Relevant bibliographies by topics / Superelastic NiTi

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Academic literature on the topic 'Superelastic NiTi'

Author: Grafiati
Published: 4 June 2021
Last updated: 12 February 2022

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Journal articles on the topic "Superelastic NiTi"

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Cameron, Nicole, and Zoheir Farhat. "Single Particle Erosion Behavior of NiTi-Based Nanolaminates and Superelastic NiTi Monolayer Coatings." Coatings 9, no. 10 (September 27, 2019): 617. http://dx.doi.org/10.3390/coatings9100617.

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Bulk NiTi is used to make parts, such as couplings and bearings, that can be found in many industries such as the automotive, aerospace and medical sectors. Forming and machining bulk superelastic NiTi is a very difficult and costly process; however, applying NiTi as a surface coating will provide an alternate manufacturing method that will minimize machining processes. The objective of this study is to produce a superelastic NiTi-based surface coating that exhibits denting, impact and wear resistance. Superelastic NiTi has been successfully produced through vacuum deposition processes, despite this, there is a lack of a full and comprehensive study on the formation of the NiTi phase during coating development. In this study, the NiTi phase is fabricated through the annealing of sputtered deposited Ti and Ni layers in a coating. To confirm the presence of the intermetallic phases, X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) analysis were performed. The erosion behavior of the coating is evaluated through single particle erosion testing, which resulted in the coatings that contained the NiTi precipitates to exhibit the best damage resistance compared to the other nanolaminates. This indicates that the superelastic NiTi phase increases the resistance to impacting particles. Microstructural evolution and NiTi formation during annealing is discussed and related to the observed damage resistance of the coatings.
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Kumaran, Deepa, Shantha Sundari, and Shyamala Chandrasekhar. "A Systematic review on aligning efficiency of superelastic NITI: in comparison with conventional NITI and multistranded stainless steel archwires." International Journal of Dental Research 5, no. 1 (April 5, 2017): 39. http://dx.doi.org/10.14419/ijdr.v5i1.7355.

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Background: The initial leveling and aligning phase of orthodontic treatment involve the use of nickel titanium wires. The nickel titanium wires exhibit unique properties like shape memory and superelasticity. In the beginning, conventional nitinol wires were used, which lacked the superelastic property. Nowadays, superelastic nickel titanium wires are being used commonly. This systematic review aims to evaluate the efficiency of Superelastic NITi in the initial alignment of orthodontic treatment in comparison with conventional NiTi and multistranded stainless steel archwires by measuring the amount of decrowding and the time taken for decrowding.Method: A systematic literature search was performed on Pubmed, Cochrane, Google scholar & Lilacs.Result: Thirty four studies were identified by the search and ten studies satisfied the inclusion criteria and one study was excluded after abstract reading. Finally nine articles were included for quality assessment.Conclusion: This systematic review concluded that there was no significant differences in the aligning efficiency of superelastic NiTi in comparison with conventional NiTi and multistranded stainless steel wires.
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Nucera, Riccardo, Elda Gatto, Chiara Borsellino, Pasquale Aceto, Francesca Fabiano, Giovanni Matarese, Letizia Perillo, and Giancarlo Cordasco. "Influence of bracket-slot design on the forces released by superelastic nickel-titanium alignment wires in different deflection configurations." Angle Orthodontist 84, no. 3 (September 25, 2013): 541–47. http://dx.doi.org/10.2319/060213-416.1.

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ABSTRACT Objective: To evaluate how different bracket-slot design characteristics affect the forces released by superelastic nickel-titanium (NiTi) alignment wires at different amounts of wire deflection. Materials and Methods: A three-bracket bending and a classic-three point bending testing apparatus were used to investigate the load-deflection properties of one superelastic 0.014-inch NiTi alignment wire in different experimental conditions. The selected NiTi archwire was tested in association with three bracket systems: (1) conventional twin brackets with a 0.018-inch slot, (2) a self-ligating bracket with a 0.018-inch slot, and (3) a self-ligating bracket with a 0.022-inch slot. Wire specimens were deflected at 2 mm and 4 mm. Results: Use of a 0.018-inch slot bracket system, in comparison with use of a 0.022-inch system, increases the force exerted by the superelastic NiTi wires at a 2-mm deflection. Use of a self-ligating bracket system increases the force released by NiTi wires in comparison with the conventional ligated bracket system. NiTi wires deflected to a different maximum deflection (2 mm and 4 mm) release different forces at the same unloading data point (1.5 mm). Conclusion: Bracket design, type of experimental test, and amount of wire deflection significantly affected the amount of forces released by superelastic NiTi wires (P < .05). This phenomenon offers clinicians the possibility to manipulate the wire's load during alignment.
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Janouchova, Katerina, Ludek Heller, and Monika Vysanska. "Functional warp-knitted fabrics with integrated superelastic niti filaments." Autex Research Journal 12, no. 2 (October 1, 2012): 34–39. http://dx.doi.org/10.2478/v10304-012-0007-7.

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Abstract We report on a particular direction of currently conducted extended research on novel textiles with integrated thin metallic filaments made of an intermetallic shape memory NiTi alloy exhibiting functional behaviour such as superelastic deformation up to 10% and a thermally induced shape memory effect. Within this research direction we focus on development of single and multi-layered warp-knitted fabrics that are directionally reinforced with superelastic NiTi filaments. First, we describe the expected properties of such novel structures and their potential applications. Second, we present the functional thermomechanical behaviour of applied superelastic NiTi filaments. Third, we address questions related to the design and fabrication of warp-knitted fabrics with integrated NiTi filaments. Then, we describe experimental methods applied on novel functional textiles in order to evaluate their functional properties. Finally, we present and discuss results of experiments carried out on these novel functional textiles.
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Della Corte, Christopher. "Novel Super-Elastic Materials for Advanced Bearing Applications." Advances in Science and Technology 89 (October 2014): 1–9. http://dx.doi.org/10.4028/www.scientific.net/ast.89.1.

