Effect of Stress Reflection on Dynamic Stress Intensity Factor in Crack Arrest Toughness Testing

In a brittle crack arrest toughness test, a brittle crack is initiated by an impact on the side-edge notch of a specimen subjected to a specified static test stress, and the crack arrest behavior is examined. The distance between the loading points of the specimen is one of the important test parameters. When the distance between the loading points is short, a running brittle crack tends to be easily arrested. This may be affected by the stress waves induced by the released stress during crack propagation, as the released stress waves are reflected at the loading points and return to the propagating crack line and can apply compressive stress dynamically to the propagating crack tip. Therefore, for correct evaluation of brittle crack arrest toughness in a brittle crack arrest toughness test, the influence of the reflected stress waves on crack arrest behavior must be eliminated. In the present work, the dynamic stress intensity factors for a running crack in the brittle crack arrest toughness test were calculated by dynamic elastic finite element method (FEM) analysis, and the required condition to avoid the influence of the reflected stress waves was investigated. In practical brittle crack arrest toughness tests, crack arrest toughness, K-ca, is calculated by an analytical formula called a tangent formula. The consistency of the stress intensity factor, K, calculated by the analytical formula with the solutions obtained by dynamic elastic FEM was also examined.