In search of physical meaning: defining transient parameters for nonlinear viscoelasticity
In search of physical meaning: defining transient parameters for nonlinear viscoelasticity
复制标题
寻找物理意义：定义非线性粘弹性的瞬态参数
作者：
S. Rogers
一套完整的模型无关的粘弹性函数理解响应瞬态非线性流变试验，使用大振幅振荡剪切应变作为模型非线性协议。推导过程中没有对对称性进行任何假设，因此适用于对任何输入的响应，使研究人员能够明确定义随时间变化的模量、粘度、顺应性、流动性和法向应力系数。一个图例用于解释在模量空间的动态轨迹，沿着与明确的定义，在该速率的模量变化。这些提供了一种定量机制来识别材料响应在变形时何时以及以何种程度变硬、变软、变厚或变薄。除了提供模数的解析表达式外，推导还需要定义一个概念上的新术语。这意味着存在三个，而不是两个，随时间变化的非线性粘弹性功能，任何响应都可以完全描述。第三个功能帐户的非线性特性，如屈服应力和应变平衡的移动。这种完整的分析方案在区分实验室和材料框架中的菌株方面是独一无二的。物理过程分析的定量序列，这是在这项工作中得到充分发展，允许全面的物理解释的任何种类的瞬态变形的响应，包括稳定交替响应大振幅振荡剪切（LAOS），时间依赖性振荡剪切启动响应，触变和反触变响应。
A complete set of model-independent viscoelastic functions for understanding responses to transient nonlinear rheological tests is presented, using large-amplitude oscillatory shear strain as a model nonlinear protocol. The derivation makes no assumptions about symmetries, and is therefore applicable to the responses to any input, allowing researchers to unambiguously define time-dependent moduli, viscosities, compliances, fluidities, and normal stress coefficients. A legend for interpreting the dynamic trajectories in modulus space is provided, along with explicit definitions of the rates at which the moduli change. These provide a quantitative mechanism to identify when, and by how much, a material response stiffens, softens, thickens, or thins while being deformed. In addition to providing analytical expressions for the moduli, the derivation requires the definition of a conceptually new term. This means there exist three, not two, time-dependent nonlinear viscoelastic functions by which any response can be fully described. The third function accounts for nonlinear properties such as yield stresses and the shifting of the strain equilibrium. This complete analysis scheme is unique in making a distinction between the strains in the lab and material frames. The quantitative sequence of physical process analysis, which is fully developed in this work, allows for comprehensive physical interpretations of responses to transient deformations of any kind to be made, including the steady alternance responses to large-amplitude oscillatory shear (LAOS), time-dependent oscillatory shear startup responses, and thixotropic and anti-thixotropic responses.