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.

Finite Element Analysis of the Influence of Balance Mode on Rolling Mill Universal Spindle Strength

2014 ◽  
Vol 548-549 ◽  
pp. 449-453 ◽  
Author(s):  
Zhi Qiang Guo ◽  
Ze Lu Xu
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Model ◽  
Rolling Mill ◽  
Loading Condition ◽  
Equivalent Stress ◽  
Bending Moment ◽  
Element Model ◽  
Element Analysis ◽  
Universal Spindle

For the problem of balance bearing of universal spindle in rolling mill being prone to damage, the paper established mechanical model and finite element model of universal spindle. The paper has analyzed that the shear and bending moment in the middle of the shaft is the largest. The fillet near shoulder of balance bearing of the spindle is dangerous part. In order to reduce principal stress of universal spindle caused by moment, the paper improved balance mode of the spindle. The equilibrant was applied from in one place of shaft to put in two places. After optimizing, equivalent stress of the spindle is slight smaller than before under the same loading condition, which illustrates that the strength of the spindle is appropriately improved. Although the effect is not obvious, this has played a guiding role for the optimization of balance mode of universal spindle.

scholarly journals Soil Interaction of Building Frame Resting on Clayey Soil: Effect of Change of Footing Size

2019 ◽  
Vol 8 (2) ◽  
pp. 4874-4879
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Shear Force ◽  
Clayey Soil ◽  
Bending Moment ◽  
Design Parameters ◽  
Element Analysis ◽  
Building Frame ◽  
Super Structure ◽  
Percentage Difference

In every structure, the super structure and the foundation executed on soil, represent an entire structural system. The analysis of a framed structure while not modeling its foundation system and its rigidity could mislead the axial forces, moments due to bending and due to settlement. It is, thus necessary to hold out the analysis considering the type of soil, foundation and above the sub structure i.e. (super structure). Hence the analysis of the single bay single storied building frame resting on soil (Clayey Soil) is taken for present study. The analysis is carried out using “ANSYS 16.0”. In this paper the effect of soil interaction on building frame design parameters as change of modulus of sub-grade reaction from 0.010 to 0.050 N/mm3 .Shear force, Bending moment and settlements have been studied for different footing sizes of 1mx1m to 4.5mx4.5m the effect of SSI is quantified using finite element analysis. The following conclusions have been drawn from the study, the shear force and axial force value in the beam and column is constant from finite element analysis are not having considerable difference. The analysis is predicting that percentage difference in bending moment in beam, column and footings are at lower EFS value i.e 0.010N/mm3 at lower footing size 1mX1m is greater than when compared to higher EFS value i.e 0.050N/mm3 at higher footing size 4.5mX4.5m which considers soil interaction. But in case of the footings they undergo some settlement the percentage difference of settlement is 14.41% and 6.72% at lower EFS value i.e 0.010N/mm3 at lower footing size 1mx1m when compared to higher EFS value i.e 0.050N/mm3 at higher footing size 4.5mx4.5m respectively, which considers soil interaction.

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.

Effects of Girth Weld on the Local Buckling Response of Conventional Grade Pipelines

2009 ◽  
Author(s):  
John Barrett ◽  
Shawn Kenny ◽  
Ryan Phillips
Keyword(s):  
Finite Element ◽  
Structural Integrity ◽  
Local Buckling ◽  
Numerical Procedure ◽  
Bending Moment ◽  
Ground Movement ◽  
Design Parameters ◽  
Element Analysis ◽  
Strain Capacity ◽  
Pipeline Design

