Effects of Initial Tube-Tubesheet Clearance and Grooves on Axial and Hoop Residual Stresses of Roller Expanded Joints

An axisymmetric finite element model is used to evaluate the effect of large initial tube-tubesheet radial clearance and the effect of grooves machined in the tubesheet hole on the distributions and magnitudes of the radial deformation of expanded tube walls, residual contact stress, residual hoop stress, and residual axial stress along the expanded length of the tube and in the transition zone. The results have revealed the presence of residual axial stresses and residual hoop stresses in the inside and outside surfaces of the tubes with various degrees of severity. These tensile residual stresses may cause crack initiation and propagation and may lead stress corrosion cracking in corrosive environments.