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유한요소법을 이용한 CT 시편의 홀확장 잔류응력 및 응력확대계수 해석
장재순,양원호,김철,고명훈,조명래,Jang, Jae-Soon,Yang, Won-Ho,Kim, Cheol,Ko, Myung-Hoon,Cho, Myoung-Rae 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.5
Cold expansion method is retarded of crack initiation due to the compressive residual stress developed on the hole surface. Previous research has just been study about residual stress distribution in the hole surrounding. But, The purpose of this study was to improve the understanding of the residual stress effect in hole surrounding as crack growth from another hole. In this paper, it is shown that residual stress is redistributed due to the application of cold expansion process for CT specimen using finite element method. It is further shown that tensile stress increases in proportion to cold expansion ratio in the vicinity of crack. It is thought that stress intensity factor increases with cold expansion ratio.
정기현(Ki-Hyun Chung),양원호(Won-Ho Yang),고명훈(Myung-Hoon Ko),성기득(Ki-Deug Sung) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Many mechanical fastened methods have been proposed in order to retard crack initiation and to improve fatigue life. In order to the crack which occurs under the cold expansion residual stress, it necessary the stress intensity factor analysis required. From this analysis, it is possible to estimate the stability of fracture mechanical behavior and fatigue life of the fastened structures. The fatigue crack growth tests were performed for the CT(compact tension) specimen in which the residual stress by cold expansion had been generated. The cold expansion method delays the crack initiation, but hasten the crack growth propagating from the hole. The crack growth rate increases due to the increase in the cold expansion ratio. da/dN- ΔK curves arc slightly different corresponding to the cold expansion ratio, but the curves me included within un agreeable band.
가상균열닫힘법에 의한 기계적 체결부에 존재하는 타원호형 관통균열의 응력확대계수 계산
허성필(Sung-Pil Heo),양원호(Won-Ho Yang),김철(Cheol Kim),고명훈(Myung-Hoon Ko) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3
It has been reported that cracks in mechanical joints usually nucleate as corner cracks at the faying surface of the joints and continuously grow as elliptical arc through cracks. In this paper mixed-mode stress intensity factors for an elliptical arc through crack in mechanical joints are obtained by three dimensional finite element analysis. The virtual crack closure technique is used to calculate stress intensity factors using nodal forces at crack tip and crack opening displacements. Stress intensity factors along elliptical crack front including two surface points are analyzed and the effects of the amount of clearance in mechanical joints on stress intensity factors are investigated.