• Title/Summary/Keyword: modal energy

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Transmission Path Analysis of Noise and Vibration in a Rotary Compressor by Statistical Energy Analysis

  • Hwang, Seon-Woong;Jeong, Weui-Bong;Yoo, Wan-Suk;Kim, Kyu-Hwan
    • Journal of Mechanical Science and Technology
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    • v.18 no.11
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    • pp.1909-1915
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    • 2004
  • The hermetic rotary compressor is one of the most important components of an air conditioning system since it has a great effect on both the performance and the noise and vibration of the system. Noise and vibration occurs due to gas pulsation during the compression process and to unbalanced dynamic force. In order to reduce noise and vibration, it is necessary to identify their sources and transmission path and effectively control them. Many approaches have been tried in order to identify the noise transmission path of a compressor. However, identification has proven to be difficult since the characteristics of compressor noise are complicated due to the interaction of the compressor parts and gas pulsation. In this study, the statistical energy analysis has been used to trace the energy flow in the compressor and to identify the transmission paths from the noise source to the exterior sound field.

Radiation Power Control by Means of Absorptive Material Arrangement in an Enclosure (흡음재 배치를 통한 닫힌 공간에서의 소음원 방사 파워 제어)

  • 조성호;김양한
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.688-691
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    • 2004
  • We have studied the possibility of global noise reduction by the sound power control through selection of distribution and impedance of absorptive materials. It is necessary to investigate the relation between the global sound energy in the field and the total sound power radiated by sources. In the previous work (1,2), the authors presented a useful design method to change boundary condition that can be useful to reduce noise in acoustically small enclosures. The possibility of total acoustic potential energy reduction by acoustic source power control is examined in an acoustically small cavity. Using acoustic energy balance equation, the relation between global noise control performance and absorptive material's arrangement/impedance is deduced. Numerical simulation is performed to interpret its physical meaning in terms of absorbent's distribution and impedance.

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An Application of the Statistical Energy Analysis for Absorbing and Soundproofing Materials of Vehicle (자동차용 흡.차음재의 성능분석을 위한 통계적 에너지 기법의 적용)

  • Lee, Chang-Myung;Lee, Jun;Kim, Dae-Gon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.1
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    • pp.33-39
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    • 2003
  • Interior parts of a vehicle are getting important to reduce interior noise. Therefore, prior analysis of cabin noise related with interior parts are necessary at first design stage. Recently, Statistical Energy Analysis(SEA) has been suggested as a possible way for high frequency range noise analysis of interior parts. The validity of noise analysis with SEA to interior parts has been preyed by comparing with experimental result, and the developed method with SEA has been applied in finding optimized interior parts package.

Fabrication of a Low Frequency Vibration Driven Electromagnetic Energy Harvester Using FR-4 Planar Spring and Its Characteristics (FR-4 평판 스프링 기반 저주파수용 진동형 전자기식 에너지 하베스터의 제작과 그 특성)

  • Lee, Byung-Chul;Chung, Gwiy-Sang
    • Journal of Sensor Science and Technology
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    • v.20 no.4
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    • pp.238-242
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    • 2011
  • This paper describes the fabrication and characteristics of a low frequency vibration driven electromagnetic energy harvester. The fabricated generator consists of a permanent magnet of NdFeB, a FR-4 planar spring and a Copper cylinder type coil. ANSYS modal analysis was used to determine the resonant frequency for the generator. The implemented generator is capable of producing up to 550 mV peak-to-peak under 7 Hz frequency, which has a maximum power of $95.5\;{\mu}W$ with load resistance of $580\;{\Omega}$. This device is shown to generate sufficient power at different resonating modes, and the experimental and simulated results are discussed and composed.

Topology optimization of tie-down structure for transportation of metal cask containing spent nuclear fuel

  • Jeong, Gil-Eon;Choi, Woo-Seok;Cho, Sang Soon
    • Nuclear Engineering and Technology
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    • v.53 no.7
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    • pp.2268-2276
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    • 2021
  • Spent nuclear fuel, which can degrade during long-term storage, must be transported intact in normal transport conditions. In this regard, many studies, including those involving Multi-Modal Transportation Test (MMTT) campaigns, have been conducted. In order to transport the spent fuel safely, a tie-down structure for supporting and transporting a cask containing the spent fuel is essential. To ensure its structural integrity, a method for finding an optimum conceptual design for the tie-down structure is presented. An optimized transportation test model of a tie-down structure for the KORAD-21 metal cask is derived based on the proposed optimization approach, and the transportation test model is manufactured by redesigning the optimized model to enable its producibility. The topology optimization approach presented in this paper can be used to obtain optimum conceptual designs of tie-down structures developed in the future.

