Journal articles: 'Nitinol'

1

van Hai, Dinh, Hoang Minh Tam, and Duong van Quang. "Application of Finite Element Method to the Simulation of Vessel Stents." Materials Science Forum 804 (October 2014): 243–47. http://dx.doi.org/10.4028/www.scientific.net/msf.804.243.

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In this study, the effects of supereslasticity of Nitinol for self-expanding (SX) stents – Stent devices which are implanted into the blood vessels in order to restore blood flow in a diseased artery segment (narrowing of the blood vessel due to plaque build-up) and keep the artery open after angioplasty were considered and analyzed. To emphasize the unique properties of Nitinol as compared to other materials, this study was conducted to differentiate the behaviors of two types of stents which are made of Nititol and 316L stainless steel during implantation. Finite element analysis was used for simulation and modeling. The study results are expected to serve well the design of vessel stents.

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Kim, Jae Hoon, Jun Sik Son, Kwi Deok Park, Jong Man Kim, Jae Jin Kim, Kwang Duk Ahn, and Dong Keun Han. "Blood Compatibility of Novel Zwitterionic PEG-Grafted Nitinol Alloy for Peripheral Arterial Stents." Key Engineering Materials 342-343 (July 2007): 805–8. http://dx.doi.org/10.4028/www.scientific.net/kem.342-343.805.

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In this study, newly synthesized zwitterionic PEG was grafted on Nitinol alloy using oxidation treatment. The surface property and blood compatibility of surface-modified Nitinols were examined. The results of surface analysis showed that the contact angle and the ratio of oxygen to carbon significantly decreased with Nitinol alloys. The total amount of fibrinogen (0.095 μg/cm2) adsorbed onto TiNi-PEG2K-N+-S- was lower than that of TiNi control (0.12 μg/cm2). The platelet adhesion decreased in the order of TiNi control > TiNi-MPEG2K > TiNi-PEG2K-N+-S. Particularly, zwitterionic PEG with PEG2K was proven better than any others. The results indicated that zwitterionic PEG surface could significantly suppress platelet adhesion and protein adsorption as compared to other samples. The present study suggested that grafted zwitterionic PEG structure may possess improved blood compatibility.

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Rehman, Ateekh Ur, Nagumothu Kishore Babu, Mahesh Kumar Talari, Yusuf Usmani, and Hisham Alkhalefah. "Characterisation of Microstructure and Mechanical Properties of Linear Friction Welded α+β Titanium Alloy to Nitinol." Applied Sciences 11, no. 22 (November 12, 2021): 10680. http://dx.doi.org/10.3390/app112210680.

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A variable area nozzle integrated into the design of a high-bypass-ratio turbofan engine effectively saves up to 10% in aircraft fuel consumption. Additionally, noise emissions can be lowered at airports during take-off and landing by having better control of the nozzle diameter. Shape memory capabilities of Nitinol alloys could be availed in the form of actuators in the construction of such a nozzle. However, these Nitinol actuators must be joined to Ti-6Al-4V, a prominent alloy making up most of the rest of the nozzle. Because of the huge differences in the physical and metallurgical properties of these alloys, fusion welding is not as effective as solid-state welding. In the current study, a linear friction welding process was adopted to join Ti-6Al-4V to Nitinol successfully. The effect of friction welding on the evolution of weld macro and microstructures; hardness and tensile properties were studied and discussed. The macrostructure of Ti-6Al-4V and Nitinol’s dissimilar joint revealed flash formation mainly on the Ti-6Al-4V side due to its reduced flow strength at high temperatures. Optical microstructures revealed fine grains in Ti-6Al-4V immediately adjacent to the interface due to dynamic recrystallisation and strain hardening effects. In contrast, Nitinol remained mostly unaffected. An intermetallic compound (Ti2Ni) was seen to have formed at the interface due to the extreme rubbing action, and these adversely influenced the tensile strength and elongation values of the joints.

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HUSSAIN, SAJJAD, and QAISER KHAN. "NITINOL STENTS." Professional Medical Journal 18, no. 04 (December 10, 2011): 654–57. http://dx.doi.org/10.29309/tpmj/2011.18.04.2657.

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Stents deployed in the carotid arteries cause significant geometric changes in the vessels, influencing the flexibility and torsion characteristics of the vessels, which are aggravated by the high degree of mobility in this area of the body. The influence of these physical characteristics on carotid blood flow could influence the long term performance of the deployed stents. Objectives: To evaluate the geometric changes in the carotid arteries after deployment of self expanding nitinol stents. Settings: AFIC-NIHD. Period: November 2003 to August 2008. Material & methods: 45 cases of carotid artery stenting (CAS) done. We selected cases where the stenting to the internal carotid artery (ICA) had been done across the bifurcation of the common carotid artery (CCA) with self expanding nitinol stents, and when DICOM videos that had pre and post stenting images in the same imaging projection were available for analysis. Based on the inclusion criteria 21 videos were selected and deemed fit for taking measurements. The measurement system proposed by Berkefeld et al which involved the measurement of the CCA-ICA (common carotid artery –internal carotid artery) angle and ICA-offset was used. These variables were measured using onscreen measuring software which can measure linear distances and angles after appropriate calibration for each image. Results: We did not find any significant changes in the ICA-offset; significant changes in the CCA-ICA angle were noted.

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Tobushi, H., and J. R. Gahoon. "Mechanical Analysis of a Solar-Powered Solid State Engine." Transactions of the Canadian Society for Mechanical Engineering 9, no. 3 (September 1985): 137–41. http://dx.doi.org/10.1139/tcsme-1985-0020.

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The mechanical principle of a solar-powered solid state engine utilizing the shape-memory effect is analyzed. The performance of a differential pulley Nitinol engine is discussed and it is calculated that a small, solar-powered differential pulley Nitinol engine could produce up to 15W with a single Nitinol wire, A higher power solar Nitinol engine producing up to 15 kW is possible by using larger Nitinol wire, and over 1 MW may be expected by applying the higher power engine system. The size of the solar energy collector needed to generate mechanical energy via a Nitinol engine is estimated to be about 0.02 m2/W and the total efficiency of the engine predicted to be about 4%, The overall efficiency and economics of a solar-powered Nitinol engine should be in the same order as that of solar energy system utilizing the photovoltaic effect.

