• Title/Summary/Keyword: Acoustic Load

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Acoustic Load Reduction in the Payload of Small Launch Vehicle by using Resonators (공명기를 이용한 소형위성발사체 탑재부의 음향하중 저감)

  • Seo, Sang-Hyeon;Jeong, Ho-Kyeong;Park, Soon-Hong;Jang, Young-Soon;Yi, Yeong-Moo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.234-237
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    • 2007
  • To protect a satellite and electronic equipment from the acoustic load generated by rocket propulsion system, many launch vehicle use acoustic blanket. Acoustic load is main source of random vibration working on the payload. Most high frequency region of the acoustic loads is reduced by payload fairing skins and acoustic blanket, but low frequency region is not. In order to reduce acoustic load of low frequency region, we designed array resonator panel which was made of composite materials. Insertion loss capacity of the payload fairing with acoustic blanket was verified from PLF acoustic test in the acoustic chamber.

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Effect of Source Line Location on Lift-off Acoustic Loads of a Launch Vehicle (음원 분포선 위치가 발사체 이륙 음향하중에 미치는 영향)

  • Choi, Sang-Hyeon;Ih, Jeong-Guon;Lee, Ik-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.8
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    • pp.539-545
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    • 2015
  • Intense acoustic load is generated when a launch vehicle lifts off, causing the damaging vibrations at the launch vehicle or satellite within the fairing. This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. As a test example, the lift-off acoustic load on the Korean launch vehicle, NARO, is predicted by the existing calculation tool, the modified Eldred's second method. Although the acoustic sources, assumed as point sources, are to be located along the center line of the exhaust plume when using the Eldred's prediction method, the exact location of the deflected center line of exhaust gas flow is not usually known. To search for the most appropriate source positions, six models of source line distribution are suggested and the acoustic load prediction results from these models are compared with the actual measurements. It is found that the predicted sound pressure spectrum of the Naro is the most similar to the measured data when the centerline of the turbulent kinetic energy contour is used as the source line.

Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1146-1151
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

Acoustic Analysis in the Payload Fairing of Launch Vehicle (위성 발사체 페어링 내부음향 해석)

  • Seo, Sang-Hyeon;Park, Soon-Hong;Jeong, Ho-Kyeong;Jang, Young-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2011.10a
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    • pp.196-201
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    • 2011
  • Acoustic load from rocket propulsion system is main source of random vibration working on the payload. To protect payload from this acoustic load, additional APS(acoustic protection system) is generally applied. Noise reduction capacity of APS can be verified through acoustic test and vibro-acoustic coupled analysis. This paper compared the results of acoustic test and vibro-acoustic coupled analysis about KSLV-I payload fairing with APS.

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Fatigue Life Prediction for the Skin Structures of Aircraft Sensor Pod Under Acoustic Load with Mean Stress (평균 응력을 고려한 음향 하중을 받는 항공기 센서 포드 외피 구조의 내구 수명 분석)

  • Min-Hyeok Jeon;Yeon-Ju Kim;Hyun-Jun Cho;Mi-Yeon Lee;In-Gul Kim;Hansol Lee;Jae Myung Cho;Jong In Bae;Ki-Young Park
    • Journal of the Korea Institute of Military Science and Technology
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    • v.26 no.1
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    • pp.1-9
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    • 2023
  • The skin structure of sensor pod mounted on the exterior of aircraft can be exposed to the acoustic dynamic load and static load such as aerodynamic pressure and inertial load during flight. Fatigue life prediction of structural model under acoustic load should be performed and also differential stiffness of model modified by static load should be considered. The acoustic noise test spectrum of MIL-STD-810G was applied to the structural model and the stress response power spectral density (PSD) was calculated. The frequency response analysis was performed with or without prestress induced by inplane static load, and the response spectrum was compared. Time series data was generated using the calculated PSD, and the time and frequency domain fatigue life were predicted and compared. The variation of stress response spectrum due to static load and predicted fatigue life according to the different structural model considering mean stress were examined and decreasing fatigue life was observed in the model with prestress of compressive static load.

Life Evaluation of CrN Coatings due to Wear Using Friction and Acoustic Emission Sensor (마찰 및 음향방출 신호를 이용한 CrN 코팅의 마모수명 평가)

  • 조정우;이영제
    • Tribology and Lubricants
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    • v.15 no.4
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    • pp.328-334
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    • 1999
  • Acoustic emission (AE) sensor was used to evaluate the wear-life of CrN-coated steel disks with 1 $\mu\textrm{m}$ and 4 $\mu\textrm{m}$ coating thickness. The relationship between Af and friction signal from scratch test and sliding test was investigated. The first spatting of CrN film was detected by AR signals in the early stage of coating failures, and overall failures by friction signals. Therefore, the conservative design for coating-life should be done using the results of AE signals. Using the percent contact load, the ratio of sliding normal load to the critical scratch load and the number of cycles to failure was measured to predict the wear-life of CrN film. On the wear-life dia-gram the percent contact loads and the number of cycles to failure showed a good linear relationship on the log coordinate. As the load percentage was decreased, the diagram showed that the wear-limits, at which the coated steels survived more than 35,000 cycles, were about 4∼5% of the critical scratch loads.

