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Transactions of the Korean Society for Noise and Vibration Engineering
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Journal DOI :
The Korean Society for Noise and Vibration Engineering
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Volume & Issues
Volume 26, Issue 6_spc - Nov 2016
Volume 26, Issue 4 - Aug 2016
Volume 26, Issue 3 - Jun 2016
Volume 26, Issue 2 - Apr 2016
Volume 26, Issue 1 - Jan 2016
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Design for Improving the Loss Factor of Composite with Sandwich Structure
Lee, C. M. ; Jeon, G.S. ; Kang, D.S. ; Kim, B.J. ; Kim, J.H. ; Kang, M.H. ; Seo, Y.S. ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 235~241
DOI : 10.5050/KSNVE.2016.26.3.235
Underwater weapon system is required to structurally strong material, since as it is directly exposed to external shock. It should also be using the lightweight material in order to take advantage of buoyancy. Composite materials meet these requirements simultaneously. Particularly in the case of submarine, composite materials are widely used. It is important to have a high strength enough to be able to withstand external shock, but it is also important to attenuate it. In a method for the shock damping, viscoelastic damping materials are inserted between the high strength composite material as a sandwich structure. Shock attenuation can be evaluated in the loss factor. In ASTM(American Society of Testing Materials), evaluation method of the loss factor of cantilever specimens is specified. In this paper, mode tests of the cantilever are performed by the ASTM standard, in order to calculate the loss factor of the viscoelastic damping material by the specified expression. Further, for verifying of the calculated loss factor, mode test of compound beams is carried out. In addition, the characteristics of the material were analyzed the effect on the loss factor.
Performance Evaluation of Active Hood Lift System of Passenger Vehicles with Different Operating Method
Lee, Tae-Hoon ; Yoon, Gun-Ha ; Park, Chun-Yong ; Kang, Je-Won ; Choi, Seung-Bok ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 242~247
DOI : 10.5050/KSNVE.2016.26.3.242
This work investigates the performances of active hood lift system(AHLS) activated by two different operating methods through the experimental test. In the AHLS, the deployment time of the system and decrement of pedestrian injury are the most important factors for the pedestrian safety during the pedestrian-vehicle impact. After introducing the working principle of AHLS using spring actuator and gunpowder actuator, the deployment time of AHLS and decrement of pedestrian injury are evaluated by the experimental test. It has been identified that the gunpowder actuator can provide a faster deploying time of AHLS.
Identification of Damping Characteristics of Free-piston Stirling Engines via Nonlinear Dynamic Model Predictions
Sim, Kyuho ; Kim, Dong-Jun ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 248~257
DOI : 10.5050/KSNVE.2016.26.3.248
Recently, researches on the free-piston Stirling engines(FPSEs) are actively investigated. FPSEs have merits in its light weight, simple structure, and little need for maintenance, thus becoming a promising solution for the power conversion of renewable energy and waste heat recycle. This paper presents the methodology that estimates damping coefficients using analytical models of linear and nonlinear dynamics for FPSEs, and validates the methodology by comparing with existing experimental results. The analysis model predicts an operable range of linear damping coefficients forming limit cycles by using the root locus, and time responses obtained by numerical integration determines nonlinear damping coefficients. The model predictions are compared with experimental results of the well-known FPSE B-10B. We also investigate the damping characteristics regarding heater temperatures and power piston motions.
Design Analysis and Derivation of Experimental Equations of Hood Frame for Vehicle
Son, In-Soo ; Ahn, Sung-Jin ; Eom, Hyeon-Soo ; Son, Jung-Ho ; Song, Yo-Sun ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 258~264
DOI : 10.5050/KSNVE.2016.26.3.258
This paper presents the experimental result and theoretical analysis result to investigate the correlation between the operating force and locking torque for vehicle hood frame. Also, we derived the experimental equations that using the results of experiment and theory. The hood frame is switching-devices used for opening and closing the vehicle hood. It needs the correlation data between locking torques of each joint and operating force of hood frame because the parameters affects the emotional quality of the vehicle. The correlation data for torque and force of hood frame obtained through experiment and theory analysis. Finally, two experimental equations of correlation are derived. Thus, the developed equations show that has high usefulness for the basic design of hood frame of vehicle.
Experimental Evaluation of Deployment Time of Active Hood Lift System According to Structural Improvement
Lee, Tae-Hoon ; Yoon, Gun-Ha ; Park, Chun-Yong ; Kang, Je-Won ; Choi, Seung-Bok ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 265~269
DOI : 10.5050/KSNVE.2016.26.3.265
In this research, the performances of active hood lift system(AHLS) are investigated according to the structural improvement through the experimental test. After introducing the working principle of the AHLS activated by a gunpowder actuator, the structural problems that cause the inefficiencies in the actuation are analyzed to reduce the deployment time of system. Sequentially, the improved structural model is proposed base on the analysis. The deployment time of AHLS are evaluated by the experimental test, and it has been identified that the improved model can provide a faster deploying time of AHLS.
