Ultrasonic tube hydroforming, a numerical and analytical study

In tube hydroforming process، due to friction condition، uniform wall thickness، as well as sharp corners may not be achieved. Use of ultrasonic vibration can improve the contact conditions at the tube-die interface. The current work studies the effect of applying ultrasonic vibration on wall thickness and corner filling of hydroformed tubes. Firstly، a numerical model based on geometric relationships and stress-strain state has been established by which wall thickness and corner radius of hydroformed tubes can be obtained. In this model، the ultrasonic vibrations affect the nonlinear friction conditions at the tube-die interface. By comparing the FEM models of tubes in two cases of with vibration and without vibration، it is possible to investigate the effects of vibration on wall thickness and corner filling. The results indicate superimposing ultrasonic vibrations to the process will increase corner filling ratio of the tube significantly، and more uniform tube wall thickness will be achieved.