Investigation on micro textured tappets from design and production to the application properties - Reck, Manuel; Orgeldinger, Christian; Tremmel, Stephan; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2022)

Investigation on pin caulking as a versatile joining process - Römisch, David; Merklein, Marion (Materials Research Proceedings, 2023)

Investigation on tailored blanks in a full forward extrusion process of sheet-bulk metal forming - Reck, Manuel; Merklein, Marion (ESAFORM 2021, 2021)

Investigation on the influence of manufacturing parameters on the fatigue strength of components - Reiss, Andrea; Engel, Ulf; Merklein, Marion (Key Engineering Materials, 2013)
With cold forging processes it is possible to produce parts characterized by high strength, high dimensional accuracy and high surface quality. In order to optimize the forming process and to be able to use the advantages of cold forging specifically and combined, it is necessary to find correlations between the manufacturing parameters, the strength and the properties, like hardness distribution and surface quality, of the component. The research work covered in this paper focuses on the influence of the components properties influenced by its manufacturing history on their fatigue strength. The used component is a flange hub, produced by a four-stage cold forging process. To obtain different component properties the production process of the hub was varied for example by changing the heat treatment or by producing the parts by turning process. First of all, the components' properties, for example hardness distribution, remaining residual stresses, orientation of fibers and surface quality, were determined. Moreover, a special experimental setup for the fatigue tests has been designed. The components' fatigue behavior was determined using a high frequency pulsator and evaluated in terms of finite life fatigue strength and fatigue endurance limit. These examinations were used to produce Woehler curves for the differently manufactured components with a certain statistical data analysis method. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1878)
Keywords: 1.0570; Cold forging; Fatigue strength; Influence of components properties on fatigue life

Investigation on the shear cutting of functional components manufactured in an orbital forming process - Hetzel, Andreas; Lechner, Michael; Merklein, Marion (Materials Research Proceedings, 2023)
Applying forming operations for the manufacturing of complex functional components instead of conventional shearing or milling is an effective way to increase the material efficiency of the process as well as the mechanical properties of the part. Nevertheless, in many cases subsequent cutting operations are mandatory to reach the final geometry or to add functional surfaces for the later assembly. During forming, hardening effects or different strain states can cause difficulties for the subsequent cutting operation. These characteristics are commonly determined for sheet metal forming processes like deep drawing or bending. However, the complex stress and strain states during sheet-bulk metal forming operations and their influence on the cutting parameters or the part properties have not been investigated comprehensively so far. Furthermore, different assigned processes, like for example orbital forming, allow a local material distribution, realizing a gradient in sheet thickness. Therefore, this contribution focuses on the establishment of a fundamental process understanding on the influence of a sheet-bulk metal forming process on the cutting parameters and the resulting part properties. Functional components are manufactured from C10 sheet metal by orbital forming and subsequently shear cut to generate the final contour. During cutting, specific force-stroke diagrams are evaluated, in order to analyze the influence on the process parameters. The resulting properties of the parts are investigated regarding the quality of the cutting surface and a potential geometrical distortion in consequence of elastic spring back. The influence of the forming process is outlined by a direct comparison with conventionally cut components.<br
Keywords: Metal forming; Cutting; Orbital forming

Investigation on the thermo-mechanical properties of hot stamped parts by using laser-implanted tool surfaces - Schirdewahn, Stephan; Carstensen, Niels; Hilgenberg, Kai; Merklein, Marion (IOP Conf. Ser.: Mater. Sci. Eng. 1270 012114, 2022)
In the automotive industry, hot stamping has been established as a key technology for manufacturing safety-related car body components with high strength-to-weight ratio. During the forming operation, however, hot stamping tools are highly stressed by cyclic thermo-mechanical loads, which encourage the formation of severe wear and high friction at the blank-die interface. Against this background, an innovative surface engineering technology named laser implantation has been investigated for improving the formability of the parts and the efficiency of the hot stamping process. The laser implantation process is based on the generation of highly wear resistant microfeatures on tool surfaces by embedding hard ceramic particles via pulsed laser radiation. As a consequence, the contact area of the tool and thus the tribological and thermal interactions at the blank-die interface are locally influenced. In previous studies, the improved tribological performance of the modified tool surfaces has already been proven. However, the thermal interactions between tool and workpiece have not been analyzed, which in turn have a significant impact on the resulting part properties. In this regard, quenching tests have been carried out under hot stamping conditions by using conventional as well as laser-implanted tooling systems. Based on these results, Vickers hardness test and optical measurements have been performed on the quenched blanks, to qualify the mechanical properties and clarify the cause-effect relations.<br
Keywords: hot stamping; laser implantation; friction; wear; quenching

Investigation on the Tribological Behavior of Tool-sided Tailored Surfaces for Controlling the Material Flow in Sheet-Bulk Metal Forming - Henneberg, Johannes; Lucas, H.; Denkena, B.; Merklein, Marion (AIP Conference Proceedings, 2019)
The increasing demand for closely tolerated and highly integrated functional components motivates the development of the innovative process class sheet-bulk metal forming (SBMF). SBMF is defined as the application of bulk forming operations on sheet metal to produce parts with integrated functional elements. Due to varying tribological loads, caused by the local forming of functional elements and the resulting complex material flow, the geometrical accuracy of the produced parts can be limited. A local increase or decrease of friction by modified surfaces also called tailored surfaces which control the material flow are an approach to improve the geometrical accuracy of the part. These tailored surfaces should be applied tool-sided to guarantee a short process chain. Consequently, the aim of this study is to analyze the potential of modified tool surfaces for a usage as tailored surfaces in SBMF processes. The tribological behavior of tailored tool surfaces is investigated to provide a basis for the selection of tailored surfaces. Different grinding and blasting strategies, as well as lubrication pockets are chosen as surface modifications and applied on the tool steel 1.3344 with a hardness of 61 ± 2 HRC. Lapped tools are chosen as a reference for the modified surfaces, since lapping is a widespread finishing process for forming tools. First of all, the topographies of the modified surfaces are characterized using optical and tactile measurements. Afterwards the tribological behavior of the surfaces is investigated using a modified ring compression test with specimens made of 1.0338. The resulting friction factors are correlated with the topography characteristics of the tailored surfaces to identify functional interrelations. Finally, the tailored surfaces are evaluated regarding their eligibility to adapt the friction and control the material flow in SBMF-processes.
CRIS-Team Scopus Importer:2019-07-23

Investigation on the wear behavior of coatings for lubricant-free deep drawing processes with a novel application-oriented test rig - Henneberg, Johannes; Merklein, Marion (Defect and Diffusion Forum, 2020)
Lubricant-free deep drawing is motivated by the avoidance of using environmentally harmful lubricants as well as the potential for shortening the process chain by eliminating lubricant application and component cleaning. Central challenges of dry deep drawing are a significant increase in friction as well as in adhesive tool wear due to a lack of a separating lubricant layer between tool and workpiece. An approach to meet these challenges is the modification of the tools through diamond-like coatings. Based on findings from laboratory tests, a-C:H and ta-C coatings were selected and their effectiveness in overcoming these challenges was demonstrated in single stroke tests in previous research. In order to use the process-specific advantages of forming technology, high tool life is required. In this context, this research aims at investigating the application behavior of a-C:H and ta-C coatings during lubricant-free deep drawing of a high number of components made of the aluminum alloy AA5182. For this purpose, a new wear test rig is applied, which enables the time and material efficient production of high quantities. Numerical methods are utilized to identify the drawing die radius as well as the blank holder as the highest loaded areas. Based on these findings, the wear of the coatings as well as that of an uncoated tool as a reference is analyzed in these areas by optical and tactile measurements. In addition, the influence of tool wear on the component surface quality is determined. It is proven that the ta-C coating increases the tool life from 10 components in uncoated condition up to 3,000 components.
CRIS-Team Scopus Importer:2020-11-27
Keywords: Coating; Sheet metal; Tribology

Investigation on tool properties for the production of components with micro textured surfaces - Reck, Manuel; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2022)

Investigations and approaches on material flow of non-uniform arranged cavities in sheet bulk metal forming processes - Gröbel, Daniel; Koch, Johannes Peter Karl; Vierzigmann, Ulrich; Engel, Ulf; Merklein, Marion (Procedia Engineering, 2014)
LFT Import::2019-07-29 (2050)
Keywords: Flow-control; Process simulation; Sheet-bulk metal forming; Tribology

Investigations of batch fluctuation regarding tribological conditions in series production of car body parts - Hansen, B.; Wagner, P.; Purr, S.; Merklein, Marion (International Journal of Material Forming, 2021)
Fluctuations of material properties are one reason for the occurrence of cracks and waviness in series production of car body parts. Especially fluctuating tribological conditions have an effect on the friction behavior and thus on the material flow. So far fluctuating material properties are not considered in the standard FE-simulation and consequently not in the tool design. In order to enhance the accuracy of the simulation result and thus improve the tool design regarding a robust process, the appearance of batch fluctuations has to be consistently understood. Therefore, the impact of varying lubricant quantities and roughness have been investigated. Several batches have been analyzed to identify the main influencing parameter regarding the friction behavior. Flat strip-drawing tests have been performed to determine the friction coefficient. The investigations have been performed by using material from the series production, as delivered. Since the amount of lubricant turns out to be the main influencing factor, the characteristics and appearance of the lubricant distribution has been analyzed in a further step. The analysis has shown that the distribution of the lubricant changes within one coil over the coil width and length. In addition, the time of storage has been identified as one main influencing factor on the homogeneity of the lubricant distribution over the coil width. Based on these findings, a method has been developed to map the series production conditions regarding the friction conditions in the simulation. Hence, simulations were performed using a side frame blank with different friction conditions, to investigate the impact on the forming result. The results reveal that by considering realistically existing tribological conditions, more scrap is to be expected compared to the conventional simulation. This leads to the conclusion that previous simulation results are too optimistic. Consequently, the introduced method offers the potential to optimize the tool design by considering fluctuating tribological conditions already in the process of development. Thus, it is possible to reduce scrap and increase productivity.
CRIS-Team Scopus Importer:2021-01-22
Keywords: Friction; Material; Tribology

Investigations of ductile damage during the process chains of toothed functional components manufactured by sheet-bulk metal forming - Isik, Kerim; Gerstein, Gregory; Schneider, Thomas; Schulte, Robert Karl; Rosenbusch, Daniel; Clausmeyer, Till; Nuernberger, Florian; Vucetic, Milan; Koch, Sergej; Huebner, Sven; Behrens, Bernd-Arno; Tekkaya, A. Erman; et al. (Production Engineering, 2016)
Sheet-bulk metal forming processes combine conventional sheet forming processes with bulk forming of sheet semi-finished parts. In these processes the sheets undergo complex forming histories. Due to in- and out-of-plane material flow and large accumulated plastic strains, the conventional failure prediction methods for sheet metal forming such as forming limit curve fall short. As a remedy, damage models can be applied to model damage evolution during those processes. In this study, damage evolution during the production of two different toothed components from DC04 steel is investigated. In both setups, a deep drawn cup is upset to form a circumferential gearing. However, the two final products have different dimensions and forming histories. Due to combined deep drawing and upsetting processes, the material flow on the cup walls is three-dimensional and non-proportional. In this study, the numerical and experimental investigations for those parts are presented and compared. Damage evolution in the process chains is simulated with a Lemaitre damage criterion. Microstructural analysis by scanning electron microscopy is performed in the regions with high mechanical loading. It is observed that the evolution of voids in terms of void volume fraction is strongly dependent on the deformation path. The comparison of simulation results with microstructural data shows that the void volume fraction decreases in the upsetting stage after an initial increase in the drawing stage. Moreover, the concurrent numerical and microstructural analysis provides evidence that the void volume fraction decreases during compression in sheet-bulk metal forming.
LFT Import::2019-07-29 (2147)
Keywords: FE simulation; Lemaitre damage model; Sheet-bulk metal forming

Investigations on austenitization parameters influencing wear behavior within hot stamping - Merklein, Marion; Wieland, Michael (Procedia Engineering, 2014)
LFT Import::2019-07-29 (2049)
Keywords: Alsi; Austenitization; Hot stamping; Wear

Investigations on different strategies for influencing the microstructural properties with respect to partial hot stamping - Stöhr, Thomas; Lechler, Jürgen; Merklein, Marion (Proceedings 2nd International Conference Hot Sheet Metal Forming of High-Performance Steel - CHS², 2009)
LFT Import::2019-08-05 (215)

Investigations on Double Sheet Hydroforming with Counterpressure - Cojutti, Massimo; Merklein, Marion; Geiger, Manfred (2nd International Conference on New Forming Technology, 2007)
LFT Import::2019-08-05 (1451)

Investigations on Formability and Tribology of Magnesium Sheets with Regard to Warm Forming processes - Geiger, Manfred; Merklein, Marion; Hecht, Joachim; Stich, A. (Proceedings of the 7th International Conference on Magnesium Alloys and their Applications, Nov 6-9, Dresden, Germany, 2006)
LFT Import::2019-08-05 (1337)

Investigations on Formability and Tribology with Regard to Warm Forming of Magnesium Sheets - Geiger, Manfred; Merklein, Marion; Hecht, Joachim (Production Engineering. Annals of the German Academic Society for Production Engineering, 2006)
LFT Import::2019-08-05 (1305)

Investigations on load spectrum and adhesive wear development in hot stamping operations - Wieland, Michael; Neubauer, Franziska; Andreas, Kolja; Merklein, Marion (The "A" Coatings Conference Proceedings, 2016)
LFT Import::2019-08-05 (2166)

Investigations on Parameters Influencing Thermal and Frictional Properties within Hot Stamping - Merklein, Marion; Stöhr, Thomas; Svec, Thomas; Wieland, Michael (Journal of Heat Treatment and Materials, 2011)
LFT Import::2019-07-29 (1772)
Keywords: Abrasive wear; Adhesive wear; Heat tnmsler; Hot stamping; Jriclion

Investigations on Residual Stress Generation in Extruded Steel Components - Jobst, Andreas; Kiener, Christoph; Merklein, Marion (9th Congress of the German Academic Association for Production Technology (WGP), 2019)
During the forming of components, inhomogeneous stress conditions lead to residual stresses, which influence the operating behaviour of the manufactured part. Compressive residual stresses generally have a positive effect, while tensile residual stresses reduce the fatigue strength and facilitate crack initiation. Full forward extrusion has been established as an industrial manufacturing technique, where cylindrical billets are formed in the die and ejected in opposite direction. In order to influence the residual stresses state, it is essential to know about its formation. A basic understanding is created by separate investigation of the forming and the ejection step. In the context of this paper, singlephase ferritic stainless steel X6Cr17 and ferritic-austenitic duplex steel X2CrNi- MoN22-5-3 are used. The quantification of the residual stresses states is carried out by X-ray diffractometry, for which a measurement method for duplex steel is validated. The influence of forming and ejection is determined separately by manufacturing components with and without an ejection operation.<br
Keywords: Residual Stress; Forward Extrusion; Stainless Steel

Investigations on residual stress generation in full-forward-extrusion - Landkammer, Philipp; Jobst, Andreas; Kiener, Christoph; Steinmann, Paul; Merklein, Marion (Production Engineering, 2019)
Within cold-forming processes, the influence of forming induced residual stresses is a critical issue regarding the life-time behaviour of the formed components. However, a targeted use of forming-induced residual stresses is also capable to improve the components properties. The rotation-symmetrical full-forward extrusion is used as a reference process to investigate the generation of residual stresses within manufacturing. A novel and generally applicable computational evaluation procedure is introduced, which achieves to compute and visualize the evolution of the residual stress state during the entire forming operation. Simulative results are compared with their experimental counterparts. The near-surface residual stresses in the formed component are evaluated in axial and tangential direction by X-ray diffraction. Indentation tests are used to determine the micro-hardness inside the components and optical instruments quantify geometrical difference
Keywords: Residual stresses· Full-forward-extrusion· Experimental validation· Advanced post processing

Investigations on sheet metal forming of hybrid parts in different stress states - Hafenecker, Jan; Merklein, Marion (Production Engineering, 2022)
Conventional processes are being pushed to their limits by growing demands in terms of sustainability and diversity of variants. Hybrid components, which are produced by a combination of two or more manufacturing processes, are a suitable way of meeting these challenges. The combination of sheet metal forming processes with additive manufacturing offers the potential to link personalized components with standardized parts. Knowing that the additively manufactured components influence the forming process, it is essential to understand the interactions in detail. Therefore, this work will compare the influence of several additively manufactured elements (AME) for deep drawing with two different punch geometries. The approach used combines experimental and numerical investigations to improve process insight in relation to sheet metal forming of hybrid components. The results show that the AMEs amplify existing stresses and strains in dependence of the present load. Sections subjected to low loads, as it is found in the bottom of the cup manufactured with a cylindrical punch, are hardly affected, whereas stronger loaded areas, e.g. the center of the parts manufactured with a hemispherical punch, are affected all the more.<br
Keywords: Additive manufacturing; Powder bed fusion; Hybrid; Sheet metal forming; FEM; 316L

Investigations on TaC Localized Dispersed X38CrMoV5-3 Surfaces with Regard to the Manufacturing of Wear Resistant Protruded Surface Textures - Spranger, Felix; Schirdewahn, Stephan; de Oliveira Lopes, Marcelo; Merklein, Marion; Hilgenberg, Kai (Lasers in Manufacturing and Materials Processing, 2019)
Purpose: The potential of lowered surface features as well as the application of wear resistant coatings have been known for many years to improve the tribological behavior of forming tools. More recent studies also discuss the capability of protruded microfeatures for adjusting the tribological behavior between contacting surfaces. The demand for a high wear resistance of such structures as well as their economical and reliable production, however, often limits the industrial application. The laser implantation process can overcome these limitations. In contrast to conventional cw-laser dispersing processes, where the formation of uniform metal matrix composite layers is intended, this surface engineering technique aims to improve the tribological behavior of contacting surfaces by a localized dispersing of pre-placed hard ceramic particles. This enables the formation of deterministic textures composed of separated wear resistant dome- or ring-shaped microstructures (implants). Since TaC shows very promising material properties for improving the wear resistance of tools exposed to severe operating conditions, this paper analyzes its suitability for pulsed laser implantation on X38CrMoV5-3 tool steel for the first time. Methods: In the experiments, the influence of the particles and the laser parameters (pulse power, pulse duration and focal diameter) on the material properties of the localized dispersed zones was studied by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The composite’s (micro-) hardness was measured and calculated by using a rule of mixture. Additionally, the influence of the laser parameters and the TaC particles on the geometrical properties of the implants was studied by optical microscopy and white light interferometry. Results: The results showed that defect-free implants with hardness values of 900 HV1 can be obtained at the focal spot, since a localized dispersing of the TaC particles is possible using a pulsed millisecond laser. However, in dependence of the laser intensity, also a partial dissolution of the initial particles occurs. This leads to the precipitation of new dendritic TaC nanoparticles and to varying contents of retained austenite in the matrix. Both effects have a strong influence on the implant hardness and must be considert by the rule of mixture. Regarding the geometrical response it was pointed out that protruded microfeatures with heights up to 10 μm can be created. In comparison to laser remelted zones, the implanted zones showed significantly altered weld pool profiles due to the influence of the particles on the melt convection. A transition of the implant shape from predominantly dome-shaped to predominantly ring-shaped was observed for intensities >1.7∙106 W/cm2 due to the onset of the keyhole effect. Conclusions: In conclusion, TaC particles seem to be very suitable for laser implantation on hot-work tool steels. The implants can be used for textures, where flat structures are needed. Since the TaC particles can be dispersed in the LIZ, it may be possible to reduce abrasive and adhesive wear due to the promising material properties of this hard phase and the improved hardness of the implants.
CRIS-Team Scopus Importer:2019-12-27
Keywords: Hot-work tool steel; Laser implantation; Localized laser dispersing; Surface texturing; TaC; Tantalum carbide; X38CrMoV5-3

