Thermoelastic Stress Analysis of Nitinol Self-Expanding Stents

2006 ◽  
Vol 3-4 ◽  
pp. 47-52 ◽  
Author(s):  
James Eaton-Evans ◽  
Janice M. Dulieu-Barton ◽  
Edward G. Little ◽  
Ian A. Brown
Keyword(s):  
Stress Analysis ◽  
Medical Devices ◽  
Thermoelastic Stress ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Thermoelastic Stress Analysis ◽  
Mesh Structure ◽  
Fine Mesh ◽  
Nitinol Stents ◽  
Thermoelastic Response

Self-expanding stents are small medical devices used to treat vascular disease and are typically fabricated from a super-elastic, shape memory alloy known as Nitinol and have a fine mesh structure. This paper describes preliminary work on the application of Thermoelastic Stress Analysis (TSA) to Nitinol stents. Uniaxial tensile tests were conducted on thin tubes of Nitinol to characterise the material mechanical properties. TSA calibration exercises were conducted, which showed that Nitinol exhibits a non-uniform thermoelastic response through its elastic region that corresponded to the superelastic behaviour. Initial TSA demonstrated that a viable thermoelastic signal could be obtained from the stents. In high resolution tests the effect of motion and noise were considerable but it was still possible to obtain a readable thermoelastic signal.

A New Approach to Stress Analysis of Vascular Devices Using High Resolution Thermoelastic Stress Analysis

2006 ◽  
Vol 5-6 ◽  
pp. 63-70 ◽  
Author(s):  
James Eaton-Evans ◽  
Janice M. Dulieu-Barton ◽  
Edward G. Little ◽  
Ian A. Brown
Keyword(s):  
High Resolution ◽  
Stress Analysis ◽  
Medical Devices ◽  
Thermoelastic Stress ◽  
Thermoelastic Stress Analysis ◽  
New Approach ◽  
Full Field ◽  
Vascular Stents ◽  
Thermoelastic Response ◽  
Quantitative Stress

Thermoelastic Stress Analysis (TSA) is a non-contacting technique that provides full field stress information and can record high-resolution measurements from small structures. The work presented in this paper summarises the application of TSA to two types of small medical devices that are used to treat diseased arteries; angioplasty balloons and vascular stents. The use of high resolution optics is described along with a calibration methodology that allows quantitative stress measurements to be taken from the balloon structure. A brief account of a study undertaken to characterise the thermoelastic response from Nitinol is also included and it is demonstrated that thermoelastic data can be obtained from a stent at high resolutions.

Damage Analysis of Internal Surface Flaws Using Thermoelastic Stress Analysis

2005 ◽  
Vol 293-294 ◽  
pp. 279-288 ◽  
Author(s):  
N. Sathon ◽  
Janice M. Dulieu-Barton
Keyword(s):  
Heat Conduction ◽  
Stress Analysis ◽  
Phase Variation ◽  
Thermoelastic Stress ◽  
Internal Surface ◽  
Thermoelastic Stress Analysis ◽  
Element Simulation ◽  
Surface Flaws ◽  
Thermoelastic Response ◽  
Phase Data

Thermoelastic Stress Analysis (TSA) has been used to detect and evaluate the severity of damage on a flat metallic plate. The damage takes the form of a semi-circular notch that represents a surface flaw. Thermoelastic data was gathered from the undamaged side of the plate. The experimental results show that shallow surface flaws can be detected by using phase information from thermoelastic data. This information can then be used to indicate the flaw severity in terms of the notch depth. It is shown that the phase data is dependent on the heat conduction effects around the notch, which enable an assessment of the damage. This is modelled using a simple finite element simulation of the effects of heat conduction on the thermoelastic response. A discussion on the potential of using phase variation across damaged regions to analyse damage severity is provided.

Identification of Damage in Composite Structures Using Thermoelastic Stress Analysis

2005 ◽  
Vol 293-294 ◽  
pp. 583-590 ◽  
Author(s):  
T.R. Emery ◽  
Janice M. Dulieu-Barton ◽  
P.R. Cunningham
Keyword(s):  
Stress Analysis ◽  
Composite Structures ◽  
Cyclic Load ◽  
Stress Component ◽  
Thermoelastic Stress ◽  
Thermoelastic Stress Analysis ◽  
Temperature Component ◽  
Thermoelastic Response ◽  
Calibration Device ◽  
Stressed Component

The application of a cyclic load on a composite material containing damage has the effect of heating due to the material viscoelasticity. This is exaggerated in the proximity of interlaminar failure because of friction between plies. Quantitatively studying a stressed component subject to these conditions using Thermoelastic Stress Analysis (TSA) has been inaccurate, as the localised heating has an effect on the thermoelastic response. Hence the thermoelastic signal from damaging composites will contain a stress-induced component and a temperature-induced component. In this paper a process is described that allows the thermoelastic signal to be de-coupled into a stress component and a temperature component. This is achieved using a combination of infra-red thermography and TSA. The process is based on the use of a special calibration device. The paper provides an experimental verification of the de-coupling using actual damaged composite components.

