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공기 유동 효과를 고려한 회전 디스크의 진동 특성 (Ⅱ)
임효석(Hyosuk Lim),임빛(Vit Yim),이승엽(Seung-Yop Lee) 대한기계학회 2008 大韓機械學會論文集A Vol.32 No.2
Experimental studies on the aerodynamic coupling effect on natural frequencies, critical speed and flutter instability of rotating disks are investigated in this paper. The theoretical analysis uses a fluid-structure model where the aerodynamic effects are represented in terms of elastic, lift and damping and stiffness components. The experiments performed using a vacuum chamber and ASMO/DVD disks rotating in vacuum, open and enclosure in several gaps with stationary wall give three main results. One is that the aerodynamic effect by the surrounding air reduces the natural frequencies and critical speeds of the vibration modes. The second is that natural frequency of disks rotating in open air is larger than that in enclosure. Finally, it is shown that the disk vibration is reduced as the gap between the disk and the rigid wall decreases.
SEA 기법을 이용한 저중량 흡, 차음재의 대시판넬 적용에 대한 연구
임효석(Hyosuk Lim),문홍준(Hongjoon Moon),박광서(Kwangseo Park),김영호(Youngho Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this Paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Insulation thickness distribution map was calculated not by measurement, but by FeGate software. AutoSEA software predicted coupling loss factor from insertion loss which was measured by using Reiter Apamat Ⅱ machine and internal damping loss factor from reverberation time according to each thickness and material density. Each predicted transmission losses between conventional insulation and light weight insulation are compared with SEA. Finally light weigh insulation system has lower sound transmission loss and higher absorption coefficient than conventional system.
SEA 방법을 이용한 Acoustic Package의 민감도 해석
임효석(Hyosuk Lim),고성규(Sunggyoo Koh),박광서(Kwangseo Park),김영호(Youngho Kim) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
In this paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Component transmission loss predictions are performed and some of main components are validated with measured data. Interior noises of full vehicle are predicted and validated with measured data. Both component transmission loss and interior noise predictions show good reliability from 400 ㎐ to 10,000㎐. Generally window test is performed to check leakage and acoustic package sensitivity. But it takes much time and man hour to prepare window wall and to test. SEA sensitivity analysis can substitute window test to find where weak area or main airborne noise path is. Comparison sensitivity priority chart through between SEA prediction and window test shows good agreement.
임효석(Hyosuk Lim),신인섭(Inseob Shin),이주형(Joohyung Lee),신용우(Yongwoo Shin),박광서(Kwangseo Park) 한국자동차공학회 2011 한국자동차공학회 학술대회 및 전시회 Vol.2011 No.11
Statistical energy analysis is very useful tool to predict and optimize acoustic performances which are transmission loss and absorption coefficient as well as high frequency interior noise in the advanced development stage. Light weight insulation that has dual impedance layers is considered to create prediction model and find optimal layer information which satisfies both low mass and high performance in this paper. Design of experiment was performed to get trusted response surface model that is almost close to analytical model and analysis of variance to check the sensitivity of input variables. Finally optimization was suggested and optimized solution was validated with test result for two different dash insulations that are optimized and comparison sample. Measured transmission loss and absorption coefficient trend for two samples shows good agreement with predicted result.