Analysis of residual stresses at weld repairs

In contrast to initial fabrication welds, residual stresses associated with finite length weld repairs tend to exhibit some important invariant features, regardless of actual component configurations, materials, and to some degree, welding procedures. Such invariant features are associated with the severe restraint conditions present in typical repair welding situations. In this paper, residual stress results from several weld repair case studies, using both advanced computational modelling procedures and experimental measurement techniques, are presented and reviewed. From these results, it is evident that weld repairs typically increase the magnitude of transverse residual stresses along the repair compared with the initial weld and that the shorter the repair length the greater the increase in the transverse stress. Also, beyond the ends of the repair the transverse stress sharply falls into compression. For selected cases, predicted stresses are compared with detailed residual stress measurements and the adequacy of finite element simulation procedures is assessed. Welding procedure related parameters (pass lumping, heat input and inter-pass temperature) appear to be more important in analysing weld repairs than in initial fabrication welds. Also great care must be taken when employing simplified two-dimensional cross-section finite element models with applied restraint conditions to simulate the residual stress field at a specific point along the length of a repair.