Investigations on the Flow Behavior of Boron-Manganese Steels at elevated strain rates - Stöhr, Thomas; Merklein, Marion (Proceedings 3rd International Conference on Hot Sheet Metal Forming of High-Performance Steel, 2011)
LFT Import::2019-08-05 (1736)

Investigations on the Mechanical Properties and Formability of Friction Stir Welded and Laser Welded Aluminium Tailored Blanks - Staud, Detlev; Merklein, Marion; Fratini, L.; Buffa, G. (5th Laser Assisted Net Shape Engineering LANE, 2007)
LFT Import::2019-08-05 (1440)

Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks - Buffa, G.; Fratini, L.; Merklein, Marion; Staud, Detlev (Proceedings of the 12th International Conference on Sheet Metal (SheMet), 2007)
Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide range of the thickness ratios has been considered. The formability of the obtained blanks has been characterized through tensile tests and cup deep drawing tests, in order to show the formability in dependency of the stress condition; what is more mechanical and metallurgical investigations have been made on the welded joints.
LFT Import::2019-08-05 (1394)
Keywords: Friction stir welding; Laser welding; Tailored blank

Investigations on the thermal behavior of ultra high strength boron manganese steels within hot stamping - Merklein, Marion; Lechler, Jürgen; Stöhr, Thomas (International Journal of Material Forming, 2009)
LFT Import::2019-07-29 (221)

Investigations on Three-Roll Bending of Plain Tubular Components - Merklein, Marion; Hagenah, Hinnerk; Cojutti, Massimo (Key Engineering Materials, 2009)
Bent metal tubes find a widespread application in many industrial sectors. Among different bending processes developed for the manufacturing of these components, three-roll bending is characterized by a high flexibility, as only one toolkit per tube diameter is necessary to form the required bending radius. In this type of forming process the part geometry is obtained by means of a relative movement of the die (setting roll) towards the fixed tools (bending and holding roll) with simultaneous feeding of the tube. This study describes the FE-model developed for the three-roll bending and presents first results of numerical investigations conducted on steel tubes made of carbon steel St37. By the FE-analysis great attention is paid on the modeling of the stiffness of the tool, on the description of the kinematics of the setting roll as well as on the characterization of the material behavior for the simulation. The results of the numerical investigations are compared with experiments conducted with a CNC-bending machine available at the Chair of Manufacturing Technology of the University of Erlangen. As a main criterion for the validation of the FE-model the radius of the tube at the extrados and the bending angle are chosen. The geometry of the part is measured by means of both optical and tactile measuring devices.© (2009) Trans Tech Publications, Switzerland.
LFT Import::2019-07-29 (916)
Keywords: FE-analysis; Three-roll bending; Tube bending

Joinability of the High-strength Aluminium Alloy AA7075 in Shear-clinching Processes - Wiesenmayer, Sebastian; Merklein, Marion (2nd International Conference on Advanced Joining Processes AJP 2021, 2021)

Joining by forming technologies: current solutions and future trends - Buffa, Gianluca; Fratini, Livan; La Commare, Umberto; Römisch, David; Wiesenmayer, Sebastian; Wituschek, Simon; Merklein, Marion (International Journal of Material Forming, 2022)
The progressively more demanding needs of emissions and costs reduction in the transportation industry are pushing engineers towards the use of increasingly lightweight structures. This goal can be achieved only if dissimilar and/or new materials, including polymers and composites, are joined together to create complex structures. Conventional fusion welding processes have often been proven inadequate to this task because of the high heat input reducing the joint mechanical properties or even making the joining process impossible. Joining by forming technologies take advantage on the plastic deformation to create sound joints out of even very dissimilar materials. Over the last 25 years, several new processes, with increasing potential in effectively joining virtually every structural material, have been invented and developed. In the paper, a comprehensive overview of the most utilized joining by forming processes is given. For each process, an analysis of the current research trends and hot topics is provided, highlighting strengths and weaknesses for industrial application
Keywords: Light alloy; Joining; Welding; Solid state; Clinching; Riveting

Joining of CFRT/Steel Hybrid Parts via Direct Pressing of Cold Formed Non-Rotational Symmetric Pin Structures - Popp, Julian; Römisch, David; Merklein, Marion; Drummer, Dietmar (Applied Sciences, 2022)
In this study, quasi-unidirectional continuous fiber reinforced thermoplastics (CFRTs) are joined with metal sheets via cold formed cylindrical, elliptical and polygonal pin structures which are directly pressed into the CFRT component after local infrared heating. In comparison to already available studies, the unique novelty is the use of non-rotational symmetric pin structures for the CFRT/metal hybrid joining. Thus, a variation in the fiber orientation in the CFRT component as well as a variation in the non-rotational symmetric pins’ orientation in relation to the sample orientation is conducted. The created samples are consequently mechanically tested via single lap shear experiments in a quasi-static state. Finally, the failure behavior of the single lap shear samples is investigated with the help of microscopic images and detailed photographs. In the single lap shear tests, it could be shown that non-rotational symmetric pin structures lead to an increase in maximum testing forces of up to 74% when compared to cylindrical pins. However, when normalized to the pin foot print related joint strength, only one polygonal pin variation showed increased joint strength in comparison to cylindrical pin structures. The investigation of the failure behavior showed two distinct failure modes. The first failure mode was failure of the CFRT component due to an exceedance of the maximum bearing strength of the pin-hole leading to significant damage in the CFRT component. The second failure mode was pin-deflection due to the applied testing load and a subsequent pin extraction from the CFRT component resulting in significantly less visible damage in the CFRT component. Generally, CFRT failure is more likely with a fiber orientation of 0° in relation to the load direction while pin extraction typically occurs with a fiber orientation of 90°. It is assumed that for future investigations, pin structures with an undercutting shape that creates an interlocking joint could counteract the tendency for pin-extraction and consequently lead to increased maximum joint strengths.
Keywords: joining of CFRT/metal; hybrid technology; mechanical properties; pin geometry; continuous fiber reinforced thermoplastics

Joining of CFRT-steel hybrid parts via hole-forming and subsequent pin caulking - Römisch, David; Popp, Julian; Drummer, Dietmar; Merklein, Marion (Production Engineering, 2021)
In times of increasing global warming, the awareness of the necessity for significant CO2 reduction is growing. Especially in the transport and aerospace sector, lightweight construction has potential to achieve emission reduction goals by reducing the overall vehicle weight. Thereby, adding lightweight fibre-reinforced composites to materials such as steel and aluminium is used to achieve weight savings. Furthermore, continuous-fibre-reinforced thermoplastics (CFRTs) begin to replace more traditional thermoset thermoplastics due to their easier bulk production and uncomplicated storage. Hybrid parts often consist of a CFRT and a higher strength metal component. Here, the joining process poses the main challenge, due to different chemical and physical properties of the components. In the current state of the art, riveted and bolted joints are commonly used, leading to increased weight due to auxiliary elements and requiring precise bolt holes often destroying load-bearing fibres. Joining with cold formed pin structures is an innovative and versatile joining process, which avoids the need for auxiliary elements. These pins are subsequently inserted in warm formed holes in the CFRT component and then caulked to create a form-fitting hybrid joint. To obtain a fundamental understanding of this joining process, hole-forming and pin-caulking, are investigated in this study. First, the hole-forming with IR-radiation is investigated with regard to suitable process parameters and resulting fibre morphology. The formed holes are consequently mechanically characterized. Second, the caulking-process is investigated by iteratively upsetting a pin and subsequently measuring the geometry. Based on these findings two different suitable caulking degrees are defined and samples for mechanical as well as microscopic investigations are manufactured. The created joints are first investigated via micro-sections and reflected light microscopy to identify possible damage in the CFRT component, which can result from the pin caulking process. Second, a mechanical characterisation under shear load as well as pin extraction loads normal to the sample surface is conducted and the normal load tests are compared with the bearing strength of CFRT samples.
CRIS-Team WoS Importer:2021-12-31

Joining of DC04 and AA5182 in a butt joint configuration by laser assisted friction stir welding - Giera, Artur; Merklein, Marion; Geiger, Manfred (5th Laser Assisted Net Shape Engineering LANE, 2007)
LFT Import::2019-08-05 (1435)

Joining of hybrid semi-finished products from sheet metal by orbital forming - Hetzel, Andreas; Lechner, Michael; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers Part L-Journal of Materials-Design and Applications, 2021)
Contrary demands like a reduction of carbon dioxide emissions and an increase in functionality are facing the manufacturing industry with growing challenges. When processing functional components, like synchronizer rings, conventional process chains, like shearing and subsequent joining, are reaching their limits due to an increased complexity of the components and a lack in efficiency, referring to the long process time. To meet these challenges, the strategy of lightweight construction combines the application of lightweight materials with efficient manufacturing processes and an innovative product design. One possibility within lightweight construction is the utilization of load-adapted hybrid components, featuring different material strength classes. In previous research, the process of orbital forming is used to manufacture semi-finished products with a varying thickness profile due to the specific radial material flow. This material flow should now be used to realize a permanent joint between materials of two different strength levels. Therefore, the process of orbital forming is modified to manufacture hybrid semi-finished products from a dual-phase steel DP600 and a naturally rigid aluminum alloy EN AW 5754, both with an initial thickness of 2.0 mm. Different joint geometries are cut by laser into a steel ring and the part is coaxially positioned around a basic aluminum disc inside a die and subsequently formed. The joint is investigated regarding the geometrical and mechanical properties, comparing a radial cross-section and the micro hardness distribution. In order to reveal the potential of orbital forming for a combined forming and joining operation, the axial as well as the peeling strength of the multi-material components are investigated and evaluated.<br
Keywords: Sheet-bulk metal forming; orbital forming; joining by forming; hybrid semi-finished products; lightweight design

Kennwertermittlung für Streck-Biege-Beanspruchungen - Merklein, Marion; Hezler, Christian; Kopp, C.; Hecht, J.; Schaller, L. (Proceedings Tagung Werkstoffprüfung, 2010)
LFT Import::2019-08-05 (719)

Konstitutives Reibgesetz zur Beschreibung und Optimierung von Tailored Surfaces - Henneberg, Johannes; Beyer, Florian; Willner, Kai; Merklein, Marion (23. Umformtechnisches Kolloquium Hannover: Aktuelle Entwicklungen im Bereich der Umformtechnik, 2020)

Laser and forming technology - an idea and the way of implementation - Geiger, Manfred; Merklein, Marion; Pitz, Matthias (Journal of Materials Processing Technology, 2004)
This paper will give a survey of some of the actual research activities at the Chair of Manufacturing Technology in Erlangen concerning laser and forming technology. In detail the paper will deal with two main focuses of development: laser forming of aluminum alloys and laser-assisted forming of high strength steels. Laser forming is a technology often used for small series productions and for adjustment of small electronic components. In contrast to laser forming, which is a forming technology that is common for over 20 years, laser-assisted forming is an example of a new production technology that is able to enhance the forming limits of high strength steels. © 2004 Elsevier B.V. All rights reserved.
LFT Import::2019-07-16 (1028)
Keywords: Laser forming; Laser-assisted forming; Mechanical properties; Microstructure

Laser assisted bending of complex-phase steel - Geiger, Manfred; Merklein, Marion; Otto, Andreas (Production Engineering - Annals of the WGP, 2004)
LFT Import::2019-08-07 (1027)

Laser assisted bending of martensite-phase steel - Pitz, Matthias; Geiger, Manfred; Merklein, Marion; Otto, Andreas (Sheet Metal 2003, Proceedings of the 9th International Conference on Sheet Metal, 2003)
LFT Import::2019-08-05 (965)

Laser-assisted Friction Stir Welding of Dissimilar Steel and Aluminium Alloys - Giera, Artur; Merklein, Marion; Baumeister, P. (2nd International Conference on New Forming Technology ICNFT, 2007)
LFT Import::2019-08-05 (1433)

Laser assisted Friction Stir Welding of drawable steel-aluminium tailored hybrids - Merklein, Marion; Giera, Artur (The 11th International conference on Material Forming, 2008)
Steel aluminium Tailor Welded Hybrids are still mentioned to be difficult to be joint as intermetallic phases appear during melting welding techniques. These phases are the reason for failure of the joint during loading or forming. As conventional friction stir welding, a solid phase welding technology, is not feasible to join steel and aluminium, laser assistance for preheating the steel sheet is adapted in order to enhance the weldability as well as the welding feed and to reduce the wear at the tool. Tensile tests are performed to achieve mechanical properties of joints, which were welded by systematic variation of process parameters. Finally deep drawing tests are conducted to demonstrate the formability of laser assisted friction stir welded steel aluminium joints. © Springer/ESAFORM 2008.
LFT Import::2019-08-05 (1510)
Keywords: Cup Deep Drawing; Laser Assisted Friction Stir Welding; Mechanical Characteristics; Microstructure; Steel-Aluminium Tailored Hybrid

Laser-assisted Property Gradients in Multi-layered Aluminum - Böhm, Wolfgang; Merklein, Marion (Physics Procedia, 2014)
The Accumulative Roll Bonding (ARB) process enables manufacturing of multi-layered aluminum sheet metals with outstanding mechanical properties. However, a significant increase in strength is accompanied by a reduced ductility. Besides, delamination effects can occur during forming operations. Therefore, property gradients will be applied by short-term laser heat treatment according to the Tailored Heat Treated Blanks technology to enhance the formability and to enable the production of components. These gradients can be realized across the plane and in thickness direction of a blank. In this paper, property gradients in thickness direction are applied to multi-layered aluminum sheet metal with nanocrystalline grain structure produced in the ARB process. Furthermore, the effect of different process parameters on the shape of the heat affected zone is presented. The property gradients are characterized using micro hardness tests. Finally, the enhancement of the formability is proven using air bending tests.
EAM Import::2019-03-12

Laser based additive manufacturing in industry and academia - Schmidt, Michael; Merklein, Marion; Bourell, David; Dimitrov, Dimitri; Hausotte, Tino; Wegener, Konrad; Overmeyer, Ludger; Vollertsen, Frank; Levy, Gideon N. (CIRP Annals - Manufacturing Technology, 2017)
Additive manufacturing (AM) is pushing towards industrial applications. But despite good sales of AM machines, there are still several challenges hindering a broad economic use of AM. This keynote paper starts with an overview over laser based additive manufacturing with comments on the main steps necessary to build parts to introduce the complexity of the whole process chain. Then from a manufacturing process oriented viewpoint it identifies these barriers for Laser Beam Melting (LBM) using results of a round robin test inside CIRP and the work of other research groups. It shows how those barriers may be overcome and points out research topics necessary to be addressed in the near future.
Created from Fastlane, Scopus look-up
Keywords: Additive manufacturing; Laser; Production

Laser based techniques to adapt the tribological conditions in dry deep drawing - Vorndran, Martin; Häfner, Tom; Rothammer, Benedict; Krachenfels, Kim; Merklein, Marion; Tremmel, Stephan; Schmidt, Michael (International Conference on Advanced Optical Technologies, 2019)
Sheet metal forming is widely used in industry to transform a flat metal sheet to a final shape. However, sheet metal forming requires the use of lubricants to prevent the direct contact between tool and workpiece. These lubricants are often toxic and have to be removed after the forming process. Therefore, the environment and the process chain will profit from the abandonment of lubricants. The use of tool sided coatings is a well-known approach to substitute lubricants and perform dry deep drawing. To achieve satisfying results in deep drawing it is beneficial to tune the tribological conditions. Here, we show laser based techniques to locally adapt the tribological conditions by either reducing the roughness of the surface or by creating structures within the surface. It is e.g. shown that the reduced peak height of coated surfaces can be decreased by a laser process. Furthermore, the resulting tribological conditions are investigated for zinc coated DC04 and AA5162 specimens. In Addition to the tribological behavior the changes of the chemical coating properties are investigated using Raman spectroscopy.<br

Laser-based ultrasonic measurement of the influence of PBF-LB/M-typical thermal cycles on sheet metal components of hybrid parts - Hafenecker, Jan; Rigas, Nikolaos; Merklein, Marion (Production Engineering, 2023)
In order to cope with the upcoming challenges from industrial trends, such as mass customization, hybrid parts made out of sheet metal and additively manufactured components offer a possible approach. Hybrid parts can be used for instance in the field of medical and aerospace industries. The combination of the two technologies forming and additive manufacturing allows to use the advantages of each while at the same time avoiding the disadvantages. During the additive manufacturing process, however, the sheet metal substrates, which are a component of the later part, are subjected to heat input such as substrate heating and laser radiation. Each heat input has a different temperature and duration, which are simulated to detect changes in the material properties. Experiments are performed for 316L and Ti-6Al-4 V, which are both commonly used in additive manufacturing. The investigations aim at proving that the substrate heating has no influence on either material. To investigate the influence of substrate heating during additive manufacturing, tensile tests in heat-treated state as well as laser-based ultrasonic measurements are used to detect changes in mechanical or microstructural properties. However, the heat input of the laser is expected to lead to a phase transformation for the titanium alloy due to the high cooling rate. Therefore, the feasibility of using a laser based ultrasonic measurement system to detect microstructural changes during heat input similar to the laser radiation during laser-based powder bed fusion processes is tested. Based on the results, the substrate heating does not influence the sheet material, despite long holding times. However, the short laser beam-like heat inputs lead to phase transformations for the titanium alloy, which can be detected temperature and time dependent via laser-based ultrasonic measurements.
CRIS-Team Scopus Importer:2023-06-30
Keywords: Additive manufacturing; Hybrid; In-situ; Laser-ultrasonic; Powder bed fusion

Laser Forming of Aluminium and Aluminium Alloys - Microstructural Investigation - Merklein, Marion; Hennige, Thomas; Geiger, Manfred (Proc. 7th Int. Conf. on Sheet Metal, SheMet 1999, 1999)

Laser forming of aluminium and aluminium alloys - microstructural investigations - Merklein, Marion; Hennige, Thomas; Geiger, Manfred (Journal of Materials Processing Technology, 2001)
This paper shows the microstructural development and changes in mechanical properties aluminium and aluminium alloys undergo during the process of laser forming. The resulting structures, grain structure and microstructure were analysed both quantitatively and qualitatively by optical and electron microscopy in order to examine the kind of existing structure zones and their extent. Zones with different substructures can be seen depending on the selected test parameters. The degree of substructural development seems to be a function of all influences and cannot entirely be explained by laser parameters and material characteristics. Obviously, during laser forming several different inhomogeneous particle and dislocation structures develop which are responsible for the strength of the whole composite on the one hand, and for the strength of individual small components of the whole on the other hand. Thus, hardness tests of laser-formed specimens prove the existence of different zones depending on the material and heat treatment. © 2001 Elsevier Science B.V. All rights reserved.
LFT Import::2019-07-15 (871)
Keywords: Aluminium and aluminium alloys; Hardness test; Laser forming; Microstructure; Rapid prototyping

Laser forming of hardenable aluminium alloys - Merklein, Marion (Proceedings of the 10th International Conference on Sheet Metal, She Met, 2003)
LFT Import::2019-08-05 (1006)

Laser Heat Treatment of Laser Welded Joints in Dual Phase Steel Sheets - Blankl, Andreas; Merklein, Marion (Proceedings of the 5th International Conference on Laser Assisted Net Shape Engineering, 2007)
LFT Import::2019-08-05 (1449)

Laser implantation of ceramic particles into hot working tool surfaces for improving the tribological performance within hot stamping - Schirdewahn, Stephan; Carstensen, Niels; Hilgenberg, Kai; Merklein, Marion (6th European Steel Technology and Application Days, 2023)

