scholarly journals Quantifying Effects of Plaque Structure and Material Properties on Stress Distributions in Human Atherosclerotic Plaques Using 3D FSI Models

2005 ◽  
Vol 127 (7) ◽  
pp. 1185-1194 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Jie Zheng ◽  
Pamela K. Woodard ◽  
Jeffrey E. Saffitz ◽  
...  
Keyword(s):  
Material Properties ◽  
Plaque Rupture ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Atherosclerotic Plaques ◽  
Plaque Vulnerability ◽  
Stress Strain ◽  
Maximal Stress ◽  
Good Potential ◽  
Stress Variations

Background: Atherosclerotic plaques may rupture without warning and cause acute cardiovascular syndromes such as heart attack and stroke. Methods to assess plaque vulnerability noninvasively and predict possible plaque rupture are urgently needed. Method: MRI-based three-dimensional unsteady models for human atherosclerotic plaques with multi-component plaque structure and fluid-structure interactions are introduced to perform mechanical analysis for human atherosclerotic plaques. Results: Stress variations on critical sites such as a thin cap in the plaque can be 300% higher than that at other normal sites. Large calcification block considerably changes stress/strain distributions. Stiffness variations of plaque components (50% reduction or 100% increase) may affect maximal stress values by 20–50 %. Plaque cap erosion causes almost no change on maximal stress level at the cap, but leads to 50% increase in maximal strain value. Conclusions: Effects caused by atherosclerotic plaque structure, cap thickness and erosion, material properties, and pulsating pressure conditions on stress/strain distributions in the plaque are quantified by extensive computational case studies and parameter evaluations. Computational mechanical analysis has good potential to improve accuracy of plaque vulnerability assessment.

Flow in the Stenotic Carotid Bifurcation

2002 ◽  
Author(s):  
Stanley A. Berger ◽  
Vitaliy L. Rayz
Keyword(s):  
Plaque Rupture ◽  
Three Dimensional ◽  
Carotid Bifurcation ◽  
Atherosclerotic Plaques ◽  
Flow Conditions ◽  
Artery Wall ◽  
Plaque Development ◽  
Irregular Geometries ◽  
A Site ◽  
Realistic Geometries

The carotid artery bifurcation is prone to the development of atherosclerotic plaques, and is a site where the consequences of this development can be severe. The most immediate effects are changes in lumenal cross-section, volumetric blood flow, and forces on the wall. The end result may be plaque rupture, possibly resulting in a stroke. Plaque development, and plaque rupture, are likely both strongly influenced by the changes of the shear stress, and possibly normal stress, at the artery wall [1]. Numerical simulations of the flow in the carotid bifurcation can elucidate the influence of the flow on the plaque and vice versa. The irregular geometries of severely stenotic vessels make numerical modeling of these flows particularly challenging [2, 3]. We describe simulations in fully three-dimensional, realistic geometries under steady and pulsatile flow conditions.

Quantifying Vessel Material Properties Using MRI Under Pressure Condition and MRI-Based FSI Mechanical Analysis for Human Atherosclerotic Plaques

2006 ◽  
Author(s):  
Chun Yang ◽  
Xueying Huang ◽  
Jie Zheng ◽  
Pamela K. Woodard ◽  
Dalin Tang
Keyword(s):  
Material Properties ◽  
Stokes Equations ◽  
Maximum Shear Stress ◽  
Maximum Principal Stress ◽  
Mechanical Analysis ◽  
Navier Stokes ◽  
Atherosclerotic Plaques ◽  
Navier Stokes Equations ◽  
Stenosis Severity ◽  
Set Up

