• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.5
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• pp.309-317
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• 2004

This paper suggested the vibration characteristic improvement by variation mode of ring type ultrasonic motor. Design for the piezoelectric ceramic and elastic body of stator were calculated by the finite element method(FEM) that consider the resonance frequency, vibration mode and coupling efficiency etc. Through the result of vibration analysis from 6 order mode to 8 mode, the 7 order mode was gained very an excellent results that it was the coupling efficient, minimum power loss and bending vibration value. Here over 7 order mode, this paper was acquired that an output current for input voltage was very a large increased results. The result of vibration calculation, from thickness 0.5[mm] to 2[mm], knew the fact that the vibration displacement at 0.5[mm] is an high value too. From such result, this paper was manufactured the ultrasonic motor of outer diameter 5O[mm] , inter 22[mm] having the about 43.86[KHz] resonance frequency. We have gated that a simulation result is 42.2[KHz] and an experiment result is 43.86[KHzl The propriety of this paper was established though comparison. investigation of simulation and experiment result.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.448-454
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• 2008

The purpose of this paper is to discuss the fabrication of $\beta$-PVDF($\beta$-Polyvinylidene fluoride, ${\beta}-PVF_2$) organic thin films through the vapor deposition method and to investigate the piezoelectric properties of the organic thin films produced. Vapor deposition was performed under the following conditions : the temperature of evaporator, the applied electric field and the pressure of reaction chamber were $270^{\circ}C$, 142.4 kV/cm and $2.0{\times}10^{-5}Torr$, respectively. The results showed that the amount of $\beta$-form PVDF increased from 72 % to 95.5 % with an increase in the substrate temperature. In the case of a sensor response characteristic by varying the force moment from $1.372{\times}10^{-5}N{\cdot}m$ to $39.2{\times}10^{-5}N{\cdot}m$, the output voltage increased from 1.39V to 7.04V.

• Journal of KSNVE
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• v.6 no.1
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• pp.65-70
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• 1996

The sensor response of a piezoelectric transducer embedded in a fluid loaded structure is modeled using a hybrid numerical approach. The structure is excited by an obliquely incident acoustic wave. Finite element modeling in the structure and fluid surrounding the transducer region, is used and a plane wave representation is exploited to match the displacement field at the mathematical boundary. On this boundary, continuity of field derivatives is enforced by using a penalty factor and to further achieve transparency at the mathematical boundary, drilling degrees of freedom (d.o.f.) are introduced to ensure continuity of all derivatives. Numerical results are presented for the sensor response and it is found that the sensor at that location is not only non-intrusive but also sensitive to the characteristic of the structure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.3
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• pp.231-234
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• 2008

For the applications which need a micro-power supply such as thin and flat displays, micro-robot, and micro-system, it is especially necessary to integrate the passive components because they typically need more than 2/3 of the space of the conventional circuit. Therefore, we have designed and fabricated a novel piezoelectric micro transformer using the PZT thin film and MEMS technologies for application to the energy supply device of the micro-systems. The dimensions of the micro-transformer is $1000{\mu}m\;{\times}\;400{\mu}m\;{\times}\;4.8{\mu}m$ $(length{\times}width{\times}thickness)$. The dynamic displacement of around $9.2{\pm}0.064{\mu}m$ was observed at 10 V. The dynamic displacement varied almost linearly with applied voltage. The average voltage gain (step-up ratio) was approximately 2.13 at the resonant frequency $(F_r=8.006KHz)$ and load resistance $(R_L)$ of 1 $M{\Omega}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.11
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• pp.892-897
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• 2001

Variations of dielectric and piezoelectric properties and associated phase transformation of <001> -oriented rhombohedral 0.92Pb (Zn$\sub$1/3/Nb$\sub$2/3/)O$_3$-0.08PbTiO$_3$ single crystals were investigated. The longitudinal strain level was found to abruptly increase at 15 kV/cm, corresponding to that where an induced phase appears within a multidomain matrix. Drastic decreases in the dielectric constant, transverse coupling, and transverse piezoelectric coefficient associated with the E-field induced phase were the result of increased crystal anisotropy in PZN-PT crystals. By contrast, the thickness coupling increased from 53 % at 0 kV/cm to 64 % at 45 kV/cm, also associated with this phase transition under the E-field. The measured dielectric and piezflelectric properties found for the induced phase state were nearly identical to those of <001> poled tetragonal (1-x)PZN-xPT (x>0.1) crystals. Based on these results, it is evident that the symmetry of induced phase is tetragonal.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.392-395
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• 2011

