Effects of Stent Design Parameters on Normal Artery Wall Mechanics

2006 ◽  
Vol 128 (5) ◽  
pp. 757-765 ◽  
Author(s):  
Julian Bedoya ◽  
Clark A. Meyer ◽  
Lucas H. Timmins ◽  
Michael R. Moreno ◽  
James E. Moore
Keyword(s):  
Radial Displacement ◽  
Design Parameters ◽  
Radius Of Curvature ◽  
Stent Design ◽  
Artery Wall ◽  
Element Analysis ◽  
Radial Strength ◽  
Stent Strut ◽  
Invasive Techniques ◽  
Normal Artery

A stent is a device designed to restore flow through constricted arteries. These tubular scaffold devices are delivered to the afflicted region and deployed using minimally invasive techniques. Stents must have sufficient radial strength to prop the diseased artery open. The presence of a stent can subject the artery to abnormally high stresses that can trigger adverse biologic responses culminating in restenosis. The primary aim of this investigation was to investigate the effects of varying stent “design parameters” on the stress field induced in the normal artery wall and the radial displacement achieved by the stent. The generic stent models were designed to represent a sample of the attributes incorporated in present commercially available stents. Each stent was deployed in a homogeneous, nonlinear hyperelastic artery model and evaluated using commercially available finite element analysis software. Of the designs investigated herein, those employing large axial strut spacing, blunted corners, and higher amplitudes in the ring segments induced high circumferential stresses over smaller areas of the artery’s inner surface than all other configurations. Axial strut spacing was the dominant parameter in this study, i.e., all designs employing a small stent strut spacing induced higher stresses over larger areas than designs employing the large strut spacing. Increasing either radius of curvature or strut amplitude generally resulted in smaller areas exposed to high stresses. At larger strut spacing, sensitivity to radius of curvature was increased in comparison to the small strut spacing. With the larger strut spacing designs, the effects of varying amplitude could be offset by varying the radius of curvature and vice versa. The range of minimum radial displacements from the unstented diastolic radius observed among all designs was less than 90μm. Evidence presented herein suggests that stent designs incorporating large axial strut spacing, blunted corners at bends, and higher amplitudes exposed smaller regions of the artery to high stresses, while maintaining a radial displacement that should be sufficient to restore adequate flow.

Experimental Analysis of Self-Folding SMA-Based Sheet Design for Simulation Validation

2014 ◽  
Author(s):  
Aaron C. Powledge ◽  
Darren J. Hartl ◽  
Richard J. Malak
Keyword(s):  
Performance Metrics ◽  
Permanent Deformation ◽  
Material Behavior ◽  
Image Correlation ◽  
Design Parameters ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
Performance Metric ◽  
3D Digital Image Correlation ◽  
Thermally Actuated

The goal of this research is to experimentally characterize the capabilities of a concept for a self-folding reconfigurable sheet for use in origami-inspired engineering design and to use this characterization to validate simulations of physics-based models of the sheet. The sheet consists of an active, self-morphing laminate that contains two shape memory alloy (SMA) mesh layers and a passive compliant medium between these layers. The SMA layers are thermally actuated, allowing bending to occur in both positive and negative directions to create soft hill and valley folds. These folds are completely reversible, allowing the structure to fold and unfold without permanent deformation. Unlike past work on self-folding structures, these sheets can have folds along any line, be subsequently unfolded, and then be folded again in a new way. To explore the effect of changing design parameters on the performance metrics of the sheet, it is desirable to use Finite Element Analysis (FEA) simulations instead of relying on time consuming experiments. Such models have been created incorporating user material subroutines (UMATs) in an FEA solver such as Abaqus to capture material behavior, but these must now be validated against experimental data to establish how well they match experimental performance. The primary performance metric of the sheet was chosen to be the radius of curvature measured perpendicularly to the line of heating. Both experiment and simulation focus on the radius of curvature achieved by the sheet for a given set of design parameters and actuation path. The goal of validation is to achieve a desirable level of agreement and repeatability in these results. To measure the deformation and curvature in the sheet as it actuates, a 3D Digital Image Correlation (3D DIC) system is employed to track the movement of points along the surface of the sample as it is heated to a temperature above the transformation temperature of the SMA and allowed to fully actuate. These tools are utilized for a number of samples so that validation of the sheet encompasses multiple values for each of the primary design parameters.

