Modeling of large scale plastic deformation during VIPIR experiment

During the VIPIR (Viscoplastic flow Ignition and Propagation Imaging of Reactions) experiment, the kinetic energy of falling weight is transferred into the sample resting on the anvil. The sample consisting of particles of explosive crystals experiences compaction and large scale plastic deformation, followed by melting, flow, and possible ignition. We use Eulerian finite element analysis to simulate the large scale plastic deformation in a cyclotrimethylene trinitramine sample. We develop an axisymmetric finite element model and use a newly proposed rate form of a dislocation density-based continuum model by Luscher et al., which is suitable for Eulerian analysis. The simulations predict localization of plastic deformation in form of shear bands. The temperature increase is caused by plastic dissipation, and shear bands coincide with high temperature regions. We propose that the plastic anisotropy causes appearance of shear bands in our simulations.