Strain rate dependence of twinning avalanches at high speed impact

The molecular dynamics simulation of the yield collapse in ferroelastic and martensitic materials under high strain rates shows power law decays of the yield energy. The energy exponent of the “jerk” distribution during yield does not depend on the strain rate and was found to be close to the mean field value of e = 1.35. The total yield energy changes dramatically during the crossover between the isothermal regime at low strain rates and the adiabatic regime at high strain rates. The crossover point is found in our simulations at 10−5/phonon time which corresponds to strain rates of approximately 108 1/s. Faster strain rates occur for high speed impact (shock deformation) with no strain absorption by twinning and no thermal equilibration while slightly slower strain rates lead to rate independent yield energies.