DOCSLIB.ORG

Evolution of Nickel–Titanium Alloys in Endodontics 1Hani F Ounsi, 2Wadih Nassif, 3Simone Grandini, 4Ziad Salameh, 5Prasanna Neelakantan, 6Sukumaran Anil

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Evolution of Nickel–Titanium Alloys in Endodontics 1Hani F Ounsi, 2Wadih Nassif, 3Simone Grandini, 4Ziad Salameh, 5Prasanna Neelakantan, 6Sukumaran Anil Hani F Ounsi et al 10.5005/jp-journals-10024-2181 REVIEW ARTICLE Evolution of Nickel–titanium Alloys in Endodontics 1Hani F Ounsi, 2Wadih Nassif, 3Simone Grandini, 4Ziad Salameh, 5Prasanna Neelakantan, 6Sukumaran Anil ABSTRACT and alloys, they have an obligation to deal more intimately with engineering consideration to not only take advantage of their To improve clinical use of nickel–titanium (NiTi) endodontic possibilities but also acknowledge their limitations. rotary instruments by better understanding the alloys that compose them. A large number of engine-driven NiTi shaping Keywords: Cyclic fatigue, Endodontics, Martensitic alloys, instruments already exists on the market and newer generations M-wire, Nickel–titanium, Surface treatment, Torsional stress. are being introduced regularly. While emphasis is being put on How to cite this article: Ounsi HF, Nassif W, Grandini S, Salameh Z, design and technique, manufacturers are more discreet about Neelakantan P, Anil S. Evolution of Nickel–titanium Alloys in alloy characteristics that dictate instrument behavior. Along Endodontics. J Contemp Dent Pract 2017;18(11):1090-1096. with design and technique, alloy characteristics of endodontic instruments is one of the main variables affecting clinical per- Source of support: Nil formance. Modification in NiTi alloys is numerous and may yield Conflict of interest: None improvements, but also drawbacks. Martensitic instruments seem to display better cyclic fatigue properties at the expense of surface hardness, prompting the need for surface treatments. INTRODUCTION On the contrary, such surface treatments may improve cutting efficiency but are detrimental to the gain in cyclic fatigue resis- The endodontic treatment requires proper cleaning and tance. Although the design of the instrument is vital, it should shaping of the root canal space, i.e., removing tissues in no way cloud the importance of the properties of the alloy whether vital or necrotic and reducing the bacterial load and how they influence the clinical behavior of NiTi instruments. in the case of infection, which is done through chemo- Clinical significance: Dentists are mostly clinicians rather mechanical detersion protocols. To reach the apical part, than engineers. With the advances in instrumentation design practitioners have to improve the rheology of the root canal by giving it a continuously tapered shape. Until 1Department of Endodontics, Faculty of Dental Medicine the early 1990s, this was conventionally done using Lebanese University, Beirut, Lebanon; Department of stainless steel instruments that have a natural tendency Endodontics and Restorative Dentistry, Siena University, Siena to straighten curved canals when used in sizes 20/100 Italy and above due to the inherent stiffness of the alloy and 2 Department of Prosthodontics, Faculty of Dental Medicine could not follow curvatures even in moderately curved Lebanese University, Beirut, Lebanon canals. They had thus to be precurved to reach length, 3 Department of Endodontics and Restorative Dentistry, Siena which in turn forced operators to use them exclusively in University, Siena, Italy filing motion. This resulted in a high incidence of proce- 4 Department of Research, Faculty of Dental Medicine, Lebanese dural errors, such as ledges, elbows, zipping, strippings, University, Beirut, Lebanon and perforations. Nickel–titanium alloys in dentistry1 5 Department of Endodontology, Faculty of Dentistry, The allowed for endodontic instruments that have reduced University of Hong Kong, Hong Kong stiffness and increased elasticity, specifically engine- 6 Department of Dental Health, Dental Biomaterials Research driven NiTi instruments that proved to be a valuable Chair, College of Applied Medical Sciences, King Saud University Riyadh, Kingdom of Saudi Arabia addition to the endodontic armamentarium. Since their introduction, these files have seen numerous improve- Corresponding Author: Hani F Ounsi, Department of Endodontics, Faculty of Dental Medicine, Lebanese University ments in not only file design and clinical sequences but Beirut, Lebanon; Department of Endodontics and Restorative also metallurgy. If modified clinical sequences and file Dentistry, Siena University, Siena, Italy, e-mail: ounsih@ design are relatively easy for practitioners to follow, gmail.com modification in the alloys may prove more challenging 1090 JCDP Evolution of Nickel–titanium Alloys in Endodontics and alloys designed to overcome a specific weakness twinned martensite structure can hence, untwin on stress, may impact on another property of the alloy. This article but the load has to be nearly constant or slightly increas- presents an overview of the NiTi alloys currently used