Molecular Dynamics Studies of Plastic Flow at High Strain Rates
Non-equilibrium molecular dynamics techniques have been developed to investigate high strain rate plastic flow in simple two and three dimensional crystals. In these simulations the long-time, steady state, values of the stress tensor and internal energy are computed as a function of the independent variables, temperature and strain rate, which are constants of the motion. Our results show that the shear stress varies as a non-integer power of the applied strain rate. The power is approximately proportional to the temperature and reaches a value of about 0.5 just before melting.1
The molecular dynamics results can be at least semi-quantitatively reproduced by a model which involves the creation, motion and annihilation of edge dislocations. It is significant that the dislocation parameters in this model are all determined from separate calculations and represent closely the exact properties of dislocations in the material.
Our calculations are consistent with experimental data and suggest that the flow of close-packed metals is described by a single physical mechanism over a range of strain rates from 10 kHz to 1 THz.
KeywordsPlastic Flow Edge Dislocation Triangular Lattice Strain Energy Release Dislocation Dynamic
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