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비선형 초음파를 이용한 화력발전소 Platen Super Heater 튜브의 고온 열화 손상 분석
김종범,오세범,박진근,김축복,윤동석 한국비파괴검사학회 2022 한국비파괴검사학회지 Vol.42 No.3
초임계압 표준 석탄 화력발전소는 증기온도 540℃의 고온의 환경에서 운전되고 있다. 일반적인 표준석탄 화력발전소의 설계 수명은 30년으로 수명관리의 목적으로 10만 시간 초과 또는 20년 이상의 설비에 대하여 진단 시 현장에서는 육안검사, 두께 측정, 경도측정 등의 방법을 사용하여 보일러 튜브의 열화 정도를 평가함으로써 수명진단을 주기적으로 실시하고 있다. 본 연구에서는 화력발전소에서 약 20년(약 16만 시간) 동안 운전한 보일러 튜브의 샘플을 여러 위치에서 확보하여 보일러 튜브의 위치에 따른 열화 정도를 표면파 비선형 초음파기법을 활용하여 평가하였고, 이를 인장시험 결과와 비교하였다. 보일러 튜브 샘플의 위치에 따라 초음파 비선형 파라미터와 인장강도, 항복강도의 변화가 높은 상관성을 보였으며, 이러한 결과로부터 보일러 튜브의 열화에 따른 기계적 특성의 변화를 비선형 초음파기법으로 평가할 수 있음을 확인하였다.
Correlation between Ultrasonic Nonlinearity and Elastic Nonlinearity in Heat-Treated Aluminum Alloy
김종범,장경영 한국비파괴검사학회 2017 한국비파괴검사학회지 Vol.37 No.2
The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke’s equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at 300°C for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke’s equation. The results showed that the variations in these parameters were in good agreement with each other.
전자빔을 이용 고농도 Xylene의 탄소화 연구 (I)
김종범,장성호,손현근,류재용 한국폐기물자원순환학회 2016 한국폐기물자원순환학회지 Vol.33 No.6
This study is to identify the effects of DRE (destruction and removal efficiency) and carbonization of Xylene when using the electron beam energy. The irradiation intensity of electron beam energy was 10 mA, 20 mA and irradiation time was 5.7, 11.4, 22.8, 45.6 sec (Absorbed dose are 41.41, 82.82, 165.64, 331.28, 662.55 kGy). The Xylene was completely removed at 331.28 kGy. Main by-products was carbon particles. Carbon particle formation was increased with irradiation intensity increasing. Most of the by-products of particle were Carbon black and Graphite.
김종범,김창혁,이승복,김경환,유재우,배귀남 한국대기환경학회 2019 한국대기환경학회지 Vol.35 No.2
Bicycle way is generally located near the motor road due to the limitation of available space and convenient use. People who use bicycle may inhale highly polluted air during the travelling over the bicycle way. In this study, spatial and temporal variation of air quality over bicycle way was investigated using a mobile laboratory equipped with real-time monitoring instruments. Size distribution of particles ranging from 5.6~560 nm, black carbon, and particle-bound PAHs (polycyclic aromatic hydrocarbons) were monitored. In addition, NO, NO2, and NOx were measured. They are indicators of vehicle exhaust. Air pollution level over bicycle way was compared with those of expressway and city road, and the nearest ambient air quality monitoring station. As expected, the air pollution level over bicycle road was high during the commuting time due to the heavy traffic volume. The air pollution level at the location close to the expressway was almost the same as that of the expressway. It is suggested that cyclists need to be cautious about highly polluted air over bicycle way.