Laser implantation of niobium and titanium-based particles on hot working tool surfaces for improving the tribological performance within hot stamping - Schirdewahn, Stephan; Spranger, Felix; Hilgenberg, Kai; Merklein, Marion (Defect and Diffusion Forum, 2020)
Within the scope of this work, a laser implantation process has been used, in order to improve the tribological performance of hot stamping tools. This surface engineering technology enables the generation of dome-shaped, elevated and highly wear resistant microfeatures on tool surfaces in consequence of a localized dispersing of hard ceramic particles via pulsed laser radiation. As a result, the topography and material properties of the tool and thus the tribological interactions at the blank-die interface are locally influenced. However, a suitable selection of hard ceramic particles is imperative for generating defect-free surface features with a high share of homogenously disturbed particles. For this purpose, different niobium (NbB2 and NbC) as well as titanium-based (TiB2 and TiC) materials were embedded on hot working tool specimens and subsequently analyzed with regard to their resulting shape and mechanical properties. Afterwards, modified pin-on-disk tests were carried out by using conventional and laser-implanted tool surfaces, in order to evaluate the wear and friction behavior of both tooling systems.<br
CRIS-Team Scopus Importer:2020-11-27
Keywords: Surface modification; Triobology; Laser implantation

Laser implantation of titanium-based particles into hot stamping tools for improving the tribological performance during hot sheet metal forming - Schirdewahn, Stephan; Carstensen, Niels; Hilgenberg, Kai; Merklein, Marion (Proceedings of the 14th International Conference on the Technology of Plasticity - Current Trends in the Technology of Plasticity, 2024)
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. In this regard, hot stamping is used to manufacture such steel grades to geometrical complex car body components with high shape accuracy. Hot stamped parts are commonly made out of boron-manganese steel sheets, which are initially austenitized and subsequently formed and quenched simultaneously. During forming, however, high thermo-mechanical tool stresses appear, which in turn promote the occurrence of severe wear and high friction at the blank-die interface. After short time production, the quality of the parts as well as the operating time of the tool is negatively affected. To counter this, an innovative surface engineering technology named laser implantation process has been investigated, in order to improve the tribological performance of hot stamping tools. Within prior studies, the effectiveness of this technology has already been proven in laboratory scale by means of modified pin-on-disk and quenching tests. However, the tribological impact under industrial-related contact pressure has not been analyzed so far. Furthermore, the transferability of this technology to a deep drawing process has not been investigated in detail. To counter this, hot strip drawing tests with surface pressures ≥ 20 MPa have been performed to evaluate the tribological behavior. Furthermore, a locally modified as well as a conventional die were utilized for hot stamping rectangular cups, in order to compare their tribological impact.<br
Keywords: Tribology; Hot Stamping; Laser Implantation; Surface Structuring

Laserstrahlumformen von Aluminiumwerkstoffen - Merklein, Marion; Geiger, Manfred (Strahltechnik, 2002)
LFT Import::2019-07-16 (1719)

Laserstrahlumformen von Aluminiumwerkstoffen unter Berücksichtigung der mechanischen Eigenschaften und der Mikrostruktur - Geiger, Manfred; Merklein, Marion (Zeitschrift für Metallkunde, 2001)
LFT Import::2019-07-15 (823)

Laserunterstützes Rührreibschweißen von Magnesium Tailored Welded Blanks - Gnibl, Tobias; Merklein, Marion (XXXI. Verformungskundliches Kolloquium, 2012)
LFT Import::2019-08-05 (1790)

Leichtbauwerkstoffe für den modernen Automobilbau - Degner, Julia; Herrmann, Jürgen; Junker, Friedhelm; Berendt, Erik; Merklein, Marion (Konstruktion, 2018)
LFT Import::2019-07-29 (2296)

Lightweight construction by means of innovative process strategies in hydroforming technology - Geiger, Manfred; Merklein, Marion; Blankl, Andreas; Cojutti, Massimo (Steel Grips, 2007)
LFT Import::2019-07-16 (1442)

Linked heat treatment and bending simulation of aluminium tailored heat treated profiles - Froeck, Hannes; Graser, Matthias; Reich, Michael; Lechner, Michael; Merklein, Marion; Kessler, Olaf (Minerals, Metals and Materials Series, 2017)
Precipitation hardening aluminium alloys enable tailoring of mechanical properties through the dissolution of strength-increasing precipitates during a local short-term heat treatment. Tailor Heat Treated Profiles (THTP) are aluminium extrusion profiles with locally different material properties, specifically optimised for succeeding bending processes. Softened areas need to be generated next to hardened areas to optimise the material flow during the forming process. To determine the optimised layout of softened and hardened areas, a process chain simulation consisting of the simulation of the short-term heat treatment and the subsequent forming process seems purposeful. The numerical modelling of short-term heat treatment requires a coupled computation of thermal and mechanical simulation with particular focus on the evaluation of microstructure and consequently on the change of mechanical properties. The dissolution and precipitation behaviour during heating and cooling of aluminium profiles 6060 T4 is investigated using differential scanning calorimetry. Thermo-mechanical analysis is applied for evaluation of the mechanical properties. This behaviour should be described in a material model with the software LS DYNA. The heat treatment simulation provides a distribution of mechanical properties along the profile, which is an important input parameter for the following forming simulation. In order to avoid a loss of information between the heat treatment simulation and forming simulation, both linked simulations are performed with the software LS DYNA.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Aluminium alloy; Differential scanning calorimetry; EN AW-6060; Tailor heat treated profiles (THTP)

Local adjustment of surface integrity of forming tools by adaptation of tool making process - Andreas, Kolja; Henneberg, Johannes; Koch, Johannes Peter Karl; Merklein, Marion (Procedia CIRP, 2016)
LFT Import::2019-07-29 (2161)
Keywords: Local surface modification; Sheet-bulk metal forming; Tool manufacturing

Localized dispersing of TiB2 and TiN particles via pulsed laser radiation for improving the tribological performance of hot stamping tools - Schirdewahn, Stephan; Spranger, F.; Hilgenberg, K.; Merklein, Marion (Procedia CIRP, 2020)
The aim of this study is to increase the tribological performance of hot stamping tools by using a laser implantation process. This technique allows the fabrication of separated, elevated and dome-shaped microfeatures on the tool surface in consequence of a localized dispersing of ceramic particles via pulsed laser radiation. Hence, the topography and material properties of the tool are modified, which influences the tribological interactions at the blank-die interface. However, an appropriate selection of ceramic particles is an essential prerequisite, in order to obtain tailored and highly wear resistant surface features. In this regard, different titanium-based hard particles (TiB2 and TiN) were laser-implanted on hot working tool specimens and subsequently tested by means of a modified pin-on-disk test regarding to their wear and friction behavior.
CRIS-Team Scopus Importer:2020-10-30
Keywords: Hot stamping; Hot working tool steel; Localized laser dispering; Surface modification; Tribology

Localized Laser Dispersing of Titanium-Based Particles for Improving the Tribological Performance of Hot Stamping Tools - Schirdewahn, Stephan; Spranger, Felix; Hilgenberg, Kai; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2020)
Within the scope of this work, a new surface engineering technology named laser implantation has been investigated, in order to improve the tribological performance of hot stamping tools. This technique is based on manufacturing highly wear-resistant, separated, and elevated microfeatures by embedding hard ceramic particles into the tool surface via pulsed laser radiation. Hence, the topography and material properties of the tool are modified, which influences the thermal and tribological interactions at the blank-die interface. To verify these assumptions and to clarify the cause-effect relations, different titanium-based particles (TiB2, TiC, TiN) were laser-implanted and subsequently analyzed regarding to their geometrical shape and mechanical properties. Afterwards, quenching tests as well as tribological experiments were carried out by using titanium-diboride as the most promising implantation material for reducing the tribological load due to high hardness value of the generated implants. Compared to conventional tooling systems, the modified tool surfaces revealed a significantly higher wear resistance as well as reduced friction forces while offering the possibility to adjust the thermal interactions at the blank-die interface. Based on these results, a tailored tool surface modification can be pursued in future research work, in order to enhance the effectiveness of the hot stamping technology.
CRIS-Team Scopus Importer:2020-10-30
Keywords: Hot stamping; Localized laser dispersing; Surface modification; Tribology

Locally Adapted Tribological Conditions as a Method for Influencing the Material Flow in Sheet-Bulk Metal Forming Processes - Löffler, Maria; Schneider, Thomas; Vierzigmann, Ulrich; Engel, Ulf; Merklein, Marion (Key Engineering Materials, 2015)
Due to ecological and economic challenges there is a growing demand for lightweight designby using closely-tolerated complex functional components with variants. Conventional sheet and bulk metal forming operations are often improvident in producing such parts. A promising approach is the process-class "sheet-bulk metal forming" (SBMF). Within SBMF bulk forming operations are applied to sheet metals, often in combination with sheet forming operations [1]. This leads to a significant gradient in load conditions regarding stress and strain states and causes locally varying tribological conditions. Thus, the investigation of the tribological conditions and the provision of suited tribological systems are essential for the successful application of SBMF processes. The objective of the current study is the experimental investigation of the applicability of tribological adaptions by local abrasive blasting on a single-stage process combination of deep drawing and upsetting to produce a component with an external gearing. The manipulation of the local tribological conditions by the use of abrasive blasting leads to a better control of the material flow and in consequence to an improved quality of the components in terms of higher mould filling of the gear teeth and cup heights
LFT Import::2019-07-29 (2067)
Keywords: Forming; Tailored Surfaces; Tribology

Local prestressing of cold forging tools by reinforcements with adapted interference - Killmann, Martin; Merklein, Marion (Procedia Structural Integrity, 2022)
With contact pressures of more than 3000 MPa cold forging dies belong to the highest loaded components in mechanical engineering. Especially in non-symmetrical dies, this leads to a complex stress state with locally varying stresses. Cyclically occurring tensile stress concentrations cause crack initiation, which is why fatigue is the most important failure mechanism for complex cold forging tools. To reduce tensile stresses and counteract fatigue failure, dies are conventionally prestressed by inserting them into a reinforcement ring with a uniformly distributed interference. However, the compressive prestress is often not enough to compensate the high local stresses occurring in processes for non-symmetrical parts. Therefore, this paper focuses on using a non-uniformly distributed interference to locally increase prestresses in critical areas. To achieve this, gaps are inserted between die and reinforcement, inducing a bending stress. A numerical model is used to analyse how to design the gaps depending on the interference fit and how effective the use of gaps is for different part geometries with an increasing number of functional elements. Results show, that gap angles between 40° and 60° are suitable for locally improving the stress state. For high interferences, too large gap angles increase tensile stresses occurring in other areas of the dies, possibly impeding tool life. Since the adapted interferences work based on a bending effect, gaps are effective for up to four uniformly distributed critical areas. For more local elements, the lever distance is too low to apply an effective bending stress and the stress state does not improve. <
Keywords: Cold forging; Die design; Tool life; Local prestressing

Local strain measurement in tensile test for an optimized characterization of packaging steel for finite element analysis - Knieps, Fabian; Köhl, Manuel; Merklein, Marion (Key Engineering Materials, 2021)
The continuous development of packaging steels for thickness reduction processes requires an advanced process design. This process is increasingly supported by finite element analysis to simplify tool construction and material selection purposes. Therefore, the fundamental basis is always the precise material characterization of packaging steel commonly based on tensile tests to determine flow curve and Lankford coefficients. However, due to strong temper rolling and the occurrence of slip bands, most packaging steels just show little elongation in tensile test. Therefore, a method of Paul et al. [1] to determine the flow curve with digital image correlation (DIC) methods in the necking zone was applied in this work to meet the requirements of packaging steel. For the use of anisotropic yield functions, it is necessary to determine Lankford coefficients. Thus, a new method is proposed to measure Lankford coefficients locally with a DIC system in tensile test, also in case that no homogenous forming condition is reached. With the presented approaches the packaging steel TH415 was characterized. In order to validate the developed methods, a demonstrator was simulated with anisotropic yield function Yld2000-2d [2]. The comparison between simulation and experiment showed clear improvements in simulation accuracy when using the newly presented methods for packaging steel.
CRIS-Team Scopus Importer:2023-03-29
Keywords: Anisotropy; Finite element method; Packaging steel

Lubricant free forming with tailored tribological conditions - Henneberg, Johannes; Rothammer, Benedict; Zhao, Rong; Vorndran, Martin; Tenner, Jennifer; Krachenfels, Kim; Häfner, Tom; Tremmel, Stephan; Schmidt, Michael; Merklein, Marion (Dry Metal Forming Open Access Journal, 2020)
Changed ecological and economic situations motivate research into environmentally friendly and efficient manufacturing processes. Forming without lubricant has the potential to meet both requirements by avoiding the usage of environmentally harmful lubricants and shortening the process chain by omitting lubricant application and component cleaning. Within the scope of the project, an increase in friction and adhesive wear were identified as major challenges, resulting in failure of components due to cracking. Therefore, this project focused on the investigation of measures to meet these challenges. Amorphous carbon coatings, the reduction of roughness and the application of discrete microtextures were considered as potential measures. Hydrogen-containing amorphous carbon coating systems (a-C:H) fabricated by reactive physical vapor deposition (PVD), plasma-enhanced chemical vapor deposition (PECVD) and PVD/PECVD hybrid techniques, as well as a PVD-generated tetrahedral hydrogen-free amorphous carbon coating (ta-C) were investigated with respect to their properties and tribological performance Three specific profile requirements –a dopant free carbon network, smooth and defect-free surfaces and a high coating adhesion to substrate –are identified as requirements, in order to prolonger the service life of the coated tools. Moreover, to enable the steering of the material flow ultrafast laser based micro texturing for locally tailored tribological conditions were investigated. Thereby two wavelength dependent ablation regimes which differ in ablation mechanism and freedom of form were identified. Using these approaches the friction coefficient could either be reduced by up to 20 % or selectively increased. To improve the efficiency of the process, several beam shaping approaches were evaluated to provide a homogeneous beam profile for uniform modification. By applying ta-C and a-C:H coatings in forming tests, the findings of the laboratory tests were validated and the feasibility of lubricant free deep drawing was proven. In order to benefit from the forming-process-specific advantages, high quantities and therefore high durability of the measures are required. An application-oriented wear test rig has been designed to investigate their durability. By this, it was proven that 3 000 components can be produced from DC04 without wear with both a-C:H and ta-C coatings, and thus increasing tool life by a factor of 15 compared to unmodified tools. Even in the case of wear-critical AA5182, 3 000 parts were produced without wear using ta-C. Within the scope of the project, a fundamental understanding of lubricant free deep drawing processes and measures was created and proof of feasibility in form of a high number of components was achieved.<br
Keywords: Dry Deep Drawing; Tribology; Carbon Based Coatings; Laser Based Surface Modification; Beam Shaping

Machines and Tools for Sheet-Bulk Metal Forming - Merklein, Marion; Tekkaya, A. Erman; Brosius, Alexander; Opel, Simon; Kwiatkowski, Lukas; Plugge, Bjoern; Schunck, Sebastian (Key Engineering Materials, 2011)
The demand on closely-tolerated and complex functional components in the automotive sector, like e.g. synchronizer rings, leads to the development of a new process-class named "sheet-bulk metal forming". Within this technology bulk metal forming operations are applied on sheet metals. In the following two novel approaches considering machines and tools for sheet-bulk metal forming are presented. The first approach aims on a technology based on rolling, which is suitable for mass production. The second one is an incremental forming solution for low batch production. Both machine concepts allow the application of different forming strategies to manufacture individual tailored semi-finished products in term of a pre-distribution of material. These products feature variable sheet thicknesses and mechanical properties, which can be adapted to their case of application. Depending on the individual batch size, the blanks can be finished to functional parts by subsequent forming processes like deep drawing and upsetting, extrusion or incremental forming. In this paper the case of an incremental tooth-forming is mainly considered. Forming sequences and resulting loads are modeled and calculated by finite elements simulations for all discussed processes to serve as a basis for the design and dimensioning of the machine components and forming tools. © (2011) Trans Tech Publications.
LFT Import::2019-08-05 (1632)
Keywords: FE-Simulation; Incremental sheet forming; Rolling; Sheet-bulk metal forming

Magnesium - Leichtbauwerkstoff der Blechumformung: Relevanz einer exakten Werkstoffcharakterisierung und -modellierung - Suttner, Sebastian; Merklein, Marion (Konstruktion, 2016)
LFT Import::2019-07-29 (2192)

Manufacturing and Characterization of Multilayered 7000-Series Aluminum with Improved Corrosion Behavior Processed via Accumulative Roll Bonding - Degner, Julia; Bohm, Wolfgang; Herrmann, Jürgen; Kohler, Markus; Merklein, Marion (MATERIALS TODAY-PROCEEDINGS, 2019)
CRIS-Team WoS Importer:2019-04-12

Manufacturing complex Sheet Metal Components by Hydroforming of Deep-Drawn Preforms - Lamprecht, Klaus; Merklein, Marion; Geiger, Manfred (Proceedings of the 24th IDDRG Congress, 20.-26.06., Besancon, France, 2005)
LFT Import::2019-08-05 (1145)

Manufacturing flexibilisation of metal forming components by tailored blanks - Merklein, Marion; Lechner, Michael (Proc. Conf. Competitive Manufacturing, 2013)
LFT Import::2019-08-05 (1821)

Manufacturing of advanced smart tooling for metal forming - Cao, Jian; Brinksmeier, Ekkard; Fu, Mingwang; Gao, Robert X.; Liang, Biao; Merklein, Marion; Schmidt, Michael; Yanagimoto, Jun (CIRP Annals - Manufacturing Technology, 2019)
Forming is widely used due to its high efficiency in material utilization and its high production rate in general. Most forming processes control the geometry of final products through a set of tooling. The increasing demands on lightweight products have challenged the performances and functionalities of tooling. This paper provides a systematic review of recent advancements related to tooling performance and functionalities, including tool materials, tooling fabrication processes (e.g., machining, heat treatment, coating, surface texturing, and additive manufacturing), sensing, and data analytics. Finally, recommendations on future research directions for metal forming tooling are provided.
CRIS-Team Scopus Importer:2019-06-28
Keywords: Integration; Metal forming; Smart tooling

Manufacturing of Complex Functional Components with Variants by Using a new Metal Forming Process – Sheet-Bulk Metal Forming - Merklein, Marion; Koch, Johannes Peter Karl; Schneider, Thomas; Opel, Simon; Vierzigmann, Ulrich (International Journal of Material Forming, 2010)
LFT Import::2019-07-29 (160)

Manufacturing of complex functional components with variants by using a new sheet metal forming process - Merklein, Marion (ICFG 2009, Proceedings of the 42nd Plenary Meeting of the International Cold Forging Group, 2009)
LFT Import::2019-08-05 (1578)

Manufacturing of complex high strength components out of high nitrogen steels at industrial level - Noneder, Hannes; Merklein, Marion (Transactions of Nonferrous Metals Society of China, 2012)
High performance components, e.g., fasteners, nowadays are usually made out of cold forged and heat treated steels like steel 1.5525 (20MnB4). To overcome the problems of heat treatment, e.g., low surface quality, new workpiece materials for cold forging should be found to achieve the needlessness of heat treatment after cold forging. One possible material is given by high nitrogen steels like steel 1.3815 (X8CrMnN19-19). Due to the high strain hardening of these materials the process and tool design for an industrial batch process are challenging and should be conducted by FE-simulation. The numerical results show that, high strength tool materials, like PM-steels or cemented carbides, in most cases, are inevitable. Additionally to the selection of suitable tool materials, the tool layout should be developed further to achieve a high loadability of the tools. The FE-models, used for process and tool design, are validated with respect to the materials' flow and occurring forming force to assure a proper design process. Also the comparison of strength of components made out of steel 1.5525 in quenched and tempered conditions and steel 1.3815 in strain hardened condition is done. The results show that the component made of steel 1.3815 has a significantly higher strength than the component made of steel 1.5525. This shows that by the use of high nitrogen steels a high performance component can be manufactured by cold forging. © 2012 The Nonferrous Metals Society of China.
LFT Import::2019-07-29 (1865)
Keywords: cold forging; FE-simulation; heat treatable steel; high nitrogen steel; Martens hardness