Energetics of In-plane Motions in Coupled Plate Structures

  • Park, Young-Ho;Park, Chang Hyun
    • Journal of Ocean Engineering and Technology
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    • v.34 no.6
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    • pp.428-435
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    • 2020
  • Energy flow analysis (EFA) has been used to predict the frequency-averaged vibrational responses of built-up structures at high frequencies. In this study, the frequency-averaged exact energetics of the in-plane motions of the plate were derived for the first time by solving coupled partial differential equations. To verify the EFA for the in-plane waves of the plate, numerical analyses were performed on various coupled plate structures. The prediction results of the EFA for coupled plate structures were shown to be accurate approximations of the frequency-averaged exact energetics, which were obtained from classical displacement solutions. The accuracy of the results predicted via the EFA increased with an increase in the modal density, regardless of various structural parameters. Therefore, EFA is an effective technique for predicting the frequency-averaged vibrational responses of built-up structures in the high frequency range.

Performance Prediction of Vibration Energy Harvester considering the Dynamic Characteristics of Rotating Tires (회전하는 타이어의 동특성을 고려한 진동에너지 하베스터 성능 예측)

  • Na, Hae-Joong
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.19 no.10
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    • pp.87-97
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    • 2020
  • In general, tires require various sensors and power supply devices, such as batteries, to obtain information such as pressure, temperature, acceleration, and the friction coefficient between the tire and the road in real time. However, these sensors have a size limitation because they are mounted on a tire, and their batteries have limited usability due to short replacement cycles, leading to additional replacement costs. Therefore, vibration energy harvesting technology, which converts the dynamic strain energy generated from the tire into electrical energy and then stores the energy in a power supply, is advantageous. In this study, the output voltage and power generated from piezoelectric elements are predicted through finite element analysis under static state and transient state conditions, taking into account the dynamic characteristics of tires. First, the tire and piezoelectric elements are created as a finite element model and then the natural frequency and mode shapes are identified through modal analysis. Next, in the static state, with the piezoelectric element attached to the inside of the tire, the voltage distribution at the contact surface between the tire and the road is examined. Lastly, in the transient state, with the tire rotating at the speeds of 30 km/h and 50 km/h, the output voltage and power characteristics of the piezoelectric elements attached to four locations inside the tire are evaluated.

Dynamic Analysis and Optimization of a Machine Tool Structure (工作機械構造 의 動的 解析 및 最適化)

  • 한규환;이장무
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.4
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    • pp.384-389
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    • 1982
  • It is necessary that machine tool structures should be designed so that they will cause a minimum chance of machining chatter. In order to do this, a computer program package is developed utilizing Finite Element Method, modal flexibility and energy balance method. Validity of the program package is verified through computer simulation analysis and impulse test of a simplified machine tool structure.

Response Of Steel Frame Structures With Added Elastic Dampers (탄성 댐퍼가 추가된 대형철골 구조물의 응답특성)

  • 배춘희;조철환;양경현;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.808-812
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    • 2002
  • The feasibility of using elastic dampers to mitigate earthquake-induced structural response is studied in this paper. The properties of elastic dampers are briefly described. A procedure for evaulating the elastic damping effect when added to a structure is proposed in which the damping effect of elastic dampers is incorporated into modal damping ratios through an energy approach. Computer simulation of the damped response of a multi-storey steel frame structure shows significant reduction in floor displacement levels.

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Optimization of LQR method for the active control of seismically excited structures

  • Moghaddasie, Behrang;Jalaeefar, Ali
    • Smart Structures and Systems
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    • v.23 no.3
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    • pp.243-261
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    • 2019
  • This paper introduces an appropriate technique to estimate the weighting matrices used in the linear quadratic regulator (LQR) method for active structural control. For this purpose, a parameter is defined to regulate the relationship between the structural energy and control force. The optimum value of the regulating parameter, is determined for single degree of freedom (SDOF) systems under seismic excitations. In addition, the suggested technique is generalized for multiple degrees of freedom (MDOF) active control systems. Numerical examples demonstrate the robustness of the proposed method for controlled buildings under a wide range of seismic excitations.