Numerical Analysis for Dynamic Damage Processes and LY-12 Aluminum Spallations

In Ref.[1], a damage-level function is proposed for analyzing the dynamic fracture processes of expanding cylindrical shell. In this paper, we extend the model to the case of planar geometry and perform numerical simulation for the dynamic damage processes under uniaxial strain case. The studied material is LY-12 aluminum and a kind of constitutive equation with viscous effect is utilized. The calculated free-surface velocity versue time relation is consistent with the experimental results. The calculated results also indicate that the spall strength c and the critical damage-level at fracture plane, c, are both monotone increase function of strain rate c', respectively. This kind of c~c' relation has been reported in many other articles, for example in Ref.[2-3]. The relation c~c' can be expressed as c'exp(-11.4c)=2 100 s-1 in the strain -rate range from 105 s-1 to 106 s-1. We think this expression could be used as a kind of spall criterion. The damage-level profiles in the spalled layer are also given from the numerical results, and the specific feature of the profiles is qualitatively in accord with that of the micro-photographic results from recovery specimens reported by Barbee, et al.