Effect of Stent Design Parameters on Coronary Artery Flow

2009 ◽  
Author(s):  
Satyaprakash Karri ◽  
Stephen Peter ◽  
Pavlos P. Vlachos
Keyword(s):  
Thrombus Formation ◽  
Design Parameters ◽  
Radius Of Curvature ◽  
Stent Design ◽  
Endovascular Stents ◽  
Long Term Performance ◽  
Artery Flow ◽  
Term Performance ◽  
Realistic Geometries

The most widely accepted modality for treating diseased arteries is the implantation of endovascular stents. Stents are metallic wireframe devices used to reopen clogged arteries. Despite their widespread use, problems persist post-implantation of these devices beginning with sub-acute thrombus formation followed by inflammation, proliferation and remodeling [1]. The specific stent design and its design parameters profoundly impact the hemodynamic environment of the stent [2], in turn affecting thrombus accumulation between struts and thus restenosis [3]. Prior research examining the hemodynamic effects of stents has been performed in simplified geometries [4] however the effects of stent design parameters such as strut thickness and crown radius of curvature or analysis in realistic geometries is generally lacking. A more thorough understanding of the effect of a stent’s geometric parameters on the arterial flow will provide insight into their long-term performance and will lead to better design.

Finite Element Analysis of a Stent Implantation in a Stenosed Artery

2005 ◽  
Vol 288-289 ◽  
pp. 571-574
Author(s):  
Dongke Liang ◽  
Da Zhi Yang ◽  
Min Qi ◽  
Wei Qiang Wang
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Stent Implantation ◽  
Quantitative Information ◽  
Stent Design ◽  
Mechanical Interaction ◽  
Artery Wall ◽  
Element Analysis ◽  
Stenosed Artery ◽  
Key Factor

Instent restenosis (ISR) has been a key factor that restricts the further use of intraoronary stents. And the mechanical interaction between the stent and the artery has been indicated as one of the significant causes for the activation of stent-related restenosis. However, there is very little quantitative information about the interaction of stent with artery. In order to improve the general understanding of coronary stenting, finite element method (FEM) has been used to model the revascularization of a stenosed artery through the insertion of a balloon-expandable stent. Given a stent design, the deformed shape of the stent and possible areas of the artery injury were presented. The fact that the distal end of stent penetrated into the artery wall may help to explain the phenomena that much restenosis occurs at the ends of stents. The recoil ratios of the stent model, the plaque-artery model and the stent-plaque-artery model were 2%, 26.7% and11.3%, respectively. They were well consistent with the experimental data. In conclusion, this work would be helpful for the general understanding of intraoronary stent implantation and stent design optimization.

Expansion Performance of Novel Balloon-Expandable Stent for Tapered Vessel

2015 ◽  
Vol 645-646 ◽  
pp. 1333-1338
Author(s):  
Xiang Shen ◽  
Yang Yang Sun ◽  
Bo Bo Wu
Keyword(s):  
Finite Element Method ◽  
Radial Displacement ◽  
Design Parameters ◽  
The Novel ◽  
Stent Design ◽  
Positioning Accuracy ◽  
Stent Restenosis ◽  
Expansion Pressure ◽  
Stent Expansion ◽  
In Stent Restenosis

In-stent restenosis still remains an obsession to cardiologist, especially in tapered vessels. In this paper, we designed a novel balloon-expandable stent for tapered vessel and proposed a finite element method (FEM) to study the expansion of the novel stent. The effect of stent design parameters on stent tapering and foreshortening were also researched. Results show that the radial displacement of stent proximal end was always larger than that of stent distal end during stent expansion, and the stent had a tapered shape as a whole after expansion. The degree of stent tapering observed increased with the expansion pressure increase. Besides, increasing the gradient of ring amplitude not only could increase the tapering degree of stent after expansion, but also could decrease stent foreshortening, improving the positioning accuracy after stent implantation. In conclusion, FEM can quantify expansion performance of novel balloon-expandable stents and help designers to devise and assess new stent designs for tapered vessel.

