• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.2
• /
• pp.93-97
• /
• 2009

An advantage of a magnetostrictive strip transducer for a long-range guided wave inspection is that the wave patterns are relatively clear and simple when compared to a conventional piezoelectric ultrasonic transducer. Therefore, if we can characterize the evolution of defect signals, it could be a promising tool for a structural health monitoring of pipes for a long period of time as well as an identification of flaws. However, when evaluating a signal during a realistic field examination, it should be careful because of some spurious signals or false indications, such as signals due to a directionality, multiple reflections, mode conversion, geometrical reflections etc. Mode converted signals from a realistic piping mockup were acquired and analysed. We found mode conversions between a torsional guided wave T(0,1) mode and a flexural F(1,3) or longitudinal L(0,2) mode generated by a magnetostrictive strip transducer. Based on the experimental observations, an interpretation of the source of the mode conversion is discussed in a viewpoint of electromagnetic properties and structure of the strip transducer.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.27 no.5
• /
• pp.393-397
• /
• 2007

Eddy current standard including an artificial slot for the calibration of absolute type surface probe was fabricated. Developed eddy current standard has the electric conductivity and dimensions, and contains artificial slot as established in ASTM E 1629. The width and depth of artificial slot are 0.1 mm and 0.5 mm respectively. This slot was only possible to measure the depth on the two side edges, and impossible for the middle part with general measurement tools. The ultrasonic test method was applied for measuring depth of the middle part of the artificial slot in the standard. Using this method the dimension could be measured successfully with uncertainty about $15\;{\mu}m$. Calibration of eddy current standard for the absolute probe can be performed by this technique.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.28 no.1
• /
• pp.9-15
• /
• 2008

A new ECT probe to separate the ECT signal distortion due to PVC (permeability variation clusters) and ordinary defects created in SG tubes has been developed. The hystersis loops of PVC which are extracted from retired SG (steam generator) tubes of Kori-1 NNP were measured. The tensile tests were performed to identify the mechanism of PVC creation. The conditions detecting the PVC created in 56 tubes were investigated using computer simulation, and the signal processing circuits were inserted in the probe for the digital signal transmission. The new Probe can measure and separate the PVC signal which is created in the SG tubes, and also measures the defects in Ni-sleeving part of SG tubes. furthermore the new ECT probe can measure the defects as fast as bobbin probe, and enhance the testing speed as well as reliability of the defect detection of SG tubes.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.24 no.6
• /
• pp.581-589
• /
• 2004

In this study, the capacitive micromachined ultrasonic transducer(cMUT) was developed based on the previous research results. The cross sectional image of the developed cMUT was characterized. To measure the membrane displacement of the cMUT, the Michelson phase modulation fiber interferometer was constructed. The measured membrane displacement was in good agreement with the result of the finite element analysis. To estimate the ultrasonic wave generated by the cMUT, an ultrasonic system including a pulser, receiver and charge amplifier was used. The cMUT developed in this study shows a good performance and hence will be widely used in the non-contact ultrasonic applications.

• Journal of Conservation Science
• /
• v.25 no.3
• /
• pp.233-244
• /
• 2009

This study was focused on the transducer and suitable contact material for stone cultural heritage, and the correlation of direct-indirect method in rock types for scientific development and quantitative evaluation technique of the ultrasonic measurements. As a result, it was identified the transducer (UTREXTX(RX)54kHz) and contact material (rubber clay) of the type 3 were appropriate for the ultrasonic measurements of stone cultural heritage. The direct-indirect correction factors of type 3 were calculated 1.50 for granite, 1.38 for gabbro, 1.58 for quartz diorite, respectively. This result is the first study for improvement in reliability for the ultrasonic measurements, and it will contribute to establishment of the ultrasonic survey method for stone cultural heritage. Also, complementary studies considering the surface irregularity of rocks and various contact materials will carry out, and the database about correlation of direct-indirect in rock types will establish.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.8C
• /
• pp.803-810
• /
• 2003

This paper addresses an image processing technique for the human papillomavirus (HPV) DNA chip to discriminate whether the probes are hybridized with the target DNA. HPV DNA chip is designed to determine HPV gene-types by using DNA probes for 22 HPV types. In addition to the probes, the HPV DNA chip has markers that always react with the sample DNA. The positions of probe-dots in the final scanned image are fixed relative to the marker- dot locations with a small variation attributable to the accuracy of the dotter and the scanner. The probes are quadruplicated to enhance diagnostic fidelity. frier knowledge including the marker relative distance and the replication information of probes is integrated into the template matching technique with normalized covariance measure. It was demonstrated that the employment of both of the prior knowledges can be accomplished by simply averaging the template matching measures over the positions of the markers and probes. The resulting proposed scheme yields stable marker locating and probe classification.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.10a
• /
• pp.218-218
• /
• 2003

• The Journal of the Acoustical Society of Korea
• /
• v.10 no.6
• /
• pp.12-22
• /
• 1991

초음파 탐촉자 성능의 이론적 평가법을 개발해 이중소자 탐촉자에 적용하였다. 본 방법은 탐촉 자의 발신, 회절, 수신특성을 주파수, 시간 영역에서 평가할 수 있으며, 특히 시간영역에서는 통상 사용 하는 역푸리에 변환법에 의존하지 않고 음파의 투과, 반사 특성을 고려해 파형을 직접 구할 수 있다.

• The Journal of the Acoustical Society of Korea
• /
• v.12 no.2E
• /
• pp.38-46
• /
• 1993

이미 발간된 바 있는 이론적 결과를 바탕으로 비파괴 검사용 분할형 초음파 탐촉자를 개발하였다. 개발과정은 각 부품의 제작, 조립, 그리고 성능평가 등을 거쳤고, 실험결과는 이론치들과 잘 일치하였다. 본 연구에서 개발된 탐촉자는 실현장에서 요구하는 기준치를 충분히 만족시킬 정도로 우수한 성능을 보였다.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2005.12a
• /
• pp.40-42
• /
• 2005