• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.8
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• pp.539-543
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• 2015

At present, the development of a detection device in order to prevent accidents due to wire deterioration in the distribution lines is required. Distribution line is not possible to check the internal state in a normal way because it is covered with the coating. Accordingly, various eddy current techniques that is the non-destructive test (NDT) techniques have been applied to solve this problem. In this paper, we have seen examining the characteristic change of the eddy current sensor according to the simplified shape of the sensor in order to solve the problems for the simplified shape that is generated when the simulation for the shape of the eddy current sensor.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.154-159
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• 2012

Condition monitoring(CM) is a method based on Non-destructive test(NDT). Therefore, recently many kind of NDT were applied for CM. Acoustic emission(AE) is widely used for the early detection of faults in rotating machinery in these days also. Because its sensitivity is higher than normal accelerometers and it can detect low energy vibration signals. A machine tool consist of many parts such as the bearings, gears, process tools, shaft, hydro-system, and so on. Condition of Every part is connected with product quality finally. To increase the quality of products, condition monitoring of the components of machine tool is done completely. Therefore, in this paper, acoustic emission method is used to detect a machine fault seeded in a gearbox. The AE signals is saved, and power spectrums and feature values, peak value, mean value, RMS, skewness, kurtosis and shape factor, were determined through Matlab.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.321-322
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• 2005

In this paper, we dealt with a partial discharge(PD) measurement system that has been accepted as an effective and non-destructive technique for estimating reliabilities of low-voltage electrical and electronic components. Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 37.6 mv/pC. In an application test on photo coupler, we could detect 0.1 pC level of partial discharge at the applied voltage of AC 520 $V_{peak}$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.572-577
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• 2011

The acoustic emission (AE) technique is a well-known non-destructive test technique, both in research and for industrial applications. It is mainly used to monitor the onset of cracking processes in materials and components. Predicting and preventing the crack phenomenon has attracted the attention of many researchers and has continued to provide a large incentive for the use of condition monitoring techniques to detect the earliest stages of cracks. In this research, goal is in grasping features of AE signal caused by crack growth. The envelope analysis with discrete wavelet transform (DWT) is used to find the characteristic of AE signal. To estimate feature of divided into three by crack length, the time waveform and the power spectrum were generated by the raw signals and the transferred signal processed by envelope analysis with DWT.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.997-1002
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• 2009

The local loosening of ballast supporting railway tract cause a differential vertical tract settlement. In the bridge, the temperature change make bridge deck to contract and expand, and this movement cause local loosening of ballast on the bridge expansion joint. Therefore, the evaluation of the status of ballast on the bridge expansion joint is important for the track maintenance of the high-speed railway. In this paper, hwaw method was applied to evaluate the status of ballast on the bridge expansion joint. HWAW method is non-destructive test to evaluate 2-D shear wave velocity map along the railway. Shear wave velocity is directly related with status of ballast. In this research, hwaw method was applied two different types of bridges and determine the degree and the range of the ballast loosening caused by movement of the bridge expansion joint.

• Corrosion Science and Technology
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• v.11 no.4
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• pp.129-134
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• 2012

UT(Ultrasonic Test), one of the non-destructive tests, is the most common thickness measurement method for evaluating the wear rate in NPPs(Nuclear Power Plants). UT is used widely because it is easy and safe for use. However some amount of error inevitably occurs in attempting to measure the thickness. The error, that could make the thickness data thicker or thinner, may affect estimation of wear rate in pipes. NPPs are composed of a lot of pipes and components. Some of them are tested to check the current status during RFO(Re-Fueling Outage). Reliability analysis of UT is essential for evaluating pipe wear rate and establishing the long-term management plan in NPPs. This paper reviewed the cause of error occurrence and presented the UT data reliability analysis method. Also, this paper shows the application result of reliability analysis to the UT data acquired in NPPs.

• Computational Structural Engineering
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• v.11 no.3
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• pp.187-198
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• 1998

지하구조물의 건전성을 평가하기 위한 비파괴시험으로써 탄성응력파를 이용한 충격반향탐사법을 수치해석적인 방법을 통하여 수행하였다. 즉, 일면만으로 접근 가능한 터널 면에서의 충격가진과 동적응답의 측정으로 이질면을 포함한 내부의 상태를 예측할 수 있다. 연구의 수행은 탄성거동을 하는 매질 내부에서 전파되는 탄성응력파의 특성을 이해하고, 이를 동적 유한요소해석으로 모형화하여 충격반향탐사법을 수치해석적으로 수행한다. 이질재료가 2개의 층을 이루고 있는 경우 표면층의 두께를 쉽게 측정할 수 있었으며, 구조물의 병진운동, 휨운동과 구조물 내에서 다중반사되는 탄성응력파에 의한 복합적인 영향을 받는 터널과 같은 원통형 구조물에서 동적응답의 주파수 특성으로부터 터널라이닝 내부에 형성된 공동의 위치와 크기의 예측이 가능하였다. 수치해석적인 방법과 병행하여 다양한 형태의 경계조건을 가지는 구조물에 대한 충격반향탐사법의 실험을 수행할 경우 실제적인 문제에 적용, 건전성 평가의 지표를 마련할 수 있을 것으로 사료된다.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.725-730
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• 1998

Recently, non-destructive tests are getting popular in evaluating concrete properties without braking specimens. Among several NDT methods, P-wave velocity measurement technique has been widely used to evaluate the stiffness and strength of concrete. The purpose of this study is to investigate factors influencing P-wave velocity measured by impact-resonant method and ultrasonic pulse velocity method, such as moisture content of concrete, existence and size of coarse aggregates, sensor and sampling rate. Test results show that rod-wave velocity measured by impact-resonant method and ultrasonic pulse velocity are significantly affected by the moisture content of concrete, i.e., the lower moisture content, the lower velocity. Moisture content influences rod-wave velocity stronger than ultrasonic pulse velocity. Rod-wave velocity is faster in concrete than in mortar and is also faster in concrete containing small size aggregates. Sensor and sampling rate have little influence on velocity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.224-225
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• 2015

Ultrasonic velocity method is applied to measure and correlate the strength of concrete to the velocity of the ultrasonic wave. With voids inside, mortar specimens may show the lower strength and it is intended to detect such change using the ultrasonic velocity method in this study. The amount of voids was varied and the measured data represented the condition of the mortar with voids. The test results can be used to predict the strength of concrete with voids using ultrasonic velocity method.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1223-1228
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• 2005

A lot of PSC railway bridges have been constructed in countries and, they are considered as cost-effective and less maintenance-demanded structures. However, recently several collapse of PSC bridges happened in Europe show that PSC bridges have some serious maintenance problems related to tendon corrosion and wire fractures. Furthermore, any reliable NDT method is not presented until recently. In this paper, AE techniques are investigated for detection of wire fractures in PSC beam. Using long-term monitoring AE techniques, two acoustic signals of wire fractures in a PSC beam are obtained. These data are compared to other noise signals. Based on the test results, the characteristics of the AE signals are classified and wire fracture signals are figured out among the other AE signals. As a result, AE techniques are certainly exposed to tendon fracture sound, and application of AE techniques are better than any other non-destructive method.