Manufacturing of functional elements by sheet-bulk metal forming processes - Gröbel, Daniel; Schulte, Robert Karl; Hildenbrand, Philipp; Lechner, Michael; Engel, Ulf; Sieczkarek, P.; Wernicke, Sebastian; Gies, Soeren; Tekkaya, A. E.; Behrens, B. A.; Huebner, S.; Vucetic, M.; et al. (Production Engineering, 2016)
Due to increasing economic and ecological restrictions, conventional sheet and bulk forming operations often reach their limits with regard to part weight and functional integration. One solution to meet those challenges is provided by sheet-bulk metal forming (SBMF) processes. SBMF is defined as the application of bulk forming operations on sheet metal. SBMF can be combined with conventional sheet forming operations and offers the opportunity to form highly functional integrated parts out of sheet metal. It contains the benefit of an optimization of the part weight and a shortening of the process chain. Recent research has found different solutions regarding the actual implementation of SBMF in several process variants. In this paper, a categorisation for functional elements on sheet metal parts is proposed. A selection of possible approaches for their manufacturing is presented. The process variants are compared by means of the main process characteristics. By these means, the choice of a suitable option shall be facilitated for practical manufacturing design and for a particular relevant product.
LFT Import::2019-07-29 (2152)
Keywords: Flow control; Sheet-bulk metal forming; Tailored blanks; Tailored surfaces

Manufacturing of geared sheet metal components by a single-stage Sheet-bulk metal forming process - Schneider, Thomas; Merklein, Marion (Proc. Conf. Competitive Manufacturing, 2013)
LFT Import::2019-08-05 (1818)

Manufacturing of geared sheet metal components using flexible rolled tailored blanks - Opel, Simon; Schneider, Thomas; Merklein, Marion (Key Engineering Materials, 2013)
Manufacturing of functional sheet metal products with integrated gear teeth by forming can be realized with the application of bulk forming operations on sheet metals. The main challenges of sheet-bulk metal forming are high resulting forming forces and the demand on a specific control of the material flow. In addition, there is a distinctive interaction between blank thickness and resulting part quality. To meet these challenges at high material efficiency, the application of tailored blanks with a defined sheet thickness distribution is a promising way. The process adapted semi-finished products used in the presented work are formed by a flexible rolling process. Firstly the developed rolling machine to produce rotational symmetric tailored blanks is shown, as well as the fundamental process influences during rolling. Based on that, the development of a suitable process strategy to produce tailored blanks with a thickened sheet area is presented. The further processing of those tailored blanks for the realization of external geared sheet metal components will show the advantages compared to the application of conventional sheet metals of constant sheet thickness. Therefore the concept of a combined deep drawing process with geared drawing die and optional upsetting is presented. The results show, that on the one hand the material efficiency is increased in comparison to the usage of conventional sheets of the same maximum thickness. On the other hand, the application of flexible rolled tailored blanks improves mold filling of the gear teeth and the component's strength. These approaches prove that the application of rolled tailored blanks is an appropriate procedure to enhance the limits of using conventional sheet metals within sheet-bulk metal forming. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1858)
Keywords: Flexible rolling; Ironing; Sheet-bulk metal forming

Manufacturing of high-strength aluminum sheet metal in the Accumulative Roll Bonding process - Böhm, Wolfgang; Merklein, Marion (New Developments in Sheet Metal Forming, 2014)
LFT Import::2019-08-05 (2019)

Manufacturing of Innovative Aluminum Components by Combining Shear Cutting Operation and Tailor Heat Treated Blank Technique - Degner, Julia; Suttner, Sebastian; Tsoupis, Ioannis; Lechner, Michael; Merklein, Marion (5th International Conference on Accuracy in Forming Technology, 2015)
LFT Import::2019-08-05 (2130)

Manufacturing of Innovative Car Seat Components by Forming of Advanced High Strength Steels - Fundamental Research and Application - Merklein, Marion; Kaupper, Markus (Key Engineering Materials, 2009)
LFT Import::2019-07-29 (208)
Keywords: Bending; Car seat; FEM; High strength steel

Manufacturing of sheet metal components with variants using process adapted semi-finished products - Merklein, Marion; Plettke, Raoul; Schneider, Thomas; Opel, Simon; Vipavc, Daniel (Key Engineering Materials, 2012)
Functional sheet metal components can be manufactured through the use of bulk forming operations on sheet metal semi-finished parts. Challenging are the high forming forces and the exact control of material flow. The manufacturing of the semi-finished parts with a defined sheet thickness characteristic occurs on the basis of the processes upsetting and orbital forming. Following a forming operation is presented for the production of an external geared component. The potential for the enhancement of the process limits by use of tailored blanks is demonstrated.© (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1783)
Keywords: Deep-drawing; FE-simulation; Orbital forming; Sheet-bulk metal forming; Upsetting

Manufacturing of tailored blanks by flexible rolling and its application in a sheet-bulk metal forming process - Vogel, Manfred; Lechner, Michael; Hildenbrand, Philipp; Schulte, Robert Karl; Merklein, Marion (Proceedings SCT2017, 2017)
LFT Import::2019-08-05 (2229)

Manufacturing of tailored blanks by orbital forming with a two-sided material thickening - Vogel, Manfred; Merklein, Marion (Journal of Materials Processing Technology, 2019)
Due to the rising lightweight construction, especially in the automotive industry, the demands focused on functional components are constantly increasing with a result of new challenges regarding the manufacturing technology. For an extension of the process limits of conventional sheet metal forming processes, semi-finished parts with a defined material pre-distribution, so-called tailored blanks, can be used to provide additional material volume in defined areas in order to achieve a proper die filling of functional elements like gearings or carriers used e.g. for synchronizer rings. However, due to the increasing component complexity and thus the forming of functional elements on both sides of the frame, a two-sided thickness profile is mandatory. As a result, the material thickenings on both sides of the tailored blank lead to an interaction, regarding the maximum achievable sheet thicknesses or dimensions of the material pre-distribution. For the manufacturing of such tailored blanks, an orbital forming process can be used. Prior investigations showed the general feasibility for the manufacturing of tailored blanks with a one-sided thickness profile. In this paper, the feasibility of using the orbital forming process to produce tailored blanks is fundamentally investigated. Therefore, a numerical model of the process was developed, with a subsequent validation by comparing the numerical with the experimental results. Afterwards, the material flow is analysed regarding different geometries of the material pre-distribution as well as the position of the thickness profile in order to allow a generally valid design.
CRIS-Team Scopus Importer:2019-12-17
Keywords: Metal forming; Orbital forming; Sheet metal; Tailored blanks

Manufacturing of Tailored Blanks with Pre-shaped Involute Gearings by Using a Flexible Rolling Process and Its Application in a Sheet–Bulk Metal Forming Process - Vogel, Manfred; Schulte, Robert Karl; Kaya, Onur; Merklein, Marion (Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity, 2021)
Nowadays, the efficient manufacturing of functional components in short process chains is important due to the goal of a further reduction of greenhouse gases. Additionally, there are also technical demands like functional integration combined with an improvement of the component’s properties. Previous investigations have shown that the application of tailored blanksTailored blank with a defined thickness profile can lead to an improvement of the geometrical and mechanical properties of functional components. However, common forming processes reach their limits. A promising approach to enlarge these process limits is the application of bulk forming operations to sheet metals, the so-called sheet–bulk metal forming (SBMF). Within this process class, one possibility for manufacturing such blanks is a flexible rollingFlexible rolling process. As a result of movement of two rolling tools in combination with a die cavity in the lower tool, a defined geometry can be manufactured perpendicular to the sheet plane. In order to raise the complexity combined with a shorter process chain and thus to fulfil the requirements defined by the subsequent forming operations, a new design that contains a preform of involute gearings is introduced. In order to acquire process knowledge, the mild deep drawing steel DC04 with an initial sheet thickness of t0 = 2.0 mm is used. Furthermore, the subsequent application of the tailored blanks in a combined deep drawing and upsetting process is shown, with a characterization of the geometrical and mechanical properties.
CRIS-Team Scopus Importer:2021-09-03
Keywords: Flexible rolling; Sheet forming; Tailored blank

Maßgeschneiderte Halbzeuge - Umformtechnische Herstellung von Funktionsbauteilen zur Realisierung von Leichtbaukomponenten - Hetzel, Andreas; Schulte, Robert Karl; Vogel, Manfred; Degner, Julia; Merklein, Marion (wt Werkstattstechnik - Online, 2019)
Sheet Bulk Metal Forming enables the efficient manufacturing of functional lightweight components with different functional elements in a combined single stage deep drawing and upsetting process. By investigating the forming results with a conventional blank, regarding the properties like grain structure and Vickers hardness distribution, process limitations such as buckling and folding can be detected. These failures occur due to a three-dimensional stress and strain state as well as an insufficient die filling. A significant improvement of the quality of the produced parts can be enabled by the use of Tailored Blanks in the investigated process chain. With the manufacturing of the semi-finished parts by orbital forming, an adapted material pre-distribution can be realized, thus improving the die filling followed by a decrease of the parts' failures. Current research at the Institute of Manufacturing Technology focuses on the extension of the applicability of Tailored Blanks.
CRIS-Team Scopus Importer:2020-02-21

Maßgeschneiderter Werkzeugoberflächen in einem flexiblen Walzprozess - Vogel, Manfred; Schulte, Robert; Freiburg, Dennis; Lechner, Michael; Biermann, Dirk; Merklein, Marion (FAU University Press, 2019)
Die Anwendung prozessangepasster Halbzeuge in Verfahren der Blechmassivumformung führt zu einigen Vorteile in Bezug auf nachgelagerte Umformprozesse. Durch eine definierte Materialvorverteilung wird sowohl eine ressourceneffizientere Nutzung des Materials als auch eine Steigerung der Bauteilqualität durch lokale Vorverfestigung erreicht. Die umformtechnische Herstellung rotationssymmetrischer, prozessangepasster Halbzeuge variabler Blechdicke ist durch ein flexibles Walzverfahren möglich, welches durch translatorische Bewegung zweier Umformwalzen einen Stofffluss in definierte Werkzeugkavitäten erzeugt. In Abhängigkeit des Aufdickungsvolumens und der Homogenität der Materialvorverteilung kann so in nachfolgenden Umformstufen, wie z. B. einem kombinierten Tiefzieh-Stauchprozess, eine höhere Formfüllung von Funktionselementen erreicht werden. Bedingt durch die tribologischen Eigenschaften zwischen Halbzeug und Walztisch kann in Abhängigkeit von Geometrie und Prozessführungsstrategie nicht immer eine homogene Materialvorverteilung erzielt werden. Durch den Einsatz von maßgeschneiderten Werkzeugoberflächen im Umformprozesssoll eine Möglichkeit zur Steigerung der Stoffflusskontrolle aufgezeigt werden, um so ein höheres Materialvolumen im Aufdickungsbereich bereitstellen zu können. Durch den anschließenden Einsatz der gewalzten Tailored Blanks in einem kombinierten Tiefzieh-Stauchprozess werden Erkenntnisse des Potentials zum Einsatz von Tailored Surfaces in der Halbzeugherstellung gewonnen und ein Prozessverständnis für den industriellen Einsatz abgeleitet.
Keywords: Blechmassivumformung; Tailored Blanks; Walzen; Inkrementelle Umformung

Maßgeschneidert – Funktionsoptimierte Strukturbauteile im Presshärtprozess - Merklein, Marion; Svec, Thomas; Stöhr, Thomas; Wieland, Michael (Lightweight Design, 2010)
LFT Import::2019-07-29 (718)

Material Characterization of Hybrid Components Manufactured by Laser-Based Directed Energy Deposition on Sheet Metal Substrates - Kreß, Maximilian; Bartels, Dominic; Schmidt, Michael; Merklein, Marion (The 25th International Conference on Material Forming (ESAFORM 2022), 2022)
Laser-based directed energy deposition (DED-LB/M) allows the application of a wear-resistant metal coating to the surface of a sheet metal substrate. Subsequent deep drawing of the part enables high material efficiency, significantly shorter production times, and lower unit costs compared to, for example, solely machined production of the entire component. At the same time, energy-intensive global heat treatment strategies can be avoided. For the numerical analysis of such hybrid process chains, both the sheet metal substrate and the additively applied coating are usually characterized individually. However, the low thickness of the coating in combination with a relatively high welding depth, which is required for a good bond to the sheet metal substrate during subsequent forming, lead to a strong gradient of the mechanical properties as well as complex mechanical interactions in the bonding zone. Therefore, appropriate characterization methods are required. In this work, an investigation of different influencing factors, like the rolling, hatch and tensile direction, is carried out with the aid of tensile tests using hybrid specimens. In this way, interactions between the influencing factors are identified. As substrate, 3.5 mm thick 16MnCr5 blanks are used, with an approximately 0.68 mm thick coating of Bainidur® AM. In addition, an optical surface roughness measurement and metallographic analysis of the tensile specimen’s edge area after laser cutting is performed.<br
Keywords: directed energy deposition; sheet metal forming; material characterization; case hardening steel

Material flow control in sheet-bulk metal forming processes using blasted tool surfaces - Merklein, Marion; Löffler, Maria; Gröbel, Daniel; Henneberg, Johannes (Proceedings of the 5th International Conference on New Forming Technology, 2018)
Highly-integrated and closely-tolerated functional components can be produced by sheet-bulk metal forming which is the application of bulk forming operations on sheet metals. These processes are characterized by a successive and/or simultaneous occurrence of different load conditions such as stress and strain states which reduce the geometrical accuracy of the functional elements. Thus, one main challenge within sheet-bulk metal forming is the identification of methods to control the material flow and thus to improve the product quality. One suitable approach is to control the material flow by local modifications of the tribological conditions. Within this study requirements regarding the needed adaption of the tribological conditions for a specific sheet-bulk metal forming process were defined by numerical investigations. The results reveal that a local increase of the friction leads to an improved die filling of the functional elements. Based on these results abrasive blasting as a method to modify the tool surface and thus influencing the tribological behaviour was investigated. For the determination of the tribological mechanism of blasted tool surfaces, the influence of different blasting media as well as blasting pressures on the surface integrity and the friction were determined. The correlations between surface properties and friction conditions were used to derive the mechanisms of blasted tool surfaces.
LFT Import::2019-08-05 (2323)
Keywords: Cold forming; Surface modification; Tribology

Material flow control in tailor welded blanks by a combination of heat treatment and warm forming - Gnibl, Tobias; Merklein, Marion (CIRP Annals - Manufacturing Technology, 2016)
LFT Import::2019-07-29 (2168)
Keywords: Aluminum; Forming; Post weld heat treatment

Material Flow in Sheet-Bulk Metal Forming - Vierzigmann, Ulrich; Koch, Johannes Peter Karl; Merklein, Marion; Engel, Ulf (Key Engineering Materials, 2012)
The trend towards closely-tolerated complex functional components with an increased functionality shows the limits of classical sheet and bulk metal forming operations. The combination of sheet and bulk metal forming operations to the new process class of sheet-bulk metal (SBMF) operations is a promising approach for producing the requested parts. Combining sheet and bulk metal operations is leading to different surface pressures and hence to different tribological conditions within the forming process. Investigations with FE-simulation have shown, that locally adapted tribological conditions can yield an improvement in material flow and thus, an increased mold filling within SBMF process. As frictional conditions are directly connected to the topography of workpiece and tool, the targeted modification of the workpiece topography can be used to adjust friction values, correspondingly. Within this paper the modification of workpiece topography by abrasive blasting and the resulting influence on the frictional conditions are investigated. Additionally, an approach for the definition of different tribological zones on a SBMF extrusion die is presented.© (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1785)
Keywords: Abrasive blasting; Material flow; Sheet-bulk metal forming; Tribology

Material Model for the Production of Steel Fibers by Notch Rolling and Fulling - Biallas, Alina; Merklein, Marion (Key Engineering Materials, 2021)
Concrete, which is reinforced by steel fibers, represents a multifunctional building material that is able to realize flexible but stable structures. As an alternative to the energy-intensive conventional production procedure wire drawing, a combination of a notch rolling and cyclic bending process is proposed by Stahl [1] to produce those fibers. Besides representing the properties of steel fibers and the overall process, the paper brings the layout of both process steps into focus. Since notch rolling for the production of wire strip is mainly unexplored, a general conceptual design of the process and the rolling tools is performed, supplemented by a similar study on the fulling process. To enable a further evaluation of the process chain and its relevant process parameters, a numerical and experimental test phase using strip of a dual phase steel DP600 with a sheet thickness of t0 = 0.8 mm is intended in future. For ensuring high-quality numerical model, relevant behavior of the test strip is characterized through appropriate experiments and according material models in the present pape
Keywords: Conceptual design; Rolling; Steel fibers

Material Modelling for Stochastic Simulation - Sturm, Vera; Annen, C.; Merklein, Marion (Proc. 50th Conference of IDDRG 2010, 2010)
LFT Import::2019-08-05 (312)

Material suited part and process design in sheet forming - Merklein, Marion; Geiger, Manfred; Vogt, Uwe (Neuere Entwicklungen in der Blechumformung: Tagungsband, Stuttgart: Werkstoff-Informationsgesellschaft, 2006)
LFT Import::2019-08-05 (1275)

Mathematical Modelling of the Flow Behaviour of Hot Stamping Steels for a FE-based Process Design - Merklein, Marion; Lechler, Jürgen; Geiger, Manfred (Tagungsband COMA'07, Südafrika, 2007)
LFT Import::2019-08-05 (1456)

Measures for controlling the material flow when extruding sheet-bulk metal forming parts from coil - Henneberg, Johannes; Merklein, Marion (Manufacturing Review, 2020)
The increasing demand for lightweight design requires functional integration. This poses challenges to conventional manufacturing processes due to the rising geometrical complexity of components. The application of bulk forming operations to sheet metal, named sheet-bulk metal forming (SBMF), is one approach to overcome these challenges. Currently, mainly pre-cut blanks are applied in research of SBMF. Production from coil, in contrast, would combine the advantages of SBMF with the advantages of manufacturing from a coil regarding high output quantity. To research SBMF from coil, a lateral and a backward extrusion process are set up. In addition to a reduced geometrical accuracy of the parts, which is known from SBMF of pre-cut blanks, an anisotropic material flow is identified as a coil-specific challenge. The aim of this research is to investigate measures that extend the forming limits by means of a material flow control. For this purpose, a combined numerical-experimental approach is applied in order to analyze and evaluate an adaption of the width of the coil, the feed width, and the local friction as measures for material flow control. Particularly local adaptation of friction by means of modified tool surfaces reduces the anisotropic material flow and improves the geometrical accuracy of the parts.
CRIS-Team WoS Importer:2020-11-06

Measuring procedures for surface evaluation of additively manufactured powder bed based polymer and metal parts - Heinl, Martin; Greiner, Sandra; Wudy, Katrin; Pobel, Christoph; Rasch, Michael; Huber, Florian; Papke, Thomas; Merklein, Marion; Schmidt, Michael; Körner, Carolin; Drummer, Dietmar; Hausotte, Tino (Measurement Science and Technology, 2020)
Powder bed-based additive manufacturing has become increasingly important for industrial applications. In the light of this, qualitative considerations such as the geometrical accuracy, the resulting mechanical properties, and the surface quality of additively manufactured parts must be taken into account. Optical measuring techniques such as confocal laser scanning microscopy, fringe projection and focus variation as well as profilometers are evaluated here, to determine the surface quality of powder bed-based manufactured parts. Even though these surface evaluation methods are established commercially, no standardized measuring procedure has yet been established. Within an experimental study the validity and accuracy of surface measurement methods are evaluated below, taking the limitations of each measurement system and the comparability of areal surface textures into account. The examinations are carried out with the powder materials EN-AW2024, Ti-6V-4Al and PA12, which are processed by electron beam melting, and laser beam melting of metals and polymers. Guidance for a consistent and comparable surface evaluation is thereby provided.
Keywords: Additive manufacturing (AM); laser beam melting (LBM); electron beam melting (EBM); guidance for consistent surface evaluation; comparison of optical and profilometer surface measurements

