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FE-BEM 및 SEA 해석 기법을 활용한 샌드위치 복합재 구조물의 전 주파수 대역 음향 해석
이대은,이윤규,김홍일,김재영,Lee, Dae-Oen,Lee, Yoon-Kyu,Kim, Hong-Il,Kim, Jae-Young 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.4
Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.
A Comparison of Vibration Isolation Characteristics of Various Forms of Passive Vibration Isolator
이대은(Lee, Dae-Oen),한재흥(Han, Jae-Hung) 한국소음진동공학회 2012 한국소음진동공학회 논문집 Vol.22 No.9
Transmission of unwanted vibration to sensitive systems can cause various problems including performance degradation and system malfunction. The most common approach to limit the transmission of harmful vibration disturbances to the sensitive system is adapting passive vibration isolator. The classical passive vibration isolator comprising a viscous damper and spring element in parallel, however, exhibits conflicting performance characteristics in that low amplification at the resonance, which is desirable, can only be achieved at the sacrifice of vibration isolation performance in high frequency region, which is undesirable. In this paper, vibration isolation characteristics of various passive isolator schemes in literature to circumvent this conflict are introduced and compared.
A Comparison of Vibration Isolation Characteristics of Various Forms of Passive Vibration Isolator
Dae-Oen Lee(이대은),Jae-Hung Han(한재흥) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.4
정밀 시스템에 전달되는 진동은 시스템의 성능 저하 및 오작동을 초래할 수 있기 때문에 저감되어야 한다. 진동을 저감시키는 가장 일반적인 방법은 진동이 전달되는 경로에 수동 진동절연 장치를 도입함으로 전달되는 진동을 절연시키는 방법이다. 탄성소자와 점성 감쇠기로 구성된 일반적인 수동 진동 절연 장치는 공진에서의 전달율을 낮추기 위해서 고주파수 대역에서 진동 절연 성능을 희생해야 하는 단점을 지니고 있다. 본 논문에서는 공진에서 낮은 전달율과 고주파수 대역에서 높은 진동 절연 성능을 동시에 가진 수동 진동 절연 장치들의 특성을 비교분석하였다. Transmission of unwanted vibration to sensitive systems can cause various problems including performance degradation and system malfunction. The most common approach to limit the transmission of harmful vibration disturbances to the sensitive system is adapting passive vibration isolator. The classical passive vibration isolator comprising a viscous damper and spring element in parallel, however, exhibits conflicting performance characteristics in that low amplification at the resonance, which is desirable, can only be achieved at the sacrifice of vibration isolation performance in high frequency region, which is undesirable. In this paper, vibration isolation characteristics of various passive isolator schemes in literature to circumvent this conflict are introduced and compared.
Development of Active Micro-Vibration Isolator using Electromagnet
Dae-Oen Lee(이대은),Gee-Yong Park(박지용),Jae-Hung Han(한재흥) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4
고정밀 광학계를 탑재한 관측 위성은 매우 높은 지향 안정성을 요구하지만 인공위성의 자세 제어를 위해 사용하는 반작용 휠, 극저온 냉각을 위한 cooler 등 다양한 진동원에 의해 미소 진동이 발행할 수 있다. 고정밀 탑재체를 외부 진동으로부터 보호하기 위한 가장 일반적인 방법은 진동이 전달되는 경로에 진동 절연장치를 도입하는 것이다. 본 논문에서는 미소진동 절연을 위한 1 축 능동 진동 절연장치의 개발 및 진동 절연 성능 시험을 기술하였다. 개발한 절연장치의 고유진동수를 조절하기 위해 원하는 강성을 갖는 membrane 구조를 설계하였으며 능동 제어를 위해 전자석을 사용하였다. 절연장치의 성능 시험 결과를 통해 능동 제어 시 고주파수 대역에서 절연성능의 저하 없이 공진의 크기를 줄일 수 있는 것과 개발된 진동 절연 장치가 미소 진동을 효과적으로 절연 할 수 있는 것을 확인하였다. Observation satellites carrying high precision optical payload require extremely stringent pointing stability that may be violated in the presence of the disturbances coming from reaction wheels, cryocoolers or other actuating components onboard the satellite. The most common method to protect the sensitive payloads from external disturbances is implementation of vibration isolator. In this paper development of a single axis active vibration isolator using electromagnet and its performance in isolating micro-vibration is presented. The main components of the developed isolator are membrane structure providing the isolator with the required stiffness and an electromagnet for active control. The performance test results show that additional damping can be achieved by active control without degrading isolation performance in high frequency region and that the developed isolator can effectively isolate micro-vibration.
금속 및 샌드위치 복합재 유도탄 구조체의 흡음 및 차음 특성에 관한 실험적 연구
이윤규,이대은,진병대,이동민,Lee, Yoon-kyu,Lee, Dae-oen,Jin, Byung-Dae,Lee, Dong-min 한국군사과학기술학회 2018 한국군사과학기술학회지 Vol.21 No.3
Recently, as the speed and performance of the launcher and the missile have been improved, it is necessary to consider the acoustic load of launching and flight in initial design step. In this paper, an experimental study on acoustic absorption and transmission characteristics of aluminium vs. sandwich composite structures were conducted. The overall noise reduction was evaluated by performing an acoustic test in the reverberation room, and the acoustic absorption and transmission loss of the structures were analyzed by conducting the sound absorption test inside the structure.