Determination of Repair Weld Residual Stress in a Tube to Tube-Sheet Joint by Neutron Diffraction and the Finite Element Method

Abstract

Repair welding is a popular method to repair the leakage zone in tube-to-tubesheet joint of shell-tube heat exchangers. But the repaired residual stresses are generated inevitably and have a great effect on stress corrosion cracking (SCC). In this paper, the effects of repair welding on residual stress were studied by finite element method (FEM) and neutron diffraction measurement. The original weld residual stresses calculated by FEM showed good agreement with neutron diffraction measurement results. After repair welding, the transverse residual stresses change very little while the longitudinal residual stresses are increased in the repair zone. In the nonrepair zone, both the transverse and longitudinal stresses are decreased. The repair welding times have little effect on residual stress distribution. With the increase of welding length and heat input, the residual stresses increase. Repair opposite to the original welding direction is recommended because the opposite welding direction minimizes the residual stresses.