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지창헌,Chi, Chang-Heon 한국음향학회 1995 韓國音響學會誌 Vol.14 No.2
타이어와 노면의 상호작용에 의해 발생하는 소음에 대한 이론적인 모델에 대하여 연구하였다. 모델은 레디얼 타이어의 벨트 운동을 얇은 셀 방정식들로 가정하고 Bohm이 유도한 운동방정식을 기초로 하였으며 이들 방정식에 요구되는 구조적인량은 타이어의 재질적인 특성을 기초로 유도하였다. 타이어의 회전형태는 이들 방정식들의 정상상태로 부터 계산되고 진통 응답은 전체 종속적인 셀 방정식에 의해 구하였다. 타이어 노면 접지면에서의 힘은 타이어 트레드의 기하학적인 형상과 접지압의 분포를 기초로 계산하였고 소음방사는 심프슨 적분에 의해 계산된다. 여러가지 설계인자의 변화에 대한 효과를 조사하여 저소음 타이어 설계의 기초자료를 확보하는데 목적이 있다. A theoretical models has been prepared which describes the noise generated by tire/road interaction for the tire structure-borne sound analysis. The model begin with a set of thin shell equations describing the motion of the belt of a radial ply tire, as drived by Bohm('mechanisms of the belted tire', Igeniur-Archiv, XXXV, 1966). Structural quantities required for these equations are derived from material properties of the tire. The rolling shape of a tire is computed from the steady-state limit of these equations. Vibrational response of the tire is treated by the full dependent shell equations. The force input at the tire/road interface is calculated on the basis of tread geometry and distribution of contact patch pressure. Radiation of noise is calculated by a simpson integral. Using the programs, the effect on noise of various tire design variations is computed and discussed. Trends which lead to quiet tire design are identified.
하중을 받고 회전하는 승용차 타이어의 반경방향 고규진동수 측정에 관한 실험적 연구
김병삼,홍동표,지창헌,Kim, Byoung-Sam,Hong, Dong-Pyo,Chi, Chang-Heon 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.1
The measurement of radial directional natural frequency ina passenger car tire rotating under the load is studied. In order to obtain theoretical matural frequency and mode shape, the ploane vibration of a tire is modeled to that of circular beam. By esing the Tieking method based on Hamiltons's principle, theoretical results are determined by considering tension horce due to tire inflation pressure, retational velocity and tangential, radial stiffness. Radial directional modal parameters varying with the inflation pressure, load, rotational velocity are experimentally determined by using frequency response function method. The results show that experimental conditions canbe considered as the parameters which shift the natural frequency.
김병삼 ( Byoung-sam Kim ),지창헌 ( Chang-heon Chi ) 한국환경기술학회 2007 한국환경기술학회지 Vol.8 No.2
공장 내에서의 소음레벨과 소음폭로레벨은 청력보존프로그램을 필요로 한다. 효과적인 청력 보존 프로그램을 수립하지 않으면 작업자의 청력 손실의 위험이 있다. 최근 수 년 동안 청력손실을 유발하는 설비를 가진 회사와 작업자 사이에서 집단 소송에 의한 청력 손실 보상 문제가 증가하고 있다. 2,000 Hz에서 98.3 dB(A)의 소음을 발생하고 있는 화장지 공장 송풍기 소음은 화장지 공장에서 작업하고 있는 작업자의 청력손실에 큰 영향을 미치고 있다. 따라서 흡음재를 이용한 방음상자의 설치로 화장지 공장 송풍기 소음을 24.4 dB(A) 저감하였다. 이는 밀폐형 방음상자가 화장지 공장 송풍기 소음을 효과적으로 저감시킬 수 있는 한 방법임을 보여주고 있다. The noise levels and individual employee noise exposure levels within a factory will determine the need for hearing conservation program. The difficulty in not having an effective hearing conservation program is the risk of hearing loss that employees may sustain. In the last few years the claims for hearing loss compensation have grown due to class action litigation brought against the employer and companies that have equipment in the factory alleged to have caused hearing loss. The Blower in restroom paper factory generates the noise of 98.3 dB(A) in the frequency range of 2,000 Hz, which may cause occupational hearing loss. By designing close type enclosures which are made of absorption material, about 24.4dB(A) reduction has been in the factory. It is demonstrated that this kind of enclosures can be effectively used to reduce the noise in the factory.
범프 로드에서 대형트럭 프레임의 탄성효과를 고려한 컴퓨터 모델 개발
문일동(Moon, Il-Dong),지창헌(Chi, Chang-Hun),김병삼(Kim, Byoung-Sam) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.10
This paper develops a computer model for estimating the bump characterisitcs of a cat)over type large-sized truck. The truck is composed of front and rear suspension systems, a frame, a cab, and ten tires. The computer model is developed using MSC.ADAMS. A shock absorber, a rubber bush, and a leaf spring affect a lot on the dynamic characteristic of the vehicle. Their stiffness and damping coefficient are measured and used as input data of the computer model. Leaf springs in the front and rear suspension systems are modeled by dividing them three links and joining them with joints. To improve the reliability of the developed computer model, the frame is considered as a flexible body. Thus, the frame is modeled by finite elements using MSC.PATRAN. A mode analysis is performed with the frame model using MSC.NASTRAN in order to link the frame model to the computer model. To verify the reliability of the developed computer model, a double wheel bump test is performed with an actual vehicle. In the double wheel bump, vortical displacement, velocity, acceleration are measured. Those test results are compared with the simulation results.
도로 교통소음의 환경평가 단위인 24시간 등가소음레벨에 대한 적정성 검토에 관한 연구
김병삼(Kim, Byoung-Sam),지창헌(Chi, Chang-Heon),최홍철(Choi, Hong-Chul) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.3
Road traffic noise is not produced by any one factor rather it occurs as a composition of various factors. Its occurrence is made by running engine noise, tire frictional, and exhaust noise etc. The quality of the noise depends on the size of the vehicles, rotation and engine speed, vehicle load, package state of the road and incline etc. The occurrence of any noise level of heavy trucks appears louder than smaller vehicles and the noise levels produced differs according to speed and load etc between similar size vehicles. Other factors such as traffic density, average speed, mixing rate of heavy vehicles, and the distance between vehicles also generate road traffic noise. In this paper we examine 2, 4, and 6-lane roads in Jeonju. Consequently, this study examines the means used to measure road traffic noise. It was found that when there is a large traffic density and the average velocity is below 70 km/h, the noise level could receive a relative proper value by the current measuring means. But in the case of night-time, it was found that the current measuring method is inapposite.
알루미늄의 Silane 표면처리에 따른 AI/CFRP 이종재의 피로특성
김만태(Man Tae Kim),이경엽(Kyong Yop Rhee),지창헌(Chang Hun Chi) 한국표면공학회 2004 한국표면공학회지 Vol.37 No.1
In this study, we investigated the fatigue characteristics of silane-treated aluminum/CFRP composite material. Three different specimens of cracked aluminum, cracked aluminum repaired with CFRP patch, and silanetreated aluminum repaired with CFRP patch were used in the fatigue tests. Load ratio and the frequency applied in the fatigue tests were 0 and 10 ㎐, respectively. The results showed that the specimen repaired by composite patch showed three times more improved fatigue life than aluminum specimen. Furthermore, the silane-treated specimen repaired by composite patch showed four times more improved fatigue life than the non-treated specimen.