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An equipment for the quality control of seal welds by the eddy-current method. (In French)
bladder that fits inside the body of the probe and expands through openings to center and align the probe in the tubing and (2) an external bladder that is stretched over the probe and secured at each end. The report provides design drawings and specifications and also suggests possible materials and manufactufing processes for constructing the probe. 42066 Myasnikov, B.L Effect of m i s a l i g n m e n t of the layers of a bimetal cylinder of the E M F of
a feedthrough eddy-current transducer Soviet J o u r n a l of N o n - D e s t r u c t i v e Testing, Vol. 24, No. 9. pp. 595-601 ( M a y 1989) The article presents theoretical data that make it possible to evaluate the possibility of checking misalignment of the layers of a bimetal cylinder by a feedthrough eddy-current transducer against the background of the effect of a change of other geometric and electrophysical parameters. The main tenets of the calculation method are explained. 41830
Certo
Non-destructive testing experience at C I S E P r o c e e d i n g s of the E l e c t r o m a g n e t i c W o r k s h o p & M e e t i n g o n the I n d u s t r i a l A p p l i c a t i o n s of the E d d y C u r r e n t C o d e s , C a p r i , Italy, 5-7 Oct. 1988, E U R 12124, pp. 117-120 (1989) Advanced automated eddy current and EMAT (electromagnetic acoustic transducer) techniques are being developed for the inspection of the inner surfaces of ferromagnetic heat exchanger tubes. The advantages and limitations of the two forms of testing are discussed.
Srivatsan, T.S.; Mantena, R.; Gibson, R.F.; Place, T.A.; Sudarshan, T.S. 41828
Electromagnetic measurement of damping capacity to detect damage in adhesively bonded material M a t e r i a l s E v a l u a t i o n , Vol. 47, No. 5, pp. 564-570 ( M a y 1989) in this study, contributions from intrinsic defects caused by improper curing, induced porosity, and improper surface preparation on the performance of double-lap adhesive joints bonded with a structural epoxy adhesive have been nondestructively evaluated through damping- capacity measurements. The damping measurements were made using the novel impulse-frequency response technique. The double-lap adhesively joined specimens were excited in flexural vibration by an electromagnetic hammer with a force transducer at its tip. The specimen response was measured with an eddy current probe. A fast- Fourier transform analyzer was used for rapid acquisition of data and the computation of the loss factor (a measure of damping) by curve- fitting to the frequency response function. Strength of the adhesive joints was determined for different types and levels (size and volume) of defects. The loss factor was found to correlate well with strength, with strength decreasing and damping increasingly with increasing severity (size and/or volume) of the defect. The potential uses of the impulse technique are highlighted.
41691
Auld, B.A.; Moulder, J.C., Je~J?ies, S.; Shall, f'.,/., Ayter, S.
Eddy-current reflection probes: theory and e x p e r i m e n t R e s e a r c h in N o n - d e s t r u c t i v e E v a l u a t i o n , Vol. 1, No. 1, pp. 1-11 (1989) A general AZ theory of reflection-type eddy-current probes was recently developed for new types of robotic proximity sensors. In this paper, the theory is applied to the characterization of surface- connected flaws. Flaw signals were calculated using a finite- difference implementation of the AZ theory developed at Stanford University. A special air-core eddy-current reflection probe was fabricated at the National lnsititute of Standards and Technology (NIST) and used to obtain flaw signals for a number of rectangular- shaped electricaldischarge-machined (EDM) notches in aluminium. An automatic impedance analyzer was used to measure flaw signals as the probe was scanned over the length of the flaw. Experimental results were then compared to predictions of the theory. 41472
Koosha, A.
Eddy current methods for the detection of defects in boiler t u b e s A s l i b I n d e x To T h e s e s , Vol. 37, Pt. 3, p. 1252 (1989) The object of this project is to design a system capable of detecting defects in highly stressed boiler tubes using the eddy-current mmdestructive evaluation method. The design operates by generating sinusoidal currents within a frequency range of 0.001 tiz to 100 KHz. The software of the system limits this frequency spectrum to 100 Hz -9 KHZ. The instrument developed produces sinusoidal signals at either a specific frequency (SPOT) or at frequencies which vary from a lower to a higher level (SWEEP). The lower and higher levels of a sweep frequency as well as the step frequency may be determined by the operator. Probes are in the main concentric coils; the outer one serves as the transmitter (SEND) coil while the inner coil works as the search (RECEIVE) component. However, an appropriate combination of two coils creates a hybrid probe suitable for detecting backwall cracks. 41470
Steblev, Yu.l.
