Swelling and axial propagation of bulging with application to aneurysm propagation in arteries

2017 ◽  
Vol 25 (7) ◽  
pp. 1459-1471 ◽  
Author(s):  
Hasan Demirkoparan ◽  
Jose Merodio
Keyword(s):  
Arterial Wall ◽  
Mechanical Response ◽  
Axial Loading ◽  
Fiber Direction ◽  
Wall Model ◽  
Analytical Methodology ◽  
Unidirectional Reinforcement ◽  
Anisotropic Character ◽  
Parameter Values ◽  
Linearly Elastic Materials

The effect of swelling on axial propagation of bulging is investigated for thin cylinders made of doubly fiber reinforced incompressible non-linearly elastic materials. The swellable tubes are exposed to both internal pressure and axial loading. The materials under consideration are Treloar models augmented with two functions that are equal, each one of them accounting for the existence of a unidirectional reinforcement. The functions provide the anisotropic character of the material and each one is referred to as a reinforcing model. Two reinforcing models that depend only on the stretch in the fiber direction are considered: the so called standard reinforcing model and an exponential one. The former model is studied to assess the analytical methodology described in this paper. The latter one is related to soft tissue mechanical response and bulging propagation in these models establishes the connection with the propagation of aneurysms in arterial wall tissue. For the standard reinforcing model, it is shown that axial propagation of bulging is not feasible. On the other hand, for the arterial wall model axial propagation of bulging is possible for a certain range of material parameter values.

Bulging bifurcation of inflated circular cylinders of doubly fiber-reinforced hyperelastic material under axial loading and swelling

2015 ◽  
Vol 22 (4) ◽  
pp. 666-682 ◽  
Author(s):  
Hasan Demirkoparan ◽  
Jose Merodio
Keyword(s):  
Potential Benefit ◽  
Arterial Wall ◽  
Axial Loading ◽  
Circular Cylinders ◽  
Orthotropic Materials ◽  
Aneurysm Formation ◽  
Inner Radius ◽  
Fiber Winding ◽  
Hoop Stresses ◽  
Winding Angle

In this paper, we examine the influence of swelling on the bulging bifurcation of inflated thin-walled cylinders under axial loading. We provide the bifurcation criteria for a membrane cylinder subjected to combined axial loading, internal pressure and swelling. We focus here on orthotropic materials with two preferred directions which are mechanically equivalent and are symmetrically disposed. Arterial wall tissue is modeled with this class of constitutive equation and the onset of bulging is considered to give aneurysm formation. It is shown that swelling may lead to compressive hoop stresses near the inner radius of the tube, which could have a potential benefit for preventing aneurysm formation. The effects of the axial stretch, the strength of the fiber reinforcement and the fiber winding angle on the onset of bifurcation are investigated. Finally, a boundary value problem is studied to show the robustness of the results.

Continuum Description of the Time- and Strain-Dependent Poisson’s Ratio of Ligament Under Finite Deformation

2013 ◽  
Author(s):  
Aaron M. Swedberg ◽  
Shawn P. Reese ◽  
Steve A. Maas ◽  
Benjamin J. Ellis ◽  
Jeffrey A. Weiss
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Large Strain ◽  
Fiber Direction ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
Strain Dependent

Ligament volumetric behavior controls fluid and thus nutrient movement as well as the mechanical response of the tissue to applied loads. The reported Poisson’s ratios for tendon and ligament subjected to tensile deformation loading along the fiber direction are large, ranging from 0.8 ± 0.3 in rat tail tendon fascicles [1] to 2.98 ± 2.59 in bovine flexor tendon [2]. These Poisson’s ratios are indicative of volume loss and thus fluid exudation [3,4]. We have developed micromechanical finite element models that can reproduce both the characteristic nonlinear stress-strain behavior and large, strain-dependent Poisson’s ratios seen in tendons and ligaments [5], but these models are computationally expensive and unfeasible for large scale, whole joint models. The objectives of this research were to develop an anisotropic, continuum based constitutive model for ligaments and tendons that can describe strain-dependent Poisson’s ratios much larger than the isotropic limit of 0.5. Further, we sought to demonstrate the ability of the model to describe experimental data, and to show that the model can be combined with biphasic theory to describe the rate- and time-dependent behavior of ligament and tendon.

