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Mizar, Shivananda Pai. "Thermomechanical characterization of NiTiNOL and NiTiNOL based structures using ACES methodology." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-021606-104515/.
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Mizar, Shivananda Pai. "Thermomechanical characterization of NiTiNOL and NiTiNOL based structures using ACES methodology." Digital WPI, 2006. https://digitalcommons.wpi.edu/etd-dissertations/61.
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Recent advances in materials engineering have given rise to a new class of materials known as active materials. These materials when used appropriately can aid in development of smart structural systems. Smart structural systems are adaptive in nature and can be utilized in applications that are subject to time varying loads such as aircraft wings, structures exposed to earthquakes, electrical interconnections, biomedical applications, and many more. Materials such as piezoelectric crystals, electrorheological fluids, and shape memory alloys (SMAs) constitute some of the active materials that have the innate ability to response to a load by either changing phase (e.g., liquid to solid), and recovering deformation. Active materials when combined with conventional materials (passive materials) such as polymers, stainless steel, and aluminum, can result in the development of smart structural systems (SSS). This Dissertation focuses on characterization of SMAs and structures that incorporate SMAs. This characterization is based on a hybrid analytical, computational, and experimental solutions (ACES) methodology. SMAs have a unique ability to recover extensive amounts of deformation (up to 8% strain). NiTiNOL (NOL: Naval Ordinance Lab) is the most commonly used commercially available SMA and is used in this Dissertation. NiTiNOL undergoes a solid-solid phase transformation from a low temperature phase (Martensite) to a high temperature phase (Austenite). This phase transformation is complete at a critical temperature known as the transformation temperature (TT). The low temperature phase is softer than the high temperature phase (Martensite is four times softer than Austenite). In this Dissertation, use of NiTiNOL in representative engineering applications is investigated. Today, the NiTiNOL is either in ribbon form (rectangular in cross-section) or thin sheets. In this Dissertation, NiTiNOL is embedded in parent materials, and the effect of incorporating the SMA on the dynamic behavior of the composite are studied. In addition, dynamics of thin sheet SMA is also investigated. The characterization is conducted using state-of-the- art (SOTA) ACES methodology. The ACES methodology facilitates obtaining an optimal solution that may otherwise be difficult, or even impossible, to obtain using only either an analytical, or a computational, or an experimental solution alone. For analytical solutions energy based methods are used. For computational solutions finite element method (FEM) are used. For experimental solutions time-average optoelectronic holography (OEH) and stroboscopic interferometry (SI) are used. The major contributions of this Dissertation are: 1. Temperature dependent material properties (e.g., modulus of elasticity) of NiTiNOL based on OEH measurements. 2. Thermomechanical response of representative composite materials that incorporate NiTiNOL“fibers". The Dissertation focuses on thermomechanical characterization of NiTiNOL and representative structures based on NiTiNOL; this type of an evaluation is essential in gainfully employing these materials in engineering designs.
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Garcia, Angelo. "Control of nitinol wire actuator." Thesis, University of Canterbury. Mechanical Engineering, 2003. http://hdl.handle.net/10092/6610.
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The Stewart Platform is well known parallel robotic mechanism often used for flight simulators. Less well known applications involve robotics and machine tools. This research deals with Stewart Platforms that use Nitinol wire, a shape memory alloy, as binary actuators that are switched on and off to control the position of the platform. Binary control of the six actuators on a platform yields sixty four possible platform positions, and four stacked platforms yield 256E12 possible positions. The design of a simple basic four stages model is described in this research.
Experiments were conducted on the Nitinol wire to investigate the shape memory effects, hysteresis and the martensite/austenite phase transformations. These results were used in the design of a high power to weight ratio Stewart Platform, overcoming many of the drawbacks of previous models that are powered by heavy hydraulics or electric motors. Due to the complexity of some of the parts and small numbers required, rapid prototyping was used to manufacture over 90% of the structure. In this research, the control system proposed is expected to be useful for not only Shape Memory Alloy (SMA) actuators but also other actuators with hysteresis, for example, piezoceramic actuators, rubber actuators driven by air supply, bellows actuators, etc.
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Di, Leo Claudio V. "Nitinol-reinforced shape-memory polymers." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59905.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 33).
Reinforced shape-memory polymers have been developed from an acrylate based thermoset shape-memory polymer and nitinol wires. A rectangular shape-memory polymer measuring approximately 1 by 2 by 0.1 inches has a ten fold increase in actuation force under three-point bending when reinforced with two 0.02 inch diameter nitinol wires. A constitutive model for shape-memory polymers and nitinol has been used to predict with good correlation the actuation-versus-time and displacement-versustime behavior of the reinforced shape-memory polymer composites. It is possible then, using finite-element modeling, to design and manufacture reinforced shape-memory polymers tailored for use as thermally-activated actuators of specific force.
by Claudio V. Di Leo.
S.B.
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McCarty, David Hughes Mary Leigh. "Durability of nitinol for structural applications." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/MCCARTY_DAVID_39.pdf.
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Shayanfard, Pejman. "Role of Plasticity in Nitinol Fatigue." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-438772.
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Disertace analyzuje vliv koncentrátorů napětí na průběh martensitické transformace, vznik plastické deformace a její vliv na přerozdělení napětí a vznik zbytkového pnutí a reziduálního martenzitu v okolí koncentrátorů v prvcích ze slitin s tvarovou pamětí NiTi. Vliv je analyzován v režimech superelastického isotermálního cyklování a aktuačního cyklování, t.j. teplotního cyklování pod vnějším napětím. Disertace využívá pro vyhodnocení vlivu experimentální přístup spolu s numerickými simulacemi metodou konečných prvků na modelových případech tenkých pásků ze slitin NiTi opatřených půlkruhovými vruby. V experimentální části je vyhodnocován vliv koncentrátorů pomocí termomechanických experimentů s využitím metod obrazové korelace a rentgenové mikrodifrakce pro lokální analýzu deformací a fázových objemových podílů v průběhu cyklování v okolí vrubů. Simulace metodou konečných prvků poskytují komplementární informace o průběhu napětí, deformací a martensitické transformaci, zejména o vývoji jednotlivých složek celkové deformace, tj. elastické a plastické, a vývoji zbytkového pnutí a s ním souvisejícím zbytkovým martensitem.Disertace je dále doplněna o numerickou analýzu vlivu konstrukce stentů na lokální cyklický průběh martensitické transformace a jeho vliv na únavové vlastnosti.
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Huß, Niklas [Verfasser]. "Endoskopische Lungenvolumenreduktion mittels Nitinol Coils / Niklas Huß." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2019. http://d-nb.info/1222973804/34.
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Feeney, Andrew. "Nitinol cymbal transducers for tuneable ultrasonic devices." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5805/.
