letters, 2022)
The increasing miniaturization of technical systems leads to a rising demand for micro components. Miniaturized drive systems with geared micro parts or micro gears are applied in various industries. Due to the demand for high production volumes, productive and resource-efficient fabrication is of major importance. Compared to industrially applied manufacturing methods like cutting and metal powder injection, cold forming provides technological, economic and ecological potential for the mass production of micro gears. It enables high productivity and advantageous mechanical properties of the gears. In the macroscopic size range, forming processes are well established in series production of gears. However, in micro-scale, according to the current state of the art, cold forming of modules m < 0.2 mm is not possible due to size effects, high tool loads and handling problems. Within this contribution, a multi-stage forming process for the fabrication of micro gears with a module of m = 0.1 mm is introduced and compared with a conventional forming process on macro-scale with a module of m = 1.0 mm. The use of coil material provides potential for easy handling of the micro parts in a progressive die for the potential application in a high-speed press. In addition, the multi-stage forming achieves a grain alignment, which enhances the formation of the micro gear profile. Based on the comparison between micro- and macro-scale, the performance of the micro process is analyzed with regard to deviations of process force as well as gear quality and possible size effects are identified. The results prove the feasibility of the process chain and the achievement of equivalent part quality and reproducibility compared to macro-scale forming.<br

Experimental Investigation and Numerical Modeling of the Bond Shear Strength of Multi-layered 6000 Series Aluminum Alloys - Herrmann, Jürgen; Suttner, Sebastian; Merklein, Marion (Procedia Engineering, 2017)
The use of high-strength aluminum alloys is one key factor for the realization of lightweight design in industrial applications. Besides alloying, it is possible to produce high-strength sheet materials using the Accumulative Roll Bonding (ARB) process. Based on a repetitive stacking and roll bonding process, multi-layered sheets with a nanocrystalline grain structure are produced. The bond formation is created by a cold welding process due to the high pressure in the rolling gap and cracks in the oxide film of the aluminum sheet material caused by the thickness reduction. The experimental investigation of the bond strength is crucial for the assessment of the formability of the multi-layered sheet material. High bonding quality is necessary in order to prevent failure mechanisms like delamination in subsequent forming operations. Furthermore, a numerical model, which contains discrete layers over the sheet thickness as well as their bonding mechanisms will be implemented in finite element analysis. This enables a process layout for forming operations by the prediction of delamination effects. Within this investigation, an experimental test method is presented to characterize the bond shear strength of multi-layered sheet material. The use of an optical strain measurement system enables the identification of the material behavior over the sheet thickness during the shear test. For this investigation a 16-layered aluminum alloy AA6014 is used. However, the bond shear strength of the last bonded respectively middle layer of the sheet material is investigated. The 16-layered material has 15 bonds over the thickness but the one in the middle has the lowest bond strength as it was only roll bonded once compared to the others, which were rolled at least twice. The bonding mechanisms are modelled using a tiebreak contact formulation in the finite element software LS-DYNA. Concluding, the numerical model is validated by comparison with the experimental results.
EAM Import::2019-03-14

Experimental investigation of a process chain combining sheet metal bending and laser beam melting of Ti-6Al-4V - Butzhammer, Lorenz; Dubjella, Patrick; Huber, Florian; Schaub, Adam; Aumüller, Markus; Baum, Alexander; Petrunenko, Oleksandra; Merklein, Marion; Schmidt, Michael (Lasers in Manufacturing LIM 2017, 2017)
In spite of several advantages such as a great freedom of design, comparatively long process times are a major drawback in additive manufacturing technologies such as laser beam melting (LBM) of metal powder. A strategy to overcome this limitation is to combine additive manufacturing with other promising manufacturing concepts. In this paper, we characterize hybrid components manufactured using a consecutive process chain including warm bending of Ti-6Al-4V sheets and LBM. With the additive process a functional structure is built on top of the bending zone using powder from the same material. As a measure for the connection strength, shear tests were performed. The shear strength is analyzed for both possible process routes of forming and LBM. Therefore a modular clamping device for bent sheets was developed in order to enable simultaneous production of additive parts on several bent sheets with different thicknesses and radii. Results show that the formability of sheets is strongly influenced by the sequence of the process route, while no significant difference in shear strength of the connection was observed, even if the energy density in the LBM process is varied to a large extent. The post heat treatment is discussed as major cause, as homogenization of the microstructure takes place, although the applied temperature is beneath the beta transus temperature.
Keywords: Laser Beam Melting; Additive Manufacturing; Bending; Titanium Alloys

Experimental investigation of distortion behavior of laser heat treated blanks - Rigas, Nikolaos; Merklein, Marion (Procedia CIRP, 2020)
Aluminum alloys fulfill the growing demands for lightweight applications and are completely recyclable. The use of high-strength aluminum alloys offers the opportunity to replace safety-relevant steel components. Currently, the use of these alloys is limited due to their low formability and high springback during forming at room temperature. The use of tailored blanks with locally adapted material properties is one opportunity to overcome these limitations. By local heat treatment, zones are locally softened and thus crack critical areas during forming can be avoided. At present, blanks with tailored properties are not used extensively. One reason for this is component distortion due to thermal stress, which makes handling the heat-treated sheets more difficult. Aim of this study is the identification and reduction of thermally caused component distortion. Therefore, in this paper the influence of the initial material condition, the sheet thickness as well as the laser spot size on the distortion behavior is investigated.
CRIS-Team Scopus Importer:2020-10-30
Keywords: Distortion; High-strength aluminum; Tailor heat threated blanks

Experimental investigation of heat-treated aluminum profiles - Merklein, Marion; Graser, Matthias; Lechner, Michael (Key Engineering Materials, 2015)
Tailor Heat Treated Profiles (THTP) are profiles that exhibit local different mechanical properties optimized for a subsequent forming operation. The property distribution is realized by short term heat treatment before a forming operation. Based on the interaction of soft and hard areas the material flow can be improved and the formability can be enhanced. Prerequisite for a successful application of the technology is a comprehensive material characterization. Therefore, within this paper the influence of short term heat treatment on the mechanical properties of profiles will be presented. In particular, different heating technologies based on heat conduction and laser radiation are compared. Based on the results, a process window will be derived. All investigations were performed using the precipitation hardenable aluminum alloy EN AW 6060.
LFT Import::2019-07-29 (2112)
Keywords: Aluminum profiles; Characterization; Tailored heat treatment

Experimental investigation of Ti-6Al-4V with a biaxial tensile test setup at elevated temperature - Merklein, Marion; Suttner, Sebastian; Schaub, Adam (Key Engineering Materials, 2014)
The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.
LFT Import::2019-07-29 (2018)
Keywords: Formability; High performance metals; Sheet metal forming

