Microstructural influences on growth of short cracks in steel under cyclic loading III
The project shall finalize the work performed on the same topic. One of the main purposes of this project is to develop a microstructural model for the simulation of fatigue micro crack growth. In the previous work, a mechanism-oriented crystal elastoplasticity model was developed, where the orientations of involved grains were considered. This model could successfully predict the initiation site of cyclic microcracks generated in interrupted cyclic bending tests. Additionally, in-situ cyclic bending tests under scanning electron microscope (SEM) observation were performed, where crack initiation and propagation at a notch tip could be analyzed in relatively high precision. These tests shall continue in the upcoming project period. The results of these tests shall be used in the final validation of the model in development. Furthermore, cyclic tests under digital image correlation (DIC) observation were performed and shall be enhanced by using ARAMIS measurement system. The latter experiments were performed on coarse-grained pure iron specimens for the purpose of parameter validation of the cyclic crystal plasticity with a kinematic hardening model for ferrite. For practical analysis of the influence of several microstructural features on the initiation and growth of short cyclic microcracks, the virtual microstructure model generator code based on weighted Voronoi tessellation, first developed in the IEHK-05-01 project, will be further developed and implemented in computations with the cyclic crystal plasticity model once validated.