• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.585-590
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• 2000

Recently, It is gradually raised necessity that thickness of thin film is measured accuracy and managed in industrial circles and medical world. Ultrasonic Signal processing method is likely to become a very powerful method for NDE method of detection of microdefects and thickness measurement of thin film below the limit of Ultrasonic distance resolution in the opaque materials, provides useful information that cannot be obtained by a conventional measuring system. In the present research, considering a thin film below the limit of ultrasonic distance resolution sandwiched between three substances as acoustical analysis model, demonstrated the usefulness of ultrasonic Signal processing technique using information of ultrasonic frequency for NDE of measurements of thin film thickness, sound velocity, and step height, regardless of interference phenomenon. Numeral information was deduced and quantified effective information from the image. Also, pattern recognition of a defected input image was performed by neural network algorithm. Input pattern of various numeral was composed combinationally, and then, it was studied by neural network. Furthermore, possibility of pattern recognition was confirmed on artifical defected input data formed by simulation. Finally, application on unknown input pattern was also examined.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.62-66
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• 2002

The preliminary results on the application of optical fiber sensor(OFS) for locations of ultrasonic signals in underwater are presented and analyzed. The OFS utilizing the principle of Sagnac interferometry was designed and the hollowed cylindrical mandrel wound by single mode optical fiber was used as sensing component. The ultrasonic signal source was simulated by the PZT actuator operated with function generator. It has been shown that the OFS could detect the signals less affected by ultrasonic path comparing to conventional acousto-electric sensor and accurate location of ultrasonic signal could be carried out using two OFSs.

• 한국해양공학회지
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• 제14권4호
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• pp.68-72
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• 2000

The ultrasonic method, which is well known as nondestructive test method, is widely used to evaluate the material damage due to degradation. However, this method is just used for measuring the crack size and the thickness loss of the tube. The purpose of this study is to investigate the application of the ultrasonic technique for the evaluation of marine diesel engine exhaust valve and to suggest the correlation between the ultrasonic characteristics and valve degradation. From the evaluation of the results obtained, the technique of using the ultrasonic property was founds to be a efficient method to degree of marine diesel engine exhaust valve by nondestructive test.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.285-288
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• 1998

Ultrasonic signal characteristics related with the growth of electrical trees in epoxy resin are examined under 67[Hz] ac voltage application along with a CCD camera and PD current method. The ultrasonic sensor with a resonant frequency of 200[Hz] supported by a mechanical spring is attached directly to the lower-side of plane electrode. The magnitude of Partial discharge and count rate of ultrasonic signals have been measured according to the tree growth from a needle tip in an epoxy sample.

• 한국정밀공학회지
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• 제20권3호
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• pp.157-164
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• 2003

The pulse-echo method is one of the most widely used ultrasonic techniques for application of nondestructive evaluation. Particularly, quantitative nondestructive evaluation of defects has been considered more important to assure the reliability and the safety of structure. Frequency energy in adhesive joints is based on the ultrasonic wave analysis. The attenuation coefficient upon wave amplitude and the frequency energy that is expressed in the term of wave pressure amplitude were utilized for the primary wave experiment. By means of a control experiment, it was confirmed that the variation of the frequency energy in adhesive joints depends on transition by stress variation. In this paper, the ultrasonic characteristics were measured for single lap joint and Double Cantilever Beam specimen with different fracture modes that was subjected to stress. Consequently, the data that was obtained from the adhesive specimen was analytically compared to the fracture mechanics parameter

• 비파괴검사학회지
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• 제22권6호
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• pp.627-636
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• 2002

Identification and sizing of surface breaking vertical cracks using angle beam ultrasonic testing in practical situation quite often become very difficult tasks due to the presence of non-relevant signals caused by geometric reflectors. The present work introduces effective and systematic approaches to take care of such a difficulty by use oi angle beam ultrasonic testing models that can predict the expected signals from various targets very accurately. Specifically, the model-based TIFD (Technique for Identification of Flaw signals using Deconvolution) is Proposed for the identification of the crack tip signals from the non-relevant geometric reflection signals. In addition, the model-based Size-Amplitude Curve is introduced for the reliable sizing of surface breaking vertical cracks.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1720-1722
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• 1999