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Tribological surfaces of mechanical components encounter harsh conditions in terrestrial, marine and aerospace environments. Brinell denting, abrasive wear and fatigue often lead to life-limiting bearing and gear failures. Novel superelastic materials based upon Nickel-Titanium (NiTi) alloys are an emerging solution. NiTi alloys are intermetallic materials that possess characteristics of both metals and ceramics. NiTi alloys have intrinsically good aqueous corrosion resistance (they cannot rust), high hardness, relatively low elastic modulus, are chemically inert and readily lubricated. NiTi alloys also belong to the family of superelastics and, despite high hardness, are able to withstand large strains without suffering permanent plastic deformation. In this paper, the use of a hard, resilient NiTi alloy for corrosion-proof, shockproof bearing and gear applications is presented. Through a series of bearing and gear development projects, it is demonstrated that NiTi’s unique blend of material properties lead to significantly improved load capacity, reduced weight and intrinsic corrosion resistance not found in any other bearing materials. NiTi thus represents a new materials solution to demanding tribological applications.
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Liu, Shifeng, Song Han, Liqiang Wang, Jingbo Liu, and Huiping Tang. "Effects of Nb on the Microstructure and Compressive Properties of an As-Cast Ni44Ti44Nb12 Eutectic Alloy." Materials 12, no. 24 (December 9, 2019): 4118. http://dx.doi.org/10.3390/ma12244118.

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The addition of Nb can form a eutectic phase with a NiTi matrix in a NiTi-based shape memory alloy, improving the transition hysteresis of the NiTi alloy. A Ni44Ti44Nb12 ingot was prepared using the vacuum induction melting technique. Under compression deformation, the yield strength of the NiTi–Nb alloy is about 1000 MPa, the maximum compressive strength and strain can reach 3155 MPa and 43%, respectively. Ni44Ti44Nb12 exhibited a superelastic recovery similar to that of the as-cast NiTi50. Meanwhile, the loading–unloading cycle compression shows that the superelastic recovery strain reached a maximum value (2.32%) when the total strain was about 15%, and the superelasticity tends to rise first and then decrease as the strain increases.
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Qian, Hui, Hongnan Li, Gangbing Song, and Wei Guo. "A Constitutive Model for Superelastic Shape Memory Alloys Considering the Influence of Strain Rate." Mathematical Problems in Engineering 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/248671.

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Shape memory alloys (SMAs) are a relatively new class of functional materials, exhibiting special thermomechanical behaviors, such as shape memory effect and superelasticity, which enable their applications in seismic engineering as energy dissipation devices. This paper investigates the properties of superelastic NiTi shape memory alloys, emphasizing the influence of strain rate on superelastic behavior under various strain amplitudes by cyclic tensile tests. A novel constitutive equation based on Graesser and Cozzarelli’s model is proposed to describe the strain-rate-dependent hysteretic behavior of superelastic SMAs at different strain levels. A stress variable including the influence of strain rate is introduced into Graesser and Cozzarelli’s model. To verify the effectiveness of the proposed constitutive equation, experiments on superelastic NiTi wires with different strain rates and strain levels are conducted. Numerical simulation results based on the proposed constitutive equation and experimental results are in good agreement. The findings in this paper will assist the future design of superelastic SMA-based energy dissipation devices for seismic protection of structures.
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Quandt, Eckhard, and C. Zamponi. "Superelastic NiTi Thin Films for Medical Applications." Advances in Science and Technology 59 (September 2008): 190–97. http://dx.doi.org/10.4028/www.scientific.net/ast.59.190.

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Shape memory alloys are able to provide high work output when due to the martensitic transformation. Therefore, they are a promising candidate for actuation mechanisms in microsystems, e.g. in microvalves. Sputter deposited SMA thin films are already in use as free-standing films or as composites. Since it is also possible to deposit and structure the SMA composites on Si substrates by photolithographic techniques, the fabrication process is compatible to MEMS and therefore most favorable for an number of applications. Superelastic shape memory materials are of special interest in medical applications due to the large strains at constant stress and their biocompatibility. Superelastic NiTi thin films have been fabricated by magnetron sputtering using cast melted targets. Special heat treatment was performed to adjust superelastic properties and transformation temperatures. A superelastic strain of up to 6.5% at 37°C was obtained. Although NiTi shows an excellent biocompatibility enhanced antibacterial properties would significantly broaden its application range. Coatings containing Ag have already been used for this application. In order to apply this approach to TiNi-based alloys thin films of different TiNiAg compositions have been prepared by sputtering.
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Gravina, Marco Abdo, Ione Helena Vieira Portella Brunharo, Cristiane Canavarro, Carlos Nelson Elias, and Cátia Cardoso Abdo Quintão. "Mechanical properties of NiTi and CuNiTi shape-memory wires used in orthodontic treatment. Part 1: stress-strain tests." Dental Press Journal of Orthodontics 18, no. 4 (August 2013): 35–42. http://dx.doi.org/10.1590/s2176-94512013000400007.