The Evolution of Electromechanical Admittance from Mode-converted Lamb Waves Reverberating on a Notched Beam
Kim, Eun Jin ; Park, Hyun Woo ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 270~280
DOI : 10.5050/KSNVE.2016.26.3.270
This paper investigates the evolution of EM admittance of piezoelectric transducers mounted on a notched beam from wave propagation perspective. A finite element analysis is adopted to obtain numerical solutions for Lamb waves reverberating on the notched beam. The mode-converted Lamb wave signals due to a notch are extracted by using the polarization characteristics of piezoelectric transducers collocated on the beam. Then, a series of temporal spectrums are computed to demonstrate the evolution of EM admittance through fast Fourier transform of the mode-converted Lamb wave signals which are consecutively truncated in the time domain. When truncation time is relatively small, the corresponding temporal spectrum is governed by the characteristics of the input driving frequency. As truncation time becomes large, however, the modal characteristics of the notched beam play a crucial role in the temporal spectrum within the input driving frequency band. This implies that mode-converted Lamb waves reverberating on the beam contributes to the resonance of the beam. The root mean square values are computed for the temporal spectrums in the vicinity of each resonance frequency. The root mean square values increase monotonically with respect to truncation time for any resonance frequencies. Finally the implications of the numerical observation are discussed in the context of damage detection of a beam.
Modal Analysis for the Rotating Cantilever Beam with a Tip Mass Considering the Geometric Nonlinearity
Kim, Hyoungrae ; Chung, Jintai ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 281~289
DOI : 10.5050/KSNVE.2016.26.3.281
In this paper, a new dynamic model for modal analysis of a rotating cantilever beam with a tip-mass is developed. The nonlinear strain such as von Karman type and the corresponding linearized stress are used to consider the geometric nonlinearity, and Euler-Bernoulli beam theory is applied in the present model. The nonlinear equations of motion and the associated boundary conditions which include the inertia of the tip-mass are derived through Hamilton`s principle. In order to investigate modal characteristics of the present model, the linearized equations of motion in the neighborhood of the equilibrium position are obtained by using perturbation technique to the nonlinear equations. Since the effect of the tip-mass is considered to the boundary condition of the flexible beam, weak forms are used to discretize the linearized equations. Compared with equations related to stiffening effect due to centrifugal force of the present and the previous model, the present model predicts the dynamic characteristic more precisely than the another model. As a result, the difference of natural frequencies loci between two models become larger as the rotating speed increases. In addition, we observed that the mode veering phenomenon occurs at the certain rotating speed.
Analysis and Estimation of Vibration Characteristics of a Reciprocal Compressor with Variable Rotating Speed
Jung, Byung-Kyoo ; Lee, Yun-Gon ; Jeong, Weui-Bong ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 290~297
DOI : 10.5050/KSNVE.2016.26.3.290
This paper deals with the vibration characteristics of a reciprocal compressor with variable rotating speed according to the change of operating frequencies. The equation of motion and exciting force of the equivalent compressor model were formulated, and the vibration responses at operating frequencies were predicted. The predicted results were compared with the measured results. Although the predicted results had little errors in operating condition, it represented good agreement in general. Especially, the natural frequencies obtained from the measurement were similar to those calculated by the eigenvalue problem of the equivalent model. The procedure and results in this paper can be utilized to the identification of the vibration characteristics of new compressor models.
Design and Dynamic Behavior Prediction of a 4-DOF Piping Joint
Lee, Yunyong ; Kang, Hwankook ; Lee, Jong Rim ; Lim, Seungchul ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 298~307
DOI : 10.5050/KSNVE.2016.26.3.298
In the building process of FPSOs(floating production, storage and offloading units) is the increasing demand of high performance piping joints that can be installed on its turret system and maintain smooth and long-term flow of ultra-high pressure crude oil, being subjected to external excitations such as wind and wave on the sea. Following such a trend, in this paper, a new-type piping joint of four effective degrees of freedom has been designed, and its dynamic characteristics predicted through mathematical modeling and computer simulations. Moreover, via an example it was shown how the yaw motion in particular can be independently controlled for future durability test despite strong kinetic couplings.
Noise Reduction of a Bank Teller Cash Recycler
Won, Hong-In ; Sim, Woojeong ; Kim, Jaewon ; Park, Changho ; Kim, Jongwoo ; Jung, Woochul ; Chung, Jintai ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 308~314
DOI : 10.5050/KSNVE.2016.26.3.308
This paper proposes design guidances for noise reduction of a bank teller cash recycler(TCR). The operating noise of a TCR is required to be reduced because it bothers bank tellers and customers. The operating noise from a TCR is measured and the most influential driving system is examined. To find the main sources of the noise, the frequency spectra are analyzed by comparing with excitation frequencies of the driving system. From the analysis results, we reveals that the main sources of the noise are gear mesh frequency of a certain gear train and its side band frequencies, which is attributed by vulnerable support condition. Consequently, to reduce the operating noise, the structural modification for the gear train support is suggested and its effectiveness for the noise reduction is confirmed experimentally.
