THREE DIMENSIONAL MECHANICAL PROPERTIES OF SOFT TISSUES

描述（由申请人提供）：了解软胶原组织（如心脏瓣膜、主动脉和韧带）的材料特性对于理解正常功能和疾病状态至关重要。许多研究报告了一维或二维材料特性;然而，很少有已发表的三维研究。这种数据的缺乏严重阻碍了3D模型的开发和验证。因此，本研究的目的是（i）开发3D，各向异性非线性粘弹性模型，和（ii）一个新的实验/分析系统，用于测量3D负载变形行为。将创建3D有限元模型，以代表单轴、压痕和剪切试验（具体目标1）。一个超弹性版本的冯准线性粘弹性理论将开发。三轴应力松弛和蠕变试验将使用一种新技术进行，用于施加拉伸、压缩和剪切载荷（具体目标2）。在加载过程中，高分辨率（appx. 15 pro），将获得试样变形的多轴3D视频。使用这些数据，然后将通过具有全局优化的逆有限元方法估计不同本构模型的3D材料特性（具体目标3）。这些模型和数据将为软组织力学的本构关系提供新的见解，并将对生物组织的有限元模型的验证，并最终对生物心脏瓣膜设计具有重要价值。

DESCRIPTION (provided by applicant): Knowledge of the material properties of soft collagenous tissues, such as heart valves, aorta, and ligaments, is fundamental to the understanding of both normal function and disease states. Many studies have reported 1 or 2D material properties; however, there are very few published 3D studies. This lack of data severely hinders development and validation of 3D models. The objective of this proposed research is therefore to (i) develop 3D, anisotropic non-linear viscoelastic models, and (ii) a new experimental/analytical system for measuring 3D load-deformation behavior. 3D finite element models will be created to represent uniaxial, indentation, and shear tests (Specific Aim 1). A hyperelastic version of Fung's quasilinear viscoelasticity theory will be developed. Triaxial stress relaxation and creep tests will be performed using a novel technique for applying combined tension, compression, and shear loads (Specific Aim 2). During loading, high-resolution (appx. 15 pro), multiaxial, 3D video of specimen deformations will be obtained. Using these data, 3D material properties will then be estimated for the different constitutive models via inverse finite element methods with global optimization (Specific Aim 3). These models and data will provide new insights into the constitutive relationships for soft tissue mechanics, and will be of paramount value for the validation of finite element models of biological tissues, and ultimately for bioprosthetic heart valve design.