A FINITE-ELEMENT SIMULATION OF POWDER COMPACTION CONFIRMED BY MODEL-MATERIAL EXPERIMENTS

Uniaxial compaction of powders is studied theoretically for plane-strain conditions, the analysis being focused upon the material flow into the holes between the powder particles. The original powder material is assumed to be built up of close packed cylinders of equal size. With this configuration, it is found sufficient to analyze the deformation of one elementary cell. The investigation is carried out by means of step-wise calculations, starting with a pore volume fraction of 16% and finishing at approximately 1.6%. The investigation is based upon a finite-element approach. After each step the deformed elementary cell is remeshed in accordance with its new shape. The agreement between the material flow as determined from plasticine experiments and that from the finite-element analysis, which latter incorporates the plasticine constitutive equation, is good. Theory and experiment are in acceptable agreement also in respect of the step-wise change of shape of the boundary surfaces defining the holes. Encouraged by this agreement, theoretical results are presented also for a linear viscoplastic material and hot, pure aluminium. It is concluded that the material flow is very sensitive to the mechanical properties of the material, such as the flow stress and its dependence of the strain rate.