Non-Destructive Evaluation of Residual Stress in Welded Partial Zone Using Continuous Indentation Test

摘要

In a welded joint, the formation of residual stress is inevitable. The stress can result in decrease of fatigue life in a welded structure under superimposed external stress. On this account it is important to evaluate the residual stress in use of structural steel. But conventional residual stress evaluating methods have difficulties of the derivation of residual stress free state in the field and destructive or lab-scale experiments. In this study, new residual stress evaluating model was suggested using continuous indentation technique. We theoretically induced load-depth curve for residual stress free state from the hardness and strength of the material. From the curve, we evaluated the residual stress in a welded joint using the difference from residual stress state. And we used invariant contact area because it is uniform value regardless of residual stress in the material or plastic deformation at the indentation test. The residual stress results from continuous indentation technique showed good agreement with conventional methods such as hole-drilling and saw cutting methods for API X65 and SS400. Therefore, this method has possibilities in actual application of industrial field.