Experimental determination of the modified Drucker-Prager cap constitutive model for KMS-92 alumina powder

Forming process of powders accompanies considerable volume change and complicated material flow. Understanding powder behavior and the ability to perform its deformation analysis may assist in reducing trial and error in die design process and providing more accurate predictions of forming loads and density distribution in the green part. Such analyses are feasible only based on the constitutive models for powder compaction. Modified Drucker-Prager cap (MDCP) mode, is a multi-surface yield model for description of the plastic behavior of powders during consolidation. In this research, the deformation behavior of the commercial ready to press alumina powder KMS-92 has been investigated using MDCP model. To this end, parameters of MDCP model as functions of density were obtained by means of experiments. The constants of the shear failure yield surface were obtained based on simple diametric and axial compressive loading cylindrical specimens with various relative densities. For determining the remaining parameters of the model, an instrumented die fitted with strain gage and load cell was designed and fabricated. Parameters of the cap surface were achieved based on the uniaxial die compaction experiments. Based on consecutive loading-unloading tests using the instrumented die, the friction coefficient and elastic moduli were derived from loading and unloading phases respectively. For finite element simulation of the uniaxial compaction, density dependent material parameters were employed in Abaqus. The variations of density were taken into account using USDFLD subroutine Simulation results prove a very good agreement with the experimental counterpart.