Oblique stretching is a special approach for the fabrication of polymer film whose product is mainly used in the optical display field, such as compensation films, retardation films, et al. Nonetheless, the previous research reports on oblique stretching processing are still lacking, and the related numerical research is almost blank. This contribution uses the FEM (finite element method) to simulate the oblique stretching process of viscoelastic polymer film for the first time. The differential viscoelastic PTT (Phan-Thien and Tanner) model, one of the most realistic constitutive models is chosen. Furthermore, the polycarbonate melt was rheologically characterized and used as input material parameters in our simulations. Based on the membrane hypothesis and stabilization algorithms like DEVSS (discrete elastic viscous stress splitting), the specific numerical scheme is derived and the algorithm implementation is summarized. Finally, a complete numerical example of oblique stretching is demonstrated and compared with symmetric stretching. Based on the simulation results, the evolution of thickness and the influence of the y-direction stretching on thickness uniformity are further investigated.

斜拉伸是制备聚合物薄膜的一种特殊方法，其产品主要用于光学显示领域，如补偿薄膜、延迟薄膜等。尽管如此，以往关于斜拉伸加工的研究报告仍然缺乏，相关数值研究几乎是空白。本贡献首次使用FEM（有限元法）模拟粘弹性聚合物薄膜的斜向拉伸过程。选择了微分粘弹性 PTT（Phan-Thien 和 Tanner）模型，这是最现实的本构模型之一。此外，聚碳酸酯熔体经过流变学表征并用作我们模拟中的输入材料参数。基于膜假设和稳定算法，如 DEVSS（离散弹性粘性应力分裂），推导出了具体的数值方案，总结了算法实现。最后，展示了一个完整的倾斜拉伸数值例子，并与对称拉伸进行了比较。基于模拟结果，厚度的演变和影响进一步研究了对厚度均匀性的y方向拉伸。