Experimental investigation of tool-sided surface modifications for dry deep drawing processes at the tool radii area - Krachenfels, Kim; Rothammer, Benedict; Tremmel, Stephan; Merklein, Marion (Procedia Manufacturing, 2019)
In conventional deep drawing processes lubricants are applied to reduce friction and wear. Demands for increased sustainability, environmental protection and resource efficiency motivate the realization of lubricant-free forming processes. The direct toolworkpiece contact during dry deep drawing leads to changed tribological conditions. Especially in the areas of increased normal and shear stresses, such as the die radius, the dry contact causes an increased risk of wear and damage to the sheet surface. A wellknown approach to face the challenges of dry deep drawing of steel sheets and aluminum alloys is the application of amorphous carbon based coatings on the tool surfaces. Within this study the tribological behavior of conventional and modified tool surfaces at the critical radii area is investigated with a strip bending rotation test. In this test, the friction coefficient is determined based on the relative movement between a rotating test cylinder and a sheet-metal strip bent in a die. For the tribological tests the sheet materials AA6014, AA5182 and zinc coated DC04 are applied. The modification of the tool sided surface was achieved by applying ta-C and a-C:H coatings to the test cylinder. In addition to tests with coated surfaces, tests with uncoated tools are carried out for reference. By analyzing the resulting friction coefficients for the different sheet materials, the suitability of ta-C and a-C:H coatings for dry deep drawing processes is evaluated comparatively. In order to investigate cause-effect relations as well as wear mechanisms, the tool and workpiece surfaces are characterized before and after testing.<br
Keywords: Dry Deep Drawing; Tribology; Carbon Based Coatings

Experimental investigations of processing the high carbon cold-work tool steel 1.2358 by laser metal deposition for the additive manufacturing of cold forging tools - Hentschel, Oliver; Scheitler, Christian Josef; Fedorov, Aleksandr; Junker, Daniel; Gorunov, Andrey; Haimerl, A.; Merklein, Marion; Schmidt, Michael (Journal of Laser Applications, 2017)
In the field of tool making, Laser Beam Melting of metals has been already used to fabricate injection moulds with complex inner cooling channels made out of the low-carbon maraging tool steel X3NiCoMoTi18-9-5 (1.2709). Furthermore, laser metal deposition (LMD) is an established technology for the repair of worn-out tools and the deposition of wear resistance coatings based on metal matrix composites. However, at the moment, the processing of high-carbon tool steels for the additive manufacturing of complete cold forging tools has only been investigated to a limited extent. Within the scope of the presented research, the processing of the high-carbon cold-work tool steel 60CrMoV18-5 (1.2358) by LMD is analyzed in detail. In this context, geometrically simple cuboidal structures are directly generated on dissimilar substrate plates made out of the hot-work tool steel X37CrMoV5-1(1.2343) via the application of various process parameter combinations. The manufactured cuboidal structures are metallographically prepared and subsequently analyzed with respect to substrate bonding, relative density, defect formation, microstructure, chemical composition, and microhardness. In this context, the influence of the particle size distribution of the used tool steel powder on the LMD process itself and the resulting relative density are extensively researched. For this purpose, high-speed camera measurements of the powder particle stream were conducted in order to determine both the powder particle stream diameter and the lateral powder particle distribution with regard to the distance z from the powder nozzle. Furthermore, the influence of an additional substrate preheating (maximum preheating temperature of 400 °C) on the resulting microstructure and hardness of the additively generated samples is the subject of the presented investigations.
CRIS-Team Scopus Importer:2022-06-05

Experimental investigations of processing the high carbon cold-work tool steel 1.2358 by LMD for the additive Manufacturing of cold forging tools - Hentschel, Oliver; Scheitler, Christian Josef; Fedorov, Aleksandr; Junker, Daniel; Gorunow, Andrej; Haimerl, Andreas; Merklein, Marion; Schmidt, Michael (Journal of Laser Applications, 2017)
LFT Import::2019-07-29 (2266)

Experimental investigations on high-precision microcutting of copper foils with microfabricated silicon punches - Hildering, Sven; Becsi, L.; Engel, Ulf; Merklein, Marion; Mescheder, U. (Proc. 12th Int. Conf. European Society for Precision Engineering and Nanotechnology, 2012)
The miniaturisation of metallic parts is considerable in various industrial sectors. This trend leads to a demand for decreasing tool dimensions. This study shows the application of monocrystalline silicon as tool material for etched punches used for microcutting of thin copper foils, as etching is a common method in microsystems technology for the economical fabrication of thin vertical structures with a high surface quality. Cutting experiments in a specially designed test rig show the applicability of silicon for microcutting of copper foils and the effect of tool wear on the punching force. The workpiece quality is characterised by a large burnish area of the sheared edges.
LFT Import::2019-08-05 (1804)

Experimental Study of a Full Forward Extrusion Process from Metal Strip - Merklein, Marion; Stellin, Tommaso; Engel, Ulf (Key Engineering Materials, 2012)

Experimental Study of a Microforging Process of Parallel Ribs from Metal Strip - Stellin, Tommaso; Engel, Ulf; Merklein, Marion (Proc. 4M/ICOMM2015 Conf., 2015)
LFT Import::2019-08-05 (2100)

Experimental study of the potential for extending the process limits in multi-stage forming of micro gears from sheet metal by a local short-term laser heat treatment - Leicht, Miriam; Kraus, Martin; Rohrmoser, Andreas; Merklein, Marion (Materials Research Proceedings 2023, 2023)
Cold forming of micro gears is currently not possible for modules m < 0.2 mm due to the occurrence of high tool stresses, handling problems and size effects. A multi-stage process chain of micro bulk forming from sheet metal offers the potential to solve these challenges. However, the industrial applicability is limited due to material efficiency. Against this background, the aim of this research work is an improvement of the material utilization as well as a further reduction of the tool stresses. Therefore, the influence of different heat treatment strategies as well as the materials copper Cu-OFE and brass CuZn30 are analyzed. Thus, a local laser heat treatment and a global heat treatment of the blanks are investigated. The focus of this research work is on the first process stage, pin extrusion, which is used for forming of the wheel blank. Since this process setup provides the material for the further forming stages, it has a huge influence on the material efficiency and on the forming of the gearing in the second process stage. Therefore, the component and process properties are evaluated to assess the influence of the measures. The results prove higher material efficiency at a similar tool stress by using local short-term heat treatmen

Experimental Study on Joining by Forming of HCT590X+Z and EN-AW 6014 Sheets Using Cold Extruded Pin Structures - Römisch, David; Kraus, Martin; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2021)
Due to stricter emission targets in the mobility sector and the resulting trend towards lightweight construction in order to reduce weight and consequently emissions, multi-material systems that allow a material to be placed in the right quantity and in the right place are becoming increasingly important. One major challenge that is holding back the rapid and widespread use of multi-material systems is the lack of adequate joining processes that are suitable for joining dissimilar materials. Joining processes without auxiliary elements have the advantage of a reduced assembly effort and no additional added weight. Conventional joining processes without auxiliary elements, such as welding, clinching, or the use of adhesives, reach their limits due to different mechanical properties and chemical incompatibilities. A process with potential in the field of joining dissimilar materials is joining without an auxiliary element using pin structures. However, current pin manufacturing processes are mostly time-consuming or can only be integrated barely into existing industrial manufacturing processes due to their specific properties. For this reason, the present work investigates the production of single- and multi-pin structures from high-strength dual-phase steel HCT590X + Z (DP600, t(0) = 1.5 mm) by cold extrusion directly out of the sheet metal. These structures are subsequently joined with an aluminium sheet (EN AW-6014-T4, t(0) = 1.5 mm) by direct pin pressing. For a quantitative evaluation of the joint quality, tensile shear tests are carried out and the influence of different pin heights, pin number, and pin arrangements, as well as different joining strategies on the joint strength is experimentally evaluated. It is proven that a single pin structure with a diameter of 1.5 mm and an average height of 1.86 mm achieves a maximum tensile shear force of 1025 N. The results reveal that the formation of a form-fit during direct pin pressing is essential for the joint strength. By increasing the number of pins, a linear increase in force could be demonstrated, which is independent of the arrangement of the pin structures.
CRIS-Team WoS Importer:2021-04-30