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Schipper, Oliver N., Samuel E. Ford, Patrick W. Moody, Bryce Van Doren, and J. Kent Ellington. "Radiographic Results of Nitinol Compression Staples for Hindfoot and Midfoot Arthrodeses." Foot & Ankle International 39, no. 2 (October 27, 2017): 172–79. http://dx.doi.org/10.1177/1071100717737740.

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Background: The purpose of this study was to determine the radiographic union rate after midfoot and hindfoot arthrodeses using a new generation of nitinol staples, and to compare outcomes between a nitinol staple construct and a nitinol staple and threaded compression screw construct. Methods: A retrospective chart review was performed to identify patients who underwent hindfoot or midfoot arthrodesis using a new generation of nitinol compression staples with or without a partially threaded cannulated screw with minimum 3-month radiographic follow-up. The primary outcome variable was radiographic evidence of arthrodesis on radiographs and, when available, computed tomographic scan in patients who underwent midfoot or hindfoot arthrodesis using nitinol staples. Ninety-six patients and 149 joints were eligible for analysis. Median radiographic follow-up was 5.7 months. Results: Radiographic union was seen in 93.8% (60/64) of patients and 95.1% (98/103) of joints using the nitinol staple construct. Radiographic union was seen in 90.6% (29/32) of patients and 95.7% (44/46) of joints using the nitinol combined staple and screw construct. There was no significant difference in radiographic union rate or revision surgery between the 2 groups. Seven patients developed nonunion, 4 in the nitinol staple construct group and 3 in the staple and screw group. Conclusions: New-generation nitinol staples were safe and effective for hindfoot and midfoot arthrodeses, with a high radiographic union rate. The use of a partially threaded screw for additional fixation was not found to either significantly increase or decrease radiographic fusion with nitinol staple fixation. Level of Evidence: Level III, comparative cohort study.

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Wang, Zheng Pin, Jian Lu Ma, Yu Hong Yao, Jiang Nan Liu, Wei Gao, and Yao Hua Jin. "Properties of Self-Expanding Nitinol Stents Treated by Addition of 600°C Heat Setting Process." Advanced Materials Research 239-242 (May 2011): 2206–9. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.2206.

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For its two unique properties of superelasticity and shape memory, nitinol is widely used in medical applications. Traditionally, most nitinol stents are normally heat set at 485°C, which induces the formation of the Ni-rich second phases such as Ti2Ni3 and Ti3Ni4, increases the austenite finish temperature and reduces material strength and fatigue performance. The addition of 600°C heat setting was applied to the nitinol stents after 485°C heat setting process and its effect on the mechanical, dimensional and functional properties of the nitinol stents were investigated. The experimental results showed that the nitinol stent tubes with the addition of 600°C heat setting process had higher elastic modulus, ultimate tensile strength, elongation percentage, inner dimension and outer dimension than those of the nitinol stents with 485°C heat setting process. Moreover, after the addition of 600°C expansion step, the nitinol stents almost had the same average deployment force and deployment accuracy as those of the nitinol stents with 485°C heat setting process and higher average inner dimension (ID) and outer dimension than that of those without the 600°C expansion step. Either treated with the addition of 600°C heat setting process or only 485°C heat setting process, the average austenite finish temperature (Af ) of the nitinol stents was both lower than the body temperature and the average Af of the fomer was 8°C lower than that of the latter.

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Maksymova, S. V., and B. V. Stefaniv. "Producing nitinol brazed joints (Review)." Paton Welding Journal 2022, no. 12 (December 28, 2022): 19–28. http://dx.doi.org/10.37434/tpwj2022.12.03.

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Galimzyanov, Bulat N., and Anatolii V. Mokshin. "Amorphous Porous Phase of Nitinol Generated by Ultrafast Isobaric Cooling." Solid State Phenomena 310 (September 2020): 150–55. http://dx.doi.org/10.4028/www.scientific.net/ssp.310.150.

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Titanium nickelide (nitinol) is of great applied interest in various industries due to unique combination of its physical and mechanical characteristics. In the present work, we consider the possibility of obtaining nitinol with mesoporous structure by rapidly cooling the molten sample to room temperature. Based on molecular dynamics simulation data, it was shown that the rapid cooling of the nitinol melt leads to formation of a porous structure. It was shown that the inner pore wall is formed mainly by titanium atoms, which provide biocompatibility of nitinol. It was found that the porosity of nitinol weakly depends on the cooling rate, while the porosity increases linearly with decreasing melt density.

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McCummiskey, Emma, William M. Dempster, D. H. Nash, T. R. Ashton, and D. G. Stevenson. "The Determination and Evaluation of Nitinol Constitutive Models for Finite Element Analysis." Applied Mechanics and Materials 7-8 (August 2007): 81–88. http://dx.doi.org/10.4028/www.scientific.net/amm.7-8.81.

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Superelastic Ni-Ti (Nitinol) is a member of the shape memory alloy (SMA) family of metals. The physical properties of Nitinol are highly dependant on a number of factors, including manufacturing method, subsequent processing, operating temperature, and strain rate. These factors complicate the prescription of material constitutive models, leading to complexities in the computational analysis of Nitinol components. The current work explores the limitations in the Nitinol material model available in existing commercial finite element (FE) software using a series of specially design experimental tests and representative FE models.

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Adeniran, Mofoluwaso Kehinde, and Sunday Ayoola Oke. "Surface Integrity Analysis of Wire Electric Discharge Machining of Nitinol Shape Memory Alloy: A Literature Review." IJIEM - Indonesian Journal of Industrial Engineering and Management 3, no. 2 (June 28, 2022): 85. http://dx.doi.org/10.22441/ijiem.v3i2.14821.

