Brittle crack propagation behavior in a member subjected to bending load

Brittle fracture is a catastrophic failure that must be avoided for steel structures. In order to prepare the case that brittle fracture occurs due to fatigue crack propagation from welding defects and toughness deterioration of heat affected zone, etc., the concept of stopping brittle crack propagation in the base material is being applied to the tank and ship fields. In this paper, the target is to develop a method to conveniently evaluate this brittle crack propagation stop characteristic, based on a bending load which can bring a dramatic decrease in load comparing tensile load system which is ordinary and expensive. Especially the transient history of stress field is evaluated thoroughly and suitable fracture criterion for description of crack propagation is investigated. As a result, it was found that when the high-speed crack propagated to the part subjected to the pre-compression, the stress field at the tip sharply dropped, and it becomes easier to stop. In order to investigate the detail of the transition of stress field, the authors constructed a finite element model that can take these into account and eventually developed a new evaluation method based on bending load.