Study on Damage and Wall Thickness Variation with Large Curvature and No-Mandrel Bending Process of Magnesium Alloy Tube

Abstract:

Based on the tube bending forming mechanism and Johnson-Cook damage theory, the influence of initial bending temperature、aid-push speed and aid-push mode of magnesium alloy tube bending process , with large curvature and no-mandrel , on the damage and wall thickness variation was analyzed by the Deform-3D finite element method. The results showed that: when the aid-push die and pressure die exerted a certain effect on the tube, the initial bending temperature was too high or too low, which was detrimental to the bending of the magnesium alloy tube, and the optimum initial bending temperature was 350℃. Under the optimum initial bending temperature , when the aid-push die moved synchronously with the pressure die, the unilateral wall thickness variations degree can only be improved, and the overall wall thickness variations can not be improved simultaneously, so the wall thickness non-uniformity of the tube was remarkable. When the aid-push die and pressure die were not synchronized, the axial tension or compression deformation degree of the tube-bending can be changed with reasonably matching the axial velocity between the aid-push die and the pressure die in the feed stage, thus the wall thickness uniformity can be achieved a rather good effect. When the external aid-push die moved synchronously with the pressure die, and the internal aid-push die moved at a velocity of the same magnitude but in opposite direction with the above two dies, the wall thickness uniformity was optimal, thus the bending quality of magnesium alloy tube with good comprehensive properties was obtained.