Room Acoustic Properties of Coupled Rooms Connected by an Aperture in the Steady State Condition
Na, Hae Joong ; Lim, Byoung-Duk ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 315~322
DOI : 10.5050/KSNVE.2016.26.3.315
Room acoustic properties of coupled rooms connected by an aperture has been analyzed using statistical acoustic model based on the diffused sound field assumption, which has limitation in dealing with the parameters such an room geometries and non uniform absorptivity of the boundary surfaces. In order to overcome these difficulties the acoustic diffusion model has been introduced, by which distribution of the acoustic energy density can be analyzed for various shapes and wall absorptivity. In this study acoustic properties of coupled rooms connected by an aperture(e.g. door) is analyzed using acoustic diffusion equation, which is solved numerically. The mean energy densities of two rooms obtained by the diffusion model are compared with those from the statistical model. The results show good agreement for various coupling aperture sizes and absorption coefficients. For a limiting case when the partition wall is substituted by an aperture and the two rooms eventually forms a single room, results of coupled room analysis using diffusion model show good agreement with those of a single room.
Real-time Unbalance Moment Compensation Method for Line of Sight(LOS) Stabilization Control System
Jo, Sihun ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 323~330
DOI : 10.5050/KSNVE.2016.26.3.323
This paper describes real-time unbalance moment compensation method for line of sight(LOS) stabilization control systems. The factors of system inertia, frictions and unbalance moment affect the control accuracy of drive systems that are equipped to on the move(OTM) platforms requiring LOS stabilization function. In case of the unbalance moment among those factors is continuously changed as variation of relative angle between gravity vector and drive torque vector. Then, consideration of the effect in real-time is very complicate. Therefore, its effect should be designed to be minimized, however, designing it almost zero is impossible in real condition. In other words, it is hard to achieve target performance overcoming stability issue of highly unbalanced systems. To solve these problems, this paper proposes calculation method of unbalance moment by using measured sensor data for LOS stabilization control and its use for control compensation. Also, kinematical converting process and control structure for compensation are explained. The effectiveness of the proposed method as variation of unbalance moment is verified under simulation circumstance modeled by assuming LOS control system with 2-axis gimbal structure.
A Study on the Acoustic Characteristics and Absorption Performance Improvement Method of Double Layered Sound Absorption System Using High Density Polyester Absorbing Materials
Yoon, Je-Won ; Jang, Kang-Seok ; Cho, Yong-Thung ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 331~339
DOI : 10.5050/KSNVE.2016.26.3.331
To improve the acoustic performance of sound absorbing materials, the thickness of the material should be increased or the sound absorbing material having an irregular surface shape should be used. In this study, the acoustic characteristics and methods to improve the acoustic performance of a sound absorbing system equipped with double layered polyester sound absorbing materials were investigated. The numerical model was set up and the results obtained from the model were compared with the actual measurement data. And, strategies to improve the acoustic performance of sound absorbing systems with double layered sound absorbing materials made of polyester with different configuration were shown. So, this study is expected to be usefully used at sites that require high acoustic absorption performance with minimal installation thickness to reduce sounds reflection in narrow spaces such as interior of subway tunnels or in noise barriers installed adjacent to rails.
Acoustic Properties of Three-room Coupled System by Connected Two Apertures
Na, Hae Joong ; Lim, Byoung-Duk ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 26, issue 3, 2016, Pages 340~349
DOI : 10.5050/KSNVE.2016.26.3.340
A coupled room system consists of adjacent rooms and apertures where the sound energy is exchanged between the two rooms. Acoustically, a coupled room system shows a non-exponential decay profile. Most of the related researches have been to analyze the acoustic properties of two-room coupled system so far whereas three-room coupled system were seldom studied. In this regard, this paper aims to analyse the distribution of sound pressure level, sound decay curve of three-room coupled system and sound energy flow between them by using the acoustic diffusion model and to further verify them through experiments. Firstly, the sound pressure level distribution and mean sound pressure level in the steady-state condition are analyzed at various frequencies and source locations. Good agreements are observed in both experiments and analysis results. Secondly, two double slope effect quantifiers of sound attenuation, LDT/EDT and LDT/T10 are compared at various frequencies and for different source locations. The result indicates that LDT/T10, less affected by the early reflection patterns than LDT/EDT, is more suitable to the analysis and experiments of a multi-slope sound decay curve. Lastly, the sound energy flow in each room is analyzed based on the acoustic diffusion model. After the early decay stage, the sound energy is observed to flow from the room with a long reverberation time to the room with a short one.