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Perspektivenwechsel. Bildinformationen anzeigen

Perspektivenwechsel.

Foto: Universität Paderborn

Dr.-Ing. Mathias Bobbert

Kontakt
Publikationen
Dr.-Ing. Mathias Bobbert

Werkstoff- und Fügetechnik

Geschäftsführer - Wissenschaftlicher Mitarbeiter - TRR285

Telefon:
+49 5251 60-3035
Fax:
+49 5251 60-3229
Büro:
P1.4.12.3
Besucher:
Pohlweg 47-49
33098 Paderborn

Sonderforschungsbereich Transregio 285

Geschäftsführer - Mitarbeiter - Teilprojekt Z

Telefon:
+49 5251 60 3035

Liste im Research Information System öffnen

2021

Joining suitability of cast aluminium for self-piercing riveting

M. Neuser, F. Kappe, M. Busch, O. Grydin, M. Bobbert, M. Schaper, G. Meschut, T. Hausotte, 2021


Concept development of a method for identifying friction coefficients for the numerical simulation of clinching processes

M. Böhnke, M.S. Rossel, C.R. Bielak, M. Bobbert, G. Meschut, The International Journal of Advanced Manufacturing Technology (2021)

<jats:title>Abstract</jats:title><jats:p>In order to reduce fuel consumption and thus pollutant emissions, the automotive industry is increasingly developing lightweight construction concepts that are accompanied by an increasing usage of aluminum materials. Due to poor weldability of aluminum in combination with other materials, mechanical joining methods such as clinching were developed and established in series production. In order to predict the relevant characteristics of clinched joints and to ensure the reliability of the process, it is simulated numerically during product development processes. In this regard, the predictive accuracy of the simulated process highly depends on the implemented friction model. In particular, the frictional behavior between the sheet metals as well as between the sheet metal and clinching tools has a significant impact on the geometrical formation of the clinched joint. No testing methods exist that can sufficiently investigate the frictional behavior in sheet materials, especially under high interface pressures, different relative velocities, and long friction paths, while allowing a decoupled consideration of the test parameters. This paper describes the development of further testing concepts based on a proven tribo-torsion test method for determining friction coefficients between sheet metal materials for the simulation of clinching processes. For this purpose, the correlation of interface pressure and the relative velocity between aluminum and steel sheet material in clinching processes is investigated using numerical simulation. Based on these findings, the developed concepts focus on determining friction coefficients at interface pressures of the above materials, yield stress, as well as the reproduction of the occurring friction conditions between sheet metal materials and tool surfaces in clinching processes using tool substitutes. Furthermore, wear investigations between sheet metal material and tool surface were carried out in the friction tests with subsequent EDX analyses of the frictioned tool surfaces. The developed method also allows an optical deformation measurement of the sheet metal material specimen by means of digital image correlation (DIC). Based on a methodological approach, the test setups and the test systems used are explained, and the functionality of the concepts is proven by experimental tests using different sheet metal materials.</jats:p>



Influence of various procedures for the determination of flow curves on the predictive accuracy of numerical simulations for mechanical joining processes

M. Böhnke, F. Kappe, M. Bobbert, G. Meschut, Materials Testing (2021), 63(6), pp. 493-500

The predictive quality of numerical simulations for mechanical joining processes depends on the implemented material model, especially regarding the plasticity of the joining parts. Therefore, experimental material characterization processes are conducted to determine the material properties of sheet metal and generate flow curves. In this regard, there are a number of procedures which are accompanied by varying experimental efforts. This paper presents various methods of determining flow curves for HCT590X as well as EN AW-6014, including varying specimen geometries and diverse hardening laws for extrapolation procedures. The flow curves thus generated are compared considering the variety of plastic strains occurring in mechanical joining processes. The material data generated are implemented in simulation models for the joining technologies, clinching and self-piercing riveting. The influence of the varied methods on the predictive accuracy of the simulation model is analysed. The evaluation of the differing flow curves is achieved by comparing the geometric formation of the joints and the required joining forces of the processes with experimentally investigated joints.



    Development of a Method for the Identification of Friction Coefficients in Sheet Metal Materials for the Numerical Simulation of Clinching Processes

    M.S. Rossel, M. Böhnke, C.R. Bielak, M. Bobbert, G. Meschut, in: Sheet Metal 2021, Trans Tech Publications Ltd, 2021, pp. 81-88

    In order to reduce the fuel consumption and consequently the greenhouse emissions, the automotive industry is implementing lightweight constructions in the body in white production. As a result, the use of aluminum alloys is continuously increasing. Due to poor weldability of aluminum in combination with other materials, mechanical joining technologies like clinching are increasingly used. In order to predict relevant characteristics of clinched joints and to ensure the reliability of the process, it is simulated numerically during product development processes. In this regard the predictive accuracy of the simulated process highly depends on the implemented friction model. In particular, the frictional behavior between the sheet metals affects the geometrical formation of the clinched joint significantly. This paper presents a testing method, which enables to determine the frictional coefficients between sheet metal materials for the simulation of clinching processes. For this purpose, the correlation of interface pressure and the relative velocity between aluminum sheets in clinching processes is investigated using numerical simulation. Furthermore, the developed testing method focuses on the specimen geometry as well as the reproduction of the occurring friction conditions between two sheet metal materials in clinching processes. Based on a methodical approach the test setup is explained and the functionality of the method is proven by experimental tests using sheet metal material EN AW6014.



      Intrinsische Hybridverbunde für Leichtbautragstrukturen

      S. Sander, M. Bobbert, G. Meschut, Springer Vieweg, 2021, pp. 332


      Joining suitability of cast aluminium for self-piercing riveting

      M. Neuser, F. Kappe, M. Busch, O. Grydin, M. Bobbert, M. Schaper, G. Meschut, T. Hausotte, IOP Conference Series: Materials Science and Engineering (2021)


      2020


      Numerical analysis of the robustness of clinching process considering the pre-forming of the parts

      C.R. Bielak, M. Böhnke, R. Beck, M. Bobbert, G. Meschut, Journal of Advanced Joining Processes. (2020)


      Investigation of influencing parameters on the joint formation of the self-piercing riveting process

      F. Kappe, S. Wituschek, M. Lechner, M. Bobbert, G. Meschut, M. Merklein, 2020


      2019


      2016

      Tolerance Analysis of Adhesive Bonds in Crash Simulation

      G. Schwarzkopf, M. Bobbert, D. Teutenberg, G. Meschut, A. Matzenmiller, Procedia CIRP (2016), pp. 321-326


      On the Design, Characterization and Simulation of Hybrid Metal-Composite Interfaces

      R. Kießling, J. Ihlemann, M. Pohl, M. Stommel, C. Dammann, R. Mahnken, M. Bobbert, G. Meschut, F. Hirsch, M. Kästner, Applied Composite Materials (2016), pp. 251-269


      2013

      Simulation und Bewertung von Fertigungstoleranzen

      G. Kruschinski, A. Matzenmiller, M. Bobbert, D. Teutenberg, G. Meschut, adhäsion KLEBEN & DICHTEN (2013), pp. 38-43


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