The application of thermoelastic stress analysis techniques to composite materials

1988 ◽  
Vol 23 (3) ◽  
pp. 137-143 ◽  
Author(s):  
P Stanley ◽  
W K Chan
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Stress Analysis ◽  
Thermoelastic Stress ◽  
Orthotropic Materials ◽  
Quantitative Interpretation ◽  
Thermoelastic Stress Analysis ◽  
Relevant Theory ◽  
Analysis Techniques ◽  
Thermoelastic Response

The application of the thermoelastic technique (SPATE) to two different composite material specimens is described and the results are critically discussed. The relevant theory, which permits a quantitative interpretation of the thermoelastic response from orthotropic materials, is outlined.

Determining Orthotropic Coefficients From, and Thermoelastic Stress Analysis of, Diametrally Loaded Composite Disk

2006 ◽  
Author(s):  
Simon Quinn ◽  
Shiang-Jiun Lin ◽  
Jonathan McCabe ◽  
Robert E. Rowlands
Keyword(s):  
Stress Analysis ◽  
Thermoelastic Stress ◽  
Orthotropic Materials ◽  
Uniaxial Tensile ◽  
Measured Signal ◽  
Loading Frequency ◽  
Thermoelastic Stress Analysis ◽  
Ambient Conditions ◽  
Orthotropic Composites ◽  
Stress Changes

Thermoelastic stress analysis measures temperature variations in loaded solids and relates these to associated stresses. For orthotropic materials, the measured signal is proportional to a linear combination of the normal stress changes in the directions of material symmetry, and K1 and K2 are thermo-mechanical coefficients. Quantitative thermoelastic stress analysis of orthotropic composites necessitates (i) determination of the above two thermo-mechanical coefficients (i.e. calibration), and (ii) separation of the stresses. Although calibration procedures can take different forms, K1 and K2 can be experimentally determined most reliably and easily from calibration specimens of the same material, paint coating, loading frequency and ambient conditions as the test structure. Such calibration specimens typically employ a geometry and loading for which the state of stress or strain is known theoretically, or independently determined. Loaded beams, a diametrically-compressed disk, or uniaxial tensile coupons have been used for isotropic materials. Orthotropic materials usually necessitate testing two calibration specimens, with their principal material directions interchanged respectively. The present paper demonstrates the ability to determine both K1 and K2 from a single diametrally-loaded orthotropic composite (graphite/epoxy) disk. To be able to determine both coefficients from a single calibration specimen is advantageous. Disks are also easy to machine and load, rendering them very convenient for calibration.

Evaluation of Sub-Surface Stresses Using Thermoelastic Stress Analysis

2007 ◽  
Vol 7-8 ◽  
pp. 153-158 ◽  
Author(s):  
Nuttaphon Sathon ◽  
Janice M. Dulieu-Barton
Keyword(s):  
Stress Analysis ◽  
Thermal Diffusion ◽  
Surface Defect ◽  
Thermoelastic Stress ◽  
Surface Damage ◽  
Thermoelastic Stress Analysis ◽  
Surface Stresses ◽  
Thermoelastic Response ◽  
Established Technique

Thermoelastic stress analysis (TSA) is a well established technique for stress analysis. Recent studies have revealed that the technique can be used to detect sub-surface defect effectively. In this study, the technique has been used to examine the thermoelastic response to sub-surface damage in simple bar specimens. The non-adiabatic thermoelastic response from areas close to the damage has been studied. The study shows that the phase of the response along with the thermal diffusion can provide a parameter that will help reveal subsurface stresses.

Thermoelastic Stress Analysis

1982 ◽  
Vol 29 (4) ◽  
pp. 555-563 ◽  
Author(s):  
L.R. Baker ◽  
J.M.B. Webber
Keyword(s):  
Stress Analysis ◽  
Thermoelastic Stress ◽  
Thermoelastic Stress Analysis
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