Research on the Regulation Mechanism of Residual Stress in Tube-to-Tubesheet Welded-and-Expanded Joints of Shell-and-Tube Heat Exchanger

Abstract In shell and tube heat exchangers, welding residual stress has a crucial impact on reliability and structural integrity of the tube-to-tubesheet joints. This paper combines numerical simulation and theoretical analysis methods to investigate the welded-and-expanded process. Previous studies typically treated welding and expansion as isolated processes. This paper explains the regulation mechanism of the expansion load on the existing welding residual stress through analyzing the residual stresses on the surface of the tube sheet and at the weld root before and after expansion. The study suggests that the welding process generates high-magnitude tensile residual stress near and in the adjacent areas of the weld. The peak of this residual stress exceeds the yield strength of the material. The stress is mainly concentrated on the joint surface and gradually decays with the thickness of the tube sheet. The expansion process significantly alters the stress field induced by welding, achieving effective stress release and redistribution. A critical expansion pressure threshold was determined, approximately 280 MPa. If this threshold is exceeded, the stress relief effect will tend to saturation, and further loading may cause local yield on the surface of the tube sheet. In addition, the agreement between numerical simulations and experiments confirms the effectiveness of expansion load in mitigating welding residual stress and provides a theoretical foundation for optimizing the welded-and-expanded process.