基于上限法的闭式冷正挤压棒料脱膜状态分析

Demoulding state analysis of closed-die cold forward extruded rod based on upper bound method

考虑一种非磷系润滑膜的脱膜长度,通过上限法分析模型对棒料的闭式冷正挤压工艺进行了分析。通过实验获得了脱膜长度随锥模半角和断面收缩率的变化规律。实验结果表明,随断面收缩率的增长,脱膜长度快速增长。随着锥模半角的增长,脱膜长度也在增长,但是锥模半角增大到一定程度后,脱膜长度的增长幅度减小。求得总功率为最小时的最佳锥模半角,范围是15°~28°,最佳锥模半角随脱膜长度的增加而增加。在成形载荷方面,与DEFORM商用有限元分析软件的仿真结果进行了比较,上限法算得的成形载荷略大于有限元仿真结果,而且两者的载荷曲线较为相近,证明了该上限法分析模型的合理性,也表明上限法更有利于成形设备的选型。

Considering the demoulding length of a non-phosphate lubrication film,the closed-die cold forward extrusion process of rod was analyzed by the upper bound method analysis model.The variation laws of demoulding length with the semi-angle of conical die and area reduction were obtained by experiments.The experimental results show that with the increase of area reduction,the demoulding length increases rapidly.With the increase of semi-angle of conical die,the demoulding length also increases,but when the semi-angle of conical die increases to a certain extent,the increase amplification of demoulding length decreases.The optimal semi-angle of conical die with the lowest total power was obtained,and it ranges from 15°to 28°,the optimal semi-angle of conical die increases with the increase of demoulding length.In terms of forming load,compared with the simulation results of commercial finite element analysis software DE-FORM,the forming load calculated by the upper bound method is slightly larger than that of the finite element simulation results,and the two load curves are similar,which proves the rationality of upper bound method analysis model,and it also indicates that the upper bound method is more conductive to the selection of forming equipment.