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Reconstruction of differential probe signals from absolute probe signals in eddy current testing
N DT Abstracts 58437
which analyses the eddy current signs provided by the axial probe. The analysis scheme includes the site procedure and complementary elements of analysis to increase the reliability of the given diagnosis. This system is based on an expert system shell (Nexpert Object) which has all the features to model the knowledge (rules, objects, inheretance mechanism). This structure allows the modelling of the analyst’s reasoning and, at the same time, allows the use of signal processing such as adaptive interpolation (filtering of the background noise signal). The prototype of SOCRATE (Systeme Operant sur Criteres et Regles pour I’Analyse des Tubes d’Echangeur) integrates the site inspection procedure with the analysis of the rolling transition and the support plates signals. Real defect signals (PWR’S 900 MW site inspection) will be presented.
Chen, G.Z.; Yoshida, Y.; Miya, K.; Uesaka, M.
Application of eddy current testing inspection to the first wall of fusion reactor with wavelet analysis Fusion Engineering and Design, Vol. 29, pp. 309-316 (Mar. 1995) With the aim of in-service inspection of the first wall, a method to evaluate cracks in the first wall1 is studied theoretically utilizing impedance signals and magnetic field data obtained from ECT. From the impedance signals, the depth of the cracks is determined using an impedance-depth calibrating curve. Since an impedance signal may be caused by some undesired factors as well as by a crack, an approach to extracting crack information from such a composite signal is developed using wavelet analysis. For reconstructionof the surface shape of the cracks, the magnetic field data are inverted into the distribution of the current vector potential T by solving an inverse. problem and the wavelet coefficient of T are calculated to characterize the shape of the cracks. It is shown that the combination of ECT and wavelet analysis provides an efficient method of non-destructive evaluation of cracks in the first wall. 57720
Rao, B.P.C.;
57354 Shyamsunder, M.T.; Rajagopalan, C.; Ray, K.K.; Raj, B. A comparative study of conventional and artificial neural network classifiers for eddy current signal classification Insight, Vol. 37, No. 1, pp. 26-30 (Jan. 1995) A series of eddy current signal trajectories have been obtained on artificial round and rectangular defects in thin stainless steel plates. These signals have been processed to achieve a single waveform characterising the eddy current trajectories from which a large number of features have been derived both in the time and frequency domains. The optimised number of features to characterise a defect has been ascertained with the help of four reported conventional classifiers and an Artificial Neural Network (ANN) classifier. A comparative assessmentof the potential of these classifiers has been carried out within the domain of the given signal trainings in this investigation. The results indicate that only five signal features are sufficient to gain an understanding about the nature of defect.
Balm, Rao, C.B.
Reconstruction of differential probe signals from absolute probe signals in eddy current testing Non-Destructive Evaluation and Quality Assurance. Edited by C.R.L. Murthy, B. Raj, 0. Frabhakar and A. Sreenivasulu. pp. 181-190. Interline Publishing (1993) ISBN 81-7296-010-7 A new methodology Locompute differential probe data from an absolute probe data has been presented. The set up required for the reconstruction is built in and around a personal computer with data acquisition card and a stepper motor controller card. Results have been validated by fabricating differential probes of various intercoil spacings. A good agreement has been observed between the reconstructed and experimental data. Relative advantages and limitations of fhis method have also been discussed. 5753 I
Hedengren,
K.H.V.;
Howard,
1 Hamann, R. Industrial testing by pulsed eddy currents - contribution of the sysmat group 5725
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 867-87 1. ECNDT (I 994) Sysmat has studied and applied Pulsed Eddy Content9 (P.E.C.) for more than four years. With the P.E.C. method, the sample is submitted to brief and high magnetic pulses. The electro-magnetic time dependant signal is analysed. Some advantages of Pulsed Eddy Currents versus usual ones are: contact - less scanning (lift-off up to 4 mm), scanning deeper (usual: 8 mm in 304L stainless steel) or through metal/air/metal interface, and a time-lag between the surface signals and the deeper ones. Metal thickness over sub-surface defects and depth of cracks can be easily evaluated. A typical P.E.C. test system is described and some examples of testing in industry are given.
