Science.gov

Sample records for eddy current signals

  1. Eddy current signal comparison for tube identification

    SciTech Connect

    Glass, S. W. E-mail: Ratko.Vojvodic@areva.com; Vojvodic, R. E-mail: Ratko.Vojvodic@areva.com

    2015-03-31

    Inspection of nuclear power plant steam generator tubes is required to justify continued safe plant operation. The steam generators consist of thousands of tubes with nominal diameters of 15 to 22mm, approximately 1mm wall thickness, and 20 to 30m in length. The tubes are inspected by passing an eddy current probe through the tubes from tube end to tube end. It is critical to know exactly which tube identification (row and column) is associated with each tube's data. This is controlled by a precision manipulator that provides the tube ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the tube ID. This can have serious consequences including lack of inspection of a tube, or if a pluggable indication is detected, the tube is likely to be mis-plugged thereby risking a primary to secondary leak.

  2. Eddy current signal comparison for tube identification

    NASA Astrophysics Data System (ADS)

    Glass, S. W.; Vojvodic, R.

    2015-03-01

    Inspection of nuclear power plant steam generator tubes is required to justify continued safe plant operation. The steam generators consist of thousands of tubes with nominal diameters of 15 to 22mm, approximately 1mm wall thickness, and 20 to 30m in length. The tubes are inspected by passing an eddy current probe through the tubes from tube end to tube end. It is critical to know exactly which tube identification (row and column) is associated with each tube's data. This is controlled by a precision manipulator that provides the tube ID to the eddy current system. Historically there have been some instances where the manipulator incorrectly reported the tube ID. This can have serious consequences including lack of inspection of a tube, or if a pluggable indication is detected, the tube is likely to be mis-plugged thereby risking a primary to secondary leak.

  3. Conjugate spectrum filters for eddy current signal processing

    SciTech Connect

    Stepinski, T.; Maszi, N. . Dept. of Technology.)

    1993-07-01

    The paper addresses the problem of detection and classification of material defects during eddy current inspection. Digital signal processing algorithms for detection and characterization of flaws are considered and a new type of filter for classification of eddy current data is proposed. In the first part of the paper the signal processing blocks used in modern eddy current instruments are presented and analyzed in terms of information transmission. The processing usually consists of two steps: detection by means of amplitude-phase detectors and filtering of the detector output signals by means of analog signal filters. Distortion introduced by the signal filters is considered and illustrated using real eddy current responses. The nature of the distortion is explained and the way to avoid it is indicated. A novel method for processing the eddy current responses is presented in the second part of the paper. The method employs two-dimensional conjugate spectrum filters (CSFs) that are sensitive both to the phase angle and the shape of the eddy current responses. First the theoretical background of the CSF is presented and then two different ways of application, matched filters and orthogonal conjugate spectrum filters, are considered. The matched CSFs can be used for attenuation of all signals with the phase angle different from the selected prototype. The orthogonal filters are able to suppress completely a specific interference, e.g. the response of supporting plate when testing heat exchanger tubes. The performance of the CSFs is illustrated by means of real and simulated eddy current signals.

  4. Automated Detection and Location of Indications in Eddy Current Signals

    SciTech Connect

    Brudnoy, David M.; Oppenlander, Jane E.; Levy, Arthur J.

    1998-06-30

    A computer implemented information extraction process that locates and identifies eddy current signal features in digital point-ordered signals, said signals representing data from inspection of test materials, by enhancing the signal features relative to signal noise, detecting features of the signals, verifying the location of the signal features that can be known in advance, and outputting information about the identity and location of all detected signal features.

  5. Automated detection and location of indications in eddy current signals

    DOEpatents

    Brudnoy, David M.; Oppenlander, Jane E.; Levy, Arthur J.

    2000-01-01

    A computer implemented information extraction process that locates and identifies eddy current signal features in digital point-ordered signals, signals representing data from inspection of test materials, by enhancing the signal features relative to signal noise, detecting features of the signals, verifying the location of the signal features that can be known in advance, and outputting information about the identity and location of all detected signal features.

  6. Correlation Between Eddy Current Signal Noise and Peened Surface Roughness

    SciTech Connect

    Wendt, S. E.; Hentscher, S. R.; Raithel, D. C.; Nakagawa, N.

    2007-03-21

    For advanced uses of eddy current (EC) NDE models in, e.g., model-assisted POD, there is a need to understand the origin of EC noise sources so that noise estimations can be made for a given set of inspection conditions, in addition to defect signal predictions. This paper focuses on the material-oriented noise sources that exhibit some universality when isolated from electrical and mechanical noises. Specifically, we report on experimental measurements that show explicit correlations between surface roughness and EC noise as seen in post-peen EC measurements of shot-peened roughness specimens. The samples are 3''-by-3'' Inconel 718 and Ti-6A1-4V blocks, pre-polished and shot-peened at Almen intensities ranging from a low of 4N to as high as 16A, created by smaller ({approx}350 {mu}m) and larger ({approx}1 mm) diameter zirconium oxide shots. Strong correlations are observed between the Almen intensities and the measured surface roughness. The EC noise correlates equally strongly with the Almen intensities for the superalloy specimens. The correlation for the Ti-alloy samples is only apparent at higher intensities, while being weak for lower intensities, indicating the grain noise dominance for smoother surfaces.

  7. An excitation signal source with anti-interference ability for eddy current testing

    NASA Astrophysics Data System (ADS)

    Jiang, Guodong; Li, Po

    2015-02-01

    An eddy current excitation signal source was designed based on the linear control theory. By analyzing the interference and characteristics of signal source, a multi-input-single-output (MISO) feedback control system was designed and created using a lock-in amplifier, and an eddy current sensor was applied in the feedback loop of the system. As a result, the noise in the loop circuit was suppressed; this resolved the current instability problem in eddy current sensor. Furthermore, a mathematical model was established, and the stability and bandwidth of the system were verified by simulations. Compared with the traditional signal sources, experimental results show that this signal source had steadier current output, smaller temperature drift and stronger load capability. Therefore, the foil thickness measurement based on this signal source had a very high accuracy.

  8. Nonlinear mixing algorithm for suppression of TSP signals in bobbin coil eddy current data

    NASA Astrophysics Data System (ADS)

    Arunchalam, K.; Ramuhalli, P.; Udpa, L.; Udpa, S.

    2002-05-01

    Multi-frequency eddy current techniques are commonly used in inspecting steam generator tubes in nuclear power plants. The measurement usually contains dominant contributions from external tube support plates that tend to mask signals from defects. This paper proposes the use of a non-linear mixing technique using radial basis function neural networks to suppress the TSP signals. Initial results presented in this paper look very promising and demonstrate the effectiveness of the proposed algorithm.

  9. Evaluation of eddy-current probe signals due to cracks in ferromagnetic parts of fast reactor

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Bowler, John R.

    2017-02-01

    Eddy current testing to evaluate the condition of metallic parts in a sodium cooled fast reactor under standby conditions is challenging due to the presence of liquid sodium at 250 °C. The eddy current test system should be sensitive enough to capture small signal changes and hence an advanced inspection systems is needed. We have developed new hardware and improved numerical models to predict the eddy current probe signal due to cracks in metallic fast reactor parts by using volume integral equation method. The analytical expressions are derived for the quasi-static time-harmonic electromagnetic fields of a circular eddy current coil which interacts with conductive plate. Naturally, the method of moment is used to approximate the integral equation and obtain the discrete approximation of the field in the crack domain. A simple and accurate analytical method for dealing with the hyper-singularity element evaluation is also provided. An accurate controlled experiment is carried out on the ferromagnetic stainless steel plate with precision made notch to obtain reference impedance changes for comparison with the theoretical model predictions. Good agreement between predictions and experiment is obtained.

  10. Reconstruction of stress corrosion cracks using signals of pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Wang, Li; Xie, Shejuan; Chen, Zhenmao; Li, Yong; Wang, Xiaowei; Takagi, Toshiyuki

    2013-06-01

    A scheme to apply signals of pulsed eddy current testing (PECT) to reconstruct a deep stress corrosion crack (SCC) is proposed on the basis of a multi-layer and multi-frequency reconstruction strategy. First, a numerical method is introduced to extract conventional eddy current testing (ECT) signals of different frequencies from the PECT responses at different scanning points, which are necessary for multi-frequency ECT inversion. Second, the conventional fast forward solver for ECT signal simulation is upgraded to calculate the single-frequency pickup signal of a magnetic field by introducing a strategy that employs a tiny search coil. Using the multiple-frequency ECT signals and the upgraded fast signal simulator, we reconstructed the shape profiles and conductivity of an SCC at different depths layer-by-layer with a hybrid inversion scheme of the conjugate gradient and particle swarm optimisation. Several modelled SCCs of rectangular or stepwise shape in an SUS304 plate are reconstructed from simulated PECT signals with artificial noise. The reconstruction results show better precision in crack depth than the conventional ECT inversion method, which demonstrates the validity and efficiency of the proposed PECT inversion scheme.

  11. Method and apparatus for correcting eddy current signal voltage for temperature effects

    DOEpatents

    Kustra, Thomas A.; Caffarel, Alfred J.

    1990-01-01

    An apparatus and method for measuring physical characteristics of an electrically conductive material by the use of eddy-current techniques and compensating measurement errors caused by changes in temperature includes a switching arrangement connected between primary and reference coils of an eddy-current probe which allows the probe to be selectively connected between an eddy current output oscilloscope and a digital ohm-meter for measuring the resistances of the primary and reference coils substantially at the time of eddy current measurement. In this way, changes in resistance due to temperature effects can be completely taken into account in determining the true error in the eddy current measurement. The true error can consequently be converted into an equivalent eddy current measurement correction.

  12. Eddy-current testing

    NASA Technical Reports Server (NTRS)

    Pasley, R. L.; Birdwell, J. A.

    1973-01-01

    Eddy-current inspection is discussed as a method for locating subsurface flaws in electrically conductive materials. The physical principles and electrical circuitry are described along with the test equipment.

  13. NONDESTRUCTIVE EDDY CURRENT TESTING

    DOEpatents

    Renken, C.J. Jr.

    1961-05-23

    An eddy current testing device is described for measuring metal continuity independent of probe-to-sample spacing. An inductance would test probe is made a leg of a variable impedance bridge and the bridge is balanced with the probe away from the sample. An a-c signal is applied across the input terminals of the bridge circuit. As the probe is brought into proximity with the metal sample, the resulting impedance change in the probe gives an output signal from the bridge whose phase angle is proportional to the sample continuity and amplitude is proportional to the probe-tosample spacing. The output signal from the bridge is applied to a compensating network where, responsive to amplitude changes from the bridge output signal, a constant phased voltage output is maintained when the sample is continuous regardless of probe-to-sample spacing. A phase meter calibrated to read changes in resistivity of the metal sample measures the phase shift between the output of the compensating network and the original a-c signal applied to the bridge.

  14. Advanced flux leakage and eddy current signal analysis for casing and pipe inspection. Final report, September 1994-October 1996

    SciTech Connect

    Merchant, G.A.

    1997-01-01

    The objective of the project was to develop signal analysis methods and algorithms which will extract from the magnetic flux leakage and eddy current (FLEC) signals all the quantitative information they inherently contain and format that information in a manner which facilitates its interpretation in terms of casing condition.

  15. Effect of asymmetrical eddy currents on magnetic diagnosis signals for equilibrium reconstruction in the Sino-UNIted Spherical Tokamak.

    PubMed

    Jiang, Y Z; Tan, Y; Gao, Z; Wang, L

    2014-11-01

    The vacuum vessel of Sino-UNIted Spherical Tokamak was split into two insulated hemispheres, both of which were insulated from the central cylinder. The eddy currents flowing in the vacuum vessel would become asymmetrical due to discontinuity. A 3D finite elements model was applied in order to study the eddy currents. The modeling results indicated that when the Poloidal Field (PF) was applied, the induced eddy currents would flow in the toroidal direction in the center of the hemispheres and would be forced to turn to the poloidal and radial directions due to the insulated slit. Since the eddy currents converged on the top and bottom of the vessel, the current densities there tended to be much higher than those in the equatorial plane were. Moreover, the eddy currents on the top and bottom of vacuum vessel had the same direction when the current flowed in the PF coils. These features resulted in the leading phases of signals on the top and bottom flux loops when compared with the PF waveforms.

  16. Shot-Peening Intensities VS. Eddy Current Signals as Seen in Iterative Treatment-Measurement Experiment

    NASA Astrophysics Data System (ADS)

    Nakagawa, N.; Frishman, A. M.; Shen, Y.; Lo, C. C. H.

    2009-03-01

    We report on progress in a swept high frequency eddy current (SHFEC) technique for characterization of surface residual stress on shot-peened superalloy surfaces. Our aim here is to demonstrate the sensitivity of our measurement for practical shot peening intensities, i.e. at 4˜6 A. First, we present our improved probe and instrumentation being sufficiently sensitive to resolve the surface conditions at these low Almen intensities, where our earlier measurements encountered noise problems. The previous coil was also larger (18 mm in diameter) than desirable. Our new probe integrates smaller coils (12 mm in diameter, forming an AC bridge) and on-board electronics on a common printed circuit board, mutually connected at the shortest possible distance. The operational-amplifier-based electronics acts as impedance buffers, and maintains the cabling impedance at the characteristic 50 Ω between the probe board and the instruments. We have thus reduced the instrumentation noises. Second, we present the result of an iterative treatment-measurement experiment, performed on a 2"-by-3" Inconel 718 block specimen, initially polished to a mirror finish. After an initial baseline SHFEC measurement, we performed shot peening, an Almen strip deflection measurement, and a SHFEC measurement as one iteration cycle, and repeated the cycles multiple times at predetermined intervals. We will show the resulting SHFEC signals (i.e. lift-off normalized vertical-component signals) plotted against the Almen intensities. We then draw several conclusions from the experimental data, including a) the SHFEC signals increase monotonically in correlation with the Almen intensity increase, and b) the SHFEC signals exhibit sufficient deviations to resolve 4˜6 A intensities, while c) the SHFEC signals indicate saturation of the Inconel 718 response against peening, but the saturation occurs later in the iteration than indicated by the A-series Almen strip.

  17. Eddy current technique for predicting burst pressure

    DOEpatents

    Petri, Mark C.; Kupperman, David S.; Morman, James A.; Reifman, Jaques; Wei, Thomas Y. C.

    2003-01-01

    A signal processing technique which correlates eddy current inspection data from a tube having a critical tubing defect with a range of predicted burst pressures for the tube is provided. The method can directly correlate the raw eddy current inspection data representing the critical tubing defect with the range of burst pressures using a regression technique, preferably an artificial neural network. Alternatively, the technique deconvolves the raw eddy current inspection data into a set of undistorted signals, each of which represents a separate defect of the tube. The undistorted defect signal which represents the critical tubing defect is related to a range of burst pressures utilizing a regression technique.

  18. Study of eddy current probes

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Wang, Morgan

    1992-01-01

    The recognition of materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques.

  19. Eddy current enhancement for EMATs

    NASA Astrophysics Data System (ADS)

    Palmer, S. B.; Jian, X.; Dixon, S.

    2007-04-01

    When an electromagnetic acoustic transducer (EMAT) is used to generate ultrasound in an electrically conducting sample, eddy currents are generated in the sample's skin depth as the first stage in transduction. The resultant acoustic wave amplitude is proportional to the amplitude of this eddy current, and so anything that we can do to increase the eddy current will lead to the generation of larger amplitude ultrasonic waves. In eddy current testing, wire coils are often wound onto a ferrite core to increase the generated eddy current, with the effect that inductance of the coil increases greatly. When we are dealing with an EMAT, any increase in the coil inductance is usually unacceptable as it leads to a reduction in the amplitude of a given frequency of eddy current from a limited voltage source. This is particularly relevant where current arises from capacitor discharge, as is typically used in EMAT driver current circuitry. We present a method for electromagnetic acoustic transduction where ferrite is used to increase eddy current amplitude, without significantly increasing coil inductance or changing the frequency content of the eddy current or the generated acoustic wave.

  20. Automated eddy current analysis of materials

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.

    1991-01-01

    The use of eddy current techniques for characterizing flaws in graphite-based filament-wound cylindrical structures is described. A major emphasis was also placed upon incorporating artificial intelligence techniques into the signal analysis portion of the inspection process. Developing an eddy current scanning system using a commercial robot for inspecting graphite structures (and others) was a goal in the overall concept and is essential for the final implementation for the expert systems interpretation. Manual scans, as performed in the preliminary work here, do not provide sufficiently reproducible eddy current signatures to be easily built into a real time expert system. The expert systems approach to eddy current signal analysis requires that a suitable knowledge base exist in which correct decisions as to the nature of a flaw can be performed. A robotic workcell using eddy current transducers for the inspection of carbon filament materials with improved sensitivity was developed. Improved coupling efficiencies achieved with the E-probes and horseshoe probes are exceptional for graphite fibers. The eddy current supervisory system and expert system was partially developed on a MacIvory system. Continued utilization of finite element models for predetermining eddy current signals was shown to be useful in this work, both for understanding how electromagnetic fields interact with graphite fibers, and also for use in determining how to develop the knowledge base. Sufficient data was taken to indicate that the E-probe and the horseshoe probe can be useful eddy current transducers for inspecting graphite fiber components. The lacking component at this time is a large enough probe to have sensitivity in both the far and near field of a thick graphite epoxy component.

  1. Automated eddy current analysis of materials

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.

    1990-01-01

    This research effort focused on the use of eddy current techniques for characterizing flaws in graphite-based filament-wound cylindrical structures. A major emphasis was on incorporating artificial intelligence techniques into the signal analysis portion of the inspection process. Developing an eddy current scanning system using a commercial robot for inspecting graphite structures (and others) has been a goal in the overall concept and is essential for the final implementation for expert system interpretation. Manual scans, as performed in the preliminary work here, do not provide sufficiently reproducible eddy current signatures to be easily built into a real time expert system. The expert systems approach to eddy current signal analysis requires that a suitable knowledge base exist in which correct decisions as to the nature of the flaw can be performed. In eddy current or any other expert systems used to analyze signals in real time in a production environment, it is important to simplify computational procedures as much as possible. For that reason, we have chosen to use the measured resistance and reactance values for the preliminary aspects of this work. A simple computation, such as phase angle of the signal, is certainly within the real time processing capability of the computer system. In the work described here, there is a balance between physical measurements and finite element calculations of those measurements. The goal is to evolve into the most cost effective procedures for maintaining the correctness of the knowledge base.

  2. Eddy current thickness measurement apparatus

    DOEpatents

    Rosen, Gary J.; Sinclair, Frank; Soskov, Alexander; Buff, James S.

    2015-06-16

    A sheet of a material is disposed in a melt of the material. The sheet is formed using a cooling plate in one instance. An exciting coil and sensing coil are positioned downstream of the cooling plate. The exciting coil and sensing coil use eddy currents to determine a thickness of the solid sheet on top of the melt.

  3. Eddy current inspection tool. [Patent application

    DOEpatents

    Petrini, R.R.; Van Lue, D.F.

    1980-10-29

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, oil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of a fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator for generating audible signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

  4. Exploratory Development on Advanced Eddy Current Coil Excitation and Signal Processing.

    DTIC Science & Technology

    1985-04-01

    Input Voltage Waveform (Bottom Trace) and Output Current Waveform (1 Ampere per Division) of the Voltage-to- Current Amplifier . . . . . . . 44 27...volts maxism sad 5 amperes maximim with an average power dissipation of less than 2.5 watts. Although the technique of PSC examination has existed for...designed for this project at SwRI. The amplifier is a wideband (approximately 50-MHz) device capable of delivering at least 2.5 Amperes into a load impedance

  5. Expert system for analyzing eddy current measurements

    DOEpatents

    Levy, Arthur J.; Oppenlander, Jane E.; Brudnoy, David M.; Englund, James M.; Loomis, Kent C.

    1994-01-01

    A method and apparatus (called DODGER) analyzes eddy current data for heat exchanger tubes or any other metallic object. DODGER uses an expert system to analyze eddy current data by reasoning with uncertainty and pattern recognition. The expert system permits DODGER to analyze eddy current data intelligently, and obviate operator uncertainty by analyzing the data in a uniform and consistent manner.

  6. Expert system for analyzing eddy current measurements

    SciTech Connect

    Levy, A.J.; Oppenlander, J.E.; Brudnoy, D.M.; Englund, J.M.; Loomis, K.C.

    1994-08-16

    A method and apparatus (called DODGER) analyzes eddy current data for heat exchanger tubes or any other metallic object. DODGER uses an expert system to analyze eddy current data by reasoning with uncertainty and pattern recognition. The expert system permits DODGER to analyze eddy current data intelligently, and obviate operator uncertainty by analyzing the data in a uniform and consistent manner. 21 figs.

  7. Remote field eddy current inspection of support plate fretting wear

    SciTech Connect

    Shatat, A.; Atherton, D.L.

    1997-03-01

    This article demonstrates how the remote field eddy current technique might be extended to measure support plate fretting wear in heat exchanger tubes. A finite element analysis was used to examine the plate`s effect on the eddy current signal. Experimental data lend support to a suggested multifrequency method for sizing fretting grooves.

  8. Observed eddy dissipation in the Agulhas Current

    NASA Astrophysics Data System (ADS)

    Braby, Laura; Backeberg, Björn C.; Ansorge, Isabelle; Roberts, Michael J.; Krug, Marjolaine; Reason, Chris J. C.

    2016-08-01

    Analyzing eddy characteristics from a global data set of automatically tracked eddies for the Agulhas Current in combination with surface drifters as well as geostrophic currents from satellite altimeters, it is shown that eddies from the Mozambique Channel and south of Madagascar dissipate as they approach the Agulhas Current. By tracking the offshore position of the current core and its velocity at 30°S in relation to eddies, it is demonstrated that eddy dissipation occurs through a transfer of momentum, where anticyclones consistently induce positive velocity anomalies, and cyclones reduce the velocities and cause offshore meanders. Composite analyses of the anticyclonic (cyclonic) eddy-current interaction events demonstrate that the positive (negative) velocity anomalies propagate downstream in the Agulhas Current at 44 km/d (23 km/d). Many models are unable to represent these eddy dissipation processes, affecting our understanding of the Agulhas Current.

  9. Observed eddy dissipation in the Agulhas Current

    NASA Astrophysics Data System (ADS)

    Braby, Laura; Backeberg, Björn; Ansorge, Isabelle; Roberts, Michael; Krug, Marjolaine; Reason, Chris

    2017-04-01

    Analyzing eddy characteristics from a global data set of automatically tracked eddies for the Agulhas Current in combination with surface drifters as well as geostrophic currents from satellite altimeters, it is shown that eddies from the Mozambique Channel and south of Madagascar dissipate as they approach the Agulhas Current. By tracking the offshore position of the current core and its velocity at 30°S in relation to eddies, it is demonstrated that eddy dissipation occurs through a transfer of momentum, where anticyclones consistently induce positive velocity anomalies, and cyclones reduce the velocities and cause offshore meanders. Composite analyses of the anticyclonic (cyclonic) eddy-current interaction events demonstrate that the positive (negative) velocity anomalies propagate downstream in the Agulhas Current at 44 km/d (23 km/d). Many models are unable to represent these eddy dissipation processes, affecting our understanding of the Agulhas Current.

  10. Eddy current correction in volume-localized MR spectroscopy

    NASA Technical Reports Server (NTRS)

    Lin, C.; Wendt, R. E. 3rd; Evans, H. J.; Rowe, R. M.; Hedrick, T. D.; LeBlanc, A. D.

    1994-01-01

    The quality of volume-localized magnetic resonance spectroscopy is affected by eddy currents caused by gradient switching. Eddy currents can be reduced with improved gradient systems; however, it has been suggested that the distortion due to eddy currents can be compensated for during postprocessing with a single-frequency reference signal. The authors propose modifying current techniques for acquiring the single-frequency reference signal by using relaxation weighting to reduce interference from components that cannot be eliminated by digital filtering alone. Additional sequences with T1 or T2 weighting for reference signal acquisition are shown to have the same eddy current characteristics as the original signal without relaxation weighting. The authors also studied a new eddy current correction method that does not require a single-frequency reference signal. This method uses two free induction decays (FIDs) collected from the same volume with two sequences with opposite gradients. Phase errors caused by eddy currents are opposite in these two FIDs and can be canceled completely by combining the FIDs. These methods were tested in a phantom. Eddy current distortions were corrected, allowing quantitative measurement of structures such as the -CH = CH- component, which is otherwise undetectable.

  11. Foam-machining tool with eddy-current transducer

    NASA Technical Reports Server (NTRS)

    Copper, W. P.

    1975-01-01

    Three-cutter machining system for foam-covered tanks incorporates eddy-current sensor. Sensor feeds signal to numerical controller which programs rotational and vertical axes of sensor travel, enabling cutterhead to profile around tank protrusions.

  12. Loop Current Eddy formation and baroclinic instability

    NASA Astrophysics Data System (ADS)

    Donohue, K. A.; Watts, D. R.; Hamilton, P.; Leben, R.; Kennelly, M.

    2016-12-01

    The formation of three Loop Current Eddies, Ekman, Franklin, and Hadal, during the period April 2009 through November 2011 was observed by an array of moored current meters and bottom mounted pressure equipped inverted echo sounders. The array design, areal extent nominally 89° W to 85° W, 25° N to 27° N with 30-50 km mesoscale resolution, permits quantitative mapping of the regional circulation at all depths. During Loop Current Eddy detachment and formation events, a marked increase in deep eddy kinetic energy occurs coincident with the growth of a large-scale meander along the northern and eastern parts of the Loop Current. Deep eddies develop in a pattern where the deep fields were offset and leading upper meanders consistent with developing baroclinic instability. The interaction between the upper and deep fields is quantified by evaluating the mean eddy potential energy budget. Largest down-gradient heat fluxes are found along the eastern side of the Loop Current. Where strong, the horizontal down-gradient eddy heat flux (baroclinic conversion rate) nearly balances the vertical down-gradient eddy heat flux indicating that eddies extract available potential energy from the mean field and convert eddy potential energy to eddy kinetic energy.

  13. Conformable eddy current array delivery

    NASA Astrophysics Data System (ADS)

    Summan, Rahul; Pierce, Gareth; Macleod, Charles; Mineo, Carmelo; Riise, Jonathan; Morozov, Maxim; Dobie, Gordon; Bolton, Gary; Raude, Angélique; Dalpé, Colombe; Braumann, Johannes

    2016-02-01

    The external surface of stainless steel containers used for the interim storage of nuclear material may be subject to Atmospherically Induced Stress Corrosion Cracking (AISCC). The inspection of such containers poses a significant challenge due to the large quantities involved; therefore, automating the inspection process is of considerable interest. This paper reports upon a proof-of-concept project concerning the automated NDT of a set of test containers containing artificially generated AISCCs. An Eddy current array probe with a conformable padded surface from Eddyfi was used as the NDT sensor and end effector on a KUKA KR5 arc HW robot. A kinematically valid cylindrical raster scan path was designed using the KUKA|PRC path planning software. Custom software was then written to interface measurement acquisition from the Eddyfi hardware with the motion control of the robot. Preliminary results and analysis are presented from scanning two canisters.

  14. Rotating concave eddy current probe

    DOEpatents

    Roach, Dennis P.; Walkington, Phil; Rackow, Kirk A.; Hohman, Ed

    2008-04-01

    A rotating concave eddy current probe for detecting fatigue cracks hidden from view underneath the head of a raised head fastener, such as a buttonhead-type rivet, used to join together structural skins, such as aluminum aircraft skins. The probe has a recessed concave dimple in its bottom surface that closely conforms to the shape of the raised head. The concave dimple holds the probe in good alignment on top of the rivet while the probe is rotated around the rivet's centerline. One or more magnetic coils are rigidly embedded within the probe's cylindrical body, which is made of a non-conducting material. This design overcomes the inspection impediment associated with widely varying conductivity in fastened joints.

  15. Eddy current measurement of tube element spacing

    DOEpatents

    Latham, Wayne Meredith; Hancock, Jimmy Wade; Grut, Jayne Marie

    1998-01-01

    A method of electromagnetically measuring the distance between adjacent tube elements in a heat exchanger. A cylindrical, high magnetic permeability ferrite slug is placed in the tube adjacent the spacing to be measured. A bobbin or annular coil type probe operated in the absolute mode is inserted into a second tube adjacent the spacing to be measured. From prior calibrations on the response of the eddy current coil, the signals from the coil, when sensing the presence of the ferrite slug, are used to determine the spacing between the tubes.

  16. Eddy current analysis in fusion devices

    SciTech Connect

    Turner, L.R.

    1988-06-01

    In magnetic fusion devices, particularly tokamaks and reversed field pinch (RFP) experiments, time-varying magnetic fields are in intimate contact with electrically conducting components of the device. Induced currents, fields, forces, and torques result. This note reviews the analysis of eddy current effects in the following systems: Interaction of a tokamak plasma with the eddy currents in the first wall, blanket, and shield (FWBS) systems; Eddy currents in a complex but two-dimensional vacuum vessel, as in TFTR, JET, and JT-60; Eddy currents in the FWBS system of a tokamak reactor, such as NET, FER, or ITER; and Eddy currents in a RFP shell. The cited studies are chosen to be illustrative, rather than exhaustive. 42 refs.

  17. Birth of a Loop Current Eddy

    NASA Image and Video Library

    2010-05-24

    The northern portion of the Gulf of Mexico Loop Current, shown in red, appears about to detach a large ring of current, creating a separate eddy. An eddy is a large, warm, clockwise-spinning vortex of water -- the ocean version of a cyclone.

  18. Unified Ultrasonic/Eddy-Current Data Acquisition

    NASA Technical Reports Server (NTRS)

    Chern, E. James; Butler, David W.

    1993-01-01

    Imaging station for detecting cracks and flaws in solid materials developed combining both ultrasonic C-scan and eddy-current imaging. Incorporation of both techniques into one system eliminates duplication of computers and of mechanical scanners; unifies acquisition, processing, and storage of data; reduces setup time for repetitious ultrasonic and eddy-current scans; and increases efficiency of system. Same mechanical scanner used to maneuver either ultrasonic or eddy-current probe over specimen and acquire point-by-point data. For ultrasonic scanning, probe linked to ultrasonic pulser/receiver circuit card, while, for eddy-current imaging, probe linked to impedance-analyzer circuit card. Both ultrasonic and eddy-current imaging subsystems share same desktop-computer controller, containing dedicated plug-in circuit boards for each.

  19. Eddy-Current Inspection Of Tab Seals On Beverage Cans

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    1994-01-01

    Eddy-current inspection system monitors tab seals on beverage cans. Device inspects all cans at usual production rate of 1,500 to 2,000 cans per minute. Automated inspection of all units replaces visual inspection by microscope aided by mass spectrometry. System detects defects in real time. Sealed cans on conveyor pass near one of two coils in differential eddy-current probe. Other coil in differential eddy-current probe positioned near stationary reference can on which tab seal is known to be of acceptable quality. Signal of certain magnitude at output of probe indicates defective can, automatically ejected from conveyor.

  20. Eddy-Current Inspection Of Tab Seals On Beverage Cans

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    1994-01-01

    Eddy-current inspection system monitors tab seals on beverage cans. Device inspects all cans at usual production rate of 1,500 to 2,000 cans per minute. Automated inspection of all units replaces visual inspection by microscope aided by mass spectrometry. System detects defects in real time. Sealed cans on conveyor pass near one of two coils in differential eddy-current probe. Other coil in differential eddy-current probe positioned near stationary reference can on which tab seal is known to be of acceptable quality. Signal of certain magnitude at output of probe indicates defective can, automatically ejected from conveyor.

  1. Eddy current inspection of graphite fiber components

    NASA Technical Reports Server (NTRS)

    Workman, G. L.; Bryson, C. C.

    1990-01-01

    The recognition of defects in materials properties still presents a number of problems for nondestructive testing in aerospace systems. This project attempts to utilize current capabilities in eddy current instrumentation, artificial intelligence, and robotics in order to provide insight into defining geometrical aspects of flaws in composite materials which are capable of being evaluated using eddy current inspection techniques. The unique capabilities of E-probes and horseshoe probes for inspecting probes for inspecting graphite fiber materials were evaluated and appear to hold great promise once the technology development matures. The initial results are described of modeling eddy current interactions with certain flaws in graphite fiber samples.

  2. Pulsed eddy current testing. [nondestructive tests of the external tank

    NASA Technical Reports Server (NTRS)

    Workman, G. L.

    1980-01-01

    Since a large number of the procedures used for inspecting the external tank are concerned with determining flaws in welds, there is a need to develop an inspection technique, which can be automated, to determine flaws in welds and structures with complex geometries. Techniques whereby an eddy current is generated in a metallic material and the changes in the circuit parameters due to material differences are observed, were chosen as one possible approach. Pulsed eddy current and its relationship to multifrequency techniques is discussed as well as some preliminary results obtained from observing pulsed waveforms with apparatus and algorithms currently in use for ultrasonic testing of welds. It can be shown the pulsed eddy current techniques can provide similar results, can eliminate some of the noncritical parameters affecting the eddy current signals, and can facilitate in the detection of critical parameter such as flaws, subsurface voids, and corrosion.

  3. Crack detection in eddy current images of jet engine disks

    NASA Astrophysics Data System (ADS)

    Eua-anant, N.; Cai, X.; Udpa, L.; Chao, J.; Elshafiey, I.

    2000-05-01

    In eddy current inspection of jet engine disk slots, there are several factors contributing to the degradation of eddy current signals. First, cracks often occur in high stress regions near slot edges where contribution of edge signals overwhelms crack signals. Furthermore, the rounded chamfer edges are hand finished and the curvature of the edges varies from slot to slot. In terms of ECI, this translates into different liftoff signals from slot to slot, for any given disk. Some disk slot surfaces are also shot peened which creates a dimple-like surface finish. Depending on the size and depth of dimples relative to the probes used, significant surface noise can be observed in the eddy current signal. In addition, mechanical jittering of the scanner, probe misalignment and fundamental difference in probe variance result in unwanted lift-off and instrument noise. Therefore, detection of cracks in jet engine disk slots requires a fairly robust algorithm. This paper presents a novel approach for crack detection and noise reduction in eddy current engine disk inspection signals. The eddy current signal can be viewed as a curve in 3-dimensional space: real-imaginary-spatial. Noise reduction is done by adjusting coordinates of the points along the curve in the direction that reduces local curvature. As a result, high frequency noise is drastically removed. After noise removal, the filtered eddy current signal is projected onto the impedance plane where embedded crack signals exhibit themselves as small loop features. A simple loop detection algorithm is employed to detect such crack features. The areas of detected loops are used as criteria for crack classification. Experimental results on real data is presented.—This material is based upon work supported by the Federal Aviation Administration under Contract #DTFA03-98-D-00008, Delivery Order #IA015 and performed at lowa State University's Center for NDE as part of the Center for Aviation Systems Reliability program.

  4. Process Specification for Eddy Current Inspection

    NASA Technical Reports Server (NTRS)

    Koshti, Ajay

    2011-01-01

    This process specification establishes the minimum requirements for eddy current inspection of flat surfaces, fastener holes, threaded fasteners and seamless and welded tubular products made from nonmagnetic alloys such as aluminum and stainless steel.

  5. Wind changes above warm Agulhas Current eddies

    NASA Astrophysics Data System (ADS)

    Rouault, M.; Verley, P.; Backeberg, B.

    2016-04-01

    Sea surface temperature (SST) estimated from the Advanced Microwave Scanning Radiometer E onboard the Aqua satellite and altimetry-derived sea level anomalies are used south of the Agulhas Current to identify warm-core mesoscale eddies presenting a distinct SST perturbation greater than to 1 °C to the surrounding ocean. The analysis of twice daily instantaneous charts of equivalent stability-neutral wind speed estimates from the SeaWinds scatterometer onboard the QuikScat satellite collocated with SST for six identified eddies shows stronger wind speed above the warm eddies than the surrounding water in all wind directions, if averaged over the lifespan of the eddies, as was found in previous studies. However, only half of the cases showed higher wind speeds above the eddies at the instantaneous scale; 20 % of cases had incomplete data due to partial global coverage by the scatterometer for one path. For cases where the wind is stronger above warm eddies, there is no relationship between the increase in surface wind speed and the SST perturbation, but we do find a linear relationship between the decrease in wind speed from the centre to the border of the eddy downstream and the SST perturbation. SST perturbations range from 1 to 6 °C for a mean eddy SST of 15.9 °C and mean SST perturbation of 2.65 °C. The diameter of the eddies range from 100 to 250 km. Mean background wind speed is about 12 m s-1 (mostly southwesterly to northwesterly) and ranging mainly from 4 to 16 m s-1. The mean wind increase is about 15 %, which corresponds to 1.8 m s-1. A wind speed increase of 4 to 7 m s-1 above warm eddies is not uncommon. Cases where the wind did not increase above the eddies or did not decrease downstream had higher wind speeds and occurred during a cold front associated with intense cyclonic low-pressure systems, suggesting certain synoptic conditions need to be met to allow for the development of wind speed anomalies over warm-core ocean eddies. In many cases

  6. A western boundary current eddy characterisation study

    NASA Astrophysics Data System (ADS)

    Ribbe, Joachim; Brieva, Daniel

    2016-12-01

    The analysis of an eddy census for the East Australian Current (EAC) region yielded a total of 497 individual short-lived (7-28 days) cyclonic and anticyclonic eddies for the period 1993 to 2015. This was an average of about 23 eddies per year. 41% of the tracked individual cyclonic and anticyclonic eddies were detected off southeast Queensland between about 25 °S and 29 °S. This is the region where the flow of the EAC intensifies forming a swift western boundary current that impinges near Fraser Island on the continental shelf. This zone was also identified as having a maximum in detected short-lived cyclonic eddies. A total of 94 (43%) individual cyclonic eddies or about 4-5 per year were tracked in this region. The census found that these potentially displaced entrained water by about 115 km with an average displacement speed of about 4 km per day. Cyclonic eddies were likely to contribute to establishing an on-shelf longshore northerly flow forming the western branch of the Fraser Island Gyre and possibly presented an important cross-shelf transport process in the life cycle of temperate fish species of the EAC domain. In-situ observations near western boundary currents previously documented the entrainment, off-shelf transport and export of near shore water, nutrients, sediments, fish larvae and the renewal of inner shelf water due to short-lived eddies. This study found that these cyclonic eddies potentially play an important off-shelf transport process off the central east Australian coast.

  7. Flux focusing eddy current probe

    NASA Technical Reports Server (NTRS)

    Simpson, John W. (Inventor); Clendenin, C. Gerald (Inventor); Fulton, James P. (Inventor); Wincheski, Russell A. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor); Nath, Shridhar C. (Inventor)

    1997-01-01

    A flux-focusing electromagnetic sensor which uses a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. The unique feature of the device is the ferrous shield isolating a high-turn pick-up coil from an excitation coil. The use of the magnetic shield is shown to produce a null voltage output across the receiving coil in the presence of an unflawed sample. A redistribution of the current flow in the sample caused by the presence of flaws, however, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. The maximum sensor output is obtained when positioned symmetrically above the crack. Hence, by obtaining the position of the maximum sensor output, it is possible to track the fault and locate the area surrounding its tip. The accuracy of tip location is enhanced by two unique features of the sensor; a very high signal-to-noise ratio of the probe's output which results in an extremely smooth signal peak across the fault, and a rapidly decaying sensor output outside a small area surrounding the crack tip which enables the region for searching to be clearly defined. Under low frequency operation, material thinning due to corrosion damage causes an incomplete shielding of the pick-up coil. The low frequency output voltage of the probe is therefore a direct indicator of the thickness of the test sample.

  8. Eddy current flowmeter for sodium flow

    NASA Astrophysics Data System (ADS)

    Pavlinov, A.; Khalilov, R.; Mamikyn, A.; Kolesnichenko, I.

    2017-06-01

    The eddy current flowmeter for liquid metal passing through the cylindrical channel is studied experimentally and numerically. The alternating magnetic field is created by an annular-shape coil and resulting field is measured by two symmetric coils. The dependence of the signal on the magnetic field frequency was obtained for a solid duralumin cylinder. The phase shift and amplitude ratio linearly depends on the flowrate in a wide range of parameters. The workability of the method was tested on a liquid sodium, flowing along a cylindrical channel. The dependencies for liquid sodium and solid duralumin cylinder differ due to the existence of a non-uniform velocity profile along the radius of the fluid. This necessitates an additional calibration procedure on the liquid metal in addition to research on the solid conductor. The developed flowmeter is used to measure the flowrate in the sodium loop.

  9. Eddy Current Testing, RQA/M1-5330.17.

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

    As one in the series of classroom training handbooks, prepared by the U.S. space program, instructional material is presented in this volume concerning familiarization and orientation on eddy current testing. The subject is presented under the following headings: Introduction, Eddy Current Principles, Eddy Current Equipment, Eddy Current Methods,…

  10. Eddy Current Rail Inspection Using AC Bridge Techniques

    PubMed Central

    Liu, Ze; Koffman, Andrew D; Waltrip, Bryan C; Wang, Yicheng

    2013-01-01

    AC bridge techniques commonly used for precision impedance measurements have been adapted to develop an eddy current sensor for rail defect detection. By using two detection coils instead of just one as in a conventional sensor, we can balance out the large baseline signals corresponding to a normal rail. We have significantly enhanced the detection sensitivity of the eddy current method by detecting and demodulating the differential signal of the two coils induced by rail defects, using a digital lock-in amplifier algorithm. We have also explored compensating for the lift-off effect of the eddy current sensor due to vibrations by using the summing signal of the detection coils to measure the lift-off distance. The dominant component of the summing signal is a constant resulting from direct coupling from the excitation coil, which can be experimentally determined. The remainder of the summing signal, which decreases as the lift-off distance increases, is induced by the secondary eddy current. This dependence on the lift-off distance is used to calibrate the differential signal, allowing for a more accurate characterization of the defects. Simulated experiments on a sample rail have been performed using a computer controlled X-Y moving table with the X-axis mimicking the train’s motion and the Y-axis mimicking the train’s vibrational bumping. Experimental results demonstrate the effectiveness of the new detection method. PMID:26401427

  11. Casimir Interaction from Magnetically Coupled Eddy Currents

    SciTech Connect

    Intravaia, Francesco; Henkel, Carsten

    2009-09-25

    We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.

  12. Development of magnetic eddy current testing techniques

    NASA Astrophysics Data System (ADS)

    Tada, Toyokazu; Suetsugu, Hidehiko

    2017-02-01

    IRIS (Internal Rotary Inspection System) has become a major maintenance inspection technique for the heat exchanger and reactor tubes. It is known that IRIS has a high precision of evaluation thickness, however there are a few disadvantages, such as slow inspection speed. Therefore, we have developed a magnetic eddy current flaw testing technique which combines a magnetic array forming a strong magnetic field, 4 coil structures for controlling the generation area of the eddy currents, and a desorption yoke structure to control the magnetizing force. In this presentation, details of this technique and practical application will be elaborated.

  13. Probability of detection models for eddy current NDE methods

    SciTech Connect

    Rajesh, S. N.

    1993-04-30

    The development of probability of detection (POD) models for a variety of nondestructive evaluation (NDE) methods is motivated by a desire to quantify the variability introduced during the process of testing. Sources of variability involved in eddy current methods of NDE include those caused by variations in liftoff, material properties, probe canting angle, scan format, surface roughness and measurement noise. This thesis presents a comprehensive POD model for eddy current NDE. Eddy current methods of nondestructive testing are used widely in industry to inspect a variety of nonferromagnetic and ferromagnetic materials. The development of a comprehensive POD model is therefore of significant importance. The model incorporates several sources of variability characterized by a multivariate Gaussian distribution and employs finite element analysis to predict the signal distribution. The method of mixtures is then used for estimating optimal threshold values. The research demonstrates the use of a finite element model within a probabilistic framework to the spread in the measured signal for eddy current nondestructive methods. Using the signal distributions for various flaw sizes the POD curves for varying defect parameters have been computed. In contrast to experimental POD models, the cost of generating such curves is very low and complex defect shapes can be handled very easily. The results are also operator independent.

  14. Eddy Current Modeling of Coils in Boreholes

    NASA Astrophysics Data System (ADS)

    Theodoulidis, Theodoros P.; Bowler, John R.

    2007-03-01

    In both aircraft bolt-hole and steam generator tube inspections, eddy current probes are utilized to scan the inner surface of the cylindrical structure for defects. A combination of integral methods and analytical approaches provide an effective means of simulating such inspections thereby quantifying their performance and providing a means of characterizing flaws. For integral methods to be successful, a knowledge of the relevant integral kernel is required but there is also a need for fast computations of the electromagnetic field. In this paper we show that by truncating the solution domain, traditional incident field calculations can be accelerated and extended to new configurations. Both the field and probe signal are expressed in the form of a double series instead of an integral and a series. The double series form provides an efficient means of evaluating the field in a finite hole or tube using analytical expressions. As an example, double-series impedance calculations for a coil whose axis is offset and parallel to that of the hole are shown to give good agreement with experiment.

  15. INNOVATIVE EDDY CURRENT PROBE FOR MICRO DEFECTS

    SciTech Connect

    Santos, Telmo G.; Vilaca, Pedro; Quintino, Luisa; Santos, Jorge dos; Rosado, Luis

    2010-02-22

    This paper reports the development of an innovative eddy current (EC) probe, and its application to micro-defects on the root of the Friction Stir Welding (FSW). The new EC probe presents innovative concept issues, allowing 3D induced current in the material, and a lift-off independence. Validation experiments were performed on aluminium alloys processed by FSW. The results clearly show that the new EC probe is able to detect and sizing surface defects about 60 microns depth.

  16. Variable current speed controller for eddy current motors

    DOEpatents

    Gerth, H.L.; Bailey, J.M.; Casstevens, J.M.; Dixon, J.H.; Griffith, B.O.; Igou, R.E.

    1982-03-12

    A speed control system for eddy current motors is provided in which the current to the motor from a constant frequency power source is varied by comparing the actual motor speed signal with a setpoint speed signal to control the motor speed according to the selected setpoint speed. A three-phase variable voltage autotransformer is provided for controlling the voltage from a three-phase power supply. A corresponding plurality of current control resistors is provided in series with each phase of the autotransformer output connected to inputs of a three-phase motor. Each resistor is connected in parallel with a set of normally closed contacts of plurality of relays which are operated by control logic. A logic circuit compares the selected speed with the actual motor speed obtained from a digital tachometer monitoring the motor spindle speed and operated the relays to add or substract resistance equally in each phase of the motor input to vary the motor current to control the motor at the selected speed.

  17. Contoured Surface Eddy Current Inspection System

    DOEpatents

    Batzinger, Thomas James; Fulton, James Paul; Rose, Curtis Wayne; Perocchi, Lee Cranford

    2003-04-08

    Eddy current inspection of a contoured surface of a workpiece is performed by forming a backing piece of flexible, resiliently yieldable material with a contoured exterior surface conforming in shape to the workpiece contoured surface. The backing piece is preferably cast in place so as to conform to the workpiece contoured surface. A flexible eddy current array probe is attached to the contoured exterior surface of the backing piece such that the probe faces the contoured surface of the workpiece to be inspected when the backing piece is disposed adjacent to the workpiece. The backing piece is then expanded volumetrically by inserting at least one shim into a slot in the backing piece to provide sufficient contact pressure between the probe and the workpiece contoured surface to enable the inspection of the workpiece contoured surface to be performed.

  18. Extremely short impulse eddy current system for titanium and inconel samples testing

    SciTech Connect

    Chady, T.; Frankowski, P.

    2011-06-23

    This paper presents a new system for eddy current testing. The system enables tests with very short current impulses. Therefore, the frequency spectrum of the excitation signal is very wide. In this paper, a study of eddy current differential transducer for testing titanium element is also presented.

  19. Eddy current X-Y scanner system

    NASA Technical Reports Server (NTRS)

    Kurtz, G. W.

    1983-01-01

    The Nondestructive Evaluation Branch of the Materials and Processes Laboratory became aware of a need for a miniature, portable X-Y scanner capable of performing eddy current or other nondestructive testing scanning operations such as ultrasonic, or small areas of flat plate. The technical description and operational theory of the X-Y scanner system designed and built to fulfill this need are covered. The scanner was given limited testing and performs according to its design intent, which is to scan flat plate areas of approximately 412 sq cm (64 sq in) during each complete cycle of scanning.

  20. Variable-Force Eddy-Current Damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1986-01-01

    Variable damping achieved without problems of containing viscous fluids. Eddy-current damping obtained by moving copper or aluminum conductors through magnetic fields. Position of magnet carrier determines amount of field engagement and, therefore, amount of damping. Three advantages of concept: Magnitudes of stiffness and damping continously varied from maximum to zero without bringing rotor or shaft to stop; used in rotating machines not having viscous fluids available such as lubricating oils; produces sizable damping forces in machines that pump liquid hydrogen at - 246 degrees C and liquid oxygen at - 183 degrees C and are compact in size.

  1. Eddy Current Assessment of Duplex Metallic Coatings

    NASA Astrophysics Data System (ADS)

    Krzywosz, K. J.

    2004-02-01

    EPRI is involved in a multi-year program with the Department of Energy to test, evaluate, and develop a field-deployable eddy current NDE system for life assessment of blade coatings for advanced gas turbines. The coatings evaluated from these advanced GE engines include CoCrAlY (GT 29) and NiCoCrAlY (GT 33) bond coats followed by top aluminide overlay coatings. These duplex metallic coatings commonly referred to as GT 29+ and GT 33+ coatings, respectively. In general, during cycling and continuous operation at higher operating temperature, coatings fail due to spallation of protective oxide layers, leading to consumption of protective coating by oxidation and to eventual failure of blades. To extend service life of these critical rotating components, an inspection-based condition assessment program has been initiated to help establish more optimum inspection intervals that are not dependent on time-in-service maintenance approach. This paper summarizes the latest results obtained to date using the state-of-the-art frequency-scanning eddy current tester with a built-in three-layer inversion analysis algorithm. Significant progress has been made in assessing and discriminating the duplex metallic coatings as normal, degraded, and/or cracked. In addition, quantitative assessment was conducted by estimating various coating and substrate conductivity values.

  2. Magnetoresistive Flux Focusing Eddy Current Flaw Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil s longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multi-layer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  3. Magnetoresistive flux focusing eddy current flaw detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Namkung, Min (Inventor); Simpson, John W. (Inventor)

    2005-01-01

    A giant magnetoresistive flux focusing eddy current device effectively detects deep flaws in thick multilayer conductive materials. The probe uses an excitation coil to induce eddy currents in conducting material perpendicularly oriented to the coil's longitudinal axis. A giant magnetoresistive (GMR) sensor, surrounded by the excitation coil, is used to detect generated fields. Between the excitation coil and GMR sensor is a highly permeable flux focusing lens which magnetically separates the GMR sensor and excitation coil and produces high flux density at the outer edge of the GMR sensor. The use of feedback inside the flux focusing lens enables complete cancellation of the leakage fields at the GMR sensor location and biasing of the GMR sensor to a location of high magnetic field sensitivity. In an alternate embodiment, a permanent magnet is positioned adjacent to the GMR sensor to accomplish the biasing. Experimental results have demonstrated identification of flaws up to 1 cm deep in aluminum alloy structures. To detect deep flaws about circular fasteners or inhomogeneities in thick multilayer conductive materials, the device is mounted in a hand-held rotating probe assembly that is connected to a computer for system control, data acquisition, processing and storage.

  4. a Macroscopic Analysis of Eddy Currents in Nonferrous Metals

    NASA Astrophysics Data System (ADS)

    Holder, Morris Eugene

    1992-01-01

    The original purpose of this research was to determine if the signals produced by the eddy currents induced into nonferrous metals as they pass through a static magnetic field could be used to distinguish between these metals. First, it was shown that for samples of the same size and shape, the maximum negative response produced by a Hall-effect sensor varied directly with the conductivity of the sample material. This was true for all shapes tested including rectangles, disks, rings, and cylinders. Samples of aluminum, brass, copper, lead, and zinc were easily distinguished from each other using the maximum negative response measured. The largest dimension of any sample tested was 4 inches, but algorithms could be developed for larger samples according to the statistics. The correlation coefficients for all sets of data collected in a randomized factorial design experiment were greater than 0.96. An algorithm was developed which correctly predicted the form of the response of the sensing apparatus to the passing of a thin copper ring through the static magnetic field. This involved writing an expression for the magnetic field produced by the eddy currents in the ring as the ring dropped from above, through, and beyond the static magnetic field. The inductive character of the nonferrous metals was incorporated into the model by introducing convolution. The currents produced by the induced emf were convolved with the residual decaying eddy currents to produce the net current. The model was responsive to the time constant associated with the conductivity, size, and shape of the samples. With convolution included, the simulated response produced by the model developed herein agreed well with the actual response measured. A new expression for the distribution of eddy currents in a nonferrous ring as it passes through a static magnetic field was developed to support the experimental findings. The new current distribution expression has the form of a fourth

  5. Anatomy of three warm-core Leeuwin Current eddies

    NASA Astrophysics Data System (ADS)

    Morrow, Rosemary; Fang, Fangxin; Fieux, Michele; Molcard, Robert

    2003-07-01

    The vertical structures of three warm-core Leeuwin Current eddies are described, as well as their temporal evolution determined from altimetric data. These warm-core eddies have large positive sea-level anomalies, although their surface temperature fields are not necessarily warmer than the ambient waters. These eddies were observed some 350 km offshore from the Leeuwin Current in September 2000, around 25-30°S, and their vertical structure and temporal evolution show they were formed at the coast in May, when the Leeuwin Current is strongest. After separation from the current, the warm-core eddies drifted WNW following isopycnal contours, and were strongly steered by bathymetry. These eddies penetrated to at least 1500 m depth; the strongest eddy, Eddy B, influenced isopycnals to 2500 m. Eddy B appeared to be trapped and intensified by a Leeuwin Current squirt that directed warm, low-salinity water offshore from August to October. The average annual eddy heat and salt fluxes for waters warmer than 8°C are estimated at 0.004 PW and 3×10 5 kg s -1, respectively. The magnitude of these eddy fluxes is 20-30% of the annual mean poleward heat and salt flux in the eastern Indian Ocean, and is within the range of values observed for Agulhas eddies entering the South Atlantic.

  6. Determining Confounding Sensitivities In Eddy Current Thin Film Measurements

    SciTech Connect

    Gros, Ethan; Udpa, Lalita; Smith, James A.; Wachs, Katelyn

    2016-07-01

    Determining Confounding Sensitivities In Eddy Current Thin Film Measurements Ethan Gros, Lalita Udpa, Electrical Engineering, Michigan State University, East Lansing MI 48824 James A. Smith, Experiment Analysis, Idaho National Laboratory, Idaho Falls ID 83415 Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs in the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It is the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy current testing is performed using a commercially available, hand held eddy current probe (ETA3.3H spring loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe is sent to a hand held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H spring loaded

  7. Eddy current scanning of niobium for SRF cavities at Fermilab

    SciTech Connect

    Boffo, C.; Bauer, P.; Foley, M.; Antoine, C.; Cooper, C.; Brinkmann, A.; /DESY

    2006-08-01

    In the framework of SRF cavity development, Fermilab is creating the infrastructure needed for the characterization of the material used in the cavity fabrication. An important step in the characterization of ''as received'' niobium sheets is eddy current scanning. Eddy current scanning is a non-destructive technique first adopted and further developed by DESY with the purpose of checking the cavity material for subsurface defects and inclusions. Fermilab has received and further upgraded a commercial eddy current scanner previously used for the SNS project. This scanner is now used daily to scan the niobium sheets for the Fermilab third harmonic, the ILC, and the Proton Driver cavities. After optical inspection, more than 400 squares and disks have been scanned and when necessary checked at the optical and electron microscopes, anodized, or measured with profilometers looking for surface imperfections that might limit the performance of the cavities. This paper gives a status report on the scanning results obtained so far, including a discussion of the classification of signals being detected.

  8. Eddy Current System for Material Inspection and Flaw Visualization

    NASA Technical Reports Server (NTRS)

    Bachnak, R.; King, S.; Maeger, W.; Nguyen, T.

    2007-01-01

    Eddy current methods have been successfully used in a variety of non-destructive evaluation applications including detection of cracks, measurements of material thickness, determining metal thinning due to corrosion, measurements of coating thickness, determining electrical conductivity, identification of materials, and detection of corrosion in heat exchanger tubes. This paper describes the development of an eddy current prototype that combines positional and eddy-current data to produce a C-scan of tested material. The preliminary system consists of an eddy current probe, a position tracking mechanism, and basic data visualization capability. Initial test results of the prototype are presented in this paper.

  9. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2007-10-30

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  10. Eddy-current-damped microelectromechanical switch

    DOEpatents

    Christenson, Todd R.; Polosky, Marc A.

    2009-12-15

    A microelectromechanical (MEM) device is disclosed that includes a shuttle suspended for movement above a substrate. A plurality of permanent magnets in the shuttle of the MEM device interact with a metal plate which forms the substrate or a metal portion thereof to provide an eddy-current damping of the shuttle, thereby making the shuttle responsive to changes in acceleration or velocity of the MEM device. Alternately, the permanent magnets can be located in the substrate, and the metal portion can form the shuttle. An electrical switch closure in the MEM device can occur in response to a predetermined acceleration-time event. The MEM device, which can be fabricated either by micromachining or LIGA, can be used for sensing an acceleration or deceleration event (e.g. in automotive applications such as airbag deployment or seat belt retraction).

  11. Material condition assessment with eddy current sensors

    NASA Technical Reports Server (NTRS)

    Goldfine, Neil J. (Inventor); Washabaugh, Andrew P. (Inventor); Sheiretov, Yanko K. (Inventor); Schlicker, Darrell E. (Inventor); Lyons, Robert J. (Inventor); Windoloski, Mark D. (Inventor); Craven, Christopher A. (Inventor); Tsukernik, Vladimir B. (Inventor); Grundy, David C. (Inventor)

    2010-01-01

    Eddy current sensors and sensor arrays are used for process quality and material condition assessment of conducting materials. In an embodiment, changes in spatially registered high resolution images taken before and after cold work processing reflect the quality of the process, such as intensity and coverage. These images also permit the suppression or removal of local outlier variations. Anisotropy in a material property, such as magnetic permeability or electrical conductivity, can be intentionally introduced and used to assess material condition resulting from an operation, such as a cold work or heat treatment. The anisotropy is determined by sensors that provide directional property measurements. The sensor directionality arises from constructs that use a linear conducting drive segment to impose the magnetic field in a test material. Maintaining the orientation of this drive segment, and associated sense elements, relative to a material edge provides enhanced sensitivity for crack detection at edges.

  12. Eddy current losses in ferromagnetic laminations

    SciTech Connect

    Serpico, C.; Visone, C.; Mayergoyz, I. D.; Basso, V.; Miano, G.

    2000-05-01

    It is demonstrated through the comparison of analytical, numerical, and experimental results that the existence of excess eddy current losses can be explained by the peculiar nature of the nonlinear diffusion of electromagnetic fields in magnetically nonlinear laminations. The essence of this peculiar nature is that nonlinear diffusion occurs as inward progress of almost rectangular profiles of magnetic flux density of variable height. Approximating actual profiles of magnetic flux density by rectangular ones, the problem of nonlinear diffusion can be treated analytically by using a simple model. The accuracy and the limit of applicability of the rectangular profile model are discussed by comparing its predictions with finite elements numerical solutions of nonlinear diffusion equation as well as with experimental results. (c) 2000 American Institute of Physics.