Atherosclerotic plaques may rupture without warning and cause acute cardiovascular syndromes such as heart attack and stroke. Mechanical image analysis using MRI-based models with fluid-structure interactions (FSI) and MRI-determined material properties may improve the accuracy of plaque vulnerability assessment and rupture predictions. A plaque-phantom was set up to acquire plaque MR images under pressurized conditions. The 3D nonlinear modified Mooney-Rivlin (M-R) model was used to describe the material properties with parameters selected to fit the MRI data. The Navier-Stokes equations were used as the governing equations for the flow model. The fully-coupled FSI models were solved by ADINA. Our results indicate that doubling parameter values in the M-R model led to 12.5% decrease in structure maximum principal stress (Stress-P1) and 48% decrease in maximum principal strain (Strain-P1). Flow maximum shear stress (MSS) was almost unchanged. Results from a modified carotid plaque with 70% stenosis severity (by diameter) showed that Stress-P1 at the plaque throat from the wall-only model is 145% higher than that from the FSI model. MSS from a flow-only model is about 40% higher than that from the FSI model. This approach has the potential to develop non-invasive patient screening and diagnosis methods in clinical applications.

Abstract 639: Deletion of Alternatively Spliced Extra Domain A of Cellular Fibronectin Stabilizes Advanced Rupture-Prone Plaques in Hyperlipidemic Mice

2016 ◽  
Vol 36 (suppl_1) ◽  
Author(s):  
Prakash Doddapattar ◽  
Nirav Dhanesha ◽  
Prem Prakash ◽  
Steven R Lentz ◽  
Anil K Chauhan
Keyword(s):  
Plaque Rupture ◽  
Gelatin Zymography ◽  
Atherosclerotic Plaques ◽  
Dependent Manner ◽  
Activated Macrophages ◽  
Plaque Vulnerability ◽  
Tlr4 Signaling ◽  
Elastin Degradation ◽  
Alternatively Spliced

Background: The most important clinical manifestation of atherosclerosis is rupture of advanced plaques. The fibronectin containing alternatively spliced extra domain A (Fn-EDA) is abundant in extracellular matrix around macrophages and endothelial cells in advanced human plaques. In vitro studies suggest that Fn-EDA is a ligand for TLR4 and upregulates MMP9, which has been shown to enhance elastin degradation and promote plaque rupture in advanced plaques of hyperlipidemic apolipoprotein E-deficient (Apoe -/- ) mice. The mechanistic role of Fn-EDA in advanced plaques remains unknown. Hypothesis: Fn-EDA/TLR4 signaling in activated macrophages contributes to plaque vulnerability by upregulating MMP9 during advanced atherosclerosis. Methods and Results: We compared atherosclerotic plaques in the brachiocephalic artery (a model artery for study of plaque vulnerability) of female Fn- EDA -/- Apoe -/- and Apoe -/- mice at 50 weeks of age (44 weeks on high-fat Western diet). Fn- EDA -/- Apoe -/- mice exhibited decreased plaque size and characteristics of stable plaques, with decreased necrosis, reduced influx of activated macrophages, increased SMC staining and greater collagen content compared to Apoe -/- mice (P<0.05, n=11-13 mice/group), although cholesterol and triglyceride levels, and circulating leukocyte counts were similar. Purified cellular FN, which contains EDA, potentiated the NFκB-mediated inflammatory pathway (increased phospho-NFκB p65/ NFκB p65, TNFα and IL1β) and MMP9 protein expression (gelatin zymography) in a dose-dependent manner in purified macrophages from Fn-EDA -/- Apoe -/- mice but not from Fn-EDA -/- TLR4 -/- Apoe -/- mice. Using immunohistochemistry, we demonstrated colocalization of macrophage TLR4 and Fn-EDA within advanced atherosclerotic plaques in murine brachiocephalic arteries and human coronary arteries. Genetic deletion of TLR4 in Apoe -/- mice stabilized advanced plaques, and parameters of plaque stability were comparable between TLR4 -/- Apoe -/- and Fn-EDA -/- TLR4 -/- Apoe -/- mice. Conclusions: These findings suggest that Fn-EDA/TLR4 signaling in macrophages is a key mechanism that upregulates MMP9, and thereby promotes plaque vulnerability in advanced atherosclerosis.

