き裂を有する溶接材の変形挙動に及ぼす残留応力の影響

抄録

Considerable reports concerned with stress and strain near a crack in the residual stress field have been published. In some of those reports, however, the redistribution of residual stress after a crack growth was not taken into account.
In the present study, a butt welded plate with a through-thickness crack is dealt with. Uniform tensile load perpendicular to the crack which initiates after welding is applied to the plate. Stress, strain, plastic zone near a crack and crack opening displacement are examined by elasto-plastic finite element analysis as well as experiment. The residual stress is considered in the analysis. The residual stress and its redistribution after crack growth are measured by means of the ultrasonic stress measurement technique, because, from a practical point of view, the stress measurement needs to be nondestructive. The effect of residual stress on the deformation near a crack is revealed. The tensile residual stress around a crack tip contributes to the decrease of fracture strength at both low-applied-stress level and high-applied-stress level. On the other hand, the compressive residual stress around a crack tip contributes to the increase of fracture strength at high-applied-stress level.