Sidewall wrinkling suppression in the hydro-mechanical deep drawing for the curved surface shell of titanium/iron composite sheets

As a new type of metal sheet, titanium/iron composite sheets are crucial in various fields. However, in the forming of the curved shells of the titanium/iron composite sheets with small thickness-to-diameter ratios, sidewall wrinkling is extremely easy to form, and it is hard to control. In this paper, an experimental setup for hydro-mechanical deep drawing was designed, and sidewall wrinkling on the hemispherical shell with a flat bottom and 0.47% thickness-to-diameter ratio of titanium/iron composite sheets was effectively suppressed while avoiding splitting. Mechanical and numerical analyses were conducted to reveal the deformation mechanism, and the effect of chamber pressure was studied. The forming defects, thickness, and stress distributions were determined to reflect the deformation behavior. Results show the greater the chamber pressure, the more significant the effect of wrinkling suppression. When the chamber pressure reaches 20 MPa, the sidewall wrinkles disappear. Enough hydraulic pressure can produce a strong backward-bulging effect, which increases the wrinkling suppression pressure and improves plastic deformation instability. Moreover, the stress state of the sidewall changes under the action of hydraulic pressure, thereby changing the in-plane deformation behavior. Thus, the wrinkles already formed in the earlier stage of sidewall formation were adjusted after contact with the punch. The forming process has considerable potential to fabricate thin-shell components.