ing. Furthermore, this untwinning is not an elastic strain: in endodontics. Atoms move from one energy minimum to another. This atom shifting phenomenon allows to absorb up to 8% of About NiTi Smart Alloys the strain as compared with the 0.1 to 0.2% strain limit of many other alloys.3 Nickel–titanium alloys (also known as NiTi or NITINOL for Naval Ordinance Laboratory) are known, when in Conventional NiTi Alloys used in Endodontics nearly equiatomic proportions, to display an array of interesting properties, such as shape memory, super- The main advantage of using NiTi alloys in root canal elasticity, and damping characteristics that arise from shaping instruments is the alloy’s high flexibility.8 reversible crystallographic changes. It is noteworthy Martensitic transformation can be stress induced from that a 0.1% change in composition will result in a 10°C the austenitic phase over a narrow range of tempera- change in the transformation temperature of the alloy tures. Superelasticity occurs when a large reversible and subsequently in its mechanical characteristics.2 The deformation occurs while increasing, stress appears to be NiTi alloys form Ni3Ti, NiTi, and NiTi2 intermetallic constant (plateau). It happens as follows: Conventional compounds. The nearly equiatomic NiTi alloy has broad NiTi alloys are in the austenite phase at body/room compositional limits in the eutectoid phase field above temperatures9-11 Activation of austenitic NiTi produces 630°C, whereas Ni3Ti and NiTi2 are sharply defined an elastic deformation that follows a linear stress/strain compounds.3 Below this temperature, a two-phase field function (the slope of the curve representing the elastic (Ni3Ti, NiTi2) stretches between around 25 to 66% Ti. It is modulus). If deformation (stress) increases, the superelas- possible to preserve the metastable phase by cooling NiTi tic deformation appears, whereas strain remains constant. beneath this temperature.4 When heated, NiTi displays a This superelastic behavior is a direct consequence of the body-centered cubic structure, i.e., known as austenite. martensitic transformation which occurs at the crystal- On cooling, a classic linear thermal contraction is visible lographic level. The strain will remain constant until the until a certain limit [martensite start (Ms)] beyond which entirety of the NiTi mass has shifted to the martensitic, the contraction accelerates. This is caused by a progres- which in turn will sign the end of the superelastic domain. sive shear transformation to a monoclinic structure Continuing the activation beyond that point will reveal called martensite.5 On further cooling, the contraction conventional martensitic deformation with a classic linear rate becomes linear again at a certain point [martensite stress/strain relationship as the crystallographic deforma- finish (Mf)], pointing to the fact that the proportion of tion’s potential to absorb strain is exhausted.8 Thus, if the martensite phase in the alloy has reached 100%. Reheating load is relieved before reaching the plastic deformation this martensite will eventually reverse the process, yield- limit, the deformation will be reversible, both ordinary ing an austenite phase similarly an austenite start (As) austenitic elasticity and the pseudoelastic deformation and an austenite finish (Af) points. Generally, the As and due to phase change. Af temperatures are about 20°K above the Mf and Ms Again, as for thermal modification, the hysteresis temperatures, signing the presence of a hysteresis phe- phenomenon is present and the loading and unloading nomenon above the temperature transformation range. curves will not match. It is noteworthy that although the A third rhombohedral phase or R-phase can also be mechanism of action is similar, the aspect of stress–strain described.6,7 In general, it appears only on cooling before curves will vary significantly depending on the diameter the martensitic transformation is complete. The face- of the wire, temperature, and annealing properties.12 centered cubic planar organization may be described as Having tested instruments from several manufacturers, A, B, C, A, B, C…. It reflects the atoms’ position in suc- Ounsi et al13 established that the earlier generations cessive planes as compared with those in a randomly of instruments were all manufactured from a unique chosen reference plane. This organization involves a 55%Ni–45%Ti. This becomes obvious when one consid- regular displacement of each plane in a specific direction. ers that transformation temperatures of such alloys are If the stacking sequence is reversed A, B, C, B, A, C… for highly sensitive to the composition and even 1% devia- instance, the crystal is said to be twinned. This happens tion in these percentages would almost yield a 100°C in some alloys when compressive
Load more

Recommended publications
  • The Use of Titanium in Dentistry
