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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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 18, Issue 12 - Dec 2008
Volume 18, Issue 11 - Nov 2008
Volume 18, Issue 10 - Oct 2008
Volume 18, Issue 9 - Sep 2008
Volume 18, Issue 8 - Aug 2008
Volume 18, Issue 7 - Jul 2008
Volume 18, Issue 6 - Jun 2008
Volume 18, Issue 5 - May 2008
Volume 18, Issue 4 - Apr 2008
Volume 18, Issue 3 - Mar 2008
Volume 18, Issue 2 - Feb 2008
Volume 18, Issue 1 - Jan 2008
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Reduction of the Residual Vibrations of a Flexible Cantilever Beam Subjected to a Transient Translation or Rotation Motion
Shin, Ki-Hong ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 3~10
DOI : 10.5050/KSNVN.2008.18.1.003
In this paper, the optimal command input is considered in order to minimize the residual vibrations of a flexible cantilever beam when the beam simply changes its position by translation or rotation. Although a cantilever beam has many modes of vibration, it is shown that the consideration of the first mode is sufficient in this case. Thus, the problem becomes a single-degree-of-freedom system subjected to a ground excitation. Two simple methods are proposed to find the optimal command input based on the shock response spectrum (SRS). The first method is the simplest and can be applied to lightly damped cases, and the second method is applicable to more general problems. The second method gives almost the same results as the input shaping method. However the proposed method gives a easier and clearer control strategy.
Development of A Small VCM Focusing Actuator Using Curved Suspensions
Shin, Young-Chul ; Lee, Seung-Yop ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 11~19
DOI : 10.5050/KSNVN.2008.18.1.011
This paper proposes small VCM(voice coil motor) type, auto-focusing and zoom actuators for mobile information devices. In order to meet the large output displacement within small height restriction, the proposed auto-focusing actuator adopts curved suspensions, which are similar to a leaf-spring type suspension of optical disk drives. The sensitivity of design parameters on output displacement and dynamic performance is implemented using ANSYS (3D FEM tool) to determine the optimal geometry and stiffness of the curved suspensions. This paper also investigates a new zoom actuator without a suspension supporting a bobbin. The zoom actuator uses a moving rail and a stoper mechanism by generating rotational force at lens holder. Magnetic flux density of the zoom actuator are calculated by both the FEM and permeance method. Experiments using prototypes of the proposed focusing and zoom models show that both actuators meet the required displacement and performance.
Sound Visualization in Time Domain by Using Spatial Envelope
Park, Choon-Su ; Kim, Yang-Hann ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 20~25
DOI : 10.5050/KSNVN.2008.18.1.020
Acoustic holography exhibits the spatial distribution of sound pressure in time or frequency domain. The obtained picture often contains far more than what we need in practice. For example. when we need to know only the locations and overall propagation pattern of sound sources. a method to show only what we need has to be introduced. One way of obtaining the necessary information is to use envelope in space. The spatial envelope is a spatially slowly-varying amplitude of acoustic waves which contains the information of sources` location. A spatial modulation method has been theoretically developed to get a spatial envelope. By applying the spatial envelope. not only the necessary information is obtained but also computation time is reduced during the process of holography. The spatial envelope is verified as an effective visualization scheme in time domain by being applied to complicated sound fields.
Radiated Noise Analysis of Marine Diesel Engine from Structural Vibration
Kim, Dae-Hwan ; Jeong, Weui-Bong ; Park, Jeong-Geun ; Hong, Chin-Suk ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 26~34
DOI : 10.5050/KSNVN.2008.18.1.026
This paper summarizes a design procedure of radiated noise from engine blocks of marine engines. This air-borne noise is one of the significant noise contributors including the aeroacoustic noise due to intake and exhaust and the re-radiation due to structure-borne noise. Excitation forces by engine operations are evaluated taking into account the power generation mechanism from the burning process to the subsequence motion of internal parts; piston, connecting rod, and crank shaft. The acoustic transfer vector method is incorporated to effectively simulate the radiated noise field under the various operation conditions. A contribution analysis for the various excitations to the radiated noise is conducted. It is found that the firing pressure is the main source of the radiated noise, and so the structure of the cylinder can be modified to significantly reduce the radiated noise from the engine block.
