• 폴리머
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• 제33권1호
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• pp.84-90
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• 2009

니티놀(Nitinol) 합금(TiNi)은 혈관 스텐트로서 널리 사용되고 있다. 본 연구에서는 니티놀 합금의 혈액적 합성을 개선시키기 위해서 화학적인 표면개질을 행하였다. 먼저 니티놀의 표면을 금으로 코팅한 다음 시스턴(L-cysteine, C/N)을 화학흡착한 후 신규 합성한 양쪽성 이온 폴리에틸렌글리콜(PEG) (PEG-$N^+-SO_3{^-}$)을 그래프트 시켜서 TiNi-C/N-PEG-N-S를 제조하였다. 양쪽성 이온 PEG가 그래프트된 니티놀의 표면은 ATR-FTIR, ESCA 및 SEM을 통해서 확인하였고 친수성 표면은 물 접촉각의 감소를 통해서 입증하였다. 또한, 단백질 흡착 및 혈소판 점착과 혈액응고시간 측정과 같은 혈액적합성 평가 결과로부터 미처리 니티놀 합금에 비해서 표면개질된 니티놀 합금이 상대적으로 훨씬 우수한 혈액적합성을 나타내었다. 이는 그래프트된 친수성 PEG와 항응혈성 양쪽성 이온의 상승효과에 의해서 혈액적합성을 대폭 개선시킨 것으로 사료된다.

• 한국생산제조학회지
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• 제18권6호
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• pp.551-557
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• 2009

A development of smart materials is becoming a prominent issue on present industries. A smart material, included in functions, is needed for micro fabrication. A shape memory alloy(SMA) in a smart material is best known material. Ni-Ti alloy, composed of nikel and titanium is one of the best shape memory alloy(SMA). Nitinol SMA is used for a lot of high tech industry such as aero space, medical device, micro actuator, sensor system. However, Ni-Ti SMA is difficult to process to make a shape and fabrications as traditional machining process. Because nitinol SMA, that is contained nikel content more than titanium content, has similar physical characteristics of titanium. In this paper, the characteristics of ECM grooving process for nitinol SMA are investigated by experiments. The experiments in this study are progressed for power, gap distance and machining time. The characteristics are found each part. Fine shape in work piece can be found on conditions; current 6A, duty factor 50%, gap distance 15%, gap distance $15{\mu}m$, machining time 10min.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.199-200
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• 2008

• 한국공작기계학회논문집
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• 제16권6호
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• pp.49-54
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• 2007

Electropolishing, the anodic dissolution process without contact with tools, is a surface treatment method to make a surface planarization using an electrochemical reaction with low current density. Nitinol is a metal alloy composed of Ni and Ti around 50% respectively which has shape memory effect. Nitinol can be put various applications which require purity and high pricision surface of products. The aim of this study is to investigate the characteristic of electropolishing effect for nitinol workpieces. In order to analyze the characteristics of electropolishing effect, surface roughness and micro-burr size were measured in terms of machining conditions such as current density, machining time and electrode gap. The tendencies about improvement of surface roughness and deburring effect by electropolishing for nitinol workpieces were determined.

• 대한치과교정학회지
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• 제40권1호
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• pp.40-49
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• 2010

본 연구의 목적은 martensitic (M-NiTi), austenitic (A-NiTi) 및 thermodynamic nickel-titanium wire (T-NiTi)의 물리적 특징과 상전이 정도를 평가하는 것이다. 재료는 $0.016\;{\times}\;0.022$ inch의 M-NiTi (Nitinol Classic, NC), A-NiTi (Optimalloy, OPTI)와 T-NiTi (Neo-Sentalloy, NEO)이었으며, differential scanning calorimetry (DSC), 3점굽힘실험, X-ray diffraction (XRD), 미세구조 분석을 시행하였으며, ANOVA test로 통계처리하였다. DSC분석 결과 OPTI와 NEO는 heating curve에서 2개의 peak, cooling curve에서 1개의 peak를 보였고, NC는 heating과 cooling curve에서 1개의 넓고 약한 peak를 보였다. Austenite finishing ($A_f$) 온도는 OPTI $19.7^{\circ}C$, NEO $24.6^{\circ}C$, NC $52.4^{\circ}C$였다. 3점굽힘실험 결과 NC, OPTI, NEO 모두 residual deflection을 보였으며, NC와 OPTI의 load range가 NEO보다 컸다. XRD와 미세구조 분석결과 OPTI와 NEO는 Martensite finishing ($M_f$)에서 martensite와 austenite가 섞여 있음이 관찰되었다. NEO와 OPTI는 NC보다 개선된 물리적 특징과 상전이 행태를 보였다. NiTi 호선의 물리적, 온도에 따른 행태는 예상되었던 상전이 정도에 의해 완벽하게 설명되지 않았으며, 그 이유는 복잡한 martensite variants의 존재와 열과 stress에 의해 유도된 독립적인 상전이에 기인한다고 생각된다.