  13. Potential and limitations of eddy current lockin-thermography

    NASA Astrophysics Data System (ADS)

    Riegert, G.; Gleiter, A.; Busse, G.

    2006-04-01

    Eddy current thermography uses an induction coil to induce eddy currents in conductive materials. The involved resistive losses heat the sample. By modulation of the eddy current amplitude, thermal waves are generated which interact with boundaries thereby revealing defects. Conventional eddy current testing has only a limited depth range due to the skin effect of metal samples. In Induction-Lockin-Thermography (ILT) the depth range is extended by the thermal penetration depth. An infrared camera monitors the modulation of the temperature field on the surface as a response to the coded excitation thereby allowing for fast imaging of defects in larger areas without the need of slow point-by-point mapping. This response is decoded by a Fourier analysis at the modulation frequency. So the extracted information is displayed by just two images where one displays local amplitude and the other local phase. ILT has significant advantages as compared to inductive heating with visual inspection of the thermographic sequence: Phase angle images are independent of most artifacts like reflections, variation in emission coefficient, or inhomogeneous heating. Due to the performed Fourier analysis of the temperature image sequence, the signal-to-noise ratio in the amplitude and phase images is significantly better than in single temperature images of the sequence. Induction heating is confined to conductive materials. However, it is applicable not only to metals but also to carbon fiber reinforced laminates (CFRP) or carbon fiber reinforced ceramics (C/C-SiC). The presented examples for applications of ILT illustrate the potential and limitations of this new non-destructive inspection method.

  14. Single-tone and Polyharmonic Eddy Current Metal Detection and Non-Destructive Testing Education Software

    NASA Astrophysics Data System (ADS)

    Svatoš, J.

    2016-11-01

    This paper describes the design of a measuring chain for polyharmonic metal detectors used for education in laboratory exercises at Czech Technical University in Prague, Faculty of Electrical Engineering, Department of Measurement. The Measuring chain is composed of DDS signal generator, Digitiser and PC with software programmed in Labview. Eddy current principles or more specifically eddy current metal detectors are an important part of nondestructive testing, instrumentations and measurement. A short introduction to the background and principles of eddy current metal detectors are presented. Next part of the article deals with a brief description of the most common methods, as well as, non-traditional polyharmonic methods for eddy current metal detection. The following part contains an implementation of the proposed algorithms in LabVIEW graphical programming language. Finally, the created program for education of eddy current metal detectors and results obtained on the metal detector ATMID are discussed.

  15. Eddy Currents: Levitation, Metal Detectors, and Induction Heating

    ERIC Educational Resources Information Center

    Wouch, G.; Lord, A. E., Jr.

    1978-01-01

    A simple and accessible calculation is given of the effects of eddy currents for a sphere in the field of a single circular loop of alternating current. These calculations should help toward the inclusion of eddy current effects in upper undergraduate physics courses. (BB)

  16. Eddy Currents: Levitation, Metal Detectors, and Induction Heating

    ERIC Educational Resources Information Center

    Wouch, G.; Lord, A. E., Jr.

    1978-01-01

    A simple and accessible calculation is given of the effects of eddy currents for a sphere in the field of a single circular loop of alternating current. These calculations should help toward the inclusion of eddy current effects in upper undergraduate physics courses. (BB)

  17. Do East Australian Current anticyclonic eddies leave the Tasman Sea?

    NASA Astrophysics Data System (ADS)

    Pilo, Gabriela S.; Oke, Peter R.; Rykova, Tatiana; Coleman, Richard; Ridgway, Ken

    2015-12-01

    Using satellite altimetry and high-resolution model output we analyze the pathway of large, long-lived anticyclonic eddies that originate near the East Australian Current (EAC) separation point. We show that 25-30% of these eddies propagate southward, around Tasmania, leave the Tasman Sea, and decay in the Great Australian Bight. This pathway has not been previously documented owing to poor satellite sampling off eastern Tasmania. As eddies propagate southward, they often "stall" for several months at near-constant latitude. Along the pathway eddies become increasingly barotropic. Eddy intensity is primarily influenced by merging with other eddies and a gradual decay otherwise. Surface temperature anomaly associated with anticyclonic eddies changes as they propagate, while surface salinity anomaly tends to remain relatively unchanged as they propagate.

  18. Biogeochemical properties of eddies in the California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Combes, Vincent

    2016-06-01

    The California Current System (CCS) has intense mesoscale activity that modulates and exports biological production from the coastal upwelling system. To characterize and quantify the ability of mesoscale eddies to affect the local and regional planktonic ecosystem of the CCS, we analyzed a 10 year-long physical-biological model simulation, using eddy detection and tracking to isolate the dynamics of cyclonic and anticyclonic eddies. As they propagate westward across the shelf, cyclonic eddies efficiently transport coastal planktonic organisms and maintain locally elevated production for up to 1 year (800 km offshore). Anticyclonic eddies, on the other hand, have a limited impact on local production over their ~6 month lifetime as they propagate 400 km offshore. At any given time ~8% of the model domain was covered by eddy cores. Though the eddies cover a small area, they explain ~50 and 20% of the transport of nitrate and plankton, respectively.

  19. Eddy-current inspection of shuttle heat exchanger tube welds

    NASA Technical Reports Server (NTRS)

    Dodd, Casius V.; Scott, G. W.; Chitwood, L. D.

    1990-01-01

    The goal of this project was to develop the system necessary to demonstrate in the laboratory that an eddy current system can inspect the tubes and welds described, screening for the existence of flaws equal in size to, or larger than, the target flaw. The laboratory system was to include the probe necessary to traverse the tubing, the electronics to drive (i.e., electrically excite) the probe and receive and process signals from it, a data display, data recording, and playback devices, and microprocessor software or firmware necessary to operate the system.

  20. Eddy-current inspection of shuttle heat exchanger tube welds

    SciTech Connect

    Dodd, C.V.; Scott, G.W.; Chitwood, L.D.

    1989-01-01

    This goal of this project was to develop the system necessary to demonstrate in the laboratory that an eddy-current system can inspect the tubes and welds described above, screening for the existence of flaws equal in size to, or larger than, the target flaw. The laboratory system was to include the probe necessary to traverse the tubing, the electronics to drive (i.e., electrically excite) the probe and receive and process signals from it, a data display, data recording and playback devices, and microprocessor software or firmware necessary to operate the system. 5 refs., 9 figs., 2 tabs.

  1. Investigating electrical resonance in eddy-current array probes

    NASA Astrophysics Data System (ADS)

    Hughes, R.; Fan, Y.; Dixon, S.

    2016-02-01

    The sensitivity enhancing effects of eddy-current testing at frequencies close to electrical resonance are explored. Var-ied techniques exploiting the phenomenon, dubbed near electrical resonance signal enhancement (NERSE), were experimentally investigated to evaluate its potential exploitation for other interesting applications in aerospace materials, in particular its potential for boosting the sensitivity of standard ECT measurements. Methods for setting and controlling the typically unstable resonant frequencies of such systems are discussed. This research is funded by the EPSRC, via the Research Centre for Non-Destructive Evaluation RCNDE, and Rolls-Royce plc.

  2. A Circuit Equation as a Limit of Eddy Current Equations

    NASA Astrophysics Data System (ADS)

    Amirat, Youcef; Touzani, Rachid

    2017-06-01

    We consider a three-dimensional time-harmonic eddy current problem formulated in terms of the magnetic field. We prove that in the case of one thin toroidal conductor, eddy current equations have as a limit Kirchhoff's algebraic equation for circuits. This approximation is valid in the case of small resistivity and voltage.

  3. Eddy Current System and Method for Crack Detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2012-01-01

    An eddy current system and method enables detection of sub-surface damage in a cylindrical object. The invention incorporates a dual frequency, orthogonally wound eddy current probe mounted on a stepper motor-controlled scanning system. The system is designed to inspect for outer surface damage from the interior of the cylindrical object.

  4. A Circuit Equation as a Limit of Eddy Current Equations

    NASA Astrophysics Data System (ADS)

    Amirat, Youcef; Touzani, Rachid

    2017-10-01

    We consider a three-dimensional time-harmonic eddy current problem formulated in terms of the magnetic field. We prove that in the case of one thin toroidal conductor, eddy current equations have as a limit Kirchhoff's algebraic equation for circuits. This approximation is valid in the case of small resistivity and voltage.

  5. Revolving Eddy-Current Probe Detects Cracks Near Rivets

    NASA Technical Reports Server (NTRS)

    Namkung, Min; Wincheski, Buzz; Fulton, James P.; Nath, Shridhar; Simpson, John

    1995-01-01

    Scanning eddy-current probe in circular pattern increases sensitivity with which probe indicates fatigue cracks and other defects in metal surfaces in vicinity of rivets. Technique devised to facilitate inspection of riveted joints in aircraft. Eddy-current probe in question described in "Electro-magnetic Flaw Detector Is Easier To Use" (LAR-15046).

  6. Determining confounding sensitivities in eddy current thin film measurements

    NASA Astrophysics Data System (ADS)

    Gros, Ethan; Udpa, Lalita; Smith, James A.; Wachs, Katelyn

    2017-02-01

    Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done by using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs in the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It was the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy-current testing was performed using a commercially available, hand-held eddy-current probe (ETA3.3H spring-loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe was sent to a hand-held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H spring-loaded eddy probe was at measuring film thickness under varying experimental conditions. This research studied the effects of a number of factors such as i) conductivity, ii) edge effect, iii) surface finish of base material and iv) cable condition.

  7. Semi-analytical solution to the 2014 eddy current benchmark problem

    NASA Astrophysics Data System (ADS)

    Miorelli, Roberto; Reboud, Christophe; Voulgaraki, Charitini; Poulakis, Nikolaos; Theodoulidis, Theodoros

    2015-03-01

    This work proposes a solution to the 2014 eddy current testing benchmark, published by the WFNDEC and proposed by the authors. The aim of this benchmark is to provide reference data for eddy current testing configurations involving magnetic sensors -here Hall sensors- as receivers, as they present some advantages in terms of resolution and sensitivity. After a presentation of the benchmark cases, the theoretical approach used to solve the equivalent electromagnetic problem is detailed and a alternative computation of eddy current signals is proposed. Then, simulations are quantitatively compared to experimental data in each case and the results are discussed.

  8. Use of eddy current mixes to solve a weld examination application

    SciTech Connect

    Ward, R.C.; LaBoissonniere, A.

    1995-12-31

    The augmentation of typical nondestructive (i.e., ultrasound) weld inspection techniques by the use of eddy current tools may significantly enhance the quality and reliability of weld inspections. One recent example is the development of an eddy current technique for use in the examination of BWR core shroud welds, where multi-frequency mixes are used to eliminate signals coming from the weld material so that the examination of the heat affected zone is enhanced. An analysis tool most commonly associated with ultrasound examinations, the C-Scan based on gated information, may be implemented with eddy current data to enhance analysis.

  9. Eddy Current Flexible Probes for Complex Geometries

    NASA Astrophysics Data System (ADS)

    Gilles-Pascaud, C.; Decitre, J. M.; Vacher, F.; Fermon, C.; Pannetier, M.; Cattiaux, G.

    2006-03-01

    The inspection of materials used in aerospace, nuclear or transport industry is a critical issue for the safety of components exposed to stress or/and corrosion. The industry claims for faster, more sensitive, and more flexible techniques. Technologies based on Eddy Current (EC) flexible array probe and magnetic sensor with high sensitivity such as giant magneto-resistance (GMR) could be a good solution to detect surface-breaking flaws in complex shaped surfaces. The CEA has recently developed, with support from the French Institute for Radiological Protection and Nuclear Safety (IRSN), a flexible array probe based on micro-coils etched on Kapton. The probe's performances have been assessed for the inspection of reactor residual heat removal pipes, and for aeronautical applications within the framework of the European project VERDICT. The experimental results confirm the very good detection of narrow cracks on plane and curve shaped surfaces. This paper also describes the recent progresses concerning the application of GMR sensors to EC testing, and the results obtained for the detection of small surface breaking flaws.

  10. Modeling of velocity effects in eddy current applications

    NASA Astrophysics Data System (ADS)

    Ida, Nathan

    1988-04-01

    The effects of velocity on moving sources are encountered in many practical eddy current applications. In many instances these effects are ignored either because velocities are relatively low, because of our inability to quantify these effects, or for purposes of simplifying the solution. There are, however, a number of important applications in which this cannot be done and full account of velocity must be taken. Some obvious applications are magnetic recording, magnetic braking, and nondestructive testing. This work presents a finite element formulation for eddy current problems that takes into account the relative movement of sources. Results are presented indicating that velocity effects are significant at high velocities, and are important for correct signal interpretation. The effect of velocity on nondestructive testing signals is investigated and shown to display significant deviation from static behavior. Because of the form of the governing equations, spurious, nonphysical solutions may be generated. These are eliminated by two separate methods. One involves refinement of the finite element mesh and the second, upwinding of the finite elements.

  11. Role of varying interface conditions on the eddy current response from cracks in multilayer structures

    NASA Astrophysics Data System (ADS)

    Cherry, Aaron; Knopp, Jeremy; Aldrin, John C.; Sabbagh, Harold A.; Boehnlein, Thomas; Mooers, Ryan

    2013-01-01

    There is a need to improve the understanding of the role of interface conditions on eddy current inspections for cracks in multilayer aircraft structures. This paper presents initial experimental and simulated results studying the influence of gaps and contact conditions between two plates with a notch in the second layer. Simulations show an amplification of the eddy current signal for a subsurface notch adjacent to an air gap as opposed to a submerged notch in a solid plate.

  12. Eddy current nondestructive testing device for measuring variable characteristics of a sample utilizing Walsh functions

    DOEpatents

    Libby, Hugo L.; Hildebrand, Bernard P.

    1978-01-01

    An eddy current testing device for measuring variable characteristics of a sample generates a signal which varies with variations in such characteristics. A signal expander samples at least a portion of this generated signal and expands the sampled signal on a selected basis of square waves or Walsh functions to produce a plurality of signal components representative of the sampled signal. A network combines these components to provide a display of at least one of the characteristics of the sample.

  13. Solitonlike solutions in loop current eddies

    NASA Technical Reports Server (NTRS)

    Nakamoto, Shoichiro

    1989-01-01

    The application of the nonlinear quasi-geostrophic equations to an isolated eddy in the western continental slope region in the Gulf of Mexico is examined for a two-layer ocean model with bottom topography. In the linear limit, solutions are topographic nondispersive waves. Form-preserving solutions, or solitons, have been found. The solution is shown to be a limiting form for a nonlinear dispersive system propagating northward along the topographic waveguide in the western continental slope region in the Gulf of Mexico. Using satellite-tracked drifter data, a linear relationship is found between the amplitude of the deduced stream function of the eddy and its observed translational velocity over the continental slope, which supports the hypothesis that some mesoscale eddies interacting with the continental slope behave as solitons.

  14. Eddy current inspection of weld defects in tubing

    NASA Technical Reports Server (NTRS)

    Katragadda, G.; Lord, W.

    1992-01-01

    An approach using differential probes for the inspection of weld defects in tubing is studied. Finite element analysis is used to model the weld regions and defects. Impedance plane signals are predicted for different weld defect types and compared wherever possible with signals from actual welds in tubing. Results show that detection and sizing of defects in tubing is possible using differential eddy current techniques. The phase angle of the impedance plane trajectory gives a good indication of the sizing of the crack. Data on the type of defect can be obtained from the shape of the impedance plane trajectory and the phase. Depending on the skin depth, detection of outer wall, inner wall, and subsurface defects is possible.

  15. Vacuum vessel eddy current modeling for TFTR adiabatic compression experiments

    SciTech Connect

    DeLucia, J.; Bell, M.; Wong, K.L.

    1985-07-01

    A relatively simple current filament model of the TFTR vacuum vessel is described. It is used to estimate the three-dimensional structure of magnetic field perturbations in the vicinity of the plasma that arise from vacuum vessel eddy currents induced during adiabatic compression. Eddy currents are calculated self-consistently with the plasma motion. The Shafranov formula and adiabatic scaling laws are used to model the plasma. Although the specific application is to TFTR, the present model is of generation applicability.

  16. Eddy Current Method for Fatigue Testing

    NASA Technical Reports Server (NTRS)

    Simpson, John W. (Inventor); Fulton, James P. (Inventor); Wincheski, Russell A. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor); Nath, Shridhar C. (Inventor)

    1997-01-01

    Flux-focusing electromagnetic sensor using a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks and material loss in high conductivity material. A ferrous shield isolates a high-turn pick-up coil from an excitation coil. Use of the magnetic shield produces a null voltage output across the receiving coil in presence of an unflawed sample. Redistribution of the current flow in the sample caused by the presence of flaws. eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. Maximum sensor output is obtained when positioned symmetrically above the crack. By obtaining position of maximum sensor output, it is possible to track the fault and locate the area surrounding its tip. Accuracy of tip location is enhanced by two unique features of the sensor; a very high signal-to-noise ratio of the probe's output resulting in an extremely smooth signal peak across the fault, and a rapidly decaying sensor output outside a small area surrounding the crack tip enabling the search region to be clearly defined. Under low frequency operation, material thinning due to corrosion causes incomplete shielding of the pick-up coil. Low frequency output voltage of the probe is therefore a direct indicator of thickness of the test sample. Fatigue testing a conductive material is accomplished by applying load to the material, applying current to the sensor, scanning the material with the sensor, monitoring the sensor output signal, adjusting material load based on the sensor output signal of the sensor, and adjusting position of the sensor based on its output signal.

  17. Biogeochemical Properties of Eddies in the California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Combes, Vincent

    2016-04-01

    The California Current System (CCS) is a coastal upwelling system characterized by intense mesoscale activity. This mesoscale activity plays a critical role in modulating biological production and exporting coastal biogeochemical materials offshore. To characterize and quantify the ability of mesoscale eddies to affect local and regional planktonic ecosystems in the CCS, we analyzed a 10-year-long physical-biological model simulation - with 5km horizontal resolution - using eddy detection and tracking to isolate the dynamics in cyclonic and anticyclonic eddies. At any given time, ~8% of the model domain was covered by eddies, and this small area belies ~50% of the cross-shelf biological transport. As they propagate westward across the shelf, cyclonic eddies efficiently transport coastal planktonic organisms, and maintain locally elevated production, Anticyclones, on the other hand, have a limited impact on local production.

  18. Inspection of laser welds with array eddy current technique

    NASA Astrophysics Data System (ADS)

    Todorov, E.; Nagy, B.; Levesque, S.; Ames, N.; Na, J.

    2013-01-01

    Three groups of laser weld specimens made of steel 316L for nuclear applications were fabricated - acceptable, missed seam (MS) and lack of penetration (LOP). An array eddy current technique was developed and investigated. The specimens top and bottom surfaces were scanned parallel and transverse to the weld line. The MS and LOP were easily imaged, detected and sized. Additional flaw indications were found in visually acceptable weld areas. Limited weld destructive testing was performed validating characteristic eddy current flaw indications.

  19. Equilibrium reconstruction with 3D eddy currents in the Lithium Tokamak eXperiment

    DOE PAGES

    Hansen, C.; Boyle, D. P.; Schmitt, J. C.; ...

    2017-04-18

    Axisymmetric free-boundary equilibrium reconstructions of tokamak plasmas in the Lithium Tokamak eXperiment (LTX) are performed using the PSI-Tri equilibrium code. Reconstructions in LTX are complicated by the presence of long-lived non-axisymmetric eddy currents generated by a vacuum vessel and first wall structures. To account for this effect, reconstructions are performed with additional toroidal current sources in these conducting regions. The eddy current sources are fixed in their poloidal distributions, but their magnitude is adjusted as part of the full reconstruction. Eddy distributions are computed by toroidally averaging currents, generated by coupling to vacuum field coils, from a simplified 3D filamentmore » model of important conducting structures. The full 3D eddy current fields are also used to enable the inclusion of local magnetic field measurements, which have strong 3D eddy current pick-up, as reconstruction constraints. Using this method, equilibrium reconstruction yields good agreement with all available diagnostic signals. Here, an accompanying field perturbation produced by 3D eddy currents on the plasma surface with a primarily n = 2, m = 1 character is also predicted for these equilibria.« less

  20. Equilibrium reconstruction with 3D eddy currents in the Lithium Tokamak eXperiment

    NASA Astrophysics Data System (ADS)

    Hansen, C.; Boyle, D. P.; Schmitt, J. C.; Majeski, R.

    2017-04-01

    Axisymmetric free-boundary equilibrium reconstructions of tokamak plasmas in the Lithium Tokamak eXperiment (LTX) are performed using the PSI-Tri equilibrium code. Reconstructions in LTX are complicated by the presence of long-lived non-axisymmetric eddy currents generated by a vacuum vessel and first wall structures. To account for this effect, reconstructions are performed with additional toroidal current sources in these conducting regions. The eddy current sources are fixed in their poloidal distributions, but their magnitude is adjusted as part of the full reconstruction. Eddy distributions are computed by toroidally averaging currents, generated by coupling to vacuum field coils, from a simplified 3D filament model of important conducting structures. The full 3D eddy current fields are also used to enable the inclusion of local magnetic field measurements, which have strong 3D eddy current pick-up, as reconstruction constraints. Using this method, equilibrium reconstruction yields good agreement with all available diagnostic signals. An accompanying field perturbation produced by 3D eddy currents on the plasma surface with a primarily n = 2, m = 1 character is also predicted for these equilibria.

  1. Thickness measuring of electroconductive pipe walls using the dual-frequency eddy-current method

    NASA Astrophysics Data System (ADS)

    Yakimov, Evgeny; Galtseva, Olga; Ustyugov, Daniil

    2017-01-01

    The paper describes a dual-frequency method for reducing the impact of changes in the gap size between the eddy-current transducer and the pipe, as well as the pipe electrical conductivity on the eddy-current thickness gauge readings. A block-diagram of the dual-frequency eddy-current thickness gauge is proposed for light-alloy drill pipes. The amplitude and signal phase dependencies on the wall thickness in the range from 6 to 17 mm and the gap in the range from 0 to 13.5 mm were studied, the results are presented. The digital signal processing algorithms based on the piecewise-linear approximation of low-frequency and high-frequency signal phase dependencies on the wall thickness are proposed. It is shown that the proposed correction algorithms can reduce the error caused by variations of electrical conductivity and the gap between the transducer and the pipe.

  2. Experimental modelling of eddy currents and deflection for tokamak limiters

    SciTech Connect

    Hua, T.Q.; Knott, M.J.; Turner, L.R.; Wehrle, R.B.

    1986-11-01

    During plasma disruptions in a tokamak fusion reactor, eddy currents are induced in the limiters and other conducting structures surrounding the plasma. Interactions between these currents with the toroidal field causes deflection and stress in the structural components. The structural motion in the strong magnetic field induces additional eddy current opposing the initial eddy current and modifying subsequent structural dynamics. Therefore, the motion and current are coupled and must be solved simultaneously. The coupling between current and deflection in cantilevered beams was investigated experimentally. The beams provide a simple model for the limiter blade of a tokamak fusion reactor. Several test pieces and various magnetic field conditions were employed to study the extend of the coupling effect from weak to strong coupling. Experimental results are compared with analytical predictions.

  3. Conductive shield for ultra-low-field magnetic resonance imaging: Theory and measurements of eddy currents

    PubMed Central

    Zevenhoven, Koos C. J.; Busch, Sarah; Hatridge, Michael; Öisjöen, Fredrik; Ilmoniemi, Risto J.; Clarke, John

    2014-01-01

    Eddy currents induced by applied magnetic-field pulses have been a common issue in ultra-low-field magnetic resonance imaging. In particular, a relatively large prepolarizing field—applied before each signal acquisition sequence to increase the signal—induces currents in the walls of the surrounding conductive shielded room. The magnetic-field transient generated by the eddy currents may cause severe image distortions and signal loss, especially with the large prepolarizing coils designed for in vivo imaging. We derive a theory of eddy currents in thin conducting structures and enclosures to provide intuitive understanding and efficient computations. We present detailed measurements of the eddy-current patterns and their time evolution in a previous-generation shielded room. The analysis led to the design and construction of a new shielded room with symmetrically placed 1.6-mm-thick aluminum sheets that were weakly coupled electrically. The currents flowing around the entire room were heavily damped, resulting in a decay time constant of about 6 ms for both the measured and computed field transients. The measured eddy-current vector maps were in excellent agreement with predictions based on the theory, suggesting that both the experimental methods and the theory were successful and could be applied to a wide variety of thin conducting structures. PMID:24753629

  4. Research of Conductive Materials by Multifrequency Measuring System on the Basis of Eddy Current Transducers

    NASA Astrophysics Data System (ADS)

    Dmitriev, S.; Ishkov, A.; Katasonov, A.; Malikov, V.; Sagalakov, A.; Shevtsova, L.; Ekkerdt, K.

    2017-04-01

    The measuring system based on subminiature eddy-current transducers has been developed to carry out local investigations of aluminum-magnesium alloy plates for flaws. The Delianna filter has been modified to allow the significant increase of signal-to-noise ratio. The transducer has been tested on a number of aluminum-magnesium alloy plates with flaws. The article presents data on the relationship of eddy-current transducer response to the presence of flaws in alloys as hidden slots at signal frequencies comprised between 300÷700 Hz on an exciting winding

  5. Automated measurement system employing eddy currents to adjust probe position and determine metal hardness

    DOEpatents

    Prince, J.M.; Dodson, M.G.; Lechelt, W.M.

    1989-07-18

    A system for measuring the hardness of cartridge cases employs an eddy current probe for inducing and sensing eddy currents in each cartridge case. A first component of the sensed signal is utilized in a closed loop system for accurately positioning the probe relative to the cartridge case both in the lift off direction and in the tangential direction, and a second component of the sensed signal is employed as a measure of the hardness. The positioning and measurement are carried out under closed loop microprocessor control facilitating hardness testing on a production line basis. 14 figs.

  6. Automated measurement system employing eddy currents to adjust probe position and determine metal hardness

    DOEpatents

    Prince, James M.; Dodson, Michael G.; Lechelt, Wayne M.

    1989-01-01

    A system for measuring the hardness of cartridge cases employs an eddy current probe for inducing and sensing eddy currents in each cartridge case. A first component of the sensed signal is utilized in a closed loop system for accurately positioning the probe relative to the cartridge case both in the lift off direction and in the tangential direction, and a second component of the sensed signal is employed as a measure of the hardness. The positioning and measurement are carried out under closed loop microprocessor control facilitating hardness testing on a production line basis.

  7. Eddy Current Sensing of Torque in Rotating Shafts

    NASA Astrophysics Data System (ADS)

    Varonis, Orestes J.; Ida, Nathan

    2013-12-01

    The noncontact torque sensing in machine shafts is addressed based on the stress induced in a press-fitted magnetoelastic sleeve on the shaft and eddy current sensing of the changes of electrical conductivity and magnetic permeability due to the presence of stress. The eddy current probe uses dual drive, dual sensing coils whose purpose is increased sensitivity to torque and decreased sensitivity to variations in distance between probe and shaft (liftoff). A mechanism of keeping the distance constant is also employed. Both the probe and the magnetoelastic sleeve are evaluated for performance using a standard eddy current instrument. An eddy current instrument is also used to drive the coils and analyze the torque data. The method and sensor described are general and adaptable to a variety of applications. The sensor is suitable for static and rotating shafts, is independent of shaft diameter and operational over a large range of torques. The torque sensor uses a differential eddy current measurement resulting in cancellation of common mode effects including temperature and vibrations.

  8. Non-Contact EDDY Current Hole Eccentricity and Diameter Measurement

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1998-01-01

    Precision holes are among the most critical features of a mechanical component. Deviations from permissible tolerances can impede operation and result in unexpected failure. We have developed an automated non-contact eddy current hole diameter and eccentricity measuring system. The operating principle is based on the eddy current lift-off effect, which is the coil impedance as a function of the distance between the coil and the test object. An absolute eddy current probe rotates in the hole. The impedance of each angular position is acquired and input to the computer for integration and analysis. The eccentricity of the hole is the profile of the impedance as a function of angular position as compared to a straight line, an ideal hole. The diameter of the hole is the sum of the diameter of the probe and twice the distance-calibrated impedance. An eddy current image is generated by integrating angular scans for a plurality of depths between the top and bottom to display the eccentricity profile. This system can also detect and image defects in the hole. The method for non-contact eddy current hole diameter and eccentricity measurement has been granted a patent by the U.S. Patent and Trademark Office.

  9. Investigation on a new inducer of pulsed eddy current thermography

    NASA Astrophysics Data System (ADS)

    He, Min; Zhang, Laibin; Zheng, Wenpei; Feng, Yijing

    2016-09-01

    In this paper, a new inducer of pulsed eddy current thermography (PECT) is presented. The use of the inducer can help avoid the problem of blocking the infrared (IR) camera's view in eddy current thermography technique. The inducer can also provide even heating of the test specimen. This paper is concerned with the temperature distribution law around the crack on a specimen when utilizing the new inducer. Firstly, relative mathematical models are provided. In the following section, eddy current distribution and temperature distribution around the crack are studied using the numerical simulation method. The best separation distance between the inducer and the specimen is also determined. Then, results of temperature distribution around the crack stimulated by the inducer are gained by experiments. Effect of current value on temperature rise is studied as well in the experiments. Based on temperature data, temperature features of the crack are discussed.

  10. Detecting defects in marine structures by using eddy current infrared thermography.

    PubMed

    Swiderski, W

    2016-12-01

    Eddy current infrared (IR) thermography is a new nondestructive testing (NDT) technique used for the detection of cracks in electroconductive materials. By combining the well-established inspection methods of eddy current NDT and IR thermography, this technique uses induced eddy currents to heat test samples. In this way, IR thermography allows the visualization of eddy current distribution that is distorted in defect sites. This paper discusses the results of numerical modeling of eddy current IR thermography procedures in application to marine structures.

  11. Eddy-current examination of large-diameter insulated pipes

    SciTech Connect

    Griffith, J.C.

    1996-12-31

    A new concept eddy-current technique has been developed to examine large-diameter insulated pipes without removing the insulation, and in many cases, without securing system operation. The new concept allows the in-place examination of piping systems using an encircling eddy-current coil that is a proven eddy-current technology. Eliminating the requirement to secure or drain the system or to remove the insulation from the pipe provides significant cost savings. The new concept also provides a significantly higher percentage of inspection volume coverage than ultrasonic techniques despite limitations of pipe brackets and other physical obstructions. The technique has been demonstrated on copper, copper nickel and limited carbon steel pipe ranging from 4 to 8 inches in diameter with insulation thicknesses from 1 to 2 inches.

  12. Non-destructive techniques based on eddy current testing.

    PubMed

    García-Martín, Javier; Gómez-Gil, Jaime; Vázquez-Sánchez, Ernesto

    2011-01-01

    Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future.

  13. Non-Destructive Techniques Based on Eddy Current Testing

    PubMed Central

    García-Martín, Javier; Gómez-Gil, Jaime; Vázquez-Sánchez, Ernesto

    2011-01-01

    Non-destructive techniques are used widely in the metal industry in order to control the quality of materials. Eddy current testing is one of the most extensively used non-destructive techniques for inspecting electrically conductive materials at very high speeds that does not require any contact between the test piece and the sensor. This paper includes an overview of the fundamentals and main variables of eddy current testing. It also describes the state-of-the-art sensors and modern techniques such as multi-frequency and pulsed systems. Recent advances in complex models towards solving crack-sensor interaction, developments in instrumentation due to advances in electronic devices, and the evolution of data processing suggest that eddy current testing systems will be increasingly used in the future. PMID:22163754

  14. Eddy current NDE performance demonstrations using simulation tools

    NASA Astrophysics Data System (ADS)

    Maurice, L.; Costan, V.; Guillot, E.; Thomas, P.

    2013-01-01

    To carry out performance demonstrations of the Eddy-Current NDE processes applied on French nuclear power plants, EDF studies the possibility of using simulation tools as an alternative to measurements on steam generator tube mocks-up. This paper focuses on the strategy led by EDF to assess and use code_Carmel3D and Civa, on the case of Eddy-Current NDE on wears problem which may appear in the U-shape region of steam generator tubes due to the rubbing of anti-vibration bars.

  15. Experimental modeling of eddy currents and defections for tokamak limiters

    SciTech Connect

    Hua, T.Q.; Knott, M.J.; Turner, L.R.; Wehrle, R.B.

    1986-01-01

    In a tokamak fusion reactor or other magnetically confined fusion device, a rapid decay of the magnetic field due to a disrupting plasma current induces eddy currents in the surrounding structures. These include the limiters, blanket, first wall, and vacuum vessel. The eddy currents, through interaction with the applied toroidal and poloidal magnetic fields, produce large mechanical torques and forces that deflect the structural components. An important coupling effect exists between the dynamic behavior of the structure and the transient eddy current. This coupling occurs when, as it deflects, the component intercepts additional magnetic flux. The coupling between deflection and eddy current could reduce the peak current, deflection, and other electromagnetic effects to a level far less severe than would be predicted if coupling is disregarded. In this study, experiments were performed to investigate deflection, current, and material stress in cantilever beams with the Fusion ELectromagnetic Induction eXperiment (FELIX) at the Argonne National Laboratory. Since structures near the plasma are typically cantilevered, the beams provide a good model for the limiter blades of a tokamak fusion reactor. 2 figs.

  16. Magnetic diagnostics for equilibrium reconstructions with eddy currents on the lithium tokamak experiment

    SciTech Connect

    Schmitt, J. C. Lazerson, S.; Majeski, R.; Bialek, J.

    2014-11-15

    The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnostic signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and the equilibrium reconstruction are presented.

  17. Magnetic diagnostics for equilibrium reconstructions with eddy currents on the lithium tokamak experimenta)

    SciTech Connect

    Schmitt, J. C.; Bialek, J.; Lazerson, S.; Majeski, R.

    2014-11-01

    The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnositc signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and the equilibrium reconstruction are presented.

  18. Magnetic diagnostics for equilibrium reconstructions with eddy currents on the Lithium Tokamak eXperiment.

    PubMed

    Schmitt, J C; Bialek, J; Lazerson, S; Majeski, R

    2014-11-01

    The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnostic signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and the equilibrium reconstruction are presented.

  19. Pulsed eddy current inspection of CF-188 inner wing spar

    NASA Astrophysics Data System (ADS)

    Horan, Peter Francis

    Royal Canadian Air Force (RCAF) CF-188 Hornet aircraft engineering authorities have stated a requirement for a Non-Destructive Evaluation (NDE) technique to detect Stress Corrosion Cracking (SCC) in the inner wing spars without fastener or composite wing skin removal. Current radiographic inspections involve significant aircraft downtime, and Pulsed Eddy Current (PEC) inspection is proposed as a solution. The aluminum inner wing spars of CF-188 Hornet aircraft may undergo stress corrosion cracking (SCC) along the spar between the fasteners that secure carbon-fiber/ epoxy composite skin to the wing. Inspection of the spar through the wing skin is required to avoid wing disassembly. The thickness of the wing skin varies between 8 and 20 mm (0.3 to 0.8 inch) and fasteners may be either titanium or ferrous. PEC generated by a probe centered over a fastener, demonstrates capability of detecting simulated cracks within spars with the wing skin present. Comparison of signals from separate sensors, mounted to either side of the excitation coil, is used to detect differences in induced eddy current fields, which arise in the presence of cracks. To overcome variability in PEC signal response due to variation in 1) skin thickness, 2) fastener material and size, and 3) centering over fasteners, a large calibration data set is acquired. Multi-dimensional scores from a Modified Principal Components Analysis (PCA) of the data are reduced to one dimension (1D) using a Discriminant Analysis method. Under inspection conditions, calibrated PCA scores combined with discriminant analysis permit rapid real time go/no-go PEC detection of cracks in CF-188 inner wing spar. Probe designs using both pickup coils and Giant Magnetoresistive (GMR) sensors were tested on samples with the same ferrous and titanium fasteners found on the CF-188. Flaws were correctly detected at lift-offs of up to 21mm utilizing a variety of insulating skin materials simulating the carbon-fibre reinforced polymer

  20. REMOTE FIELD EDDY CURRENT INSPECTION OF UNPIGGABLE PIPELINES

    SciTech Connect

    Albert Teitsma

    2004-03-01

    The Remote Field Eddy Current (RFEC) technique is ideal for inspecting unpiggable pipelines because all its components can be made much smaller than the diameter of the pipe to be inspected. We reviewed the technique, and used demonstrations from prior work by others in presentations on the technique and how we plan to develop it. Coils were wound; a jig for pulling the coils through the pipe was manufactured; defects were machined in one six-inch diameter, ten-foot long pipe; and the equipment was assembled. After completing first crude pullout test to show that RFEC inspection would work, we repeated the experiment with a proper jig and got excellent results. The test showed the expected behavior, with the direct field dominating the signal to about two pipe diameters from the drive coil, and the remote field dominating for greater separations between the drive coil and the sensing coils. Response of RFEC to a typical defect was measured, as was the sensitivity to defect size. Before manufacturing defects in the pipe, we measured the effect of defect separation and concluded that defects separated by 18 inches or 1/3rd of the pipe diameter did not interfere with each other. We manufactured a set of 13 defects, and measured the RFEC signals. We found a background variation that was eventually attributed to permeability variations in the seamless pipe. We scanned all thirteen defects and got satisfactory results. The two smallest defects did not show a signal, but these were much too small to be reported in a pipeline inspection. We acquired a ten-foot seam welded pipe that has much less background variation. We are measuring the sensitivity of RFEC signals to mechanical variations between the exciter and sensing coils.

  1. On the influence of eddy aging processes on colliding East Australian Current warm core eddies

    NASA Astrophysics Data System (ADS)

    Bowman, M.; Dietrich, D.; Sanderson, B.

    2003-04-01

    DieCAST, a 4th-order-accurate numerical model of the East Australian Current (EAC), having low total dissipation and numerical dispersion, is used to study the kinematics and dynamics of the collisions and mergings of previously pinched-off EAC anticyclonic eddies. Earlier studies show that eddies which extrude and reside for months to the south of the EAC retroflection region east of Sydney, a) naturally tend to become more barotropic and less buoyant under quasi-geostrophic dynamics with near-surface energy propagating to deeper levels; and b) by having been modified through air-sea exchange in cooler, more southern latitudes (especially after a winter season) are even less buoyant and more nearly barotropic. During merging, less dense surface water from younger eddies arriving from the north has been observed by Cresswell to override the less buoyant water of the older eddies. This process is being theoretically and numerically investigated. The high-resolution model is nested in a Southwest Pacific Ocean regional model that provides realistic upstream conditions for the East Australian Current. In order to address the nature and function of frontal eddies and other small-scale features which form around the edges of the main anticyclones during water-mass transformations, the model uses physically-based surface heat fluxes and E-P. These are derived using a new method that does not damp small-scale surface features by restoring to climatology, while leading to (by construction) the ensemble-mean annual cycle while converging to the observed annual surface cycle climatology as time progresses.

  2. Recent freshening of the East Australian Current and its eddies

    NASA Astrophysics Data System (ADS)

    Rykova, Tatiana; Oke, Peter R.

    2015-11-01

    The East Australian Current (EAC) has a relatively weak mean flow and an energetic eddy field that dominates the circulation. The properties of the mean flow have been studied in detail, but the changes in the eddy field have received little attention. We analyze Argo temperature and salinity profiles for 2005-2012 to construct a picture of the time-mean and time-varying properties of EAC eddies. We find that eddies and the surrounding waters of the western Tasman Sea are freshening at a rate of 0.017-0.025 practical salinity unit/yr over the top 100 m, with no significant temperature change. Consistent with the observations, fields from an eddy-resolving ocean model show freshening, with no temperature trend. Moreover, the model results indicate that observed changes are significant in the context of the variability over the last 20 years and may be part of a multiyear (perhaps decadal) cycle. We attribute the freshening of the region to increased precipitation off Eastern Australia.

  3. 53. Drive shaft, motors, eddie currents, brakes, and differential gears ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    53. Drive shaft, motors, eddie currents, brakes, and differential gears in south machinery room (interior of both machinery rooms is identical). Facing east. - Henry Ford Bridge, Spanning Cerritos Channel, Los Angeles-Long Beach Harbor, Los Angeles, Los Angeles County, CA

  4. Vibration attenuation of conductive beams by inducing eddy currents

    NASA Astrophysics Data System (ADS)

    Irazu, L.; Elejabarrieta, M. J.

    2016-09-01

    The increasing requirements for structural vibration control in many industries, require innovative attenuation techniques. In this work, the phenomenon of eddy currents is proposed to reduce the vibration of conductive and non-magnetic beam-like structures without modifying the system, neither the weight nor the stiffness. The motion of a conductive material in a stationary magnetic field induces eddy currents, which in turn generate a repulsive force and attenuate the vibration. In this study, the vibrational response of a thin aluminium beam under a partial and stationary magnetic field is analysed. The influence of the eddy currents is experimentally studied in the bandwidth from 0 to 1 kHz and a preliminary numerical model is proposed. The results show the vibration of all the length of the beam can be attenuated by inducing eddy currents, whereas the natural frequencies of the system remain unmodified. The attenuation of the vibration is more remarkable at low frequencies and when the position of the magnetic field coincides with a maximum vibration of a mode.

  5. Differential-Coil Eddy-Current Material Sorter

    NASA Technical Reports Server (NTRS)

    Nummelin, J.; Buckley, D.

    1985-01-01

    Small metal or other electrically conductive parts of same shape but different composition quickly sorted with differential-coil eddy-current sorter. Developed to distinguish between turbine blades of different alloys, hardnesses, and residual stress, sorter generally applicable to parts of simple and complex shape.

  6. A study of eddy current measurement (1986-1987)

    SciTech Connect

    Ramachandran, R.S.; Armstrong, K.P.

    1989-06-22

    A study was conducted in 1986 to evaluate a modified eddy current system for measuring copper thickness on Kapton. Results showed a measurement error of 0.42 {mu}in. for a thickness range of 165 to 170 {mu}in. and a measurement variability of 3.2 {mu}in.

  7. Pulsed eddy current thickness measurements of transuranic waste containers

    SciTech Connect

    O`Brien, T.K.; Kunerth, D.C.

    1995-12-31

    Thickness measurements on fifty five gallon waste drums for drum integrity purposes have been traditionally performed at the INEL using ultrasonic testing methods. Ultrasonic methods provide high resolution repeatable thickness measurements in a timely manner, however, the major drawback of using ultrasonic techniques is coupling to the drum. Areas with severe exterior corrosion, debonded paper labels or any other obstacle in the acoustic path will have to be omitted from the ultrasonic scan. We have developed a pulsed eddy current scanning system that can take thickness measurements on fifty five gallon carbon steel drums with wall thicknesses up to 65 mils. This type of measurement is not susceptible to the problems mentioned above. Eddy current measurements in the past have excluded ferromagnetic materials such as carbon steel because of the difficulty in penetrating the material and in compensating for changes in permeability from material to material. New developments in data acquisition electronics as well as advances in personal computers have made a pulsed eddy current system practical and inexpensive. Certain aspects of the pulsed eddy current technique as well as the operation of such a system and features such as real time pass/fail thresholds for overpacking identification and full scan data archiving for future evaluation will be discussed.

  8. Eddy Processes of the Western Adriatic Current Near Cape Gargano

    DTIC Science & Technology

    2010-01-01

    Marine Science, Venezia, Italy 3 University of Durham, Durham, U.K. 4 NATO Undersea Research Centre, La Spezia, Italy 5 C.N.R.-Institute of Marine...Science, La Spezia, Italy 6 Institute of Oceanography and Fisheries, Split, Croatia Abstract Eddy processes of the Western Adriatic Current near Cape

  9. A Laboratory Activity on the Eddy Current Brake

    ERIC Educational Resources Information Center

    Molina-Bolivar, J. A.; Abella-Palacios, A. J.

    2012-01-01

    The aim of this paper is to introduce a simple and low-cost experimental setup that can be used to study the eddy current brake, which considers the motion of a sliding magnet on an inclined conducting plane in terms of basic physical principles. We present a set of quantitative experiments performed to study the influence of the geometrical and…

  10. Physical interpretation and separation of eddy current pulsed thermography

    NASA Astrophysics Data System (ADS)

    Yin, Aijun; Gao, Bin; Yun Tian, Gui; Woo, W. L.; Li, Kongjing

    2013-02-01

    Eddy current pulsed thermography (ECPT) applies induction heating and a thermal camera for non-destructive testing and evaluation (NDT&E). Because of the variation in resultant surface heat distribution, the physical mechanism that corresponds to the general behavior of ECPT can be divided into an accumulation of Joule heating via eddy current and heat diffusion. However, throughout the literature, the heating mechanisms of ECPT are not given in detail in the above two thermal phenomena and they are difficult to be separated. Nevertheless, once these two physical parameters are separated, they can be directly used to detect anomalies and predict the variation in material properties such as electrical conductivity, magnetic permeability and microstructure. This paper reports physical interpretation of these two physical phenomena that can be found in different time responses given the ECPT image sequences. Based on the phenomenon and their behaviors, the paper proposes a statistical method based on single channel blind source separation to decompose the two physical phenomena using different stages of eddy current and thermal propagation from the ECPT images. Links between mathematical models and physical models have been discussed and verified. This fundamental understanding of transient eddy current distribution and heating propagation can be applied to the development of feature extraction and pattern recognition for the quantitative analysis of ECPT measurement images and defect characterization.

  11. A Laboratory Activity on the Eddy Current Brake

    ERIC Educational Resources Information Center

    Molina-Bolivar, J. A.; Abella-Palacios, A. J.

    2012-01-01

    The aim of this paper is to introduce a simple and low-cost experimental setup that can be used to study the eddy current brake, which considers the motion of a sliding magnet on an inclined conducting plane in terms of basic physical principles. We present a set of quantitative experiments performed to study the influence of the geometrical and…

  12. Subminiature eddy current transducers for studying boride coatings

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. F.; Ishkov, A. V.; Malikov, V. N.; Sagalakov, A. M.

    2016-07-01

    Strengthening of parts and units of machines, increased reliability and longer service life is an important task of modern mechanical engineering. The main objects of study in the work were selected steel 65G and 50HGA, wear-resistant boride coatings ternary system Fe-B-Fe n B which were investigated by scanning electron microscopy and eddy-current nondestructive methods.

  13. Eddy current modeling of silicon steel for use on SPICE

    SciTech Connect

    Fujiwara, Toru; Tahara, Ryoichi

    1995-11-01

    The relation between the equivalent eddy current field He and the instantaneous flux density rate dB/dt is experimentally obtained for current transformers made of silicon steel. The results show that He is proportional to (dB/dt){sup 0.6-0.7} in the operating frequency range ({approximately}100 Hz) of the current transformers. The ac B-H loop calculated by combining the proposed eddy current model with the Jiles-Atherton model agrees well with the measured data. In addition, this combined model allows magnetic component characteristics using SPICE to be simulated. The simulated secondary voltage waveforms of current transformers are in satisfactory agreement with the measured values.

  14. Analytical modeling for transient probe response in eddy current testing

    NASA Astrophysics Data System (ADS)

    Desjardins, Daniel

    Analytical models that describe the electromagnetic field interactions arising between field generating and sensing coils in close proximity to conducting structures can be used to enhance analysis and information extracted from signals obtained using electromagnetic non-destructive evaluation technologies. A novel strategy, which enables the derivation of exact solutions describing all electromagnetic interactions arising in inductively coupled circuits due to a voltage excitation, is developed in this work. Differential circuit equations are formulated in terms of an arbitrary voltage excitation and of the magnetic fields arising in inductive systems, using Faraday's law and convolution, and solved using the Fourier transform. The approach is valid for systems containing any number of driving and receiving coils, and include nearby conducting and ferromagnetic structures. In particular, the solutions account for feedback between a ferromagnetic conducting test piece and the driving and sensing coils, providing correct voltage response of the coils. Also arising from the theory are analytical expressions for complex inductances in a circuit, which account for real (inductive) and imaginary (loss) elements associated with conducting and ferromagnetic structures. A novel model-based method for simultaneous characterization of material parameters, which includes magnetic permeability, electrical conductivity, wall thickness and liftoff, is subsequently developed from the forward solutions. Furthermore, arbitrary excitation waveforms, such as a sinusoid or a square wave, for applications in conventional and transient eddy current, respectively, may be considered. Experimental results, obtained for a square wave excitation, are found to be in excellent agreement with the analytical predictions.

  15. Eddy-Current Sensors with Asymmetrical Point Spread Function

    PubMed Central

    Gajda, Janusz; Stencel, Marek

    2016-01-01

    This paper concerns a special type of eddy-current sensor in the form of inductive loops. Such sensors are applied in the measuring systems classifying road vehicles. They usually have a rectangular shape with dimensions of 1 × 2 m, and are installed under the surface of the traffic lane. The wide Point Spread Function (PSF) of such sensors causes the information on chassis geometry, contained in the measurement signal, to be strongly averaged. This significantly limits the effectiveness of the vehicle classification. Restoration of the chassis shape, by solving the inverse problem (deconvolution), is also difficult due to the fact that it is ill-conditioned. An original approach to solving this problem is presented in this paper. It is a hardware-based solution and involves the use of inductive loops with an asymmetrical PSF. Laboratory experiments and simulation tests, conducted with models of an inductive loop, confirmed the effectiveness of the proposed solution. In this case, the principle applies that the higher the level of sensor spatial asymmetry, the greater the effectiveness of the deconvolution algorithm. PMID:27782033

  16. Distributed point source method for the modeling of a three-dimensional eddy current NDE problem

    NASA Astrophysics Data System (ADS)

    Bore, T.; Joubert, P.-Y.; Placko, D.

    2014-03-01

    This paper deals with modeling in electromagnetism in the field of eddy current for Non Destructive Evaluation. Several techniques could be used to diagnose structural damages. In eddy current application, a magnetic field generates by an excitation coil (or primary coil), interacts with a conductive target and generates eddy current. Variations in the phase and the magnitude of these eddy currents can be monitored using a second "receiver" coil. Variations in the physical properties (electrical conductivity, magnetic permeability,..) or the presence of any flaw in the target will cause a change in eddy current and a corresponding change in the phase and amplitude of measured signal. The interpretation of the signals requires a good understanding of the interaction between eddy current and structure. Therefore, researchers need analytical or numerical techniques to obtain a clear understanding of wave propagation behaviors. However, modeling of wave scattering phenomenon by conventional numerical techniques such as finite elements requires very fine mesh and heavy computational power. To go further, an innovative implementation of a semi-analytical modeling method, called the Distributed Points Source Method (DPSM), has been developed and used. The DPSM has already shown great potentialities for the versatile and computationally efficient modeling of complex electrostatic, electromagnetic or ultrasounic problems. In this paper, we report on a new implementation of the DPSM, called differential DPSM, which shows interesting prospects for the modeling of complex eddy current problems. In parallel, an Eddy Current Imager (ECI) has been recently developed in our laboratory in the aim of imaging cracks in metallic structures. In this paper, a simplified modeling of the ECI is presented using DPSM technique, the basics of DPSM formalism being firstly developed. A comparison between experimental and computed data obtained for a millimetric surface defect is presented in

  17. Eddy Current Probe for Surface and Sub-Surface Inspection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2014-01-01

    An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required.

  18. Characterization of Retrogression and Re-Aging Heat Treatment of AA7075-T6 Using Nonlinear Acoustics and Eddy Current

    SciTech Connect

    Ananthula, Rajeshwar; Ko, Ray T.; Sathish, Shamachary; Blodgett, Mark

    2004-02-26

    Nonlinear acoustic parameter and eddy current methods have been utilized to characterize the heat treatment process of retrogression and re-aging of aluminum 7075-T6. The results of nonlinear acoustic parameter measurements show two distinct peaks at 30 minutes and 45 minutes of retrogression time. The phase of the through-thickness eddy current signal shows a minimum at 42 minutes of retrogression time. Application of combined methods for identifying the optimized properties in the material is discussed.

  19. Solar wind eddies and the heliospheric current sheet

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Mccomas, D. J.; Bame, S. J.; Goldstein, B. E.

    1995-01-01

    Ulysses has collected data between 1 and 5 AU during, and just following solar maximum, when the heliospheric current sheet (HCS) can be thought of as reaching its maximum tilt and being subject to the maximum amount of turbulence in the solar wind. The Ulysses solar wind plasma instrument measures the vector velocity and can be used to estimate the flow speed and direction in turbulent 'eddies' in the solar wind that are a fraction of an astronomical unit in size and last (have either a turnover or dynamical interaction time of) several hours to more than a day. Here, in a simple exercise, these solar wind eddies at the HCS are characterized using Ulysses data. This character is then used to define a model flow field with eddies that is imposed on an ideal HCS to estimate how the HCS will be deformed by the flow. This model inherently results in the complexity of the HCS increasing with heliocentric distance, but the result is a measure of the degree to which the observed change in complexity is a measure of the importance of solar wind flows in deforming the HCS. By comparison with randomly selected intervals not located on the HCS, it appears that eddies on the HCS are similar to those elsewhere at this time during the solar cycle, as is the resultant deformation of the interplanetary magnetic field (IMF). The IMF deformation is analogous to what is often termed the 'random walk' of interplanetary magnetic field lines.

  20. Automated Eddy Current Inspection on Space Shuttle Hardware

    NASA Technical Reports Server (NTRS)

    Hartmann, John; Felker, Jeremy

    2007-01-01

    Over the life time of the Space Shuttle program, metal parts used for the Reusable Solid Rocket Motors (RSRMs) have been nondestructively inspected for cracks and surface breaking discontinuities using magnetic particle (steel) and penetrant methods. Although these inspections adequately screened for critical sized cracks in most regions of the hardware, it became apparent after detection of several sub-critical flaws that the processes were very dependent on operator attentiveness and training. Throughout the 1990's, eddy current inspections were added to areas that had either limited visual access or were more fracture critical. In the late 1990's. a project was initiated to upgrade NDE inspections with the overall objective of improving inspection reliability and control. An automated eddy current inspection system was installed in 2001. A figure shows one of the inspection bays with the robotic axis of the system highlighted. The system was programmed to inspect the various case, nozzle, and igniter metal components that make up an RSRM. both steel and aluminum. For the past few years, the automated inspection system has been a part of the baseline inspection process for steel components. Although the majority of the RSRM metal part inventory ts free of detectable surface flaws, a few small, sub-critical manufacturing defects have been detected with the automated system. This paper will summarize the benefits that have been realized with the current automated eddy current system, as well as the flaws that have been detected.

  1. Eddy current characterization of magnetic treatment of materials

    NASA Technical Reports Server (NTRS)

    Chern, E. James

    1992-01-01

    Eddy current impedance measuring methods have been applied to study the effect that magnetically treated materials have on service life extension. Eddy current impedance measurements have been performed on Nickel 200 specimens that have been subjected to many mechanical and magnetic engineering processes: annealing, applied strain, magnetic field, shot peening, and magnetic field after peening. Experimental results have demonstrated a functional relationship between coil impedance, resistance and reactance, and specimens subjected to various engineering processes. It has shown that magnetic treatment does induce changes in a material's electromagnetic properties and does exhibit evidence of stress relief. However, further fundamental studies are necessary for a thorough understanding of the exact mechanism of the magnetic-field processing effect on machine tool service life.

  2. Practical Application of Eddy Currents Generated by Wind

    NASA Astrophysics Data System (ADS)

    Dirba, I.; Kleperis, J.

    2011-06-01

    When a conductive material is subjected to time-varying magnetic fluxes, eddy (Foucault) currents are generated in it and magnetic field of opposite polarity as the applied one arises. Due to the internal resistance of the conductive material, the eddy currents will be dissipated into heat (Joule heating). Conventional domestic water heaters utilize gas burners or electric resistance heating elements to heat the water in the tank and substantial part of the energy to use for it is wasted. In this paper the origin of electromagnetic induction heat generated by wind turbine in special heat exchange camera connected to water boiler is discussed and material evaluation performed using mathematical modelling (comparing the 2D finite element model with analytical and numerical calculation results).

  3. Eddy current analysis of thin film recording heads

    NASA Astrophysics Data System (ADS)

    Shenton, D.; Cendes, Z. J.

    1984-03-01

    Due to inherently thin pole tips which enhance the sharpness of read/write pulses, thin-film magnetic recording heads provide a unique potential for increasing disk file capacity. However, the very feature of these heads which makes them attractive in the recording process, namely, their small size, also makes thin-film heads difficult to study experimentally. For this reason, a finite element simulation of the thin-film head has been developed to provide the magnetic field distribution and the resistance/inductance characteristics of these heads under a variety of conditions. A study based on a one-step multipath eddy current procedure is reported. This procedure may be used in thin film heads to compute the variation of magnetic field with respect to frequency. Computations with the IBM 3370 head show that a large phase shift occurs due to eddy currents in the frequency range 1-10 MHz.

  4. Limitations of eddy current testing in a fast reactor environment

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Bowler, John R.

    2016-02-01

    The feasibility of using eddy current probes for detecting flaws in fast nuclear reactor structures has been investigated with the aim of detecting defects immersed in electrically conductive coolant including under liquid sodium during standby. For the inspections to be viable, there is a need to use an encapsulated sensor system that can be move into position with the aid of visualization tools. The initial objective being to locate the surface to be investigated using, for example, a combination of electromagnetic sensors and sonar. Here we focus on one feature of the task in which eddy current probe impedance variations due to interaction with the external surface of a tube are evaluated in order to monitor the probe location and orientation during inspection.

  5. A magnetic bearing based on eddy-current repulsion

    NASA Technical Reports Server (NTRS)

    Nikolajsen, J. L.

    1987-01-01

    This paper describes a new type of electromagnetic bearing, called the Eddy-Current Bearing, which works by repulsion between fixed AC-electromagnets and a conducting rotor. The following advantages are expected: inherent stability, higher load carrying capacity than DC-electromagnetic bearings, simultaneous radial, angular and thrust support, motoring and generating capability, and backup mode of operation in case of primary power failure. A prototype is under construction.

  6. Eddy current inspection of concrete embedded steel elements

    NASA Astrophysics Data System (ADS)

    Minesawa, G. V.; Sasaki, E.; Miki, C.; Kozaki, K.; Suzuki, K.

    2013-01-01

    The research studies applicability of an Eddy Current NDT inspection method for detection of corrosion in steel structural members including at locations where direct access to the steel element surface is not possible. The method is evaluated by 3D numerical analysis. Parametric study is conducted for selection of appropriate inspection probe parameters. The inspection is applied to inspection of corrosion in areas where H-shaped steel truss elements are passing through RC deck.

  7. Recent Improvements in High-Frequency Eddy Current Conductivity Spectroscopy

    NASA Astrophysics Data System (ADS)

    Abu-Nabah, Bassam A.; Nagy, Peter B.