Analysis of Harmonic Vibration of Cracked Rotor
Jun, Oh-Sung ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 35~46
DOI : 10.5050/KSNVN.2008.18.1.035
Harmonic vibration characteristics for the general rotor model having a breathing crack are analyzed. Analyses are performed at the half critical speed ranges. The vibration characteristics are explained by using the additional slope and bending moment at the crack position and the influence coefficient showing the structural dynamic characteristics of the rotor. With the low crack depth the magnitude of the additional slope is kept constant even at the speed range at which the orbit magnitude is very sensitive to the rotational speed change. At this speed range the vibration is affected by the influence coefficient only. As the dynamic bending moment exceeds the static bending moment with the increase of crack depth. the additional slope affects the vibration amplitude of cracked rotor and the crack propagation rate increases.
A Study on the Fault Detection of Auto-transmission according to Gear Damage
Park, Ki-Ho ; Jung, Sang-Jin ; Wee, Hyuk ; Kim, Jin-Seong ; Han, Kwan-Su ; Kim, Min-Ho ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 47~56
DOI : 10.5050/KSNVN.2008.18.1.047
This paper presents a detecting technique for the improvement in quality by appling the various vibrational characteristics theory. The object of this study is to objectively point out faulty gear by developing the program which can be used to analyze and predict the vibrational characteristics caused by gear wear, deformation and nick of auto-transmission. The fault detection methods by vibrational signal analysis of gear have been progressed in the various fields of industry. These methods have the advantage of being easy to attach the accelerometer without discontinuance of the structure. But not all the methods are efficient for finding early faults. So in the thesis, we completed development of the inspection system of vibration by appling the most efficient detecting methods and verified the system`s reliability through experiments.
Sound Quality Evaluation of Interior Noise of Driving Vehicle Using Mahalanobis Distance
Park, Sang-Gil ; Lee, Hae-Jin ; Bae, Chul-Yong ; Lee, Bong-Hyun ; Oh, Jae-Eung ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 57~60
DOI : 10.5050/KSNVN.2008.18.1.057
Since human listening is very sensitive to sound, for evaluating of a sound quality is required. Therefore, in the analysis for each situation, the sound evaluation is composed with sound quality factor. My researchers spends their effort to make a more reliable and more accurate of sound in term of sound quality index for various system noise. The previous methods to evaluation of the SQ about vehicle interior noise are linear regression analysis of subjective SQ metrics by statistics and the estimation of the subjective SQ values by neural network. But these are highly dependent on jury test and have many difficulties due to various environmental factors. So, to reduce jury test weight. we suggested a new method using Mahalanobis distance for SQ evaluation. Threrefore, in this study Mahalanobis distance for the vehicle interior noise was derived using the objective SQ except jury test. Finnaly, the results of the SQ evaluation was analyzed discrimination between reference and abnormal group.
Characteristics of Modal Acoustic Power of Broadband Noise by Interaction of a Cascade of Flat-plate Airfoils with Inflow Turbulence
Cheong, Cheol-Ung ; Jurdic, Vincent ; Joseph, Phillip ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 61~70
DOI : 10.5050/KSNVN.2008.18.1.061
This paper investigates the modal acoustic power by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. Basic formulation for the acoustic power upstream and downstream is based on the analytical theory of Smith and its generalization due to Cheong et al. The acoustic power spectrum has been expressed as the sum of cut-on acoustic modes, whose modal power is the product of three terms: a turbulence series, an upstream or downstream power factor and an upstream or downstream acoustic response function. The effect of these terms in the modal acoustic power has been examined. For isotropic turbulence gust, the turbulent series are only reducing factor of the modal acoustic power. The power factor tends to reduce the modal acoustic power in the upstream direction, although the power factor is liable to increase the modal acoustic power in the downstream direction. The modes close to cut-off are decreasing strongly, especially in the downstream direction. Therefore the modes close to cut-off don`t contribute highly to the radiated acoustic power in the downstream direction, although the modal acoustic pressure is high for these modes.
