Research on marginal-restraint mandrel-free spinning of large thin-walled aluminum alloy heads with large bottom reserves

Abstract

Abstract The marginal-restraint mandrel-free spinning method can solve the problem of instability when spin-forming thin-walled head blanks. However, when shear-expansion compound forming is adopted for a large diameter head, the sinking phenomenon that occurs during the expansion spinning stage makes it impossible to accurately form the head. Through finite element simulation, it is found that the smaller the roller fillet radius is, the smaller the feed ratio, and the larger the angle is between passes, the more obvious the sinking phenomenon and the worse the forming accuracy. It is further revealed that the mechanism of the sinking phenomenon is shear deformation in addition to expansion deformation in the expansion spinning stage. To solve the sinking problem, this paper proposes a marginal-restraint mandrel-free spinning method with a large bottom reserve. Research shows that a larger roller fillet radius and more passes can improve the contour accuracy of the head by using the cylindrical roller structure. Finally, it is verified that the new spinning method can achieve accurate forming of large thin-walled aluminum alloy heads with a diameter of 2250 mm and a forming angle of 60°.