Marion Merklein

Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Bavaria, Germany

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Publications (212)107.21 Total impact

  • S. Suttner · M. Merklein ·
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    ABSTRACT: Complex parts with sharp corners are on the rise to satisfy increasing customer demands on the design. To realize these parts in single or multistage forming processes the information of the material behavior under linear and non-linear strain paths is essential. As Bauschinger already showed for the material behavior under cyclic loading, a reduction of the subsequent beginning of plastic yielding can be observed. Different research works studied the Bauschinger effect under cyclic proportional loading or non-proportional strain paths mostly with uniaxial pre-straining of the material. In this paper the material behavior under shearing after previous biaxial stretching in the Marciniak test is analyzed for the aluminum alloy AA5182 and the advanced high strength steel DP600. The Marciniak test is suited for biaxial pre-straining due to an almost almost equibiaxial strain state and a homogeneous strain distribution in-plane on the bottom of the specimen up to higher strains than in a biaxial tensile test. The subsequent shear test is realized with a modified shear test specimen according to the ASTM standard. Finally, the influence of biaxal pre-straining on the beginning of plastic yielding under shear condition, the hardening behavior and the maximum reachable shear strain is investigated for a better understanding of the material behavior under non-proportional loading paths.
    12/2015; 2:S98-S106. DOI:10.1016/j.matpr.2015.05.025
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    Hinnerk Hagenah · Marion Merklein · Michael Lechner · Adam Schaub · Stefan Lutz ·
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    ABSTRACT: Hot stamping is a well-established process in car manufacturing today. However, the resulting mechanical properties of a hot stamped part and its behaviour during a crash are still open questions. The usual procedure includes destructive experiments to determine the mechanical properties resulting from the forming and quenching process. The gained information is then used for crash simulation. Using images from micrographs to determine the proportion of bainite and martensite resulting from the hot stamping process has proved to be difficult, as these structures are fairly similar and hard to distinguish.
  • Marion Merklein · Christoph Kiener · Andrea Reiss ·

    11/2015; 805:154-161. DOI:10.4028/
  • Maria Löffler · Daniel Groebel · Ulf Engel · Kolja Andreas · Marion Merklein ·

    10/2015; 794:81-88. DOI:10.4028/
  • Philipp Hildenbrand · Robert Schulte · Marion Merklein ·

    10/2015; 794:144-151. DOI:10.4028/
  • Martin Müller · Réjane Hörhold · Gerson Meschut · Marion Merklein ·

    10/2015; 794:304-311. DOI:10.4028/
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    ABSTRACT: The paper gives a review of the main research activities recently carried out in the framework of hot stamping of boron steel sheets with tailored properties. The focus is on the process variants developed to locally adjust the mechanical properties of the hot stamped component as well as on the testing and modeling techniques needed to calibrate the numerical models of the tailored tempering processes and to evaluate the post-forming properties of the stamped products.
    Journal of Materials Processing Technology 09/2015; DOI:10.1016/j.jmatprotec.2015.09.023 · 2.24 Impact Factor
  • Stefania Bruschi · Marion Merklein ·