A Study on the Acoustic Absorption Performance of a Helmholtz Resonator
Song, Hwa-Young ; Lee, Dong-Hoon ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 71~79
DOI : 10.5050/KSNVN.2008.18.1.071
A helmholtz resonator has been widely used for the purpose of suppressing the low frequency noises propagated from various heat and fluid machineries. However, the conventional resonator has demerits that the effective absorption bandwidth is narrow and the absorption performance is not so outstanding in the only limited configurations of neck and cavity as well. In order to overcome these problems, in this paper, a resonator with perforated neck is proposed. The absorption performances of the resonator are measured by two-microphone method and estimated by transfer matrix method. The measured values of normal absorption coefficients agree well with the estimated values. By introducing the perforated plates at the neck of a resonator, it is shown that the absorption performance have been significantly improved.
A Study on Noise Reduction for the Driving System of a Forklift
Kim, Woo-Hyung ; Hong, Il-Hwa ; Chung, Jin-Tai ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 80~86
DOI : 10.5050/KSNVN.2008.18.1.080
In this study. the noise sources were identified and the noise and vibration were reduced for an industrial forklift. To identify the noise sourses, noise signals were measured by a microphone on a driver seat and these signals were analyzed with a waterfall plot. For this purpose, the gear mesh frequencies from the gear box of a reducer were not only investigated but noise/vibration sourses of an electric motor were also examined. Furthermore, the frequency response functions were obtained to confirm the vibration and noise sourses. It was found that severe vibration and noise were generated in the casing and the connecting part of the reducer. The severe vibration and noise could be reduced by a structure modification.
Equivalent Damping Ratio Based on Earthquake Characteristics of a SDOF Structure with an MR Damper
Moon, Byoung-Wook ; Park, Ji-Hun ; Lee, Sung-Kyung ; Min, Kyung-Won ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 87~93
DOI : 10.5050/KSNVN.2008.18.1.087
Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall`s equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.
Evaluation of the Performance of the Noise Barrier Using the BEM
Hwang, Cheal-Ho ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 94~100
DOI : 10.5050/KSNVN.2008.18.1.094
Noise barriers are being used more often to solve problems of noise pollution from traffic noise. Several types of noise barriers are being installed to increase the cost-effectiveness of noise barrier installation. In this study, the insertion loss is analyzed to evaluate the effectiveness of the noise barrier by using the BEM. In order to check the validity of the BEM, the BEM and Lam`s theoretical analysis are compared with measurement, which is performed in the anechoic chamber for the 1/10 scale-down model, and good agreements are obtained. By using the two dimensional boundary element method, the insertion loss is calculated and analyzed for several typical noise barriers such as the vertical barrier, the barrier with an oblique edge on top, the T-shaped barrier and the barrier with interference device on top. With these analyses, it is possible to design more cost-effective noise barriers appropriate for a particular area.
