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오환섭(H.S.Oh),박철희(C.H.Park),허민구(M.G.Hur) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
When tension and bending act on plate simultaneously. S.I.F at the point of surface(2φ/π=0. a) and maximum depth(2φ/π=1. b) of crack is calculated. and configuration for stress distribution is analys with using B.E.M(Boundary Element Method). Consequently. Crack grows to semi-elliptical crack of low b/a ratio.and larger effect of bending gives larger this trend.<br/>
회전굽힘응력하에서 표면균열을 갖는 환봉재의 응력확대계수해석 및 수명예측
오환섭(H.S.Oh),박철희(C.H.Park),박재석(J.S.Park) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.5_2
In this study. First we analysis 3-dimensional stress intensity factor(SIF) K of surface crack of round bar under rotary bending by using boundary element method (BEM). And compare it with S.I.F K of 2-dimensional plane stress gained from experiment at the same condition. Then. With this resule. Life prediction is attempted.<br/> In propagation of surface crack. Scattering of 3-D K considering aspect ratio and ligament ratio is less than that of K of 2-D plane stress. And 3-D K is more close to Paris’ formula da/Dn=CKM. Futhermore. The results of life prediction based on paris’ and Walker’s law are well met with experimental data.<br/>
宋森弘(S. H. Song),吳煥燮(H. S. Oh) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.2
This study has been made to investigate into the behavior of fatigue limit, of fatigue crack initiation, and of fatigue crack propagation under the condition of rotating bending stress; specifically on the independency of stress field as well as the crack behavior of surface micro hole defect, which is made artificially through the specimen. The results obtained can be summarized as follows;<br/> 1) For the single micro hole defect, initiation of fatigue crack is occurred at both tips of micro hole defect simultaneosly along the slip which are produced in the range of maximum principal stress arround micro hole defect independent of the size of micro hole defect.<br/> 2) For the neighbored double micro hole defects with equal size, in the range (L/r) ratio? 3 defined as the size of micro hole defect(2r) to the distance between the centers of micro hole defects (2L), the crack behavior of the micro hole defects is same as single one. However, for the range of L/r<3, the interference effect becomes significant as the ratio approaches to 1.
宋森弘(S. H. Song),吳煥燮(H. S. Oh) 한국해양공학회 1989 韓國海洋工學會誌 Vol.3 No.2
The behavior of fatigue fracture was studied by using low carbon steel bar with microhole(artificial small defect) under the condition of rotary bending stress which is made artificially at smooth surface and round notch root.<br/> The results obtained can be summerized ; The behavior of non-propagating cracks which are produced at both tips of small defect occurred to dissymmetry, and it is found to be double size of small defect. For the range of l>lc, threshold stress intensity is constant. However, for the range of l<lc, it approaches to fatigue limit which artificial small defect is not contained. For the small defect within round notch root, its effect on fatigue limit is lower than the case of smooth surface, and it is no more effective than the round notch is.