• Proceedings of the KWS Conference
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• 1997.10a
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• pp.43-45
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• 1997

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.102-108
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• 2016

A dental ultrasonic surgical instrument, commercially known as a scaler, is a high-value-added advanced technology that is used for tartar removal, implant operations, and gum and jaw bone surgery. In this study, the piezoelectric phenomenon for making linear motion associated with input electrical signals was studied, and the behavior of the ultrasonic vibrator was investigated by using the commercially available finite element program ANSYS(R) for the purpose of designing dental surgery tools. Modal analysis was carried out, and the optimal frequency range was calculated from the analyzed results. The ultrasonic vibrator was then redesigned based on the calculated optimal frequency range. The performance of the system was tested, and consequently, the proposed methodology was proven useful in vibrator design.

• Journal of the Korean Society of Safety
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• v.17 no.1
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• pp.39-44
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• 2002

This paper shows error in the polarization direction on ultrasonic transducers how sensitive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasonic waves $0{\circ},\;45{\circ}$ and $90{\circ}$. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to cach other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with a modeling solutions which was based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to thickness direction along in-plane fibers.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.135-141
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• 1999

Recently, advance signal analysis which is called "Time-Frequency Analysis" has been developed. Wavelet and Wigner Distribution are used to the method. Wavelet transform(WT) is applied to time-frequency analysis of waveforms obtained by an ultrasonic pulse-echo technique. The Gabor function is adopted as the analyzing wavelet. Wavelet analysis method is an attractive technique for evolution of material characterization evoluation. In this paper, the feasibility of suppression of ultrasonic background noise signal using WT has been presented. These results suggest that ultrasonic background noise ginal can be suppressed and enhanced even for SNR of 20.8 dB. This property of the WT is extremely useful for the detecting flaw echos embedded in background noise.und noise.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.19-24
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• 1998

Elastic-plastic fracture toughness($J_{IC}$) by ultrasonic method is evaluated in terms of width and thickness. Widths of specimen in 6061-T6 aluminum alloy are 50mm and 100mm, thicknesses of those are 20mm and 25mm, respectively. Elastic-plastic fracture toughness by ultrasonic method is independent of specimen thickness and side groove. Angle beam probe which are placed on the end of the compact specimen detect the maximum crack extension effectively. Comparing with elastic-plastic fracture toughness by ultrasonic method and that of unloading compliance method, $J_{IC}$ of ultrasonic method are underestimated to that of unloading compliance method. Elastic-plastic fracture toughness of width 100mm specimen are underestimated to that of width 50mm specimen about 20%.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.48-49
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• 2017

In order to examine the effect of voids on the ultrasonic wave velocity, specimens made of Silica-Sand with voids were prepared for the measurements. The volume fraction of 0, 15, and 30% of voids were used to compare the differences. Because of its more homogeneous distribution of materials properties, the Silica-Sand specimens were used, as compared to mortar specimens. The results showed clear change in ultrasonic wave velocity with different volume fraction of voids. This result is to be used for the estimation of the integrity of concrete structures using ultrasonic wave velocity method as nondestructive testing.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.6
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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.

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.301-308
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• 2024

Concrete carbonation is a continuous and slow process from the outside to the inside, in which its penetration slows down with the increased depth of carbonation. In this paper, the results of the evaluation of the measurement of concrete carbonation depth using a non-destructive ultrasonic testing method are presented. According to the results, the relative nonlinear parameter caused more sensitivity in carbonation changes compared to Rayleigh's fuzzy velocity. Thus, the acoustic nonlinear parameter is expected to be applied as a quantitative index to recognize carbonation effects. In this research, combo diagrams were developed based on the results of ultrasonic testing and the experiment to determine carbonation depth using a phenolphthalein solution, which could be considered as instructions in the projects involving non-destructive ultrasonic test methods. The minimum and maximum accuracy of this method were 89% and 97%, respectively, which is a reasonable range for operational projects. From the analysis performed, some useful expressions are found by applying the regression analysis for the nonlinearity index and the carbonation penetration depth values as a guideline.

• Composites Research
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• v.30 no.6
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• pp.356-364
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• 2017

Composite lattice structures are tried to be used in various fields because of its benefit in physical properties. With increase of demand of the composite lattice structure, nondestructive testing technology is also required to certificate the quality of the manufactured structures. Recently, research on the development of the composite lattice structure in Republic of Korea was started and accordingly, fast and accurate non-destructive evaluation technology was needed to finalize the manufacturing process. This paper studied non-destructive testing methods for composite lattice structure using laser ultrasonic propagation imaging systems. Pulse-echo ultrasonic propagation imaging system was able to inspect a rib structure wrapped with a skin structure. To reduce the time of inspection, a band divider, which can get signal in different frequency bands at once, was developed. Its performance was proved in an aluminum sandwich panel. In addition, to increase a quality of results, curvature compensating algorithm was developed. On the other hand, guided wave ultrasonic propagation imaging system was applied to inspect delamination in a rib structure. To increase an area of inspection, multi-source ultrasonic wave propagation image was applied, and defects were successfully highlighted with variable time window amplitude mapping algorithm. These imply that ultrasonic propagation imaging systems provides fast and accurate non-destructive testing results for composite lattice structure in a stage of the manufacturing process.