• 한국생산제조학회지
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• 제9권1호
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• pp.38-44
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• 2000

The background of this study lies in he investigation of the formation mechanism of ductile mode(nkanometer-size) chips of brittle materials such as fine ceramics glass and silicon. As the first step to achieve this purpose this paper intends to observe the micro-deformation behavior of these materials in sub${\mu}{\textrm}{m}$ depth indentation tests using a diamond indentor. In this study it was developed Ultra-Micro Indentation. Device using the PZT actuator. Experimentally by using the Ultra-Micro Indentation device the micro fracture behavior of the silicon wafer was investigated. It was possible that ductile-brittle transition point in ultimate surface of brittle material can be detected by adding an acoustic emission sensor system to the Ultra-Micro Indentation appartus.

• 대한기계학회논문집B
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• 제30권4호
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• pp.350-357
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• 2006

A new valveless micropump for bi-directional application has been developed and tested. The micropump was fabricated on silicon and glass substrates by micromachining process. The micropump in this study consists of a membrane actuator, a pumping chamber, fluidic channels and two piezoelectric ceramic films. The channels and pumping chamber were etched on a glass wafer and the membrane was made on a silion wafer which is actuated by a piezoelectric ceramic (PZT) film. The geometry of the micropump was optimized by numerical analysis and the performance of the micropump was investigated by the experiments. The maximum flow rate was $323{\mu}L/min$ and the maximum back pressure was 294 Pa when the membrane actuator of $10{\times}10mm^2$ was driven at 130 Hz and 385 V.

• Smart Structures and Systems
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• 제16권5호
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• pp.835-851
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• 2015

This paper presents theoretical and experimental evaluation of the structural health monitoring (SHM) capability of piezoelectric wafer active sensors (PWAS) at elevated temperatures. This is important because the technologies for structural sensing and monitoring need to account for the thermal effect and compensate for it. Permanently installed PWAS transducers have been One of the extensively employed sensor technologies for in-situ continuous SHM. In this paper, the electro-mechanical impedance spectroscopy (EMIS) method has been utilized as a dynamic descriptor of PWAS behavior and as a high frequency standing wave local modal technique. Another SHM technology utilizes PWAS as far-field transient transducers to excite and detect guided waves propagating through the structure. This paper first presents how the EMIS method is used to qualify and quantify circular PWAS resonators in an increasing temperature environment up to 230 deg C. The piezoelectric material degradation with temperature was investigated and trends of variation with temperature were deduced from experimental measurements. These effects were introduced in a wave propagation simulation software called Wave Form Revealer (WFR). The thermal effects on the substrate material were also considered. Thus, the changes in the propagating guided wave signal at various temperatures could be simulated. The paper ends with summary and conclusions followed by suggestions for further work.

• 반도체디스플레이기술학회지
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• 제22권3호
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• pp.21-27
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• 2023

In this article, a plate-type megasonic cleaning system with cooling pins is proposed for the sliced ingot, which is a raw material of silicon (Si) wafers. The megasonic system is operated with a lead zirconate titanate (PZT) actuator, which has high electric resistance, thus when it is being operated, it dissipates much heat. So this article proposes a megasonic system with cooling pins. In the design process, finite element analysis was performed and the results were used for the design of the waveguide. The frequency with the maximum impedance value was 998 kHz, which agreed well with the measured value of 997 kHz with 0.1 % error. Based on the results, the 1 MHz waveguide was fabricated. Acoustic pressures were measured, and analyzed. Finally, cleaning tests were performed, and 90 % particle removal efficiency (PRE) was achieved over 10 W power. These results imply that the developed 1 MHz megasonic will effectively clean sliced ingot wafer surfaces.

• 한국전산구조공학회논문집
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• 제24권5호
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• pp.553-567
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• 2011

최근 3년간 판 구조물 건전성 감시분야에서 시간반전램파(Time reversal Lamb waves)의 가능성이 주목받고 있다. 이 연구에서는 직사각형 평판에서 시간반전램파의 공간모임을 적은 연산비용으로 효과적으로 모사할 수 있는 수치기법을 제안한다. 제안된 기법에서는 파 반사에 의해 발생하는 실제 탐지자의 거울상 효과와 등가를 이루는 활성 가상탐지자를 이용하여 시간반전과정을 주파수 영역에서 정식화한다. 시간반전램파의 공간모임 모사에서 필요한 순방향 및 역방향 파 전달은 스칼라 형태의 함수로 표현한다. 제안된 방법을 웨이퍼 형태의 압전소자가 병치된 직사각형 평판에서 시간반전램파의 공간 모임 문제에 적용하고 유한요소해석 결과와 비교하여 타당성을 검증한다.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1514-1519
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• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• 대한토목학회논문집
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• 제37권1호
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• pp.217-229
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• 2017