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When nitinol is machined, quantitative details regarding the surfaces such as the surface crack density, utmost peak-to-valley heights, recast layer thickness and the mean peak-to-valley height among others offer the most appropriate features to consider in the integrity of the surfaces of machined nitinol. This quantitative information directs the integrity and the projected future performance of the machined nitinol in the components. Consequently, the research question of how to achieve optimal surface integrity of the machined nitinol is important. A literature review is conducted to study the surface integrity analysis of wire electrical discharged machined nitinol. In particular, published papers between 2007 and 2021 have been reviewed. Literature is explored concerning the method of analysis, parameters of research interest and the problems/issues arising from the literature. Diverse methods were employed to evaluate the surface integrity of nitinol after machining. Commonly, both mathematical optimization and microstructural characterizations are used to suggest ideas. Mathematical optimization has been in two broad perspectives, namely, experimental design-based methods such as orthogonal arrays, signal-to-noise ratios, Taguchi's utility and quality loss function, Box-Behnken design and response surface methodology. The non-traditional optimization schemes such as the differential evolution, multi-objective optimization based on ratio analysis and teaching learning-based optimization have been applied. For microstructural characterization, tools to evaluate the surface integrity of nitinol such as field emission scanning electron microscope and energy dispersive X-ray have been deployed. Parameters such as residual stress, geometric deviation, microhardness and profile accuracy are pursued to be optimized. It is known that various literature reviews in previous years have studied the surface integrity problem of nitinol using large-scale approaches. However, in this article, a brief review is prescribed and this work reveals how the surface integrity analysis of nitinol has been tackled in the literature.

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12

McNichols, J. L., and J. S. Cory. "Thermodynamics of Nitinol." Journal of Applied Physics 61, no. 3 (February 1987): 972–84. http://dx.doi.org/10.1063/1.338151.

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13

Ryhänen, J. "Biocompatibility of Nitinol." Minimally Invasive Therapy & Allied Technologies 9, no. 2 (January 2000): 99–105. http://dx.doi.org/10.3109/13645700009063056.

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Rapp, Bob. "Nitinol for stents." Materials Today 7, no. 5 (May 2004): 13. http://dx.doi.org/10.1016/s1369-7021(04)00225-1.

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Goldstein, David M. "Nitinol Strain Effects." JOM 39, no. 9 (September 1987): 23–27. http://dx.doi.org/10.1007/bf03257646.

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Siegel, Bianca, John P. Bent, and Robert F. Ward. "Endotracheal Nitinol Stents." Otolaryngology–Head and Neck Surgery 148, no. 4 (January 15, 2013): 671–77. http://dx.doi.org/10.1177/0194599812474235.

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Navickaitė, Kristina, Lucia Ianniciello, Jaka Tušek, Kurt Engelbrecht, Christian R. H. Bahl, Michael Penzel, Klaus Nestler, Falko Böttger-Hiller, and Henning Zeidler. "Plasma Electrolytic Polishing of Nitinol: Investigation of Functional Properties." Materials 14, no. 21 (October 27, 2021): 6450. http://dx.doi.org/10.3390/ma14216450.

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A novel, environmentally friendly, fast, and flexible polishing process for Nitinol parts is presented in this study. Nitinol samples with both superelastic and shape memory properties at room temperature were investigated. The chemical contamination and surface roughness of superelastic Nitinol plates were examined before and after plasma electrolytic polishing. The shift in phase transformation temperature and tensile strength before and after the polishing process were analysed using Nitinol wire with shape memory properties. The obtained experimental results were compared to the data obtained on reference samples examined in the as-received condition. It was found that plasma electrolytic polishing, when the right process parameters are applied, is capable of delivering Nitinol parts with extremely high surface quality. Moreover, it was experimentally proven that plasma electrolytic polishing does not have a negative impact on functionality or mechanical properties of polished parts.

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CHEN, WEI, H. WANG, LEI ZHANG, and XIUSHAN TANG. "DEVELOPMENT OF HOT DRAWING PROCESS FOR NITINOL TUBE." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 1968–74. http://dx.doi.org/10.1142/s0217979209061913.

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In recent years, Nitinol, near-equiatomic nickel-titanium alloys, have found growing applications in medical technology and joining technology, due to their special characteristics such as shape memory, superelasticity and biocompatibility. The production of Nitinol tube cost-effectively remains a technical challenge. In this paper, we describe a hot drawing process for Nitinol tube production. A Nitinol tube blank and a metal core are assembled together. The assembly is hot drawn for several passes to a final diameter. The metal core is then plastically stretched to reduce its diameter and removed from the tube. Hot drawing process has been applied to Ni 50.7 Ti and Ni 47 Ti 44 Nb 9 alloys. Nitinol tubes of 13.6 mm outer diameter and 1 mm wall thickness have been successfully produced from a tube blank of 20 mm outer diameter and 3.5 mm thickness.

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de Aragon, Javier S. Martinez, Jose R. Villada, and Jose M. Ruiz-Moreno. "Ocular Biocompatibility of a Nitinol Capsular Tension Ring (CTR)." EuroBiotech Journal 6, no. 4 (October 1, 2022): 167–73. http://dx.doi.org/10.2478/ebtj-2022-0016.

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Abstract Introduction: The biocompatibility of nitinol in the human body has extensively been demonstrated. Although nitinol is already being used for intraocular surgeries such as lens fragmentation and foreign body extraction, little is known about its intracapsular, long-term behavior. The purpose of this study is to evaluate the long-term uveal and capsular biocompatibility of a nitinol CTR placed in the capsular bag after cataract surgery in an animal model. Method: After approval of the study by the Institutional Animal Care and the Ethics Committee, bilateral phacoemulsification was performed in 6 rabbits; 1 eye received a nitinol CTR and the other a control polymethylmethacrylate (PMMA) open-ended ring. Ophthalmic evaluation for the presence of infections in all 12 eyes was performed after 7 days, 4 weeks, 3 months, and 6 months follow-up period. After a follow-up period of 6 months, the eyes were enucleated, and a histopathologic evaluation was performed. Results: Neither of the groups showed any clinical signs of posterior capsule opacification (PCO) or inflammation. The nitinol group showed slightly less inflammation during histopathologic examination compared to the PMMA group. No biocompatibility issues have been observed in this animal study. Conclusions: There were no histological differences between eyes implanted with nitinol and eyes implanted with PMMA rings. Nitinol has proven to show high biocompatibility when implanted in the capsular bag of the rabbit eye.

