Variation law of micro-void distribution characteristics in early stage of spallation damage

Abstract

The development trend of spallation damage mechanics is to construct physical models coupled with material micro-mesoscale structure information, which also promotes the development of numerical calculation methods, experimental techniques and theoretical research. The mechanisms responsible for plastic deformation and failure of structural metallic materials at high strain rates are complex and are affected by heterogeneities in the micro-mesoscale structure that comprises the distribution of grain boundaries, interfaces, and preexisting densities voids. The distribution of these mesoscale heterogeneities can provide either strengthening behavior or void nucleation sites and influence spall failure behavior. Due to the lack of evolution information of micro-mesoscopic void distribution characteristics, the current spallation damage model is not only restricted in application in extreme environments of high strain rates, high pressures, and shock, but also do not effectively provide some information about the correlation between material damage and final material fragmentation particle size, which is very concerned in engineering. Therefore, it is urgent to develop a spallation damage model that reflects the variation law of micro-mesoscopic void distribution characteristics in damaged materials. Based on the analysis of various influencing factors in the process of void nucleation, combined with the characteristics of early void growth, and considering the convenience of analytical solution, the probability distribution function of void nucleation based on cosine function is given in this paper. The analytical calculation results of the new probability function of void nucleation are not only consistent with the results of the variation of void number with time calculated by molecular dynamics, but also in good agreement with the experimental results of tantalum spallation in the early stage of damage development, that is to say, the new probability function of void nucleation can reflect the variation law of micro-void distribution characteristics in the early stage of spallation damage to a certain extent.