3D modeling of material microstructure and crystal plasticity finite element simulation

Three dimensional polycrystalline aggregate models with random grain shapes are generated by Voronoi diagram method and the crystal orientation is assigned for each grain. A user defined material subroutine (UMAT) developed based on rate-dependent crystal plasticity theory is embedded into the finite element software to simulate the stress-strain response of FCC material during uniaxial tension, and the effects of the mesh refinement and the crystal orientation on simulation results are investigated. The results indicate that the magnitude of stress reduces slightly with the mesh refinement and no less than five elements should be used to averagely disperse per grain to ensure the reliability. The differences between stress-strain response caused by the random orientations become smaller with the increase of grain number in the polycrystalline aggregate, and it is reasonable that the aggregate is composed of more than 50 grains. The simulation result agrees well with the experimental data and the true stress becomes higher with greater strain rate which indicates a high reliability of the model.