In the current study, simulating residual stress distributions has been investigated for an AISI 316H austenitic stainless steels weld header and compared to actual measured residual stresses. These welds connect the outlet nozzle to the archetypal header 1B1/1 which was ex-serviced from Heysham power plant in UK. Finite element (FE) analyses of different load and boundary conditions have been performed to predict the optimum stress distribution around the cracking region to compare with available measured residual stress distributions in the literature. The FE predictions show that a remote displacement control tensile load on the nozzle with fixed vertical movement of cylinder can best fit the measured residual stress distribution.
Hardness profile across the weld cross section indicates that the hardness gradually decease from HV 210 in weld metal to HV 160 in base metal, however, in the fusion away from 3 mm, the hardness were over HV 240. The facts indicate that the primary crack is likely to initiate at high hardness boundary and propagate in the direction of the highest principal stress regardless of the material hardness. Hypothesis of mechanism to the crack propagation is considered and proposals to predict damage and cracking in the header using FEM are presented.