Experimental study on the flow behavior during hot forming and quenching of the high-strength aluminum alloy AA6111 - Degner, Julia; Horn, Alexander; Merklein, Marion (XXXVI. Verformungskundliches Kolloquium, 2017)
LFT Import::2019-08-05 (2221)

Experimental study on the warm forming and quenching behaviour for hot stamping of high-strength aluminum alloys - Degner, Julia; Horn, Alexander; Merklein, Marion (Journal of Physics: Conference Series, 2017)
LFT Import::2019-08-05 (2228)

Experimentelle Ermittlung der Formgebungsgrenzen metallischer Werkstoffe unter reiner Scherung - Merklein, Marion; Kuppert, Andreas; Biasutti, Manfredi (12. Workshop - Simulation in der Umformtechnik (26.03.2009), 2009)
LFT Import::2019-08-05 (197)

Experimentelle Untersuchung des zweiachsigen Spannungszustands im Kreuzzugversuch zur Identifikation von Werkstoffmodellen für die Finite-Elemente Simulation - Suttner, Sebastian; Merklein, Marion (Tagungsband Werkstoffprüfung, 2013)
LFT Import::2019-08-05 (1920)

Ex-situ and in-situ investigations of the microstructural evolution of AA6082 aluminum alloy during heat treatment - Lypchanskyi, Oleksandr; Rigas, Nikolaos; Korpala, Grzegorz; Merklein, Marion; Prahl, Ulrich (Materials Science and Engineering A-Structural Materials Properties Microstructure and Processing, 2023)
The present study investigated the microstructural evolution of AA6082 aluminum alloy using ex-situ and in-situ methods. Microstructural characterization was performed for the individual steps of the heat treatment parameters. To identify the morphology and kinetics of changes in precipitation and grain, the microstructure of the alloy was examined using scanning electron microscopy/electron backscatter diffraction in combination with energy dispersive X-ray spectrometry. Analysis of the microstructural changes revealed coarser β-Mg2Si nucleation and growth activity, but it showed no changes related to grain growth or α-Al(FeMn)Si precipitation activity. Additionally, the formation of rod-shape β' precipitates was evaluated. Higher temperature promoted the growth and increase in length of β' rods and the appearance of β' rods outside of contact with the intermetallic precipitation. The influences of different isothermal holding temperatures on the relative change in signal velocity generated by a laser ultrasonics for metallurgy (LUMet) system were evaluated. The strong correlation between the findings of microstructural analysis and the results derived from ultrasonic measurement confirmed the efficacy of the novel in-situ model test for predicting microstructural change
Keywords: Aluminum alloy; Precipitation behavior; Ultrasonic signal; Mg2Si

Extension of the forming limits of extrusion processes in sheet-bulk metal forming for production of minute functional elements - Pilz, Florian; Henneberg, Johannes; Merklein, Marion (Manufacturing Review, 2020)

Fabrication and Characterization of Laser Beam Melted Ti-6Al-4V Geometries on Sheet Metal - Schaub, Adam; Ahuja, Bhrigu; Karg, Michael; Schmidt, Michael; Merklein, Marion (Proceedings DDMC 2014 Fraunhofer direct digital Manufacturing conference, 2014)
Laser beam melting is a well-established additive manufacturing process for fabricating fully dense 3-dimensional structures from micro size metal powders using a high intensity laser beam. Ti-6Al-4V is a state of the art alloy used in the Laser Beam Melting process. For light weight applications specifically within the aerospace and medical industry, it is essential to understand and evaluate the interaction of additively manufactured structures with conventionally fabricated sheet metal. The following paper illustrates steps that have been taken in this direction. The paper details various process related modifications undertaken in order to achieve the appropriate mechanical properties of the Laser Beam Melted structure on pre-fabricated thin sheet metal. In order to evaluate mechanical properties, the tensile bond strength is determined. Further the paper also takes into account the development of parameters and scanning strategies for processing Ti-6Al-4V on Realizer SLM 50. An important focus of the conducted experiments is the application of additional strategies in order to reduce the effect of factors, such as oxidation and temperature gradient in the initial layers, adversely affecting the mechanical properties of the hybrid structure. One of the future applications of this initial research could be the fabrication of intricate elements using laser based additive manufacturing processes on sheet metal in order to develop ultra-light weight structures for potential use in critical high technology application
LFT Import::2019-08-05 (1981)
Keywords: Additive Manufacturing; Laser Beam Melting; Sheet Metal; Ti-6Al-4V

Failure behavior of different sheet metals after passing a drawbead - Schmid, Harald; Hetz, Peter; Merklein, Marion (47th SME North American Manufacturing Research Conference, NAMRC 47, Pennsylvania, USA, 2019)
LFT Import::2019-08-05 (2364)

Fatigue Behavior of Cemented Carbide Based Forming Tools - Andreas, Kolja; Merklein, Marion; Engel, Ulf (Proc. 18th Plansee Seminar, 2013)
LFT Import::2019-08-05 (1893)

Fatigue testing of cold forging tools using elastomer compression - Killmann, Martin; Merklein, Marion (CIRP Annals - Manufacturing Technology, 2023)
Cold forging is an ecological production technology for high-strength metal parts. Tool fatigue is the most significant constraint preventing the enhancement of process limits towards complex part geometries. To better analyse tool fatigue, a test method for dies under high inner pressure is researched. The load usually transmitted by the workpiece is applied by compression of elastomers. Results show that the test is able to accurately model the fatigue behaviour of forging tools including crack propagation and the influence of prestressing systems. Compared to conventional fatigue tests, the analysis of different reinforcements and tool geometries is enabled. <
Keywords: Cold Forming; Die; Fatigue

FE-based study of the cutting operation within joining by forming of dissimilar materials using shear-clinching technology - Müller, Martin; Hörhold, Réjane; Meschut, Gerson; Merklein, Marion (Advanced Materials Research, 2015)
LFT Import::2019-07-29 (2109)

FE-basierte Prozess- und Werkzeugauslegung zur Herstellung von Hochleistungsbauteilen mit dem Ziel einer gezielten Einstellung von Bauteileigenschaften - Merklein, Marion; Engel, Ulf; Noneder, Johannes; Zimmermann, Andrea (Tagungsband 13. RoundTable - Simulation in der Umformtechnik, 2012)
LFT Import::2019-08-05 (1806)

Fertigung funktionsoptimierter Bauteile beim Presshärten - Horn, Alexander; Merklein, Marion (Tagungsband zum 13. Erlanger Workshop Warmblechumformung, 2018)
LFT Import::2019-08-05 (2330)

Fertigung innovativer Bauteile aus hochfesten Stählen: Biegen und Schneiden – Risse vermeiden - Merklein, Marion; Tsoupis, Ioannis; Hildering, Sven (Zukunftstechnologien in Bayern - Neue Materialien, Verfahren und Produkte, 2012)
LFT Import::2019-07-29 (206)

Fertigungsaspekte zur umformtechnischen Herstellung von Bauteilen aus Magnesiumblech für den Fahrzeugbau - Geiger, Manfred; Merklein, Marion; Hecht, Joachim; Stich, A. (Tagungsband EFB-Kolloquium 2006 "Konstruktionskonzepte der Gegenwart und Zukunft - Herausforderungen an die Blechbearbeitung", 2006)
LFT Import::2019-08-05 (1271)

