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허용학(Y.-H. Huh),김동일(D.I.Kim),김동진(D.J. Kim),이경호(K.Lee),김동진(D. Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Adhesion strength of single layer ceramic capacitor sheet was measured using a peel testing system developed in this study. The peel test specimens with various dimensions were prepared from the ceramic sheet cast on the PET film. In peel test, the sheet specimen was adhered on the glass jig floating on the liquid media, which was designed to minimize the friction, and the specimen was then pulled up by micro-actuator. During the separation of the sheet from the PET film, peel force was measured. To normalize the testing condition, 3 different widths of the specimen were selected: 5, 10 and 20 ㎜. was used Furthermore, testing speed effect was investigated in this study. From the resullts using various testing conditions, the standard method for the peel strength testing may be suggested. Based on the testing condition, effect of peel angle on the strength was experimentally examined. It was found that the adhesive strength for the ceramic sheet is nearly identical, irrespective of the specimen width ranged from 5 to 20 ㎜, while the adhesive strength was increased with increasing testing speed. Furthermore, the strength was shown to be dependent on the peel angle.
허용학(Y.-H Huh),이해무(H.M. Lee),김동진(D.J. Kim),박종서(J.S. Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Estimation of measurement uncertainty of tensile properties of material was carried out. Sources of uncertainty affecting the measurement of tensile properties were classified and analyzed. The model for evaluation of the uncertainty was suggested and the measurement uncertainty of tensile properties was evaluated from the experimental data of SUS316LN obtained according to ISO 6892. The model was derived from the mathematical relation of the measurands, such as elastic modulus, yield strength and tensile strength, and measuring quantities by calculating each sensitivity coefficient of the quantities. Based on these models, the measurement uncertainty of the elastic modulus, yield and tensile strengths were evaluated.
허용학(Y.-H Huh),김동진(D.J. Kim),이해무(H.M. Lee),홍성구(S.G. Hong),박준협(J.H. Park) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Fatigue limit of the copper film coated by Sn was estimated by using Goodman diagram and Gerber diagram. To obtain the high cycle fatigue life S-N curve of the film, the high cycle fatigue test was carried out by applying the constant amplitude load to the film specimen with three different stress ratio of 0.1, 0.3 and 0.5 and the frequency of 40 ㎐ at room temperature in air. The film specimen 15.26㎛ thick was fabricated by etching process. The fatigue limits and S-N curves at the respective stress ratios were determined from the experimental works. It was shown that the S-N curves were dependent on the stress ratio and the fatigue limit was increased with decreasing the stress ratio. The dependency of the fatigue behavior was presented in empirical relationship. Using these relationships, the fatigue limit was predicted.
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허용학(Y.H. Huh),박휘립(P.Park),김동진(D.J. Kim),이완규(W.K. Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Effect of phase difference on fatigue crack initiation around a hole subjected to biaxial fatigue loads was investigated. Axial and torsional biaxial fatigue loads with different phase differences and biaxiality of 1/√3 were applied to thin-walled tubular specimens. Five phase differences of 0. 45, 90, 145 and 180 degrees were selected. Direction of the fatigue crack initiation around the hole was found to approach to the circumferential direction of the specimen with increment of the phase difference for<br/> fatigue tests with phase difference less than 90˚. Whereas the direction for tests with phase<br/> difference greater than 90˚ was symmetric to that for tests with phase difference less than 90˚. Furthermore, it was shown that the fatigue initiation life decreased with increment of phase difference but it increased for tests with phase difference greater than 90˚ . The crack initiation direction can be successfully explained by using the direction of the maximum tangential stress range obtained around the hole and at far-field.
허용학(Y.-H Huh),이해무(H.M. Lee),김동진(D.J. Kim),박종서(J.S. Park) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.1
재료의 인장 물성 측정 불확도 평가가 수행되었다. 인장 물성 측정에 영향을 주는 불확도의 요인이 구분되어 분석되었고 인장 시험으로부터 측정되는 측정량, 즉 탄성계수, 항복 강도 그리고 인장 강도의 불확도 평가 모델이 본 연구에서 제시되었고 각 측정량에 대한 대응하는 수학적 모델과 측정치로부터 각 측정치의 감도계수를 계산함으로서 유도 되었다. 각 모델에 근거하여 ISO 6892에 따라 결정되는 SUS316LN의 실험적 데이터로부터 인장 물성의 불확도가 평가되었다. Estimation of tensile properties measurement uncertainty of material was carried out. Sources of uncertainty affecting the measurement of tensile properties were classified and analyzed. The models for uncertainty evaluation of measurands to be determined from tensile test, such as elastic modulus, yield strength and tensile strength, were suggested and derived from the mathematical relations, corresponding to the respective measurands, and the measuring quantities by calculating each sensitivity coefficient of the quantities. Based on these models, the uncertainty of the tensile properties was evaluated from the experimental data of SUS316LN determined according to ISO 6892.