Understanding and modeling the constitutive behavior of soft tissues represents an important challenge with significant relevance in medicine and biology. In this paper, we propose a new visco-hyperelastic model to describe the constitutive behavior of soft tissues as an isotropic and homogeneous material. The model is based on the nonlinear framework of continuum mechanics. A generalized Rivlin strain energy and a short-term viscous strain energy are used to describe the elastic part and time-dependence viscous part, respectively, while a long-term viscous function is derived through an integral framework of the applied stretch. To calibrate the material parameters, a set of self-designed uniaxial compression and relaxation tests are carried out on cylindrical samples of bovine liver. Moreover, the model is also validated against the experimental data of synthetic tissues reported by Khan et al. The good agreement between the predicted results and experimental data establishes the relevance of the proposed model. To investigate the model reliability, we have developed a “user-defined materials” subroutine to implement the constitutive behavior of the liver tissue in ABAQUS. By using the model, we simulate in vitro bovine liver behavior under compression and in relaxation and study the relative effects of the hyperelastic and viscous components on liver biomechanics.

中文翻译：

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对各向同性软组织的短期和长期粘性影响的粘超弹性本构模型

理解和建模软组织的本构行为是一个重要的挑战，在医学和生物学中具有重要意义。在本文中，我们提出了一种新的粘超弹性模型来描述作为各向同性和均质材料的软组织的本构行为。该模型基于连续介质力学的非线性框架。广义 Rivlin 应变能和短期粘性应变能分别用于描述弹性部分和时间相关粘性部分，而长期粘性函数是通过应用拉伸的整体框架推导出来的。为了校准材料参数，对牛肝的圆柱形样品进行了一组自行设计的单轴压缩和松弛试验。而且，该模型还根据 Khan 等人报告的合成组织的实验数据进行了验证。预测结果和实验数据之间的良好一致性确立了所提出模型的相关性。为了研究模型的可靠性，我们开发了一个“用户定义材料”子程序来在 ABAQUS 中实现肝组织的本构行为。通过使用该模型，我们模拟了体外牛肝在压缩和松弛状态下的行为，并研究了超弹性和粘性成分对肝脏生物力学的相对影响。我们开发了一个“用户定义材料”子程序来在 ABAQUS 中实现肝组织的本构行为。通过使用该模型，我们模拟了体外牛肝在压缩和松弛状态下的行为，并研究了超弹性和粘性成分对肝脏生物力学的相对影响。我们开发了一个“用户定义材料”子程序来在 ABAQUS 中实现肝组织的本构行为。通过使用该模型，我们模拟了体外牛肝在压缩和松弛下的行为，并研究了超弹性和粘性成分对肝脏生物力学的相对影响。