Numerical and experimental investigation of the ultrasonic vibrations effects on the tube hydroforming process in a die with a square cross-section

Abstract

The use of tube hydroforming process to produce integrated parts is growing in various industries. In this research, the hydroforming process has been used to convert the circular cross-section of the tube into a square one. In this process, due to the high hydrostatic pressure of the fluid, the friction in the contact area between the tube and the die surface increases significantly. High friction prevents the metal flowing of the tube material on the die surface and therefore it becomes very difficult to completely form the tube inside the die and obtain sharp corners. In this research, in order to improve the tube formability, applying ultrasonic vibrations to the hydroforming die has been used, which causes a temporary gap to be created in the contact surface of the tube and the die, and therefore the amount of friction is reduced and the tube material can slide more easily. By developing a 3D finite element model, the ultrasonic tube hydroforming process was evaluated. Modal analysis was used to evaluate the different shape modes of the die. The effects of ultrasonic vibrations on the deformation process have been evaluated using two variables: corner radius of square die and average wall thickness. An ultrasonic hydroforming setup was designed to form the annealed copper tube and was stimulated using selected resonance frequencies. The results of the finite element model were validated with the deformed tube in the experimental test. After confirming the results, the numerical model was used to evaluate the process parameters.