用Wagner本构方程对聚合物挤出胀大的三维有限元分析

采用有限元方法分析粘弹性聚合物熔体的三维挤出胀大。采用积分型本构方程 Wagner模型描述聚合物熔体的粘弹性记忆特性 ,并引入了非线性衰减函数。对于本构方程中偏应力张量给出了计算方法 ,采用迭代方法求解非线性方程组。并根据自由面处的边界条件 ,确定出口处自由面的最终位置。对圆形流道进行分析 ,结果与轴对称分析和实验相吻合 ,最后对矩型流道进行计算 ,得出挤出物的形状

Three-dimensional Finite Element Analysis for Extrudate Swell of Polymer Melts by Wagner Constitutive Equation

D extrudate swell of polymer melts was analyzed by the finite element method. The constitutive equation used is integral Wagner model in which the nonlinear decay function is contained, and it is generally recognized better one to describe the memory effects for polymer melts. The method used to compute the extra stresses in the constitutive model was given here. Therefore, the solution of the finite element nonlinear equations can be obtained by suitable iteration. Simultaneously, according to the boundary conditions of free surface, the final position and shape of exit free surface can also be found. Based on the above technique, as a test, the 3D extrudate swell of LDPE melt in the circular die was simulated. Results are in good agreement with those of 2D axial symmetry analysis and experimental data. Finally, the analysis of 3D extrudate swell in rectangle die was done and the extrudate shape was obtained.