L型异型材挤出口模内聚合物熔体三维等温幂律流动的数值模拟

Numerical simulation of three dimensiona isothermal power-law polymer melt flow within an extrusion die with the “L”shaped cross section

利用罚有限元法,采用幂律本构模型,对聚合物熔体在L型异型材挤出口模内的三维等温流动进行了数值模拟,分析了口模内熔体流动的速度场和应力场。分析表明:L型异型材挤出口模截面不能简单视作两矩形截面的几何组合,因为其上有三个特征流动区;过渡区对熔体在口模内的流动有非常大的影响,它不但影响成型区熔体的流动,而且对稳流区熔体的熔体的流动产生一定的影响;此外,因为在过渡区产生了熔体拉伸取向,需要一定的成型区长度使高分子链段充分松弛。

The numerical simulation was implemented for the theree dimensional isothermal power-law polymer melt flow within an extrusion die with the “L”shaped cross section by means of penalty fimite element method Especially,the velocity and stress distributions wereanalyzed in details.The analysis shows that for polymer melt flow because there are three marked flow domains on the “L”shaped cross section it cannot be treated simply as the geometric combinaion of two rectangles,the transition zone of the die plays a rather important role in the polymer melt flow througth the die because it has significant effects on both the flow in the forming zone and that in the flow stabilizing zone,and because of the melt elongational orientation existing in the transition zone a definite part of the forming zone is essential for the relax of the macromolecule chain.