• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.14-20
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• 2003

Piezoelectric ultrasonic transducers for high temperature contact measurement were developed. These high temperature ultrasonic transducers (HTUT) consisted of bismuth titanate piezoceramic element whose Curie temperature is higher than $600^{\circ}C$, a backing material of the mixture of tungsten powder and inorganic binder, an inner alumina tube, a wear Plate and a housing. The operational frequencies or the HTUT were 1.04 and 2.08 MHz, respectively. Various commercially available couplants for high temperature were evaluated and compared. As a couplant for high temperature ultrasonic testing between HTUT and test specimen, gold epoxy was selected. The peak amplitude of pulse-echo signals from steel test specimen decreased with increasing temperature. The operational temperature of the HTUT reached up to $500^{\circ}C$ at which the continuous contact measurement was possible.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.378-383
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• 2004

The Korean Performance Demonstration(KPD) System for the ultrasonic testing personnel, equipments and procedures applicable to the Class 1 and 2 piping examination for nuclear power plant in Korea has been established. A round robin test was conducted in order to compare the examination results by the method of Performance Demonstration(PD) with the traditional dB-drop method. The round robin test shows that the reliability of the PD method is better than that of the dB-drop method. As a result, adoption of the PD method to the in-service inspection of the nuclear power plants will improve the reliability of the ultrasonic test results.

• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.25-31
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• 1996

Steel wires are made by elongating hot billets. If the billets have internal or surface defects, the wire can be broken during elongation process. After testing surface defect, we are testing internal defect by ultrasonic transducers. POSCO is producing two kinds of billets, hot rolled billet and cast billet. Hot rolled one is denser than cast billet. Because of the low density and rough surface, ultrasonic testing is difficult for the cast billet. Size of the transducer was related with the size and density of the billet. A transducer having 21mm long, 8.5mm wide and 0.95mm thick piezoelectric ceramic plate was best for $160mm\;{\times}\;160mm$ cast billet. Center frequency of the transducer was 2.25MHz and the focus distance was 70mm.

• 기계와재료
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• v.14 no.3 s.53
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• pp.85-92
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• 2002

• Journal of Welding and Joining
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• v.21 no.4
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• pp.11-18
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• 2003

• Proceedings of the KWS Conference
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• 1996.05a
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• pp.104-107
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• 1996

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.2
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• pp.150-161
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• 2000

• Journal of the Korean Society for Nondestructive Testing
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• v.2 no.1
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• pp.17-24
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• 1982

• 한국정보통신설비학회:학술대회논문집
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• 2002.08a
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• pp.49-52
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• 2002

본 논문에서는 강자성체 물질을 사용하는 구조물들에 발생되는 결함을 와전류탐상을 이용하여 검출하기 위한 비파괴검사방법에 대하여 제시하였다. 와전류탐상은 전자기비파괴검사방법으로 초음파탐상법과 같은 방법에 비교하여 비접촉식이며 고속으로 검사가 가능하다는 장점이 있다. 본 연구에서 사용되는 매질인 강자성체의 경우 비자성체에 비하여 표피효과에 의한 침투깊이가 얇기 때문에 강자성체를 위한 주파수를 별도로 선정하여야 한다. 또한 고속으로 움직이는 경우 속도기전력에 의한 효과를 고려하여야 한다. 본 연구에서는 와전류센서를 제작하여 실제 강자성체에 적용하는 경우 어떠한 특성을 나타내는가에 대하여 고찰하였다.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.35-40
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• 1994

비파괴검사(NDT)란 시험품에 손상을 주지 않고 내.외부에 존재하는 불연속부(결함)을 찾아내는 방법으로 다음과 같이 그 종류를 분류할 수 있다. (1) 표면결함 검출을 위한 비파괴검사 - 육안검사(VT) : 확대경 등에 의한 치수, 형상확인 - 자분탐상검사(MT) : 강자성체에 적용, 표면(하) 결함검출 - 침투탐상검사(PT) : 금속, 비철금속에 적용, 표면개구 결함검출 - 와류탐상검사(ET) : 도체 표층부(봉, 관 등) (2) 내부결함 검출을 위한 비파괴검사 - 방사선 투과검사(RT) : 결함의 종류, 형상의 판별 우수 - 초음파 탐상검사(UT) : 균열 등 면상 결함검출 등 우수 (3) 기타 비파괴검사 - Strain 측정 : 안전성 평가 - 음향방출시험(AET) - 누설시험(LT) - 중성자 방사선시험(NRT) 이상에서 보는 바와 같이 여러 종류의 비파괴검사가 있으나, 그 중에서 용접부에 적용되는 가장 일반적인 검사방법인 방사선 투과검사에 대해 기술하고자 한다.