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전제춘,장영원,이종수,박기종,권동일 대한금속재료학회(대한금속학회) 1993 대한금속·재료학회지 Vol.31 No.8
In this study, the crack closure phenomenon was investigated for conservative prediction of fatigue life time. Based on previous experimental results and theoretical analysis, it was expected that the variation of normalized crack closure stress with ΔK could be classified into three regimes. This classification concept was reflected in considering a fatigue crack growth rate equation. In addition to crack opening displacement method and back face strain gage method, acoustic emission technique was introduced to measure local microbehavior of crack closure at the crack tip of CT specimens of 2024-T8 Al alloy. Acoustic emission technique was found to yield better closure results successfully. Finally, FASTRAN program was adapted and executed to predict crack growth rates in the cyclic stress state. The predicted values were relatively consistent with experimental ones except near ΔK_(th) in both CCT and one through crack at hole specimens.
전제춘,이종수,임영목,정희돈 대한금속재료학회(대한금속학회) 1994 대한금속·재료학회지 Vol.32 No.11
The crack closure phenomenon is important in the aspect of effecitve driving force for crack growth. Therefore, the precise measurement of crack closure load is an essential prerequisite for the determination of the effective driving force. In this study, the acoustic emission(AE) technique was employed as one of crack closure measurement methods and the results were compared with those of crack opening displacement method(CD), back face strain gage method(BFS) and surface strain gage method. Results have shown that the intrinsic fatigue Life curve(da/dN vs. ΔK_(eff)) obtained by use of the AE technique vvas best fit with the curve of high stress ratio (R=0.8) test, which implied that the AE technique could be considered as a reliable crack closure measurement method.
Graphite/Epoxy 적층복합판의 저속충격에 의한 손상거동
옹장우,김재훈,전제춘 忠南大學校 産業技術硏究所 1995 산업기술연구논문집 Vol.10 No.2
Damage behavior of quasi-isotropic circular composite plates of Herculus AS4/3501-6 graphite/epoxy were investigated and the residual compressive strength after impact under low-velocity impact type loads was evaluated. The locations and lengths of damages inside the plate after the impact were calculated by means of a three-dimensional finite element method and compared with the impact test results. Also, the load-deflection curves for impact were used to predict the major damage characteristics of the impact force in the laminated composites.
옹장우,전제춘,오상진 대한기계학회 1986 대한기계학회논문집 Vol.10 No.5
The strain distribution on a welded aluminum alloy transition joint produced by a static tensile load has been measured using a moire method combined with photoelastic coating method. The test specimens were made of aluminum alloy 6061-T6 and 2014-T6 butt welded with ER-4043 filler metal, and were post welded heat treated (solid solution heat treatment 502.deg. C 70min.) and precipitated (artificial aging 171.deg. C 600min.) to cause an abrupt change of mechanical properties between the base metals and weld metal. The photoelastic epoxy rubber was cemented on the specimen grating which had been reproduced on the specimen surface by using an electropolishing. The measurements were compared with strains computed by Finite Element Analysis. The following results were abtained. (1) The maximum strain were distributed along the center line in the transverse directiion of the weld metal. (2) The strain gradient along the fusion line increased approaching the V-groove tip and the maximum value was observed at a quarter of width from the V-groove tip. (3) The moire method combined with photoelastic coating was proved very useful for real time strain measurement in the welded aluminum alloy transition joint. 본 연구에서는 알루미늄 합금인 알루미늄 2014와 6061의 이재를 V형 맞대기 이음을 한 후 정적인장하중을 가하여 모아레법에 광탄성 피복법을 조합한 방법에 의 해 변형율을 실시간(real time)에서 측정하고 유한요소법으로 해석한 결과와 비교검 토하였다.