PERTURBATION ANALYSIS OF EXTRUSION OF POROUS METAL MATERIALS

In this paper nn analysis of the axisymmetric extrusion process of por ous metal materials is presented using the regular perturbation theory . Gurson's plasticity is employed to simulate the constitutive behavio r of the porous metal whose matrix is presumed rigid-perfectly-plastic . Combining Coulomb's model with Siebel's model a new model of frictio n is proposed to take into account the friction forces at the die-work piece interface. Assuming that the die tapers slowly down the extrudin g axis, the original problem is reduced to a mathematical model which is solved using a regular perturbation method. The perturbed expressio ns of the velocity components and stress components as well as porosit y are calculated. Numerical results are finally given to show the vari ations of the field variables with the die parameters and the initial porosity in the metal material.