Thickness improvement in hydroforming of a variable diameter tubular component by using wrinkles and preforms.

A combination method of beneficial wrinkle and preform shape is proposed to solve the problem of non-uniform thickness distribution during hydroforming of a variable diameter tubular component. The effect of loading path for the hydroform part and the preform shape are simulated by LS-DYNA. At the same time, the wall thickness deviation of the maximum and minimum of the hydroformed part is considered as the optimal target and the loading path for the preform shape is optimized to obtain the beneficial wrinkles by response surface methodology. Simultaneously, hydroforming experiments were conducted to verify the simulation results. Study shows that the loading path plays an important role in the forming of the beneficial wrinkles, which influence the cracking and the wrinkling defects. Only the loading path is appropriate can the beneficial wrinkles be formed and the wrinkles are flattened in the subsequent calibrating process. Response surface methodology is an effective way to obtain the optimal loading path, and the desired loading path can be achieved by controlling the relationship of the axial feeding and the internal pressure. [ABSTRACT FROM AUTHOR]