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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Nondestructive Testing
Journal Basic Information
Journal DOI :
The Korean Society for Nondestructive Testing
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Volume & Issues
Volume 21, Issue 6 - Dec 2001
Volume 21, Issue 5 - Oct 2001
Volume 21, Issue 4 - Aug 2001
Volume 21, Issue 3 - Jun 2001
Volume 21, Issue 2 - Apr 2001
Volume 21, Issue 1 - Feb 2001
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Complete Modeling of an Ultrasonic NDE Measurement System - An Electroacoustic Measurement Model
Dang, Changjiu ; Lester W. Schmerr, Jr. ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 1~21
It will be shown how models can simulate all the elements of an ultrasonic NDE measurement system, including the pulser/receiver, cabling, transducer(s), and the acoustic/elastic waves fields. When combined, these models form what is called the electroacoustic measurement model. It will be demonstrated how this electroacoustic measurement model can be used to conduct parametric transducer and system studies and how the model can form the basis for experimentally characterizing all the elements of the ultrasonic measurement system, using purely electrical measurements.
Sensitive NDE of Small Fatigue Cracks
Saka, Masumi ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 22~31
Some techniques developed recently for sizing smalt fatigue cracks are described. One is an ultrasonic technique which deals with a small closed crack, where both the stress closing the crack and the crack size are determined by analyzing inverse problem. Here, difficulties encountered in NDE of closed cracks by usual ultrasonic techniques are summarized in advance. Secondly, the closely coupled probes potential drop (CCPPD) technique, which is based on d-c potential drop measurement, is explained fur sizing small cracks. The CCPPD technique is not affected by crack closure. Finally, a discussion is given on NDE of materials degradation in conjunction with sensitive NDE of small cracks.
Fatigue Damage Evaluation of Cr-Mo Steel with In-Situ Ultrasonic Surface Wave Assessment
Kim, Sang-Tae ; Lee, Hei-Dong ; Yang, Hyun-Tae ; Choi, Young-Geun ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 32~38
Although the ultrasonic method has been developed and used widely in the fields, it has been used only for measuring the defect size and thickness loss. In this study, the relationship between surface wave attenuation through micro-crack growth and variation of velocity under repeated cyclic loading has been investigated. The specimens are adopted from 2.25Cr-1Mo steel, which is used for power plant and pipeline system, and have dimensions of
. The results of ultrasonic test with a 5MHz transducer show that surface wave velocity gradually decreases from the point of 60% of fatigue life and the crack length of 2mm with the increasing fatigue cycles. From the results of this study, it is found that the technique using the ultrasonic velocity change is one of very useful methods to evaluate the fatigue life nondestructively.
Fracture Behavior of CFRP by Time-Frequency Analysis Method
Nam, Ki-Woo ; Ahn, Seok-Hwan ; Lee, Sang-Kee ; Kim, Hyun-Soo ; Moon, Chang-Kwon ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 39~45
Fourier transform has been one of the most common tools to study the frequency characteristics of signals. With the Fourier transform alone, however, it is difficult to tell whether signal's frequency contents evolve in time or not. Except for a few special cases, the frequency contents of most signals encountered in the real world change with time. Time-frequency analysis methods are developed recently to overcome the drawbacks of Fourier transform, which can represent the information of signals in time and frequency at the same time. In this study, damage process of a cross-ply carbon fiber reinforced plastic (CFRP) under monotonic tensile loading was characterized by acoustic emission. Different kinds of CFRP specimens were used to determine the characteristics of AE signals. Time-frequency analysis methods were employed for the analysis of fracture mechanisms in CFRP such as mix cracking, debonding, fiber fracture and delamination.
Development of Feature Selection Method for Neural Network AE Signal Pattern Recognition and Its Application to Classification of Defects of Weld and Rotating Components
Lee, Kang-Yong ; Hwang, In-Bom ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 46~53
The purpose of this paper is to develop a new feature selection method for AE signal classification. The neural network of back propagation algorithm is used. The proposed feature selection method uses the difference between feature coordinates in feature space. This method is compared with the existing methods such as Fisher's criterion, class mean scatter criterion and eigenvector analysis in terms of the recognition rate and the convergence speed, using the signals from the defects in welding zone of austenitic stainless steel and in the metal contact of the rotary compressor. The proposed feature selection methods such as 2-D and 3-D criteria showed better results in the recognition rate than the existing ones.