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Chekotu, Josiah, Robert Groarke, Kevin O’Toole, and Dermot Brabazon. "Advances in Selective Laser Melting of Nitinol Shape Memory Alloy Part Production." Materials 12, no. 5 (March 8, 2019): 809. http://dx.doi.org/10.3390/ma12050809.

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Nitinol (nickel-titanium or Ni-Ti) is the most utilized shape memory alloy due to its good superelasticity, shape memory effect, low stiffness, damping, biocompatibility, and corrosion resistance. Various material characteristics, such as sensitivity to composition and production thermal gradients, make conventional methods ineffective for the manufacture of high quality complex Nitinol components. These issues can be resolved by modern additive manufacturing (AM) methods which can produce net or near-net shape parts with highly precise and complex Nitinol structures. Compared to Laser Engineered Net Shape (LENS), Selective Laser Melting (SLM) has the benefit of more easily creating a high quality local inert atmosphere which protects chemically-reactive Nitinol powders to a higher degree. In this paper, the most recent publications related to the SLM processing of Nitinol are reviewed to identify the various influential factors involved and process-related issues. It is reported how powder quality and material composition have a significant effect on the produced microstructures and phase transformations. The effect of heat treatments after SLM fabrication on the functional and mechanical properties are noted. Optimization of several operating parameters were found to be critical in fabricating Nitinol parts of high density. The importance of processing parameters and related thermal cooling gradient which are crucial for obtaining the correct phase structure for shape memory capabilities are also presented. The paper concludes by presenting the significant findings and areas of prospective future research in relation to the SLM processing of Nitinol.

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Ma, Jia Li, Ming Zhu, Wei Dong Miao, Jun Tao Li, and Ya Ming Kou. "The Research Progress of Nitinol Vascular Stent." Advanced Materials Research 690-693 (May 2013): 425–28. http://dx.doi.org/10.4028/www.scientific.net/amr.690-693.425.

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Nitinol alloy is used widely in biomedical science because of their good performances. The radial support force, biocompatibility and fatigue performance of nitinol alloy blood stent meet the requirement correctly. With the development of computer simulation technology, the stent structure, materials and so on will get further improvement and innovation under the help of statuses on the finite element analysis and blood flow dynamics simulation of nitinol alloy stent.

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Zhao, Haibo, and Kun Wu. "Experimental and numerical investigation of the transient thermal characteristics of twisted nitinol wires in a continuous torsional refrigeration system." PLOS ONE 17, no. 11 (November 17, 2022): e0277415. http://dx.doi.org/10.1371/journal.pone.0277415.

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Twistocaloric cooling technology is a novel solid elastocaloric refrigeration to be promising alternatives to conventional compression refrigeration. The transient thermal characteristics of the twistocaloric-effect material and its cooling capacity are critical for this technology. A test rig of the continuous torsional refrigeration system (CTRS) using nitinol wires twisted by a stepping motor was built. The experimental tests show that, the surface temperatures increased as the stepping motor twisted the nitinol wires clockwise, and decreased by untwisting them counterclockwise under the stepping motor speed of 40, 45 and 45rpm. The maximum temperature rise and drop relative to the ambient temperature for the two-twisted-nitinol-wire combinations were 7.1 and 2.6°C, higher than those of 1.4 and 0.6°C for the single nitinol wire, respectively. An optimization program based on a heat conduction model was constructed to attain the potential cooling and heating capacities (PHCCs) of the nitinol wires. Then, PHCCs were introduced into the coupled flow and convective heat transfer model to predict the actual cooling and heating capacities of the CTRS. They were discovered to increase as the number of nitinol wires, the stepping motor speed, and the air velocity. The results can be referred in developing a continuous torsional refrigeration prototype.

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Sinha, Sarmita, Prabir Chandra Pramanik, Howa Begam, and Abhijit Chanda. "Study on the Effect of Strain Rate and Temperature on Mechanicalproperties of Nitinol." Applied Mechanics and Materials 592-594 (July 2014): 1185–89. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1185.

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The successful use of Nickel-Titanium (Nitinol) in biomedical applications requires an accurate control of its unique mechanical properties. The purpose of this study is to analyze the effects of a wide range of heat treatments on the mechanical behaviour of Nitinol. We have taken two different grades of Nitinol with different heat treatment history and surface characteristics. The sample with protective oxide coating showed higher elastic strain with comparatively large hysteresis.

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Eaton-Evans, James, Janice M. Dulieu-Barton, Edward G. Little, and Ian A. Brown. "Thermoelastic Stress Analysis of Nitinol Self-Expanding Stents." Applied Mechanics and Materials 3-4 (August 2006): 47–52. http://dx.doi.org/10.4028/www.scientific.net/amm.3-4.47.

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

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Dyer, Patrick. "Integration of Small Diameter Wire Form SMA for the Creation of Dynamic Shape Memory Textiles." Advances in Science and Technology 80 (September 2012): 53–58. http://dx.doi.org/10.4028/www.scientific.net/ast.80.53.

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The integration of Nitinol wire directly into flexible textile structures has seen limited successful research outcomes. This has mainly been due to issues with shape training and the accurate positioning of the Nitinol components. A new approach is investigated here, which utilises small diameter (0.15mm - 0.10mm) Nitinol components and the manipulation of the woven structure. This combined approach has the potential to improve the dynamic control of the resulting textiles, giving the textile designer further latitude to adapt a combination of functional and visual properties, as well as expanding application possibilities. This investigation focuses on the development of composite samples that integrate Nitinol directly into woven cotton, Kevlar, polyester and polypropylene textiles, demonstrating the potential for medical and healthcare applications. The prototype composite textiles developed, investigate a range of controlled surface manipulations as well as larger scale shape changes, including the creation of arced forms, pleating, expansion and compression. With supporting data, the evaluation of these samples explores the potential of integrating small diameter Nitinol wires into woven structures and the resultant levels of shape transfer, control and cyclic speed achievable.

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Roque, L. Reis, M. Donato, G. Almeida, L. Castelhano, and P. Escada. "Nitinol versus non-Nitinol prostheses in otosclerosis surgery: a meta-analysis." Acta Otorhinolaryngologica Italica 38, no. 4 (August 2018): 279–85. http://dx.doi.org/10.14639/0392-100x-1950.

