Plastic deformation and yield criterion for compressible sintered powder materials

This paper analyses the basic aspects of plastic deformation behaviours of compressible sintered powder materials, such as plastic volume change, mass constancy, small Poissonʹs ratio and the effect of hydrostatic pressure on yield. Based on the uniaxial compression tests using sintered powder copper as a model material, the true stress–strain equation, a generalized yield criterion and some plastic constitutive equations for compressible sintered powder materials are proposed. The proposed generalized yield criterion can depict both the initial yield and successive yield of compressible sintered powder materials in the form of unified yield function, and reflect comprehensively the effects of initial density and deformation strengthening on yield of compressible sintered powder materials as well. Experiments show that the generalized yield criterion can be applied to materials with various densities from loose powder to fully dense metal.