The Effect of Collagen Fiber Directional Distribution on the Mechanical Response of the Vascular Wall

2009 ◽  
Author(s):  
Rana Rezakhaniha ◽  
Nikos Stergiopulos
Keyword(s):  
Constitutive Equations ◽  
Mechanical Response ◽  
Vascular Tissue ◽  
Constitutive Models ◽  
Morphological Characteristics ◽  
Nonlinear Behavior ◽  
Vascular Wall ◽  
Incompressible Material ◽  
Collagen Fibers ◽  
Strain Energy Functions

Constitutive equations reflecting well the microstructure are fundamental for the detailed stress analysis of the arterial tissue. Vascular tissue is an inhomogeneous and incompressible material which undergoes large deformations and shows highly anisotropic nonlinear behavior. These properties make strain energy functions (SEFs) a suitable tool to derive constitutive equations. Structural constitutive models try to integrate the histological and morphological characteristics of the tissue by introducing parameters with physical meaning, such as the fraction of each wall constituent, the elastic properties of single elastin or collagen fibers or the angle of collagen fibers.

scholarly journals Effect of High-Fat Diet upon Inflammatory Markers and Aortic Stiffening in Mice

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Andre Bento Chaves Santana ◽  
Thais Cristina de Souza Oliveira ◽  
Barbara Lobo Bianconi ◽  
Valerio Garrone Barauna ◽  
Ed Wilson Cavalcante Oliveira Santos ◽  
...  
Keyword(s):  
Protein Expression ◽  
High Fat Diet ◽  
Vascular Tissue ◽  
Body Weight Gain ◽  
Vascular Diseases ◽  
Vascular Wall ◽  
Collagen Fibers ◽  
Standard Diet ◽  
High Fat ◽  
Aortic Stiffening

Changes in lifestyle such as increase in high-fat food consumption are an important cause for vascular diseases. The present study aimed to investigate the involvement of ACE and TGF-βin the aorta stiffness induced by high-fat diet. C57BL/6 male mice were divided in two groups according to their diet for 8 weeks: standard diet (ST) and high-fat diet (HF). At the end of the protocol, body weight gain, adipose tissue content, serum lipids and glucose levels, and aorta morphometric and biochemical measurements were performed. Analysis of collagen fibers by picrosirius staining of aorta slices showed that HF diet promoted increase of thin (55%) and thick (100%) collagen fibers deposition and concomitant disorganization of these fibers orientations in the aorta vascular wall (50%). To unravel the mechanism involved, myeloperoxidase (MPO) and angiotensin I converting enzyme (ACE) were evaluated by protein expression and enzyme activity. HF diet increased MPO (90%) and ACE (28%) activities, as well as protein expression of ACE. TGF-βwas also increased in aorta tissue of HF diet mice after 8 weeks. Altogether, we have observed that the HF diet-induced aortic stiffening may be associated with increased oxidative stress damage and activation of the RAS in vascular tissue.

scholarly journals Contractile Smooth Muscle and Active Stress Generation in Porcine Common Carotids

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Boran Zhou ◽  
David A. Prim ◽  
Eva J. Romito ◽  
Liam P. McNamara ◽  
Francis G. Spinale ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Vascular Wall ◽  
Stress Generation ◽  
Ground Substance ◽  
Active Components ◽  
Decomposition Approach ◽  
Active Stress ◽  
Disease States

The mechanical response of intact blood vessels to applied loads can be delineated into passive and active components using an isometric decomposition approach. Whereas the passive response is due predominantly to the extracellular matrix (ECM) proteins and amorphous ground substance, the active response depends on the presence of smooth muscle cells (SMCs) and the contractile machinery activated within those cells. To better understand determinants of active stress generation within the vascular wall, we subjected porcine common carotid arteries (CCAs) to biaxial inflation–extension testing under maximally contracted or passive SMC conditions and semiquantitatively measured two known markers of the contractile SMC phenotype: smoothelin and smooth muscle-myosin heavy chain (SM-MHC). Using isometric decomposition and established constitutive models, an intuitive but novel correlation between the magnitude of active stress generation and the relative abundance of smoothelin and SM-MHC emerged. Our results reiterate the importance of stretch-dependent active stress generation to the total mechanical response. Overall these findings can be used to decouple the mechanical contribution of SMCs from the ECM and is therefore a powerful tool in the analysis of disease states and potential therapies where both constituent are altered.

