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디스크 브레이크에서 열섬 천이가 저더 현상 발생에 미치는 영향
조호준(Hojoon Cho),조종두(Chongdu Cho),맹주원(Joowon Maeng),이용산(Yongsan Lee),조기철(Kicheul Cho) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Hot judder phenomenon makes serious problems such as to be uneasiness to drivers or to decrease braking force of vehicle. Because judder vibration makes high magnitude vibration occurrence and thermal problem of brake disk in accordance with hot spots growth at the same time. Therefore it is necessary to reduce or eliminate judder phenomenon by understanding and analyzing origins of hot spot phenomenon. In this experimental study, mode shapes and frequencies related to hot spots were measured by modal testing. For increasing results of modal testing, mode analysis was calculated by finite element analysis. For coupled analysis of disk thickness variation (DTV) and judder vibration, temperature distribution of brake disk, DTV and vibration were measured by interval of 30 seconds in accordance with pressure of master cylinder at the same time. These were conducted by chassis-dynamometer. Hot spot measurements were photographed by using infrared camera. As results, coupled analysis of DTV and judder vibration was performed and relationship between temperature distribution and mode shapes was analyzed.
차량용 브레이크 코너 모듈에서 패드 접촉 면압 분포가 스퀼 현상에 미치는 영향
조호준(Hojoon Cho),이재한(Jaehan Lee),이종화(Jongwha Lee),장진희(Jinhee Jang),김인동(Indong Kim) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Automotive disk brakes generally perform braking by means of friction between the brake disk and pads. Due to the friction, various brake noise can generate from low frequency vibration and high frequency noise. Especially, squeal noise, which generates high frequency noise of pure tone, leads to unpleasant feeling not only to driver but also pass-by people and makes warranty issue of high level. This paper is a study of pad contact pressure distribution on squeal noise phenomenon based on finite element analysis and experiment. For this, modal testing of components and assembly model in a brake corner module is performed and correlated with finite element model. Mode map of components and assembly is composed by performing modal simulation of a correlated finite element model. Operating deflection shape is obtained at squeal noise occurrence condition by using 3D laser vibrometer. Instability mode of complex eigenvalue analysis result is correlated with ODS through changing boundary conditions of FE model. Static pad pressure distributions are measured before and after squeal noise dynamo test, and are simulated in accordance with pad arc lengths of radial chamfer. The Effective pad pressure distribution is determined through analysis of pressure distribution results. Instability mode and mode map is analyzed for finding main factors of squeal noise occurrence. Finally, this paper proposes the design recommendation and complex eigenvalue analysis model using effective pressure distribution.
차세대 원자력 구조용 고온 SiC<SUB>f</SUB>/SiC 복합재료의 기계적 특성
조호준(Ho-Jun Cho),윤한기(Han-Ki Yoon) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
SiC<SUB>f</SUB>/SiC composites are well-known materials for high temperature structural applications because of their intrinsic properties using fusion power reactors such as shield and divertor coolant channel. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC<SUB>f</SUB>/SiC composite can be considered as a promising for structural materials because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the fiber. Therefore, an improvement of the coating fiber is key requirements for fabrication of SiC<SUB>f</SUB>/SiC composites by LPS method. In this paper, The SiC<SUB>f</SUB>/SiC composites were fabricated by the LPS method and investigated effects of SiC fiber coating. The SiC<SUB>f</SUB>/SiC composites were fabricated with coated and uncoated Tyranno-SA fibers. The thickness of the coating fiber was 0.25 ㎛ and 0.5 ㎛. In order to investigate effects of coating, the flexural strength were carried out at room temperature, respectively. The densification and microstructure of LPS-SiC<SUB>f</SUB>/SiC composites were observed by FE-SEM.