Mechanical Behaviour of Ceramic Beads Used as Medium for Hydroforming at Elevated Temperatures - Grüner, Martin; Merklein, Marion (Key Engineering Materials, 2009)
The need of light weight construction for high efficient vehicles leads to the use of new materials like aluminium and magnesium alloys or high strength and ultra high strength steels. At elevated temperatures the formability of steel increases as the flow stresses decrease. Forming high complex geometries like chassis components or components of the exhaust system of vehicles can be done by hydroforming. The hydroforming process by oils is limited to temperatures of approximately 300 °C and brings disadvantages of possible leakage and fouling. Using granular material like small ceramic beads as medium could be an approach for hydroforming of ultra high strength steels like MS-W1200 and CP-W800 at temperatures up to 600 °C. The material properties of granular material are in some points similar to solid bodies, in other points similar to liquids. For understanding and simulation of the behaviour of the medium a basic characterisation of ceramic beads with different ball diameters is necessary. Powder mechanics and soil engineering give ideas for experimental setups. For the conversion of these approaches on the one hand the behaviour of the ceramic beads itself has to be characterized, on the other hand the contact between a blank and the beads have to be investigated. For the tests three different kinds of spheres with a diameter between 63 microns and 850 microns are used. In unidirectional compression test compressibility, pressure distribution in compression direction and transversal compression direction and the effect of bead fracture are investigated. The tests are carried out at different compression velocities and for multiple compressions. For determination of friction coefficients between blank and beads and determination of shear stress in bulk under compression a modified Jenike-Shear-Cell for use in universal testing machines with the possibility of hydraulic compression of the beads is built up. The gained data can be used for material modelling in ABAQUS using Mohr-Coulomb or Drucker-Prager model. © (2009) Trans Tech Publications, Switzerland.
LFT Import::2019-07-29 (301)
Keywords: Elevated temperatures; Granular material; Hydroforming

Mechanical joining of high-strength multi-material systems - trends and innovations - Merklein, Marion; Jäckisch, Manuel; Kuball, Clara-Maria; Römisch, David; Wiesenmayer, Sebastian; Wituschek, Simon (Mechanics & Industry, 2023)

Mechanical joining without auxiliary element by cold formed pins for multi-material-systems - Kraus, Martin; Frey, Philipp; Kleffel, Tobias; Drummer, Dietmar; Merklein, Marion (22nd International ESAFORM Conference on Material Forming (ESAFORM 2019), 2019)

Mechanical properties and plastic anisotropy of the quenchable high strengt steel 22MnB5 at elevated temperatures - Merklein, Marion; Lechler, Jürgen; Sturm, Vera; Bruschi, S.; Ghiotti, A.; Truetta, A. (Tagungsband SheMet'07, 2007)
LFT Import::2019-08-05 (1457)

Mechanical properties of an innovative shear-clinching technology for ultra-high-strength steel and aluminium in lightweight car body structures - Hoerhold, Rejane; Müller, Martin; Merklein, Marion; Meschut, Gerson (Welding in the World, 2016)
LFT Import::2019-07-29 (2167)
Keywords: Aluminium alloys; High strength steels; Mechanical fastening; Mechanical properties; Nonwelded joints; Vehicle bodies

Mechanical Properties of Laser Heat Treated 6 mm Thick UHSS-Steel - Jarvenpaa, Antti; Mantyjarvi, Kari; Merklein, Marion; Maatta, Antti; Hietala, Mikko; Karjalainen, Jussi (The 14th International ESAFORM Conference on Material Forming, 2011)
In this work abrasion resistant (AR) steel with a sheet thickness of 6 mm was heat treated by a 4 kW Nd:YAG and a 4 kW Yb:Yag-laser, followed by self-quenching. In the delivered condition, test material blank (B27S) is water quenched from 920°C. In this condition, fully martensitic microstructure provides excellent hardness of over 500 HB. The test material is referred to AR500 from now onwards. Laser heat treatment was carried out only on top surface of the AR500 sheet: the achieved maximum temperature in the cross-section varies as a function of the depth. Consequently, the microstructure and mechanical properties differ between the surfaces and the centre of the cross-section (layered microstructure). For better understanding, all layers were tested in tensile tests. For a wide heat treatment track, the laser beam was moved by scanning. Temperatures were measured using thermographic camera and thermocouples. Laser heat treated AR500 samples were tested in hardness tests and by air bending using a press brake machine. Microstructures were studied using a light microscope and FE-SEM/SEM-EBSD. At least three kind of microstructure layers were observed: 1) Dual-Phase ferritic/martensitic (T=AC1-AC3), 2) ferritic (T∼AC3) and 3) bainitic/martensitic (T>AC3). © 2011 American Institute of Physics.
LFT Import::2019-08-05 (1693)
Keywords: bending; Laser heat treatment; layered microstructure

Mechanical response of Ti-6Al-4V alloy on deformation at moderate temperatures - Merklein, Marion; Hagenah, Hinnerk; Kaupper, Markus; Schaub, Adam (Key Engineering Materials, 2013)
Due to beneficial characteristics such as high specific strength, corrosion resistance and biocompatibility Ti-6Al-4V alloy has become the most important industrially produced titanium alloy during the last decades. Commonly used for aerospace technology and medical products, nowadays Ti-6Al-4V covers 50% of the worldwide produced titanium alloy parts. Different deformation operations as forging and casting as well as machining are used to shape titanium alloy components. For sheet metals, cost and time of fabrication can be reduced significantly via the near net shape technology sheet metal forming. Materials such as the α + β alloy Ti-6Al-4V with high yield stress and comparatively low elastic modules need to be formed at elevated temperatures to increase their formability. Numerical simulations are applied to calculate the forming behavior during the process and conclude the characteristics of the shaped part. Therefore in this paper the mechanical behavior of this titanium alloy is investigated by uniaxial tensile test within elevated temperatures ranging from 250 to 500 °C. Finally, the experimental results are adapted to models which predict the flow response in order to describe material behavior in finite element analysis of the forming process. © (2013) Trans Tech Publications.
LFT Import::2019-07-29 (1875)
Keywords: Plastic deformation; Temperature effects; Tensile test; Ti-6Al-4V alloy

Mechanical Testing of Additive Manufactured Metal Parts - Merklein, Marion; Plettke, Raoul; Junker, Daniel; Schaub, Adam; Ahuja, Bhrigu (Key Engineering Materials, 2015)
The quality of additive manufactured parts depends, however, a lot on the workers experience to control porosity, layer linkage and surface roughness. To analyze the robustness of the Laser Beam Melting (LBM) process, a Round Robin test was made in which specimens from four institutes from different countries were tested and compared. For the tests, each institute built a set of specimens out of the stainless steel 1.4540. The aim of this work is to analyze the influence of the process parameters on the mechanical properties. The results show that there is a high potential for additive manufacturing but also a lot of further research is necessary to optimize this technology.
LFT Import::2019-07-29 (2079)
Keywords: Additive manufacturing; Mechanical testing; Stainless steel

Mechanical Weld Zone Characterization for the Numerical Simulation of Forming Friction Stir Welded Aluminum Blanks - Gnibl, Tobias; Suttner, Sebastian; Merklein, Marion (AIP Conference Proceedings, 2013)
LFT Import::2019-07-29 (1942)

Mechanisms of residual stress generation in full-forward-extrusion - Landkammer, Philipp; Jobst, Andreas; Kiener, Christoph; Steinmann, Paul; Merklein, Marion (Production Engineering, 2019)
LFT Import::2019-07-29 (2366)

Mehrlagenbeschichtungen für den beanspruchungsgerechten Einsatz bei Kaltmassivumformwerkzeugen - Schrader, Tobias; Engel, Ulf; Geiger, Manfred; Merklein, Marion (Moderne Beschichtungen zum Verschleißschutz von Werkzeugen, 2012)
LFT Import::2019-08-05 (1845)

Metal forming ensures innovation and future in Europe - Geiger, Manfred; Merklein, Marion; Tolazzi, Massimo (Proceedings of the 8th International Conference on TEchnology of Plasticity (ICTP), 2005)
The role of the European Union in the field of research funding is becoming more and more important for the strategic choices of the single countries of the Old Continent. The new framework programs receive increased investments and at the same time give precise the-matic areas for the possible application of research proposal. However it can be surprisingly observed that topics concerning metal forming technology have strongly lost consideration in the 6th Framework Program. Metal forming remains in fact a key technology, being es-sential for almost all the manufacturing processes and fundament of the most important aspects of our society: mobility, health, communication. The extraordinary developments of the Industrial Society in the 20th Century showed the importance and potential of a scien-tifically driven technology development, in which an idea can become an invention, be ap-plied and completely change the world in few decades. If we want to ensure our future we cannot give up innovation and research, especially in metal forming; on the contrary we should properly fund them at a public level. There are in fact many promising innovations in metal forming, which are emerging in these years and will be presented in this paper, which may become key technologies for the manufacturing of tomorrow.
LFT Import::2019-08-05 (1219)
Keywords: Funding; Innovation; Metal forming; Research

Metallographic analysis of failure mechanisms during Nakajima tests for the evaluation of forming limits on a dual-phase steel - Affronti, Emanuela; Weidinger, Mario; Merklein, Marion (IOP Conference Series: Materials Science and Engineering, 2018)
The material characterization is the first step for an accurate numerical design of forming operations. Since its first definition in the 1960s, the forming limit curve (FLC), usually evaluated with Nakajima or Marciniak tests, is still one of the most used criteria in the industrial and scientific field for the determination of the forming limits under different stress conditions. Despite the several signs of progress in terms of measurement techniques, thanks to the introduction of optical measurement systems, the European standard method for the evaluation of the FLC remains the cross-section-method of 2008. This method is basically suitable for materials with a pronounced necking evolution. For materials with an abrupt localization, like modern high-strength materials, the standard evaluation shows weaknesses. Investigations in 2015 based on pattern recognition on Nakajima tests show that the pattern evolution of the strain distribution during the test can be used for the prediction of the material failure. However, a definition of the pattern development is needed. In order to investigate new possibilities for the determination of the FLC, the knowledge about the failure mechanisms during Nakajima tests for these materials has to be increased. The aim of the present work is an analysis of the changes on the surface and the microstructure during the Nakajima tests at different stress states and drawing depths. The correlation between material modifications and failure behavior is conducted on the dual-phase steel DP800. For the analysis of the surface and the thickness, the scanning electron microscope (SEM) is employed. Moreover, considerations about the forming mechanisms of the DP800 at different stress conditions are given and compared with the forming limit prediction of the FLC.
LFT Import::2019-07-29 (2326)

Metallographic Analysis of Nakajima Tests for the Evaluation of the Failure Developments - Affronti, Emanuela; Merklein, Marion (Procedia Engineering, 2017)
The material characterisation in sheet metal forming is significantly improved with the introduction of optical measurement systems. The optical measurement is based on the digital image correlation (DIC) technique, which provides accurate strain measurement of the local strain distribution on specimens. The changes of the stochastic distribution due to the forming are therefore used in order to measure displacements and deformations. An acknowledged application of the DIC technique is the evaluation of the forming limit curve (FLC) for sheet metals. Typically, the FLC is evaluated by conducting Nakajima tests. The Nakajima test is a stretch forming-based test and allows the analysis of stretching at different stress conditions. A previous investigation based on pattern recognition on Nakajima tests has shown that for a conventional deep drawing steel DC04 the pattern evolution on the strain distribution during the test can be examined in order to predict the material failure. However, even if the investigation shows promising results, the correspondence between pattern on the surface and changes in the material structure is missing. The aim of the present work is an analysis of the surface structure of Nakajima tests at different stress states and drawing depths. The correlation between surface modifications and failure behaviour is conducted on the deep drawing steel DC04. The scanning electron microscope (SEM) (Merlin Zeiss GmbH) is employed in order to investigate the evolution of the surface at different strain conditions. The results of the surface and the metallographic investigation are finally compared with the forming limit prediction of the FLC and the failure behaviour at different stress conditions is discussed.
LFT Import::2019-08-05 (2227)
Keywords: forming limit; metal forming; metallography

Metallurgical Short-Term Effects in Laser Forming of Alluminium Alloys - Merklein, Marion; Geiger, Manfred (Proceedings of the 3rd ESAFORM Conference on Material Forming, 2000)
LFT Import::2019-08-05 (790)

Methodengestützte Referenzvorgehensweise für neue Umformverfahren - Weckenmann, Albert; Reithmeier, Eduard; Merklein, Marion; Behrens, B.-A.; Wartzack, Sandro; Kästner, M.; Akkasoglu, Gökhan; Ohrt, Christoph; Schneider, Thomas; Salfeld, V.; et al. (Zeitschrift für wirtschaftlichen Fabrikbetrieb, 2012)
LFT Import::2019-07-29 (1782)

Methodik zur Analyse und Charakterisierung von Biegeprozessen - Merklein, Marion; Kaupper, Markus (Zukunftstechnologien in Bayern - Neue Materialien, Verfahren und Produkte, 2008)
LFT Import::2019-07-29 (1811)

Methodik zur Parameteridentifikation des kinematischen Verfestigungsmodells nach Chaboche und Rousselier - Suttner, Sebastian; Rosenschon, Martin; Merklein, Marion (Tagungsband Werkstoffprüfung, 2014)
LFT Import::2019-08-05 (2061)

Methodology for the analysis of the process behaviour of advanced high strength steels in bending and shearing operations - Tsoupis, Ioannis; Hildering, Sven; Merklein, Marion (Key Engineering Materials, 2012)
In the automotive sector the application of advanced high strength steels (AHSS) for structural and safety relevant components plays an important role. Typical manufacturing processes concerning these parts are bending and cutting operations. However, the forming and cutting potential of these steel grades is different compared to conventional steels, as the process behaviour is changing. For an improved workpiece quality the fundamental knowledge of the damage and failure mechanisms is essential. This study presents a methodology for the analysis of AHSS in bending and out-of-plane shearing operations. Two micro alloyed high strength steels are investigated within this work. First results are presented concerning material characterisation by tensile tests, the material performance in air bending tests and the development of a modular punching tool. The study is closed by summarizing the damage behaviour along the process chain considering both bending and cutting. This shows the applicability of the presented methodology for analysing the process behaviour with respect to occurring failure.© (2012) Trans Tech Publications.
LFT Import::2019-07-29 (1781)
Keywords: Advanced high strength steel; Bending; Cutting; Damage

Methods for Determination of Residual Stress of a Formed Plate using Laser Ablation, Wire EDM and Milling - Lamsa, Janne; Mantyjarvi, Karl; Jarvenpaa, Antti; Grüner, Martin; Merklein, Marion; Karjalainen, Jussi A. (Key Engineering Materials, 2011)
In this work laser ablation was used for the determination of residual stress of a formed plate. Manufacturing processes, like bending, create residual stresses in the product and those can be very disadvantageous for fatigue durability. Residual stresses that are generated during the manufacturing of products can cause distortions, dimensional errors or can even break the products. The research material was ultra-high-strength steel (UHSS) with a yield strength of 1100 MPa. Specimens with a 90 degree bent angle were made by air bending using a press brake. Air bending causes variable residual stress patterns in the cross section of the material. The residual stresses of the formed area were determined by removing material and measuring strains caused by the release of stresses. A slot with the width of 1 mm has been manufactured parallel to the edge, both on the outer and on the inner side of the bend. True residual stress distribution can be calculated from the measured strains. A pumped 1064 nm Nd:YVO 4 ablation laser, whose pulse length is 90 ns, was used for the removal of material. This process creates a negligible heat affected zone (HAZ) and laser ablation doesn't increase stresses in the specimen. The results were compared with those obtained when slots were produced by milling and wire-EDM, as well as with the stress values measured by X-ray diffraction. © (2011) Trans Tech Publications.
LFT Import::2019-07-29 (1654)
Keywords: Bending; Laser ablation; Residual stress

Microstructural evolution and geometrical properties of TiB2 metal matrix composite protrusions on hot work tool steel surfaces manufactured by laser implantation - Spranger, Felix; de Oliveira Lopes, Marcelo; Schirdewahn, Stephan; Degner, Julia; Merklein, Marion; Hilgenberg, Kai (International Journal of Advanced Manufacturing Technology, 2019)
The laser implantation–named technique aims to address the tribological problems frequently seen on tool surfaces during hot stamping. It is based on the creation of elevated dome- or ring-shaped hard structures on the surface of tool steels by a localized dispersing of hard particles. Therefore, a combination of the two distinct approaches that are normally used in surface technology for optimizing friction and wear, i.e., surface texturing and surface material optimization, are realized in one processing step. In experimental studies, a localized dispersing of TiB2 particles in the surface layer of the hot work tool steel X38CrMoV5-3 was considered and compared with punctual laser–remelted textures. The structures (micro-) hardness was measured at top- and cross-sections. With the aid of a scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction the interaction between the hard particles and the substrate material were studied. From the results, an optimal parameter range was identified for laser implantation. To the investigation’s end, the implant geometry was measured by optical microscopy and white light microscopy. Furthermore, a mathematic model was introduced, which allows a prediction of the implant geometry as a response to the laser parameters. It was shown that the implantation of TiB2 particles leads to a significant hardness increase up to 1600 HV1 due to the dispersion of initial particles and an in situ precipitation of new titanium-rich phases. It was possible to create defect-free dome- and ring-shaped microstructures on the surfaces. It was also shown that the implants geometry highly depends on the applied laser parameters. The applied central composite design shows a good agreement with the experimental results.
CRIS-Team Scopus Importer:2019-12-03
Keywords: Hot stamping; Hot work tool steel; Laser implantation; Localized laser dispersing; Surface texturing; TiB2

Microstructural Investigations of Aluminium Tailored Heat Treated Blanks - Geiger, Manfred; Merklein, Marion; Kerausch, Michael (Production Engineering. Annals of the German Academic Society for Production Engineering WGP, 2004)
LFT Import::2019-08-05 (1094)

Microstructured surfaces in highly loaded EHD-contacts - manufacturing and tribological performance - Schrader, Tobias; Weschta, Martin; Engel, Ulf; Tremmel, Stephan; Merklein, Marion; Wartzack, Sandro (Proc. 10th International Conference THE "A" Coatings in Manufacturing Engineering, 2013)
In low loaded sliding contacts, as journal bearings or piston contacts, defined microstructures on surfaces were identified for friction reduction purposes and are well established in industrial applications. It is stated that microstructures act as lubricant reservoirs and support lubricant film development. Within the scope of these investigations microstructures are specifically adapted for the tribological load collective of cam follower systems as a representative of highly loaded contacts. For those contacts, the effects of microstructures are still subject of investigations. In this paper a method for efficient microstructuring by micro laser ablation is described. The investigations focus on the determination of the geometric and mechanical properties of the microstructures as well as on the tribological behavior of the microstructured surfaces by two tribological tests.
UnivIS-Import:2015-04-16:Pub.2013.tech.FT.FT-KLMEFK.micros_0

Microstructured surfaces in highly loaded elastohydrodynamic (EHD)-contacts - manufacturing and tribological performance - Schrader, Tobias; Weschta, Martin; Engel, Ulf; Tremmel, Stephan; Merklein, Marion; Wartzack, Sandro (Materialwissenschaft und Werkstofftechnik, 2013)
In low loaded sliding contacts, as journal bearings or piston contacts, defined microstructures on surfaces were identified for friction reduction purposes and are well established in industrial applications. It is stated that microstructures act as lubricant reservoirs and support lubricant film development. Within the scope of these investigations microstructures are specifically adapted for the tribological load collective of cam follower systems as a representative of highly loaded contacts. For those contacts, the effects of microstructures are still subject of investigations. In this paper a method for efficient microstructuring by micro laser ablation is described. The investigations focus on the determination of the geometric and mechanical properties of the microstructures as well as on the tribological behavior of the microstructured surfaces by two tribological tests.
UnivIS-Import:2015-03-09:Pub.2013.tech.FT.FT-KLMEFK.micros_6
Keywords: EHD-Kontakt; Mikrolaserablation; Mikrostrukturen; Reibversuche; Tribologie

