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혼합 모드 파괴 기준에서의 T 응력의 영향에 관한 연구
구재민,최태주 한국산업안전학회 2000 한국안전학회지 Vol.15 No.2
Under the mixed mode loading, it has been known that the influence of non-singular terms in the stress fields is serious, because the critical distance, γ_o - the distance of nonlinear elastic region near the crack tip has no negligible value. In this paper, it has been studied on the influence of non-singular terms, T-stress, and the case of T=0, σcos²β, σcos(2β) and 0.05 σcos(2β), under uniaxial tension and compression. It has been seen that the T-stress of σcos(2β) has better than others as comparing to the experimental data.
혼합모드 하중하의 A5052 합금판재에서의 피로시험에 관한 연구
구재민,Gu, Jae-Min 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.5
In this paper, for the mixed mode fatigue problem, the method of determining testing load was proposed. It is based on the plastic zone size and the limited maximum stress intensity factor by ASTM STANDARD E 647-00. The application method of maximum tangential stress criterion and the stress intensity factor for the finite width specimen was proposed. In the result of applying the method to mixed mode fat gut test for A5052 H34, it obtained the satisfactory experimental results on the stable crack growth.
DEVELOPMENT OF A HYDRAULIC LIMITED SLIP DIFFERENTIAL SYSTEM USING A PRESSURE GENERATOR
구재민,C. H. CHOI,Y. HUH,C.-S. SEOK 한국자동차공학회 2008 International journal of automotive technology Vol.9 No.3
The limited slip differential (LSD) is a device that enables the driving force to be transmitted from one slipping wheel to the other by temporarily restraining the differential function when unwanted slipping occurs on muddy or icy roads. Many types of LSD have been developed, such as mechanical lock, disk clutch, viscous coupling, torsen and multiple clutch. This study designed a new type of hydraulic LSD using a pressure generator base on a trochoid gear pump and evaluated the performance of the new design.
최소 변형에너지 밀도 기준의 모호성과 최대 극소 변형에너지 밀도 기준
구재민,Gu, Jae-Min 대한기계학회 2001 大韓機械學會論文集A Vol.25 No.7
Sihs minimum strain energy density criterion(SED) often used in the mixed mode problem has the ambiguity of the choice of minimum values. In this paper, as the method to solve the problem of SED, maximum minimum strain energy density criterion is proposed that the crack propagates in the direction of having the maximum among the minimum values of modified strain energy density factor(MS), i.e., sign($\sigma$(sub)$\theta$).Smin.
구재민(Jae-Mean Koo),석창성(Chang-Sung Seok),강민성(Min-Sung Kang),김대진(Dae-Jin Kim),이동훈(Dong-Hoon Lee),김문영(Mun-Young Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.4
가스터빈 블레이드는 터빈 가동 시 발생하는 고온화염으로부터 블레이드를 보호하고, 구조물의 표면 온도를 안전한 수준으로 낮추기 위하여 블레이드 표면에 열차폐 코팅(TBC; Thermal barrier coating)을 하여 사용하고 있다. 본 논문에서는 가스터빈 1단 블레이드에 적용되는 코팅 방식을 이용하여 코인형 시험편을 제작하였고 열화 온도 및 유지 시간의 변화에 따른 코팅 계면 산화물의 성장 거동을 분석하였다. 코팅 단면에 대하여 코팅 계면 산화물의 두께와 마이크로 비커스 경도를 측정하여 열화 특성을 평가 하였다. 또한 성분분석을 통하여 미세조직의 변화를 관찰함으로써 열차폐 코팅의 열적 열화특성을 평가하였다. The thermal barrier coating of a gas turbine blade was degraded by isothermal heating in a furnace and by varying the exposure time and temperature. Then, a micro-Vickers hardness test was conducted on the cross section of the bond coat and Ni-based superalloy substrate. Further, the thickness of TGO(Thermally Grown Oxide) was measured by using an image analyzer, and the changes in the microstructure and element contents in the coating were analyzed by using an optical microscope and by performing SEM-EDX analysis. No significant change was observed in the Vickers hardness of the bond coat when the coated specimen was degraded at a high temperature; delamination was observed between the top coat and the bond coat when the coating was degraded for 50 h at a temperature 1,151℃.