变径管内高压成形的厚度分界圆

Thickness dividing circle in hydroforming of variable diameter tubes

为了研究变径管内高压成形过程中工艺参数和管坯几何尺寸对壁厚分布的影响,通过力学分析和全量本构方程,推导出变径管内高压成形厚度分界圆的解析公式.该公式反映了摩擦系数、膨胀系数、管端轴向应力与内压之比、送料区相对长度、管坯相对壁厚、零件过渡锥角等参数与厚度分界圆相对位置之间的定量关系,并与数值模拟规律一致.研究表明:随着摩擦系数、管端轴向应力与内压之比、送料区相对长度的增加,壁厚不变的厚度分界圆距离管端越来越近,即膨胀区壁厚减薄区域是越来越大的;而随着管坯相对壁厚的增加,壁厚不变的厚度分界圆距离管端越来越远,即膨胀区壁厚减薄区域是越来越小的.

To investigate the effect of process hydroforming of variable diameter tubes, the parameters and geometry of the tube on thickness distributions in analytic formula of the thickness dividing circle was derived by using the mechanical analysis and the total strain theory. The effect of friction coefficient, expansion coefficient, ratio of axial stress to internal pressure, relative length of feeding zone, relative thickness of tube, and transition cone angle of workpiece on the relative position of thickness dividing circle can be given by this formula quantitatively, and the analytic results are in good agreement with the FEM. The results show that with the increasing of friction coefficient, the relative length of feeding zone, the ratio of axial stress to internal pressure, the distance between thickness dividing circle without thinning and tube end decreases, that means the increase of the thinning zone; and with the increasing of relative thickness of tube, the distance between thickness dividing circle without thickness thinning and tube end increases, that means the decrease of the thinning zone.