Mikrostrukturierung von Tassenstößeln zur Reibungsreduzierung im Ventiltrieb – Herstellung, Simulation und tribologische Charakterisierung - Weschta, Martin; Schrader, Tobias; Tremmel, Stephan; Merklein, Marion; Wartzack, Sandro; Engel, Ulf (Tribologie und Schmierungstechnik, 2014)
Im Rahmen der in einem Verbundprojekt durchgeführten Untersuchungen wurden Mikrostrukturen mit dem Ziel der Reibungsreduzierung speziell an das tribologische System eines Nocken/Stößel-Kontaktes, als Beispiel für hochbelastete Wälz-Gleit-Kontakte, angepasst. Für diese Art von Reibkontakten sind die Effekte von Mikrostrukturen noch nicht abschließend geklärt. Zur Erlangung disziplinübergreifender Erkenntnisse wurden Mikrostrukturformen durch numerische Simulationen ausgelegt sowie die Genauigkeit der Fertigung und das tribologische Verhalten der mikrostrukturierten Komponenten untersucht. Für die Herstellung der Mikrostrukturen wurde aufgrund der Perspektive für die Großserienanwendung auf den Prozess des Mikroprägens fokussiert, der der Mikrolaserablation hinsichtlich seiner Genauigkeit gegenübergestellt wurde. Für die mikrostrukturierten Ventiltassenoberflächen wurde im Prüfstand eine signifikante Reibungsreduzierung gegenüber polierten Oberflächen erreicht.
LFT Import::2019-07-29 (1977)

Mikrostrukturierung von Tassenstößeln zur Reibungsreduzierung im Ventiltrieb - Herstellung, Simulation und tribologische Charakterisierung - Weschta, Martin; Schrader, Tobias; Tremmel, Stephan; Merklein, Marion; Wartzack, Sandro; Engel, Ulf (54. Tribologie-Fachtagung. Reibung, Schmierung und Verschleiß. Band II, 2013)
Im Rahmen der in einem Verbundprojekt durchgeführten Untersuchungen wurden Mikrostrukturen mit dem Ziel der Reibungsreduzierung speziell an das tribologische System eines Nocken-Stößel-Kontaktes, als Beispiel für hochbelastete Wälz-Gleit-Kontakte, angepasst. Für diese Art von Reibkontakten sind die Effekte von Mikrostrukturen noch nicht abschließend geklärt. Zur Erlangung disziplinübergreifender Erkenntnisse wurden Mikrostrukturformen durch numerische Simulationen ausgelegt sowie die Genauigkeit der Fertigung und das tribologische Verhalten der mikrostrukturierten Komponenten untersucht. Die tribologische Wirkung der Mikrostrukturen wurde in einem zweidimensionalen elastohydrodynamischen Simulationsmodell bestimmt. Für die Herstellung der Mikrostrukturen wurde aufgrund der Perspektive zur Großserienanwendung auf den Prozess des Mikroprägens fokussiert, der der Mikrolaserablation hinsichtlich seiner Genauigkeit gegenübergestellt wurde. Für die mikrostrukturierten Ventiltassenoberflächen wurde im Prüfstand eine signifikante Reibungsreduzierung gegenüber polierten Oberflächen erreicht.
UnivIS-Import:2015-04-16:Pub.2013.tech.FT.FT-KLMEFK.mikros

Modeling Laser Heating for Roller Hemming Applications - Kleeh, Tobias; Merklein, Marion; Roll, Karl (Key Engineering Materials, 2011)
LFT Import::2019-07-29 (1694)
Keywords: FEM; Heat treatment; Roller hemming

Modeling material behavior of AA5083 aluminum alloy sheet using biaxial tensile tests and its application in numerical simulation of deep drawing - Prakash, Ved; Kumar, D. Ravi; Horn, Alexander; Hagenah, Hinnerk; Merklein, Marion (International Journal of Advanced Manufacturing Technology, 2020)
Improvement in accuracy of the predicted results from numerical simulation results into a reduction of cost and time involved in tool design and experimental trials. However, the predicted results from finite element simulations are significantly affected by the chosen yield criterion and work hardening law. The selection of yield criterion and work hardening law depends on the characterization methods used for defining the material behavior. In this work, the mechanical behavior of AA5083-O aluminum alloy sheet is modeled by performing biaxial tensile tests using cruciform specimen and hydraulic bulging experiments in addition to uniaxial tensile tests. Biaxial to uniaxial yield stress ratios are determined using the equal plastic work principle from the flow curves obtained from these tests. The obtained ratios are used to find the coefficients of Yld2000-2d and Hill48 yield criteria which is then used in the numerical simulations of cylindrical cup deep drawing. Numerical simulations are also carried out using uniaxial and biaxial flow curves fitted with different isotropic hardening laws. Thickness distributions and the load-displacement curves are predicted and validated by performing cylindrical cup deep drawing experiments.
CRIS-Team Scopus Importer:2019-12-17
Keywords: Aluminum alloy; Cruciform specimen; Deep drawing; Finite element simulation; Hardening laws; Hydraulic bulge test; Yield criteria

Modeling of the Behavior of a Cold Forging Process Considering the Deflection of Tooling System and Press - Kroiss, Thomas; Engel, Ulf; Merklein, Marion (Proc. 2nd Int. Conf. on Process Machine Interactions (PMI), 2010)
LFT Import::2019-08-05 (500)

Modeling of the Plastic Characteristics of AA6082 for the Friction Stir Welding Process - Pellegrino, Sergio; Fratini, Livan; Merklein, Marion; Böhm, Wolfgang; Hung Nguyen, (Key Engineering Materials, 2015)
Focus of this paper is to model the plastic forming behavior of AA6082, in order to develop the numerical FE analysis of the friction stir welding processes and the simulation of subsequent forming processes. During the friction stir welding process, the temperatures reached can range up to 500 °C and have a fundamental role for the correct performance of the process, so the material data has to show a temperature dependency. Because of the tool rotation a strain rate sensitivity of the material has to be respected as well. In this context, the general material characteristics of AA6082 were first identified for different stress states. For the uniaxial state the standard PuD-Al used in the automotive industry was applied, for the shear state the ASTM B831-05 was used and for biaxial states the ISO 16842 was exploited. To characterize the plastic flow behavior of the AA6082 at elevated temperatures, tensile tests were performed according to DIN EN ISO 6892-2 from 25 °C to 500 °C with a strain rate from 0.1 s-1 up to 6.5 s-1.
EAM Import::2019-03-12

Modellierung des Verfestigungsverhaltens von Blechwerkstoffen - Merklein, Marion; Biasutti, Manfredi; Lupino, Roberto; Kuppert, Andreas (13. Workshop - Simulation in der Umformtechnik (19.03.2010), 2010)
LFT Import::2019-08-05 (201)

Modellierung und Simulation der Warmblechumformung: Aktueller Stand und zukünftiger Forschungsbedarf - Brosius, A.; Karbasian, H.; Tekkaya, A.E.; Lechler, Jürgen; Merklein, Marion; Geiger, Manfred; Springer, R.; Schaper, M.; Bach, F.W.; Hoffmann, H. (Tagungsband 2. Erlanger Workshop Warmblechumformung, 2007)
LFT Import::2019-08-05 (1499)

Modelling Aspects in Accumulative Roll Bonding Process by Explicit Finite Element Analysis - Fratini, Livan; Merklein, Marion; Böhm, Wolfgang; Campanella, Davide (Key Engineering Materials, 2013)
Accumulative Roll-Bonding (ARB) process is a severe plastic deformation (SPD) process, capable of developing grains below 1 extgreekmm in diameter and improving mechanical properties of the material. In this study, the authors compared two different FE-codes with respect of its applicability for numerical analysis of the ARB process. Modelling this process was achieved using the explicit code for Abaqus/CAE both in 2D and 3D. The proposed model was used to assess the impact of ARB cycles on the final material properties. The numerical results in 2D and 3D were compared and contrasted. The research work presented in this paper is focused on the simulation optimization based on CPU time minimization. The numerical simulations were also validated through a comparison with the experimental results.
EAM Import::2019-03-12

Modelling, Construction and Manufacture of a Lightweight Robot Arm - Hagenah, Hinnerk; Böhm, Wolfgang; Breitsprecher, Thilo; Merklein, Marion; Wartzack, Sandro (Proceedings of the 8th CIRP International Conference on Intelligent Computation in Manufacturing Engineering, 2012)
This contribution will show how modern materials as cellular titanium and nanocrystalline aluminium can be used to build advanced lightweight robot arms. Cellular titanium allowing a specific density distribution and the manufacture of fine structures with desirable properties is produced by selective electron beam melting while the nanocrystalline aluminium results from accumulative roll bonding. The specific properties of both materials will be highlighted. The paper will cover the definition of the product specification, the setting of a basic design and the optimisation of this by means of topology optimisation. This optimisation requires an intelligent modelling to be able to investigate different initial settings and boundary conditions. The optimised part will then be finished with regards to manufacturability. The paper will close with a brief report about the actual manufacture of one of the investigated variants.
UnivIS-Import:2015-04-16:Pub.2012.tech.FT.FT-KLMEFK.modell

Modelling kinetics of phase transformation for the indirect hot stamping process - Hippchen, Paul; Merklein, Marion; Lipp, Arnulf; Fleischer, Michael; Grass, Hannes; Philipp, Craighero (Key Engineering Materials, 2013)
To configure the indirect hot stamping process, a finite-element-based prediction of the part's geometry and mechanical properties is required. In case of indirect hot stamping, inhomogeneous cooling schedules cause different phase transformation points and products. The volume expansion caused by phase transformation of fcc into bcc leads to transformation induced stresses that are important for the calculation of overall stresses in press hardened components. To calculate theses stresses correctly, it is necessary to study the kinetics of phase transformation in consideration of the cooling path of an indirect hot stamping process. Dilatometer tests are employed to obtain the kinetics of phase transformation is determined in dilatometer tests. These results are used to identify the parameters for the phase transformation models implemented in the material model *MAT-244 [1] that is implemented in the finite-element-code LS-DYNA [2]. In this context the material model parameters are identified by using evolutionary optimization strategies. Based on the identified parameters the predictive quality of the implemented phase transformation models will be studied in order to improve their prediction accuracy for the indirect hot stamping process. © (2013) Trans Tech Publications.
LFT Import::2019-07-29 (2072)
Keywords: Hot stamping; Kinetics of phase transformation; LS-DYNA; Simulation

Modelling kinetics of phase transformation for the indirect hot stamping process to focus on car body parts with tailored properties - Hippchen, Paul; Lipp, Arnulf; Grass, Hannes; Craighero, Philipp; Fleischer, Michael; Merklein, Marion (Journal of Materials Processing Technology, 2015)
LFT Import::2019-07-29 (2071)

Modelling of Hybrid Parts Made of Ti-6Al-4V Sheets and Additive Manufactured Structures - Hafenecker, Jan; Papke, Thomas; Huber, Florian; Schmidt, Michael; Merklein, Marion (Proceedings of the 10th Congress of the German Academic Association for Production Technology (WGP), 2020)
Keywords: Additive Manufacturing; Forming; Titanium.

Modification of Tribological Conditions for Influencing the Material Flow in Bulk Forming of Microparts from Sheet Metal - Kraus, Martin; Andreas, Kolja; Stellin, Tommaso; Engel, Ulf; Merklein, Marion (AIP Conference Proceedings 1896, 2017)
LFT Import::2019-08-05 (2269)

Nachhaltige Blechumformung durch Trockentiefziehen - Krachenfels, Kim; Tenner, Jennifer; Merklein, Marion (wt Werkstattstechnik - Online, 2018)
Werkstattstechnik online 108 (2018), S. 652-656
LFT Import::2019-07-29 (2328)

Nachhaltige Umformtechnik - Merklein, Marion (VDI-Z Integrierte Produktion, 2023)
CRIS-Team Scopus Importer:2023-03-24

Neue Entwicklungen bei IHU von Blechen und deren Einsatzpotenziale für Leichtbauteile - Geiger, Manfred; Merklein, Marion; Celeghini, Martino; Novotny, Stefan; Vahl, Meik (Innenhochdruck-Umformen für Karosseriekomponenten, 2002)
LFT Import::2019-07-16 (1706)

Neuere Entwicklungen zur Umformung höchstfester Stahlwerkstoffe - Merklein, Marion; Pitz, Matthias; Hoff, Cornelia; Lechler, Jürgen (Multifunktionale Bauteile und Verfahren zur Erhöhung der Wertschöpfung in der Blechbearbeitung, 2005)
LFT Import::2019-07-16 (1178)

New approaches to determine the bending contour of the 3-roll-push-bending process - Vatter, Peter; Plettke, Raoul; Merklein, Marion (7th Int. Conf. on Design and Production of Machines and Dies/Molds, 2013)
LFT Import::2019-08-05 (1880)

New Approach on the Allocation of Wear Allowances - a Case Study - Schubert, Dominik; Rohrmoser, Andreas; Hertle, Sebastian; Wartzack, Sandro; Hagenah, Hinnerk; Merklein, Marion; Drummer, Dietmar (22nd International Conference on Engineering Design (ICED19), 2019)

New developments and perspectives of forming technology at the LFT - Geiger, Manfred; Merklein, Marion; Celeghini, Martino; Eckstein, Ralf; Novotny, Stefan (Proceedings of the 10th International Conference on Sheet Metal, SheMet 2003, 14.-16.04., Jordanstown, 2003)
LFT Import::2019-08-05 (957)

New process strategies to manufacture tailored blanks out of DP600 by orbital forming - Hildenbrand, Philipp; Schulte, Robert Karl; Merklein, Marion (Applied Mechanics and Materials, 2015)
LFT Import::2019-07-29 (2115)

New Time Dependent Method for Determination of Forming Limit Curves Applied to SZBS800 - Merklein, Marion; Kuppert, Andreas; Mütze, S.; Geffert, A. (Proc. 50th Conference of IDDRG 2010, 2010)
LFT Import::2019-08-05 (298)

New Tribological Aspects of Dry Film Lubricated Aluminium Sheet Metal - Pfestorf, Markus; Meiler, M.; Merklein, Marion; Geiger, Manfred (Proceedings of the 4th International Conference THE coatings in Manufacturing Engineering, 2004)
LFT Import::2019-08-05 (1096)

Novel concept of experimental setup for characterisation of plastic yielding of sheet metal at elevated temperatures - Geiger, Manfred; van der Heyd, Gerhard; Merklein, Marion; Hußnätter, Wolfgang (Advanced Materials Research, 2005)
In times of highest significance of process modelling and numerical simulation characterisation of material properties is of special importance for tools' and components' dimensioning. But in general material properties depend on many different influencing variables, e.g. temperature, humidity and many others. Especially in fields of sheet metal forming the mechanical behaviour of components highly differs according to real stress condition. In particular yield loci combine the information of beginning of yielding with a biaxial stress condition, but nevertheless for many materials they have not been determined yet. For all others the existing values are available only at room temperature. In this paper a novel concept of the experimental setup is shown, with which plastic yielding of sheet metal can be examined also at elevated temperatures. In usual biaxial tension tests cruciform specimen are drawn in plane. The new machine-concept, which is presented in this paper, is based on a punch-load moving perpendicular to the sheet. By clamping the specimen restoring forces are induced, which cause in dependence of special developed tool and work piece geometries defined stress conditions. Using an optical measurement system for determination of strains with CCDcameras of very high frame rate allows exact identification of starting plastification by offline analysis. Experiments at elevated temperatures are realised by local heating with a diode laser and a special optical system to reach a homogenous distribution of temperatures in the forming zone. On the one hand these investigations are necessary for many materials to achieve further information on characteristic properties in warm forming, because their data are only known at room temperature. On the other hand some materials, e.g. magnesium wrought alloys, are mostly formed at elevated temperatures (here in the range of 200°C to 250°C), because of its significant higher formability. Thus, material behaviour must be characterised at these temperatures.
LFT Import::2019-07-16 (1135)
Keywords: Material characterisation; Sheet metal forming; System technology

Novel setup for the investigation of tribological behavior of sheet metal surfaces - Merklein, Marion; Engel, Ulf; Vierzigmann, Ulrich (International Journal of Material Forming, 2009)
In sheet metal forming processes tribological conditions have a significant influence on the quality of the produced part, the tool life time as well as the process stability. Due to the contact pressures in the workpiece-tool interface, mixed lubrication is predominant. Thus, the appearing real contact area has a major influence on the frictional conditions. During the forming process the real contact area increases, because of the flattening of topography asperities. For the investigation of flattening behaviour and the so connected changes in friction a new modular test rig for strip drawing tests has been developed. To gain additional information about the contact behaviour of texturized sheet metal surfaces during the tests, it is possible to alternate between two different measurement setups to investigate changes in the workpiece-tool interface in-situ. In the first setup, an ultrasonic inspection system is used while the second setup is based on optical techniques. In this paper the two measurement setups and the planned investigations are described. © Springer/ESAFORM 2009.
LFT Import::2019-07-29 (287)
Keywords: Flattening behaviour; In-situ investigation; Real contact area

Numerical and Experimental evaluation of thermal dependent flc - Hora, P.; Merklein, Marion; Tong, L.; Lechler, Jürgen (Tagungsband IDDRG Conference 2007, Györ, Ungarn, 2007)
LFT Import::2019-08-05 (1458)

Numerical and experimental investigation of a backward extrusion process for forming geared components from coil - Leicht, Miriam; Henneberg, Johannes; Merklein, Marion (Materials Research Proceeding, 2023)
Stricter political regulations, increasing ecological awareness of society as well as the pursuit for higher performance of components motivate lightweight construction. Functional integration is one way to realize lightweight design, resulting in increased demands on component geometry. Sheet-bulk metal forming (SBMF) offers the potential to enable an economic and ecological production of functional components through short process chains. SBMF from coil also provides additional advantages regarding high output quantity and short cycle times. However, the industrially application of SBMF from coil is limited due to high tool load and coil-specific challenges like an anisotropic material flow, which negatively affects the part accuracy. In this study, a backward extrusion process from coil for forming functional components with gearing is investigated. Therefore, a numerical process model was built and validated based on experimental results. In order to generate a profound process understanding, a combined numerical-experimental approach was chosen for a fundamental process analysis. The influence of the semi-finished product geometry was investigated by forming rotationally symmetric, pre-cut blanks and coil material. The application of the different sheet geometries was compared based on component- and process-side target quantities. The results indicate an anisotropic material flow as a coil-specific challenge, which leads to a direction-dependent component formin

Numerical and experimental investigation of dry deep drawing of aluminum alloys with conventional and coated tool surfaces - Tenner, Jennifer; Andreas, Kolja; Radius, Adrian; Merklein, Marion (International Conference on the Technology of Plasticity (ICTP), 2017)
LFT Import::2019-08-05 (2245)
Keywords: deep drawing; DLC coatings; dry forming; tribology