Cyclic Bending of Coronary Plaques Leads to Much Higher Stress Variations: A Major Factor Contributing to Plaque Rupture Risk

2007 ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Jie Zheng ◽  
Shunichi Kobayashi ◽  
Gregorio A. Sicard ◽  
...  
Keyword(s):  
Plaque Rupture ◽  
Strain Analysis ◽  
Atherosclerotic Plaques ◽  
Rupture Risk ◽  
Cyclic Bending ◽  
Clinical Events ◽  
Stenosis Severity ◽  
Atherosclerotic Plaque Rupture ◽  
Component Models ◽  
Stress Variations

Mechanical forces play an important role in the complicated process of atherosclerotic plaque rupture which often leads to serious clinical events such as stroke and heart attack [4]. Factors causing the vulnerable plaque cap to fracture are important clinically [2–7]. It is known that coronary plaques are more likely to rupture compared to carotid plaques under comparable conditions (such as stenosis severity at about 50% by diameter). One possible reason is that coronary arteries are under cyclic bending caused by heart motions and compressions. We hypothesize that cyclic bending of coronary atherosclerotic plaques may be a major contributor to critical stress variations in the plaque leading to increased plaque rupture risk. We have developed MRI-based 3D multi-component models with fluid-structure interactions (FSI) in order to perform flow and stress/strain analysis for atherosclerotic plaques and identify possible mechanical and morphological indices for accurate plaque vulnerability assessment [6–7].

Coupled thermo-electro-mechanical analysis of sandwiched hybrid functionally graded elastic material and piezoelectric plates under thermal loads

2017 ◽  
Vol 232 (10) ◽  
pp. 1851-1870 ◽  
Author(s):  
Chih-Ping Wu ◽  
Shuang Ding
Keyword(s):  
Elastic Material ◽  
Material Properties ◽  
Convergence Rates ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Mechanical Analysis ◽  
Functionally Graded ◽  
Thermal Loads ◽  
Finite Layer ◽  
Finite Layer Methods

Based on Reissner’s mixed variational theorem, a weak-form formulation of finite layer methods is developed for the three-dimensional coupled thermo-electro-mechanical analysis of simply-supported, functionally graded elastic material plates integrated with surface-bonded piezoelectric layers and under thermal loads. The material properties of the functionally graded elastic material core are assumed to obey the power-law distributions varying through-the-thickness coordinate of the core according to the volume fractions of the constituents, and those of the functionally graded elastic material core and piezoelectric face sheets are also temperature dependent. The effective material properties of the functionally graded elastic material are estimated using the Mori-Tanaka scheme. Two different thermal conditions, i.e. the convection conditions and specified temperature conditions, on the top and bottom surfaces of the plate are considered. The accuracies and convergence rates of the finite layer methods with various orders used for expanding the elastic and electric variables in the thickness direction are assessed by comparing their solutions with the exact three-dimensional ones available in the literature.

Quantifying Effects of Artery Shrinkage Using In Vivo MRI-Based 3D FSI Models for Carotid Atherosclerotic Plaques With Bifurcation

2008 ◽  
Author(s):  
Xueying Huang ◽  
Chun Yang ◽  
Chun Yuan ◽  
Thomas Hatsukami ◽  
Fei Liu ◽  
...  
Keyword(s):  
Stress State ◽  
Computational Models ◽  
Initial Conditions ◽  
Plaque Rupture ◽  
Mechanical Analysis ◽  
Western World ◽  
Plaque Morphology ◽  
Atherosclerotic Plaques ◽  
Atherosclerotic Vascular Disease

Atherosclerotic vascular disease leads to changes of the arterial wall and lumen narrowing, and it is the No.1 killer in the western world. Magnetic resonance image (MRI)-based computational models with fluid-structure interactions (FSI) for atherosclerotic plaques have been introduced to perform mechanical analysis to quantify critical flow and stress/strain conditions related to plaque rupture which often leads directly to heart attack or stroke [2]. There are three groups of information needed as model input: plaque morphology, material properties, and flow conditions. Pre shrinkage-stretch process is used to recover the in vivo geometry from zero-stress state with associated initial conditions which are required to achieve building the computational model. An important issue for this process is how to determine zero stress state from in vivo plaque geometry. However, few publications can be found in the current literature about how to quantify human carotid artery shrinkage.