    Cells and Materials Volume 5 Number 2 Article 9 1995 The Use of Titanium in Dentistry Toru Okabe Baylor College of Dentistry, Dallas Hakon Hero Scandinavian Institute of Dental Materials, Haslum Follow this and additional works at: https://digitalcommons.usu.edu/cellsandmaterials Part of the Dentistry Commons Recommended Citation Okabe, Toru and Hero, Hakon (1995) "The Use of Titanium in Dentistry," Cells and Materials: Vol. 5 : No. 2 , Article 9. Available at: https://digitalcommons.usu.edu/cellsandmaterials/vol5/iss2/9 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Cells and Materials by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Cells and Materials, Vol. 5, No. 2, 1995 (Pages 211-230) 1051-6794/95$5 0 00 + 0 25 Scanning Microscopy International, Chicago (AMF O'Hare), IL 60666 USA THE USE OF TITANIUM IN DENTISTRY Toru Okabe• and HAkon Hem1 Baylor College of Dentistry, Dallas, TX, USA 1Scandinavian Institute of Dental Materials (NIOM), Haslum, Norway (Received for publication August 8, 1994 and in revised form September 6, 1995) Abstract Introduction The aerospace, energy, and chemical industries have Compared to the metals and alloys commonly used benefitted from favorable applications of titanium and for many years for various industrial applications, tita­ titanium alloys since the 1950's. Only about 15 years nium is a rather "new" metal. Before the success of the ago, researchers began investigating titanium as a mate­ Kroll process in 1938, no commercially feasible way to rial with the potential for various uses in the dental field, produce pure titanium had been found.
    [Show full text]
  • A Review on Nickel Titanium and It's Biomedical Applications
    International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 09 | Sep 2020 www.irjet.net p-ISSN: 2395-0072 A Review on Nickel Titanium and it’s Biomedical Applications Agnesh Rao K1, Ayush Kothari2, Dhanush L Prakash3, Jeevan S Hallikeri4, Nesar V Shetty5 1,2,3,4,5Bachelor’s in Mechanical Engineering, Dept. of Mechanical Engineering, BNM Institute of Technology, Karnataka, India ------------------------------------------------------------------------***----------------------------------------------------------------------- Abstract - NiTinol is a super alloy that has influenced Fields like Aeronautics and Biomedicine. Modern Medicine tremendous change in science and technology, since its has accepted and acknowledged the usage of Shape Memory inception in 1959. It has provided novel solutions to our pre- Alloys. Industrial and commercial applications of SMA haven’t existing challenges and has affected many fields in our been exploited still but rather given trivial importance. This paper pertains only to Nitinol, Its properties and its scientific community bringing funding for research and applications in the field of Biomedical Engineering. positively impacting many industries to help in their development. One such impact is in the bio medical industry. The bio medical industry is the most fast paced section of our 1.2 An Overview about the Material Science of scientific community and sees a lot of development in a short Nickel-Titanium Alloy span of time. This review provides an understanding of the history, manufacturing methods, shape memory effect and the use of NiTinol in biomedicine & orthodontics; how NiTinol has William J. Buehler along with Frederick Wang, discovered the helped improve pre-existing solutions to medical problems that SME of Nitinol and its properties during research at the Naval affect a large demographic and how NiTinol has helped in Ordnance Laboratory in 1959.
    [Show full text]
  • The Aerospace Applications of Nickel-Titanium As a Superelastic Material
    Session A8 Paper #3 Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly available information and may not provide complete analyses of all relevant data. If this paper is used for any purpose other than these authors’ partial fulfillment of a writing requirement for first year (freshman) engineering students at the University of Pittsburgh Swanson School of Engineering, the user does so at his or her own risk. THE AEROSPACE APPLICATIONS OF NICKEL-TITANIUM AS A SUPERELASTIC MATERIAL Arsha Mamoozadeh, [email protected], Mena 1:00, Nick Fratto, [email protected], Mena 1:00 Abstract—Nickel-titanium, commonly referred to as Nitinol, is The alloy is called Nitinol, named from its two key ingredients a shape-memory alloy with superelastic properties that make (nickel and titanium), and from its place of discovery at the it useful in certain environments and applications. These Naval Ordnance Laboratory in White Oak, Maryland [1]. properties include shape-memory, flexibility, and durability. Nitinol has superelastic properties that manifest in increased Titanium, a primary material, is a material that reacts with flexibility and durability, as well as the shape-memory carbon and oxygen when molten and is not easy to work with. properties, which allow the material to change shape during a Consequently, there are two commercially viable methods for heat treatment processes. All these properties can be adjusted producing Nitinol that account for titanium’s reactivity: by adding other materials and making a more complicated vacuum induction melting and vacuum arc re-melting.
