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적외선 열화상기법을 이용한 원공노치를 갖는 금속의 피로한도 측정
이건일(Geonil Lee),박정훈(Jung-Hoon Park),최낙삼(Nak-Sam Choi) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.5
열화상기법을 이용한 피로한도 측정은 시편 형상에 따른 불확실성이 있다. 본 연구에서는 비접촉식 열화상기법을 이용하여 Al6061과 STS304 소재의 원공노치 시편의 피로시험 시 소산열 거동을 분석하고 피로한도 측정법을 제안하였다. 원공노치의 선단부에서 측정위치를 변수로 소산열 거동을 측정하였으며 완전교번응력 하에서 1 Hz, 5 Hz의 하중주파수로 피로시험을 수행하였다. 하중주파수 5 Hz, 원공노치 앞 1 mm에서 가장 뚜렷한 소산열의 변화거동을 보였으며, 이렇게 구한 최적실험조건을 고정하고 Hayabusa 방법을 개선하여 OCM(one curve method)으로 피로한도를 구한 결과 1.1%의 낮은 오차를 보여 열화상기법에 의한 피로한도 측정의 정확성을 제시하였다. The fatigue limit measurement using the thermography method has uncertainties depending on the shape of the specimen. In this study, we analyzed the behavior of heat dissipation during the fatigue tests of circular hole notched specimens of Al6061 and STS304 using a non-contact thermography method and proposed an adequate measuring method of the fatigue limit. Dissipated heat behavior was measured according to various measurement locations ahead of the hole notch tip, and fatigue tests were performed with full alternating stress and load frequencies of 1 Hz and 5 Hz. The fatigue limit measurement was the most accurate at the load frequency of 5 Hz and 1 mm in front of the hole notch. Based on the optical experimental conditions and by improving the Hayabusa method, the fatigue limit was calculated using the one curve method that showed a low error of 1.1%, suggesting an excellent accuracy of the fatigue limit measurement by the thermography method.
사육면적 증가를 위한 반층돈사의 활용이 이유자돈의 성장 및 스트레스에 미치는 영향
정우림,이건일,홍진수,정재학,김유용,Chung, Woolim,Lee, Geonil,Hong, Jinsu,Jeong, Jaehark,Kim, Yooyong 한국축산환경학회 2016 한국축산시설환경학회지 Vol.22 No.1
The objective of this study was to increased breeding area in same size pig pen and growth performance of weaning pigs. A total of 330 crossbred ($6.68{\pm}0.36kg$) weaning pigs were subjected to a 42-day feeding trial(3 pens/treatment) in which effects of the semi-floor were compared : NC; Negative control ($0.23m^2/pig$; 40 pigs/pen), PC; Positive control($0.30m^2/pig$; 30 pigs/pen) and Semi-floor($0.30m^2/pig$; 40 pigs/pen). There was a significant effect on BW at 6 week along all treatment(P<0.01). There was a effect of Semi-floor treatment on ADG(average daily gain) only during the first 3 week after weaning(P<0.01). No significant effect was observed in the ADFI during the experiment period. NC treatment had significantly lower BUN value than other treatments(P<0.05). The results from immune and stress response with semi-floor suggest that no negative effects in their blood analysis. Consequently, semi floor treatments increased additional breeding area and also growth performance rather than other treatments in weaning pigs.
적외선 열화상 측정법을 이용한 하중 모드별 응력비에 따른 Al6061의 피로 한도 예측
윤상훈(SangHoon Yun),박정훈(Jung-Hoon Park),이건일(Geonil Lee),왕량(Liang Wang),최낙삼(Nak-Sam Choi) 대한기계학회 2020 大韓機械學會論文集A Vol.44 No.7
Al6061 시험편에 대해 응력비(stress ratio, R=σmin/σmax)를 압축 반복 응력(R=-∞), 인장 반복 응력(R=0), 완전 교번 응력(R=-1)으로 하여 피로 시험을 수행하였다. Risitano 방법을 적용하여 OCM(One Curve Method)과 TCM(Two Curve Method)으로 피로 한도를 예측하고 계단식 측정법의 결과를 기준으로 오차를 산출하고 비교하였다. 압축 반복 응력인 경우 좌굴에 의한 파괴가 발생하여 피로 한도 응력이 매우 낮게 예측되었다. 인장 반복 응력의 경우 초기 평균 응력에 의한 열탄성 효과로 온도 감소가 발생하여 오차가 크게 나타났으나 온도 보정 이후 오차가 20% 이내로 감소하였다. 완전 교번 응력인 경우 초기 열탄성 효과에 의한 온도 변화가 없어 다른 응력비에 비해 오차가 작았다. 본 연구에 사용된 모든 응력비에서 OCM이 TCM보다 더 정확한 예측이 가능하였다. Al6061 specimens were tested under fatigue loading of repetitive compressive stress (stress ratio, R=-∞), repetitive tensile stress (R=0), and alternating tensile/compressive stress (R=-1). The Risitano method was applied to predict the fatigue limits using one curve method (OCM) and two curve method (TCM). Furthermore, error from these methods was calculated and compared with that of the staircase method. For repetitive compressive stress, the fatigue limit was predicted to be very low due to buckling deformation. For repetitive tensile stress, the temperature decreased due to the thermoelastic effect in the initial tensile stress range. Hence, the error increased significantly. After temperature correction, the error was reduced to within 20. In case of alternating tensile/compressive stress, there was no temperature change due to the initial thermoelastic effect. Hence, the error was low when compared to that when other stress ratios were used. Consequently, for Al6061, regardless of the stress ratio, prediction by OCM was more accurate than by TCM because the change in temperature, with the exception of the thermoelastic effect in the elastic region, was quite small.