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장경천(K.C. Jang),국중민(J.M. Kuk),최병희(B.H. Choi),정재강(J.K. Chung),최병기(B.K. Choi) 한국생산제조학회 2004 한국생산제조시스템학회 학술발표대회 논문집 Vol.2004 No.4
Effects of Nb(Niobium) contents and solution annealing on the strength and fatigue life of 18%Ni maraging steel commonly using in aircraft, space field, nuclear energy, and vehicle etc. were investigated. Also the fatigue life stress intensity factor were compared experiment result and FEA(finite element analysis) result. The more Nb content, the higher or the lower fatigue life on base metal specimens or solution annealed specimens showing that the fatigue life was almost the same. The maximum stresses of X, Y, and Z axis direction showed about 2.12×10²㎫, 4.40×10²㎫ and 1.32×10²㎫ respectively. The Y direction stress showed the highest because of the same direction as the loading direction. The fatigue lives showed about 7% lower FEA result than experiment result showing almost invariable error every analyzed cycle. Stress intensity factor of the FEA result was lower about 3.5~10% than that of the experiment result showing that the longer fatigue crack length, the higher error. It considered that the cause for the difference was the modeled crack tip having always the same shape and condition regardless of the crack growth.
온도변화에 따른 자동차 전륜구동축재의 피로크랙전파거동에 관한 연구
이상열(S.R.Lee),정재강(J.K.Chung) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
In this study, the rotary bending fatigue test was carried out with two kinds of material, S43C and S50C, using in the Front engine and Front drive wheels(F.F.) of vehicle. The one part of specimens was heated by high frequency induction method(about 1mm depth and H_RC 56~60) and tested environment temperature were -30℃, +25℃ and +80℃ in order to look over the influence of the heat treatment and the temperatures.<br/> In the experimented result at +25℃ and +80℃, the fatigue life of non-heated specimens were decreased about 35%, but that of heated specimens were decreased about only 5% at +80℃ more than at 25℃. And in the experiment result at -30℃ and +25℃, the non-heated and heated specimens were about 110%, 120% higher fatigue life at -30℃ than at the +25℃ each other. On the other hand, the fatigue crack propagation rate of S50C was higher than that of S43C.
이종 마찰용접 경계부에서 피로크랙 발생거동에 관한 연구
정재강 朝鮮大學校 機械技術硏究所 2005 機械技術硏究 Vol.8 No.2
The fatigue crack initiation behavior in dissimilar friction weld interface rigion of two kind of heat-resisting steel A and B commonly using in valve material for vehicles were investigated. A small circular artificial defect was machined to induce fatigue crack at the interface rigion of welded specimens. From the result of experiment. fatigue limits of the materials were obtained. The base metal of material B showed 185% higher fatigue life than that of material A. But the fatigue life of bond line notched specimen was shown about 21% for material A and about 70% for material B shorter than that of the base metal specimen.
장경천,국중민,최병희,정재강,최병기 한국공작기계학회 2004 한국공작기계학회 춘계학술대회논문집 Vol.2004 No.-
Effects of Nb(Niobium) contents and solution annealing on the strength and fatigue life of 18%Ni maraging steel commonly using in aircraft, space field, nuclear energy, and vehicle etc. were investigated. Also the fatigue life stress intensity factor were compared experiment result and FEA(finite element analysis) result. The more Nb content, the higher or the lower fatigue life on base metal specimens or solution annealed specimens showing that the fatigue life was almost the same. The maximum stresses of X, Y, and Z axis direction showed about 2.12×10²MPa, 4.40×10²MPa and 1.32x10²MPa respectively. The Y direction stress showed the highest because of the same direction as the loading direction. The fatigue lives showed about 7% lower FEA result than experiment result showing almost invariable error every analyzed cycle. Stress intensity factor of the FEA result was lower about 3.5~10% than that of the experiment result showing that the longer fatigue crack length, the higher error. It considered that the cause for the difference was the modeled crack tip having always the same shape and condition regardless of the crack growth.