Keith A. Gonthier
Professor of Mechanical Engineering
3261D Patrick F. Taylor Hall
Department of Mechanical & Industrial Engineering
Louisiana State University
Baton Rouge, LA 70803
225-578-5915
Educational Background
- Ph.D., Mechanical Engineering, University of Notre Dame, 1996
- B.S., Aerospace Engineering, Auburn University, 1990
- B.S., Biochemistry, Louisiana State University, 1988
Research Goal
Computational Characterization of Impact Induced Multi-Scale Dissipation in Reactive Solids
Reactive solid composites often consist of mixtures of high-explosive and metal particles (size ~ 0.001-200 microns), and polymeric binder. It remains fundamentally unclear, even for idealized systems, how microstructure (particle size, shape, and packing), component thermomechanical properties, and metal and binder mass fractions, affect impact induced heating of the explosive component which establishes their impact sensitivity and survivability. This modeling and computational study has three key objectives: 1) To examine particle-scale dissipation by compaction shocks in low density granular/particulate explosives (HMX, and HMX-Al composites). For this objective, mesoscale Modeling and Simulation (M&S) is performed using a technique that characterizes both volumetric and surface dissipation in granular systems that can induce thermally activated phenomena. The technique incorporates a thermoelastic-viscoplastic and stick-slip friction theory for each component to describe nonlinear deformation and motion, inter-particle friction, and plastic work. The relative importance of volumetric and surface dissipation within shock profiles is characterized, and its dependence on shock strength and metal mass fraction is examined. 2) To characterize how the microstructure and composition of low density granular explosives (HMX, and HMX-Al composites) affect shock induced formation of hot-spots. For this objective, inert temperature field predictions at the particle scale are combined with a thresholding strategy to identify hot-spot fields and to characterize their distributions in intensity, geometry, and spatial proximity in the deformed material configuration behind shocks. Such distributions are significant because they establish local ignition and control the rate of spread within the material. 3) To develop a thermodynamically compatible macroscale ignition and burn model that explicitly incorporates computationally derived relations between microstructure, shock strength, and hot-spots. The model is used to computationally examine how shock induced transition to detonation in low density HMX is affected by input shock strength and initial packing density.
Sponsors
Air Force Research Laboratory (AFRL/RWMES), Defense Threat Reduction Agency (DTRA)
Selected Publications
Chakravarthy, N., and Gonthier, K. A., 2016, “Analysis of Microstructure-Dependent Shock Dissipation and Hot-Spot Formation in Granular Metalized Explosive,” Journal of Applied Physics, 120(2):024901, doi: 10.1063/1.4956302
Rao, T., Gonthier, K. A., and Chakravarthy, S., 2016, “Compaction Shock Dissipation in Low Density Granular Explosive,” Journal of Applied Physics, 119(22):224904, doi: 10.1063/1.4953650
Chakravarthy, , Gonthier, K. A., and Panchadhara, R., 2013, “Analysis of Meso-Scale Heating by Piston Supported Waves in Granular Metalized Explosive,” Modeling and Simulation in Materials Science and Engineering, 21(5):055016, url=http://stacks.iop.org/0965-0393/21/i=5/a=055016
Gilbert, N., Chakravarthy, S., and Gonthier, K. A., 2013, “Computational Analysis of Hot-Spot Formation by Quasi-Steady Deformation Waves in Porous Explosive,” Journal of Applied Physics, 113:194901-19, doi: 10.1063/1.4804932
Panchadhar, , and Gonthier, K. A., 2010, “Mesoscale Analysis of Volumetric and Surface Dissipation in Granular Explosive Induced by Uniaxial Deformation Waves,” Shock Waves, 21(1):43-61, doi: 10.1007/s00193-010-0287-6
Figure: (a) Illustration of explosive microstructure and heterogeneous deformation wave propogation in granular HMX (84% TMD); the input wave has an effective particle speed of 50 m/s. (b) Predicted temperature contours and hot-spot mass fractions for granular HMX (84%) TMD for an effective shock particle speed of 500 m/s.
Research Goal
Computational Analysis of Weak Shock Initiation of Low Density Granular Explosive
Low pressure (weak) initiation of low density granular HMX occurs by a complex mechanism that leads to a prompt (or discontinuous) transition to detonation within the material due to compaction shock interactions. These interactions influence ignition, flame spread, and subsequent transition by affecting dissipative heating within the microstructure during pore collapse. Details of the transition mechanism depend on initial packing density and input shock strength. In this effort, computations are performed using a multiphase reactive flow model to examine how the transition mechanism varies with input shock strength for granular. The model accounts for pressure-dependent ignition, and subsequent burn depends on the local dissipative work, porosity, and pressure. The dependence on dissipative work is motivated by mesoscale M&S that indicated a significant increase in hot-spot size and spatial proximity within the microstructure as shock induced dissipative work increases, suggesting an increase in flame spread rate. Predictions highlight the variation in transition mechanism with increasing input shock strength and identify conditions that favor the formation of retonation waves during transition.
Sponsors
Air Force Research Laboratory (AFRL/RWMES), Defense Threat Reduction Agency (DTRA)
Selected Publications
Rao, , and Gonthier, K. A., “The Evolution of Retonation During DDT of Low Density HMX," AIAA 2016-4614, presented at the 2016 AIAA Propulsion and Energy Forum and Exposition (AIAA Propulsion and Energy 2016), Salt Lake City, Utah, July 25-27, 2016. doi: 10.2514/6.2016-4614
Rao, , and Gonthier, K. A., “Analysis of Dissipation Induced by Successive Planar Shock Loading of Granular Explosive,” AIAA-2015-3708, presented at the 2015 AIAA Propulsion and Energy Forum and Exposition (AIAA Propulsion and Energy 2015), Orlando, Florida, July 27-29, 2015. doi: 10.2514/6.2015-3708
Rao, , and Gonthier, K. A., “Analysis of Compaction Shock Interactions During DDT of Low Density HMX,” Shock Compression of Condensed Matter—2015, American Institute of Physics Conference Proceedings, in production. (Presented at the 19th Biennial APS Conference on Shock Compression of Condensed Matter, Tampa, Florida, June 14-19, 2015.) doi: 10.1103/BAPS.2015.SHOCK.E3.5
Rao, , and Gonthier, K. A., “Mesostructure-Dependent Reactive Burn Modeling of Porous Solid Explosives,” AIAA 2014-3810, presented at the AIAA Propulsion and Energy Forum and Exposition (AIAA Propulsion and Energy 2014), Cleveland, Ohio, July 28-30, 2014. doi: 10.2514/6.2014-3810
Figure: Predicted (a) bulk/mixture pressure contours showing compaction shock and ignition front trajectories in the characteristic plane; (b) solid/explosive volume fraction contours in the characteristic plane. The material is low density HMX (68% TMD) and the input shock has a particle speed of 200 m/s. Position is shown in a piston-attached reference frame.