• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.300-302
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• 1999

The standing waves of the fourth bending mode of vibration and first longitudinal mode of vibrator were utilized to construct a ultrasonic linear motor. The geometrical dimensions of the vibrator were determined by Euler-Bernoulli theoty. FEM(finite element method) employed to calculate the vibration mode of the metal-piezoceramic composite thin plate vibrator. ANSYS was used to design positions of the projections and calculate displacement of vibrator.

• Advances in nano research
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• v.13 no.2
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• pp.147-164
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• 2022

This article investigates the longitudinal vibration of a nanorod embedded in viscoelastic medium according to the nonlocal strain gradient theory. Viscoelastic medium is considered based on Kelvin-Voigt model. Governing partial differential equation is derived based on longitudinal equilibrium and analytical solution is obtained by adopting harmonic motion solution for the nanorod. Modal frequencies and corresponding damping ratios are presented to demonstrate the influences of nonlocal parameter, material length scale, elastic and damping parameters of the viscoelastic medium. It is observed that material length scale parameter is very influential on modal frequencies especially at lower values of nonlocal parameter whereas increase in length scale parameter has less effect at higher values of nonlocal parameter when the medium is purely elastic. Elastic stiffness and damping coefficient of the medium have considerable impacts on modal frequencies and damping ratios, and the highest impact of these parameters on frequency and damping ratio is seen in the first mode. Results calculated based on strain gradient theory are quite different from those calculated based on classical elasticity theory. Hence, nonlocal strain gradient theory including length scale parameter can be used to get more accurate estimations of frequency response of nanorods embedded in viscoelastic medium.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.142-150
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• 2004

A preliminary study of the behavior of ultrasonic guided wave mode in a pipe using a comb transducer for maintenance inspection of power plant facilities has been verified experimentally. The mode identification has been carried out in a pipe using the time-frequency analysis methods such as the wavelet transform(WT) and the short time Fourier transform (STFT), compared with theoretically calculated group velocity dispersion curves for longitudinal and flexural modes. The results are in good agreement with analytical predictions and show the effectiveness of using the time-frequency analysis method to identify the individual modes. It was found out that the longitudinal mode(0,1) is less affected by mode conversion compared with the other modes. Therefore, L(0,1) is selected as an optimal mode for the evaluation of the surface defect in a pipe.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.180-188
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• 2007

In this paper the longitudinal control problem for the large WIG(wing-in-ground effect) craft is considered in the sense of the control augmentation system(CAS) derived by control surface of elevator. In order to achieve longitudinally stable systems, two modes of CAS are applied to the control systems which are pitch rate hold mode and pitch hold mode for steady flight. Since the employed CASs include the dynamic properties of the actuator time delay and the low pass filter, it provides the possible solution to be applicable to real systems. Nonlinear model simulations are fulfilled to investigate the effectiveness of the applied CASs with wind disturbance.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.48-56
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• 2011

A Possibility of combustion instability on longitudinal mode has a high level at large scale of L/D. Solid propellant has a metal particle and a grain of control to pressure oscillation. Solid rocket motor in slotted-tube grain controls pressure oscillation of longitudinal mode. Slotted-tube grain restrains longitudinal 1st pressure oscillation. But cavity volume of aft. insulation ablation amplifies 2nd pressure o scillation by vortext shedding. A study has suppressed combustion instability and vortex shedding by modified 4 slotted tube solid rocket motor design.

• Journal of KSNVE
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• v.8 no.6
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• pp.1172-1180
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• 1998

Elastic wave scattering from an acoustically rigid or soft object is studied and compared with the acoustic wave scattering. The behavior of phases as well as magnitudes of partial waves and their total summation of scattered wave are numerically analyzed and discussed. The effect of mode conversion, which occurs between longitudinal and transversal waves in elastic wave scattering. on the magnitudes and phases of scattered waves is identified.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1025-1031
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• 2000

An ultrasonic linear motors consist of a slider and an ultrasonic vibrator which generates an elliptical oscillations. The ultrasonic linear motors mainly consist of an ultrasonic vibrator which generates elliptical oscillations. The ultrasonic linear motor fabricated in this paper was the use of the 1st longitudinal(L1) and 4th bending vibrations(B4). In order to low driving voltage and improve the life time of the ultrasonic motor, we used stacked piezoceramics. Stacked piezoceramics are adhered to aluminum elastic material. The finite element method was used to optimize dimension of ultrasonic vibrator and direction of vibratory displacement. As a result of estimating the characteristics of the ultrasonic linear motor, no-load velocity was 0.204[m/s] when applied voltage was 70[ $V_{rms}$] in resonance frequency.y.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.93-96
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• 2004

An ultrasonic linear motor was composed of a slider and a stator vibrator including piezoelectric material and elastic material. The ultrasonic linear motors mainly consist of an ultrasonic vibrator which generates elliptical oscillations. L1-B4 ultrasonic linear motor use longitudinal and bending multi-vibration. In order to design stators which has high efficiency and driving characteristics, The finite element method was used to optimize dimension of ultrasonic vibrator and direction of vibratory displacement. stator vibrator of respectively width 3, 5, 7[mm] was fabricated and experimented. as results When width was 5[mm], the driving characteristics was good.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.728-731
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• 2003

This paper deals with a flat type ultrasonic motor, which uses a longitudinal-bending multi mode vibrator of rectangular form. A linear ultrasonic motor was designed by combination of the first longitudinal and eighth bending mode, and the motor consisted of a straight aluminum alloy bar bonded with piezoelectric ceramic elements as a driving element. The geometrical dimensions of the rectangular aluminum vibrator were determined by Euler-Bernoulli theory ANSYS was used to analyze the resonance frequency and the displacement of the stator vibrator. The resonance frequency of the motor provides the elliptical motion. and ANSYS was used to analyze elliptical motion and elliptical trajectory of stator vibrator when thickness of piezoelectric ceramics was varied respectively 0.763, 1.526, 2.289[mm] and width of stator vibrator was varied respectively 16, 12, 8, 4[mm]. When thickness of piezoelectric ceramics was decreased, the displacement of the stator vibrator was increased. And when width of stator vibrator was decreased, the displacement of the stator vibrator was increased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.730-733
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• 2004

An ultrasonic linear motor was composed af a slider and a stator vibrator including piezoelectric material and elastic material. The ultrasonic linear motors mainly consist of an ultrasonic vibrator which generates elliptical oscillations. $L_1-B4$ ultrasonic linear motor use longitudinal and bending multi-vibration. In order to design stators which has high efficiency and diriving characteristics. The finite element method was used to optimize dimension of ultrasonic vibrator and direction of vibratory displacement. stator vibrator of respectively width 3, 5, 7[mm] was fabricated an experimented. as results When width was 5[mm], the driving characteristics was good