聚合物熔体在直线型异型材挤出口模内三维粘弹流动分析  

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

作　　者：柳和生[1] 涂志刚[1] 熊洪槐[1] 

机构地区：[1]南昌大学机电工程学院聚合物加工研究室,江西南昌330029

出　　处：《应用基础与工程科学学报》2004年第1期73-79,共7页Journal of Basic Science and Engineering

基　　金：国家自然科学基金(项目号:59763002);江西省自然科学基金

摘　　要：利用罚函数有限元法,采用PTT粘弹模型,对聚合物熔体在直线型异型材挤出口模内的三维等温流动进行了数值模拟,得出了不同挤出量下的速度和应力分布。结果表明:口模截面上流动中心位于流动阻力较小的部分,而且这部分的流速较快;必须依据流动阻力的大小来匹配组成口模截面的各部分所对应的成型区长度,流动阻力大的部分,长度应较小,以免产生流动不平衡从而导致挤出物离模后的扭曲;过渡区对熔体在其上游的稳流区和在其下游的成型区内的流动均有明显影响;聚合物熔体的松弛时间对熔体流速无影响,对剪切应力的影响非常小,随着松弛时间的增大,熔体的粘弹性拉伸应力下降,而且熔体粘弹性拉伸应力对总拉伸应力的贡献很大。By using penalty finite element method and PTT viscoelastic constitutive model, numerical simulation was implemented for the three dimensional viscoelastic polymer melt flow through the extrusion die with an irregular cross section composed of lined up components. The distributions of velocity and stress under various conditions were worked out. On the cross section of the die, the flow centre lies in the region where the flow resistance is lower, and the extrusion velocity is higher over there. The length of the forming zone corresponding to each constitutional component of the cross section of the die must be decided according to the flow resistance in that component so as to eliminate the unbalanced flow and the distortion of the extrusion product. The transitional zone has significant effect on the flow within both the flow stabilizing zone and forming zone. The relax time of polymer melt has no effect on melt velocity and has little effect on the shear stress. The viscoelastic extension stress makes large contribution to the total extensional stress and it decreases when the relax time increases.

关 键 词：聚合物熔体 直线型异型材 挤出口模 三维粘弹流动 数值模拟 罚函数有限元法 

分 类 号：O357[理学—流体力学] TQ320.663[理学—力学]