Filament stretching rheometry is a prominent experimental method to determine rheological properties in extensional flow whereby the separating plates determine the extension rate. In literature, several correction factors that can compensate for the errors introduced by the shear contribution near the plates have been introduced and validated in the linear viscoelastic regime. In this work, a systematic analysis is conducted to determine if a material-independent correction factor can be found for non-linear viscoelastic polymers. To this end, a finite element model is presented to describe the flow and resulting stresses in the filament stretching rheometer. The model incorporates non-linear viscoelasticity and a radius-based controller for the plate speed is added to mimic the typical extensional flow in filament stretching rheometry. The model is validated by comparing force simulations with analytical solutions. The effects of the end-plates on the extensional flow and resulting force measurements are investigated, and a modification of the shear correction factor is proposed for the non-linear viscoelastic flow regime. This shows good agreement with simulations performed at multiple initial aspect ratios and strain rates and is shown to be valid for a range of polymers with non-linear rheological behaviour.

长丝拉伸流变测定法是一种重要的实验方法，用于确定拉伸流中的流变特性，由此分离板确定拉伸速率。在文献中，已经在线性粘弹性状态中引入并验证了几个可以补偿由板附近的剪切贡献引入的误差的校正因子。在这项工作中，进行了系统分析以确定是否可以为非线性粘弹性聚合物找到与材料无关的校正因子。为此，提出了一个有限元模型来描述长丝拉伸流变仪中的流动和由此产生的应力。该模型结合了非线性粘弹性，并添加了一个基于半径的板速度控制器，以模拟长丝拉伸流变学中的典型拉伸流。通过比较力模拟与解析解来验证模型。研究了端板对拉伸流动和合力测量的影响，并针对非线性粘弹性流态提出了剪切修正系数的修改。这表明与在多个初始纵横比和应变率下进行的模拟非常吻合，并且显示出对一系列具有非线性流变行为的聚合物有效。