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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 13, Issue 12 - Dec 2003
Volume 13, Issue 11 - Nov 2003
Volume 13, Issue 10 - Oct 2003
Volume 13, Issue 9 - Sep 2003
Volume 13, Issue 8 - Aug 2003
Volume 13, Issue 7 - Jul 2003
Volume 13, Issue 6 - Jun 2003
Volume 13, Issue 5 - May 2003
Volume 13, Issue 4 - Apr 2003
Volume 13, Issue 3 - Mar 2003
Volume 13, Issue 2 - Feb 2003
Volume 13, Issue 1 - Jan 2003
Selecting the target year
Integrated Test and Evaluation for Improvement of Vehicle Road Noise
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 327~333
DOI : 10.5050/KSNVN.2003.13.5.327
Several tests are performed to evaluate road booming noise. Baseline test delivers the information of road noise characteristics. Coupling effect between structure and acoustics is obtained from the mode shapes and the natural frequencies by the modal test. Equivalent stiffness at joint areas between chassis and car-body system can be determined by the input point inertance test. Noise sensitivity of body mounting point of a chassis part can be obtained from the noise transfer function test with input point inertance test. Operational deflection shape makes us analyze the actual vibration modes of the chassis system under actual leading and find noise sources very easily. Finally, the transfer path analysis is used to Identify noise Paths through the chassis system. The objectives and the procedures of the tests are described in this Paper Also, the guideline for efficient road noise evaluation test can be found.
FRF Distortion Caused by Exponential Window Function on Impact Hammer Testing and Its Solution
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 334~340
DOI : 10.5050/KSNVN.2003.13.5.334
Exponential window function Is widely used In impact hammer testing to reduce leakage error as well as to get a good S/N ratio. The larger its decaying rate is, the more effectively the leakage errors are reduced. But if the decay rate of the exponential window is too large, the FRF is distorted. And the modal parameters of the system can not be exactly identified by modal analysis technique. Therefore, it is a difficult problem to determine proper decay rate in impact hammer testing. In this paper, amount of the FRF distortion caused by exponential window is theoretically uncovered. A new circle fitting method is also proposed so that the modal parameters are directly extracted from impulse response spectrum distorted by the exponential-windowed impulse response data. The results by the conventional and proposed circle fitting method are compared through a numerical example.
A Study on Vibration Characteristics Caused by Backlash of Gearbox in Escalator with Chain-sprocket Drive Mechanism
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 341~347
DOI : 10.5050/KSNVN.2003.13.5.341
This paper presents an improved escalator dynamic model so as to reflect the experimental observation on the pseudo-resonance affected by load applied. The experimental evidence reveals that backlash on gearbox as well as sag of driving Chain are most critical factors to the pseudo-resonance in escalators. The dynamic model effectively reflects vibration characteristics measured in real escalators with respect to different conditions of driving chain and the number of passengers. For validation of the dynamic model developed. numerical results from the model are compared with experimental results. The developed model and its simulation results are used rigorously for the design of escalator systems in enhancing the ride comfort.
Development of Active Vibration Control Algorithms for the Compensator of Medium-to-large Size Reciprocating Engines
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 348~356
DOI : 10.5050/KSNVN.2003.13.5.348
Active vibration control algorithms for the compensator and proto-type testing system have been developed for the suppression of vibrations from the reciprocating engines. At first, the developed algorithm determines optimal control vibration phases by detecting vibration responses of the engine without and with compensator, and then performs the continuous optimal control functions by tracking the change of the vibration frequency and phase. This algorithm is comparatively simple. robust for the external excitations and needless of supplementary operation since the control process is serially carried out. To validate the performance of compensator and algorithm, testing system including excitation device are constructed and tested, and the reductions of vibration levels are observed over than 80 % of the uncontrolled levels at various frequency ranges.
An Experimental Investigation of Noise Reduction by Blades in a Duct
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 357~363
DOI : 10.5050/KSNVN.2003.13.5.357
There have been lots of studies on noise transmission analysis and noise reduction In ducts. In order to reduce the noise transmission in ducts. active noise cancellation techniques have often been employed and a rotation shaft with blades has sometimes been suggested. These Ideas were not successfully commercialized because of the limitation of real life such as size or application difficulties. This study investigated how a rotational shaft with blades could reduce the noise transmission in a duct. To do so, an assembly of the shaft and the $haft housing was built In the middle of a duct. and the clearance between the blades and the housing was 0.2 mm. The noise reduction was experimentally evaluated with respect to the number of blades. the rotation speed, and the rotation or stop. This paper showed that the noise reduction resulted in about 14∼19 dBA regardless of the three test conditions only If the blades always blocked the duct. And. the noise reduction increased due to the higher number of blades and the lower speed of the shaft.
