Results 1 - 10 of 34
Results 1 - 10 of 34. Search took: 0.015 seconds
|Sort by: date | relevance|
[en] This proceedings contains articles of the Korean Society for Nondestructive Testing Fall Meeting, 2004. It was held on Nov. 5, 2004 in Seoul, Korea and subject of the Korean Society for Nondestructive Testing Fall Meeting 2004. This proceedings is comprised of 5 sessions.
[en] A magnetostrictive transducer was applied to investigate the guided wave propagation and the effect of outer supports of a small bore tube. The width of Ni strip for the static magnetic bias was optimized for the small bore tube. Because of the geometrical limitation of Ni strip, a F(1,1) mode vibration was accompanied with the main T(0,1) mode vibration. In the viewpoint of long range attenuation the L(0,1) mode vibration is better than the T(0,1) mode vibration for the case of the small bore tube and unwanted signals from the tube holders or pads were not able to eliminate or suppressed in this experiment. After the review of various wave structures and dispersion characteristics of the tube, the frequency and vibration mode could be optimized to reduce the reflections from those outer support structures.
[en] In order to evaluate the corrosion of reinforcing steel-bars (rebar) in concrete, a nondestructive evaluation by the half-cell potential method is currently applied. In this study, potentials measured on a concrete surface are compensated into those on the concrete-rebar interface by the inverse boundary element method (IBEM). Because these potentials are obtained three-dimensionally (3-D), 3-D visualization is desirable. To this end, a visualization system has been developed by using VRML (Virtual Reality Modeling Language). As an application, results of a reinforced concrete (RC) slab with corroded rebars are visualized and discussed.
[en] Ultrasonic backward radiation profile is frequency-dependent when incident region has deptional gradient of acoustical properties or multi-layers. Until now, we have measured the profiles of principal frequencies of used transducers so that it was not easy to understand the change of the frequency component and spectrum of backward radiation from the profile. We tried to measure the spectral backward radiation profiles using DFP(digital filer package) Lecroy DSO. The very big changes in the shape and pattern of spectral backward radiation profiles leads to the conclusion that this new try could be very effective tool to evaluate frequency dependent surface area.
[en] We developed the nondestructive material characterization devises using a microwave TE mode. We observed the changes of frequency and reflection coefficient S11 of resonator coupled to the sample. In order to better characterize the metal and dielectric materials, we take advantage of the nondestructive evaluation method using a microwave TE mode.
[en] The objective of this study is to estimate the feasibility of acoustic emission method for the internal leak from the valves. In this study, valve leak tests using various types of specimen simulated seat damage were performed in order to analyzer acoustic emission properties when leaks arise in valve seat. As a result of leak test for specimens simulated valve seat, we conformed that leak sound level increased in proportion to the increase of hole diameter and leak velocity, and decreased in proportion to the increase of leak depth. And also, leak sound level has hysteresis for leak velocity. From the experimental results, it was suggested that the acoustic emission method for monitoring of leak was feasible.
[en] In this paper, we studied resolution to the FBP(Filtered Sack-Propagation) tomographic image reconstruction algorithms. In order to analyze the resolution to the tomographic images, we derived ambiguity function to this algorithm which can be reconstructed from the improved FBP image reconstruction algorithm by using fixed coordinate system practically. Through simulation using this function, we determined the lateral and depth resolution quantitatively and then analyzed respectively. Simulation results show that the lateral and depth resolution to the improved FBP image reconstruction algorithm was determined 0.27 λ and 0.70 λ at the 3dB, and also 0.89 λ and 0.96 λ at the 6dB respectively, This results proved that improved FBP reconstruction algorithms for diffraction tomography of incident planar wave is useful to developed the tomographic image system.
[en] A modular multi-Gaussian beam model is used to simulate some nondestructive testing configurations where multiple interfaces or anisotropic material properties are involved. We consider two NDE problems in this paper: (1) angle beam, contact shear wave testing, and (2) wave propagation through water-anisotropic solid interface. The ultrasonic transducer fields are modeled by superposing 10 single Gaussian beams. The resulting expressions given in a modular matrix form is implemented in a personal computer using MATLAB program. Simulation results are presented for these problems with available experimental results.
[en] Many problems arising in rotating machinery are linked to bearing defects. Hence the early detection of the bearing defects in rotating machinery is very important since the critical failure of bearing cause a machinery shutdown. However it is not easy to detect the vibration signal caused by the initial defects of bearing because of high level of broadband noise. A signal processing technique, called the adaptive line enhancer(ALE) as one of adaptive filter, is used in this study. This technique is to eliminate random noise with little a prior knowledge of the noise and signal characteristics. Also we propose the optimal methods for selecting the three main ALE parameters such as correlation length, filter order and adaptation constant. Vibration signals from three abnormal bearings, including inner and outer raceways and ball defects, were acquired by Anderon (angular derivative of radius on) meter. The experimental results showed that ALE is very useful for detecting the bearing defective signals overlapped with random noise.
[en] This paper reports on the development of a quantitative method for defect evaluation inside of impact-damaged composite plate by Electronic speckle pattern interferometry(ESPI) which is an optical technique to measure the deformation of object surface. Delamination of the first interface and the second interface from the impacted-surface are quantitatively inspected. In order to extract the quantitative results from the measured images, numerical processing technique of surface displacement distribution is proposed. the ESPI results in each interface is compared with those of visual inspection.