Numerical validation of fatigue properties and investigation of local deformation of heat-affected zones in P91 steel's weld joint

The low cycle fatigue (LCF) behavior of P91 steel weld joint (WJ), prepared by gas tungsten arc welding, has been investigated both experimentally and numerically. However, due to the smaller size and complex geometry of various zones of the WJ, the experimental investigation of the local fatigue behavior of different sub-regions of the heat-affected zones (HAZ) could not be made. Hence, the sub-regions of the WJ were reproduced at bulk scale by physical-thermal simulation (PTS) (i.e., heat treatment) to study the LCF behavior of the individual zones of P91 WJ. In the literature, the accuracy of such physical-thermally simulated bulk-scale specimens, which correspond to different sub-regions in the weld joint, is confirmed by comparing the microstructures and microhardness. In this article, a new method, based on the LCF experiment and finite element simulation, is proposed to validate the PTS method and the fatigue properties of the sub-regions of the weld joint. The simulation accurately predicted the failure location and also the most vulnerable sub-region within the WJ, as observed experimentally. Moreover, significant ratcheting and heterogeneous deformation were observed in the sub-regions of the WJ.