中文摘要：

管筒形零件机械扩径最终制品的横断面尺寸精度和形状精度，不同程度地受到各种工艺参数、模具参数、材料性能参数以及摩擦条件的影响。机械扩径工艺设计的重要内容之一，就是针对特定的毛坯规格，合理选择各种成形参数并使其成为一种最优组合，以获得最佳的制品尺寸和形状精度。文章基于MSC,Marc非线性有限元分析软件和遗传优化算法，应用Python语言设计了机械扩径成形参数优化的遗传算法程序，通过对MSC．Marc软件的二次开发，实现了遗传优化算法与MSC．Marc软件的连接，为管筒形零件机械扩径工艺过程的成形参数优化提供了一种新方法。针对大直径管线钢管机械扩径工艺，得到了以最终制品形状精度（横断面圆度误差）为优化目标的扩径率、模具直径和模具边缘圆角半径等成形参数的最优组合。采用最优的成形参数组合，可以显著提高最终制品的横断面形状精度。

英文摘要：

The precision of cross-sectional shape and its dimension of finished cylinders in mechanical expanding process depends on parameters of forming process and die, mechanical properties of material and friction condition in various degrees. It is one of important matters to the design of forming process how the various parameters of mechanical expanding are determined properly in order to get a fine precision of cylinder for a certain blank. Based on MSC. Marc, a nonlinear software of finite element method, and genetic algorithm of optimization, a program of optimization for the forming parameters of mechanical expanding process is developed in Python by means of the development of MSC. Marc in this paper. MSC. Marc and the program of optimization are united in a new method by which the forming parameters of mechanical expanding process for cylinders can be optimized. An optimum combination of forming parameters of expanding ratio, diameter of sectorial die and corner radius of die rim is concluded from a functional relation between roundness error of cross section and forming parameters for the process of mechanical expanding of large diameter line pipe in the paper. With optimum forming parameters, the precision of cross-sectional shape of finished cylinders is improved significantly.