    2008-02-01

    Due to its frequency-dependent penetration depth, eddy current measurements are capable of mapping near-surface residual stress profiles based on the so-called piezoresistivity effect, i.e., the stress-dependence of electric conductivity. To capture the peak compressive residual stress in moderately shot-peened (Almen 4-8A) nickel-base superalloys, the eddy current inspection frequency has to go as high as 50-80 MHz. Recently, we have reported the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz. Unfortunately, spurious self- and stray-capacitance effects render the complex coil impedance variation with lift-off more nonlinear as the frequency increases, which makes it difficult to achieve accurate apparent eddy current conductivity (AECC) measurements with the standard four-point linear interpolation method beyond 25 MHz. In this paper, we will demonstrate that reducing the coil size reduces its sensitivity to capacitive lift-off variations, which is just the opposite of the better known inductive lift-off effect. Although reducing the coil size also reduces its absolute electric impedance and relative sensitivity to conductivity variations, a smaller coil still yields better overall performance for residual stress assessment. In addition, we will demonstrate the benefits of a semi-quadratic interpolation scheme that, together with the reduced lift-off sensitivity of the smaller probe coil, minimizes and in some cases completely eliminates the sensitivity of AECC measurements to lift-off uncertainties. These modifications allow us to do much more robust measurements up to as high as 80-100 MHz with the required high relative accuracy of +/-0.1%.

  8. Eddy-Current Detection of Cracks in Tubes

    NASA Technical Reports Server (NTRS)

    Parent, R.; Kettering, D.

    1987-01-01

    Nondestructive device tests narrow, sharply-bent metal tubes. Eddycurrent probe detects incipient cracks inside small metal tubes. Tube-centering device consisting of pair of opposed bars ensures tube centered on eddy-current coil. Probe moves along length of bent tube to inspect repeatably for cracks. Compatible with tubes of different cross sections, oval, flattened, square, rectangular,or irregular. Adapts for inspecting formed tubes in petrochemical, automotive, nuclear, and medical equipment.

  9. Performance demonstration requirements for eddy current steam generator tube inspection

    SciTech Connect

    Kurtz, R.J.; Heasler, P.G.; Anderson, C.M.

    1992-10-01

    This paper describes the methodology used for developing performance demonstration tests for steam generator tube eddy current (ET) inspection systems. The methodology is based on statistical design principles. Implementation of a performance demonstration test based on these design principles will help to ensure that field inspection systems have a high probability of detecting and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented. Probability of detection and flaw sizing tests are described.

  10. Subsurface Defect Detection in Metals with Pulsed Eddy Current

    SciTech Connect

    Plotnikov, Yuri A.; Bantz, Walter J.

    2005-04-09

    The eddy current (EC) method is traditionally used for open surface crack detection in metallic components. Subsurface voids in bulk metals can also be detected by the eddy current devices. Taking into consideration the skin effect in conductive materials, a lower frequency of electromagnetic excitation is used for a deeper penetration. A set of special specimens was designed and fabricated to investigate sensitivity to subsurface voids. Typically, flat bottom holes (FBHs) are used for subsurface defect simulation. This approach is not very representative of real defects for eddy current inspection because the FBH depth extends to the bottom of the specimen. Two-layer specimens with finite depth FBHs were fabricated and scanned with conventional EC of variable frequency. Sensitivity and spatial resolution of EC diminish with flaw depth. The pulsed EC approach was applied for flaw detection at variable distance under the surface. The transient response from multi-layer model was derived and compared to experiments. The multi-frequency nature of pulsed excitation provides effective coverage of a thick layer of material in one pass. Challenging aspects of subsurface flaw detection and visualization using the EC technique are discussed.

  11. Comparison of analytical eddy current models using principal components analysis

    NASA Astrophysics Data System (ADS)

    Contant, S.; Luloff, M.; Morelli, J.; Krause, T. W.

    2017-02-01

    Monitoring the gap between the pressure tube (PT) and the calandria tube (CT) in CANDU® fuel channels is essential, as contact between the two tubes can lead to delayed hydride cracking of the pressure tube. Multifrequency transmit-receive eddy current non-destructive evaluation is used to determine this gap, as this method has different depths of penetration and variable sensitivity to noise, unlike single frequency eddy current non-destructive evaluation. An Analytical model based on the Dodd and Deeds solutions, and a second model that accounts for normal and lossy self-inductances, and a non-coaxial pickup coil, are examined for representing the response of an eddy current transmit-receive probe when considering factors that affect the gap response, such as pressure tube wall thickness and pressure tube resistivity. The multifrequency model data was analyzed using principal components analysis (PCA), a statistical method used to reduce the data set into a data set of fewer variables. The results of the PCA of the analytical models were then compared to PCA performed on a previously obtained experimental data set. The models gave similar results under variable PT wall thickness conditions, but the non-coaxial coil model, which accounts for self-inductive losses, performed significantly better than the Dodd and Deeds model under variable resistivity conditions.

  12. Nondestructive Testing Eddy Current Basic Principles RQA/M1-5330.12 (V-I).

    ERIC Educational Resources Information Center

    National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.

    As one in the series of programmed instruction handbooks, prepared by the U.S. space program, home study material is presented in this volume concerning familiarization and orientation on basic eddy current principles. The subject is presented under the following headings: Basic Eddy Current Concepts, Eddy Current Generation and Distribution,…

  13. Separation of conductivity and distance measurements for eddy current nondestructive inspection of graphite composite materials

    NASA Astrophysics Data System (ADS)

    Dufour, Isabelle; Placko, Dominique

    1993-06-01

    This article deals with the study of a process based on the principle of eddy current sensors for the nondestructive evaluation of graphite composite plates. This research has been carried out in the Laboratoire d'Electricitd Signaux et Robotique by the team working on datacollecting sensors for robotics in collaboration with Aerospatiale. Eddy current sensors are characterized by their impedance, which varies when a conducting material is approached in their sensitive area. For a given sensor, the output signal depends directly on the electrical and geometrical properties of the object. In the case discussed here, the interesting data are the distance between the sensor and the object, and its local conductivity. In order to invert the relationships between the sensor signal and the properties of the material, an external parametrical model has been developed. A scanning of the surface with a sensor designed for good spatial resolution measurements gives two accurate maps of the useful data.

  14. Eddy current gauge for monitoring displacement using printed circuit coil

    DOEpatents

    Visioli, Jr., Armando J.

    1977-01-01

    A proximity detection system for non-contact displacement and proximity measurement of static or dynamic metallic or conductive surfaces is provided wherein the measurement is obtained by monitoring the change in impedance of a flat, generally spiral-wound, printed circuit coil which is excited by a constant current, constant frequency source. The change in impedance, which is detected as a corresponding change in voltage across the coil, is related to the eddy current losses in the distant conductive material target. The arrangement provides for considerable linear displacement range with increased accuracies, stability, and sensitivity over the entire range.

  15. An electromagnetic microscope for eddy current evaluation of materials

    SciTech Connect

    Podney, W.N.; Czipott, P.V. )

    1991-03-01

    This paper presents the concept of a new instrument for nondestructive evaluation (NDE). Called an electromagnetic microscope, formed by superconductive microprobes arrayed in parallel rows. When moved over a test piece, the array generates a scanned image of flaws, stress variations, or changes in composition. Each microprobe comprises drive coils a few mm in radius that encircle pickup loops forming a concentric, coplanar gradiometer 1 mm or less in diameter coupled to a superconducting quantum interference device (SQUID). Drive coils transmit an oscillating magnetic field that induces eddy or magnetization currents in conductive or ferromagnetic materials, respectively. The gradiometer senses distortions in paths of induced currents.

  16. Crack detection using pulsed eddy current stimulated thermography

    SciTech Connect

    Kostson, E.; Weekes, B.; Almond, D. P.; Wilson, J.; Tian, G. Y.

    2011-06-23

    This contribution presents results from studies investigating factors that influence the detection of surface breaking cracks using pulsed eddy current thermography. The influences of the current strength and crack orientation in both ferromagnetic and non-ferromagnetic metals have been investigated. It has been found that crack detection is far more sensitive to crack orientation in non-ferromagnetic metals than in ferromagnetic metals. The effects of crack size on detectability are presented for a large number of steel, nickel alloy and titanium samples. Results of studies comparing crack images obtained prior and after coating a nickel alloy sample with a thermal barrier coating are presented.

  17. Advances in Modeling Eddy-Current NDE of Ferromagnetic Bodies

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.

    2003-03-01

    We apply our proprietary volume-integral eddy-current code, VIC-3D©, to the solution of challenging NDE problems that involve ferromagnetic anomalies or workpieces. These include problems with "wear scars and permeable crusts" in steam-generator tubing, characterization of coatings with electrical and magnetic layers, and flaws in ferromagnetic workpieces. Validation of the code by the use of benchmark experiments will also be described. Finally, we will explain the development of the mathematical model in terms of volume-integral equations through the use of Amperian currents for magnetic effects.

  18. Eddy current heating in the cold structure in TPX

    SciTech Connect

    Rodovinsky, A.L.; Pillsbury, R.D. Jr.; Schultz, J.H.; Myatt, R.L.

    1994-09-01

    The toroidal field coil cases and support structure for the TPX are at cryogenic temperatures. The time varying currents In the poloidal field coil system will Induce eddy currents In these structures. The associated Joule dissipation will cause local heating and require heat removal which will show up as a load on the cryogenic system. Knowledge of the heat load distribution in both space and time is important to the design of the system. Analyses have been performed using programs EDDYCUFF and ANSYS and the results presented.

  19. Evaluating passively shielded gradient coil configurations for optimal eddy current compensation

    NASA Astrophysics Data System (ADS)

    Sanchez Lopez, Hector; Poole, Michael; Crozier, Stuart

    2010-05-01

    In magnetic resonance imaging, rapidly switching magnetic fields are used to spatially encode the signal. The temporal change of these fields induces eddy currents in nearby conducting structures of the scanner. These eddy currents, in turn, generate a secondary magnetic field that opposes and distorts the desired gradient field. Eddy current compensation methods are generally applied assuming that the primary and secondary magnetic field gradients possess similar spatial characteristics in the imaging volume (field matching). In this work an optimization method is used to deform the shape of the coil support and/or a highly conductive passive shield in order to improve the field matching and reduce the inductive coupling between the gradient coil and the passive shield. Using the residual field after eddy current compensation as the objective function, the coil support and/or conducting surfaces were deformed to obtain passively shielded x- and z-gradient coils with improved field matching and eddy current compensation. Assuming a single frequency, quasi-static simulation, it was demonstrated that the residual field was reduced up to 24 times by reshaping the coil and passive shield surfaces due to the improved field matching. However, using transient analyses we showed that in the case of the passively shielded x-gradient coil the residual field may only be reduced by five times from a cylindrical coil configuration. A bulge shape is created in the conducting surface as a mechanism of matching the field and at the same time reducing the mutual inductive coupling between the coil and the passive shield. An actively shielded coil with control over the magnetic field produced by the induced current was used as a reference coil that produces the minimal residual field. The actively shielded gradient coil produces minimal residual field for short and long pulses in the transient analyses.

  20. Unsupervised Classification of Surface Defects in Wire Rod Production Obtained by Eddy Current Sensors

    PubMed Central

    Saludes-Rodil, Sergio; Baeyens, Enrique; Rodríguez-Juan, Carlos P.

    2015-01-01

    An unsupervised approach to classify surface defects in wire rod manufacturing is developed in this paper. The defects are extracted from an eddy current signal and classified using a clustering technique that uses the dynamic time warping distance as the dissimilarity measure. The new approach has been successfully tested using industrial data. It is shown that it outperforms other classification alternatives, such as the modified Fourier descriptors. PMID:25938201

  1. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design

    PubMed Central

    Rifai, Damhuji; Abdalla, Ahmed N.; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A.

    2017-01-01

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient. PMID:28335399

  2. An Eddy Current Testing Platform System for Pipe Defect Inspection Based on an Optimized Eddy Current Technique Probe Design.

    PubMed

    Rifai, Damhuji; Abdalla, Ahmed N; Razali, Ramdan; Ali, Kharudin; Faraj, Moneer A

    2017-03-13

    The use of the eddy current technique (ECT) for the non-destructive testing of conducting materials has become increasingly important in the past few years. The use of the non-destructive ECT plays a key role in the ensuring the safety and integrity of the large industrial structures such as oil and gas pipelines. This paper introduce a novel ECT probe design integrated with the distributed ECT inspection system (DSECT) use for crack inspection on inner ferromagnetic pipes. The system consists of an array of giant magneto-resistive (GMR) sensors, a pneumatic system, a rotating magnetic field excitation source and a host PC acting as the data analysis center. Probe design parameters, namely probe diameter, an excitation coil and the number of GMR sensors in the array sensor is optimized using numerical optimization based on the desirability approach. The main benefits of DSECT can be seen in terms of its modularity and flexibility for the use of different types of magnetic transducers/sensors, and signals of a different nature with either digital or analog outputs, making it suited for the ECT probe design using an array of GMR magnetic sensors. A real-time application of the DSECT distributed system for ECT inspection can be exploited for the inspection of 70 mm carbon steel pipe. In order to predict the axial and circumference defect detection, a mathematical model is developed based on the technique known as response surface methodology (RSM). The inspection results of a carbon steel pipe sample with artificial defects indicate that the system design is highly efficient.

  3. Finite element analysis of gradient z-coil induced eddy currents in a permanent MRI magnet.

    PubMed

    Li, Xia; Xia, Ling; Chen, Wufan; Liu, Feng; Crozier, Stuart; Xie, Dexin

    2011-01-01

    In permanent magnetic resonance imaging (MRI) systems, pulsed gradient fields induce strong eddy currents in the conducting structures of the magnet body. The gradient field for image encoding is perturbed by these eddy currents leading to MR image distortions. This paper presents a comprehensive finite element (FE) analysis of the eddy current generation in the magnet conductors. In the proposed FE model, the hysteretic characteristics of ferromagnetic materials are considered and a scalar Preisach hysteresis model is employed. The developed FE model was applied to study gradient z-coil induced eddy currents in a 0.5 T permanent MRI device. The simulation results demonstrate that the approach could be effectively used to investigate eddy current problems involving ferromagnetic materials. With the knowledge gained from this eddy current model, our next step is to design a passive magnet structure and active gradient coils to reduce the eddy current effects.

  4. A tale of two eddies: The biophysical characteristics of two contrasting cyclonic eddies in the East Australian Current System

    NASA Astrophysics Data System (ADS)

    Roughan, M.; Keating, S. R.; Schaeffer, A.; Cetina Heredia, P.; Rocha, C.; Griffin, D.; Robertson, R.; Suthers, I. M.

    2017-03-01

    Mesoscale cyclonic eddies are known to be highly productive. Less well-known are the dynamics and productivity of smaller cyclonic eddies, known as frontal eddies, that form on the landward side of western boundary currents. In this study, we investigate the physical and biogeochemical properties of two contrasting cyclonic eddies in the East Australian Current (EAC). The first ("Murphy"), a mesoscale cyclonic eddy that formed at ˜28°S with a diameter of ˜160 km and high surface chlorophyll-a concentrations, which lived ˜47 days. The second ("Freddy"), a smaller frontal eddy (˜35 km diameter) that formed from a shelf water billow ˜7 days prior to sampling at ˜31.5°S and was advected off the shelf along the EAC front (from ˜200 m to 4000 m of water). Both eddies were at least 1000 m deep with a similar steric height anomaly. We introduce and employ "the method of closest approach" using shipboard ADCP velocities to estimate the eddy centers, which reveals significant tilting through the water column. We estimate rotation rates of 4-10 days and 1-9 days and Rossby numbers 0.25-0.1 and 0.6-0.1, from the surface to 600 m for Murphy and Freddy, respectively. High-resolution altimetry measurements from the SARAL/AltiKA satellite provide estimates of the ageostrophic component of rotation. Our results show that the frontal eddy is significantly more ageostrophic, energetic, and productive than the mesoscale cyclone, despite its small size and short life (˜4 weeks). We suggest that frontal eddies have potential to contribute significantly to the net productivity of the Tasman Sea region.

  5. Numerical analysis of eddy current NDT for a tube with cracks using 3D indirect BIEM

    SciTech Connect

    Lee, H.B.; Kim, D.H.

    1999-09-01

    In this paper, the 3-dimensional indirect boundary integral equation method (BIEM) is applied to the numerical analysis of eddy current non-destructive testing (NDT) for a tube with cracks. The indirect BIEM is developed in terms of the equivalent surface current density and equivalent surface charge density on the interface. The existence and type of the crack in the pipe can be known from the distortion of the magnetic charge density distribution. The impedance signal is calculated from the equivalent surface charge density without calculating the self inductance. The axisymmetric and the 90-degree circular outer crack problems are calculated as an example. The result shows the usage of the indirect BIEM in the area of eddy current NDT.

  6. A Lagrangian approach to the Loop Current eddy separation

    NASA Astrophysics Data System (ADS)

    Andrade-Canto, F.; Sheinbaum, J.; Zavala, L.

    2013-05-01

    Determining when and how a Loop Current eddy (LCE) in the Gulf of Mexico will finally separate is a difficult task, since several detachment re-attachment processes can occur during one of these events. Separation is usually defined based on snapshots of Eulerian fields such as sea surface height (SSH) but here we suggest that a Lagrangian view of the LCE separation process is more appropriate and objective. The basic idea is very simple: separation should be defined whenever water particles from the cyclonic side of the Loop Current move swiftly from the Yucatan Peninsula to the Florida Straits instead of penetrating into the NE Gulf of Mexico. An Eulerian metric is defined, based on the slope of the strain direction of the instantaneous hyperbolic point of the Loop Current anticyclone that provides useful information to forecast final LCE detachments. We highlight cases in which an LCE separation metric based on SSH contours (Leben, 2005) suggests there is a separated LCE that later reattaches, whereas the slope method and the Finite Time Lyapunov Exponent structure indicate the eddy remains dynamically connected to the Loop Current during the process.

  7. A Lagrangian approach to the Loop Current eddy separation

    NASA Astrophysics Data System (ADS)

    Andrade-Canto, F.; Sheinbaum, J.; Zavala Sansón, L.

    2013-01-01

    Determining when and how a Loop Current eddy (LCE) in the Gulf of Mexico will finally separate is a difficult task, since several detachment re-attachment processes can occur during one of these events. Separation is usually defined based on snapshots of Eulerian fields such as sea surface height (SSH) but here we suggest that a Lagrangian view of the LCE separation process is more appropriate and objective. The basic idea is very simple: separation should be defined whenever water particles from the cyclonic side of the Loop Current move swiftly from the Yucatan Peninsula to the Florida Straits instead of penetrating into the NE Gulf of Mexico. The properties of backward-time finite time Lyapunov exponents (FTLE) computed from a numerical model of the Gulf of Mexico and Caribbean Sea are used to estimate the "skeleton" of flow and the structures involved in LCE detachment events. An Eulerian metric is defined, based on the slope of the strain direction of the instantaneous hyperbolic point of the Loop Current anticyclone that provides useful information to forecast final LCE detachments. We highlight cases in which an LCE separation metric based on SSH contours (Leben, 2005) suggests there is a separated LCE that later reattaches, whereas the slope method and FTLE structure indicate the eddy remains dynamically connected to the Loop Current during the process.

  8. Experimental verification of an eddy-current bearing

    NASA Technical Reports Server (NTRS)

    Nikolajsen, Jorgen L.

    1989-01-01

    A new type of electromagnetic bearing was built and tested. It consists of fixed AC-electromagnets in a star formation surrounding a conducting rotor. The bearing works by repulsion due to eddy-currents induced in the rotor. A single bearing is able to fully support a short rotor. The rotor support is inherently stable in all five degrees of freedom. No feedback control is needed. The bearing is also able to accelerate the rotor up to speed and decelerate the rotor back to standstill. The bearing design and the experimentation to verify its capabilities are described.

  9. Eddy-current transducer based on flat spiral coils

    SciTech Connect

    Franyuk, V.A.; Ivan'kovich, L.F.

    1988-12-01

    The article deals with the experimental investigation of flat-coil eddy current transducers with spiral windings. It is shown that it is possible to use them for detecting discontinuities on electrically conducting products with different configuration of the surface. The instrument is described. The use of crossed flat coils makes it possible effectively to detect flaws in electrically conducting products of any shape. A transducer containing crossed flat coils helps, in addition to detecting flaws, in evaluating anisotropy (magnetic and mechanical) from which conclusions as to the physicomechanical properties of the product can be drawn.

  10. Assessing thermal barrier coatings by eddy-current inversion

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Sabbagh, Elias H.; Kim Murphy, R.; Nyenhuis, John

    2002-05-01

    The nondestructive evaluation (NDE) of high-temperature coatings is one of the important factors in achieving a high level of structural integrity in advanced gas turbines. In this paper, we demonstrate that sophisticated eddy-current techniques can be utilized to measure the thickness and remaining-life of high-temperature coatings. We discuss the difficult in-service case, in which the time-temperature exposure of the combustion turbine blade has created a four-layered system, in addition to the base metal.

  11. A Model for Axial Magnetic Bearings Including Eddy Currents

    NASA Technical Reports Server (NTRS)

    Kucera, Ladislav; Ahrens, Markus

    1996-01-01

    This paper presents an analytical method of modelling eddy currents inside axial bearings. The problem is solved by dividing an axial bearing into elementary geometric forms, solving the Maxwell equations for these simplified geometries, defining boundary conditions and combining the geometries. The final result is an analytical solution for the flux, from which the impedance and the force of an axial bearing can be derived. Several impedance measurements have shown that the analytical solution can fit the measured data with a precision of approximately 5%.

  12. Methods of and apparatus for levitating an eddy current probe

    DOEpatents

    Stone, William J.

    1988-05-03

    An eddy current probe is supported against the force of gravity with an air earing while being urged horizontally toward the specimen being examined by a spring and displaced horizontally against the force of the spring pneumatically. The pneumatic displacement is accomplished by flowing air between a plenum chamber fixed with respect to the probe and the surface of the specimen. In this way, the surface of the specimen can be examined without making mechanical contact therewith while precisely controlling the distance at which the probe stands-off from the surface of the specimen.

  13. Eddy current system for inspection of train hollow axles

    NASA Astrophysics Data System (ADS)

    Chady, Tomasz; Psuj, Grzegorz; Sikora, Ryszard; Kowalczyk, Jacek; Spychalski, Ireneusz

    2014-02-01

    The structural integrity of wheelsets used in rolling stock is of great importance to the safety. In this paper, electromagnetic system with an eddy current transducer suitable for the inspection of hollow axles have been presented. The transducer was developed to detect surface braking defects having depth not smaller than 0.5 mm. Ultrasound technique can be utilized to inspect the whole axle, but it is not sufficiently sensitive to shallow defects located close to the surface. Therefore, the electromagnetic technique is proposed to detect surface breaking cracks that cannot be detected by ultrasonic technique.

  14. Eddy current system for inspection of train hollow axles

    SciTech Connect

    Chady, Tomasz; Psuj, Grzegorz; Sikora, Ryszard; Kowalczyk, Jacek; Spychalski, Ireneusz

    2014-02-18

    The structural integrity of wheelsets used in rolling stock is of great importance to the safety. In this paper, electromagnetic system with an eddy current transducer suitable for the inspection of hollow axles have been presented. The transducer was developed to detect surface braking defects having depth not smaller than 0.5 mm. Ultrasound technique can be utilized to inspect the whole axle, but it is not sufficiently sensitive to shallow defects located close to the surface. Therefore, the electromagnetic technique is proposed to detect surface breaking cracks that cannot be detected by ultrasonic technique.

  15. Vacuum chamber eddy current correction coil for the AGS Booster

    SciTech Connect

    Danby, G.; Jackson, J.

    1988-01-01

    The AGS Booster injector will perform a variety of functions. Heavy ion acceleration requires a bakeable, ultra-high vacuum system (VC). Acceleration for intense proton beams requires rapid cycling (B /preceq/ 10T/sec). If straight forward heavy walled VC are used, the field perturbations due to eddy currents are large. The state of the art lattice has highly distributed lumped sextupoles capable of substantially correcting the induced field nonlinearity. Nevertheless, for the very highest space charge-intensity limits, it is desirable to have the capability to remove eddy current fields at the source. Correction coils attached to the outside of the VC cancel its current aberrations over the required good field aperture. These can be passively powered by transformer action, using two turn windings around the magnet yoke. Programmed power supplies can also be used. This inexpensive additional correction option uses a three turn per quadrant coil which follows the local contour of the VC. Transverse movements of several mms of the VC will have no beam optical effect since the large field aberrations and their corrections have the same displaced coordinates. Experimental and computer studies will be presented, as well as mechanical and electrical design of a simple method of construction. 6 figs.

  16. Eddy surface properties and propagation at Southern Hemisphere western boundary current systems

    NASA Astrophysics Data System (ADS)

    Pilo, G. S.; Mata, M. M.; Azevedo, J. L. L.

    2015-08-01

    Oceanic eddies exist throughout the world oceans, but are more energetic when associated with western boundary currents (WBC) systems. In these regions, eddies play an important role in mixing and energy exchange. Therefore, it is important to quantify and qualify eddies associated with these systems. This is particularly true for the Southern Hemisphere WBC system where only few eddy censuses have been performed to date. In these systems, important aspects of the local eddy population are still unknown, like their spatial distribution and propagation patterns. Moreover, the understanding of these patterns helps to establish monitoring programs and to gain insight in how eddies would affect local mixing. Here, we use a global eddy data set to qualify eddies based on their surface characteristics in the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) systems. The analyses reveal that eddy propagation within each system is highly forced by the local mean flow and bathymetry. Large values of eddy amplitude and temporal variability are associated with the BC and EAC retroflections, while small values occur in the centre of the Argentine Basin and in the Tasman Sea. In the AC system, eddy polarity dictates the propagation distance. BC system eddies do not propagate beyond the Argentine Basin, and are advected by the local ocean circulation. EAC system eddies from both polarities cross south of Tasmania but only the anticyclonic ones reach the Great Australian Bight. For all three WBC systems, both cyclonic and anticyclonic eddies present a geographical segregation according to radius size and amplitude. Regions of high eddy kinetic energy are associated with the eddies' mean amplitudes, and not with their densities.

  17. Pattern recognition approaches for the detection and characterization of discontinuities by eddy current testing

    SciTech Connect

    Shyamsunder, M.T.; Rajagopalan, C.; Raj, B.; Dewangan, S.K.; Rao, B.P.C.; Ray, K.K.

    2000-01-01

    Eddy current signals (ECS) generated under varied experimental conditions from different types of discontinuities like partial/through thickness holes and notches of various dimensions, fatigue cracks, stress corrosion cracks, etc. in AISI type 316 stainless steel sheets/plates have been analyzed using pattern recognition (PR) approaches to understand their quality of performance for detection and characterization of several aspects of the discontinuities. The PR analyses have been carried out using linear discriminant (LD), minimum distance (MD), empirical Bayesian (EB) and K-nearest neighbor (KNN) statistical classifiers, and multilayered perceptron (MLP) and Kohonen's artificial neural network (KANN). The MLP approach has been extended to eddy current images also to achieve deblurring. The practical feasibility and application potential of ANNs is demonstrated through a case study on nuclear fuel cladding tubes where both the online and the offline approaches have been implemented.

  18. Tone burst eddy current thermography for estimation of corrosion defects in aircraft components

    NASA Astrophysics Data System (ADS)

    Libin, M. N.; Balasubramaniam, Krishnan; Krishnamurthy, C. V.; Engelbart, Roger

    2012-05-01

    Tone Burst Eddy Current Thermography (TBET) technique was used for the evaluation of corrosion type damage in Aluminum plate like structures. Both flat and curved components were considered. The effect of the parameters affecting the eddy current generation of head in the metal, including excitation frequency, electrical conductivity, standoff distances, etc were considered in optimizing the heat generation. The thermal diffusivity and thickness of the metal structure were considered while selecting the detection of the signal using a thermal sensitive IR Camera. The experiments were conducted using test samples that had simulated defects with different wall thickness losses. The experiments were supported by a multiphysics 3D Finite Element Model (FEM) using COMSOL. The results were compared with the experimental results. It was determined that this technique has some advantages for the inspection aircraft structural components compared to other modalities, particularly in curved regions.

  19. Detection of Real Flaw using Uniform Eddy Current Multi-probe

    NASA Astrophysics Data System (ADS)

    Fukuoka, Katsuhiro; Hashimoto, Mitsuo

    The establishment of the nondestructive inspection technology with plant structures has been stimulated by the recent occurrence of cracks in the nuclear power plant structures. In this research, a uniform eddy current multi-probe to apply to the complex structure and inspect the cracks at high-speed data acquisition was developed. Pick-up coils of the developed probe were arranged on a flexible printed circuit board. This probe was able to obtain clear signal for an EDM (electro-discharge machining) slit with 0.5 mm depth and distinguish EDM slits arranged at 2 mm intervals. It was confirmed that the SCC (stress corrosion cracking) of real flaw was able to be detected with developed uniform eddy current multi-probe by using the ferrite core for the exciting coil and considering the impedance matching of the exciting coil and the flaw detection device.

  20. New Eddy Current Probe for Thickness Gauging of Conductive Materials

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Namkung, Min

    1993-01-01

    The accurate measure of material thickness is important for many non-destructive evaluation applications. Factors such as corrosion damage can jeopardize structural integrity through material thinning and process control considerations often mandate strict limits on material dimensions. Access to the material under test can be limited to a single side and large areas may need to be examined in a small time period. In an effort to enhance the effectiveness of material thickness measurements a flux focusing eddy current probe has been developed at NASA Langley Research Center. The probe provides an accurate measure of the thickness of conducting materials from a single sided measurement. It is straight forward to use and can be easily automated for production line testing. The probe also requires only minimal instrumentation and power so that extremely portable units can be manufactured at a low cost. This new eddy current probe has been used to accurately measure the thickness of aluminum alloy plates with a resolution of greater than 0.001 in. (25 microns). Simulated corrosion damage has also been detected on both single layer and multi-layer samples. The present work will explain the output voltage dependence of the device as a function of material thickness and present experimental results for thickness gauging and corrosion detection.

  1. Multiple sensor multifrequency eddy current monitor for solidification and growth

    NASA Technical Reports Server (NTRS)

    Wallace, John

    1990-01-01

    A compact cylindrical multisensor eddy current measuring system with integral furnace was develop to monitor II-VI crystal growth to provide interfacial information, solutal segregation, and conductivities of the growth materials. The use of an array of sensors surrounding the furnace element allows one to monitor the volume of interest. Coupling these data with inverse multifrequency analysis allows radial conductivity profiles to be generated at each sensor position. These outputs were incorporated to control the processes within the melt volume. The standard eddy current system functions with materials whose electric conductivities are as low as 2E2 Mhos/m. A need was seen to extend the measurement range to poorly conducting media so the unit was modified to allow measurement of materials conductivities 4 order of magnitude lower and bulk dielectric properties. Typically these included submicron thick films and semiinsulating GaAs. This system was used to monitor complex heat transfer in grey bodies as well as semiconductor and metallic solidification.

  2. Optimization design of the coil of the eddy current sensor

    NASA Astrophysics Data System (ADS)

    Pu, Tiecheng; Fan, Shangchun

    2006-11-01

    An eddy current sensor is usually used to measure the departure of a shaft from its axes, in order to avoid destroying the system because of collision. The design of the coil as the sense organ of an eddy current sensor is to search a set of proper sizes (includes the outer radius, the inner radius and tallness of the coil) in which the quality factor and the grads of magnetic field strength is great as soon as possible but the length of the lead is not much long. So an optimization function is introduced here for efficient design. This function is direct ratio with the quality factor of the core and the magnetic grads product by the coil and inverse ratio with the lead length. The proportions of three parameters can be changed according to the instance. When the value of the function reaches the maximum, the sizes of coil are the anticipant optimal sizes and the integration capability of the coil is at the high-point. To search the maximum of the function, the genetic algorithm is adopted. The simulation result by Matlab proves the practicability of the method.

  3. Anomalous diffusion of electromagnetic eddy currents in geological formations

    NASA Astrophysics Data System (ADS)

    Weiss, Chester J.; Everett, Mark E.

    2007-08-01

    Controlled-source electromagnetic (EM) induction in some geological formations is shown here to be compactly described by an anomalous subdiffusion process. Such a process, which is not universal, is governed by a fractional diffusion equation or alternatively the convolutional form of Ohm's law. A subdiffusing eddy current vortex, or electromagnetic smoke ring, propagates in such a way that its position of median intensity overruns its position of peak intensity. This behavior is not allowed in classical diffusion but is a simple consequence of diffusion within a stationary fractal medium. A similar analysis has been applied to understand heavy-tailed traveltime distributions that appear in certain hydrological time series. The tell-tale signature of anomalous electromagnetic diffusion is a slope β of the magnetic zero-crossing moveout curve that is constant with transmitter-receiver (RX) offset and significantly different from unity. Neither lateral heterogeneity nor unixial anisotropy can generate such a constant-slope moveout curve with an economy of model parameters. Controlled-source EM data from two sites in Texas and one in New Mexico are used in this study to test the eddy current subdiffusion hypothesis.

  4. Bayesian flaw characterization from eddy current measurements with grain noise

    NASA Astrophysics Data System (ADS)

    McMahan, Jerry A.; Aldrin, John C.; Shell, Eric; Oneida, Erin

    2017-02-01

    The Bayesian approach to inference from measurement data has the potential to provide highly reliable characterizations of flaw geometry by quantifying the confidence in the estimate results. The accuracy of these confidence estimates depends on the accuracy of the model for the measurement error. Eddy current measurements of electrically anisotropic metals, such as titanium, exhibit a phenomenon called grain noise in which the measurement error is spatially correlated even with no flaw present. We show that the most commonly used statistical model for the measurement error, which fails to account for this correlation, results in overconfidence in the flaw geometry estimates from eddy current data, thereby reducing the effectiveness of the Bayesian approach. We then describe a method of modeling the grain noise as a Gaussian process (GP) using spectral mixture kernels, a type of non-parametric model for the covariance kernel of a GP This provides a broadly applicable, data-driven way of modeling correlation in measurement error. Our results show that incorporation of this noise model results in a more reliable estimate of the flaw and better agreement with the available validation data.

  5. Behavior of an eddy-current magnetic bearing

    SciTech Connect

    Ting Leehua.

    1991-01-01

    The perturbation method (PM) in conjunction with the symbolic computing software MATHEMATICA' is employed to solve Maxwell's equations to obtain the theoretical results of forces, stiffness, and damping coefficients for a simplified eddy current magnetic bearing (ECMB). In addition, a finite element method software FLUX2D' and some deliberately designed experiments are employed to check some of the results obtained by the perturbation method. Finally, the results are used to evaluate the dynamic behavior of the ECMB, and are extended to conjecture concerning the prospect of a similar application, Maglev (Magnetically Levitated High-Speed Trains). The theoretical results of forces, stiffness, and damping coefficients obtained by the perturbation method show that such kind of bearing has extremely low damping, probably negative, and moderately low stiffness and forces, compared to ordinary bearings. Data are also obtained by inputting the presumed Maglev features to the perturbation method solutions. It is found that the eddy current type magnetic suspension is more practical in the large scale application (Maglev) than in small scale application (ECMB).

  6. Design and optimization of a flexible arrayed eddy current sensor

    NASA Astrophysics Data System (ADS)

    Sun, Zhenguo; Cai, Dong; Zou, Cheng; Zhang, Wenzeng; Chen, Qiang

    2017-04-01

    The inspection of the hollow axle inner surfaces is a key process to guarantee the safety of high-speed trains. A novel flexible arrayed eddy current sensor was developed to improve the reliability of the non-destructive testing of the hollow axle inner surfaces, whose main innovative aspect was the new design of excitation/sensing traces to achieve a differential and arrayed configuration. Only two independent excitation traces were used in the sensor to induce eddy currents, which can be detected by 16 differential sensing elements. The lift-off effects and the influence of the excitation frequency and geometrical parameters of the proposed sensor was investigated and presented in this paper. Finite element models were built to analyze the effects of each parameter on the sensor response amplitude. Experimental validations were conducted using a representative set of sensors. Results from experiments and simulations were consistent with each other, which showed that the sensor design can substantially suppress the lift-off effects and modifications of the studied parameters can substantially improve the sensor performance.

  7. Effects of eddy currents on selective spectral editing experiments at 3T.

    PubMed

    Oeltzschner, Georg; Snoussi, Karim; Puts, Nicolaas A; Mikkelsen, Mark; Harris, Ashley D; Pradhan, Subechhya; Tsapkini, Kyrana; Schär, Michael; Barker, Peter B; Edden, Richard A E

    2017-07-22

    To investigate frequency-offset effects in edited magnetic resonance spectroscopy (MRS) experiments arising from B0 eddy currents. Macromolecule-suppressed (MM-suppressed) γ-aminobutyric acid (GABA)-edited experiments were performed at 3T. Saturation-offset series of MEGA-PRESS experiments were performed in phantoms, in order to investigate different aspects of the relationship between the effective editing frequencies and eddy currents associated with gradient pulses in the sequence. Difference integrals were quantified for each series, and the offset dependence of the integrals was analyzed to quantify the difference in frequency (Δf) between the actual vs. nominal expected saturation frequency. Saturation-offset N-acetyl-aspartate-phantom experiments show that Δf varied with voxel orientation, ranging from 10.4 Hz (unrotated) to 6.4 Hz (45° rotation about the caudal-cranial axis) and 0.4 Hz (45° rotation about left-right axis), indicating that gradient-related B0 eddy currents vary with crusher-gradient orientation. Fixing the crusher-gradient coordinate-frame substantially reduced the orientation dependence of Δf (to ∼2 Hz). Water-suppression crusher gradients also introduced a frequency offset, with Δf = 0.6 Hz ("excitation" water suppression), compared to 10.2 Hz (no water suppression). In vivo spectra showed a negative edited "GABA" signal, suggesting Δf on the order of 10 Hz; with fixed crusher-gradient coordinate-frame, the expected positive edited "GABA" signal was observed. Eddy currents associated with pulsed field gradients may have a considerable impact on highly frequency-selective spectral-editing experiments, such as MM-suppressed GABA editing at 3T. Careful selection of crusher gradient orientation may ameliorate these effects. 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017;00:000-000. © 2017 International Society for Magnetic Resonance in Medicine.

  8. Eddy current probe with foil sensor mounted on flexible probe tip and method of use

    DOEpatents

    Viertl, John R. M.; Lee, Martin K.

    2001-01-01

    A pair of copper coils are embedded in the foil strip. A first coil of the pair generates an electromagnetic field that induces eddy currents on the surface, and the second coil carries a current influenced by the eddy currents on the surface. The currents in the second coil are analyzed to obtain information on the surface eddy currents. An eddy current probe has a metal housing having a tip that is covered by a flexible conductive foil strip. The foil strip is mounted on a deformable nose at the probe tip so that the strip and coils will conform to the surface to which they are applied.

  9. Plankton dynamics in a cyclonic eddy in the Southern California Current System

    NASA Astrophysics Data System (ADS)

    Chenillat, Fanny; Franks, Peter J. S.; Rivière, Pascal; Capet, Xavier; Grima, Nicolas; Blanke, Bruno

    2015-08-01

    The California Current System is an eastern boundary upwelling system (EBUS) with high biological production along the coast. Oligotrophic offshore waters create cross-shore gradients of biological and physical properties, which are affected by intense mesoscale eddy activity. The influence of eddies on ecosystem dynamics in EBUS is still in debate. To elucidate the mechanisms that influence the dynamics of ecosystems trapped in eddies, and the relative contribution of horizontal and vertical advection in determining local production, we analyze a particular cyclonic eddy using Lagrangian particle-tracking analyses of numerical Eulerian. The eddy formed in a coastal upwelling system; coastal waters trapped in the eddy enabled it to leave the upwelling region with high concentrations of plankton and nutrients. The ecosystem was initially driven mainly by recycling of biological material. As the eddy moved offshore, production in its core was enhanced compared to eddy exterior waters through Ekman pumping of nitrate from below the euphotic zone; this Ekman pumping was particularly effective due to the shallow nitracline in the eddy compared to eddy exterior waters. Both eddy trapping and Ekman pumping helped to isolate and maintain the ecosystem productivity in the eddy core. This study shows the importance of cyclonic eddies for biological production in EBUS: they contribute both to the redistribution of the coastal upwelling ecosystem and are local regions of enhanced new production. Together, these processes impact cross-shore gradients of important biological properties.

  10. Flaws Identification Using Eddy Current Differential Transducer and Artificial Neural Networks

    SciTech Connect

    Chady, T.; Lopato, P.

    2006-03-06

    In this paper we present a multi-frequency excitation eddy current differential transducer and dynamic neural models which were used to detect and identify artificial flaws in thin conducting plates. Plates are made of Inconel600. EDM notches have relative depth from 10% to 80% and length from 2 mm to 7 mm. All flaws were located on the opposite surface of the examined specimen. Measured signals were used as input for training and verifying dynamic neural networks with a moving window. Wide range of ANN (Artificial Neural Network) structures are examined for different window length and different number of frequency components in excitation signal. Observed trends are presented in this paper.

  11. Inverse problem in nondestructive testing using arrayed eddy current sensors.

    PubMed

    Zaoui, Abdelhalim; Menana, Hocine; Feliachi, Mouloud; Berthiau, Gérard

    2010-01-01

    A fast crack profile reconstitution model in nondestructive testing is developed using an arrayed eddy current sensor. The inverse problem is based on an iterative solving of the direct problem using genetic algorithms. In the direct problem, assuming a current excitation, the incident field produced by all the coils of the arrayed sensor is obtained by the translation and superposition of the 2D axisymmetric finite element results obtained for one coil; the impedance variation of each coil, due to the crack, is obtained by the reciprocity principle involving the dyadic Green's function. For the inverse problem, the surface of the crack is subdivided into rectangular cells, and the objective function is expressed only in terms of the depth of each cell. The evaluation of the dyadic Green's function matrix is made independently of the iterative procedure, making the inversion very fast.

  12. Finite element modeling of pulsed eddy current NDT phenomena

    SciTech Connect

    Allen, B.; Ida, N.; Lord, W.

    1985-05-15

    Transient fields for nondestructive testing (pulsed eddy current methods) have been used experimentally for such applications as coating thickness measurements and the inspection of reactor fuel tubing. The lack of suitable models to facilitate understanding of the interaction of the pulsed field with the test specimen has hindered a wider acceptance of the method as a tool in NDT. Two models, based on the finite element technique are described. The first model, used for repetitive pulse train sources makes use of the Fourier series of the source current to solve a steady state problem for each significant harmonic. The harmonic solutions are then summed to produce the total EMF in the pickup coil. The second model is used for single pulse application. The response is calculated using an iterative time stepping solution. In both cases axisymmetric geometries are studied using a magnetic vector potential formulation. Solutions are compared with experimental results. 3 refs., 3 figs.

  13. A comparison of the structure, properties, and water mass composition of quasi-isotropic eddies in western boundary currents in an eddy-resolving ocean model

    NASA Astrophysics Data System (ADS)

    Rykova, Tatiana; Oke, Peter R.; Griffin, David A.

    2017-06-01

    Using output from a near-global eddy-resolving ocean model, we analyse the properties and characteristics of quasi-isotropic eddies in five Western Boundary Current (WBC) regions, including the extensions of the Agulhas, East Australian Current (EAC), Brazil-Malvinas Confluence (BMC), Kuroshio and Gulf Stream regions. We assess the model eddies by comparing to satellite and in situ observations, and show that most aspects of the model's representation of eddies are realistic. We find that the mean eddies differ dramatically between these WBC regions - all with some unique and noteworthy characteristics. We find that the vertical displacement of isopycnals of Agulhas eddies is the greatest, averaging 350-450 m at depths of over 800-900 m. EAC (BMC) eddies are the least (most) barotropic, with only 50% (85-90%) of the velocity associated with the barotropic mode. Kuroshio eddies are the most stratified, resulting in small isopycnal displacement, even for strong eddies; and Gulf Stream eddies carry the most heat. Despite their differences, we explicitly show that the source waters for anticyclonic eddies are a mix of the WBC water (from the boundary current itself) and water that originates equatorward of the WBC eddy-field; and cyclonic eddies are a mix of WBC water and water that originates poleward of the WBC eddy-field.

  14. Preliminary Investigations of Eddy Current Effects on a Spinning Disk

    SciTech Connect

    Piggott, W T; Walston, S; Mayhall, D

    2006-09-08

    The design of the positron source target for the International Linear Collider (ILC) envisions a Ti6Al4V wheel rotating in a large magnetic field (5-10 Tesla) being impacted by a photon beam to produce positrons. One of the many challenges for this system is determining how large a motor will be needed to spin the shaft. The wheel spinning in the magnetic field induces an eddy current in the wheel, which retards the spinning motion of the wheel. Earlier calculations by Mayhall [1] have shown that those eddy forces could be quite large, and resulted in the preliminary design being moved from a solid disk to a rim and spoke design, as shown in Figure 1. A series of experiments with a spinning metal disk were run at the Stanford Linear Accelerator Center (SLAC) to provide experimental validation of the Maxwell 3D simulations. This report will give a brief outline of the experimental setup and results. In addition, earlier work by Smythe [2] will be used to compare with the experimental results.

  15. Non-destructive testing of composite materials used in military applications by eddy current thermography method

    NASA Astrophysics Data System (ADS)

    Swiderski, Waldemar

    2016-10-01

    Eddy current thermography is a new NDT-technique for the detection of cracks in electro conductive materials. It combines the well-established inspection techniques of eddy current testing and thermography. The technique uses induced eddy currents to heat the sample being tested and defect detection is based on the changes of induced eddy currents flows revealed by thermal visualization captured by an infrared camera. The advantage of this method is to use the high performance of eddy current testing that eliminates the known problem of the edge effect. Especially for components of complex geometry this is an important factor which may overcome the increased expense for inspection set-up. The paper presents the possibility of applying eddy current thermography method for detecting defects in ballistic covers made of carbon fiber reinforced composites used in the construction of military vehicles.

  16. The eddy current probe array for Keda Torus eXperiment

    NASA Astrophysics Data System (ADS)

    Li, Zichao; Li, Hong; Tu, Cui; Hu, Jintong; You, Wei; Luo, Bing; Tan, Mingsheng; Adil, Yolbarsop; Wu, Yanqi; Shen, Biao; Xiao, Bingjia; Zhang, Ping; Mao, Wenzhe; Wang, Hai; Wen, Xiaohui; Zhou, Haiyang; Xie, Jinlin; Lan, Tao; Liu, Adi; Ding, Weixing; Xiao, Chijin; Liu, Wandong

    2016-11-01

    In a reversed field pinch device, the conductive shell is placed as close as possible to the plasma so as to balance the plasma during discharge. Plasma instabilities such as the resistive wall mode and certain tearing modes, which restrain the plasma high parameter operation, respond closely with conditions in the wall, in essence the eddy current present. Also, the effect of eddy currents induced by the external coils cannot be ignored when active control is applied to control instabilities. One diagnostic tool, an eddy current probe array, detects the eddy current in the composite shell. Magnetic probes measuring differences between the inner and outer magnetic fields enable estimates of the amplitude and angle of these eddy currents. Along with measurements of currents through the copper bolts connecting the poloidal shield copper shells, we can obtain the eddy currents over the entire shell. Magnetic field and eddy current resolutions approach 2 G and 6 A, respectively. Additionally, the vortex electric field can be obtained by eddy current probes. As the conductivity of the composite shell is high, the eddy current probe array is very sensitive to the electric field and has a resolution of 0.2 mV/cm. In a bench test experiment using a 1/4 vacuum vessel, measurements of the induced eddy currents are compared with simulation results based on a 3D electromagnetic model. The preliminary data of the eddy currents have been detected during discharges in a Keda Torus eXperiment device. The typical value of toroidal and poloidal eddy currents across the magnetic probe coverage rectangular area could reach 3.0 kA and 1.3 kA, respectively.

  17. The eddy current probe array for Keda Torus eXperiment.

    PubMed

    Li, Zichao; Li, Hong; Tu, Cui; Hu, Jintong; You, Wei; Luo, Bing; Tan, Mingsheng; Adil, Yolbarsop; Wu, Yanqi; Shen, Biao; Xiao, Bingjia; Zhang, Ping; Mao, Wenzhe; Wang, Hai; Wen, Xiaohui; Zhou, Haiyang; Xie, Jinlin; Lan, Tao; Liu, Adi; Ding, Weixing; Xiao, Chijin; Liu, Wandong

    2016-11-01

    In a reversed field pinch device, the conductive shell is placed as close as possible to the plasma so as to balance the plasma during discharge. Plasma instabilities such as the resistive wall mode and certain tearing modes, which restrain the plasma high parameter operation, respond closely with conditions in the wall, in essence the eddy current present. Also, the effect of eddy currents induced by the external coils cannot be ignored when active control is applied to control instabilities. One diagnostic tool, an eddy current probe array, detects the eddy current in the composite shell. Magnetic probes measuring differences between the inner and outer magnetic fields enable estimates of the amplitude and angle of these eddy currents. Along with measurements of currents through the copper bolts connecting the poloidal shield copper shells, we can obtain the eddy currents over the entire shell. Magnetic field and eddy current resolutions approach 2 G and 6 A, respectively. Additionally, the vortex electric field can be obtained by eddy current probes. As the conductivity of the composite shell is high, the eddy current probe array is very sensitive to the electric field and has a resolution of 0.2 mV/cm. In a bench test experiment using a 1/4 vacuum vessel, measurements of the induced eddy currents are compared with simulation results based on a 3D electromagnetic model. The preliminary data of the eddy currents have been detected during discharges in a Keda Torus eXperiment device. The typical value of toroidal and poloidal eddy currents across the magnetic probe coverage rectangular area could reach 3.0 kA and 1.3 kA, respectively.

  18. Correction for Eddy Current-Induced Echo-Shifting Effect in Partial-Fourier Diffusion Tensor Imaging.

    PubMed

    Truong, Trong-Kha; Song, Allen W; Chen, Nan-Kuei

    2015-01-01

    In most diffusion tensor imaging (DTI) studies, images are acquired with either a partial-Fourier or a parallel partial-Fourier echo-planar imaging (EPI) sequence, in order to shorten the echo time and increase the signal-to-noise ratio (SNR). However, eddy currents induced by the diffusion-sensitizing gradients can often lead to a shift of the echo in k-space, resulting in three distinct types of artifacts in partial-Fourier DTI. Here, we present an improved DTI acquisition and reconstruction scheme, capable of generating high-quality and high-SNR DTI data without eddy current-induced artifacts. This new scheme consists of three components, respectively, addressing the three distinct types of artifacts. First, a k-space energy-anchored DTI sequence is designed to recover eddy current-induced signal loss (i.e., Type 1 artifact). Second, a multischeme partial-Fourier reconstruction is used to eliminate artificial signal elevation (i.e., Type 2 artifact) associated with the conventional partial-Fourier reconstruction. Third, a signal intensity correction is applied to remove artificial signal modulations due to eddy current-induced erroneous T2(∗) -weighting (i.e., Type 3 artifact). These systematic improvements will greatly increase the consistency and accuracy of DTI measurements, expanding the utility of DTI in translational applications where quantitative robustness is much needed.

  19. Eddy current testing, an emerging NDT method for ferritic weld inspection

    SciTech Connect

    Goldberg, L.O.

    1998-02-01

    This article discusses the emergence and acceptance of manual eddy current weld inspection as a high quality and cost saving NDT method for in-service inspections. In a recent American Welding Society journal article on NDT, eddy current testing was not mentioned as a basic weld inspection method. In fact, it has become common in the European sector, and American oil and gas companies are now beginning to use eddy current. In this month`s column, the author compares the use of eddy current testing and magnetic particle testing (MT) for ferritic weld inspection.

  20. Eddy Current Examination of Spent Nuclear Fuel Canister Closure Welds

    SciTech Connect

    Arthur D. Watkins; Dennis C. Kunerth; Timothy R. McJunkin

    2006-04-01

    The National Spent Nuclear Fuel Program (NSNFP) has developed standardized DOE SNF canisters for handling and interim storage of SNF at various DOE sites as well as SNF transport to and SNF handling and disposal at the repository. The final closure weld of the canister will be produced remotely in a hot cell after loading and must meet American Society of Mechanical Engineers (ASME) Section III, Division 3 code requirements thereby requiring volumetric and surface nondestructive evaluation to verify integrity. This paper discusses the use of eddy current testing (ET) to perform surface examination of the completed welds and repair cavities. Descriptions of integrated remote welding/inspection system and how the equipment is intended function will also be discussed.

  1. Surface Characterization of Stainless Steel Part by Eddy Current

    SciTech Connect

    Andersen, Eric S.; Hockey, Ronald L.; Prince, James M.; Good, Morris S.

    2003-10-01

    The Pacific Northwest National Laboratory (PNNL) has nearly a 40 year history of research and development in the field of nondestructive evaluation (NDE). One area of NDE expertise at PNNL is electromagnetic testing which includes a field of eddy current testing (ET). One benefit is that ET can typically be performed at high speeds, and as a result has found many applications in process monitoring and poduction lines. ET has been used in the nuclear, aerospace, and automotive industries for many years. Et technology lends itself well to the detection of near-surface or surface breaking defects such as surface scratches. This paper provides an overview of theory regarding the usage of ET, selected application studies performed by PNNL, a safety analysis, and a wrtie up pertaining to the operations of ET to detect surface scratches.

  2. Computer programs for eddy-current defect studies

    SciTech Connect

    Pate, J. R.; Dodd, C. V.

    1990-06-01

    Several computer programs to aid in the design of eddy-current tests and probes have been written. The programs, written in Fortran, deal in various ways with the response to defects exhibited by four types of probes: the pancake probe, the reflection probe, the circumferential boreside probe, and the circumferential encircling probe. Programs are included which calculate the impedance or voltage change in a coil due to a defect, which calculate and plot the defect sensitivity factor of a coil, and which invert calculated or experimental readings to obtain the size of a defect. The theory upon which the programs are based is the Burrows point defect theory, and thus the calculations of the programs will be more accurate for small defects. 6 refs., 21 figs.

  3. Development of eddy current probes based on magnetoresistive sensors arrays

    NASA Astrophysics Data System (ADS)

    Sergeeva-Chollet, N.; Decitre, J.-M.; Fermon, C.; Pelkner, M.; Reimund, V.; Kreutzbruck, M.

    2014-02-01

    Eddy Current Technique is a powerful method for detection of surface notches and of buried flaws during inspection of metallic parts. Recent EC array probes have demonstrated a fast and efficient control of large surfaces. Nevertheless, when the size of flaws decreases or the defect is rather deep, traditional winding coil probes turn out to be useless. Magnetoresistive sensors present the advantages of flat frequency response and micron size. These sensors are hence very attractive for the detection of buried defects that require low frequencies because of skin depth effect. An optimization of the probe with magnetoresistive sensors as receivers has been made by simulations using CIVA software and finite elements methods with OPERA. EC probes for buried flaw detection have been designed. Experimental results have been compared with simulations.

  4. A laboratory activity on the eddy current brake

    NASA Astrophysics Data System (ADS)

    Molina-Bolívar, J. A.; Abella-Palacios, A. J.

    2012-05-01

    The aim of this paper is to introduce a simple and low-cost experimental setup that can be used to study the eddy current brake, which considers the motion of a sliding magnet on an inclined conducting plane in terms of basic physical principles. We present a set of quantitative experiments performed to study the influence of the geometrical and electromagnetic properties of the magnet on the magnetic drag force. This video-based experiment is ideal for the study of kinematic graphs and the application of Newton's laws. Video motion analysis software enables students to make precise measurements of the magnet's position at incremental times during its motion, thus allowing them to quantify electromagnetic induction phenomena. The equipment needed for this experiment and data collection software are present in most physics teaching laboratories or are inexpensive and available.

  5. Gas turbine coatings eddy current quantitative and qualitative evaluation

    NASA Astrophysics Data System (ADS)

    Ribichini, Remo; Giolli, Carlo; Scrinzi, Erica

    2017-02-01

    Gas turbine blades (buckets) are among the most critical and expensive components of the engine. Buckets rely on protective coatings in order to withstand the harsh environment in which they operate. The thickness and the microstructure of coatings during the lifespan of a unit are fundamental to evaluate their fitness for service. A frequency scanning Eddy Current instrument can allow the measurement of the thickness and of physical properties of coatings in a Non-Destructive manner. The method employed relies on the acquisition of impedance spectra and on the inversion of the experimental data to derive the coating properties and structure using some assumptions. This article describes the experimental validation performed on several samples and real components in order to assess the performance of the instrument as a coating thickness gage. The application of the technique to support residual life assessment of serviced buckets is also presented.

  6. Workshops and problems for benchmarking eddy current codes

    SciTech Connect

    Turner, L.R.; Davey, K.; Ida, N.; Rodger, D.; Kameari, A.; Bossavit, A.; Emson, C.R.I.

    1988-08-01

    A series of six workshops was held in 1986 and 1987 to compare eddy current codes, using six benchmark problems. The problems included transient and steady-state ac magnetic fields, close and far boundary conditions, magnetic and non-magnetic materials. All the problems were based either on experiments or on geometries that can be solved analytically. The workshops and solutions to the problems are described. Results show that many different methods and formulations give satisfactory solutions, and that in many cases reduced dimensionality or coarse discretization can give acceptable results while reducing the computer time required. A second two-year series of TEAM (Testing Electromagnetic Analysis Methods) workshops, using six more problems, is underway. 12 refs., 15 figs., 4 tabs.

  7. An approach to ERO problem in displacement eddy current sensor

    NASA Astrophysics Data System (ADS)

    Yu, Yating; Tian, Guiyun; Li, Xinhua; Simm, Anthony

    2013-09-01

    Eddy current (EC) sensors are widely applied in displacement (proximity) measurement as well as nondestructive testing and evaluation for defect detection or material characterisation. For displacement measurement, one of the research aims is to overcome measurement uncertainties due to material variation and inhomogeneity. This problem is called as electrical runout (ERO) problem. In this paper, an approach to ERO problem is presented based on the coaxial ellipse distribution (CED) pattern of the EC sensor. In the CED pattern, the real and the imaginary parts of the magnetic flux density in the z-component (B z ), with the variation of the sample conductivity under the different lift-offs, are located on an ellipse curve. Furthermore, the CED pattern is verified by the different sensor specifications, such as excitation frequency and probe coil geometry. According to the CED pattern, the ERO problem in EC sensors can be overcome well when the sample is magnetised to saturation.

  8. Estimation of surface crack dimensional characteristics by an eddy current method using a single magnetic tunnel junction device

    NASA Astrophysics Data System (ADS)

    Jin, Zhenhu; Abe, Masahiko; Oogane, Mikihiko; Fujiwara, Kousuke; Ando, Yasuo

    2017-07-01

    Eddy current testing plays a significant role in detecting surface defects in a nondestructive testing field. The magnetoresistive sensors based on magnetic tunnel junction devices attracted considerable attention for their use in eddy current testing owing to their high sensitivity and capability of being miniaturized. We investigated the detection of surface cracks in eddy current testing using a single magnetic tunnel junction. A perpendicular component with a secondary magnetic field from an eddy current was measured by using an optimized rectangular magnetic tunnel junction device with an aspect ratio of 4 (20 × 80 µm2). Furthermore, according to the extracted ΔX and ΔV from the sensor output signal, surface cracks with various widths (0.1, 0.3, and 0.5 mm) and depths (0.5, 1.0, 1.5, and 3.0 mm) in aluminum specimens were successfully estimated using the magnetic tunnel junction device in eddy current testing when an excitation frequency of 1000 Hz was used.