• 소성∙가공
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• 제33권5호
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• pp.330-340
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• 2024

The martensitic Ni-Ti shape memory alloys(SMA) can achieve a two-way shape memory effect (TWSME) through thermomechanical training/cycling. In this study, the surface of Ni-Ti SMA sheets was treated by depositing a certain number of titanium (Ti) powder layers using a selective laser meling (SLM) process to enhance TWSME. The results showed that a unique TWSME of approximately 12% with good stability was achieved after 100 training cycles when the optimum number of five Ti layers was deposited. A larger HAZ and lower cooling rate pushed more Ti particles into the grains rather than the grain boundaries, providing more time for Ti to react with NiTi to form Ti-rich intergranular Ti2Ni(Ox) precipitates. This resulted in further hindering of dislocation movement within the grains and the generation of internal stress fields required for attaining a larger TWSME. With an increase in the number of Ti-deposited layers, there was no noticeable reduction in the one-way shape memory effect (OWSME) through the initial cycling. This was due to the high residual tensile stress caused by the lower thermal expansion of the Ti layer compared to the Ni-Ti sheet.

• Smart Structures and Systems
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• 제21권3호
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• pp.257-262
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• 2018

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.

• 열처리공학회지
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• 제22권6호
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• pp.368-374
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• 2009

Nickel titanium shape memory alloys (NiTi) have been investigated for applications in the biomedical industry. However, little is known about the influences of surface modifications on the propertise of these alloys. The effect of electropolishing and heat treatments was found to exhibit significant surface roughness. Change of phase was B2, r-phase and B19' by heat treatments. In this study, effect of the electropolishing conditions on surface roughness is investigated in Ni-Ti alloys (Nitinol). Variation in phases with heat treatment temperature is investigated for a Ni-Ti alloy by X-ray diffraction and DSC. Characteristic of the microstructure have been observed by SEM. Surface roughness have been measured by AFM. The results clearly show that significant different in surface property to heat treated at $500^{\circ}C$ (R-phase). $TiO_2$ phases preciritated all of the specimens. It is not good effect of surface roughness because made to surface relief. The surface roughness appears to be important in the property of Ni-Ti alloys for biomedical applications.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.426-429
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• 2003

In this study, phase transformation characteristics of Nitinol shape memory alloy with 54.5wt%Ni-45.5wt%Ti were investigated by varying with annealing treatment and cutting conditions through DSC(differential scanning calorimetry). Annealing treatment conditions were considered as heat treated time of 5 min, 15 min, 30 min, and 45 min, heat treated temperature of 40$0^{\circ}C$, 50$0^{\circ}C$, 5$25^{\circ}C$, 55$0^{\circ}C$, 575$^{\circ}C$, $600^{\circ}C$, $700^{\circ}C$, 80$0^{\circ}C$, and 90$0^{\circ}C$, and environmental condition of heat treatment under vacuum or air. Cutting conditions were considered as no cutting, one side cutting, and two side cutting. Tensile test was also conducted on Nitinol shape memory alloy to investigate thermomechanical characteristics by varying with annealing heat treatment histories. According to the results, annealing treatment and cutting conditions were found to significantly affect on phase transformation and thermomechanical characteristics of Nitinol shape memory alloy.

• 대한치과교정학회지
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• 제48권3호
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• pp.153-162
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• 2018

Objective: The aim of this trial was to compare the alignment efficiency and intermaxillary arch dimension changes of nickel-titanium (NiTi) or copper-nickel-titanium (CuNiTi) round archwires with increasing diameters applied sequentially to the mandibular arch. Methods: The initial alignment phase of fixed orthodontic treatment with NiTi or CuNiTi round archwires was studied in a randomly allocated sample of 66 patients. The NiTi group comprised 26 women, 10 men, and the CuNiTi ($27^{\circ}C$) group comprised 20 women, 10 men. The eligibility criteria were as follows: anterior mandibular crowding of minimum 6 mm according to Little's Irregularity Index (LII), treatment requiring no extraction of premolars, 12 to 18 years of age, permanent dentition, skeletal and dental Class I malocclusion. The main outcome measure was the alignment of the mandibular anterior dentition; the secondary outcome measure was the change in mandibular dental arch dimensions during 12 weeks. Simple randomization (allocation ratio 1:1) was used in this single-blind study. LII and mandibular arch dimensions were measured on three-dimensional digital dental models at 2-week intervals. Results: No statistically significant difference was observed between NiTi and CuNiTi according to LII (p > 0.05). Intercanine and intermolar arch perimeters increased in the CuNiTi group (p < 0.001). Inter-first premolar width showed a statistically significant interaction in week ${\times}$ diameter ${\times}$ application (p < 0.05). Conclusions: The effects of NiTi and CuNiTi round archwires were similar in terms of their alignment efficiency. However, the intercanine and intermolar arch perimeters, and the inter-first premolar width changes differed between groups.