Nonlinear Viscoelasticity and Damage of Soft Tissue: Experimental and Constitutive Study of Ligament

本研究主要针对软结缔组织的非线性粘弹性行为，特别是本构行为进行研究。由于其简单性，我们选择韧带作为实验模型。研究组织如下：(i)将进行一项实验研究，定义整个可逆韧带变形范围内的粘弹性行为。本研究将使用蠕变和松弛加上恢复协议，以允许各种非线性之间的区分。（ii）根据实验数据建立鲁棒粘弹性本构模型。该模型将适当地考虑非线性和相互关联的蠕变和松弛。（iii）应用应力和应变水平的可逆变形极限（作为加载时间的函数）将通过实验从(I)中的数据中确定，从而定义单次过载的亚失效组织损伤的开始。将制定损伤开始的亚失效准则。（iv）蠕变和松弛试验将在额外的试样上进行，以量化在更高的载荷和变形产生更大程度的组织损伤（来自单一过载）后力学行为的妥协。与不可逆变形有关的微创伤和损伤将使用扫描电子显微镜进行形态学表征。

The research is primarily directed toward study of nonlinearly viscoelatic behavior of soft connective tissues, particularly the constitutive behavior. Because of their simplicity, ligaments are chosen as an experimental model. The research is organized as follow (i) an experimental study will be performed that defines viscoelastic behavior throughout the range of reversible ligament deformations. This study will use creep and relaxation plus recovery protocols to allow discrimination among various nonlinearities. (ii) a robust viscoelastic constitutive model will be developed from experimental data. This model will appropriately account for nonlinearities and interrelate creep and relaxation. (iii) The reversible deformation limits for levels of applied stress and strain (as a function of load-time) will be experimentally identified from the data in (I), thus defining the onset of sub-failure tissue damage for a single overload. A sub-failure criterion for the onset of damage will be formulated. (iv) Creep and relaxation testing will be performed on additional specimens to quantify the compromise in mechanical behavior after higher loading and deformations produce greater levels of tissue damage (from a single overload). (v) The microtrauma and damage associated with irreversible deformations will be morphologically characterized using scanning electron microscopy.