Fertigungsmethoden - Lechner, Michael; Böhm, Wolfgang; Merklein, Marion; et al. (Konstruktion, 2013)
CRIS-Team Scopus Importer:2024-02-29

FE Simulation of Laser Assisted Bending - Pitz, Matthias; Merklein, Marion (Sheet Metal 2005, Proceedings of the 11th International Conference on Sheet Metal, 2005)
Steel has a long tradition and is used in nearly every application. In order to be able to compete with other lightweight materials over and over again new steel grades are developed. Interesting steel grades, which are especially suitable for the lightweight construction in the automotive industry, are the multi-phase steels. Multi-phase steels reach already yield strengths over 1000 MPa. This is a challenge for the production engineering. Drawing, forming and cutting tools must be stiff and hard and/or coated, lubricants have to decrease friction to avoid damages induced by the high surface pressures. The designers have to consider the small forming capability by large radii or reduced drawing depths. To overcome these disadvantages new, innovative forming processes, e.g. laser assisted bending or roll forming, have to be developed. In the forming technique it is known that the forming limits can be increased by warm forming. But the conventional heating systems may cause unwanted changes of the material regarding to the structure and the mechanical properties. In the case of multi-phase steels e.g. the hard phases martensite and bainit can be transformed into ferrite and therefore the yield stresses can be changed clearly. In contrast to this laser assisted bending minimizes structural changes due to the local heating of the forming area. Beside the advantage, that only a small area of the bending part is exposed with a thermal load, the heating up with the laser permits high heating rates and also a controlling of the heating and cooling rates, so that the heating and cooling can be adapted to the material and its properties. In the context of this paper parameter studies with FE simulations of the laser assisted bending process are presented.
LFT Import::2019-08-05 (1173)
Keywords: Bending; Simulation; Steel

FE-Simulation of the heat transfer by defined cooling conditions during the hot stamping process - Svec, Thomas; Grüner, Martin; Merklein, Marion (Key Engineering Materials, 2011)
LFT Import::2019-07-29 (1642)
Keywords: Heat transfer; Hot stamping; Numerical simulation; Tailored tempering

Fiber Orientation Mechanism of Continuous Fiber Reinforced Thermoplastics Hybrid Parts Joined with Metallic Pins - Popp, Julian; Kleffel, Tobias; Römisch, David; Papke, Thomas; Merklein, Marion; Drummer, Dietmar (Applied Composite Materials, 2021)
Continuous Fiber Reinforced Thermoplastic (CFRT) hybrid parts offer interesting possibilities for lightweight application, which can exceed the capabilities of mono material metal or CFRT parts. In this case, the joining technology oftentimes is the limiting factor. This study investigates a joining operation with metal pin structures which are additively manufactured via powder bed fusion featuring different diameters and tip geometries, which are inserted into the locally infrared heated CFRT part. The resulting fiber rearrangement is assessed using transmitted light microscopy, confocal laser scanning microscopy as well as micro-computer-tomography. It could be shown that for all assessed pin variants a similar distinct fiber displacement can be seen and that the pin diameter has a significant effect on the resulting fiber orientation with smaller pin diameters being advantageous because of gentle fiber displacement and reduced undulation. The tip geometry has only minor effect on the fiber orientation. Especially in the X/Y plane no systematic influence of the tip geometry on the fiber displacement could be observed. Based on the gained insights a three-stage model of the fiber orientation processes is proposed.
CRIS-Team Scopus Importer:2021-05-07
Keywords: Continuous fiber reinforced thermoplastics; Fiber orientation; Hybrid part; Joining; Organo sheet; Pin

Finite-Element basierte Auslegung funktionsoptimierter Bauteile im Tailored Tempering Prozess - Svec, Thomas; Merklein, Marion (6. Erlanger Workshop Warmblechumformung, 2011)
LFT Import::2019-08-05 (1773)

Finite Elemente Simulation of Deep Drawing of Tailored Heat Treated Blanks - Geiger, Manfred; Merklein, Marion; Kerausch, Michael (Annals of the CIRP, 2004)
LFT Import::2019-08-05 (1055)

Flexibilisierung der Fertigung umformtechnisch erzeugter Bauteile durch prozessangepasste Halbzeuge - Merklein, Marion; Lechner, Michael (11. Umformtechnisches Kolloquium Darmstadt, 2012)
LFT Import::2019-08-05 (1802)

Flexible Rolling of Process Adapted Semi-finished Parts and its Application in a Sheet-Bulk Metal Forming Process - Hildenbrand, Philipp; Schneider, Thomas; Merklein, Marion (Key Engineering Materials, 2015)
By applying bulk forming processes on sheet metals, thin-walled functional components with locally restricted wall thickness variations can be manufactured by forming operations. Using tailored blanks with a modified sheet thickness gradient instead of conventional blanks, an efficient controlling of the material flow can be achieved. One possible process to manufacture these semifinished parts is a flexible rolling process. Based on an established process strategy new results for steels of differing strength and work-hardening behavior are presented in this paper. The influences of each material on the resulting process forces and blank properties regarding the same target geometry are discussed. The tailored blanks are hereby analyzed by their geometrical dimensions, like sheet thickness, and their mechanical properties, e.g. hardness distribution. Additionally, the possibilities of processing these tailored blanks in a deep-drawing and upsetting process are presented with a hereby focus on the residual formability of the tailored blanks.
LFT Import::2019-07-29 (2069)
Keywords: Forming; Rolling; Sheet metal

Flexible rolling of rotational symmetric tailored blanks with a two-sided thickness profile - Vogel, Manfred; Merklein, Marion (Procedia Manufacturing, 2019)
The application of bulk forming operations to sheet metals leads to an increase of the material efficiency due to the enhancement of the process limits compared to conventional forming processes. The main challenges within the process class of sheet-bulk metal forming are high resulting forming forces and a defined control of the material flow. Additionally, the initial blank thickness influences the resulting quality of the geometrical and mechanical properties of functional components, like synchronizer rings. Previous investigations have shown that the application of tailored blanks with a defined one-sided thickness profile can meet these challenges which lead to an increase of the sufficient die filling of functional elements in subsequent forming processes. Due to the further increase of the geometrical complexity with functional elements in- and outside of the frame like carriers or gear teeth, the layout of the tailored blank has to be adapted. Thus, a two-sided thickness profile is necessary, for achieving the sufficient die filling of the functional elements. One possibility for manufacturing these semi-finished parts is a flexible rolling process which is used within the presented work. Thereby, it is necessary to develop a new process strategy for achieving a material thickening on both sides, rolled- as well as die-sided. For enabling a homogeneous material flow, the deep drawing mild steel DC04 with an initial sheet thickness of t0 = 3 mm is used, due to a high formability of this material. The tailored blanks are hereby analyzed regarding the resulting process forces, geometrical dimensions like the sheet thickness, mechanical properties such as the hardness distribution and the resulting surface roughness in important areas.
CRIS-Team Scopus Importer:2019-09-27
Keywords: Cold forming; Rolling; Sheet metal; Tailored blanks

Fließkurvenermittlung für die Kaltmassivumformung druckaufgestickter Stähle - Merklein, Marion; Noneder, Johannes; Engel, Ulf (Proceedings Tagung Werkstoffprüfung, 2010)
LFT Import::2019-08-05 (746)