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OBJECTIVE: This research aimed to compare, through traction tests, eight types of superelastic and heat-activated NiTi archwires, by six trade companies (GAC, TP, Ormco, Masel, Morelli and Unitek) to those with addition of copper (CuNiTi 27ºC and 35ºC, Ormco). METHODS: The tests were performed in an EMIC mechanical testing machine, model DL10000, capacity of 10 tons, at the Military Institute of Engineering (IME). RESULTS: The results showed that, generally, heat-activated NiTi archwires presented slighter deactivation loadings in relation to superelastic. Among the archwires that presented deactivation loadings biologically more adequate are the heat-activated by GAC and by Unitek. Among the superelastic NiTi, the CuNiTi 27ºC by Ormco were the ones that presented slighter deactivation loadings, being statistically (ANOVA) similar, to the ones presented by the heat-activated NiTi archwires by Unitek. When compared the CuNiTi 27ºC and 35ºC archwires, it was observed that the 27ºC presented deactivation forces of, nearly, ⅓ of the presented by the 35ºC. CONCLUSION: It was concluded that the CuNiTi 35ºC archwires presented deactivation loadings biologically less favorable in relation to the other heat-activated NiTi archwires, associated to lower percentage of deformation, on the constant baselines of deactivation, showing less adequate mechanical behavior, under traction, in relation to the other archwires.
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Sprincenatu, Roxana, Madalin Condel, Sergiu Barbos, Andrei Novac, Ion Mitelea, and Corneliu Craciunescu. "Superelastic Behavior in NiTi Shape Memory Alloy Wires and Ribbons." Solid State Phenomena 254 (August 2016): 278–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.254.278.

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Shape memory alloy ribbons in austenitic state were studied in a tensile testing machine in order to assess their superelastic behavior. They were compared with conventional materials and hair wire. The shape memoy alloy ribbon shows a particular behavior, with an ultimate tensile stress of about 1450 MPa reached at 9.5 % strain. The superelastic plateau was recorded around 590 MPa on loading and around 350 MPa on the unloading branch. Following multiple loading and unloading cycles, the superelastic behavior was not affected, nor was affected the ultimate tensile strength, that remained in the same range as for the one tested before cycling. The advantages of the superelastic ribbon compared to the ones of conventional materials are discussed. The superelastic properties of the ribbon are in the range of single crystals on what concerns the recoverable strains. This is attributed to the particular fine microstructure of the NiTi ribbon.
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Dissertations / Theses on the topic "Superelastic NiTi"

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Alarcon, Tarquino Eduardo Augusto. "Structural fatigue of superelastic NiTi wires." Thesis, Brest, 2018. http://www.theses.fr/2018BRES0019/document.

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Ce travail de thèse aborde les conditions et les mécanismes qui conduisent des fils superélastiques de NiTi à la rupture sous chargement mécanique cyclique. Les alliages à mémoire de forme du type NiTi présentent des propriétés thermomécaniques fonctionnelles comme la superélasticité et l’effet de mémoire de forme simple et double, lesquels sont générées grâce aux transformations de phase martensitiques provoquées soit par un changement de la contrainte ou de la température. Ces transformations de phase sont en principe des processus totalement réversibles et sans endommagement. Cependant, lorsque le NiTi est soumis à des transformations de phase induites par des contraintes cycliques, la performance en fatigue de l’alliage chute considérablement par rapport au NiTi non-transformant. La plupart des courbes S-N de fatigue rapportant cette chute ont été mesurées sur des fils NiTi a section constante dans lesquels les transformations martensitiques se développent de façon hétérogene par nucléation et propagation de bandes de cisaillement. De plus, d'après notre expérience, des essais de fatigue sur des échantillons de fils à section constante entrainent la rupture à l'intérieur des mors de la machine d'essai. Par conséquent, les valeurs de contrainte-déformation rapportées dans les courbes S-N ne sont pas nécessairement représentatives des conditions mécaniques critiques qui conduisent le matériau à la rupture. Dans le but de mieux caractériser les performances en fatigue des fils NiTi, nous avons effectué une série de tests de fatigue en traction-traction, tout en utilisant des échantillons sous forme ≪ diabolo ≫. La géométrie de ces échantillons nous a permis de confiner tous les processus de transformation martensitique et de fatigue dans un volume utile bien défini. La caractérisation du comportement thermomécanique de ces échantillons a été réalisée en combinant plusieurs techniques expérimentales et d'analyse telles que la corrélation d'image numérique(DIC), la thermographie infrarouge, la diffraction des rayons X à source synchrotron, la microscopie optique, la microscopie électronique à balayage et l'analyse par éléments finis. Une attention particulière à été portée à la performance de NiTi dans le régime à grand nombre de cycles (HCF) dans laquelle le matériau présente un comportement élastique ou une transformation de phase intermédiaire (appelée R-phase). Les résultats des tests de fatigue nous ont permis de distinguer les étapes de nucléation et de propagation des fissures pendant la durée de vie totale de nos échantillons. Afin de mieux comprendre les mécanismes qui conduisent à la nucléation des fissures, nous avons appliqué la méthode de l’auto-échauffement, qui a démontré son efficacité dans la prédiction de fatigue dans les cas des alliages d'aluminium et des alliages d'acier. Cette méthode corrèle l'élévation de température d'un échantillon soumis à différentes amplitudes de charge cyclique avec des mécanismes de dissipation d'énergie. Ces mécanismes dissipatifs sont après associés à l’accumulation d’endommagement locale dans le matériau. La méthode d'autoéchauffement a été réalisée en utilisant des mesures de champs thermiques des d'échantillons de NiTi sous forme diabolo pendant de chargement cyclique
This Ph.D. dissertation thesis addresses the conditions and mechanisms that lead superelastic NiTi wires to fail under cyclic mechanical loads. NiTi shape memory alloys exhibit functional thermomechanical properties (superelasticity, shape memory effect, thermal actuation) due to martensitic phase transformations caused by a change of the applied stress and temperature. These phase transformations are though as fully reversible damage-free processes, however, when NiTi is subjected to repetitive stress-induced phase transformations its fatigue performance drops drastically in comparison to non-transforming NiTi. Most of fatigue S-N curves reporting this drop were measured on straight NiTi wires in which martensitic transformations proceed heterogeneously through nucleation and propagation of shear bands. Moreover, from our experience fatigue testing straight wire samples results in undesired failure inside the testing machine clamps. Hence, the reported stress-strain values in S-N curves are not necessarily representative of the critical mechanical conditions that lead the material to failure. With the aim of better characterize the fatigue performance of NiTi wires, we started by carrying out a series of pull-pull fatigue tests using hourglass-shaped samples. This sample geometry allowed us to confine all martensitic transformation and related material fatigue processes into a well-defined gauge volume. The samples’ characterization was performed by combining several experimental and analysis techniques such as Digital Image Correlation, Infrared Thermography, Synchrotron-source X-ray diffraction, Optical Microscopy, Scanning Electron Microscopy and Finite Element Analysis. A special attention was paid to the High Cycle Fatigue (HCF) performance of NiTi in which the material shows elastic behavior and/or an intermediate phase transformation (so-called R-phase). The results from HCF tests allowed us to distinguish crack nucleation and crack propagation stages during the total life of our NiTi samples. In order to get a better understanding of the mechanisms that lead to crack nucleation, we applied the nonconventional Self-Heating fatigue assessment method, which has shown efficiency in the case of aluminum and steel alloys. This method correlates the temperature elevation of a sample subjected to different cyclic load amplitudes with energy dissipating mechanisms that contribute to accumulating local damage in the material. The Self-Heating method was performed using full-field thermal measurements of cyclically loaded NiTi hourglass-shaped samples
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Li, Zhiqi. "Experimental investigation on phase transformation of superelastic NiTi microtubes /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?MECH%202002%20LI.

