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조진형(Jin Hyung Cho),이세재(S J Lee),오현승(H S Oh),백성선(S S Baek),김옥재(O J Kim),김병극(B K Kim),정경수(K S Jeong),박상훈(S H Park),권대철(D C Kwon),고재호(J H Ko),유지현(J H Ryu),심성철(S C Shim) 한국산업경영시스템학회 2014 한국산업경영시스템학회지 Vol.37 No.4
Until now, because a new product (or facility) launched in market has been retired from one year of age, we can have had ASL by stub-curve method by Iowa curve. Recently, many innovative products with important role in market like display and solar-cell etc. are more durable and, what are better, they have the constant variance in ASL because of their good quality. Of course, there are some ones like smart mobile phone with relatively big dispersion in ASL. Estimating ASL of products like display and solar-cell etc., the new approach is needed. In this paper a new method applied traditional Iowa curve with accelerated reliability test (indoor/outdoor) etc. is proposed.
김병극,김영환 경북대학교 센서기술연구소 1991 센서技術學術大會論文集 Vol.2 No.1
탄성파원 해석과 재질 평가를 위하여 표면의 진동 단위와 속도를 넓은 주파수 영역에서 일정한 감도로 검출할 수 있는 광대역 센서들이 요구되어진다. 본 연구에서는 광대역 변위 및 속도 센서로서 원추형 및 PVDF 압전 센서를 각각 제작하였다. 또한 noise 차폐 및 부착이 용이하여 현장에서 사용 가능하도록 housing안에 내장된 원추형의 광대역 단위 센서를 제작하였다. Step-like force의 과도파를 발생할 수 있는 실험계를 구성하여 진앙점에서 센서들의 출력과 주파수 스펙트럼을 조사하였으며 Green 함수를 이용하여 이론적인 변위 및 속도와 주파수 스펙트럼을 계산하고 센서의 출력과 비교 분석하였다. 그 결과 원추형 압전 센서는 변위에 비례하는 출력 전압을 발생하며 DC에서 5 MHz까지 최대감도편차 ±7 dB이내로 일정한 감도의 광대역 특성을 보여 표면 변위가 정량적으로 검출되어짐을 알 수 있었다. PVDF 압천 센서는 속도에 비례하는 출력을 발생하여 표면 진동의 속도를 직접적으로 측정하는데 이용될 수 있음을 알 수 있었다. Acoustic emission sensors of a flat response characteristic in a wide frequency band have been developed to evaluate elastic source event and material. The present work showed that conical PZT sensors are suited for the direct measurement of vertical displacement and PVDF sensors for the vertical velocity of a plate surface. The transient outputs of the sensors due to step-like forces were compared with calculated results, and both signals were consistent with each other. Also, the frequency characteristics of the sensors were examined and compared with calculated results.
김병극,박용기 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.1
Piezoelectric elements, backing and shoe material are the important components of the ultrasonic transducer. In this study, characteristic constants in the domestic and the foreign PZT ceramic elements are investigated. The acoustic properties of the domestic and the foreign backing and shoes are characterized. The effects of components characteristics, the kinds of the piezoelectric elements and the thickness of the wear plates are investigated for the manufactured normal beam ultrasonic transducers.
이재옥,이세경,김병극 한국비파괴검사학회 1990 한국비파괴검사학회지 Vol.10 No.1
In materials with the large grain size, ultrasonic waves are highly attenuated by the grain boundary acting as scattering centers due to discontinuity of elastic constant. In this study, the improved probes were developed so that they minimized the effect of grain scattering in order to detect deep flaws in coarse grained materials. As the result, the developed ultrasonic transducers showed the better sensitivity and signal to noise ratio when compared with the commercial probes in testing the interior of coarse grained material.