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자동차용 경량화 AI/CFRP 하이브리드 복합재료의 굽힘강도 특성
윤한기(Han-Ki Yoon),이경봉(Kyung-Bong Lee) 한국자동차공학회 2002 한국자동차공학회 지부 학술대회 논문집 Vol.2002 No.3
Al/CFRP Hybrid composites by using automobile were made with alternating Al7075 sheets and CFRP preparers by autoclave co-curing process. There are many factors influencing the performances of the laminate. We made it changing volume fraction and fiber orientation of CFRP. In this paper, 3-point bending test was conducted to investigate the influence of volume fraction and fiber orientation of CFRP on Bending strength characteristics.<br/>
Al 7075/CFRP 다적층 하이브리드 복합재료의 피로수명에 대한 연구
윤한기(Han-Ki Yoon),김연겸(Youn-Kyoum Kim),박준수(Joon-Soo Park),이경봉(Kyung-Bong Lee) 한국해양공학회 1996 韓國海洋工學會誌 Vol.10 No.4
In this research, to develope the Al 7075/CFRP multilayered hybrid composites, CRALL(Carbon Reinforced aluminum laminate) specimens were processed by autoclave curing system that curing temperature, time, surface pretreatment condition of aluminum were constant. And the fatigue life and failure mechanism on CFRP volume fraction and fiber orientation of CRALL specimens were investigated. A fatigue life was greatly influenced by effect of CFRP fiber volume fraction but it was less effected than those of fiber orientation. The fatigue failure arised from interface delamination of CFRP and aluminum sheet after shear fracture of aluminum layer. The failure mechanism is assumed that the aluminum laminates which divide the CFRP into many thin layers tend to arrest the failure propagation.
吳世旭(Sae-Wook Oh),?在煥(Jae-Whan Yoo),李敬奉(Kyung-Bong Lee) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.1
In order to investigate the dynamic fracture characteristics of dual phase steel was made with a suitable heat treatment of SS41 steel, a dynamic fracture toughness was performed under an instrumented impact testing machine with the constant loading velocity at the variation of temperature.<br/> The validity of dynamic fracture toughness in the precracked V-notch charpy specimen could be confirmed through the aspect of the dynamic fracture surface.<br/> The lower self of the absorbed energy curve, the upper self of 50% brittle rupture point and the behaviour of the dynamic fracture toughness (K1d) curve were the same tendency as the factor of temperature (-80℃ RT).<br/> The value of the dynamic fracture toughness obtained by the fracture surface with shear-lip could not be assure of the application of the plane strain problem.
윤한기,박원조,이경봉 東義大學校産業技術開發硏究所 1991 産業技術硏究誌 Vol.5 No.-
Low-cycle fatigue behavior of AISI 4340 steel which was carried out under full reversed strain control fatigue system, and was investigated by the Mason-Coffin equation and the ASTM test methods. And cyclic hardening exponent was calculated from the relationship of the plastic strain and stress range in stable cycles. The modified cyclic hardening exponent calculated by the Hysteresisloop in stable load cycles was compared with cyclic hardening exponent, and predicted the fatigue failure cycles. And so, a possibility was examined about substitution the modified cyclic hardening exponent for the established cyclic hardening exponent for the established cyclic hardening exponent on the ASTM test method.
打擊速度 및 溫度變化가 豫크랙을 가진 衝擊試驗片의 動的破壞靭性에 미치는 影響
兪在煥,李敬奉,金重吉,李致雨,吳世旭 慶南大學校 附設 工業技術硏究所 1989 硏究論文集 Vol.7 No.-
計裝化衝擊試驗에서 打擊速度와 溫度의 變化가 豫크랙을 揷入한 衝擊試驗片의 動的破壞靭性에 미치는 影響을 考察한 結果 다음을 알 수 있었다. 豫크랙을 揷入한 試驗片이 V-노치 試驗片에 比하여 實驗値의 分散度가 적으며 0℃以下의 溫度領域에서 動的破壞靭性의 有效性이 있었다. 또한 打擊速度와 實驗溫度의 影響은 溫度가 速度보다 훨씬 上廻하는 傾向이었다. The effect of various impact velocity and temperature on dynamic fracture toughness is tested with precracked Charpy specimen, and conclude following results. Precracked specimen has less dispersion of test results than V-notched specimen, unstable crack initiation load didn't agreed to maximum load at room temperature but at 0℃ below, thus, the availability of dynamic fracture toughness is relatively high. Comparing V-notched specimen, the precracked Charpy specimen represented lower shelf of temperature different. But, at this time, the absorbed energy is estimated equivalently. With the decrease of temperature, the reduction of fracture toughness was obvious, but the effect of impact velocity didn't appear.
