• Title/Summary/Keyword: shape memory alloy material

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A study on the Improvement of the Performance of Biodirectional NITINOL Actuator (NITINOL을 이용한 차동식 액츄에이터의 동작성능 향상을 위한 연구)

  • Jung, Sang-Hwa;Kim, Hyun-Wook;Cha, Kyung-Rae;Song, Seok;Shin, Byung-Soo;Lee, Kyung-Hyung
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1577-1580
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    • 2003
  • In the recent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. The dynamic characteristic analysis of SMA is necessary for actuator application and many common researches report the material characteristics of SMA sufficiently. However, the research on dynamic characteristics is very deficient. In this paper, the helical spring are fabricated with NiTi SMA wire of high resistivity. The force, response speed, temperature, and displacement are measured by digital force gauge, infrared thermometer, and laser displacement sensor so that the dynamic characteristics of this SMA is analyzed. Also, bidirectional actuator was fabricated and experimented for its performance.

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Experimental Test and Numerical Simulation on the SMA Characteristics and Behaviors through the Load-Training (하중 트레이닝을 통한 형상기억합금의 특성 실험과 거동 전산 모사)

  • Kim, Sang-Haun;Cho, Maeng-Hyo
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.700-705
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    • 2007
  • In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loading-unloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

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Experimental Test and Numerical Simulation on the SMA Characteristics and Behaviors for Repeated Actuations (반복적인 작동을 위한 형상기억합금의 특성 실험과 거동 전산 모사)

  • Kim, Sang-Haun;Cho, Maeng-Hyo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.3 s.258
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    • pp.373-379
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    • 2007
  • In this study, we observe the application of shape memory alloy(SMA) into smart structures for repeatable actuation, because SMA changes its material properties and characteristics progressively under cyclic loading conditions and finally reaches stable path(state) after a certain number of stress/temperature loading-unloading cycles, so called 'training'. In this paper, SMA wires that have been in a stable state through the training are used. Stress-strain curve of the SMA wire at different temperature levels are measured. In addition, we observe other important effects such as the rate effect according to strain rates for rapid actuation response. The current work presents the experimental test using SMA wire after training completion by mechanical cycling. Through these tests, we measure the characteristics of SMA. With the estimated SMA properties and effects, we compare the experimental results with the simulation results based on the SMA constitutive equations.

An efficient vibration control strategy for reliability enhancement of HAWT blade

  • Sajeer, M. Mohamed;Chakraborty, Arunasis;Das, Sourav
    • Smart Structures and Systems
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    • v.26 no.6
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    • pp.703-720
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    • 2020
  • This paper investigates the safety of the wind turbine blade against excessive deformation. For this purpose, the performance of the blade in the along-wind direction is improved by longitudinal stiffener made of shape memory alloy. The rationale behind the selection of this smart material is due to its ability to offer excellent thermo-mechanical behaviour at low strain. Here, Liang-Roger model is adopted for vibration control, and the super-elastic effects are utilised for blade stiffening. Turbulent wind fields are generated at the hub height using TurbSim and the corresponding loads are evaluated using blade element momentum theory. An efficient switching algorithm is developed along with performance curves that enable the designer to select an optimal mode of heating depending upon the operational scenario. Numerical results presented in this paper clearly demonstrate the performance envelope of the proposed stiffener and its influence on the reliability of the blade.

Seismic performance of concrete frames reinforced with superelastic shape memory alloys

  • Youssef, M.A.;Elfeki, M.A.
    • Smart Structures and Systems
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    • v.9 no.4
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    • pp.313-333
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    • 2012
  • Reinforced concrete (RC) framed buildings dissipate the seismic energy through yielding of the reinforcing bars. This yielding jeopardizes the serviceability of these buildings as it results in residual lateral deformations. Superelastic Shape Memory Alloys (SMAs) can recover inelastic strains by stress removal. Since SMA is a costly material, this paper defines the required locations of SMA bars in a typical RC frame to optimize its seismic performance in terms of damage scheme and seismic residual deformations. The intensities of five earthquakes causing failure to a typical RC six-storey building are defined and used to evaluate seven SMA design alternatives.

Closed-form solution for the buckling behavior of the delaminated FRP plates with a rectangular hole using super-elastic SMA stitches

  • Soltanieh, Ghazaleh;Yam, Michael CH.;Zhang, Jing-Zhou;Ke, Ke
    • Structural Engineering and Mechanics
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    • v.81 no.1
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    • pp.39-50
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    • 2022
  • Layer separation (delamination) is an essential threat to fiber-reinforced polymer (FRP) plates under dynamic, static, and fatigue loads. Under compressive load, the growth of delamination will lead to structural instability. The aim of this paper is to present a method using shape memory alloy (SMA) stitches to suppress the delamination growth in a FRP plate and to improve the buckling behavior of the plate with a rectangular hole. The present paper is divided into two parts. Firstly, a closed-form (CF) formulation for evaluating the buckling load of the FRP plate is presented. Secondly, the finite element method (FEM) will be employed to calculate the buckling loads of the plates which serves to validate the results obtained from the closed-form method. The novelty of this work is the development of the closed-form solution using the p-Ritz energy approach regarding the stress-dependent phase transformation of SMA to trace the equilibrium path. For the FEM, the Lagoudas constitutive model of the SMA material is implemented in FORTRAN programming language using a user material subroutines (VUMAT). The model is simulated in ABAQUS/Explicit solver due to the nature of the loading type. The cohesive zone model (CZM) is applied to simulate the delamination growth.

