带内锥冲头挤压过程中金属变形流动行为研究

针对平模挤压过程中易产生死区、缩孔等流动缺陷,设计一种带内锥冲头用以改善成形过程中金属的变形流动行为.对冲头有、无内锥两种形式挤压过程进行数值模拟,利用罗德系数、J2应力偏量不变量等特征量进行变形分区,并利用7050铝合金进行挤压试验验证.结果表明,带内锥冲头能有效改善挤压过程中速度场的分布,显著减小死区,并避免产生缩孔缺陷.因此,带内锥冲头更利于金属的挤出成形.

Study of Metal Flow Behavior during Extruding with Inner Cone Punch

For the defects such as dead zone and shrinkage cavity in conventional extrusion process,an inner cone punch was proposed to improve the metal flow behavior.Numerical simulations on extrusion process with and without the inner cone punch were carried out,and the division of deformation was proposed by employing the characteristic quantity such as Lode parameter and invariant of the deviator(J_2).Numerical simulation results were tested by the 7050 aluminium alloy extrusion experiments,the results showed that,by employing the inner cone punch,velocity field distribution during extrusion process would be improved greatly,the risk in generation of dead zone was reduced remarkably,and shrinkage cavity would be avoided,therefore,the inner cone punch made the metal much easier of extruding.