Mesoscale simulation of reactive pressed energetic materials under shock loading

Kumar, Nirmal; Udaykumar, H. S.

doi:10.1063/1.4938581

Cited by 69 publications

(55 citation statements)

References 37 publications

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“…While the phenomenon of void collapse has been extensively studied via experiments [9][10][11] and numerical simulations [6,8,[12][13][14][15][16][17][18], the focus has primarily been on ideal-shaped voids such as cylindrical, elliptical, conical, or spherical voids. There have only been a few published papers that have studied deviations from cylindrical shape.…”

Section: Importance Of Void Shape and Void-void Interactions In Energmentioning

confidence: 99%

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Roy

Sen

et al. 2019

Shock Waves

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Surrogate models for hotspot ignition and growth rates were presented in Part I, where the hotspots were formed by the collapse of single cylindrical voids. Such isolated cylindrical voids are idealizations of the void morphology in real meso-structures. This paper therefore investigates the effect of non-cylindrical void shapes and void-void interactions on hotspot ignition and growth. Surrogate models capturing these effects are constructed using a Bayesian Kriging approach. The training data for machine learning the surrogates are derived from reactive void collapse simulations spanning the parameter space of void aspect ratio (AR), void orientation ( ), and void fraction ( ). The resulting surrogate models portray strong dependence of the ignition and growth rates on void aspect ratio and orientation, particularly when they are oriented at acute angles with respect to the imposed shock. The surrogate models for void interaction effects show significant changes in hotspot ignition and growth rates as the void fraction increases. The paper elucidates the physics of hotspot evolution in void fields due to the creation and interaction of multiple hotspots. The results from this work will be useful not only for constructing meso-informed macro-scale models of HMX, but also for understanding the physics of void-void interactions and sensitivity due to void shape and orientation.

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Section: Importance Of Void Shape and Void-void Interactions In Energmentioning

confidence: 99%

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Roy

Sen

et al. 2019

Shock Waves

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“…With advanced computing technology, to perform meso-resolved simulations of detonation phenomena in high explosives has recently become feasible. Via performing meso-resolved simulations, Rai et al 33 and Kim et al 34 demonstrated that the characteristics of mesoscale features determine the macroscopic ignition behavior of HMX and polymer-bonded explosives (PBXs), respectively. These simulations, however, have not yet been extended to time or length scales over which a complete SDT process occurs.…”

Section: Introductionmentioning

confidence: 99%

Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavities

Michael

Ioannou

et al. 2019

Journal of Applied Physics

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Two-dimensional, meso-resolved numerical simulations are performed to investigate the complete shock-to-detonation transition (SDT) process in a mixture of liquid nitromethane (NM) and air-filled, circular cavities. The shock-induced initiation behaviors resulting from the cases with neat NM, NM with an array of regularly spaced cavities, and NM with randomly distributed cavities are examined. For the case with randomly distributed cavities, hundreds of cavities are explicitly resolved in the simulations using a diffuse-interface approach to treat two immiscible fluids and GPUenabled parallel computing. Without invoking any empirically calibrated, phenomenological models, the reaction rate in the simulations is governed by Arrhenius kinetics. For the cases with neat NM, the resulting SDT process features a superdetonation that evolves from a thermal explosion after a delay following the passage of the incident shock wave and eventually catches up with the leading shock front. For the cases wherein mesoscale heterogeneities are explicitly considered, a gradual SDT process is captured. These two distinct initiation behaviors for neat NM and heterogeneous NM mixtures agree with experimental findings. Via examining the global reaction rate of the mixture, a unique time scale characterizing the SDT process, i.e., the overtake time, is measured for each simulation. For an input shock pressure less than approximately 9.4 GPa, the overtake time resulting from a heterogeneous mixture is shorter than that for neat NM. This sensitizing effect is more pronounced for lower input shock pressures. A random distribution of cavities is found to be more effective in enhancing the SDT process than a regular array of cavities. Statistical analysis on the meso-resolved simulation data provides more insights into the mechanism of energy release underlying the SDT process. Possible directions towards a quantitatively better agreement between the experimental and meso-resolved simulation results are discussed. arXiv:1905.05727v2 [physics.comp-ph]

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“…Due to the scarcity of direct measurements probing these microscale mechanisms, numerical simulations provide insights on these phenomena. Numerical studies have investigated sensitivities to impact pressure, pore size, pore morphology, multiple pores and grains, anisotropic crystal plasticity, rate-dependent strength, melt viscosity, and chemical kinetics [7][8][9][10][11][12][13][14][15][16][17][18]. Only recently have experimental studies measured hot spot temperatures in shocked HMX [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Modeling Hot Spot Experiments on Shocked Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine

Springer

Bassett

Bastea

et al. 2019

Propellants Explo Pyrotec

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For the first time, mesoscale simulations of shocked explosives are validated with hot spot temperature data. Following recent experiments, we simulate a 25 μm aluminum flyer impacting a powder bed of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) with an initial speed of 1.4 to 3.6 km s−1. The powder bed has a density of 0.56 g cm3, or 29 % crystal density, and an average grain size of 4 μ m. Simulations are performed in the multi‐physics code, ALE3D. We employ a comprehensive HMX material model that accounts for the chemistry, unreacted and product equation‐of‐states (EOSs), elastic‐plastic response, as well as melting and melt viscosity. Simulations show compaction, reaction, and gas jetting during the initial stages of shock in the powder bed. Shock reflection at the glass window interface increases hot spot temperatures in HMX product gas in excess of 7000 K at higher impact speeds which is readily observable using pyrometry techniques. We extract a temperature histogram from simulations at discrete times, using it to calculate an effective emission spectrum and effective temperature, Teff, for comparison to data. Simple T‐ and T4‐based methods inadequately weight the higher temperature regions and result in a low Teff that is in poor agreement with data. However, calculating Teff based on Planck's Law with a gray body assumption demonstrates good agreement with hot spot temperature data. A modified Arrhenius model is fit to the normalized reaction rates predicted by mesoscale simulations and inferred temperatures range from 1544 K to 1779 K; these temperatures are approximately 4x lower than the peak hot spot temperatures but 2‐3x higher than the bulk shock temperatures. The agreement with experimental results validates our mesoscale simulations as useful tools for elucidating the role of hot spot mechanisms in the shock initiation of heterogeneous explosives.

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Mesoscale simulation of reactive pressed energetic materials under shock loading

Cited by 69 publications

References 37 publications

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Modeling mesoscale energy localization in shocked HMX, Part II: training machine-learned surrogate models for void shape and void–void interaction effects

Meso-resolved simulations of shock-to-detonation transition in nitromethane with air-filled cavities

Modeling Hot Spot Experiments on Shocked Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine

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