Nonlinear Transient Responses of Isotropic Plates Under Thermo-Acoustic Load (열-음향 복합하중에 놓인 등방성 평판의 비선형 응답특성)

  • Oh, Il-Kwon;Cheng, Tai-Hong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2006.11a
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    • pp.235-238
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    • 2006
  • For high-speed aircraft and high-speed civil transport planes, certain structural skin components are subjected to very large acoustic loads in an elevated thermal environment. In this study, we used the single-mode Fokker-Panck distribution to predict displacements of isotropic plates subject to thermo-acoustic combined load. The single mode was formulated to predict the nonlinear dynamic responses of postbuckled plates under acoustic random excitation. Acoustic random excitation was used with Gauss distribution. Some important effects of the snap-through motion on the dynamic responses of the postbuckled plates are described.

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Improved Prediction of Lift-off Acoustic Loads for a Launch Vehicle (발사체 이륙 시 음향 하중 예측 정확도 향상)

  • Choi, Sang-Hyeon;Ih, Jeong-Guon;Lee, Ik-Jin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.04a
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    • pp.207-210
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    • 2014
  • This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. Intense acoustic load is generated when a launch vehicle is lifted off, and it can induce vibrations of a launch vehicle which cause damage or malfunction of a launch vehicle and a satellite. Lift-off acoustic loads of NARO are predicted by the modified Eldred's second method and the result is compared with the measured data in flight test. The prediction shows similar peak and shape of spectrum to the test data, but some discrepancy can be observed due to the predicted margin. In order to reduce such discrepancy, the sound pressure levels with four source distribution assumptions are calculated. Also, the surface diffraction effects are considered in the predict ion of lift-off acoustic loads, and the predicted result is more similar to the test data.

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Combustion Instability of Gas Turbine with Segmented Dynamic Thermo-Acoustic Model under Load Follow-Up (이산형 열-음향 모델을 이용한 부하 변동시 가스터빈 연소 불안정 특성)

  • JEONG, JIWOONG;HAN, JAEYOUNG;JEONG, JINHEE;YU, SANGSEOK
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.5
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    • pp.538-548
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    • 2018
  • The thermo-acoustic instability in the combustion process of a gas turbine is caused by the interaction of the heat release mechanism and the pressure perturbation. These acoustic vibrations cause fatigue failure of the combustor and decrease the combustion efficiency. This study is to develop a segmented dynamic thermo-acoustic model to understand combustion instability of gas turbine. Therefore, this study required a dynamic analysis rather than static analysis, and developed a segmented model that can analyze the performance of the system over time using the Matlab/Simulink. The developed model can confirm the thermo-acoustic combustion instability and exhaust gas concentration in the combustion chamber according to the equivalent ratio change, and confirm the thermo-acoustic combustion instability for the inlet temperature and the load changes. As a result, segmented dynamic thermo-acoustic model has been developed to analyze combustion instability under the operating condition.

ACOUSTIC EMISSION CHARACTERISTIC OF THE RAT FEMUR AFTER ADMINISTRATION OF SODIUM FLUORIDE (불소섭취에 따른 백서 대퇴골의 파절특성에 관한 Acoustic Emission 연구)

  • Song, Keun-Bae;Lee, Young-Eun;Kim, Hye-Young;Lee, Sang-Han
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.28 no.1
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    • pp.16-23
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    • 2002
  • To understand the micro-mechanical changes and the effects of the fluoride on rat's femur after administration of sodium fluoride, the three-point bending test, acoustic emission analysis during the three-point bending test and scanning electron microscopy were performed. The obtained results were as follows: 1. Bone strength increased in the rats given 1, 5, 10 and 20 ppm of fluoride but, there were no statistical significances (p>0.05). 2. With increasing the concentration of fluoride, most AE events released rapidly just before the maximum load and smaller events were recorded than the control group's. The average of cumulative AE event counts until maximum load of the femur in 20 ppm group were significantly small with respect to the control group's (p<0.05). 3. Fracture surfaces were well coincide with the results of acoustic emission behavior. Analyses of fracture surfaces indicated that, consistent with its the highest load, rat femur in 20 ppm fluoride group displays the roughest surface.