Crack development characteristics of synthetic minerals containing galena in high-voltage pulse discharge breakage

Herein, the crack development characteristics of synthetic galena-bearing minerals in high-voltage pulse discharge (HVPD) were investigated. The breakdown current, breakdown time, and dielectric strength all decreased with increasing galena content in synthetic minerals. The quartz-containing synthetic minerals and pure cement specimen fractured until the pulse number reached 40 and 50. Meanwhile, the breakage predominantly occurred at the edges and vertices of synthetic. In contrast, galena-bearing synthetic minerals fractured much more readily due to the electrical induction effect of galena. A distinct vertical gradient phenomenon of increased crack density while crack width decreased from top to bottom of the synthetic mineral samples was observed. The distribution of cracks became denser gradually and presented a network structure. Besides, the driving force and expansion speed of cracks growth declined to generate the dendritic cracks. Consequently, the mechanical properties of synthetic minerals were rapidly weakened to promote the macroscopic rupture. Finally, the distorted electric field strength at the interface between various minerals increases with increasing applied voltage. The high temperature generated during HVPD induced thermal expansion stresses at the mineral interface, promoting the initiation, propagation, and eventual penetration of grain boundary cracks, which further damaged the internal structure of samples.