보의 표면에 부착된 압전웨이퍼를 통해 가진되고 측정되는 고주파수 대역의 전기역학적 신호는 보에 발생한 미세 손상에 매우 민감하다. 이러한 부착형 압전웨이퍼의 장점을 이용한 보의 손상 진단을 효과적으로 수행하기 위해서는 압전웨이퍼의 탐지범위 예측이 필요하다. 고주파수 대역에서 압전웨이퍼의 탐지범위에 영향을 주는 여러 가지 요인 중 가장 지배적인 인자는 보의 감쇠이다. 이 연구에서는 보에 부착된 압전웨이퍼의 전기역학적 신호를 이용하여 보의 감쇠를 추정할 수 있는 기법을 제시한다. 공진이 발생하는 과정에서 보의 감쇠효과를 고려하여 압전웨이퍼의 전기역학적 신호를 파전달 관점에서 정식화한다. 실제 계측된 전기역학적 신호로부터 구한 측정 감쇠비 함수값과 정식화된 전기역학적 신호로부터 계산된 감쇠비 함수값의 차이를 최소화하는 최소자승법을 통해 보의 감쇠비를 추정한다. 제시된 방법을 압전웨이퍼가 병치되어 있는 알루미늄 보 수치 및 실험 예제에 적용하여 타당성을 검증한다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.337-341
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• 2010

In this paper, an extremely low voltage operated micro corner cube retroreflector (CCR) was fabricated for free-space optical communication applications by using bulk silicon micromachining technologies. The CCR was comprised of an orthogonal vertical mirror and a horizontal actuated mirror. For low voltage operation, the horizontal actuated mirror was designed with two PZT cantilever actuators, torsional bars, hinges, and a mirror plate with a size of $400{\mu}m{\times}400{\mu}m$. In particular, the torsional bars and hinges were carefully simulated and designed to secure the flatness of the mirror plate by using a finite element method (FEM) simulator. The measured tilting angle was approximately $2^{\circ}$ at the applied voltage of 5 V. An orthogonal vertical mirror with an extremely smooth surface texture was fabricated using KOH wet etching and a double-SOI (silicon-on-insulator) wafer with a (110) silicon wafer. The fabricated orthogonal vertical mirror was comprised of four pairs of two mutually orthogonal flat mirrors with $400{\mu}m4 (length) $\times400{\mu}m$ (height) $\times30{\mu}m$ (thickness). The cross angles and surface roughness of the orthogonal vertical mirror were orthogonal, almost $90^{\circ}$ and 3.523 nm rms, respectively. The proposed CCR was completed by combining the orthogonal vertical and horizontal actuated mirrors. Data transmission and modulation at a frequency of 10 Hz was successfully demonstrated using the fabricated CCR at a distance of approximately 50 cm.

• 한국항공우주학회지
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• 제30권5호
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• pp.94-100
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• 2002

본 논문은 곡면형 압전 복합재료 작동기 LIPCA의 개발 및 성능 실험에 관한 것이다. LIPCA는 압전 세라믹을 중심으로 상층부는 탄성계수가 크면서 열팽창계수가 낮은 섬유강화 복합재료층이 위치하며, 하층부는 탄성계수가 작으면서 열팽창계수가 큰 섬유강화 복합재료층이 위치한다. 작동기의 성능 검증을 위해 작동지그 및 전압 공급 장치 그리고 비접촉 레이저 센서로 이루어진 실험 시스템을 구성하였다. 성능 실험은 양단 단순지지상태에서 압전 재료의 전극에 $100\sim400V_{pp}$의 교류 전압을 1Hz로 가하였을 경우 작동기 중앙부에서 발생하는 수직방향의 변위를 측정하는 것으로 수행하였다. LIPCA와 THUNDER의 성능 검증 결과 LIPCA-C2는 THUNDER에 비해 34% 경량화 되었으며, 작동변위는 13% 향상되었다.

• 한국소음진동공학회논문집
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• 제26권3호
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• pp.270-280
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• 2016

노치가 있는 보에 부착된 압전소자의 전기역학적 어드미턴스 전이과정을 파전달 관점에서 규명한다. 유한요소 해석을 통해 노치가 있는 보에서 잔향하는 램파에 대한 수치해를 구한다. 보에 병치된 압전소자의 분극을 이용하여 노치에 의해 발생하는 모드변환된 램파 신호를 추출한다. 전기역학적 어드미턴스의 전이과정을 보여줄 수 있는 일련의 템포럴 스펙트럼은 모드변환된 램파 신호들을 시간영역에서 순차적으로 절단한 후, 고속 푸리에 변환을 적용하여 계산한다. 절단 시간이 상대적으로 작을 때 이에 대응되는 템포럴 스펙트럼은 입력 주파수 대역의 특성이 지배적이다. 그러나, 절단 시간이 증가함에 따라 입력 주파수 대역 내에 존재하는 보의 모달 특성이 템포럴 스펙트럼에 중대한 영향을 준다. 이는 보에서 잔향하는 모드변환램파가 보의 공진에 기여함을 의미한다. 각 공진주파수 부근에서 템포럴 스펙트럼에 대한 제곱평균제곱근을 계산한다. 모든 공진주파수 부근에서 절단시간에 따라 제곱평균제곱근은 증가한다. 마지막으로, 보의 손상 진단 측면에서 수치해석 결과의 시사점에 대해 논의한다.