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Sample records for eddy current flowmeter

  1. Pulsed eddy current testing

    NASA Astrophysics Data System (ADS)

    Workman, G. L.

    1980-10-01

    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.

  2. 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.

  3. Micromagnetics with eddy currents

    NASA Astrophysics Data System (ADS)

    Iyer, R.; Millhollon, J.; Long, K.

    2011-01-01

    In this paper, we study the modified Landau-Lifshitz-Gilbert (LLG) equation for of a conducting, magnetic body. The modified LLG equations include the magnetic field due to eddy currents in the total effective magnetic field. We derive an expression for the magnetic field due to eddy current losses and show that it is well defined. We then show that the work done by the eddy currents in opposing the change of magnetization is a Rayleigh type dissipation function, and derive the modified LLG equations using the calculus of variations. Finally, we show that the modified LLG equations lead to a decrease in the Gibbs energy. This implies that the LLG equations describes a dynamic process proceeding spontaneously forward in time.

  4. FLOWMETER

    DOEpatents

    November, G.S.; Schute, F.

    1962-02-20

    A fluid flowmeter is designed in which a standing pressure wave is established. The amplitude of this standing wave is a function of the fluid flow rate so that pressure sensing devices may be used to indicate fluid flow and variations thereof. (AEC)

  5. Eddy current damper

    NASA Technical Reports Server (NTRS)

    Ellis, R. C.; Fink, R. A.; Rich, R. W.

    1989-01-01

    A high torque capacity eddy current damper used as a rate limiting device for a large solar array deployment mechanism is discussed. The eddy current damper eliminates the problems associated with the outgassing or leaking of damping fluids. It also provides performance advantages such as damping torque rates, which are truly linear with respect to input speed, continuous 360 degree operation in both directions of rotation, wide operating temperature range, and the capability of convenient adjustment of damping rates by the user without disassembly or special tools.

  6. 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.

  7. 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.

  8. Eddy current scanning at Fermilab

    SciTech Connect

    Boffo, C.; Bauer, P.; Foley, M.; Brinkmann, A.; Ozelis, J.; /Jefferson Lab

    2005-07-01

    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 the 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 sub-surface defects and inclusions. Fermilab has received and further upgraded a commercial eddy current scanner previously used for the SNS project. The upgrading process included developing new filtering software. This scanner is now used daily to scan the niobium sheets for the Fermilab third harmonic and transverse deflecting cavities. This paper gives a status report on the scanning results obtained so far, including a discussion of the typology of signals being detected. We also report on the efforts to calibrate this scanner, a work conducted in collaboration with DESY.

  9. 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.

  10. Inexpensive Eddy-Current Standard

    NASA Technical Reports Server (NTRS)

    Berry, Robert F., Jr.

    1985-01-01

    Radial crack replicas serve as evaluation standards. Technique entails intimately joining two pieces of appropriate aluminum alloy stock and centering drilled hole through and along interface. Bore surface of hole presents two vertical stock interface lines 180 degrees apart. These lines serve as radial crack defect replicas during eddy-current technique setup and verification.

  11. electromagnetics, eddy current, computer codes

    Energy Science and Technology Software Center (ESTSC)

    2002-03-12

    TORO Version 4 is designed for finite element analysis of steady, transient and time-harmonic, multi-dimensional, quasi-static problems in electromagnetics. The code allows simulation of electrostatic fields, steady current flows, magnetostatics and eddy current problems in plane or axisymmetric, two-dimensional geometries. TORO is easily coupled to heat conduction and solid mechanics codes to allow multi-physics simulations to be performed.

  12. Remote field eddy current inspection

    SciTech Connect

    Atherton, D.L.

    1995-11-01

    The Remote Field Eddy Current (RFEC) technique uses an internal probe to inspect conducting tubes nondestructively. A coaxial solenoidal exciter, energized with low frequency AC, and detector coils near the inside of the pipe wall are separated by about two pipe diameters to obtain through wall transmission and equal sensitivity to defects on the outside or inside of the pipe wall. Calculation methods are outlined and the voltage plane polar plot signal representation for defect measurement is described. Slit defect interactions in ferromagnetic and non-ferromagnetic tubes are discussed. Defect-induced anomalous fields are interpreted in terms of anomalous source eddy current and missing magnetization defect models. The use of computer animations to represent the time variations of high resolution field measurements and calculations is described.

  13. 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.

  14. 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.

  15. Transient eddy current flow metering

    NASA Astrophysics Data System (ADS)

    Forbriger, J.; Stefani, F.