    [Show full text]
  • Multi-Objective Optimization of Micro-Electrical Discharge Machining of T Nickel-Titanium-Based Shape Memory Alloy Using MOGA-II ⁎ Mustufa H
    Measurement 125 (2018) 336–349 Contents lists available at ScienceDirect Measurement journal homepage: www.elsevier.com/locate/measurement Multi-objective optimization of micro-electrical discharge machining of T nickel-titanium-based shape memory alloy using MOGA-II ⁎ Mustufa H. Abidia, Abdulrahman M. Al-Ahmaria,b, Usama Umera, , Mohammed Sarvar Rasheedc a Princess Fatima Alnijris Research Chair for Advanced Manufacturing Technology (FARCAMT Chair), Advanced Manufacturing Institute, King Saud University, Riyadh, Saudi Arabia b Industrial Engineering Department, College of Engineering, King Saud University, Riyadh, Saudi Arabia c Baynounah Institute of Science and Technology, Abu Dhabi Vocational Education Training Institute, Madinat Zayed, Abu Dhabi, United Arab Emirates ARTICLE INFO ABSTRACT Keywords: Shape memory alloys (SMAs) have received significant attention especially in biomedical and aerospace in- Micro-EDM (µEDM) dustries owing to their unique properties. However, they are difficult-to-machine materials. Electrical discharge Micro-machining machining (EDM) can be used to machine difficult to cut materials with good accuracy. However, several Shape memory alloy challenges and issues related with the process at micro-level continue to exist. One of the aforementioned issues MOGA-II is that the micro-EDM (µEDM) process is extremely slow when compared to other non-conventional processes, such as laser machining, although it offers several other benefits. The study considers the analysis and opti- mization of µEDM by using a multi-objective genetic algorithm (MOGA-II). Drilling of micro-holes is performed by using a tabletop electrical discharge machine. Nickel-Titanium (Ni-Ti) based SMA (a difficult to cut advance material) is used as a specimen. The objective involves determining optimal machining parameters to obtain better material removal rate with good surface finish.
    [Show full text]
  • Tini Shape Memory Alloys Duerig, Pelton Materials Properties
    We are Nitinol.™ TiNi Shape Memory Alloys Duerig, Pelton Materials Properties Handbook Titanium Alloys pp. 1035‐1048 1994 www.nitinol.com 47533 Westinghouse Drive Fremont, California 94539 t 510.683.2000 f 510.683.2001 25 March 2009 Letterhead (scale 80%) Option #1 NDC Business System R2 Ti-Ni Shape Memory Alloys 11 035 I Ti-Ni Shape Memory Alloys T.w. Duerig and A.R. Pelton, Nitino/ Development CofpoIation Effect of phase transformation This datasheet describes some of the key prop­ erties of equiatomic and near-equiatomic tita· nium-nickel alloys with compositions yielding ~ C~ i shape memory and superelastic properties. Shape memory and superelasticity per se will not be reo D viewed; readers are referred to Ref 1 to 3 for basic Manensile Auslenile {pa.ent) information on these subjects. These alloys are Typically 20 ~ commonly referred to as nickel-titanium, tita· D- M, .. Manensl1e stan nium-nickel, Tee-nee, Memorite.... , Nitinol, Tinel"', temperature and Flexon"" . These terms do not refer to single al· Heating ' j A, lIAr ~ Manensite linish loys or alloy compositions, but to a family ofalloys .. temperalure with properties that greatly depend on exact com­ A" "Stan of reverse positional make-up, processing history, and small " transformation of manGnsHe A. = Fin iS!' ot lI!Verse ternary additions. Each manufacturer has its own transformatIon 01 martens;t series of alloy designations and specifications within the "Ti·N i~ range. A second complication that readers must ac­ Temperature -> knowledge is that all properties change signifi­ Sd"Iemane "U$tra~OI'1 of It.. ",Heels on a phase transformation on cantly at the transformation temperatures M Mr, !tie phySical prope~s ofT,·Ni.
