Type of Document	Dissertation
Author	Panchadhara, Rohan
Author's Email Address	rpanch1@lsu.edu
URN	etd-07032009-131245
Title	Meso-Scale Heating Predictions for Weak Impact of Granular Energetic Solids
Degree	Doctor of Philosophy (Ph.D.)
Department	Mechanical Engineering
Advisory Committee	Advisor Name Title Keith A. Gonthier Committee Chair Michael M. Tom Committee Co-Chair Dimitris E. Nikitopoulos Committee Member Glenn Sinclair Committee Member Guoqiang Li Committee Member John P. Wefel Dean's Representative
Keywords	Dynamic compaction Hot-spots Granular energetic solids Meso-scale
Date of Defense	2009-06-17
Availability	unrestricted
Abstract An explicit, two-dimensional, Lagrangian finite and discrete element technique is formulated and used to computationally characterize meso-scale fluctuations in thermomechanical fields induced by low pressure deformation waves propagating through particulate energetic solids. Emphasis is placed on characterizing the relative importance of plastic and friction work as meso-scale heating mechanisms which may cause bulk ignition of these materials and their dependence on piston speed (vp ~ 50-500 m/s). The numerical technique combines conservation principles with a plane strain, thermoelastic-viscoplastic constitutive theory to describe deformation within the material meso-structure. An energy consistent, penalty based, distributed potential force method, coupled to a penalty regularized Amontons Coulomb law, is used to enforce kinematic and thermal contact constraints between particles. The technique is shown to be convergent, and its spatial (~ 2.0) and temporal (~ 1.5) convergence rate is established. Predictions show that alhough plastic work far exceeds friction work, considerably higher local temperatures result from friction work. Most mass within the deformation wave (~ 99.9%) is heated to approximately 330, 400, and 500 K, for vp = 50, 250, and 500 m/s, respectively, due to plastic work, whereas only a small fraction of mass (~ .001%) is respectively heated to temperatures in excess of 600, 1100 and 1400 K due to friction work. In addition to low speed impact, and contrary to conventional belief, friction work is shown to also be an important heating mechanism at higher impact speeds. The variation in spatial partitioning of bulk energy within the deformation wave structure with particle morphology and material properties is demonstrated.
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