Measurement of local brittle fracture stress for dynamic crack propagation in steel

The authors measured the local fracture stress of brittle crack propagation in steel plates. Many studies on brittle crack propagation in steel plates have been implemented based on energy balance, but they have not been able to provide full theoretical explanation to brittle crack propagation and arrest behavior in steel plates. On the other hand, although the local fracture stress concept has been emerging as a factor governing the behavior recently, the local fracture stress has not been evaluated sufficiently because the crack front shape and forming of shear lip have prevent us from implementing accurate FEM analysis of brittle crack propagation. So, we implemented brittle crack propagation tests using specimen with side groove which is designed to increase stress near the plate surface and make the crack front straight. Inputting crack velocities obtained from experiments, FEM analyses were implemented. Our analyses showed the local fracture stress is higher in low temperature than in high temperature. This trend can be explained from the aspect of forming of tear ridge, which is main mechanism to absorb energy during brittle crack propagation in steel plates.