The extrapolation of the Drucker-Prager/Cap material parameters to low and high relative densities

The present study explores new approaches to extract Drucker-Prager/Cap (DPC) constitutive model parameters at low and high densities of compacted powders for which it is not possible to get solid, undamaged samples for model calibration purposes. Extrapolations were carried out by invoking a number of physically plausible assumptions for high density conditions and the addition of the experimental shear cell testing procedure for low density extrapolations. The effects of these extrapolations on finite element model (FEM) results of both die compaction and roller compaction were examined. The sensitivity of the extrapolated DPC parameters on compaction model results was explored by performing parametric studies for both low and high density extrapolations. Examination of die compaction model results for low density showed little sensitivity to extrapolations; however, we are able to show that extrapolations of DPC parameters to low density may have a significant effect on roller compaction modeling results. High density die compaction FEM simulations reveal a significant effect on the way in which the DPC model parameters are extrapolated to high density. A method of extrapolating the DPC model parameters to high density is presented in this work. The work presented here demonstrates the significance of properly calibrating the DPC model at low and high densities and provides the necessary guidance for this purpose. (C) 2015 Published by Elsevier B.V.