Estimation of Residual Stresses in Hydraulically Expanded Tube-to-Tubesheet Joints

Abstract

The knowledge of residual stresses introduced in the tubes of heat exchangers during their expansion in the tubesheet holes is important because of their effect on the structural integrity of components. This paper presents a simplified theoretical method to calculate the maximum residual stresses introduced in the transition zone of expanded tube-to-tubesheet joint. The higher positive values of tensile residual stresses and their corresponding axial locations are determined by using a standard deviation analysis. The validation of the proposed equations was accomplished by comparing their results to those obtained by the finite element method for some arbitrary cases. An upper limit has been imposed on the expansion pressure level, depending on the combination of the geometrical and material parameters that are involved in the design of the tube-to-tubesheet joints.

Connection strength and tightness of hydraulically expanded tube-to-tubesheet joints

“…Sang et al [4] presented some results of a preliminary study to validate experimentally the reliability efficiencies listed in Table A2 of Appendix A of Section VIII, Division 1, of the Boiler and Pressure Vessel Code, and the tightness of the expanded joints. Some results obtained from analytical and finite element models were presented, which mainly focused on the residual stresses and axial strength of expanded joints [5][6][7]. It was pointed out in reference [7] that the nonlinear element method may give reliable results when the type of solid and contact elements, mesh refinement, number of increments and iteration to reach the convergence for an appropriate tolerance, etc., were properly selected.…”

“…Some results obtained from analytical and finite element models were presented, which mainly focused on the residual stresses and axial strength of expanded joints [5][6][7]. It was pointed out in reference [7] that the nonlinear element method may give reliable results when the type of solid and contact elements, mesh refinement, number of increments and iteration to reach the convergence for an appropriate tolerance, etc., were properly selected.…”

Effects of friction on roller expanded tube–tubesheet joint strength

“…Existing work has relied mainly on hydraulic expansion simulation. Allam et al [8,9] used experimental method to evaluate the actual friction coefficient at the condition parameters used in their research. Merah et al [10] used FE to study the effect of initial clearance and material strain hardening on residual contact stress for hydraulic tube-to-tubesheet expansion.…”

Investigation of welded structures on mechanical properties of 304L welded tube-to-tubesheet joints

“…The tube-to-tubesheet joints made by the expansion method must provide a tight seal between the tube side and the shell side fluids and sufficient strength to sustain the axial load, which have been investigated deeply [2][3][4][5][6][7][8][9][10][11].…”