Title page for ETD etd-07032009-131245


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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