Institute of Solid Mechanics, Mechatronics and Biomechanics, Technicka 2896/2, 616 69, Brno University of Technology, Czech Republic.
Department of Solid Mechanics, The Royal Institute of Technology, Stockholm, Sweden.
Acta Biomater. 2015 Mar;14:133-45. doi: 10.1016/j.actbio.2014.11.043. Epub 2014 Nov 29.
Structure-based constitutive models might help in exploring mechanisms by which arterial wall histology is linked to wall mechanics. This study aims to validate a recently proposed structure-based constitutive model. Specifically, the model's ability to predict mechanical biaxial response of porcine aortic tissue with predefined collagen structure was tested. Histological slices from porcine thoracic aorta wall (n=9) were automatically processed to quantify the collagen fiber organization, and mechanical testing identified the non-linear properties of the wall samples (n=18) over a wide range of biaxial stretches. Histological and mechanical experimental data were used to identify the model parameters of a recently proposed multi-scale constitutive description for arterial layers. The model predictive capability was tested with respect to interpolation and extrapolation. Collagen in the media was predominantly aligned in circumferential direction (planar von Mises distribution with concentration parameter bM=1.03 ± 0.23), and its coherence decreased gradually from the luminal to the abluminal tissue layers (inner media, b=1.54 ± 0.40; outer media, b=0.72 ± 0.20). In contrast, the collagen in the adventitia was aligned almost isotropically (bA=0.27 ± 0.11), and no features, such as families of coherent fibers, were identified. The applied constitutive model captured the aorta biaxial properties accurately (coefficient of determination R(2)=0.95 ± 0.03) over the entire range of biaxial deformations and with physically meaningful model parameters. Good predictive properties, well outside the parameter identification space, were observed (R(2)=0.92 ± 0.04). Multi-scale constitutive models equipped with realistic micro-histological data can predict macroscopic non-linear aorta wall properties. Collagen largely defines already low strain properties of media, which explains the origin of wall anisotropy seen at this strain level. The structure and mechanical properties of adventitia are well designed to protect the media from axial and circumferential overloads.
基于结构的本构模型可能有助于探索动脉壁组织学与壁力学之间的联系机制。本研究旨在验证最近提出的基于结构的本构模型。具体来说，测试了该模型预测具有预定胶原结构的猪主动脉组织力学双轴响应的能力。使用自动处理的猪胸主动脉壁组织的组织学切片来定量胶原纤维组织，并且通过力学测试确定了壁样品（n=18）在广泛的双轴拉伸范围内的非线性特性。使用组织学和力学实验数据来识别最近提出的动脉层多尺度本构描述的模型参数。针对内插和外推，测试了模型的预测能力。中膜中的胶原主要沿周向排列（平面 von Mises 分布，浓度参数 bM=1.03±0.23），并且从管腔到腔外组织层，其一致性逐渐降低（内中膜，b=1.54±0.40；外中膜，b=0.72±0.20）。相比之下，外膜中的胶原几乎呈各向同性排列（bA=0.27±0.11），并且没有发现纤维一致家族等特征。所应用的本构模型准确地捕捉了主动脉的双轴特性（决定系数 R(2)=0.95±0.03），在整个双轴变形范围内以及具有物理意义的模型参数下。在远离参数识别空间的情况下，观察到了良好的预测性能（R(2)=0.92±0.04）。配备现实微观组织数据的多尺度本构模型可以预测宏观非线性主动脉壁特性。胶原在很大程度上决定了中膜的低应变特性，这解释了在该应变水平下看到的壁各向异性的起源。外膜的结构和机械性能设计良好，可防止中膜受到轴向和周向过载。
