Effect of Geometry of Grooves on Connection Strength of Hydraulically Expanded Tube-to-Tubesheet Joints

The object of this paper is to investigate the effect of the geometry of circumferential grooves on the connection strength of hydraulically expanded tube-to-tubesheet joints of heat exchangers. Seven-tube models with different groove widths, depths, spacings, and locations were fabricated under the same expansion pressure by commercial hydraulic expanders. Then the corresponding pullout forces were gained by experimental means. In addition, the process of hydraulic expansion of tube-to-tubesheet joints was simulated using the nonlinear finite element method based on a two-dimensional (2D) axisymmetrical model. The residual stress and deformation of joints were determined, and the effect of geometrical parameters of the grooves on the connection strength of joints was studied in terms of the average residual contact pressure of the joints. The experimental and calculation results indicate that the most important geometrical factor for determining the connection strength is the groove width. Groove depth, spacing, and location have a secondary effect. Optimum geometrical sizes of grooves are proposed based on maximum axial strength. These can provide a reference for the revision of design and manufacturing codes.