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In recent years, there has been notable interest in the integration of smart and active materials, such as shape memory alloys, in the design of tuneable and multiple frequency devices. There is a growing desire to be able to tune transducers for a range of applications. As an example, surgical procedures could be enhanced by using an ultrasonic device whose performance could be tailored to penetrate more than one material, such as bone and soft tissue. Research conducted on cymbal transducers, a type of Class V flextensional transducer developed at Pennsylvania State University in the early 1990s, has been largely limited to low power applications, such as for hydrophone systems, and their performance in high power applications has only recently been studied. As such, the integration of smart materials to expand the useful applications of this type of transducer has not been fully explored. In this investigation, a shape memory alloy (SMA) called nickel-titanium, or Nitinol, has been adopted in two forms, one being superelastic and the other shape memory, as the end-cap material in the classical cymbal transducer configuration. The resonant frequencies of these transducers can be tuned by changes to the temperature of the Nitinol, which alters the microstructure, and the modulus, of the material. The microstructure of Nitinol can also be controlled by changes in applied stress. The phases present in the Nitinol microstructure are relatively hard cubic austenite and comparably soft monoclinic martensite. An intermediate phase, called the R-phase, can also appear. This is a rhombohedral distortion of austenite, and has been known to be a source of inconvenience for those who wish to avoid multiple stage transformations. An advantage of using Nitinol end-caps in the classical cymbal transducer configuration is that they are very small, hence minimal thermal energy is required to generate a phase transformation. Also, cymbal transducers are very simple and inexpensive to fabricate. The first part of this research focuses on the development of a dual resonance cymbal transducer using steel and titanium as the end-cap materials. Dynamic analysis techniques comprising electrical impedance measurements, experimental modal analysis (EMA) and vibration resonance response characterisation (VRRC) using laser Doppler vibrometry are introduced and form the dynamic characterisation process. The experimental data is supported in part by finite element analysis (FEA). It is demonstrated that a major problem in cymbal transducer fabrication is the difficulty in controlling the deposition of epoxy resin which is used to create the mechanical coupling in the transducer. This means that the bond layers in a transducer will likely be dissimilar, thereby introducing asymmetry into the transducer. This asymmetry can contribute to the dual resonance in a cymbal transducer. The cymbal transducer is designed to be actively tuneable by the incorporation of Nitinol end-caps in the transducer assembly. The characterisation of Nitinol transducers is performed using the dynamic characterisation methods in conjunction with differential scanning calorimetry (DSC). This is a thermoanalytical technique which has been adopted to estimate the transformation temperatures of Nitinol, and hence the temperatures at which each transducer must be driven to generate the desired operating frequencies. It is demonstrated that in certain cases, particularly with respect to superelastic Nitinol, the estimations of the transformation temperatures from the DSC analysis of Nitinol can be misinterpreted. The dynamic performance of Nitinol vibrating at ultrasonic frequencies has not before been the subject of detailed investigation, including the influence of superelasticity on the vibration response of an ultrasonic transducer. Superelasticity occurs in the austenite phase of Nitinol, where austenite reorients to martensite after a characteristic stress threshold is passed, thereby accommodating very large strains. The results show that whilst Nitinol can be used to fabricate cymbal transducers with tuneable resonant frequencies, there is no evidence that superelasticity contributes to the vibration response of the transducers. The incorporation of shape memory Nitinol in a simple prototype actuator device is also considered, where it appears that the transformation of the shape memory Nitinol is affected by the affixed cylinders used to create the device.
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Karjalainen, T. (Teemu). "Nitinol shape memory alloy in flexor tendon repair." Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789514299803.
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Abstract Early motion is crucial for tendon healing and functional results after flexor tendon repair in the fingers. Motion, however, causes stress in the repair site, which can result in failure of the repair. A flexor tendon repair is made with fine calibre sutures, which sets exceptional requirements for the suture materials used in flexor tendon repair. Nitinol (nickel-titanium alloy) is a shape memory alloy, which can exist in two temperature-dependent forms, soft martensite and stiff austenite. It is possible to fabricate a nitinol wire that is soft and pliable, yet has high tensile strength. It also has excellent biocompatibility. Therefore, it is a potential candidate flexor tendon repair suture material. This study evaluates biomechanical aspects of martensite nitinol wire as a flexor tendon repair suture material. The study hypothesis was that nitinol wire improves the strength of the repairs compared with the repairs made with conventional suture materials. It was found that nitinol core repairs and circumferential repairs performed significantly better when compared with repairs made with commonly used braided polyester and polypropylene of equal calibre. To further optimise the performance of the nitinol wire in tendon surgery, two experimental models were developed to study the suture-tendon interface. The aim was to prevent pull-out of the suture loop so that surgeons could have full advantage of the tensile strength of the nitinol suture. First, it was tested whether it is possible to improve the suture’s ability to grip the tendon tissue by changing the suture type from monofilament to multifilament. Multifilament suture loops reached higher pull-out strength when compared with round monofilament loops when a locking loop was used. Subsequently, the grip of four different previously reported core repair loops was tested. Based on their failure mechanism, two novel loops were developed. The novel loops demonstrated superior ability to grip the tendon. The novel loops can be useful with high tensile strength suture materials and in repairs, which are prone to suture pull-outTiivistelmä Varhainen korjauksen jälkeinen aktiivinen kuntoutus on osoittautunut hyödylliseksi jänteen paranemiselle. Varhainen liike altistaa korjauksen kuormitukselle, joka voi johtaa korjauksen pettämiseen. Korjaukset tehdään ohuilla langoilla. Tämä asettaa erityisiä vaatimuksia jännekorjauksessa käytettävälle ommelainemateriaalille. Nikkeli-titaani (nitinoli) on nk. muistimetalli. Sillä on kaksi lämpötilariippuvaista muotoa: pehmeä martensiitti ja jäykkä austeniitti. Nitinolista voidaan valmistaa ohutta pehmeää ja taipuisaa lankaa, jonka vetolujuus on suuri. Nitinolin siedettävyys jännekudoksessa on todettu hyväksi, minkä vuoksi se on lupaava materiaali käytettäväksi jännekorjauksissa. Tässä tutkimuksessa kokeiltiin martensiittisen nitinolilangan käyttöä jänteen ydinompeleena ja pintaompeleena. Olettamuksena oli, että nitinolilangalla saadaan kestävämpiä korjauksia kuin nykyään käytössä olevilla langoilla. Tulosten mukaan nitinolilangalla tehdyt korjaukset olivat kestävämpiä, kun niitä verrattiin saman paksuiseen punottuun polyesteriin ja polypropyleeniin. Lisäksi kehitimme kaksi mallia, joiden tarkoituksena oli parantaa nitinolilankasilmukan pitoa jännekudoksesta. Tarkoituksena oli löytää keinoja, joilla langan otetta jännekudoksesta voidaan parantaa ja langan hyvät vetolujuusominaisuudet pääsevät oikeuksiinsa. Ensin muutimme langan muotoa perinteisestä yksisäikeisestä pyöreästä monisäikeiseen muotoon. Monisäikeisen langan läpileikkausvoima oli huomattavasti suurempi kuin yksisäikeisen pyöreän langan. Ero oli havaittavissa vain, kun käytettiin lukitsevaa silmukkaa. Tämän jälkeen testasimme neljän perinteisesti käytetyn korjaustekniikan silmukan pitokykyä ja tulosten perusteella kehitimme kaksi uutta silmukkaa. Työssä kehitetyt silmukat pitivät kiinni jänteestä huomattavasti paremmin kuin perinteiset silmukat. Työssä kehitetyillä silmukoilla voidaan optimoida vahvojen ommelainemateriaalien suorituskyky jännekirurgiassa
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Pulletikurthi, Chandan. "Biocompatibility Assessment of Biosorbable Polymer Coated Nitinol Alloys." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1552.
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Owing to an increased risk of aging population and a higher incidence of coronary artery disease (CAD), there is a need for more reliable and safer treatments. Numerous varieties of durable polymer-coated drug eluting stents (DES) are available in the market in order to mitigate in-stent restenosis. However, there are certain issues regarding their usage such as delayed arterial healing, thrombosis, inflammation, toxic corrosion by-products, mechanical stability and degradation. As a result, significant amount of research has to be devoted to the improvement of biodegradable polymer-coated implant materials in an effort to enhance their bioactive response.
