• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.347-351
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• 2010

판과 같은 구조물의 손상 감지를 위해, 손상 전 구조물의 임피던스 신호를 기저신호(Baseline impedance signal)로 이용하여 직접적으로 비교하지 않는 새로운 개념의 무기저 손상진단 기법(Reference-free impedance method)을 제시한다. 박막 압전소자(이하 PZT)를 판의 상하 표면에 부착시킨 한 쌍의 병치 PZT를 이용하여 손상으로 인해 모드변환을 일으키는 전기역학적 신호(Electro Mechanical Signatures ; 이하 EMS)를 추출한다. 이 연구에서는 스펙트럼 요소법(Spectral Element Method ; 이하 SEM)을 이용하여 주파수 영역에서 병치된 PZT의 EMS를 파악하기 위한 수치해석을 수행한다. 특히, 손상에 의해 발생된 모드변환 EMSMC를 병치된 PZT의 극성에 기인한 신호분해 기법을 적용하여 추출하고, 분해된 모드변환 EMSMC가 손상의 위치와 크기에 따라 받는 영향을 추가로 분석한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.567-573
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• 2014

Since the development of microelectromechanical systems (MEMS) technology for the medical field, various micro-fluid transfer systems have been studied. This paper proposes a micro-piezoelectric pump that imitates a stomach's peristalsis by using two separate piezoelectric elements, in contrast to existing micro-pumps. This piezoelectric pump is operated by using the valve-less traveling wave of peristalsis movement. If the piezoelectric plates at the two separated plates are actuated at the input voltage, a traveling wave occurs between the two plates. Then, the fluid migrates by the pressure difference generated by the traveling wave. Finite element analysis was performed to understand the mechanics of the combined system with piezoelectric elements, elastic structures, and fluids. The effects of design variables such as the chamber height and number of ceramics on the flow rate of the fluid were examined.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1997.11a
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• pp.251-257
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• 1997

압전 바이몰프형 엑츄에이터에 진동판을 부착한 압전팬은 압전 바이몰프의 굴곡진동을 이용한 요동식 팬으로, 코일식 모타 팬에 비해 구조 및 풍량의 조절이 간단하고 미소량의 풍량 (1m/s)을 일으킬 수 있다. 또한 전자적인 잡음이 발생치 않는다. 수명이 재래 전자팬은5,000-10,000시간인데 비해 약 25,000시간으로 길며 압전체이기 때문에 대응한 전자석 로타리 팬 전력의 1/15mw이하의 저 소비전력을 갖는등의 잇점을 가지고 있다. (중략)

• Composites Research
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• v.18 no.6
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• pp.26-33
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• 2005

The mechanical properties of composite materials may severely degrade in the presence of damage. Especially, the high-velocity impact such as bird strike, a hailstorm, and a small piece of tire or stone during high taxing, can cause considerable damage to the structures and sub-system in spite of a very small mass. However, it is not easy to detect the damage in composite plates using a single technique or any conventional methods. In this paper, the PVDF(polyvinylidene fluoride) film sensors were used for monitoring high-velocity impact damage initiation and propagation in composite laminates. The WT(wavelet transform) and STFT(short time Fourier transform) are used to decompose the sensor signals. A ultrasonic C-scan and a digital microscope are also used to examine the extent of the damage in each case. This research shows how various sensing techniques, PVDF sensor in particular, can be used to characterize high-velocity impact damage in advanced composite.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.497-502
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• 2015

In this paper, a stress function-based approach was proposed to analyze the reduction of free-edge peeling stress in smart composite laminates using piezoelectric actuator under bending load. Electro-mechanically coupled governing equation was obtained by complimentary virtual work principle. The stress state was solved by the generalized eigenvalue procedure. The free-edge peeling stress of smart composite laminates was reduced by the piezoelectric actuation. The reduction rate of peeling stress in cross-ply composite laminate is larger than that in angle ply composite laminate.

• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.12-17
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• 1997

In this work, we developed a new type ultrasonic dehumidifier with piezoelectric ceramics, which and efficiently repel waterdrops on outdoor glass plates exposed to raindrops. Through finite element analysis of a certain type of glass plates to analyze its dynamic behavior, the structure of the ultrasonic device we determined to get the optimal performance. A supplemental metal plate was attached to the glass plate for uniform cleaning. Based on the theoretical results, experimental samples were fabricated and evaluated with various dimensions of the glass plate and the piezoceramic vibrator. Driving circuit for the dehumidifier made use of the frequency sweeping technique to keep track of the resonant frequency of the glass plate that was variant with environmental conditions.

• The Journal of the Acoustical Society of Korea
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• v.17 no.3
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• pp.37-46
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• 1998

본 연구에서는 압전 세라믹인 PZT를 이용하여 두께 진동모드의 다중모드 필터를 설계, 제작하였다. 다중모드 세라믹필터의 등가회로를 설계하였고, 이를 이용하여 설계변수 인 물성변수와 형상변수에 따른 필터전달특성의 경향을 분석하였다. 이를 바탕으로 10.7MHz의 중심주파수를 가지는 세라믹필터를 제작하였고, 설계변수 중에서 압전세라믹 기 판과 전극형상의 변화에 따른 필터의 전달특성의 변화를 실험적으로 검증하였다. 본 연구를 통한 경향분석결과는 다양한 진동모드와 다양한 주파수대를 가지는 다중모드 필터를 설계하 는데 있어서 유용한 도구로 사용될 수 있을 것이다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.994-1000
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• 2011

In this study, the piezoelectric fan cooling system is investigated. In order to find the proper geometry and configuration, the numerical model for the flow field and heat transfer investigation is used. A simplified nonlinear deformation model is employed for transient solutions of a piezoelectric fan with the dynamic mesh and user defined function capability. The results show that the cooling is most effective when the length of a piezoelectric fan is 5 cm and the cooling plate is 3 cm. The results can be used to develop a new design method of heat sink for piezoelectric fans.

• Journal of Korean Association for Spatial Structures
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• v.7 no.6
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• pp.83-90
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• 2007

Today, many studies are progressed about source of vibration oscillator in reinforcement concrete structures. Source of vibration oscillator is load when it is happen from walking inhabitant. It is transmitted to another inhabitant through reinforcement concrete plate, and it is type of elastic wave. Those descriptions are ram wave and primary wave, secondary wave, and the are through the surface and inside plate. Analysis studies of those waves are used to piezoelectric materials. But, they are difficult to 3 axial type of transmitting elastic wave in concrete element. In this study, a fundamental study for source estimations of vibration oscillator using micro accelerometer are discussed.

• The Journal of the Acoustical Society of Korea
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• v.29 no.8
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• pp.483-490
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• 2010

In this paper, an Inter-Digital Transducer (IDT) type Lamb wave sensor is proposed to estimate the geometry and number of cracks on a plate structure, and its validity is checked through experiments. This IDT type sensor is more readily controllable than conventional patch type piezoelectric sensors to modify its operation frequency and directionality by altering its finger patterns. In this work, omni-directional annular IDT and highly directional rectangular IDT sensors are designed and fabricated. The IDT sensors are used to diagnose the length, number and orientation of cracks on an aluminum plate by measuring the amplitude and time of flight of Lamb waves. The results are analyzed to discuss the efficacy of the IDT sensors.