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김철(Cheol Kim),양원호(Wonho Yang),석창성(Changsung Seok),허성필(Sungpil Heo) 한국자동차공학회 2001 한국 자동차공학회논문집 Vol.9 No.6
The hole-drilling method makes a little hole through the metal surface that has residual stress and measures the relieved stress with a strain gage. It is used widely in measuring the residual stress of surfaces. In this method, the inclined hole is one of the source of error. This paper presents a finite element analysis of influence of the inclined hole for the uniaxial residual stress field. The stress differences between measured and applied residual stress increase proportionally to inclined angle of the hole. The correction equations which easily obtain the residual stress taking account of the inclined angle and direction are derived. The measurement error of stress due to the inclined hole can be reduced to around I % through this study.<br/>
확장유한요소법을 이용한 타이어 비드부 균열 진전 가시화 기법 개발
박한석(Hanseok Park),김성래(Seongrae Kim),강민성(Mingsung Kang),성기득(Kideug Sung),석창성(Changsung Seok) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
The durability of the tire is a very important performance and a matter that should be considered a top priority during tire development in terms of passenger safety and vehicle protection. Also, social necessity for the eco-friendly cars are rapidly growing because of high oil prices and environmental regulations, so the early commercialization of electric vehicles is becoming possible. For this reason, the development of high durability tire was required in the tire industry that can endure the high weight of the electric car. To ensure tire durability, it is necessary to evaluate and analyze about bead crack propagation. Estimation of the cracking problem has been studied by various methods. Of them, using the FEM(Finite Element Method) requires re-mesh process and computing time. However XFEM (eXtended Finite Element Method) developed by Belytschko does not require re-mesh process according to the crack propagation, so it is easy to apply to the crack propagation method. Because of these advantages, XFEM has been used to deal with crack problems in many recent papers. Therefore, in this paper, we apply XFEM to tire fracture problem to visualize crack propagation in the bead area and aspects of fracture is compared with FMVSS 109 endurance test result.
김주형(Joohyung Kim),성덕환(Dukhwan Sung),송한림(Hanlim Song),임채홍(Chaehong Lim),김정준(Jungjune Kim),석창성(Changsung Seok),김현수(Hyunsoo Kim) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_2
Shift force simulator for a manual transmission is developed to estimate the shift force that is transmitted to the drivers hand. In order to develop the simulator, dynamic models of the external linkage, internal linkage, synchronizer and drivetrain are obtained. The synchronizing motion is modelled as eleven steps depending on the relative displacement of the sleeve to the ring spring, outer ring chamfer, and gear chamfer. The contact mechanism between the chamfer to chamfer is modelled as a linear spring. Based on the dynamic model of each element, a shift force simulator is developed. The simulator calculates the sleeve displacement, cone torque, poppet ball torque, sleeve force, shift force and the speed of the input and output shaft. It is found that the shift force by the simulator shows a good correlation with the test results and it is expected that the shift force simulator developed in this study can be used as a useful design tool to evaluate the shift feeling in the initial design stage.
단결정 CMSX-4의 상온 및 고온 기계적 물성에 관한 연구
김태형(Taehyung Kim),안성철(Sungchul Ahn),홍석우(Seokwoo Hong),윤병관(Byounggwan Yun),안종기(Jongkee Ahn),석창성(Changsung Seok),한착희(Chakheui Han),김기태(Kitae Kim),신동익(Dongick Shin),장병문(Byungmoon Chang),김용련(Yeongryeon Ki 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
Ni기 초내열합금은 고온에서 강도를 유지할 수 있기 때문에 가스터빈 엔진의 블레이드와 같은 고온 부품에 널리 사용된다. 이런 초내열합금 중 단결정 응고를 통해 만들어진 부품은 고온에서 크리프 특성이 우수하여 최근 가스터빈 엔진에 많이 사용된다. CMSX-4는 이런 단결정 소재로 본 연구에서는 단결정 CMSX-4가 가지는 상온 및 고온에서의 기계적 물성을 평가하였다. 인장 강도 평가 결과 800℃ 근방에서 가장 우수한 인장 강도를 보였고 크리프 시험 결과에서는 고응력에서 파단 수명이 급격하게 감소하였다. 이런 결과는 슬립 시스템의 변화로 고온 또는 고응력에서 강도가 급격하게 변화하는 것으로 판단된다. Ni base superalloy is widely used for blade of gas turbine engine, since it has high strength at high temperature. Among superalloys, single-crystal solodified components are much used in recent gas turbine engine. Single-crystal superalloy. has not only high strength but also high creep resistance than equiaxed structured superalloys. CMSX-4 is representative single-crystal materials and we evaluated mechanical properties at room and high temperature. Tensile test results show that strength is highest around 800℃. Creep test results show that rupture-time was much shortened than predicted time. We can conclude that this results are come from variation slip system along temperature and stress.
박기범(Kibum Park),박수(Soo Park),최재구(Jaegu Choi),이정민(Jungmin Lee),김가연(Gayeon Kim),석창성(Changsung Seok) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.1
HRV40 is used in the engine valves of vehicles. Since an automobile engine operates at a high temperature of 750 °C or more, it is necessary to study the creep behavior of the valve material to ensure safety and reliability. In this paper, the results of the creep tests at 750~800 °C and a stress range of 50~250 MPa, based on ASTM E139 of HRV40 steel, are included. The data were analyzed by using the Monkman-Grant equation that is related to the steady-state creep rate and rupture time, and the modified Monkman-Grant equation, which is also associated with creep deformation. Larson-Miller parameter, one of the TTP (time-temperature parameters), was used in lifetime prediction. Then, verification testing was conducted.