    Journal of Materials Processing Technology 09/2015; DOI:10.1016/j.jmatprotec.2015.09.006 · 2.24 Impact Factor
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    ABSTRACT: Metal forming is not only shaping the form of a product, it is also influencing its mechanical and physical properties over its entire volume. Advanced analysis methods recently enable accurate prediction of these properties and allow for setting these properties deterministically during the forming process. Effective measurement methods ensure the setting of these predicted properties. Several real examples demonstrate the impressive achievements and indicate the necessity of a paradigm change in designing products by including manufacturing-induced effects in the initial dimensioning. This paradigm change will lead to lightweight components and serve environmentally benign designs.
    CIRP Annals - Manufacturing Technology 07/2015; 64(2). DOI:10.1016/j.cirp.2015.05.001 · 2.54 Impact Factor
  • Alexander Kahrimanidis · Daniel Wortberg · Marion Merklein ·
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    ABSTRACT: Tailor heat treated blanks (THTB) are a well-known approach to considerably enhance the forming limits of 6xxx-aluminum alloys. This is realized by locally adjusting the mechanical properties with regard to a forming operation using a short term heat treatment. However, the resulting temperature distribution unavoidably leads to distortion of the blank due to thermal expansion of the heated areas. This is challenging for automated processing of THTB since dimensional accuracy and stackability must be assured. In this work the influence of heating parameters, tool design and blank thickness on the distortion behavior of 6xxx THTB are investigated by laboratory experiments. To show that it is in principle possible to predict the distortion behavior in advance, a thermo-mechanical simulation is used to recalculate one of the findings. The results from laboratory experiments are transferred and validated on a near-series heating tool. It is demonstrated that distortion can be minimized and controlled in a way that automated processing of THTB becomes possible. © 2015, German Academic Society for Production Engineering (WGP).
    Production Engineering 07/2015; 9(5). DOI:10.1007/s11740-015-0628-5
  • Marion Merklein · Raoul Plettke · Daniel Junker · Adam Schaub · Bhrigu Ahuja ·
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    ABSTRACT: 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.
    Key Engineering Materials 07/2015; 651-653:713-718. DOI:10.4028/ · 0.19 Impact Factor
  • Marion Merklein · Emanuela Affronti · Jennifer Steiner ·

    Key Engineering Materials 07/2015; 651-653:1029-1035. DOI:10.4028/ · 0.19 Impact Factor
  • Marion Merklein · Matthias Graser · Michael Lechner ·

    Key Engineering Materials 07/2015; 651-653:59-64. DOI:10.4028/ · 0.19 Impact Factor
  • Daniel Junker · Oliver Hentschel · Michael Schmidt · Marion Merklein ·
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    ABSTRACT: The desire for individualized products forces the companies to a great diversity of combinable parts. This way, the clients can compile their personalized product. As this trend is not just limited on visual parts but also for functional components, laser additive manufacturing of metals is used more and more often in manufacturing. To bring more additive manufacturing into mass production, Laser Beam Melting and Laser Metal Deposition will be qualified for the use in tool manufacturing within the Bavarian research association "ForNextGen - Next Generation Tools". The first subproject within this research association investigates the potential of Laser Metal Deposition in the production of hot and cold forging tools. Within initial tests optimized process, parameters for the processing of the hot-work steel 1.2709 are determined by single welding beads. The achieved density and the inner structure are analyzed within cubes that were built with the investigated parameters. As forging tools are usually made of high-carbon tool steel, the processing of materials with a rising percentage of carbon will be part of further investigations.
    Key Engineering Materials 07/2015; 651-653:707-712. DOI:10.4028/ · 0.19 Impact Factor
  • Sven Hildering · Ulf Engel · Marion Merklein ·