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Zheng, Qingli, Pengfei Dong, Zhiqiang Li, Ying Lv, Meiwen An, and Linxia Gu. "Braided composite stent for peripheral vascular applications." Nanotechnology Reviews 9, no. 1 (November 27, 2020): 1137–46. http://dx.doi.org/10.1515/ntrev-2020-0056.

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AbstractBraided composite stent (BCS), woven with nitinol wires and polyethylene terephthalate (PET) strips, provides a hybrid design of stent. The mechanical performance of this novel stent has not been fully investigated yet. In this work, the influence of five main design factors (number of nitinol wires, braiding angle, diameter of nitinol wire, thickness and stiffness of the PET strip) on the surface coverage, radial strength, and flexibility of the BCS were systematically studied using computational models. The orthogonal experimental design was adopted to quantitatively analyze the sensitivity of multiple factors using the minimal number of study cases. Results have shown that the nitinol wire diameter and the braiding angle are two most important factors determining the mechanical performance of the BCS. A larger nitinol wire diameter led to a larger radial strength and less flexibility of the BCS. A larger braiding angle could provide a larger radial strength and better flexibility. In addition, the impact of the braiding angle decreased when the stent underwent a large deformation. At the same time, the impact of the PET strips increased due to the interaction with nitinol wires. Moreover, the number of PET strips played an important role in the surface coverage. This study could help understand the mechanical performance of BCS stent and provides guidance on the optimal design of the stent targeting less complications.

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Lokhande, Pravin R., Sethuraman Balaguru, and G. Deenadayalan. "A Review of Contemporary Fatigue Analysis and Biomaterials Studies in Endodontics." Materials Science Forum 969 (August 2019): 193–98. http://dx.doi.org/10.4028/www.scientific.net/msf.969.193.

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The objective of this review article is to review literature on fatigue analysis and biomaterials studies in Endodontics. The nitinol and gutta-percha are widely used biomaterials in the Endodontic fields. The nitinol is used to manufacture the Endodontic files which are used for preparation of the root canal. The preparation of the root canal consist of removal of dead tissue, substrates and debris from the decayed root canal. During the preparation of root canal shaping of the root canal is done to develop the perfectly prepared cavity. The gutta-percha is used to fill the prepared cavity. The nitinol and gutta-percha are important contributing biomaterial for success of root canal treatment. This review article has been reviewed contemporary studies on nitinol and gutta-percha biomaterials. For the success of root canal treatment the fatigue of Endodontic file and three dimensional filling of root canal are two important aspect. The Endodontic files during the cleaning and shaping of the canal gets subjected to torsion fatigue failure or cyclic fatigue failure. The past studies lacks the exact knowledge about these failures as well as analysis approaches to be followed for correct diagnosis. This review article helps to overcome this difficulties. Moreover, the fatigue factors are discussed so that researcher can get little idea about failure point of the nitinol rotary files. The review consist of A contemporary review of nitinol alloy studies, A review of fatigue failure diagnosis, A contemporary review of gutta-percha quality assessment techniques studies, A novel approach for fatigue analysis of nitinol file and A novel approach for quality assessment of gutta-percha etc.

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Atiyah, Qasim Abbas, Ammar Saleem Hameed, and Baqer Jabbar Assi. "Vibration Analysis of Uniform and Tapered Composite Beams with Embedded Shape Memory Alloy." Journal of University of Babylon for Engineering Sciences 27, no. 1 (January 28, 2019): 82–93. http://dx.doi.org/10.29196/jubes.v27i1.1972.

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In this study, laminated composite materials were hybridized with E-glass fiber and Nitinol (Nickel-Titanium) wires. Hand lay-up technique was used to prepare the samples, epoxy resin type (Sikadur 52 N) was used as matrix reinforced by one fiber from E-glass fiber woven roving with embedded nitinol wires with a diameter 0.5 mm for samples and number of wires such as 0, 1, 3, 5 and 9 to find the effect of the number of wires on the natural frequency. The samples were fixed as a cantilever beam. The effects of increasing the number of nitinol wires, the diameter of nitinol wires, the length of the cantilever beam and the thickness of beam on the natural frequencies of the beam were studied. Also, the effects of the tapered in width side and thickness side on the natural frequencies of cantilever beam were studied. The results showed that the increasing in the number of nitinol wires and the diameter of nitinol wires lead to decrease the natural frequency in martensite phase and increase the natural frequency in austenite phase. Also, the increasing in thickness of beam and width ratio of the beam lead to increase the natural frequency. As well as, the increasing in the thickness ratio leads to increase the first natural frequency and decrease the second and third ones. In addition, the increasing in the length of the beam decreases the natural frequency.

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Stepan, Lenka L., Daniel S. Levi, and Gregory P. Carman. "A Thin Film Nitinol Heart Valve." Journal of Biomechanical Engineering 127, no. 6 (July 6, 2005): 915–18. http://dx.doi.org/10.1115/1.2049311.

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In order to create a less thrombogenic heart valve with improved longevity, a prosthetic heart valve was developed using thin film nitinol (NiTi). A “butterfly” valve was constructed using a single, elliptical piece of thin film NiTi and a scaffold made from Teflon tubing and NiTi wire. Flow tests and pressure readings across the valve were performed in vitro in a pulsatile flow loop. Bio-corrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material’s in vivo biocompatibility, thin film nitinol was implanted in pigs using stents covered with thin film NiTi. Flow rates and pressure tracings across the valve were comparable to those through a commercially available 19 mm Perimount Edwards tissue valve. No signs of corrosion were present on thin film nitinol samples after immersion in Hank’s solution for one month. Finally, organ and tissue samples explanted from four pigs at 2, 3, 4, and 6 weeks after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation. Although long term testing is still necessary, thin film NiTi may be very well suited for use in artificial heart valves.

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Murugesan, Kannan, Kalaichelvan K., M. P. Jenarthanan, and Sornakumar T. "Enhancement of vibration characteristics in filament wound FRP composite shafts using nitinol wires." Pigment & Resin Technology 47, no. 5 (September 3, 2018): 377–85. http://dx.doi.org/10.1108/prt-11-2017-0087.