Design and Optimization of Functionally Graded Superelastic NiTi Stents

2020 ◽  
Author(s):  
Jivtesh B. Khurana ◽  
Mary Frecker ◽  
Eric M. Pauli
Keyword(s):  
Mechanical Model ◽  
Bending Moment ◽  
Material Design ◽  
Functionally Graded ◽  
Design Parameters ◽  
Stent Design ◽  
Niti Wire ◽  
Element Analysis ◽  
Off Label ◽  
Initial Location

Abstract Endoscopic stents are being used by surgeons in off-label uses to manage leaks and perforations in the gastrointestinal tract. Commercially available stents are primarily designed to open strictures in the esophagus through tissue compression. The stents incorporate a woven NiTi wire to produce a stiff and linear tubular shape that conforms to the esophagus. In off-label uses, where the stents are placed in non-esophageal locations the stents must bend, the stents show a high propensity to migrate from their initial location causing unwanted complications. In this paper, a new stent design incorporating functionally graded NiTi is presented and explored. First, a functionally graded NiTi stent design is proposed. Next, a mechanical model using finite element analysis is developed to predict the bending moment and stiffness of the functionally graded stent designs. Finally, the mechanical model is coupled with a genetic algorithm in MATLAB to identify optimal designs. For a 90° bending angle, the best design parameters of the newly proposed flexible stents are found for three different stent design families. The results of the functionally graded stents show how tailoring the material properties locally in a structure can lead to highly compliant behavior. The tailoring of the geometric and material design developed may be applied to design of highly flexible and optimized medical devices.

Experimental and Numerical Investigation into the Quasi-Static Crushing Behaviour of the S-Shape Square Tubes

2011 ◽  
Vol 27 (4) ◽  
pp. 585-596 ◽  
Author(s):  
A. Khalkhali ◽  
A. Masoumi ◽  
A. Darvizeh ◽  
M. Jafari ◽  
A. Shiri
Keyword(s):  
Numerical Investigation ◽  
Parametric Study ◽  
Experimental Tests ◽  
Deformation Mode ◽  
Numerical Approach ◽  
Vehicle Body ◽  
Design Parameters ◽  
Radius Of Curvature ◽  
Element Analysis ◽  
Static Tests

ABSTRACTVehicle energy absorbing components usually have a curved shape to avoid interference with other components like engine, driving system and fuel tank, etc. Crush behaviour of the S-shape square tubes, as a simplified model of front member of a vehicle body, is investigated in the present study. Experimental and numerical investigation into the quasi static crushing of such tubes was performed. Experimental tests were carried out with cross head speed of 5mm/min. Finite element analysis was performed using ABAQUS/Explicit to simulate quasi-static tests conditions. The predicted crushing characteristics such as global deformation mode, plastic folding mode and load-displacement response obtained by numerical approach were found to be in good agreement with the experimental results. The validated numerical model was then used in the parametric study to examine the effect of design parameters such as wall thickness, web width, curve angle and radius of curvature on the energy absorption capability of the S-shape square tubes. It is shown that some interesting relationships can be discovered by the parametric study to be used as useful design approach for improving the performance of the S-shape tubes.

THE EFFECTS OF IMPLANTING DIFFERENT STENTS ON THE BLOOD HEMODYNAMIC IN CORONARY ARTERIES

2013 ◽  
Vol 25 (04) ◽  
pp. 1350056
Author(s):  
Alireza Sanati ◽  
Kamran Hassani ◽  
Mahdi Navidbakhsh
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Coronary Arteries ◽  
Stent Implantation ◽  
Three Dimensional ◽  
Design Parameters ◽  
Stent Design ◽  
Stent Strut ◽  
Wall Shear