In this investigation, magneto-electropolished (MEP) and a novel biodegradable polymer coated ternary Nitinol alloys, NiTiTa and NiTiCr were prepared to study their bio and hemocompatibility properties. The initial interaction of a biomaterial with its surroundings is dependent on its surface characteristics such as, composition, corrosion resistance, work of adhesion and morphology. In-vitro corrosion tests such as potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) studies were conducted to determine the coating stability and longevity. In-vitro hemocompatibility studies and HUVEC cell growth was performed to determine their thrombogenic and biocompatibility properties. Critical delamination load of the polymer coated Nitinol alloys was determined using Nano-scratch analysis. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions leached from Nitinol alloys on the viability of HUVEC cells. Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), contact angle meter and X-ray diffraction (XRD) were used to characterize the surface of the alloys.
MEP treated and polymer coated (PC) Nitinol alloys displayed a corrosion resistant polymer coating as compared to uncoated alloys. MEP and PC has resulted in reduced Ni and Cr ion leaching from NiTi5Cr and subsequently low cytotoxicity. Thrombogenicity tests revealed significantly less platelet adhesion and confluent endothelial cell growth on polymer coated and uncoated ternary MEP Nitinol alloys. Finally, this research addresses the bio and hemocompatibility of MEP + PC ternary Nitinol alloys that could be used to manufacture blood contacting devices such as stents and vascular implants which can lead to lower U.S. healthcare spending.
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Dye, Tracy Earl. "An experimental investigation of the behavior of Nitinol." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/45048.
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Shape memory alloys (SMA) have the unique ability to recover large strains and generate large recovery stresses via a repeatable martensitic transformation. Stress-strain and shape memory effect characteristics are needed in order to develop SMA force actuator design methods. Moreover, constitutive models able to quantitatively predict these characteristics and thus be useful as engineering design tools are also needed.
An experimental apparatus designed to characterize the mechanical behavior of SMA was built and utilized. The apparatus is used specifically to gather stress-strain and shape memory effect characteristics from nitinol wire whereby mechanical properties associated with the material are determined. Phenomena such as the R-phase and stress induced martensite serration are investigated. A one-dimensional constitutive model is presented that quantitatively predicts stress-strain and shape memory effect behavior and was developed with the intention of being an engineering design tool for SMA force actuators. Experimental stress-strain and shape memory effect
results are compared against that predicted by the model with the intention of verifying the model. The model displays the ability to predict stress-strain behavior that is in good quantitative agreement with experiment. The model also displays the ability to predict hysteric shape memory effect behavior for free, controlled, and restrained recovery cases of selected prestrains that is in good quantitative agreement with experiment. The model is unable to predict shape memory effect behavior such as the R-phase. Demonstrating the ability to experimentally investigate a constitutive model will hopefully inspire further combined experimental and theoretical SMA research.Master of Science
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Karbaschi, Zohreh. "Torsional Behavior of Nitinol: Modeling and Experimental Evaluation." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1336762958.
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Daly, Samantha Hayes Bhattacharya Kaushik Ravichandran G. Bhattacharya Kaushik Ravichandran G. "Deformation and fracture of thin sheets of nitinol /." Diss., Pasadena, Calif. : California Institute of Technology, 2007. http://resolver.caltech.edu/CaltechETD:etd-05252007-000127.
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Espinoza, Castillo Carolina Belén. "Caracterización de las Propiedades Superelásticas de Barras de Nitinol." Tesis, Universidad de Chile, 2007. http://www.repositorio.uchile.cl/handle/2250/104573.
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Kujala, S. (Sauli). "Biocompatibility and biomechanical aspects of Nitinol shape memory metal implants." Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514271246.
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Abstract
Nickel-titanium shape memory metal Nitinol (NiTi) is a new kind of implant material, which provides a possibility to prepare functional implants activated at body temperature and withstands kinking better than conventional metals. Applications utilizing these unique properties are a target of active research interest. Host reactions to NiTi and to the forces created by functional implants should also be studied.
A functional NiTi intramedullary nail, which causes a bending force on the bone, was developed for correcting bone deformities. In the present studies, the action of the device was inverted to induce a bone deformity instead of correcting one, in order to test the hypothesis that bone modelling can be controlled using such functional nail. Implanting the nail into the medullary cavity of rat femur for twelve weeks caused bowing of the bone, retardation of its longitudinal growth, and thickening of the bone and the cortex. In another study the effects of functional and straight nails were compared. Bowing of the bone and significant overall thickening of the bone and the cortex were associated only with the functional nail, while the straight nail induced only minor thickening of the bone. Retardation of longitudinal growth was seen in both groups, and this may have been caused by perforating the distal epiphyseal plate during the nailing. Finite element model of the bone-nail combination was also created.
Porous NiTi was studied as a bone graft substitute by filling a bone defect in the distal femoral metaphysis of a rat bone with porous NiTi implants of different porosities. After 30 weeks, porosity of 66.1% (mean pore size (MPS) 259μm) showed the best bone-implant contact (51%). However, porosity of 46.6% (MPS 505μm) with 39% bone-implant contact was not significantly inferior in this respect and showed a significantly lower incidence of fibrosis within the implant and thus seemed to be the best choice for a bone graft substitute, out of the porosities tested here. The porosity of 59.2% (MPS 272μm) showed lower contact values.
NiTi tendon suture material was studied by implanting NiTi sutures into rabbit tendon and subcutaneous tissues for two, six, and twelve weeks. NiTi proved to be stronger than polyester, which served as control material. The encapsulating membrane was minimal with both materials, suggesting good biocompatibility in tendon tissue. The implantation did not affect the strength properties of either material.
On the basis of the present studies, NiTi provides a possibility to develop new kinds of implants for correcting bone deformities, for filling bone defects in weight-bearing locations and a good candidate for a tendon suture material.
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Haider, Waseem. "Enhanced Biocompatibility of NiTi (Nitinol) Via Surface Treatment and Alloying." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/177.
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It is projected that by 2020, there will be 138 million Americans over 45, the age at which the increased incidence of heart diseases is documented. Many will require stents. This multi-billion dollar industry, with over 2 million patients worldwide, 15% of whom use Nitinol stents have experienced a decline in sales recently, due in part to thrombosis. It is a sudden blood clot that forms inside stents. As a result, the Food and Drug Administration and American Heart Association are calling for a new generation of stents, new designs and different alloys that are more adaptable to the arteries. The future of Nitinol therefore depends on a better understanding of the mechanisms by which Nitinol surfaces can be rendered stable and inert. In this investigation, binary and ternary Nitinol alloys were prepared and subjected to various surface treatments such as electropolishing (EP), magnetoelectropolishing (MEP) and water boiling & passivation (W&P). In vitro corrosion tests were conducted on Nitinol alloys in accordance with ASTM F 2129-08. The metal ions released into the electrolyte during corrosion tests were measured by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). Biocompatibility was assessed by observing the growth of human umbilical vein endothelial cells (HUVEC) on the surface of Nitinol alloys. Static and dynamic immersion tests were performed by immersing the Nitinol alloys in cell culture media and measuring the amount of metal ions released in solution. Sulforhodamine B (SRB) assays were performed to elucidate the effect of metal ions on the growth of HUVEC cells. The surfaces of the alloys were studied using Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Finally, wettability and surface energy were measured by Contact Angle Meter, whereas surface roughness was measured by Atomic Force Microscopy (AFM). All the surface treated alloys exhibited high resistance to corrosion when compared with untreated alloys. SRB assays revealed that Ni and Cu ions exhibited greater toxicity than Cr, Ta and Ti ions on HUVEC cells. EP and MEP alloys possessed relatively smooth surfaces and some were composed of nickel oxides instead of elemental nickel as determined by XPS. MEP exhibited lowest surface energy and lowest surface roughness.
