Panda Satish Kumar, Buist Martin Lindsay
Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore.
Department of Biomedical Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117583, Singapore.
J Biomech. 2018 Mar 1;69:121-128. doi: 10.1016/j.jbiomech.2018.01.025. Epub 2018 Feb 1.
Soft tissues exhibit highly nonlinear rate and time-dependent stress-strain behaviour. Strain and strain rate dependencies are often modelled using a hyperelastic model and a discrete (standard linear solid) or continuous spectrum (quasi-linear) viscoelastic model, respectively. However, these models are unable to properly capture the materials characteristics because hyperelastic models are unsuited for time-dependent events, whereas the common viscoelastic models are insufficient for the nonlinear and finite strain viscoelastic tissue responses. The convolution integral based models can demonstrate a finite viscoelastic response; however, their derivations are not consistent with the laws of thermodynamics. The aim of this work was to develop a three-dimensional finite hyper-viscoelastic model for soft tissues using a thermodynamically consistent approach. In addition, a nonlinear function, dependent on strain and strain rate, was adopted to capture the nonlinear variation of viscosity during a loading process. To demonstrate the efficacy and versatility of this approach, the model was used to recreate the experimental results performed on different types of soft tissues. In all the cases, the simulation results were well matched (R⩾0.99) with the experimental data.
软组织表现出高度非线性的速率和时间依赖性应力应变行为。应变和应变率依赖性通常分别使用超弹性模型和离散（标准线性固体）或连续谱（准线性）粘弹性模型进行建模。然而，这些模型无法正确捕捉材料特性，因为超弹性模型不适用于时间依赖性事件，而常见的粘弹性模型不足以描述非线性和有限应变的粘弹性组织响应。基于卷积积分的模型可以表现出有限的粘弹性响应；然而，它们的推导与热力学定律不一致。这项工作的目的是使用热力学一致的方法开发一种用于软组织的三维有限超粘弹性模型。此外，采用了一个依赖于应变和应变率的非线性函数来捕捉加载过程中粘度的非线性变化。为了证明这种方法的有效性和通用性，该模型被用于重现对不同类型软组织进行的实验结果。在所有情况下，模拟结果与实验数据都有很好的匹配（R⩾0.99）。