Stent implantation alters coronary artery hemodynamic and wall shear stress during cardiac cycles. In this study, three-dimensional models were used to analyze the effects of different stent designs and strut thicknesses on the hemodynamic of the artery. The flow was assumed to be pulsatile and stent models were expanded in the artery the same as angioplasty procedure that uses balloon. The data was applied to Fluent-ANSYS package as a UDF MATLAB code. A non-slip condition was applied to the artery walls. The pressure variation in different stents and the wall shear stress distribution were studied. Furthermore, the hemodynamic effects on the flow were investigated for two different thickness values of the same stent design. These results showed that stent implanting is one of the main parameters of pressure drop in the artery. Moreover, the surface of the stent is the location of maximum wall shear stress and the thicker stent strut did not vary this stress much. Our study implies that some design parameters such as thickness affect the hemodynamic factors of blood after stent implantation. Even stent implanting causes re-stenosis in the coronary artery. Using new real models is suggested to investigate new aspects of stent design and related effects on the hemodynamic of coronary arteries.

A Simplified Design Model for Modular Steel Buildings Subject to Vapor Cloud Explosions (VCEs)

2020 ◽  
Vol 14 ◽  
Author(s):  
Osama Bedair
Keyword(s):  
Dynamic Response ◽  
Minimum Cost ◽  
Design Parameters ◽  
Front Wall ◽  
Steel Buildings ◽  
Element Analysis ◽  
Analysis And Design ◽  
Vapor Cloud ◽  
Building Components ◽  
Analytical Expressions

Background: Modular steel buildings (MSB) are extensively used in petrochemical plants and refineries. Limited guidelines are available in the industry for analysis and design of (MSB) subject to accidental vapor cloud explosions (VCEs). Objectives: The paper presents simplified engineering model for modular steel buildings (MSB) subject to accidental vapor cloud explosions (VCEs) that are extensively used in petrochemical plants and refineries. Method: A Single degree of freedom (SDOF) dynamic model is utilized to simulate the dynamic response of primary building components. Analytical expressions are then provided to compute the dynamic load factors (DLF) for critical building elements. Recommended foundation systems are also proposed to install the modular building with minimum cost. Results: Numerical results are presented to illustrate the dynamic response of (MSB) subject to blast loading. It is shown that (DLF)=1.6 is attained at (td/t)=0.4 for front wall (W1) with (td/T)=1.25. For side walls (DLF)=1.41 and is attained at (td/t)=0.6. Conclusions: The paper presented simplified tools for analysis and design of (MSB) subject accidental vapor cloud blast explosions (VCEs). The analytical expressions can be utilized by practitioners to compute the (MSB) response and identify the design parameters. They are simple to use compared to Finite Element Analysis.

scholarly journals Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saurabhi Samant ◽  
Wei Wu ◽  
Shijia Zhao ◽  
Behram Khan ◽  
Mohammadali Sharzehee ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Patient Specific ◽  
Wall Structure ◽  
Left Main ◽  
Element Analysis ◽  
Stent Expansion ◽  
Radial Strength ◽  
Different Diameters

AbstractLeft main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

Analysis of a Tubular Linear Permanent Magnet Motor for Reciprocating Compressor Applications

2013 ◽  
Vol 448-453 ◽  
pp. 2114-2119 ◽  
Author(s):  
Izzeldin Idris Abdalla ◽  
Taib Ibrahim ◽  
Nursyarizal Mohd Nor
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Outer Radius ◽  
Design Parameters ◽  
Reciprocating Compressor ◽  
Permanent Magnet Motors ◽  
Permanent Magnet Motor ◽  
Element Analysis ◽  
Split Ratio ◽  
Single Coil

This paper describes a design optimization to achieve optimal performance of a two novel single-phase short-stroke tubular linear permanent magnet motors (TLPMMs) with rectangular and trapezoidal permanent magnets (PMs) structures. The motors equipped with a quasi-Halbach magnetized moving-magnet armature and slotted stator with a single-slot carrying a single coil. The motors have been developed for reciprocating compressor applications such as household refrigerators. It is observed that the TLPMM efficiency can be optimized with respect to the leading design parameters (dimensional ratios). Furthermore, the influence of mover back iron is investigated and the loss of the motor is computed. Finite element analysis (FEA) is employed for the optimization, and the optimal values of the ratio of the axial length of the radially magnetized magnets to the pole pitch as well as the ratio of the PMs outer radius-to-stator outer radius (split ratio), are identified.

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