Experimental study on cavitation-induced micro-spallation in Sn under double explosively driven shock

The micro-spallation damage behavior of low-melting-point metals under double shock is a critical concern in advanced equipment design. However, there is currently a lack of detailed spatial distribution information on micro-spallation after the second shock. In this study, two experiments on tin under different loading paths were conducted using a double-shock apparatus with adjusted backing plates. In addition, the loading histories were accurately measured using photonic Doppler velocimetry and Asay window diagnostics. To overcome the limitation in conventional approaches for extracting spatial information from the Asay window, an innovative inversion method for the micro-spallation material impacting Asay windows in vacuum was proposed. A dedicated post-processing procedure was further implemented to reconstruct the corresponding spatial volume density distribution. Comparison of the reconstructed volume density distributions under different loading paths reveals a consistent increasing trend from the free surface toward the rear interface. However, the slopes of these trends differ, particularly in the region near the free surface. Further analysis indicated that the shorter time interval between the first and second shock and the stronger secondary loading affect the damage microstructure of the porous, cavitated regions, leading to a more extensive porous zone adjacent to the free surface. This study provides insights into the micro-spallation distribution under double-shock and serves as a foundation for further investigations.