近壁平面裂纹在动力荷载作用下的失稳扩展研究OA

This study investigates the propagation and instability of a planar crack near a free boundary in brittle materials under dynamic loading.Based on the slip-crack model and the Zlatin-Khrapkov semi-infinite crack theory,an analytical relation between the crack-tip dynamic stress intensity factor and the external dynamic load is estab-lished.Combined with Freund's dynamic fracture theory,the crack-initiation criterion and dynamic equation for the evolution of crack tip propagation speed with time are derived.Furthermore,the rock bridge between the crack and the free boundary is idealized as a slender structural member subjected to the combined axial and transverse loading.By incorporating compression-member stability theory and a strength criterion,a model for the propaga-tion-instability judgment of near-wall cracks under dynamic loads is constructed.Numerical analysis results show that the dynamic propagation process of near-wall cracks is significantly controlled by boundary effects.The closer the crack is to the free boundary,the faster the growth rate of the stress intensity factor,crack initiation occurs earlier,and the crack-tip velocity becomes significantly higher;With the increase of crack length,the critical instability load of the rock bridge structure decreases continuously.The research results can provide a mechanical model and criterion basis forjudging the propagation of rock bridge and instability of cracks near free boundaries under dynamic loading.