Upper Bound Theory for Deformation of Porous Materials

Abstract

A porous material is idealized in such a way that it possesses an identical yield surface for any volume element throughout the material during a deformation processing. This makes it possible to derive an upper bound theorem on the basis of the plasticity theory for porous metals already proposed by the authors. The theorem is utilized to estimate extrusion pressures and the final density ratios for given initial densities. The estimated values agree well with experimental data. An alternative way of deriving an upper bound to the load is also presented on a modified yield criterion for porous metals.