扩径模具直径对成形件品质的影响

Influence of expanding-die diameter on the quality of finished products

机械扩径是制造管筒形零件的一种精密成形方法。扩径时 ,筒形件的变形、应力应变分布以及成形件的轮廓形状、壁厚变化都具有明显的局部特征。这些特征不仅与毛坯断面的形状误差有关 ,而且还与模具的分瓣结构及其结构参数密切相关。由于以前缺乏对机械扩径过程的深入研究 ,所以对这些变形特征和规律的认识也欠深刻。作者通过有限元数值模拟和实验方法 ,系统地分析了扩径模具的结构参数与成形件品质之间的关系。本文专门论述了机械扩径模具直径对成形件品质的影响 ,提出了相对凸模半径的概念 ,系统分析了它对变形分布、成形件轮廓形状、椭圆度和壁厚的影响。研究结果表明 ,成形件的横断面轮廓形状与相对凸模半径有关 ;最大塑性等效应变是相对凸模半径的递增函数 ;椭圆度随相对凸模半径的增加而减小。基于研究结果 ,本文给出了相对凸模半径的设计原则。

Mechanical Expanding is one of the finishing processes in cylindrical part forming. The deformation distribution of the cylindrical blank and the outer-diameter and wall-thickness distribution of the finished products, having clearly regional features, are influenced by the shape tolerance of cylindrical blank and the sectorial structure of dies. We really have known a little about these features for lack of a thorough research for the mechanical expanding technology. By elastic-plastic finite element method and experiments, the relation between the quality of finished products and the structural parameters of expanding-die is analyzed systematically. The influence of expanding-die diameter on the quality of finished products, such as the uniformity of deformation, the contour of a cross section and its ellipticity as well as the wall thickness of finished products, is discussed specially; a conception of relative radius of punch and the design criterion of it are given in this paper. According to the results, the contour of cross section is related to the relative radius of punch; the maximum equivalent plastic strain is an increasing function of it and the ellipticity is a decreasing function of it.