Wall Thinning Characteristics of Ti-3Al-2.5V Tube in Numerical Control Bending Process

A finite element(FE) model for the numerical control(NC) bending of Ti-3 Al-2.5 V titanium alloy seamless tube is established, considering the variation in the contractile strain ratio(CSR) and elastic modulus(E). The wall thinning characteristics of Ti-3 Al-2.5 V tube under different geometric and process conditions were investigated. The results showed that the CSR-E variation can change the wall thickness, but has no remarkable effect on the change characteristics. The reasonable parameter ranges are as follows: a bending-radius range not less than 1.5 times the outer diameter, a bend angle up to 180?, and a mandrel extension of 0-3 mm. The friction coefficient between the pressure die and the tube should be in the range of 0.20-0.35, and between the bending die and the tube should be in the range of 0.05-0.15. As long as the performance meets the requirements, the relative push-assistant speed should be as small as possible.