Stress analysis of the interaction of a running crack and blasting waves by caustics method

The purpose of this work is to investigate the mechanism of crack-wave interaction in blasting engineering. Transient effects of blasting waves on a running crack are evaluated by estimating crack-tip stress field from measurements of distorted shadow spots by caustics method. An optically geometrical superposition of light deflections from the running crack and blasting waves is proposed, considering concave and convex lens effects of waviness of initially flat plane under blasting waves. The stress field near the running crack tip in crack-wave interaction is obtained. Simulations of caustic curves derived from this superposition agree with those from instant records by a high-speed camera, highlighting that this superposition is a powerful way to evaluate the stress field near the crack tip and to extend classical caustics method to the application of unknown transient loadings by blasting waves. At last, similar photoelasticity experiments are made and results from two optical methods are discussed.