PJ.
Eddy current inspection method employing a probe array with test and reference data acquisition and signal processing U.S. Patent No. 5.37 1,462 ‘(6 Dec. 1994) An eddy current method for inspecting a component with at least one edge is described. The structural portion is scanned by an eddy current probe array. Each test data set and corresponding background reference dalaset is combined to emphasise flow signals. 57482
Wnn,q, B.S.; Tan, KS.
Software developed to analyse the signals from the eddy current inspection of heat exchanger tubes
57238
Insight, Vol. 37, No. 2, pp. 87-92 (Feb. 1995) This paper describes software which has been developed to analyse the signals from the eddy current inspection of heat exchanger tubes. The software logic follows the procedure adopted by human operators in the analysis of the eddy signals. In almost all cases, defects causing the greatest wall thinning due to corrosion can be identified and their location determined with respect lo an identified support signal. 57480
Delsarte,
G.
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 1319-1323. ECNDT (1994) Non-ferromagnetic tube inspection by axial probes is a major application of Eddy Current Techniques. Modelling software able to correlate the defect features with the actual signals recorded on site appears lo be a complementary suited tool for this widely used nondestructive testing method. “MASCOTTE” is an evolutive model which simulates the eddy current signals of discominuities with various shapes. It is based on a simplified theory leading to the analytical formulation of the impedance variation of a thin toroidal coil moving along a very small defect. The software operates with defects such as wall thinning, void-type flaws as well as small over- thickness effects. The impedance plane trajectory and time proportional representation are simultaneously displayed step by step while the probe is moving. This feature is very useful for specialists training and signal analysis. Ben&t,
Ph.; Chadian.
K.; Hoshikawa,
H.: Kaneko, N.
Superannuated tubings of the heat exchanger and condenser in power plants-and chemical plants are able to generate cracks and corrosions. Inservice inspection of those tubings has to he conducted periodically. Eddy current testing has been applied to the inservice inspection of the tubings in heat exchangers and condensers. The authors have investigated the flaw depth discrimination in eddy current testing by using neural network. As a result, it is confirmed that neural network can classify flaw depth by making use of appropriate flaw signal parameters. Phase of Fourier descriptor coefficients provide better flaw depth discrimination than flaw signal phase.
Eddy current signals simulation with MASCOTTE (In French, English abstract)
51473
Koyama,
Flaw depth discrimination in eddy current testing by using neural network (In Japanese, English abstract) Journal of JSNDI, Vol. 43, No. I I, pp. 713-718 (Nov. 1994)
57050
Horn, M.
Non-destructive eddy current part testing printing U.S. Patent No. $363,040 (8 Nov. 1994)
using thermal
The apparatus for mapping sub-surface defects in a part comprises a housing to scan a surface which contains a probe. A threshold detector detects the probe output and a thermal print head detects a defect signal. Thermal paper is mounted on the surface to be scanned on which permanent marks map the defects is made by the print head. 57049
Hosohara,
Y.; Suzuki, K.; Fujiwara,
S.; Kawabe,
T.
Remote field eddy current flaw detector for metal material including attenuator adder, phase shiftery and phase comparator
P.