Flow Behaviour of Advanced Aluminium Materials - Merklein, Marion; Biasutti, Manfredi; Hung Nguyen,; Böhm, Wolfgang (Steel research international: Special Edition: 10th International Conference on Technology of Plasticity, 2011)
The Accumulative Roll Bonding (ARB) process enables manufacturing lightweight sheet metals with outstanding mechanical properties. However, the significant increase In strength Is accompanied by a loss in ductility. The low formability obviously limits the Implementation of these sheet products for automotive applications but It may be enhanced by a local short term heat treatment according to the Tailored Heat Treated Blanks technology. The finite-element based design of the latter method needs accurate information about the plastic behaviour of these advanced materials. In this paper, the flow characteristics of the as-received and by accumulative roll bonding manufactured AA6016 sheets are investigated. Different stress - strain paths are considered testing both products using the tensile test and the layer compression test at room temperature with and without a previous heat treatment. The short term heat treatment Is realized to simulate the conditions occurring in the Tailored Heat Treated Blanks process. The experimental results are presented in form of true stress - strain curves and yield loci determined from different criteria and represented In a principal stress state. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
LFT Import::2019-08-05 (1754)
Keywords: Accumulative roll bonding; Aluminium alloy; Material properties; Tailored heat treated blanks

Flow behaviour of magnetorheological fluids, considering the challenge of sealing in blank hydroforming in the flange area with rectangular leakage area cross-sections - Rösel, Sebastian; Merklein, Marion (Key Engineering Materials, 2011)
The need of light weight constructions and parts with tailored or even more homogeneous mechanical properties especially for structural components leads to the use of alternative forming technologies. These forming processes like sheet metal hydroforming are established to gain more flexibility and to increase the forming limits. But to apply this forming technology successfully, it is necessary to overcome some obstacles. One typical challenge for hydroforming of blanks, which has prevented further application of this technology, is the sealing of the cavity in the flange area. Nowadays there are a lot of basic approaches to accomplish a sealing in this tool area. Commonly a sealing can be reached by increasing the contact pressure in the outer region of the blank. This approach reduces the possible blank draw in and hence abates the possible realisation of complex part geometries. One possible approach to increase the ratio between cavity pressure and contact pressure in the flange area is the choice of a capable active fluid medium. The aim is to reduce the contact pressure in the flange area and nevertheless ensure a complete sealing. In this case the magnetorheological fluid (MR-fluid) BASF Basonetic 5030 is used as a pressure medium for hydroforming. For characterizing this fluid under different amounts of magnetic flux density and in comparison to a common hydraulic medium, an experimental setup was built up to gain process relevant data for hydroforming processes. Therefore different experiments were carried out with different media and different flux densities for the MR-fluid. To get more information about the mode of action and the accessible amounts of cavity pressure and related contact pressures in the flange area, these two process parameters were varied. © (2011) Trans Tech Publications.
LFT Import::2019-07-29 (1635)
Keywords: Active fluid media; Hydroforming; Magnetorheological fluid (MR-fluid); Sheet metal forming

Fluid elements in machine tools - Wegener, Konrad; Mayr, Josef; Merklein, Marion; Behrens, Bernd-Arno; Aoyama, Tojiro; Sulitka, Matej; Fleischer, Juergen; Groche, Peter; Kaftanoglu, Bilgin; Jochum, Nicolas; Moehring, Hans-Christian (CIRP Annals - Manufacturing Technology, 2017)
Fluids play a major role for production machinery and serve for very different tasks as lubricating, tempering, cleaning, transmitting force and energy. Due to maintenance requirements and the environmental impact their utilization is under discussion and alternatives are looked for. In this paper an overview of the latest research activities in the field of fluidic elements on machine tools is presented. The topic of the paper includes an overview of the fluids used in machine tools, the usage of fluidic elements, supply and treatment units, and their influence on machine tools performance. A link to fluidic media on energy efficiency is given. Research challenges in order to increase the performance of machine tools are discussed. The paper excludes metal working fluids, which have been treated in Brinksmeier et al. [33].
CRIS-Team Scopus Importer:2023-03-29
Keywords: Fluid; Machine tool; Performance

Formability Improvement with Tailored Heat Treated Blanks through an Inverse Simulation Approach - Staud, Detlev; Merklein, Marion (Proceedings of the 7th International Conference on Numerical Simulation of 3D Sheet Metal Forming Processes, 2008)
LFT Import::2019-08-05 (1557)

Formability of accumulative roll bonded aluminum AA1050 and AA6016 investigated using bulge tests - Topic, Irena; Höppel, Heinz Werner; Staud, Detlev; Merklein, Marion; Geiger, Manfred; Göken, Mathias (Advanced Engineering Materials, 2008)
The paper reports one of the very first attempts to investigate the formability of ultrafine- grained aluminum sheets produced by a severe plastic deformation process known as accumulative roll bonding. During hydraulic bulge testing the samples showed a tendency to higher achievable burst pressures and/or von Mises equivalent strains with increasing number of accumulative roll bonding cycles, indicating promising deformation behaviour and good formability.
WW1::765

Formability of the magnesium alloy AZ31 at elevated temperatures - Merklein, Marion; Beccari, S. (The 9th International Conference on Material Forming, ESAFORM 2006, Glasgow, United Kingdom, April 26-28, 2006)
LFT Import::2019-08-05 (1302)

Formability of ultrafine-grained AA6016 sheets processed by accumulative roll bonding - Hausöl, Tina; Schmidt, Christian; Maier, Verena; Böhm, Wolfgang; Nguyen, Manh Hung; Merklein, Marion; Höppel, Heinz Werner; Göken, Mathias (Key Engineering Materials, 2012)
Aluminium alloy AA6016 was accumulative roll bonded up to eight cycles in order to produce an ultrafine-grained microstructure. The formability of these sheets was investigated by means of bending tests. Furthermore the influence of a local laser heat treatment at the bending edge is observed. The strength of the UFG samples is increased by a factor of around two compared to the conventionally grained T4 condition which also results in up to 50 % higher punch forces needed for bending of ARB processed samples. An anisotropic bending behaviour is observed. By applying a tailored laser heat treatment along the bending edge prior to the bending tests a local recrystallization and recovery at the deformation zone of the samples is achieved. Thus, ductility is increased locally whereby bending to an angle of 80° is possible with lower forming forces compared to the non-heat treated specimens. The results are compared to previous studies on mechanical properties and formability investigations of ARB processed AA6016.
WW1::929

Forming characteristics of artificial aging Al-Mg-Si-Cu sheet alloys - Klos, Artur; Kellner, Sven; Wortberg, Daniel; Walter, Philipp; Bassi, Corrado; Merklein, Marion (AIP Conference Proceedings, 2017)
AA6111 is a commonly used aluminum alloy for body-in-white (BIW) components with good bake-hardening response, high strength and excellent formability. For industrial applications various process strategies are considered to reach strength of about 250 MPa in the final body part with that type of alloy. The purpose of this paper is to discuss recent process strategies of high-strength AA6111 sheets to evaluate the forming characteristics, precipitation kinetics dissolution and mechanical properties in the final condition. The forming behavior is investigated by four potential process chains after single-stage or multi-stage heat treatment including T4 (pre-aged at > 80 °C after quenching), T61 (T4 + artificial aged at 120-150 °C for 10-18 h), T6 (T4 + artificial aged at 180-220°C up to 12 h) and PFHT (T4 + post form heat treatment at 205°C for 30 min). The experimental input for characterization of the formability consists of tensile tests, bending tests and drawing tests. Differential Scanning Calorimetry (DSC) is used, to correlate the forming behavior with the precipitation distribution in the advanced stages of aging. The study shows that the forming behavior is strongly dependent on the condition the alloy.
CRIS-Team Scopus Importer:2023-03-29