Multi Layered Polycaprolactone-Elastin-Collagen Small Diameter Conduits for Vascular Tissue Engineering

2008 ◽  
Author(s):  
Michael J. McClure ◽  
Scott A. Sell ◽  
Gary L. Bowlin
Keyword(s):  
Tissue Engineering ◽  
Blood Flow ◽  
Mechanical Response ◽  
Vascular Tissue ◽  
Small Diameter ◽  
Vascular Wall ◽  
Biomechanical Properties ◽  
Dynamic Mechanical Properties ◽  
Elastic Behavior ◽  
Vessel Rupture

The architecture of the vascular wall is highly intricate and requires unique biomechanical properties in order to function properly. Native artery is composed of a mix of collagens, elastin, endothelial cells (ECs), smooth muscle cells (SMC), fibroblasts, and proteoglycans arranged into three distinct layers: the intima, media, and adventitia. Throughout artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery while undergoing pulsatile deformations [1]. The low-strain mechanical response of artery to blood flow is dominated by the elastic behavior, of elastin, which prevents pulsatile energy from being dissipated as heat [2]. A higher amount of energy loss indicates a decrease in recoverability, which could lead to eventual disruption of blood flow. An effective way to quantify recoverability is through hysteresis and compliance measurement. The hypothesis of this study was that the fabrication of a multi-layered electrospun tissue engineering scaffold composed of polycaprolactone (PCL), elastin, and collagen would demonstrate dynamic mechanical properties indicative of a highly elastic material, similar to the three distinct layers of native arterial tissue, while remaining conducive to tissue regeneration. PCL was chosen, in this case, to provide mechanical integrity and elasticity, while elastin and collagen would provide further elasticity and bioactivity [3,4].

Constitutive modelling of passive myocardium: a structurally based framework for material characterization

2009 ◽  
Vol 367 (1902) ◽  
pp. 3445-3475 ◽  
Author(s):  
Gerhard A. Holzapfel ◽  
Ray W. Ogden
Keyword(s):  
Mechanical Response ◽  
Constitutive Models ◽  
Ventricular Myocardium ◽  
Incompressible Material ◽  
Left Ventricular ◽  
Constitutive Modelling ◽  
Left Ventricular Myocardium ◽  
Fibre Direction ◽  
Biaxial Tests ◽  
Nonlinearly Elastic

In this paper, we first of all review the morphology and structure of the myocardium and discuss the main features of the mechanical response of passive myocardium tissue, which is an orthotropic material. Locally within the architecture of the myocardium three mutually orthogonal directions can be identified, forming planes with distinct material responses. We treat the left ventricular myocardium as a non-homogeneous, thick-walled, nonlinearly elastic and incompressible material and develop a general theoretical framework based on invariants associated with the three directions. Within this framework we review existing constitutive models and then develop a structurally based model that accounts for the muscle fibre direction and the myocyte sheet structure. The model is applied to simple shear and biaxial deformations and a specific form fitted to the existing (and somewhat limited) experimental data, emphasizing the orthotropy and the limitations of biaxial tests. The need for additional data is highlighted. A brief discussion of issues of convexity of the model and related matters concludes the paper.

scholarly journals Ability of Constitutive Models to Characterize the Temperature Dependence of Rubber Hyperelasticity and to Predict the Stress-Strain Behavior of Filled Rubber under Different Defor Mation States

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 369
Author(s):  
Xintao Fu ◽  
Zepeng Wang ◽  
Lianxiang Ma
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Chain Model ◽  
Stress Strain ◽  
Filled Rubber ◽  
Yeoh Model

