聚合物熔体在曲线型异型材挤出口模内三维粘弹流动数值模拟

Numerical Simulation of Three Dimensional Viscoelastic Polymer Melt Flow Through the Extrusion Die with an Irregular Cross Section Composed of Curved Components

利用罚函数有限元法,采用PTT粘弹本构模型,对聚合物熔体在C形和Y形截面异型材挤出口模内的三维粘弹流动进行了数值模拟。在相同挤出流量下,得到了口模内不同截面上的速度和应力分布。对模拟结果的分析表明:异型流道中存在的突出棱角会使局部流道截面的有效流动面积减小,产生收敛效应,收敛角越大,收敛效应越强。因而要保证熔体稳定流动,过渡区与成型区流线必须平滑连接;异型流道中不同的部位熔体所受的剪切和拉伸应力都有所不同,熔体受力历史差异可能导致制品质地不均匀,挤出口模设计中必须考虑熔体受力史。

By means of penalty finite element method and PTT viscoelastic constitutive model,numerical simulations were implemented for the three dimensional viscoelastic polymer melt flow through the extrusion dies with the ＂C＂ and ＂Y＂ shaped cross section.The distributions of velocity and stress under the same flow rate were worked out.The protruding edges and corners in the die will cause convergence effect which results in the reduction of the effective flowing area of local runner.The sharper the convergence angle is,the stronger the convergence effect is.The connection between transitional zone and forming zone should be smooth to ensure the melt flow stably.The shear stress and tensile stress of the melt are different in various part of the die.The difference of the stress history will cause uniformity in the products＇ textile.The stress history must be considered during the design of the die.