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디스코 브레이크에서 열섬 현상이 발생되는 원인과 저더진동에 미치는 영향
조종두(Cho, Chong-Du),김명구(Kim, Myoung-Gu),조호준(Cho, Ho-Joon) 한국소음진동공학회 2006 한국소음진동공학회 논문집 Vol.16 No.8
Hot spot phenomenon is caused by non-uniform contact area between brake pad and disk frequent braking. Brake disk deformed by locally concentrated heat increases magnitude of frictional vibration. And this deformation can highly influence the judder vibration. In this experimental study, vibration and hot spot was measured in accordance with rotation of disk and pressure of master cylinder for finding the factors that causes hot spot phenomena. For comparing hot spot aspects with mode shapes of disk, mode shapes were measured by conducting modal test, and analyzed by using finite element analysis. Relation between hot spot phenomenon, and mode shape, pressure of master cylinder and rotation speed of disk respectively, was achieved by hot spot measurement and frequency analysis.
조종두,안수익,Cho, Chong-Du,Ahn, Soo-Ick 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.11
This paper investigated plane strain stress intensity factors caused by thermal impact on a center-crack strip. The crack was aligned perpendicularly to the strip boundary. The problem was analysed by determining the dislocation density function in the singular integral equations formulated by the dislocation theory. Under the abrupt temperature change along the edge, the center crack behaved as a mode I crack due to the symmetric geometry. The value of maximum stress intensity factor monotonically increased until the ratio of dimensionless crack length approached to about 0.3, followed by gradual decrease. As a result, a critical corresponding crack length was determined.
조호준(Ho-Joon Cho),김명구(Myoung-Gu Kim),맹주원(Ju-Won Maeng),조종두(Chong-Du Cho) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_2
In this experimental paper, the juddering of automotive disk brake was analyzed by the finite element method, and compared with the experimental results. The relationship between specific modes of disk and pad, and hot spot were investigated. The characteristics of judder vibration were measured by using chassis-dynamo and the hot spots were photographed by using high-speed infrared camera. The vibration modes of the disk and pad were measured and a specific relationship between mode shape and hot spots was found. Results show that the judder vibration occurred due to the frequency modulation of the specific mode frequency of disk brake due to the non-linearity phenomenon. This relationship was analyzed by the frequency analysis of judder vibration.
FEM 을 이용한 용접형 금속 벨로우즈의 스프링 상수 해석
박창호(Piao Chang-hao),조종두(Cho Chong-du),허준용(Heo Jun-yong),김명구(Kim Myung-gu),이재한(Lee Jae-han) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
This study tries to analyze the spring constant of welded metal bellows by using FEM. For the purpose of application and newly design of welded metal bellows, the prediction of spring constant is very important. We employ a commercial package of ANSYS 8.0 to analysis the spring constant and use UTM to test the spring constant. Plane 42 and shell 51 element are used for spring constant analysis. The predicted spring constants are compared with the experimental one to discuss the rationality of spring constant analysis process. The analytical result agrees well with experimental data hence explaining the validity of FEM model.
지능형 포탄의 저 감속 회수장치를 이용한 포탄의 감속방법
김명구(Kim, Myoung-Gu),조종두(Cho, Chong-Du),이승수(Lee, Seung-Su),유일용(Yu, Il-Young),장쾌현(Chang, Kwe-Hyun) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.9
With the development of micro electronic circuits and optical equipment, the demand for developing smart munitions with the ability to autonomously search for and attack targets has increased. Since the electronic components within smart munitions are affected by high temperatures, pressure, and impulsive forces upon the combustion of gunpowder, stability and reliability need to be secured for them. Securing those stability and reliability requires soft recovery system which can decelerate smart munitions. A theoretical analysis of flow is performed for the secure recovery of bullets on the basis of Euler equation for compressible fluids. The inner pressure on a pressure tube, the speeds of bullets, and the deceleration of munitions are calculated theoretically. Theoretical results are compared with the data from the experiment with soft recovery system set up at the laboratory.
박철희(Park, Chul-Hui),조종두(Cho, Chong-Du),박창호(Piao, Chang-Hao) 한국소음진동공학회 2004 한국소음진동공학회 논문집 Vol.14 No.12
The non-linear responses of a slender rectangular cantilever beam subjected to lateral harmonic base-excitation are investigated by the 2-channel FFT analyzer. Both linear and nonlinear behaviors of the cantilever beam are compared with each other. Bending mode, torsional mode, and transverse mode are coupled in such a way that the energy transfer between them are observed. Especially, superharmonic, subharmonic, and chaotic motions which result from the unstable inertia terms in the transverse mode are analyzed by the FFT analyzer The aim is to give the explanations of the route to chaos, i.e., harmonic motion \longrightarrow superharmonic motion \longrightarrow subharmonic motion \longrightarrow chaos.
박철희(Pak, Chul-Hui),조종두(Cho, Chong-Du),조기철(Cho, Ki-Cheol),김명구(Kim, Myoung-Gu) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.1
The cantilever beam with nonlinearity has many dynamic characteristics of nonlinear vibration. Nonlinear terms of a flexible cantilever beam include inertia, spring, damping, and warping. When the beam is given basic harmonic excitation, it shows planar and nonplanar vibrations due to one-to-one resonance. And when the one-to-one resonance occurs, the flexible beam shows different behaviors in those vibrations. For the one-to-one resonance occurring in each mode, the phase value of the planar vibration is different from that of the nonlinear vibration. This paper investigates the phase change and the phase difference between such planar and nonplanar vibrations which are caused by one-to-one resonance.