Wall thinning characteristics and prediction in numerical control bending of high strength Ti-3Al-2.5V tube

Abstract

Owing to the unique properties of high strength Ti-3Al-2.5V tube, wall thinning is prone to happen in tube bending. To accomplish tube precision bending forming, the wall thinning needs to be precisely predicted and effectively controlled. A theoretical model considering circumferential deformation was presented to reveal the inherent relationship for wall thickness distribution versus tube geometrical parameters, and its reliability was validated by published experimental results. Using finite element (FE) simulation combined with orthogonal test, the effect rules and significances of process parameters on wall thinning in numerical control (NC) bending for high strength Ti-3Al-2.5V tube were investigated. The results show that the significant factors sort from the largest to the smallest for wall thinning in tube bending as the clearance of tube versus mandrel Cm, axial feed of mandrel e, friction of tube versus mandrel fm, clearance of tube versus bending die Cb, clearance of tube versus wiper die Cw and push assistant speed of pressure die vp; the wall thinning decreases for the larger Cm and vp, while increases for the larger Cb, Cw, fm, and e. Furthermore, the prediction model of maximum wall thinning ratio was established based on the significant process parameters by multiple linear regression method. Compared with the results of orthogonal test, the relative error of that is less than 6.5%, which can be employed for rapidly predicting the wall thinning in tube bending.

Inhibiting thinning in tube bending by a superposition effect under a boosting movement

“…For supporting straight sections of the tube, the gap between the mandrel and the inner diameter of the tube affects the material flow of the tube, which has a significant impact on the thinning of the outer wall and the thickening and wrinkling of the inner wall of the tube [27]. In addition, the extension of the mandrel projection has a specific effect on the thinning of the outer wall.…”