계장화충격시험에 의한 복합조직강의 파괴인성에 관한 연구
오세욱,유재환,박원조,이경봉 동아대학교 공과대학 부설 한국자원개발연구소 1989 硏究報告 Vol.13 No.1
The dynamic fracture toughness (K_(Id)) is measured using the precracked standard Charpy specimen with an instrumented impact machine. The value of K_(Id) is determined as a function of yield strength and microstructure, and correlations are established between K_(Id) and both energy of initial fracture and total energy of fracture. Since the K_(Id) values of the precracted impact specimens are in accordance with their theoretical ones, this test method is sufficiently practical.
저-사이클피로에서 히스테리시스 곡선에 의한 수명예측의 실험적 연구
이경봉,유재환,윤한기 東義大學校産業技術開發硏究所 1989 産業技術硏究誌 Vol.3 No.-
The MEF dual phase steel was made of the heat treatment of the SS41 steel, which are uniform in the volume fraction and are varied with three kinds in the ferrite grain size. The materials are fatigue tested under the control of constant total strain of fully reversed tensile and compression in the low-cycle fatigue region. The cyclic hardening and softening procedure of the two steel is compared with when the tow steels experience the cyclic strain. In this study, the characteristics of the MEF dual phase steel is investigated with the exponent and constant calculated from substituting the plastic strain and the failure life in Manson-Coffin equation ; the cyclic hardening exponent is calculated from the relation hysteresis by the experiment is the modified cyclic hardening exponent is calculated from the relation equation of the plastic strain and the stress range in stable state and computed from the hysteresis by the experiment is the modified cyclic hardening exponent corresponding to the cyclic hardening exponent is examined and the extimation of the low-cycle fatigue life time is execuated from substituting the modified cyclic hardening exponent in the established equation.
A Study on Bonded Composite Patch Repair of Fatigue Cracked Al 2024-T3 Alloy
Yoon,Han Ki,Lee,Kang Kil,Park,Won Jo,Lee,Kyung Bong 東義大學校産業技術開發硏究所 1995 産業技術硏究誌 Vol.9 No.-
항공기 부재로 사용된 Al합금에 피로크랙이 발생하였을 경우 이를 수리하는 방법으로 복합 재료를 이용한 접착의 방법이 사용되고 있다. 이러한 수리방법은 기존의 금속 재료로서 보강 수리하는 방법과 비교하여 낮은 응력집중, 내피로성 복합재료 선택, 간단한 수리공정 및 기밀성에 잇점을 가지고 있다. 그러나 복합재료를 이용한 수리 방법은 Al합금의 크랙성장 거동 및 복합재료의 크랙지연효과등에 대한 명확한 역할을 규명하여 적용되어져야 한다. 본 연구에서는 Al 2024-T3 시험편에 아라미드 프리프랙(Aramid prepreg)을 ±45。 및 0。/90。로 1층 및 2층으로 적층하여 본딩한 APAL(Aramid patched Aluminum alloy)시험편을 제작하였다. 이를 응력비 R=0.2, R=0.5의 조건으로 크랙전파 실험을 실시하여 Al 2024-T3시험편에 비해서 APAL 시험편의 피로균열 저항성에 의한 피로수명이 현저히 증가함을 확인하였으며, 적층수 및 부착 방위의 영향과 평균응력의 영향을 규명하여 복합재료 접착수리의 효과를 입증하였다.