Modelling of plasticity and damage in a polycrystalline microstructure

The mesomechanical behavior of a polycrystalline microstructure subjected to monotonic and cyclic loadings is investigated. The analysis is based on a Voronoi polygonization strategy for generation of grains embedded in a contiguous matrix. The main emphasis is to investigate the interaction between the microconstituents and the failure processes along grain boundaries. A rational interface theory based on damage development coupled to inelastic slip and dilatation is developed. The theory uses the interface width as a constitutive parameter, which regularizes the theory of LEMAITRE [1992], that is restricted to perfect bond between grain and matrix. In a series of FE-analyses parameter variations were performed: The unit cell size (as compared to the average grain diameter), the grain-matrix area ratio, the interface width and constitutive parameters. It appears that the composite behavior can be designed as brittle or ductile solely depending on the strength and rate of damage development in the interfaces. A localization band was detected, and its orientation is in the range that is predicted within continuum theory.