Modeling shockwave deformation via molecular dynamics
Molecular dynamics (MD), where the equations of motion of up to thousands of interacting atoms are solved on the computer, has proven to be a powerful tool for investigating a wide variety of nonequilibrium processes from the atomistic viewpoint. Simulations of shock waves in three-dimensional (3D) solids and fluids have shown conclusively that shear-stress relaxation is achieved through atomic rearrangement. In the case of fluids, the transverse motion is viscous, and the constitutive model of Navier-Stokes hydrodynamics has been shown to be accurate - even on the time and distance scales of MD experiments. For strong shocks in solids, the plastic flow that leads to shear-stress relaxation in MD is highly localized near the shock front, involving a slippage along close-packed planes. For shocks of intermediate strength, MD calculations exhibit an elastic precursor running out in front of the steady plastic wave, where slippage similar in character to that in the very strong shocks leads to shear-stress relaxation. An interesting correlation between the maximum shear stress and the Hugoniot pressure jump is observed for both 3D and fluid shockwave calculations, which may have some utility in modeling applications. At low shock strengths, the MD simulations show only elastic compression, with no permanent transverse atomic strains. The result for perfect 3D crystals is also seen in calculations for 1D chains. It is speculated that, if it were practical, a very large MD system containing dislocations could be expected to exhibit more realistic plastic flow for weak shock waves, too.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6197371
- Report Number(s):
- LA-UR-87-2367; CONF-870753-46; ON: DE87013157; TRN: 87-033207
- Resource Relation:
- Conference: 5. topical conference of the American Physical Society on shockwaves in condensed matter, Monterey, CA, USA, 20 Jul 1987; Other Information: Paper copy only, copy does not permit microfiche production
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
FLUIDS
SHOCK WAVES
COMPUTER CALCULATIONS
COMPUTERIZED SIMULATION
SOLIDS
DISLOCATIONS
EQUATIONS OF MOTION
IMPACT SHOCK
MOLECULAR MODELS
NAVIER-STOKES EQUATIONS
SHEAR PROPERTIES
STRESS RELAXATION
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFERENTIAL EQUATIONS
EQUATIONS
LINE DEFECTS
MATHEMATICAL MODELS
MECHANICAL PROPERTIES
PARTIAL DIFFERENTIAL EQUATIONS
RELAXATION
SIMULATION
990200* - Mathematics & Computers
360603 - Materials- Properties