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Purpose The purpose of this paper is to investigate the use of embedded Shape Memory Alloy (SMA) nitinol wire for the enhancement of vibration and damping characteristics of filament-wound fiber-reinforced plastic composite hollow shafts. Design/methodology/approach The plain Glass Fiber-Reinforced Plastic (GFRP) and plain Carbon Fiber-Reinforced Plastic (CFRP) hollow shafts were manufactured by filament winding technique. Experimental modal analysis was conducted for plain hollow shafts of C1045 steel, GFRP and CFRP by subjecting them to flexural vibrations as per ASTM standard C747, with both ends clamped (C-C) end condition to investigate their vibration and damping behavior in terms of first natural frequency, damping time and damping ratio. Nitinol wires pre-stressed at various pre-strains (2, 4 and 6 per cent) were embedded with CFRP hollow shafts following same manufacturing technique, and similar experimental modal analysis was carried out by activating nitinol wires. The first natural frequencies of all the shaft materials were also predicted theoretically and compared with experimental measurements. Findings Among the three materials C1045 steel, plain GFRP and plain CFRP, the vibration and damping behavior were found to be the best for plain CFRP. Hence, CFRP shafts were considered for further improvement by embedding nitinol wires at pre-stressed condition. For CFRP shafts embedded with nitinol wires, the damping time decreased; and damping ratio and first natural frequency increased with increase in percentage of pre-strain. In comparison with plain CFRP, 7 per cent increase in first natural frequency and 100 per cent increase in damping ratio were observed for nitinol embedded CFRP shafts with 6 per cent pre-strain. Theoretical predictions of the first natural frequencies agree well with the experimental results for all the shaft materials. Originality/value The effect of nitinol on vibration and damping characteristics of filament wound hollow CFRP composite shafts with different pre-strains has not been studied extensively by the previous researchers. This paper addresses the effect of embedded nitinol wires pre-stressed at three varied pre-strains, that is, 2, 4 and 6 per cent on the vibration and damping characteristics of composite hollow CFRP shafts manufactured by filament winding technique.

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Takagi, Toshiyuki, Takanori Takeno, Hiroyuki Miki, and Yun Luo. "Metal-Containing DLC: Toward a Smart Coating on Smart Materials." Materials Science Forum 706-709 (January 2012): 2014–19. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2014.

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NiTi shape memory alloys (NiTi-SMA or Nitinol) have successful application thanksto their excellent and unique material properties. However, considering the practical applicationto human body, elution from the toxic Ni ions into human body should be taken into account.Many researchers have dealt with the issue and already proposed various surface treatmenttechniques including the surface oxidation and ion implantation.Our focus is to enhance thefunctionality of Nitinol. We have been developing the smart sensor utilizing metal-containingDiamond-like Carbon (Me-DLC) thin coating. Emphasis can be made on the unique propertiesof Me-DLC deposited on the Nitinol. Strong adhesive strength has been obtained in Me-DLCand Nitinol system. In this paper, we propose a novel Me-DLC coating with multifunctionalityof the suppression of the toxic Ni ions. The paper includes deposition technique, performanceof the coating concerning adhesive strength and suppression of the toxic Ni ions, and ﬁnallymultilayered structure aiming at multifunctionality.

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Salemizadeh Parizi, Fatemeh, Reza Mehrabi, and Mohammad Reza Karamooz-Ravari. "Finite element analysis of NiTi self-expandable heart valve stent." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 233, no. 10 (July 28, 2019): 1042–50. http://dx.doi.org/10.1177/0954411919865404.

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Transcatheter aortic valve implantation is a minimally invasive treatment for severe symptomatic aortic valve stenosis. Nitinol stents are proposed for aortic stenosis patients at high risk. In the present study, at different implantation depths in the aortic valve, the crimping and performance of Nitinol stents are investigated. To do so, a constitutive model based on Microplane theory is utilized and implemented through the finite element to express the constitutive characteristics of Nitinol. The self-expanding stent made of NiTi is designed and simulated using the finite element method. To validate the developed model, the obtained results using beam and solid finite element models are compared with those reported in the literature. Superelastic behavior as well as shape memory effect of the Nitinol stent is studied during crimping and deployment. The simulated results show that the produced radial force increases by increasing the implantation depth in a cardiac cycle.

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Pelton, A. R., D. Stöckel, and T. W. Duerig. "Medical Uses of Nitinol." Materials Science Forum 327-328 (January 2000): 63–70. http://dx.doi.org/10.4028/www.scientific.net/msf.327-328.63.

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Malito, Louis G., Matthew L. Bowers, Paul L. Briant, Gabriel S. Ganot, and Brad James. "Fatigue Fracture of Nitinol." Journal of Failure Analysis and Prevention 22, no. 2 (March 23, 2022): 441–45. http://dx.doi.org/10.1007/s11668-022-01380-2.

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36

Haider, Waseem, N. Munroe, V. Tek, C. Pulletikurthi, P. K. S. Gill, and S. Pandya. "Surface Modifications of Nitinol." Journal of Long-Term Effects of Medical Implants 19, no. 2 (2009): 113–22. http://dx.doi.org/10.1615/jlongtermeffmedimplants.v19.i2.30.

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Reineke, U., J. Ebmeyer, D. Plett, H. Winkler, and H. Sudhoff. "Superelastische Nitinol Stapes Prothesen." Laryngo-Rhino-Otologie 89, no. 05 (March 10, 2010): 271–75. http://dx.doi.org/10.1055/s-0029-1246209.

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Reese, S., and D. Christ. "FEM optimization with Nitinol." Minimally Invasive Therapy & Allied Technologies 13, no. 4 (January 2004): 228–39. http://dx.doi.org/10.1080/13645700410017362.

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39

Slezak, Jane A., and Ronald W. Veresko. "Undergraduate investigation of nitinol." Physics Teacher 30, no. 1 (January 1992): 42–43. http://dx.doi.org/10.1119/1.2343465.

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Shabalovskaya, Svetlana, Gianni Rondelli, and Markus Rettenmayr. "Nitinol Surfaces for Implantation." Journal of Materials Engineering and Performance 18, no. 5-6 (August 2009): 470–74. http://dx.doi.org/10.1007/s11665-009-9498-3.

