Sensitivity of pore collapse heating to the melting temperature and shear viscosity of HMX

Kroonblawd, Matthew P.; Austin, Ryan

doi:10.1016/j.mechmat.2020.103644

Cited by 36 publications

(91 citation statements)

References 33 publications

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“…Melting places an upper temperature limit on plastic work, which serves as a primary source for energy localization at hot spots and in shock heating of bulk crystal. In the case of HMX (octahydro-1,3,5,7tetranitro-1,3,5,7-tetrazocine), estimates of the melt curve based on the Lindemann law [32] were shown to be substantially lower than predictions obtained from MD simulations at GPa-range pressures [24]. Application of MD-derived melt curves for HMX [24] and TATB (1,3,5-triamino-2,4,6-trinitrobenzene) [21] in grain scale simulations of supported shocks were shown to effectively suppress melting during the collapse of micron-and sub-micron scale pores [24,28,29].…”

Section: Introductionmentioning

confidence: 94%

“…Parameters for these properties are often difficult to isolate in focused experiments at high pressures and temperatures so placeholder values are often used in grain scale models. All-atom modeling using molecular dynamics (MD) simulations has proven to be a robust tool for obtaining many of these missing material parameters [15][16][17][18][19][20][21][22][23][24]. Scale bridging between atomistic and grain scale simulations at commensurate…”

Section: Introductionmentioning

confidence: 99%

“…[a] M. P. Kroonblawd length and time scales has recently been used to calibrate and validate grain scale model terms through direct comparison [25][26][27][28][29][30][31]. Despite the promise of a one-and-done approach to calibration through scalebridging simulations, it is often more advantageous to gradually increase grain scale model complexity and independently determine physics terms due to the highly coupled and nonlinear nature of dynamic material response [24,28,29]. This is especially true for material parameters that vary significantly within the applicable temperature and pressure domain such as the melt curve and liquid shear viscosity [15,21,24].…”

Section: Introductionmentioning

confidence: 99%

“…Despite the promise of a one-and-done approach to calibration through scalebridging simulations, it is often more advantageous to gradually increase grain scale model complexity and independently determine physics terms due to the highly coupled and nonlinear nature of dynamic material response [24,28,29]. This is especially true for material parameters that vary significantly within the applicable temperature and pressure domain such as the melt curve and liquid shear viscosity [15,21,24]. We focus here on obtaining predictions for two key physics terms influencing hot spot formation, namely the melt curve and liquid shear viscosity, for the explosive RDX (hexahydro-1,3,5-trinitro-s-triazine) to near detonation conditions where there is a lack of data to parametrize and constrain grain scale models.…”

Section: Introductionmentioning

confidence: 99%

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Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Kroonblawd

Springer

2021

Preprint

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Recent grain scale simulations of HMX and TATB have shown that predictions for hot spot formation in high explosives are particularly sensitive to accurate determinations of the pressure-dependent melt curve and the shear viscosity of the liquid phase. These physics terms are poorly constrained beyond ambient pressure for the explosive RDX. We adopt an all-atom modeling approach using molecular dynamics (MD) simulations to predict the melt curve of RDX near to detonation conditions (30 GPa) and determine the shear viscosity of the liquid as a function of temperature and pressure above the melt curve. Phase-coexistence simulations were used to determine the melt curve, which is predicted to vary by almost 1100 K as the pressure increases from 0 GPa to 30 GPa. Equilibrium MD simulations and the Green-Kubo formalism were used to obtain the pressure-temperature dependent shear viscosity. The shear viscosity of RDX is predicted to be of similar magnitude to the viscosity of TATB at low GPa-range pressures, and to be roughly an order of magnitude lower than the viscosity of HMX. The temperature dependence of the shear viscosity is Arrhenius at a given pressure, and the exponential pre-factor and activation term exhibit a strong, yet complicated, pressure dependence. An empirical pressure-temperature dependent function for RDX shear viscosity is developed that simultaneously captures a wide range of MD predictions while taking an analytic form that extrapolates smoothly beyond the fitted regime. The relative strength of the pressure and temperature dependencies of these two physics terms is found to be of similar magnitude for RDX, HMX, and TATB, which motivates incorporating these results in future RDX grain scale modeling.

