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RISS 인기검색어
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- 저자 : 안봉영(B. Y. Ahn) (검색결과 9 건)
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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.
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초음파 음향임피던스 변환기를 이용한 저압 저진공 측정기술 연구
홍승수,신용현,조승현,안봉영,임종연,최인묵,Hong, S.S.,Shin, Y.H.,Cho, S.H.,Ahn, B.Y.,Lim, J.Y.,Choi, I.M. 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.5
Pressure vacuum measurement technique using acoustic impedance change of ultrasonic transducers was studied. The sensor has been setup using two air-coupled ultrasonic transducers, one as a transmitter and the other as a receiver, and put it into vacuum chamber and measured pressure versus ultrasonic amplitude. The result confirms that the standard deviations of four repeat measurements were from 0.0093 to 0.3325 at pressure 6.66 kPa to 202.65 kPa(about two atmosphere), and the relative percents were 0.018% and 0.164% at pressure 133.32 kPa and 202.65 kPa, respectively. 초음파 변환기의 기체 음향임피던스 변화를 이용해서 압력진공 측정기술을 연구하였다. 상용화된 한 쌍의 500 kHz 공중 초음파 변환기(air-coupled ultrasonic transducer)를 진공용기에 넣고 초음파 진폭을 측정하였다. 그 결과 6.66 kPa에서 202.65 kPa (약 2기압)까지 4회 반복 측정값으로부터 계산된 표준편차는 0.0093에서부터 0.3325 사이에 있었으며, 표준편차를 압력으로 나누어서 백분율로 나타낸 값은 133.32 kPa에서 0.018%이었고 202.65 kPa에서는 0.164%이었다.
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안봉영,이승석,김영길 韓國非破壞檢査學會 1997 한국비파괴검사학회지 Vol.17 No.4
소성이방성은 판재의 가공성을 결정하는 중요한 인자로써 주로 기계적인 인장시험에 의해 측정되고 평가되어 왔다. 압연 방향에 대하여 상대적인 방향으로 진행하는 초음파의 속도로부터 집합조직의 결정분포함수를 구할 수 있으며, 결정분포함수의 계수인 결정방위계수는 소성이방성의 평균값들과 상관 관계를 갖는다. 본 실험에서는 초음파 속도로 구한 결정방위계수와 압연강판의 소성이방성을 비교하여 서로의 상관 관계를 구하였으며, 측정결과 average normal anisotropy, (??)는 ±0.082, average planar anisotropy, Δr는 ±0.096 의 편차 내에서 예측 가능 하였다. 초음파 속도 측정에는 공진주파수측정법이 적용되었고, 초음파의 송수신에는EMAT가 이용되었다. Plasitc anisotropy is one of important factors which determine the drawability of a steel sheet. It has been mainly measured by mechanical tensile test. From the ultrasonic velocities propagating along the relative directions to the rolling direction. CODF(crystallite orientation distribution function) can be measured and ODC's(orientation distribution coefficients) has some correlations with the plastic anisotropy. In this study the correlations between the plastic anisotropy and ODC's of the cold rolled steel sheet were measured. From the results of ultrasonic velocity measurements the average normal anisotropy, (??) and the average planar anisotropy, Δr could be predicted within the accuracy of ±0.082 and ±0.096, respectively. Acoustic resonance method was applied to measure the ultrasonic velocities and EMAT's were used for generating and detecting the waves.
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이승석,안봉영 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.2
Welding residual stress was measured by ultrasonic briefringence technique. Acoustoelastic constant was taken by averaging the values in the literature. The initial briefringence from prefered orientation of grains was measured. The EMAT transducers were used to remove couplant effect. The results show that the distribution and magnitude of welding residual stress from ultrasonic measurement are in good agreements with those from semi destructive hole drilling measurement.
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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.
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DC Potential Drop 측정을 이용한 S45C강의 템퍼링과정 비파괴 평가
박용기,안봉영 韓國非破壞檢査學會 1989 한국비파괴검사학회지 Vol.9 No.1
DC poteatial drop(DCPD) measurement system was made and the optimum measuring conditions have been studied. The room temperature resistivity of commercially available medium carbon steel(S45C) was measured using this technique. DCPD was measured in the specimens which were hardened and tempered at different temperatures. It was found that DCPD reflected the change of the microstructure during tempering very sensitively. It was possible to monitor the stage of tempering of S45C steel nondestructively using DCPD measurement.
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CODF 개념을 이용한 CFRP 복합재료의 Fiber Orientation 측정기술연구
이재락,이승석,안봉영 한국비파괴검사학회 1990 한국비파괴검사학회지 Vol.10 No.2
The specific strength of the fiber reinforced composite material is closely related to the anisotropy of the material. For the quantitative characterization of the anisotropy in the composite material, applied was CODF concept which was extensively used in the metallic material. As the results, the anisotropy of the material could be quantitatively analysed from the measurement of the phase velocities of the angular dependent SH。waves.
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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.
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