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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 마찰재의 온도와 압력에 따른 물성치 변화를 고려한 스퀼 소음 해석 연구
조호준(Hojoon Cho),김정태(Jeong-Tae Kim),채호중(Ho-Joong Chae) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.10
This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.
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.
조호준(Ho-Jun Cho),정제평(Je-Pyong Jeong) 한국콘크리트학회 2021 한국콘크리트학회 학술대회 논문집 Vol.33 No.1
철근콘크리트 구조물에 균열이 발생하면 실제 휨모멘트는 선형탄성해석 결과와 다르게 나타난다. 휨모멘트의 분포는 지점부에서 균열이 발생하면 달라지기 시작한다. 철근콘크리트 보에 균열이 발생하면 강성변화가 일어난다. 따라서, 본 연구는 모멘트분배 과정의 매트리스 구조해석을 하였다. When a crack occurs in a reinforced concrete structure, the actual bending moment appears different from the results of the linear elastic analysis. The distribution of the bending moment starts to change when a crack occurs at the point. When cracks occur in reinforced concrete beams, stiffness changes occur. Therefore, this study performed a matrix structure analysis of the moment distribution process.
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.
조호준(Hojoon Cho),조종두(Chongdu Cho),김명구(Myoung-Gu Kim),맹주원(Juwon Maeng),이용산(Yongsan Lee) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Hot spot phenomenon that occurs, during judder vibration, is locally concentrated heat due to friction between brake disk and pad. It is important to understand the reason behind hot spot phenomenon, for reduction of judder vibration. In this experimental study, experiments were performed in accordance with rotation speed of brake disk, pressure of master cylinder and pad length for achieving different aspects of hot spot phenomenon. Temperature distribution of hot spot was obtained by using the infrared camera. As the hot spot occurred, vibration was measured and frequency analysis was performed. Finite element analysis of thermal deformation of disk was performed by using temperature distribution that was achieved by experimental results. It was observed that the excitation frequency band of frictional contact and frictional force mainly affects the hot spot phenomenon.
Intermediate bracket 재료선정에 따른 진동전달 특성의 변화
조호준(Hojoo Cho),조환철(Whanchul Cho),이충도(Choongdo Lee),김인동(Indong Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
This paper presents an experimental verification of the effects of material properties on the automotive performance, by conducting experiments on intermediate brackets. For the experimental purpose, same shapes of Intermediate brackets are used but different materials. It measures the engine side vibration, body side vibration, and interior noise of intermediate brackets for different materials, in the state of wide-open throttle. Analytical result of engine mount attenuation for each axis show that more stiff and massive it is the lower the automotive performance is. The important design variable for the intermediate bracket is the proper selection of material in the side of noise and vibration.
LPS법에 의한 카본코팅 Tyranno-SA 섬유 보강한 복합재료의 굽힘 강도 특성
조호준(Ho-Jun Cho),문승현(Seung-Hyun Moon),윤한기(Han-Ki Yoon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
A recently developed SiC fiber, Tyranno-SA (2D plain-woven), was used as the reinforcemnet in several SiC<SUB>f</SUB>/SiC composites. The composites were fabricated by liquid phase sintering (LPS) process. The mechanical properties and fracture behaviors of LPS-SiC<SUB>f</SUB>/SiC composites, with the fiber volume fraction, were investigated in conjunction with a detailed analysis of their microstructure. The fiber preforms were prepared to keep a fiber volume fraction of about 20%, 30% and 40%, respectively. The flexural strength of LPS-SiC<SUB>f</SUB>/SiC composites were also carried out at room temperature thought three point bending test. A decrease in the fiber volume fraction led to an increase in the flexural strength of the LPS-SiC<SUB>f</SUB>/SiC composites, accompanying nearly full-density and a highly dense matrix with fiber bundle.