• Journal of Urban Science
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• v.11 no.1
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• pp.1-8
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• 2022

As the magnitude and frequency of earthquakes increase in Korea, interest in earthquake damage reduction technology has increased. Therefore, research on vibration damping devices that directly respond to seismic loads is being actively researched. After an earthquake, damage or destruction of the device occurs due to the yield of materials, and thus it takes considerable cost and time for restoration and replacement. To supplement the problems of the existing earthquake damage reduction technology, a study was conducted on the recentering smart damper that can be used continuously after an earthquake. In this study, the recentering smart damper that can be restored to its original shape after load removal was developed using superelastic shape memory alloy, pre-compressed polyurethane. General steel was commonly applied to verify the seismic performance of the superelastic shape memory alloy, and the performance of the smart damper was verified according to the amount of polyurethane pre-compressed

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.219-222
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• 2013

Alloy 690 has been selected as a steam generator tubing material for SMART owing to a near immunity to primary water stress corrosion cracking. The steam generators of SMART are faced with a neutron flux due to the integrated arrangement inside a reactor vessel, and thus it is important to know the irradiation effects of the thermal conductivity of Alloy 690. Alloy 690 was irradiated at HANARO to fluences of (0.7-28) ${\times}10^{19}n/cm^2$ (E>0.1MeV) at $250^{\circ}C$, and its thermal conductivity was measured using the laser-flash equipment in the IMEF. The thermal conductivity of Alloy 690 was dependent on temperature, and it was a good fit to the Smith-Palmer equation, which modified the Wiedemann-Franz law. The irradiation at $250^{\circ}C$ did not degrade the thermal conductivity of Alloy 690, and even showed a small increase (1%) at fluences of (0.7~28) ${\times}10^{19}n/cm^2$ (E>0.1MeV).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.579-580
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• 2010

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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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.

• Journal of the Korean Society of Clothing and Textiles
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• v.44 no.6
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• pp.1154-1162
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• 2020

In this study, the soft textile actuator is produced for a smart wearable with the shape memory effects from linear shape memory alloys of Nickel and Titanium using the driving force through the fabrication process. The measurement model was designed to measure dynamic characteristics. The heating method, and memory shape of the linear shape memory alloy were set to measure the operating temperature. A shape memory alloy at 40.13℃, was used to heat the alloy with a power supply for the selective operation and rapid reaction speed. The required amount of current was obtained by calculating the amount of heat and (considering the prevention of overheating) set to 1.3 A. The fabrication process produced a soft textile actuator using a stitching technique for linear shape memory alloys at 0.5 mm intervals in the general fabric. The dynamic characteristics of linear shape memory alloys and actuators were measured and compared. For manufactured soft textile actuators, up to 0.8 N, twice the force of the single linear shape memory alloy, 0.38 N, and the response time was measured at 50 s.

• Smart Structures and Systems
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• v.8 no.4
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• pp.367-384
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• 2011

This paper presents the design and experimental evaluation of fast output sampling feedback controller to minimize structural vibration of a cantilever beam using Shape Memory Alloy (SMA) wires as control actuators and piezoceramics as sensor and disturbance actuator. Linear dynamic models of the smart cantilever beam are obtained using online recursive least square parameter estimation. A digital control system that consists of $Simulink^{TM}$ modeling software and dSPACE DS1104 controller board is used for identification and control. The effectiveness of the controller is shown through simulation and experimentation by exciting the structure at resonance.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.4
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• pp.328-338
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• 2007

One of main advantages of composite using smart material as reinforcement can be controlled cracks behavior inside the composite. If the smart composite is applied as part of the structure, the use of the shape memory effect of the smart material is the best way to protect the propagation of cracks generated in the structure while use. In this study, the optical manufacturing conditions for the smart composite were derived. In order to evaluate the shape memory effect by shape memory alloy, the tensile load was applied to the smart composite and stress distribution was inspected. And then, the smart composite was heated to a certain temperature and the shape memory alloy would shrink to the original shape. Finally, at this point the recovering status of stress using photoelastic instrument was discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.25-31
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• 2022

Recently, investment in the aerospace industry has increased, and titanium alloys have been widely adopted for manufacturing parts in the aerospace industry. The Ti-6Al-4V alloy has high strength in high-temperature and high-pressure environments and is evaluated as a material with excellent heat, corrosion, and abrasion. However, titanium alloys are expensive, difficult to cut, and possess a large cutting load during the drilling process. In this study, the cutting force generated in the drilling process of Ti-6Al-4V alloy was verified via finite element analysis (FEM) and cutting force measurement experiments. A structural analysis was performed based on the cutting analysis data to verify the plastic deformation occurring during the drilling process of cylindrical Ti-6Al-4V alloy aircraft parts. Methods were proposed to predict the amount of deformation that occur during the manufacturing process of titanium-alloy aircraft parts and control the external environment, to minimize the amount of deformation.

• Wind and Structures
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• v.30 no.2
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• pp.211-217
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• 2020

Vibrations of a wind turbine blade have a negative impact on its performance and result in failure of the blade, therefore an approach to effectively control vibration in turbine blades are sought by wind industry. The small domestic horizontal axis wind turbine blades induce flap wise (out-of-plane) vibration, due to varying wind speeds. These flap wise vibrations are transferred to the structure, which even causes catastrophic failure of the system. Shape memory alloys which possess physical property of variable stiffness across different phases are embedded into the composite blades for active vibration control. Previously Shape memory alloys have been used as actuators to change their angles and orientations in fighter jet blades but not used for active vibration control for wind turbine blades. In this work a GFRP blade embedded with Shape Memory Alloy (SMA) and tested for its vibrational and material damping characteristics, under martensitic and austenite conditions. The embedment portrays 47% reduction in displacement of blade, with respect to the conventional blade. An analytical model for the actuated smart blade is also proposed, which validates the harmonic response of the smart blade.

• Journal of Powder Materials
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• v.27 no.2
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• pp.139-145
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• 2020

The powder manufacturing process using the gas atomizer process is easy for mass production, has a fine powder particle size, and has excellent mechanical properties compared to the existing casting process, so it can be applied to various industries such as automobiles, electronic devices, aviation, and 3D printers. In this study, a modified A4032-xSn (x = 0, 1, 3, 5, and 10 wt.%) alloy with low melting point properties is investigated. After maintaining an argon (Ar) gas atmosphere, the main crucible is tilted; containing molten metal at 1,000℃ by melting the master alloy at a high frequency, and Ar gas is sprayed at 10 bar gas pressure after the molten metal inflow to the tundish crucible, which is maintained at 800℃. The manufactured powder is measured using a particle size analyzer, and FESEM is used to observe the shape and surface of the alloy powder. DSC is performed to investigate the change in shape, according to the melting point and temperature change. The microstructure of added tin (Sn) was observed by heat treatment at 575℃ for 10 min. As the content of Sn increased, the volume fraction increased to 1.1, 3.1, 6.4, and 10.9%.