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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.
Includes bibliographical references (leaves 155-160). Also available in electronic version. Access restricted to campus users.
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Aun, Diego Pinheiro. "Flexible TiO₂ coating on superelastic NiTi alloys for bioapplications." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI098.

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Dans cette étude, nous avons élaboréun revêtementde TiO₂ par sol-gel sur des alliages super-élastiques de NiTi. L’idée générale était de développer couche mince de TiO₂ protectrice et flexible. Le film mince est formé en immergeant les échantillons de NiTi, préalablement chimiquement gravés, dans une solution réactive à 7,5 mm/s, puis en effectuant plusieurs traitements thermiques :un premier traitement thermique à 100 °C pendant 45 minutes dans une atmosphère humide, un deuxième traitement à 110 °C pendant 2 heures dans une atmosphère sèche et enfin un dernier traitement à 500 °C pendant 10 minutes. Les couches minces de TiO₂ ont été caractérisé par de la flexion trois points, par MEB, par MET, par AFM, par GIXRD, par XPS et par de la cartographie Raman. Les résultats de l’étude ont montré un film nanocomposite, avec ~100nmde TiO2 amorphe formé à l’interface externe de la couche et d'un mélange de grains cristallisés de ~10 nm, d'anatase et de rutile à l'interface interne métal/oxyde.Cette hétéro-structure est capable de soutenir 6,4% de déformation sans l’apparition de défauts plastiques majeurs (cloques, fissures...). Une faible concentration de Ni a été observé au niveau de la surface externe des couches minces de TiO₂, ce qui se traduit par une augmentation de la biocompatibilité du matériau. La technique sol-gel a été utilisée pour revêtir des instruments endodontiques de RaCe. Ce deuxième système a été testé à la fois en fatigue pour estimer sa durée de vie, et à la résistance à la corrosion en NaClO, et à des températures correspondant aux transformations de phase. Les résultats ont montré une augmentation statistiquement significative de la durabilité en fatigue, en particulier après les essais de corrosion. L'efficacité de la « coupe », mesurée par une procédure originale, a été similaire aux instruments revêtus et non revêtus. Le traitement thermique n'a pas été suffisant efficient pour modifier de façon significative les températures de transformation de phase : le comportement mécanique d'origine de l'instrument a été maintenu
In this work, a dip-coating sol-gel deposition route was developed to coat superelastic NiTi alloy with a flexible TiO₂ protective layer. The film was formed by emerging the samples at 7.5 mm/s and thermally treating at 100ºC in a humid atmosphere for 45 min, 110ºC in a dry atmosphere for 2 hours and at 500ºC for 10 minutes.The film was first deposited over chemically etched substrates and characterized by SEM, TEM, AFM, GIXRD, XPS, Raman cartographyand three-point bending tests. Results showed that a ~100 nm nanocomposite film constituted of amorphous TiO₂ on the upper half and a mixture of ~10 nm anatase and rutile grains on the oxide/metal interfacewas formed. This film was capable of sustaining up to 6.4% strain without cracking or peeling. A high decrease in the concentration of Ni at the surface was measured, indicating an that an increase in the biocompatibilityof the material was achieved. This route was used to coat RaCe endodontic instruments, which were tested regarding fatigue life, cutting efficiency and corrosion resistance in NaClO. Results showed a statistically significant improvement in fatigue life for the coated instruments, mainly after corrosion tests. Cutting efficiency measured by an original developed technique was similar for coated and uncoated samples
Neste trabalho foi desenvolvida uma rota de deposição sol-gel por imersão para revestirligas de NiTi superelásticas com uma camada protetora e flexível de TiO2. O filmeformado pela emersão de amostras a 7,5 mm/s seguida de tratamentos térmicos a 100ºCpor 45 minutos em atmosfera úmida, 110ºC por 2 horas em atmosfera seca e 500ºC por10 minutos. O filme foi depositado sobre substratos decapados quimicamente ecaracterizados por MEV, MET, AFM, GIXRD, XPS, cartografia Raman e dobramentode três pontos. Resultados mostraram que um filme nanocompósito com ~100 nmconstituído de TiO2 amorfo na metade superior e uma mistura de grãos de 10 a 50 nmde anatase e rutila na interface metal/óxido foi formado. Este filme é capaz de sustentar6,4% de deformação sem trincar ou descamar. Uma grande redução na concentração deNi na superfície foi detectada, indicando um aumento na biocompatibilidade domaterial. A rota foi usada para revestir instrumentos endodônticos de NiTi modeloRaCe 25/0.06 que foram testados em relação à vida em fadiga, eficiência de corte,resistência à corrosão em NaClO. Detectou-se um aumento estatisticamentesignificativo na vida em fadiga, especialmente após os ensaios de corrosão. A eficiênciade corte, medida por um procedimento original desenvolvido, foi similar parainstrumentos revestidos e não revestidos. O tratamento térmico não foi suficiente paraalterar significativamente as temperaturas de transformação de fases, mantendo ocomportamento mecânico original do instrumento
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Russo, Analisa. "Variation of electrical resistance in superelastic NiTi for sensor applications." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/57875.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 32).
Nickel-Titanium (NiTi) is a most commonly known as a heat-activated shape memory alloy. However, the material sometimes displays a constant-temperature property called "superelasticity." A superelastic material is one which can undergo very high reversible strains due to stress-induced change in crystal structure. In the case of Superelastic NiTi, Martensitic transformation occurs. The two crystal structures differ to the extent that the gradual phase transformation is coupled to a gradual change in resistivity. In fact, resistive sensing is a common characterization technique for shape memory alloys. The unique material properties of superelastic NiTi could also be the basis for creating a resistive sensor that is sensitive enough to measure small displacements, and robust enough to measures large displacements. This study focuses on NiTi which displays superelastic behavior above room temperature. To assess the material's potential as a strain sensing medium, the NiTi wire is shape-set into coil springs which amplify the sensor's net deformation. The relationship between strain and resistance is measured. The study shows that various aspects of the strain-resistance response, including non-linear hysteretic behavior and temperature dependence of electrical resistivity, pose challenges to sensor design. Though the accuracy of the spring sensors is still under development, several recommendations are made with regard to effective device design. In addition, the design of a one-axis strain rate sensor, which differentiates between only two modes of behavior, is explored.
by Analisa Russo.
S.B.
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Vaidyanathan, Rajan 1973. "Mechanical properties of superelastic and shape-memory NiTi and NiTi-TiC composites investigated by neutron diffraction." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84744.

