2009:16 Influence of Hardening Model on Weld Residual Stress Distribution

Weld residual stresses have a large influence on the behavior of cracks growing under normal operation loads and on the leakage-flow from a through-wall crack. Accurate prediction of these events is important in order to arrive at proper conclusions when assessing detected flaws, for inspection planning and for assessment of leak-before-break margins. Therefore, it is very important to have verified procedures to estimate weld residual stresses (WRS). During the latest years, there has been a strong development in both analytical procedures to numerically determine WRS and experimental measurements of WRS. The present report is the result of an effort to acquire and to develop the latest research results in the field of WRS and especially the influence of hardening model. The choice of hardening model has been the subject of intense studies lately among research groups around the world for simulating weld residual stresses.

Welding simulations were conducted using isotropic, kinematic and mixed hardening models. The isotropic hardening model gave the best overall agreement with experimental measurements; it is therefore recommended for use in welding simulations. The mixed hardening model gave good agreement for predictions of the hoop stress but tended to under predict the magnitude of the axial stress. The kinematic hardening model consistently under predicted the magnitude of both the axial and hoop stress and is not recommended for use.