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2.25Cr-1Mo 강 인공 열화재의 고주파수 초음파 감쇠특성에 관한 연구
박익근,박은수,김정석,김현묵,권숙인,변재원 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.4
재료나 설비의 고온 장시간 사용으로 인하여 발생되는 재질열화 평가에는 파괴적인 방법이 널리 사용되고 있으며, 신뢰도가 높다. 그러나, 시험편의 채취가 어렵고 많은 경비와 시간이 소요된다. 전기저항법, 레프리카법, 바크하우젠 노이즈법, 전기화학적방법, 초음파법 등과 같은 비파괴적인 열화손상 평가 방법이 주목을 받고 있다. 본 연구에서는 2.25Cr-1Mo 강을 630℃에서 장시간 등온열처리로 모의 열화시험편을 제작하고, 고온설비부재에서 발생되는 미세조직의 변화와 고주파 초음파의 전파특성(감쇠계수)과의 일대일 상관관계를 규명하여 초음파 비파괴평가에 의한 열화도 평가의 유용성 유무를 실험적으로 검증하였다. 그 결과 2.25Cr-1Mo 인공열화재의 경우 열화가 진행됨에 따라 탄화물의 석출 및 조대화가 일어나며 초음파 감쇠계수는 증가하는 경향을 나타내었으며, 그 정도는 침상의 탄화물이 거의 소멸되는 1,000 시간 이후에 초음파 감쇠계수가 급격히 증가하는 매우 좋은 상관성을 나타내었다. The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at 630℃ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.
정운익,강문일,진영화,Chung Un-ik,Kang Mun-il,Jean Young-hwa 대한수의사회 1985 대한수의사회지 Vol.21 No.1
A disease characterized by an acute respiratory syndrome occured in a large fattening farm for calves located in Chung-nam Province, July, 1983. The first onset of the disease was in the herd consisting of 12 calves transported and mixed from the surburbs
Un Ik Chung(鄭雲翼) 한국예방수의학회 1979 예방수의학회지 Vol.3 No.2
The detection and elimination of the damaged meat are the most important steps in meat hygiene. This paper described the physiological nature of the muscular tissue and discussed the differential diagnosis of meat damages with reference to causes. Discussions were also made on various factors affecting the deleterious changes of marketing meat.
Synthesis and Antifungal Activity of 2,5-Disubstituted-6-arylamino-4,7-benzimidazolediones
Ryu, Chung-Kyu,Song, Eun-Ha,Shim, Ju-Yeon,You, Hea-Jung,Choi, Ko Un,Choi, Ik Hwa,Lee, Eun Young,Chae, Mi Jin 梨花女子大學校 藥學硏究所 2002 藥學硏究論文集 Vol.- No.11
2,5-Disubstituted-6-arylamino-4,7-benzimidazolediones were synthesized and tested for in vitro antifungal activity against pathogenic fungi. Among them, 6-arylamino-5-chloro-2-(2-pyridyl)-4,7-benzimidazolediones exhibited potent antifungal activity against Candida specis and Aspergillus niger.
김정석,박은수,박익근,김현묵 한국공작기계학회 2000 한국공작기계학회 추계학술대회논문집 Vol.2000 No.-
This study has been achieved on the characteristics of ultrasonic wave in 2.25Cr-1Mo steel to evaluate the feasibility of ultrasonic nondestructive technique on the assessment of aging degradation. The measured values were used find a relationship between the ultrasonic propagation properties and degradation such as coarsening of carbides and precipitates. The ultrasonic attenuation coefficient was mainly affected by the grain size of prior austenitic phase as well as degradation. In this results, degradation and grain size in 2.25Cr-IMo steel was able to cope with the changes in ultrasonic wave properties by applying the nondestructive evaluation method