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It has been shown that geometrical, structural properties vary along the length of the aortic arch. There is a scarcity of studies focus on the variation in the vessel wall thickness of aortic arch. The central premise of this study is that considering the variation in the vessel wall thickness along the circumference of the aortic arch to be governed by the uniform stress distribution across the vessel wall, meeting the principle of optimal mechanical operation of which the distribution of stress across the vessel wall is assumed to be uniform so as to create a favorable mechanical environment for the mechanosensitive resident vascular cells. Aortic arch was created with image-derived three-dimensional (3D) reconstruction technique. A structure-motivated constitutive model was utilized in the numerical modeling and direct boundary value problem was solved. Stress distribution across the vessel wall under physiological loading condition was predicted in circumferential direction to test the role of the wall thickness. The results showed the variation of the vessel wall thickness in the circumferential direction and uniform distribution of the circumferential stress in the aortic wall which implies a favorable mechanical environment for the resident mechano-sensitive vascular smooth muscle cells. Correlation of geometrical and simulation data support the proposed principle of optimal mechanical operation for the aortic arch., Comment: 15 pages, 7 figures

Arterial tissue failures lead to a number of clinical conditions that develop rapidly and unpredictably in vivo. Structural components and their interfacial mechanical strength of arterial tissue play a critical role in the process of arterail delamination. Therefore, there is a pressing need to understand the micromechanical mechanisms of arterial delamination. The objective of this study was to investigate various failure mechanisms (e.g. failure of collagen fibers) responsible for arterial interfacial delamination. In-situ tensile tests of fibers were performed on a micro-tester in the scanning electron microscope. A 3D unit cell model containing an individual fiber bridging two arterial tissue layers was constructed. An exponential cohesive zone model (CZM) was used to assess the stiffening and softening mechanical behaviors of collagen fiber bundles between the two arterial layers. An anisotropic constitutive model was implemented for characterizing the mechanical properties of the amorphous matrix which includes the fibrous cap and the underlying plaque tissue and a nonlinear elastic model was adopted for characterizing the mechanical properties of the fibers. The CZM and elastic parameter values of fibers were identified through an inverse boundary value approach that matches the load-displacement curves from simulation predictions of tensile test of collagen fibers with experimental measurements. The identified parameter values were then used as input in the 3D unit cell model, through which micromechanical factors affecting the resultant traction-separation relation for the unit cell were investigated via a parametric analysis. Results of the parametric analysis showed the applicability of the 3D unit cell model approach for evaluating the micromechanical mechanisms of arterial tissue failure processes., Comment: 33 pages, 11 figures

Atherosclerotic plaque failure results from various pathophysiological events, with the existence of fibrous cap mode I tearing in the arterial wall, having the potential to block the aortic lumen and correspondingly induce serious clinical conditions.The aim of this study was to quantify the interfacial strength and critical energy release rate of the fibrous tissue across the thickness. in this study, an inverse analysis method via finite element modeling and simulation approach was presented. A cohesive zone model (CZM) was applied to simulate the tearing of the fibrous cap tissue under uniaxial tensile tests along the circumferential direction. A fiber-reinforced hyperelastic model (Holzapfel-Gasser-Ogden) was implemented for characterizing the mechanical properties of bulk material. With the material parameter values of HGO model from inverse analysis process as the input for the bulk material, the interfacial strength and critical energy release rate along the tearing path or failure zones are obtained through the same method as material identification process of HGO model. Results of this study demonstrate the fibrous cap tissue tearing failure processes., Comment: 26 pages, 7 figures

The viscoelastic properties of arterial tissue dictate vessel behavior in certain disease states, injury modalities, and during some endovascular procedures. In this study, we characterized the viscoelastic mechanical response of porcine abdominal aortic tissue via uniaxial mechanical experiments on vascular tissue samples coupled with full-field surface strain measurements using the 2-D digital image correlation (DIC) technique. The measured stress relaxation response and intimal surface strain field were used to identify material parameters for a proposed viscoelastic anisotropic (VA) constitutive model of the passive arterial wall. The obtained results show that the VA constitutive model is able to capture the viscoelastic mechanical behavior of the arterial tissue over clinically-relevant time scales. The identified material model and numerical simulations provide a comprehensive description of the passive viscoelastic tissue properties of the arterial wall, and a quantitative understanding of the spatial and directional variability underlying arterial tissue mechanical behavior., Comment: 42 pages, 7 figures