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Olsson, Sara. "Evaluation of a production route for cold-drawn Nitinol wires." Thesis, KTH, Industriell produktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192190.
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This master thesis has summarized articles and patents found that have been evaluating and optimizing cold-drawing of nitinol wire. The nitinol wire of interest is where the nitinol is used as a core-wire in guidewires. The super-elastic and linear-elastic property of nitinol is attractive in this application. It has been found that cold-drawing of wire is performed in a number of steps, depending on how thin the target wire should be. The process starts with pre-annealing followed by cold-drawing with inter-annealing in between each pass. After the final drawing pass a final annealing in combination with mechanical straightening should be done at a lower temperature than the inter-annealing. This process was tried out and it showed that with the existing equipment at one certain production plant of wire-drawing of nitinol following parameters showed superelastic and high-strength properties: pre-annealing at 550 °C for 10 min in air, drawing down to 55 % area reduction, inter-annealing at 675 °C for 15 min in hydrogen, drawing down to 61 % area reduction, final annealing at 450 °C for 2 min and 30 s. In order to realize a production line of nitinol wire more work must be done. Recommended is to perform a design of experiment at the final annealing times and temperatures in order to optimize the superelastic and high-strength properties of the nitinol wire to best suit as core wire for guidewires.Detta examensarbete har sammanfattat artiklar och patent där kalldragning av nitinoltråd har utvärderats och optimerats. Den typ av nitinoltråd som varit av intresse för denna rapport är den del av styrtråden som utgör kärnan i styrtråden. Superelasticitet och linjär elasticitet är intressanta egenskaper från nitinol som passar för denna applikation i styrtrådar. Det har visat sig att kalldragning av nitinol utförs i ett antal steg. Processen börjar med en förglödgning som sedan följs av kalldragning med mellanglödgning mellan varje dragning. Efter den sista kalldragningen då den önskade tråddimensionen uppnåtts utförs en slutglödgning i kombination med mekanisk sträckning av tråden. Slutglödgningen bör göras i en lägre temperatur än mellanglödgningen. Denna process testades och det resulterade i att med den utrustning som fanns tillgänglig på en specifik produktionsanläggning vid kalldragning av nitinol, visade följande parametrar upp superelastiska och höghållfasta egenskaper: förglödgning i 550 °C i 10 min i luft, kalldragning ned till 55 % areareduktion, mellanglödning i 675 °C i 15 min i en omgivning av vätas, kalldragning ned till 61 % areareduktion, slutglödning i 450 °C i både 2 min och 30 s i en omgivning av vätgas. För att realisera en produktionslina av kalldragning av nitinoltråd måste mer arbete utföras. Rekommenderat är att utföra ”design of experiment” på final glödgningstemperatur och tid för att kunna optimera de superelastiska och höghållfasta egenskaperna hos nitinoltråd som bäst lämpar sig för styrtrådar.
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Gbur, Janet L. "Inclusion Effects on the Lifetime Performance of Superelastic Nitinol Wires." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case153256740897449.
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Stepan, Lenka Lan-Sun. "Development and testing of a thin film nitinol heart valve." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1324380381&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Keller, Tanja. "Osseointegration einer mit Plasma-Immersions-Ionen-Implantation behandelten Autokompressionsklammer aus Nitinol." Diss., lmu, 2004. http://nbn-resolving.de/urn:nbn:de:bvb:19-20903.
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Barker, Daniel Keith. "Active dynamic response tuning of adaptive composites utilizing embedded nitinol actuators." Thesis, This resource online, 1989. http://scholar.lib.vt.edu/theses/available/etd-03042009-041038/.
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Bobanga, John. "Small Scale Production of Nitinol throughVacuum Arc Melting and Indirect Extrusion." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1417775292.
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Kiesling, Thomas C. "Impact failure modes of graphite epoxy composites with embedded superelastic nitinol." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-09162005-115046/.
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Kotamala, Sreenath. "PRESTRESSING OF SIMPLY SUPPORTED CONCRETE BEAM WITH NITINOL SHAPE MEMORY ALLOY." Text at OhioLINK ETD Center (Requires Adobe Acrobat Reader for viewing), 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1091806884.
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Thesis (M.S.V.)--University of Toledo, 2004.Typescript. "A thesis [submitted] as partial fulfillment of the requirements of the Master of Science degree in Civil Engineering." Includes bibliographical references (leaves 63-64).
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Heintz, Carsten Christian [Verfasser]. "Korrosion von Nitinol als Versagensmechanismus von Aorten-Endoprothesen / Carsten Christian Heintz." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2011. http://d-nb.info/1010758365/34.
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Kennedy, Sean P. "Material Characterization of Nitinol Wires for the Design of Actuation Systems." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1076.
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A series of tests were performed on nickel-titanium alloy wire, also known as nitinol, to determine the plausibility of designing an actuator using this wire as the method of actuation. These tests have been designed to fully characterize how the wire behaves under steady state and transient conditions allowing for a specific wire selection to be made given known actuator specifications which will result in an efficient design. The wire transient data can be used to design a controller which reduces the actuation time. The research done for the overall project covers a wide scope including wire hysteresis, nitinol transition temperature, variable wire resistance, wire actuation as a function of current and pull force, cable fabrication, and wire actuation control to optimize performance. Using these test results, a prototype actuator has been designed using nitinol wire. It has been determined that an actuator can be efficiently designed using this material.
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Freitag, Marlena. "Struktura i właściwości modyfikowanych powierzchni stopów NiTi." Doctoral thesis, Katowice : Uniwersytet Śląski, 2012. http://hdl.handle.net/20.500.12128/5376.
Full textAbstract:
W przedstawionej pracy dokonano charakterystyki warstw wierzchnich
wytworzonych na stopie NiTi w wyniku niskotemperaturowego azotowania
i tlenoazotowania jarzeniowego. Zbadano również wpływ tych procesów na strukturę
i efekty pamięci kształtu samego podłoża - stopu NiTi. Przeprowadzone w Instytucie Nauki o Materiałach badania dotyczące modyfikacji
powierzchni stopów NiTi wskazują, iż:Istnieje możliwość modyfikacji powierzchni stopów NiTi techniką
niskotemperaturowego azotowania i tlenoazotowania jarzeniowego w celu
poprawy ich biokompatybilności poprzez wytworzenie warstw o podwyższonej
biokompatybilności oraz odpornych na odkształcenia związane z indukowaniem
efektu pamięci kształtu i efektu nadsprężystości.
W celu osiągnięcia założonego celu, należało zrealizować następujące zadania
badawcze:
> Otrzymanie warstw azotkowych i tlenkowoazotkowych metodą jarzeniową
w niskich temperaturach.
> Wytworzenie w wyniku sterylizacji w autoklawie warstw tlenkowych, jako bazy
odniesienia dla warstw azotkowych i tlenkowoazotkowych.
> Przeprowadzenie pełnej charakterystyki strukturalnej otrzymanych warstw.
> Szczegółowe zbadanie mechanizmu i kinetyki korozji elektrochemicznej
wytworzonych warstw w środowisku sztucznych płynów ustrojowych.
> Zbadanie odporności warstw azotkowych i tlenkowoazotkowych na
odkształcenia związane z indukowaniem efektów pamięci kształtu.
> Określenie wpływu warunków procesu jarzeniowego na strukturę i właściwości
podłoża ze stopów NiTi.
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Brodie, Robbie. "Characterization of superelastic nitinol wire for application to aortic stent graft design." Thesis, University of Strathclyde, 2018. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=30136.
