Effect of bending speed on springback and thinning behavior of commercially pure titanium sheets under V-bending

• Bending speed affects deformation evolution of pure Ti sheet during bending. • Distinct twinning is activated in the inner and outer zones during bending. • High-speed bending exacerbates springback but improves thickness uniformity. • Trade-off exists between minimizing springback and achieving thickness uniformity. This study investigates the influence of bending speed on the springback and thinning behavior of pure titanium sheets, with a particular focus on microstructural evolution during bending. To evaluate these effects, V-bending tests were performed at bending speeds of 1, 10, and 100 mm/min, which approximately correspond to strain rates of 1.3 × 10 -4 , 1.3 × 10 -3 , and 1.3 × 10 -2 s −1 , respectively. The results reveal that increased bending speed leads to greater springback. During bending, plastic deformation initiates from both the inner and outer surfaces of the sheet and gradually penetrates toward the mid-thickness. However, this penetration is increasingly suppressed as the bending speed rises, resulting in the formation of a thick, deformation-free middle zone. This undeformed middle zone enhances elastic recovery and intensifies springback. On the other hand, faster bending promotes more uniform thickness reduction across the sheet, thereby mitigating localized thinning. These findings highlight a trade-off between minimizing springback and achieving uniform thickness, underscoring the complexity of simultaneously optimizing both parameters in the forming of pure titanium sheets. This study offers valuable insights for improving the precision and efficiency of titanium sheet forming processes.