Micromechanical modeling of strength of tempered martensitic steels based on crystal plasticity
PhD Thesis, Ruhr-Universität Bochum (2016)
In tempered martensitic steels, the mechanical properties are highly dependent on the orientation and morphology of microstructural entities (laths, blocks and packets). These relationships are investigated by crystal plasticity finite element modeling (CPFEM) of these microstructures. The mechanical properties of simplified representative volume elements (RVE) have been computationally homogenized by using CPFEM and macroscopic response is evaluated through volume averaging. Yield surfaces are calculated for various RVEs with different microstructures. In these steels, the size of microstructural features directly influences the materials strength. Therefore, size effects are also investigated by using the non-local CP model via GND hardening. Furthermore, due to the bcc nature of lath martensitic steels, a non-Schmid constitutive model is utilized. So that the influence of non-Schmid stress contributions can be investigated to model material behavior close to experiments.
Keyword(s): finite element method; crystal; martensite; microstructure