    [Show full text]
  • Machinability Analysis and Optimization in Wire EDM of Medical Grade Nitinol Memory Alloy
    materials Article Machinability Analysis and Optimization in Wire EDM of Medical Grade NiTiNOL Memory Alloy Vinayak N. Kulkarni 1 , V. N. Gaitonde 1,* , S. R. Karnik 2, M. Manjaiah 3 and J. Paulo Davim 4 1 School of Mechanical Engineering, KLE Technological University, Hubballi, Karnataka 580 031, India; [email protected] 2 Department of Electrical and Electronics Engineering, KLE Technological University, Hubballi, Karnataka 580 031, India; [email protected] 3 Department of Mechanical Engineering, National Institute of Technology, Warangal, Telangana 506 004, India; [email protected] 4 Department of Mechanical Engineering, University of Aveiro, Campus Santiago, 3810-193 Aveiro, Portugal; [email protected] * Correspondence: [email protected]; Tel.: +918362378270 Received: 9 April 2020; Accepted: 7 May 2020; Published: 9 May 2020 Abstract: NiTiNOL (Nickel–Titanium) shape memory alloys (SMAs) are ideal replacements for titanium alloys used in bio-medical applications because of their superior properties like shape memory and super elasticity. The machining of NiTiNOL alloy is challenging, as it is a difficult to cut material. Hence, in the current research the experimental studies on machinability aspects of medical grade NiTiNOL SMA during wire electric discharge machining (WEDM) using zinc coated brass wire as electrode material have been carried out. Pulse time (Ton), pause time (Toff), wire feed (WF), and servo voltage (SV) are chosen as varying input process variables and the effects of their combinational values on output responses such as surface roughness (SR), material removal rate (MRR), and tool wear rate (TWR) are studied through response surface methodology (RSM) based developed models. Modified differential evolution (MDE) optimization technique has been developed and the convergence curve of the same has been compared with the results of differential evolution (DE) technique.
    [Show full text]
  • Coated and Uncoated Nickel-Titanium Archwires: Mechanical Property
    COATED AND UNCOATED NICKEL-TITANIUM ARCHWIRES: MECHANICAL PROPERTY AND SURFACE TOPOGRAPHY RESPONSE TO A SIMULATED ORAL ENVIRONMENT WITH AND WITHOUT BRACKET-RELATED LOAD-DEFLECTION INDUCED STRESS A THESIS IN Oral and Craniofacial Sciences Presented to the Faculty of the University of Missouri-Kansas City in partial fulfillment of the requirements for the degree MASTER OF SCIENCE by KELCEY LOVELAND B.S., Utah State University, 2008 D.M.D., University of Nevada – Las Vegas, 2015 Kansas City, Missouri 2017 COATED AND UNCOATED NICKEL-TITANIUM ARCHWIRES: MECHANICAL PROPERTY AND SURFACE TOPOGRAPHY RESPONSE TO A SIMULATED ORAL ENVIRONMENT WITH AND WITHOUT BRACKET-RELATED LOAD DEFLECTION INDUCED STRESS Kelcey Loveland, DMD, Candidate for the Master of Science Degree University of Missouri-Kansas City, 2017 ABSTRACT This study examined the effect of exposure to bracket-related load deflection on the mechanical properties and surface characteristics of esthetic coated and uncoated nickel- titanium archwires. Two types of coated archwires were tested: one with a rhodium ion coating and another with a polymer coating. Corresponding uncoated wires of the same size were also tested. These four different wires were divided into treatment groups based on exposure to bracket-related load deflection and storage in PBS at 37±1°C. A three-point bend test in DI water at 37±1°C was performed on specimens at three time points: 4 weeks, 8 weeks, and 12 weeks. Unloading forces at 1, 2, and 3 mm of deflection were recorded. After 12 weeks exposure, three representative specimens from each treatment group along with untested wires were viewed using scanning electron microscopy (SEM) to provide a qualitative surface topography analysis.
