基于有限元法的空心铝型材挤压过程瞬态分析

Analysis on transient extrusion process of hollow aluminum profile based on finite element method

采用有限元软件,对一非对称截面列车上侧梁型材挤压分流、焊合直至稳态挤出的整个非稳态过程进行了数值模拟。着重研究了挤压成形过程中变形体的速度、温度、应变速率等物理场量的分布与变化情况,以及模具应力分布情况。针对模拟过程中出现的挤出物前端存在严重变形的问题,对模具的二级焊合室尺寸、阻流块高度以及工作带尺寸作出优化。模具结构优化后模孔出口截面速度均匀性得到明显改善,其速度差从22 mm·s-1减小到7 mm·s-1。通过分析等效应变速率与温度分布的关系,发现坯料温度升高所需的热量主要来源于坯料变形产生的塑性变形能。通过模具应力分析得知模具在各挤压阶段的应力分布情况。

The non-steady extrusion process from the dividing,welding stages to steady extrusion for an upside beam on the train with unsymmetrical cross-sectional profile was numerically simulated by FEM（ finite element method）. The distribution and variation of the velocity,temperature and strain rate for the deformation material were researched during the whole non-steady extrusion process. The die stress distribution were analyzed too. For the issue of severe deformation of extrusion head in the whole extrusion process simulation,the optimizations for the second chamber structure sizes,baffle-block height and bearing length were performed. As a result the outlet velocity uniformity was improved obviously. The velocity difference between the maximum and the minimum reduces from 22 mm · s- 1to7 mm·s- 1. After analyzing the distribution relationship between effective strain rate and temperature,it is found that the quantity of heat needed for blank temperature rising is mainly derived from the energy of plastic deformation generated by blank deformation. The stress distribution of die in each stage of extrusion is obtained by die stress analysis.