scholarly journals 3D MRI-Based Anisotropic FSI Models With Cyclic Bending for Human Coronary Atherosclerotic Plaque Mechanical Analysis

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Dalin Tang ◽  
Chun Yang ◽  
Shunichi Kobayashi ◽  
Jie Zheng ◽  
Pamela K. Woodard ◽  
...  
Keyword(s):  
Atherosclerotic Plaque ◽  
Vulnerability Assessment ◽  
Computational Models ◽  
Plaque Rupture ◽  
Maximum Velocity ◽  
Coronary Plaque ◽  
Plaque Vulnerability ◽  
Stress Strain ◽  
Axial Stretch ◽  
Cyclic Bending

Heart attack and stroke are often caused by atherosclerotic plaque rupture, which happens without warning most of the time. Magnetic resonance imaging (MRI)-based atherosclerotic plaque models with fluid-structure interactions (FSIs) have been introduced to perform flow and stress/strain analysis and identify possible mechanical and morphological indices for accurate plaque vulnerability assessment. For coronary arteries, cyclic bending associated with heart motion and anisotropy of the vessel walls may have significant influence on flow and stress/strain distributions in the plaque. FSI models with cyclic bending and anisotropic vessel properties for coronary plaques are lacking in the current literature. In this paper, cyclic bending and anisotropic vessel properties were added to 3D FSI coronary plaque models so that the models would be more realistic for more accurate computational flow and stress/strain predictions. Six computational models using one ex vivo MRI human coronary plaque specimen data were constructed to assess the effects of cyclic bending, anisotropic vessel properties, pulsating pressure, plaque structure, and axial stretch on plaque stress/strain distributions. Our results indicate that cyclic bending and anisotropic properties may cause 50–800% increase in maximum principal stress (Stress-P1) values at selected locations. The stress increase varies with location and is higher when bending is coupled with axial stretch, nonsmooth plaque structure, and resonant pressure conditions (zero phase angle shift). Effects of cyclic bending on flow behaviors are more modest (9.8% decrease in maximum velocity, 2.5% decrease in flow rate, 15% increase in maximum flow shear stress). Inclusion of cyclic bending, anisotropic vessel material properties, accurate plaque structure, and axial stretch in computational FSI models should lead to a considerable improvement of accuracy of computational stress/strain predictions for coronary plaque vulnerability assessment. Further studies incorporating additional mechanical property data and in vivo MRI data are needed to obtain more complete and accurate knowledge about flow and stress/strain behaviors in coronary plaques and to identify critical indicators for better plaque assessment and possible rupture predictions.

An Analysis Model of the Dynamic Characteristics of Brake Pads in Response to Changes in Material Properties

2017 ◽  
Vol 730 ◽  
pp. 601-606
Author(s):  
Myeong Jae Han ◽  
Tae Won Park ◽  
Ink Yeong Hwang ◽  
Jung Min Park
Keyword(s):  
Material Properties ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Thickness Variation ◽  
Fe Model ◽  
Brake Pad ◽  
Analysis Model ◽  
Brake Pads ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The sense of stability during vehicle braking is largely related to brake performance. Among the brake parts, the brake pad must be working properly to ensure the braking performance and stability of the vehicle. That is, brake pads are required to maintain a uniform pressure distribution during braking. In addition, brake pads must maintain a proper braking force during rapid increases in temperature. In this study, the three-dimensional finite element (FE) model was developed to determine the distribution of the contact pressure of the brake pad. The temperature distribution on the pad surface was confirmed. The sensitivity to changes in material properties was verified using the developed model. Pad wear due to friction can be predicted by confirming the thickness variation due to heat. A fully coupled thermo-mechanical analysis of the developed FE model was performed using ABAQUS.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

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