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C. S. Angani,D. G. Park,C. G. Kim,P. Kollu,Y. M. Cheong 한국자기학회 2010 Journal of Magnetics Vol.15 No.4
Local wall thinning in pipelines affects the structural integrity of industries like nuclear power plants (NPPs). In the present study, a pulsed eddy current (PEC) differential probe with two excitation coils and two Hall-sensors was fabricated to measure the wall thinning in insulated pipelines. A stainless steel test sample was prepared with a thickness that varied from 1 ㎜ to 5 ㎜ and was laminated by plastic insulation to simulate the pipelines in NPPs. The excitation coils in the probe were driven by a rectangular current pulse, the difference of signals from two Hall-sensors was measured as the resultant PEC signal. The peak value of the detected signal is used to describe the wall thinning. The peak value increased as the thickness of the test sample increased. The results were measured at different insulation thicknesses on the sample. Results show that the differential PEC probe has the potential to detect wall thinning in an insulated NPP pipelines.
D. G. Park,C. S. Angani,M. B. Kishore,G. Vertesy,D. H. Lee 한국자기학회 2013 Journal of Magnetics Vol.18 No.3
Local wall thinning in pipelines affects the structural integrity of industries, such as nuclear power plants (NPPs). In the present study, a development of pulsed eddy current (PEC) technology that detects the wall thinning of pipelines covered with insulation is reviewed. The methods and experimental results, which have two kinds of probe with a single and double core, were compared. For this purpose, the single and double core probes having one and two excitation coils have been devised, and the differential probe with two Hall sensors has been fabricated to measure the wall thinning in insulated pipelines. The test sample is a stainless steel having different thickness, laminated by plastic insulation to simulate the pipelines in NPPs. The excitation coils in the probe is driven by a rectangular current pulse, the difference of two Hall sensors has been measured as a resultant PEC signal. The peak value of the detected signal is used to describe the wall thinning. The double core probe has better performance to detect the wall thinning covered with insulation; the single core probe can detect the wall thinning up to an insulation thickness of 18 mm, whereas the double probe can detect up to 25 mm. The results show that the double core PEC probe has the potential to detect the wall thinning in an insulated pipeline of the NPPs
The Effects of Lift-Off from Wall Thinning Signal in Pulsed Eddy Current Testing
Duck-Gun Park,C. S. Angani,M. B. Kishore,C. G. Kim,D. H. Lee 한국자기학회 2012 Journal of Magnetics Vol.17 No.4
In order to know the effect of surface irregularity in the detection of local wall thinning of pipeline using pulsed eddy current (PEC), the lift-off effects on PEC signal have been investigated. Three kinds of parameters in the PEC signal, which is “peak amplitude”, “time to peak amplitude” and “time to zero crossing” are analyzed to separate the lift-off effects in the PEC signal. The distance from sensor to the bottom of sample which is the total thickness of combined insulator and sample is kept constant. The magnitude of the differential peak amplitude is increased with increasing sample thickness, the time to peak amplitude is increased with increasing the sample thickness. To determine the effect of lift-off, a number of balanced transient responses combining wall thinning locations and lift-off distances were plotted.
Ion-Irradiation-Induced Effects on the Magnetic Properties of Co-Based Amorphous Ribbon
Park, D.G.,Lee, I.J.,Park, C.Y.,Angani, C.S.,Kim, C.G.,Cheong, Y.M. IEEE 2010 IEEE transactions on magnetics Vol.46 No.2
<P>The N and Ar ions have been irradiated on the Co-based amorphous ribbon to investigate the mechanism of the abrupt increase of the giant magneto-impedance (GMI) response. The M-H loop parameters and grazing incident X-ray diffraction were used to characterize the samples before and after ion irradiation. The GMI ratio increased considerably in the ion irradiated samples and GMI response showed strong dependency on the irradiated ion species and driving frequencies. Substantial modifications of the magnetic properties such as increase of coercivity and change of saturation magnetization were observed in the ion irradiated samples.</P>
Analysis of the Domain Wall Motion in the Ion Irradiated Amorphous Ribbon
Park, D.G.,Song, H.,Park, C.Y.,Angani, C.S.,Kim, C.G.,Cheong, Y.M. IEEE 2009 IEEE transactions on magnetics Vol.45 No.10
<P>The mechanism of abrupt increase of the giant magneto impedance (GMI) ratio in the ion irradiated Co-based amorphous ribbon has been investigated. The GMI-ratio considerably increased in the ion irradiated samples and the GMI response showed strong dependence on the driving frequencies. The Barkhausen noise (BN) signals are decreased up to 46% for the Ar ion irradiated sample with energy of 100 keV. The power spectrum density of BN was decreased with increasing ion bombardment energy. The results are interpreted in terms of permeability variation associated with domain wall dynamics.</P>
K. Sambasiva Rao,T. V. Beatriceveena,C. S. Angani,Lucky Agarwal 한국자기학회 2020 Journal of Magnetics Vol.25 No.3
Pulsed eddy current (PEC) testing is an electromagnetic nondestructive evaluation (NDE) technique which is used for detection and classification of flaws. This paper presents an approach for the extraction of novel timedomain flaw parameters viz. amplitude ratio (V1/V0) and time constant (τ) for detection and classification of different flaws. Experiments are carried out on stainless steel (SS-316) plate with artificial EDM notches whose width (1.0 mm & 3.0 mm) and depth (1.0 mm to 6.0 mm) varied. The proposed approach can classify both surface and sub-surface flaws in an 8.0 mm thick SS plate. The advantage of the proposed approach is that it doesn’t require a reference signal subtraction or signal processing methodologies for the detection and classification of flaws.