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이중혁(Junghyeok Lee),김석현(Seockhyun Kim) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.5
Aluminum extruded panel used in a high speed train shows high stiffness, however, its sound insulation performance is remarkably decreased by local resonance phenomena. In this paper, improvement strategy of the sound insulation performance is proposed for the floor extruded panel used in HEMU-400x, 400km/h class next generation high speed train under development, and the improvement effect is verified by experiment. Aluminum extruded panel specimen for the floor is manufactured and urethane foam is installed in the core of the panel. Based on ASTM E2249-02, intensity transmission loss is measured and the improvement effect in local resonance frequency band is verified. Finally, improvement effect of the sound insulation performance is estimated on the layered floor structure including the foamed aluminum panel.
이중혁(Joong Hyeok Lee),변준호(Jun Ho Byeon),김석현(Seockhyun Kim) 대한기계학회 2018 大韓機械學會論文集A Vol.42 No.5
2018 평창 동계올림픽대종(이하 올림픽대종)은 2018 동계올림픽의 성공적인 개최를 기원하기 위하여 제작되었다. 올림픽대종은 항아리 모양의 전통 범종 구조에 세계 스포츠 축제를 기념하는 역동적인 소리를 내도록 설계되었다. 종소리가 힘차게 들리기 위해서는 맥놀이가 선명하고 주기가 너무 짧거나 길지 않아야 한다. 그러나 맥놀이는 주조과정에서 발생하는 미세한 비대칭성에 기인하므로 설계단계에서는 예측이 불가능하다. 주조 후 올림픽대종의 맥놀이는 거의 들리지 않을 정도로 주기가 지나치게 길었다. 본 연구에서는 등가 종 모델을 이용하여 맥놀이 주기를 조절하였다. 맥놀이를 만드는 진동 모드쌍을 측정하여 등가 종의 유한요소모델을 구성하였다. 등가 종 모델의 하부 두께를 국부적으로 감소시키면서 맥놀이의 변화를 해석적으로 구하였다. 해석 결과를 이용하여 선명하고 적절한 주기의 1차음 맥놀이를 만들었고, 힘차고 역동적인 소리를 내는 것을 실험적으로 확인하였다. The Great Bell of 2018 Pyeongchang Winter Olympics (Olympic Bell) was built to symbolize hope for the successful hosting of the 2018 Winter Olympics. Olympic Bell was designed to provide a dynamic sound at the world sports festival in the form of a traditional Korean bell shaped like a jar. For the dynamic sound of the bell, the beating sound should be clear and not too short or too long. However, beating was not predictable at the design stage because it was caused by the minute asymmetry in the casting process. After the casting, the beat period of the Olympic Bell was too long for the sound to be heard as desired. In this study, we improved the beat period using an equivalent bell model. A finite element model of the equivalent bell was constructed using the measured vibration modes that compose the beat. The change in beat period was analytically determined while gradually reducing the local thickness of the equivalent bell model. As a result, we created a strong and appropriate period of beat, and experimently confirmed that it produces powerful, dynamic sounds.