Welding residual stress analysis and fatigue crack growth characteristics of multi-pass welded pipe weldment

Welding residual stresses are generated as a result of the large nonlinear thermal loading by a moving heat source. Moreover, multi-pass welding of thick section subjects to multiple thermal cycles and inelastic strain patterns. Thus, more complex residual stress distribution is generated through the plate thickness. When these residual stresses are tensile, it makes increase the crack driving force and reduce the resistance of brittle fracture. Therefore, accurate prediction of residual stresses is very important. In this study, welding residual stresses of the multi-pass welded A106 Gr B steel pipe weldment were analyzed by finite element analysis (FEA) using the element rebirth technique, and compared with experimental results. And then, in order to estimate fatigue crack growth characteristics considered the effect of residual stresses, concept of crack closure effect was introduced. From the results, the trend of welding residual stress distribution that was calculated by using the element rebirth technique of FEA was well agreed with the experimental result. And crack closure phenomena was not observed above R=0.5. And also, K-op/K-max was independent of K-max. Considering crack closure phenomenon in A106 Gr B Steel weldment, fatigue crack growth characteristic curves can be effectively estimated.