| The processing of powder metallurgy (P/M) metals represents an integral part of the manufacturing industry. The finite element method (FEM) has evolved into a very useful tool for the simulation of P/M forging processes. The key to the successful application of the FEM is the use of accurate models to describe the mechanical and metallurgical aspects during powder forging (PF). The focus of this work is on the finite element simulation of the PF operation.; The yield criteria for porous materials are reviewed and finite element plasticity equations are developed for a general ellipsoidal yield function. The ellipsoidal yield functions considered were the ones developed by Shima and Oyane, Doraivelu et al., and Gurson (quadratic approximation). Associated flow was assumed. The three yield functions were compared in terms of their mechanical response.; Several numerical simulations of PF are presented. The simulations show good agreement with available experimental data and numerical results cited by various researchers and provide valuable information which can be used to better understand the process variables like flow patterns, density distributions, stress/strain gradients, temperature distributions, and forging loads.; The predictions from the Shima and Oyane yield function are higher than the predictions of the Doraivelu et al., yield function and the quadratic approximation of the Gurson yield function--for hydrostatic pressure, relative density, forging pressures, and strains. The quadratic approximation does not seem to be an accurate model unless the initial relative density of the preform is more than 0.95. |
