Computation of Residual Stresses due to Multipass Welds in Piping Systems

In this paper, a computational model is developed to calculate the magnitude and distribution of residual stresses for multipass girth-butt welded pipes. The model consists of two parts, a temperature analysis model and a finite element stress analysis model. Elastic-plastic temperature dependent mechanical properties and unloading due to stress reversals are included in the model. While computational models for predicting residual stress distributions due to one- and two-pass welds have been developed, there are certain difficulties associated with predicting the behavior of multipass welds in an economical way. An approach for handling these types of problems is described. Residual stresses obtained with the model for a seven-pass weld and a thirty-pass weld are compared with residual stresses obtained from laboratory measurements. Good agreement is found between the computed and measured values of residual stresses for for both welds.