Grain-Resolving Simulation of Mock-High-Explosives with Ratel Implicit MPM

Abstract: Ratel is a matrix-free, high-order, implicit finite element (FEM) and material point method (MPM) solid mechanics package. In this work, Ratel is used to simulate consolidation experiments for mock plastic-bonded explosives (mock-PBX) manufacturing. The consolidation experiments consider the confined compression of a 5 mm-diameter cylindrical die filled with prills—clumps of crystalline mock-high-explosive grains coated with a nitro-plasticized polymer binder. Due to the granular nature of the materials, the irregular distribution of each material within the sample, and the presence of large voids, the material point method is well-suited to this problem. The distribution of grain size is bimodal with peaks between 150-300 um and less than 45 um; thus, resolving the fine grains requires on the order of 1 billion material points. We discuss the methods for initializing material properties from voxelized computed tomography (CT) data and tracking deformation of the material points, challenges of scaling to hundreds of millions of points, and current simulation results.