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모드법에 의한 클램프 조건 사각평판의 음향방사특성 예측모델
유지우(Yoo, Ji-Woo) 한국소음진동공학회 2011 한국소음진동공학회 논문집 Vol.21 No.4
A numerical model based on a mode method coupling beams and a rectangular plate is proposed to estimate radiation characteristics of an edge-clamped rectangular plate. The radiation efficiency and radiation power in the audio frequency range including the critical frequency can be predicted. The proposed model is rather simple and straightforward and gives reliable results comparing to the previous studies. The estimated radiation characteristics are compared to those of the pinned condition plates and also to those based on the formulae proposed by Maidanik. The radiation efficiency of the clamped plate seems a little higher than that of the pinned plate in the frequency range of corner and edge modes. It is explicitly shown that the power as well as efficiency at high frequencies is not influenced by these edge boundary conditions.
승용차량의 중주파수 대역 구조기인 소음예측을 위한 FE-SEA 하이브리드 모델 개발
유지우(Ji Woo Yoo),채기상(Ki-Sang Chae),A. Charpentier,임종윤(Jong Yun Lim) 한국소음진동공학회 2014 한국소음진동공학회 논문집 Vol.24 No.8
Vehicle simulation models for noise and vibration prediction have been developed so far generally in two schemes. One is FE models generally used for problems below 200 Hz such as booming noise, and the other is SEA models for high frequencies of more than 1 kHz, representatively related to sound packages. There have been many researches to develop a simulation model for 200~1000 Hz, so-called mid-frequency region, and this paper shows one practical result that covers the trimmed body of a sedan vehicle. The simulation model is developed based on an FE model, and then FE elements at some areas are substituted with SEA elements to reduce DOFs. SEA panels are described by modal density, radiation efficiency, stiffness and damping characteristics that are found from some numerical assessments. Sound packages are modeled similarly as a conventional SEA model. The results obtained from the hybrid model were compared to experimental results. Predicted pressure and vibrational velocity generally show a good agreement. The developed simulation model and related technology are successfully being used in vehicle development process.
보-판 결합 구조물에서 에너지 흡수체로 작용하는 판의 특성에 따른 파워 전달 특성에 관한 연구
유지우(Yoo, Ji-Woo) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.1
In the built-up structure consisting of a stiff beam and a flexible plate, Grice showed that the plate behaves as an energy absorber in narrow frequency bands(called plate blocking effect). This paper deals with such beam-plate coupled structures, where the plate is an energy absorber and the excited beam is an energy path. It is found that such energy dissipation can occur in the relatively broad bands, if different stiffnesses are used in the rectangular plate. It was experimentally verified by Heckl that the energies in terms of one-third octave band averages transferred to the plate(or dissipated in the plate) increase for increased plate damping. This Paper, however, shows that the energy absorption suddenly reduces at the certain narrow frequency bands where the plate damping effect upon the coupled beam is maximum. Also, in order to minimize energy transfer through the beam in terms of one-third octave band averages, it is advantageous to increase the plate damping closer to the excitation point All these results are based on the wane method.
방사소음 및 투과소음에 대한 승용차량 대시패널의 설계인자 별 영향도 분석
유지우(Yoo, Ji-Woo),채기상(Chae, Ki-Sang),박철민(Park, Chul-Min),서진관(Suh, Jin-Kwan),이기용(Lee, Ki-Yong) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.1
While a dash panel component, close to passengers, plays a very important role to protect heat and noise from a power train, it is also a main path that transfers vibration energy and eventually radiates acoustic noise into the cavity. Therefore, it is important to provide optimal design schemes incorporating sound packages such as a dash isolation pad and a floor carpet, as well as structures. The present study is the extension of the previous investigation how design variables affect sound radiation, which was carried out using the simple plate and framed system. A novel FE-SEA hybrid simulation model is used for this study. The system taken into account is a dash panel component of a sedan vehicle, which includes front pillars, front side members, a dash panel and corresponding sound packages. Design variables such as panel thicknesses and sound packages are investigated how they are related to two main NVH indexes, sound radiation power(i.e. structure-borne) and sound transmission loss(i.e. air borne). In the viewpoint of obtaining better NVH performance, it is shown that these two indexes do not always result in same tendencies of improvement, which suggests that they should be dealt with independently and are also dependent on frequency regions.
형상변경에 따른 구조물 감쇠특성 및 소음 특성 예측기술 연구
유지우(Ji Woo Yoo),서진관(Jin-Kwan Suh),이상우(Sang Woo Lee),박정원(Jong Won Park),박준홍(Jun Hong Park) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
Applying damping sheets or dampers (dynamic or mass) can reduce noise from vibrating structure as well as vibration. However, this approach requires increases of weight and cost. If one can reduce structural noise by only modifying the structural shape, which would be the best practice. It is natural that the noise characteristics change when the structure is modified, but the recent experiment on the sunroof frame showed that the modification of the frame beads results in change of the structural damping, so that the corresponding noise can be reduced. In this context, the reason why the structural damping and the related noise upon an impact excitation is changed is theoretically investigated. The change of dynamic and damping characteristics of the strip panels when their shapes are modified is experimentally found and it is shown that such behaviours can be predicted by computer simulation. Some experimental specimen, mainly striptype panels, are examined for the numerical verification, and especially damping ratios are investigated.
1kHz 이하 구조기인 소음예측을 위한 트림바디 모델의 개발과 적용
유지우(Ji Woo Yoo),채기상(Ki-Sang Chae),A. Charpentier,임종윤(Jong Yun Lim) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.10
Vehicle CAE models for NVH predictions are largely developed in two schemes. One is FE models generally used for below 200 Hz problems such as booming noise, and the other is SEA models for high frequencies of more than 1 kHz, representatively related to sound packages. HMC has tried to develop a CAE model for 200-1000 Hz, so-called mid-frequency region, and this paper is one of the corresponding results. The CAE model is developed based on an FE model, and then FE elements at some areas are substituted with SEA elements to reduce DOFs. SEA panels are described by modal density, radiation efficiency, stiffness and damping characteristics that are found from some numerical assessments. Sound packages are modeled similarly as a conventional SEA model. The CAE model developed in this manner, the hybrid model, was compared to experimental results. Predicted pressure and vibrational velo city generally show a good agreement. The developed CAE model and related technology are successfully being used in vehicle development process.