Synthesis of exciting fields of eddy-current transducers for inspecting locally heterogeneous components and media Soviet J o u r n a l of N o n d e s t r u c t i v e Testing, Vol. 24, No. 5, pp. 337-344 (Jan. 1989) The author examines the problem of syntbesising two-dimensional excitation fields from eddy-current transducers designed for inspecting locally heterogeneous components and media and for detecting inclusions and metallic objects. The synthesis equations were derived and examined. The solution of these equations makes it possible to determine the spatial structure of the excitation magnetic field on the basis of the given output characteristics of the transducer from the coordinate of the local heterogeneities or surface defects in inspected components. 41469 Bowler, J.R.; Sabbagh, L.D.; Sabbagh, H.A. A theoretical and computational model of eddy-current
probes
incorporating volume integral and conjugate gradient methods 41826
Verite, J.C.
Numerical modelling in non-destructive testing by eddy-currents P r o c e e d i n g s of the E l e c t r o m a g n e t i c W o r k s h o p a n d M e e t i n g o n the I n d u s t r i a l A p p l i c a t i o n s of the E d d y C u r r e n t C o d e s , C a p r i , Italy, 5-7 Oct. 1988. E U R 12124, pp. 113-116 (1989) Two experiments are described using numerical modelling of nondestructive testing by eddy currents. The studies were of tubes of steam generators in a nuclear power station using two kinds of probe, and axial probe and a rotating iffm" Two dimensional modelling was very successful. The initial three ensional work was promising. In both cases numerical modelling offered improved understanding of the physical phenomena present, because of the graphic display of local fields. 41824
Fastritskii, V.S.; Vingris, L.T.
Analysis of the operation of a two-section superposed eddy-current transducer Soviet J o u r n a l of N o n d e s t r u c t i v e Testing, Vol. 24, No. 8, pp. 551-555 ( A p r . 1989) The article deals with a two-section superposed parametric eddy-current transducer with winding sections connected in opposition. The article substantiates its application, presents theoretical dependences, analyzes special features of operation. Recommendations are given for its practical use. 41692
Van Dijk, G.M.; Noteboom, J. W.
An equipment for the quality control of seal welds by the eddy-current method. (In French) Q u a l i t e . R e v u e P r a t i q u e d e C o n t r o l e I n d u s t r i e l , Vol. 28, 156 bis, pp. 34-40 (1989) A new piece of equipment, called ROTILAS, has been developed for the eddy-current testing of tube-to-plate welds in power station steam condensers. The tubes are made of titanium in preference to cupro- nickel or aluminium bronze because of its greater corrosion resistance. The equipment comprises a scanner unit (to control probe movement), and electronics unit and any commercially available eddy-current testing unit. The probe is guided round the circumference of each weld. These values prevent interference from adjacent welds (which are almost touching). About 350,000 welds have now been examined, at a rate of about 500/h. These welds have also passed a helium leak test. The system is easy to use and reliable in heavy use over long periods. Its use immediately after welding is recommended.
362
I E E E T r a n s a c t i o n s o n M a g n e t i c s , Vol. 25, No. 3, pp. 2650-2664 ( M a y (1989) A general three-dimensional computational model of ferrite-core eddycurrent probes has been developed for research and design studies in nondestructive evaluation. The model is based on a volume integral approach for finding the magnetization of the ferrite core excited by an ac current-carrying coil m the presence of a conducting workpiece. By using the moment method, the integral equation is approximated by a matrix equation and solved using conjugate gradient techniques. Illustrative results are presented showing the impedance characteristics and field distributions for practical eddy-current probe configurations. 41468
Bowler, J.R.; Sabbagh, H.A.; Sabbagh, L.D.
The reduced impedance function for cup-core eddy-current probes I E E E T r a n s a c t i o n s on M a g n e t i c s , Vol. 25, No. 3, pp. 2646-2649 ( M a y 1989) Eddy-current nondestructive evaluation makes use of ferrite-core probes for exciting alternating currents in the test piece. The effectiveness of the probe for detecting flaws in the material through changes in its impedance may be assessed from its interaction with an unflawed conductor. For an important class ot eddy-current probes, those with ferrite cup-cores, the measured impedance characteristics are governed by a rule-based behavior found from experiments. These findings are in conflict with the elementary circuit theory model of probe-workpieee interaction but are confirmed by a general field-theory probe model. 41467
Vernon, S.N.