    2015-10-01

    Measuring local velocities or entire flow rates in liquid metals or semiconductor melts is a notorious problem in many industrial applications, including metal casting and silicon crystal growth. We present a new variant of an old technique which relies on the continuous tracking of a flow-advected transient eddy current that is induced by a pulsed external magnetic field. This calibration-free method is validated by applying it to the velocity of a spinning disk made of aluminum. First tests at a rig with a flow of liquid GaInSn are also presented.

  16. Modern ultrasonic flowmeters

    NASA Astrophysics Data System (ADS)

    Gurevich, V. M.; Truman, S. G.

    1986-01-01

    The current status of ultrasonic flowmeters were reviewed on the basis of materials published in the Soviet Union and elsewhere. The following advantages of ultrasonic flowmeters over earlier instruments are cited. A comparative analysis is made of the design methods employed in ultrasonic flowmeters. The evolution of ultrasonic flowmetering is traced from the first generation and trends in their development are analyzed.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Tracking Loop Current eddies with satellite altimetry

    NASA Astrophysics Data System (ADS)

    Leben, Robert R.; Born, George H.

    1993-11-01

    Geosat altimeter derived sea surface height (SSH) anomaly fields have been optimally interpolated onto a regular space time grid using both crossover data from the nonrepeating Geodetic Mission (Geosat-GM) and collinear data from the Exact Repeat Mission (Geosat-ERM). Over four years of data were collected from the combined missions, spanning the time period from April 1985 through August 1989, during which six major and at least two minor Loop Current eddies were directly observed. Eddy paths determined by automated tracking of the local maximum values in the SSH anomaly fields were compared with eddy centers estimated from drifting buoy trajectories, validating the data processing and tracking techniques. Accurate tracking of eddy centers allowed transits of 90°W to be used as a benchmark for determination of eddy shedding periods. For this data set the average period between major eddy transits was 9.8 months, with individual separation periods ranging from 6 to 14 months. The two minor eddies observed were associated with the deepest penetrations of the Loop Current into the gulf, and were nearly coincident with the shedding of the strongest major Loop Current eddies.

  2. 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.

  3. Improved Imaging With Laser-Induced Eddy Currents

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    System tests specimen of material nondestructively by laser-induced eddy-current imaging improved by changing method of processing of eddy-current signal. Changes in impedance of eddy-current coil measured in absolute instead of relative units.

  4. Eddy currents in a conducting sphere

    NASA Technical Reports Server (NTRS)

    Bergman, John; Hestenes, David

    1986-01-01

    This report analyzes the eddy current induced in a solid conducting sphere by a sinusoidal current in a circular loop. Analytical expressions for the eddy currents are derived as a power series in the vectorial displacement of the center of the sphere from the axis of the loop. These are used for first order calculations of the power dissipated in the sphere and the force and torque exerted on the sphere by the electromagnetic field of the loop.

  5. Thin film eddy current impulse deicer

    NASA Technical Reports Server (NTRS)

    Smith, Samuel O.; Zieve, Peter B.

    1990-01-01

    Two new styles of electrical impulse deicers has been developed and tested in NASA's Icing Research Tunnel. With the Eddy Current Repulsion Deicing Boot (EDB), a thin and flexible spiral coil is encapsulated between two thicknesses of elastomer. The coil, made by an industrial printed circuit board manufacturer, is bonded to the aluminum aircraft leading edge. A capacitor bank is discharged through the coil. Induced eddy currents repel the coil from the aluminum aircraft structure and shed accumulated ice. A second configuration, the Eddy Current Repulsion Deicing-Strip (EDS) uses an outer metal erosion strip fastened over the coil. Opposite flowing eddy currents repel the strip and create the impulse deicing force. The outer strip serves as a surface for the collection and shedding of ice and does not require any structural properties. The EDS is suitable for composite aircraft structures. Both systems successfully dispelled over 95 percent of the accumulated ice from airfoils over the range of the FAA icing envelope.

  6. 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.

  7. Eddy-current sensor measures bolt loading

    NASA Technical Reports Server (NTRS)

    Burr, M. E.

    1980-01-01

    Thin wire welded to bottom of hole down center of bolt permits measurement of tension in bolt. Bolt lengthens under strain, but wire is not loaded, so gap between wire and eddy-current gap transducer mounted on bolt head indicates bolt loading. Eddy-current transducer could measure gap within 0.05 mm. Method does not require separate "standard" for each bolt type, and is not sensitive to dirt or oil in bolt hole, unlike ultrasonic probes.