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Aortic stent graft devices are required to treat patients with life-threatening vascular disease. These devices depend on superelastic Nitinol material for their ability to be delivered through a minimally invasive endovascular approach and then to self-expand for long-term implantation at the target site. In this safety-critical application, Nitinol stent components are subjected to challenging in-service conditions in terms of thermo-mechanical loading. Characterization of the material’s response to these loading conditions is therefore essential for its safe and effective implementation in the design of medical devices. This thesis reports material characterization work performed on superelastic Nitinol stent wire under conditions relevant to its in-service application. The product life cycle of Nitinol stent graft components is investigated, highlighting the importance of the material’s bending behaviour and the associated tensile and compressive mechanical responses. With tensile behaviour and test methods already well established for Nitinol, the work first focuses on developing a method for compressive testing of representative Nitinol wire material, building on a previous method to enable testing to higher strains. This allows characterization of the material in compression for thermo-mechanical loading representative of large compaction deformations, in-vivo cycling and different temperatures seen during production, sterilization and implantation. The results also allow a clear understanding of the material’s tension-compression stress-strain asymmetry, which is essential to understanding its bending behaviour. This investigation concludes with a feasibility study into a novel compression test method developed by the author, using short wire samples with high-resolution ‘microtester’ equipment to obtain improved results. The work then focuses on development of a test method for bend testing of thin Nitinol wires to investigate the load response to in-service deformations at relevant test temperatures. This allows characterization of the wire’s load-history dependent bending response, whereby the force exerted at a given deflection during unloading depends on the maximum deflection during loading, with interesting application possibilities for stent components. The testing also allows the material’s temperature dependence, cyclic behaviour and large deformation response in bending to be studied. Following this, full-field strain measurement of thin Nitinol wires in bending is presented, achieved through application of 3-D microscopic Digital Image Correlation(DIC) technology. The development of a novel test method, together with extensive data analysis, provides results for characterization of the material’s complex bending behaviour, allowing new insight to its tension–compression asymmetry, localised deformation, load-unload strain hysteresis and load-history dependence of strain state inbending. This testing provides useful quantitative characterisation data including neutral axis eccentricity at high bend deformations. Finally, Abaqus FEA software is used to investigate the effectiveness of its in-built superelastic constitutive model for representing the Nitinol stent wire’s bending behaviour, and ultimately its suitability for use in stent design and analysis. The uniaxial stress-strain test results are used for input to the model, and then bending simulation results are compared against the experimental results, both in terms of force and strain outputs. Key findings include the model’s inability to represent the strain localisation seen in bending experiments, leading to under-representation of the maximum strains for ‘intermediate’ bend deflections, and also the model’s under-representation of unloading forces at these deflections (unless input parameters are adapted to compensate). Despite these limitations of the model, the cyclic stiffness and strain changes in bending are shown to be reasonably well represented, validating it for its primary use in fatigue analysis of stent components.
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Tan, Aoyong. "In-Vitro Drug Delivery and Corrosion Study of Polymer Coated Nitinol Stents." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1619629037334744.
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Lenahan, Kristie M. "Thermoelastic control of adaptive composites for aerospace applications using embedded nitinol actuators." Thesis, Virginia Tech, 1996. http://hdl.handle.net/10919/44955.
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Aerospace structures have stringent pointing and shape control requirements during long-term exposure to a hostile environment with no scheduled maintenance. This makes them excellent candidates for a smart structures approach as current passive techniques prove insufficient. This study investigates the feasibility of providing autonomous dimensional control to aerospace structures by embedding shape memory alloy elements inside composite structures. Increasing volume fractions of nitinol wire were embedded in cross-ply graphite/ epoxy composite panels. The potential of this approach was evaluated by measuring the change in longitudinal strain with increasing temperature and volume fraction. Reduction of thermal expansion is demonstrated and related to embedded volume fraction.
Classical lamination theory is used to formulate a two-dimensional model which
included the adaptive properties of the embedded nitinol. The model was used to predict
the increased modulus and reduction of thermal strain in the modified plates which was
verified by the experimental data.
Master of Science
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Nguyen, Tuan Minh. "MODELING OF THERMO-MECHANICAL BEHAVIOR OF NITINOL ACTUATOR FOR SMART NEEDLE APPLICATION." Master's thesis, Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/192929.
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Mechanical EngineeringM.S.M.E.
A large and increasing number of cancer interventions, including both diagnosis and therapy, involve precise placement of needles, which is extremely difficult. This challenge is due to lack of proper actuation of the needle (i.e., actuated from the proximal end, which is far away from the needle tip). To overcome this challenge, we propose to bend the needle using a smart actuator that applies bending forces on the needle body; thereby, improving the navigation of the needle. The smart actuator is designed with shape memory alloy (SMA) wires, namely Nitinol, due to their unique properties such as super-elasticity, shape memory effect, and biocompatibility. For accurate steering of the smart needle, there is a need to understand Nitinol thermo-mechanical behaviors. Various existing SMA constitutive models were investigated and compared. Since SMA is used as an actuator in this project, only one dimensional constitutive models are considered. Two distinct models with different phase transformation kinetic approaches were chosen. The first model was proposed by Terriault and Brailovski (J. Intell. Mat. Systems Structures, 2011) using a modified one dimensional Likhachev formulation. The second model was developed by Brinson (J. Intell. Mat. Systems Structures , 1993). Since all SMA constitutive models are empirically based, several important materials' constants such as Phase Transformation Temperatures are needed. The four Transformation Temperatures are: Martensite start (Ms), Martensite finish (Mf), Austenite start (As), Austenite finish (Af). Differential Scanning Calorimetry (DSC) was used to obtain these constants. These temperatures are also influenced by stress, defined by the Clausius-Clayperon coefficients. The coefficients were obtained by measuring Nitinol temperature and displacement response under various constant stress conditions. In order to study its actuation behavior, Nitinol wires under constant strain configuration and resistance heating were tested for their force response. The thermo-mechanical responses were then compared with numerical simulations. While Terriault and Brailovski resistance heating formulation agrees strongly with temperature responses, the model cannot be used to simulate the actuator mechanical responses. Brinson model simulations of the force responses were found to agree well with experimental results. In conclusion, Terriault and Brailovski resistance heating formulation should be coupled with Brinson model to accurately simulate Nitinol actuation behavior for the smart needle.
Temple University--Theses
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Kalidindi, Arvind R. (Arvind Rama). "Assessing the opportunity to produce Nitinol medical device components using additive manufacturing." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122273.
Full textAbstract:
Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 64-69).
Nitinol is an important alloy for medical device applications due to its exceptional combination of strength and elasticity. Most Nitinol is produced in wire form and then braided or laser cut into the complex geometries needed for medical device applications. These manufacturing processes are costly and can be labor-intensive. Additive manufacturing, or 3D printing, offers a tantalizing alternative to the status quo of Nitinol manufacturing as the desired part can be printed to shape, greatly simplifying the operations and cost of producing medical device components. Working with Boston Scientific in Clonmel, Ireland, roughly 100 Nitinol samples were additively manufactured to determine whether quality parts could be printed. Through a design of experiment procedure, the 3D printing parameters were optimized to develop settings for parts with high relative density, low internal defects, and low impurity concentrations, meeting the ASTM F2063 standards for medical device-grade Nitinol. The main challenge from an engineering perspective is the loss of Ni during printing, which could require either higher power lasers or sourcing high Ni content powder to reach the desired properties. Operationally, a cost accounting model was developed to match the expected operational setup for additively manufacturing Nitinol, with smaller components comparing favorably cost-wise to traditionally manufactured Nitinol components. The engineering and business analyses were combined to determine the best applications considering Nitinol properties used (superelasticity, shape memory, and ductility) and the opportunity for 3D printing (prototyping, replacing existing Nitinol parts, developing new Nitinol parts). The best opportunities in the short-term for this technology were identified to be prototyping and developing new Nitinol components targeting ductility and shape memory Nitinol applications.
by Arvind R. Kalidindi.
