Tube-to-Tubesheet Joints: A Review and Finite Element Analysis

Abstract

The tube-to-tubesheet (T/TS) joint is commonly used in the heat exchanger industry where a leak-tight joint is required to perform in an adverse environment. Over the past years, the interest of the researchers has focused on the study of the joint pull-out strength, its leak- tightness, stress corrosion cracking resistance and its performance under the effect of heat cycling. Since there are numerous factors affecting the joint performance, the question of defining an optimum joint has always been raised without a definite answer. This paper presents a comprehensive literature review covering the available past publications starting from 1927 when Oppenheimer published the first English literature on the subject. The review covers TITS joints manufactured by roller or hydraulic expanders. The review is divided into three sections dealing with experimental, theoretical and numerical methods employed in the analysis of TITS joints manufacturing and performance. Within each section, the review is set up in a chronological order followed by a concluding note. The attention is focused on the method of analysis, the encountered design parameters and the results of the analysis. It is observed that much research is needed in order to be able to produce a reliable joint meeting the strength and quality requirements. The effects of the several parameters involved have to be critically examined. Despite being a very powerful tool in stress analysis in general, and metal forming in particular, the finite element method employed, so far, had a limited contribution to the analysis of TITS joints. The second part of this paper presents a finite element modelling of the TITS hydraulically expanded joint. An axisymmetric geometry and elastic-plastic isotropic strain hardening material model are adopted. The analysis is completed using the general purpose finite element program INDAP. The radial and axial deformation distributions along the inner and outer tube surfaces are presented at the maximum loading and after complete unloading. The radial, axial and hoop residual stress components are displayed. In addition, the distribution of the residual contact stresses are shown.