Pipeline structural integrity is a critical component of pipeline design in extreme environmental conditions. Severe loads may be an issue in pipeline design if differential ground movement is prevalent in the design region, e.g. ground faulting and permafrost heave and settlement. Iceberg or ice keel interaction and large seabed deformations interacting may also be a critical design integrity issue for offshore pipelines in ice environments. Numerical finite element modelling procedures have been developed to assess the bending moment and strain capacity of several pipelines over various typical pipeline parameters. This study looks at the effects of girth-weld imperfection on the bending response of welded pipelines. Limited guidance is provided by pipeline design standards, for example DNV OS-F101 and CSA Z662, as to how to account for girth weld effects on the local buckling response. This paper investigates girth weld effects across a range of practical design parameters. Calibration of the numerical analysis was performed using available data, from full-scale tests and finite element analysis, for girth welded pipes in order to obtain confidence in the numerical procedure. The significance of girth weld effects was to reduce the peak bending moment capacity by 10% whereas strain capacity was reduced by as much as 35% based on the degree of girth weld imperfection. Girth weld effects have been acknowledged in industry, however, further research and physical testing is required to fully understand the problem, as shown in this paper.

Finite Element Analysis of Functionally Graded Thick-Cylinders Subjected to Mechanical and Thermal Loads

2012 ◽  
Author(s):  
Jasem A. Ahmed ◽  
M. A. Wahab
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Radial Direction ◽  
Coefficient Of Thermal Expansion ◽  
Stress Component ◽  
Pressure Vessels ◽  
Functionally Graded ◽  
Design Parameters ◽  
Element Analysis

Functionally graded materials (FGM) are used to design structures used in high temperature environment. Hybrid pressure vessels can be designed from FGMs to incorporate improved strength, weight reduction, thermal properties, impact resistance etc. Progressive research in this area will lead to the determination of optimum design parameters and provide insight in developing manufacturing techniques of full-scale hybrid pressure vessels and experimental validation. In future, an accurate damage model will help in planning component examinations in a selective manner in order to provide useful information about material condition and predict the remaining life of the structure. A functionally graded thick-walled cylindrical vessel with varying material properties in the radial direction is considered. The cylinder is assumed to be made of one phase spatially dispersed in a matrix of another. Volume fractions of the phases are assumed to vary along the radial direction according to power laws. The gradation is represented by dividing the radial domain into finite sub-domains. The effective material properties such as modulus of elasticity, Poisson’s ratio, thermal conductivity and coefficient of thermal expansion are estimated using Mori-Tanaka [1], Hashin–Shtrikman [2], Hatta-Taya [3] and Rosen-Hashin [4] relations. The hollow cylinder is subjected to axisymmetric mechanical and thermal loadings. Finite Element Analysis is performed using a commercial package, ANSYS, to obtain temperature and stress component distribution along the thickness of the cylinder. Results are presented graphically to show the effect of internal pressure, temperature change, and gradient variation of material properties on stress components throughout the thickness.

Shape Optimization of Elliptical and Vaulted Reinforced Concrete Domes

2016 ◽  
Vol 24 ◽  
pp. 35-43
Author(s):  
Mohamed Amine Touzout ◽  
Rachid Chebili
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Bending Moment ◽  
Research Field ◽  
Design Parameters ◽  
Membrane Action ◽  
Civil Structures ◽  
Element Analysis ◽  
Ongoing Research ◽  
Proper Orthogonal

Optimum design in civil structures like domes and vaults is a very old and ongoing research field. These structures are preferably designed to transport loads via membrane action. In this paper, we have considered a reinforced concrete dome and vault, where the bending moment and strain energy were used as objective function to be minimized using genetic algorithm, and model reduction method by proper orthogonal decomposition based on the results of finite element analysis of gradually changed design parameters. The proposed approach results are of a high accuracy compared to finite element based optimization.

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.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

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.

ANSYS Simply Supported Deep Beams Based on the Study of Mechanical Properties

2013 ◽  
Vol 351-352 ◽  
pp. 782-785
Author(s):  
Yong Bing Liu ◽  
Xiao Zhong Zhang
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Mechanical Model ◽  
Work Performance ◽  
Deep Beam ◽  
Analysis Software ◽  
Deep Beams ◽  
Element Analysis ◽  
Simply Supported ◽  
Force Characteristics

Established the mechanical model of simply supported deep beam, calculation and analysis of simple supported deep beams by using finite element analysis software ANSYS, simulated the force characteristics and work performance of the deep beam. Provides the reference for the design and construction of deep beams.

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