On prismatic and bending bifurcations of fiber-reinforced elastic membranes under swelling with application to aortic aneurysms

2021 ◽  
pp. 108128652110587
Author(s):  
Murtadha J. Al-Chlaihawi ◽  
Heiko Topol ◽  
Hasan Demirkoparan ◽  
José Merodio
Keyword(s):  
Axial Loading ◽  
Material Constant ◽  
Exponential Model ◽  
Aortic Aneurysms ◽  
Orthotropic Materials ◽  
Fiber Direction ◽  
Fiber Reinforced ◽  
The Matrix ◽  
Elastic Membranes ◽  
Fiber Winding

The influence of swelling on prismatic and bending bifurcation modes of inflated thin-walled cylinders under axial loading is examined. The bifurcation criteria for a membrane cylinder subjected to combined axial loading, internal pressure, and swelling is provided. We consider orthotropic materials with two preferred directions which are mechanically equivalent and symmetrically disposed. The mechanical behavior of the matrix is described by a swellable isotropic model. The isotropic material is augmented with two functions that are equal, each one of them accounting for the existence of a unidirectional reinforcement. Two reinforcing models that depend only on the stretch in the fiber direction are considered: the so-called standard reinforcing model and an exponential one. The analysis of bifurcation modes for these models under the conditions at hand may establish the connection with modeling of the normal and diseased aorta in arterial wall tissue. The effects of the axial stretch, the strength of the fiber reinforcement and the fiber winding angle on the onset of prismatic and bending bifurcations are investigated. It is shown that for membranes without fibers, prismatic bifurcation is not feasible. On the other hand, bending bifurcation is more likely to occur for swollen cylinders. However, for a particular model of fiber-reinforced membranes, the standard model, there exists a domain of deformation values together with material constant values that may trigger prismatic bifurcation. The exponential model does not allow prismatic bifurcations. Both models allow bending bifurcation and may or may not trigger it depending on the deformation together with material parameters.

Biaxial Mechanical Properties of Passive Right Ventricular Free Wall Myocardium

1993 ◽  
Vol 115 (2) ◽  
pp. 202-205 ◽  
Author(s):  
M. S. Sacks ◽  
C. J. Chuong
Keyword(s):  
Mechanical Properties ◽  
Right Ventricular ◽  
Mechanical Response ◽  
Ventricular Free Wall ◽  
Fiber Direction ◽  
Free Wall ◽  
Right Ventricular Free Wall ◽  
Tissue Specimens ◽  
Excised Tissue ◽  
Biaxial Mechanical Properties

The biaxial mechanical properties of right ventricular free wall (RVFW) myocardium were studied. Tissue specimens were obtained from the sub-epicardium of potassium-arrested hearts and different stretch protocols were used to characterize the myocardium’s mechanical response. To assess regional differences, we excised tissue specimens from the conus and sinus regions. The RVFW myocardium was found to be consistently anisotropic, with a greater stiffness along the preferred (or averaged) fiber direction. The anisotropy in the conus region was more pronounced than in the sinus region. A comparison with studies of left ventricle (LV) midwall myocardium revealed that, 1) the fiber direction stiffnesses are greater in the RVFW than in the LV, 2) the degree of anisotropy is greater in the RVFW than in the LV.

Misinterpretation of the Functional Severity of Coronary Stenosis Due To Variability in Arterial Wall Compliance

2010 ◽  
Author(s):  
Bhaskar Chandra Konala ◽  
Ashish Das ◽  
Mohamed Effat ◽  
Arif Imran ◽  
Rupak K. Banerjee
Keyword(s):  
Arterial Wall ◽  
Coronary Intervention ◽  
Diagnostic Parameter ◽  
Carreau Model ◽  
Newtonian Viscosity ◽  
Coronary Stenoses ◽  
Wall Compliance ◽  
Wall Interaction ◽  
Stenotic Arteries ◽  
Parameter Values

Effect of arterial wall compliance on the invasive coronary diagnostic parameters for various severities of coronary stenoses was assessed. The Mooney-Rivlin model was used to define the non-linear properties of the arterial wall and the plaque regions. The non-Newtonian viscosity of blood was modeled using the Carreau model. A finite element method was employed to solve the pulsatile fluid (blood)-structure (arterial wall) interaction (FSI) equations. Variability in the diagnostic parameter values can occur near the cut-off value due to change in compliance of stenotic arteries between the range of 84% and 89% area stenosis. This may lead to misdiagnosis and might wrongly lead to postponement of coronary intervention.

