Kinetics and stability in compressive and tensile loading of porous bodies

The continuum theory of sintering is used for the analysis of the kinetics of compressive and tensile loading (forging, drawing, isostatic pressing, etc.) of a cylindrical powder specimen. The constitutive properties of the powder material are assumed to be nonlinear viscous, corresponding to the power-law creep mechanism. The calculations are conducted for various models developed for the description of the deformation processing of viscous porous materials. The calculation results for uniaxial compression are compared with the experimental data on forging of stainless steel 304 porous specimens. Both linear and nonlinear stability analyses are carried out. Stability criteria are derived for uniform and nonuniform porosity perturbation modes and for two different kinds of boundary conditions: constant axial force and constant imposed cross-head velocity under uniaxial loading. Stability maps are obtained for forging of copper powder components.