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Wednesday, May 15, 2019
3:30 PM - 4:30 PM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Meso-informed reactive burn model for heterogeneous energetic materials

Nirmal Rai
The University of Iowa

Predictive modeling of shock-to-detonation transitions (SDT) in heterogeneous energetic (HE) materials (plastic-bonded explosives, neat pressed HMX etc.) is useful for several applications, including controlled energy release and safe handling of propellant and explosive materials. Initiation of detonations in heterogeneous energetic materials occurs at the meso-scale, i.e., at the scale of the HE grains or particles. When shock loads are imposed, energy localization occurs at defects in the material, which leads to the formation of hotspots; reaction fronts propagate from such hotspots and may strengthen the imposed shock, leading to detonation. The microstructure of HE materials is replete with defects at which hotspots can form, including voids, cracks, and crystal-crystal and crystal-binder interfaces. To simulate the macro-scale response of the HEs, the meso-scale dynamics and localization of energy must be captured accurately. Capturing localized meso-scale events like hotspot formation in macroscopic samples of HEs is computationally infeasible due to stringent spatial and temporal resolution requirements. Therefore, for the macro-scale analysis, the desired meso-scale physics is transmitted to the macro-scale through appropriate closure models. In this work, a meso-informed reactive burn model for porous HE materials is developed, where the meso-scale physics is derived from the high-fidelity reactive void collapse simulations. The meso-informed burn model is applied to perform SDT simulations of pressed HMXs with different porosities, void diameters and microstructural features. The computations are successfully validated against experimental pop-plots and Hugh-James threshold criteria for different samples of pressed HMX.

Host: Ed Kober