Alternate deep drawing process for spherical parts in near equal-thickness wall

Double-directional alternate deformation can improve the uniformity of strain hardening in deformation regions. Based on this principle, a new alternate deep drawing process for spherical parts was presented and experiment was carried out. Results show that the limit number of repeated deep drawing for spherical parts is 3, and spherical parts’ height cannot exceed 3/4 of the punch radius after each drawing. Compared with once deep drawing, the thickness strain in the ball bottom zone of parts formed by alternate deep drawing is significantly reduced. The thinning rates of forming parts in the thinnest point for 1-step deep drawing, 2-step alternate drawing, and 3-step alternate deep drawing are 0.127, 0.092, and 0.009, respectively. Alternate deep drawing can improve the mechanical properties of materials, such as hardness and Young’s modulus, and improve the global formability of the sheet metal. After 3-step alternate deep drawing, the sheet metal can be formed with near equal-thickness wall. During alternate deep deformation, a lot of twins impede dislocation motion, thereby improving the local work hardening ability in local areas and extending the deformation to low strain areas, and thus, the materials exhibit very high elongation and the global formability of the sheet metal is improved.