弯管横截面畸变的试验与分析

在管材弯曲成形系列研究中，针对弯管壁厚变薄及横截面形状变形现象，展开了试验及有限元模拟分析。在平面应力和三向应力状态假设下，分别推导出弯管壁厚减薄率和横截面短轴变化率相互关系的近似计算公式。通过弯曲试验对公式计算值进行了比较和验证，结果表明，平面应力假设条件下的公式计算值相对准确。相对弯曲半径较大时，弯管外侧管壁材料的径向变形较小，外侧管壁变薄是导致弯管横截面畸变得主要原因。公式计算值与试验结果仍存在一定偏差，通过大量试验进一步修正后，可应用于实际生产。

Experiment and Analysis on the Distortion of Cross-section of Bended-tube

In the series-study of tube-bending-forming, the experiment and finite element simulation analysis, aiming at the phenomenon of wall-thinning and the cross-section shape deformation of the bended-tube, were carried out. Based on the assumption of the plane-stress and three-dimensional stress state, the approximate calculation formulae of the mutual relation between the wall-thinningratio and the change-ratio of short axis of the cross-section were deduced respectively. Through bending-experiments, the calculative value of the formula is contrasted and verified. It is proven that the calculative value of the formula based on the assumption of the plane-stress is relatively accurate. If the relative bending radius is bigger, the radial-deformation of the outer-wall material of bended-tube is smaller. The main reason which leads to the cross-section distortion of bended-tube is the thinning of the outer wall. Although there is a certain deviation in the calculative value of the formula, it can be applied to practice through further amendment with a great number of experiments.