    06/2015; 3(2). DOI:10.1115/1.4029629
  • Marion Merklein · Maria Löffler · Thomas Schneider ·
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    ABSTRACT: 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.
    CIRP Annals - Manufacturing Technology 04/2015; 64(1). DOI:10.1016/j.cirp.2015.04.078 · 2.54 Impact Factor
  • N. Jaburek · M. Merklein ·
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    ABSTRACT: The investigated material is the copper-free Al–Zn–Mg-alloy EN AW-7020 (AlZn4,5Mg1) in the artificial aged T6 temper. In this temper the 7xxx series alloys show a high strength level, but also a high stress corrosion sensitivity. Therefore, the retrogression and reaging (RRA)-treatment has been developed to combine stress corrosion resistance with high strength. The aim of this study is the description of the course of the mechanical behavior influenced by a RRA treatment. The changes of the mechanical properties are represented by changes in the microstructure as recorded by thermal analysis. Therefore typical mechanical properties and thermal analysis curves are determined according to temperature and time in each of the retrogression annealing and of the RRA-treatment. The temperature for retrogression annealing was between 220 and 360 °C. Reaging was performed on material at 130 °C for 16 h and 160 °C for 5 h after a storage of 7 days at room temperature. The results of the thermal analysis are generally described on the curve of the T6 tempered material and transferred to the changes by the retrogression temperature and the reaging parameter. The results show a main influence of the precipitation structure and mechanical properties after the retrogression and reaging treatment by the temperature of the retrogression annealing. For all investigated parameters, an overaging of the material after the RRA-treatment is recognizable.
    Production Engineering 04/2015; 9(2). DOI:10.1007/s11740-014-0593-4
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    Marion Merklein · Kolja Andreas · Jennifer Steiner ·
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    ABSTRACT: The realization of lubricant free forming processes is motivated by an increasing demand for resource efficiency and higher environmental standards. Further potentials are the reduction of production steps and time. The dry conditions lead to an intensive interaction between tool and workpiece. Increasing friction and wear are the consequences. One approach to face these challenges is the implementation of tailored tool surfaces. Within this study the behavior of different tool surfaces under dry and lubricated conditions is investigated. In this regards, a flat strip drawing test was conducted to determine the friction coefficients depending on the tool surface properties resulting from various machining processes. Furthermore, a surface characterization before and after the experiments was performed to gain knowledge about the wear mechanisms. The tests series with dry strips lead to a higher friction level. Furthermore, the results show that the friction can be reduced when the grinding marks are orientated transversal to the drawing direction. A further friction reduction is achieved when applying polished tools.
    International Journal of Precision Engineering and Manufacturing-Green Technology 04/2015; 2(2):131-137. DOI:10.1007/s40684-015-0017-8
  • Davide Campanella · Gianluca Buffa · Livan Fratini · Marion Merklein ·
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    ABSTRACT: Solid Bonding based welding processes allow to obtain defect free joints with low residual stress and low distortion. However, the engineering and optimization of solid bonding processes is difficult and requires a large number of time and cost consuming test trials. In this way, proper numerical models are essential tools permitting effective process design. The aim of this research was the comparison of the material process conditions during two different manufacturing processes taking advantage of the same metallurgical phenomenon, namely solid bonding. Linear Friction Welding, used to weld non-axisymmetric components and Accumulative Roll Bonding, used to increase the mechanical properties of sheet metals, were considered. Numerical models were set up, validated and used to design the process by studying the complex material behavior during the solid bonding of different aluminum alloys. An implicit approach was used for the Linear Friction Welding and Accumulative Roll Bonding processes, leading to the understanding of the main process variables influence on the field variables distribution and the occurrence of actual bonding.
    Key Engineering Materials 03/2015; 639:485-491. DOI:10.4028/ · 0.19 Impact Factor
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    ABSTRACT: Global competition as well as social and scientific megatrends strongly influence the modern car manufacturing industry. One of the most important approaches is the implementation of lightweight constructions. Therefore, the usage of high performance materials with tailored properties gains importance. For safety-relevant components such as automotive passenger cells it is necessary to minimize deformation to reduce the risk of injury for the vehicle occupants during a car accident. Thus, hot stamped high-strength steels have been established. High-strength and low formability of this kind of materials represent new challenges for joining technologies. One possibility to join high-strength steels is the newly developed shear-clinching technology. Due to the use of a combined cutting and joining process, the connection of dissimilar materials with high difference in strength and formability can be achieved. Further research to ensure process reliability and to improve the strength of the joint is required. One possible approach for this is the numerical investigation of the material flow during the joining process. Therefore, the definition of process parameters for the finite element model is necessary. A big impact on the quality of the results has the accuracy of the used friction values. As established testing methods are not suitable for modeling the rather complex tribological system between the joining partners of the shear-clinching process, an innovative testing method is needed. Studies in the field of sheet-bulk metal forming already demonstrated the applicability of the ring compression test for sheet metals. This paper presents a concept for the adaption of the ring compression test to the specific needs of the investigated shear-clinching process. The numerical identification of the friction coefficients is validated by experimental data and first results are qualified by experimental and simulative shearclinching joints.
    Key Engineering Materials 03/2015; 639:469-476. DOI:10.4028/ · 0.19 Impact Factor