A. Ma

A dislocation density based constitutive model for crystal plasticity FEM

Crystallographic slip, i.e. movement of dislocations on distinct slip planes, is the main source of plastic deformation of most metals. Therefore, it was an obvious idea to build a constitutive model based on dislocation densities as internal state variables in the crystal plasticity. In this paper the dislocation model recently proposed by Ma and Roters (Ma A. and Roters F., Acta Materialia, 52, 3603-3612, 2004) has been extended to a nonlocal model through separating the statistically stored dislocation and geometrically necessary dislocation densities. A nonlocal integration algorithm is proposed, which can be more easily used in conjunction with commercial software such as MARC and ABAQUS than the model proposed in the work of Evers(Evers L.P., Brekelmans W.A.M., Geers M.G.D., Journal of the Mechanics and Physics of Solids, 52, 2379-2401, 2004).

Experiments and Simulations on the micromechanics of single‐ and polycrystalline metals

Crystallographic slip, i.e. movement of dislocations on distinct slip planes, is the main source of plastic deformation of most metals. The Crystal Plasticity FEM combines this basic process with the Finite Element Method by assuming that the plastic velocity gradient is composed out of the shear contributions of all slip systems. To apply the method to forming simulation of “real” parts suffered from the fact, that a huge number of single orientations is needed to approximate the crystallographic texture of such parts. This problem was recently solved by the introduction of the Texture Component Crystal Plasticity FEM (TCCP‐FEM), which uses orientation distributions (texture components) for the texture approximation instead of single orientations. Excellent agreement of experiments and numerical simulations for different forming operations has shown the feasibility of this idea. Most crystal plasticity codes use simple empirical constitutive equations. However, as crystal plasticity is build on dislocati...