In this paper, we studied the properties of small-size disk-type ultrasonic motor using travelling wave for the application to the precise control robotic joint motor and fabricated it. The diameter of the ultrasonic motor fabricated was 13mm. Also, the piezoelectric vibrator was constructed by piezoelectric ceramic and elastic material. The piezoelectric ceramic was composed to PZ-PT-PMN which was shown the high electromechanical stability under high vibration level and stainless steel was used as the elastic material in which configuration was disk-type. To conform the capability of application to robotic motor, we measured the change of rotational speed according to applied voltage and applied frequency. As the results, the small-size disk-type ultrasonic motor was able to fabricate, and the revolution speed was 350 [rpm] when input voltage was 55 [Vrms] and applied frequency 160.4 [kHz] under pre-load.

• Ocean Systems Engineering
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• 제9권4호
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• pp.391-407
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• 2019

Tracking the location (position) of a surface or underwater marine vehicle is important as part of guidance and navigation. While the Global Positioning System (GPS) works well in an open sea environment but its use is limited whenever testing scaled-down models of such vehicles in the laboratory environment. This paper presents the design, development and implementation of a low energy ultrasonic augmented single beacon-based localization technique suitable for such requirements. The strategy consists of applying Extended Kalman Filter (EKF) to achieve location tracking from basic dynamic distance measurements of the moving model from a fixed beacon, while on-board motion sensor measures heading angle and velocity. Iterative application of the Extended Kalman Filter yields x and y co-ordinate positions of the moving model. Tests performed on a free-running ship model in a wave basin facility of dimension 30 m by 30 m by 3 m water depth validate the proposed model. The test results show quick convergence with an error of few centimeters in the estimated position of the ship model. The proposed technique has application in the real field scenario by replacing the ultrasonic sensor with industrial grade long range acoustic modem. As compared with the existing systems such as LBL, SBL, USBL and others localization techniques, the proposed technique can save deployment cost and also cut the cost on number of acoustic modems involved.

• 한국수소및신에너지학회논문집
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• 제12권2호
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• pp.129-136
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• 2001

An investigation on the A/V(ampere/volt) gradient according to the concentration and the kind of solution in a electrolyzer is carried out to obtain the basic data on the ultrasonic application for the efficiency elevation of the hydrogen fuel production. KOH is selected as an electrolyte and concentrations are 0%, 10%, 20% and 30%. The solutions are city water, city water with nitrogen. distilled water and distilled water with nitrogen. The Electrochemical analyzer(BAS Co.) is used as a measuring device to observe the A/V gradient. And the limit of volt is from -3000mV to +3000mV. The 28kHz magnetic transducer is selected to give them ultrasonic forcing. In results, it is clarified that ultrasonic influences the A/V gradient in the electrolytic solution.

• 대한기계학회논문집A
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• 제24권1호
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• pp.52-61
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• 2000

The role of quantitative nondestructive evaluation of defects is becoming more important to assure the reliability and the safety of structure, which can eventually be used for residual life evaluation of structure on the basis of fracture mechanics approach. Although ultrasonic technique is one of the most widely used techniques for application of practical field test among the various nondestructive evaluation technique, there are still some problems to be solved in effective extraction and classification of ultrasonic signal from their noisy ultrasonic waveforms. Therefore, crack size determination through a neural network based on the back-propagation algorithm using back-scattered ultrasonic signals is established in this study. For this purpose, aluminum plate containing vertical or inclined surface breaking crack with different crack length was used to receive the back-scattered ultrasonic signals by pulse echo method. Some features extracted from these signals and sizes of cracks were used to train neural network and the neural network's output of the crack size are compared with the true answer.