Variant of the plasticity condition for powdered solids

A plasticity criterion is proposed for powdered materials to account for th e local character of slip and plastic deformation of the particles. The deg ree of localization of the contact interaction between the panicles is quan titatively evaluated by using the relative fraction of the active volume, a fter M. Yu. Balshin. Good agreement is obtained between the theoretical and experimental data in describing of the process of the isostatic pressing o f spherical powders of lead and tin. The effect of the density of the mater ial and pressure on the form of the yield surface and the character of the volume dt formation is examined. A method is presented for determination of the empirical parameters of the plasticity criterion. These parameters are evaluated for sand.