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Roberto-Pereira, Francisco Fernando. "Extraction of superelastic parameter values from instrumented indentation data." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290218.

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Interest in superelastic (and shape memory) materials continues to rise, and there is a strong incentive to develop techniques for monitoring of their superelastic characteristics. This is conventionally done via uniaxial testing, but there are many advantages to having a capability for obtaining these characteristics (in the form of parameter values in a constitutive law) via indentation testing. Specimens can then be small, require minimal preparation and be obtainable from components in service. Interrogation of small volumes also allows mapping of properties over a surface. On the other hand, the tested volume must be large enough for its response to be representative of behaviour. Precisely the same arguments apply to more "mainstream" mechanical properties, such as yielding and work hardening characteristics. Indeed, there has been considerable progress in that area recently, using FEM simulation to predict indentation outcomes, evaluating the "goodness of fit" for particular sets of parameter values and converging on a best-fit combination. A similar approach can be used to obtain superelastic parameters, but little work has been done hitherto on sensitivities, uniqueness characteristics or optimal methodologies and the procedures are complicated by limitations to the constitutive laws in current use. The current work presents a comprehensive examination of the issues involved, using experimental (uniaxial and indentation) data for a NiTi Shape Memory Alloy. It was found that it is possible to obtain the superelastic parameter values using a single indenter shape (spherical). Information is also presented on sensitivities and the probable reliability of such parameters obtained in this way for an unknown material.
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Rutherford, Benjamin Andrew. "Beneficial Tensile Mean Strain Effects on the Fatigue Behavior of Superelastic NiTi." Thesis, Mississippi State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10266594.

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In this work, beneficial effects of tensile mean strain on fatigue behavior and microstructure of superelastic NiTi (i.e. Nitinol) are studied. Most applications, such as endovascular stents made with NiTi, are subjected to a combination of constant and cyclic loading; thus, understanding the fatigue behavior of NiTi undergoing mean strain loading is necessary. Cyclic strain-controlled fatigue tests are designed to investigate the effects of tensile mean strain on fatigue of superelastic NiTi. Experimental observations show that combinations of large tensile mean strains and small strain amplitudes improve the fatigue life of superelastic NiTi. This behavior arises from reversible, stress-induced phase transformations. The phase transformations cause “stress plateaus” or strain ranges with no change in stress value. Scanning electron microscopy (SEM) of the fracture surfaces of specimens revealed generally short crack growth. Electron backscatter diffraction (EBSD) found the amount of residual martensite to be about ~8%, regardless of loading conditions.

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Koludrovich, Michael. "Design, Analysis, and Experimental Evaluation of a Superelastic NiTi Minimally Invasive Thrombectomy Device." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399370551.

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Sargin, Irmak. "Effect Of Stress Assisted Aging On Superelastic Behavior Of A Hot-rolled Niti Shape Memory Alloy." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613184/index.pdf.