  8. 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.

  9. 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

  10. 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,…

  11. 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.

  12. Eddy current heating in magnetic refrigerators

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1990-01-01

    Eddy current heating can be a significant source of parasitic heating in low temperature magnetic refrigerators. To study this problem a technique to approximate the heating due to eddy currents has been developed. A formula is presented for estimating the heating within a variety of shapes commonly found in magnetic refrigerators. These shapes include circular, square, and rectangular rods; cylindrical and split cylindrical shells; wire loops; and 'coil foil. One set of components evaluated are different types of thermal radiation shields. This comparison shows that a simple split shield is almost as effective (only 23 percent more heating) as using a shield, with the same axial thermal conductivity, made of 'coil foil'.

  13. 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.

  14. Eddy current sensing of intermetallic composite consolidation

    NASA Technical Reports Server (NTRS)

    Dharmasena, Kumar P.; Wadley, Haydn N. G.

    1991-01-01

    A finite element method is used to explore the feasibility and optimization of a probe-type eddy current sensor for determining the thickness of plate specimens during a hot isostatic pressing cycle. The dependence of the sensor's impedance upon sample-sensor separation in the high frequency limit is calculated, and factors that maximize sensitivity to the final stages of densification are identified.

  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. Innovative Eddy Current Probe for Micro Defects

    NASA Astrophysics Data System (ADS)

    Santos, Telmo G.; Vilaça, Pedro; dos Santos, Jorge; Quintino, Luísa; Rosado, Luís

    2010-02-01

    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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Remote-field eddy current signal representation

    SciTech Connect

    Atherton, D.L.; Mackintosh, D.D.; Sullivan, S.P.; Dubois, J.M.S.; Schmidt, T.R. . Dept. of Physics.)

    1993-07-01

    While conventional reflected impedance eddy current testing (ET) techniques are limited by skin depth considerations to near surface defects, the RFEC (remote field eddy current) technique exploits skin effects. The RFEC method is a through-wall inspection technique. Only the field which has made a double transit of the pipe wall is detected. The skin depth equation can be used to predict the approximate effect of metal loss on the RFEC signal. Metal loss effectively reduces the shielding so that the attenuation and phase lag of the field is less. A method of analyzing RFEC defect signals is therefore to compare the signals with the phase and amplitude in uncorroded pipe. RFEC probes are used for inspecting ferromagnetic and nonferromagnetic tubulars for corrosion and, since eddy current detectors are generally well suited to crack detection, there is considerable interest in their potential to detect stress corrosion cracking in pipelines. Here the authors first of all summarize the impedance plane representation and scope monitor displays customarily used for conventional exploring coil ET probes in tubes. They then present the normalized voltage plane and monitor displays that are most appropriate for RFEC probes. They discuss the similarities and differences between the preferred monitor displays.

  3. The influence of eddy currents on magnetic actuator performance

    NASA Technical Reports Server (NTRS)

    Zmood, R. B.; Anand, D. K.; Kirk, J. A.

    1987-01-01

    The present investigation of the effects of eddy currents on EM actuators' transient performance notes that a transfer function representation encompassing a first-order model of the eddy current influence can be useful in control system analysis. The method can be extended to represent the higher-order effects of eddy currents for actuators that cannot be represented by semiinfinite planes.

  4. Eddy-Current Inspection Of Graphite-Fiber Composites

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    NASA technical memorandum describes initial research on, and proposed development of, automated system for nondestructive eddy-current inspection of parts made of graphite-fiber/epoxy-matrix composite materials. Sensors in system E-shaped or U-shaped eddy-current probes like those described in "Eddy-Current Probes For Inspecting Graphite-Fiber Composites" (MFS-26129).

  5. An expert system for analyzing eddy current measurements

    SciTech Connect

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

    1991-12-31

    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, an obviate operator uncertainty by analyzing the data in a uniform and consistent manner.

  6. Eddy-Current Monitoring Of Composite Layups

    NASA Technical Reports Server (NTRS)

    Fox, Robert L.; Buckley, John D.

    1993-01-01

    Eddy-current-probe apparatus used to determine predominant orientations of fibers in fiber/matrix composite materials. Apparatus nondestructive, noninvasive means for monitoring composite prepregs and layups during fabrication to ensure predictable and repeatable mechanical properties of finished composite panels. Consists essentially of electromagnet coil wrapped around horseshoe-shaped powdered-iron or ferrite ore. Optionally, capacitor included in series or parallel with coil to form resonant circuit. Impedance monitor excites radio-frequency current in coil and measures impedance of probe circuit. Affected by whatever material placed near ends of core, where material intercepts alternating magnetic field excited in core by current in coil.

