| Description |
By using mesoscale simulations of realistic synthetic microstructures combined with new material-point-method (MPM) techniques, this work aims to improve the understanding of ceramic material failure under high-rate loading. Aluminum oxynitride (AlON) is chosen as the ceramic material of interest, due to the benefit of its optical transparency for experimental analysis, as well as its unusually large grain size. To characterize the AlON, two samples, each a one millimeter cube, are analyzed using high energy X-ray direction microscopy (HEDM). From these experiments, the three-dimensional grain geometries and orientations are extracted. The relevant statistics from these microstructures are used for the construction of statistical volume elements (SVEs), which are then exported as voxels or surface-based geometry descriptions. New techniques are established to import the grain geometries into Uintah [1], which is an open-source MPM code from the University of Utah. The synthetic microstructures are then used in simulations under a variety of loading conditions. A convicted-particle tetrahedron interpolation (CPTI) method allows for the more accurate description of complex geometries that closely match the actual shapes and structures of real-world events. Since each CPTI particle domain is a tetrahedron, a new conforming- boundary triangle-integration (CBTI) technique is developed to replace the spuriously ragged (stair-stepped) surfaces of raw voxel data with smoother triangular tessellations, which facilitate modeling contact and friction between particle domains. Subsequent mesoscale simulations of ceramics using the new CPTI technique with frictional contact model the deformation of synthetic grains and failure in a statistical volume element (SVE). The results are used (hierarchically) to inform the macroscale material response of ceramic materials. This is the rest study to investigate the effect of mesoscale models utilizing a convicted- particle tetrahedron interpolation technique in the material-point method. The simulated material grain response under various loading conditions is demonstrated for AlON. The inclusion of a three-dimensional mesoscale model of aluminum oxynitride using HEDM reconstruction, synthetic generation, and simulation in the MPM has not been attempted before. A better understanding of the mesoscale (grain-scale) response of brittle materials will greatly enhance the current macroscale plasticity modeling capabilities. The techniques developed combine the benefits of both traditional Eulerian and Lagrangian modeling into an efficient and novel MPM code capable of simulating a wide variety of physics and dynamic events. The use of a large variety of mesoscale grain geometries and orientations greatly improves the statistics for macroscale ceramic models in any code. |
