Linear viscoelastic region is important to investigate material properties. We investigated boundary of linear viscoelasticity for simple shear flows with various time functions of shear strain. We used Phan-Thien and Tanner (PTT) model and Giesekus model in order to extract the linearity criterion. We determined critical strain (γ_c) as a function of dimensionless number such as De or Wi and the nonlinear parameter of the models. We found a superposition of the critical strain at start-up shear flow and oscillatory shear flow. Replacing relaxation time by mean relaxation time (\(\left({\overline {\rm{\lambda }} = {J_{\rm{e}}}{{\rm{\eta }}_{\rm{o}}}} \right)\)), we checked the validity of the equation with experimental data.

中文翻译：

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简单剪切流中线性粘弹性边界的研究：模型计算

线性粘弹性区对于研究材料性能很重要。我们研究了具有各种剪力时间函数的简单剪力流的线性粘弹性边界。为了提取线性准则，我们使用了Phan-Thien和Tanner（PTT）模型和Giesekus模型。我们确定的临界应变（γ _Ç）作为无量纲数，如德或Wi和模型的非线性参数的函数。我们在启动剪切流和振荡剪切流处发现了临界应变的叠加。用平均松弛时间（\（\ left（{\ overline {\ rm {\ lambda}} = {J _ {\ rm {e}}} {{\ rm {\ eta}} _ {\ rm {o }}}} \ right）\）），我们用实验数据检查了方程的有效性。