In this research, Idealized Explicit FEM (IEFEM), which was developed to achieve analysis of welding residual stress of actual structures, was applied to V groove and X groove multi-pass pipe welding problem. Both problems have more than 3 million degrees of freedom. In the analysis of V groove problem, the influence of work hardening rule was discussed through the comparison of residual stress obtained by using isotropic, kinematic and composite hardening rule. As a result, it was found that residual stress is evaluated excessively in the case of isotropic hardening. In the analysis of X groove problem, the influence of welding pass grouping technique on residual stress distribution was investigated. By comparing the residual stress distributions among the analysis considering the actual welding pass sequence, using welding pass grouping technique and experimental measurement, it was found that the residual stress might be different if the welding pass grouping technique is used. In addition, the influence of welding pass sequence on residual stress was also investigated in the analysis of X groove problem. By comparing the residual stress among the cases considering actual welding pass sequence, reversed in-layer sequence, reversed build-up sequence, it was found that the influence of welding sequence on residual stress is small.
In the analysis of V groove problem and X groove problem, the analyses were finished in 70 hours and 250 hours, respectively. These computing times were short enough for the practical use.