In this paper, some representative hyperelastic constitutive models of rubber materials were reviewed from the perspectives of molecular chain network statistical mechanics and continuum mechanics. Based on the advantages of existing models, an improved constitutive model was developed, and the stress–strain relationship was derived. Uniaxial tensile tests were performed on two types of filled tire compounds at different temperatures. The physical phenomena related to rubber deformation were analyzed, and the temperature dependence of the mechanical behavior of filled rubber in a larger deformation range (150% strain) was revealed from multiple angles. Based on the experimental data, the ability of several models to describe the stress–strain mechanical response of carbon black filled compound was studied, and the application limitations of some constitutive models were revealed. Combined with the experimental data, the ability of Yeoh model, Ogden model (n = 3), and improved eight-chain model to characterize the temperature dependence was studied, and the laws of temperature dependence of their parameters were revealed. By fitting the uniaxial tensile test data and comparing it with the Yeoh model, the improved eight-chain model was proved to have a better ability to predict the hyperelastic behavior of rubber materials under different deformation states. Finally, the improved eight-chain model was successfully applied to finite element analysis (FEA) and compared with the experimental data. It was found that the improved eight-chain model can accurately describe the stress–strain characteristics of filled rubber.

Wrinkling of a Fiber-Reinforced Membrane

2008 ◽  
Vol 76 (1) ◽  
Author(s):  
E. Shmoylova ◽  
A. Dorfmann
Keyword(s):  
Boundary Conditions ◽  
Energy Function ◽  
Mechanical Response ◽  
Transverse Isotropy ◽  
Base Material ◽  
Strain Energy Function ◽  
Transversely Isotropic ◽  
Incompressible Material ◽  
Fiber Reinforced ◽  
Relaxed Energy

In this paper we investigate the response of fiber-reinforced cylindrical membranes subject to axisymmetric deformations. The membrane is considered as an incompressible material, and the phenomenon of wrinkling is taken into account by means of the relaxed energy function. Two cases are considered: transversely isotropic membranes, characterized by one family of fibers oriented in one direction, and orthotropic membranes, characterized by two family of fibers oriented in orthogonal directions. The strain-energy function is considered as the sum of two terms: The first term is associated with the isotropic properties of the base material, and the second term is used to introduce transverse isotropy or orthotropy in the mechanical response. We determine the mechanical response of the membrane as a function of fiber orientations for given boundary conditions. The objective is to find possible fiber orientations that make the membrane as stiff as possible for the given boundary conditions. Specifically, it is shown that for transversely isotropic membranes a unique fiber orientation exists, which does not affect the mechanical response, i.e., the overall behavior is identical to a nonreinforced membrane.

Uncertainty Quantification in Predicting Behaviour of Rubber-Like Materials in Uni-Axial Loading

2020 ◽  
Author(s):  
Aref Ghaderi ◽  
Vahid Morovati ◽  
Pouyan Nasiri ◽  
Roozbeh Dargazany
Keyword(s):  
Uncertainty Quantification ◽  
Mechanical Response ◽  
Pure Shear ◽  
Constitutive Models ◽  
Material Behavior ◽  
Elastic Behavior ◽  
Deterministic Models ◽  
Data Set ◽  
Material Parameters ◽  
Axial Extension

Abstract Material parameters related to deterministic models can have different values due to variation of experiments outcome. From a mathematical point of view, probabilistic modeling can improve this problem. It means that material parameters of constitutive models can be characterized as random variables with a probability distribution. To this end, we propose a constitutive models of rubber-like materials based on uncertainty quantification (UQ) approach. UQ reduces uncertainties in both computational and real-world applications. Constitutive models in elastomers play a crucial role in both science and industry due to their unique hyper-elastic behavior under different loading conditions (uni-axial extension, biaxial, or pure shear). Here our goal is to model the uncertainty in constitutive models of elastomers, and accordingly, identify sensitive parameters that we highly contribute to model uncertainty and error. Modern UQ models can be implemented to use the physics of the problem compared to black-box machine learning approaches that uses data only. In this research, we propagate uncertainty through the model, characterize sensitivity of material behavior to show the importance of each parameter for uncertainty reduction. To this end, we utilized Bayesian rules to develop a model considering uncertainty in the mechanical response of elastomers. As an important assumption, we believe that our measurements are around the model prediction, but it is contaminated by Gaussian noise. We can make the noise by maximizing the posterior. The uni-axial extension experimental data set is used to calibrate the model and propagate uncertainty in this research.