M.B.A.
M.B.A. Massachusetts Institute of Technology, Sloan School of Management
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Jones, Wendy Michele. "An investigation of the interfacial characteristics of nitinol fibers in a thermoset composite." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12302008-063746/.
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Boseniuk, Arne. "Implantation von Nitinol-Stents in der Arteria femoralis superficialis - langfristige Effektivität und Einflussfaktoren -." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-172241.
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Hintergrund: Diese Studie wurde initiiert, um die langfristige Wertigkeit der Implantation von selbstexpandierenden Nitinol-Stents in der Arteria femoralis superficialis zu untersuchen. Die Effektivität wurde anhand von Primärerfolg, Offenheitsraten und klinischem Erfolg überprüft. Komplikationsraten und unerwünschte Folgeereignisse definierten die Sicherheit dieser interventionellen Therapiemethode.
Methoden: Retrospektiv wurden 278 Zielextremitäten von 263 Patienten über durchschnittlich 4,7 ± 1,9 Jahre hinweg beobachtet. Die Daten wurden aus internen Krankenakten sowie externen Befunden gewonnen. Gruppenvergleiche wurden mit t-Test, Fisher-Exact-Test und multivariater logistischer Regression durchgeführt. Überlebenszeitanalysen wurden mit der Kaplan-Meier-Methode berechnet. Univariate Risikofaktoren wurden mit dem Log-Rank-Test bestimmt und anschließend in das multivariate Cox-Model eingeschlossen.
Ergebnisse: Das Durchschnittsalter der Patienten betrug 67,2 ± 9,5 Jahre, 74,1 % waren männlich, 21,2 % litten an einer kritischen Extremitätenischämie. Die mittlere Läsionslänge maß 11,5 ± 7,9 cm. Es handelte sich in 21,1 % um Restenosen und in 31,6 % um TASC-II-C/D-Läsionen.
Der primäre technische Erfolg der Stentimplantation belief sich auf 96,8 %. Nach ein, drei und fünf Jahren lagen die primären Offenheitsraten bei 77 %, 56 % und 46 %, die sekundären Offenheitsraten bei 98 %, 94 % und 89 % sowie die Majoramputations-raten bei 0,4 %, 1,4 % und 4,2 %. Das Rutherford-Stadium ist von 3 ± 0,9 auf 1,8 ± 1,8 gesunken. Ein Todesfall war Folge eines Stentverschlusses.
Signifikante Risikofaktoren für verkürzte Stentoffenheiten waren lange Gefäßläsionen, TASC-II-C/D-Läsionen sowie Luminexx®-Stents. Diabetes mellitus, Adipositas und kritische Extremitätenischämie waren mit erhöhten Amputationsraten assoziiert.
Fazit: Hohe technische Erfolgsraten, relativ niedrige Komplikationsraten, befriedigende kurz- und mittelfristige Offenheitsraten sowie zufriedenstellender klinischer Erfolg zeichnen die Stentimplantationen in der Arteria femoralis superficialis aus.
Langfristig stellen die Entstehung von In-Stent-Restenosen und damit verbundene Folgen jedoch ein Problem dar. Allerdings ist die Einführung von medikamenten-freisetzenden Ballons zur Sekundärbehandlung in dieser Hinsicht erfolgversprechend.
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Lukina, Elena. "An investigation of nitinol and titanium alloys for the correction of spinal scoliosis." Thesis, Kingston University, 2014. http://eprints.kingston.ac.uk/29996/.
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Surgery for early onset scoliosis (EOS) often requires instrumentation which enables the pediatric patient’s spine to grow. The drawback of growing rods (Ellipse Technologies, USA) is the requirement of periodical extension (at least twice a year). In contrast, in growth- guidance sliding devices such as the Shilla (Medtronic, USA) or LSZ-4D (Conmet, Russia) the extension procedure is not necessary since only one or few fixtures are locked whilst other fixtures make it possible for rods to slide allowing growth of the spine. However, due to the absence of fusion in sliding devices increased rate of fractures of rods is possible. Additionally, movement of rods against fixtures may result in the generation of wear debris. Among traditional metallic materials used for such instrumentation titanium alloys are the most biocompatible and are widely used as fixtures material, while Nitinol, an alloy with Shape memory effect, is a promising material for rods due to having potential for more gradual and sustained correction associated with its shape memory effect and potentially reducing adjacent segment degeneration due to its super-elastic properties. The aim of this thesis was to investigate complications associated with implantation of growth-guidance sliding LSZ-4D in pediatric patients and to investigate the use of Nitinol and titanium alloy (Ti6Al4V) for this application. Analysis of retrieved components of LSZ growth-guidance sliding device (LSZ-4D) made from titanium alloy (Ti6Al4V) implanted in paediatric patients together with associated tissues showed metallosis which in some cases led to the development of complications including seromas and fistula formation. These complications occurred in 5 out of the 25 patients investigated. Another 4 patients encountered fatigue fracture of rods. The volume wear rate measured for the retrieved components of LSZ-4D was found to be 12.5 mm3 per year. In these 25 patients with implanted LSZ-4D devices there was a statistically significant increase in titanium and vanadium ions in the whole blood. With a view to replacing titanium alloy rods with Nitinol an investigation on the fatigue behaviour of Nitinol revealed that creating a microstructure which increased deformation due to a martensitic phase transformation improved high strain amplitude fatigue resistance of Nitinol, whereas precipitation of nanosize Ni-rich particles and decreasing of Ti4Ni2ox inclusions resulted in an increase in low strain fatigue resistance. The wear behaviour of Nitinol in comparison to titanium alloy was also investigated and showed that the wear resistance of Nitinol tested against titanium alloy (Ti6Al4V) in the simulated body environment is approximately 100 fold greater compared to titanium alloy (Ti6Al4V) and is similar to that of CoCr alloy. Nevertheless, Nitinol - Ti6Al4V combination still generates high volumetric wear associated with debris release from the Ti6Al4V component. Coating and treating the surface with TiN (titanium nitride), DLC (diamond like carbon) coatings and ion implantation of nitrogen ions in some instances reduced the wear. The deposition of a TiN coating only on the titanium component in a Nitinol - Ti6Al4V combination significantly improved the wear performance and this was associated with the protection of titanium component whereas the application of DLC improved the wear performance of both titanium and Nitinol. [on implantation or deposition of TiN or DLC coatings on both counterparts was found to be less effective. The current study indicates the importance and potential of reducing the reliance on titanium alloy by using Nitinol for patients with scoliosis and especially in those cases where relative moment of the fixtures is required, such as in growing patients.
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Rocco, Pete Angelo. "Actuation training and its effects on actuation fatigue of Nitinol Shape Memory Wires." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1564737605232559.
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Paine, Jeffrey Steven Nelson. "The performance of nitinol shape memory alloy actuators embedded in thermoplastic composite material systems /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-10102009-020117/.
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Waihrich, Eduardo Siqueira. "Ativação in vitro de neutrófilos expostos a stents carotídeos de nitinol e cobalto-cromo." reponame:Repositório Institucional da UnB, 2013. http://repositorio.unb.br/handle/10482/15329.
