Effect of pre-bulging on wrinkling of curved surface part by hydromechanical deep drawing

Wrinkling in sidewall for curved surface part is a big obstacle by traditional deep drawing, and which severely influence the surface quality and service performance of part. The pre-bulging hydromechanical deep drawing process was introduced on wrinkles controlling of a complicated curved surface part, effects of pre-bulging pressure and chamber pressure on behavior of wrinkles were investigated both by experiments and numerical simulations, the mechanism of pre-bulging process on wrinkles controlling was discussed by plastic stress and strain analysis. The study shows that the pre-bulging hydromechanical deep drawing process can be used to eliminate wrinkle by reducing the tangential compressive stress on unsupported region and increasing the area of sheet adhered to the punch surface. Furthermore, higher pre-bulging pressure can increase tangential plastic strain of unsupported region and have the biaxial tension effect, which result higher ability of avoiding wrinkles of the blank on unsupported region.