表面き裂のき裂先端応力場とQファクタ

抄録

Three dimensional elastic-plastic analyses are conducted by FEM for several kinds of surface cracked problems. They are: (a) CT specimen with stationary cracks, (b) CT specimen during stable crack growth, (c) surface cracked plates with different aspect ratios subjected to three point bending, (d) a pipe with an inner surface crack subjected to four point bending, and (e) CT- and surface cracked-specimens made of welded plates. The crack tip stress fields are compared with HRR solutions, and the effects of the specimen shape, loading condition and fusion line on the crack tip singular fields are studied. The Q factor, which is defined as the difference of the crack tip field from the HRR solution, is evaluated based on these analyses. It is shown that the crack tip fields deviate from the HRR solution gradually due to the increse of the elastic-plastic deformation. It is also found that the Q factor expressed the stress triaxiality at the crack tip well, and it has a close relation with the dimple fracture of the specimen. In the welded plate, Q factor controls the behavior of stable crack growth locally near the fusion line, though the J integral controls the entire behavior of stable crack growth.