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유효 K_Id 산정을 위한 샬피 충격시험편의 노치형상에 관한 연구
강동명(D.M.Kang),이하성(H.S.Lee),우상훈(S.H.Woo),조진호(J.H.Jo),우창기(C.G.Woo) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_1
This investigation evaluates effects of notch depth, fatigue precrack length and side groove in impact specimen for estimation of a valid K_id by instrumented charpy impact test. Specimen used is 6005-T6. For notch depth 2.0mm and 2.5mm specimens or within about 2 mm fatigue precrack length with notch depth 2.0mm specimens, the formula of dynamic fracture toughness obtained by crack initiation load(Pm) should be used to determined K_id. Dynamic fracture toughness of side grooved specimens are overestmated to that of standard impact specimen about 15^ ~ 20%. It is confirmed that the formula of dynamic fracture toughness obtained by impact absorbed energy is inappropriate for ductile materials.<br/>
계장화 샬피 충격시험에 의한 노치형상에 따른 동적파괴인성치의 평가
우창기(C. K. Woo),박홍기(H. K. Park),이장규(J. G. Lee),강동명(D. M. Kang),이하성(H. S. Lee) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
Dynamic fracture toughness is evaluated in terms of notch shape, notch depth and impact velocity of instrumented Charpy test. Specimen used is SM4SC. The results obtained are as follows: (1) Dynamic calibration of instrumented tup is important in addition to static calibration for the reliance of instrumented Charpy test. (2) Magnitude of inertia force in instrumented Charpy test has no relation with notch shape or notch depth. However, It increases as the impact velocity increases. (3) For the U-notch of notch depth 2mm and 3mm, the fomula obtained by crack initiation load should be used to determine the dynamic fracture toughness. (4) For the V-notch of any notch depth, either the formula obtained by crack initiation load or that by impact energy may be used to determine the dynamic fracture toughness. However, for the notch depth 2mm and 3mm, the formula by crack initiation load should be used.
초음파법을 이용한 탄소성 파괴인성치 평가에 있어서 시험편 크기의 영향
강동명,함경춘,우창기 한국산업안전학회 1998 한국안전학회지 Vol.13 No.4
Elastic-plastic fracture toughness(J_(IC)) by ultrasonic method is evaluated in terms of width and thickness. Widths of specimen in 6061-T6 aluminum alloy are 50㎜ and 100㎜, thicknesses of those are 20㎜ and 25㎜, respectively. Elastic-plastic fracture toughness by ultrasonic method is independent of specimen thickness and side groove. Angle beam probe which are placed on the end of the compact specimen detect the maximum crack extension effectively. Comparing with elastic-plastic fracture toughness by ultrasonic method and that of unloading compliance method, J_(IC) of ultrasonic method are underestimated to that of unloading compliance method. Elastic-plastic fracture toughness of width 100㎜ specimen are underestimated to that of width 50㎜ specimen about 20%.