  7. 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.

  8. 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.

  9. 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.

  10. Equilibrium Reconstructions and Eddy Currents in LTX

    NASA Astrophysics Data System (ADS)

    Schmitt, J. C.; Bialek, J.; Hansen, C. H.; Majeski, R.; Menard, J. E.

    2015-11-01

    The Lithium Tokamak eXperiment (LTX) is a spherical tokamak with a close-fitting low-recycling wall of lithium deposited on a stainless steel-lined copper shell. The combination of low resistivity of the copper shell, toroidal and poloidal breaks in the shell and transient coil and plasma currents results in long-lived non-axisymmetric eddy currents in the shell which produce a non-axisymmetric magnetic field. Magnetic sensors measure a ``local'' magnetic field in the toroidal break region that differs from the toroidally-averaged field. To use these signals as constraints in 2-D axisymmetric equilibrium reconstructions requires compensation of the 3-D components present in the signals. The work will will discuss the results of the 3-D modeling of the eddy currents and magnetic fields with the VALEN code, along with the progress made with equilibrium reconstructions with PSI-TRI and LRDfit. Work supported by US DOE contract DE-AC02-09CH11466.

  11. Two contra-rotating eddies of the Mozambique Ridge Current

    NASA Astrophysics Data System (ADS)

    Gründlingh, Marten L.

    1989-01-01

    The combined existence of a cyclonic and anticyclonic eddy pair on the Mozambique Ridge tends to confirm the hypothesis that they are created by a westward-flowing Mozambique Ridge Current. The eddies are mutually comparable in size but smaller than cyclonic eddies previously observed in the region.

  12. Tone Burst Eddy-Current Thermography (tbet)

    NASA Astrophysics Data System (ADS)

    Kumar, Ch. N. Kiran; Krishnamurthy, C. V.; Maxfield, Bruce W.; Balasubramaniam, Krishnan

    2008-02-01

    This paper reports on a Tone Burst Eddycurrent Thermography (TBET) technique that uses short-time bursts of eddy-currents induced in conducting media to generate local heating inside the material. The transient diffusion of the heat inside the material, induced by pulsed/short-time induction heating, is imaged by measuring the transient temperature profiles on the surface of the material. The presence and characteristics of the defects inside the materials changes the surface temperature transients and thus can be used for the nondestructive evaluation (NDE) of conducting materials. Axisymmetric numerical models of the conventional transient thermography technique are used to benchmark the TBET technique. From the temperature profile data, temperature contrast information is obtained for the different defect depths. Temperature contrast data obtained for TBET, in this process, was compared with that obtained from conventional transient thermography data. It was found that the frequency of the eddy-current and, consequently, the skin-depth of the induced field play an important role in the effective utilization of this technique. Simulation details and the experimental results are presented in the paper. Possible advantages of TBET over conventional flash thermography are also discussed and supported by experimental data.

  13. 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.

  14. 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.

  15. Finite element calculations for eddy current interactions with collinear slots

    SciTech Connect

    Atherton, D.L.; Czura, W. . Dept. of Physics)

    1994-01-01

    The results of finite element calculations detailing the interactions of eddy currents with fine collinear slots in nonferromagnetic and ferromagnetic conductors are presented. These are applicable to both remote field eddy current inspection tools and conventional reflected impedance eddy current probes. The calculations show that, while fine slots have little interaction with collinear induced currents in nonferromagnetic conductors, there are much larger effects in ferromagnetic conductors. This is due to magnetic field interactions. The term eddy current inspection' is therefore somewhat restrictive and the much broader term electromagnetic inspection' is proposed.

