1992 Volume 10 Issue 3 Pages 373-377
Considerable papers which experimentally examined the effect of residual stress on the brittle fracture strength of weldment have been published. The effect of stress-relieving on the brittle fracture strength has been experimentally examined too. In those papers, the residual stress distributions were measured by the stress-relaxation method, assumed as a simple curve and represented by a simple function. There have been, however, few analytical works concerned with stress and strain near a crack in the residual weld stress field.
In the present study, an as-welded plate and a welded plate stress-relieved mechanically are dealt with. Each of them has a through-thickness center crack perpendicular to the welding bead. The crack initiates after welding or after stress-relieving. The residual stresses due to welding and those after stress-relieving by the uniform pre-straining are measured by means of the ultrasonic technique, because, from a practical point of view, the residual stress should be measured nondestructively. A uniform tensile load perpendicular to the crack 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. Considering the residual stresses distributed after pre-cracking, the deformation near the tip of a crack in a plane stress field are analyzed. The effect of residual stresses and that of stress-relieving on the deformation near a crack are revealed. The tensile residual stress around a crack tip contributes to the increase of stress, strain, plastic zone size near the crack and crack opening displacement. The stress-relieving contributes to the increase of fracture strength of welded plate.
