Crack dynamic propagation properties and arrest mechanism under impact loading

Abstract

Crack dynamic propagation and arrest behaviors have received extensive attention over the years. However, there still remain many questions, e.g. under what conditions will a running crack come to arrest? In this paper, drop weight impact (DWI) tests were conducted to investigate crack arrest mechanism using single cleavage triangle (SCT) rock specimens. Green sandstone was selected to prepare the SCT specimens. Dynamic stress intensity factors (DSIFs) were calculated by ABAQUS code, and the critical DSIFs were determined by crack propagation speeds and fracture time measured by crack propagation gauges (CPGs). The test results show that the critical DSIF at propagation decreases with crack propagation speed. Numerical simulation for SCT specimens under different loading waves was performed using AUTODYN code. The reflected compressive wave from the incident and transmitted plates can induce crack arrests during propagation, and the number of arrest times increases with the wave length. In order to eliminate the effect of the incident and transmitted plates, models consisting of only one SCT specimen without incident and transmitted plates were established, and the same trapezoid-shaped loading wave was applied to the SCT specimen. The results show that for the SCT specimen with transmitted boundary (analogous to an infinite plate), the trapezoid-shaped loading wave cannot induce crack arrest anymore. The numerical results can well describe the occurrence of crack arrest in the experiments.

Keywords

• Crack arrest
• Stress wave
• Fracture toughness
• Reflected wave
• Impact loading