Expert system to increase the reliability of the multifrequency eddy current testing of steam generator tubes (In French: English abstract)
U.S. Patent No. 5,365,169 (15 Nov. 1994) The flaw detector comprises a reference signal generator and an exciting coil to generate eddy current signals in the pipe. The exciting signal is attenuated at a predetermined level and a phase signal delays this signal to a predetermined phase angle. The attenuated and delayed signal are added to
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 1095- 1099. ECNDT (1994) The aim of this paper is to present a prototype of an automatic system
the received signal and a flaw data generator phase-compares the added and
173
which analyses the eddy current signs provided by the axial probe. The analysis scheme includes the site procedure and complementary elements of analysis to increase the reliability of the given diagnosis. This system is based on an expert system shell (Nexpert Object) which has all the features to model the knowledge (rules, objects, inheretance mechanism). This structure allows the modelling of the analyst’s reasoning and, at the same time, allows the use of signal processing such as adaptive interpolation (filtering of the background noise signal). The prototype of SOCRATE (Systeme Operant sur Criteres et Regles pour I’Analyse des Tubes d’Echangeur) integrates the site inspection procedure with the analysis of the rolling transition and the support plates signals. Real defect signals (PWR’S 900 MW site inspection) will be presented.
Chen, G.Z.; Yoshida, Y.; Miya, K.; Uesaka, M.
Application of eddy current testing inspection to the first wall of fusion reactor with wavelet analysis Fusion Engineering and Design, Vol. 29, pp. 309-316 (Mar. 1995) With the aim of in-service inspection of the first wall, a method to evaluate cracks in the first wall1 is studied theoretically utilizing impedance signals and magnetic field data obtained from ECT. From the impedance signals, the depth of the cracks is determined using an impedance-depth calibrating curve. Since an impedance signal may be caused by some undesired factors as well as by a crack, an approach to extracting crack information from such a composite signal is developed using wavelet analysis. For reconstructionof the surface shape of the cracks, the magnetic field data are inverted into the distribution of the current vector potential T by solving an inverse. problem and the wavelet coefficient of T are calculated to characterize the shape of the cracks. It is shown that the combination of ECT and wavelet analysis provides an efficient method of non-destructive evaluation of cracks in the first wall. 57720
Rao, B.P.C.;
57354 Shyamsunder, M.T.; Rajagopalan, C.; Ray, K.K.; Raj, B. A comparative study of conventional and artificial neural network classifiers for eddy current signal classification Insight, Vol. 37, No. 1, pp. 26-30 (Jan. 1995) A series of eddy current signal trajectories have been obtained on artificial round and rectangular defects in thin stainless steel plates. These signals have been processed to achieve a single waveform characterising the eddy current trajectories from which a large number of features have been derived both in the time and frequency domains. The optimised number of features to characterise a defect has been ascertained with the help of four reported conventional classifiers and an Artificial Neural Network (ANN) classifier. A comparative assessmentof the potential of these classifiers has been carried out within the domain of the given signal trainings in this investigation. The results indicate that only five signal features are sufficient to gain an understanding about the nature of defect.
Balm, Rao, C.B.
Reconstruction of differential probe signals from absolute probe signals in eddy current testing Non-Destructive Evaluation and Quality Assurance. Edited by C.R.L. Murthy, B. Raj, 0. Frabhakar and A. Sreenivasulu. pp. 181-190. Interline Publishing (1993) ISBN 81-7296-010-7 A new methodology Locompute differential probe data from an absolute probe data has been presented. The set up required for the reconstruction is built in and around a personal computer with data acquisition card and a stepper motor controller card. Results have been validated by fabricating differential probes of various intercoil spacings. A good agreement has been observed between the reconstructed and experimental data. Relative advantages and limitations of fhis method have also been discussed. 5753 I
Hedengren,
K.H.V.;
Howard,
1 Hamann, R. Industrial testing by pulsed eddy currents - contribution of the sysmat group 5725
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 867-87 1. ECNDT (I 994) Sysmat has studied and applied Pulsed Eddy Content9 (P.E.C.) for more than four years. With the P.E.C. method, the sample is submitted to brief and high magnetic pulses. The electro-magnetic time dependant signal is analysed. Some advantages of Pulsed Eddy Currents versus usual ones are: contact - less scanning (lift-off up to 4 mm), scanning deeper (usual: 8 mm in 304L stainless steel) or through metal/air/metal interface, and a time-lag between the surface signals and the deeper ones. Metal thickness over sub-surface defects and depth of cracks can be easily evaluated. A typical P.E.C. test system is described and some examples of testing in industry are given.
