Effect of wrinkling behavior on formability and thickness distribution in tube hydroforming

An experiment and simulation was conducted to investigate the influence of wrinkling behavior on formability and thickness distribution in tube hydroforming. The wrinkles can be classified into three categories, i.e. useful wrinkles, dead wrinkles, and bursting wrinkles. The dead wrinkles and the bursting wrinkles are defects in tube hydroforming. The formability improvement and the sound part with a larger expansion ratio can be obtained by the useful wrinkles with an advantage of no additional preform process. The thickness of the part is not uniform along the axial direction in the forming area. The top zone of wrinkle waves has the minimum thickness, whereas the maximum thickness appears in the bottom zone of wrinkle wave. The useful wrinkle should meet both the stress condition and the geometrical condition during calibrating. If the stress condition cannot be met, then bursting wrinkles occur. If the geometrical condition is not satisfaction, then dead wrinkles appear.