Marion Merklein

Nuremberg University of Music, Nuremberg, Bavaria, Germany

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Publications (159)92.22 Total impact

  • Sven Hildering, Ulf Engel, Marion Merklein
    06/2015; 3(2). DOI:10.1115/1.4029629
  • 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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    ABSTRACT: To design the indirect hot stamping process, a finite element method (FEM) based prediction of the part geometry and the mechanical properties is required. In case of indirect hot stamping processes, producing car body parts with tailored properties, cooling paths occur causing diffusionless and diffusion controlled phase transformations. The volume expansion caused by the phase transformation of face-centred cubic (fcc) into body-centred cubic (bcc) and the martensitic formation of body-centred tetragonal (bct) leads to transformation induced strains that are important for the calculation of overall stresses in hot stamped car body parts. To calculate the strain and stress state correctly, it is necessary to model the diffusionless and diffusion controlled phase transformation phenomena, taking into account the boundary conditions of indirect hot stamping processes. The existing material models are analysed and extended in order to improve their prediction accuracy in calculating the amount and distribution of ferrite, perlite, bainite and martensite during the whole process of annealing. For industrial use the new approaches are implemented in the FE-code LS-DYNA 971 (Livermore Software Technology Corporation, 2006).
    Journal of Materials Processing Technology 01/2015; 20. DOI:10.1016/j.jmatprotec.2015.01.003 · 2.04 Impact Factor
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    ABSTRACT: Demonstrated that textured tool possessed a lower friction coefficient than the nontextured tool.•Demonstrated that the amount of reduction depends on the relative orientation between the sliding direction and the sheet orientation.•The flat-on-cylindrical test apparatus effectively simulated the critical bending area in the sheet metal stamping operation.
    Tribology International 01/2015; 81. DOI:10.1016/j.triboint.2014.09.001 · 2.12 Impact Factor
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    ABSTRACT: The increasingly investigated and applied production process sheet-bulk metal forming (SBMF) has novel requirements for the forming tools, e.g., the need of an adaptive material flow at different areas of the tool for an adequate form filling. One new method to realize different, defined tribological conditions are tailored surfaces (TS). During the design of forming tools, it is imperative to have profound knowledge about the tribology between the tool and the workpiece. This article introduces structuring with high-feed milling tools as one possibility for influencing the material flow during forming processes and presents a ring-compression test for the quantification of the tribological conditions, which is adapted for SBMF. On the basis of various machined structures, surface parameters are analyzed to identify a correlation with the friction coefficient to gain knowledge about the mechanisms of TS and to be able to choose structures according to the needs of SBMF processes.
    Production Engineering 12/2014; DOI:10.1007/s11740-014-0597-0
  • icat 2014; 10/2014
  • Martin Grüner, Marion Merklein
    Production Engineering 10/2014; 8(5):577-584. DOI:10.1007/s11740-014-0551-1
  • Marion Merklein, Sebastian Suttner, Adam Schaub
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    ABSTRACT: The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.
    Key Engineering Materials 09/2014; 622-623:273-278. DOI:10.4028/ · 0.19 Impact Factor
  • 09/2014; 1018:309-316. DOI:10.4028/
  • 09/2014; 1018:229-236. DOI:10.4028/
  • 09/2014; 1018:215-222. DOI:10.4028/
  • Sebastian Suttner, Marion Merklein
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    ABSTRACT: Increased requirements for sheet metal parts and the use of advanced high-strength steels and other materials with lightweight potential set new standards for material characterization methods. Especially in the automotive sector with complex, multi-stage forming processes, new challenges are placed to model the real material behavior numerically. Thus, the requirements can be met to the numerical design of forming processes, advanced knowledge in the field of material characterization is needed. Therefore characterization methods under cyclic load are used. Two possibilities to investigate the cyclic behavior of the material are the tension-compression test and the cyclic shear test. The differences in the material properties of sheet metals during a reversal of load are marked by the Bauschinger effect and lead to a decrease of the beginning of plastic yielding. In this paper, the cyclic material behavior of different materials is characterized with experimental tension-compression tests and compared to the results of cyclic shear tests from a modified ASTM simple shear test preparation. The aim is the analysis of the Bauschinger effect through the identification of the kinematic hardening model according to Chaboche and Rousselier for the investigated materials. Moreover an estimation of the characteristic of the Bauschinger effect is presented.