  9. Lagrangian and Eulerian characterization of two counter-rotating submesoscale eddies in a western boundary current

    NASA Astrophysics Data System (ADS)

    Mantovanelli, Alessandra; Keating, Shane; Wyatt, Lucy R.; Roughan, Moninya; Schaeffer, Amandine

    2017-06-01

    In recent decades, high-spatial resolution ocean radar and satellite imagery measurements have revealed a complex tangle of submesoscale filaments and eddies, in the surface velocity, temperature, and chlorophyll a fields. We use a suite of high-resolution data to characterize two counter-rotating, short-lived eddies formed at the front between the warm East Australian Current (EAC) and temperate coastal waters (30°S, Eastern Australia). In this region, submesoscale filaments and short-lived eddies are dynamically generated and decay at time scales of hours to days. Dominant cyclonic filaments of O(1) Rossby number formed along frontal jets and eddy boundaries, generating localized ageostrophic circulations at the submesoscale. Measurements of over-ocean wind direction and surface currents from high-frequency radars reveal the influence of the short-term, small-scale wind forcing on the surface circulation, enhancement of the horizontal shear, frontal jet destabilization, and the generation and decay of the cyclonic eddy. By contrast, the anticyclonic eddy formation was most likely associated with EAC mesoscale instability and anticyclonic vorticity. Lagrangian tracks show that surface particles can be temporarily trapped in the eddies and frontal convergent zones, limiting their transport. Mixing between EAC-derived and coastal waters was increased along the frontal regions, and particles starting at the divergent regions around the eddies experienced significant dispersion at submesoscales. The cyclonic cold-core eddy entrained high chlorophyll a shelf waters on its convergent side, suggesting spiral eddy cyclogenesis.

  10. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications

    PubMed Central

    Rifai, Damhuji; Abdalla, Ahmed N.; Ali, Kharudin; Razali, Ramdan

    2016-01-01

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper. PMID:26927123

  11. 3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

    PubMed

    O'Brien, Kieran; Daducci, Alessandro; Kickler, Nils; Lazeyras, Francois; Gruetter, Rolf; Feiweier, Thorsten; Krueger, Gunnar

    2013-08-01

    Clinical use of the Stejskal-Tanner diffusion weighted images is hampered by the geometric distortions that result from the large residual 3-D eddy current field induced. In this work, we aimed to predict, using linear response theory, the residual 3-D eddy current field required for geometric distortion correction based on phantom eddy current field measurements. The predicted 3-D eddy current field induced by the diffusion-weighting gradients was able to reduce the root mean square error of the residual eddy current field to ~1 Hz. The model's performance was tested on diffusion weighted images of four normal volunteers, following distortion correction, the quality of the Stejskal-Tanner diffusion-weighted images was found to have comparable quality to image registration based corrections (FSL) at low b-values. Unlike registration techniques the correction was not hindered by low SNR at high b-values, and results in improved image quality relative to FSL. Characterization of the 3-D eddy current field with linear response theory enables the prediction of the 3-D eddy current field required to correct eddy current induced geometric distortions for a wide range of clinical and high b-value protocols.

  12. Hot-cell design considerations for interfacing eddy-current systems

    SciTech Connect

    Franklin, E.M.; Webb, J.P.; Larson, J.M.

    1985-01-01

    The Hot Fuel Examination Facility/North conducts remote eddy-current examination of irradiated fuel elements. Applications include cladding breach detection and irradiation-induced ferrite examination. The seccussful use of remote eddy-current techniques is achieved by applying basic test parameters and interfacing considerations. These include impedance matching, operating frequency, and feedthrough considerations.

  13. Giant Magnetoresistance Sensors: A Review on Structures and Non-Destructive Eddy Current Testing Applications.

    PubMed

    Rifai, Damhuji; Abdalla, Ahmed N; Ali, Kharudin; Razali, Ramdan

    2016-02-26

    Non-destructive eddy current testing (ECT) is widely used to examine structural defects in ferromagnetic pipe in the oil and gas industry. Implementation of giant magnetoresistance (GMR) sensors as magnetic field sensors to detect the changes of magnetic field continuity have increased the sensitivity of eddy current techniques in detecting the material defect profile. However, not many researchers have described in detail the structure and issues of GMR sensors and their application in eddy current techniques for nondestructive testing. This paper will describe the implementation of GMR sensors in non-destructive testing eddy current testing. The first part of this paper will describe the structure and principles of GMR sensors. The second part outlines the principles and types of eddy current testing probe that have been studied and developed by previous researchers. The influence of various parameters on the GMR measurement and a factor affecting in eddy current testing will be described in detail in the third part of this paper. Finally, this paper will discuss the limitations of coil probe and compensation techniques that researchers have applied in eddy current testing probes. A comprehensive review of previous studies on the application of GMR sensors in non-destructive eddy current testing also be given at the end of this paper.

  14. Enhancing pulsed eddy current for inspection of P-3 Orion lap-joint structures

    NASA Astrophysics Data System (ADS)

    Butt, D. M.; Underhill, P. R.; Krause, T. W.

    2016-02-01

    During flight, aircraft are subjected to cyclic loading. In the Lockheed P-3 Orion airframe, this cyclic loading can lead to development of fatigue cracks at steel fastener locations in the top and second layers of aluminum wing skin lap-joints. An inspection method that is capable of detecting these cracks, without fastener removal, is desirable as this can minimize aircraft downtime, while subsequently reducing the risk of collateral damage. The ability to detect second layer cracks has been demonstrated using a Pulsed Eddy Current (PEC) probe design that utilizes the ferrous fastener as a flux conduit. This allows for deeper penetration of flux into the lap-joint second layer and consequently, sensitivity to the presence of cracks. Differential pick-up coil pairs are used to sense the eddy current response due to the presence of a crack. The differential signal obtained from pick-up coils on opposing sides of the fastener is analyzed using a Modified Principal Components Analysis (MPCA). This is followed by a cluster analysis of the resulting MPCA scores to separate fastener locations with cracks from those without. Probe design features, data acquisition system parameters and signal post-processing can each have a strong impact on crack detection. Physical probe configurations and signal analysis processes, used to enhance the PEC system for detection of cracks in P-3 Orion lap-joint structures, are investigated and an enhanced probe design is identified.

  15. Experimental modeling of eddy currents and deflections for tokamak limiters

    SciTech Connect

    Hua, T.Q.; Knott, M.J.; Turner, L.R.; Wehrle, R.B.

    1986-01-01

    In this study, experiments were performed to investigate deflection, current, and material stress in cantilever beams with the Fusion ELectromagnetic Induction eXperiment (FELIX) at the Argonne National Laboratory. Since structures near the plasma are typically cantilevered, the beams provide a good model for the limiter blades of a tokamak fusion reactor. The test pieces were copper, aluminum, phosphor bronze, and brass cantilever beams, clamped rigidly at one end with a nonconducting support frame inside the FELIX test volume. The primary data recorded as functions of time were the beam deflection measured with a noncontact electro-optical device, the total eddy current measured with a Rogowski coil and linking through a central hole in the beam, and the material stress extracted from strain gauges. Measurements of stress and deflection were taken at selected positions along the beam. The extent of the coupling effect depends on several factors. These include the size, the electrical and mechanical properties of the beam, segmenting of the beam, the decay rate of the dipole field, and the strength of the solenoid field.

  16. Healing of Fatigue Crack in 1045 Steel by Using Eddy Current Treatment

    PubMed Central

    Yang, Chuan; Xu, Wenchen; Guo, Bin; Shan, Debin; Zhang, Jian

    2016-01-01

    In order to investigate the methods to heal fatigue cracks in metals, tubular specimens of 1045 steel with axial and radial fatigue cracks were treated under the eddy current. The optical microscope was employed to examine the change of fatigue cracks of specimens before and after the eddy current treatment. The results show that the fatigue cracks along the axial direction of the specimen could be healed effectively in the fatigue crack initiation zone and the crack tip zone under the eddy current treatment, and the healing could occur within a very short time. The voltage breakdown and the transient thermal compressive stress caused by the detouring of eddy current around the fatigue crack were the main factors contributing to the healing in the fatigue crack initiation zone and the crack tip zone, respectively. Eddy current treatment may be a novel and effective method for crack healing. PMID:28773761

  17. Surface-mounted periodic field eddy current sensors for structural health monitoring

    NASA Astrophysics Data System (ADS)

    Goldfine, Neil J.; Zilberstein, Vladimir A.; Schlicker, Darrell E.; Sheiretov, Yanko; Walrath, Karen; Washabaugh, Andrew P.; Van Otterloo, Douglas

    2001-07-01

    Surface mountable eddy current sensors are a revolutionary new concept in nondestructive inspection. These eddy current sensors can be mounted, like a strain gage, at critical locations for detection of crack initiation and monitoring of crack growth. This can be accomplished on a fatigue test article, as well as on in-service aircraft or other structures (patents pending). The mountable periodic field eddy current sensors, described in this paper, can be used as a replacement for standard eddy-current sensors without introducing new requirements. This is not the case with other proposed health monitoring sensors. For critical structures, substantially reduced inspection costs and life extension is possible with permanently mounted eddy current sensors. This is particularly true for difficult-to-access locations that require surface preparation (e.g., sealant or insulation removal) and disassembly when conventional eddy current testing is performed. By enabling eddy current testing in areas currently not accessible to conventional inspection, such as locations deep in an aircraft structure, damage tolerance can be achieved with low cost inspections. Embedded versions might even be mounted between layers, such as in a lapjoint. Surface mountable eddy current sensors are suitable for on-line monitoring and in-service inspections. This paper provides an introduction to surface mountable eddy current sensors, presents specific results from fatigue coupon tests and describes upcoming full-scale aircraft fatigue tests. Also, ongoing efforts to implement this technology on commercial and military aircraft are described. This research has been funded in part by the U.S. Navy, U.S. Air Force, JENTEK Sensors, Inc., and Lockheed Martin Aeronautics Company. The goal of this paper is to provide a basic understanding of surface mounted eddy current sensor capabilities and potential, and to promote their broader use in fatigue testing, aircraft health monitoring as well as for

  18. Topographic Effects on the Path and Evolution of Loop Current Eddies

    DTIC Science & Technology

    2008-12-01

    August 2008; accepted 2 September 2008; published 30 December 2008. [1] Eddy-topography (ET) interactions are important in determining the path and...evolution of oceanic eddies, including Loop Current Eddies (LCE) in the Gulf of Mexico (GOM). We use the Hybrid Coordinate Ocean Model and satellite...altimetry data to investigate the ET interactions and the impact on LCE pathway evolution in the GOM. Satellite altimetry reveals that LCEs translate

  19. Calculation of Eddy Currents In the CTH Vacuum Vessel and Coil Frame

    SciTech Connect

    A. Zolfaghari, A. Brooks, A. Michaels, J. Hanson, and G. Hartwell

    2012-09-25

    Knowledge of eddy currents in the vacuum vessel walls and nearby conducting support structures can significantly contribute to the accuracy of Magnetohydrodynamics (MHD) equilibrium reconstruction in toroidal plasmas. Moreover, the magnetic fields produced by the eddy currents could generate error fields that may give rise to islands at rational surfaces or cause field lines to become chaotic. In the Compact Toroidal Hybrid (CTH) device (R0 = 0.75 m, a = 0.29 m, B ≤ 0.7 T), the primary driver of the eddy currents during the plasma discharge is the changing flux of the ohmic heating transformer. Electromagnetic simulations are used to calculate eddy current paths and profile in the vacuum vessel and in the coil frame pieces with known time dependent currents in the ohmic heating coils. MAXWELL and SPARK codes were used for the Electromagnetic modeling and simulation. MAXWELL code was used for detailed 3D finite-element analysis of the eddy currents in the structures. SPARK code was used to calculate the eddy currents in the structures as modeled with shell/surface elements, with each element representing a current loop. In both cases current filaments representing the eddy currents were prepared for input into VMEC code for MHD equilibrium reconstruction of the plasma discharge. __________________________________________________

  20. An ink-jet printed eddy current position sensor.

    PubMed

    Jeranče, Nikola; Bednar, Nikola; Stojanović, Goran

    2013-04-18

    An eddy current sensor with an ink-jet printed flexible inductor has been designed and fabricated. The inductor has been designed by means of software developed in-house. It has been fabricated by ink-jet printing with silver ink on a flexible substrate. The inductor is a part of the oscillator circuit whose oscillating frequency is measured by a microcontroller. The sensor characteristics have been analyzed for two types of application. The first considered application is the displacement of a large conductive target in a direction perpendicular to the inductor plane. The second considered application is the displacement of a small steel ball parallel to the inductor plane. Inductance and oscillating frequency have been measured in order to completely characterize the sensor. The obtained results validate the use of the sensor for both considered applications, and are in good agreement with the simulations. The advantages of this type of sensor are low cost, the possibility for the inductor to match any curved surface and flexibility and precision of the inductor design.

  1. Inverse problem of pulsed eddy current field of ferromagnetic plates

    NASA Astrophysics Data System (ADS)

    Chen, Xing-Le; Lei, Yin-Zhao

    2015-03-01

    To determine the wall thickness, conductivity and permeability of a ferromagnetic plate, an inverse problem is established with measured values and calculated values of time-domain induced voltage in pulsed eddy current testing on the plate. From time-domain analytical expressions of the partial derivatives of induced voltage with respect to parameters, it is deduced that the partial derivatives are approximately linearly dependent. Then the constraints of these parameters are obtained by solving a partial linear differential equation. It is indicated that only the product of conductivity and wall thickness, and the product of relative permeability and wall thickness can be determined accurately through the inverse problem with time-domain induced voltage. In the practical testing, supposing the conductivity of the ferromagnetic plate under test is a fixed value, and then the relative variation of wall thickness between two testing points can be calculated via the ratio of the corresponding inversion results of the product of conductivity and wall thickness. Finally, this method for wall thickness measurement is verified by the experiment results of a carbon steel plate. Project supported by the National Defense Basic Technology Research Program of China (Grant No. Z132013T001).

  2. Electrical resonance eddy current sensor for submillimeter defect detection

    NASA Astrophysics Data System (ADS)

    Hor, Yew Li; Zhong, Yu; Bui, Viet Phuong; Png, Ching Eng

    2017-04-01

    Electrical resonance based eddy current methods are being investigated and developed for the detection of sub-millimeter surface defects in low conductivity material such as superalloy in aircraft. The probe has high sensitivity due to the noise elimination by evaluate the relative resonance shift on the impedance change cause by material properties variance. This method has reported analytically with experimental validation recently. In this paper, the detecting system includes the coil sensor and the coaxial connection is modelled using full wave electromagnetic simulation with integration of the circuit co-simulator. The finite element simulation is to study the probe behavior while the circuit model simulator is used to investigate the influence of the component such as capacitance and resistance in the detection system. With our model, further investigation on the sensitivity of the detection system due to the variation of sensor parameters, such as ferrite core and liftoff as well as and capacitance and effective resistance from the electronic component, is performed. This study not only contributes to the optimization and sensitivity enhancement of the detecting system, but also provide accurate detection of submillimeter defect.

  3. Thickness and conductivity of metallic layers from eddy current measurements

    NASA Astrophysics Data System (ADS)

    Moulder, John C.; Uzal, Erol; Rose, James H.

    1992-06-01

    A robust method that uses eddy current measurements to determine the conductivity and thickness of uniform conductive layers is described. The method was tested by estimating the conductivity and thickness of aluminum and copper layers on various substrate metals, and the thickness and conductivity of free-standing foils of aluminum. The electrical impedance was measured for air-core and ferrite-core coils in the presence and absence of the layer for frequencies ranging from 1 kHz to 1 MHz. The thickness and conductivity of the metal layers were inferred by comparing the data taken with air-core coils to the exact theoretical solution of Dodd and Deeds [J. Appl. Phys. 39, 2829 (1968)] using a least-squares norm. The inferences were absolute in the sense that no calibration was used. We report experimental tests for eight different thicknesses of aluminum (20-500 μm) in free space and on four different substrates: Ti-6Al-4V, 304 stainless steel, copper, and 7075 aluminum, and for five different thicknesses of copper (100-500 μm) on 304 stainless steel. Both the thickness and conductivity could be determined accurately (typically within 10%) and simultaneously if the ratio of the layer thickness to the coil radius was between 0.20 and 0.50. For thinner samples either the thickness could be found if the conductivity were known, or vice versa.

  4. An Ink-Jet Printed Eddy Current Position Sensor

    PubMed Central

    Jeranče, Nikola; Bednar, Nikola; Stojanović, Goran

    2013-01-01

    An eddy current sensor with an ink-jet printed flexible inductor has been designed and fabricated. The inductor has been designed by means of software developed in-house. It has been fabricated by ink-jet printing with silver ink on a flexible substrate. The inductor is a part of the oscillator circuit whose oscillating frequency is measured by a microcontroller. The sensor characteristics have been analyzed for two types of application. The first considered application is the displacement of a large conductive target in a direction perpendicular to the inductor plane. The second considered application is the displacement of a small steel ball parallel to the inductor plane. Inductance and oscillating frequency have been measured in order to completely characterize the sensor. The obtained results validate the use of the sensor for both considered applications, and are in good agreement with the simulations. The advantages of this type of sensor are low cost, the possibility for the inductor to match any curved surface and flexibility and precision of the inductor design. PMID:23598504

  5. Diffusion of electromagnetic eddy currents in unconsolidated alluvium

    NASA Astrophysics Data System (ADS)

    Gilliland, E. S.; Weiss, C. J.

    2007-12-01

    Recent studies on the diffusive transport of electromagnetic eddy currents in complex geologic materials have invited speculation on novel theoretical frameworks to encapsulate the macroscopic effects of multi-scale geologic complexity. These ideas have been based on a limited amount of data from a restricted suite of geologic environments. To test the veracity of the various diffusion theories proposed in the literature, a new data set is presented here which consists of transient electromagnetic data collected over an alluvial fill aquifer in the Estancia Basin of central New Mexico. Geologic mapping and correlation of historical well-log data show the experiment site to consist of mainly unconsolidated felsic alluvium with intermittent cobble horizons. Analysis of the electromagnetic data in terms of its diagnostic move-out behavior of the source wavelet shows some similarity to previously obtained results in floodplain environments. Further analysis of the data shows that this behavior is dominated by the alluvial texture and not influenced by the underlying basement rock.

  6. Improved eddy-current inspection for steam generator tubing

    SciTech Connect

    Dodd, C.V.; Pate, J.R.; Allen, J.D. Jr.; Allen , Knoxville, TN )

    1989-01-01

    Computer programs have been written to allow the analysis of different types of eddy-current probes and their performance under different steam generator test conditions. The probe types include the differential bobbin probe, the absolute bobbin probe, the pancake probe and the reflection probe. The generator test conditions include tube supports, copper deposits, magnetite deposits, denting, wastage, pitting, cracking and IGA. These studies are based mostly on computed values, with the limited number of test specimens available used to verify the computed results. The instrument readings were computed for a complete matrix of the different test conditions, and then the test conditions determined as a function of the readings by a least-squares technique. A comparison was made of the errors in fit and instrument drift for the different probe types. The computations of the change in instrument reading due to the defects have led to an inversion'' technique in which the defect properties can be computed from the instrument readings. This has been done both experimentally and analytically for each of these probe types. 3 refs., 13 figs., 1 tab.

  7. Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

    DOEpatents

    Petrini, R.R.; Van Lue, D.F.

    1983-10-25

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.

  8. Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

    DOEpatents

    Petrini, Richard R.; Van Lue, Dorin F.

    1983-01-01

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment (12) with a probe coil (11), and associated coaxial coil cable (13), coil energizing means (21), and circuit means (21, 12) responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube 17 of fiberoptic scope 10. The scope 10 is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means (19, 20) for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

  9. Analysis of pulsed eddy current data using regression models for steam generator tube support structure inspection

    NASA Astrophysics Data System (ADS)

    Buck, J. A.; Underhill, P. R.; Morelli, J.; Krause, T. W.

    2016-02-01

    Nuclear steam generators (SGs) are a critical component for ensuring safe and efficient operation of a reactor. Life management strategies are implemented in which SG tubes are regularly inspected by conventional eddy current testing (ECT) and ultrasonic testing (UT) technologies to size flaws, and safe operating life of SGs is predicted based on growth models. ECT, the more commonly used technique, due to the rapidity with which full SG tube wall inspection can be performed, is challenged when inspecting ferromagnetic support structure materials in the presence of magnetite sludge and multiple overlapping degradation modes. In this work, an emerging inspection method, pulsed eddy current (PEC), is being investigated to address some of these particular inspection conditions. Time-domain signals were collected by an 8 coil array PEC probe in which ferromagnetic drilled support hole diameter, depth of rectangular tube frets and 2D tube off-centering were varied. Data sets were analyzed with a modified principal components analysis (MPCA) to extract dominant signal features. Multiple linear regression models were applied to MPCA scores to size hole diameter as well as size rectangular outer diameter tube frets. Models were improved through exploratory factor analysis, which was applied to MPCA scores to refine selection for regression models inputs by removing nonessential information.

  10. Angular approach combined to mechanical model for tool breakage detection by eddy current sensors

    NASA Astrophysics Data System (ADS)

    Ritou, M.; Garnier, S.; Furet, B.; Hascoet, J. Y.

    2014-02-01

    The paper presents a new complete approach for Tool Condition Monitoring (TCM) in milling. The aim is the early detection of small damages so that catastrophic tool failures are prevented. A versatile in-process monitoring system is introduced for reliability concerns. The tool condition is determined by estimates of the radial eccentricity of the teeth. An adequate criterion is proposed combining mechanical model of milling and angular approach.Then, a new solution is proposed for the estimate of cutting force using eddy current sensors implemented close to spindle nose. Signals are analysed in the angular domain, notably by synchronous averaging technique. Phase shifts induced by changes of machining direction are compensated. Results are compared with cutting forces measured with a dynamometer table.The proposed method is implemented in an industrial case of pocket machining operation. One of the cutting edges has been slightly damaged during the machining, as shown by a direct measurement of the tool. A control chart is established with the estimates of cutter eccentricity obtained during the machining from the eddy current sensors signals. Efficiency and reliability of the method is demonstrated by a successful detection of the damage.

  11. Eddy current power loss in structural steel due to cables carrying current in a perpendicular direction

    SciTech Connect

    Namjoshi, K.V.; Lavers, J.D.; Biringer, P.P. . Dept. of Electrical and Computer Engineering)

    1994-01-01

    This paper deals with eddy current power loss in structural steel, in the vicinity of cables carrying current in a perpendicular direction. The configuration is approximated by a long cylinder perpendicular to a filament current. An analytical method is used. Expressions are provided which describe the frequency dependence of the power loss. The influence of the permeability and the physical dimensions is considered. Formulae are given for the impedance of the cylinder in different frequency regions. Numerical results are presented to show the behavior.

  12. Design and Development of Rogowski Coil Sensors for Eddy Currents Measurement on Toroidal Vessel

    NASA Astrophysics Data System (ADS)

    Prakash, N. Ravi; Flora, Kanikdeep; Babu, Rajan; Gangradey, R.; Patel, H. K.

    2013-04-01

    In tokamak, eddy currents are produced due to change in plasma positions during plasma instabilities that result into generation of electromagnetic forces on interaction with the induced currents. Measurement of this current is essential to design a mechanical structure that can withstand this force. Principle objective of this paper is the development of Rogowski coil sensor to measure eddy currents on a toroidal vessel. The paper presents an elaborative and practical construction technique of a Rogowski coil. The calibration method for the Rogowski coil is also presented. Rogowski coils as an eddy currents diagnostics are tested and experiments to measure induced currents on the toroidal vessel are performed using the coils. Experimental values of eddy currents are compared with the ANSYS simulation results.

  13. Analysis of eddy current induced in track on medium-low speed maglev train

    NASA Astrophysics Data System (ADS)

    Li, Guanchun; Jia, Zhen; He, Guang; Li, Jie

    2017-06-01

    Electromagnetic levitation (EMS) maglev train relies on the attraction between the electromagnets and rails which are mounted on the train to achieve suspension. During the movement, the magnetic field generated by the electromagnet will induce the eddy current in the orbit and the eddy current will weaken the suspended magnetic field. Which leads to the attenuation of the levitation force, the increases of suspension current and the degradation the suspension performance. In this paper, the influence of eddy current on the air gap magnetic field is solved by theoretical analysis, and the correction coefficient of air gap magnetic field is fitted according to the finite element data. The levitation force and current are calculated by the modified formula, and the velocity curves of the levitation force and current are obtained. The results show that the eddy current effect increases the load power by 61.9% in the case of heavy loads.

  14. Using eddy currents for noninvasive in vivo pH monitoring for bone tissue engineering.

    PubMed

    Beck-Broichsitter, Benedicta E; Daschner, Frank; Christofzik, David W; Knöchel, Reinhard; Wiltfang, Jörg; Becker, Stephan T

    2015-03-01

    The metabolic processes that regulate bone healing and bone induction in tissue engineering models are not fully understood. Eddy current excitation is widely used in technical approaches and in the food industry. The aim of this study was to establish eddy current excitation for monitoring metabolic processes during heterotopic osteoinduction in vivo. Hydroxyapatite scaffolds were implanted into the musculus latissimus dorsi of six rats. Bone morphogenetic protein 2 (BMP-2) was applied 1 and 2 weeks after implantation. Weekly eddy current excitation measurements were performed. Additionally, invasive pH measurements were obtained from the scaffolds using fiber optic detection devices. Correlations between the eddy current measurements and the metabolic values were calculated. The eddy current measurements and pH values decreased significantly in the first 2 weeks of the study, followed by a steady increase and stabilization at higher levels towards the end of the study. The measurement curves and statistical evaluations indicated a significant correlation between the resonance frequency values of the eddy current excitation measurements and the observed pH levels (p = 0.0041). This innovative technique was capable of noninvasively monitoring metabolic processes in living tissues according to pH values, showing a direct correlation between eddy current excitation and pH in an in vivo tissue engineering model.

  15. Eddy-Current Inspection of Cracking in Land-Based Gas Turbine Blades

    NASA Astrophysics Data System (ADS)

    Fukutomi, H.; Ogata, T.

    2004-02-01

    There has been a growing need in the electric utility industry to assess the remaining life of blades in gas turbines. It is quite important to nondestructively comprehend the depths of surface-breaking cracks in blades. Flexible eddy current array probes have been developed to overcome the major limitations of existing eddy current inspection systems. The use of an array of sensors allows cracks of all lengths to be detected and will ultimately allow real time data imaging to provide rapid inspection and easy interpretation. For this study using eddy current techniques, crack detection equipment has been developed and applied to gas turbine Stage 1 blades for field use.

  16. Immersed transient eddy current flow metering: a calibration-free velocity measurement technique for liquid metals

    NASA Astrophysics Data System (ADS)

    Krauter, N.; Stefani, F.

    2017-10-01

    Eddy current flow meters are widely used for measuring the flow velocity of electrically conducting fluids. Since the flow induced perturbations of a magnetic field depend both on the geometry and the conductivity of the fluid, extensive calibration is needed to get accurate results. Transient eddy current flow metering has been developed to overcome this problem. It relies on tracking the position of an impressed eddy current system that is moving with the same velocity as the conductive fluid. We present an immersed version of this measurement technique and demonstrate its viability by numerical simulations and a first experimental validation.

  17. Behavior of magnetic field and eddy current in a magnetostriction based bi-layered composite

    NASA Astrophysics Data System (ADS)

    Zhang, Kewei; Zhang, Kehao; Liu, Huifeng; Li, Junlin

    2016-12-01

    In this paper, we presented a theoretical method for studying the behavior of magnetic field intensity and eddy current inside a magnetostriction based bi-layered composite. Firstly, the mathematical model for the electromagnetic field in the composite was established. Then, the governing equation for determining the magnetic field intensity and eddy current was solved. Furthermore, the effect of the composite's conductivity on the magnetic field intensity and eddy current were discussed. Lastly, by comparing with the well known R.L. Stoll's equation, the magnetic field intensity calculated based on our equation showed a less than 0.5% error.

  18. Methods for shielding a flexible, PCB-made eddy current array probe against edge effects

    NASA Astrophysics Data System (ADS)

    Lepage, B.

    2012-05-01

    Probe shielding has been used in combination with eddy current and eddy current array sensors for quite some time to improve detection of defects located near component edges. Conventional methods of providing such shielding are not suitable for coils etched on printed circuit board. This paper describes an innovative shielded coil design suitable for highly flexible, printed circuit board eddy current array probes. The benefits of the new design will be demonstrated for the inspection of dovetails, where detection of defects along the edge is critical.

  19. Research and Development of Automated Eddy Current Testing for Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Carver, Kyle L.; Saulsberry, Regor L.; Nichols, Charles T.; Spencer, Paul R.; Lucero, Ralph E.

    2012-01-01

    Eddy current testing (ET) was used to scan bare metallic liners used in the fabrication of composite overwrapped pressure vessels (COPVs) for flaws which could result in premature failure of the vessel. The main goal of the project was to make improvements in the areas of scan signal to noise ratio, sensitivity of flaw detection, and estimation of flaw dimensions. Scan settings were optimized resulting in an increased signal to noise ratio. Previously undiscovered flaw indications were observed and investigated. Threshold criteria were determined for the system software's flaw report and estimation of flaw dimensions were brought to an acceptable level of accuracy. Computer algorithms were written to import data for filtering and a numerical derivative filtering algorithm was evaluated.

  20. A Study of Applying Pulsed Remote Field Eddy Current in Ferromagnetic Pipes Testing.

    PubMed

    Luo, Qingwang; Shi, Yibing; Wang, Zhigang; Zhang, Wei; Li, Yanjun

    2017-05-05

    Pulsed Remote Field Eddy Current Testing (PRFECT) attracts the attention in the testing of ferromagnetic pipes because of its continuous spectrum. This paper simulated the practical PRFECT of pipes by using ANSYS software and employed Least Squares Support Vector Regression (LSSVR) to extract the zero-crossing time to analyze the pipe thickness. As a result, a secondary peak is found in zero-crossing time when transmitter passed by a defect. The secondary peak will lead to wrong quantification and the localization of defects, especially when defects are found only at the transmitter location. Aiming to eliminate the secondary peaks, double sensing coils are set in the transition zone and Wiener deconvolution filter is applied. In the proposed method, position dependent response of the differential signals from the double sensing coils is calibrated by employing zero-mean normalization. The methods proposed in this paper are validated by analyzing the simulation signals and can improve the practicality of PRFECT of ferromagnetic pipes.

  1. Two Dimensional Steady State Eddy Current Analysis of a Spinning Conducting Cylinder

    DTIC Science & Technology

    2017-03-09

    UNCLASSIFIED UNCLASSIFIED AD-E403 855 Technical Report ARMET-TR-16045 TWO-DIMENSIONAL STEADY-STATE EDDY CURRENT ANALYSIS OF A...any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN...August 2014 4. TITLE AND SUBTITLE TWO-DIMENSIONAL STEADY-STATE EDDY CURRENT ANALYSIS OF A SPINNING CONDUCTING CYLINDER 5a. CONTRACT NUMBER 5b

  2. Effects of Dynamic and Static Loading on Eddy Current Nde of Fatigue Cracks

    NASA Astrophysics Data System (ADS)

    Lo, C. C. H.; Nakagawa, N.

    2009-03-01

    This paper reports on a study of the effects of dynamic and static loading on eddy current (EC) crack signals in aerospace materials. In situ EC measurements were performed on a series of fatigue crack samples grown in Al 6061 bars under dynamic loading. The EC signals detected at a fixed location on the fatigue cracks were found to vary periodically with cyclic loading. Under dynamic tension, the amplitude of the vertical component of the crack signal, which is perpendicular to the lift off direction, increases with the load amplitude and the effect is stronger for longer cracks. Such changes in EC signals are attributable to crack morphology changes (i.e. crack opening) under tension. In contrast, the amplitude of crack signal remains relatively unchanged under compression, possibly due to the insulation effect of the oxidation layer on the crack face. The loading effects on crack signals in the Al samples were confirmed by obtaining c-scan images of the fatigue cracks under static loads. C-scans conducted on a series of Ti 64 fatigue crack samples under static loads revealed significantly stronger stress-induced changes of crack signal for Ti 64 than for the Al samples. The results are interpreted in terms of load-induced crack morphology changes, taking into account of likely differences between the Al and Ti alloy samples.

  3. Measurement of toroidal vessel eddy current during plasma disruption on J-TEXT

    SciTech Connect

    Liu, L. J.; Yu, K. X.; Zhang, M. Zhuang, G.; Li, X.; Yuan, T.; Rao, B.; Zhao, Q.

    2016-01-15

    In this paper, we have employed a thin, printed circuit board eddy current array in order to determine the radial distribution of the azimuthal component of the eddy current density at the surface of a steel plate. The eddy current in the steel plate can be calculated by analytical methods under the simplifying assumptions that the steel plate is infinitely large and the exciting current is of uniform distribution. The measurement on the steel plate shows that this method has high spatial resolution. Then, we extended this methodology to a toroidal geometry with the objective of determining the poloidal distribution of the toroidal component of the eddy current density associated with plasma disruption in a fusion reactor called J-TEXT. The preliminary measured result is consistent with the analysis and calculation results on the J-TEXT vacuum vessel.

  4. Measurement of toroidal vessel eddy current during plasma disruption on J-TEXT.

    PubMed

    Liu, L J; Yu, K X; Zhang, M; Zhuang, G; Li, X; Yuan, T; Rao, B; Zhao, Q

    2016-01-01

    In this paper, we have employed a thin, printed circuit board eddy current array in order to determine the radial distribution of the azimuthal component of the eddy current density at the surface of a steel plate. The eddy current in the steel plate can be calculated by analytical methods under the simplifying assumptions that the steel plate is infinitely large and the exciting current is of uniform distribution. The measurement on the steel plate shows that this method has high spatial resolution. Then, we extended this methodology to a toroidal geometry with the objective of determining the poloidal distribution of the toroidal component of the eddy current density associated with plasma disruption in a fusion reactor called J-TEXT. The preliminary measured result is consistent with the analysis and calculation results on the J-TEXT vacuum vessel.

  5. Measurement of toroidal vessel eddy current during plasma disruption on J-TEXT

    NASA Astrophysics Data System (ADS)

    Liu, L. J.; Yu, K. X.; Zhang, M.; Zhuang, G.; Li, X.; Yuan, T.; Rao, B.; Zhao, Q.

    2016-01-01

    In this paper, we have employed a thin, printed circuit board eddy current array in order to determine the radial distribution of the azimuthal component of the eddy current density at the surface of a steel plate. The eddy current in the steel plate can be calculated by analytical methods under the simplifying assumptions that the steel plate is infinitely large and the exciting current is of uniform distribution. The measurement on the steel plate shows that this method has high spatial resolution. Then, we extended this methodology to a toroidal geometry with the objective of determining the poloidal distribution of the toroidal component of the eddy current density associated with plasma disruption in a fusion reactor called J-TEXT. The preliminary measured result is consistent with the analysis and calculation results on the J-TEXT vacuum vessel.

  6. MEASUREMENTS AND MODELING OF EDDY CURRENT EFFECTS IN BNL'S AGS BOOSTER.

    SciTech Connect

    BROWN, K.A.; AHRENS, L.; GARDNER, C.; GLENN, J.W.; HARVEY, M.; MENG, W.; ZENO, K.

    2006-06-23

    Recent beam experiments at BNL's AGS Booster have enabled us to study in more detail the effects of eddy currents on the lattice structure and our control over the betatron tune. The Booster is capable of operating at ramp rates as high as 9 T/sec. At these ramp rates eddy currents in the vacuum chambers significantly alter the fields and gradients seen by the beam as it is accelerated. The Booster was designed with these effects in mind and to help control the field uniformity and linearity in the Booster Dipoles special vacuum chambers were designed with current windings to negate the affect of the induced eddy currents. In this report results from betatron tune measurements and eddy current simulations will be presented. We will then present results from modeling the accelerator using the results of the magnetic field simulations and compare these to the measurements.

  7. Effect of eddy current damping on phononic band gaps generated by locally resonant periodic structures

    NASA Astrophysics Data System (ADS)

    Ozkaya, Efe; Yilmaz, Cetin

    2017-02-01

    The effect of eddy current damping on a novel locally resonant periodic structure is investigated. The frequency response characteristics are obtained by using a lumped parameter and a finite element model. In order to obtain wide band gaps at low frequencies, the periodic structure is optimized according to certain constraints, such as mass distribution in the unit cell, lower limit of the band gap, stiffness between the components in the unit cell, the size of magnets used for eddy current damping, and the number of unit cells in the periodic structure. Then, the locally resonant periodic structure with eddy current damping is manufactured and its experimental frequency response is obtained. The frequency response results obtained analytically, numerically and experimentally match quite well. The inclusion of eddy current damping to the periodic structure decreases amplitudes of resonance peaks without disturbing stop band width.

  8. Depth sizing of intergranular attack with multi-frequency analysis of eddy current data

    NASA Astrophysics Data System (ADS)

    Lei, Jia; Horn, Dag

    2014-02-01

    Depth sizing of intergranular attack (IGA) with conventional eddy-current analysis is difficult, and typically gives results of poor accuracy. This paper presents a sizing technique using multi-frequency analysis for bobbin probe and X-Probe eddy-current data, along with a case study of outer-surface IGA in 0.510" (12.95 mm) diameter, 0.044" (1.12 mm) wall Alloy 600 tubing. A mathematical framework for the expected eddy-current phase and amplitude response is provided. Using this formulation, eddy-current amplitude and phase responses at four inspection frequencies are calculated, and compared to the corresponding measured responses. IGA flaw geometry is approximated through the optimization of flaw parameters via a least-squares minimization of the residual from the comparison.

  9. Eddy current imaging for electrical characterization of silicon solar cells and TCO layers

    NASA Astrophysics Data System (ADS)

    Hwang, Byungguk; Hillmann, Susanne; Schulze, Martin; Klein, Marcus; Heuer, Henning

    2015-03-01

    Eddy Current Testing has been mainly used to determine defects of conductive materials and wall thicknesses in heavy industries such as construction or aerospace. Recently, high frequency Eddy Current imaging technology was developed. This enables the acquirement of information of different depth level in conductive thin-film structures by realizing proper standard penetration depth. In this paper, we summarize the state of the art applications focusing on PV industry and extend the analysis implementing achievements by applying spatially resolved Eddy Current Testing. The specific state of frequency and complex phase angle rotation demonstrates diverse defects from front to back side of silicon solar cells and characterizes homogeneity of sheet resistance in Transparent Conductive Oxide (TCO) layers. In order to verify technical feasibility, measurement results from the Multi Parameter Eddy Current Scanner, MPECS are compared to the results from Electroluminescence.

  10. Radially Focused Eddy Current Sensor for Detection of Longitudinal Flaws in Metallic Tubes

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor); Fulton, James P. (Inventor); Nath, Shridhar C. (Inventor); Todhunter, Ronald G. (Inventor); Namkung, Min (Inventor)

    1999-01-01

    A radially focused eddy current sensor detects longitudinal flaws in a metal tube. A drive coil induces eddy currents within the wall of the metal tube. A pick-up cod is spaced apart from the drive coil along the length of the metal tube. The pick@up coil is positioned with one end thereof lying adjacent the wall of the metal tube such that the pick-up coil's longitudinal axis is perpendicular to the wall of the metal tube. To isolate the pick-up coil from the magnetic flux of the drive coil and the flux from the induced eddy currents. except the eddy currents diverted by a longitudinal flaw. an electrically conducting material high in magnetic permeability surrounds all of the pick-up coil except its one end that is adjacent the walls of the metal tube. The electrically conducting material can extend into and through the drive coil in a coaxial relationship therewith.

  11. Magnetic resonance imaging inside cylindrical metal containers with an eddy current self-compensated method

    NASA Astrophysics Data System (ADS)

    Han, Hui; Balcom, Bruce J.

    2011-11-01

    Magnetic resonance imaging (MRI) measurements inside cylindrical metal structures have recently been proposed and form the basis for new high-pressure MRI studies. The critical problem for MRI inside cylindrical metal structures is significant eddy currents induced by the switched magnetic field gradients, which usually corrupt spatial and motion encoding without appropriate correction. In this work a so-called standard SPRITE (single point ramped imaging with T1 enhancement) technique is applied for imaging inside cylindrical metal structures. We show that the standard SPRITE technique is fundamentally immune to large-scale eddy current effects and yields artifact-free high-quality images with no eddy current correction required. Standard SPRITE image acquisition avoids the complications involved in the measurement and compensation of eddy current effects for MRI with cylindrical metal structures. This work is a substantial advance toward the extension of MRI to new challenging systems, which are of practical importance.

  12. Evaluation and Improvement of Eddy Current Position Sensors in Magnetically Suspended Flywheel Systems

    NASA Technical Reports Server (NTRS)

    Dever, Timothy P.; Palazzolo, Alan B.; Thomas, Erwin M., III; Jansen, Ralph H.; McLallin, Kerry (Technical Monitor); Soeder, James (Technical Monitor)

    2001-01-01

    Eddy current position sensor performance is evaluated for use in a high-speed flywheel development system. The flywheel utilizes a five axis active magnetic bearing system. The eddy current sensors are used for position feedback for the bearing controller. Measured characteristics include sensitivity to multiple target materials and susceptibility to noise from the magnetic bearings and from sensor-to-sensor crosstalk. Improvements in axial sensor configuration and techniques for noise reduction are described.

  13. Transient Eddy-Current Nondestructive Evaluation: Benchmark Data for Backface Slots in a Plate

    DTIC Science & Technology

    2011-12-01

    DO and Chimenti DE, (Plenum Press, New York), p. 241-248. [9] Bowler J and Johnson M (1997), "Pulsed eddy-current response to a conducting half...UNCLASSIFIED Transient Eddy-Current Nondestructive Evaluation: Benchmark Data for Backface Slots in a Plate S K Burke and M E...Ibrahim Maritime Platforms Division Defence Science and Technology Organisation DSTO-TN-1047 ABSTRACT The results of a benchmark

  14. Eddy Currents Signatures Classification by Using Time Series: a System Modeling Approach

    DTIC Science & Technology

    2014-12-23

    maintenance. In this paper we propose to classify flaws in ferromagnetic materials by measuring Eddy currents. Our approach consists of two steps. First... materials without causing damage. This is useful for pre- dictive maintenance. The most important methods for non- destructive detection of structural flaws...monitoring of ferromagnetic materials based on Eddy currents. Our approach is based on two steps. First, using the measured data, we find a parametric

  15. Method for removal of random noise in eddy-current testing system

    DOEpatents

    Levy, Arthur J.

    1995-01-01

    Eddy-current response voltages, generated during inspection of metallic structures for anomalies, are often replete with noise. Therefore, analysis of the inspection data and results is difficult or near impossible, resulting in inconsistent or unreliable evaluation of the structure. This invention processes the eddy-current response voltage, removing the effect of random noise, to allow proper identification of anomalies within and associated with the structure.

  16. Quantitative void fraction measurement with an eddy current flowmeter for generation IV Sodium cooled Fast Reactor

    SciTech Connect

    Kumar, M.; Tordjeman, Ph.; Bergez, W.; Cavaro, M.; Paumel, K.; Jeannot, J.P.

    2015-07-01

    This study was carried out to understand the response of an eddy current type flowmeter in two phase liquid-metal flow. We use the technique of ellipse fit and correlate the fluctuations in the angle of inclination of this ellipse with the void fraction. The effects of physical parameters such as coil excitation frequency and flow velocity have been studied. The results show the possibility of using an eddy current flowmeter as a gas detector for large void fractions. (authors)

  17. Quantitative void fraction detection with an eddy current flowmeter for generation IV Sodium cooled Fast Reactor

    SciTech Connect

    Kumar, M.; Tordjeman, Ph.; Bergez, W.; Cavaro, M.; Paumel, K.; Jeannot, J. P.

    2015-07-01

    This study was carried out to understand the response of an eddy current type flowmeter in two phase liquid-metal flow. We use the technique of ellipse fit and correlate the fluctuations in the angle of inclination of this ellipse with the void fraction. The effects of physical parameters such as coil excitation frequency and flow velocity have been studied. The results show the possibility of using an eddy current flowmeter as a gas detector for large void fractions. (authors)

  18. A fast integral equation model with a dedicated Green's kernel for eddy-current inspection of fastener holes

    NASA Astrophysics Data System (ADS)

    Pipis, Konstantinos; Skarlatos, Anastassios; Lesselier, Dominique; Theodoulidis, Theodoros

    2015-03-01

    A fast integral equation model for the eddy-current signal calculation of thin cracks breaking the wall of a borehole in a conducting plate is presented. The model is based on the surface integral equation formalism using a dedicated Green's function, which takes into account the effect of the borehole. The approach followed for the construction of the Green's kernel and the primary field is the Truncated Region Eigenfunction Expansion (TREE) method.

  19. High-temperature eddy current probe sensor for monitoring TMC consolidation

    NASA Astrophysics Data System (ADS)

    Rowland, Roderick

    1996-11-01

    Eddy current sensors provide non-contact monitoring of advanced materials during industrial manufacturing. Inducing an alternating electromagnetic field which surrounds and penetrates the material being measured, the eddy current sensor performs highly accurate monitoring of the process. An eddy current sensor is capable of measuring the electrical conductivity and magnetic permeability of a material which can then be correlated to changes in shape and density as well as other properties critical to meet final product design requirements. The proliferation of eddy current technology in the non-destructive evaluation field has been limited to temperatures that are well below those encountered during consolidation of powdered metal and metal matrix composite materials. The drive for net shape forming and cost effective manufacturing, especially with advanced materials, has led to the recent development of a high temperature eddy current monitoring system. The system has been successfully demonstrated at industrial hot isostatic pressing sites. This paper describes the latest high temperature eddy current probe sensor design and how the sensor can be used to monitor and control consolidation of titanium matrix composites.

  20. Rotating flux-focusing eddy current probe for flaw detection

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A. (Inventor); Fulton, James P. (Inventor); Nath, Shridhar C. (Inventor); Simpson, John W. (Inventor); Namkung, Min (Inventor)

    1997-01-01

    A flux-focusing electromagnetic sensor which uses a ferromagnetic flux-focusing lens simplifies inspections and increases detectability of fatigue cracks about circular fasteners and other circular inhomogeneities in high conductivity material. The unique feature of the device is the ferrous shield isolating a high-turn pick-up coil from an excitation coil, The use of the magnetic shield is shown to produce a null voltage output across the receiving coil in the presence of an unflawed sample. A redistribution of the current flow in the sample caused by the presence of flaws, however, eliminates the shielding condition and a large output voltage is produced, yielding a clear unambiguous flaw signal. By rotating the probe in a path around a circular fastener such as a rivet while maintaining a constant distance between the probe and the center of a rivet, the signal due to current flow about the rivet can be held constant. Any further changes in the current distribution, such as due to a fatigue crack at the rivet joint, can be detected as an increase in the output voltage above that due to the flow about the rivet head.

  1. Variables Affecting Probability of Detection in Bolt Hole Eddy Current Inspection

    NASA Astrophysics Data System (ADS)

    Lemire, H.; Krause, T. W.; Bunn, M.; Butcher, D. J.

    2009-03-01

    Physical variables affecting probability of detection (POD) in a bolt-hole eddy current inspection were examined. The POD study involved simulated bolt holes in 7075-T6 aluminum coupons representative of wing areas on CC-130 and CP-140 aircraft. The data were obtained from 24 inspectors who inspected 468 coupons, containing a subset of coupons with 45 electric discharge machined notches and 72 laboratory grown fatigue cracks located at the inner surface corner of the bi-layer structures. A comparison of physical features of cracks and notches in light of skin depth effects and probe geometry was used to identify length rather than depth as the significant variable producing signal variation. Probability of detection based on length produced similar results for the two discontinuity types, except at lengths less than 0.4 mm, where POD for cracks was found to be higher than that of notches.

  2. Reconstruction of rectangular tight cracks separated by a ligament from eddy current impedance change data

    NASA Astrophysics Data System (ADS)

    Bouden, Didier; Lemahieu, Ignace; Basart, John

    2001-04-01

    In eddy-current impedance change scans, the signals from nearby lying cracks may not be resolved. The presence of one or more cracks can be made visible by using a deconvolution approach. This knowledge is used in an iterative inversion scheme to retrieve the dimensions (length, depth) of each crack. Reconstructions are shown based on computer generated data for an air core pancake coil over a metallic half-space. We also looked at the influence of an artificially added lift-off distortion. For the iterative inversion scheme, the speed and accuracy of the forward model calculations are of utmost importance. To test the inversion principle, we used the volume integral method. To speed up the forward model calculations, we used a neural network forward model. The minimization of the cost function was done using a simplex search algorithm.

  3. Variability of the Somali Current and eddies during the southwest monsoon regimes

    NASA Astrophysics Data System (ADS)

    Trott, Corinne B.; Subrahmanyam, Bulusu; Murty, V. S. N.

    2017-09-01

    The meso-scale eddies and currents in the Arabian Sea are analyzed using different satellite observations, Simple Oceanic Data Assimilation (SODA) reanalysis, and Ocean Reanalysis System 4 (ORAS4) from 1993 to 2016 to investigate the impacts of Southwest (SW) Monsoon strength on Somali Current (SC) mesoscale circulations such as the Great Whirl (GW), the Socotra Eddy (SE), the Southern Gyre (SG), and smaller eddies. Increased Ekman pumping during stronger SW monsoons strengthens coastal upwelling along the Somali coast. The Arabian Sea basin-wide anticyclonic circulation and presence of the GW form mesoscale circulation patterns favourable to advection of upwelled waters eastward into the central Arabian Sea. In September, after the SW monsoon winds reach peak strength in July and August, a higher number of discrete anticyclonic eddies with higher (> 20 cm) sea surface height anomalies develop in strong and normal intensity SW monsoon seasons than weaker SW monsoon seasons.

  4. Remote Field Eddy Current Probes for the Detection of Stress Corrosion in Transmission Pipelines

    SciTech Connect

    Ivanov, Plamen Alexandroz

    2002-01-01

    Magnetic flux leakage (MFL) is a technique used widely in non-destructive testing (NDT) of natural gas and petroleum transmission pipelines. This inspection method relies on magnetizing the pipe-wall in axial direction. The MFL inspection tool is equipped with an array of Hall sensors located around the circumference of the pipe, which registers the flux leakage caused by any defects present in the pipe-wall. Currently, the tool magnetizes the pipewall in axial direction making it largely insensitive to axially oriented defects. One type of defect, which is of a growing concern in the gas and petroleum industry is the stress corrosion crack (SCC). The SCCs are a result of aging, corrosion, fatigue and thermal stresses. SCCs are predominantly axially oriented and are extremely tight, which makes them impossible to be detected using current inspection technology. A possible solution to this problem is to utilize the remote field eddy current (RFEC) effect to detect axially oriented defects. The RFEC method has been widely used in industry in the inspection of tubular products. The method uses a pair of excitation and pick-up coils. The pick-up coil located in the remote field region, usually two, three pipe-diameters away from the excitation coil. With RFEC the presence of defects is detected by the disturbance in the phase of the signal measured by the pick-up coil relative to that of the excitation coil. Unlike conventional eddy current testing the RFEC method is sensitive to defects on the exterior of the inspected product, which makes it a good candidate for the development of in-line inspection technology. This work focuses on the development of non-destructive testing technique, which uses remote field eddy currents induced by rotating magnetic field (RMF). A major advantage of the RMF is that it makes possible to not only detect a defect but also localize its position in circumferential direction. Also, it could potentially allow detection of defects

  5. Eddy current-nulled convex optimized diffusion encoding (EN-CODE) for distortion-free diffusion tensor imaging with short echo times.

    PubMed

    Aliotta, Eric; Moulin, Kévin; Ennis, Daniel B

    2017-04-25

    To design and evaluate eddy current-nulled convex optimized diffusion encoding (EN-CODE) gradient waveforms for efficient diffusion tensor imaging (DTI) that is free of eddy current-induced image distortions. The EN-CODE framework was used to generate diffusion-encoding waveforms that are eddy current-compensated. The EN-CODE DTI waveform was compared with the existing eddy current-nulled twice refocused spin echo (TRSE) sequence as well as monopolar (MONO) and non-eddy current-compensated CODE in terms of echo time (TE) and image distortions. Comparisons were made in simulations, phantom experiments, and neuro imaging in 10 healthy volunteers. The EN-CODE sequence achieved eddy current compensation with a significantly shorter TE than TRSE (78 versus 96 ms) and a slightly shorter TE than MONO (78 versus 80 ms). Intravoxel signal variance was lower in phantoms with EN-CODE than with MONO (13.6 ± 11.6 versus 37.4 ± 25.8) and not different from TRSE (15.1 ± 11.6), indicating good robustness to eddy current-induced image distortions. Mean fractional anisotropy values in brain edges were also significantly lower with EN-CODE than with MONO (0.16 ± 0.01 versus 0.24 ± 0.02, P < 1 x 10(-5) ) and not different from TRSE (0.16 ± 0.01 versus 0.16 ± 0.01, P = nonsignificant). The EN-CODE sequence eliminated eddy current-induced image distortions in DTI with a TE comparable to MONO and substantially shorter than TRSE. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  6. Eddy currents in a nonperiodic vacuum vessel induced by axisymmetric plasma motion

    SciTech Connect

    DeLucia, J.

    1985-12-01

    A method is described for calculating the two-dimensional trajectory of a vertically or horizontally unstable axisymmetric tokamak plasma in the presence of a resistive vacuum vessel. The vessel is not assumed to have toroidal symmetry. The plasma is represented by a current-filament loop that is free to move vertically and to change its major radius. Its position is evolved in time self-consistently with the vacuum vessel eddy currents. The plasma current, internal inductance, and poloidal beta can be specified functions of time so that eddy currents resulting from a disruption can be modeled. The vacuum vessel is represented by a set of current-filaments whose positions and orientations are chosen to model the dominant eddy current paths. Although the specific application is to TFTR, the present model is of general applicability. 7 refs., 4 figs., 2 tabs.

  7. View of cold water eddies in Falkland Current off southern Argentina

    NASA Image and Video Library

    1973-12-14

    SL4-137-3608 (14 Dec. 1973) --- A view of cold water eddies in the Falkland Current off the South Atlantic coast of southern Argentina as seen from the Skylab space station in Earth orbit. This picture was taken by one of the Skylab 4 crewmen using a hand-held 70mm Hasselblad camera. This land area (left corner) extends south along the coast from Puerto Deseado (center left border) for about 50 miles. Within the ocean, several light blue areas are visible and represent the occurrence of plankton with the Falkland Current. Over the ocean, the cold water eddies are identified by the circular cloud-free areas within the cloud street pattern and bordered by cumulus cloud buildup (white). The cloud streets indicate the wind is from the southwest and do not form over eddies because energy form the atmosphere is absorbed by the cold ocean water. On the downwind side of the eddies, cumulus clouds tend to form as the cold moist air flows over the warmer water. Similar cloud and eddy features have been observed by the Skylab 4 crewmen in the Yucatan Current off Yucatan Peninsula and in some parts of the South Pacific. Studies are underway by Dr. George Maul, NOAA, and Dr. Robert Stevenson, ONR, to determine the significance of the cold water eddies to ocean dynamics. Photo credit: NASA

  8. Key factors of eddy current separation for recovering aluminum from crushed e-waste.

    PubMed

    Ruan, Jujun; Dong, Lipeng; Zheng, Jie; Zhang, Tao; Huang, Mingzhi; Xu, Zhenming

    2017-02-01

    Recovery of e-waste in China had caused serious pollutions. Eddy current separation is an environment-friendly technology of separating nonferrous metallic particles from crushed e-waste. However, due to complex particle characters, separation efficiency of traditional eddy current separator was low. In production, controllable operation factors of eddy current separation are feeding speed, (ωR-v), and Sp. There is little special information about influencing mechanism and critical parameters of these factors in eddy current separation. This paper provided the special information of these key factors in eddy current separation of recovering aluminum particles from crushed waste refrigerator cabinets. Detachment angles increased as the increase of (ωR-v). Separation efficiency increased with the growing of detachment angles. Aluminum particles were completely separated from plastic particles in critical parameters of feeding speed 0.5m/s and detachment angles greater than 6.61deg. Sp/Sm of aluminum particles in crushed waste refrigerators ranged from 0.08 to 0.51. Separation efficiency increased as the increase of Sp/Sm. This enlightened us to develop new separator to separate smaller nonferrous metallic particles in e-waste recovery. High feeding speed destroyed separation efficiency. However, greater Sp of aluminum particles brought positive impact on separation efficiency. Greater Sp could increase critical feeding speed to offer greater throughput of eddy current separation. This paper will guide eddy current separation in production of recovering nonferrous metals from crushed e-waste. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. A model of the telluric current eddy: a case from eastern China

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Liu, Jun; Du, Xuebin

    2017-06-01

    Electromagnetic induction in the Earth’s interior is an important contributor to the near-Earth geomagnetic and telluric current. The telluric current induced by geomagnetic storms generates secondary geoelectric storms. This motionally induced geoelectric field can be detected in the sea or inland and has potential for electrical soundings of the Earth. This work is aimed at gaining an understanding of the distribution of the current signal due to geomagnetic storms. In this paper, by comparing the geoelectric field during storms and at quiet times, as well as comparing the telluric current calculation results of eastern China and local stations, the following conclusions are obtained. (1) A large range of amplitude change ratios of geoelectric storms is affected by latitude: the amplitude ratio rises at higher latitudes, and the high-frequency composition of geoelectric storms is more complicated than that of geomagnetic storms. (2) The storm creates a large area of electromagnetic fluctuations, and influences the distribution of the telluric current. (3) On the basis of previous studies, a spatial eddy current model is used, which can explain the observation phenomena well. At the same time, a further study direction is put forward on Earth’s electromagnetism.