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Effect of stress-assisted aging on stress induced martensitic transformation in hot-rolled Ni-rich 50.7at. Ni%-Ti alloy has been investigated. Alloys are aged freely and under 20 MPa, 100 MPa, and 200 MPa stress at 400 o C for 90 minutes. Aging procedure affected both stress-induced and thermally induced transformation behavior. Superelasticity behavior is correlated with the multistep transformation in aged Ni-rich NiTi alloys and the aging stress level is found to be effective. Relative to the free aged alloy, the alloy aged under 20 MPa exhibited a slight and the alloy aged under 100 MPa exhibited a considerable reduction, whereas the alloy aged under 200 MPa exhibited an increase in the critical transformation stress. DSC studies have shown that the transformation is multistep for freely aged and aged under 20 MPa alloys, whereas it is single step and two-step for alloys aged under 100 MPa and 200 MPa, respectively, and this has been attributed to the effect of stress on nucleation and growth rates. As a result of the different response mechanisms to the applied stress upon loading during superelasticity testing, the recovered strain amounts varied considerably depending on the aging conditions and the test temperatures.
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Manjeri, Radhakrishnan. "Low Temperature and Reduced Length Scale Behavior of Shape Memory and Superelastic NiTi and NiTiFe Alloys." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6227.

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Shape memory and superelastic applications of NiTi based alloys have typically been limited to near room temperature or to bulk length scales. The objective of this work is two-fold: first, to investigate shape memory behavior at low temperatures in the context of the R-phase transformation in NiTiFe alloys by recourse to arc-melting, differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and mechanical testing at low temperatures; and second, to investigate superelasticity and two-way shape memory behavior at reduced length scales in the context of NiTi by recourse to micro-compression, micro-indentation and TEM studies. Selected compositions of ternary NiTiFe shape memory alloys were arc-melted and thermo-mechanically processed to investigate the influence of composition and processing parameters on the formation of the R-phase. The methodology used for the processing and characterization of the alloys was established and included microprobe analysis, DSC, TEM and mechanical testing. No phase transformation was observed in alloys with Fe content in excess of 4 at.%. The rmo-mechanical treatments facilitated the formation of the R-phase in Ni-rich alloys. The range of the transformation between the R-phase and austenite, and the hysteresis associated with it were influenced by the distribution and size of metastable Ni4Ti3 precipitates. The investigation of the microstructural, thermal and mechanical properties of the R-phase transformation in NiTiFe alloys revealed a complex dependence of these properties on processing parameters. The present work also highlighted the hitherto unexplored competition between the two inelastic deformation modes operating in the R-phase (detwinning and stress-induced transformation) and establishedthe preference of one mode over the other in stress-temperature space. The complete micromechanical response of superelastic NiTi was examined by performing careful micro-compression experiments on single crystal pillars of known orientations using a nanoindenter tip. Specifically, the orientation dependence of the elastic deformation of austenite, the onset of its transformation to martensite, the gradient and the hysteresis in the stress-strain response during transformation, the elastic modulus of the stress-induced martensite and the onset of plasticity of the stress-induced martensite were analyzed in separate experiments. A majority of the results were explained by recourse to a quantitative determination of strains associated with austenite grains transforming to martensite variants or twinning in martensite. Microstructural studies were also performed on a micro-indentation trained NiTi shape memory alloy specimen to understand the mechanisms governing the two-way shape memory effect. In situ TEM studies at temperature on specimens obtained at different depths below the indent showed the presence of retained martensite along with the R-phase. Previously, while such two-way shape memory behavior has typically been associated with large dislocation densities, this work provides evidence of the role of retained martensite and the R-phase in cases with reduced dislocation densities. Funding support for this work from NSF (CAREER DMR-0239512), NASA (NAG3-2751) and SRI is acknowledged.
Ph.D.
Doctorate
Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
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Book chapters on the topic "Superelastic NiTi"

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Quandt, Eckhard, and C. Zamponi. "Superelastic NiTi Thin Films for Medical Applications." In Advances in Science and Technology, 190–97. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908158-16-8.190.

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Zickel, Michael J., and Christopher S. Welch. "Thermoelastic Coating Characterization using a Superelastic NiTi Alloy." In Review of Progress in Quantitative Nondestructive Evaluation, 1821–28. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1987-4_233.

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Boccaccini, Aldo R., E. J. Minay, and D. Krause. "Bioglass® Coatings on Superelastic NiTi Wires by Electrophoretic Deposition (EPD)." In Electrophoretic Deposition: Fundamentals and Applications II, 219–24. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-998-9.219.

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Louche, H., D. Favier, L. Orgéas, V. Delobelle, and P. Schlosser. "Heat source estimations to study the localized behaviour of superelastic NiTi shape memory alloys." In Application of Imaging Techniques to Mechanics of Materials and Structures, Volume 4, 225–28. New York, NY: Springer New York, 2012. http://dx.doi.org/10.1007/978-1-4419-9796-8_27.

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Sun, Q. P., Z. Q. Li, and K. K. Tse. "On Superelastic Deformation of NiTi Shape Memory Alloy Micro-Tubes and Wires — Band Nucleation and Propagation." In IUTAM Symposium on Smart Structures and Structronic Systems, 113–20. Dordrecht: Springer Netherlands, 2001. http://dx.doi.org/10.1007/978-94-010-0724-5_15.

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Hsu, Jui-Ting, Li-Chun Wu, Yin-Yu Chang, Tzu-Ning Weng, Heng-Li Huang, and Chein-Hung Yu. "Frictional Forces of Conventional and Improved Superelastic NiTi-Alloy Orthodontic Archwires in Stainless Steel and Plastic Brackets." In IFMBE Proceedings, 312–15. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03891-4_83.

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"NiTi is also superelastic, in that it possesses incredible amounts of flexibility and kink resistance. It has a strain recovery of about 8%, which makes it more re-silient than stainless steel. Work on the corrosion resistance of NiTi in the case of biomedical implants [26] has shown it to be very resistant to corrosio n in the harshest environments due to the formation of a passive Ti0 layer on the surface." In Surface Contamination and Cleaning, 317–18. CRC Press, 2003. http://dx.doi.org/10.1201/9789047403289-45.

