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Micro-texturing한 미끄럼 베어링의 윤활해석
박태조(Taejo Park),김민정(Minjeong Kim),정요한(Yohan Jeong) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4
Friction reduction is essential to improve efficiency and reliability of all machines. It is recently reported that the micro-textured machine components such as thrust bearings, mechanical face seals and piston rings can reduce the friction force drastically. The results are mainly experimentally reported, however, precise theoretical results are not enough. In this paper, a commercial computational fluid dynamics(CFD) code, FLUENT is used to investigate the lubrication characteristics of two types of sliding bearing having 3-dimensional micro-dimple. The results show that the pressure distributions and bearing load capacities are highly affected by dimple location and film shapes. And reduction of friction force acting on micro-dimpled sliding bearing surface are obtained regardless of sliding bearing types. Therefore the numerical results can be use in optimum sliding bearings.
유막온도경계조건이 평행 슬라이더 베어링의 윤활성능에 미치는 영향
박태조(TaeJo Park),김민규(MinGyu Kim) 한국트라이볼로지학회 2017 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.33 No.5
In sliding bearings, viscous friction due to high shear acting on the bearing surface raises the oil temperature. One of the mechanisms responsible for generating the load-carrying capacity in parallel surfaces is known as the viscosity wedge effect. In this paper, we investigate the effect of film-temperature boundary conditions on the thermohydrodynamic (THD) lubrication of parallel slider bearings. For this purpose, the continuity equation, Navier-Stokes equation, and the energy equation with temperature-viscosity-density relations are numerically analyzed using the commercial computational fluid dynamics (CFD) code FLUENT. Two different film-temperature boundary conditions are adopted to investigate the pressure generation mechanism. The temperature and viscosity distributions in the film thickness and flow directions were obtained, and the factors related to the pressure generation in the equation of motion were examined in detail. It was confirmed that the temperature gradients in the film and flow directions contribute heavily to the thermal wedge effect, due to which parallel slider bearing can not only support a considerable load but also reduce the frictional force, and its effect is significantly changed with the film-temperature boundary conditions. The present results can be used as basic data for THD analysis of surface-textured sliding bearings; however, further studies on various film-temperature boundary conditions are required.
Application of Artificial Insemination Technology for Dairy Breeding in Mongolia
Hyun‐Tae Jo,Jong‐In Jin,Seong‐Su Kim,Byung‐Hyun Choi,Tumor Baldan,Jung‐Gyu Lee,Yun‐Shik Kim,Sam‐Churl Kim,Il‐Keun Kong 한국동물생명공학회(구 한국동물번식학회) 2011 발생공학 국제심포지엄 및 학술대회 Vol.2011 No.1
This study was focused on improvement of milk production in Mongolia dairy industry by artificial insemination (AI) technology, of which was supported from ODA project of KOICA in Republic of Korea. The study was started from January 2009 to present and 3rd years in this year. So, all data, especially synchronization and pregnancy of dairy cows (Holstein) will be summarized in final result in this year. For synchronization, total 81 dairy cows selected from 4 private farms that were 38, 30, 8 and 5 in Undarmal milk, Onjin (Enkhbayer), Jargalant, and BRM School, respectively. All the dairy cows were injected intramuscular (IM) of 5 ml PGF2α in the vulva and detected estrus 2 to 3 days after PGF2α injection. Total 78 out of 81 dairy cows (96.3%) were detected estrus by only 1 time injection of PGF2α. The dairy cows that were induced estrus, inseminated with 0.5 ml dairy frozen semen by conventional AI techniques. The pregnancy diagnosis of the AI dairy cows was detected by uterus palpation after 60 days of insemination. Total 75 from 78 inseminated dairy cows (90.1%) were diagnosis pregnant. The estrus induction and pregnant rate were very effective using PGF2α injection and conventional AI techniques in Mongolia dairy cow. The results indicated that AI after estrus induction in Mongolia dairy cows could be applied to dairy breeding technology to improve the breeding efficiency and milk production.