ON THE COLD COMPACTION OF POWDERS

Constitutive models are developed for stage I cold compaction of powders under general loading. Densification is assumed to occur by plastic deformation at the isolated contacts between particles. The shape of the yield surface is found to be sensitive to the cohesive strength between particles and to be less sensitive to the degree of inter-particle friction. An internal state variable model is used to describe the evolution of anisotropy under general loading. The theory assumes that the distribution of contacts between particles can be approximated by a second order tenser BI a prescription is given for updating B as deformation proceeds. The predicted compaction behaviour for a state of uniaxial strain is in good agreement with experimental observations reported in the literature.