TR73

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C2 - Material Model (funding period 2)



Development of a material model for metal sheets at finite deformation

Project Status: finished

Last Update: 23.01.2017



Members


Within their granular microstructure, metals show crystalline nature: the atoms are arranged on a regular space lattice. The macroscopically observable plastic deformation can be traced back to shearing or sliding of atoms on defined slip planes in the crystal. Depending on the present structure, predictions can be made about the slip behaviour. At the same time, crystal grains can be observed in the microstructure; regions, where atomic dislocation movements in the same directions take place and at whose borders atoms can pile up.
 
 

                         survey_photo                             EBSD_01_DC04

                            Real microstructure of a DC04 steel                                                 EBSD image of a DC04 steel

 

A suitable material model considering plastic anisotropy through atomic dislocations is to be found on the microstructural level, whereas the elastic and plastic material parameters will be determined in cooperation with the research project C4. For the representative volume elements, randomly distributed geometries on the microscale are assumed, based on the received microstructural data. Through homogenisation, effective stress-strain relations are gained for different boundary conditions being the outcome for an effective material model. After an assumption for an effective material model has been made, the material parameters have to be determined through optimisation techniques. The results obtained by simulations will be validated with experimental data obtained from material specimens and formed structures.

 Displacement field around crack in poly crystal

Displacement field around crack in poly crystal

Another critical effect occurring during the forming process is the initiation and propagation of microcracks. This effect will lead to a stiffness reduction or even to failure of the entire structure. Therefore it is essential to study the degradation mechanisms of the crystallographic microstructure. A nonlocal damage model will be used to induce microcracks. For propagating the crack existing models have to be extended to nonlinear anisotropic and inelastic materials. Especially a criterion has to be found when cracks collide with grain boundaries. For the case of stable crack growth with a statistical simulation series a representative volume element can be found. This is used to produce a micromechanically motivated stress strain relationship by a homogenization procedure. With this material response the effective material model of period 1 of the SFB/TR73 will be extended. Here it is important to capture the softening effects with a nonlocal damage model which is for example used and developed at the IUL.

In a last step the two approaches will be combined for the construction of a material model capturing thermomechanical effects and cracks on the microstructural level.


Working Groups


Publications

    2016

    • Löhnert, S.; Beese, S.: A regularization technique for the XFEM: extension to finite deformations, inelastic material behaviour and multifield problems. In: Proceedings in Applied Mathematics and Mechanics, 16(2016), Wiley, pp. 153 - 154
    • Beese, S.; Löhnert, S.; Wriggers, P.: Modeling of Fracture in Polycrystalline Materials. In: Formaggia, Luca, Pedregal, Pablo (Edt.): SEMA SIMAI special issue on extended discretisation methods, 12(2016), Berlin, New York, Heidelberg: Springer, pp. 79-102
    • Beese, S.; Beyer, F.; Blum, H.; Isik, K.; Kumor, D.; Rademacher, A.; Tekkaya, A.; Willner, K.; Wriggers, P.; Zeller, S.; Löhnert, S.: Simulation of Sheet-Bulk Metal Forming Processes with Simufact.forming using User-Subroutines. In: ESAFORM (Edt.): Proceedings of the 19th International ESAFORM Conference on Material Forming, DOI: 10.1063/1.4963457, (2016), Nantes, Frankreich, published

    2015

    • Zeller, S.; Beese, S.; Gerstein, G.; Isik, K.; Löhnert, S.; Nürnberger, F.; Wriggers, P.; Maier, H.; Tekkaya, A.: Möglichkeiten der simulativen Vorhersage von Temperaturentwicklung und Bauteilversagen infolge plastischer Deformation bei DP600 Bauteilen. In: Tekkaya, A. E.; Liewald, M.; Merklein, M.; Behrens, B.-A. (Edt.): Tagungsband zum 18. Workshop Simulation in der Umformtechnik & 3. Industriekolloquium Blechmassivumformung 2015 - DFG Transregio 73, (2015), Aachen: Shaker Verlag, pp. 113-128
    • Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling thermoplastic material behaviour of dual-phase steels on a microscopic length scale. In: Proc. Appl. Math. Mech., 15(2015)1, pp. 373 - 374
    • Löhnert, S.: Stabilizing the XFEM for static and dynamic crack simulations. In: G. Zavarise, P. Cinnella and M. Campiti (Edt.): PAMM - Proc. Appl. Math. Mech., 15(2015)1, WILEY-VCH Verlag, pp. 137-138
    • Beese, S.; Löhnert, S.; Wriggers, P.: 3D Ductile crack propagation with the XFEM. In: G. Zavarise, P. Cinnella and M. Campiti (Edt.): PAMM - Proc. Appl. Math. Mech., 15(2015)1, WILEY-VCH Verlag, pp. 747-748