Forming limits in sheet metal forming for non-proportional loading conditions? experimental and theoretical approach - Offenheimer, A.; Buchmayr, B.; Kolleck, R.; Merklein, Marion (Proceedings of the 6th International Conference and Workshop on Numerical Simulation of 3D Sheet forming Processes (NumiSheet), 15.-19.08., Detroit, USA, 2005)
The influence of strain paths (loading history) on material formability is well known in sheet forming processes. Sophisticated experimental methods are used to determine the entire shape of strain paths of forming limits for aluminum AA6016-T4 alloy. Forming limits for sheet metal in as-received condition as well as for different pre-deformation are presented. A theoretical approach based on Arrieux's intrinsic Forming Limit Stress Curve (FLSC) concept is employed to numerically predict the influence of loading history on forming severity. The detailed experimental strain paths are used in the theoretical study instead of any linear or bilinear simplified loading histories to demonstrate the predictive quality of forming limits in the state of stress. © 2005 American Institute of Physics.
LFT Import::2019-08-05 (1225)
Keywords: FLSC; Formability; Non-proportional loading; Pre-deformation; Strain path

Forming of complex functional elements on sheet metal - Reck, Manuel; Rohrmoser, Andreas; Jobst, Andreas; Pilz, Florian; Merklein, Marion (Sheet Bulk Metal Forming, 2021)

Forming of Components with Microgearings from Coil Material—Numerical Modeling of the Process Chain and Experimental Validation - Rohrmoser, Andreas; Kraus, Martin; Merklein, Marion (Micromachines, 2021)
Compared to alternative production methods, cold forming offers technological, economic and ecological potential for the mass production of microgears. Within the current boundaries of the technology, the cold forming of modules m < 0.2 mm is not possible due to size effects, high tool stresses and handling problems. The investigations of this contribution present a novel process chain for the multi-step forming of microgears with a module of m = 0.1 mm. For this purpose, a numerical model of the first two steps of the process chain is set up and confirmed based on experimental forming tests. The results have proven the feasibility of the process chain by a complete forming of the gear teeth.
Keywords: micro forming; microgear; sheet-bulk metal forming; multi-step micro forming

Forming of metal-based composite parts - Bruschi, S.; Cao, J.; Merklein, Marion; Yanagimoto, J. (CIRP Annals - Manufacturing Technology, 2021)
In the last few decades, metal-based composites and related manufacturing methods have attained a significant research attention thanks to the possibilities they offer to tailor both the material properties and the part in-service performances. A variety of metal-based composite parts is available for commercial applications since more affordable and robust manufacturing processes and quality control techniques have recently overcome many challenging technological issues. The paper aims at describing the forming processes applied to metal-based composites, with particular emphasis on the process features, part obtainable characteristics, and modelling issues for a convincing design and optimization of the process itself. The most recent progresses and challenges are illustrated in detail, including innovative materials and processes that are emerging to answer the requirements of advanced engineering applications as well as new modelling techniques and current approaches to face economic and environmental issues.
CRIS-Team Scopus Importer:2021-07-30
Keywords: Composite; Forming; Metal

Forming Process Parameter Dependent Recrystallization Phenomena in Friction Stir Welded Aluminium Sheets - Gnibl, Tobias; Merklein, Marion (7th International Conference and Exhibition on Design and Production of Machines and Dies/Mold, 2013)
LFT Import::2019-08-05 (2033)

Fortschritte in der Fügetechnik für Aluminium - Schmidt, Michael; Mys, I.; Albert, F.; Merklein, Marion; Giera, Artur; Staud, Detlev (Proceedings Euroform-Konferenz, Aluminium, Anwendungen, Märkte, Produktion, 2006)
LFT Import::2019-08-05 (1317)

Forward and Reverse Simple Shear Test Experiments for Material Modeling in Forming Simulations - Merklein, Marion; Biasutti, Manfredi (Proc. of the 10th International Conference on Technology of Plasticity (ICTP), 2011)
The planar simple shear test has become of Increasing Interest for the material parameter Identification as well as validation of material models In sheet metal forming simulations. In this paper, a modified shear specimen geometry based on the ASTM standard B831, optimized for performing monotone and reverse simple shear test, Is presented. Experiments are carried out under monotone loading for an aluminum sheet alloy AA6016 and found in good agreement with previous results obtained from a Mlyauchi based simple shear test. Following this verification Bauschinger simple shear tests conducted with reversal of shear after different amounts of forward prestrain are performed and compared by means of applying an anisotropic yield function with the more standard tension-compression test. In conclusion, a further development of the simple shear setup is presented for characterizing sheet metals at elevated temperatures by means of electric conductive warming of the modified shear sample. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
LFT Import::2019-08-05 (1762)
Keywords: Bauschinger effect; Material characterization; Simple shear test

Friction Conditions in Sheet-Bulk Metal Forming - Vierzigmann, Ulrich; Merklein, Marion; Engel, Ulf (Procedia Engineering, 2011)
LFT Import::2019-08-07 (1753)

Friction reduction in EHL contacts by surface microtexturing – tribological performance, manufacturing and tailored design - Tremmel, Stephan; Marian, Max; Zahner, Michael; Wartzack, Sandro; Merklein, Marion (Industrial Lubrication and Tribology, 2019)
Purpose – This paper aims to derive tailor-made microtextures for elastohydrodynamically lubricated (EHL) contacts under consideration of manufacturing possibilities. Design/methodology/approach – Component tests were used for the evaluation of the influence of surface texturing on the friction behavior in the cam/tappet contact. Furthermore, the manufacturing possibilities and limitations of a combined mEDM and micro coining process and the feasibility of integration into a forming process were studied. Finally, a methodology based on transient EHL simulations and a meta-model of optimal prognosis was exemplarily used for microtexture optimization. Findings – It was found that surface texturing in EHL contacts with high amount of sliding is promising. Moreover, the combination of mEDM and micro coining and the integration into established production processes allow the manufacturing of microtextures with desirable structural parameters and sufficient accuracy. Originality/value – This paper gives a holistic view on surface microtexturing over several phases of the product life cycle, from the design, over efficient manufacturing to application-related testin
Keywords: Friction; Elastohydrodynamic lubrication; Micro coining

Friction stir knead welding of steel aluminium butt joints - Geiger, Manfred; Micari, F.; Merklein, Marion; Fratini, Livan; Contorno, D.; Giera, Artur; Staud, Detlev (International Journal of Machine Tools and Manufacture, 2008)
To develop steel aluminium-tailored hybrids in a butt joint for sheets in a thickness of about 1 mm conventional Friction Stir Welding is not feasible due to a high distortion of the welded specimen. Contrary to Friction Stir Welding the tool used for Friction Stir Knead Welding has no pin wherefore higher welding speeds can be realised. Due to the fact that this is a newer process, applied for patent in 2005, the cut contours of the edges and their variations have to be optimised by numerical analysis to transfer a maximum of load in order to improve the formability. The examined materials in this paper are steel DC04, as well as the aluminium alloys AA5182 and AA6016 in sheet thicknesses of 1 mm. Accompanying experimental investigations, as tensile tests, will evaluate the quality of the welding mechanism. As the mechanics of the new welding technology is not fundamentally investigated until now, metallographic investigations are performed, and additionally micro hardness measurements are carried out to verify the changes in the hardness distribution in the welding zone after stirring and welding. © 2007 Elsevier Ltd. All rights reserved.
LFT Import::2019-07-29 (1509)
Keywords: Aluminium; Friction Stir Knead Welding; Simulation; Steel

