Aspects of simulating the dynamic compaction of a granular ceramic

Abstract

Mesoscale hydrodynamic calculations have been conducted in order to gain further insight into the dynamic compaction characteristics of granular ceramics. With a mesoscale approach each individual grain, as well as the porosity, is modeled explicitly; the bulk behavior of the porous material can be resolved as a result. From these calculations bulk material characteristics such as shock speed, stress and density have been obtained and compared with experimental results. A parametric study has been conducted in order to explore the variation and sensitivity of the computationally derived dynamic response characteristics to micro-scale material properties such as Poisson's ratio, dynamic yield and tensile failure strength; macro-scale parameters such as volume fraction, particle morphology and size distribution were explored as well. The results indicate that the baseline bulk Hugoniot response under-predicts the experimentally measured response. These results are sensitive to the volume fraction, dynamic yield strength and particle arrangement, somewhat sensitive to failure strength and insensitive to the micro-scale Hugoniot and grain morphology. A discussion as to the shortcomings in the mesoscale modeling technique, as well as future considerations, is included.

Stress and temperature distributions of individual particles in a shock wave propagating through dry and wet sand mixtures

“…As discussed in literature [1], the difference in volume fraction affects the overall shock response. The volume fractions for each experimental impact are: 66% for 413 mps, 64% for 618 mps, 65% for 754 mps, 65% for 998 mps, and 66 % for 1430 mps.…”

“…The setup in this document is proven in literature and validated by experiments when observing the heterogeneity of granular materials [1,[5][6]. The simulations used a smaller domain in comparison to experiments to reduce computational time.…”

“…The "SLIDE" option sets the shearing gradients of mixed cells to zero and is indicative of what happens during a shock event for heterogeneous granular materials [6]. For the quartz particles, we assigned a Mie Grüneisen equation of state (EOS) along with a Von-Mises strength model with parameters and yield strengths found in literature and included with CTH [5,[8][9][10][11][12][13] The resolution maintained throughout the computational domain follows from literature [1], in that ten cells across each grain allows for convergence to a solution. Tracers placed at the driver sand interface, inside the sand, and at the sand window interface, helped to mimic the experimental setup as well as develop the shock Hugoniot states; each location contained 100 tracers.…”

“…This can include stress distributions of dynamically shocked granular ceramics [1] or even the temperature field of dynamically compacted industrial powders [2] to determine sintering. Currently, experimental measurement methods provide limited information in determining the stress and temperatures of individual particles during a dynamic loading event.…”

Mesoscale simulations of granular materials with peridynamics

“…Insight into the fine scale behavior relevant to the dynamic response of granular materials via computational mesoscale modeling at the scale of grains was pioneered by Benson [3] and later explored using Eulerian hydrodynamic calculations [4][5]. While the results of these studies have shown general agreement with experiment, the Eulerian framework lacks grain-to-grain contact dynamics and fracture.…”