基于三维粘弹性罚函数有限元分析的塑料异型材挤出口模设计

以Y形截面异型材挤出为研究对象,采用PTT粘弹本构模型和罚函数有限元法,对塑料熔体在挤出口模内的三维粘弹性等温流动进行了数值模拟。通过分析数值模拟得到的流速分布,修正了挤出口模的初始设计,并依据流率平衡原则来确定成型区各部分的长度。研究还表明:对于异型材挤出口模设计,不能把口模截面视作若干规则形状截面的简单几何组合,必须把其当成一个整体来对待;过渡区不仅影响成型区的流动,而且对稳流区的流动也有不可忽视的影响,设计时应对过渡区给予足够的重视。提出的异型材挤出口模设计方法可以容易地推广到更复杂截面异型材挤出口模设计中。

Design of extrusion die for plastic profiled bar based on 3D viscoelasticity penalty function finite element analysis

The 3D viscoelasticity isothermal flow of plastic melts in the extrusion die for a Y-shaped plastic profiled bar was numerically simulated by using PTT viscoelastic constitutive model and penalty function finite element method.After an analysis on the velocity distribution obtained from numerical simulation, the original die design was modified;and the length of each part of molding zone was determined according to the principle of flow rate equilibrium.The investigation shows that in design of extrusion die for a profiled bar,the cross section of die should be considered as a group instead of a simple geometric integration of several regular parts.The transition zone affects the plastic flow both in molding zone and steady-flow zone and should be considered in die design.