  16. Remote Field Eddy Current Transition Zone

    NASA Astrophysics Data System (ADS)

    Dubois, Joseph Maurice Stephane

    1992-01-01

    The Remote Field Eddy Current (RFEC) technique is a non-destructive inspection technique used for anomaly detection in tubulars. The RFEC technique uses exciter and detector coils, both located inside the pipe, to detect interior and exterior corrosion with approximately equal sensitivity. The presence of both direct and indirect electromagnetic coupling paths distinguishes the RFEC technique from conventional reflected impedance eddy current techniques. The RFEC pipe inspection technique normally operates with the detector coil in the remote field region at distances of two or more pipe diameters from the internal exciter coil. At this spacing, the direct coupled field, dominant near the exciter (less than 1 pipe ID), is strongly attenuated and is overshadowed by the indirect field generated by an indirect energy transmission path which diffuses outwardly at the exciter coil location and tends to be guided by the pipe wall. In the remote field region, the field energy is greater outside than inside the pipe and some of the energy diffuses back inside the pipe. In the intermediate region (from 1 to 2 pipe diameters), called the transition zone, direct and indirect fields interact. The transition zone interaction produces a resultant field which is very sensitive to variations in pipe properties or wall thickness. The effect is maximal at the point where the indirect and direct fields have equal magnitudes and opposite phases. Small variations in the indirect field at this crossover point produce large changes in the resultant field. Experimental examples of the resultant axial magnetic field are presented to demonstrate the transition zone characteristics. An improved understanding of the effects of localized inner and outer wall defects and of pipe wall thinning on the direct and indirect field components in the transition zone is needed to better exploit the RFEC technique. Operating the RFEC probe in the transition zone with carefully selected frequency and

  17. 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.

  18. Eddy Current Assessment of Engineered Components Containing Nanofibers

    NASA Astrophysics Data System (ADS)

    Ko, Ray T.; Hoppe, Wally; Pierce, Jenny

    2009-03-01

    The eddy current approach has been used to assess engineered components containing nanofibers. Five specimens with different programmed defects were fabricated. A 4-point collinear probe was used to verify the electrical resistivity of each specimen. The liftoff component of the eddy current signal was used to test two extreme cases with different nano contents. Additional eddy current measurements were also used in detecting a missing nano layer simulating a manufacturing process error. The results of this assessment suggest that eddy current liftoff measurement can be a useful tool in evaluating the electrical properties of materials containing nanofibers.

  19. 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).

  20. 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).

  1. 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.

  2. 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.

  3. Eddy current arrays for wheel inspection

    NASA Astrophysics Data System (ADS)

    Leclerc, Rémi

    2001-04-01

    Wheel inspections are routine and very time-consuming, especially for large aircraft wheels where a single-coil probe is moved manually taking precious long minutes. Eddy current arrays can decrease the inspection time by reducing to one the number of rotations needed to completely cover the wheel surface. Since the EC array probe fits the profile of the wheel, manipulation is easy and the lift-off is kept constant improving signal quality. C-scan displays assist the analysis and help locate the defect by dividing the inspected wheel surface into a small grid. Furthermore, the impedance plane and the strip chart, for all the channels used to build the C-scan, are accessible to provide better sizing accuracy of the defect.

  4. 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)

  5. 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.

  6. 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.

  7. 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.

  8. 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).

  9. 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.

  10. Advanced Eddy current NDE steam generator tubing.

    SciTech Connect

    Bakhtiari, S.

    1999-03-29

    As part of a multifaceted project on steam generator integrity funded by the U.S. Nuclear Regulatory Commission, Argonne National Laboratory is carrying out research on the reliability of nondestructive evaluation (NDE). A particular area of interest is the impact of advanced eddy current (EC) NDE technology. This paper presents an overview of work that supports this effort in the areas of numerical electromagnetic (EM) modeling, data analysis, signal processing, and visualization of EC inspection results. Finite-element modeling has been utilized to study conventional and emerging EC probe designs. This research is aimed at determining probe responses to flaw morphologies of current interest. Application of signal processing and automated data analysis algorithms has also been addressed. Efforts have focused on assessment of frequency and spatial domain filters and implementation of more effective data analysis and display methods. Data analysis studies have dealt with implementation of linear and nonlinear multivariate models to relate EC inspection parameters to steam generator tubing defect size and structural integrity. Various signal enhancement and visualization schemes are also being evaluated and will serve as integral parts of computer-aided data analysis algorithms. Results from this research will ultimately be substantiated through testing on laboratory-grown and in-service-degraded tubes.

  11. 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.

  12. Rare earth magnets resisting eddy currents

    SciTech Connect

    Pan, W.; Li, W.; Cui, L.Y.; Li, X.M.; Guo, Z.H.

