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Signal processing of eddy current three-dimensional maps
approach allows greater flexibility in probe design; size, parameters which can be optimized. This paper describes various probes, and their performance, which were developed at the Chalk River Laboratories of Atomic Energy of Canada. Included are probes for detecting defects at tubesheet regions in heat exchanger tubes, defects at expansion-transition regions in finned tubes, and defects in ferromagnetic tubes. All of these probes can be used with conventional commercially available instruments. 40480
Werner, R.; Bernus, L. V.; Jacob, H.
Development of a multi-channel eddy current examination system for automated inspection of steam generator tubing Non-Destructive Testing, Proceedings of the 4th European Conference, London (United Kingdom), 13-17 Sep. 1987, Vol. 4, pp. 2572-2580. Edited by J.M. Farley and R.W. Nichols. Pergamon Press, 1988 A segmented absolute 8-coil probe for inspection of heat exchanger tubing has been developed together with the appropriate multi-channel eddy current instrument and evaluation algorithm in order to achieve higher inspection sensitivity and accuracy especially in the region of roller transitions or dents. A spring loaded probe is used which can adapt to variable tube ID. A map-like representation of the measured wall thickness allows for circumferential resolution. For suppression of noise caused by lift-off and/or conductive material on the tube OD (outer diameter), three frequencies are gated linearly according to the multi-frequency mixing technique. Four mix settings with different amplitude/depth characteristics have been investigated in the laboratory. The system has been tested in the laboratory on artificially induced flaws and in the field by comparing results obtained on actual flaws with data from ultrasonic wall thickness measurements.
David, D.; Lamant, D.; Cherpentier, C.; Paradis, L.; Pigeon, M.; Birac, C.
40477
Signal processing of eddy current three-dimensional maps Non-Destructive Testing, Proceedings of the 4th European Conference, London (United Kingdom), 13-17 Sep. 1987. Vol. 4, pp. 2543-2553. Edited by J.M. Farley and R.W. Nichols. Pergamon Press, 1988 Digital processing of eddy current three-dimensional maps improves accuracy of detection : flattening, filtering, computing deconvolution, mapping new variables . . . . . give new possibilities for difficult test problems. With simulation of defects, probes, probe travels, it is now possible to compute new eddy current processes without machining defects or building probes. 40475
Palanisamy, R.; Jackson, K.E.
Eddy current sizing of case depth in bearing components Nondestructive Characterisation of Materials 2, Montreal (Canada), 21- 23 Jul. 1986. pp. 363-372. Edited by J.F. Bussiere, J.P. Monchalin, C.O. Ruud, R.E. Green Jr. Plenum Press, 1987 This paper addresses the problem of eddy current variations as a function of depth from the raceway or rolling contact surface, in an attempt to improve spatial resolution. The experimental determination of magnetic permeability and electrical conductivity of an induction hardened case and unhardened core of a tapered roller bearing cup is described and results presented. Finite element predicted magnetic field penetration and eddy current distribution in the induction hardened specimen are presented for various frequencies and two types of probe. 40339
Muennemann, F. G.
40155
Kahn, A.H.; Mester, M.L.
An eddy current sensor for the measurement of resistivity and temperature of aluminum rod during extrusion processing Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1599-1606. Edited by D . D . T h o m p s o n and D.E. Chimenti, Plenum Press, 1988. Optimization of the speed of production and the control of quality of extruded aluminum products requires the measurement of the temperature of the extruded product during processing. An eddy current sensor which performs an on-line measurement of resistivity and converts the measurement to the corresponding temperature has been developed. The temperature of the extruded product depends on the initial temperature of the input billet and the speed of extrusion, which is determined by the hydraulic ram pressure. Friction in the die generates heat which can damage the product if excessive. On-line feedback is to be used to regulate extrusion speed. The temperature measurement also would be used to control the furnace which prepares the billets for extrusion. In this report, results are presented on laboratory tests and a plant demonstration of temperature measurements on solid round, solid square, and hollow square extrusion shapes. 40153
Bowler, J.R.; Sabbagh, H.A.; Sabbagh, L.D.
