• 센서학회지
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• 제18권6호
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• pp.461-466
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• 2009

This paper represents a piezoelectric ultrasonic linear actuator with flexural vibration mode. The actuator is composed of two piezo ceramics, the elastic body, and the connecting tip. It is driven by the frictional force between the connecting tip and the linear motion guide. Unimorph actuators have flexural vibration. Its middle point is fixed so that suitable to the flexural vibration of $3/2\lambda$. These vibrations contribute to elliptical motion by mixed mode between longitudinal and transverse mode. It was generated when the ultrasonic electrical signals with 90 degree phase difference are applied to two ceramics. A linear movement can be easily obtained using the elliptical motion. The ATILA, FEM simulator has been used to design actuator and verify the kinetic and dynamic analysis. We used the ceramics of $20\times10\times1$ mm size and confirmed the flexural vibration of the $3/2\lambda$ at the 79 kHz through the scanning of 3D-vibrometer. The maximum velocity of actuator was 221 mm/sec and the thrust force of actuator was 2.7 N in 200Vp-p of additional voltage.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.135-138
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• 2000

본 논문에서는 열팽창계수(CTE)가 거의 없는 카본게폭시, PZT 세라믹 박판, 그리고 열팽창계수가 큰 글래스/에폭시 층으로 이루어진 곡면형 복합재료 작동기(LIPCA)의 설계, 제작 및 성능실험에 대한 연구성과를 제시하고 있다. LIPCA의 른 요점은 기존 THUNDER의 성능을 유지하면서 이를 경량화 하기 위하여 THUNDER의 금속 층을 상대적으로 가벼운 섬유 강화 복합재료로 대체하는 것이다. 이러한 경량화 작업으로 LIPCA는 기존 THUNDER 보다 약 30~40% 정도의 무게를 감소시킬 수 있으며, 복합재료의 특성에 따라 설계의 유연성을 가질 수 있는 장점이 있다. 또한, 에폭시 수지를 사용함으로써 접착제 없이 평판 몰드에서 오토클레이브에서 177$^{\circ}C$로 경화되어, 탈형된 후 충분한 곡률을 형성하였다. 작동 성능 실험에서, LIPCA는 기존 THUNDER보다 작동변위가 향상됨을 보였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.126-129
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• 2001

LIPCA (LIghtweight Piezo-composite Curved Actuator) is an actuator device which is lighter than other conventional piezoelectric ceramic type actuator. LIPCA is composed of a piezoelectric ceramic layer and fiber reinforced light composite layers, typically a PZT ceramic layer is sandwiched by a top fiber layer with low CTE (coefficient of thermal expansion) and base layers with high CTE. LIPCA has curved shape like a typical THUNDER (thin-layer composite unimorph feroelectric driver and sensor), but it is lighter an than THUNDER. Since the curved shape of LIPCA is from the thermal deformation during the manufacturing process of unsymmetrically laminated lay-up structure, an analysis for the thermal deformation and residual stresses induced during the manufacturing process is very important for an optimal design to increase the performance of LIPCA. To investigate the thermal deformation behavior and the induced residual stresses of LIPCA at room temperature, the curvatures of LIPCA were measured and compared with those predicted from the analysis using the classical lamination theory. A methodology is being studied to find an optimal stacking sequence and geometry of LIPCA to have larger specific actuating displacement and higher force. The residual stresses induced during the cooling process of the piezo-composite actuators have been calculated. A lay-up geometry for the PZT ceramic layer to have compression stress in the geometrical principal direction has been designed.

• 대한기계학회논문집A
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• 제31권8호
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• pp.870-879
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• 2007

In this study, various damage modes in bending unimorph piezoelectric composite actuators with a thin sandwiched PZT plate during bending fracture tests have been evaluated by monitoring acoustic emission (AE) signals in terms of waveform and peak frequency as well as AE parameters. Three kinds of actuator specimens consisting of woven fabric fiber skin layers and a PZT ceramic core layer are loaded with a roller and an AE activity from the specimen is monitored during the entire loading using an AE transducer mounted on the specimen. AE characteristics from a monolithic PZT ceramic with a thickness of $250{\mu}m$ are examined first in order to distinguish different AE signals from various possible damage modes in piezoelectric composite actuators. Post-failure observations and stress analyses in the respective layers of the specimens are conducted to identify particular features in the acoustic emission signal that correspond to specific types of damage modes. As a result, the signal classification based on waveform and peak frequency analyses successfully describes the failure process of the bending piezoelectric composite actuator exhibiting diverse failure mechanisms. Furthermore, it is elucidated that when the PZT ceramic embedded actuators are loaded mechanical bending loads, the failure process of actuator specimens with different lay-up configurations is almost same irrespective of their lay-up configurations.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.275-276
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• 2002

Active-head sliders with a unimorph piezoelectric actuator for flying height control were experimentally evaluated. It was found that the normalized stroke of the actuator is 5.2 to 6 nm/V/mm without flying over the disk. However, the normalized adjustment range of flying height is about 1.6 nm/V/mm when the active-head slider is flying over the disk. This value is smaller than the measured value when the slider is not flying, because of the air pressure generated at the active pad when the pad approaches the disk surface.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 봄 학술발표회 논문집
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• pp.461-469
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• 2002