  10. Original non-stationary eddy current imaging process for the evaluation of defects in metallic structures

    NASA Astrophysics Data System (ADS)

    Placko, Dominique; Bore, Thierry; Rivollet, Alain; Joubert, Pierre-Yves

    2015-10-01

    This paper deals with the problem of imaging defects in metallic structures through eddy current (EC) inspections, and proposes an original process for a possible tomographical crack evaluation. This process is based on a semi analytical modeling, called "distributed point source method" (DPSM) which is used to describe and equate the interactions between the implemented EC probes and the structure under test. Several steps will be successively described, illustrating the feasibility of this new imaging process dedicated to the quantitative evaluation of defects. The basic principles of this imaging process firstly consist in creating a 3D grid by meshing the volume potentially inspected by the sensor. As a result, a given number of elemental volumes (called voxels) are obtained. Secondly, the DPSM modeling is used to compute an image for all occurrences in which only one of the voxels has a different conductivity among all the other ones. The assumption consists to consider that a real defect may be truly represented by a superimposition of elemental voxels: the resulting accuracy will naturally depend on the density of space sampling. On other hand, the excitation device of the EC imager has the capability to be oriented in several directions, and driven by an excitation current at variable frequency. So, the simulation will be performed for several frequencies and directions of the eddy currents induced in the structure, which increases the signal entropy. All these results are merged in a so-called "observation matrix" containing all the probe/structure interaction configurations. This matrix is then used in an inversion scheme in order to perform the evaluation of the defect location and geometry. The modeled EC data provided by the DPSM are compared to the experimental images provided by an eddy current imager (ECI), implemented on aluminum plates containing some buried defects. In order to validate the proposed inversion process, we feed it with computed

  11. The strengthening East Australian Current, its eddies and biological effects — an introduction and overview

    NASA Astrophysics Data System (ADS)

    Suthers, Iain M.; Young, Jock W.; Baird, Mark E.; Roughan, Moninya; Everett, Jason D.; Brassington, Gary B.; Byrne, Maria; Condie, Scott A.; Hartog, Jason R.; Hassler, Christel S.; Hobday, Alistair J.; Holbrook, Neil J.; Malcolm, Hamish A.; Oke, Peter R.; Thompson, Peter A.; Ridgway, Ken

    2011-03-01

    The poleward flowing East Australian Current (EAC) is characterised by its separation from the coast, 100-200 nautical miles north of Sydney, to form the eastward flowing Tasman Front and a southward flowing eddy field. The separation zone greatly influences coastal ecosystems for the relatively narrow continental shelf (only 15-50 km wide), particularly between 32-34°S. In this region the continental shelf has a marked shift in the seasonal temperature-salinity relationship and elevated surface nitrate concentrations. This current parallels the portion of the coast where Australia's population is concentrated and has a long history of scientific research. However, understanding of physical and biological processes driven by the EAC, particularly in linking circulation to ecosystems, is limited. In this special issue of 16 papers on the EAC, we examine the effects of climatic wind-stress forced ocean dynamics on EAC transport variability and coastal sea level, from ENSO to multi-decadal time scales; eddy formation and structure; fine scale connectivity and larval retention. Comparisons with the poleward-flowing Leeuwin Current on Australia's west coast show differences in ecosystem productivity that can be attributed to the underlying physics in each region. On average there is double the chlorophyll a concentration on the east coast than the west. In comparison to the Leeuwin, the EAC may have less local retention of larvae and act as a partial barrier to onshore transport, which may also be related to the local spawning and early life history of small pelagic fish on each coast. Inter-annual variations in the EAC transport produce a detectable sea-level signal in Sydney Harbour, which could provide a useful fisheries index as does the Fremantle sea level and Leeuwin Current relationship. The EAC's eddy structure and formation by the EAC are examined. A particular cold-core eddy is shown to have a "tilt" towards the coast, and that during a rotation the flow of

  12. Eddy Current Flaw Testing Probe with High Performance in Detecting Flaws during In-Service Inspection of Tubing

    NASA Astrophysics Data System (ADS)

    Koyama, Kiyoshi; Hoshikawa, Hiroshi

    Eddy current flaw testing that uses changes in the impedance of the test coil as the electromagnetic field interacts with the test material is a non-destructive testing method. It can be used to inspect test material at high speed without bringing the test coil into contact with the test material. Therefore, it is widely used for product inspection. In the inspection of heat exchanger tubing in power plants and chemical plants, eddy current flaw testing is performed by using an inner probe, because of the structural restrictions of such plants. However, high levels of wobble noise and support plate noise occur in the conventional method using a rotating pancake coil. The authors therefore propose new minimal-noise eddy current inner probes. Two new types of probes have been developed: one for detecting axial flaws, and the other for detecting circumference flaws. These probes can detect flaws with a low level of noise. The phase of the flaw signal by the new probes changes according to the flaw depth. As a result, the signal phase by the new probes can be used for evaluating the depth of surface flaws.

  13. Sailfish ( Istiophorus platypterus) spawning and larval environment in a Florida Current frontal eddy

    NASA Astrophysics Data System (ADS)

    Richardson, David E.; Llopiz, Joel K.; Leaman, Kevin D.; Vertes, Peter S.; Muller-Karger, Frank E.; Cowen, Robert K.

    2009-09-01

    Fronts and eddies are widely hypothesized to be critical spawning habitat for large pelagic fishes, due to increased larval and/or adult feeding opportunities at these features. We examined sailfish ( Istiophorus platypterus) spawning around a cyclonic, submesoscale (∼13 × 7 km) Florida Current frontal eddy. The temporal progression of eddy dynamics over a 65 h period was determined using ocean color satellite imagery, continuous surface measurements along the cruise track, and non-linear least-squares fitting of the positions of three drifters deployed within the eddy. A peak in larval sailfish densities ( n = 2435, stations = 49), composed primarily of yolk-sac and first-feeding larvae, occurred at the eddy frontal zone. A majority of these larvae were estimated to have been spawned during the formation of the eddy. A comparison between the distribution of similar-age sailfish and scombrid larvae indicated that the peak in larval sailfish density likely resulted from spawning directly at the front, rather than transport by convergent flow. The first-feeding prey items of larval sailfish ( Farranula and Corycaeus copepods) were most abundant at the frontal zone and to a lesser extent inside the eddy. Egg distributions were used to indirectly assess the distribution of adult sailfish prey items. Euthynnus alleteratus and Auxis spp. eggs were in highest abundance outside the eddy, while the eggs of small carangids were in highest abundance at the eddy frontal zone. Overall, this study indicates that sailfish spawn at small-scale oceanographic features that provide a favorable feeding environment for their larvae and potentially also for the adults.

  14. A Multi-Frequency Eddy Current Inversion Method for Characterizing Conductivity Gradients on Water Jet Peened Components

    NASA Astrophysics Data System (ADS)

    Sundararaghavan, V.; Balasubramaniam, K.; Babu, N. R.

    2004-02-01

    This paper describes a multi-frequency eddy current inversion procedure for characterizing specimens that are water jet peened. Multi-frequency inductance data was obtained by using well-characterized eddy current probes. The inversion uses a multi-layer axi-symmetric finite element model as the forward model and the conductivity of each layer is found through interpolation of the inductance-conductivity data generated by the forward model. Skin depth approximation was used to isolate the integral effects of the conductivity variation on the inductance signal. Inverted conductivity profiles of the water jet peened specimens was found to resemble the predicted profiles. Information regarding the shape of residual stress gradients and relative intensities of peening were inferred from the conductivity profiles.

  15. Pulsed eddy current inspection of broach support plates in steam generators

    NASA Astrophysics Data System (ADS)

    Mokros, Sarah Gwendolyn

    Steam Generators (SGs) are a critical component of nuclear reactors, employing thousands of SG tubes to convert heat generated in the reactor core into useable energy. SG tubes are supported at numerous locations by Broach Support Plates (BSPs) that have trefoil shaped holes, which prevent excessive tube vibrations, while allowing water to easily flow through the support structures. A number of degradation modes occur in SGs, such as SG tube fretting, cracking or denting, requiring periodic inspection. Currently, conventional Eddy Current Testing (ECT) is used to non-destructively assess the condition of SG tubes and components. However, as reactors age, new modes of degradation will likely appear that may be difficult to detect and characterize using conventional ECT, such as wall loss in BSPs and build-up of corrosion products, which typically form as a hard sludge called magnetite. Pulsed Eddy Current (PEC) technologies are an emerging technique that is presented in this work as a method to further advance inspection techniques used in CANDURTM nuclear reactors. A PEC probe was designed to inspect the unique shape of the trefoil shaped hole to detect and characterize wall loss and the presence of magnetite in A516 carbon steel BSPs with trefoil shaped holes from within 15.9 mm (5/8") Alloy-800 SG tubes. PEC was also used to observe how measurements of wall loss were affected by the presence of magnetite. This work presents Finite Element Method (FEM) simulations and experimental results collected to observe these degradation modes. The probe was demonstrated to be capable of detecting far side wall loss as low as 20%, locating and characterizing the relative permeability of magnetite, and of detecting wall loss when magnetite was present. FEM simulations and experimental results were found to be in good agreement, suggesting that additional investigations of the effects of BSP degradation on PEC signal response may also be performed using FEM models.

  16. A multi-frequency impedance analysing instrument for eddy current testing

    NASA Astrophysics Data System (ADS)

    Yin, W.; Dickinson, S. J.; Peyton, A. J.

    2006-02-01

    This paper presents the design of a high-performance multi-frequency impedance analysing instrument (MFIA) for eddy current testing which has been developed primarily for monitoring a steel production process using an inductive sensor. The system consists of a flexible multi-frequency waveform generator and a voltage/current measurement unit. The impedance of the sensor is obtained by cross-spectral analysis of the current and voltage signals. The system contains high-speed digital-to-analogue, analogue-to-digital converters and dual DSPs with one for control and interface and one dedicated to frequency-spectra analysis using fast Fourier transformation (FFT). The frequency span of the signal that can be analysed ranges from 1 kHz to 8 MHz. The system also employs a high-speed serial port interface (USB) to communicate with a personal computer (PC) and to allow for fast transmission of data and control commands. Overall, the system is capable of delivering over 250 impedance spectra per second. Although the instrument has been developed mainly for use with an inductive sensor, the system is not restricted to inductive measurement. The flexibility of the design architecture is demonstrated with capacitive and resistive measurements by using appropriate input circuitry. Issues relating to optimizing the phase of the spectra components in the excitation waveform are also discussed.

  17. Adjoint sensitivity studies of loop current and eddy shedding in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, Ganesh; Cornuelle, Bruce D.; Hoteit, Ibrahim

    2013-07-01

    Adjoint model sensitivity analyses were applied for the loop current (LC) and its eddy shedding in the Gulf of Mexico (GoM) using the MIT general circulation model (MITgcm). The circulation in the GoM is mainly driven by the energetic LC and subsequent LC eddy separation. In order to understand which ocean regions and features control the evolution of the LC, including anticyclonic warm-core eddy shedding in the GoM, forward and adjoint sensitivities with respect to previous model state and atmospheric forcing were computed using the MITgcm and its adjoint. Since the validity of the adjoint model sensitivities depends on the capability of the forward model to simulate the real LC system and the eddy shedding processes, a 5 year (2004-2008) forward model simulation was performed for the GoM using realistic atmospheric forcing, initial, and boundary conditions. This forward model simulation was compared to satellite measurements of sea-surface height (SSH) and sea-surface temperature (SST), and observed transport variability. Despite realistic mean state, standard deviations, and LC eddy shedding period, the simulated LC extension shows less variability and more regularity than the observations. However, the model is suitable for studying the LC system and can be utilized for examining the ocean influences leading to a simple, and hopefully generic LC eddy separation in the GoM. The adjoint sensitivities of the LC show influences from the Yucatan Channel (YC) flow and Loop Current Frontal Eddy (LCFE) on both LC extension and eddy separation, as suggested by earlier work. Some of the processes that control LC extension after eddy separation differ from those controlling eddy shedding, but include YC through-flow. The sensitivity remains stable for more than 30 days and moves generally upstream, entering the Caribbean Sea. The sensitivities of the LC for SST generally remain closer to the surface and move at speeds consistent with advection by the high-speed core of

  18. Multiple dipole eddies in the Alaska Coastal Current detected with Landsat thematic mapper data

    NASA Astrophysics Data System (ADS)

    AhlnäS, Kristina; Royer, Thomas C.; George, Thomas H.

    1987-11-01

    Seventeen dipole eddies, including five large, well-formed ones, three second-generation eddies, and two double eddies, were observed in the Alaska Coastal Current near Kayak Island in one single scene of the Landsat thematic mapper (TM) on April 22, 1985. The digital Landsat TM satellite data were computer analyzed to extract details in the near coastal circulation in the northern Gulf of Alaska. Enhancement techniques were applied to the visible and thermal IR bands. The features are evident only in the visible bands because of the ability of these bands to detect the distribution of sediments in the near surface. These eddies did not have a significant thermal signature. The sources of these sediments are the glacial streams found throughout the Gulf of Alaska coast. Eddies of this configuration and frequency have never been observed here previously. However, the oceanographic and meteorological conditions are typical for this time of year. These eddies should be important to the cross-shelf mixing processes in the Alaska Coastal Current and are an indicator that the flow here can be unstable at certain times of the year.

  19. Multiple dipole eddies in the Alaska Coastal Current detected with Landsat thematic mapper data

    NASA Technical Reports Server (NTRS)

    Ahlnas, Kristina; Royer, Thomas C.; George, Thomas H.

    1987-01-01

    Seventeen dipole eddies, including five large, well-formed ones, three second-generation eddies, and two double eddies, were observed in the Alaska Coastal Current near Kayak Island in one single scene of the Landsat thematic mapper (TM) on April 22, l985. The digital Landsat TM satellite data were computer analyzed to extract details in the near coastal circulation in the northern Gulf of Alaska. Enhancement techniques were applied to the visible and thermal IR bands. The features are evident only in the visible bands because of the ability of these bands to detect the distribution of sediments in the near surface. These eddies did not have a significant thermal signature.The sources of these sediments are the glacial streams found throughout the Gulf of Alaska coast. Eddies of this configuration and frequency have never been observed here previously. However, the oceanographic and meteorological conditions are typical for this time of year. These eddies should be important to the cross-shelf mixing processes in the Alaska Coastal Current and are an indicator that the flow here can be unstable at certain times of the year.

  20. Satellite Studies of Interactions Between Antarctic Circumpolar Current Eddies and Sea Ice

    NASA Astrophysics Data System (ADS)

    Springer, S. R.; Padman, L.; Dinniman, M. S.

    2015-12-01

    Wintertime sea ice extent around Antarctica has shown a positive trend during at least the past decade. The maximum northward expansion of sea ice is likely to be limited by the strong ocean temperature gradients associated with fronts of the Antarctic Circumpolar Current (ACC). The ACC is, however, very dynamically unstable, with mesoscale eddies accounting for a large fraction of the variance in surface currents and sea surface temperature (SST). We combine satellite-observed sea-ice concentration, SST, and geostrophic eddy velocities to explore the hypothesis that dynamic and thermodynamic interactions between mesoscale eddies and sea ice exert an additional influence on the location of the winter sea ice margin. Advancing sea ice develops meridional deviations at horizontal scales of ~100 km, lengthening the perimeter of the ice-covered area by 30-70%. In many cases, this "scalloping" of the ice margin can be attributed to advection by eddy velocities. The effect varies regionally, depending on the proximity of the ice edge to the ACC. From the Amundsen Sea eastward through the Drake Passage the southern limit of eddy variability coincides with the northernmost extent of sea ice, and scalloping is common. By deforming the ice margin, eddies increase the potential for ice-edge melting and destruction by Southern Ocean surface wave action, while eddy-driven ice advection modifies the mean thermodynamic exchanges responsible for mass loss from the base of the ice pack. We use observations and models to estimate sea-ice loss caused by eddy/ice interactions.

  1. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

    SciTech Connect

    B.Mi; X. Zhao; R. Bayles

    2006-05-26

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with different surface preparation conditions before applying the coating, e.g., grit-blasted surface, wire-brush cleaned surface, and a dirty surface. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that the three surface preparation conditions can be successfully differentiated by looking into the impedance difference observed from the eddy current probe. The measurement is fairly robust and consistent. More specimens are also prepared with variations of process parameters, such as spray angle, stand-off distance, and application of corrosion protective sealant, etc. They are blindly tested to evaluate the reliability of the eddy current system. Quantitative relations between the coating bond strength and the eddy current response are also established with the support of destructive testing. This non-contact, non-destructive, easy to use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  2. An integrated eddy current detection and imaging system on a silicon chip

    NASA Technical Reports Server (NTRS)

    Henderson, H. Thurman; Kartalia, K. P.; Dury, Joseph D.

    1991-01-01

    Eddy current probes have been used for many years for numerous sensing applications including crack detection in metals. However, these applications have traditionally used the eddy current effect in the form of a physically wound single or different probe pairs which of necessity must be made quite large compared to microelectronics dimensions. Also, the traditional wound probe can only take a point reading, although that point might include tens of individual cracks or crack arrays; thus, conventional eddy current probes are beset by two major problems: (1) no detailed information can be obtained about the crack or crack array; and (2) for applications such as quality assurance, a vast amount of time must be taken to scan a complete surface. Laboratory efforts have been made to fabricate linear arrays of single turn probes in a thick film format on a ceramic substrate as well as in a flexible cable format; however, such efforts inherently suffer from relatively large size requirements as well as sensitivity issues. Preliminary efforts to fully extend eddy current probing from a point or single dimensional level to a two dimensional micro-eddy current format on a silicon chip, which might overcome all of the above problems, are presented.

  3. Eddy current analysis and optimization of fast scanning magnet for a proton therapy system

    NASA Astrophysics Data System (ADS)

    Liu, Xu; Qin, Bin; Liu, Kaifeng; Chen, Wei; Liang, Zhikai; Chen, Qushan; Chen, Dezhi; Fan, Mingwu

    2017-08-01

    Proton therapy is now recognized as one of the most effective radiation therapy methods for cancers. A proton therapy facility with multiple gantry treatment rooms is under development in HUST (Huazhong University of Science and Technology), which is based on isochronous superconducting cyclotron scheme. In the beam line, the scanning system spreads out the proton beam on the target according to the complex tumour shape by two scanning magnets for horizontal and vertical scanning independently. Since these two magnets are excited by alternating currents and the maximum repetition frequency is up to 100 Hz, eddy currents and losses are expected to be significant. Slits are proven to be an effective way to reduce the eddy currents. To evaluate the heat distribution due to eddy losses in the pole end of the scanning magnet, the transient electromagnetic analysis and steady-state thermal analysis are performed. This paper describes design considerations of the scanning system and mainly analyses the eddy current effect of the scanning magnets. Different coil shapes and slit arrangements are simulated and compared to obtain the optimal configuration. The maximum temperatures of two magnets are optimized below 70 °C. In addition, the lag effect due to eddy currents is also discussed.

  4. Model development and validation of geometrically complex eddy current coils using finite element methods

    NASA Astrophysics Data System (ADS)

    Brown, Alexander; Eviston, Connor

    2017-02-01

    Multiple FEM models of complex eddy current coil geometries were created and validated to calculate the change of impedance due to the presence of a notch. Capable realistic simulations of eddy current inspections are required for model assisted probability of detection (MAPOD) studies, inversion algorithms, experimental verification, and tailored probe design for NDE applications. An FEM solver was chosen to model complex real world situations including varying probe dimensions and orientations along with complex probe geometries. This will also enable creation of a probe model library database with variable parameters. Verification and validation was performed using other commercially available eddy current modeling software as well as experimentally collected benchmark data. Data analysis and comparison showed that the created models were able to correctly model the probe and conductor interactions and accurately calculate the change in impedance of several experimental scenarios with acceptable error. The promising results of the models enabled the start of an eddy current probe model library to give experimenters easy access to powerful parameter based eddy current models for alternate project applications.

  5. [A rapid method of eddy current compensation in magnetic resonance imaging systems].

    PubMed

    Liu, Zheng-min; Zhou, He-qin; Wu, Hai-cheng

    2005-11-01

    Imaging objects are spatially encoded by gradient magnetic fields in magnetic resonance imaging systems. The eddy current caused by rapid switches of gradient fields will result in artifacts in the images. A method of eddy current compensation based on pre-emphasis of gradient current is presented in this thesis. The compensation parameters are acquired rapidly utilizing Faraday's induction theorem and data fitting method. The experiments prove that the method is efficient for reduction of the debugging time and for the improvement of the image quality.

  6. Numerical simulation of the Mindanao Eddy and Tropical Currents of Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Li, Rongfeng; Zeng, Qingcun; Ji, Zhongzhen

    1992-09-01

    Results of numerical simulation of currents in the western North Tropical Pacific Ocean by using a barotropic primitive equation model with fine horizontal resolution agreed well with observations and showed that the Mindanao Cyclonic Eddy located north of the equator and east of Mindanao Island exists during most of the year with monthly (and large seasonal) variations in scope, strength and central location. In June, an anticyclonic eddy occurs northeast of Halmahera Island, strength-circulation systems such as the North Equatorial Current, the Mindanao Current and the North Equatorial Countercurrent are all very well reproduced in the simulations.

  7. Characterizing frontal eddies along the East Australian Current from HF radar observations

    NASA Astrophysics Data System (ADS)

    Schaeffer, Amandine; Gramoulle, A.; Roughan, M.; Mantovanelli, A.

    2017-05-01

    The East Australian Current (EAC) dominates the ocean circulation along south-eastern Australia, however, little is known about the submesoscale frontal instabilities associated with this western boundary current. One year of surface current measurements from HF radars, in conjunction with mooring and satellite observations, highlight the occurrence and propagation of meanders and frontal eddies along the inshore edge of the EAC. Eddies were systematically identified using the geometry of the high spatial resolution (˜1.5 km) surface currents, and tracked every hour. Cyclonic eddies were observed irregularly, on average every 7 days, with inshore radius ˜10 km. Among various forms of structures, frontal eddies associated with EAC meanders were characterized by poleward advection speeds of ˜0.3-0.4 m/s, migrating as far as 500 km south, based on satellite imagery. Flow field kinematics show that cyclonic eddies have high Rossby numbers (0.6-1.9) and enhance particle dispersion. Patches of intensified surface divergence at the leading edge of the structures are expected to generate vertical uplift. This is confirmed by subsurface measurements showing temperature uplift of up to 55 m over 24 h and rough estimates of vertical velocities of 10s of meters per day. While frontal eddies propagate through the radar domain independently of local wind stress, upfront wind can influence their stalling and growth, and can also generate large cold core eddies through intense shear. Such coherent structures are a major mechanism for the transport and entrainment of nutrient rich coastal or deep waters, influencing physical and biological dynamics, and connectivity over large distances.

  8. Application of Hilbert-Huang transform for defect recognition in pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Liu, Baoling; Huang, Pingjie; Hou, Dibo; Chen, Xiao; Zhang, Guangxin

    2015-07-01

    Defect recognition plays an important role in the structure integrity and health monitor of in-service equipment. However, it is difficult to recognise deep-layer defect or small-size defect in conductive structure during pulsed eddy current (PEC) testing. Aiming at the issue, this article proposes a method based on Hilbert-Huang transform which consists of two modules: data processing and defect recognition. In the data processing module, the PEC response signal is decomposed into a few of intrinsic mode functions (IMFs) using ensemble empirical mode decomposition method. The IMFs whose variance contribution rates are bigger than 1% are chosen to reconstruct signal in order to remove noise. In the defect recognition module, the features based on specific frequency components of marginal spectrum (MS) of the reconstructed signals are extracted to discriminate those defects in surface and subsurface. Furthermore, the normalisation MS energy ratio is proposed to quantify defects which cannot be distinguished using peak value in time domain. Experiments show that the proposed method can achieve better de-noising effect and defect evaluation, which contributes to the recognition of those complicated defects such as deep-layered and small-sized defect.

  9. Signal-to-noise issues in measuring nitrous oxide fluxes by the eddy covariance method

    NASA Astrophysics Data System (ADS)

    Cowan, Nicholas; Levy, Peter; Langford, Ben; Skiba, Ute

    2016-04-01

    Recently-developed fast-response gas analysers capable of measuring atmospheric N2O with high precision (< 50 ppt) at a rate of 10 Hz are becoming more widely available. These instruments are capable of measuring N2O fluxes using the eddy covariance method, with significantly less effort and uncertainty than previous instruments have allowed. However, there are still many issues to overcome in order to obtain accurate and reliable flux data. The signal-to-noise ratio of N2O measured using these instruments is still two to three orders of magnitude smaller than that of CO2. The low signal-to-noise ratio can lead to systematic uncertainties, in the eddy covariance method, the most significant being in the calculation of the time lag between gas analyser and anemometer by maximisation of covariance (Langford et al., 2015). When signal-to-noise ratio is relatively low, as it is with many N2O measurements, the maximisation of covariance method can systematically overestimate fluxes. However, if constant time lags are assumed, then fluxes will be underestimated. This presents a major issue for N2O eddy covariance measurements. In this presentation we will focus on the signal to noise ratio for an Aerodyne quantum cascade laser (QCL). Eddy covariance flux measurements from multiple agricultural sites across the UK were investigated for potential uncertainties. Our presentation highlights some of these uncertainties when analysing eddy covariance data and offers suggestions as to how these issues may be minimised. Langford, B., Acton, W., Ammann, C., Valach, A. and Nemitz, E.: Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection, Atmos Meas Tech, 8(10), 4197-4213, doi:10.5194/amt-8-4197-2015, 2015.

  10. Remote Field Eddy Curent Signal Modeling for the Gap Measurement of Neighboring Tubes

    NASA Astrophysics Data System (ADS)

    Jung, H. K.; Lee, D. H.; Lee, Y. S.

    2005-04-01

    The fuel channels in the Canadian Deuterium Uranium (CANDU) reactor consist of the coaxial pressure tube (PT) and the calandria tube (CT). The Liquid injection nozzle (LIN) is cross aligned with the fuel channel to control the reactor by injecting poison. For a safe operation, the gap between the LIN and CT should be maintained in order to prevent a contact of the neighboring tubes. The remote field eddy current (RFEC) method was applied to measure the gap between a nonmagnetic Zircaloy-2 liquid injection nozzle (LIN) and a Zircaloy-2 calandria tube. Under the condition of inserting the RFEC probe into the coaxial tubes and of crossing a LIN above or under the CT, the modeling of a LIN signal is needed to check the possibility of a gap measurement. The Volume Integral Code S/W which covers the axi-symmetric 3D configuration has been very rarely applied to obtain a LIN signal. This problem was solved by assuming a LIN as a flaw which can be described as a complete 3D object. This simulated LIN signal was verified by performing the laboratory experiment. The gap between the LIN and CT can be correlated with the amplitude of the LIN signals in the voltage plane. Typical noises in the fuel channel were the relative constriction, the change in the pressure tube diameter (fill-factor), thickness variation, and so on. These noise signals were simulated by using the modeling and were analyzed by considering their dependency on the phase angle and amplitude of the voltage plane in order to separate the gap signal from them. It could be concluded that the voltage plane analysis of the simulated RFEC signals were effective for obtaining the gap measurement of the neighboring tube.

  11. Observational evidence of seasonality in the timing of loop current eddy separation

    NASA Astrophysics Data System (ADS)

    Hall, Cody A.; Leben, Robert R.

    2016-12-01

    Observational datasets, reports and analyses over the time period from 1978 through 1992 are reviewed to derive pre-altimetry Loop Current (LC) eddy separation dates. The reanalysis identified 20 separation events in the 15-year record. Separation dates are estimated to be accurate to approximately ± 1.5 months and sufficient to detect statistically significant LC eddy separation seasonality, which was not the case for previously published records because of the misidentification of separation events and their timing. The reanalysis indicates that previously reported LC eddy separation dates, determined for the time period before the advent of continuous altimetric monitoring in the early 1990s, are inaccurate because of extensive reliance on satellite sea surface temperature (SST) imagery. Automated LC tracking techniques are used to derive LC eddy separation dates in three different altimetry-based sea surface height (SSH) datasets over the time period from 1993 through 2012. A total of 28-30 LC eddy separation events were identified in the 20-year record. Variations in the number and dates of eddy separation events are attributed to the different mean sea surfaces and objective-analysis smoothing procedures used to produce the SSH datasets. Significance tests on various altimetry and pre-altimetry/altimetry combined date lists consistently show that the seasonal distribution of separation events is not uniform at the 95% confidence level. Randomization tests further show that the seasonal peak in LC eddy separation events in August and September is highly unlikely to have occurred by chance. The other seasonal peak in February and March is less significant, but possibly indicates two seasons of enhanced probability of eddy separation centered near the spring and fall equinoxes. This is further quantified by objectively dividing the seasonal distribution into two seasons using circular statistical techniques and a k-means clustering algorithm. The estimated

  12. Energy loss due to eddy current in linear transformer driver cores

    NASA Astrophysics Data System (ADS)

    Kim, A. A.; Mazarakis, M. G.; Manylov, V. I.; Vizir, V. A.; Stygar, W. A.

    2010-07-01

    In linear transformer drivers [Phys. Rev. ST Accel. Beams 12, 050402 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.050402; Phys. Rev. ST Accel. Beams 12, 050401 (2009)PRABFM1098-440210.1103/PhysRevSTAB.12.050401] as well as any other linear induction accelerator cavities, ferromagnetic cores are used to prevent the current from flowing along the induction cavity walls which are in parallel with the load. But if the core is made of conductive material, the applied voltage pulse generates the eddy current in the core itself which heats the core and therefore also reduces the overall linear transformer driver (LTD) efficiency. The energy loss due to generation of the eddy current in the cores depends on the specific resistivity of the core material, the design of the core, as well as on the distribution of the eddy current in the core tape during the remagnetizing process. In this paper we investigate how the eddy current is distributed in a core tape with an arbitrary shape hysteresis loop. Our model is based on the textbook knowledge related to the eddy current generation in ferromagnetics with rectangular hysteresis loop, and in usual conductors. For the reader’s convenience, we reproduce some most important details of this knowledge in our paper. The model predicts that the same core would behave differently depending on how fast the applied voltage pulse is: in the high frequency limit, the equivalent resistance of the core reduces during the pulse whereas in the low frequency limit it is constant. An important inference is that the energy loss due to the eddy current generation can be reduced by increasing the cross section of the core over the minimum value which is required to avoid its saturation. The conclusions of the model are confirmed with experimental observations presented at the end of the paper.

  13. Development of high resolution eddy current imaging using an electro-mechanical sensor

    NASA Astrophysics Data System (ADS)

    Cherry, M. R.; Sathish, S.; Welter, J.; Reibel, R.; Blodgett, M. P.

    2012-05-01

    Typical eddy current probes are based on measuring the impedance change of a coil excited by an AC current when the coil is placed above a conductive sample. These types of probes are limited in spatial resolution to the dimensions of the coil, and coil diameter is limited by operating frequency. Because of this, the highest resolution available with these probes is on the order of 100 um. While detecting the impedance change of the probe has limited special resolution, various methods of detecting the change in magnetic field in and around the coil have been shown to improve the resolution of a standard coil. These methods have improved the resolution in eddy current imaging to 25 nm. To date, the resolutions achievable by modern eddy current technology have failed to encompass the 100nm - 100 um range, which would be ideal for microstructure characterization of conductive materials. In this paper, a new probe, called the electro-mechanical eddy current sensor (EMECS), is presented that is based on the electromechanical design to fill this resolution gap. The new probe is designed and developed with a sharpened magnetic tip attached to the membrane of an electret microphone. The magnet is actuated by an external coil with a low current AC voltage. The motion of the magnet produces eddy currents in a conductive sample, which then result in a damping force on the magnet. The results of the experimental measurements demonstrate that this probe has spatial resolution that is much higher compared with the measurements using the external excitation coil only. The role of competing eddy currents produced by the motion of the magnet and the excitation coil in the material are examined with numerical analysis and the effects of the eddy currents from the excitation coil are shown to be negligible. A governing equation for the probe is presented that treats the magnet as a magnetic dipole and uses the eddy current forces as a damping term in the equation of motion for the

  14. Non-Destructive Evaluation of Thermal Spray Coating Interface Quality By Eddy Current Method

    SciTech Connect

    B. Mi; G. Zhao; R. Bayles

    2006-08-10

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  15. Evaluation and field validation of Eddy-Current array probes for steam generator tube inspection

    SciTech Connect

    Dodd, C.V.; Pate, J.R.

    1996-07-01

    The objective of the Improved Eddy-Current ISI for Steam Generator Tubing program is to upgrade and validate eddy-current inspections, including probes, instrumentation, and data processing techniques for inservice inspection of new, used, and repaired steam generator tubes; to improve defect detection, classification, and characterization as affected by diameter and thickness variations, denting, probe wobble, tube sheet, tube supports, copper and sludge deposits, even when defect types and other variables occur in combination; to transfer this advanced technology to NRC`s mobile NDE laboratory and staff. This report describes the design of specialized high-speed 16-coil eddy-current array probes. Both pancake and reflection coils are considered. Test results from inspections using the probes in working steam generators are given. Computer programs developed for probe calculations are also supplied.

  16. Multifrequency eddy-current inspection of seam weld in steel sheath

    SciTech Connect

    Smith, J.H.; Dodd, C.V.; Chitwood, L.D.

    1985-04-01

    Multifrequency eddy-current techniques were used to perform a continuous on-line inspection of the seam weld in the steel jacket for a superconducting cable. The inspection was required to detect both surface and internal weld flaws in the presence of a large, highly conductive central conductor. Raw eddy-current data were recorded on magnetic tape, and test properties such as discontinuity size and weld penetration were determined by mathematically fitting these data to coefficients developed with representative standards. A sophisticated computer-controlled scanning technique was applied, and a unique scanning device was developed to provide full coverage of the weld and heat-affected zone. The techniques used to develop this multifrequency eddy-current examination are described in this report along with the test equipment, test procedures, and computer programs.

  17. Nondestructive Evaluation of Thermal Spray Coating Interface Quality by Eddy Current Method

    NASA Astrophysics Data System (ADS)

    Mi, Bao; Zhao, Xiaoliang (George); Bayles, Robert

    2007-03-01

    Thermal spray coating is usually applied through directing molten or softened particles at very high velocities onto a substrate. An eddy current non-destructive inspection technique is presented here for thermal spray coating interface quality characterization. Several high-velocity-oxy-fuel (HVOF) coated steel plates were produced with various surface preparation conditions or spray process parameters. A quad-frequency eddy current probe was used to manually scan over the coating surface to evaluate the bonding quality. Experimental results show that different surface preparation conditions and varied process parameters can be successfully differentiated by the impedance value observed from the eddy current probe. The measurement is fairly robust and consistent. This non-contact, nondestructive, easy-to-use technique has the potential for evaluating the coating quality immediately after its application so that any defects can be corrected immediately.

  18. The early stage wheel fatigue crack detection using eddy current pulsed thermography

    NASA Astrophysics Data System (ADS)

    Peng, Jianping; Zhang, Kang; Yang, Kai; He, Zhu; Zhang, Yu; Peng, Chaoyong; Gao, Xiaorong

    2017-02-01

    The in-service wheel-set quality is one of critical challenges for railway safety, especially for the high-speed train. The defect in wheel tread, initiated by rolling contact fatigue (RCF) damage, is one of the most significant phenomena and has serious influence on rail industry. Eddy current pulsed thermography is studied to compensate the UT method for detection these early stage of fatigue cracks in wheel tread surface. This paper proposes approximately uniform magnetic field, excited by Helmholtz coils, based pulsed eddy current thermography to achieve open-view image and meet the irregular surface in wheel tread through numerical way. Some features are extracted and studied also to quantify the fatigue crack in term of eddy current pulsed thermography. The proposed method enhances the capability for cracks detection and quantitative evaluation compared with previous NDT method in railway.

  19. Eddy current braking experiment using brake disc from aluminium series of A16061 and A17075

    NASA Astrophysics Data System (ADS)

    Baharom, M. Z.; Nuawi, M. Z.; Priyandoko, G.; Harris, S. M.

    2012-09-01

    The electromagnetic braking using eddy current was studied, focused on two series of aluminium as the brake disc which are A16061 and A17075. This paper presents the comparison for both series in a few varied parameters related to eddy current braking such as air-gap, number of turns and brake disc thickness. Optical tachometer has been used along with PULSE analyzer to capture the speed (rpm) and time (s). The findings shows that the smaller the air-gap, the larger of electromagnet turns and the thicker disc thickness is, will generate higher braking torque to stop the rotational motion of disc brake and give great performance for eddy current braking. Thos parameters that been evaluated also addressed a potential on expanding this knowledge to develop an electromagnetic braking system to replace the conventional braking system.

  20. Theory of thin-skin eddy-current interaction with surface cracks

    NASA Astrophysics Data System (ADS)

    Harfield, N.; Bowler, J. R.

    1997-11-01

    Eddy-current non-destructive evaluation is commonly performed at relatively high frequencies at which the skin depths are significantly smaller than the dimensions of a typical crack. A thin-skin analysis of eddy currents is presented in which the electromagnetic fields on the crack faces are described in terms of a potential which obeys a two-dimensional Laplace equation. Solutions of this equation for defects in both magnetic and non-magnetic materials are determined by applying thin-skin boundary conditions at the crack perimeter. The impedance change of an eddy-current coil due to the defect is then calculated by numerical evaluation of one-dimensional integrals over the line of the crack mouth, the impedance integrals having been derived with the aid of a reciprocity relationship. Theoretical predictions are compared with experimental data for long, uniformly deep slots in aluminium and mild steel and good agreement between theory and experiment is obtained.

  1. The atmospheric ocean: eddies and jets in the Antarctic Circumpolar Current.

    PubMed

    Thompson, Andrew F

    2008-12-28

    Although the Antarctic Circumpolar Current (ACC) is the longest and the strongest oceanic current on the Earth and is the primary means of inter-basin exchange, it remains one of the most poorly represented components of global climate models. Accurately describing the circulation of the ACC is made difficult owing to the prominent role that mesoscale eddies and jets, oceanic equivalents of atmospheric storms and storm tracks, have in setting the density structure and transport properties of the current. The successes and limitations of different representations of eddy processes in models of the ACC are considered, with particular attention given to how the circulation responds to changes in wind forcing. The dynamics of energetic eddies and topographically steered jets may both temper and enhance the sensitivity of different aspects of the ACC's circulation to changes in climate.

  2. Motion-induced eddy current thermography for high-speed inspection

    NASA Astrophysics Data System (ADS)

    Wu, Jianbo; Li, Kongjing; Tian, Guiyun; Zhu, Junzhen; Gao, Yunlai; Tang, Chaoqing; Chen, Xiaotian

    2017-08-01

    This letter proposes a novel motion-induced eddy current based thermography (MIECT) for high-speed inspection. In contrast to conventional eddy current thermography (ECT) based on a time-varying magnetic field created by an AC coil, the motion-induced eddy current is induced by the relative motion between magnetic field and inspected objects. A rotating magnetic field created by three-phase windings is used to investigate the heating principle and feasibility of the proposed method. Firstly, based on Faraday's law the distribution of MIEC is investigated, which is then validated by numerical simulation. Further, experimental studies are conducted to validate the proposed method by creating rotating magnetic fields at different speeds from 600 rpm to 6000 rpm, and it is verified that rotating speed will increase MIEC intensity and thereafter improve the heating efficiency. The conclusion can be preliminarily drawn that the proposed MIECT is a platform suitable for high-speed inspection.

  3. PSF mapping-based correction of eddy-current-induced distortions in diffusion-weighted echo-planar imaging.

    PubMed

    In, Myung-Ho; Posnansky, Oleg; Speck, Oliver

    2016-05-01

    To accurately correct diffusion-encoding direction-dependent eddy-current-induced geometric distortions in diffusion-weighted echo-planar imaging (DW-EPI) and to minimize the calibration time at 7 Tesla (T). A point spread function (PSF) mapping based eddy-current calibration method is newly presented to determine eddy-current-induced geometric distortions even including nonlinear eddy-current effects within the readout acquisition window. To evaluate the temporal stability of eddy-current maps, calibration was performed four times within 3 months. Furthermore, spatial variations of measured eddy-current maps versus their linear superposition were investigated to enable correction in DW-EPIs with arbitrary diffusion directions without direct calibration. For comparison, an image-based eddy-current correction method was additionally applied. Finally, this method was combined with a PSF-based susceptibility-induced distortion correction approach proposed previously to correct both susceptibility and eddy-current-induced distortions in DW-EPIs. Very fast eddy-current calibration in a three-dimensional volume is possible with the proposed method. The measured eddy-current maps are very stable over time and very similar maps can be obtained by linear superposition of principal-axes eddy-current maps. High resolution in vivo brain results demonstrate that the proposed method allows more efficient eddy-current correction than the image-based method. The combination of both PSF-based approaches allows distortion-free images, which permit reliable analysis in diffusion tensor imaging applications at 7T. © 2015 Wiley Periodicals, Inc.

  4. Eddy current simulation in thick cylinders of finite length induced by coils of arbitrary geometry

    NASA Astrophysics Data System (ADS)

    Sanchez Lopez, Hector; Poole, Michael; Crozier, Stuart

    2010-12-01

    Eddy currents are inevitably induced when time-varying magnetic field gradients interact with the metallic structures of a magnetic resonance imaging (MRI) scanner. The secondary magnetic field produced by this induced current degrades the spatial and temporal performance of the primary field generated by the gradient coils. Although this undesired effect can be minimized by using actively and/or passively shielded gradient coils and current pre-emphasis techniques, a residual eddy current still remains in the MRI scanner structure. Accurate simulation of these eddy currents is important in the successful design of gradient coils and magnet cryostat vessels. Efficient methods for simulating eddy currents are currently restricted to cylindrical-symmetry. The approach presented in this paper divides thick conducting cylinders into thin layers (thinner than the skin depth) and expresses the current density on each as a Fourier series. The coupling between each mode of the Fourier series with every other is modeled with an inductive network method. In this way, the eddy currents induced in realistic cryostat surfaces by coils of arbitrary geometry can be simulated. The new method was validated by simulating a canonical problem and comparing the results against a commercially available software package. An accurate skin depth of 2.76 mm was calculated in 6 min with the new method. The currents induced by an actively shielded x-gradient coil were simulated assuming a finite length cylindrical cryostat consisting of three different conducting materials. Details of the temporal-spatial induced current diffusion process were simulated through all cryostat layers, which could not be efficiently simulated with any other method. With this data, all quantities that depend on the current density, such as the secondary magnetic field, are simply evaluated.

  5. Transient Eddy Current Response Due to a Subsurface Crack in a Conductive Plate

    SciTech Connect

    Fu, Fangwei

    2006-01-01

    Eddy current nondestructive evaluation (NDE) is usually carried out by exciting a time harmonic field using an inductive probe. However, a viable alternative is to use transient eddy current NDE in which a current pulse in a driver coil produces a transient .eld in a conductor that decays at a rate dependent on the conductivity and the permeability of the material and the coil configuration. By using transient eddy current, it is possible to estimate the properties of the conductive medium and to locate and size potential .aws from the measured probe response. The fundamental study described in this dissertation seeks to establish a theoretical understanding of the transient eddy current NDE. Compared with the Fourier transform method, the derived analytical formulations are more convenient when the transient eddy current response within a narrow time range is evaluated. The theoretical analysis provides a valuable tool to study the effect of layer thickness, location of defect, crack opening as well as the optimization of probe design. Analytical expressions have been developed to evaluate the transient response due to eddy currents in a conductive plate based on two asymptotic series. One series converges rapidly for a short time regime and the other for a long time regime and both of them agree with the results calculated by fast Fourier transform over all the times considered. The idea of asymptotic expansion is further applied to determine the induced electromotive force (EMF) in a pick-up coil due to eddy currents in a cylindrical rod. Starting from frequency domain representation, a quasi-static time domain dyadic Green's function for an electric source in a conductive plate has been derived. The resulting expression has three parts; a free space term, multiple image terms and partial reflection terms. The dyadic Green's function serves as the kernel of an electric field integral equation which defines the interaction of an ideal crack with the transient

  6. Model-based study for evaluating the sensitivity of eddy current GMR probe inspection of multilayer structures

    NASA Astrophysics Data System (ADS)

    Su, Zhiyi; Rosell, Anders; Udpa, Lalita; Tamburrino, Antonello

    2017-02-01

    In eddy current nondestructive testing (EC-NDT) of a multilayer riveted structure, rotating current excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. The signal of a defect is not only a function of its size but also of the geometrical features in vicinity to the rivet such as edges, adjacent rivets and properties of the layered structure. Numerical models can be used to provide fast and accurate estimates of defect signals. In this paper the sensitivity of the eddy current system with rotating current excitation and GMR sensors is evaluated by considering the effect of rivet permeability, lift-off, thickness of first layer as well as defect orientation related to adjacent rivets and edges on the signal measured. A numerical model capable of simulating these combinations of defect and test geometry parameters at an acceptable computation time is used. A meta-model is developed based on these simulation results and utilized for sensitivity evaluation.

  7. Development of High Resolution Eddy Current Imaging Using an Electro-Mechanical Sensor (Postprint)

    DTIC Science & Technology

    2011-08-01

    coil and detecting the magnetic field using sensors like Hall Effect (HE) [5-7], Magneto-Resistance (MR) and Giant Magneto-Resistance (GMR) [8-10...sensors, Flux Gate sensors [11,12], SQUID sensors [13,14] etc. In all these methods, large electromagnetic coils are used to generate eddy currents in...Bowler and K. Miya, (IOS Press, Amsterdam, 1995), pp. 115–124. 8. T. Dogaru and S. T. Smith, “ Giant Magnetoresistance-Based Eddy-Current Sensor,” in

  8. Effect of vacuum chamber eddy current and compensation by digital feedback

    SciTech Connect

    Chung, Y.

    1992-07-27

    Measurement of the effect of the eddy current induced in the APS storage ring vacuum chamber by the storage ring sextupole magnet and its compensation using digital feedback with proportional, integral, and derivative (PID) control algorithm are presented. The magnetic field in the vacuum chamber shows strong quadrupole and sextupole components varying with frequency, in addition to significant attenuation and phase shift. Large changes in the magnet resistance and inductance were also observed. Development of a theory of digital feedback to obtain system responses and the conditions for optimal control will be described, in conduction with design of a digital filter to compensate for the eddy current effect.

  9. Procedure for Automated Eddy Current Crack Detection in Thin Titanium Plates

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.

    2012-01-01

    This procedure provides the detailed instructions for conducting Eddy Current (EC) inspections of thin (5-30 mils) titanium membranes with thickness and material properties typical of the development of Ultra-Lightweight diaphragm Tanks Technology (ULTT). The inspection focuses on the detection of part-through, surface breaking fatigue cracks with depths between approximately 0.002" and 0.007" and aspect ratios (a/c) of 0.2-1.0 using an automated eddy current scanning and image processing technique.

  10. Diagnostics of flexible workpiece using acoustic emission, acceleration and eddy current sensors in milling operation

    NASA Astrophysics Data System (ADS)

    Filippov, A. V.; Tarasov, S. Yu.; Filippova, E. O.; Chazov, P. A.; Shamarin, N. N.; Podgornykh, O. A.

    2016-11-01

    Monitoring of the edge clamped workpiece deflection during milling has been carried our using acoustic emission, accelerometer and eddy current sensors. Such a monitoring is necessary in precision machining of vital parts used in air-space engineering where a majority of them made by milling. The applicability of the AE, accelerometers and eddy current sensors has been discussed together with the analysis of measurement errors. The appropriate sensor installation diagram has been proposed for measuring the workpiece elastic deflection exerted by the cutting force.

  11. Note: Void effects on eddy current distortion in two-phase liquid metal

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Tordjeman, Ph.; Bergez, W.; Cavaro, M.

    2015-10-01

    A model based on the first order perturbation expansion of magnetic flux in a two-phase liquid metal flow has been developed for low magnetic Reynolds number Rem. This model takes into account the distortion of the induced eddy currents due to the presence of void in the conducting medium. Specific experiments with an eddy current flow meter have been realized for two periodic void distributions. The results have shown, in agreement with the model, that the effects of velocity and void on the emf modulation are decoupled. The magnitude of the void fraction and the void spatial frequency can be determined from the spectral density of the demodulated emf.

  12. A constitutive model for the forces of a magnetic bearing including eddy currents

    NASA Technical Reports Server (NTRS)

    Taylor, D. L.; Hebbale, K. V.

    1993-01-01

    A multiple magnet bearing can be developed from N individual electromagnets. The constitutive relationships for a single magnet in such a bearing is presented. Analytical expressions are developed for a magnet with poles arranged circumferencially. Maxwell's field equations are used so the model easily includes the effects of induced eddy currents due to the rotation of the journal. Eddy currents must be included in any dynamic model because they are the only speed dependent parameter and may lead to a critical speed for the bearing. The model is applicable to bearings using attraction or repulsion.

  13. Eddy Current Analysis and Optimization for Superconducting Magnetic Bearing of Flywheel Energy Storage System

    NASA Astrophysics Data System (ADS)

    Arai, Yuuki; Yamashita, Tomohisa; Hasegawa, Hitoshi; Matsuoka, Taro; Kaimori, Hiroyuki; Ishihara, Terumasa

    Levitation and guidance force is electromagnetic generated between a superconducting coil and zero field cooled bulk superconductors used in our flywheel energy storage system (FESS). Because the magnetic field depends on the configuration of the coil and the bulks, the eccentricity and the vibration of a rotor cause fluctuation in the magnetic field which induces eddy current and consequent Joule heat on electric conductors such as cooling plates. Heat generation in the cryogenic region critically reduces the efficiency of the FESS. In this paper, we will report the result of the electromagnetic analysis of the SMB and propose an optimal divided cooling plate for reducing the eddy current and Joule heat.

  14. Three Dimensional Eddy Current Analysis by Multi-Order Vector Finite Elements

    NASA Astrophysics Data System (ADS)

    Hano, Mitsuo; Hotta, Masashi

    In this paper, we propose new method based on multi-order vector finite elements in three dimensional eddy current analysis. Edges, faces, and volume of the multi-order element have orders of shape functions, respectively. In order to realize high efficiency of numerical calculation, high-order elements are assigned in the important area of the eddy current model, and low-order elements in the surrounding area, and multi-order elements in the middle area to bond two areas, respectively. The results obtained by multi-order elements are compared with those by full high-order elements and by full low-order elements.

  15. Eddy current measurements of the new high T(sub c) ceramic superconductors

    NASA Astrophysics Data System (ADS)

    Telschow, K. L.; Kunerth, D. C.

    The major properties of superconductors are zero resistance and diamagetism (Meissner effect). Eddy current techniques provide a means of determining these properties simultaneously with a noncontacting probe. We present the results of CW measurements obtained for YBa sub 2 Cu sub 3 O sub 7-x prepared by solid state reaction and sol-gel powder fabrication techniques, along with concurrent dc resistive measurements of the transition. The data are interpreted in light of the sample's superconducting properties and the general effects of superconductivity on the eddy current measurement method.

  16. Compulsory Checking of Nuclear Power Engineering Materials by Direct and Eddy Current

    NASA Astrophysics Data System (ADS)

    Larionov, V. V.; Lider, A. M.; Sednev, D. A.; Xu, Shupeng

    2016-08-01

    The testing technology of copper parts designed for dry storage of spent nuclear fuel with application of direct and eddy current has been developed. Measurements results of flaw quantity caused hydrogenation and oxidation processes are presented. Evolution of copper M 001 flaw structure during hydrogenation from gaseous medium is analyzed. It has been demonstrated that the dependence of copper p electrical resistance on number of flaws in its structure has dome shaped character and changes with eddy current frequency change. Number of flaws formed by hydrogen depends on direction (100) or (200) of the crystal structure of copper lattice.

  17. Mesoscale eddy variability in the southern extension of the East Madagascar Current: Seasonal cycle, energy conversion terms, and eddy mean properties

    NASA Astrophysics Data System (ADS)

    Halo, Issufo; Penven, Pierrick; Backeberg, Björn; Ansorge, Isabelle; Shillington, Frank; Roman, Raymond

    2014-10-01

    In this study, we used more than 17 years of satellite altimetry observations and output from an ocean model to investigate the mesoscale eddy variability and forcing mechanisms to the south of Madagascar. Analysis of energy conversion terms in the model has shown seasonality on eddy formation, both by barotropic and baroclinic instabilities: maximum in winter (JJA) and minimum in summer (DJF). The eddies were mainly formed in the upper ocean (0-300 m) and at intermediate depths (800-2000 m) by barotropic and baroclinic instabilities, respectively. The former dominated in the southeastern margin of Madagascar, and the latter to the southwest, where the South-East Madagascar Current (SEMC) separates from the continental shelf. Seasonality of the eddy formation appeared linked with the seasonal intensification of the SEMC. The energy conversion terms indicated that the eddies have a significant contribution to the large-scale circulation, but not being persistent throughout the year, occurring mainly during the fall season (MAM). Eddy demography from altimetry and model provided information on eddy preferential sites for birth, annual occurrence (6-13 per year), eddy mean diameter (124-178 km), mean amplitude (9-28 cm), life-time (90-183 days), and maximum traveling distances (325-1052 km). Eddies formed to the southwest of Madagascar exhibited distinct characteristics from those formed in the southeast. Nevertheless, all eddies were highly nonlinear, suggesting that they are potential vectors of connectivity between Madagascar and Africa. This may have a significant impact on the ecology of this region.

  18. Evidences on eddy variability and density currents in the deep flow of the Strait of Otranto

    NASA Astrophysics Data System (ADS)

    Kovacevic, Vedrana; Ursella, Laura; Gacic, Miroslav

    2010-05-01

    ; turbidity rises at V4; eastward velocity is maximum at V3 and V4. More precisely, the turbidity maximum occurred in concomitance with the beginning of the rotational event, when the currents are directed from the continental slope towards the centre of the Strait and are rather strong (up to 20 cm/s). As soon as the current turns southward the turbidity reduces and reaches the background levels. A detailed bottom topography of the zone, obtained from a multibeam survey, revealed existence of a canyon, about 2 km wide and 15 km long, just 3 km upstream of the measurement transect. This structure deepens in the E-W direction from the shelf (200 m) to the bottom of the Strait (800 m). The canyon probably represents a conduit for cross-shore water and bottom sediment transport from the western shelf down to the abyssal depths at least about 40 km from the mouth of the canyon. Moreover, eddies on their passage trap colder and less saline Adriatic outflowing waters from the shelf-break area (T and S drop). Location V2 (shallowest station) is out of its trajectory, being shallower and to the west with respect to the mouth of the canyon. This might be corroborated by temperature/salinity signal at V2, for which no correspondence with the other two locations is seen. Moreover, salinity at V2 rises during the first event, which may be due to the more saline intermediate waters that are trapped and advected by the eddy from the centre of the channel toward the shelf break. We would like to stress that the presence of possible density currents and associated sediment transport has been hinted for the first time, thanks to the opportune mooring equipment and high resolution multibeam survey.

  19. Mapping B(1)-induced eddy current effects near metallic structures in MR images: a comparison of simulation and experiment.

    PubMed

    Vashaee, S; Goora, F; Britton, M M; Newling, B; Balcom, B J

    2015-01-01

    Magnetic resonance imaging (MRI) in the presence of metallic structures is very common in medical and non-medical fields. Metallic structures cause MRI image distortions by three mechanisms: (1) static field distortion through magnetic susceptibility mismatch, (2) eddy currents induced by switched magnetic field gradients and (3) radio frequency (RF) induced eddy currents. Single point ramped imaging with T1 enhancement (SPRITE) MRI measurements are largely immune to susceptibility and gradient induced eddy current artifacts. As a result, one can isolate the effects of metal objects on the RF field. The RF field affects both the excitation and detection of the magnetic resonance (MR) signal. This is challenging with conventional MRI methods, which cannot readily separate the three effects. RF induced MRI artifacts were investigated experimentally at 2.4 T by analyzing image distortions surrounding two geometrically identical metallic strips of aluminum and lead. The strips were immersed in agar gel doped with contrast agent and imaged employing the conical SPRITE sequence. B1 mapping with pure phase encode SPRITE was employed to measure the B1 field around the strips of metal. The strip geometry was chosen to mimic metal electrodes employed in electrochemistry studies. Simulations are employed to investigate the RF field induced eddy currents in the two metallic strips. The RF simulation results are in good agreement with experimental results. Experimental and simulation results show that the metal has a pronounced effect on the B1 distribution and B1 amplitude in the surrounding space. The electrical conductivity of the metal has a minimal effect.

  20. Western boundary currents regulated by interaction between ocean eddies and the atmosphere.

    PubMed

    Ma, Xiaohui; Jing, Zhao; Chang, Ping; Liu, Xue; Montuoro, Raffaele; Small, R Justin; Bryan, Frank O; Greatbatch, Richard J; Brandt, Peter; Wu, Dexing; Lin, Xiaopei; Wu, Lixin

    2016-07-28

    Current climate models systematically underestimate the strength of oceanic fronts associated with strong western boundary currents, such as the Kuroshio and Gulf Stream Extensions, and have difficulty simulating their positions at the mid-latitude ocean's western boundaries. Even with an enhanced grid resolution to resolve ocean mesoscale eddies-energetic circulations with horizontal scales of about a hundred kilometres that strongly interact with the fronts and currents-the bias problem can still persist; to improve climate models we need a better understanding of the dynamics governing these oceanic frontal regimes. Yet prevailing theories about the western boundary fronts are based on ocean internal dynamics without taking into consideration the intense air-sea feedbacks in these oceanic frontal regions. Here, by focusing on the Kuroshio Extension Jet east of Japan as the direct continuation of the Kuroshio, we show that feedback between ocean mesoscale eddies and the atmosphere (OME-A) is fundamental to the dynamics and control of these energetic currents. Suppressing OME-A feedback in eddy-resolving coupled climate model simulations results in a 20-40 per cent weakening in the Kuroshio Extension Jet. This is because OME-A feedback dominates eddy potential energy destruction, which dissipates more than 70 per cent of the eddy potential energy extracted from the Kuroshio Extension Jet. The absence of OME-A feedback inevitably leads to a reduction in eddy potential energy production in order to balance the energy budget, which results in a weakened mean current. The finding has important implications for improving climate models' representation of major oceanic fronts, which are essential components in the simulation and prediction of extratropical storms and other extreme events, as well as in the projection of the effect on these events of climate change.

  1. Coupled circuit numerical analysis of eddy currents in an open MRI system.

    PubMed

    Akram, Md Shahadat Hossain; Terada, Yasuhiko; Keiichiro, Ishi; Kose, Katsumi

    2014-08-01

    We performed a new coupled circuit numerical simulation of eddy currents in an open compact magnetic resonance imaging (MRI) system. Following the coupled circuit approach, the conducting structures were divided into subdomains along the length (or width) and the thickness, and by implementing coupled circuit concepts we have simulated transient responses of eddy currents for subdomains in different locations. We implemented the Eigen matrix technique to solve the network of coupled differential equations to speed up our simulation program. On the other hand, to compute the coupling relations between the biplanar gradient coil and any other conducting structure, we implemented the solid angle form of Ampere's law. We have also calculated the solid angle for three dimensions to compute inductive couplings in any subdomain of the conducting structures. Details of the temporal and spatial distribution of the eddy currents were then implemented in the secondary magnetic field calculation by the Biot-Savart law. In a desktop computer (Programming platform: Wolfram Mathematica 8.0®, Processor: Intel(R) Core(TM)2 Duo E7500 @ 2.93GHz; OS: Windows 7 Professional; Memory (RAM): 4.00GB), it took less than 3min to simulate the entire calculation of eddy currents and fields, and approximately 6min for X-gradient coil. The results are given in the time-space domain for both the direct and the cross-terms of the eddy current magnetic fields generated by the Z-gradient coil. We have also conducted free induction decay (FID) experiments of eddy fields using a nuclear magnetic resonance (NMR) probe to verify our simulation results. The simulation results were found to be in good agreement with the experimental results. In this study we have also conducted simulations for transient and spatial responses of secondary magnetic field induced by X-gradient coil. Our approach is fast and has much less computational complexity than the conventional electromagnetic numerical simulation

  2. Reynolds Stress Distributions and the Measurement and Calculation of Eddy Viscosity in Gravity Currents

    NASA Astrophysics Data System (ADS)

    Kelly, R. W.; Chalk, C.; Dorrell, R. M.; Peakall, J.; Burns, A. D.; Keevil, G. M.; Thomas, R. E.; Williams, G.