Eddy current probe impedances due to interaction with advanced composites Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1021-1028. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Electromagnetic fields in uniaxial conductors have been studied in order to examine the induced current distributions excited by external alternating current sources. The problem is motivated by the need to evaluate eddy current testing techniques for the inspection of composites such as graphite-epoxy or boron-epoxy. In particular it is important to understand how eddy currents behave in anisotropic materials, especially uniaxial conductors in which the conductivity in the axial direction may be several hundred times greater than the transverse conductivity. 40152
Udpa, S.S.; Ou-Yang, T.H.; Lord, W.
Signal processing for remote field eddy current inspection technique Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 831-838. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Eddy current methods of nondestructive testing have become an industry standard for the inspection of tubing. The popularity of the method can be attributed to the simplicity of the technique as well as the fact that elaborate schemes for coupling the energy into the test medium are not required. Typical testing schemes involve the use of a differential eddy current probe, which consists of two appropriately spaced coils mounted on a common axis and excited by an alternating current source. When the probe is moved past a defect, the differential impedance of the coils traces a trajectory on the impedance plane that is characteristic of the nature of the defect. Defect characterization involves deduction of the nature of the defect on the basis of an examination of the shape of the impedance plane trajectory. Manual as well as automatic defect classification methods have been proposed. 40151
Stohe, J.; Udpa, L.; Lord, W.
The interpretation of electromagnetic nondestructive flaw detection in metals
Multifrequency eddy current testing of steam generator tubes using optimal affine transformation
Dissertation Abstracts International, Vol. 49, No. 3, p. 792B (Sep. 1988) This thesis discusses the physics of electromagnetic eddy current flaw detection devices. Methods of predicting flaw parameters from precision measurements of eddy current probe impedance changes are presented. The results of experiments which verify the validity of these techniques are also presented. The physics of eddy current devices, applied to prediction of flaw signals, with various approximations, deduction of crack dimensions from flaw signals (signal inversion) and optimal selection of probes and operating conditions for crack sensitivity and for ease of signal inversion are also covered.
Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 821-830. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Conventional eddy current inspection techniques, for defect characterization in steam generator tubes in nuclear power plants, involve the interpretation of eddy current probe response signals obtained using single frequency excitation. One of the limitations inherent in single frequency eddy current testing is the sensitivity of the response signal to a variety to test variables such as specimen electrical conductivity, magnetic permeability, test specimen thickness and other geometrical parameters, coupling between probe coil and specimen resulting in unwanted contributions to the signal due to probe wobble, presence of cracks and so on. Simultaneous presence of two or more of these anomalies result in complex eddy current response caused by vector addition of the corresponding signals. Multifrequency testing is proposed using optimal affine transformation.
40159
Beissner, R.E.; Barrels, K.A.; Fisher, J.L.
Prediction of the probability of eddy current flaw detection Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1753-1761. Edited by D . D . T h o m p s o n and D.E. Chimenti, Plenum Press, 1988. The approach to probability of detection (POD) prediction followed here, is to simulate, on a digital computer, the measurements one would make in an experimental determination. In general, this approach requires that reliable methods are available for predicting flaw signals and background noise as a function of flaw size and shape, probe configuration and other inspection parameters. For eddy current testing, necessary to supplement theoretical predictions with experimental data where theory is inadequate. However, existing eddy current theory is sufficiently advanced so that POD predictions can be made using experimental data only for noise statistics and normalization of predicted flaw signals. Accordingly, the principal purpose of the present work was to demonstrate such an application of theory and experiment to POD prediction.
NDT International December 1 990
40150
Capobianco, T.E.; Vecchia, D.F.
Coil parameter influence on eddy current probe sensitivity Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 487-492. Edited by D . D . T h o m p s o n and D.E.Chimenti, Plenum Press, 1988. In the course of developing a draft standard for characterizing eddy current probes a test method has been devised for predicting probe sensitivity. This test can determine sensitivity, but it provides no information as to the causes of sensitivity variations. The construction and characterization of a precisionwound, controlled- variation coil set has been undertaken to provide these answers. Some of the coil construction variables being investigated include: wire gauge; number of turns; coil winding cross section; ferrite permeability and
365
Werner, R.; Bernus, L. V.; Jacob, H.
