破壊靱性値を維持する局部圧縮法

抄録

ISO12135 and 15653, which provide test method for obtaining fracture toughness, require the fatigue precrack straightness. Specimens of base material meet to the requirements without special technique, however, crack front of welds specimens are often bowing due to compressive welding residual stress and do not meet to them. Therefore, Annex C to ISO15653 provides local compression technique in order to make crack front straight. It makes crack front straight in welds specimen, however, some interested parties have reported that it decreases fracture toughness value. Authors investigated the local compression, which seems to make crack front straight and keep fracture toughness value, by using numerical analysis based on Weibull stress criterion. In addition, we operated fracture toughness test with some kinds of local compression obtained from the numerical analysis. As a result, we found new local compression, which does not compress the future crack tip and is superior to that recommended in ISO15653.