Numerical and experimental investigations for distortion-reduced laser heat treatment of aluminum - Rigas, Nikolaos; Merklein, Marion (Production Engineering, 2021)
In the field of mobility, increased safety and emission requirements lead to steadily rising demands on materials used and their performance. Over the last decades, 5000 and 6000 series aluminum alloys have become more and more attractive as lightweight material due to their beneficial weight to strength ratio. The 7000 series offers extended lightweight potential due to its high strength. Until now, this class of alloys has not been widely used in mass production due to its limited corrosion resistance and poor forming behavior. By using so-called Tailor Heat Treated Blanks, it is possible to set increased forming limits of previously locally heat treated components. The reason for the enhanced formability is the local softening, with the resulting improved material flow and the reduced critical forming stresses of the sheet metal before the forming operation. Despite these advantages, the use of previously heat treated materials has been very limited so far. For example, the distortion that occurs during local heat treatment reduces geometrical accuracy and thus automated handling. Therefore, the focus of this thesis is the investigation of tailored heat treatment strategies, permitting a distortion-reduced local short-term heat treatment. For this purpose, the distortion behavior is represented and quantified both numerically and experimentally. The generated knowledge is then transferred to a large volume component and characterized.
CRIS-Team Scopus Importer:2021-03-26
Keywords: AA7075; Distortion; Mechanical properties; Simulation; Tailor Heat Treated Blanks

Numerical and experimental investigations on the mechanical properties of milled specimens from an AA7020 tube - Reblitz, Jonas; Reuther, Franz; Trân, Ricardo; Kräusel, Verena; Merklein, Marion (Achievements and Trends in Material Forming, 2022)
The reduction of weight is crucial in the automotive sector to reach a lower energy consumption and an increased range, especially for electrically powered vehicles. In this regard, body-in-white parts offer a high potential for the application of lightweight construction. The required weight savings can be achieved by implementing parts with a high strength-to-weight ratio. A promising approach is the combination of lightweight materials and lightweight design, which can be realized by tubular components made of high strength aluminum. Due to their structural stiffness and high crashworthiness, those structures are often used as safety-relevant car body components. However, the material characterization of tube profiles is a major challenge, which in turn impedes an accurate numerical simulation and precise process design. In contrast to flat semi-finished parts, various effects of the production process and the geometry, regarding the stress state under load, must be taken into account. For this purpose, adapted testing methods considering the geometrical and mechanical properties of the tubular parts have to be investigated, in order to generate an accurate material model and process design. Within this research work, tubular components made out of AA7020 in W-temper condition were used to analyze the mechanical properties. In this regard, several tensile specimens are milled from a tube, so they also have a curvature profile. The experimental tensile tests have been performed at different strain rates by using a universal testing machine from type Gleeble 3500. To ensure a proper measurement of the mechanical properties, the clamping jaws of the testing machine are adjusted to the curved samples. The investigated material parameters are subsequently transferred to an FE model with curved specimen to enable an accurate prediction of the forming behavior. In addition, an FE model of a flat tensile specimen was also created for comparison, in order to gain a profound knowledge regarding the influence of the geometric and mechanical properties of tubular components. <
Keywords: Material characterization; W-temper condition; tensile test; tubes

Numerical Investigation for Superplastic Forming Tool Development Within the Combined Process Chain of Forming and Additive Manufacturing - Schaub, Adam; Degner, Julia; Ahuja, B.; Schmidt, M.; Merklein, Marion (Int. Conf. Competitive Manufacturing, 2016)
Key motivation behind the combination of superplastic forming and additive manufacturing is to merge the advantages of two different manufacturing methods. On the one hand the efficiency to form large scaled parts by superplastic forming and on the other hand additive manufacturing of highly customised products. While the combination of additive manufacturing with bulk structures is state of the art, combining sheet metal parts with additive functional elements is hardly investigated. Few research works have been published regarding additively manufactured functional elements on deep drawn sheet parts. As forming is limited for Ti-6Al-4V at room temperature and even at moderate temperatures, this paper presents a new and innovative manufacturing process chain, where superplastic forming and additive manufacturing is combined to merge the advantages of both. Within this work the possibilities of additive manufacturing on sheet metal is presented in addition to the numerical simulation of superplastic forming of Ti-6Al-4V to produce a semi-finished sheet part for subsequent additive manufacturing process. As a result of this study a LS-DYNA based numerical model is presented for tool development as well as process simulation for superplastic forming of semi-finished parts which can be utilized for consecutive additive manufacturing operation.<br
LFT Import::2019-08-05 (2154)
Keywords: Superplastic Forming; Additive Manufacturing; Ti-6Al-4V

Numerical investigation of dry and lubricated sheet metal forming processes - Merklein, Marion; Affronti, Emanuela; Steiner, Jennifer (Key Engineering Materials, 2015)
LFT Import::2019-08-05 (2091)
Keywords: Dry forming; Metal forming; Sheet metal

Numerical investigation of small curvature bendability of high strength low alloyed steel in air and die bending processes - Tsoupis, Ioannis; Hildering, Sven; Merklein, Marion (Proc. IDDRG 2013, 2013)
LFT Import::2019-08-05 (1884)

Numerical investigation of temperature and phase development of (deformation-) dilatometer specimens - Lutz, Stefan; Weninger, Johannes; Helldoerfer, Bastian; Merklein, Marion (Material Forming - ESAFORM 2014, 2014)
The Gleeble 3500 thermo-mechanical testing machine with ISO-Q dilatometer set-up allows the creation of time temperature transformation diagrams at high cooling rates, after deformation and under constant load with a simple experimental set-up. An isothermal plane with temperature gradients perpendicular to this plane arises in the sample which is used for dilatometrical evaluation. The homogeneity and size of this isothermal region has a decisive influence on the measurement results, but cannot be measured with sufficient accuracy. To gain an accurate understanding of the processes in the sample, a coupled thermo-electrical, thermo-metallurgical, thermo-mechanical finite element model of the experiments is set up. To map the temperature control circuit of the machine, a PID controller is implemented, which controls the voltage of the conductive sample heating between the simulation steps. By comparing the temperature and hardness distribution with the experiments, it is shown that in this way the temperature distribution and phase transformation can be mapped. By the findings, the experimental setup was adjusted. This led to an improvement of the measurement results. © 2014 Trans Tech Publications, Switzerland.
LFT Import::2019-08-05 (2016)
Keywords: Closed loop control; Heat treatment; Numerical simulation; Quenching dilatometry

Numerical Investigation of the Tool Load in Joining by Forming of Dissimilar Materials Using Shear-Clinching Technology - Wiesenmayer, Sebastian; Müller, Martin; Dornberger, Peter; Han, Daxin; Hörhold, Réjane; Meschut, Gerson; Merklein, Marion (Key Engineering Materials, 2018)
LFT Import::2019-07-29 (2301)
Keywords: Finite element method; Joining; Shear-clinching; Tool

Numerical investigation on the deep drawing of sheet metals with an additively applied coating - März, Raphaela; Hafenecker, Jan; Bartels, Dominic; Schmidt, Michael; Merklein, Marion (Material Forming, 2023)
A promising approach to meet ecological and economical challenges in production industry is the combination of additive manufacturing and forming, which enables the production of hybrid parts. The fusion of the two technologies has the potential to use the benefits of both process classes. One example for the combination of additive manufacturing and forming is a process chain consisting of laser-based directed energy deposition (DED-LB/M) to apply a wear resistant coating on a sheet metal and a subsequent deep drawing process to achieve the final geometry of the component. However, the presence of the local reinforcement influences the subsequent sheet metal forming process. In order to gain more knowledge about the process chain a numerical approach is performed. In this work, the influence of a coating using Bainidur® AM applied by DED-LB/M on the formability of the case hardening steel 16MnCr5 in a deep drawing process is evaluated. For this purpose, a numerical model is built and validated by comparison with experimental results. The finite-element-model serves as the basis for the investigation on the influence of the location of the additively applied coating on the deep drawing process and also enables a deeper understanding of the proces
Keywords: Additive Manufacturing; Forming; Hybrid Parts

Numerical investigations on the influence of process parameters on the forming of gears in forward extrusion - Merklein, Marion; Kiener, Christoph; Zimmermann, Andrea (Applied Mechanics and Materials, 2015)
LFT Import::2019-07-29 (2128)

Numerical modelling approach for the temperature dependent forming behaviour of Ti-6Al-4V - Papke, Thomas; Graser, Matthias; Merklein, Marion (Proceedings of the 5th International Conference on New Forming Technology, MATEC Web of Conferences, 2018)
Titanium alloys offer several beneficial characteristics, such as high specific strength, metallurgical stability at elevated temperature, biocompatibility and corrosion resistance. With regard to these superior properties, Ti-6Al-4V is a commonly used titanium alloy for aerospace components and medical products. The production of parts made of Ti-6Al-4V can be done in various ways. One approach is forming at elevated temperature, which requires a focused design of parts, processes and numerical modelling of the forming process. Essential input parameters for the numerical models are temperature dependent material parameters. Since, the yield stress and Young's modulus of the material decrease significantly at elevated temperature, the forming limits are enhanced. For the characterization of the forming behaviour, uniaxial tensile tests at temperatures from 250 °C to 400 °C have been conducted. The samples are heated by conduction in a thermal-mechanical simulator for the tensile test. However, the resulting inhomogeneous temperature distribution along the longitudinal axis of the specimen is a challenge in order to measure proper material properties. Inhomogeneous temperature distribution leads to varying mechanical properties and temperature dependent forming behaviour. To overcome this issue, simple numerical models based on experimental data are necessary, which allow the estimation of the influence of the inhomogeneous temperature distribution. In this paper, therefore, the temperature distribution and the subsequent tensile test are investigated using electrical-thermal and mechanical numerical simulations of the tensile test at elevated temperature. With the combined approach of experimental tests and numerical simulations, the forming behaviour of Ti-6Al-4V can be modelled.
LFT Import::2019-08-05 (2305)
Keywords: Modelling; Thermal effects; Titanium

Numerical modelling of the process chain for aluminium Tailored Heat-Treated Profiles - Fröck, Hannes; Graser, Matthias; Reich, Michael; Lechner, Michael; Merklein, Marion; Kessler, Olaf (Advanced Modeling and Simulation in Engineering Sciences, 2023)
Lightweight construction in modern car design leads to an increased usage of various aluminium semi-finished products. Besides sheet material, aluminium extrusion profiles are frequently used due to their high stiffness and variety of possible cross-sections. However, similar to sheet material, aluminium profiles exhibit limited formability in comparison to mild steel materials. One possibility to increase the forming limits of precipitation hardened aluminium alloys is the so-called Tailored Heat Treatment technology. By a local short-term heat treatment, the material is softened and the material flow can be controlled to reduce stresses in critical forming zones. The purposeful definition of the heat treatment zones is mandatory to improve the forming results. Therefore, numerical methods are necessary. In this investigation, a numerical process chain is presented. It combines the thermo-mechanical simulation of a local laser heat treatment with a subsequent bending process of the heat-treated profile using the alloy EN AW-6082. The temperature distribution, mechanical properties, and finally, the bending result of the numerical model are validated by experimental tests.
CRIS-Team Scopus Importer:2023-06-30
Keywords: Aluminium alloy; Anisotropy; Bending simulation; EN AW-6082; LS-Dyna; Material model; Process chain simulation; Tailored Heat-Treated Profiles

Numerical Model of Tube Freeform Bending by Three-Roll-Push-Bending - Hagenah, Hinnerk; Vipavc, Daniel; Plettke, Raoul; Merklein, Marion (2nd International Conference on Engineering Optimization, 2010)
LFT Import::2019-08-05 (508)

Numerical optimisation of a shear specimen geometry according to ASTM - Merklein, Marion; Hofmann, Maren; Biasutti, Manfredi; Lechner, Michael (Key Engineering Materials, 2013)
Complex material models used for the numerical representation of forming processes need in addition to tension and compression tests also shear tests to completely analyse the behaviour of the material under different loading conditions. There are two concepts of shear test - one uses symmetrical specimens with two shear zones (according to Miyauchi) the other one specimens with a single shear zone. In both cases, a homogeneous distribution of the strain in the shear zone is essential for the validity of the shear test. Therefore, the length and width of the shear zone in a single shear specimen made from high strength steel according to the ASTM standard geometry were varied. Analysing the resulting strain distribution numerically an optimised sample geometry with a more uniform strain distribution than the ASTM standard was achieved. The numerical results were also validated with experimental shear tests. © (2013) Trans Tech Publications.
LFT Import::2019-07-29 (1857)
Keywords: ASTM specimen geometry; Numerical optimisation; Simple shear test

Numerical Prediction of Failure within Small Curvature Bending of Advanced High Strength Steels - Tsoupis, Ioannis; Merklein, Marion (Key Engineering Materials, 2015)
Within this paper a numerical study of the Continuum Damage Mechanics based damage model Lemaitre in commercial software LS-DYNA is performed in order to correctly predict failure in terms of crack occurrence within small curvature bending of AHSS steels. A strain based calibration method is used for the effective adaption of the Lemaitre model to the bending operation, which is based on the comparison and adaption of the numerically calculated and the experimentally measured deformation field on the outer surface of the bent specimen. Within this method the material dependent damage parameter S is systematically varied in the simulation in order to represent maximum major strain. The new method is proved by numerical simulation of experiments provoking crack initiation using smaller bending radii. It can be shown that failure in terms of crack initiation can be correctly predicted by the model with the damage parameters, which were determined by the method of strain based calibration and an additional optimisation of the parameter Dc. Thus, within this study a user friendly and effective way for the application of Lemaitre damage model to small curvature bending processes of AHSS steels is developed.
LFT Import::2019-07-29 (2076)
Keywords: Bending; Damage; Simulation

Numerical process design of hot stamping processes based on verified thermo mechanical characteristics - Karbasian, H.; Brosius, A.; Tekkaya, A. E.; Lechler, Jürgen; Merklein, Marion (Technology Conference MS&T’08, 2008)
This paper presents a Finite Element Simulation of hot stamping processes by means of experimentally calculated material and process data for the process design. The quality and the significance of the simulation results are strongly dependent on the accuracy of the thermal and mechanical parameters used in FE models. Therefore, the process and material parameters used in the FE model in this investigation were optimized with a statistical method and by means of an experimental analysis. The identification of interaction between the thermal and mechanical parameters was based on design of experiments. This statistical method ensured an efficient analysis of the process parameters consisting of heat transfer coefficients as well as thermal and mechanical characteristics of material. Insights from design of experiments need to be applied in order to enable an efficient FE modeling of hot stamping for process optimization and process design. © 2008 MS&T'O8®.
LFT Import::2019-08-05 (1549)
Keywords: FEM; Hot stamping; Material properties 22MnB5; Process design

Numerical simulation of hydraulic bulging using uniaxial and biaxial flow curves and different yield criteria - Prakash, Ved; Kumar, D. Ravi; Merklein, Marion; Hagenah, Hinnerk (IOP Conference Series: Materials Science and Engineering, 2019)
In sheet metal forming industry, finite element analysis has become a necessary step before actual production of the parts. It helps in the improvement of part quality as well reduces the effort applied in experimental trials. However, the success of finite element simulation mainly depends on the constitutive model used for defining the plastic deformation behaviour of the sheet material. Material characterization in biaxial stress state helps in selecting advanced constitutive models in numerical simulations. In this work, aluminium alloy AA5083 sheet material is characterized in uniaxial and biaxial tension conditions. Hydraulic bulge tests are performed to obtain the flow curves and material properties which are then used to find the coefficients in different yield criteria. These coefficients and the flow curves, fitted using different work hardening laws, are used in finite element simulation of the hydraulic bulge test and the results are validated by experiments.
CRIS-Team Scopus Importer:2020-02-21

Numerical Simulation of Hydroforming at Elevated Temperatures with Granular Material Used as Medium Compared to the Real Part Geometry - Grüner, Martin; Merklein, Marion (International Journal of Material Forming, 2010)
LFT Import::2019-07-29 (299)

Numerical simulation of sheet metal forming of an Al-Mg alloy incorporating plane strain properties in the yield criterion - Prakash, Ved; Digavalli, Ravi Kumar; Lenzen, Matthias; Hagenah, Hinnerk; Merklein, Marion (Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2022)
In this work, numerical simulation of AA5083-O aluminum alloy sheets is carried out using Yld2000-2d yield criterion to predict thinning and variation of load with displacement in sheet metal forming. It has been found that the accuracy of predictions in numerical simulation depends on the coefficients and the stress exponent used in the yield criterion. Hydraulic bulge tests with circular and elliptical die cavities are performed to characterize the material in equi-biaxial and plane strain conditions. An improved stress exponent is determined by incorporating the material properties obtained in plane strain in the existing criterion. The improved stress exponent is validated by using it in the numerical simulations of cylindrical cup deep drawing and stretch forming at room temperature. The same exponent is also used in the numerical simulations carried out for the case of experiments conducted at 250 degrees C. The predicted thinning and load-displacement variations from the numerical simulations are validated with the experimental measurements. A considerable improvement in the results predicted using the improved stress exponent is observed at both the temperatures.
CRIS-Team WoS Importer:2022-11-25

Numerical simulation of the staking process of clinching fasteners - Weiss, Miriam; Merklein, Marion; Plettke, Raoul (Proceedings SCT2011, 2011)
LFT Import::2019-08-05 (1648)

Numerical simulation to improve robustness in sheet metal forming process chains - Hagenah, Hinnerk; Geiger, Manfred; Merklein, Marion (AIP Conference Proceedings, 2013)
The paper will present developments towards the improvement of the robustness of sheet metal forming process chains. The possibilities and challenges will be demonstrated using two examples. Firstly, the effect of heat treatment to precipitation hardened aluminum sheet metals in order to enlarge the process window for deep drawing operations will be discussed. Numerical simulation can be used to predict the effects of the heat treatment. Using more sophisticated approaches the heat treatment layout and its effects on the forming process can be computed and predicted. Thus the process window can be enlarged and in consequence the process chain will receive an increased robustness. Secondly the integrated tube and sheet hydroforming process that also includes joining operation will be used as an example of the positive impact numerical simulation can have on complex process chains. This highly integrated process chains needs carefully designed tools that ensure robust production. Furthermore, several effects occurring during the forming operations are difficult to understand since the process cannot be stopped at arbitrary moments or easily investigated in situ. The needed understanding and therefor the mandatory input for successful and robust process design has to be derived from advanced numerical models and the according simulation runs. © 2013 AIP Publishing LLC.
LFT Import::2019-07-29 (1899)
Keywords: Robust process chains; sheet hydroforming; tailored heat treatment

Numerical study on local short-term heat treatments for joining by forming of high-strength 7xxx aluminum - Wiesenmayer, Sebastian; März, Raphaela; Merklein, Marion (Production Engineering, 2023)
7xxx aluminum alloys have very high specific strengths, making them interesting for manufacturing car bodies. However, the limited formability of the precipitation hardenable alloys in the artificially aged T6 temper is challenging for forming and joining processes. The pre-conditioning of aluminum sheets by a short-term retrogression is a promising approach to enhance the process limits of joining by forming technologies. In addition, localizing the heat treatment enables the control of the material flow. However, for a targeted material flow, a deeper understanding of the relation between the heat treatment layout and its influence on joining processes is needed, which can be achieved with the aid of numerical analyses. Therefore, within the scope of this work, an approach for the numerical simulation of locally limited heat treatment layouts for the control of the material flow of high-strength aluminum sheets in joining by forming process is shown. The investigations are conducted for the simulation software LS-DYNA and the innovative shear-clinching process. Process models for the local retrogression heat treatment of punch-sided AA7075 T6 and the subsequent shear-clinching as well as an approach to couple the individual models are presented. By performing a localized retrogression from the T6 temper, the radial material displacement of the upper sheet in the shear-clinching process can be reduced in comparison to joining AA7075 in the W temper. The control of the material flow in the joining process thereby causes the improvement of geometric features, which are critical for the joint strength.
CRIS-Team Scopus Importer:2023-05-26
Keywords: Heat treatment; High-strength aluminum; Joining; Numerical simulation; Shear-clinching

Numerische Abbildung des Tailored Tempering Prozess: Wärmeübergang, FE-Simulation und Ableitung des resultierenden Gefüges - Svec, Thomas; Merklein, Marion (14. Workshop - Simulation in der Umformtechnik, 2011)
LFT Import::2019-08-05 (1651)