Development of a multi-channel eddy current examination system for automated inspection of steam generator tubing Non-Destructive Testing, Proceedings of the 4th European Conference, London (United Kingdom), 13-17 Sep. 1987, Vol. 4, pp. 2572-2580. Edited by J.M. Farley and R.W. Nichols. Pergamon Press, 1988 A segmented absolute 8-coil probe for inspection of heat exchanger tubing has been developed together with the appropriate multi-channel eddy current instrument and evaluation algorithm in order to achieve higher inspection sensitivity and accuracy especially in the region of roller transitions or dents. A spring loaded probe is used which can adapt to variable tube ID. A map-like representation of the measured wall thickness allows for circumferential resolution. For suppression of noise caused by lift-off and/or conductive material on the tube OD (outer diameter), three frequencies are gated linearly according to the multi-frequency mixing technique. Four mix settings with different amplitude/depth characteristics have been investigated in the laboratory. The system has been tested in the laboratory on artificially induced flaws and in the field by comparing results obtained on actual flaws with data from ultrasonic wall thickness measurements.
David, D.; Lamant, D.; Cherpentier, C.; Paradis, L.; Pigeon, M.; Birac, C.
40477
Signal processing of eddy current three-dimensional maps Non-Destructive Testing, Proceedings of the 4th European Conference, London (United Kingdom), 13-17 Sep. 1987. Vol. 4, pp. 2543-2553. Edited by J.M. Farley and R.W. Nichols. Pergamon Press, 1988 Digital processing of eddy current three-dimensional maps improves accuracy of detection : flattening, filtering, computing deconvolution, mapping new variables . . . . . give new possibilities for difficult test problems. With simulation of defects, probes, probe travels, it is now possible to compute new eddy current processes without machining defects or building probes. 40475
Palanisamy, R.; Jackson, K.E.
Eddy current sizing of case depth in bearing components Nondestructive Characterisation of Materials 2, Montreal (Canada), 21- 23 Jul. 1986. pp. 363-372. Edited by J.F. Bussiere, J.P. Monchalin, C.O. Ruud, R.E. Green Jr. Plenum Press, 1987 This paper addresses the problem of eddy current variations as a function of depth from the raceway or rolling contact surface, in an attempt to improve spatial resolution. The experimental determination of magnetic permeability and electrical conductivity of an induction hardened case and unhardened core of a tapered roller bearing cup is described and results presented. Finite element predicted magnetic field penetration and eddy current distribution in the induction hardened specimen are presented for various frequencies and two types of probe. 40339
Muennemann, F. G.
40155
Kahn, A.H.; Mester, M.L.
An eddy current sensor for the measurement of resistivity and temperature of aluminum rod during extrusion processing Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1599-1606. Edited by D . D . T h o m p s o n and D.E. Chimenti, Plenum Press, 1988. Optimization of the speed of production and the control of quality of extruded aluminum products requires the measurement of the temperature of the extruded product during processing. An eddy current sensor which performs an on-line measurement of resistivity and converts the measurement to the corresponding temperature has been developed. The temperature of the extruded product depends on the initial temperature of the input billet and the speed of extrusion, which is determined by the hydraulic ram pressure. Friction in the die generates heat which can damage the product if excessive. On-line feedback is to be used to regulate extrusion speed. The temperature measurement also would be used to control the furnace which prepares the billets for extrusion. In this report, results are presented on laboratory tests and a plant demonstration of temperature measurements on solid round, solid square, and hollow square extrusion shapes. 40153
Bowler, J.R.; Sabbagh, H.A.; Sabbagh, L.D.
Eddy current probe impedances due to interaction with advanced composites Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1021-1028. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Electromagnetic fields in uniaxial conductors have been studied in order to examine the induced current distributions excited by external alternating current sources. The problem is motivated by the need to evaluate eddy current testing techniques for the inspection of composites such as graphite-epoxy or boron-epoxy. In particular it is important to understand how eddy currents behave in anisotropic materials, especially uniaxial conductors in which the conductivity in the axial direction may be several hundred times greater than the transverse conductivity. 40152
Udpa, S.S.; Ou-Yang, T.H.; Lord, W.
