Weld lines are one of the typical quality issues of injection molded parts. They are unavoidable even for moderate complex products. To explore the formation of weld lines in injection molding, a flow model based on viscoelastic constitutive equation is presented in this article to predict and evaluate of weld lines location and properties, in which Rolie-Poly constitutive equation is used to describe the viscoelastic properties of polymer melts and level set method is used to capture melt front. Furthermore, the formation and evolution processes of weld lines are investigated by co-injection molding technique in simulation, since the processes are determined by the flow front and rheological history of the melt streams. Numerical results show that weld lines can be predicted accurately, and the formation and evolution processes of weld line can be shown more clearly by co-injection molding technique. In addition, properties of polymer melt such as velocity, pressure, principal stress difference, and molecular orientation in the weld line regions are investigated and presented.

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基于粘弹性本构方程的注塑成型过程中熔接线位置及特性建模与仿真

焊缝是注塑件的典型质量问题之一。即使对于中等复杂的产品，它们也是不可避免的。为了探讨注塑成型中熔接线的形成，本文提出了一种基于粘弹性本构方程的流动模型来预测和评估熔接线的位置和性能，其中 Rolie-Poly 本构方程用于描述粘弹性聚合物熔体和水平设置方法用于捕获熔体前沿。此外，在模拟中通过共注射成型技术研究了熔接线的形成和演变过程，因为这些过程是由熔体流的流动前沿和流变历史决定的。数值结果表明可以准确预测熔接线，并且通过共注射成型技术可以更清楚地显示熔接线的形成和演变过程。此外，还研究并介绍了聚合物熔体的特性，例如速度、压力、主应力差和熔接线区域中的分子取向。