Department of Biomedical Engineering, National University of Singapore, Singapore.
Int J Numer Method Biomed Eng. 2019 Dec;35(12):e3269. doi: 10.1002/cnm.3269. Epub 2019 Nov 28.
The biomechanical properties of gastrointestinal (GI) tissue play a significant role in the normal functioning of the organ. GI soft tissues exhibit a highly nonlinear rate- and time-dependent stress-strain behaviour. In recent years, many constitutive relations have been proposed to characterize these properties. However, a constitutive relation is not sufficient to analyse the biomechanics at the organ level with complex loading and boundary conditions. Hence, for a refined mechanical analysis, a finite element (FE) implementation of the constitutive relation is needed. Here, we propose an FE implementation of a finite nonlinear hyperviscoelastic model suitable for soft biological tissues. The FE model has been validated at first by comparing its results with the analytical solutions of a standard linear solid, and then it has been used to recreate experimental observations performed on tissue strips obtained from different animals. We have also proposed a method, in this work, to construct a residually stressed FE model so that the consequences of residual stresses on GI mechanics can be examined. Our FE formulation was able to capture the nonlinear soft tissue properties and also demonstrated that the addition of residual stresses reduces stress concentrations and the stress gradient in the GI wall.
胃肠道（GI）组织的生物力学特性在器官的正常功能中起着重要作用。GI 软组织表现出高度非线性的率相关和时相关的应力-应变行为。近年来，已经提出了许多本构关系来描述这些特性。然而，对于具有复杂加载和边界条件的器官水平的生物力学分析，一个本构关系是不够的。因此，需要对本构关系进行有限元（FE）实现，以进行更精细的力学分析。在这里，我们提出了一种适用于软生物组织的有限非线性超粘弹性模型的 FE 实现。首先，通过将其结果与标准线性固体的解析解进行比较，对 FE 模型进行了验证，然后使用该模型再现了从不同动物获得的组织条带上进行的实验观察。我们还在这项工作中提出了一种构造残余应力 FE 模型的方法，以便可以检查残余应力对 GI 力学的影响。我们的 FE 公式能够捕捉到非线性软组织特性，并且还表明残余应力的增加可以减少 GI 壁中的应力集中和应力梯度。