Signal processing for remote field eddy current inspection technique Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 831-838. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Eddy current methods of nondestructive testing have become an industry standard for the inspection of tubing. The popularity of the method can be attributed to the simplicity of the technique as well as the fact that elaborate schemes for coupling the energy into the test medium are not required. Typical testing schemes involve the use of a differential eddy current probe, which consists of two appropriately spaced coils mounted on a common axis and excited by an alternating current source. When the probe is moved past a defect, the differential impedance of the coils traces a trajectory on the impedance plane that is characteristic of the nature of the defect. Defect characterization involves deduction of the nature of the defect on the basis of an examination of the shape of the impedance plane trajectory. Manual as well as automatic defect classification methods have been proposed. 40151
Stohe, J.; Udpa, L.; Lord, W.
The interpretation of electromagnetic nondestructive flaw detection in metals
Multifrequency eddy current testing of steam generator tubes using optimal affine transformation
Dissertation Abstracts International, Vol. 49, No. 3, p. 792B (Sep. 1988) This thesis discusses the physics of electromagnetic eddy current flaw detection devices. Methods of predicting flaw parameters from precision measurements of eddy current probe impedance changes are presented. The results of experiments which verify the validity of these techniques are also presented. The physics of eddy current devices, applied to prediction of flaw signals, with various approximations, deduction of crack dimensions from flaw signals (signal inversion) and optimal selection of probes and operating conditions for crack sensitivity and for ease of signal inversion are also covered.
Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 821-830. Edited by D.D. Thompson and D.E. Chimenti, Plenum Press, 1988. Conventional eddy current inspection techniques, for defect characterization in steam generator tubes in nuclear power plants, involve the interpretation of eddy current probe response signals obtained using single frequency excitation. One of the limitations inherent in single frequency eddy current testing is the sensitivity of the response signal to a variety to test variables such as specimen electrical conductivity, magnetic permeability, test specimen thickness and other geometrical parameters, coupling between probe coil and specimen resulting in unwanted contributions to the signal due to probe wobble, presence of cracks and so on. Simultaneous presence of two or more of these anomalies result in complex eddy current response caused by vector addition of the corresponding signals. Multifrequency testing is proposed using optimal affine transformation.
40159
Beissner, R.E.; Barrels, K.A.; Fisher, J.L.
Prediction of the probability of eddy current flaw detection Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7B, pp. 1753-1761. Edited by D . D . T h o m p s o n and D.E. Chimenti, Plenum Press, 1988. The approach to probability of detection (POD) prediction followed here, is to simulate, on a digital computer, the measurements one would make in an experimental determination. In general, this approach requires that reliable methods are available for predicting flaw signals and background noise as a function of flaw size and shape, probe configuration and other inspection parameters. For eddy current testing, necessary to supplement theoretical predictions with experimental data where theory is inadequate. However, existing eddy current theory is sufficiently advanced so that POD predictions can be made using experimental data only for noise statistics and normalization of predicted flaw signals. Accordingly, the principal purpose of the present work was to demonstrate such an application of theory and experiment to POD prediction.
NDT International December 1 990
40150
Capobianco, T.E.; Vecchia, D.F.
Coil parameter influence on eddy current probe sensitivity Review of Progress in Quantitative Nondestructive Evaluation, Williamsburg, Virginia (United States), 22-26 Jun. 1987. Vol. 7A, pp. 487-492. Edited by D . D . T h o m p s o n and D.E.Chimenti, Plenum Press, 1988. In the course of developing a draft standard for characterizing eddy current probes a test method has been devised for predicting probe sensitivity. This test can determine sensitivity, but it provides no information as to the causes of sensitivity variations. The construction and characterization of a precisionwound, controlled- variation coil set has been undertaken to provide these answers. Some of the coil construction variables being investigated include: wire gauge; number of turns; coil winding cross section; ferrite permeability and
365