Mechanical strength of aneurysmatic and dissected human thoracic aortas at different shear loading modes.
Mechanical strength of aneurysmatic and dissected human thoracic aortas at different shear loading modes.
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DOI：
10.1016/j.jbiomech.2016.02.042
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发表时间：
2016-08-16
影响因子：
2.4
通讯作者：
Holzapfel GA
中科院分区：
文献类型：
--
作者：
Sommer G;Sherifova S;Oberwalder PJ;Dapunt OE;Ursomanno PA;DeAnda A;Griffith BE;Holzapfel GA
动脉瘤破裂和胸主动脉急性夹层是危及生命的事件，每年影响数万人。潜在的机制仍不清楚，并且已知主动脉壁会失去其结构完整性，这反过来会影响其对负荷条件的机械响应。因此，对此类主动脉疾病的研究是生物力学的一个重要领域。本研究通过三轴剪切和单轴拉伸测试研究了动脉瘤和解剖的人类胸主动脉的机械特性，重点是前者。特别是，确定了主动脉正交各向异性微观结构不同方向三轴剪切试验以及径向、周向和纵向单轴拉伸试验的极限应力值。总共对 16 个人类胸主动脉进行了研究，从中可以明显看出，主动脉中膜在“平面外”剪切载荷下比在“平面内”剪切载荷下具有更强的抗破裂能力。在不同的剪切载荷下，主动脉组织表现出各向异性破坏特性，纵向极限剪切应力和剪切量高于周向。此外，主动脉中膜的抗拉强度按如下顺序降低：周向>纵向>径向。从实验数据中可以看出各向异性和非线性组织特性。结果清楚地显示了受供者病史（例如主动脉疾病或结缔组织疾病）影响的样本间差异，例如，解剖样本平均表现出明显低于动脉瘤样本的机械强度。基于三轴剪切和单轴延伸测试相结合的破裂数据是独一无二的，为开发患病人类胸主动脉中膜的 3D 失效标准奠定了良好的基础。这是朝着更真实地模拟机械引起的组织衰竭（即动脉瘤破裂或主动脉夹层进展）迈出的一步。
Rupture of aneurysms and acute dissection of the thoracic aorta are life-threatening events which affect tens of thousands of people per year. The underlying mechanisms remain unclear and the aortic wall is known to lose its structural integrity, which in turn affects its mechanical response to the loading conditions. Hence, research on such aortic diseases is an important area in biomechanics. The present study investigates the mechanical properties of aneurysmatic and dissected human thoracic aortas via triaxial shear and uniaxial tensile testing with a focus on the former. In particular, ultimate stress values from triaxial shear tests in different orientations regarding the aorta's orthotropic microstructure, and from uniaxial tensile tests in radial, circumferential and longitudinal directions were determined. In total, 16 human thoracic aortas were investigated from which it is evident that the aortic media has much stronger resistance to rupture under ‘out-of-plane’ than under ‘in-plane’ shear loadings. Under different shear loadings the aortic tissues revealed anisotropic failure properties with higher ultimate shear stresses and amounts of shear in the longitudinal than in the circumferential direction. Furthermore, the aortic media decreased its tensile strength as follows: circumferential direction > longitudinal direction > radial direction. Anisotropic and nonlinear tissue properties are apparent from the experimental data. The results clearly showed interspecimen differences influenced by the anamnesis of the donors such as aortic diseases or connective tissue disorders, e.g., dissected specimens exhibited on average a markedly lower mechanical strength than aneurysmatic specimens. The rupture data based on the combination of triaxial shear and uniaxial extension testing are unique and build a good basis for developing a 3D failure criterion of diseased human thoracic aortic media. This is a step forward to more realistic modeling of mechanically induced tissue failure i.e. rupture of aneurysms or progression of aortic dissections.