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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Ciências da Saúde, Programa de Pós-Graduação em Ciências da Saúde, 2013.Submitted by Alaíde Gonçalves dos Santos (alaide@unb.br) on 2014-03-17T14:22:54Z No. of bitstreams: 1 2013_EduardoSiqueiraWaihrich.pdf: 20462730 bytes, checksum: 1d1637519c85d625be378e13e978582e (MD5)
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Introdução: A angioplastia de carótida com interposição de stent (AS) é uma alternativa para tratamento da doença ateromatosa oclusiva. Em médio prazo, a maior complicação da AS é a re-estenose intra-Stent(4,8% em 2 anos), cujo principal fator desencadeante é a resposta inflamatória tipo corpo estranho contra o Stent Carotídeo. Estão disponíveis diferentes tipos de SC, formados basicamente por duas ligas metálicas diferentes: liga de cobalto-cromo (CoCr) (WallStent®) e de Nitinol (NiTi) (Protegè®). Método: Comparamos as características estruturais e a ativação inflamatória dos neutrófilos quando expostos aos dois tipos de SC, aferindo a produção de radicais livres por meio de espectroscopia óptica. 20 ml de sangue de 19 voluntários hígidos foram centrifugados em gradiente de Percoll® para separação dos neutrófilos. Os neutrófilos foram expostos à superfície do Stent por períodos de 40 minutos, em solução com o Nitro Blue Tetrazolium. Após o período de incubação, os resultados foram mensurados em transmitância por espectrofotometria óptica, utilizando comprimento de onda de 550 nm conforme técnica padrão. A seguir, um exemplar de cada amostra foi enviado à microscopia eletrônica de varredura para análise estrutural dos stents carotídeos e dos neutrófilos aderidos. Resultados: A leitura do espectrofotômetro evidenciou que a liga de NiTi desencadeou maior produção estatisticamente significante de espécies reativas de oxigênio que a liga de CoCr (0,115 +/- 0,058 vs 0,081 +/- 0,050 em transmitância; p = 0,002 e IC95% 0,00052 a 0,0534). As imagens de microscopia eletrônica sugerem que a secção transversal da malha de NiTi é retangular e que a de CoCr é cilíndrica. As duas ligas foram capazes de ativar a formação de radicais livres pelos neutrófilos. A liga de NiTi apresentou significativamente maior reatividade que a liga de CoCr. Conclusão: Esse resultado pode estar relacionado à maior e mais precoce liberação de íons níquel pela liga de NiTi. ____________________________________________________________________________________________ ABSTRACT
Introduction: Carotid artery Stenting (CAS) is an alternative treatment to the atherosclerotic occlusive disease. In the medium term, the main complication of CAS is the in-Stent restenosis (4.8% in 2 years), for which the main triggering factor is the foreign body inflammatory response to the Carotid Stent (CS). There are different types of CS available, and they basically consist of two different alloys: cobaltchrome (WallStent®) and Nitinol (Protégé®). Method: This study compared the structural characteristics and the inflammatory activation of neutrophils when exposed to both types of CS, checking the production of free radicals with the use of optical spectroscopy. 20 ml of blood collected from 19 healthy volunteer patients were centrifuged using the Percoll method for neutrophil separation. Neutrophils were exposed to the Stent surface for 40-minute periods Nitro Blue Tetrazolium (NBT) in solution. After the incubation period, the results were transmittance-measured using an optical spectrophotometer, at 550 nm wavelength, as standard procedures. After that, a portion of each sample was sent for scanning electron microscopy and morpho-physiological analysis of the CS and the adherent neutrophils. Results: Spectrophotometer reading showed that the NiTi alloy was responsible for a statistically significant increased production of reactive species of oxygen when compared to the CoCr alloy (0.115 +/- 0.058 vs 0.081 +/- 0.050 transmittance level, p = 0.002 and CI 95% 0.00052 to 0.0534). Scanning electron microscope images showed that the NiTi CS mesh has rectangular cross sections, and the CoCr CS mesh has cylindrical cross sections. Both alloys triggered free radical formation by neutrophil activation. Conclusion: The NiTi alloy showed significantly higher reactivity than the CoCr alloy. This result may be caused by a greater and earlier release of nickel ions by the NiTi alloy.
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Vearick, Samanta Bianchi. "Confecção e avaliação de órtese de nitinol auto-expansível com aplicação em vias aéreas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/6856.
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Este trabalho tem como objetivo a confecção de órtese auto-expansível, utilizando fios da liga de nitinol para aplicação em vias aéreas. O processo iniciou na obtenção de um trançado manual e posterior determinação de gabaritos para a confecção das órteses. Após a trançagem, as órteses são submetidas a tratamento térmico a 530ºC, o que gera uma coloração superficial que varia com o tempo de permanência no forno. Essas colorações apresentam variações da cor parda, roxa, azul escura e azul clara, que foram avaliadas mediante testes de variação dimensional, ensaios de compressão e fadiga. Sendo apresentada também a metalografia do fio utilizado na trançagem. As órteses de cor azul escura apresentaram melhor comportamento mecânico e com estas foram realizados ensaios de fadiga. A avaliação da órtese in vivo, foi feita na traquéia de gatos, utilizados na experimentação animal, pelo Hospital de Clínicas de Porto Alegre. Devido ao resultado positivo dessa avaliação, obteve-se autorização para novo estudo do Ministério da Saúde, pela sua Comissão Nacional de Ética em Pesquisa – CONEP, para o implante em vias aéreas humanas, em fase de implementação.
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Paine, Jeffrey S. "The performance of nitinol shape memory alloy actuators embedded in thermoplastic composite material systems." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/45109.
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Intelligent materials are a class of material systems usually consisting of a composite or hybrid material system with fibrous or distributed actuators, various sensors and a control system. One type of actuator being developed for intelligent material systems is made of nitinol or shape memory alloy wire. In order for nitinol and other actuators to be a reliable part of the system, the effect of composite manufacturing on the actuators’ performance and behavior must be determined. The results of a study investigating the effects of a "high temperature" thermoplastic composite processing cycle on the nitinol actuator’s performance is presented. A study of the interfacial strength between the actuators and APC-2 thermoplastic composite is also reported.
The nitinol actuators were exposed to high temperature (400°C) composite processing cycles. Critical parameters of the processing cycles were varied to determine their effect on the actuators’ performance. After the processing cycles, the nitinol actuators demonstrated useable recovery stresses (σru) of 173-265 MPa. The σru of a nitinol actuator in the virgin state, subjected to a thermoset processing cycle, and embedded in a specimen of APC-2 thermoplastic composite was also tested to develop a basis for comparison. The quality of the actuator-composite interface bond was tested by pull-out testing and fatigue loading to determine if the actuator is adequately bonded with the host composite. Pull-out forces of 30-50 N could fracture the actuator-composite interface, but 1000 activation cycles of the actuator produced no damage in the bond between actuator and host composite.Master of Science
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Andersen, Kayla B. Andersen. "A Nitinol Actuated Worm-Inspired Robot Capable of Forward Motion, Turning, and Climbing Obstacles." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1497021593146329.
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Khalil, Heidi F. "Changes in the mechanical behavior of Nitinol following variations of heat treatment duration and temperature." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31852.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Gall, Kenneth; Committee Member: McDowell, David; Committee Member: Thadhani, Naresh. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Fong, Jeffrey Chun Kit. "Wireless MEMS drug delivery device enabled by a micromachined Nitinol actuator as a pumping mechanism." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51782.