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Middleton, L. A., N. F. Kennon, and D. P. Dunne. "Metallographic method for nitinol." Metallography 18, no. 1 (February 1985): 51–59. http://dx.doi.org/10.1016/0026-0800(85)90033-3.

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Middleton, L. A., N. F. Kennon, and D. P. Dunne. "Martensitic transformation in nitinol." Metallography 18, no. 1 (February 1985): 61–72. http://dx.doi.org/10.1016/0026-0800(85)90034-5.

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43

Rosenthal, D., M. B. Herring, R. A. McCready, and A. M. Levy. "Angioscope-Assisted Endovascular Occlusion of Venous Tributaries: Preclinical Studies." Cardiovascular Surgery 1, no. 3 (June 1993): 225–27. http://dx.doi.org/10.1177/096721099300100305.

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The feasibility of angioscope-assisted occlusion of venous tributaries from within a vein using a steerable ‘shaped-memory’ nickel-titanium (nitinol) alloy catheter and occlusion coils was evaluated. An initial series of tests was designed to establish the necessary pressure (275 p.s.i., 1897.5kPa), time (1.5s) and volume (2.5 ml normal saline) requirements for hydraulic delivery of platinum occlusion coils from the nitinol catheter through a 3-Fr tracking catheter. In a second series, 25 side branches of the saphenous vein in 11 amputated limbs were visualized angioscopically and cannulated with the nitinol catheter under angioscopic and fluoroscopic surveillance to determine whether the catheter tip could be positioned and coils deployed. In a third series of studies, ten canine femoral vein tributaries were successfully cannulated with an 8-Fr nitinol catheter and 19 occlusion coils delivered under angioscopic surveillance. Fluoroscopy verified coil placement and all embolized venous tributaries were thrombosed. An ideal approach for femoropopliteal in situ saphenous vein bypass would allow the surgeon to divide saphenous vein valves while occluding venous side branches from within the saphenous vein. These initial studies demonstrate that the nitinol catheter can occlude venous tributaries from within a vein by coil embolization. Further development of this technique for clinical investigation is warranted.

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Conceição, Isabella Carolina, Luiz Carlos Martins Dias, Amanda Martins Fernandes, Ricardo Luiz Perez Teixeira, Francisco Moura Filho, Haroldo Lhow Hasegawa, and José Carlos De Lacerda. "PRODUÇÃO DE LIGAS DE MEMÓRIA DE FORMA DE Ni-Ti-Al COM ELEMENTO LIGANTE DE NIÓBIO - RESULTADOS PARCIAIS." Journal of Engineering and Exact Sciences 3, no. 8 (September 6, 2017): 1038–50. http://dx.doi.org/10.18540/jcecvl3iss8pp1038-1050.

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Os materiais metálicos conhecidos como ligas com memória de forma (LMF) apresentam recuperação à sua forma original, depois de serem deformados por alguma carga aplicada, por meio de um tratamento térmico controlado. Dentre os materiais metálicos que apresentam EFM, destaca-se o nitinol (NiTi), que é uma liga equiatômica dos elementos metálicos de titânio e de níquel e que possui ampla aplicação. Neste trabalho, obtiveram-se algumas LMF com o acréscimo de alumínio metálico e de ligante metálico de nióbio ao nitinol. alumínio e o nióbio são materiais estabilizadores da fase α e da fase β do titânio no nitinol, respectivamente. O processamento na obtenção das LMFs se deu por fusão em forno a plasma pelo processo Plasma Skull Push Pull (PSPP). Os tarugos de LMF produzidos e o nitinol foram caracterizados cristalográfica, química, mecânica e termicamente. Observou-se ainda que os elementos ligantes aumentam a dureza do material, fato relacionado, principalmente, a estabilização da fase martensita.

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Ehmann, Tim, M. Geraldine Zuniga, Thomas Lenarz, and Thomas S. Rau. "A method to determine the accuracy of shape setting thin, spirally shaped Nitinol wires." Current Directions in Biomedical Engineering 7, no. 2 (October 1, 2021): 93–96. http://dx.doi.org/10.1515/cdbme-2021-2024.

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Abstract Electric stimulation of the auditory nerve using a cochlear implant (CI) is presumed to be superior when the electrode array (EA) is placed close to the inner wall of the cochlea. Nitinol is investigated as an actuator that enables an intracochlear shape change of the EA from a straight configuration (also necessary for the insertion) to a spiral shape fitting to the inner wall. As shape setting of the thin Nitinol wires is crucial, a method to quantify the accuracy of the shape setting is presented. To measure the trained shape of thin Nitinol wires (ø 100 μm) a contactless, optical method was developed. For each wire, a photomicrograph was captured and processed using a custom Matlab algorithm. Threshold based segmentation followed by morphological operations to remove artefacts were applied to extract the wire’s shape. Utilizing an iterative closest point (ICP) algorithm the actual shape was registered to the desired spiral path. Finally, the root mean squared error describing the deviation between both spirals was calculated as a measure for the “shape error” (εshape). In total 147 Nitinol wires of 16 batches were analyzed to quantify the reliability of the shape setting procedure. The proposed method was successfully applied in all samples. On average εshape was 0.06 ± 0.02 mm. Deviation from the desired shape was < 0.1 mm (< 0.15 mm) in 95% (99%) of the samples. In summary, the presented method is suitable to control the trained shape of thin Nitinol wires. Furthermore, our results confirm a high reliability of the shape setting procedure used for our thin Nitinol actuators intended for future applications in CI EAs.

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Lee, Pei-Yuan, Yen-Nien Chen, Jin-Jia Hu, and Chih-Han Chang. "Comparison of Mechanical Stability of Elastic Titanium, Nickel-Titanium, and Stainless Steel Nails Used in the Fixation of Diaphyseal Long Bone Fractures." Materials 11, no. 11 (November 1, 2018): 2159. http://dx.doi.org/10.3390/ma11112159.