Dynamic Stability of Rotating Cantilever Pipe Conveying Fluid with Tip mass and Crack
Son, In-Soo ; Yoon, Han-Ik ; Kim, Dong-Jin ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 101~109
DOI : 10.5050/KSNVN.2008.18.1.101
The stability of a rotating cantilever pipe conveying fluid with a crack and tip mass is investigated by the numerical method. That is, the effects of the rotating angular velocity, mass ratio, crack severity and tip mass on the critical flow velocity for flutter instability of system are studied. The equations of motion of rotating pipe are derived by using the Euler-Bernoulli beam theory and the extended Hamilton`s principle. The crack section of pipe is represented by a local flexibility matrix connecting two undamaged pipe segments. Also, the crack is assumed to be in the first mode of fracture and always opened during the vibrations. When the tip mass and crack are constant, the critical flow velocity for flutter is proportional to the rotating angular velocity of pipe. In addition, the stability maps of the rotating pipe system as a rotating angular velocity and mass ratio
Amplitude-dependent Complex Stiffness Modeling of Dual-chamber Pneumatic Spring for Pneumatic Vibration Isolation Table
Lee, Jeung-Hoon ; Kim, Kwang-Joon ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 110~122
DOI : 10.5050/KSNVN.2008.18.1.110
Pneumatic vibration isolator typically consisting of dual-chamber pneumatic springs and a rigid table are widely employed for proper operation of precision instruments such as optical devices or nano-scale equipments owing to their low stiffness- and high damping-characteristics. As environmental vibration regulations for precision instruments become more stringent, it is required to improve further the isolation performance. In order to facilitate their design optimization or active control, a more accurate mathematical model or complex stiffness is needed. Experimental results we obtained rigorously for a dual-chamber pneumatic spring exhibit significantly amplitude dependent behavior, which cannot be described by linear models in earlier researches. In this paper, an improvement for the complex stiffness model is presented by taking two major considerations. One is to consider the amplitude dependent complex stiffness of diaphragm necessarily employed for prevention of air leakage. The other is to employ a nonlinear model for the air flow in capillary tube connecting the two pneumatic chambers. The proposed amplitude-dependent complex stiffness model which reflects dependency on both frequency and excitation amplitude is shown to be very valid by comparison with the experimental measurements. Such an accurate nonlinear model for the dual-chamber pneumatic springs would contribute to more effective design or control of vibration isolation systems.
Free Vibration of a Rectangular Plate Partially in Contact with a Liquid at Both Sides
Jeong, Kyeong-Hoon ; Lee, Gyu-Mahn ; Kim, Tae-Wan ; Park, Keun-Bae ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 123~130
DOI : 10.5050/KSNVN.2008.18.1.123
An analytical method for the free vibration of a flexible rectangular plate in contact with water is developed by the Rayleigh-Ritz method. The plate clamped along the edges is partially contacted with water at both sides. It is assumed that the contained water is incompressible and inviscid. The wet mode shape of the plate is assumed as a combination of the dry mode shapes of a clamped beam. The liquid motion is described by using the liquid displacement potential and determined by using the compatibility conditions along the liquid interface with the plate. Minimizing the Rayleigh quotient based on the energy conservation gives an eigenvalue problem. It is found that the theoretical results can predict excellently the fluid-coupled natural frequencies comparing with the finite element analysis result.
Performance Evaluation of a Large-scale MR Damper for Controlling Seismic Responses Using a Real-time Hybrid Test Method
Park, Eun-Churn ; Lee, Sung-Kyung ; Youn, Kyung-Jo ; Chung, Hee-San ; Lee, Heon-Jae ; Choi, Kang-Min ; Moon, Suk-Jun ; Jung, Hyung-Jo ; Min, Kyung-Won ;
Transactions of the Korean Society for Noise and Vibration Engineering, volume 18, issue 1, 2008, Pages 131~138
DOI : 10.5050/KSNVN.2008.18.1.131
This paper presents real-time hybrid test method of large-scale MR damper applied to a building structure under seismic excitation. The real-time hybrid test using an actuator for the control performance evaluation of a MR damper controlling the response of earthquake-excited building structure is experimentally implemented. In the test, the building structure is used as a numerical part, on which a large-scale MR damper adopted as an experimental part was installed to reduce its response. At first, the force that is acting between a MR damper and building structure is measured from the load cell attached on the actuator system and is fed-back to the computer to control the motion of the actuator. Then, the actuator is so driven that the error between the interface displacement computed from the numerical building structure with the excitations of earthquake and the fed-back interface force and that measured from the actuator. The control efficiency of the MR damper used in this paper is experimentally confirmed by implementing this process of experiment on real-time.