Analytical model for the expansion of tubes under tension

This paper focuses on the expansion of metallic tubes subjected to large radial and circumferential plastic deformations. This process can be achieved by driving rigid conical mandrels of various diameters through them either mechanically or hydraulically in order to obtain desirable expansion ratios. A mathematical model was developed to predict the stress field in the expanded zone, the drawing force required for expansion, and the resulting dissipated energy from which optimum mandrel shapes were obtained. A finite element analysis was used to validate the theoretical results. A good agreement was obtained in terms of drawing force and dissipated energy for different geometric constraints and friction coefficients. The study showed that the optimum mandrel angle ranges between 22 and 25 degrees for low friction and increases non-linearly when friction increases.