PJ.
Eddy current inspection method employing a probe array with test and reference data acquisition and signal processing U.S. Patent No. 5.37 1,462 ‘(6 Dec. 1994) An eddy current method for inspecting a component with at least one edge is described. The structural portion is scanned by an eddy current probe array. Each test data set and corresponding background reference dalaset is combined to emphasise flow signals. 57482
Wnn,q, B.S.; Tan, KS.
Software developed to analyse the signals from the eddy current inspection of heat exchanger tubes
57238
Insight, Vol. 37, No. 2, pp. 87-92 (Feb. 1995) This paper describes software which has been developed to analyse the signals from the eddy current inspection of heat exchanger tubes. The software logic follows the procedure adopted by human operators in the analysis of the eddy signals. In almost all cases, defects causing the greatest wall thinning due to corrosion can be identified and their location determined with respect lo an identified support signal. 57480
Delsarte,
G.
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 1319-1323. ECNDT (1994) Non-ferromagnetic tube inspection by axial probes is a major application of Eddy Current Techniques. Modelling software able to correlate the defect features with the actual signals recorded on site appears lo be a complementary suited tool for this widely used nondestructive testing method. “MASCOTTE” is an evolutive model which simulates the eddy current signals of discominuities with various shapes. It is based on a simplified theory leading to the analytical formulation of the impedance variation of a thin toroidal coil moving along a very small defect. The software operates with defects such as wall thinning, void-type flaws as well as small over- thickness effects. The impedance plane trajectory and time proportional representation are simultaneously displayed step by step while the probe is moving. This feature is very useful for specialists training and signal analysis. Ben&t,
Ph.; Chadian.
K.; Hoshikawa,
H.: Kaneko, N.
Superannuated tubings of the heat exchanger and condenser in power plants-and chemical plants are able to generate cracks and corrosions. Inservice inspection of those tubings has to he conducted periodically. Eddy current testing has been applied to the inservice inspection of the tubings in heat exchangers and condensers. The authors have investigated the flaw depth discrimination in eddy current testing by using neural network. As a result, it is confirmed that neural network can classify flaw depth by making use of appropriate flaw signal parameters. Phase of Fourier descriptor coefficients provide better flaw depth discrimination than flaw signal phase.
Eddy current signals simulation with MASCOTTE (In French, English abstract)
51473
Koyama,
Flaw depth discrimination in eddy current testing by using neural network (In Japanese, English abstract) Journal of JSNDI, Vol. 43, No. I I, pp. 713-718 (Nov. 1994)
57050
Horn, M.
Non-destructive eddy current part testing printing U.S. Patent No. $363,040 (8 Nov. 1994)
using thermal
The apparatus for mapping sub-surface defects in a part comprises a housing to scan a surface which contains a probe. A threshold detector detects the probe output and a thermal print head detects a defect signal. Thermal paper is mounted on the surface to be scanned on which permanent marks map the defects is made by the print head. 57049
Hosohara,
Y.; Suzuki, K.; Fujiwara,
S.; Kawabe,
T.
Remote field eddy current flaw detector for metal material including attenuator adder, phase shiftery and phase comparator
P.
Expert system to increase the reliability of the multifrequency eddy current testing of steam generator tubes (In French: English abstract)
U.S. Patent No. 5,365,169 (15 Nov. 1994) The flaw detector comprises a reference signal generator and an exciting coil to generate eddy current signals in the pipe. The exciting signal is attenuated at a predetermined level and a phase signal delays this signal to a predetermined phase angle. The attenuated and delayed signal are added to
6th European Conference on Non Destructive Testing, Nice (France), 24- 28 Oct. 1994. Vol. 2, pp. 1095- 1099. ECNDT (1994) The aim of this paper is to present a prototype of an automatic system
the received signal and a flaw data generator phase-compares the added and
173