    2014

    • Dr.-Jürgen-Ulderup-Preis. In: Preis für herrausragende Leistungen in der Promotion, (2014), published
    • Lehmann, E.: Dr.-Jürgen-Ulderup-Preis. In: Dr.-Jürgen-Ulderup-Stiftung (Edt.): Preis für herrausragende Leistungen in der Promotion, (2014), published
    • Lehmann, E.: Dr.-Jürgen-Ulderup-Preis. In: Dr.-Jürgen-Ulderup-Stiftung (Edt.): Preis für herrausragende Leistungen in der Promotion, (2014), Hannover: Dr.-Jürgen-Ulderup-Stiftung, published

    2013

    • Lehmann, E.; Faßmann, D.; Löhnert, S.; Schaper, M.; Wriggers, P.: Texture development and formability prediction for pre-textured cold rolled body-centred cubic steel. In: International Journal of Engineering Science, 68(2013), pp. 24-37
    • Faßmann, D.; Isik, K.; Zeller, S.; Beese, S.; Nürnberger, F.; Schaper, M.; Tekkaya, A.; Löhnert, S.; Wriggers, P.: Abbildung des Werkstoffverhaltens von ferritischem Stahl in numerischen Modellen zur Darstellung von Blechmassivumformprozessen bei zyklischen Belastungspfaden. In: M. Merklein, B.-A. Behrens, A.E. Tekkaya (Edt.): Tagungsband zum 2. Erlanger Workshop Blechmassivumformung 2013, (2013), pp. 69-84
    • Lehmann, E.: Computational homogenisation of polycrystalline elastoplastic microstructures at finite deformation. In: Prof. Dr.-Ing. habil. Dr. h.c. mult. Peter Wriggers (Edt.): Dissertation, (2013)2, Hannover: Institut für Kontinuumsmechanik, published

    Presentations

      2016

      • 08.03.2016: Löhnert, S.: A regularization technique for the XFEM: extension to finite deformations, inelastic material behaviour and multifield problems, GAMM Annual Workshop
      • 27.04.2016: Kumor, D.: Simulation of Sheet-Bulk Metal Forming Processes with Simufact.forming using User-Subroutines, 19th ESAFORM Conference, Nantes, Frankreich

      2015

      • 31.01.2015: Zeller, S.; Löhnert, S.; Wriggers, P.: Modellierung der Temperaturentwicklung während der Blechmassivumformung unter Berücksichtigung der Mikrostruktur des Werkstoffes, Norddeutsches Mechanik-Kolloquium, Hannover, Germany
      • 27.03.2015: Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling the Thermoplastic Material Behaviour of Dual-Phase Steels on a Microscopic Length Scale and Deducing Corollaries for Material Models on a Macroscopic Length Scale, GAMM 2015, Lecce, Italy
      • 06.05.2015: Beese, S.: Duktiler Rissfortschritt mit der XFEM, http://cfrac2015.sciencesconf.org/
      • 13.05.2015: Löhnert, S.; Zeller, S.; Wriggers, P.: Modelling the Thermomechanical Behaviour of the Polycrystalline Microstructure of Dual-Phase Steels during Sheet-Bulk Metal Forming, ICM 2015, Karlsruhe, Germany
      • 02.09.2015: Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling the Thermoplastic Material Behaviour of Dual-Phase Steels on a Microscopic Length Scale and Deducing Corollaries for Material Models on a Macroscopic Length Scale, COMPLAS 2015, Barcelona, Spain
      • 02.09.2015: Wriggers, P.; Zeller, S.; Löhnert, S.: Multiscale Analysis Applied to Material Modeling, COMPLAS 2015, Barcelona, Spain
      • 10.09.2015: Beese, S.: Rissfortschritt in polykristallinen Materialien, http://x-dms2015.sciencesconf.org/

      2014

      • 11.03.2014: Beese, S.; Löhnert, S.; Wriggers, P.: Nichtlokale Modellierung duktiler Schädigung für elasto-plastische Materialien unter großen Deformationen, GAMM
      • 11.03.2014: Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling the temperature development during sheet-bulk-metal forming considering the microstructure of the material, GAMM 2014, Erlangen, Germany

      2013

      • 19.03.2013: Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling the temperature development during sheet-bulk-metal forming using material isomorphism, GAMM 2013, Novi Sad, Serbia
      • 04.09.2013: Zeller, S.; Löhnert, S.; Wriggers, P.: Modelling the temperature development during sheet-bulk-metal forming using material isomorphism, COMPLAS 2013, Barcelona, Spain
      • 12.09.2013: Beese, S.; Löhnert, S.; Wriggers, P.: Modellierung von Rissen in elastoplastischen Materialien unter großen Deformationen, XFEM
      • 01.10.2013: Beese, S.; Löhnert, S.; Wriggers, P.: Modellierung von Rissen in elastoplastischen Materialien unter großen Deformationen,