The universal impedance diagram of the ferrite pot core eddy current transducer I E E E T r a n s a c t i o n s o n M a g n e t i c s , Vol. 25, No. 3, pp. 2639°2645 ( M a y 1989) Experimental results indicate that the shapes of normalized impedance diagrams of ferrite pot core eddy current transducers are independent ol transducers design parameters, lift-off, and material resistivity. When reduced with respect to coupling coefficient, normalized impedance diagrams of this class of transducers are represented by a universal curve. This curve is functionally described by two relationships. The first is that between reactance and the lift-off angle (angle whose tangent is the ratio of the change in the imaginar~ component of the impedance to the change in the real component). The second is the linear relationship between the tangent of the lift-off angle and the
NDT International December 1990
a feedthrough eddy-current transducer Soviet J o u r n a l of N o n - D e s t r u c t i v e Testing, Vol. 24, No. 9. pp. 595-601 ( M a y 1989) The article presents theoretical data that make it possible to evaluate the possibility of checking misalignment of the layers of a bimetal cylinder by a feedthrough eddy-current transducer against the background of the effect of a change of other geometric and electrophysical parameters. The main tenets of the calculation method are explained. 41830
Certo
Non-destructive testing experience at C I S E P r o c e e d i n g s of the E l e c t r o m a g n e t i c W o r k s h o p & M e e t i n g o n the I n d u s t r i a l A p p l i c a t i o n s of the E d d y C u r r e n t C o d e s , C a p r i , Italy, 5-7 Oct. 1988, E U R 12124, pp. 117-120 (1989) Advanced automated eddy current and EMAT (electromagnetic acoustic transducer) techniques are being developed for the inspection of the inner surfaces of ferromagnetic heat exchanger tubes. The advantages and limitations of the two forms of testing are discussed.
Srivatsan, T.S.; Mantena, R.; Gibson, R.F.; Place, T.A.; Sudarshan, T.S. 41828
Electromagnetic measurement of damping capacity to detect damage in adhesively bonded material M a t e r i a l s E v a l u a t i o n , Vol. 47, No. 5, pp. 564-570 ( M a y 1989) in this study, contributions from intrinsic defects caused by improper curing, induced porosity, and improper surface preparation on the performance of double-lap adhesive joints bonded with a structural epoxy adhesive have been nondestructively evaluated through damping- capacity measurements. The damping measurements were made using the novel impulse-frequency response technique. The double-lap adhesively joined specimens were excited in flexural vibration by an electromagnetic hammer with a force transducer at its tip. The specimen response was measured with an eddy current probe. A fast- Fourier transform analyzer was used for rapid acquisition of data and the computation of the loss factor (a measure of damping) by curve- fitting to the frequency response function. Strength of the adhesive joints was determined for different types and levels (size and volume) of defects. The loss factor was found to correlate well with strength, with strength decreasing and damping increasingly with increasing severity (size and/or volume) of the defect. The potential uses of the impulse technique are highlighted.
41691
Auld, B.A.; Moulder, J.C., Je~J?ies, S.; Shall, f'.,/., Ayter, S.
Eddy-current reflection probes: theory and e x p e r i m e n t R e s e a r c h in N o n - d e s t r u c t i v e E v a l u a t i o n , Vol. 1, No. 1, pp. 1-11 (1989) A general AZ theory of reflection-type eddy-current probes was recently developed for new types of robotic proximity sensors. In this paper, the theory is applied to the characterization of surface- connected flaws. Flaw signals were calculated using a finite- difference implementation of the AZ theory developed at Stanford University. A special air-core eddy-current reflection probe was fabricated at the National lnsititute of Standards and Technology (NIST) and used to obtain flaw signals for a number of rectangular- shaped electricaldischarge-machined (EDM) notches in aluminium. An automatic impedance analyzer was used to measure flaw signals as the probe was scanned over the length of the flaw. Experimental results were then compared to predictions of the theory. 41472
Koosha, A.
Eddy current methods for the detection of defects in boiler t u b e s A s l i b I n d e x To T h e s e s , Vol. 37, Pt. 3, p. 1252 (1989) The object of this project is to design a system capable of detecting defects in highly stressed boiler tubes using the eddy-current mmdestructive evaluation method. The design operates by generating sinusoidal currents within a frequency range of 0.001 tiz to 100 KHz. The software of the system limits this frequency spectrum to 100 Hz -9 KHZ. The instrument developed produces sinusoidal signals at either a specific frequency (SPOT) or at frequencies which vary from a lower to a higher level (SWEEP). The lower and higher levels of a sweep frequency as well as the step frequency may be determined by the operator. Probes are in the main concentric coils; the outer one serves as the transmitter (SEND) coil while the inner coil works as the search (RECEIVE) component. However, an appropriate combination of two coils creates a hybrid probe suitable for detecting backwall cracks. 41470
Steblev, Yu.l.
