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남영현(Y. H. Nam),안봉영(B. Ahn),이승석(S. S. Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
It is advantageous to use NDE methods to assess the mechanical properties of materials since the<br/> conventional method is time-consuming and sometimes requires cutting of sample from the component. The<br/> NDE parameters such as ultrasonic velocity and attenuation, electric resistivity, and magnetic coercive force<br/> and remanance have been utilized to evaluate changes of material properties due to heat treatment condition.<br/> It has been found that changes of materials properties under quenched and tempered/PWHT treatments could<br/> not be detected using EMAT and Electrical resistivity methods. However, vickers hardness and magnetic<br/> hysteresis loop decreased with heat treatment procedures. These results were obtained using 3Cr-1Mo-0.25V<br/> steel. The magnetism parameters were found to be most sensitive to changes of material properties.
Barkhausen noise를 이용한 용접 잔류응력 측정
이승석,안봉영 한국비파괴검사학회 1990 한국비파괴검사학회지 Vol.10 No.1
Welding residual stress was measured by Barkhausen noise method. The calibration experiment was done for the quantitative analysis. The specimen for the calibration experiment must has the same thermo-mechanical history as the actual material to be tested. The Barkhausen noise were analysed by the pulse-height distribution. The results show that the distribution and magnitude of welding residual stress from Barkhausen noise method are in good agreement with those from blind hole method.
이세경,정민화,김영주,안봉영 韓國非破壞檢査學會 1997 한국비파괴검사학회지 Vol.17 No.3
열 전달 효율을 증가시키기 위하여 튜브의 내 ㆍ외면에 울퉁불퉁한 지느러미가 부착된 fin 튜브의 와전류탐상을 위하여 와전류 탐촉자를 설계하고 시험하였다. fin 튜브는 거친 표면으로 인하여 와전류탐상으로 결함을 찾기 위해서는 많은 주의가 필요하다. 본 연구에서는 규격이 다른 와전류 탐촉자를 제작하고 인공 결함 시험편에 대하여 탐상을 실시하였다. 실험한 와전류탐상 신호에 대하여 FFT를 통하여 주파수 스펙트럼을 구하였고 디지털 필터링의 신호 처리를 하여 신호의 주파수 특성을 고찰하였다. 신호와 주파수 특성을 분석한 결과, 본 연구 대상 시험편에서와 같이 1mm 피치의 fin 튜브의 경우 4mm의 코일 거리를 지닌 탐촉자가 가장 좋은 S/N비를 나타내었다. The eddy current probe was designed for the test of fin tubes that have uneven outer and inner surfaces to enhance the efficiency of heat emission. Because of the surface roughness of the fin tube, it needs much care to detect flaws in the tube employing eddy current test(ECT). We made ECT probes with different coil lengths and performed eddy current test using these probes for artificially flawed specimens. By the fast Fourier transform and digital filtering, signals from these probes were processed to characterize frequency spectra. From the analysis of eddy current signals and their frequency spectra, we concluded that, for the effective testing of the tubes with the fins of 1mm pitch, 4mm coil length gave the highest S/N ratio.