Impact hydroforming characteristics for a half-tube part with curvature

Taking half-tube part with curvature as an example, the impact hydroforming (IHF) characteristics were studied by combining the actual forming experiment and numerical simulation. The IHF experiment showed that wrinkles appeared at the bottom of the part during single-step forming, but no wrinkles were observed during double-step forming. The thinning rate and deviation of the wall thickness of the part in each area were less than 20% and 2.7 mm, correspondingly, and the drawing depth of the part reached 45.8 mm. The effect of double-step forming was better than that of single-step forming, which was related to the IHF forming law. Besides, the characteristics of the IHF process were studied by numerical simulation. The results indicated that when double-step forming was utilized, there was almost no velocity field in the opposite direction of deformation after the bottom of the part contacted the die, and the existence of stress state at the bottom would restrain and eliminate the wrinkles. The inertia effect evolved with the driving pressure. Specially, the inertia effect can improve the flow of metal and reduce the deviation of the wall thickness of the part under double-step forming.