Effect of micro-structure on yield strength of porous solid: A comparative study of two simple cell models

An objective of this paper is to estimate an extent to which the yield strength of a powder compact is affected by its micro-structure. For this purpose, two opposite idealized structures of porous solid were investigated numerically. The first of them is a continuous matrix with isolated spherical pores simulating micro-geometry of the products obtained by the free sintering technology. The second one, being an array of spherical particles with isolated finite-sized contact spots, is typical for the powder compacts produced by cold pressing or intensive electro sintering. Their comparative study shows that the yield strength of porous solid is rather structure-sensitive and, therefore, the micro-structure parameters (and their evolution during consolidation) should be incorporated in the model in order to provide adequate description of their elastic-plastic behavior. It is found that behavior of both the considered materials can be described satisfactory by the Gurson-Tvergaard-Needleman (GTN) model. Numerical study shows that the coefficients entering the GTN-model are structure-dependent and, hence, can be effectively used as the internal state variables of porous solid. It opens a way of utilizing the available GTN-model based finite element software in computer simulation of the powder metallurgy technologies, with adequate account for micro-structure evolution of the consolidated powder compacts. (C) 2007 Elsevier B.V. All rights reserved.