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Conference papers on the topic "Superelastic NiTi"

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Amerinatanzi, Amirhesam, Hashem Zamanian, Narges Shayesteh Moghaddam, Hamdy Ibrahim, Mohamed Samir Hefzy, and Mohammad Elahinia. "On the Advantages of Superelastic NiTi in Ankle Foot Orthoses." In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9267.

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Foot drop usually happens due to neurological and muscular diseases. It limits individuals’ abilities in ankle and toe represented in dorsiflexion during swing phase, and plantar flexion during heel strike. A non-surgical solution to such weakness is the use of ankle foot orthoses (AFOs) which can assist in such abnormal ambulation. The purpose of this work is to develop a new ankle foot orthosis that helps patients to have more normal ankle joint behavior. The proposed AFO device takes advantage of the superelastic behavior of Ni-rich NiTi alloys. In order to evaluate the performance of the Ni-rich NiTi hinged ankle foot orthoses, several motion analysis tests for a normal walking of a healthy subject were conducted. Also, a finite element model were developed to evaluate the performance of superelastic versus stainless steel springs. A Ni-rich NiTi wire was wrapped around a designed rod and the two heads were fixed to the rod (to get the shape of a spring). Then a heat treatment process was performed in a furnace to shape set the NiTi wires and to provide them with the needed superelastic behavior. The produced springs were connected to a designed hinged ankle foot orthoses. Motion analysis was performed on a healthy subject during normal walking in the case of using conventional stainless steel springs, and with using the produced NiTi springs. Joint kinematics and kinetics data of left lower limb (which was equipped with the AFO brace) were collected and calculated to compare normal walking patterns to the resultant walking patterns with the proposed ankle foot orthosis. The CAD file of the AFO, hinge structure and the springs were developed. Each component was meshed and the convergence study were conducted. A finite element model was developed after assembling and introducing all the interactions between parts in Abaqus. The boundary conditions were applied to the system in a way simulating normal walking conditions. Different material properties (stainless steel and superelastic NiTi) were assigned to the springs in the model to evaluate the performance of the system under the aforementioned loading scenario. The results of the motion analysis on a healthy subject during walking indicate that the use of the superelastic NiTi springs causes more normal walk compare to the use of the conventional stainless steel springs, especially during swing phase and heel strike. Moreover, the ankle has closer stiffness profile to the normal walking in the case of using NiTi springs. The results of the finite element analysis show that the super elastic behavior of NiTi results in more hinge rotation while the stress concentration developed on the springs is within the safe levels and cannot cause failure of the NiTi springs. Motion analysis and finite element models were conducted for the proposed hinged AFO and the results were compared with conventional AFO. By taking advantage of the super elastic characteristic of NiTi, more normal walking behavior was observed in the case of using the proposed AFO with Ni-rich NiTi springs.
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Khurana, Jivtesh B., Mary Frecker, and Eric M. Pauli. "Design and Optimization of Functionally Graded Superelastic NiTi Stents." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22706.

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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.
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Koon, Henry, Jack Laven, and Julianna Abel. "Manufacture of Ultra-Dense Knitted Superelastic Structures." In ASME 2018 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/smasis2018-8225.

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Knitted Textiles made from Nickel-Titanium (NiTi) shape memory alloy wires are a new structural element with enhanced properties for a variety of applications. Potential advantages of this structural form include enhanced bending flexibility, tailorable in-plane, and through-thickness mechanical performance, and energy absorption and damping. Inspection of the knit pattern reveals a repeating cell structure of interlocking loops. Because of this repeating structure, knits can be evaluated as cellular structures that leverage their loop-based architecture for mechanical robustness and flexibility. The flexibility and robustness of the structure can be further enhanced by manufacturing with superelastic NiTi. The stiffness of superelastic NiTi, however, makes traditional knit manufacturing techniques inadequate, so knit manufacturing in this research is aided by shape setting the superelastic wire to a predefined pattern mimicking the natural curve of a strand within a knit fabric. This predefined shape-set geometry determines the outcome of the knit’s mechanical performance and tunes the mechanical properties. In this research, the impact of the shape setting process on the material itself is explored through axial loading tests to quantify the effect that heat treatment has on a knit sample. A means of continuously shape setting and feeding the wire into traditional knitting machines is described. These processes lend themselves to mass production and build upon previous textile manufacturing technologies. This research also proposes an empirical exploration of superelastic NiTi knit mechanical performance and several new techniques for manufacturing such knits with adjustable knit parameters. Displacement-controlled axial loading tests in the vertical (wale) direction determined the recoverability of each knit sample in the research and were iteratively increased until failure resulted. Knit samples showed recoverable axial strains of 65–140%, which could be moderately altered based on knit pattern and loop parameters. Furthermore, this research demonstrates that improving the density of the knit increases the stiffness of the knit without any loss in recoverable strains. These results highlight the potential of this unique structural architecture that could be used to design fabrics with adjustable mechanical properties, expanding the design space for aerospace structures, medical devices, and consumer products.
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Chun, Youngjae, Daniel S. Levi, K. P. Mohanchandra, Fernando Vinuela, Fernando Vinuela, Jr., and Gregory P. Carman. "Superelastic NiTi thin film small vessel graft for vascular repair." In SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, edited by Mehdi Ahmadian and Mehrdad N. Ghasemi-Nejhad. SPIE, 2009. http://dx.doi.org/10.1117/12.815400.

