Effect of loading mode and impact velocity on crack propagation of coal

Abstract

In order to study the influence of loading mode and impact velocity on coal crack propagation law, asymmetric semi-circular bend specimens were used to develop test and numerical simulation with multiple impact speeds under three loading modes of mode Ⅰ, mode II and mixed mode Ⅰ-Ⅱ under impact loading. The effects of loading mode and impact velocity on the dynamic fracture propagation process, crack initiation time and failure form of coal samples were studied. The results show that the crack of coal sample is linear under mode Ⅰ dynamic loading; under mode II and mixed mode Ⅰ-Ⅱ loading, the crack is in the form of a curve extending to the upper left; under three different loading modes, the crack initiation time of coal sample decreases with the increase of impact velocity, and its influence gradually weakens, the crack initiation time of coal samples under mode II loading is significantly longer than the other two loading methods; the destruction degree of coal samples increases with the increase of impact velocity, the impact of mode Ⅰ loading is small, and the mixed mode Ⅰ-Ⅱ and mode II loading is large.

Keywords

• loading mode
• impact velocity
• fracture propagation
• initiation time
• form of destruction