Spall behavior of pure aluminum under plate-impactand high energy laser shock loadings

Spall experiments of pure aluminum were performed on the light-gas gun equipment and SG Ⅱ high energy laser facility. An improved target configuration was applied to address the problem that the residual vibration was often lost in laser-loading spall experiments. By virtue of distinguishing the obvious difference in the strain rate between the two experiments, the material and rate-dependent issues related with the nucleation, growth and coalescence of micro-damage were examined using numerical simulations, which is important for developing predictive theoretical models. Results show that for our previously proposed model the average diameter, the critical pressure, and the nucleation rate parameter for micro-void nucleation can be regarded as material constants and the same is true with the critical pressure for micro-void growth, whereas the specific effective surface energy for micro-void growth and the critical damage for coalescence are typical rate-dependent. Furthermore, our simulations indicate that at the local spall position, although the spall strength has an apparent strain rate effect, the critical behavior of the transformation of the sample from continuous stretch to compression is determined by a critical damage, whose value is very small and is probably a material constant.