    [Show full text]
  • PREPARATION of the NITI SHAPE MEMORY ALLOY by the TE-SHS METHOD – INFLUENCE of the SINTERING TIME Jaroslav ČAPEK, Vojtěch KU
    15. - 17. 5. 2013, Brno, Czech Republic, EU PREPARATION OF THE NITI SHAPE MEMORY ALLOY BY THE TE-SHS METHOD – INFLUENCE OF THE SINTERING TIME Jaroslav ČAPEK, Vojtěch KUČERA, Michaela FOUSOVÁ, Dalibor VOJTĚCH Department of Metals and Corrosion Engineering, Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic, [email protected] Abstract A NiTi shape memory alloy, known as nitinol, has been intensively studied for last five decades. This big interest is caused by its unique properties, such as pseudoplasticity, superelasticity, shape memory, as well as good corrosion resistance and sufficient biocompatibility. Unfortunately, its common manufacture methods (vacuum induction melting, vacuum arc remelting) possess some disadvantages, such as a contamination or an insufficient homogeneity of the fabricated ingots. Therefore, new fabrication methods have been recently intensively studied. The self-propagating high-temperature synthesis seems to be a promising approach to the NiTi fabrication. It has been performed in both (thermal explosion and plane wave propagation) regimes. The thermal explosion one seems to be more suitable for the fabrication of compact materials. In this work, the NiTi samples were prepared by the thermal explosion mode of self-propagating high- temperature synthesis (TE-SHS). The influence of a sintering time on the samples properties, such as microstructure, transformation and compression behaviour, as well as hardness HV 5 was studied. Keywords: NiTi, powder metallurgy, thermal explosion mode of self-propagating high-temperature synthesis 1. INTRODUCTION Recently, an approximately equiatomic alloy, known as nitinol, has been intensively studied. It is due to its unique properties, such as pseudoplasticity, superelasticity, shape memory as well as good corrosion resistance and sufficient biocompatibility.
    [Show full text]
  • Galvanic Corrosion of Some Copper Alloys Coupled with Titanium in Synthetic Sea Water
    GALVANIC CORROSION OF SOME COPPER ALLOYS COUPLED WITH TITANIUM IN SYNTHETIC SEA WATER Hiroshi Kunieda, Hiroshi Yamamoto and Naomichi Nishijima Furukawa Metals Co., Ltd., Amagasaki-shi, Japan Introduction Titanium tube is a promising material for heat exchangers installed in thermal power plants, nuclear power plants, desali­ nation plants and various chemical plants because it has superi­ or corrosion resistance in sea water. However, consideration is necessary when selecting tube sheet materials because titanium shows noble potential in sea water. In Japan, thin wall tita­ nium tubes made by welding are already being widely used in the air cooling zone of condensers in thermal power plants but exam­ ples of galvanic corrosion of the naval brass sheets of the air cooling zone have been reported [1]. Numerous studies (1,2,3,4) have been carried out on galvanic corrosion of copper alloys coupled with titanium in normal temperature sea water and also, coating and cathodic protection of the tubes and sheets of the air cooling zone in practical condensers have been investigated. On the other hand, desalinatio11 plants are progressing rap­ idly, and being constructed in the f'llidd_le East. The corrosion environment is deaerated, concentrated, high temperature sea water when a combination of titanium tubes and copper alloy sheets are used in sea water desalination plants and it is be­ lieved that galvanic corrosion of copper alloy sheets indicates different behavior from that of power condenser environment. Particularly in the deaerated environment, whether galvanic cor­ rosion occurs or not is an interesting problem. Fukuzuka et al. [5] studied galvanic corrosion of copper alloys coupled with titanium by immersion test in deaerated, high temperature and concentrated NaCl solution but it is inevitable that a violent flow condition is added in practical equipment.
