Three-dimensional microstructure-explicit and void-explicit mesoscale simulations of detonation of HMX at millimeter sample size scale

Abstract

Fully three-dimensional (3D) microstructure-explicit and void-explicit mesoscale simulations of the shock-to-detonation (SDT) process of pressed granular HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) are performed. The overall size scale of the models is up to 3 × 3 × 15 mm3, with ∼30 000 grains and 206 265 voids. The models account for the heterogeneous material microstructure, constituent distribution, constituent morphology, and voids. Loading conditions considered involve piston velocities in the range of 600–1200 m/s or pressures in the range of 4–8 GPa. The focus is on analyzing the SDT process and the effects of microstructure and voids on the run-to-detonation distance (RDD). Companion two-dimensional (2D) simulations are also carried out to assess the differences between 2D and 3D. Statistically equivalent microstructure sample sets (SEMSSs) are generated and used for both 2D and 3D, allowing the prediction of the statistical and probabilistic Pop plots (PPs). The predictions are in general agreement with trends in available experimental data in the literature. It is found that both the microstructure (heterogeneous grain size, morphology, and size distribution) and voids significantly affect the RDD and the PPs. These effects are systematically delineated and quantified via the use of SEMSSs with different combinations of attributes. A recently developed probabilistic formulation for the PPs is used to characterize the results, allowing uncertainties in the relations between the shock pressure and RDD arising from material heterogeneities to be quantified. The probabilistic formulation is further used to quantify the confidence levels in the ranked order of influences of different combinations of microstructure and voids on the PPs.

Computational Design of Three-Dimensional Multi-Constituent Material Microstructure Sets with Prescribed Statistical Constituent and Geometric Attributes

“…It is known that micro voids play a very important role in determining the SDT response of energetic materials [55]. However, macroscale simulations with explicit account of voids have been rare or non-existent.…”

“…This distance as a function of applied shock pressure (called Pop plot) is a well-established macroscopic measure of the SDT threshold of energetic materials. Such 3D SEMSS have been used by Miller et al [55] to predict the macroscopic SDT threshold as functions of microstructure and void attributes. This is the first time such a 3D simulation has been carried out at the mm size scale, as far as we are aware of.…”

“…When D < 1 or D > 1 , the data point falls below or above the 50% line, respectively. The probability distribution for UQ analyses in the entire distance-pressure space is [55] where H is a material-dependent scaling parameter, m is a material-dependent exponent, x * is the run-to-detonation distance, P s is the shock pressure, and d is the standard deviation of the data about the Pop plot line. P 0 is the shock pressure below which no SDT occurs, and x * 0 is the theoretical minimum run distance for observing SDT.…”

“…More details on how the 3D and 2D SEMSS designed using the capability (4) presented in this paper can allow the multiphysics ME and VE simulations, prediction of microscopic behaviors, and probabilistic UQ are given in Refs. [3,17,29,55].…”

Systematic Builder for All‐Atom Simulations of Plastically Bonded Explosives

“…To bridge the gap between atomistic simulations and experimental measurements, continuum and mesoscale work have also been applied to model hotspot formation mechanisms such as pore collapse, crack propagation, and friction [25,[46][47][48][49][50]. These simulations have been used to characterize simple isolated defects or microstructural features [51][52][53][54][55][56] and also realistic microstructures [57][58][59][60][61][62]. However, these methods necessarily approximate many of the underlying mechanisms responsible for energy localization, including localized plastic deformation, amorphization, jetting, pore collapse, and recompression.…”