Optimal Design of a Flextensional Transducer Considering All the Cross-coupled Effects of the Design Variables
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 364~374
DOI : 10.5050/KSNVN.2003.13.5.364
The performance of an acoustic transducer is determined by the effects of many design variables. and mostly the influences of these design variables are not linearly independent of each other To achieve the optimal performance of an acoustic transducer, we must consider the cross-coupled effects of the design variables. In this study with the FEM. we analyzed the variation of the resonance frequency and sound pressure of a flextensional transducer in relation to Its design variables. Through statistical multiple regression analysis of the results, we derived functional forms of the resonance frequency and sound pressure in terms of the design variables, and with which we determined the optimal structure of the transducer by means of a constrained optimization technique, SQP-PD. The proposed method can reflect all the cross-coupled effects of multiple design variables, and can be utilized to the design of general acoustic transducers.
Effects of Rotational Stiffness of Isolators on Vibration Power Transmission in Vibration Isolation Systems over High Frequency Range
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 375~383
DOI : 10.5050/KSNVN.2003.13.5.375
For a performance analysis of vibration isolation systems, the concept of vibration power flow can be employed preferably when noise radiated from the supporting structure with finite impedances is of interest. The idea is basically simple to understand and formulas for precise estimation of the vibration power are easy to derive. However, It is often required to simplify the process of experimentation under several assumptions due to instrumental limitations. For an example, rotational degree of freedom has not been well treated in bending vibrations of beam or plate-like structures. Yet, several recent studies showed that the moments and rotations play an important role in power transmission and should be taken into consideration carefully as the frequency range of interest goes to audibly high. Therefore, it is readily agreed that reduction of the noise radiation over the high frequency range can be effectively accomplished by adjusting the rotational stiffness of the isolator without changing the vibration isolator efficiency in low frequency range relevant to the translational stiffness of the isolator In this paper, the vibration power flow approach is applied to an AC motor installed on a finite plate in order to illustrate the contribution of the rotational vibration power to the total vibration power transmission. The effects of rotational stiffness of the isolator on the vibration power transmission are investigated by inserting various shapes of Isolators with different rotational stiffness but with $ame translational stiffness between the motor and the plate. The resultant noise radiation from the plate is presented to verify the proposed approach.
Vibration Analysis of Beam Supported by Plate Type Springs Considering a Contact
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 384~392
DOI : 10.5050/KSNVN.2003.13.5.384
The fuel rods in the Pressurized water reactor are continuously supported by a spring system called a spacer grid which is one of the main structural components for the fuel rod cluster(fuel assembly). The fuel rods vibrate within the reactor due to coolant flow. Since the vibration, which is called flow-induced vibration(FIV) can wear away the surface of the fuel rod, it is important to understand it's vibration characteristics. In this paper, the vibration analyses and the tests for the dummy rods supported by New Doublet(ND) spacer grids are described. A new FE model which reflects the contact area between the rod and ND spacer grid spring is developed to replace the previous one by which a good agreement could not be obtained with the vibration test. The natural frequency and mode shape calculated by both the Previous FE model and the new one are compared with those of experiment for a single-spanned rod supported by two ND spacer grids. The results of the new model showed good agreement with the experiment compared with those of previous model. In addition. the new FE model is applied to the vibration analysis for the dummy rod of 2.189 mm tall continuously supported by five ND spacer grids. It is also obtained that the analysis results of the new FE model well agreed to experiment ones as the single-spanned rod.
A Study on Shortcomings of Mechanical Model with Lumped Mass for Dynamic Characterization of Hydraulic Mounts and Confirmation of Hydraulic Model by Improvement of Experimentations
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 393~399
DOI : 10.5050/KSNVN.2003.13.5.393
Hydraulic mounts show strong1y frequency-dependent stiffness and damping characteristics in low frequency range, which result from so called inertia track dynamics. A lumped mass has been incorporated in several mechanical models of the literature to take the inertia effect of the fluid in the track into consideration. Although complex s%illness by the mechanical model showed good agreements with the measured values, there exists a critical pitfall. In this paper, the shortcomings of mechanical models with lumped mass for hydraulic founts are clearly identified by illustrating actual measurements of the stiffness parameters for a hydraulic mount. It is conclusively discussed that the inertia effect of the fluid flow through the circular track is significant but latent. As an alternative to the mechanical model, a hydraulic model is claimed to be used for further dynamic analysis of engine/mount system or whole car system.
Vibration Characteristics of Steam Generator U-tubes with Defect
Transactions of the Korean Society for Noise and Vibration Engineering, volume 13, issue 5, 2003, Pages 400~408
DOI : 10.5050/KSNVN.2003.13.5.400
This paper investigates the vibration characteristics of steam generator (SG) U-tubes with defect. The operating SG shell-side flow field conditions for determining the fluidelastic instability parameters such as added mass are obtained from three-dimensional SG flow calculation. Modal analyses are performed for the U-tubes either with axial or circumferential flaw with different sizes. Special emphases are on the effects of flaw orientation and size on the modal and instability characteristics of tubes, which are expressed in terms of the natural frequency, corresponding mode shape and stability ratio. Also, addressed is the effect of the internal pressure on the vibration characteristics of the tube.