Numerische Auslegung eines kombinierten Umform- und Abschreckprozesses zur Herstellung hochfester Aluminiumbauteile - Degner, Julia; Merten, M.; Merklein, Marion (Tagungsband zum 13. Erlanger Workshop Warmblechumformung 2018, 2018)
LFT Import::2019-08-05 (2350)

Numerische Untersuchung des Werkstoffflusses beim Fügen artungleicher Werkstoffe mittels Schneidclinchen - Müller, Martin; Hörhold, R.; Meschut, G.; Merklein, Marion (Tagungsband SFU 2016, 2016)
LFT Import::2019-08-05 (2191)

Numerische Untersuchungen der Temperatur- und Phasenentwicklung in (Umform-) Dilatometerproben - Lutz, Stefan; Weninger, J.; Helldörfer, B.; Merklein, Marion (Tagungsband "Simulationsforum Schweißen und Wärmebehandlung 2013", 2014)
LFT Import::2019-08-05 (1978)

Oberflächenanalyse von Tailored Blanks hergestellt durch ein Taumelverfahren - Vogel, Manfred; Merklein, Marion (XXXVII. Verformungskundliches Kolloquium, 2018)
LFT Import::2019-08-05 (2292)

Oberflächenmodifizierung von Presshärtewerkzeugen durch einen drahtbasierten Laserstrahllegierungsprozess - Neubauer, Franziska; Hofmann, K.; Tenner, Jennifer; Andreas, Kolja; Merklein, Marion (11. Erlanger Workshop Warmblechumformung, 2016)
LFT Import::2019-08-05 (2203)

On the evaluation of strength of cold forged components made of high nitrogen steel - Noneder, Johannes; Merklein, Marion; Engel, Ulf (Proceedings of the 3rd International Conference on Steels in Cars and Trucks, 2011)
LFT Import::2019-08-05 (1738)

On The Friction Stir Welding of Titanium Alloys: Experimental Measurements and FEM Model Fine Tuning - Buffa, Gianluca; Fratini, Livan; Gnibl, Tobias; Wieland, Michael; Merklein, Marion (Steel Research International, 2012)
LFT Import::2019-07-29 (1791)
Keywords: FEM model; Friction stir welding; Temperature

On the hot deformation behavior of Ti-6Al-4V made by additive manufacturing - Bambach, Markus; Sizova, Irina; Szyndler, Joanna; Bennett, Jennifer; Hyatt, Greg; Cao, Jian; Papke, Thomas; Merklein, Marion (Journal of Materials Processing Technology, 2021)
Innovative process chains that use additive manufacturing (AM) to produce pre-forms for hot forging have been proposed recently, but almost no scientific knowledge on the hot deformation behavior of AM material exists. The combination of AM and metal forming may allow for producing pre-forms by AM which can be forged to the final shape in a single forming operation, thus saving tooling costs compared to conventional multi-stage forging processes. In this work, Ti-6Al-4 V samples made from powder using Directed Energy Deposition (DED) and Selective Laser Melting (SLM) are investigated under typical hot working conditions. An increasing cooling rate in AM promotes the formation of martensite. When heated to forming temperature, the martensite decomposes and yields intermediate microstructures with improved hot working properties compared to conventional wrought material. Differences in the flow stress and activation energy for hot working are analyzed for conventional and as-built Ti-6Al-4 V. AM material exhibits both lower flow stresses and a faster globularization rate, which is explained by non-equilibrium phase fractions and the spatial arrangement of the β-phase. A model is proposed to predict flow stresses and microstructure evolution in Ti-6Al-4 V specimens with a conventional and AM microstructure, which takes the spatial arrangement into account. The findings can be used to design new process chains that allow for single-stage net-shape forging of Ti-6Al-4 V parts at reduced forming forces and with improved mechanical properties.
CRIS-Team Scopus Importer:2020-07-31
Keywords: Additive manufacturing; Hot deformation; Titanium

On the influence of TiB2, TiC, and TiN hard particles on the microstructure of localized laser dispersed AISI D2 tool steel surfaces - Spranger, Felix; Schirdewahn, Stephan; Kromm, Arne; Merklein, Marion; Hilgenberg, Kai (Journal of Laser Applications, 2020)
The control of friction and wear is a major concern in many industrial applications. A promising method for tailored surface modification is the so-called laser implantation technique. This method combines surface texturing and material optimization in one processing step by a localized dispersing of hard ceramic particles using pulsed laser radiation. Wear resistant, protruding micrometric features (implants) with defined geometry can be created in a deterministic pattern where needed on highly stressed surfaces, i.e., on forming or cutting tools. However, in order to maintain the implants over the tool's lifetime, a suitable selection of hard ceramic particles is a prerequisite. They must provide a defect-free metal matrix composite with a high share of homogeneously distributed particles and, especially, high implant hardness. In this study, TiN, TiC, and TiB2 hard particles were compared as implant materials for the first time. By a systematic variation of pulse power and pulse duration, their dispersing behavior and influence on the material properties of AISI D2 tool steel were investigated. Although all powder materials had grain sizes smaller than 10 mu m, it was possible to disperse them by pulsed laser radiation and to obtain defect-free protruding implants. The highest share of dispersed particles (similar to 64%) was observed for TiB2. By scanning electron microscopy and energy dispersive x-ray spectroscopy, it was also shown that a significant share of the preplaced particles was dissolved by the laser beam and precipitated as nanometer sized particles within the matrix during solidification. These in situ formed particles have a decisive influence on the material properties. While the TiN and TiC implants have shown maximum hardness values of 750 and 850 HV1, the TiB2 implants have shown the highest hardness values with more than 1600 HV1. By x-ray diffraction, it was possible to ascribe the lower hardness values of TiC and TiN implants to high amounts of retained austenite in the metal matrix. By implanting TiB2, the formation of retained austenite was successfully suppressed due to the in situ formation of TiC particles, which was proven by electron backscatter diffraction. In conclusion, all the implant materials are basically suitable for laser implantation on AISI D2 tool steel. However, TiB2 has shown the most promising results.
CRIS-Team WoS Importer:2020-05-22

On the inverse identification of Lankford coefficients using geometrical changes under quasi-biaxial loading - Graser, Matthias; Lenzen, Matthias; Merklein, Marion (International Journal of Material Forming, 2019)
Finite element simulation has become an important tool of process and production design in various fields, especially in the automotive industry. The calculation of forming processes in the early concept phase of new cars allows virtual adaptions, which can reduce costs of later phases in the product development significantly. Therefore, the precise characterization and modelling of the material behavior is necessary to ensure a robust and reliable numerical process design. The mechanical properties of numerous materials are highly influenced by the rolling or extrusion direction in the production process. This necessitates the characterization of materials in different loading directions. However, depending on the dimensional aspects of the semi-finished product, the manufacturing of specimens can be challenging or even impossible. Thus, in this investigation, an innovative, indirect approach for the identification of the Lankford coefficient in transversal direction is presented. Based on numerical and experimental data of layer compression tests the Lankford coefficient is determined by inverse modelling of the resulting specimen contour. Due to the characteristics of the layer compression test, it can even be used for semi-finished products with small transversal dimensions like extruded profiles. The presented methodology is on the one hand verified by conventional uniaxial tensile tests for aluminum as well as steel blank material. On the other hand it is used to determine Lankford coefficients for an aluminum extrusion hollow profile and the inversely identified material model is validated by comparison of strain distributions of experimental and numerical square tube bending tests.
CRIS-Team Scopus Importer:2019-08-06
Keywords: Inverse parameter identification; Lankford coefficient; Layer compression test; Material modelling

On the tribological influence of coatings in cold forging - Andreas, Kolja; Merklein, Marion (Proc. 11th Int. Conf. THE "A" Coatings in Manufacturing Engineering, 2014)
LFT Import::2019-08-05 (2047)

Optical forming analysis of functional components manufactured in an orbital forming process - Hetzel, Andreas; Sawodny, Annette; Lechner, Michael; Merklein, Marion (XL. Colloquium on Metal Forming, 2022)
Global challenges like an increased sustainability or reduced carbon dioxide emissions demand for efficient process solutions and innovative products. Functional integration and lightweight design propose one way to meet these challenges, nevertheless resulting in increased component complexity as well as long process chains, bringing conventional manufacturing processes to their limits. The process of orbital forming can be applied to efficiently manufacture functional components with varying sheet thickness, like in gear systems. This process is assigned to Sheet-Bulk Metal Forming (SBMF), featuring multi-dimensional stress and strain states in the sheet metal. In order to increase the forming behaviour, the control of the material flow was identified as major challenge in previous research. Therefore, this contribution focuses on the optical forming analysis of the functional components, to increase the understanding regarding the cause-effect relations on the indicated material flow. The components are manufactured out of the high-strength tempered steel 51CrV4 with an initial sheet thickness of 2.0 mm and feature different rotational and cyclic-symmetric elements. The aim of this investigation is the establishment of an extended process understanding on the interdependencies between an occurring three-dimensional material flow and the forming in the context of SBMF processes, in order to increase formability and quality of the manufactured parts.<br
Keywords: sheet-bulk metal forming; orbital forming; forming analysis; sheet metal; functional component

Optimisation of Specimen's Geometry for Characerisation of Plastic Yielding - Geiger, Manfred; Merklein, Marion; Hußnätter, Wolfgang (Proceedings of the 8th ESAFORM Conference on material forming, 2005)
LFT Import::2019-08-05 (1170)

Optimization of the heat treatment layout and blank outline of THTB - Lechner, Michael; Kuppert, Andreas; Hagenah, Hinnerk; Merklein, Marion (Key Engineering Materials, 2013)
Tailored heat treated blanks (THTB) is the generic term for an innovative approach to enhance the formability of blanks made out of high strength steel or aluminum alloys. Key idea of the technology is the adaption of the mechanical properties by a local heat treatment. Based on the new property distribution, the material flow during the forming operation can be improved and the forming limit can be enhanced. In comparison to conventional temperature assisted approaches the forming is performed at room temperature and therefore all advantages of a cold forming process can be used. Most challenging within the application is the definition of the heat treatment layout. Up to now the layout is dimensioned in a time-consuming trial and error procedure. In this paper a new approach for the automatic optimization of the heat treatment layout and the blank outline is presented. Copyright © 2013 Trans Tech Publications Ltd.
LFT Import::2019-07-29 (1856)
Keywords: Enhancement of formability; Optimization; Tailored heat treated blanks

Optimized Process Control Strategy for the Laser Cutting and Welding of Complex Hydroforming Parts - Blankl, Andreas; Kreis, Oliver; Merklein, Marion (Proceedings of the Lasers in Manufacturing, 2005)
LFT Import::2019-08-05 (1167)

Orbital forming of tailored blanks from sheet metal - Merklein, Marion; Plettke, Raoul; Opel, Simon (CIRP Annals - Manufacturing Technology, 2012)
LFT Import::2019-07-29 (1787)
Keywords: Incremental bulk forming; Sheet metal; Simulation

Orbital forming of tailored blanks with two-sided local material thickening - Hildenbrand, Philipp; Lechner, Michael; Vogel, Manfred; Herrmann, H.; Merklein, Marion (International Journal of Advanced Manufacturing Technology, 2018)
Economic and ecological demands like saving resources and improved material efficiency can be achieved by the application of process adapted semi-finished parts, so-called tailored blanks, for the manufacturing of for example gearings or synchronizer rings. Functional components require the locally restricted distribution of an adequate amount of material at defined positions in order to properly form functional elements like gearings or carriers. As these elements can be formed on one or both sides of the component, an appropriate material provision on one or both sides of the sheet metal is necessary. Having material thickenings on two sides lead to the interaction between both sides for example with regard to the maximum die filling. One process to produce tailored blanks is orbital forming. While manufacturing these tailored blanks with a local material thickening on one side of the sheet metal is state-of-the-art, the realization of these tailored blanks on both sides has not been investigated yet. In this paper, the results regarding the manufacturing of tailored blanks with a two-sided local material thickening will be presented for the first time. By analyzing three different tailored blank geometries, the influence of the interactions of two-sided material thickenings will be investigated. The results will be evaluated in terms of the resulting geometrical and mechanical properties.
LFT Import::2019-07-29 (2310)
Keywords: Forming; Orbital forming; Sheet-bulk metal forming; Tailored blank

Overview on sheet-bulk metal forming processes - Merklein, Marion; Tekkaya, A. E.; Brosius, A.; Opel, Simon; Koch, Johannes Peter Karl (Proceedings ICTP 2011, 2011)
The process class sheet-bulk metal forming (SBMF) provides the manufacturing of local functional features in the magnitude of the sheet thickness through a controlled material flow. This paper gives an overview on the technology and application of various bulk forming operations on sheet metals. Based on the variety on the processes a classification by the specific kinematics is developed. The tools movement can be divided in a linear and rotational tool motion. It has been shown that the intended geometry is nearly impossible to achieve using conventional tooling systems even applying extremely high forces. Therefore multi-stage forming operations and several combinations of the presented SBMF processes often are used. An overview of existing SBMF operations in literature will be given. In addition some numerical studies and physical experiments will be shown, that can be used for analysis of materials flow, the interaction of tooling systems and the material flow within SBMF processes. © 2011 IBF (RWTH Aachen) & IUL (TU Dortmund).
LFT Import::2019-08-05 (1727)
Keywords: Process Control; Sheet-bulk metal forming; Simulation

Parameters Influencing Adhesive Wear Behavior within Hot Stamping Operations - Wieland, Michael; Merklein, Marion (Proc. 5th Int. Conf. Hot Sheet Metal Forming of High-Performance Steel, 2015)
LFT Import::2019-08-05 (2097)

Perfomance of Hot Forging Tools built by Laser Metal Deposition of Hot Work Tool Steel X37CrMoV5-1 - Junker, Daniel; Hentschel, O.; Schramme, R.; Schmidt, M.; Merklein, Marion (Laser in Manufacturing Conference 2017, 2017)
LFT Import::2019-08-05 (2268)

Performance of Silicon Punches for Microblanking of Thin Metal Foils - Hildering, Sven; Merklein, Marion; Engel, Ulf (4th International Conference on Nanomanufacturing (nanoMan), 2014)
LFT Import::2019-07-29 (2024)

Pin Extrusion for Mechanical Joining from Orbital Formed Tailored Blanks with Local Material Pre-Distribution - Römisch, David; Hetzel, Andreas; Wituschek, Simon; Lechner, Michael; Merklein, Marion (Journal of Manufacturing and Materials Processing, 2022)
Pin extrusion is a common process to realise pin structures in different geometrical dimensions for a subsequent joining operation. Nevertheless, the process of pin extrusion offers process limits regarding sheet thinning as a consequence of the punch penetration depth into the sheet. Thereby, cracks at the residual sheet thickness can occur during strength tests, resulting in a failure of the complete joint due to severe thinning. Therefore, measures have to be taken into account to reduce the thinning. One possibility is the application of orbital formed tailored blanks with a local material pre-distribution, which allows a higher sheet thickness in the desired area. Within this contribution, the novel approach of a process combination of orbital forming and pin extrusion is investigated. To reveal the potential of a local material pre-distribution, conventional specimens are compared with previously orbital formed components. Relevant parameters such as the residual sheet thickness, the pin height as well as the average hardness values are compared. The results show a significant positive influence of a local material pre-distribution on the residual sheet thickness as well as the resulting pin height. Furthermore, the strain hardening during orbital forming can be seen as an additional advantage. To conclude the results, the process limits of conventional pin extrusion can be expanded significantly by the application of specimens with a local material pre-distribution.<br

Plastic flow and its control in sheet-bulk metal forming of thin-walled functional components - Merklein, Marion; Löffler, Maria; Schneider, Thomas (CIRP Annals - Manufacturing Technology, 2015)
This paper deals with a manufacturing process for sheet metal components with integrated functional elements by sheet-bulk metal forming. In a single forming stage a cup-shaped base body with thin-walled features is deep drawn and its geometry is calibrated by upsetting. The fundamental numerical and experimental investigations include the analysis of the die filling behaviour, part geometry and mechanical properties due to strain hardening with respect to the variation of the blank layout, forming force and material strength. Finally, the process limits are identified and approaches for their enhancement by the application of tailored surfaces are presented.
LFT Import::2019-07-29 (2088)
Keywords: Forming; Processing; Surface modification

Potentiale der Kombination von Umformtechnik und additiver Fertigung in hybriden Prozessketten - Papke, Thomas; Huber, F.; Hagenah, Hinnerk; Schmidt, M.; Merklein, Marion (6. Industriekolloquium des Sonderforschungsbereichs 814 - Additive Fertigung, 2018)
LFT Import::2019-08-05 (2351)

Potential of Joining Dissimilar Materials by Cold Formed Pin-Structures - Kraus, Martin; Merklein, Marion (Journal of Materials Processing Technology, 2020)
Joining dissimilar materials brings established joining techniques to their limits due to different thermal expansion, unequal stiffness/strength and chemical incompatibilities. The use of pin-structures has proven an appropriate strategy to join multi-material-systems in laboratory scale. At present, the industrial application of this joining technology is limited due to the time-consuming pin manufacturing process and the inadequately researched achievable joint strengths. In this study, extrusion of the pin-structures from sheet metal is used to investigate an approach that can be directly integrated into existing production processes and does not require auxiliary joining elements. With direct-pin-pressing and caulking, two different joining strategies are analysed to join multi-material systems of sheet steel (DC04, t0 = 2 mm) and aluminium (EN AW 6016-T4, t0 = 2 mm). The basic feasibility of the joining technique is experimentally proven by using single-pin-structures. The joint strength is analysed by tensile shear tests, micro sections and failure patterns. Based on the experimental results, a failure criterion for the joint is defined. Parallel to the experiments, numerical finite element models (FE-models) for the single-pin-joint are developed and validated. In a further step, numerical investigations for multi-pin-structures are carried out in order to derive predictions on achievable joint strengths with this joining technique. It is shown that the form-fit is crucial for the joint strength. Thus, 93 % higher shear strength is achieved for caulked joints. By multi-pin-structures the strength can be increased considerably. For a 5 × 3 pin-structure, shear strength of 9.9 kN can be achieved.
CRIS-Team Scopus Importer:2020-05-22
Keywords: Forming; Joining; Multi-material-system; Pin extrusion

Potential of Joining Dissimilar Materials by Cold Formed Pin-Structures - Kraus, Martin; Merklein, Marion (AJP 2019, 2019)

Potential of Orbital Formed Tailored Blanks for Industrial Application - Hetzel, Andreas; Lechner, Michael; Aman, Alexander; Büdicker, Kai; Merklein, Marion (Steel in Cars and Trucks (SCT), 2022)
Due to economic and ecologic framework conditions like fuel reduction or sustainability, the manufacturing industry is facing greater challenges than ever before. One way to meet these challenges is the combination of lightweight construction and functional integration with an increased material efficiency. Nowadays, components like synchronizer rings or clutch plates are manufactured by machining, producing scrap and thus reducing the efficiency drastically. Orbital forming is an innovative manufacturing process, providing the possibility to efficiently produce functional components with a varying sheet thickness. Thereby, a tumbling motion of the punch reduces the contact area between workpiece and tool, thus enabling a significantly lower process force. The material distribution is realized by a tangential and radial material flow into the cavities. Until now, orbital formed Tailored Blanks have only been investigated as semi-finished products used in a single-stage process combination of deep drawing and upsetting. With regard on the potential for an industrial application, a Tailored Blank layout with different functional elements is introduced. The demonstrator for this investigation is manufactured out of the case-hardenable steel C10 and is depicting a clutch disc carrier with both-sided cyclic as well as rotational-symmetric material thickenings. To evaluate the industrial applicability, the components are analyzed regarding their geometrical and mechanical properties and are compared to the target contour. To demonstrate the operational advantages of the orbital formed components in comparison to conventionally manufactured parts, the fatigue life is evaluated as indicator for the functional behavior.<br
Keywords: Sheet-Bulk Metal Forming; Tailored Blank; Orbital Forming; Endurance Strength; Functional Component; Lightweight Design; Industrial Application