부산대학교 도서관

A dislocation density based crystal plasticity model is used to simulate sheet metal forming processes under different temperature. In the present model, dislocation densities in each slip system are taken as internal state variables. An extended Kocks-Mecking-Estrin evolution law is adopted to describe the athermal storage, and the strain rate and temperature sensitive annihilation, of dislocation densities. The critical resolved stress on a specified slip system is related with dislocation densities in all slip systems, the corresponding mesoscopic coefficients of interaction between different slip systems are determined by recent dislocation dynamics simulations. On the basis of thermally activated dislocation motion, this physically based model is capable of describing the softening resulted from dynamic recovery. This model incorporated with a hyperelastic constitutive law is then implemented into an explicit finite element code, to make it deal with the strong nonlinear problems more efficiently. An iteration-free semi-implicit method, which is more suitable for explicit FEM, is adopted as the integration algorithm of the model. This model is used to investigate the deformation characteristics of warm forming of Al-Mg alloy under different temperatures. The simulation results show that the model is robust and efficient, has the potential to be used in the practical engineering simulation. It also confirms that the micromechaincs models can be used to simulate conventional sheet metal forming.