Analysis of hydraulically expanded tube-to-tubesheet joints

Expanded tube-to-tubesheet joints often fail during service conditions because of losing the initial tightness set up by the expansion process.; The study presented in this thesis is an attempt to investigate the hydraulically expanded tube-to-tubesheet joints using various techniques, namely: analytical, numerical and experimental.; Three different finite element models are used for the numerical analysis, namely: 2-D plane stress/strain, 2-D axisymmetric and 3-D. The 2-D axisymmetric model is extensively used during the analysis to overcome the limitation (e.g. calculation of residual stress in the tube transition zone) of the 2-D plane stress/strain model and to economically replace the full 3-D model that normally consumes huge CPU (Central Processing Unit) time and requires extensive hardware memory. The results have been compared to experimental and analytical data reported in the literature.; Pull-out tests are performed to verify our analytical and numerical models. The pull-out strength is obtained together with the micro tangential relative displacement at the tube and annular sleeve contacting surfaces. Another experimental setup is performed to determine the coefficient of friction that can be used for the numerical and analytical analyses.; An initial parametric study shows that both the strain hardening level and the radial clearance have a significant effect on the level of the residual contact pressure but have less influence on the maximum tensile residual stresses.; Both the finite element and analytical methods are also used to investigate the relationship between the pull-out joint strength and the initial residual contact pressure. They indicate a linear relation between those two parameters. However, a difference of about 40% is observed between pull-out strength calculated by the finite element method and that provided by the simple equation often used in the industrial application to calculate the joint pull-out load. The experimental measurement for the pull-out load confirms the adequacy of the finite element solution.; Finally, the parametric study is extended further to investigate the effect of the working conditions (e.g. temperature effect and mechanical loading) on both the residual contact pressure and maximum tensile residual stresses.; The optimum level of expansion defined by the closed form equation is recommended for use in the industrial application. (Abstract shortened by UMI.)...