Graduate School

Project A12: Thermomechanical Homogenization of Multi-Phase Steels

Person in Charge: Dipl.-Ing. Florian Rieger
  Motivation and goals:
Up to the present date, the effective thermomechanical properties of dual-phase steels cannot be sufficiently reproduced by micromechanical Models. Within this project, the thermomechanical material behaviour of dual-phase steels will be modelled based on a non-linear homogenization method of the Hashin-Shtrikman type.
Therefore, the intrinsic hardening behaviour and the grain size of the ferrite matrix are taken into account together with the volume content and the grain size of the martensite inclusions. The model will be used for single gauss-point calculations within the finite element method. The final aim of the project is the two-scale strongly coupled simulaton of complete structure parts.  
Examinations Findings
Firstly the actual dislocation state after the austenite-martensite phase transformation will be examined. In order to create a sufficient statistical description of the material the grain size distribution will be taken into account as well. Beside these properties, also texture development will be modelled in later stages of the project. To enable a two-scale strong coupling, the local thermomechanical interaction of the problem will be realized on the microscale and within the homogenization. In view of all following simulations a first step was the implementation of the non-linear Hashin-Shtrikman homogenization scheme for the commercial finite element tool ABAQUS. Initial simulations indicate, that the influence of the grain size distribution is within the same order of magnitude as the effect of plastic material anisotropy itsself. Influence and mathematical description of the martensite morphology are the scope of recent examination. Dislocation based hardening models are formulated in terms of morphology parameters.