Applicability of Cu-Al-Mn shape memory alloy bars to retrofitting of historical masonry constructions

  • Shrestha, Kshitij C.;Araki, Yoshikazu;Nagae, Takuya;Omori, Toshihiro;Sutou, Yuji;Kainuma, Ryosuke;Ishida, Kiyohito
    • Earthquakes and Structures
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    • v.2 no.3
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    • pp.233-256
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    • 2011
  • This paper investigates the applicability of newly developed Cu-Al-Mn shape memory alloy (SMA) bars to retrofitting of historical masonry constructions by performing quasi-static tests of half-scale brick walls subjected to cyclic out-of-plane flexure. Problems associated with conventional steel reinforcing bars lie in pinching, or degradation of stiffness and strength under cyclic loading, and in their inability to restrain residual deformations in structures during and after intense earthquakes. This paper attempts to resolve the problems by applying newly developed Cu-Al-Mn SMA bars, characterized by large recovery strain, low material cost, and high machinability, as partial replacements for steel bars. Three types of brick wall specimens, unreinforced, steel reinforced, and SMA reinforced specimens are prepared. The specimens are subjected to quasi-static cyclic loading up to rotation angle enough to cause yielding of reinforcing bars. Corresponding nonlinear finite element models are developed to simulate the experimental observations. It was found from the experimental and numerical results that both the steel reinforced and SMA reinforced specimens showed substantial increment in strength and ductility as compared to the unreinforced specimen. The steel reinforced specimen showed pinching and significant residual elongation in reinforcing bars while the SMA reinforced specimen did not. Both the experimental and numerical observations demonstrate the superiority of Cu-Al-Mn SMA bars to conventional steel reinforcing bars in retrofitting historical masonry constructions.

Adaptive-length pendulum smart tuned mass damper using shape-memory-alloy wire for tuning period in real time

  • Pasala, Dharma Theja Reddy;Nagarajaiah, Satish
    • Smart Structures and Systems
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    • v.13 no.2
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    • pp.203-217
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    • 2014
  • Due to the shift in paradigm from passive control to adaptive control, smart tuned mass dampers (STMDs) have received considerable attention for vibration control in tall buildings and bridges. STMDs are superior to tuned mass dampers (TMDs) in reducing the response of the primary structure. Unlike TMDs, STMDs are capable of accommodating the changes in primary structure properties, due to damage or deterioration, by tuning in real time based on a local feedback. In this paper, a novel adaptive-length pendulum (ALP) damper is developed and experimentally verified. Length of the pendulum is adjusted in real time using a shape memory alloy (SMA) wire actuator. This can be achieved in two ways i) by changing the amount of current in the SMA wire actuator or ii) by changing the effective length of current carrying SMA wire. Using an instantaneous frequency tracking algorithm, the dominant frequency of the structure can be tracked from a local feedback signal, then the length of pendulum is adjusted to match the dominant frequency. Effectiveness of the proposed ALP-STMD mechanism, combined with the STFT frequency tracking control algorithm, is verified experimentally on a prototype two-storey shear frame. It has been observed through experimental studies that the ALP-STMD absorbs most of the input energy associated in the vicinity of tuned frequency of the pendulum damper. The reduction of storey displacements up to 80 % when subjected to forced excitation (harmonic and chirp-signal) and a faster decay rate during free vibration is observed in the experiments.

Analytical Behavior Characteristics Analysis of Automatic Restoring Friction Slit Damper (자동복원 마찰슬릿댐퍼의 해석적 거동특성 분석)

  • Lee, Heon-Woo;Hu, Jong-Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.44 no.4
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    • pp.425-432
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    • 2024
  • In this study, we propose a self-restoring friction slit damper by combining the concepts of self-restoring dampers, friction dampers, and steel dampers that are currently used and researched. For this purpose, an innovative damper structure was designed using superelastic shape memory alloy for automatic recovery and combining the concepts of friction damper and slit damper. Afterwards, detailed design was carried out and variables such as material, with of strut, and bolt fastening force were set. Modeling was performed using the ABAQUS program for a total of 12 dampers, and finite element analysis was performed by substituting the designed loading protocol. As a result, the self-recovering friction slit damper using superelastic shape memory alloy was excellent in terms of load, but the energy dissipation ability was not significantly secured due to the excellent recovery performance. However, friction slit dampers made of Gr.50 steel have dramatically improved performance in terms of load and energy dissipation through innovative structural improvements. Through this, the innovative structure of the damper, which combines the mechanisms of a friction damper and a steel damper, was demonstrated.