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Tabesh, Majid, Mohammad Elahinia, and Mehdi Pourazady. "Modeling NiTi Superelastic-Shape Memory Antagonistic Beams: A Finite Element Analysis." In ASME 2009 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2009. http://dx.doi.org/10.1115/smasis2009-1365.

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Shape memory alloys (SMA) have received widespread attention from researchers in various fields of engineering sciences due to their exceptional properties of shape memory and superelasticity. NiTi equiatomic alloys among other SMA, show acceptable biocompatibility to be implemented in biomedical applications. Applications of NiTi in biomedical areas specifically orthopedics, demonstrate its unique performance which is not achievable with conventional materials. Pedicle screws, which are used as an anchoring point for implanting spinal instrumentations in spinal fracture and deformity treatments, entail a major drawback; i.e. loosening and back-out. The strength of screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. A “Smart” pedicle screw design was developed to address this issue which uses NiTi superelastic-shape memory coils wrapped around it. The smart assembly consists of external superelastic tubing which is responsible for expanding the designed protrusions when they reach body temperature; also an internal shape memory wire inserted into the tubing is sought to retract the assembly when locally heated to above body temperature. The whole assembly was modeled as a beam structure in COMSOL Multiphysics Finite Element software. The behavior of shape memory alloy was defined in the software via its Partial Differential Equation (PDE) module. The SMA model has is a Tanaka-based model and is capable of capturing shape memory effect, superelasticity and hysteresis behavior, and partial transformation in both positive and negative directions. This 1D model was further modified to be included in a 3D framework such that it makes it possible for simulation of a beam under bending. The functionality of the smart screw design can be studied via this FEM model as a future work and the outcomes of the simulation can be compared with experimental tests on the prepared sample of the screw comprising NiTi tubing and wires.
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Birnbaum, Andrew J., and Y. Lawrence Yao. "The effects of laser forming on superelastic NiTi shape memory alloys." In ICALEO® 2006: 25th International Congress on Laser Materials Processing and Laser Microfabrication. Laser Institute of America, 2006. http://dx.doi.org/10.2351/1.5060940.

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Bogdan, Lucian, Cristian Nes, Agelica Enkelhardt, Nicolae Faur, and Jenel Marian Patrascu. "Bending-rotation tests of Niti superelastic wires used in medical applications." In 2013 E-Health and Bioengineering Conference (EHB). IEEE, 2013. http://dx.doi.org/10.1109/ehb.2013.6707340.

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Jovanova, Jovana, Mary Frecker, Reginald F. Hamilton, and Todd A. Palmer. "Target Shape Optimization of Functionally Graded Shape Memory Alloy Compliant Mechanism." In ASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/smasis2016-9070.

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Nickel Titanium (NiTi) shape memory alloys (SMAs) exhibit shape memory and/or superelastic properties, enabling them to demonstrate multifunctionality by engineering microstructural and compositional gradients at selected locations. This paper focuses on the design optimization of NiTi compliant mechanisms resulting in single-piece structures with functionally graded properties, based on user-defined target shape matching approach. The compositionally graded zones within the structures will exhibit an on demand superelastic effect (SE) response, exploiting the tailored mechanical behavior of the structure. The functional grading has been approximated by allowing the geometry and the superelastic properties of each zone to vary. The superelastic phenomenon has been taken into consideration using a standard nonlinear SMA material model, focusing only on 2 regions of interest: the linear region of higher Young’s modulus of elasticity and the superelastic region with significantly lower Young’s modulus of elasticity. Due to an outside load, the graded zones reach the critical stress at different stages based on their composition, position and geometry, allowing the structure morphing. This concept has been used to optimize the structures’ geometry and mechanical properties to match a user-defined target shape structure. A multi-objective evolutionary algorithm (NSGA II - Non-dominated Sorting Genetic Algorithm) for constrained optimization of the structure’s mechanical properties and geometry has been developed and implemented.
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Jovanova, Jovana, Angela Nastevska, and Mary Frecker. "Target Shape Optimization of 3D Compliant Mechanism With Superelastic Joints and Shape Memory Actuation." In ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/smasis2019-5639.

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Abstract The shape memory effect and the superelasticity of nickel titanium (NiTi) alloys are beneficial for design of compliant mechanisms. The superelastic behavior of NiTi can be tailored for optimal flexure design in the compliant mechanism, allowing large deformation and shape change. The shape memory effect can also be utilized to actuate the compliant mechanism flexures enabling programing of the material to take on variety of shapes at different temperatures over time. The compliant mechanism analyzed in this work is inspired from 3D multi leg spider-like locomotion, enabling movement in all directions by triggering different target shapes in time. The control of the material spatial distribution facilitated by additive manufacturing will enable tailored superelastic and shape memory behavior in the flexures of the multifunctional 3D compliant mechanism. Design optimization and analyses as well as overall shape change are explored in this work. Superelastic joints are introduced as flexures to enable segment flexibility. The temperature change is used for actuation taking in consideration different initial strain conditions.
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Karbaschi, Zohreh, and Mohammad Elahinia. "Modeling the Torsional Behavior of Superelastic Wires." In ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2011. http://dx.doi.org/10.1115/smasis2011-5174.

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Torsional behavior of shape memory alloys can be employed in different biomedical applications. The goal of this paper is to investigate the behavior of these alloys under torsional loading conditions. To this end a torsional model is developed in MATLAB, in which a uniaxial model is extended to predict the torque-angle behavior of superelastic wires/rods. Tensile and torsional testing are performed on NiTi wires to determine martial properties and to verify this model. The material properties are determined based on ASTM standards. The effect of different parameters such as lengths and radii on the torque-angle behavior are investigated with the model. Moreover, the effect of temperature on the torsional behavior of SMA wires are presented.
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