    2016-12-01

    In the natural environment, gravity currents transport large volumes of sediment great distances and are often considered one of the most important mechanisms for sediment transport in ocean basins. Deposits from many individual submarine gravity currents, turbidites, ultimately form submarine fan systems. These are the largest sedimentary systems on the planet and contain valuable hydrocarbon reserves. Moreover, the impact of these currents on submarine technologies and seafloor infrastructure can be devastating and therefore they are of significant interest to a wide range of industries. Here we present experimental, numerical and theoretical models of time-averaged turbulent shear stresses, i.e. Reynolds stresses. Reynolds stresses can be conceptually parameterised by an eddy viscosity parameter that relates chaotic fluid motion to diffusive type processes. As such, it is a useful parameter for indicating the extent of internal mixing and is used extensively in both numerical and analytical modelling of both open-channel and gravity driven flows. However, a lack of knowledge of the turbulent structure of gravity currents limits many hydro- and morphodynamic models. High resolution 3-dimensional experimental velocity data, gathered using acoustic Doppler profiling velocimetry, enabled direct calculation of stresses and eddy viscosity. Comparison of experimental data to CFD and analytical models allowed the testing of eddy viscosity-based turbulent mixing models. The calculated eddy viscosity profile is parabolic in nature in both the upper and lower shear layers. However, an apparent breakdown in the Boussinesq hypothesis (used to calculate the eddy viscosity and upon which many numerical models are based) is observed in the region of the current around the velocity maximum. With the use of accompanying density data it is suggested that the effect of stratification on eddy viscosity is significant and alternative formulations may be required.

  3. The influence of Loop Current perturbations on the formation and evolution of Tortugas eddies in the southern Straits of Florida

    NASA Astrophysics Data System (ADS)

    Fratantoni, Paula S.; Lee, Thomas N.; Podesta, Guillermo P.; Muller-Karger, Frank

    1998-10-01

    Large cyclonic eddies on the northern edge of the Florida Current are the dominant mesoscale features within the southern Straits of Florida. The most prominent of these features is a quasi-stationary eddy that forms near the Dry Tortugas. Our observations, compiled from 3 years of advanced very high resolution radiometer measurements in the Straits of Florida and Gulf of Mexico, demonstrate a strong relationship between the generation of anticyclonic rings from the Gulf of Mexico Loop Current and the evolution of Tortugas eddies within the southern Straits of Florida. In six cases, Tortugas eddies evolve from cyclonic frontal eddies which form along the boundary of the Loop Current. The eddies remain stationary near the Dry Tortugas until they are impacted by an approaching Loop Current frontal eddy. The length of time an eddy spends near the Dry Tortugas is increased when the Loop Current sheds an anticyclonic ring. The involvement of a Loop Current frontal eddy in the ring-shedding process results in a delay in its, and hence the Tortugas eddy's, downstream propagation. Results suggest that the lifetime of a Tortugas eddy can be as long as 140 days when a ring-shedding event occurs, or as short as 50 days in the absence of any ring-shedding events. Upon entering the Straits of Florida, the Tortugas eddies are deformed by the narrowing topography and shrink to approximately 55% of their original size as they propagated downstream. The shrinking of these eddies is accompanied by an accelerated translation from 5 km/d in the western Straits of Florida to 16 km/d in the east.

  4. Computer programs for the acquisition and analysis of eddy-current array probe data

    SciTech Connect

    Pate, J.R.; Dodd, C.V.

    1996-07-01

    Objective of the Improved Eddy-Curent ISI (in-service inspection) for Steam Generators Tubing program is to upgrade and validate eddy-current inspections, including probes, instrumentation, and data processing techniques for ISI of new, used, and repaired steam generator tubes; to improve defect detection, classification and characterization as affected by diameter and thickness variations, denting, probe wobble, tube sheet, tube supports, copper and sludge deposits, even when defect types and other variables occur in combination; to transfer this advanced technology to NRC`s mobile NDE laboratory and staff. This report documents computer programs that were developed for acquisition of eddy-current data from specially designed 16-coil array probes. Complete code as well as instructions for use are provided.

  5. Simulations of the Arctic Boundary Current in an eddy-resolving global ocean model

    NASA Astrophysics Data System (ADS)

    Aksenov, Y.; Nurser, A. J. G.; Bacon, S.; Coward, A. C.

    2012-04-01

    The Arctic Ocean is shielded from winds by sea ice and is strongly stratified, resulting in extremely low mixing rates. In this quiescent ocean, currents along the continental shelves become the principal dynamical features of the circulation. Observations and model results suggest the existence of a fast oceanic current in the Arctic Ocean, the Arctic Circumpolar Boundary Current (ACBC). The current flows counterclockwise (cyclonically) along the shelf break of the Siberian, Alaskan and Canadian Arctic shelves all way around the Arctic Ocean margins, leaving through western Fram Strait, and taking about two decades to complete the circuit (Aksenov et al., 2011). Simulations with an eddy-resolving global 1/12 degree NEMO model show that the ACBC consists of several jets with the fastest flow occurring at the shelf break. We compare the models results with observations and examine mechanisms driving the ACBC. Through the analysis of the NEMO simulations performed with eddy-resolving, eddy-permitting and non-eddying model configurations we investigate the effect of resolution on the current. Reference Aksenov, Y., V. V. Ivanov, A. J. G. Nurser, S. Bacon, I. V. Polyakov, A. C. Coward, A. C. Naveira-Garabato, and A. Beszczynska-Moeller (2011), The Arctic Circumpolar Boundary Current, J. Geophys. Res., 116, C09017, doi:10.1029/2010JC006637.

  6. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique

    PubMed Central

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-01-01

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112

  7. Frequency Optimization for Enhancement of Surface Defect Classification Using the Eddy Current Technique.

    PubMed

    Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun

    2016-05-07

    Eddy current testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances.

  8. Eddy current characterization of small cracks using least square support vector machine

    NASA Astrophysics Data System (ADS)

    Chelabi, M.; Hacib, T.; Le Bihan, Y.; Ikhlef, N.; Boughedda, H.; Mekideche, M. R.

    2016-04-01

    Eddy current (EC) sensors are used for non-destructive testing since they are able to probe conductive materials. Despite being a conventional technique for defect detection and localization, the main weakness of this technique is that defect characterization, of the exact determination of the shape and dimension, is still a question to be answered. In this work, we demonstrate the capability of small crack sizing using signals acquired from an EC sensor. We report our effort to develop a systematic approach to estimate the size of rectangular and thin defects (length and depth) in a conductive plate. The achieved approach by the novel combination of a finite element method (FEM) with a statistical learning method is called least square support vector machines (LS-SVM). First, we use the FEM to design the forward problem. Next, an algorithm is used to find an adaptive database. Finally, the LS-SVM is used to solve the inverse problems, creating polynomial functions able to approximate the correlation between the crack dimension and the signal picked up from the EC sensor. Several methods are used to find the parameters of the LS-SVM. In this study, the particle swarm optimization (PSO) and genetic algorithm (GA) are proposed for tuning the LS-SVM. The results of the design and the inversions were compared to both simulated and experimental data, with accuracy experimentally verified. These suggested results prove the applicability of the presented approach.

  9. Approach for removing ghost-images in remote field eddy current testing of ferromagnetic pipes

    NASA Astrophysics Data System (ADS)

    Luo, Q. W.; Shi, Y. B.; Wang, Z. G.; Zhang, W.; Zhang, Y.

    2016-10-01

    In the non-destructive testing of ferromagnetic pipes based on remote field eddy currents, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.

  10. Approach for removing ghost-images in remote field eddy current testing of ferromagnetic pipes.

    PubMed

    Luo, Q W; Shi, Y B; Wang, Z G; Zhang, W; Zhang, Y

    2016-10-01

    In the non-destructive testing of ferromagnetic pipes based on remote field eddy currents, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.

  11. Pulsed eddy current differential probe to detect the defects in a stainless steel pipe

    NASA Astrophysics Data System (ADS)

    Angani, C. S.; Park, D. G.; Kim, C. G.; Leela, P.; Kishore, M.; Cheong, Y. M.

    2011-04-01

    Pulsed eddy current (PEC) is an electromagnetic nondestructive technique widely used to detect and quantify the flaws in conducting materials. In the present study a differential Hall-sensor probe which is used in the PEC system has been fabricated for the detection of defects in stainless steel pipelines. The differential probe has an exciting coil with two Hall-sensors. A stainless steel test sample with electrical discharge machining (EDM) notches under different depths of 1-5 mm was made and the sample was laminated by plastic insulation having uniform thickness to simulate the pipelines in nuclear power plants (NPPs). The driving coil in the probe is excited by a rectangular current pulse and the resultant response, which is the difference of the two Hall-sensors, has been detected as the PEC probe signal. The discriminating time domain features of the detected pulse such as peak value and time to zero are used to interpret the experimental results with the defects in the test sample. A feature extraction technique such as spectral power density has been devised to infer the PEC response.

  12. Interactions between the Somali Current eddies during the summer monsoon: insights from a numerical study

    NASA Astrophysics Data System (ADS)

    Akuetevi, C. Q. C.; Barnier, B.; Verron, J.; Molines, J.-M.; Lecointre, A.

    2016-02-01

    Three hindcast simulations of the global ocean circulation differing by resolution (1/4 or 1/12°) or parametrization or atmospheric forcing are used to describe the interactions between the large anticyclonic eddies generated by the Somali Current system during the Southwest Monsoon. The present investigation of the Somalian coherent eddy structures allows us to identify the origin and the subsequent development of the cyclones flanked upon the Great Whirl (GW) previously identified by Beal and Donohue (2013) in satellite observations and to establish that similar cyclones are also flanked upon the Southern Gyre (SG). These cyclones are identified as potential actors in mixing water masses within the large eddies and offshore the coast of Somalia. All three simulations bring to light that during the period when the Southwest Monsoon is well established, the SG moves northward along the Somali coast and encounters the GW. The interaction between the SG and the GW is a collision without merging, in a way that has not been described in observations up to now. During the collision the GW is pushed to the east of Socotra Island, sheds several smaller patches of anticyclonic vorticity, and often reforms into the Socotra Eddy, thus proposing a formation mechanism for that eddy. During this process the GW gives up its place to the SG. This process is robust throughout the three simulations.

  13. Predicting the influence of plate geometry on the eddy-current pendulum

    NASA Astrophysics Data System (ADS)

    Weigel, Catherine; Wachter, Jeremy M.; Wagoner, Paul; Atherton, Timothy J.

    2016-09-01

    We quantitatively analyze a familiar classroom demonstration, Van Waltenhofen's eddy current pendulum, to predict the damping effect for a variety of plate geometries from first principles. Results from conformal mapping, finite element simulations, and a simplified model suitable for introductory classes are compared with experiments.

  14. Analytical modeling of a simple passive electromagnetic eddy current friction damper

    NASA Astrophysics Data System (ADS)

    Amjadian, Mohsen; Agrawal, Anil K.

    2016-04-01

    This paper presents analytical modeling of a novel type of passive friction damper for seismic hazard mitigation of structural systems. This seismic protective device, which is termed as Passive Electromagnetic Eddy Current Friction Damper (PEMECFD), utilizes a solid-friction mechanism in parallel with an eddy current damping system to dissipate a larger amount of input seismic energy than that by a device with based on solid friction only. In this passive damper, friction force is produced through a magnetic repulsive action between two permanent magnets (PMs) magnetized in the direction normal to the friction surface. The eddy current damping force in the damper is generated because of the motion of the PMS in the vicinity of a conductor. Friction and eddy current damping parts of the damper are able to produce ideal rectangular and elliptical hysteresis loops individually. Seismic hazard mitigation effectiveness of the proposed damper has been demonstrated through an implementation on a two-degree-of-freedom frame building structure. Numerical results show that the proposed damper is more efficient in dissipating input seismic energy than a Passive Linear Viscous Damper (PLVD) with same force capacity.

  15. Eddy Current, Magnetic Particle and Hardness Testing, Aviation Quality Control (Advanced): 9227.04.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This unit of instruction includes the principles of eddy current, magnetic particle and hardness testing; standards used for analyzing test results; techniques of operating equipment; interpretation of indications; advantages and limitations of these methods of testing; care and calibration of equipment; and safety and work precautions. Motion…

  16. Design and Application of Hybrid Magnetic Field-Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Wallace, Terryl; Newman, Andy; Leser, Paul; Simpson, John

    2013-01-01

    The incorporation of magnetic field sensors into eddy current probes can result in novel probe designs with unique performance characteristics. One such example is a recently developed electromagnetic probe consisting of a two-channel magnetoresistive sensor with an embedded single-strand eddy current inducer. Magnetic flux leakage maps of ferrous materials are generated from the DC sensor response while high-resolution eddy current imaging is simultaneously performed at frequencies up to 5 megahertz. In this work the design and optimization of this probe will be presented, along with an application toward analysis of sensory materials with embedded ferromagnetic shape-memory alloy (FSMA) particles. The sensory material is designed to produce a paramagnetic to ferromagnetic transition in the FSMA particles under strain. Mapping of the stray magnetic field and eddy current response of the sample with the hybrid probe can thereby image locations in the structure which have experienced an overstrain condition. Numerical modeling of the probe response is performed with good agreement with experimental results.

  17. Parallel transmission RF pulse design for eddy current correction at ultra high field

    NASA Astrophysics Data System (ADS)

    Zheng, Hai; Zhao, Tiejun; Qian, Yongxian; Ibrahim, Tamer; Boada, Fernando

    2012-08-01

    Multidimensional spatially selective RF pulses have been used in MRI applications such as B1 and B0 inhomogeneities mitigation. However, the long pulse duration has limited their practical applications. Recently, theoretical and experimental studies have shown that parallel transmission can effectively shorten pulse duration without sacrificing the quality of the excitation pattern. Nonetheless, parallel transmission with accelerated pulses can be severely impeded by hardware and/or system imperfections. One of such imperfections is the effect of the eddy current field. In this paper, we first show the effects of the eddy current field on the excitation pattern and then report an RF pulse the design method to correct eddy current fields caused by the RF coil and the gradient system. Experimental results on a 7 T human eight-channel parallel transmit system show substantial improvements on excitation patterns with the use of eddy current correction. Moreover, the proposed model-based correction method not only demonstrates comparable excitation patterns as the trajectory measurement method, but also significantly improves time efficiency.

  18. Evaluation of outer flaws in titanium alloys using eddy current measuring system

    SciTech Connect

    Chady, T.; Psuj, G.; Kowalczyk, J.

    2011-06-23

    In this paper results of shallow outer flaw detection in thick titanium alloy specimens is presented. In order to increase efficiency of inspections of minor defects an eddy current measuring system with a lock-in amplifier was used. The measurements were carried out for flat and cylindrical specimens with artificial flaws.

  19. Reduction of lift-off effect in high-frequency apparent eddy current conductivity spectroscopy

    NASA Astrophysics Data System (ADS)

    Abu-Nabah, Bassam A.

    2017-05-01

    Eddy current spectroscopy is capable of mapping conductivities and thicknesses of layered structures due to its frequency-dependent penetration depth. High-frequency apparent eddy current conductivity (AECC) spectroscopy applications typically mandate covering a frequency range beyond 10 MHz to capture depth-dependent conductivity profiles. Following the standard four-point linear system calibration method beyond 10 MHz makes it difficult to achieve accurate AECC measurements due to spurious self- and stray-capacitive effects where complex eddy current coil impedance variation with lift-off becomes more nonlinear. In this study, two different approaches are presented to reduce AECC measurement sensitivity to lift-off. First, a nonlinear lift-off correction is developed as a function of measured apparent eddy current lift-off. Second, a semi-quadratic system calibration is developed to capture the lift-off curvature as a function of frequency and hence minimizes the measurement sensitivity to lift-off variations. Presented calibration techniques allow more robust AECC measurements up to 80-100 MHz with one-order of magnitude improvement in accuracy in comparison to the use of standard four-point linear system calibration in a lift-off range of  ±25.4 µm.

  20. Numerical method for calculating the apparent eddy current conductivity loss on randomly rough surfaces

    NASA Astrophysics Data System (ADS)

    Yu, Feng; Nagy, Peter B.

    2004-06-01

    Because of their frequency-dependent penetration depth, eddy current measurements are capable of mapping the near-surface depth profile of the electrical conductivity. This technique is used to nondestructively characterize the subsurface residual stress and cold work distributions in shot-peened metal components. Unfortunately, the spurious surface roughness produced by the shot peening process causes an apparent loss of eddy current conductivity, thereby decreasing the accuracy of the measurements, especially in thermally relaxed specimens where the primary material effects are significantly reduced. In this paper, a numerical method is introduced based on the Rayleigh approximation for calculating the apparent eddy current conductivity loss exhibited by 1D randomly rough surfaces. The relevant boundary conditions are satisfied using the so-called point-by-point technique, and the results are first compared to the previously developed Rayleigh-Fourier technique for a 1D sinusoidal corrugation. Pseudorandom surface profiles of different autocorrelation functions are considered. It is found that the Gaussian model lends itself the best to numerical simulations, but it significantly underestimates the apparent eddy current conductivity loss expected on real shot-peened surfaces, which exhibit essentially exponential correlation function. It is also demonstrated that the Lorentzian model is numerically less stable, but physically closer to the exponential one. The latter could not be simulated reliably by the present numerical technique because of its slowly decaying high-frequency spectral components.

  1. Field errors introduced by eddy currents in Fermilab main injector magnets

    SciTech Connect

    Walbridge, D.G.C.; Brown, B.C.; Dinanco, J.B.; Sharoran, S.A.; Sim, J.W.

    1997-10-01

    The Fermilab Main Injector ramps from 8 GeV to 120 GeV in about half a second. The rapidly changing magnetic field induces eddy currents in the stainless steel vacuum tubes, which in turn produce error fields that can affect the beam. Field calculations and measurements are presented for the dipole and quadrupole magnets.

  2. Low eddy current RF shielding enclosure designs for 3T MR applications.

    PubMed

    Lee, Brian J; Watkins, Ronald D; Chang, Chen-Ming; Levin, Craig S

    2017-06-06

    Magnetic resonance-compatible medical devices operate within the MR environment while benefitting from the superior anatomic information of MRI. Avoiding electromagnetic interference between such instrumentation and the MR system is crucial. In this work, various shielding configurations for positron emission tomography (PET) detectors were studied and analyzed regarding radiofrequency (RF) shielding effectiveness and gradient-induced eddy current performances. However, the results of this work apply to shielding considerations for any MR-compatible devices. Six shielding enclosure configurations with various thicknesses, patterns, and materials were designed: solid and segmented copper, phosphor bronze mesh (PBM), and carbon fiber composite (CFC). A series of tests was performed on RF shielding effectiveness and the gradient-induced eddy current. For the shielding effectiveness, the solid copper with various thickness and PBM configurations yield significantly better shielding effectiveness (>15 dB) compared with CFC and segmented configurations. For the gradient-induced eddy current performance, the solid copper shielding configurations with different thicknesses showed significantly worse results, up to a factor of 3.89 dB, compared with the segmented copper, PBM, and the CFC configurations. We evaluated the RF shielding effectiveness and the gradient-induced eddy current artifacts of several shielding designs, and only the PBM showed positive outcomes for both aspects. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  3. A Simple Demonstration of the Effect of Eddy Currents

    ERIC Educational Resources Information Center

    Sapple, Paul; Reilly, Lee M.

    2013-01-01

    Demonstrating that a moving magnet can induce an electromagnetic force by causing an electric current in a conducting material can be shown by a number of methods. A common method is dropping a magnet down a copper pipe and showing that the rate of fall is much slower than expected owing to the induced electric current in the copper pipe. This…

  4. A Simple Demonstration of the Effect of Eddy Currents

    ERIC Educational Resources Information Center

    Sapple, Paul; Reilly, Lee M.

    2013-01-01

    Demonstrating that a moving magnet can induce an electromagnetic force by causing an electric current in a conducting material can be shown by a number of methods. A common method is dropping a magnet down a copper pipe and showing that the rate of fall is much slower than expected owing to the induced electric current in the copper pipe. This…

  5. Effects of Angular Variation on Split D Differential Eddy Current Probe Response (Postprint)

    DTIC Science & Technology

    2016-02-10

    magnetization, and J is the true electric current density. × = (1)× = + × + (2) 090022-2 2 Distribution A. Approved for public release (PA): distribution...AFRL-RX-WP-JA-2016-0327 EFFECTS OF ANGULAR VARIATION ON SPLIT D DIFFERENTIAL EDDY CURRENT PROBE RESPONSE (POSTPRINT) Ryan D...be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE

  6. Eddy-Current-Based Nondestructive Inspection System Using Superconducting Quantum Interference Device for Thin Copper Tubes

    NASA Astrophysics Data System (ADS)

    Hatsukade, Yoshimi; Kosugi, Akifumi; Mori, Kazuaki; Tanaka, Saburo

    2004-11-01

    An eddy-current-based nondestructive inspection (NDI) system using superconducting quantum interference device (SQUID) cooled using a coaxial pulse tube cryocooler was constructed for the inspection of microflaws on copper tubes employing a high-Tc SQUID gradiometer and a Helmholtz-like coil inducer. The detection of artificial flaws several tens of μm in depth on copper tubes 6.35 mm in outer diameter and 0.825 mm in thickness was demonstrated using the SQUID-NDI system. With an excitation field of 1.6 μT at 5 kHz, a 30-μm-depth flaw was successfully detected by the system at an SN ratio of at least 20. The magnetic signal amplitude due to the flaw was proportional to both excitation frequency and the square of flaw depth. With consideration of the system’s sensitivity, the results indicate that sub-10-μm-depth flaws are detectable by the SQUID-NDI system.

  7. Testing of inductively coupled Eddy current position sensor of diverse safety rod in sodium

    SciTech Connect

    Vijayashree, R.; Veeraswamy, R.; Nashine, B. K.; Dash, S. K.; Sharma, P.; Rajan, K. K.; Vijayakumar, G.; Rao, C. B.; Sosamma, S.; Kalyanasundaram, P.

    2011-07-01

    Prototype Fast Breeder Reactor (PFBR) is 500 MWe sodium cooled reactor under construction at Kalpakkam (India)). To improve the reliability of shutdown, Diverse Safety Rods (DSRs) are used in-addition to normal Control and Safety rods. During reactor operating condition, the DSR is parked above the active core and held in its top position by an electromagnet. In the event of a scram signal from the safety logic, the electromagnet holding the DSR is de-energised. Hence the DSR is released into the active core and at the end of travel DSR gets deposited in its bottom position. Because of the mechanical constraints, hard wired connectivity is not permitted from the DSR subassembly to the instrumentation outside the reactor. Hence an inductively coupled Eddy Current Position Sensor (ECPS) has been conceptualized to detect that the DSR has reached its bottom most position and to measure the drop time. Results of feasibility study on laboratory model have been reported earlier. Testing of a 1:1 scale engineering model of ECPS is reported in this paper. Results obtained from the high temperature sodium testing of ECPS indicate a clearly measurable change in pick up voltage with sensitivity of 11 % at 675 Hz. The ECPS is in advanced stage of implementation in DSRDM of PFBR. (authors)

  8. Multiplexed HTS rf SQUID magnetometer array for eddy current testing of aircraft rivet joints

    NASA Astrophysics Data System (ADS)

    Gärtner, S.; Krause, H.-J.; Wolters, N.; Lomparski, D.; Wolf, W.; Schubert, J.; Kreutzbruck, M. v.; Allweins, K.

    2002-05-01

    Using three rf SQUID magnetometers, a multiplexed SQUID array was implemented. The SQUIDs are positioned in line with 7 mm spacing and operated using one feedback electronics with sequential read out demodulation at different radio frequencies (rf). The cross-talk between SQUID channels was determined to be negligible. To show the performance of the SQUID array, eddy current (EC) measurements of aluminum aircraft samples in conjunction with a differential (double-D) EC excitation and lock-in readout were carried out. With computer-controlled continuous switching of the SQUIDs during the scan, three EC signal traces of the sample are obtained simultaneously. We performed measurements with an EC excitation frequency of 135 Hz to localize an artificial crack (sawcut flaw) of 20 mm length in an aluminum sheet with 0.6 mm thickness. The flaw was still detected when covered with aluminum of up to 10 mm thickness. In addition, measurements with varying angles between scanning direction and flaw orientation are presented.

  9. COCMP Surface Current Mapping Reveals Eddy and Upwelling Jet off Cape Mendocino

    NASA Astrophysics Data System (ADS)

    Crawford, G. B.; Halle, C.; Largier, J.; Stone, S.

    2008-12-01

    Ocean surface currents are now being measured continuously over a roughly 2000 km stretch of the western US continental shelf from south of Tijuana, Mexico to the Columbia River. A long-standing gap in this coverage was finally filled on August 12, 2008, with the installation of a long-range Seasonde radar system at Shelter Cove, California (as a part of California's COCMP project). During its first three weeks of operation, this radar has revealed a large (~170 km diameter), stable, anticyclonic eddy southwest of Cape Mendocino in this poorly studied region. Upwelling-favorable winds appear to create an upwelling jet along the eastern edge of the eddy, leading to maximum daily-averaged current speeds up to 80 cm/s, and MODIS-derived chlorophyll concentrations up to 30 mg/m3 in the jet (compared to ~1 mg/m3 in the eddy center). AVHRR data reveal SST differences between the jet and the eddy center of 1.5 to 2.5 °C during these 3 weeks. These complex circulation structures modify water pathways and may interrupt nutrient delivery to locations farther south. We discuss the spatial and temporal evolution of these features.

  10. Simultaneous absolute and differential operation of eddy current bobbin probes for heat exchanger tube inspection

    SciTech Connect

    Sullivan, S.P.; Smith, S.P.; Sharp, F.L.

    2000-05-01

    Here the authors try to dissolve some commonly held misconceptions about the operation of eddy current probes used for inspecting heat exchanger tubes. With the help of computer model results, the authors demonstrate that, for optimized operation, absolute/differential probes should be operated with coil current flowing in phase with another. This month's feature should be of interest to researchers as well as for NDT field personnel.

  11. Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers

    DOEpatents

    Danby, G.T.; Jackson, J.W.

    1990-03-19

    A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations (dB/dt) in the particle beam.

  12. Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers

    SciTech Connect

    Danby, Gordon T.; Jackson, John W.

    1991-01-01

    A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations in the particle beam.

  13. Reduction of magneto rheological dampers stiffness by incorporating of an eddy current damper

    NASA Astrophysics Data System (ADS)

    Asghar Maddah, Ali; Hojjat, Yousef; Reza Karafi, Mohammad; Reza Ashory, Mohammad

    2017-05-01

    In this paper, a hybrid damper is developed to achieve lower stiffness compared to magneto rheological dampers. The hybrid damper consists of an eddy current damper (ECD) and a Magneto Rheological Damper (MRD). The aim of this research is to reduce the stiffness of MRDs with equal damping forces. This work is done by adding an eddy current passive damper to a semi-active MRD. The ECDs are contactless dampers which show an almost viscous damping behavior without increasing the stiffness of a system. However, MRDs increase damping and stiffness of a system simultaneously, when a magnetic field is applied. Damping of each part is studied theoretically and experimentally. A semi-empirical model is developed to explain the viscoelastic behavior of the damper. The experimental results showed that the hybrid damper is able to dissipate energy as much as those of MRDs while its stiffness is 12% lower at a zero excitation current.

  14. Energy exchange between the jets of the Antarctic Circumpolar Current and synoptic eddies in the Drake Passage and Scotia Sea

    NASA Astrophysics Data System (ADS)

    Koshlyakov, Mikhail; Savchenko, Darya; Tarakanov, Roman

    2017-04-01

    Energy exchange between the jets of the Antarctic Circumpolar Current (ACC) and ocean synoptic eddies in the surface layer of the Drake Passage and Scotia Sea is studied on the base of the satellite altimeter data for the period from 1993 to 2014 with the assumption that every ACC jet is enclosed between some fixed isopleths of the ocean surface absolute dynamics topography (ADT). All the ACC jets are dynamically unstable what results in the jet meandering, formation of cyclonic and anticyclonic eddies inside the meanders, intensification of the eddies up to reaching their maximum energy, subsequent eddy attenuation and their reverse merging with the mother jets. Corresponding fluctuations of the kinetic energy of the ACC jets and the eddies, generated by different jets, in the surface ocean layer were computed and analysed for the above mentioned 22 years period. As a main result of the analysis, if was confirmed that the kinetic energy of the ACC jets depends strongly on the intensivity of jet meandering and processes of eddy formation and reverse eddy absorption by the jets. Mean and extreme energy parameters of the jets and eddies were also estimated. The northern and middle jets of the South Polar Current are in the lead with respect to the formation of the ocean synoptic eddies.

  15. Conductivity Profile Determination by Eddy Current for Shot Peened Superalloy Surfaces Toward Residual Stress Assessment

    SciTech Connect

    Shen, Y.; Lo, C. C. H.; Frishman, A. M.; Lee, C.; Nakagawa, N.

    2007-03-21

    This paper describes an eddy current model-based method for inverting near-surface conductivity deviation profiles of surface treated materials from swept-high frequency eddy current (SHFEC) data. This work forms part of our current research directed towards the development of an electromagnetic nondestructive technique for assessing residual stress of shot-peened superalloy components. The inversion procedure is based on the use of a parameterized function to describe the near-surface conductivity as a function of depth for a shot-peened surface, and the laterally uniform multi-layer theory of Cheng, Dodd and Deeds to calculate the resulting coil impedance deviations. The convergence of the inversion procedure has been tested against synthesized eddy current data. As a demonstration, the conductivity deviation profiles of a series of Inconel 718 specimens, shot peened at various Almen intensities, have been obtained by inversion. Several consistency tests were conducted to examine the reliability of the inverted conductivity profiles. The results show that conductivity deviation profiles can be reliably determined from SHFEC data within the accuracy of the current measurement system.

  16. Quantifying residual, eddy, and mean flow effects on mixing in an idealized circumpolar current

    DOE PAGES

    Wolfram, Phillip J.; Ringler, Todd D.

    2017-05-23

    Meridional diffusivity is assessed in this paper for a baroclinically unstable jet in a high-latitudeIdealized Circumpolar Current (ICC) using the Model for Prediction Across Scales-Ocean (MPAS-O) and the online Lagrangian In-situ Global High-performance particle Tracking (LIGHT) diagnostic via space-time dispersion of particle clusters over 120 monthly realizations of O(106) particles on 11 potential density surfaces. Diffusivity in the jet reaches values of O(6000 m2 s-1) and is largest near the critical layer supporting mixing suppression and critical layer theory. Values in the vicinity of the shelf break are suppressed to O(100 m2 s-1) due to the presence of westward slopemore » front currents. Diffusivity attenuates less rapidly with depth in the jet than both eddy velocity and kinetic energy scalings would suggest. Removal of the mean flow via high-pass filtering shifts the nonlinear parameter (ratio of the eddy velocity to eddy phase speed) into the linear wave regime by increasing the eddy phase speed via the depth-mean flow. Low-pass filtering, in contrast, quantifies the effect of mean shear. Diffusivity is decomposed into mean flow shear, linear waves, and the residual nonhomogeneous turbulence components, where turbulence dominates and eddy-produced filamentation strained by background mean shear enhances mixing, accounting for ≥ 80% of the total diffusivity relative to mean shear [O(100 m2 s-1)], linear waves [O(1000 m2 s-1)], and undecomposed full diffusivity [O(6000 m2 s-1)]. Finally, diffusivity parameterizations accounting for both the nonhomogeneous turbulence residual and depth variability are needed.« less

  17. Modeling eddy current analysis data to determine depth of weld penetration

    SciTech Connect

    Hench, K. W.; Christensen, W.; Gallant, D.A.; Hinde, R. F. , Jr.; Lopez, A. A.; Martin, Chuck; Phillips, T. T.

    2002-01-01

    The Applied Engineering Technology Croup in the Engineering Sciences and Applications Division at Los Alamos National Laboratory is currently providing the design, engineering, assembly, and testing of an eddy current instrument for weld inspection. This instrument is designed to provide an in situ weld depth measurement of nuclear weapons primary components during fabrication. The goal of this effort is to improve the accuracy and reliability of the measurement of the weld joint depth and provide a mechanism for inspection without removing the part from the fixture. This feature is essential to accommodate the re-welding process if the inspection fails. The production system consists of a commercially available eddy current instrument and eddy current probe connected to a portable PC. The objective of the system software is acquire and analyze voltage and phase angle data to produce a near-real time estimate of weld depth. The data obtained from the instrument are perfectly suited for analysis by a neural network technique. This paper compares the effectiveness of a neural network application with traditional mathematical models for the analysis of weld depth information.

  18. Magnetic diagnostics for equilibrium reconstructions in the presence of nonaxisymmetric eddy current distributions in tokamaks (invited).

    PubMed

    Berzak, L; Jones, A D; Kaita, R; Kozub, T; Logan, N; Majeski, R; Menard, J; Zakharov, L

    2010-10-01

    The lithium tokamak experiment (LTX) is a modest-sized spherical tokamak (R(0)=0.4 m and a=0.26 m) designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 °C. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.

  19. Eddy-Current Testing of Welded Stainless Steel Storage Containers to Verify Integrity and Identity

    SciTech Connect

    Tolk, Keith M.; Stoker, Gerald C.

    1999-07-20

    An eddy-current scanning system is being developed to allow the International Atomic Energy Agency (IAEA) to verify the integrity of nuclear material storage containers. Such a system is necessary to detect attempts to remove material from the containers in facilities where continuous surveillance of the containers is not practical. Initial tests have shown that the eddy-current system is also capable of verifying the identity of each container using the electromagnetic signature of its welds. The DOE-3013 containers proposed for use in some US facilities are made of an austenitic stainless steel alloy, which is nonmagnetic in its normal condition. When the material is cold worked by forming or by local stresses experienced in welding, it loses its austenitic grain structure and its magnetic permeability increases. This change in magnetic permeability can be measured using an eddy-current probe specifically designed for this purpose. Initial tests have shown that variations of magnetic permeability and material conductivity in and around welds can be detected, and form a pattern unique to the container. The changes in conductivity that are present around a mechanically inserted plug can also be detected. Further development of the system is currently underway to adapt the system to verifying the integrity and identity of sealable, tamper-indicating enclosures designed to prevent unauthorized access to measurement equipment used to verify international agreements.

  20. Magnetic Diagnostics for Equilibrium Reconstructions in the Presence of Nonaxisymmetric Eddy Current Distributions in Tokamaks

    SciTech Connect

    Kaita, R.; Kozub, T.; Logan, N.; Majeski, R.; Menard, J.; Zakharov, L.

    2010-12-10

    The lithium tokamak experiment LTX is a modest-sized spherical tokamak R0=0.4 m and a =0.26 m designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 oC. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.

  1. Turbulent jets and eddies in the california current and inferred cross-shore transports.

    PubMed

    Mooers, C N; Robinson, A R

    1984-01-06

    The instantaneous California Current is seen to consist of intense meandering current filaments (jets) intermingled with synoptic-mesoscale eddies. These quasi-geostrophic jets entrain cold, upwelled coastal waters and rapidly advect them far offshore; this behavior accounts for the elongated, cool surface features that are seen extending across the California Current region in satellite infrared imagery. The associated advective mechanism should provide significant cross-shore transports of heat, nutrients, biota, and pollutants. The dynamics of the current system should be crucially influenced by its highly variable structure.

  2. Florida Current meandering and evolution of cyclonic eddies along the Florida Keys Reef Tract: Are they interconnected?

    NASA Astrophysics Data System (ADS)

    Kourafalou, Vassiliki H.; Kang, Heesook

    2012-05-01

    The Florida Current (FC) is the branch of the Gulf Stream system within the Straits of Florida, connected to the Loop Current in the Gulf of Mexico. Cyclonic, cold-core eddies travel along this oceanic current system, entering the Straits of Florida in the vicinity of the Dry Tortugas and evolving along the Florida Keys island chain and coral reefs. The development of the high-resolution (˜900 m) hydrodynamic model Florida Straits, South Florida, and Florida Keys (FKeyS), nested within a Gulf of Mexico model (both based on the Hybrid Coordinate Ocean Model), has enabled new findings in eddy variability. Together with high-resolution (˜1 km) ocean color imagery, multiyear model archives have been employed to study the changes in the position of the FC front and the relationship with eddy evolution. It was found that eddy interactions and transformations are common, with multiple eddy cells within individual eddies or new cells emerging from existing vortices. Features in the Dry Tortugas area previously thought to be semipermanent are shown to be frequently transformed and/or replenished. A mechanism of local cyclogenesis is also proposed. Incoming eddies interact with and influence the downstream propagation of previous eddies. Systems of eddies, rather than individual vortices, can form the elongated features observed between the FC front and the Atlantic Florida Keys Shelf. Topography plays an important role in eddy dissipation or growth. A close synergy between eddy evolution and FC meandering is revealed. The results have implications on the connectivity of remote coastal and reef ecosystems.

  3. Analysis and experiment of eddy current loss in Homopolar magnetic bearings with laminated rotor cores

    NASA Astrophysics Data System (ADS)

    Jinji, Sun; Dong, Chen

    2013-08-01

    This paper analyses the eddy current loss in Homopolar magnetic bearings with laminated rotor cores produced by the high speed rotation in order to reduce the power loss for the aerospace applications. The analytical model of rotational power loss is proposed in Homopolar magnetic bearings with laminated rotor cores considering the magnetic circuit difference between Homopolar and Heteropolar magnetic bearings. Therefore, the eddy current power loss can be calculated accurately using the analytical model by magnetic field solutions according to the distribution of magnetic fields around the pole surface and boundary conditions at the surface of the rotor cores. The measurement method of rotational power loss in Homopolar magnetic bearing is proposed, and the results of the theoretical analysis are verified by experiments in the prototype MSCMG. The experimental results show the correctness of calculation results.

  4. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization

    PubMed Central

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-01-01

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks. PMID:27338389

  5. Development of eddy current testing system for inspection of combustion chambers of liquid rocket engines

    NASA Astrophysics Data System (ADS)

    He, D. F.; Zhang, Y. Z.; Shiwa, M.; Moriya, S.

    2013-01-01

    An eddy current testing (ECT) system using a high sensitive anisotropic magnetoresistive (AMR) sensor was developed. In this system, a 20 turn circular coil with a diameter of 3 mm was used to produce the excitation field. A high sensitivity AMR sensor was used to measure the magnetic field produced by the induced eddy currents. A specimen made of copper alloy was prepared to simulate the combustion chamber of liquid rocket. Scanning was realized by rotating the chamber with a motor. To reduce the influence of liftoff variance during scanning, a dual frequency excitation method was used. The experimental results proved that ECT system with an AMR sensor could be used to check liquid rocket combustion chamber.

  6. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization.

    PubMed

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-06-08

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks.

  7. Development of eddy current testing system for inspection of combustion chambers of liquid rocket engines.

    PubMed

    He, D F; Zhang, Y Z; Shiwa, M; Moriya, S

    2013-01-01

    An eddy current testing (ECT) system using a high sensitive anisotropic magnetoresistive (AMR) sensor was developed. In this system, a 20 turn circular coil with a diameter of 3 mm was used to produce the excitation field. A high sensitivity AMR sensor was used to measure the magnetic field produced by the induced eddy currents. A specimen made of copper alloy was prepared to simulate the combustion chamber of liquid rocket. Scanning was realized by rotating the chamber with a motor. To reduce the influence of liftoff variance during scanning, a dual frequency excitation method was used. The experimental results proved that ECT system with an AMR sensor could be used to check liquid rocket combustion chamber.

  8. Magnetic, eddy-current, and electrical methods. Electromagnetic quality control of carburization of steel products

    SciTech Connect

    Gorkunov, E.S.; Kogan, L.Kh.; Baraz, E.M.; Korolev, A.L.

    1994-08-01

    We have studied the effect that the casehardening (carburizing) temperature and time, carburizer activity, and variation of the conditions of subsequent heat treatment has on the electromagnetic properties of carburized specimens of 12Kh2N4A steel. The possibilities of nondestructive testing for the main parameters that determine the quality of carburization of 12Kh2N4A steel products, using coercimetric and eddy-current methods, are considered. The optimal depth of penetration of the magnetic flux in the portion of the inspected carburized product for greater inspection reliability is determined. The joint use of coercimetric and eddy-current methods makes it possible to monitor the depth and wear resistance of the carburized case and also to estimate the amount of retained austenite in the layer and reveal the effect of the decarburized surface zone.

  9. Design of Diaphragm and Coil for Stable Performance of an Eddy Current Type Pressure Sensor

    PubMed Central

    Lee, Hyo Ryeol; Lee, Gil Seung; Kim, Hwa Young; Ahn, Jung Hwan

    2016-01-01

    The aim of this work was to develop an eddy current type pressure sensor and investigate its fundamental characteristics affected by the mechanical and electrical design parameters of sensor. The sensor has two key components, i.e., diaphragm and coil. On the condition that the outer diameter of sensor is 10 mm, two key parts should be designed so as to keep a good linearity and sensitivity. Experiments showed that aluminum is the best target material for eddy current detection. A round-grooved diaphragm is suggested in order to measure more precisely its deflection caused by applied pressures. The design parameters of a round-grooved diaphragm can be selected depending on the measuring requirements. A developed pressure sensor with diaphragm of t = 0.2 mm and w = 1.05 mm was verified to measure pressure up to 10 MPa with very good linearity and errors of less than 0.16%. PMID:27376306

  10. Reliability assessment at airline inspection facilities. Volume 2: Protocol for an eddy current inspection reliability experiment

    NASA Astrophysics Data System (ADS)

    Spencer, Floyd; Borgonovi, Giancarlo; Roach, Dennis; Schurman, Don; Smith, Ron

    1993-05-01

    The Aging Aircraft NDI Development and Demonstration Center (AANC) at Sandia National Laboratories is charged by the FAA to support technology transfer, technology assessment, and technology validation. A key task facing the center is the establishment of a consistent and systematic methodology to assess the reliability of inspections through field experiments. This task is divided into three major areas: reliability of eddy current lap splice inspections at transport aircraft maintenance facilities; reliability of inspection at commuter aircraft maintenance facilities; and reliability of inspection associated with visual inspection of aircraft structural parts. Volume 2 is the second document in a series of three describing the planning, execution, and results of an eddy current inspection field experiment. This document provides a detailed description of the experimental hardware and protocols. It also describes the methodology to be used in the analysis of the data.

  11. Passive eddy-current damping as a means of vibration control in cryogenic turbomachinery

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1986-01-01

    Lateral shaft vibrations produced by a rotating unbalance weight were damped by means of eddy currents generated in copper conductors that were precessing cyclicly in the gap formed by the pole faces of C-shaped, permanent magnets. The damper assembly, which was located at the lower bearing support of a vertically oriented rotor was completely immersed in liquid nitrogen during the test run. The test rotor was operated over a speed range from 800 to 10,000 rpm. Three magnet/conductor designs were evaluated. Experimental damping coefficients varied from 180 to 530 N sec/m. Reasonable agreement was noted for theoretical values of damping for these same assemblies. Values of damping coefficients varied from 150 to 780 N sec/m. The results demonstrate that passive eddy-current damping is a viable candidate for vibration control in cryogenic turbomachinery.

  12. Analysis of an eddy-current brake considering finite radius and induced magnetic flux

    NASA Astrophysics Data System (ADS)

    Lee, Kapjin; Park, Kyihwan

    2002-11-01

    Since the eddy-current problem usually depends on the geometry of the moving conductive sheet and the pole shape, there is no general method to find an analytical solution. The analysis of the eddy currents in a rotating disk with an electromagnet is performed in the case of time-invariant field with the consideration of the boundary conditions of the rotating disk and induced magnetic flux. First, the concept of Coulomb's law and the method of images are introduced with the consideration of the boundary conditions. Second, the induced magnetic flux density is calculated by using Ampere's law. Third, the net magnetic flux density is introduced by defining the magnetic Reynolds number Rm as the ratio of the induced magnetic flux density to the applied magnetic flux density. Finally, the braking torque is calculated by applying the Lorentz force law and the computed results are compared with experimental ones.

  13. Magnetic damping: Analysis of an eddy current brake using an airtrack

    NASA Astrophysics Data System (ADS)

    Cadwell, Louis H.

    1996-07-01

    A simple theory is proposed using Faraday's law and the Lorentz force to analyze the effect of magnetic damping on an aluminum plate moving on a horizontal air track as it passes between the poles of a horseshoe magnet. The position, velocity, and acceleration of the nonmagnetic conducting plate are measured as a function of time using a motion detector. Using some simplifying assumptions, a theoretical model is obtained in which a single free parameter is used to fit the experimental data. This parameter corresponds to an effective length (LR) in which the eddy current encounters resistance as it moves around a closed path in the conductor. This leads to some interesting, but unexpected, results about the shape and magnitude of induced eddy currents.

  14. Design of permanent magnet eddy current brake for a small scaled electromagnetic launch model

    NASA Astrophysics Data System (ADS)

    Zhou, Shigui; Yu, Haitao; Hu, Minqiang; Huang, Lei

    2012-04-01

    A variable pole-pitch double-sided permanent magnet (PM) linear eddy current brake (LECB) is proposed for a small scaled electromagnetic launch model. A two-dimensional (2D) analytical steady state model is presented for the double-sided PM-LECB, and the expression for the braking force is derived. Based on the analytical model, the material and eddy current skin effect of the conducting plate are analyzed. Moreover, a variable pole-pitch double-sided PM-LECB is proposed for the effective braking of the moving plate. In addition, the braking force is predicted by finite element (FE) analysis, and the simulated results are in good agreement with the analytical model. Finally, a prototype is presented to test the braking profile for validation of the proposed design.

  15. Pulsed Eddy Current Non-destructive Testing and Evaluation: A Review

    NASA Astrophysics Data System (ADS)

    Sophian, Ali; Tian, Guiyun; Fan, Mengbao

    2017-05-01

    Pulsed eddy current (PEC) non-destructive testing and evaluation (NDT&E) has been around for some time and it is still attracting extensive attention from researchers around the globe, which can be witnessed through the reports reviewed in this paper. Thanks to its richness of spectral components, various applications of this technique have been proposed and reported in the literature covering both structural integrity inspection and material characterization in various industrial sectors. To support its development and for better understanding of the phenomena around the transient induced eddy currents, attempts for its modelling both analytically and numerically have been made by researchers around the world. This review is an attempt to capture the state-of-the-art development and applications of PEC, especially in the last 15 years and it is not intended to be exhaustive. Future challenges and opportunities for PEC NDT&E are also presented.

  16. Numerical study on the interactions between the Kuroshio current in the Luzon Strait and a mesoscale eddy

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Chun; Chern, Ching-Sheng; Zheng, Zhe-Wen

    2017-02-01

    The Luzon Strait (LS) connects the northwestern Pacific Ocean and the South China Sea (SCS) and is the western boundary gap for the Kuroshio current (KC). Satellite observations indicate that a cyclonic mesoscale eddy can trigger westward extension of the KC into the SCS and shed a smaller anticyclonic eddy to the west of the LS. We used a nonlinear reduced-gravity (primitive equation) model to study this phenomenon and analyzed the dynamic process. The location of the collision between the eddy and the KC could be critical for varying the circulation in the LS. The eddy's deformation rate, associated with its decaying speed, is also closely related to the location of the eddy during collision. When a cyclonic eddy moved from a region to the east of the Luzon Island toward the LS, the KC intruded into the SCS with growing negative vorticity during the collision of the eddy and KC. This tendency for negative vorticity is attributed to the beta effect and squeezing of the planetary vorticity caused by the flow divergence. As the eddy dissipated, the KC in the LS recovered its original pattern. When the collision of the eddy occurred at the center of the LS, the momentum balance of the KC loop was dominated by the inertial term, and the circulation in the LS remained in a leaping state.

  17. Investigation of Acoustic Fields Generated by Eddy Currents Using an Atomic Force Microscope (Postprint)

    DTIC Science & Technology

    2012-08-01

    AFRL-RX-WP-JA-2014-0230 INVESTIGATION OF ACOUSTIC FIELDS GENERATED BY EDDY CURRENTS USING AN ATOMIC FORCE MICROSCOPE (POSTPRINT) V...Institute of Physics AIR FORCE RESEARCH LABORATORY MATERIALS AND MANUFACTURING DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750 AIR... FORCE MATERIEL COMMAND UNITED STATES AIR FORCE NOTICE AND SIGNATURE PAGE Using Government drawings, specifications, or other data included in

  18. Reconstruction of Flaw Profiles Using Neural Networks and Multi-Frequency Eddy Current System

    SciTech Connect

    Chady, T.; Caryk, M.

    2005-04-09

    The objective of this paper is to identify profiles of flaws in conducting plates. To solve this problem, application of a multi-frequency eddy current system (MFES) and artificial neural networks is proposed. Dynamic feed-forward neural networks with various architectures are investigated. Extended experiments with all neural models are carried out in order to select the most promising configuration. Data utilized for the experiments were obtained from the measurements performed on the Inconel plates with EDM flaws.

  19. a Parametric Study of Eddy Current Response for Probability of Detection Estimation

    NASA Astrophysics Data System (ADS)

    Hoppe, W. C.

    2010-02-01

    In the study reported here, historical Probability of Detection (POD) data for eddy current inspections were analyzed using an extension of the "a-hat versus a" model in order to better account for known crack variables and thereby better separate system and crack factors influencing the POD parameters. Intriguing insights have been gained in the process suggesting a simple model for POD estimation. The parametric model will be presented including results of the study and suggestions for further research.

  20. Calculation of eddy currents and associated losses in electrical steel laminations

    SciTech Connect

    Gyselinck, J.; Vandevelde, L.; Melkebeek, J. . Lab. for Electrical Machines and Power Electronics); Dular, P.; Henrotte, F.; Legros, W. . Dept. of Electrical Engineering)

    1999-05-01

    Starting from the well known analytical formula for the eddy current losses in electrical steel laminations, saturation and edge effects are studied by means of 1D and 2D finite element models of a single lamination. A novel method for directly including the laminated core energy dissipation in a time stepped 2D model of a complete (rotating) machine is proposed. By way of example the method is applied to a tooth model enforced flux waveforms.

  1. Improved multi-directional eddy current inspection test apparatus for detecting flaws in metal articles

    DOEpatents

    Nance, Roy A.; Hartley, William H.; Caffarel, Alfred J.

    1984-01-01

    Apparatus is described for detecting flaws in a tubular workpiece in a single scan. The coils of a dual coil bobbin eddy current inspection probe are wound at a 45.degree. angle to the transverse axis of the probe, one coil having an angular position about the axis about 90.degree. relative to the angular position of the other coil, and the angle of intersection of the planes containing the coils being about 60.degree..

  2. [An automatic torque control system for a bicycle ergometer equipped with an eddy current brake].

    PubMed

    Kikinev, V V

    2007-01-01

    The main elements of the loading device of a bicycle ergometer, including an eddy current brake and a torque sensor, are described. The automatic torque control system, which includes the loading device, is equipped with a stabilizing feedback controller that optimally approximates the closed-loop transfer function of the target model. The reduced transfer function model of the controller is of the fourth order. A method featuring a modulation-demodulation loop is suggested for implementation of the control system.

  3. Assessment of eddy current effects on compression experiments in the TFTR tokamak

    SciTech Connect

    Wong, K.L.; Park, W.

    1986-05-01

    The eddy current induced on the TFTR vacuum vessel during compression experiments is estimated based on a cylindrical model. It produces an error magnetic field that generates magnetic islands at the rational magnetic surfaces. The widths of these islands are calculated and found to have some effect on electron energy confinement. However, resistive MHD simulation results indicate that the island formation process can be slowed down by plasma rotation.

  4. Analytical model development of an eddy-current-based non-contacting steel plate conveyance system

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-Tsung; Lin, Sheng-Yang; Yang, Yung-Yi; Hwang, Chang-Chou

    A concise model for analyzing and predicting the quasi-static electromagnetic characteristics of an eddy-current-based non-contacting steel plate conveyance system has been developed. Confirmed by three-dimensional (3-D) finite element analysis (FEA), adequacy of the analytical model can be demonstrated. Such an effective approach, which can be conveniently used by the potential industries for preliminary system operational performance evaluations, will be essential for designers and on-site engineers.

  5. COMPARATIVE ANALYSIS OF SELECTED EDDY CURRENT TRANSDUCERS FOR TITANIUM ALLOY EVALUATION

    SciTech Connect

    Chady, T.; Sikora, R.; Baniukiewicz, P.; Lopato, P.; Kowalczyk, J.; Psuj, G.; Caryk, M.

    2010-02-22

    Titanium alloy based details due to their mechanical properties continue to be in extensive use in various structures (mainly aerospace, automotive and petro-chemical industrial applications). In this paper comparative study of various types of eddy current NDT transducers for testing titanium elements was done. Probes of absolute, differential and array configurations were constructed and analyzed. Two and three dimensional numerical analysis (FEM) were done in order to find the best type and configuration of the proposed transducers.

  6. Fundamental Feature Extraction Methods for the Analysis of Eddy Current Data (Preprint)

    DTIC Science & Technology

    2006-12-01

    5d. PROJECT NUMBER 4349 5e. TASK NUMBER RG 6. AUTHOR(S) Jeremy S. Knopp (AFRL/RXLP) John C. Aldrin (Computational Tools ) 5f. WORK UNIT...NUMBER M04R1000 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Computational Tools Gurnee...1 and John C. ALDRINb a Air Force Research Laboratory, USA b Computational Tools ,USA Abstract. Features are investigated in eddy current

  7. Differential geometry based model for eddy current inspection of U-bend sections in steam generator tubes

    NASA Astrophysics Data System (ADS)

    Mukherjee, Saptarshi; Rosell, Anders; Udpa, Lalita; Udpa, Satish; Tamburrino, Antonello

    2017-02-01

    The modeling of U-Bend segment in steam generator tubes for predicting eddy current probe signals from cracks, wear and pitting in this region poses challenges and is non-trivial. Meshing the geometry in the cartesian coordinate system might require a large number of elements to model the U-bend region. Also, since the lift-off distance between the probe and tube wall is usually very small, a very fine mesh is required near the probe region to accurately describe the eddy current field. This paper presents a U-bend model using differential geometry principles that exploit the result that Maxwell's equations are covariant with respect to changes of coordinates and independent of metrics. The equations remain unaltered in their form, regardless of the choice of the coordinates system, provided the field quantities are represented in the proper covariant and contravariant form. The complex shapes are mapped into simple straight sections, while small lift-off is mapped to larger values, thus reducing the intrinsic dimension of the mesh and stiffness matrix. In this contribution, the numerical implementation of the above approach will be discussed with regard to field and current distributions within the U-bend tube wall. For the sake of simplicity, a two dimensional test case will be considered. The approach is evaluated in terms of efficiency and accuracy by comparing the results with that obtained using a conventional FE model in cartesian coordinates.

  8. Progress and Pitfalls in Satellite Surveillance of Loop Current Frontal Eddy Cyclones

    NASA Astrophysics Data System (ADS)

    Walker, N. D.; Leben, R. R.; Anderson, S. P.; Balasubramanian, S.

    2007-05-01

    In the last decade, significant advances in active and passive remote sensing have transpired that are enabling researchers to better quantify and model time and space scales of ocean processes. This paper presents recent attempts to track the motion and development of rapidly propagating cyclonic mesoscale eddies along the outer margin of the Loop Current in the Gulf of Mexico. Recent research has shown the critical role that these features play in the intensification of surface currents and as trigger mechanisms for deep flows in oil and gas producing areas in the northern Gulf of Mexico. The rapid motion of these cyclonic frontal features (35 km/day) has made their study problematic. In this paper, we discuss the use of several remote sensing systems and the integration of data from these systems to better understand the behavior and impacts of the frontal eddy cyclones on Gulf circulation processes. Mid-infrared (3.5-3.9 micron) measurements from GOES GVAR, available in real-time every 15 minutes over the Gulf, provide an excellent source of "de-clouded" night-time surface temperature information, from which sea surface temperatures (SST) are estimated with daily updates (http:www.esl.lsu.edu). Measurements in this atmospheric window maximize the sampling frequency of ocean information in cloudy and humid ocean regions such as the Gulf of Mexico. On the other hand, satellite altimetry measurements provide the only remote sensing technique that directly measures a dynamical variable of ocean state - the sea surface height (SSH). Detection of mesoscale eddies has been improved by combining multi-mission measurements from TOPEX-Poseidon, ERS- 2, GFO, Jason-1 and Envisat into a gridded product, updated daily (http:argo.colorado.edu/~realtime/welcome). Ocean color sensors (SeaWiFS, MODIS, Oceansat-1 OCM) provide surface pigment information (chlorophyll a, CDOM) that can aid in the discrimination of Gulf features as cold core eddies contain more chlorophyll a, due to

  9. Vacuum chamber eddy current self-correction for the AGS Booster Accelerator

    SciTech Connect

    Danby, G.T.; Jackson, J.W.

    1989-01-01

    The large sextupole and other multipoles induced by eddy currents in the vacuum chamber (VC) designed for the AGS Booster dipoles have been cancelled by simple coils attached to the VC surface. A two turns per pole back leg winding provides the mmf required to power the correction coil by transformer action, automatically correcting even for the variable {dot B} magnet excitation. Much larger VC positional errors of translation and rotation are acceptable because the coils follow the VC contour: the aberrations and their corrections locally have the same misplaced coordinate system. The self-correction concept could be applied to quadrupoles. However, Booster quadrupole measurements show that induced higher harmonics from VC and other eddy current sources are very small. Thus, with self-correction of the dipole VC eddy current fields, {dot B} effects on the proton rapid cycling Booster optics are reduced to tracking of the fundamental dipole and quadrupole fields. This can be automatically controlled using field monitoring transducers located in a dipole and quadrupole operated in series with the Booster magnets. 2 refs., 4 figs.

  10. Application of projection methods of multivariate data analysis in eddy current testing of materials

    NASA Astrophysics Data System (ADS)

    Polyakov, V. V.; Egorov, A. V.; Pirogov, A. A.; Kolubaev, E. A.

    2015-10-01

    The paper considers the applicability of projection methods of multivariate data analysis to discriminate between the factors that simultaneously affect the results of multi-frequency eddy current testing of nonmagnetic metals and alloys. Measurements were carried out for copper, magnesium, aluminum alloy and bronze specimens with different electrical conductivity equal to 57, 22, 16 and 7.5 S/m, respectively. The measured probe impedance changes were used to plot hodographs within the frequency range from 100 Hz to 6.4 kHz. The gap width between an attachable parametric probe and the specimen surface was specified using dielectric spacers within the range from 0 to 1 mm. The principal component analysis applied to experimental hodographs allowed us to safely discriminate between the influence of such factors as electrical conductivity of the material and gap width. The proposed approach to discriminating between individual factors that strongly affect eddy current measurement results is an enhancement in eddy current testing of materials.

  11. Simulated Design Strategies for SPECT Collimators to Reduce the Eddy Currents Induced by MRI Gradient Fields

    NASA Astrophysics Data System (ADS)

    Samoudi, Amine M.; Van Audenhaege, Karen; Vermeeren, Günter; Verhoyen, Gregory; Martens, Luc; Van Holen, Roel; Joseph, Wout

    2015-10-01

    Combining single photon emission computed tomography (SPECT) with magnetic resonance imaging (MRI) requires the insertion of highly conductive SPECT collimators inside the MRI scanner, resulting in an induced eddy current disturbing the combined system. We reduced the eddy currents due to the insert of a novel tungsten collimator inside transverse and longitudinal gradient coils. The collimator was produced with metal additive manufacturing, that is part of a microSPECT insert for a preclinical SPECT/MRI scanner. We characterized the induced magnetic field due to the gradient field and adapted the collimators to reduce the induced eddy currents. We modeled the x-, y-, and z-gradient coil and the different collimator designs and simulated them with FEKO, a three-dimensional method of moments / finite element methods (MoM/FEM) full-wave simulation tool. We used a time analysis approach to generate the pulsed magnetic field gradient. Simulation results show that the maximum induced field can be reduced by 50.82% in the final design bringing the maximum induced magnetic field to less than 2% of the applied gradient for all the gradient coils. The numerical model was validated with measurements and was proposed as a tool for studying the effect of a SPECT collimator within the MRI gradient coils.