    [Show full text]
  • Characterizing Fatigue Response of Nickel-Titanium Alloys by Rotary Beam Testing
    Journal of ASTM International, Vol. 4, No. 6 Paper ID JAI100390 Available online at www.astm.org Mitesh M. Patel1 Characterizing Fatigue Response of Nickel-Titanium Alloys by Rotary Beam Testing ABSTRACT: Fatigue information has been reliable in predicting wire critical structural integrity. The aim of this study is to expound on the characterization technique of rotary beam fatigue testing ͑RBT͒. By alternating tension and compression stress states through RBT, it is possible to determine the life expectancy of Nitinol monofilament round wires. Fatigue testing has been employed to characterize the influence of subtle changes in inclusion content, chemistry variations of raw mate- rial, ingot transformation temperatures of Nitinol ͑NiTi͒, and surface finish conditions for implant grade wires. Currently, an ASTM standard does not exist that concentrates solely on fatigue testing shape memory alloys. By exploiting part geometry, this testing technique serves to compliment other characterization methods. Evaluation of fracture surfaces has proven useful in diagnosing the factors influencing failures. The utilization of fatigue data and fracture mechanics compliments tensile test- ing in providing information to the design engineer. Results from studying flexural endurance, statis- tical Weibull life assessment analysis, fracture analysis, and a determination of stress/strain levels at the site of failure have proven useful in determining desired material properties for next generation medical devices. KEYWORDS: Nitinol, round wire, rotary beam, fatigue, fracture, RϭϪ1, controlled strain Introduction Some common fatigue test methods include axial, bending, and torsion. In 2000, a study was con- ducted using a wire diameter of 0.267 mm to investigate the impact of melt origin on fatigue performance ͓1͔.
    [Show full text]
  • Cyclic Behavior of Superelastic Nickel-Titanium and Nickel-Titanium-Chromium Shape Memory Alloys
    Cyclic Behavior of Superelastic Nickel-Titanium and Nickel-Titanium-Chromium Shape Memory Alloys A Thesis Presented to The Academic Faculty by Laura Isabel Barbero Bernal In Partial Fulfillment of the Requirements for the Degree Master of Science in Civil Engineering Georgia Institute of Technology December, 2004 Cyclic Behavior of Superelastic Nickel-Titanium and Nickel-Titanium-Chromium Shape Memory Alloys Approved by: Dr. Reginald DesRoches, Advisor Dr. Laurence Jacobs Dr. Barry Goodno November 22, 2004 Acknowledgements I would like to thank my advisor, Dr. Reginald DesRoches, for his guidance, vision and support. I would also like to thank my Thesis Advisory Committee members, Dr. Laurence Jacobs and Dr. Barry Goodno for reading and reviewing my thesis with great care. A big thank you goes to Dr. Kenneth “Mac” Will for always being there to answer my questions and offer his guidance. I want to thank my husband, Michael Buffa, for his encouragement, and for trying to get me to stop procrastinating so I could get my research and my schoolwork done on time. Without him, I would have never gotten out. I would also like to thank my parents for all the sacrifices they made to allow me the opportunity to study at Georgia Tech, and for their continuing support in everything I do. I would also like to thank my officemates, Jason McCormick, Brad Penar, Jamie Padgett, and Monique Hite, thank you for putting up with my ramblings and for never telling me to shut up (except Brad that one time), even though you were probably all thinking about it.
    [Show full text]
  • Fundamental Characteristics and Design Method for Nickel-Titanium Shape Memory Alloy
    PERIODICA POLYTECHNICA SER. MECH. ENG. VOL. 45, NO. 1, PP. 75–86 (2001) FUNDAMENTAL CHARACTERISTICS AND DESIGN METHOD FOR NICKEL-TITANIUM SHAPE MEMORY ALLOY István MIHÁLCZ Department of Precision Engineering and Optics Budapest University of Technology and Economics H–1521 Budapest, Hungary Phone: +36-20-9460769, Fax: +36-1-4633787 E-mail: [email protected] Received: April 5, 2000 Abstract Shape memory alloys (SMA), because of their unique mechanical characteristics and shape memory effect (SME), have been widely used as force and displacement actuators in many fields [DUERING et al, 1990]. In the industrial applications, it is necessary not only to calculate the mechanical response of the actuator in terms of recovery force or deformation, but also to evaluate its temporal characteristics, i.e., the actuation and reset times. This paper presents the fundamental characteristics of SMA and a complete design model, which requires a close connection between three models: a mechanical model to predict the response of the actuator to a given temperature increment, a thermal model to compute the temperature change in the device, and a continuum-mechanical model to predict the martensite fraction on the SMA. The methodology is applied to a linear wire actuator. Keywords: shape memory alloys (SMA), shape memory effect (SME), martensitic transformation, NiTi, superelasticity. 1. History of Shape Memory Alloys The first reported steps towards the discovery of the shape memory effect were taken in 1932 by A. ÖLANDER [R. GILBERTSON, 1994]. He discovered the pseudoelastic behavior of the Au-Cd alloy. GRENINGER and MOORADIAN observed in 1938 the formation and disappearance of a martensitic phase by decreasing and increasing the temperature of a Cu-Zn alloy.
    [Show full text]