Friction stir welding and cup deep drawing of aluminium tailored blanks - Merklein, Marion; Giera, Artur; Staud, Detlev (Proceedings of the 8th ESAFORM Conference on material forming, 2005)
LFT Import::2019-08-05 (1162)

Friction stir welding of thin steel aluminium hybrid blanks - Merklein, Marion; Giera, Artur (The 9th International Conference on Material Forming, ESAFORM 2006, 2006)
LFT Import::2019-08-05 (1306)

Friction Stir Welds Made Out of Precipitation Hardenable Aluminum Alloys - Experimental Investigations of Formability Potential - Merklein, Marion; Wieland, Michael; Staud, Detlev (International Journal of Material Forming, 2009)
The industrial application of aluminum alloys in lightweight constructions is basically connected to two fundamental manufacturing requirements. First, the formability of aluminum blanks must be adequate in order to shape the required geometries. This requirement can be fulfilled by using precipitation hardenable aluminum alloys which can be formed well in natural aged condition. In common, these alloys are artificially aged afterwards for getting a higher strength. Second, suitable joining technologies must be available for connecting the formed elements to a complex lightweight construction. One such joining technology could be friction stir welding (FSW), because of better mechanical properties due to lower heat input compared to other joining technologies, for example laser welding. Thereby also Tailored Welded Blanks (TWB), which are used for reducing the number of parts or for locally reinforcing structures, can be used for aluminum lightweight constructions. Beside these attributes dominated by production technology weld seams must also fulfill utilization based requirements. One such criterion is that a misapplication of aluminum lightweight constructions, which are commonly used in transportation systems, is not leading to a complete failure. Therefore aluminum joints, which are connecting the formed parts, should have certain formability to balance a local overstraining. For the implementation of this consideration the formability of FSW joints made out of AA6016 aluminum is investigated in this paper. Therefore local martens hardness distribution of unformed, formed and artificially aged welds are conducted and the results are compared to each other. © Springer/ESAFORM 2009.
LFT Import::2019-07-29 (309)
Keywords: Aluminum; Deep drawing; Friction stir welding

Fringe projection profilometry in production metrology: A multi-scale comparison in sheet-bulk metal forming - Hinz, Lennart; Metzner, Sebastian; Müller, Philipp; Schulte, Robert Karl; Besserer, Hans-Bernward; Wackenrohr, Steffen; Sauer, Christopher; Kästner, Markus; Hausotte, Tino; Hübner, Sven; Nuernberger, Florian; Schleich, Benjamin; et al. (Sensors, 2021)
Fringe projection profilometry in combination with other optical measuring technologies has established itself over the last decades as an essential complement to conventional, tactile measuring devices. The non-contact, holistic reconstruction of complex geometries within fractions of a second in conjunction with the lightweight and transportable sensor design open up many fields of application in production metrology. Furthermore, triangulation-based measuring principles feature good scalability, which has led to 3D scanners for various scale ranges. Innovative and modern production processes, such as sheet-bulk metal forming, thus, utilize fringe projection profilometry in many respects to monitor the process, quantify possible wear and improve production technology. Therefore, it is essential to identify the appropriate 3D scanner for each application and to properly evaluate the acquired data. Through precise knowledge of the measurement volume and the relative uncertainty with respect to the specimen and scanner position, adapted measurement strategies and integrated production concepts can be realized. Although there are extensive industrial standards and guidelines for the quantification of sensor performance, evaluation and tolerancing is mainly global and can, therefore, neither provide assistance in the correct, application-specific positioning and alignment of the sensor nor reflect the local characteristics within the measuring volume. Therefore, this article compares fringe projection systems across various scale ranges by positioning and scanning a calibrated sphere in a high resolution grid.
CRIS-Team Scopus Importer:2021-04-09
Keywords: Coordinate metrology; Fringe projection; Production metrology; Sheet-bulk metal forming

Fügen durch Umformen - Das Spannungsfeld zwischen Umform- und Fügetechnik - Merklein, Marion; Grüner, Martin; Müller, Martin; Wieland, Michael (Effiziente Fertigung von Hochleistungsverbundsystemen - Proc. 18. Paderborner Symposium Fügetechnik, 2013)
LFT Import::2019-08-05 (2009)

Functional Analysis of Components Manufactured by a Sheet-Bulk Metal Forming Process - Hetzel, Andreas; Schulte, Robert Karl; Vogel, Manfred; Lechner, Michael; Besserer, Hans-Bernward; Maier, Hans Juergen; Sauer, Christopher; Schleich, Benjamin; Wartzack, Sandro; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2021)
Due to rising demands regarding the functionality and load-bearing capacity of functional components such as synchronizer rings in gear systems, conventional forming operations are reaching their limits with respect to formability and efficiency. One way to meet these challenges is the application of the innovative process class of sheet-bulk metal forming (SBMF). By applying bulk forming operations to sheet metal, the advantages of both process classes can be combined, thus realizing an optimized part weight and an adapted load-bearing capacity. Different approaches to manufacturing relevant part geometries were presented and evaluated regarding the process properties and applicability. In this contribution, a self-learning engineering workbench was used to provide geometry-based data regarding a novel component geometry with circumferential involute gearing manufactured in an SBMF process combination of deep drawing and upsetting. Within the comprehensive investigations, the mechanical and geometrical properties of the part were analyzed. Moreover, the manufactured components were compared regarding the increased fatigue strength in cyclic load tests. With the gained experimental and numerical data, the workbench was used for the first time to generate the desired component as a CAD model, as well as to derive design guidelines referring to the investigated properties and fatigue behavior.<br
Keywords: sheet-bulk metal forming; mechanical properties; self-learning engineering workbench; functional behavior; fatigue life modeling; Z-integral approach

Functional Integration of Sheet Metal Parts by Deep Drawing - Merklein, Marion; Schneider, Thomas (Steel Research International, 2011)
A novel deep drawing process for manufacturing rotationally symmetric components with shape elements In the cup wall Is presented. Aim of this Investigation Is the Integration of functional elements at deep drawn workpleces In a single forming stage to meet the trend towards high Integration density at short process chains. The challenge of this process Is the realization of minimum fillets In relation to the sheet thickness as miniaturization and integration density are major targets in the development of functional components. The results show, that the filigree design of the shape elements can cause sharp bending of the blank and thus non-uniform draw-in as well as inhomogeneous strain-hardening. Furthermore, the geometry of the component and the corresponding die and punch design lead to non-uniform application of the forming force, which particularly acts at the shape elements and results in local sheet thinning. In combination with the specific draw- in, this results in locally varying contact conditions. High contact normal stresses occur at the minimum fillets whereas curvature of the blank during draw-in Inhibits even local contact between workplece and drawing die. In addition, the effects of deep drawing a cup with integrated shape elements are discussed and appropriate modifications of the process are shown to improve accuracy of shape. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Weinheim.
LFT Import::2019-07-29 (1726)
Keywords: Functional integration; Sheet drawing; Tools and dies