Geometry Governs Mechanics of Cardiovascular Stents

2009 ◽  
Author(s):  
Graeham R. Douglas ◽  
Tho Wei Tan ◽  
Tim Bond ◽  
A. Srikantha Phani
Keyword(s):  
Arterial Wall ◽  
Mechanical Response ◽  
Neointimal Hyperplasia ◽  
Stent Migration ◽  
Contributing Factors ◽  
Poisson Effect ◽  
Element Analysis ◽  
Cardiovascular Stents ◽  
Stent Restenosis ◽  
Longitudinal Strains

Cardiovascular stents are tubular lattice structures implanted into a stenosed artery to provide adequate lumen support and promote circulation. Commonly encountered complications are stent migration, NeoIntimal Hyperplasia (NIH), and damage to the arterial wall. Central to all these problems is the mechanical response of a stent to forces operating in situ including stent-artery interaction. The influence of geometry or repetitive pattern of the stent upon its mechanical response is the subject of this study. We focus on damage to the arterial wall caused by the stent which can lead to eventual in-stent restenosis. Stent-artery compliance mismatch and longitudinal strain due to Poisson effect are hypothesized as the main contributing factors to restenosis. Finite Element Analysis (FEA) is employed to compare radial compliance and longitudinal strains of different stent geometries. Existing geometrical calculations in the literature [1] are applied to stents of different geometries to compute a non-dimensional NIH index. The main finding is that hybrid lattice stent designs exhibit negligible longitudinal strains (Poisson effect) as the stent expands/contracts during each Cardiac cycle. Wall stresses can be minimized though a careful tailoring of stent geometry.

Second Messenger Regulation of Lipoprotein Uptake by an Arterial Wall Model

1993 ◽  
Vol 55 (2) ◽  
pp. 176-181
Author(s):  
J.Jeffrey Alexander ◽  
Remedios Miguel ◽  
Joseph J. Piotrowski
Keyword(s):  
Arterial Wall ◽  
Second Messenger ◽  
Wall Model ◽  
Lipoprotein Uptake

scholarly journals Polyjet 3D printing of tissue-mimicking materials: how well can 3D printed synthetic myocardium replicate mechanical properties of organic myocardium?

2019 ◽  
Author(s):  
Leah Severseike ◽  
Vania Lee ◽  
Taycia Brandon ◽  
Chris Bakken ◽  
Varun Bhatia
Keyword(s):  
Mechanical Properties ◽  
Biological Tissue ◽  
Mechanical Response ◽  
Axial Loading ◽  
Stress Concentrations ◽  
Friction Forces ◽  
Compliance Testing ◽  
3D Printed ◽  
Printed Materials ◽  
Digital Anatomy

AbstractAnatomical 3-D printing has potential for many uses in education, research and development, implant training, and procedure planning. Conventionally, the material properties of 3D printed anatomical models have often been similar only in form and not in mechanical response compared to biological tissue. The new Digital Anatomy material from Stratasys utilizes composite printed materials to more closely mimic the mechanical properties of tissue. Work was done to evaluate Digital Anatomy myocardium under axial loading for comparison with porcine myocardium regarding puncture, compliance, suturing, and cutting performance.In general, the Digital Anatomy myocardium showed promising comparisons to porcine myocardium. For compliance testing, the Digital Anatomy was either within the same range as the porcine myocardium or stiffer. Specifically, for use conditions involving higher stress concentrations or smaller displacements, Digital Anatomy was stiffer. Digital Anatomy did not perform as strongly as porcine myocardium when evaluating suture and cutting properties. The suture tore through the printed material more easily and had higher friction forces both during needle insertion and cutting. Despite these differences, the new Digital Anatomy myocardium material was much closer to the compliance of real tissue than other 3D printed materials. Furthermore, unlike biological tissue, Digital Anatomy provided repeatability of results. For tests such as cyclic compression, the material showed less than two percent variation in results between trials and between parts, resulting in lower variability than tissue. Despite some limitations, the myocardium Digital Anatomy material can be used to configure structures with similar mechanical properties to porcine myocardium in a repeatable manner, making this a valuable research tool.

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