In this paper, a vibration energy harvesting circuit using the piezoelectric element has been designed. MPPT (maximum power point tracking control) control function has been implemented to deliver the maximum power to the load by using the electric power-voltage characteristic of the piezoelectric element. The designed MPPT circuit traces the maximum power point by sampling periodically the open circuit voltage of the full wave rectifier circuit and delivers the maximum available power to the load. The vibration energy harvesting circuit is designed with $0.18{\mu}m$ CMOS process. The maximum power efficiency is 91%, and the chip area except pads is $1,100{\mu}m{\times}730{\mu}m$.

• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.194-200
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• 1999

In this paper studied was the piezoelectric properties of the $\beta$-PVDF organic thin films prepared by physical vapour deposition method. The molecular orientation of organic thin films was controlled by the application of an electric field and variation of substrate temperature during the evaporation process. Optimum conditions of manufacturing $\beta$-PVDF organic thin film by physical vapor deposition method is to keep at the substrate temperature of $80^{\circ}C$, at the applied electric field of 142.8 kV/cm. The voltage output coefficient increased from 1.39 to 7.04V increasing the force moment.

• Smart Structures and Systems
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• v.18 no.3
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• pp.471-484
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• 2016

Optical fiber sensors have been proven that they have the potential to detect high-frequency ultrasonic signals, in structural health monitoring field which generally refers to acoustic emission signals from active structural damages and guided waves excited by ultrasonic actuators and propagating in waveguide. In this work, the sensing properties of optical fiber sensors based on Mach-Zehnder interferometer were investigated in the metal plate. Analytical formulas were conducted first to explore the parameters affecting its sensing performances. Due to the simple and definable frequency component, the Lamb wave excited by the piezoelectric wafer was employed to study the sensitivity of the proposed optical fiber sensors with respect to the frequency, rather than the acoustic emission signals. In the experiments, according to above investigations, spiral shape optical fiber sensors with different size were selected to increase their sensitivity. Lamb waves were excited by a circular piezoelectric wafer, while another piezoelectric wafer was used to compare their voltage responses. Furthermore, by changing the excitation frequency, the tuning frequency characteristic of the proposed optical fiber sensor was also investigated experimentally.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.51-59
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• 2012

Piezoelectric langasite crystals have superior properties such as high temperature performance and high quality Q and can be applied in combustion pressure sensors and surface acoustic wave (SAW) filters. Crystal growth, crystal structure and properties of langasite group are reviewed, and the mechanism of piezoelectricity of langasite is presented based on the crystal structure and deformation under high pressure. Finally, for the discovery of new piezoelectric materials, this paper presents the role of the framework, and recommends the search of framework crystal structure, because the characteristic of the mechanism exists on the framework of the crystal structure.

• Journal of the Korean Society for Nondestructive Testing
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• v.12 no.4
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• pp.9-17
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• 1993

Three types of piezoelectric sensors to detect acoustic emission signals were developed and characterized. Epicentral displacement and velocity of a plate to have infinite boundary were calculated by convolution between a Green's function and a simulated source time function to show parabolic rising characteristic. The sensor calibration system set up was composed of a steel plate, a glass capillary, an indentor and a load cell indicator The transient elastic signals were detected by the sensors. The results were compared with the theoretical results and Fast Fourier Transformed. As the results, the sensor fabricated using a disk shape of a piezoelectric PZT element showed resonant characteristics. The sensors fabricated using a conical shape PZT element and a PVDF polymer film showed the wide band characteristics for particle displacement and velocity, respectively. The calculated results showed good agreements with the transient responses in the cases of the wide band sensors and it was confirmed that the simulated source time function had been properly assumed.