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Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Kroonblawd

Springer

2021

Preprint

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“…The evaluation is only useful up to the melt temperature of RDX. The melt temperature increases with pressure starting from approximately 200 °C at atmospheric pressure to greater than 500 °C at 1 GPa [8, 54]. A model result of interest is therefore the volume of the powder layer reaching this temperature threshold.…”

Section: Resultsmentioning

confidence: 99%

Modeling and Simulation of RDX Powder Thermo‐Mechanical Response to Drop Impact

Yakaboski

Kumar

2021

Propellants Explo Pyrotec

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A computational framework to predict the deformation, flow, and compaction of an energetic material (EM) powder subjected to drop impact is discussed. Explicit dynamic finite element analysis was performed to simulate drop‐weight impact tests for comparison with experimental results and to gain insight into the ignition sensitivity of RDX powder. The computations simulated the Thermo‐Mechanical behavior of a thin layer of energetic powder subjected to drop impact to study the dependence of ignition sensitivity on the anvil material properties. By modeling high strength steel and a low strength copper anvil, a direct comparison is made on how energy dissipation within the EM is influenced by anvil properties. A hybrid finite element model is introduced that captures the mesoscale discrete particle nature of the powder response in regions of interest while using a continuum model elsewhere to reduce computational cost. To capture the mesoscale behavior, a multi‐particle finite element method (MPFEM) approach was used in selected regions in the hybrid model. Powder temperatures were computed to understand how the striker impact energy is dissipated by plasticity and friction into localized heating of the EM that triggers the ignition. Munition designers can use such a framework to study the low‐level impact sensitivity of munitions in a computationally efficient manner. Results of the simulation using the hybrid model suggest that copper anvil undergoes plastic deformation which absorbs a significant portion of the impact energy reducing the energy dissipated within the EM and suppressing ignition.

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Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Kroonblawd

Springer

2022

Propellants Explo Pyrotec

Self Cite

View full text Add to dashboard Cite

Recent grain‐scale simulations of HMX and TATB have shown that predictions for hot spot formation in high explosives are particularly sensitive to accurate determinations of the pressure‐dependent melt curve and the shear viscosity of the liquid phase. These physics terms are poorly constrained beyond ambient pressure for the explosive RDX. We adopt an all‐atom modeling approach using molecular dynamics (MD) simulations to predict the melt curve of RDX near to detonation conditions (30 GPa) and determine the shear viscosity of the liquid as a function of temperature and pressure above the melt curve. Phase‐coexistence simulations were used to determine the melt curve, which is predicted to vary by almost 1100 K as the pressure increases from 0 GPa to 30 GPa. Equilibrium MD simulations and the Green‐Kubo formalism were used to obtain the pressure‐temperature‐dependent shear viscosity. The shear viscosity of RDX is predicted to be of similar magnitude to the viscosity of TATB at low GPa‐range pressures, and to be roughly an order of magnitude lower than the viscosity of HMX. The temperature dependence of the shear viscosity is Arrhenius at a given pressure, and the exponential pre‐factor and activation term exhibit a strong, yet complicated, pressure dependence. An empirical pressure‐temperature dependent function for RDX shear viscosity is developed that simultaneously captures a wide range of MD predictions while taking an analytic form that extrapolates smoothly beyond the fitted regime. The relative strength of the pressure and temperature dependencies of these two physics terms is found to be of similar magnitude for RDX, HMX, and TATB, which motivates incorporating these results in future RDX grain‐scale modeling.

show abstract

Sensitivity of pore collapse heating to the melting temperature and shear viscosity of HMX

Cited by 36 publications

References 33 publications

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

Modeling and Simulation of RDX Powder Thermo‐Mechanical Response to Drop Impact

Predicted Melt Curve and Liquid Shear Viscosity of RDX up to 30 GPa

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