• Journal of KSNVE
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• v.7 no.3
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• pp.477-488
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• 1997

In order to control vibration in structures, it is desirable to be able to identify dominant paths of vibration transmission from sources through the structure to some points of interest. Structural intensity vector(power flow per width of cross section) using cross spectra is able to measure the vibration power flow at a point in a structure. This paper describes the structural intensity measurement of 2-dimensional structure. Structural intensity of 2-dimensional structure can be obtained from eight point cross spectral measurement per axis, or two point measurement per axis on the assumption of far field. Approximate formulation of the relation between bending waves in structures and structural intensity makes it possible to separate the wave components by which one can get a state of the vibration field. Experimental results are obtained on an infinite plate at the near and far field in flexural vibration. The measurement error of two point measurement is rather bigger than eight point measurement on account of the assumption that Poisson's ratio is 1. The structural intensity vectors on the plate are checked the ability to identify the path of vibration power flow in random excitation and 200Hz sine excitation, the result of two point measurememt is almost the same as the result of eight point measurement in 200Hz sine excitation.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.10
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• pp.1011-1016
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• 2015

Gas piping systems in power plants and factories are always influenced by the mechanical vibrations of rotational machines such as pumps, blowers, and compressors. Unusual vibrations in a gas piping system influence possible leakages of liquids or gases, which can lead to large explosive accidents. Real-time measurements of unusual vibrations in piping systems in situ prohibit them from being possible leakages owing to the repeated fatigue of vibrations. In this paper, a non-contact 3-dimensional measurement system that can detect the vibrations of a solid body and monitor its vibrational modes is introduced. To detect the displacements of a body, a stereoscopic camera system is used, through which the major vibration types of solid bodies (such as X-axis-major, Y-axis-major, and Z-axis-major vibrations) can be monitored. In order to judge the vibration types, an artificial neural network is used. The measurement system consists of a host computer, stereoscopic camera system (two-camera system, high-speed high-resolution camera), and a measurement target. Through practical application on a flat plate, the measured data from the non-contact measurement system showed good agreement with those from the original vibration mode produced by an accelerator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.935-939
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• 2012

3D vibration measurement is achieved using one laser scanning vibrometer(LSV) and Laser scanner(LS) by moving the LSV to three arbitrarily locations from the principle that vibration analysis based on the frequency domain is independent of the vibration signal based on time domain. The proposed system has the same effect as using three sets of LSVs. It has an advantage of reducing equipment costs. Analytical approach of obtaining in-plane and out-of-plane vibration of surface is introduced using geometrical relations between three LSV coordinates and vibration measured at three different locations.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1303-1310
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• 2000

GPS carrier phase is supposed to provide the tool for the most precise 3 dimensional positioning information. The FAST, an OTF technique, has been developed by the GPS System Laboratory of Konkuk University, and has been shown several millimeter level accuracy in root-mean-square sense. This OTF's high precision positioning capability provides an adequate tool of low frequency vibration monitoring of large structures. In this paper, the possibility of vibration measurement of a cantilever beam using FAST has been tested, which is supposed to be extended to more practical applications. The results of the experiment have been compared with those by a strain gage and laser sensor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.107-108
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• 2011

A methodology to measure 3-dimensional vibrational displacement of a structure by digital photogrammetry is proposed in this paper. Stereo digital images of a vibrating structure were obtained by two non-metric cameras. Then by applying the collinearity condition to the images, the 3-d displacement time history data of a point or many points can be calculated by the present methodology. Experimental work was performed to measure the displacement time history for a cantilever beam excited by a piezoelectric patch, in which the in-depth displacement data obtained by the proposed method well matched the laser sensor data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8C
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• pp.1104-1112
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• 2004

In this paper, we establish measurement methods of vibration frequency for three-dimensional behavior measurement of large-scale structure using laser and high-speed CCD camera. We project the diode laser having a smaller fluctuation on the object plane attached to the structure and measure the displacement of the structure using a precise relative measurement algorithm. When we use high-speed(120 frames/sec) CCD camera, we can measure the vibration frequency having the uncertainty within 0.5% by taking FFT on the displacement, from 0Hz to 40Hz. And we also confirm the reliability and economical string of the suggested measurement method of vibration frequency of the structure by showing the accuracy of displacement measurement using laser is comparable to that of relative positioning methods using GPS.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.3
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• pp.208-219
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• 2002

A novel measurement method to obtain the 6-DOF motions of arbitrary rigid bodies is proposed in this paper. The method adopts a specially fabricated mirror called 3-facet mirror, which looks like a triangular pyramid haying an equilateral cross-sectional shape. The mirror is mounted on the objects to be measured, illuminated by a laser beam having circular profile, and reflects the laser beam in three different directions. Three PSDs(position sensitive detector) detect the three beams reflected by the mirror, respectively. From the signals of the PSDs, we can calculate the 3-dimensional position and orientation of the 3-facet mirror, and thus enabling us to determine the 3-dimensional position and orientation of the objects. In this paper, we model the relationship between the 3-dimensional position and orientation of an object in motion and the outputs of three PSDs. A series of experiments are performed to demonstrate the effectiveness and accuracy of the proposed method. The experimental results show that the proposed sensing system can be an effective means of obtaining 3-dimensional position and orientation of arbitrary objects and provide resonable measurement accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.300-305
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• 2012

The vibration and stress analysis program of comprehensive vibration assessment program (CVAP) is to verify theoretically the structural integrity of reactor vessel internals (RVI) and to provide the basis for selecting the locations monitored in measurement and inspection programs. This paper covers the verification of the vibration and stress analysis methodology of APR1400 RVI CVAP. The analysis methodology was developed to use 3-dimensional hydraulic and structural models with ANSYS and CFX. To validate the methodology, the hydraulic loads and structural reponses of OPR1000 were predicted and compared with the calculated and measured data in the OPR1000 RVI CVAP. Since the results predicted with this methodology were close to the measured values considerably, it was confirmed that the analysis methodology was developed properly.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1098-1103
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• 2011

The structural integrity of APR1400 reactor vessel internals has been being assessed referring the US Nuclear Regulatory Commission regulatory guide 1.20, comprehensive vibration assessment program. The program is composed of a vibration and stress analysis, a vibration and stress measurement, and an inspection. This paper covers the vibration and stress analysis on the reactor vessel internals by the pulsation of reactor coolant pump. 3-dimensional models to calculate the hydraulic loads and structural responses were built and the pressure distributions and the structural responses were predicted using ANSYS. This paper presents that APR1400 reactor vessel internals have enough structural integrity against the pulsation of reactor coolant pump as the peak stress of the reactor vessel internals is much lower than the acceptance limit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1704-1709
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• 2000

This paper proposes a spherical probe allowing acoustic intensity measurements in three dimensions to be made, which creates a diffracted field that is well-defined, thanks to analytic solution of diffraction phenomena. Six microphones are distributed on the surface of the sphere along three rectangular axes. Its measurement technique is not based on finite difference approximation, as is the case for the ID probe but on the analytic solution of diffraction phenomena. In fact, the success of sound source identification depends on the inverse models used to estimate inverse diffraction phenomena, which has non-linear properties. In this paper, we introduce the concept of nonlinear inverse diffraction modeling using a neural network and the idea of 3 dimensional sound source identification with several tests.