CRYSTAL PLASTICITY - MICRO-SMEAR BANDING IN POLYCRYSTALS USING VORONOI TESSELLATION

A Taylor-type polycrystalline model, together with a new time-integrat ion scheme, has been developed and implemented into a finite element p rogram to simulate the development of micro shear bands in single- and polycrystal of fee metals. In order to take numerical advantages asso ciated with a symmetric stiffness matrix, the stiffness tensor which a rises from the crystal plasticity formulation is symmetrized and the c onstitutive equation is rearranged accordingly. It is shown that this approach yields significant reduction in computational time without af fecting the numerical results. The mesoscopic behavior of polycrystals is analyzed using Voronoi tessellation in which the randomness of the microstructure is generated using a Delaunay network from which a ran dom distribution of grains is generated. The use of 3-node and 4-node elements to analyze the phenomena of shear banding in polycrystals is investigated. It is shown that the use of triangular elements to captu re the shear banding phenomenon in polycrystals depends critically on the mesh design, since the resulting mesh is highly nonuniform. Howeve r, this problem is resolved by using a 4-node element with reduced int egration, illustrating the formation of micro shear bands in a polycry stal using a nonuniform mesh. (C) 1998 Elsevier Science Ltd. All right s reserved.