Functional optimization of hot-stamped components by local carburization - Horn, Alexander; Merklein, Marion (International Journal of Lightweight Materials and Manufacture, 2020)
One of the major challenges in modern car body construction is the reduction of component weight while still maintaining passenger safety. In terms of these requirements, the substitution of conventional steel grades by ultra-high strength materials is the most promising approach. Hot stamping of these steels has developed to a state of the art process for manufacturing safety-relevant car body parts such as B-pillars or front bumpers. By locally adjusting the mechanical properties, for example, increasing the ductility, passive safety can be further improved. For this purpose, the hot stamping process is adapted in different ways. Varying from these established methods, tailored carburization is an alternative approach for manufacturing functional optimized components by combining hot stamping with prior local carburization. Within this work, the potential of local carburization is analyzed by a fundamental investigation of the influence of the process parameters on the mechanical properties as well as the transition zones between carburized and non-carburized areas. Besides the mechanical properties, the heat transfer between carburized sheets and tools is studied. The process suitability is validated by a demonstrator.
CRIS-Team Scopus Importer:2020-05-22

Fundamental analysis For the application of hybrid semi-finished products in sheet-bulk metal forming - Schulte, Robert Karl; Lechner, Michael; Merklein, Marion (Journal of Materials Processing Technology, 2020)
Sheet-bulk metal forming is an expedient approach to efficiently manufacture functional components out of sheet metal. In order to reduce weight of the component manufactured, an application-adapted approach was developed to replace the conventional steel blank by a semi-finished product consisting of two blanks with half the thickness to enable the tailored combination of different materials in a combined deep drawing and upsetting process. To establish a basis for the application of these hybrid semi-finished products, first of all multilayer steel semi-finished products are drawn and upset in the process combination. Thereby, the upsetting process induces a three dimensional material flow and at the same time an interlocking connection of the two blanks. The gained results are the transferred onto the combination of steel and aluminium alloys within one semi-finished product. Fundamental dependencies as well as the influence of the application of different steel grades are investigated.
CRIS-Team Scopus Importer:2020-04-28
Keywords: Metal forming; Sheet metal; Simulation

Fundamental investigations concerning forming limit diagrams - Merklein, Marion (Advanced Technology of Plasticity, Proceedings of the 7th ICTP, 2002)
LFT Import::2019-08-05 (1718)

Fundamental Investigations on Friction Stir Knead Welding - Contorno, D.; Fonti, V.; Giera, Artur; Fratini, L.; Merklein, Marion (2nd International Conference on New Forming Technology, 2007)
LFT Import::2019-08-05 (1452)

Fundamental investigations on the material flow at combined sheet and bulk metal forming processes - Merklein, Marion; Koch, Johannes Peter Karl; Opel, Simon; Schneider, Thomas (CIRP Annals - Manufacturing Technology, 2011)
The class of combined sheet and bulk metal forming (SBMF) processes denotes the forming of sheet metals with typical bulk forming operations. As a consequence, simultaneous 2D and 3D stress and strain states are present. Furthermore the local shape elements formed out of the sheet plane are in the magnitude of the sheet thickness. This paper deals with process combinations upsetting/lateral extrusion and deep drawing/upsetting. It has been shown that an insufficient mould filling is nearly inevitable using conventional tooling systems. Hence, the prospect of newly developed forming approaches will be discussed. © 2011 CIRP.
LFT Import::2019-07-29 (1633)
Keywords: Forming; Processing; Simulation

Fundamental Investigations to Evaluate the Influence of Notching Processes on a Subsequent Cyclic Bending Process for the Production of Wire Cores - Biallas, Alina; Ohmayer, Sophia; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2023)
The production of wire cores by notch rolling and cyclic bending promises an ecologically and economically efficient manufacturing option for steel fibers. The paper at hand evaluates the influence of wire strips on cyclic bending by applying rolled wire strips of DP600 sheet metal (t0 = 0.8 mm) and a new cyclic bending testing tool. Analysis of material separation with varying parameters, rolling gap d and bending angle β, proves the interdependency of both process step, but indicates reduced adjustability of the notch rolling process. To enable better adjustability of the wire strip’s characteristics and analysis of their effects, wire strip production in the laboratory by notch stamping instead of rolling is aspired. The prior interaction analysis states the web height b, the notch angle α, and the hardening distribution as relevant wire strip’s characteristics to be replicated. Based on experimental analysis, an equivalent of notch rolling by notch stamping is deduced by considering the web height b identical for stamping and rolling, by adjusting the tool’s notch angle αt based on an equation considering geometric evaluations of α, and by taking advantage of the asymmetric hardening distribution of the outer notch which is comparable to rolled wire stri
Keywords: stamping; rolling; wire strip

Fundamental mechanisms and their interactions in shear‐clinching technology and investigation of the process robustness - Wiesenmayer, Sebastian; Han, D.; Müller, Manuel; Hoerhold, R.; Meschut, G.; Merklein, Marion (Materialwissenschaft und Werkstofftechnik, 2019)
The compliance with increasingly stricter emission standards is a challenge for the automotive industry, which requires the utilization of lightweight materials e. g. aluminium and high-strength steels. Hereby, the load-optimized design of body parts and the reduction of wall thicknesses are enabled. But, due to the use of dissimilar materials, common joining technologies are reaching their limits. On the one hand, joining by welding is often not possible because of different melting temperatures. On the other hand, joining by forming with additional fasteners increases the cycle time and the costs. However, joining by forming without fasteners is often limited by the mechanical properties of the joining partners. The innovative shear-clinching technology combines shear-cutting and clinching in a single stage process and thereby enables joining by forming of materials with high differences regarding their mechanical properties. However, by the combination of the sub-processes cutting and joining, the complexity of the technology is increased. Thus, within the scope of this work, the fundamental mechanisms in shear-clinching and their interactions as well as the robustness of the process are analysed, in order to promote the applicability of the technology.
CRIS-Team WoS Importer:2019-08-09

Fundamental Studies on a Novel Die Concept for Round-Point Shear-Clinching - Hoerhold, Rejane; Müller, Martin; Merklein, Marion; Meschut, Gerson (AIP Conference Proceedings, 2016)
LFT Import::2019-07-29 (2190)

Funktionsintegration durch die Kombination additiver Fertigungsprozesse mit der Blechumformung - Schaub, Adam; Merklein, Marion; Jüchter, Vera; Singer, Robert; Körner, Carolin (2. Industriekolloquium des Sonderforschungsbereichs 814 - Additive Fertigung, 2013)
None
LFT Import::2019-08-05 (1930)

Geometric and corrosive influences on load-bearing capacity of multi-element shear-clinching specimen - Han, Daxin; Wiesenmayer, Sebastian; Merklein, Marion; Meschut, Gerson (AIP Conference Proceedings, 2019)
The influences in the experimental investigation are divided into the geometry of the specimen and the corrosion phenomenon. The 8-element specimens were joined with various overlaps in the form of a single lap shear load multi-element specimen. Afterwards, the multi-element specimens were segmented into one-element specimens, which were tested under quasistatic shear load in order to detect possible influences of the specimen geometry. The effect of corrosion on the load-bearing capacity was investigated with the same multi-element specimen according to VDA 621-415. In addition, two arrangements of corrosion protection were generated in order to guarantee the joint quality in a corrosive surrounding atmosphere. It was found that the load-bearing capacity of specimens as well as the joint characteristics can be ensured using corrosion protection. The study gave a recommendation for planning the shear-clinching on a flange facing and showed promising potential for shear-clinching when joining multi-element specimens.
CRIS-Team Scopus Importer:2019-07-23

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

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

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

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

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