Multi-scale Simulation Of Powder Forming Process Based On FEM-DEM

In order to simulate the powder forming process accurately, the multi-scale method of coupling FEM and DEM is used in this dissertation. ANSYS/LS-DYNA and PFC2D are adopted and through secondary development, effective data delivery and orderly circular computation between them are achieved.This dissertation analyses macro-scale parameter, meso-scale parameter and micro-scale parameter of powder forming process, and studies the influence of pressing speed and powder properties on the parameters.The results show that the stress profiles in the die wall correspond to the force chain distributions in the powder particles. In the powder forming process, macro friction coefficient is not constant. The density distribution of granular system obtained from simulation correspond to the green density distribution introduced by Huang Peiyun, which proves the accuracy of the simulation results. The powder forming process includes three stages. In the first stage, granular system changes from loose packing state to tight contact state, and the variation range of meso-scale parameter and slip ratio is relatively large. In the second stage, small particles fill pore, and the variation range of meso-scale parameter and slip ratio is small, In the third stage, particles occur plastic deformation and even break, and the variation range of meso-scale parameter and slip ratio is almost none. Excepting slip ratio, the variation range of micro-parameter parameter is relatively small in the first and second stage, and becomes large in the third stage. In different stages, pressing speed has different effects on the parameters of powder forming process. Also, different powder property has different effects on same parameter.The simulation proves the accuracy of the multi-scale model established in this dissertation, and provides cogent reference for research and industrial production in the future.