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Elastic nails made of the nickel-titanium shape memory alloy (Nitinol) have been reported to control bone modeling in animal studies. However, the mechanical stability of the Nitinol nail in the fixation of long bone fractures remains unclear. This study compared mechanical stability among nails made of three materials, namely Nitinol, titanium, and stainless steel, in the fixation of long bone fractures. These three materials had identical shapes (arc length: π/2 and radius: 260 mm). A cylindrical sawbone with a 10-mm gap and fixed with two C-shaped elastic nails was used to examine the stability of the nails. A finite element (FE) model was developed based on the sawbone model. The end cap for elastic nails was not used in the sawbone test but was considered based on a constraint equation in FE simulation. The results of stability tests appeared to depend on the presence or absence of the end cap. In the sawbone test, the titanium nail yielded a higher ultimate force against the applied load than did the stainless steel and Nitinol nails before the gap completely closed; the difference in linear stiffness between the nails was nonsignificant. In FE simulation, the titanium nail produced smaller gap shortening than did stainless steel and Nitinol nails without the end cap; the difference in gap shortening between the nails was minor with the end cap. The titanium elastic nail should be a better choice in managing diaphyseal long bone fractures when the end cap is not used. For Nitinol and stainless steel nails, the end cap should be used to stop the nail from dropping out and to stabilize the fractured bone.

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SHABALOVSKAYA, SVETLANA, ANDREAS UNDISZ, MARKUS RETTENMAYR, and GIANNI RONDELLI. "FUNCTIONALITY OF BARE NITINOL SURFACES." Functional Materials Letters 02, no. 02 (June 2009): 67–71. http://dx.doi.org/10.1142/s1793604709000582.

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The results of pilot in situ studies of the responses of Nitinol surfaces to deformation are presented. It is shown that the mechanical behavior of Nitinol surfaces differs, depending on oxide thickness and its chemical composition. The corrosion resistance of the surfaces evaluated in strain-free and strained states using potentiodynamic and potentiostatic cyclic polarization at the body potentials demonstrated quite stable behavior.

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Kondo, Daisuke, Tomohiko Yoshioka, Toshiyuki Ikoma, Kensuke Takamatsu, Kunihiro Ohta, and M. Tanaka. "Electrolytic Deposition of Calcium Phosphates Films on Nitinol Stents." Key Engineering Materials 529-530 (November 2012): 243–46. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.243.

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Calcium phosphates films were deposited onto pipes and stents of nitinol alloys by an electrolytic deposition (ELD) method. Monocalcium phosphate (Ca (H2PO4)2·H2O) solutions were used as the electrolyte, and electric depositions were carried out at the constant cathode current of 1.59 mA/cm2 at 65°C for 60 min. From the deposition on nitinol pipes, deposition rates were changed in 15 minutes and the precipitates were identified to be octacalcium phosphate (Ca8H2(PO4)6·5H2O) and dicalcium phosphate anhydrous (CaHPO4). The electrolytic depositions on the nitinol alloys were useful for the formation of calcium phosphates films on the complex shape of stents.

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Wang, Binhao, Bin He, Guohua Fu, Mingjun Feng, Xianfeng Du, Jing Liu, Yibo Yu, and Huimin Chu. "Safety and Efficacy of Left Atrial Catheter Ablation in Patients with Left Atrial Appendage Occlusion Devices." Journal of Clinical Medicine 11, no. 11 (May 31, 2022): 3110. http://dx.doi.org/10.3390/jcm11113110.

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Background: Left atrial appendage occlusion (LAAO) is an alternative to oral anticoagulation for thromboembolic prevention in patients with atrial fibrillation (AF). Left atrial (LA) catheter ablation (CA) in patients with LAAO devices has not been well investigated. Here, we report on the safety and efficacy of LA CA in patients with nitinol cage or plug LAAO devices. Methods: A total of 18 patients (aged 67 ± 11 years; 14 males; 5 paroxysmal AF) with LAAO devices (nitinol cage, n = 10; nitinol plug, n = 8) and symptomatic LA tachyarrhythmias were included. Periprocedural and follow-up data were assessed. Results: A total of 20 LA CA procedures were performed at a median of 130 (63, 338) days after LAAO. The strategy of CA consisted of circumferential pulmonary vein isolation (n = 16), linear lesions (n = 14) and complex fractionated atrial electrogram ablation (n = 6). No major adverse events occurred periprocedurally. Repeated transesophageal echocardiography showed no device-related thrombus, newly developed peridevice leakage or device dislodgement. After a median follow-up period of 793 (376, 1090) days, four patients (22%) experienced LA tachyarrhythmias recurrence and two received redo LA CA. No patients suffered stroke or major bleeding events during follow-up. Conclusions: LA CA in patients with LAAO devices (either nitinol cages or nitinol plugs) seems to be safe and efficient in our single-center experience.

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Stepputat, Vincent N., Henning Zeidler, Daniel Safranchik, Evgeny Strokin, and Falko Böttger-Hiller. "Investigation of Post-Processing of Additively Manufactured Nitinol Smart Springs with Plasma-Electrolytic Polishing." Materials 14, no. 15 (July 22, 2021): 4093. http://dx.doi.org/10.3390/ma14154093.

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Additive manufacturing of Nitinol is a promising field, as it can circumvent the challenges associated with its conventional production processes and unlock unique advantages. However, the accompanying surface features such as powder adhesions, spatters, ballings, or oxide discolorations are undesirable in engineering applications and therefore must be removed. Plasma electrolytic polishing (PeP) might prove to be a suitable finishing process for this purpose, but the effects of post-processing on the mechanical and functional material properties of additively manufactured Nitinol are still largely unresearched. This study seeks to address this issue. The changes on and in the part caused by PeP with processing times between 2 and 20 min are investigated using Nitinol compression springs manufactured by Laser Beam Melting. As a benchmark for the scanning electron microscope images, the differential scanning calorimetry (DSC) measurements, and the mechanical load test cycles, conventionally fabricated Nitinol springs of identical geometry with a medical grade polished surface are used. After 5 min of PeP, a glossy surface free of powder adhesion is achieved, which is increasingly levelled by further polishing. The shape memory properties of the material are retained without a shift in the transformation temperatures being detectable. The decreasing spring rate is primarily attributable to a reduction in the effective wire diameter. Consequently, PeP has proven to be an applicable and effective post-processing method for additively manufactured Nitinol.

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Journal articles on the topic 'Nitinol'

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