    1999-09-01

    Magnets with high electrical resistance were prepared by electrically isolating Sm{sub 2}Co{sub 17} and Nd{sub 2}Fe{sub 14}B powder particles. It is done by a polymer mixture consisting of epoxy polyester-insulant (EPI), polyvinylbutyral (PVB), epoxy resin (ER) and silane coupling (SC). The properties of interest for anisotropic Sm{sub 2}Co{sub 17} and isotropic Nd{sub 2}Fe{sub 14}B magnets respectively are {rho} = 1 x 10{sup 5} {Omega} {minus}cm{sup 2}/m, Br = 6.8 kGs, {sub 1}H{sub c} = 10.0 kOe, (BH){sub max} = 9.2 MGOe in 5% EPI, 4%PVB, 2%ER, 1%SC and {rho} = 9.4 x 10{sup 4} {Omega} {minus}cm{sup 2}/m, Br = 4.5kG, {sub i}H{sub c} = 9.5 kOe, (BH){sub max} = 4.3 MGOe in 4%EPI, 3%PVB, 2% ER, 1%SC. The insulated magnets exhibit far better magnetic stability than those of sintered and bonded magnets after magnetizing in radio frequency. The insulated Sm{sub 2}Co{sub 17} magnet has the best performance in resisting eddy current. In 500 kHz frequency, 830 Oe magnetizing-field and in one minute, the irreversible loss of recoil remanence is 1.47% and 22.2% respectively for insulated Sm{sub 2}Co{sub 17} and Nd{sub 2}Fe{sub 14}B magnets.

  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 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.

  15. 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.

  16. 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.

  17. Eddy-Current Probes For Inspecting Graphite-Fiber Composites

    NASA Technical Reports Server (NTRS)

    Workman, Gary L.; Wang, Morgan

    1992-01-01

    Eddy-current probes with E-shaped and U-shaped magnetic cores developed to detect flaws in graphite-fiber/epoxy and other composites. Magnetic fields more concentrated, yielding better coupling with specimens.

  18. Remote field eddy current-crack and defect detection

    SciTech Connect

    Lord, W.

    1989-03-16

    No single nondestructive evaluation (NDE) technique is currently capable of detecting and characterizing all the defect types that can occur in gas pipeline. Conventional in-line inspection tools for example, have not shown significant sensitivity to intergranular stress corrosion cracking. For this reason considerable research and development work is still needed in order to provide the in-line inspection tools whose results are essential for structural integrity evaluations. The remote field eddy current method shows more promise than conventional eddy current methods, in gas pipeline inspection, due to the increased sensitivity to inner and outer pipe wall inhomogeneities. Even though the fundamental physical principles governing the conventional eddy current method and the remote field eddy current method is one and the same (that of electromagnetic induction), the differences in operating frequencies in the two methods result in field patterns that have different characteristic properties, such as extremely small skin depths associated with conventional eddy currents testing and the phenomena of potential valley'' and phase knot'' associated with remote field eddy current technique. 20 refs., 26 figs.

  19. Eddy current pulsed phase thermography and feature extraction

    NASA Astrophysics Data System (ADS)

    He, Yunze; Tian, GuiYun; Pan, Mengchun; Chen, Dixiang

    2013-08-01

    This letter proposed an eddy current pulsed phase thermography technique combing eddy current excitation, infrared imaging, and phase analysis. One steel sample is selected as the material under test to avoid the influence of skin depth, which provides subsurface defects with different depths. The experimental results show that this proposed method can eliminate non-uniform heating and improve defect detectability. Several features are extracted from differential phase spectra and the preliminary linear relationships are built to measure these subsurface defects' depth.

  20. Eddy-Current Measurement Of Turning Or Curvature

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J.

    1993-01-01

    Rotatable conductive plate covers sensing coil to varying degree. Curvature of pipe at remote or otherwise inaccessible location inside pipe measured using relatively simple angular-displacement eddy-current probe. Crawler and sensor assemblies move along inside of pipe on wheels. Conductive plate pivots to follow curvature of pipe, partly covering one of eddy-current coils to degree depending on local curvature on pipe.

  1. Handheld, giant magnetoresistive-sensor-based eddy current probes

    NASA Astrophysics Data System (ADS)

    Brady, S. K.; Palmer, D. D.

    2012-05-01

    The minimum crack length detectable with conventional eddy current probes increases dramatically as the thickness of metal through which the inspection is performed increases. The skin depth phenomenon is unavoidable, and demands low frequency inspection, hindering sensitivity. However, one time derivative introduced by Faraday's Law can be avoided by using giant magnetoresistive sensors to detect eddy currents instead of conventional coils, improving sensitivity. The theory will be explained, along with some probe designs and the observed benefits in sensitivity.

