中文摘要：

extrudate 的数字模拟胀大在挤出处理是重要的。extrudate 的精确预言胀大对控制慈悲融化流动和最后的产品的质量。一个数学模型三维(3D ) 通过椭圆的戒指的粘弹性的流动死因为聚合物挤出被调查。粘弹性的不可压缩的液体的惩罚功能明确的表达被介绍给有限元素模型分析 3D 挤出问题。分离橡皮粘滞切开应力(DEVSS ) ，优化迎风的 Petrov-Galerkin (SUPG ) 技术被用来获得稳定的模拟结果。免费表面被更新需要更少的记忆空间的 streamlines 更新。根据数字模拟，结果，零砍粘性的效果和 extrudate 上的延伸参数胀大是细微的，但是随容量的流动的增加评估并且放松时间 extrudate 胀大显著地增加的比率。最后， extrudate 的数字模拟胀大为低密度的聚乙烯(LDPE ) 的流动融化被调查，结果与其它的工作同意了很好。这些结论为预报 extrudate 提供了量的基础胀大比率并且控制挤出生产率塑造。

英文摘要：

The numerical simulation of extrudate swell is significant in extrusion processing.Precise prediction of extrudate swell is propitious to the control of melt flow and the quality of final products.A mathematical model of three-dimensional（3D）viscoelastic flow through elliptical ring die for polymer extrusion was investigated.The penalty function formulation of viscoelastic incompressible fluid was introduced to the finite element model to analyze 3D extrusion problem.The discrete elastic viscous split stress（DEVSS）and streamline-upwind PetrovGalerkin（SUPG）technology were used to obtain stable simulation results.Free surface was updated by updating the streamlines which needs less memory space.According to numerical simulation results,the effect of zero-shear viscosity and elongation parameter on extrudate swell was slight,but with the increase of volumetric flow rate and relax time the extrudate swell ratio increased markedly.Finally,the numerical simulation of extrudate swell flow for low-density polyethylene（LDPE）melts was investigated and the results agreed well with others’work.These conclusions provided quantitative basis for the forecasting extrudate swell ratio and the controlling of extrusion productivity shape.