This paper deals with a fully coupled piezoelectric-mechanical assumed strain solid element that can be used for geometric and material nonlinear modeling of thin piezoelectric actuators. Since the assumed strain solid element can alleviate locking, the element is suitable for performance analysis of very thin actuators without locking. A finite element code is developed based on the finite element formulation and validated by solving typical numerical examples such as bimorph and unimorph beams. Using thecode, we have conducted performance analysis for LIPCA actuator. The estimated actuation displacement of LIPCA agrees well with experimental data under low prescribed voltage.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1282-1285
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• 2004

The high voltage driving system with multi-phase shifter including piezoelectric actuators comprised a driving power unit for outputting the driving power by converting input alternate current into direct current, a frequency shifting unit for supplying the direct current power and shifting or generating a frequency, a high-voltage amplification unit for amplifying the input signal outputted from the driving power unit and the frequency shifting unit into a high-voltage signal, and a phase shifting unit for shifting the phase difference of the amplified signal applied to the high-voltage amplification unit and driving plural piezoelectric actuators sequentially. The results that the operating voltage was stable, the voltage loss ratio was low and the response velocity was fast could be obtained. An experiment on performance of the high voltage driving system with multi-phase shifter designed and manufactured as above described was conducted by using a piezoelectric pump having 3 sheets of round unimorph piezoelectric actuators laminated respectively in a rectangular case. It sucks any fluid by causing the first piezoelectric actuator to shift from the inlet porter side, the phase delay of 60$^{\circ}$ causes the second piezoelectric actuator to begin to shift, and the phase delay of 120$^{\circ}$ causes the third piezoelectric actuator to begin to shift. As a result of measuring each change in the outlet flow rate of the piezoelectric pump, it was shown that the frequency-flow rate characteristic, the voltage-flow characteristic, and the load pressure-flow rate characteristic were improved.

• Journal of Mechanical Science and Technology
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• 제18권4호
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• pp.622-629
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• 2004

In this paper, effects of elastic energy of magnetostrictive film on the deflection of a cantilevered film-substrate system are investigated. The total energy including the elastic energy of magnetostrictive film is formulated. And it is minimized to give the curvatures and the position of neutral axis of the cantilevered system. To discuss the effects of the elastic energy of film in a measured system, three magnetostrictive unimorph cantilevers and a bimorph cantilever reported elsewhere are reviewed. It is shown that the assumption, since the thickness of film is much smaller than that of substrate the film elastic energy is negligible, can cause considerable error in evaluating magnetostrictive coefficients. Not the ratio of thicknesses but elastic energies between film and substrate is also shown to play important role in making decision whether the assumption is valid or not.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1521-1527
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• 2000

A micromirror actuated by piezoelectric unimorph cantilevers is proposed as a tine-tracking device for high-density optical data storage. Bending motions of the metal/PZT/metal unimorphs translate an integrated micromirror along the out-of-plane vertical direction. The micromirror alters the optical path of the incident laser beam and linearly steers the reflected laser beam by its out-of-plane parallel actuation. Numerical analysis shows that the actuated micromirror can satisfy the tracking speed imposed by the requirement on the access time for the high-density optical data storage up to few tens Gbitlin2 owing to the light mass of the micromirror. In this paper, preliminary characteristics of the micro-machined PZT actuated micromirror (PAM) are reported. Only a 360 nm-thick PZT film deposited by sol-gel process shows both good electrical and mechanical characteristics for the fine-tracking actuator. The micromirror can be easily actuated up to several micrometers under low voltage operation condition well below 10 volts.

• 폴리머
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• 제26권1호
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• pp.113-120
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• 2002

전기변형(electrostriction)이란 물체에 전압을 인가했을 때 맥스웰 응력이 나타나고, 이로 인하여 물체가 변형되는 현상을 말한다. 이러한 성질은 대부분의 유전체에서 나타나는데, 특히 탄성계수가 낮은 엘라스토머에 적용하면 전기에너지가 효율적으로 변환되어 큰 변형과 힘을 발현한다. 이렇게 전기변형을 크게 일으키는 고분자를 전기변형 고분자(electrostrictive polymer, EP)로 분류하며, 이들은 구동체 및 센서, 인공근육, 음향전달 장치 분야로의 활용이 유망한 재료로 예견되고 있다. 본 연구에서는 폴리우레탄과 아크릴 고무 등의 유전성 탄성체(dielectric elastomer)를 이용하여 전극-EP-전극의 적층을 이루는 유니모프 구동체를 제조하여 구동시켰고 주파수를 증가시키면서 작동시킬 때 구동체의 운동범위가 감소하는 현상을 전기적, 기계적으로 해석하고자 유전율과 탄성율을 주파수에 따라 측정하는 한편, 고전적 적층이론을 이용하여 EP의 구동역학을 모델링 하였다. 실험결과, 주파수 증가에 따른 구동체의 운동 변위 감소는 재료의 유전 완화시간과 밀접한 관계를 가졌음을 알 수 있었고, 고전적 적층이론으로 해석한 유니모프 구동체의 운동은 실제 적용한 우레탄 구동체의 운동과 상당히 유사한 거동을 보였다.