Computational Analysis of a Shear Punch Test

摘要

The intense shearing that occurs in propellants and explosives during impulsive loading can lead to initiation. In an effort to determine useful shear initiation criteria, the U.S. Army Research Laboratory (ARL) has developed a shear punch test using a modified Kolsky bar. Varying the striker bar's velocity and length controls the shear rate and duration. Shear velocities approaching 100 m/s and durations as long as 200 microns are possible. Experimental results have been obtained for several energetic materials and a nonreacting polymer, polycarbonate (PC). This report presents a detailed computational analysis of the shear punch test using the Arbitrary- Lagrangian-Eulerian code ALEGRA. The inert PC was selected for this preliminary study since a more complete set of dynamic property data is available for this material. The validity of a conventional viscoplastic constitutive relation and the failure criterion for PC is determined based on their ability to predict the observed mechanical response. An alternative viscoelastic-plastic model is presented for improving the predicted material response.