不同背压方式对静液挤压过程影响的模拟研究

Simulation on Influences of Different Back Pressure Methods on Hydrostatic Extrusion Process

目的研究两种常用的背压方式在静液挤压工艺中对材料变形过程的影响。方法通过选取合理的背压工艺和压力数值,减小静液挤压过程中坯料的拉应力区域,降低材料开裂的风险。基于有限元分析(FEA)软件ANSYS,采用压力加载的方式对顶杆背压和静水背压静液挤压工艺中坯料内部应力应变分布以及材料流动性能的影响开展分析和讨论。结果两种背压方式均存在临界值,适当的压力范围可以抑制裂纹,并且可以获得较好的挤压样品;顶杆背压较静水背压更明显地抑制了轴向拉应力,但会导致其余两项拉应力的滋生;静水背压对三向拉应力都有一定的抑制效果。结论顶杆背压适合于在塑性材料的大挤压比加工中抑制表面纵向裂纹的萌生,也适用于塑性一般的材料的静液挤压变形;静水背压对三向拉应力都有一定的抑制作用,适用于加工变形能力较差的材料。

The purpose of this paper is to study the influences of two commonly used back pressure methods on the deformation behavior of materials in hydrostatic extrusion (HE) process. By selecting reasonable back pressure method and pressure value,the tensile stress region in the billet of hydrostatic extrusion process was reduced and the cracking trend of the material was restrained. Based on the finite element analysis (FEA) software ANSYS, the stress and strain distribution of billet and the effects of material flow behavior were analyzed and discussed by means of pressure loading under two different back pressure methods in hydrostatic extrusion processes. The results showed that there were critical values of the solid back pressure and the fluid back pressure. A proper pressure range could restrain the crack and obtain better extruding samples.The solid back pressure could restrain the axial tensile stress more obviously than that of fluid back pressure, but it would lead to the breeding of the other two tensile stresses. The fluid back pressure could restrain the triaxialtensile stress to a certain extent. In conclusion, the solid back pressure is suitable for restraining the initiation of longitudinal surface cracks in large extrusion ratio processing, and it is also suitable for hydrostatic extrusion deformation of materialswith general plasticity. Hydrostatic backpressure can restrain the three-dimensional tensile stress to a certain extent, and it is suitable for processing materials with poor deformation ability.