Improvement of formability in T-shape hydroforming of tubes by pulsating pressure

Abstract

The effect of oscillations in the internal pressure on tube wall thickness and die corner filling in the pulsating hydroforming of T-shape tubes is examined using finite element simulation and experiments. The thinning behaviour of the tube during the pulsating hydroforming is studied for different coefficients of friction to investigate the mechanism of the improvement in formability. It is shown that the thinning behaviour is similar for different friction conditions. It is also illustrated that the pulsating pressure improves the formability, even for frictionless tube hydroforming. Thus, the reason for the improvement in the formability may not be due to a reduction in the friction level. In addition, the effects of the amplitude and frequency of the pulsating pressure on the thinning behaviour of tubes and die corner filling are examined. It is shown that, while a small number of cycles and a large amplitude of the pulsating pressure decrease the filling ratio of the die corner, they are more effective in improving the formability.