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Traditional drug delivery methods utilize systemic administration where the medication is circulated through the entire body. These methods require a high dosage at the point of entry in order to reach the therapeutic level at the targeted location and can result in serious side effects. Implantable drug delivery devices can be used to increase efficacy by targeting specific regions in the body and by safely using higher drug concentrations. Microfabrication allows for the creation of these minimally invasive devices to treat conditions not previously possible due to the limited amount of space surrounding the target area. Devices with passive releasing mechanisms have been commercialized but ones with active mechanisms are still in the works.
In this thesis, a shape memory alloy (SMA) actuator is micromachined into a rectangular, planar coil to perform cantilever-like actuation. The SMA-coil actuator forms a passive resonant circuit that functions as a wireless heat source activated using external radio-frequency (RF) electromagnetic fields. SiO₂ stress layers are selectively patterned on the Nitinol SMA structure to manipulate the cantilever profile at the nominal cold state. RF radiation with varying field frequencies showed strong frequency dependence of wireless heating, actuation displacement, and force generation by several actuators with resonant frequencies of 170-245 MHz. When excited at resonance, these actuators exhibited maximum out-of-plane displacement and force of 215 µm and 71 mN, respectively. The actuator was integrated into a 10.0×10.5×2.1 mm³ polyimide-packaged chip containing a micromachined Parylene-C pump chamber to force the release of the drug from the reservoir by wirelessly activating the actuator. Experimental operation of the prototypes showed successful release of the test agents from devices placed in liquid and excited by radiating tuned RF fields with an output power of 1.1 W. These tests revealed a single release volume of 219 nL, suggesting that the device’s capacity of 76 µL is equivalent to ~350 individual ejections. Thermal behavior of the activated device is also reported in detail. This proof-of-concept prototype validates the effectiveness of wireless RF pumping for fully controlled, long-lasting drug delivery, a key step towards enabling patient-tailored, targeted local drug delivery through highly miniaturized implants.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Sakaguchi, Yasuto. "Development of a novel tissue-engineered nitinol-frame artificial trachea with native-like physical characteristics." Kyoto University, 2018. http://hdl.handle.net/2433/235063.
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Ademosu, Omowunmi. "Corrosion and biocompatibility behaviour of surface modified nitinol wire exposed to physiological and biological solutions." Thesis, University of the West of Scotland, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.738479.
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Honarvar, Mohammad. "THERMOMECHANICAL CHARACTERIZATION OF ONE-WAY SHAPE MEMORY NITINOL AS AN ACTUATOR FOR ACTIVE SURGICAL NEEDLE." Diss., Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/301891.
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Mechanical EngineeringPh.D.
Needle-based intervention insertion is one of the common surgical techniques used in many diagnostic and therapeutic percutaneous procedures. The success of such procedures highly depends on the accuracy of needle placement at target locations. An active needle has the potential to enhance the accuracy of needle placement as well as to improve clinical outcome. Bending forces provided by the attached actuators can assist the maneuverability in order to reach the targets following a desired trajectory. There are three major research parts in the development of active needle project in the Composites Laboratory of Temple University. They are thermomechanical characterization of shape memory alloy (SMA) or Nitinol as an actuator for smart needle, mechanical modeling and design of smart needles, and study of tissue needle interaction. The characterization of SMA is the focus of this dissertation. Unique thermomechanical properties of Nitinol known as shape memory effect and superelasticity make it applicable for different fields such as biomedical, structural and aerospace engineering. These unique behaviors are due to the comparatively large amount of recoverable strain which is being produced in a martensitic phase transformation. However, under certain ranges of stresses and temperatures, Nitinol wires exhibit unrecovered strain (also known as residual strain); which limits their applicability. Therefore, for applications that rely on the strain response in repetitive loading and unloading cycles, it is important to understand the generation of the unrecovered strain in the Nitinol wires. In this study, the unrecovered strain of Nitinol wires with various diameters was investigated, using two experimental approaches: constant stress and uniaxial tensile tests. Moreover, a critical range of stress was found beyond which the unrecovered strain was negligible at temperatures of 70 to 80C depending on the wire diameter. Wire diameters varied from 0.10 to 0.29 mm were tested and different ranges of critical stress were found for different wire diameters. The transformation temperatures of different wire diameters at zero stress have been achieved by performing the Differential Scanning Calorimetry (DSC) test. The actuation force created by Nitinol wire is measured through constant strain experiment. X-Ray Diffraction (XRD) study was also performed to investigate the phase of Nitinol wires under various thermomechanical loading conditions. In summary, the effect of wire diameter on the required critical stresses to avoid the unrecovered strain between first and second cycle of heating and cooling are presented and the results of both mechanical tests are justified by the results obtained from the XRD study.
Temple University--Theses
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Fretwell, Grant Michael. "On the biocompatibility of nickel titanium alloys." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366485.
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Schiller, Ean H. "Heat Engine Driven by Shape Memory Alloys: Prototyping and Design." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35185.
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This work presents a novel approach to arranging shape memory alloy (SMA) wires into a functional heat engine. Significant contributions include the design itself, a preliminary analytical model and the realization of a research prototype; thereby, laying a foundation from which to base refinements and seek practical applications.
Shape memory alloys are metallic materials that, if deformed when cold, can forcefully recover their original, "memorized" shapes, when heated. The proposed engine consists of a set of SMA wires stretched between two crankshafts, synchronized to rotate in the same direction. Cranks on the first crankshaft are slightly longer than cranks on the second. During operation, the engine is positioned between two distinct thermal reservoirs such that half of its wires are heated while the other half are cooled. Wires on the hot side attempt to contract, driving the engine in the direction that relieves the heat-induced stress. Wires on the cold side soften and stretch as the engine rotates. Because the force generated during heated recovery exceeds that required for cooled deformation, the engine is capable of generating shaft power.
Limited experimental measurements of shaft speed were performed. An analytical model of the engine predicts that the maximum output power for the prototype, under test conditions, should be 0.75 W. Thermal efficiency, though not measured or calculated in this work, is expected to be low. Potential applications may include the conversion of waste heat into shaft power.
Master of Science
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Ingendaay, Christina. "Intramedulläre Frakturversorgung bei der Katze - Verriegelungsnagel und Form-Gedächtnis-Implantat im biomechanischen Vergleich." Berlin mbv, 2009. http://d-nb.info/998057568/04.
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Contreras, Mario Melendrez. "Design, analysis, and control of a nitinol shape memory alloy rotary actuator for spacecraft deployable structures." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123260.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 34-35).
Small satellites known as CubeSats are becoming more and more popular in the aerospace industry and in academia. The new availability of rockets such as SpaceX's Falcon 9 or even dedicated CubeSat rockets such as Rocket Lab's Electron rocket have provided a new opportunity for many organizations to launch satellites. Depending on the goals of each satellite, they can be configured with many different payloads and mechanisms. Solar panels are one of the most common payloads on CubeSats but are mostly spring-actuated, meaning they cannot be deployed to precise angles. Shape memory alloys have been used to create rotary mechanisms in the past but closed loop control of shape memory alloys in a bending architecture is relatively novel. A rotary shape memory alloy actuator was designed with the use case of precisely pointing solar panels to maximize energy collection. Here we show identification of a system transfer function through multiple step responses and the use of a closed-loop PID control to achieve rise times of about 15 seconds with overshoot errors of 2 to 8 degrees. The experiments also showed the possibility of achieving rapid rise times of less than 2 seconds and accuracy within 2 degrees with some slight changes to the control system. This actuator prototype further develops the possibilities of precision angular actuation in a lightweight, robust, low volume, low power, and simple mechanical system.
by Mario Melendrez Contreras.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering