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Inspection of electrically conducting objects with eddy-current facilities
is briefly reviewed and operation principle of the eddy current systems for
testing of hot slabs, blooms as well as rounds and bars are presented. A report from the industrial tests of the EC system, installed in the continuous bloom casting line, is presented as an illustration of the recent development. 39126
Zuern, J.; Hoffmann, T.
Crack depth-measurement and crack shape-reproduction by the eddycurrent-technique (In German) Materialprufung, Vol. 29, No. 10, pp. 294-297 (Oct. 1987) A new method will be introduced for measuring and visualizing the development of cracks during fatigue tests. It can be utilized for a variety of different specimen or part geometries. A two dimensional graph of the crack shape and its development is shown. Cracks outside the zone excited by a stationary coil will be detected as well, because the complete specimen area of possible fatigue cracking is scanned. The exact load cycle to crack initiation can be measured independent of its location. 39125
Capobianco, T.E.; Yu, K.
Pickup coil spacing effects on eddy current reflection probe sensitivity National Bureau of Standards (NEL), Boulder, Colorado (United States), PB87-233854, 5 pp. (1987) Not held at Harwell The authors report the results of an experiment investigating the effect of pickup coil spacing on differential probe sensitivity. The probe configuration for these experiments consists of an air core excitation coil surrounding two air core pickup coils. All three coils have vertical axes with respect to the flat plate test piece. Measurements were taken for three different pickup coil spacings on an aluminum test piece with four electrical discharge machined (EDM) notches. The effect of pickup coil unbalance on probe response is also reported. 39124
Capobianco, T.E.
Field mapping and performance characterization of commercial eddy current probes National Bureau of Standards (NEL), Boulder, Colorado (United States), PB87-233847, 8 pp. (1987) Not held at Harwell Variations in the sensitivity of commercial eddy current probes are common, and this fact can cause reliability problems for those using eddy current inspection techniques. The National Bureau of Standards in Boulder, Colorado, is conducting research to characterize eddy current probe performance. The authors have developed a unique capability to map the near magnetic field of these probes, and results are presented comparing field maps to measurements of electrical and other performance parameters. 39123
Vernon, S.N.
Eddy current nondestructive inspection of graphite epoxy using ferrite cup core probes Naval Surface Warfare Center, Silver Spring, Maryland (United States), AD-AI89-823 72 pp. (Sep. 1987) This report summarizes the results of a three-year project to develop the eddy current technical base for the detection and measurement of broken-fiber damage in graphite epoxy using eddy current. Since graphite epoxy components are frequently made of panels having only one accessible surface, a single-sided technique using a probe coil was required. Parameters of ferrite pot core probes which affect the defect sensitivity of the probe were identified and evaluated in terms of the coil efficiency factor or coupling coefficient. As a result of this investigation, it is possible to optimize eddy current probes for the single-sided inspection of graphite epoxy and other high resistivity materials. 39122
Baron, J.A.; Leemans, D.V.; Dolbey, M.P.
An eddy current technique to estimate dimensions of crevice corrosion
pits Corrosion monitoring in industrial plants using nondestructive testing and electrochemical methods. Proceedings of a symposium, Montreal (Canada), 22-24 Mar. 1984 pp. 124-137. Edited by G.C. Moran and P. Labine. ASTM, 515 pp., 1986. A model of an eddy current probe in the presence of an open defect, such as an elongated crevice corrosion pit, is developed. Assumptions are made in respect to field shape, field width, and lift-off function, which are then justified using experimental data. The technique generates estimates of both crevice depth and width without resorting to microminiature probes; other models tend to generate a response to 'volume lost' rather than the more important geometrical parameters. The model is tested against experimental data from artificial pits in a zirconium-niobium material in the range 50 to 800 microns deep, 500 to 2000 microns wide, and 5 to 20 mm long. The technique is also useful in assessing eddy current probe performance. 39121
Zatsepin, N.N.; Tsukerman, V.L.; Mal'ko, 1.I.
UTTs.I digital eddy-current thickness gauge Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 426-429 (Feb. 1988) The operating principle and structural diagram of U'VFs-1 eddy-current digital thickness gauge are described. The main technical characteristics of the thickness gauge are given. 39120
Sandovskii, V.A.; Dyakin, V.V.; Dudarev, M.S.
A method of examining hydrographs of an eddy-current transducer by expansion into a spectrum using the transformation kernel Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 422-426 (Feb. 1988) The authors examine the method of investigating hodographs of eddy-
178
current transducers which makes it possible to increase the information content and accuracy of inspection thus expanding the possibilities of inspection in solving various flaw inspection problems. Simplified equations were derived for approximating hodographs for any values of the complex argument. This is essential for developing eddy-current devices incorporating computers. 39119
Volkov, B.I.; Agafonov, V.A.; Bologov, G.A.; Fedorov,
A.L. Evaluation of prefailure stages of heat-resisting steels by the eddycurrent method Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 417-422 (Feb. 1988) Experiments were carried out to consider the possibilities of evaluating, by the nondestructive eddy current method, early stages of damage in heat-resisting chrome-molybdenum-vanadium steels used in the development of the creep deformation process. A correlation was found between the parameters of the signal of eddy current attached transducer and the degree of damage in the metal of bends of steam by- pass pipes of 12KhlMF steel can be evaluated using, as the information- carrying parameter, the modulus of the signal of the eddy current attached transducer. 39118
Shaternikov, V.E.; Mikhaikov, V.1.; Lazarev, S.F.
Inspection of electrically conducting objects with eddy-current facilities Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 412-416 (Feb. 1988) Nondestructive inspection is discussed for spatially distributed parameters of electrically conducting objects using eddy-current facilities in which an inspection area scans the space to be inspected. An arrangement is described for scanning, by controlling the currents in spatially distributed conductors, and also a method of improving accuracy for a determination of the parameters' spatial distribution in the objects. 39117
Bubeck, E.
Eddy current probe arrangements for nondestructive testing of rails, profile sections and sheets (In German) Materialprufung, Vol. 30, No. 7-8, pp. 243-245 (Jul.Aug. 1988) Growing demands for quality concerning defect free surfaces of semifinished products require reliable and reproducible defect detection even under rough in-line testing conditions. Testing systems are described which fulfill these requirements. Eddy current testing for defects of plane and curved surfaces and of edges is applied on rails, profile sections, and sheets. A few different probe systems for different defect types and surface geometries may be combined to various arrangements for individual solutions of a variety of nondestructive testing problems. 39116
Mayos, M.; Muller, J.L.
Geometrically anisotropic probes: an improved eddy current technique Journal of Nondestructive Evaluation, Vol. 6, No. 2, pp. 109-116 (Jun. 1987) Geometrically anisotropic eddy current probes are a type of separate function probes especially fit to the detection of defects showing a preferential direction. This kind of flaw induces a coupling between the transmitter and the receiver by guiding eddy currents from the one to the other. On the other hand, this coupling will be almost non- existent in the presence of defects or spurious effects not displaying this geometrical particularity. Basic studies on an elementary two- coil set-up allow the acknowledgment of the intrinsic qualities of such probes: good signal-to-noise ratio, influence field practically constant on the whole defect length, ability to detect 'bridged' defects, insensitivity to lift off. These results can be improved by achieving mulficoils probes adapted to different kinds of problems. An application to continuous casting slabs testing yields very interesting results in the detection of cracks, while getting rid of the effect of oscillation marks with no need of any signal processing. These achievements are promising for the improvement of eddy current testing, in terms of detection sensitivity as well as rapidity to obtain information. 38829
Sadek, H.M.
Eddy current inspection of steam turbine components Materials Evaluation, Vol. 46, No. 4, pp. 442-446 (Mar. 1988) Improvements in sensitivity and resolution make eddy current testing more valuable for steam turbine blades as it does not require disassembly and cleaning. Specially constructed focused-field eddy current probes are described. The advantages of improved eddy current testing are outlined. 38828
Palanisamy, R.
Finite element study of the anomalous behavior of remote field eddy currents in tubular products Proceedings of the 7th International Offshore Mechanics and Arctic Engineering Symposium, Houston, Texas (United States), 7-12 Feb. 1988. pp 71-76. The American Society of Mechanical Engineers. Testing an electrically conductive tube using an I.D. (internal diameter) or O.D. (outer diameter) solenoidal exciter, and an I.D. sensor kept beyond a minimum distance between the exciter and the sensor, is known as remote field eddy current (RFEC) testing. Despite the early experimental observation in the 1950s and commercial utilization in the 1960s for the down-hole inspection of oil well casing, further advancements and applications of this nondestructive testing (NDT) technique had suffered from a lack of adequate theoretical models that could explain its abstruse phenomenon. Finite element predicted magnetic field plots (amplitude and phase) and probe responses are presented in this paper for some test geometries.
NDT International June 1989
testing of hot slabs, blooms as well as rounds and bars are presented. A report from the industrial tests of the EC system, installed in the continuous bloom casting line, is presented as an illustration of the recent development. 39126
Zuern, J.; Hoffmann, T.
Crack depth-measurement and crack shape-reproduction by the eddycurrent-technique (In German) Materialprufung, Vol. 29, No. 10, pp. 294-297 (Oct. 1987) A new method will be introduced for measuring and visualizing the development of cracks during fatigue tests. It can be utilized for a variety of different specimen or part geometries. A two dimensional graph of the crack shape and its development is shown. Cracks outside the zone excited by a stationary coil will be detected as well, because the complete specimen area of possible fatigue cracking is scanned. The exact load cycle to crack initiation can be measured independent of its location. 39125
Capobianco, T.E.; Yu, K.
Pickup coil spacing effects on eddy current reflection probe sensitivity National Bureau of Standards (NEL), Boulder, Colorado (United States), PB87-233854, 5 pp. (1987) Not held at Harwell The authors report the results of an experiment investigating the effect of pickup coil spacing on differential probe sensitivity. The probe configuration for these experiments consists of an air core excitation coil surrounding two air core pickup coils. All three coils have vertical axes with respect to the flat plate test piece. Measurements were taken for three different pickup coil spacings on an aluminum test piece with four electrical discharge machined (EDM) notches. The effect of pickup coil unbalance on probe response is also reported. 39124
Capobianco, T.E.
Field mapping and performance characterization of commercial eddy current probes National Bureau of Standards (NEL), Boulder, Colorado (United States), PB87-233847, 8 pp. (1987) Not held at Harwell Variations in the sensitivity of commercial eddy current probes are common, and this fact can cause reliability problems for those using eddy current inspection techniques. The National Bureau of Standards in Boulder, Colorado, is conducting research to characterize eddy current probe performance. The authors have developed a unique capability to map the near magnetic field of these probes, and results are presented comparing field maps to measurements of electrical and other performance parameters. 39123
Vernon, S.N.
Eddy current nondestructive inspection of graphite epoxy using ferrite cup core probes Naval Surface Warfare Center, Silver Spring, Maryland (United States), AD-AI89-823 72 pp. (Sep. 1987) This report summarizes the results of a three-year project to develop the eddy current technical base for the detection and measurement of broken-fiber damage in graphite epoxy using eddy current. Since graphite epoxy components are frequently made of panels having only one accessible surface, a single-sided technique using a probe coil was required. Parameters of ferrite pot core probes which affect the defect sensitivity of the probe were identified and evaluated in terms of the coil efficiency factor or coupling coefficient. As a result of this investigation, it is possible to optimize eddy current probes for the single-sided inspection of graphite epoxy and other high resistivity materials. 39122
Baron, J.A.; Leemans, D.V.; Dolbey, M.P.
An eddy current technique to estimate dimensions of crevice corrosion
pits Corrosion monitoring in industrial plants using nondestructive testing and electrochemical methods. Proceedings of a symposium, Montreal (Canada), 22-24 Mar. 1984 pp. 124-137. Edited by G.C. Moran and P. Labine. ASTM, 515 pp., 1986. A model of an eddy current probe in the presence of an open defect, such as an elongated crevice corrosion pit, is developed. Assumptions are made in respect to field shape, field width, and lift-off function, which are then justified using experimental data. The technique generates estimates of both crevice depth and width without resorting to microminiature probes; other models tend to generate a response to 'volume lost' rather than the more important geometrical parameters. The model is tested against experimental data from artificial pits in a zirconium-niobium material in the range 50 to 800 microns deep, 500 to 2000 microns wide, and 5 to 20 mm long. The technique is also useful in assessing eddy current probe performance. 39121
Zatsepin, N.N.; Tsukerman, V.L.; Mal'ko, 1.I.
UTTs.I digital eddy-current thickness gauge Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 426-429 (Feb. 1988) The operating principle and structural diagram of U'VFs-1 eddy-current digital thickness gauge are described. The main technical characteristics of the thickness gauge are given. 39120
Sandovskii, V.A.; Dyakin, V.V.; Dudarev, M.S.
A method of examining hydrographs of an eddy-current transducer by expansion into a spectrum using the transformation kernel Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 422-426 (Feb. 1988) The authors examine the method of investigating hodographs of eddy-
178
current transducers which makes it possible to increase the information content and accuracy of inspection thus expanding the possibilities of inspection in solving various flaw inspection problems. Simplified equations were derived for approximating hodographs for any values of the complex argument. This is essential for developing eddy-current devices incorporating computers. 39119
Volkov, B.I.; Agafonov, V.A.; Bologov, G.A.; Fedorov,
A.L. Evaluation of prefailure stages of heat-resisting steels by the eddycurrent method Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 417-422 (Feb. 1988) Experiments were carried out to consider the possibilities of evaluating, by the nondestructive eddy current method, early stages of damage in heat-resisting chrome-molybdenum-vanadium steels used in the development of the creep deformation process. A correlation was found between the parameters of the signal of eddy current attached transducer and the degree of damage in the metal of bends of steam by- pass pipes of 12KhlMF steel can be evaluated using, as the information- carrying parameter, the modulus of the signal of the eddy current attached transducer. 39118
Shaternikov, V.E.; Mikhaikov, V.1.; Lazarev, S.F.
Inspection of electrically conducting objects with eddy-current facilities Soviet Journal of Nondestructive Testing, Vol. 23, No. 6, pp. 412-416 (Feb. 1988) Nondestructive inspection is discussed for spatially distributed parameters of electrically conducting objects using eddy-current facilities in which an inspection area scans the space to be inspected. An arrangement is described for scanning, by controlling the currents in spatially distributed conductors, and also a method of improving accuracy for a determination of the parameters' spatial distribution in the objects. 39117
Bubeck, E.
Eddy current probe arrangements for nondestructive testing of rails, profile sections and sheets (In German) Materialprufung, Vol. 30, No. 7-8, pp. 243-245 (Jul.Aug. 1988) Growing demands for quality concerning defect free surfaces of semifinished products require reliable and reproducible defect detection even under rough in-line testing conditions. Testing systems are described which fulfill these requirements. Eddy current testing for defects of plane and curved surfaces and of edges is applied on rails, profile sections, and sheets. A few different probe systems for different defect types and surface geometries may be combined to various arrangements for individual solutions of a variety of nondestructive testing problems. 39116
Mayos, M.; Muller, J.L.
Geometrically anisotropic probes: an improved eddy current technique Journal of Nondestructive Evaluation, Vol. 6, No. 2, pp. 109-116 (Jun. 1987) Geometrically anisotropic eddy current probes are a type of separate function probes especially fit to the detection of defects showing a preferential direction. This kind of flaw induces a coupling between the transmitter and the receiver by guiding eddy currents from the one to the other. On the other hand, this coupling will be almost non- existent in the presence of defects or spurious effects not displaying this geometrical particularity. Basic studies on an elementary two- coil set-up allow the acknowledgment of the intrinsic qualities of such probes: good signal-to-noise ratio, influence field practically constant on the whole defect length, ability to detect 'bridged' defects, insensitivity to lift off. These results can be improved by achieving mulficoils probes adapted to different kinds of problems. An application to continuous casting slabs testing yields very interesting results in the detection of cracks, while getting rid of the effect of oscillation marks with no need of any signal processing. These achievements are promising for the improvement of eddy current testing, in terms of detection sensitivity as well as rapidity to obtain information. 38829
Sadek, H.M.
Eddy current inspection of steam turbine components Materials Evaluation, Vol. 46, No. 4, pp. 442-446 (Mar. 1988) Improvements in sensitivity and resolution make eddy current testing more valuable for steam turbine blades as it does not require disassembly and cleaning. Specially constructed focused-field eddy current probes are described. The advantages of improved eddy current testing are outlined. 38828
Palanisamy, R.
Finite element study of the anomalous behavior of remote field eddy currents in tubular products Proceedings of the 7th International Offshore Mechanics and Arctic Engineering Symposium, Houston, Texas (United States), 7-12 Feb. 1988. pp 71-76. The American Society of Mechanical Engineers. Testing an electrically conductive tube using an I.D. (internal diameter) or O.D. (outer diameter) solenoidal exciter, and an I.D. sensor kept beyond a minimum distance between the exciter and the sensor, is known as remote field eddy current (RFEC) testing. Despite the early experimental observation in the 1950s and commercial utilization in the 1960s for the down-hole inspection of oil well casing, further advancements and applications of this nondestructive testing (NDT) technique had suffered from a lack of adequate theoretical models that could explain its abstruse phenomenon. Finite element predicted magnetic field plots (amplitude and phase) and probe responses are presented in this paper for some test geometries.
NDT International June 1989