  12. Eddy Current Influences on the Dynamic Behaviour of Magnetic Suspension Systems

    NASA Technical Reports Server (NTRS)

    Britcher, Colin P.; Bloodgood, Dale V.

    1998-01-01

    This report will summarize some results from a multi-year research effort at NASA Langley Research Center aimed at the development of an improved capability for practical modelling of eddy current effects in magnetic suspension systems. Particular attention is paid to large-gap systems, although generic results applicable to both large-gap and small-gap systems are presented. It is shown that eddy currents can significantly affect the dynamic behavior of magnetic suspension systems, but that these effects can be amenable to modelling and measurement. Theoretical frameworks are presented, together with comparisons of computed and experimental data particularly related to the Large Angle Magnetic Suspension Test Fixture at NASA Langley Research Center, and the Annular Suspension and Pointing System at Old Dominion University. In both cases, practical computations are capable of providing reasonable estimates of important performance-related parameters. The most difficult case is seen to be that of eddy currents in highly permeable material, due to the low skin depths. Problems associated with specification of material properties and areas for future research are discussed.

  13. Application of Eddy Current Techniques for Orbiter Reinforced Carbon-Carbon Structural Health Monitoring

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Simpson, John

    2005-01-01

    The development and application of advanced nondestructive evaluation techniques for the Reinforced Carbon-Carbon (RCC) components of the Space Shuttle Orbiter Leading Edge Structural Subsystem (LESS) was identified as a crucial step toward returning the shuttle fleet to service. In order to help meet this requirement, eddy current techniques have been developed for application to RCC components. Eddy current technology has been found to be particularly useful for measuring the protective coating thickness over the reinforced carbon-carbon and for the identification of near surface cracking and voids in the RCC matrix. Testing has been performed on as manufactured and flown RCC components with both actual and fabricated defects representing impact and oxidation damage. Encouraging initial results have led to the development of two separate eddy current systems for in-situ RCC inspections in the orbiter processing facility. Each of these systems has undergone blind validation testing on a full scale leading edge panel, and recently transitioned to Kennedy Space Center to be applied as a part of a comprehensive RCC inspection strategy to be performed in the orbiter processing facility after each shuttle flight.

  14. Open-loop correction for an eddy current dominated beam-switching magnet.

    PubMed

    Koseki, K; Nakayama, H; Tawada, M

    2014-04-01

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10(-4) to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10(-3). By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10(-4), which is an acceptable value, was achieved.

  15. Open-loop correction for an eddy current dominated beam-switching magnet

    SciTech Connect

    Koseki, K. Nakayama, H.; Tawada, M.

    2014-04-15

    A beam-switching magnet and the pulsed power supply it requires have been developed for the Japan Proton Accelerator Research Complex. To switch bunched proton beams, the dipole magnetic field must reach its maximum value within 40 ms. In addition, the field flatness should be less than 5 × 10{sup −4} to guide each bunched beam to the designed orbit. From a magnetic field measurement by using a long search coil, it was found that an eddy current in the thick endplates and laminated core disturbs the rise of the magnetic field. The eddy current also deteriorates the field flatness over the required flat-top period. The measured field flatness was 5 × 10{sup −3}. By using a double-exponential equation to approximate the measured magnetic field, a compensation pattern for the eddy current was calculated. The integrated magnetic field was measured while using the newly developed open-loop compensation system. A field flatness of less than 5 × 10{sup −4}, which is an acceptable value, was achieved.

  16. Concept and model of eddy current damper for vibration suppression of a beam

    NASA Astrophysics Data System (ADS)

    Sodano, Henry A.; Bae, Jae-Sung; Inman, Daniel J.; Keith Belvin, W.

    2005-12-01

    Electromagnetic forces are generated by the movement of a conductor through a stationary magnetic field or a time varying magnetic field through a stationary conductor and can be used to suppress the vibrations of a flexible structure. In the present study, a new electromagnetic damping mechanism is introduced. This mechanism is different from previously developed electromagnetic braking systems and eddy current dampers because the system investigated in the subsequent manuscript uses the radial magnetic flux to generate the electromagnetic damping force rather than the flux perpendicular to the magnet's face as done in other studies. One important advantage of the proposed mechanism is that it is simple and easy to apply. Additionally, a single magnet can be used to damp the transverse vibrations that are present in many structures. Furthermore, it does not require any electronic devices or external power supplies, therefore functioning as a non-contacting passive damper. A theoretical model of the system is derived using electromagnetic theory enabling us to estimate the electromagnetic damping force induced on the structure. The proposed eddy current damper was constructed and experiments were performed to verify the precision of the theoretical model. It is found that the proposed eddy current damping mechanism could increase the damping ratio by up to 150 times and provide sufficient damping force to quickly suppress the beam's vibration.

  17. Approximate expressions of mean eddy current torque acted on space debris

    NASA Astrophysics Data System (ADS)

    Lin, Hou-yuan; Zhao, Chang-yin

    2017-02-01

    Rotational state of space debris will be influenced by eddy current torque which is produced by the conducting body rotating within the geomagnetic field. Former expressions of instantaneous torque established in body-fixed coordinate system will change in space during rotation due to the variation of the coordinate system. In order to further investigate the evolution of the rotation of space debris subjected to the eddy current torque, approximate expressions of mean eddy current torque in inertial coordinate system are obtained from the average of the Euler dynamics equations under the assumption that two of the principal moments of inertia of the space debris are similar. Then the expressions are verified through numerical simulation, in which the orientation of the averaged variation of angular momentum is in agreement with the torque from the expressions, which is on an identical plane with magnetic field and the angular momentum. The torque and the averaged variation of the angular momentum have the same evolution trend during rotation in spite of minor deviations of their values.

  18. Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy-Current Phase Rotation

    DTIC Science & Technology

    2016-08-01

    is a well-established NDI method that employs the induced magnetic fields and electrical currents produced by a small probe coil to detect defects...UNCLASSIFIED UNCLASSIFIED Discrimination between Fatigue Cracking and Mechanical Damage in Aircraft Fastener Holes by Eddy- Current Phase...using the nondestructive inspection technique of bolt-hole eddy- current (BHEC) testing. BHEC testing is based on detection of a disturbance in the

  19. A numerical modeling study of the East Australian Current encircling and overwashing a warm-core eddy

    NASA Astrophysics Data System (ADS)

    MacDonald, H. S.; Roughan, M.; Baird, M. E.; Wilkin, J.