    IDDRG 2014 Conference; 06/2014
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    ABSTRACT: An ever increasing mobility and a shortage of resources lead to restrictive politically driven limits for fuel consumption as well as an increasing demand of customers for efficient vehicles. Though electrification of cars proceeds, combustion engines will play an important role for conventional and hybrid concepts within next decades. Thus, for a contribution to increasing energy efficiency of vehicles it is vital to trace sources of friction losses and to identify possibilities for friction reduction in combustion engines. Therefore, the follower as a main contributor to friction losses in valve trains was chosen as a demonstrator for friction reduction effects by microstructured components. However, the realization of theoretically advantageous microstructures with filigree geometries is challenging for manufacturing technologies. The present study focuses on the elaboration of a technological basis for a repeatable production of components with microstructured surfaces by a combined cup backward extrusion micro coining process, coping with the demands of large-lot production. For realization of a high accuracy the influence of friction on geometry of microstructured components was investigated. In addition, running-in of components is decisive for final geometry and tribological behavior of microstructured surfaces and hence considered as well.
    06/2014; 966-967:323-335. DOI:10.4028/
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    ABSTRACT: Within this paper the characterization of hybrid components consisting of selective electron beam melting (SEBM) additive structures and sheet metal of alloy Ti-6Al-4V will be presented. Key idea of the new production approach is the combination of the advantages of two different manufacturing processes. On the one hand the very high flexibility of the additive manufacturing process and on the other hand the economic production of conventional geometries by deep drawing operations. Main challenge within this new and innovative process is the identification and quality of the properties of the new hybrid components after the manufacturing process. The necessary evaluation consists of three parts: the analysis of the deep drawing blanks, the additive manufactured structure and finally the connection between both. Whereas standardized testing methods are available for the testing of the blanks and the additive structure, there are hardly scientific publication which deals with the investigation of the connection between them. Therefore, a new testing methods and consequently a new tool design was developed in order analyze the specimens in dependency of different strain- and stress conditions. At the end microstructural investigations were performed to identify the fundamental mechanisms which lead to the different properties on macroscopic scale. The result proofed that in particular the electron beam power has a high influence on the production process and thereby the connection quality.
    Key Engineering Materials 05/2014; 611-612:609-614. DOI:10.4028/ · 0.19 Impact Factor
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    ABSTRACT: The on-going trend in product miniaturization, together with the increasing quality and reduction of costs of micro-components, leads to the need of a robust process design, which might additionally avoid the occurrence of defects in the workpiece. Processes like microforming are affected by variations which can be foreseen but not totally mastered in the design stage. One approach is seen in an adaptive control system based on a metamodel processing the data of online measuring. This approach is grounded on in-depth knowledge based on correct and precise process modelling. This paper presents both experimental and simulative study of a microforging process, part of a more complex forming chain. It consists of six parallel ribs on metal strip. The ribs have a width of 250 µm and are spaced by a gap of 150 µm. The process has been studied by different punch forces, analyzing the final geometry of the workpiece. In particular the rib height is considered as critical to quality parameter. The simulations show reliable results that can be used for the design of the model interfacing measurement and control of the whole microforming process.
    Key Engineering Materials 05/2014; 611-612:565-572. DOI:10.4028/ · 0.19 Impact Factor
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    ABSTRACT: Mixed-Materials parts have great light-weight potential for the automotive application to reduce the carbon footprint. But the joining of fibre composite plastic sheets to metal sheets is in practical application limited to adhesive bonding or mechanical joining with additional fastener elements due to the large differences in physical properties. A new process chain based on plastic joining without fastener elements is proposed and first results on the mechanism and on the achievable strength of the new joints are shown. The process chain consists of three steps: First joining pins are added to the sheet metal by an additive manufacturing process. In a second step these pins are pierced through the fibre composite sheet with a local heating of the thermoplastic in an overlap setup. In the third and last step the joint is created by forming the pins with the upsetting process to create a shape lock. The shear strength of the joined specimens was tested in a tensile testing machine. The paper shows that even with a non-optimized initial setup joints can be realised and that the new process chain is a possible alternative to adhesive bonding.