Synthesis of exciting fields of eddy-current transducers for inspecting locally heterogeneous components and media Soviet J o u r n a l of N o n d e s t r u c t i v e Testing, Vol. 24, No. 5, pp. 337-344 (Jan. 1989) The author examines the problem of syntbesising two-dimensional excitation fields from eddy-current transducers designed for inspecting locally heterogeneous components and media and for detecting inclusions and metallic objects. The synthesis equations were derived and examined. The solution of these equations makes it possible to determine the spatial structure of the excitation magnetic field on the basis of the given output characteristics of the transducer from the coordinate of the local heterogeneities or surface defects in inspected components. 41469 Bowler, J.R.; Sabbagh, L.D.; Sabbagh, H.A. A theoretical and computational model of eddy-current
probes
incorporating volume integral and conjugate gradient methods 41826
Verite, J.C.
Numerical modelling in non-destructive testing by eddy-currents P r o c e e d i n g s of the E l e c t r o m a g n e t i c W o r k s h o p a n d M e e t i n g o n the I n d u s t r i a l A p p l i c a t i o n s of the E d d y C u r r e n t C o d e s , C a p r i , Italy, 5-7 Oct. 1988. E U R 12124, pp. 113-116 (1989) Two experiments are described using numerical modelling of nondestructive testing by eddy currents. The studies were of tubes of steam generators in a nuclear power station using two kinds of probe, and axial probe and a rotating iffm" Two dimensional modelling was very successful. The initial three ensional work was promising. In both cases numerical modelling offered improved understanding of the physical phenomena present, because of the graphic display of local fields. 41824
Fastritskii, V.S.; Vingris, L.T.
Analysis of the operation of a two-section superposed eddy-current transducer Soviet J o u r n a l of N o n d e s t r u c t i v e Testing, Vol. 24, No. 8, pp. 551-555 ( A p r . 1989) The article deals with a two-section superposed parametric eddy-current transducer with winding sections connected in opposition. The article substantiates its application, presents theoretical dependences, analyzes special features of operation. Recommendations are given for its practical use. 41692
Van Dijk, G.M.; Noteboom, J. W.
An equipment for the quality control of seal welds by the eddy-current method. (In French) Q u a l i t e . R e v u e P r a t i q u e d e C o n t r o l e I n d u s t r i e l , Vol. 28, 156 bis, pp. 34-40 (1989) A new piece of equipment, called ROTILAS, has been developed for the eddy-current testing of tube-to-plate welds in power station steam condensers. The tubes are made of titanium in preference to cupro- nickel or aluminium bronze because of its greater corrosion resistance. The equipment comprises a scanner unit (to control probe movement), and electronics unit and any commercially available eddy-current testing unit. The probe is guided round the circumference of each weld. These values prevent interference from adjacent welds (which are almost touching). About 350,000 welds have now been examined, at a rate of about 500/h. These welds have also passed a helium leak test. The system is easy to use and reliable in heavy use over long periods. Its use immediately after welding is recommended.
362
I E E E T r a n s a c t i o n s o n M a g n e t i c s , Vol. 25, No. 3, pp. 2650-2664 ( M a y (1989) A general three-dimensional computational model of ferrite-core eddycurrent probes has been developed for research and design studies in nondestructive evaluation. The model is based on a volume integral approach for finding the magnetization of the ferrite core excited by an ac current-carrying coil m the presence of a conducting workpiece. By using the moment method, the integral equation is approximated by a matrix equation and solved using conjugate gradient techniques. Illustrative results are presented showing the impedance characteristics and field distributions for practical eddy-current probe configurations. 41468
Bowler, J.R.; Sabbagh, H.A.; Sabbagh, L.D.
The reduced impedance function for cup-core eddy-current probes I E E E T r a n s a c t i o n s on M a g n e t i c s , Vol. 25, No. 3, pp. 2646-2649 ( M a y 1989) Eddy-current nondestructive evaluation makes use of ferrite-core probes for exciting alternating currents in the test piece. The effectiveness of the probe for detecting flaws in the material through changes in its impedance may be assessed from its interaction with an unflawed conductor. For an important class ot eddy-current probes, those with ferrite cup-cores, the measured impedance characteristics are governed by a rule-based behavior found from experiments. These findings are in conflict with the elementary circuit theory model of probe-workpieee interaction but are confirmed by a general field-theory probe model. 41467
Vernon, S.N.
The universal impedance diagram of the ferrite pot core eddy current transducer I E E E T r a n s a c t i o n s o n M a g n e t i c s , Vol. 25, No. 3, pp. 2639°2645 ( M a y 1989) Experimental results indicate that the shapes of normalized impedance diagrams of ferrite pot core eddy current transducers are independent ol transducers design parameters, lift-off, and material resistivity. When reduced with respect to coupling coefficient, normalized impedance diagrams of this class of transducers are represented by a universal curve. This curve is functionally described by two relationships. The first is that between reactance and the lift-off angle (angle whose tangent is the ratio of the change in the imaginar~ component of the impedance to the change in the real component). The second is the linear relationship between the tangent of the lift-off angle and the
NDT International December 1990