Statistical analysis of ductile fracture surfaces under dynamic loading

Spalling is a fundamental damage phenomenon observed in materials under dynamic loading. It occurs when two release waves interact after shock reflections, generating a high-stress region that drives the nucleation, growth, and coalescence of voids in ductile materials. By adjusting strain rates and shock pressures through different shock generation methods it is possible to modify fracture properties. A key parameter in inertial damage models is the initial outer radius of the hollow sphere representing a void. This parameter governs the overall behavior of these models by influencing, for instance, the void growth rate and, consequently, the macroscopic response of the material. However, accurately determining this parameter experimentally remains a major challenge.

This study combines shock experiments with statistical analysis to reveal the spatial distribution of pore sizes, and examine variations in pore areal density with strain rate. Using scanning electron microscopy and stereo-imaging, we perform a statistical analysis of 3D reconstructions of post-mortem spall surfaces. Experimental results are compared with numerically generated surfaces based on a Boolean island model, enabling the determination of the void radius distribution from height fluctuations of each spall surface. The objective is to quantify the void size distribution under various loading conditions, to identify the type and nature of elements that should be incorporated into damage models to improve their accuracy.