Micro-damage characteristics of incipient spall in high-purity copper

Abstract

Dynamic damage of material is a complex process that is dependent on lots of effects on a mesoscale, including grain size, morphology and micro-voids. In order to study the shocked lead micro-damage characteristics in oxygen-free high-purity copper, the variational thickness values of flyers and samples are designed to vary pulse duration and strain rate in plate-impact experiment, and the special recovery chamber and surface profile measurement system are used for soft-recovery and cross-section measure respectively. Based on the reconstruction, quantitative and statistical analysis, it is found that the longer pulse duration and higher shock loading stress bring about more serious local damage in oxygen-free high-purity copper. The mensurable damage width of sample cross-section results from the damage evolution on a sub-micron scale. Critical evolution time of sub-micron is observed to decrease with strain rate increasing, suggesting that damage evolution speed of sub-micron becomes faster as strain rate increases. The void size distribution of recovered sample is presented, and the topological characteristic transition accompanied with nucleation, growth, and coalescence processes of microscopic voids is also discussed. Through a comparison of difference between this work and the literature of previous research, a physical explanation of voids size distribution characteristics of oxygen-free high-purity copper is presented.