镁合金管材大曲率无芯弯曲损伤及壁厚变化研究

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

摘要:

基于管材弯曲成形机理及Johnson-Cook损伤理论,利用Deform-3D有限元方法分析了AZ31B镁合金管材大曲率无芯弯曲初始弯曲温度、助推速度及助推形式对损伤及管材壁厚变化影响。结果表明：当助推模和压力模对管材施加的作用一定时,初始弯曲温度过低或过高均不利于镁合金管材弯曲成形,最佳初始弯曲温度为350℃; 在最佳初始弯曲温度条件下,当助推模与压力模同步运动时,仅能改善一侧壁厚变化程度,无法同时改善弯管整体壁厚变化,内外侧壁厚不均匀度较大；当助推模与压力模不同步时,通过合理匹配助推模与压力模二者之间的轴向速度来改变镁合金管材在进给阶段轴向拉伸或压缩变形程度,使得内外侧壁厚均匀度达到较理想效果；当外助推模和压力模同步,内助推模和以上二者等速反向运动时,内外侧壁厚均匀度最佳,获得综合性能良好的镁合金管材弯曲成形质量。

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.