  2. Crack detection and recognition using an eddy current differential probe

    SciTech Connect

    Chady, T.; Enokizono, M. . Faculty of Engineering); Sikora . Dept. of Theoretical Electrotechnics)

    1999-05-01

    This paper proposes a new eddy current differential sensor and a system for multi-frequency testing of conducting plates. Precise crack imaging was achieved by the use of spectrograms obtained from an eddy-current probe multi-frequency response and application of a neural network. Results of experiments with test specimens made of SUS304 showing very good sensitivity and spatial resolution are presented. The possibility of detection of an opposite side 20% crack was also confirmed.

  3. Interannual forcing mechanisms of California Current transports II: Mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Davis, Andrew; Di Lorenzo, Emanuele

    2015-02-01

    Mesoscale eddies exert dominant control of cross-shelf exchanges, yet the forcing dynamics underlying their interannual and decadal variability remain uncertain. Using an ensemble of high-resolution ocean model hindcasts of the central and eastern North Pacific from 1950 to 2010 we diagnose the forcing mechanisms of low-frequency eddy variability in the California Current System (CCS). We quantify eddy activity by developing eddy counts based on closed contours of the Okubo-Weiss parameter and find that the spatial and temporal features of model-derived counts largely reproduce the short AVISO observational record. Comparison of model ensemble members allows us to separate the intrinsic and deterministic fractions of eddy variability in the northern CCS (34.5-50°N) and in the southern CCS (28.5-34.5°N). In the North, a large fraction of low-frequency eddy variability (30% anticyclones, 20% cyclones) is deterministic and shared with satellite observations. We develop a diagnostic model based on indices of the large-scale barotropic and baroclinic states of the CCS which recovers this deterministic variance. This model also strongly correlates with local atmospheric forcing. In contrast to the North, Southern CCS eddy counts exhibit very little deterministic variance, and eddy formation closely resembles a red-noise process. This new understanding of the external forcings of eddy variability allows us to better estimate how climate variability and change impact mesoscale transports in the California Current. The skill of our diagnostic model and its close association with local wind stress curl indicate that local atmospheric forcing is the dominant driver of eddy activity on interannual and decadal time scales north of pt. conception (~33°N).

  4. Multiple-element eddy current probes for enhanced inspection

    SciTech Connect

    Clark, W.G. Jr. )

    1993-07-01

    Eddy current inspection methods are widely used for the nondestructive evaluation (NDE) of tubular products. Specifically, the sensors and instrumentation are designed to detect and characterize changes in a material's electrical and magnetic properties produced by the presence of discontinuities. A recent major enhancement in eddy current inspection technology has been the development of computer interfacing for data collection, analysis, and display. This breakthrough has led to multiple-frequency testing, eddy current imaging, and automated data interpretation systems that significantly enhance both capabilities and reliability of the eddy current inspection. In addition to the clear advantages in data processing, computer interfacing also permits the design and creation of unique sensors that further enhance eddy current inspection capabilities. Perhaps the most promising area of computer interactive probe design is multiple element sensors. Westinghouse engineers and scientists have pioneered this area of probe development. This paper describes four unique probes that illustrate the advantages of computer interactive multiple element sensors for additional eddy current inspection options.

  5. 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.

  6. Eddy current detection of pitting corrosion around fastener holes

    NASA Astrophysics Data System (ADS)

    Heida, J. H.; Thart, W. G. J.

    1995-01-01

    An evaluation of the eddy current technique for the detection and depth assessment of corrosion around fastener holes in F-16 lower wing skins is described. The corrosion type in this structure is pitting corrosion at the countersink edge of the fastener holes. Due to a corrosion clean-up limit of only 1.5 - 2.5 percent, a maximum thickness reduction in the range of 0.08 - 0.32 mm is allowed (depending on local skin thickness). This specifies the needed sensitivity for in-service corrosion inspection. In the evaluation use was made of specimens cut out of the F-16 lower wing skin structure. In total twelve specimens were exposed to an accelerated corrosion test (EXCO-test). Eddy current inspection of the specimens with installed fasteners was performed with a standard eddy scope and four different eddy current probes. After the eddy current inspection cross-sections of the twelve-specimens were made to determine the extent of pitting corrosion at the countersink edges. After evaluation of the inspection results the following conclusions can be drawn: for in-service detection of countersink edge corrosion standard visual inspection is the preferred technique regarding the simplicity, sensitivity and reliability of inspection; and for the purpose of depth assessment the eddy current technique is capable of detecting countersink edge corrosion with a depth from about 0.1 mm. Due to the corrosion clean-up limit of only 1.5 - 2.5 percent (0.08 - 0.32 mm), however, the eddy current technique is considered not applicable for in-service depth assessment of countersink edge corrosion in F-16 lower wing skins.

