A micromechanics finite-strain constitutive model of fibrous tissue

Chang, Huan; Liu, Yi; Zhao, Xuefeng; Lanir, Yoram; Kassab, Ghassan S.

doi:10.1016/j.jmps.2011.05.012

Cited by 47 publications

(32 citation statements)

References 57 publications

(114 reference statements)

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“…Mechanical predictions are thought to be more accurate than those of phenomenological models, as these models account for microstructural features of vessel components, as well as heterogeneity of material properties. The microstructural parameters have been ad hoc rather than based on experimental measurements, due to limited morphological data of the vessel wall (4,17,23,51). The microstructure of the vessel wall, which includes elastin and collagen fibers, smooth muscle cells, and ground substance, is distributed differently in individual vessel layers, i.e., tunica media and adventitia (8,36,43).…”

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A validated 3D microstructure-based constitutive model of coronary artery adventitia

et al. 2016

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Chen H, Guo X, Luo T, Kassab GS. A validated 3D microstructure-based constitutive model of coronary artery adventitia. J Appl Physiol 121: 333-342, 2016. First published May 12, 2016 doi:10.1152/japplphysiol.00937.2015.-A structure-based model that accurately predicts micro-or macromechanical behavior of blood vessels is necessary to understand vascular physiology. Based on recently measured microstructural data, we propose a three-dimensional microstructural model of coronary adventitia that incorporates the elastin and collagen distributions throughout the wall. The role of ground substance was found to be negligible under physiological axial stretch z ϭ 1.3, based on enzyme degradation of glycosaminoglycans in swine coronary adventitia (n ϭ 5). The thick collagen bundles of outer adventitia (n ϭ 4) were found to be undulated and unengaged at physiological loads, whereas the inner adventitia consisted of multiple sublayers of entangled fibers that bear the majority of load at higher pressures. The microstructural model was validated against biaxial (inflation and extension) experiments of coronary adventitia (n ϭ 5). The model accurately predicted the nonlinear responses of the adventitia, even at high axial force (axial stretch ratio z ϭ 1.5). The model also enabled a reliable estimation of material parameters of individual fibers that were physically reasonable. A sensitivity analysis was performed to assess the effect of using mean values of the distributions for fiber orientation and waviness as opposed to the full distributions. The simplified mean analysis affects the fiber stress-strain relation, resulting in incorrect estimation of mechanical parameters, which underscores the need for measurements of fiber distribution for a rigorous analysis of fiber mechanics. The validated structure-based model of coronary adventitia provides a deeper understanding of vascular mechanics in health and can be extended to disease conditions. constitutive model; collagen; elastin; microstructure; adventitia; material parameters MICROSTRUCTURAL APPROACHES have been advocated for modeling blood vessels to understand better the nonlinear mechanical responses of vessels (7,17,18,25). Mechanical predictions are thought to be more accurate than those of phenomenological models, as these models account for microstructural features of vessel components, as well as heterogeneity of material properties. The microstructural parameters have been ad hoc rather than based on experimental measurements, due to limited morphological data of the vessel wall (4,17,23,51). The microstructure of the vessel wall, which includes elastin and collagen fibers, smooth muscle cells, and ground substance, is distributed differently in individual vessel layers, i.e., tunica media and adventitia (8,36,43). A microstructural constitutive model should be specific for a particular layer based on experimental measurements of microstructure (2).The coronary adventitia consists of three major constituents-elastin, collagen fibers, and ground substance-and...

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A validated 3D microstructure-based constitutive model of coronary artery adventitia

et al. 2016

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“…[13,28]) and non-affine models (e.g. [29,30]). The last ones emphasize the fact that the stress and strain fields are different for the components and then contradict the assumption made in affine models.…”

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confidence: 99%

Determination and Finite Element Validation of the WYPIWYG Strain Energy of Superficial Fascia from Experimental Data

2016

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What-You-Prescribe-Is-What-You-Get (WYPIWYG) procedures are a novel and general phenomenological approach to modelling the behavior of soft materials, applicable to biological tissues in particular. For the hyperelastic case, these procedures solve numerically the nonlinear elastic material determination problem. In this paper we show that they can be applied to determine the stored energy density of superficial fascia. In contrast to the usual approach, in such determination no user-prescribed material parameters and no optimization algorithms are employed. The strain energy densities are computed solving the equilibrium equations of the set of experiments. For the case of superficial fascia it is shown that the mechanical behavior derived from such strain energies is capable of reproduc- * Corresponding author Email addresses: m.latorre.ferrus@upm.es (Marcos Latorre), fany@unizar.es (Estefanía Peña), fco.montans@upm.es (Francisco J. Montáns) Preprint submitted to Annals of Biomedical EngineeringAugust 3, 2016 ing simultaneously the measured load-displacement curves of three experiments to a high accuracy.

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“…The finite strain theory was employed since it allows arbitrarily large deformations and it is suitable for modeling biological soft tissue [22]. The equilibrium equations were solved by Newton's method.…”

Section: Methodsmentioning

confidence: 99%

Fluid-Structure Interaction Model of Aortic Valve With Porcine-Specific Collagen Fiber Alignment in the Cusps

Marom¹,

Peleg²,

Halevi³

et al. 2013

Journal of Biomechanical Engineering

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Native aortic valve cusps are composed of collagen fibers embedded in their layers. Each valve cusp has its own distinctive fiber alignment with varying orientations and sizes of its fiber bundles. However, prior mechanical behavior models have not been able to account for the valve-specific collagen fiber networks (CFN) or for their differences between the cusps. This study investigates the influence of this asymmetry on the hemodynamics by employing two fully coupled fluid-structure interaction (FSI) models, one with asymmetric-mapped CFN from measurements of porcine valve and the other with simplified-symmetric CFN. The FSI models are based on coupled structural and fluid dynamic solvers. The partitioned solver has nonconformal meshes and the flow is modeled by employing the Eulerian approach. The collagen in the CFNs, the surrounding elastin matrix, and the aortic sinus tissues have hyperelastic mechanical behavior. The coaptation is modeled with a master-slave contact algorithm. A full cardiac cycle is simulated by imposing the same physiological blood pressure at the upstream and downstream boundaries for both models. The mapped case showed highly asymmetric valve kinematics and hemodynamics even though there were only small differences between the opening areas and cardiac outputs of the two cases. The regions with a less dense fiber network are more prone to damage since they are subjected to higher principal stress in the tissues and a higher level of flow shear stress. This asymmetric flow leeward of the valve might damage not only the valve itself but also the ascending aorta.

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A micromechanics finite-strain constitutive model of fibrous tissue

Cited by 47 publications

References 57 publications

A validated 3D microstructure-based constitutive model of coronary artery adventitia

A validated 3D microstructure-based constitutive model of coronary artery adventitia

Determination and Finite Element Validation of the WYPIWYG Strain Energy of Superficial Fascia from Experimental Data

Fluid-Structure Interaction Model of Aortic Valve With Porcine-Specific Collagen Fiber Alignment in the Cusps

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