• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.96-103
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• 2005

One of the major problems limiting the accuracy of piezoelectric transducers fur cylinder pressure measurements in an internal combustion (IC) engine is the thermal shock. Thermal shock is generated from the temperature variation during the cycle. This temperature variation results in contraction and expansion of the diaphragm and consequently changes the force acting on the quartz in the pressure transducer An empirical equation for compensation of the thermal shock error was derived from consideration of the diaphragm thermal deformation and actual pressure data. The result indicate that the thermal shock equation provides reliable correction based on known surface temperature swing.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.1-5
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• 2002

This paper is concerned with the dynamic modeling of a rectangular plate with piezoelectric actuators and sensors. The experimental frequency response plots can be used to verify the theoretical modeling. Theoretical analysis will follow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.309.1-309
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• 2002

This paper is concerned with the dynamic modeling of a rectangular plate with piezoelectric actuators and sensors. The experimental frequency response plots can be used to verify the theoretical modeling. The active vibration control was achived by using positive position feedback controller. Theoretical analysis will follow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.471-475
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• 2001

This paper is concerned with the experiments on the dynamic characteristics and active vibration control of plate with piezoceramic sensors and actuators. The experimental frequency response plots can be used to verify the theoretical modeling. The active vibration control was achived by using a single-input single-output positive position feedback controller. Theoretical analysis will follow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.483-488
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• 2002

This paper is concerned with the experiments on the dynamic characteristics and modeling of plate with piezoceramic sensors and actuators. The experimental frequency response plots can be used to verify the theoretical modeling. Theoretical analysis will follow.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06d
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• pp.13-17
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• 1998

집속음장이 고조파성분을 이용한 초음파영상의 특성을 해석하는 초기단계로서 음축에 수직하게 놓인 강체판의 직선 edge가 집속 가우스빔을 회절시킨다고 가정하고, edge의 전후에서 발생하는 제 2고조파를 고려해서 회절음장을 해석하였다. 계산에서는 그린함수의 간단화를 위해 , Fresnel 근사를 이용하였고 실험에서는 성형전극을 형성시킨 요면 압전진동자에 의한 1.9MHz 집속가우스음원에 의해 만들어지는 초음파 빔에 수직하게 edge을 삽입시켰다. 회절 edge 후방에서 음장을 관측한 결과, 제 2고조파의 빔형상을 제외하고는 계산치와 실험치가 잘 일치하고 있다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.4 s.97
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• pp.395-403
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• 2005

The dynamic characteristics of delaminated smart composite laminates are studied using animproved layerwise laminate theory. The theory is capable of capturing interlaminar shear stresses that are critical to delamination. The presence of discrete delamination is modeled through the use of Heaviside unit step functions. Stress free boundary conditions are enforced at all free surfaces. Continuity in displacement field and transverse shear stresses are enforced at each ply level. In modeling piezoelectric composite plates, a coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. Numerical analysis is conducted to investigate the effect of nonlinearity in the transient vibration of bimodular behavior caused by the contact impact of delaminated interfaces. Composite plates with delamination, subject to external loads and voltage history from surface bonded sensors, are investigated and the results are compared with corresponding experimental results and plates without delamination.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.553-567
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• 2011

During the last three years, the possibility of the time reversal Lamb waves has been paid attention to for structural health monitoring of a plate. This study proposes a numerical scheme which can simulate the spatial focusing of time reversal Lamb waves on a rectangular plate. In this scheme, a time reversal process is formulated in the frequency domain using active virtual sensors being equivalent to the mirror effects of an actual sensor due to wave reflection on the plate boundary. Forward and backward Lamb wave propagations are represented by scalar functions for simulating the spatial focusing of time reversal Lamb waves. The validity of the proposed scheme is demonstrated through the comparison to the results of finite element analysis in which the spatial focusing of time reversal Lamb waves is realized by wafer-type piezoelectric(PZT) transducers collocated on a rectangular plate.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.308-317
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• 2009

In the present work, a sensor system composed of an oscillator sensor and a Lamb wave sensor is proposed for the purpose of structural health monitoring. The oscillator sensing system detecting the shift of a structural resonant frequency in proportion to the amount of defects in the structure is a pretty sensitive and simple device, but its detectable range is limited to its local zone. The Lamb wave sensor system, however, is applicable to global detection of the defects. This study is aimed at investigating the feasible combination of the two systems to exploits their merits simultaneously. The scheme to use PZT patches as the oscillator sensor as well as the Lamb wave sensor was proposed to identify the position, length and number of cracks by means of TOF and amplitude of signals, and its validity was confirmed through experiments.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2
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• pp.18-24
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• 1999

In this paper, we have investigated on the development of ultrasonic speakers that have higher directivity and much wider bandwidth than those of conventional loudspeakers. For optimal structure of speaker, we have analyzed material properties and dimension of the piezoelectric element and the vibrating metal plate, and their support type as well as the housing case. Based on the design, we have fabricated ultrasonic speaker prototypes, measured their performance, and verified validity of the design theory. For higher sound pressure level, the ultrasonic array speaker prototype has been fabricated in the form of an array. The design and fabrication method worked in this paper can be utilized in development of various ultrasonic speakers with higher directivity and broader bandwidth.