Development of Defect Classification Program by Wavelet Transform and Neural Network and Its Application to AE Signal Deu to Welding Defect
Kim, Seong-Hoon ; Lee, Kang-Yong ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 54~61
A software package to classify acoustic emission (AE) signals using the wavelet transfrom and the neural network was developed Both of the continuous and the discrete wavelet transforms are considered, and the error back-propagation neural network is adopted as m artificial neural network algorithm. The signals acquired during the 3-point bending test of specimens which have artificial defects on weld zone are used for the classification of the defects. Features are extracted from the time-frequency plane which is the result of the wavelet transform of signals, and the neural network classifier is tamed using the extracted features to classify the signals. It has been shown that the developed software package is useful to classify AE signals. The difference between the classification results by the continuous and the discrete wavelet transforms is also discussed
Study on Characteristics of SCC and AE Signals for Weld HAZ of HT-60 Steel
Na, Eui-Gyun ; Yu, Hyo-Sun ; Kim, Hoon ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 62~68
In order to characterize the microscopic fracture behaviour of the weldment din stress corrosion cracking(SCC) phenomena, SCC and acoustic emission(AE) tests were carried out simultaneously and the correlation between mechanical paramenters obtained from SCC and AE tests was investigated. In the case of base metal, much more AE events were produced at -0.5V than at -0.8V because of the dissolution mechanism before the maximum load. Regardless of the applied voltages to the specimens, however, AE events decreased after the maximum load. In the case of weldment, lots of AE events with larger amplitude
were produced because of the singularities of weld HAZ in comparision to the base metal and post-weld heat-treated(PWHT) specimens. Numerous and larger cracks for the weldment were observed on the fractured surfaces by SEM examination. From these results, it was concluded that SCC for the weldment appeared most severely in synthetic seawater. Weld HAZ was softened by PWHT which also contributed to the reduced susceptibility to corrosive environment in comparison to the weldment.
Numerical Modeling of Elastic Wave Scattering in an Isotropic Medium Containing an Orthotropic Inclusion
Lee, Jung-Ki ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 69~79
A volume integral equation method(VIEM) is applied for the effective analysis of elastic wave scattering problems in unbounded solids containing general anisotropic inclusions. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems since only the Green's function for the unbounded isotropic matrix is Involved In their formulation for the analysis. nis new method can also be applied to general two-dimensional elastodynamic problems with arbitrary shapes and number of anisotropic inclusions. Through the analysis of plane elastodynamic problems in unbounded isotropic matrix with an orthotropic inclusion, it is established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing general anisotropic inclusions.
Analysis on Correlation between AE Parameters and Stress Intensity Factor using Principal Component Regression and Artificial Neural Network
Kim, Ki-Bok ; Yoon, Dong-Jin ; Jeong, Jung-Chae ; Park, Phi-Iip ; Lee, Seung-Seok ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 80~90
The aim of this study is to develop the methodology which enables to identify the mechanical properties of element such as stress intensity factor by using the AE parameters. Considering the multivariate and nonlinear properties of AE parameters such as ringdown count, rise time, energy, event duration and peak amplitude from fatigue cracks of machine element the principal component regression(PCR) and artificial neural network(ANN) models for the estimation of stress intensity factor were developed and validated. The AE parameters were found to be very significant to estimate the stress intensity factor. Since the statistical values including correlation coefficients, standard mr of calibration, standard error of prediction and bias were stable, the PCR and ANN models for stress intensity factor were very robust. The performance of ANN model for unknown data of stress intensity factor was better than that of PCR model.
Integrity Evaluation of Oil and Gas Pipelines
Choi, Jae-Boong ;
Journal of the Korean Society for Nondestructive Testing, volume 21, issue 1, 2001, Pages 91~99