    Key Engineering Materials 05/2014; 611-612:1468-1475. DOI:10.4028/ · 0.19 Impact Factor
  • Marion Merklein, Wolfgang Böhm
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    ABSTRACT: The Accumulative Roll Bonding (ARB) process enables the manufacturing of high strength sheet metals with outstanding mechanical properties by repeated rolling. However, the significant increase in strength leads to loss in ductility, especially regarding aluminum alloys of the 6000 series. The low formability obviously limits the implementation of these sheet products for formed components in automotive applications. To enhance formability, a local short term heat treatment according to the Tailored Heat Treated Blanks technology is used. For the finite element based design of forming operations accurate information about the plastic behavior of these tailored materials is required. Therefore, different stress - strain paths are considered using the tensile test and the layer compression test. In this context, heat treated and non-heat treated specimens out of ARB processed AA6016 were tested at room temperature. With the experimental results true stress strain curves and yield loci determined from different criteria and represented in a principal stress state were established. Regarding the experimental setup of the ARB process, an upscaling is essential for the production of sufficiently large strips to cut out blanks for the forming of components such as B-pillars. However, this requires the adaptation of the different process steps of the ARB process. In this context, the surface treatment before rolling of such large sheets is investigated, since it is particularly relevant for obtaining a strong bonding between the sheets. Another aspect is the investigation of the rolling process using the finite element analysis. In this regard, a thermal mechanical coupled simulation model of the roll bonding operation will be developed for the evaluation of different material combinations, different process temperatures and varying roller geometries. These investigations will enable the production of lightweight automotive components made of ARB processed high strength aluminum sheet metal with tailored properties.
    04/2014; 907:3-16. DOI:10.4028/
  • Sebastian Rösel, Marion Merklein
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    ABSTRACT: Within this paper a new approach to enhance the process window in sheet metal hydroforming processes will be presented. The key idea of the technology is the local adaption of the properties of the active fluid medium. In this case the magnetorheological fluid (MRF) Basonetic® 5030 is used and the fluid behavior is changed due to a partially applied external magnetic field. Based on the new property distribution the medium can be used as forming and sealing medium at the same time. The results are compared to the values reached with mineral oil. The presented work covers all necessary steps for a successful application of the technology. After the presentation of the used fluids, a material characterization and the tools, which are developed for this reason, as the sealing limits for two different configurations are determined. Based on these investigations forming operations are carried out at the related process parameters to show up the potential of the MRF. At the end a numerical model is built up and validated for both fluids used to offer a qualified tool for process design.
    Production Engineering 03/2014; 8(1-2). DOI:10.1007/s11740-013-0496-9
  • Kolja Andreas, Marion Merklein
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    ABSTRACT: Cold forging enables mass production of steel based components. High loads within cold forging presuppose high loadable tool materials. This is why apart from tool steels cemented carbides are mainly used as tool materials. Due to brittleness of these materials, fatigue is one of the major limits of tool life. Tool manufacturing requires a combination of hard machining and subsequent machining steps. For hard machining of complex tool geometries electrical discharge machining (EDM) represents the industrial standard. The thermal influenced surface layer has to be removed by post and fine machining steps. The resulting surface integrity has a major influence on the internal strength of a tool. Correlations between tool manufacturing, surface properties and tool behavior will gain knowledge for an optimized tool production. In this context, scope of the present paper are the investigation and description of the interactions between tool manufacturing and resulting surface properties for tools made of cemented carbide and tool steel. Within the article, the surface properties caused by a conventional process chain consisting of EDM and polishing are quantified. In addition, these results are compared to an adapted process chain with an integrated peening process. The results reveal that the conventional and the adapted process chain lead to similar surface topographies and roughness values. However, the integration of a peening process shifts the residual stress level towards higher compressive stresses.
    Production Engineering 03/2014; 8(1-2). DOI:10.1007/s11740-013-0522-y
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    ABSTRACT: Tailored Blanks is the collective for semi-finished sheet products which are characterised by a local variation of the sheet thickness, sheet material, coating or material properties. With these adaptions the tailored blanks are optimised for a subsequent forming process or the final application. In principle four different approaches can be distinguished to realise tailored blanks: joining materials with different grade, thickness or coating by a welding process (tailor welded blanks), locally reinforcing the blank by adding a second blank (Patchwork blanks), creating a continuous variation of the sheet thickness via a rolling process (tailor rolled blanks) and adapting the material properties by a local heat treatment (tailor heat treated blanks). The major advantage of products made from tailored blanks in comparison to conventional products is a weight reduction. This paper covers the state of the art in scientific research concerning tailored blanks. The review presents the potentials of the technology and chances for further scientific investigations.
    Journal of Materials Processing Technology 02/2014; 214(2):151–164. DOI:10.1016/j.jmatprotec.2013.08.015 · 1.95 Impact Factor