A study on thinning of curved bottom cup by deep drawing process

This study examined the thinning mechanism of a 1 mm thick 5052-H32 aluminum alloy sheet during the deep drawing process of a cylindrical cup with a curved bottom. It investigated the effect of the punch’s curve ratio on the forming process and evaluates the feasibility of using punches with different curve ratios for two different drawing ratios. The results indicate that a punch with a low curve ratio causes the greatest thinning in the curved bottom area of the cup. In contrast, a punch with a high curve ratio leads to maximum thinning in the straight wall area near the punch radius, particularly in cups where the curved bottom area is large relative to the sidewall (low drawing ratio). For cups with a greater sidewall proportion (high drawing ratio), the forming of the straight sidewall becomes dominant, shifting the area of maximum thinning to the straight wall near the cup radius, regardless of bottom curvature. Additionally, the study explores the impact of a two-step forming process using redrawing on part thinning. The findings show that redrawing helps reduce thinning, with punch having a high curve ratio being more effective in minimizing thinning compared to that with a low curve ratio.