    2013-01-01

    AbstractWarm-core <span class="hlt">eddies</span> (WCEs) often form in the meanders of Western Boundary <span class="hlt">Currents</span> (WBCs). WCEs are frequently overwashed with less dense waters sourced from the WBC. We use the Regional Ocean Modelling System to investigate the ocean state during the overwashing of one such WCE in October 2008 in the East Australian <span class="hlt">Current</span> (EAC). Comparisons of model outputs with satellite sea surface temperature and vertical profiles show that the model provides a realistic simulation of the <span class="hlt">eddy</span> during the period when the EAC encircled and then overwashed the <span class="hlt">eddy</span>. During the encircling stage, an <span class="hlt">eddy</span> with closed circulation persisted at depth. In the surface EAC water entered from the north, encircled the <span class="hlt">eddy</span> and exited to the east. The overwashing stage was initiated by the expulsion of cyclonic vorticity. For the following 8 days after the expulsion, waters from the EAC washed over the top of the <span class="hlt">eddy</span>, transferring heat and anticyclonic vorticity radially-inward. After approximately one rotation period of overwashing, the <span class="hlt">eddy</span> separated. The overwashing creates a two-layer system that forms a subsurface maximum velocity at the interface of the two layers. Analysis of water mass properties, Eulerian tracer dynamics, and Lagrangian particle tracks show that the original <span class="hlt">eddy</span> sinks 10-50 m during the overwashing period. Overwashing has been observed in many WBCs and occurs in most WCEs in the western Tasman Sea.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSPO14D2827N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSPO14D2827N"><span><span class="hlt">Eddies</span> on the boundary between the Kuroshio <span class="hlt">current</span> and coastal waters observed by HF ocean surface radar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nadai, A.</p> <p>2016-02-01</p> <p>The HF ocean surface radar (HFOSR) is one of the powerful tools to measure the ocean <span class="hlt">current</span> parameters like surface <span class="hlt">currents</span>. Three observations of the Kuroshio <span class="hlt">current</span> in the Tokara straight using HFOSR had done by the National Institute of Information and Comunications Technology (NICT: the former name is the Communications Research Laboratory). The first-order echoes on Doppler spectra of HFOSR shows broaden and splitting shape in the region of the border between the Kuroshio <span class="hlt">currents</span> and coastal waters. The surface velocity maps show the existence of <span class="hlt">eddy</span> on the border. The investigation of the mechanism of broadening first order-echoes by Nadai (2006) revealed that the modulation of wave fields from surface <span class="hlt">currents</span> like <span class="hlt">eddy</span> is the cause of broadening and the measured <span class="hlt">current</span> fields also influenced the modulated wave fields. Moreover, Nadai (2006) also suggested that the influence is able to reduce using the average of two radial velocities extracted by the first-order echoes. In this paper, the results of <span class="hlt">current</span> field observation around the border between the Kuroshio <span class="hlt">current</span> and coastal waters are presented. Many small scale <span class="hlt">eddies</span> are observed at the border of the Kuroshio <span class="hlt">current</span> and coastal waters. The typical radius of the <span class="hlt">eddies</span> is about 10km. Usury the observation of such a small scale <span class="hlt">eddy</span> is difficult, but the <span class="hlt">eddies</span> with same scale are observed by airborne synthetic aperture radar in the same area at different time. The <span class="hlt">eddies</span> shows strong rotation as the typical tangential speed is about 1m/s. While the typical speed of the Kuroshio <span class="hlt">current</span> is about 1.5m/s, the typical speed of the <span class="hlt">eddy</span> movements is about 0.7m/s. No <span class="hlt">eddies</span> generated in the radar coverage, but one or two <span class="hlt">eddies</span> entered in the radar coverage a day. Therefore the origin of these <span class="hlt">eddies</span> will exist in the upstream area of the radar coverage. Using the compensation method for the influence of the modulated wave field suggested by Nadai (2006), the <span class="hlt">eddies</span> shows weak divergence. It is</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1511.1278S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1511.1278S"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> measurement system evaluation for corrosion depth determination on cast aluminum aircraft structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Surendra; Greving, Dan; Kinney, Andy; Vensel, Fred; Ohm, Jim; Peeler, Mike</p> <p>2013-01-01</p> <p>An <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) technique was developed to determine the corrosion depth on a bare flange face of a cast aluminum A356-T6 aircraft engine structure. The EC response and the corrosion depths determined through metallurgical cross sections were used to develop an empirical relation between EC response and depth. The EC technique and depth determination are used to inspect the engine structures during overhaul to determine if they are fit for continued service. An accurate and reliable Non-Destructive Inspection is required to ensure that structures returned to service are safe for continued operation. NDE system reliability demonstrations of the <span class="hlt">eddy</span> <span class="hlt">current</span> technique are traditionally reported in terms of Probability of Detection (POD) data using MIL-HDBK-1823A. However, the calculation of POD data is based on a simple linear predictive model that is valid only if certain criteria are met. These are: 1) NDE system response is measurable (i.e. continuous data), 2) Flaw size is known and measurable (i.e. continuous data), 3) relationship between the NDE system response and flaw size is linear (or linear on a log scale), 4) variation in measured responseresponse around a predicted response for a given flaw size is normally distributed, 5) the variation around the predicted response is constant (i.e. variation does not change with flaw size), and 6) inherent variability in the NDE system is known and fully understood. In this work, a Measurement System Evaluation (MSE) of the <span class="hlt">Eddy</span> <span class="hlt">Current</span> System was used to address some of these concerns. This work was completed on two aircraft structures having varying corrosion depths. The data were acquired in a random manner at fifty regions of interests (ROIs). Three operators participated in this study, and each operator measured <span class="hlt">Eddy</span> <span class="hlt">Current</span> response three times in each ROI. In total, there were four hundred and fifty data points collected. Following this, the two structures were sectioned for measuring corrosion depth. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1637.1406H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1637.1406H"><span>Non destructive technique for cracks detection by an <span class="hlt">eddy</span> <span class="hlt">current</span> in differential mode for steel frames</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harzalla, S.; Belgacem, F. Bin Muhammad; Chabaat, M.</p> <p>2014-12-01</p> <p>In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. <span class="hlt">Eddy</span> <span class="hlt">current</span> testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental <span class="hlt">signals</span>, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22390775','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22390775"><span>Non destructive technique for cracks detection by an <span class="hlt">eddy</span> <span class="hlt">current</span> in differential mode for steel frames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harzalla, S. Chabaat, M.; Belgacem, F. Bin Muhammad</p> <p>2014-12-10</p> <p>In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. <span class="hlt">Eddy</span> <span class="hlt">current</span> testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental <span class="hlt">signals</span>, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DyAtO..76..306J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DyAtO..76..306J"><span>Observed air-sea interactions in tropical cyclone Isaac over Loop <span class="hlt">Current</span> mesoscale <span class="hlt">eddy</span> features</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaimes, Benjamin; Shay, Lynn K.; Brewster, Jodi K.</p> <p>2016-12-01</p> <p>Air-sea interactions during the intensification of tropical storm Isaac (2012) into a hurricane, over warm oceanic mesoscale <span class="hlt">eddy</span> features, are investigated using airborne oceanographic and atmospheric profilers. Understanding these complex interactions is critical to correctly evaluating and predicting storm effects on marine and coastal facilities in the Gulf of Mexico, wind-driven mixing and transport of suspended matter throughout the water column, and oceanic feedbacks on storm intensity. Isaac strengthened as it moved over a Loop <span class="hlt">Current</span> warm-core <span class="hlt">eddy</span> (WCE) where sea surface warming (positive feedback mechanism) of ∼0.5 °C was measured over a 12-h interval. Enhanced bulk enthalpy fluxes were estimated during this intensification stage due to an increase in moisture disequilibrium between the ocean and atmosphere. These results support the hypothesis that enhanced buoyant forcing from the ocean is an important intensification mechanism in tropical cyclones over warm oceanic mesoscale <span class="hlt">eddy</span> features. Larger values in equivalent potential temperature (θE = 365   ∘K) were measured inside the hurricane boundary layer (HBL) over the WCE, where the vertical shear in horizontal <span class="hlt">currents</span> (δV) remained stable and the ensuing cooling vertical mixing was negligible; smaller values in θE (355   ∘K) were measured over an oceanic frontal cyclone, where vertical mixing and upper-ocean cooling were more intense due to instability development in δV . Thus, correctly representing oceanic mesoscale <span class="hlt">eddy</span> features in coupled numerical models is important to accurately reproduce oceanic responses to tropical cyclone forcing, as well as the contrasting thermodynamic forcing of the HBL that often causes storm intensity fluctuations over these warm oceanic regimes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........82P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........82P"><span>Dynamic suspension modeling of an <span class="hlt">eddy-current</span> device: An application to Maglev</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paudel, Nirmal</p> <p></p> <p>When a magnetic source is simultaneously oscillated and translationally moved above a linear conductive passive guideway such as aluminum, <span class="hlt">eddy-currents</span> are induced that give rise to a time-varying opposing field in the air-gap. This time-varying opposing field interacts with the source field, creating simultaneously suspension, propulsion or braking and lateral forces that are required for a Maglev system. In this thesis, a two-dimensional (2-D) analytic based steady-state <span class="hlt">eddy-current</span> model has been derived for the case when an arbitrary magnetic source is oscillated and moved in two directions above a conductive guideway using a spatial Fourier transform technique. The problem is formulated using both the magnetic vector potential, A, and scalar potential, o.Using this novel A-o approach the magnetic source needs to be incorporated only into the boundary conditions of the guideway and only the magnitude of the source field along the guideway surface is required in order to compute the forces and power loss. The performance of this analytic based steady-state <span class="hlt">eddy-current</span> model has been validated by comparing it with a 2-D finite-element model. The magnetic source used for the validation is a radially magnetized Halbach rotor, called an electrodynamic wheel (EDW). The 2-D analytic based transient <span class="hlt">eddy-current</span> force and power loss equations are derived for the case when an arbitrary magnetic source is moving and oscillating above a conductive guideway. These general equations for force and power loss are derived using a spatial Fourier transform and temporal Laplace transform technique. The derived equations are capable of accounting for step changes in the input parameters, in addition to arbitrary continuous changes in the input conditions. The equations have been validated for both step changes as well as continuous changes in the input conditions using a 2-D transient finite-element model. The dynamics of an EDW Maglev is investigated by using both steady</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5454348','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5454348"><span><span class="hlt">Eddy-current</span> inspection for steam generator tubing program. Annual progress report for period ending December 31, 1979</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dodd, C.V.; Deeds, W.E.; McClung, R.W.</p> <p>1980-07-01</p> <p><span class="hlt">Eddy-current</span> methods provide the best in-service inspection of steam generator tubing, but present techniques can produce ambiguity because of the many independent variables that affect the <span class="hlt">signals</span>. The <span class="hlt">current</span> development program has used mathematical models and developed or modified computer programs to design optimum probes, instrumentation, and techniques for multifrequency, multiproperty examinations. Interactive calculations and experimental measurements have been made with the use of modular <span class="hlt">eddy-current</span> instrumentation and a minicomputer. These establish the coefficients for the complex equations that define the values of the desired properties (and the attainable accuracy) despite changes in other significant variables. The computer programs for calculating the accuracy with which various properties can be measured indicate that the tubing wall thickness and the defect size can be measured much more accurately than is <span class="hlt">currently</span> required, even when other properties are varying. Our experimental measurements have confirmed these results, although more testing is needed for all the different combinations of cases and different types of defects. To facilitate the extensive laboratory scanning of the matrix of specimens that are necessary to develop algorithms for detection and analysis for all the possible combinations of positions of flaws, tube supports, and probe coils, we have designed, constructed, and begun operation of a computer-controlled automatic positioner. We have demonstrated the ability to overcome the large <span class="hlt">signals</span> produced by the edge of the tube supports. An advanced microcomputer has been designed, constructed, and installed in the instrumentation to control the examination and provide real-time calculations of the desired properties for display recording during the scanning of the tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9875B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9875B"><span>New observations of <span class="hlt">eddies</span> and boundary <span class="hlt">currents</span> in the Red Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bower, Amy S.; Swift, Stephen A.; Churchill, James H.; McCorkle, Daniel C.; Abualnaja, Yasser; Limeburner, Richard; Zhai, Ping</p> <p>2013-04-01</p> <p>Physical oceanographic studies of the Red Sea have often focused on the large-scale overturning circulation, in which water entering the sea from the Gulf of Aden becomes cooler, saltier and more dense as it flows northward, due mainly to strong evaporation (~2 m/y), and then flows back southward and exits the sea as a dense overflow through Bab al Mandeb. Less attention has been focused on the details of the horizontal circulation, in large part due to the dearth of high-resolution observations of the three-dimensional structure of water properties and <span class="hlt">currents</span>. Two high-resolution hydrographic and <span class="hlt">current</span> surveys were recently carried out in the eastern Red Sea, in March 2010 and September-October 2011. Of particular note are the continuous measurements of <span class="hlt">current</span> velocity, taken along the cruise tracks from the sea surface to 600 m with a hull-mounted Acoustic Doppler <span class="hlt">Current</span> Profiler, which revealed the presence and structure of several basin-scale <span class="hlt">eddies</span> and eastern boundary <span class="hlt">currents</span>. In March 2010, a strong, 200-km diameter anticyclonic <span class="hlt">eddy</span> was found centered near 23oN, with peak azimuthal velocities of nearly 1 m/s, a transport of 6-7 Sv and <span class="hlt">eddy</span> <span class="hlt">currents</span> extending to ~400 m depth. The <span class="hlt">eddy</span>'s core was in solid body rotation, with six-day rotation period and a relative vorticity of 0.5f (i.e., 1/2 the local Coriolis parameter). Surface drifters deployed in the <span class="hlt">eddy</span> core remained trapped for their entire lifetimes (up to 5 months). An <span class="hlt">eddy</span> was observed several times previously in this location-20 years of satellite-derived altimetric measurements of sea level anomaly indicate that it is a quasi-permanent feature of the Red Sea circulation and that there is an annual cycle in its strength. This may be linked to the annual cycle in buoyancy forcing and the strength of the cyclonic circulation in the northern Red Sea. In September 2011, cross-basin transects in the southern Red Sea (17-19oN) revealed a layer of relatively cold, fresh, low-oxygen, high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15616560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15616560"><span>Break-up of the Atlantic deep western boundary <span class="hlt">current</span> into <span class="hlt">eddies</span> at 8 degrees S.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dengler, M; Schott, F A; Eden, C; Brandt, P; Fischer, J; Zantopp, R J</p> <p>2004-12-23</p> <p>The existence in the ocean of deep western boundary <span class="hlt">currents</span>, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago. These ocean <span class="hlt">currents</span> have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary <span class="hlt">current</span> is estimated to carry (10-40) x 10(6) m3 s(-1) of water, transporting North Atlantic Deep Water--from the overflow regions between Greenland and Scotland and from the Labrador Sea--into the South Atlantic and the Antarctic circumpolar <span class="hlt">current</span>. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary <span class="hlt">current</span> breaks up at 8 degrees S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating <span class="hlt">eddies</span>, rather than by a continuous flow. Our model simulation indicates that the deep western boundary <span class="hlt">current</span> breaks up into <span class="hlt">eddies</span> at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999DSRI...46..415S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999DSRI...46..415S"><span><span class="hlt">Eddies</span> and a mesoscale deflection of the slope <span class="hlt">current</span> in the Faroe Shetland Channel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sherwin, T. J.; Turrell, W. R.; Jeans, D. R. G.; Dye, S.</p> <p>1999-03-01</p> <p>The mesoscale dynamics of the Scottish side of the Faroe-Shetland Channel have been investigated using synoptic in situ and remote sensing observations. A cold core cyclonic <span class="hlt">eddy</span>, identified from an AVHRR image, had a diameter of about 50 km and surface <span class="hlt">current</span> speeds of up to 50 cm s -1; it appeared to be attached to the 800 m isobath as it moved north-eastward along the edge of the channel at about 8 cm s -1. Speeds in the slope <span class="hlt">current</span> were about 50 cm s -1 but increased to 70 cm s -1 where the <span class="hlt">current</span> was compressed by the <span class="hlt">eddy</span>. Offshore, over the 1000 m isobath in the cooler water, speeds in the <span class="hlt">current</span> were slower (ca. 20 cm s -1). North-west of the Shetlands the offshore edge of the slope <span class="hlt">current</span> was deflected across the channel for a distance of about 70 km from the shelf edge. The speed of drifters in the slope <span class="hlt">current</span> increased to over 60 cm s -1 as they moved anti-cyclonically around this deflection. CTD profiles suggest that the movement of the surface waters was mirrored in the deep water of the channel. The deflection carried a very large quantity of North Atlantic Water into the central part of the channel; its cause and ultimate fate are not known, although it is likely to have had a significant impact on the dynamics of the channel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.3695K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.3695K"><span>The parameterization of <span class="hlt">eddy</span>-induced transports sets the simulated strength of the Antarctic Circumpolar <span class="hlt">Current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuhlbrodt, Till; Wang, Zhaomin; Gregory, Jonathan M.</p> <p>2010-05-01</p> <p>Within the class of global coupled climate models used for the IPCC AR4, the strength of the Antarctic Circumpolar <span class="hlt">Current</span> (ACC) is not well constrained. At the end of the control runs, the volume transport through Drake Passage ranges from 34 Sv to 338 Sv, compared with the observed 137 Sv (1 Sv = 106 m3 s-1). We have looked into which field or quantity explains best this large variation across the climate models. A simple scaling based on theoretical work by Marshall and Radko (2003) predicts a linear dependence of the ACC strength on the zonal wind stress and on the meridional density gradient, and a reciprocal dependence on the <span class="hlt">eddy</span>-induced diffusivity coefficient used in the Gent & McWilliams parameterization of the <span class="hlt">eddy</span>-induced transports. In our analysis of 23 climate models, the correlations of the ACC strength with the wind stress and the density gradient individually are weak, while the correlation with the <span class="hlt">eddy</span>-induced diffusivity coefficient is strongly negative as predicted, at least for those models where this coefficient is fixed. The correlation coefficient of the ACC with the simple scaling is 0.93. The results bring out the paramount role of the Gent & McWilliams parameterization in setting the strength of the ACC in coupled climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRC..119.4351C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRC..119.4351C"><span>Long-term trends in the East Australian <span class="hlt">Current</span> separation latitude and <span class="hlt">eddy</span> driven transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cetina-Heredia, P.; Roughan, M.; van Sebille, E.; Coleman, M. A.</p> <p>2014-07-01</p> <p>An observed warming of the Tasman Sea in recent decades has been linked to a poleward shift of the maximum wind stress curl, and a strengthening of the poleward flow along the coast of southeastern Australia. However, changes in the East Australian <span class="hlt">Current</span> (EAC) separation latitude, as well as in the contribution of the EAC, the EAC extension and its <span class="hlt">eddy</span> field to the total southward transport due to such a strengthening remain unknown. This study uses 30 years (1980-2010) of the Ocean Forecast for the Earth Simulator (OFES) sea surface height and velocity outputs to obtain a three decade long-time series of (i) the EAC separation latitude, (ii) the southward transport along the coast of southeastern Australia (28°S-39°S), and (iii) the southward transport across the EAC separation latitude. A Lagrangian approach is implemented and the spin parameter Ω is used to provide a quantitative distinction between the transports occurring outside and inside (cyclonic and anticyclonic) <span class="hlt">eddies</span>. Significant positive trends of the low pass southward transports indicate that the intensification of the poleward flow has occurred both within the EAC and in the EAC extension. In addition, a significant increase in southward transport inside and outside <span class="hlt">eddies</span> is found. Importantly, the contribution of <span class="hlt">eddy</span> driven transport has a large temporal variability and shows a sharp increase from 2005 onward. Finally our results show that the EAC has not penetrated further south but it has separated more frequently at the southernmost latitudes within the region where it typically turns eastward.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26329187','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26329187"><span>Measurement of <span class="hlt">eddy-current</span> distribution in the vacuum vessel of the Sino-UNIted Spherical Tokamak.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, G; Tan, Y; Liu, Y Q</p> <p>2015-08-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">currents</span> have an important effect on tokamak plasma equilibrium and control of magneto hydrodynamic activity. The vacuum vessel of the Sino-UNIted Spherical Tokamak is separated into two hemispherical sections by a toroidal insulating barrier. Consequently, the characteristics of <span class="hlt">eddy</span> <span class="hlt">currents</span> are more complex than those found in a standard tokamak. Thus, it is necessary to measure and analyze the <span class="hlt">eddy-current</span> distribution. In this study, we propose an experimental method for measuring the <span class="hlt">eddy-current</span> distribution in a vacuum vessel. By placing a flexible printed circuit board with magnetic probes onto the external surface of the vacuum vessel to measure the magnetic field parallel to the surface and then subtracting the magnetic field generated by the vertical-field coils, the magnetic field due to the <span class="hlt">eddy</span> <span class="hlt">current</span> can be obtained, and its distribution can be determined. We successfully applied this method to the Sino-UNIted Spherical Tokamak, and thus, we obtained the <span class="hlt">eddy-current</span> distribution despite the presence of the magnetic field generated by the external coils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712816A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712816A"><span>A description of <span class="hlt">eddy</span>-mean flow feedbacks in equatorial and boundary <span class="hlt">current</span> systems of the South Indian Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aguiar-González, Borja; Ponsoni, Leandro; Maas, Leo R. M.; Ridderinkhof, Herman; van Aken, Hendrik</p> <p>2015-04-01</p> <p>While many observational and modeling efforts have addressed <span class="hlt">eddy</span>-mean flow interactions acting over nearly idealized zonal jets, little is know about whether findings in those studies can be extended to <span class="hlt">current</span> systems with different configurations in the real ocean. This topic is of special interest for ocean-climate models where <span class="hlt">eddy</span> interactions with the mean flow may be unresolved, demanding further insight on the mechanism by which the <span class="hlt">eddy</span> field and the mean circulation should feed back in a realistic representation of future climate change scenarios. Following this motivation, we investigate local exchange of momentum and kinetic energy operating in a variety of <span class="hlt">eddy</span>-mean flow systems of the South Indian Ocean (SIO). To this aim we use 21 years (1993-2013) of newly processed satellite altimetry observations, and adopt a definition of the mean flow as a seasonally-dependent temporal mean where the <span class="hlt">eddy</span> field encompasses the daily instantaneous deviation from the altimeter-derived velocities. This approach allows time-varying feedbacks to evolve throughout the year. We find that the <span class="hlt">eddy</span> field feeds back on the mean circulation, contributing importantly to the overall seasonal strengthening and weakening of all <span class="hlt">current</span> systems involved in the tropical and subtropical gyre of the SIO. Although significant contributions to the momentum and energy balances were also obtained along the Agulhas (Return) <span class="hlt">Current</span> and the Antarctic Circumpolar <span class="hlt">Current</span> (ACC), they exhibit a weak/absent seasonal cycle, suggesting that the strength of these dynamical processes is mostly persistent throughout the year. Spatial distribution of the <span class="hlt">eddy</span> kinetic energy conversion rates and the convergence of horizontal <span class="hlt">eddy</span> momentum fluxes indicate that over regions where the <span class="hlt">eddy</span> field draws energy from the mean flow through barotropic instabilities, the <span class="hlt">current</span> is importantly decelerated by alongstream <span class="hlt">eddy</span> forces on its upstream side, while further downstream the situation reverses with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19272885','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19272885"><span>A new method for electric impedance imaging using an <span class="hlt">eddy</span> <span class="hlt">current</span> with a tetrapolar circuit.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahsan-Ul-Ambia; Toda, Shogo; Takemae, Tadashi; Kosugi, Yukio; Hongo, Minoru</p> <p>2009-02-01</p> <p>A new contactless technique for electrical impedance imaging, using an <span class="hlt">eddy</span> <span class="hlt">current</span> managed along with the tetrapolar circuit method, is proposed. The <span class="hlt">eddy</span> <span class="hlt">current</span> produced by a magnetic field is superimposed on a constant <span class="hlt">current</span> that is normally used in the tetrapolar circuit method, and thus is used to control the <span class="hlt">current</span> distribution in the body. By changing the <span class="hlt">current</span> distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862838','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862838"><span><span class="hlt">Eddy-current</span> system for the vibration-testing of blades</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Jacobs, Martin E.</p> <p>1977-01-01</p> <p>This invention is an improved system for the vibration-testing of cantilevered non-ferrous articles by inducing <span class="hlt">eddy</span> <span class="hlt">currents</span> therein. The principal advantage of the system is that relatively little heat is generated in the article being vibrated. Thus, a more accurate measurement of the fatigue characteristics of the article is obtained. Furthermore, the generation of relatively little heat in the blade permits tests to be conducted in low-pressure atmospheres simulating certain actual processes environments. Heat-generation in the vibrated article is minimized by utilizing <span class="hlt">eddy</span> <span class="hlt">currents</span> which are generated by an electromagnet whose magnetic field varies but does not change polarity. The typical winding for the electromagnet is excited with pulsating d.c. That is, the winding is alternately charged by connecting it across a d.c. power supply and then discharged by connecting it across a circuit for receiving <span class="hlt">current</span> generated in the winding by self-induction. Preferably, the discharge circuit is designed so that the waveform of the discharging <span class="hlt">current</span> approximates that of the charging <span class="hlt">current</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS43C1291A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS43C1291A"><span>How to diagnose the horizontal flux of mesoscale / Rossby <span class="hlt">eddy</span> energy in the extension regions of western boundary <span class="hlt">currents</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aiki, H.</p> <p>2014-12-01</p> <p>There have been few studies on the horizontal flux of energy associated with mesoscale <span class="hlt">eddies</span> and Rossby <span class="hlt">eddies</span>. (Many studies in the past decade are on either energy conversions or the flux-divergence of <span class="hlt">eddy</span> energy). This is partly attributed to the fact that, in general, the pressure flux in the traditional <span class="hlt">eddy</span> energy equation does not look in the direction of the group velocity of Rossby waves. This has been a limitation in the understanding of the maintenance mechanism of the extension of western boundary <span class="hlt">currents</span> (WBCs). The present study has developed a new <span class="hlt">eddy</span> energy equation which (is independent of the quasi-geostrophic approximation but) allows us to diagnose the horizontal flux of <span class="hlt">eddy</span> / wave energy with retaining the direction of the group velocity of a wide-array of Rossby-wave types. The types of Rossby waves include that are associated with both pure and equivalent beta effects, namely variants of Rossby waves concerning the horizontal gradient of (i) planetary vorticity, (ii) relative vorticity associated with mean <span class="hlt">currents</span> (which is as in atmospheric dynamics), and (iii) the background stratification (which is associated with the slope of thermocline and yields an effect similar to topographic Rossby waves). A diagnosis of an idealised experiment shows that, in the regions of the extension of WBCs, the effects (ii) and (iii) prevail over the effect (i) to yield the eastward flux of <span class="hlt">eddy</span> / wave energy. The result is that the total westward flux of <span class="hlt">eddy</span> / wave energy by an array of Rossby-wave types may sometimes cancel out the eastward flux of <span class="hlt">eddy</span> / wave energy owing to advection by mean <span class="hlt">currents</span> in the extension regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DContinental%2Bshelf','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DContinental%2Bshelf"><span>Observations of a loop <span class="hlt">current</span> frontal <span class="hlt">eddy</span> intrusion onto the west Florida shelf</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paluszkiewicz, T.; Atkinson, L. P.; Posmentier, E. S.; Mcclain, C. R.</p> <p>1983-01-01</p> <p>Data were examined to determine the structure of this intrusion (April 1-7, 1982) and to investigate its effects on water masses in the outer shelf region. A frontal <span class="hlt">eddy</span>, made up of a warm filament separated from the main <span class="hlt">current</span> by a region of cooler water, propagated southeastward at 30 cm/s, intruding onto the shelf near 26 deg N between April 4 and 6. It was found from temperature-salinity (T-S) properties that water in the filament was Loop <span class="hlt">Current</span> water that had been contiguous with Loop <span class="hlt">Current</span> water 80 m deeper in the main body of the <span class="hlt">current</span>. It is noted that water in the cold region was Continental Edge water, a transitional water mass with cooler, fresher T-S characteristics. Under this region, upwelling of deeper Loop <span class="hlt">Current</span> water occurred, and elevated nutrient concentrations were found in the upwelled dome under the cold region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JAP....81.6397W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JAP....81.6397W"><span>Wavelets in the solution of the volume integral equation: Application to <span class="hlt">eddy</span> <span class="hlt">current</span> modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Bing; Moulder, John C.; Basart, John P.</p> <p>1997-05-01</p> <p>There is growing interest in the applications of wavelets as basis functions in solutions of integral equations, especially in the area of electromagnetic field problems. In this article we apply a wavelet expansion to the solution of the three-dimensional <span class="hlt">eddy</span> <span class="hlt">current</span> modeling problem based on the volume integral method. Although this method shows promise for <span class="hlt">eddy</span> <span class="hlt">current</span> modeling of three-dimensional flaws, it is restricted by the computing power required to solve a large linear system. In this article we show that applying a wavelet basis to the volume integral method can dramatically reduce the size of the linear system to be solved. In our approach, the unknown total field is expressed as a twofold summation of shifted and dilated forms of a properly chosen basis function that is often referred to as the mother wavelet. The wavelet expansion can adaptively fit itself to the total field distribution by distributing the localized functions near the flaw boundary, where the field change is large, and the more spatially diffused functions over the interior of the flaw where the total field tends to be smooth. The approach is thus best suited to modeling large three-dimensional flaws where the large number of elements used in the volume integral method requires extremely large memory space and computational capacity. The feasibility of the wavelet method is discussed in the context of the physical nature of <span class="hlt">eddy-current</span> modeling problems. Numerical examples using both Haar wavelets and Daubechies compactly supported wavelets with periodic extension are given. The results of the wavelet method are also compared with experimental results from a cylindrical flat-bottom hole in an aluminum plate. These numerical examples and comparisons indicate that the wavelet method can greatly reduce the numerical complexity of the problem with negligible loss in accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/496665','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/496665"><span>Wavelets in the solution of the volume integral equation: Application to <span class="hlt">eddy</span> <span class="hlt">current</span> modeling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, B.; Moulder, J.C.; Basart, J.P.</p> <p>1997-05-01</p> <p>There is growing interest in the applications of wavelets as basis functions in solutions of integral equations, especially in the area of electromagnetic field problems. In this article we apply a wavelet expansion to the solution of the three-dimensional <span class="hlt">eddy</span> <span class="hlt">current</span> modeling problem based on the volume integral method. Although this method shows promise for <span class="hlt">eddy</span> <span class="hlt">current</span> modeling of three-dimensional flaws, it is restricted by the computing power required to solve a large linear system. In this article we show that applying a wavelet basis to the volume integral method can dramatically reduce the size of the linear system to be solved. In our approach, the unknown total field is expressed as a twofold summation of shifted and dilated forms of a properly chosen basis function that is often referred to as the mother wavelet. The wavelet expansion can adaptively fit itself to the total field distribution by distributing the localized functions near the flaw boundary, where the field change is large, and the more spatially diffused functions over the interior of the flaw where the total field tends to be smooth. The approach is thus best suited to modeling large three-dimensional flaws where the large number of elements used in the volume integral method requires extremely large memory space and computational capacity. The feasibility of the wavelet method is discussed in the context of the physical nature of <span class="hlt">eddy-current</span> modeling problems. Numerical examples using both Haar wavelets and Daubechies compactly supported wavelets with periodic extension are given. The results of the wavelet method are also compared with experimental results from a cylindrical flat-bottom hole in an aluminum plate. These numerical examples and comparisons indicate that the wavelet method can greatly reduce the numerical complexity of the problem with negligible loss in accuracy. {copyright} {ital 1997 American Institute of Physics.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993215','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993215"><span>The RF performance of cavity made from defective niobium material determined by <span class="hlt">Eddy</span> <span class="hlt">Current</span> Scanning</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, G.; Cooley, L.; Sergatskov, D.; Ozelis, J.; Brinkmann, A.; Singer, W.; Singer, X.; Pekeler, M.</p> <p>2010-10-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> scanning (ECS) has been used to screen niobium sheets to avoid defective material being used in costly cavity fabrication. The evaluation criterion of this quality control tool is not well understood. Past surface studies showed some features were shallow enough to be removed by chemical etching. The remaining features were identified to be small number of deeper inclusions, but mostly unidentifiable features (by chemical analysis). A real cavity made of defective niobium material has been tested. The cavity achieved high performance with comparable results to the cavities made from defect free cavities. Temperature mapping could help to define the control standard clearly.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090009966','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090009966"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> System for Detection of Cracking Beneath Braiding in Corrugated Metal Hose</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Buzz; Simpson, John; Hall, George</p> <p>2008-01-01</p> <p>In this paper an <span class="hlt">eddy</span> <span class="hlt">current</span> system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/634112','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/634112"><span>Crack detection on HC-130H aircraft using low frequency <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moore, D.G.; Mihelic, J.E.; Barnes, J.D.</p> <p>1998-02-01</p> <p>An <span class="hlt">eddy</span> <span class="hlt">current</span> inspection method was developed at the Federal Aviation Administration`s Airworthiness Assurance NDI Validation Center (AANC) to easily and rapidly detect subsurface fatigue cracks in the wheel well fairing on the US Coast Guard (USCG) HC-130H aircraft caused by fatigue. The inspection procedure locates cracks as small as 10.2 millimeters in length at 2.54 mm below the skin surface at raised fastener sites. The test procedure developed baseline three USCG aircraft. Inspection results on the three aircraft reveals good correlation with results made during subsequent structural disassembly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21260289','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21260289"><span><span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> SYSTEM FOR DETECTION OF CRACKING BENEATH BRAIDING IN CORRUGATED METAL HOSE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wincheski, Buzz; Simpson, John; Hall, George</p> <p>2009-03-03</p> <p>In this paper an <span class="hlt">eddy</span> <span class="hlt">current</span> system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10123845','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10123845"><span>Flowpath evaluation and reconnaissance by remote field <span class="hlt">Eddy</span> <span class="hlt">current</span> testing (FERRET)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Smoak, A.E.; Zollinger, W.T.</p> <p>1993-12-31</p> <p>This document describes the design and development of FERRET (Flowpath Evaluation and Reconnaisance by Remote-field <span class="hlt">Eddy</span> <span class="hlt">current</span> Testing). FERRET is a system for inspecting the steel pipes which carry cooling water to underground nuclear waste storage tanks. The FERRET system has been tested in a small scale cooling pipe mock-up, an improved full scale mock-up, and in flaw detection experiments. Early prototype designs of FERRET and the FERRET launcher (a device which inserts, moves, and retrieves probes from a piping system) as well as the field-ready design are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6565949','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6565949"><span>FELIX experiments and computational needs for <span class="hlt">eddy</span> <span class="hlt">current</span> analysis of fusion reactors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Turner, L.R.</p> <p>1984-01-01</p> <p>In a fusion reactor, changing magnetic fields are closely coupled to the electrically-conducting metal structure. This coupling is particularly pronounced in a tokamak reactor in which magnetic fields are used to confine, stabilize, drive, and heat the plasma. Electromagnetic effects in future fusion reactors will have far-reaching implications in the configuration, operation, and maintenance of the reactors. This paper describes the impact of <span class="hlt">eddy-current</span> effects on future reactors, the requirements of computer codes for analyzing those effects, and the FELIX experiments which will provide needed data for code validation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150012191','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150012191"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> Minimizing Flow Plug for Use in Flow Conditioning and Flow Metering</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>England, John Dwight (Inventor); Kelley, Anthony R. (Inventor)</p> <p>2015-01-01</p> <p>An <span class="hlt">eddy-current</span>-minimizing flow plug has open flow channels formed between the plug's inlet and outlet. Each open flow channel includes (i) a first portion that originates at the inlet face and converges to a location within the plug that is downstream of the inlet, and (ii) a second portion that originates within the plug and diverges to the outlet. The diverging second portion is approximately twice the length of the converging first portion. The plug is devoid of planar surface regions at its inlet and outlet, and in fluid flow planes of the plug that are perpendicular to the given direction of a fluid flowing therethrough.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA553019','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA553019"><span>Development of High Resolution <span class="hlt">Eddy</span> <span class="hlt">Current</span> Imaging Using an Electro-Mechanical Sensor (Preprint)</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-11-01</p> <p>7], Magneto-Resistance (MR) and Giant Magneto-Resistance (GMR) [8-10] sensors, Flux Gate sensors [11-12], SQUID sensors [13,14] etc. In all these...IOS Press, Amsterdam, 1995), pp. 115–124. 8. T. Dogaru and S. T. Smith, “ Giant Magnetoresistance-Based <span class="hlt">Eddy-Current</span> Sensor,” in IEEE Transactions...on Magnetics, Vol. 37, No. 4, pp.2790-2793 (2001). 9. Buzz Wincheski and Min Namkung, ‘Deep flaw detection with giant magnetoresistive (GMR) based</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21511638','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21511638"><span>Simulation for the assessment of wall thinning using <span class="hlt">eddy</span> <span class="hlt">current</span> method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cheng, W.; Komura, I.</p> <p>2011-06-23</p> <p>A pipe with protective cladding and insulation was simplified to a four-layered structure when the diameter of a pipe is large enough, and analytical solutions for sinusoidal and pulsed wave excitation were derived. Simulation implemented by using the analytical solutions showed that sinusoidal excitation is not appropriate for the monitoring of inner thinning, while pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> method can be used to measure wall-thickness regardless of inner or outer thinning by using the decay rate of log(Bz) as a particular parameter to evaluate wall thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21371028','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21371028"><span>PULSED <span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> THICKNESS MEASUREMENT OF SELECTIVE PHASE CORROSION ON NICKEL ALUMINUM BRONZE VALVES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krause, T. W.; Harlley, D.; Babbar, V. K.; Wannamaker, K.</p> <p>2010-02-22</p> <p>Nickel Aluminum Bronze (NAB) is a material with marine environment applications that under certain conditions can undergo selective phase corrosion (SPC). SPC involves the removal of minority elements while leaving behind a copper matrix. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) was evaluated for determination of SPC thickness on a NAB valve section with access from the surface corroded side. A primarily linear response of PEC amplitude, up to the maximum available SPC thickness of 4 mm was observed. The combination of reduced conductivity and permeability in the SPC phase relative to the base NAB was used to explain the observed sensitivity of PEC to SPC thickness variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459"><span>Research on Defects Inspection of Solder Balls Based on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Pulsed Thermography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe</p> <p>2015-01-01</p> <p>In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on <span class="hlt">eddy</span> <span class="hlt">current</span> pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720008638','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720008638"><span>Evaluation of <span class="hlt">eddy-current</span> proximity devices for measuring thin potassium film thicknesses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Asadourian, A. S.</p> <p>1972-01-01</p> <p>Two <span class="hlt">eddy</span> <span class="hlt">current</span> proximity probe systems were tested over a range of 0 to 508 micrometers (0 to 20 mils) of simulated potassium film thicknesses for simulated temperatures of 66 C (150 F), 232 C (450 F), and 666 C (1230 F). The results of short time calibration tests are presented. Instrument drift was a problem throughout the testing and, without correction, may limit the use of such systems to short periods of time. Additional development will be required prior to their being usable as practical instrumentation systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840008494','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008494"><span>Design study of magnetic <span class="hlt">eddy-current</span> vibration suppression dampers for application to cryogenic turbomachinery</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gunter, E. J.; Humphris, R. R.; Severson, S. J.</p> <p>1983-01-01</p> <p>Cryogenic turbomachinery used to pump high pressure fuel (liquid H2) and oxidizer (liquid O2) to the main engines of the Space Shuttle have experienced rotor instabilities. Subsynchronous whirl, an extremely destructive instability, has caused bearing failures and severe rubs in the seals. These failures have resulted in premature engine shutdowns or, in many instances, have limited the power level to which the turbopumps could be operated. The feasibility of using an <span class="hlt">eddy</span> <span class="hlt">current</span> type of damping mechanism for the Space Shuttle Main Engine is outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA261355','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA261355"><span>Wind-Driven Coastal Generation of Annual Mesoscale <span class="hlt">Eddy</span> Activity in the California <span class="hlt">Current</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-02-01</p> <p>DATES COVERED 12/93 FINAL 10/ 1 /90-11/30/91 4. TintL AND SUBTITLE S. FUNDING NUMBERS Wind-driven Coastal Generation of Annual Mesoscale <span class="hlt">Eddy</span> Activity in...winds. The other is a I 1 /2-layer primitive equation (PE) model with the ability to represent the coastal response to winds but not baroclinic...California <span class="hlt">Current</span> ALEJANDRO PARES-SIERRA* WARREN B. WHITE " AD C_-K TA:* ’Cenifo de InrwoitCenriai£ ivnp S9,PCYw’ . 1 ,r Lnu~naaj (.Msnucnpt tecei~ed 𔄀 S c</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA033376','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA033376"><span>Non-Destructive Inspection and Volume Fraction Determination of CFRP Using an <span class="hlt">Eddy</span> <span class="hlt">Current</span> Method</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1976-06-01</p> <p>thickness 9 4.3 Edge effect 11 4.4 Response to volume fraction 12 5 RESULTS FROM DIRECTIONAL PROBE 13 6 DISCUSSION 14 7 CONCLUSIONS 15 Acknowledgment...use of one unique probe. 4.3 Edge effect It has been demonstrated in section 4.1 that the important part of the <span class="hlt">eddy</span> <span class="hlt">current</span> path covers an area 7.5mm...in diameter on cross ply and 15 x 7.5mm on unidirectional CFRP. As might be expected, this results in an edge effect which arises when part of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28858230','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28858230"><span>A Smart <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Dedicated to the Nondestructive Evaluation of Carbon Fibers Reinforced Polymers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Naidjate, Mohammed; Helifa, Bachir; Feliachi, Mouloud; Lefkaier, Iben-Khaldoun; Heuer, Henning; Schulze, Martin</p> <p>2017-08-31</p> <p>This paper propose a new concept of an <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) multi-element sensor for the characterization of carbon fiber-reinforced polymers (CFRP) to evaluate the orientations of plies in CFRP and the order of their stacking. The main advantage of the new sensors is the flexible parametrization by electronical switching that reduces the effort for mechanical manipulation. The sensor response was calculated and proved by 3D finite element (FE) modeling. This sensor is dedicated to nondestructive testing (NDT) and can be an alternative for conventional mechanical rotating and rectangular sensors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5621124','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5621124"><span>A Smart <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Dedicated to the Nondestructive Evaluation of Carbon Fibers Reinforced Polymers</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Naidjate, Mohammed; Helifa, Bachir; Feliachi, Mouloud; Lefkaier, Iben-Khaldoun; Heuer, Henning; Schulze, Martin</p> <p>2017-01-01</p> <p>This paper propose a new concept of an <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) multi-element sensor for the characterization of carbon fiber-reinforced polymers (CFRP) to evaluate the orientations of plies in CFRP and the order of their stacking. The main advantage of the new sensors is the flexible parametrization by electronical switching that reduces the effort for mechanical manipulation. The sensor response was calculated and proved by 3D finite element (FE) modeling. This sensor is dedicated to nondestructive testing (NDT) and can be an alternative for conventional mechanical rotating and rectangular sensors. PMID:28858230</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MaCom..78.1929A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MaCom..78.1929A"><span>An boldsymbol{E} -based mixed formulation for a time-dependent <span class="hlt">eddy</span> <span class="hlt">current</span> problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acevedo, Ramiro; Meddahi, Salim; Rodriguez, Rodolfo</p> <p>2009-12-01</p> <p>In this paper, we analyze a mixed form of a time-dependent <span class="hlt">eddy</span> <span class="hlt">current</span> problem formulated in terms of the electric field boldsymbol{E} . We show that this formulation admits a well-posed saddle point structure when the constraints satisfied by the primary unknown in the dielectric material are handled by means of a Lagrange multiplier. We use Nedelec edge elements and standard nodal finite elements to define a semi-discrete Galerkin scheme. Furthermore, we introduce the corresponding backward-Euler fully-discrete formulation and prove error estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AmJPh..80..800T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AmJPh..80..800T"><span>Rolling magnets down a conductive hill: Revisiting a classic demonstration of the effects of <span class="hlt">eddy</span> <span class="hlt">currents</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomasel, Fernando G.; Marconi, Mario C.</p> <p>2012-09-01</p> <p>We re-examine the case of rare-earth magnets rolling down an inclined plane, presenting an approach to conducting quantitative investigations that results in high-quality experimental data connecting simple experiments to a handful of important applications of <span class="hlt">eddy</span> <span class="hlt">currents</span>. These include not only magnetic braking but also the characterization of conductive materials, measurement of the thickness of dielectric coatings, and nondestructive evaluation of conductive objects. The simplicity of the proposed experimental setups, which include the use of widely available smart phones to record video that can be post-processed with free software, makes these experiments appealing to high school and college physics students.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706i0008F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706i0008F"><span>Identification of rebars in a reinforced mesh using <span class="hlt">eddy</span> <span class="hlt">current</span> method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frankowski, P. K.; Sikora, R.; Chady, T.</p> <p>2016-02-01</p> <p>The aim of this paper is to present an expert system for identification of the basic reinforcement concrete structures parameters like: rebars diameter, thickness of a concrete cover and a kind of rebar's alloy (class). The results of measurement carried out by the <span class="hlt">eddy</span> <span class="hlt">current</span> transducers were utilized for the designed system. Measured waveforms are represented by two kinds of attributes, the d-factors represent a waveform shape, and a maximal amplitude. In order to extract an association rules between the specific attributes and the structure parameters a rough set theory was used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NTE....31..191Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NTE....31..191Z"><span>Thickness measurement of multi-layer conductive coatings using multifrequency <span class="hlt">eddy</span> <span class="hlt">current</span> techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Dejun; Yu, Yating; Lai, Chao; Tian, Guiyun</p> <p>2016-07-01</p> <p>To ensure the key structural performance in high-temperature and high-stress environments, thermal barrier coatings (TBCs) are often adopted in engineering. The thickness of these multi-layer conductive coatings is an important quality indicator. In order to measure the thickness of multi-layer conductive coatings, a new measurement approach is presented using <span class="hlt">eddy</span> <span class="hlt">current</span> testing techniques, and then, an inversion algorithm is proposed and proved efficient and applicable, of which the maximum experimental relative error is within 10%. Therefore, the new approach can be effectively applied to thickness measurement of multi-layer conductive coatings such as TBCs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..177a2111D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..177a2111D"><span>Non-destructive testing of nanomaterials by using subminiature <span class="hlt">eddy</span> <span class="hlt">current</span> transducers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dmitriev, S. F.; Ishkov, A. V.; Katasonov, A. O.; Malikov, V. N.; Sagalakov, A. M.; Shevtsova, L. I.</p> <p>2017-02-01</p> <p>A sensor for studying nanomaterials has been developed on the basis of a transformer-type <span class="hlt">eddy-current</span> transducer. The basic technical data are stated (the number of windings is 100-400 turns, and the value of the initial permeability of the core is µmax = 36000). Measurements technique which allows high-precision measuring the electrical conductivity in thin film Ce-Nb. The electrical conductivity of Niobium-Selenium varies from 3.3·105 to 3.7·105 MS/m in the ratio of four from 4 to 60 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AIPC.1048..286J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AIPC.1048..286J"><span>Solution to the <span class="hlt">Eddy-Current</span> Problem for Type-II Superconductors by Relaxation Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Janíková, Edita; Slodička, Marián</p> <p>2008-09-01</p> <p>The fast developing industrial applications of superconductors require rigorous mathematical models of their physical behaviour and efficient numerical methods to solve them. We propose and study theoretically a new approximation scheme to solve the 3D <span class="hlt">eddy-current</span> problem of diffusion of the electric field in type-II superconductors. The method is based on the relaxation principle, where the nonlinear time- and space-dependent partial differential equation (PDE) is split into a linear time-independent PDE coupled with a nonlinear equation involving no partial derivatives.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706b0025P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706b0025P"><span>Experimental validation of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe for defect detection in thick conducting specimen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahesh Raja, P.; Arunachalam, Kavitha; Balasubramanian, Krishnan</p> <p>2016-02-01</p> <p>This paper presents numerical modeling and experimental measurements of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) probe for detecting subsurface defects in 10 mm to 15 mm thick conducting specimen. Measurements are presented for a pancake air core coil to detect subsurface defect in 10 mm thick aluminum slab. EC coil parameters namely inner radius(r1), and outer radius(r2), and operating frequency (f) are optimized for deeper penetration in the conducting plate (35 MS/m) for a given coil height(h), and lift off distance (d). Preliminary simulation results are presented for a subsurface defect in 15 mm thick aluminium plate for the optimized EC coil parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AIPC..657..359K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AIPC..657..359K"><span>Simulation of <span class="hlt">Eddy-Current</span> Corrosion Detection Using a Sensor Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Katyal, V.; Bowler, J. R.</p> <p>2003-03-01</p> <p>A computer simulation has been developed to evaluate <span class="hlt">eddy-current</span> probes containing magnetic field sensor arrays for the detection and evaluation of hidden corrosion. The simulation is used to assess probes that incorporate magneto-resistive or Hall devices in a closely-spaced, linear array. These probes will allow rapid data acquisition over a track width determined by the length of the array. The benefit of the simulation is that adjustments to the virtual probe parameters are easily made allowing improvements in sensitivity, imaging capability and resolution. A number of probe designs have been studied in this way including the "racetrack" probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ChJME..27..768Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ChJME..27..768Y"><span>Transient-spatial pattern mining of <span class="hlt">eddy</span> <span class="hlt">current</span> pulsed thermography using wavelet transform</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Hailong; Gao, Bin; Tian, Guiyun; Ren, Wenwei; Woo, Wai Lok</p> <p>2014-07-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> pulsed thermography(ECPT) is an emerging Non-destructive testing and evaluation(NDT & E) technique, which uses hybrid <span class="hlt">eddy</span> <span class="hlt">current</span> and thermography NDT & E techniques that enhances the detectability from their compensation. <span class="hlt">Currently</span>, this technique is limited by the manual selection of proper contrast frames and the issue of improving the efficiency of defect detection of complex structure samples remains a challenge. In order to select a specific frame from transient thermal image sequences to maximize the contrast of thermal variation and defect pattern from complex structure samples, an energy driven approach to compute the coefficient energy of wavelet transform is proposed which has the potential of automatically selecting both optimal transient frame and spatial scale for defect detection using ECPT. According to analysis of the variation of different frequency component and the comparison study of the detection performance of different scale and wavelets, the frame at the end of heating phase is automatically selected as an optimal transient frame for defect detection. In addition, the detection capabilities of the complex structure samples can be enhanced through proper spatial scale and wavelet selection. The proposed method has successfully been applied to low speed impact damage detection of carbon fibre reinforced polymer(CFRP) composite as well as providing the guidance to improve the detectability of ECPT technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...117o4104M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...117o4104M"><span><span class="hlt">Eddy</span> <span class="hlt">currents</span>: A misleading contribution when measuring magnetoelectric voltage coefficients of thin film devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>More-Chevalier, J.; Cibert, C.; Bouregba, R.; Poullain, G.</p> <p>2015-04-01</p> <p>Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) magnetoelectric (ME) thin films were deposited on Pt/TiO2/SiO2/Si substrate. The ME voltage coefficient αHME was determined at room temperature using a lock-in amplifier and by applying to the sample an alternating magnetic field of a few mT. Surprisingly, very similar responses were obtained from a simple commercial capacitor set in series with a small loop of wire. This allowed us first to accurately model and reproduce the frequency response of the ferroelectric PZT layer alone. We also observed that, at low frequency, the voltage across the ferroelectric capacitor and the <span class="hlt">current</span> in the circuit did not decrease significantly when diminishing then removing, the area of the conductive loop. One major conclusion is that <span class="hlt">eddy</span> <span class="hlt">currents</span> in the lead wires, rather than the classical electromotive force across conductive loops, contribute significantly to the total voltage response, at least for thin film ME devices. A model taking into account <span class="hlt">eddy</span> <span class="hlt">currents</span> was then developed for the extraction of the true αHME. A large αHME of 4.6 V/cm.Oe was thus obtained for the Terfenol-D/Pt/PZT thin film device, without DC magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA527308','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA527308"><span>Inter-annual Variability and Prediction of <span class="hlt">Eddies</span> in the Gulf of Aden and the Somali <span class="hlt">Current</span> Region</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2009-01-01</p> <p>in the Gulf of Aden and the Somali <span class="hlt">Current</span> Region Julian P. McCreary , Jr. International Pacific Research Center University of Hawaii at Manoa...and Indian Ocean Dipole years. Manuscript in progress. Jensen, T.G, Z. Yu and J. P. McCreary : <span class="hlt">Eddies</span> in the Gulf of Aden – an overview. Manuscript...Z., T. G. Jensen, A. Ishida, R. Furue and J. P. McCreary (2009): Mesoscale <span class="hlt">Eddies</span> in the Gulf of Aden. Powerpoint presentation IMPACT</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcScD..11.1949A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcScD..11.1949A"><span>Influence of frontal cyclones evolution on the 2009 (Ekman) and 2010 (Franklin) Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> detachment events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Androulidakis, Y. S.; Kourafalou, V. H.; Le Hénaff, M.</p> <p>2014-07-01</p> <p>The anticyclonic Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> (LCE) shedding events are strongly associated with the evolution of Loop <span class="hlt">Current</span> Frontal <span class="hlt">Eddies</span> (LCFEs) over the eastern Gulf of Mexico (GoM). A numerical simulation, in tandem with in situ measurements and satellite data, was used to investigate the Loop <span class="hlt">Current</span> (LC) evolution and the surrounding LCFEs formation, structure, growth and migration during the <span class="hlt">Eddy</span> Ekman and <span class="hlt">Eddy</span> Franklin shedding events in the summers of 2009 and 2010, respectively. During both events, Northern GoM LCFEs appeared vertically coherent to at least 1500 m in temperature observations. They propagated towards the base of the LC where, together with the migration of Campeche Bank <span class="hlt">eddies</span> from south of the LC, contributed to its "necking down". Growth of Campeche Bank LCFEs involved in <span class="hlt">Eddy</span> Franklin was partially attributed to Campeche Bank waters following upwelling events. Slope processes associated with such upwelling include offshore exports of high positive vorticity that may trigger cyclone formation and growth. The advection and growth of LCFEs, originating from the northern and southern GoM, and their interaction with the LC over the LCE detachment area favor shedding conditions and may lead to the final separation of the LCE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcSci..10..947A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcSci..10..947A"><span>Influence of frontal cyclone evolution on the 2009 (Ekman) and 2010 (Franklin) Loop <span class="hlt">Current</span> <span class="hlt">eddy</span> detachment events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Androulidakis, Y. S.; Kourafalou, V. H.; Le Hénaff, M.</p> <p>2014-11-01</p> <p>The anticyclonic Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> (LCE) shedding events are strongly associated with the evolution of Loop <span class="hlt">Current</span> Frontal <span class="hlt">Eddies</span> (LCFEs) over the eastern Gulf of Mexico (GoM). A numerical simulation, in tandem with in situ measurements and satellite data, was used to investigate the Loop <span class="hlt">Current</span> (LC) evolution and the surrounding LCFE formation, structure, growth and migration during the <span class="hlt">Eddy</span> Ekman and <span class="hlt">Eddy</span> Franklin shedding events in the summers of 2009 and 2010, respectively. During both events, northern GoM LCFEs appeared vertically coherent to at least 1500 m in temperature observations. They propagated towards the base of the LC, where, together with the migration of Campeche Bank (southwest GoM shelf) <span class="hlt">eddies</span> from south of the LC, contributed to its "necking-down". Growth of Campeche Bank LCFEs involved in <span class="hlt">Eddy</span> Franklin was partially attributed to Campeche Bank waters following upwelling events. Slope processes associated with such upwelling included offshore exports of high positive potential vorticity that may trigger cyclone formation and growth. The advection and growth of LCFEs, originating from the northern and southern GoM, and their interaction with the LC over the LCE detachment area favor shedding conditions and may contribute to the final separation of the LCE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..369Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..369Z"><span>The <span class="hlt">eddy</span>-mean flow interaction and the intrusion of western boundary <span class="hlt">current</span> into the South China Sea type basin in an idealized model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Linhao</p> <p>2016-04-01</p> <p>In this paper, an ideal model on the role of mesoscale <span class="hlt">eddies</span> in the Kuroshio intruding into the South China Sea (SCS) is developed, which represents the northwestern Pacific and the SCS by two rectangle basins connected by a gap. In the case of only considering intrinsic ocean variability, a time-dependent western boundary <span class="hlt">current</span> (WBC) driven by steady wind is modeled under both <span class="hlt">eddy</span>-resolving and non-<span class="hlt">eddy</span>-resolving resolutions. Almost all simulated WBC intrudes into the adjacent sea in the form of loop <span class="hlt">current</span> with multiple-state transitions and <span class="hlt">eddy</span>-shedding process, which has aperiodic variations on intraseasonal or interannual scales, determined by the <span class="hlt">eddy</span>-induced WBC variation. For the parameters considered in this paper, the WBC intrusion exhibits a 30~90-day cycle in the presence of the subgrid-scale <span class="hlt">eddy</span> forcing (SSEF), but a 300~500-day cycle in the absence of SSEF. Moreover, the roles of the resolved (grid-scale) and unresolved (subgrid-scale) <span class="hlt">eddies</span> in the WBC intrusion are studied. It is found that the unresolved <span class="hlt">eddy</span>-flow interaction strongly regulates the WBC intrusion through the PV forcing induced by shear flows and baroclinic processes. But the resolved <span class="hlt">eddy</span> forcing, which is dominated by the <span class="hlt">eddy-eddy</span> interaction solely through baroclinic processes, shows weak correlation to the WBC intrusion. The associated <span class="hlt">eddy</span>-induced PV exchange between the two basins is mainly accomplished by isopycnal-thickness <span class="hlt">eddy</span> fluxes, particularly by the cross-front PV fluxes due to the unresolved <span class="hlt">eddy</span>. And the unresolved <span class="hlt">eddy</span>-flow interaction, as well as resolved and unresolved <span class="hlt">eddy-eddy</span> interactions, mainly governs the PV transport for the WBC intrusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828"><span>Fatigue Crack Length Sizing Using a Novel Flexible <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Array</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying</p> <p>2015-01-01</p> <p>The <span class="hlt">eddy</span> <span class="hlt">current</span> probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar <span class="hlt">eddy</span> <span class="hlt">current</span> sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm. PMID:26703608</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NTE....28..354Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NTE....28..354Y"><span>Pulsed remote field <span class="hlt">eddy</span> <span class="hlt">current</span> technique applied to non-magnetic flat conductive plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin</p> <p>2013-12-01</p> <p>Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950020358','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020358"><span>Combined investigation of <span class="hlt">Eddy</span> <span class="hlt">current</span> and ultrasonic techniques for composite materials NDE</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Davis, C. W.; Nath, S.; Fulton, J. P.; Namkung, M.</p> <p>1993-01-01</p> <p>Advanced composites are not without trade-offs. Their increased designability brings an increase in the complexity of their internal geometry and, as a result, an increase in the number of failure modes associated with a defect. When two or more isotropic materials are combined in a composite, the isotropic material failure modes may also combine. In a laminate, matrix delamination, cracking and crazing, and voids and porosity, will often combine with fiber breakage, shattering, waviness, and separation to bring about ultimate structural failure. This combining of failure modes can result in defect boundaries of different sizes, corresponding to the failure of each structural component. This paper discusses a dual-technology NDE (Non Destructive Evaluation) (<span class="hlt">eddy</span> <span class="hlt">current</span> (EC) and ultrasonics (UT)) study of graphite/epoxy (gr/ep) laminate samples. <span class="hlt">Eddy</span> <span class="hlt">current</span> and ultrasonic raster (Cscan) imaging were used together to characterize the effects of mechanical impact damage, high temperature thermal damage and various types of inserts in gr/ep laminate samples of various stacking sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AIPC..509..457K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..509..457K"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> monitoring of fatigue crack growth in Zr-2.5% Nb pressure tube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krause, T. W.; Martin, A. E.; Sheppard, R. R.; Schankula, J. J.</p> <p>2000-05-01</p> <p>Zr-2.5% wt. Nb pressure tubes (PTs) form the core of the heat transport system in CANDU nuclear reactors. These 6 m long, 100 mm diameter tubes are operated at elevated temperatures (nominally 300 °C) and at pressures that produce hoop stresses that are 25% of the ultimate tensile strength of the PT (120 Mpa). Therefore, detection and characterization of flaws in these components becomes crucial for their continued pressure retaining integrity. If a flaw is detected, however, the cost of PT replacement is expensive. Periodic in-service inspection of a flaw that demonstrates no change in flaw characteristics can be used to allow a pressure tube to remain in-service. This requires confidence in the accuracy and reliability of methods used to inter flaw characteristics. Such confidence can only be developed by comparing nondestructive predictions with results from destructive examinations. In this work, <span class="hlt">eddy</span> <span class="hlt">current</span> testing was used to monitor the progressive stages of a fatigue crack, grown through pressure cycling from a notch on the inner surface of a PT. Results from a differential lift-off compensated <span class="hlt">eddy</span> <span class="hlt">current</span> probe were used to produce sizing estimates of the crack grown between 35% (base of notch) and 74% of the PT wall. A comparison with a destructive examination of the crack demonstrated sensitivity too changes in crack depth accurate to 5% of the tube wall thickness. Such results, combined with similar information obtained from ultrasonics will increase confidence in interpretation of PT inspection data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..MAR.K1177Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..MAR.K1177Y"><span>Suppressing local hot spots due to <span class="hlt">eddy</span> <span class="hlt">currents</span> in magnetic coil systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yao, Zhen; Shojinaga, Aaron; Wu, Yong; Shvartsman, Shmaryu; Eagan, Timothy; Chmielewski, Thomas; Brown, Robert</p> <p>2011-03-01</p> <p>A particular goal in magnetic field applications is to avoid <span class="hlt">eddy</span> <span class="hlt">current</span> heating in coils and shields. It is important, in MRI, for example, to avoid hot spots near the patient to be imaged as well as in the vicinity of soldering joints. We develop effective analytical formulas for the <span class="hlt">eddy</span> <span class="hlt">current</span> behavior of sources close to surrounding conductors, we verify these via numerical simulations, and we make successful comparisons to corresponding experimental temperature distributions. Optimized patterns of incisions made in the conductors are discovered for addressing particularly troublesome heating locations. The criteria include the need to minimize the number and length of the cuts. Theory and experiment are in agreement on the efficacy of this method for reducing steady-state temperatures. An example of results in the practical design of commercial coils and shields is that a single cut parallel to the long edge of rectangular conductors reduces the temperatures much more than making multiple cuts parallel to the short edge. Supported by Ohio Third Frontier Program</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007IJTPE.127..929F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007IJTPE.127..929F"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> Analysis of Thin Metal Container in Induction Heating by Line Integral Equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujita, Hagino; Ishibashi, Kazuhisa</p> <p></p> <p>In recent years, induction-heating cookers have been disseminated explosively. It is wished to commercialize flexible and disposable food containers that are available for induction heating. In order to develop a good quality food container that is heated moderately, it is necessary to analyze accurately <span class="hlt">eddy</span> <span class="hlt">currents</span> induced in a thin metal plate. The integral equation method is widely used for solving induction-heating problems. If the plate thickness approaches zero, the surface integral equations on the upper and lower plate surfaces tend to become the same and the equations become ill conditioned. In this paper, firstly, we derive line integral equations from the boundary integral equations on the assumption that the electromagnetic fields in metal are attenuated rapidly compared with those along the metal surface. Next, so as to test validity of the line integral equations, we solve the <span class="hlt">eddy</span> <span class="hlt">current</span> induced in a thin metal container in induction heating and obtain power density given to the container and impedance characteristics of the heating coil. We compare computed results with those by FEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0013A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0013A"><span>Model-based probe state estimation and crack inverse methods addressing <span class="hlt">eddy</span> <span class="hlt">current</span> probe variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aldrin, John C.; Oneida, Erin K.; Shell, Eric B.; Sabbagh, Harold A.; Sabbagh, Elias; Murphy, R. Kim; Mazdiyasni, Siamack; Lindgren, Eric A.; Mooers, Ryan D.</p> <p>2017-02-01</p> <p>A model-based calibration process is introduced that estimates the state of the <span class="hlt">eddy</span> <span class="hlt">current</span> probe. First, a carefully designed surrogate model was built using VIC-3D® simulations covering the critical range of probe rotation angles, tilt in two directions, and probe offset (liftoff) for both transverse and longitudinal flaw orientations. Some approximations and numerical compromises in the model were made to represent tilt in two directions and reduce simulation time; however, this surrogate model was found to represent the key trends in the <span class="hlt">eddy</span> <span class="hlt">current</span> response for each of the four probe properties in experimental verification studies well. Next, this model was incorporated into an iterative inversion scheme during the calibration process, to estimate the probe state while also addressing the amplitude/phase fit and centering the calibration notch indication. Results are presented showing several examples of the blind estimation of tilt and rotation angle for known experimental cases with reasonable agreement. Once the probe state is estimated, the final step is to transform the base crack inversion surrogate model and apply it for crack characterization. Using this process, results are presented demonstrating improved crack inversion performance for extreme probe states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26703608','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26703608"><span>Fatigue Crack Length Sizing Using a Novel Flexible <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Array.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying</p> <p>2015-12-21</p> <p>The <span class="hlt">eddy</span> <span class="hlt">current</span> probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar <span class="hlt">eddy</span> <span class="hlt">current</span> sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4963313','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4963313"><span>A Novel Application of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Braking for Functional Strength Training during Gait</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Washabaugh, Edward P.; Claflin, Edward S.; Gillespie, R. Brent; Krishnan, Chandramouli</p> <p>2016-01-01</p> <p>Functional strength training is becoming increasingly popular when rehabilitating individuals with neurological injury such as stroke or cerebral palsy. Typically, resistance during walking is provided using cable robots or weights that are secured to the distal shank of the subject. However, there exists no device that is wearable and capable of providing resistance across the joint, allowing over ground gait training. In this study, we created a lightweight and wearable device using <span class="hlt">eddy</span> <span class="hlt">current</span> braking to provide resistance to the knee. We then validated the device by having subjects wear it during a walking task through varying resistance levels. Electromyography and kinematics were collected to assess the biomechanical effects of the device on the wearer. We found that <span class="hlt">eddy</span> <span class="hlt">current</span> braking provided resistance levels suitable for functional strength training of leg muscles in a package that is both lightweight and wearable. Applying resistive forces at the knee joint during gait resulted in significant increases in muscle activation of many of the muscles tested. A brief period of training also resulted in significant aftereffects once the resistance was removed. These results support the feasibility of the device for functional strength training during gait. Future research is warranted to test the clinical potential of the device in an injured population. PMID:26817456</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984RScI...55.1533M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984RScI...55.1533M"><span>Foucault pendulum with <span class="hlt">eddy-current</span> damping of the elliptical motion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mastner, G.; Vokurka, V.; Maschek, M.; Vogt, E.; Kaufmann, H. P.</p> <p>1984-10-01</p> <p>A newly designed Foucault pendulum is described in which the mechanical Charron ring, used throughout in previous designs for damping of the elliptical motion of the pendulum, is replaced by an electromagnetic <span class="hlt">eddy-current</span> brake, consisting of a permanent magnet attached to the bottom of the bob and a metallic ring. This damping device is very efficient, as it is self-aligning, symmetrical in the damping effect, and never wears out. The permanent magnet is also used, together with a coil assembly and an electronic circuitry, for the dipole-torque drive of the pendulum as well as for accurate stabilization of the amplitude of the swing. A latched time display, controlled by Hall probes activated by the magnet, is used to visualize the Foucault rotation. The pendulum system and its associated electronic circuitry are described in detail. The optimizing of the drive mode is discussed. Measurements of deviations from theoretical value of the Foucault rotation velocity made automatically in a continuous run show a reproducible accuracy of ±1% or better in individual 360° rotations during the summer months. The quality factor of the pendulum as mechanical resonator was measured as a function of the amplitude in the presence of the <span class="hlt">eddy-current</span> damping ring.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26817456','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26817456"><span>A Novel Application of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Braking for Functional Strength Training During Gait.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Washabaugh, Edward P; Claflin, Edward S; Gillespie, R Brent; Krishnan, Chandramouli</p> <p>2016-09-01</p> <p>Functional strength training is becoming increasingly popular when rehabilitating individuals with neurological injury such as stroke or cerebral palsy. Typically, resistance during walking is provided using cable robots or weights that are secured to the distal shank of the subject. However, there exists no device that is wearable and capable of providing resistance across the joint, allowing over ground gait training. In this study, we created a lightweight and wearable device using <span class="hlt">eddy</span> <span class="hlt">current</span> braking to provide resistance to the knee. We then validated the device by having subjects wear it during a walking task through varying resistance levels. Electromyography and kinematics were collected to assess the biomechanical effects of the device on the wearer. We found that <span class="hlt">eddy</span> <span class="hlt">current</span> braking provided resistance levels suitable for functional strength training of leg muscles in a package that is both lightweight and wearable. Applying resistive forces at the knee joint during gait resulted in significant increases in muscle activation of many of the muscles tested. A brief period of training also resulted in significant aftereffects once the resistance was removed. These results support the feasibility of the device for functional strength training during gait. Future research is warranted to test the clinical potential of the device in an injured population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JPhD...37..501S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JPhD...37..501S"><span>Calibration of <span class="hlt">eddy</span> <span class="hlt">current</span> carburization measurements in ethylene production tubes using ion beam analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stevens, K. J.; Trompetter, W. J.</p> <p>2004-02-01</p> <p>Nuclear reaction analysis using a 12C(d, p0)13C reaction and a 16O(d, p1)17O reaction, with 1.02 MeV deuterons in an accelerator microprobe, has been used to produce quantitative linescans of the carbon and oxygen levels in ex-service ethylene pyrolysis tubes of HPM, HK40 and Manaurite XM alloy. Particle induced x-ray emission in the ion beam microprobe and energy dispersive analysis of x-rays in a scanning electron microscope were used for linescans of the heavier elements (Cr, Ni, Fe, Si and Ti). The composition linescans were used to calibrate the response and accuracy of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe system for measuring carburization near the inner surface of the tubes. The influence of the ferromagnetic outer oxide surface layers has been clarified. A two-dimensional ANSYS finite element model (FEM) was used for interpretation of the <span class="hlt">eddy</span> <span class="hlt">current</span> scans. Good correlation was obtained between the ion beam analysis results, the impedance scans and the FEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6773J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6773J"><span><span class="hlt">Eddy</span> <span class="hlt">currents</span> in the anisotropy of out-of-phase magnetic susceptibility measurement - A model study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jezek, Josef; Hrouda, Frantisek</p> <p>2016-04-01</p> <p>Analytical solutions of Maxwell equations for <span class="hlt">eddy</span> <span class="hlt">currents</span> caused by AC field in a conductive sphere, known from 1950s, provide a general formula for magnetic susceptibility. It contains the parameters describing the sphere (its size, conductivity and permeability), surrounding medium (permeability) and the applied field (frequency). The formula is complex and without numerical evaluation it is difficult to distinguish the real (in-phase) and imaginary (out-of-phase) part of susceptibility. Representing all the parameters by only two, relative permeability (sphere vs. medium) and skin ratio (summarizing the effect of sphere size, conductivity and permeability, and frequency of the field), we derive approximate formulas for both phases and the phase angle. These are valid for a reasonable range of parameters (from rock magnetism point of view) and enable us to study their influence. The in-phase susceptibility depends very weakly on the fourth power of the skin ratio while the out-of-phase susceptibility depends more strongly on its second power. The coefficients of the dependence are expressed by means of relative permeability. The approximations of in-phase and out-of-phase susceptibilities provide a possibility to assess possible effects of <span class="hlt">eddy</span> <span class="hlt">currents</span> in rocks in case of low content of conductive minerals and solve problems of the type by which size one piece of a mineral in the measured sample can produce a phase shift that is observed by measurement. Examples of magnetite and pyrrhotite are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5551909','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5551909"><span>Calculation of <span class="hlt">eddy-currents</span> induced in a compact synchrotron superconducting magnet structure during a <span class="hlt">current</span> ramp</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalsi, S. . Space and Electronics Systems Div.); Heese, R. )</p> <p>1991-01-01</p> <p>Under DARPA sponsorship, a compact Superconducting X-Ray Light Source (SXSL) is being designed and built by the Brookhaven National Laboratory (BNL) with industry participation from Grumman Corporation and General Dynamics. The SXLS machine employs two 180{degrees} curved 4 telsa superconducting dipole magnets. These magnets are required to produce a dipole field for bending the beam but at the same time they must produce finite amounts of higher multipoles which are required for conditioning the beam. In fact uniformity of the field to less than 1 part in 10,000 must be maintained under all operating conditions. When a superconducting magnet is ramped from zero to full field, the changing magnetic field produces <span class="hlt">eddy-currents</span> in the magnet structure which in turn can produce undesirable multipoles. This paper discusses a simple method for estimating these <span class="hlt">eddy-currents</span> and their effect on the field harmonics. The paper present the analysis basis and its application to the SXLS magnet support structure and to the beam chamber components. 5 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012IJTIA.132..185S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012IJTIA.132..185S"><span>Development of Ground Coils with Low <span class="hlt">Eddy</span> <span class="hlt">Current</span> Loss by Applying the Compression Molding Method after the Coil Winding</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suzuki, Masao; Aiba, Masayuki; Takahashi, Noriyuki; Ota, Satoru; Okada, Shigenori</p> <p></p> <p>In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an <span class="hlt">eddy</span> <span class="hlt">current</span> will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the <span class="hlt">eddy</span> <span class="hlt">current</span> loss is extremely important. This study examined ground coils in which both the <span class="hlt">eddy</span> <span class="hlt">current</span> loss and temperature increase were small. Furthermore, quantitative comparison for the <span class="hlt">eddy</span> <span class="hlt">current</span> loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low <span class="hlt">eddy</span> <span class="hlt">current</span> loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20959261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20959261"><span>An efficient 3-D <span class="hlt">eddy-current</span> solver using an independent impedance method for transcranial magnetic stimulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Geeter, Nele; Crevecoeur, Guillaume; Dupre, Luc</p> <p>2011-02-01</p> <p>In many important bioelectromagnetic problem settings, <span class="hlt">eddy-current</span> simulations are required. Examples are the reduction of <span class="hlt">eddy-current</span> artifacts in magnetic resonance imaging and techniques, whereby the <span class="hlt">eddy</span> <span class="hlt">currents</span> interact with the biological system, like the alteration of the neurophysiology due to transcranial magnetic stimulation (TMS). TMS has become an important tool for the diagnosis and treatment of neurological diseases and psychiatric disorders. A widely applied method for simulating the <span class="hlt">eddy</span> <span class="hlt">currents</span> is the impedance method (IM). However, this method has to contend with an ill conditioned problem and consequently a long convergence time. When dealing with optimal design problems and sensitivity control, the convergence rate becomes even more crucial since the <span class="hlt">eddy-current</span> solver needs to be evaluated in an iterative loop. Therefore, we introduce an independent IM (IIM), which improves the conditionality and speeds up the numerical convergence. This paper shows how IIM is based on IM and what are the advantages. Moreover, the method is applied to the efficient simulation of TMS. The proposed IIM achieves superior convergence properties with high time efficiency, compared to the traditional IM and is therefore a useful tool for accurate and fast TMS simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650..336G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650..336G"><span>Quantitatively analyzing dielectrical properties of resins and mapping permittivity variations in CFRP with high-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> device technology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gäbler, Simone; Heuer, Henning; Heinrich, Gert; Kupke, Richard</p> <p>2015-03-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> testing is well-established for non-destructive characterization of electrical conductive materials. The development of high-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> technology (with frequency ranges up to 100 MHz) made it even possible to extend the classical fields of application towards less conductive materials like CFRP. Maxwell's equations and recent research show that the use of high-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> technology is also suitable for non-conductive materials. In that case the change of complex impedance of the probing coil contains information on sample permittivity. This paper shows that even a quantitative measurement of complex permittivity with high-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> device technology is possible using an appropriate calibration. Measurement accuracy is comparable to commercial capacitive dielectric analyzers. If the sample material is electrically conductive, both, permittivity and conductivity influence the complex impedance measured with high-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> devices. Depending on the measurement setup and the sheet resistance of the sample a parallel characterization of both parameters is possible on isotropic multi-layer materials. On CFRP the permittivity measurement is much more complex due to the capacitive effects between the carbon rovings. However, first results show that at least the local permittivity variations (like those caused by thermal damages) are detectable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......314B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......314B"><span>Inspection of ferromagnetic support structures from within alloy 800 steam generator tubes using pulsed <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buck, Jeremy Andrew</p> <p></p> <p>Nondestructive testing is a critical aspect of component lifetime management. Nuclear steam generator (SG) tubes are the thinnest barrier between irradiated primary heat transport system and the secondary heat transport system, whose components are not rated for large radiation fields. Conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ECT) and ultrasonic testing are <span class="hlt">currently</span> employed for inspecting SG tubes, with the former doing most inspections due to speed and reliability based on an understanding of how flaws affect coil impedance parameters when conductors are subjected to harmonically induced <span class="hlt">currents</span>. However, when multiple degradation modes are present simultaneously near ferromagnetic materials, such as tube fretting, support structure corrosion, and magnetite fouling, ECT reliability decreases. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC), which induces transient <span class="hlt">eddy</span> <span class="hlt">currents</span> via square wave excitation, has been considered in this thesis to simultaneously examine SG tube and support structure conditions. An array probe consisting of a central driver, coaxial with the tube, and an array of 8 sensing coils, was used in this thesis to perform laboratory measurements. The probe was delivered from the inner diameter (ID) of the SG tube, where support hole diameter, tube frets, and 2D off-centering were varied. When considering two variables simultaneously, scores obtained from a modified principal components analysis (MPCA) were sufficient for parameter extraction. In the case of hole ID variation with two dimensional tube off-centering (three parameters), multiple linear regression (MLR) of the MPCA scores provided good estimates of parameters. However, once a fourth variable, outer diameter tube frets, was introduced, MLR proved insufficient. Artificial neural networks (ANNs) were investigated in order to perform pattern recognition on the MPCA scores to simultaneously extract the four measurement parameters from the data. All models throughout this thesis were created and validated using</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAG....92..137S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAG....92..137S"><span>Simple wideband models for disks and wires in the <span class="hlt">eddy</span> <span class="hlt">current</span> approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, Waymond R.; McFadden, Michael</p> <p>2013-05-01</p> <p>Wideband electromagnetic induction systems have shown improved false alarm rates when compared with traditional metal detectors. Calibration of these sensors and the development of algorithms for target discrimination could be assisted by a set of models for common targets. In this paper, simple wideband models of the <span class="hlt">eddy</span> <span class="hlt">current</span> response for a wire and disk are provided. These are provided in the form of a singularity expansion of the polarizability dyadic. In an effort to make this form more concrete, a major focus of the paper is on relating the terms of the expansion to graphs of the <span class="hlt">currents</span> present on the disk. The models provided in the paper are based on limiting forms of a cylinder as computed using the body-of-revolutions finite element method. Measured polarizability dyadics are also shown to fit the forms provided reasonably well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/712807','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/712807"><span><span class="hlt">Eddy-current</span> inspection of ferromagnetic tubing using pulsed magnetic saturation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dodd, C V; Deeds, W E</p> <p>1986-07-01</p> <p>A pulsed <span class="hlt">eddy-current</span> system has been designed and developed for nondestructive evaluation of 2.25Cr-1Mo steam generator tubing from the bore side. Since the tubing is ferromagnetic, a large <span class="hlt">current</span> pulse is sent through a driver coil to produce magnetic saturation all the way through the tube wall. A pickup coil produces an output pulse that is dependent upon the tube properties as well as the driving pulse. The output pulse heights at selected times are used as data that are computer-correlated with calibration data taken from machined standards. Performance data, circuit diagrams, and computer programs are given for the system, which has been demonstrated to detect small flaws located near the outside of a thick ferromagnetic tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090027875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090027875"><span>Large-<span class="hlt">Eddy</span> Simulation: <span class="hlt">Current</span> Capabilities, Recommended Practices, and Future Research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Georgiadis, Nicholas J.; Rizzetta, Donald P.; Fureby, Christer</p> <p>2009-01-01</p> <p>This paper presents the results of an activity by the Large <span class="hlt">Eddy</span> Simulation (LES) Working Group of the AIAA Fluid Dynamics Technical Committee to (1) address the <span class="hlt">current</span> capabilities of LES, (2) outline recommended practices and key considerations for using LES, and (3) identify future research needs to advance the capabilities and reliability of LES for analysis of turbulent flows. To address the <span class="hlt">current</span> capabilities and future needs, a survey comprised of eleven questions was posed to LES Working Group members to assemble a broad range of perspectives on important topics related to LES. The responses to these survey questions are summarized with the intent not to be a comprehensive dictate on LES, but rather the perspective of one group on some important issues. A list of recommended practices is also provided, which does not treat all aspects of a LES, but provides guidance on some of the key areas that should be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0025W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0025W"><span>Electromagnetic modeling of an <span class="hlt">eddy-current</span> position sensor for use in a fast reactor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Tao; Bowler, John R.</p> <p>2017-02-01</p> <p>In this article, we proposed a novel theoretical electromagnetic model of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe used as a position sensor with respect to a tube in a fast reactor under standby conditions. In these circumstances the coil position cannot be guided by optical aids but electromagnetic sensing can be used. Initially, we derived analytical expressions for the quasi-static time-harmonic electromagnetic field of a circular <span class="hlt">current</span> filament via the transverse magnetic potential expressed in terms of a single layer potential. This is then used to deduce the field of a circular sensor coil near a conductive tube, the axis of the coil having an arbitrary direction with respect to that of the tube. The fields for an external coil have been determined and can be used to deduce coil impedance variations with frequency, location and orientation. The model predictions can be used to guide the probe to a desire position with respect to the tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/876522','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/876522"><span>On the modeling, design and validation of two dimensional quasi-static <span class="hlt">eddy</span> <span class="hlt">current</span> forces in a mechanical oscillator.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mitchell, John Anthony; Epp, David S.; Wittwer, Jonathan W.</p> <p>2005-10-01</p> <p>Damping vibrations is important in the design of some types of inertial sensing devices. One method for adding damping to a device is to use magnetic forces generated by a static magnetic field interacting with <span class="hlt">eddy</span> <span class="hlt">currents</span>. In this report, we develop a 2-dimensional finite element model for the analysis of quasistatic <span class="hlt">eddy</span> <span class="hlt">currents</span> in a thin sheet of conducting material. The model was used for design and sensitivity analyses of a novel mechanical oscillator that consists of a shuttle mass (thin sheet of conducting material) and a set of folded spring elements. The oscillator is damped through the interaction of a static magnetic field and <span class="hlt">eddy</span> <span class="hlt">currents</span> in the shuttle mass. Using a prototype device and Laser Dopler Velocimetry (LDV), measurements were compared to the model in a validation study using simulation based uncertainty analyses. Measurements were found to follow the trends predicted by the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..760..425J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..760..425J"><span>Studies into the Effects of Surface Roughness on Spatial <span class="hlt">Eddy-Current</span> Data from Nickel-Based Engine Alloys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, M. J.; Nakagawa, N.; Wendt, S. E.; Hentscher, S. R.; Nelson, D. L.; Buhr, K. T.; Kilbugh, B. A.; Raithel, D. C.</p> <p>2005-04-01</p> <p><span class="hlt">Eddy-current</span> scans have been carried out on two Inconel-718 specimens following the application of various levels of shot peening and heat treatments. The conventional analysis of roughened or shot peened surfaces looks at multi-frequency impedance measurements and interprets the data as a change in conductivity or liftoff. An approach involving the statistical analysis of scanned <span class="hlt">eddy-current</span> impedance data is suggested as an alternative that may provide a more sensitive way of determining the treatment history of a component. It is possible that an analysis of these statistical distributions in spatial <span class="hlt">eddy-current</span> data could be used to determine the level of remaining residual stress in engine components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.6926A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.6926A"><span>On the shape of sea level anomaly <span class="hlt">signal</span> on periphery of mesoscale ocean <span class="hlt">eddies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amores, A.; Monserrat, S.; Melnichenko, O.; Maximenko, N.</p> <p>2017-07-01</p> <p>Good knowledge of mesoscale <span class="hlt">eddy</span> properties and their spatial and temporal distribution in the world ocean is important for an accurate estimate of their role in heat, salt, and/or momentum transports. Composites of satellite sea level anomaly, used to evaluate internal <span class="hlt">eddy</span> structure, commonly produce, at larger radii, a series of rings of alternating sign. We suggest that these secondary rings are not a part of the dynamical structure of the "central" <span class="hlt">eddy</span> but are a rectified signature of the surrounding <span class="hlt">eddies</span>. We show that statistical distribution of <span class="hlt">eddy</span> polarities is not random but that an <span class="hlt">eddy</span> of given polarity tends to be surrounded by <span class="hlt">eddies</span> of opposite polarity. This observed spatial <span class="hlt">eddy</span> polarity distribution, which is hypothesized to be a result of <span class="hlt">eddy</span> self-organization, is not only responsible for the secondary rings observed in the composite estimates but also causes a reduction of around 20% of the <span class="hlt">eddy</span> composite amplitude and an increment of around 10% in the maximum rotational velocity, while it has negligible effect on the estimated <span class="hlt">eddy</span> scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21054941','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21054941"><span>Multifrequency <span class="hlt">Eddy</span> <span class="hlt">Current</span> Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Okafor, A. C.; Natarajan, S.</p> <p>2007-03-21</p> <p>Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of <span class="hlt">eddy</span> <span class="hlt">current</span> inspection, corrosion product removal and fatigue testing are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21190168','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21190168"><span>Effects of <span class="hlt">eddy</span> <span class="hlt">currents</span> due to a vacuum chamber wall in the airgap of a moving-magnet linear actuator</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jansen, J. W.; Lomonova, E. A.; Rovers, J. M. M.</p> <p>2009-04-01</p> <p>This paper discusses the effects of <span class="hlt">eddy</span> <span class="hlt">currents</span> induced in an electrically conducting plate which is placed in the airgap of a linear synchronous actuator with moving permanent magnets. The <span class="hlt">eddy</span> <span class="hlt">currents</span> induced in this plate, which is part of a controlled atmosphere chamber, cause not only damping but also deteriorate the actuator performance by disturbing the position measurement with Hall sensors. Furthermore, feed-forward controllers are less effective due to the suppression of high frequent armature fields. These effects are analyzed with an analytical model and verified with finite element simulations and measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/899424','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/899424"><span>Computer Calculations of <span class="hlt">Eddy-Current</span> Power Loss in Rotating Titanium Wheels and Rims in Localized Axial Magnetic Fields</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mayhall, D J; Stein, W; Gronberg, J B</p> <p>2006-05-15</p> <p>We have performed preliminary computer-based, transient, magnetostatic calculations of the <span class="hlt">eddy-current</span> power loss in rotating titanium-alloy and aluminum wheels and wheel rims in the predominantly axially-directed, steady magnetic fields of two small, solenoidal coils. These calculations have been undertaken to assess the <span class="hlt">eddy-current</span> power loss in various possible International Linear Collider (ILC) positron target wheels. They have also been done to validate the simulation code module against known results published in the literature. The commercially available software package used in these calculations is the Maxwell 3D, Version 10, Transient Module from the Ansoft Corporation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20632918','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20632918"><span>Development of a 3D Electromagnetic Model for <span class="hlt">Eddy</span> <span class="hlt">Current</span> Tubing Inspection: Application to Steam Generator Tubing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pichenot, G.; Premel, D.; Sollier, T.; Maillot, V.</p> <p>2004-02-26</p> <p>In nuclear plants, the inspection of heat exchanger tubes is usually carried out by using <span class="hlt">eddy</span> <span class="hlt">current</span> nondestructive testing. A numerical model, based on a volume integral approach using the Green's dyadic formalism, has been developed, with support from the French Institute for Radiological Protection and Nuclear Safety, to predict the response of an <span class="hlt">eddy</span> <span class="hlt">current</span> bobbin coil to 3D flaws located in the tube's wall. With an aim of integrating this model into the NDE multi techniques platform CIVA, it has been validated with experimental data for 2D and 3D flaws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AIPC..700..321P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AIPC..700..321P"><span>Development of a 3D Electromagnetic Model for <span class="hlt">Eddy</span> <span class="hlt">Current</span> Tubing Inspection: Application to Steam Generator Tubing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pichenot, G.; Prémel, D.; Sollier, T.; Maillot, V.</p> <p>2004-02-01</p> <p>In nuclear plants, the inspection of heat exchanger tubes is usually carried out by using <span class="hlt">eddy</span> <span class="hlt">current</span> nondestructive testing. A numerical model, based on a volume integral approach using the Green's dyadic formalism, has been developed, with support from the French Institute for Radiological Protection and Nuclear Safety, to predict the response of an <span class="hlt">eddy</span> <span class="hlt">current</span> bobbin coil to 3D flaws located in the tube's wall. With an aim of integrating this model into the NDE multi techniques platform CIVA, it has been validated with experimental data for 2D and 3D flaws.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ChPhy..15.1903Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ChPhy..15.1903Z"><span>High-Tc planar SQUID gradiometer for <span class="hlt">eddy</span> <span class="hlt">current</span> non-destructive evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Ming-Jian; Lang, Pei-Lin; Peng, Zhi-Hui; Chen, Ying-Fei; Chen, Ke; Zheng, Dong-Ning</p> <p>2006-08-01</p> <p>This paper reports the fabrication and test of a high-Tc SQUID planar gradiometer which is patterned from YBCO thin film deposited on a SrTiO3 bicrystal substrate. The measurement of noise spectrum at 77K shows that the white noise at 200 Hz is about 1×10-4Φ0/(Hz)1/2. The minimal magnetic gradient is measured and the results suggest that the minimal magnetic gradient is 94 pT/m. The planar gradiometer is used in non-destructive evaluation (NDE) experiments to detect the artifacts in conducting aluminium plates by performing <span class="hlt">eddy</span> <span class="hlt">current</span> testing in an unshielded environment. The effect of the exciting coil dimension on the NDE results is investigated. By mapping out the induced field distribution, flaws about 10mm below the plate surface can be clearly identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21054940','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21054940"><span>Application of Millimeter Wave, <span class="hlt">Eddy</span> <span class="hlt">Current</span> and Thermographic Methods for Detection of Corrosion in Aluminum Substrate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ryley, A. C.; Ghasr, M. T.; Kharkovsky, S.; Zoughi, R.; Steffes, Gary</p> <p>2007-03-21</p> <p>Aluminum structures exposed to the elements are susceptible to corrosion. Corrosion may cause various mechanical and structural deficiencies such as material thinning. It is desirable to rapidly detect and evaluate the properties of an aluminum substrate early in the corrosion process to avoid costly maintenance actions later. There are several nondestructive testing methods for this purpose. To investigate capabilities of millimeter wave, conventional <span class="hlt">eddy</span> <span class="hlt">current</span>, and flash thermography techniques for detection of large corrosion areas in aluminum substrates, two corroded samples were inspected with and without dielectric coating (applique). This paper presents the results of the c-scan imaging of these samples using the methods mentioned above. The attributes of these methods for detection and evaluation of large, severe and non-uniform corrosion areas with and without a dielectric coating are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/257304','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/257304"><span>Performance demonstration tests for <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of steam generator tubing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kurtz, R.J.; Heasler, P.G.; Anderson, C.M.</p> <p>1996-05-01</p> <p>This report describes the methodology and results for development of performance demonstration tests for <span class="hlt">eddy</span> <span class="hlt">current</span> (ET) inspection of steam generator tubes. Statistical test design principles were used to develop the performance demonstration tests. Thresholds on ET system inspection performance were selected to ensure that field inspection systems would have a high probability of detecting and and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented in detail. Statistical test design calculations for probability of detection and flaw sizing tests are described. A recommended performance demonstration test based on the design calculations is presented. A computer program for grading the probability of detection portion of the performance demonstration test is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/572689','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/572689"><span>Nondestructive inspection assessment of <span class="hlt">eddy</span> <span class="hlt">current</span> and electrochemical analysis to separate inconel and stainless steel alloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moore, D.G.; Sorensen, N.R.</p> <p>1998-02-01</p> <p>This report presents a nondestructive inspection assessment of <span class="hlt">eddy</span> <span class="hlt">current</span> and electrochemical analysis to separate inconel alloys from stainless steel alloys as well as an evaluation of cleaning techniques to remove a thermal oxide layer on aircraft exhaust components. The results of this assessment are presented in terms of how effective each technique classifies a known exhaust material. Results indicate that either inspection technique can separate inconel and stainless steel alloys. Based on the experiments conducted, the electrochemical spot test is the optimum for use by airframe and powerplant mechanics. A spot test procedure is proposed for incorporation into the Federal Aviation Administration Advisory Circular 65-9A Airframe & Powerplant Mechanic - General Handbook. 3 refs., 70 figs., 7 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MeScT..27k5016W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MeScT..27k5016W"><span>Precise on-machine extraction of the surface normal vector using an <span class="hlt">eddy</span> <span class="hlt">current</span> sensor array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Yongqing; Lian, Meng; Liu, Haibo; Ying, Yangwei; Sheng, Xianjun</p> <p>2016-11-01</p> <p>To satisfy the requirements of on-machine measurement of the surface normal during complex surface manufacturing, a highly robust normal vector extraction method using an <span class="hlt">Eddy</span> <span class="hlt">current</span> (EC) displacement sensor array is developed, the output of which is almost unaffected by surface brightness, machining coolant and environmental noise. A precise normal vector extraction model based on a triangular-distributed EC sensor array is first established. Calibration of the effects of object surface inclination and coupling interference on measurement results, and the relative position of EC sensors, is involved. A novel apparatus employing three EC sensors and a force transducer was designed, which can be easily integrated into the computer numerical control (CNC) machine tool spindle and/or robot terminal execution. Finally, to test the validity and practicability of the proposed method, typical experiments were conducted with specified testing pieces using the developed approach and system, such as an inclined plane and cylindrical and spherical surfaces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMEP...23.2083M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMEP...23.2083M"><span>Characterization of Heat Treated Titanium-Based Implants by Nondestructive <span class="hlt">Eddy</span> <span class="hlt">Current</span> and Ultrasonic Tests</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mutlu, Ilven; Ekinci, Sinasi; Oktay, Enver</p> <p>2014-06-01</p> <p>This study presents nondestructive characterization of microstructure and mechanical properties of heat treated Ti, Ti-Cu, and Ti-6Al-4V titanium-based alloys and 17-4 PH stainless steel alloy for biomedical implant applications. Ti, Ti-Cu, and 17-4 PH stainless steel based implants were produced by powder metallurgy. Ti-6Al-4V alloy was investigated as bulk wrought specimens. Effects of sintering temperature, aging, and grain size on mechanical properties were investigated by nondestructive and destructive tests comparatively. Ultrasonic velocity in specimens was measured by using pulse-echo and transmission methods. Electrical conductivity of specimens was determined by <span class="hlt">eddy</span> <span class="hlt">current</span> tests. Determination of Young's modulus and strength is important in biomedical implants. Young's modulus of specimens was calculated by using ultrasonic velocities. Calculated Young's modulus values were compared and correlated with experimental values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20798254','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20798254"><span>Detection of Hidden Cracks on Aircraft LAP Joints with GMR Based <span class="hlt">Eddy</span> <span class="hlt">Current</span> Technology</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Na, J. K.; Franklin, M. A.; Linn, J. R.</p> <p>2006-03-06</p> <p>Cracks occurring on commercial aircraft fuselage lap joints made of aluminum alloys often caused by scribe lines made during the removal of process of moisture sealing materials between two layers. These cracks on thinner bottom skin layers can be obscured by thicker top plates with paint. A portable GMR (Giant Magnetoresistive) sensor based <span class="hlt">eddy</span> <span class="hlt">current</span> system has been developed and tested on several simulated aircraft lap joints samples with EDM notches. Various thicknesses of layers are used to simulate the test as used on different combinations of lap joints. Length and depth of cracks are important factors for the safety of aircraft. Test results are used to come up with a portable nondestructive inspection system which is easy and fast with a high reliability of detecting cracks longer than a half inch in length and 0.010 inches in depth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20655379','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20655379"><span>Code Validation for <span class="hlt">Eddy</span> <span class="hlt">Current</span> Modeling: Tube Inspection with Reflection Differential Probes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schumm, A.; Nakagawa, N.</p> <p>2005-04-09</p> <p>Simulation results of the <span class="hlt">eddy</span> <span class="hlt">current</span> modeling code ECSIM on an Inconel tube mock-up were compared to existing experimental results on inner and outer circumferential notches inspected at two different frequencies, observing the influence of a geometrical effect such as tube thickness. The EC probe used for this setup represented a number of difficulties, such as a ferrite core for the excitation coil and a differential pickup coil arrangement with a small inner diameter. The results were instructive, showing that special care must be taken to generate highly symmetrical meshes, as minor differences are amplified by the differential setup. We present qualitative and quantitative results and focus on the lessons learned from this code validation exercise.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016mecs.conf..371Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016mecs.conf..371Z"><span>Analysis of Dissimilar Material Defect Based on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Conductivity Testing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xiaofan; Li, Lifu</p> <p></p> <p>In this experiment, the conductivity distribution of lack of penetration (LOP) in friction stir welding (FSW) of dissimilar materials has been tested, and has been compared with the conductivity distribution of the same kind of material, by using <span class="hlt">eddy</span> <span class="hlt">current</span> conductivity meter. CZ state and M state LY12 aluminum alloy has been studied. The results show that when the depth of LOP is small, the conductivity of M state is the highest, the conductivity decreases gradually to the weld center, reduce to the minimum until reach the CZ state base metal. When the depth of LOP is larger, the conductivity of the weld center decreases sharply with the depth of LOP increases gradually. Scilicet, the larger the depth of LOP, the lower the conductivity. The conductivity distribution of other areas is similar to the distribution when the depth of LOP is small.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080001613','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080001613"><span>Validation Test Results for Orthogonal Probe <span class="hlt">Eddy</span> <span class="hlt">Current</span> Thruster Inspection System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Russell A.</p> <p>2007-01-01</p> <p>Recent nondestructive evaluation efforts within NASA have focused on an inspection system for the detection of intergranular cracking originating in the relief radius of Primary Reaction Control System (PCRS) Thrusters. Of particular concern is deep cracking in this area which could lead to combustion leakage in the event of through wall cracking from the relief radius into an acoustic cavity of the combustion chamber. In order to reliably detect such defects while ensuring minimal false positives during inspection, the Orthogonal Probe <span class="hlt">Eddy</span> <span class="hlt">Current</span> (OPEC) system has been developed and an extensive validation study performed. This report describes the validation procedure, sample set, and inspection results as well as comparing validation flaws with the response from naturally occuring damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MS%26E..161a2001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MS%26E..161a2001S"><span>Silent Flange Coupling Design Used for the Schenck <span class="hlt">Eddy</span> <span class="hlt">Current</span> Dynamometer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schinteie, D.; Croitorescu, V.</p> <p>2016-11-01</p> <p>The silent flange used for coupling different machines/systems to an <span class="hlt">eddy</span> <span class="hlt">current</span> dynamometer represents one of the modular components each test-bench should use. By introducing a silent flange into a dynamometer, the coupling steps are easier and faster. For an appropriate design, the silent flange was analyzed using dedicated software during different operation procedures and scenarios, for materials that allow easy manufacturing. This study shows that the design for this silent flange model has no danger of failure due to the small deformation and the values for the equivalent stresses. The silent flange coupling is suitable for the dynamometer for his high positioning accuracy, the zero backlash and the fact that there is no motion between the shafts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008SPIE.6929E..1WE','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008SPIE.6929E..1WE"><span>Fully-coupled magnetoelastic model for Galfenol alloys incorporating <span class="hlt">eddy</span> <span class="hlt">current</span> losses and thermal relaxation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evans, Phillip G.; Dapino, Marcelo J.</p> <p>2008-03-01</p> <p>A general framework is developed to model the nonlinear magnetization and strain response of cubic magnetostrictive materials to 3-D dynamic magnetic fields and 3-D stresses. Dynamic <span class="hlt">eddy</span> <span class="hlt">current</span> losses and inertial stresses are modeled by coupling Maxwell's equations to Newton's second law through a nonlinear constitutive model. The constitutive model is derived from continuum thermodynamics and incorporates rate-dependent thermal effects. The framework is implemented in 1-D to describe a Tonpilz transducer in both dynamic actuation and sensing modes. The model is shown to qualitatively describe the effect of increase in magnetic hysteresis with increasing frequency, the shearing of the magnetization loops with increasing stress, and the decrease in the magnetostriction with increasing load stiffness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150007196','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007196"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> Minimizing Flow Plug for Use in Flow Conditioning and Flow Metering</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>England, John Dwight (Inventor); Kelley, Anthony R. (Inventor)</p> <p>2015-01-01</p> <p>An <span class="hlt">eddy-current</span>-minimizing flow plug has an outer radial wall with open flow channels formed between the plug's inlet and outlet. The plug has a central region coupled to the inner surface of the outer radial wall. Each open flow channel includes (i) a first portion originating at the inlet and converging to a location in the plug where convergence is contributed to by changes in thickness of the outer radial wall and divergence of the central region, and (ii) a second portion originating in the plug and diverging to the outlet where divergence is contributed to by changes in thickness of the outer radial wall and convergence of the central region. For at least a portion of the open flow channels, a central axis passing through the first and second portions is non-parallel with respect to the given direction of the flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0005B"><span>Evaluation of machine learning tools for inspection of steam generator tube structures using pulsed <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buck, J. A.; Underhill, P. R.; Morelli, J.; Krause, T. W.</p> <p>2017-02-01</p> <p>Degradation of nuclear steam generator (SG) tubes and support structures can result in a loss of reactor efficiency. Regular in-service inspection, by conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ECT), permits detection of cracks, measurement of wall loss, and identification of other SG tube degradation modes. However, ECT is challenged by overlapping degradation modes such as might occur for SG tube fretting accompanied by tube off-set within a corroding ferromagnetic support structure. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) is an emerging technology examined here for inspection of Alloy-800 SG tubes and associated carbon steel drilled support structures. Support structure hole size was varied to simulate uniform corrosion, while SG tube was off-set relative to hole axis. PEC measurements were performed using a single driver with an 8 pick-up coil configuration in the presence of flat-bottom rectangular frets as an overlapping degradation mode. A modified principal component analysis (MPCA) was performed on the time-voltage data in order to reduce data dimensionality. The MPCA scores were then used to train a support vector machine (SVM) that simultaneously targeted four independent parameters associated with; support structure hole size, tube off-centering in two dimensions and fret depth. The support vector machine was trained, tested, and validated on experimental data. Results were compared with a previously developed artificial neural network (ANN) trained on the same data. Estimates of tube position showed comparable results between the two machine learning tools. However, the ANN produced better estimates of hole inner diameter and fret depth. The better results from ANN analysis was attributed to challenges associated with the SVM when non-constant variance is present in the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/467901','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/467901"><span>Transmit-receive <span class="hlt">eddy</span> <span class="hlt">current</span> probes for defect detection and sizing in steam generator tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Obrutsky, L.S.; Cecco, V.S.; Sullivan, S.P.</p> <p>1997-02-01</p> <p>Inspection of steam generator tubes in aging Nuclear Generating Stations is increasingly important. Defect detection and sizing, especially in defect prone areas such as the tubesheet, support plates and U-bend regions, are required to assess the fitness-for-service of the steam generators. Information about defect morphology is required to address operational integrity issues, i.e., risk of tube rupture, number of tubes at risk, consequential leakage. A major challenge continues to be the detection and sizing of circumferential cracks. Utilities around the world have experienced this type of tube failure. Conventional in-service inspection, performed with <span class="hlt">eddy</span> <span class="hlt">current</span> bobbin probes, is ineffectual in detecting circumferential cracks in tubing. It has been demonstrated in CANDU steam generators, with deformation, magnetite and copper deposits that multi-channel probes with transmit-receive <span class="hlt">eddy</span> <span class="hlt">current</span> coils are superior to those using surface impedance coils. Transmit-receive probes have strong directional properties, permitting probe optimization according to crack orientation. They are less sensitive to lift-off noise and magnetite deposits and possess good discrimination to internal defects. A single pass C3 array transmit-receive probe developed by AECL can detect and size circumferential stress corrosion cracks as shallow as 40% through-wall. Since its first trial in 1992, it has been used routinely for steam generator in-service inspection of four CANDU plants, preventing unscheduled shutdowns due to leaking steam generator tubes. More recently, a need has surfaced for simultaneous detection of both circumferential and axial cracks. The C5 probe was designed to address this concern. It combines transmit-receive array probe technology for equal sensitivity to axial and circumferential cracks with a bobbin probe for historical reference. This paper will discuss the operating principles of transmit-receive probes, along with inspection results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950031117&hterms=Recruitment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DRecruitment','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950031117&hterms=Recruitment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DRecruitment"><span>Wave-<span class="hlt">current</span> interaction study in the Gulf of Alaska for detection of <span class="hlt">eddies</span> by synthetic aperture radar</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, Antony K.; Peng, Chich Y.; Schumacher, James D.</p> <p>1994-01-01</p> <p>High resolution Esa Remote Sensing Satellite-1 (ERS-1) Synthetic Aperture Radar (SAR) images are used to detect a mesoscale <span class="hlt">eddy</span>. Such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the Gulf of Alaska. During high sea states and high winds, the direct surface signature of the <span class="hlt">eddy</span> was not clearly visible, but the wave refraction in the <span class="hlt">eddy</span> area was observed. The rays of the wave field are traced out directly from the SAR image. The ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave <span class="hlt">current</span> interaction. These observations are simulated by a ray-tracing model which incorporates a surface <span class="hlt">current</span> field associated with the <span class="hlt">eddy</span>. The numerical results of the model show that the waves are refracted and diverge in the <span class="hlt">eddy</span> field with energy density decreasing. The model-data comparison for each ray shows the model predictions are in good agreement with the SAR data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1581.1352K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1581.1352K"><span>A pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> probe for inspection of support plates from within Alloy-800 steam generator tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krause, T. W.; Babbar, V. K.; Underhill, P. R.</p> <p>2014-02-01</p> <p>Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC <span class="hlt">signals</span> to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled <span class="hlt">signal</span> amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22263748','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22263748"><span>A pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> probe for inspection of support plates from within Alloy-800 steam generator tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krause, T. W.; Babbar, V. K.; Underhill, P. R.</p> <p>2014-02-18</p> <p>Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC <span class="hlt">signals</span> to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled <span class="hlt">signal</span> amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhD...48s5002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhD...48s5002D"><span>A model-based method for the characterisation of stress in magnetic materials using <span class="hlt">eddy</span> <span class="hlt">current</span> non-destructive evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahia, Abla; Berthelot, Eric; Le Bihan and, Yann; Daniel, Laurent</p> <p>2015-03-01</p> <p>A precise knowledge of the distribution of internal stresses in materials is key to the prediction of magnetic and mechanical performance and lifetime of many industrial devices. This is the reason why many efforts have been made to develop and enhance the techniques for the non-destructive evaluation of stress. In the case of magnetic materials, the use of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) techniques is a promising pathway to stress evaluation. The principle is based on the significant changes in magnetic permeability of magnetic materials subjected to mechanical stress. These modifications of magnetic permeability affect in turn the <span class="hlt">signal</span> obtained from an EC probe inspecting the material. From this principle, a numerical tool is proposed in this paper to predict the EC <span class="hlt">signal</span> obtained from a material subjected to stress. This numerical tool is a combination of a 3D finite element approach with a magneto-mechanical constitutive law describing the effect of stress on the magnetic permeability. The model provides the variations of impedance of an EC probe as a function of stress. An experimental setup in which a magnetic material subjected to a tension stress is inspected using EC techniques is tailored in order to validate the model. A very good agreement is found between experimental and modelling results. For the Iron-Cobalt alloy tested in this study, it is shown that a uniaxial tensile stress can be detected with an error lower than 3 MPa in the range from 0 to 100 MPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007MSSP...21..441D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007MSSP...21..441D"><span>Tool vibration detection with <span class="hlt">eddy</span> <span class="hlt">current</span> sensors in machining process and computation of stability lobes using fuzzy classifiers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Devillez, Arnaud; Dudzinski, Daniel</p> <p>2007-01-01</p> <p>Today the knowledge of a process is very important for engineers to find optimal combination of control parameters warranting productivity, quality and functioning without defects and failures. In our laboratory, we carry out research in the field of high speed machining with modelling, simulation and experimental approaches. The aim of our investigation is to develop a software allowing the cutting conditions optimisation to limit the number of predictive tests, and the process monitoring to prevent any trouble during machining operations. This software is based on models and experimental data sets which constitute the knowledge of the process. In this paper, we deal with the problem of vibrations occurring during a machining operation. These vibrations may cause some failures and defects to the process, like workpiece surface alteration and rapid tool wear. To measure on line the tool micro-movements, we equipped a lathe with a specific instrumentation using <span class="hlt">eddy</span> <span class="hlt">current</span> sensors. Obtained <span class="hlt">signals</span> were correlated with surface finish and a <span class="hlt">signal</span> processing algorithm was used to determine if a test is stable or unstable. Then, a fuzzy classification method was proposed to classify the tests in a space defined by the width of cut and the cutting speed. Finally, it was shown that the fuzzy classification takes into account of the measurements incertitude to compute the stability limit or stability lobes of the process.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. Their policies may differ from this site.</small> </div> </center> <div id="footer-wrapper"> <div class="footer-content"> <div id="footerOSTI" class=""> <div class="row"> <div class="col-md-4 text-center col-md-push-4 footer-content-center"><small><a href="http://www.science.gov/disclaimer.html">Privacy and Security</a></small> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center col-md-pull-4 footer-content-left"> <img src="https://www.osti.gov/images/DOE_SC31.png" alt="U.S. Department of Energy" usemap="#doe" height="31" width="177"><map style="display:none;" name="doe" id="doe"><area shape="rect" coords="1,3,107,30" href="http://www.energy.gov" alt="U.S. Deparment of Energy"><area shape="rect" coords="114,3,165,30" href="http://www.science.energy.gov" alt="Office of Science"></map> <a ref="http://www.osti.gov" style="margin-left: 15px;"><img src="https://www.osti.gov/images/footerimages/ostigov53.png" alt="Office of Scientific and Technical Information" height="31" width="53"></a> <div class="visible-sm visible-xs push_footer"></div> </div> <div class="col-md-4 text-center footer-content-right"> <a href="http://www.science.gov"><img src="https://www.osti.gov/images/footerimages/scigov77.png" alt="science.gov" height="31" width="98"></a> <a href="http://worldwidescience.org"><img src="https://www.osti.gov/images/footerimages/wws82.png" alt="WorldWideScience.org" height="31" width="90"></a> </div> </div> </div> </div> </div> <p><br></p> </div><!-- container --> <script type="text/javascript"><!-- // var lastDiv = ""; function showDiv(divName) { // hide last div if (lastDiv) { document.getElementById(lastDiv).className = "hiddenDiv"; } //if value of the box is not nothing and an object with that name exists, then change the class if (divName && document.getElementById(divName)) { document.getElementById(divName).className = "visibleDiv"; lastDiv = divName; } } //--> </script> <script> /** * Function that tracks a click on an outbound link in Google Analytics. * This function takes a valid URL string as an argument, and uses that URL string * as the event label. */ var trackOutboundLink = function(url,collectionCode) { try { h = window.open(url); setTimeout(function() { ga('send', 'event', 'topic-page-click-through', collectionCode, url); }, 1000); } catch(err){} }; </script> <!-- Google Analytics --> <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-1122789-34', 'auto'); ga('send', 'pageview'); </script> <!-- End Google Analytics --> <script> showDiv('page_1') </script> </body> </html>