Investigations of PMN-PT Single Crystal Performance

2010 ◽  
Author(s):  
Virginia G. DeGiorgi ◽  
E. P. Gorzkowski ◽  
M.-J. Pan ◽  
M. A. Qidwai ◽  
Stephanie A. Wimmer
Keyword(s):  
Finite Element ◽  
Electric Field ◽  
Single Crystals ◽  
Domain Switching ◽  
Fatigue Behavior ◽  
Constitutive Models ◽  
Nonlinear Behavior ◽  
Computational Effort ◽  
Basic Material ◽  
Poling Direction

Application of new materials, such as PMN-PT single crystals, requires a good understanding of basic material performance under both electrical and mechanical loading. Over the past 5 years the authors have used both computational and experimental techniques to examine the relationships between poling direction, crystal orientation, and electric field actuation. Experiments show mixed results indicating that the relationship between material orientation and loading is more complex than originally imagined. In some cases crack initiation and propagation perpendicular to the applied field was observed within a few thousand cycles but in other cases no failure was observed even after a few hundred thousand cycles despite crack growth in the presence of introduced defects. Computational effort quickly identified a gap between development of theoretical constitutive models that addressed domain switching based nonlinear behavior and what was available in workable form as part of commercial finite element codes. This led to the implementation of a macro-mechanical constitutive model which addresses domain switching, into a commercially available finite element code. The rate independent version has been used to investigate issues of electric field actuation and poling direction. Presented here are insights into the fracture and fatigue behavior of piezoelectric single crystals from both experimental and computational studies.

Constitutive Modeling of Biaxial Mechanical Response of Arteries Subjected to Gradual Elastin Degradation

2013 ◽  
Author(s):  
Shahrokh Zeinali-Davarani ◽  
Ming-Jay Chow ◽  
Raphaël Turcotte ◽  
Katherine Yanhang Zhang
Keyword(s):  
Tensile Test ◽  
Mechanical Behavior ◽  
Test Data ◽  
Constitutive Modeling ◽  
Mechanical Response ◽  
Collagen Fibers ◽  
Biaxial Tensile Test ◽  
Elastin Degradation ◽  
Adaptive Processes ◽  
Tensile Test Data

The passive mechanical response of arteries is believed to be mainly dominated by elastin and collagen fibers. Many arterial diseases are accompanied by significant changes in quantity and as well as the microstructure of these constituents due to the mechanical and biological adaptive processes. In this study we focus on the biaxial tensile test data of elastase-treated porcine aortic tissues [1]. We study the mechanical behavior of aortic tissues under gradual elastin degradation through constitutive modeling and associate the mechanical response with the microstructure of collagen observed in the microscopic images of fresh and digested tissues.

A Spectral Microplane Model for the Anisotropic Damage Behavior of Shales

2020 ◽  
Vol 87 (8) ◽  
Author(s):  
Mingyao Li ◽  
Xin Chen ◽  
Dong Zhou ◽  
Yewang Su
Keyword(s):  
Damage Model ◽  
Constitutive Models ◽  
Nonlinear Behavior ◽  
Bedding Plane ◽  
Anisotropic Elasticity ◽  
Anisotropic Damage ◽  
Microplane Model ◽  
Damage Behavior ◽  
Softening Behavior ◽  
Confining Pressures

Abstract The development of constitutive models for shales has been a challenge for decades due to the difficulty of characterizing the strongly anisotropic macroscopic behavior related to the inherent mesostructure and damage mechanisms. In this paper, a spectral microplane damage model is developed for the anisotropic damage behavior of shales. The modeling challenge of the anisotropic elasticity in the microplane model is theoretically overcome by the spectral decomposition theory without limitation on the degree of the anisotropy compared with other microplane models. The stiffness tensor of anisotropic shales is effectively decomposed into four different eigenmodes with the activation of certain groups of microplanes corresponding to the specific orientation of the applied stresses. The inherent and the induced anisotropic behavior is thus characterized by proposing suitable microplane relations on certain eigenmodes directly reflecting the initial mesostructure and the failure mechanisms. For the challenge of the postpeak softening behavior, two-scalar damage variables are introduced to characterize the tensile and the shear damage related to the opening and the closure of microcracks under different stress conditions. Comparison between numerical simulation and experimental data shows that the proposed model provides satisfactory predictions for both weakly and highly anisotropic shales including prepeak nonlinear behavior, failure strengths, and postpeak softening under different confining pressures and different bedding plane orientations.

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