Abstract
The study presented deals with an industrial case and relates to the calculation of the residual stresses in a butt weld of two shells of large diameter, high thickness and great length constituting part of pressure equipment.
After completion of the weld, it can be repaired if unacceptable defects are detected and then stress relieved by a local heat treatment.
The objective of the study is therefore to calculate the residual stresses after completion of the weld, then the residual stresses after repair and finally the residual stresses after the local heat treatment.
The residual stresses at the different stages are carried out using finite element modeling of the assembled elements and by digital simulation of the production of the weld and its repairs by metal deposition in multiple passes.
The local stress-relieving post-treatment is carried out at an average temperature of 615°C in the weld and according to a well-defined thermal cycle.
The residual stresses at the end of the simulation are calculated by using the laws of behavior of the materials in plasticity and in creep and by taking account of the longitudinal thermal gradients generated by the locally heated zone.
The scientific calculation tool used is SYSWELD [1], dedicated specifically to welding and the total digital simulation is carried out continuously, successively welding, repair(s) and PWHT. Stress calculations are carried out with the viscoplastic laws of the materials involved and the metallurgical transformation laws for the deposited metal.
The expected results are the values and the distribution of the residual stresses at the end of the welding plus repairs simulations and PWHT to evaluate whether they must be considered further in the stress analyzes or not.