  7. 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.

  8. High frequency eddy current device for near surface material characterizations

    NASA Astrophysics Data System (ADS)

    Hillmann, S.; Heuer, H.; Meyendorf, N.

    2009-03-01

    For near surface characterization a new high frequency eddy current device was been developed. By using a measurement frequency up to 100 MHz information of near surface areas can be acquired. Depending on the investigated material high resolution depth profiles can be derived. The obtained data with the new device were compared to those obtained with a high precision impedance analyser. It could be demonstrated that the new device measures the eddy current conductivity signal in the high frequencies much better than the impedance analyser. By sweeping the frequency from 100 kHz up to 100 MHz the technique delivers a depth profile of the electrical conductivity of the material. This kind of high frequency eddy current technique can be used for quality assurance, surface contamination control or near surface material characterization e.g. microstructure and cold work influences. It can be a powerful tool to obtain information for process control or a good / bad decision in mass production processes like for example rolling, coating, and surface treatments. The big advantage of the high frequency eddy current method is that it is fast und precise. This paper presents results with a new developed prototype Eddy-Current-Device for measurement frequencies up to 100 MHz which is first time suitable in rough industrial environment and makes expensive lab network analysers unnecessary for this kind of investigations.

  9. Comparative study of eddy current testing methods used in tube inspection

    NASA Astrophysics Data System (ADS)

    Si, Jiatun

    1998-03-01

    This paper presents a comparative analysis of three different eddy current testing methods for tube inspection: (1) conventional one side eddy current testing, (2) through- transmission eddy current testing, and (3) remote field eddy current testing. The author also studied the results from different arrangements of exciter coil and receiver coil of the eddy current testing method for tube inspection. The author concludes that the remote field eddy current testing is a through-transmission eddy current testing with exciter coil and receiver coil in the same side of a tube.

  10. 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

  11. Eddy current pulsed thermography for fatigue evaluation of gear

    NASA Astrophysics Data System (ADS)

    Tian, Gui Yun; Yin, Aijun; Gao, Bin; Zhang, Jishan; Shaw, Brian

    2014-02-01

    The pulsed eddy current (PEC) technique generates responses over a wide range of frequencies, containing more spectral coverage than traditional eddy current inspection. Eddy current pulsed thermography (ECPT), a newly developed non-destructive testing (NDT) technique, has advantages such as rapid inspection of a large area within a short time, high spatial resolution, high sensitivity and stand-off measurement distance. This paper investigates ECPT for the evaluation of gear fatigue tests. The paper proposes a statistical method based on single channel blind source separation to extract details of gear fatigue. The discussion of transient thermal distribution and patterns of fatigue contact surfaces as well as the non-contact surfaces have been reported. In addition, the measurement for gears with different cycles of fatigue tests by ECPTand the comparison results between ECPT with magnetic Barkhausen noise (MBN) have been evaluated. The comparison shows the competitive capability of ECPT in fatigue evaluation.

  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. PMID:22163754

  13. Eddy Current Testing for Detecting Small Defects in Thin Films

    SciTech Connect

    Obeid, Simon; Tranjan, Farid M.; Dogaru, Teodor

    2007-03-21

    Presented here is a technique of using Eddy Current based Giant Magneto-Resistance sensor (GMR) to detect surface and sub-layered minute defects in thin films. For surface crack detection, a measurement was performed on a copper metallization of 5-10 microns thick. It was done by scanning the GMR sensor on the surface of the wafer that had two scratches of 0.2 mm, and 2.5 mm in length respectively. In another experiment, metal coatings were deposited over the layers containing five defects with known lengths such that the defects were invisible from the surface. The limit of detection (resolution), in terms of defect size, of the GMR high-resolution Eddy Current probe was studied using this sample. Applications of Eddy Current testing include detecting defects in thin film metallic layers, and quality control of metallization layers on silicon wafers for integrated circuits manufacturing.

  14. Eddy current step heating thermography for quantitatively evaluation

    NASA Astrophysics Data System (ADS)

    He, Yunze; Pan, Mengchun; Chen, Dixiang; Tian, GuiYun; Zhang, Hong

    2013-11-01

    This Letter proposed eddy current step heating thermography (ECSHT) combing eddy current excitation with SHT. It has been verified through numerical and experimental studies that the temperature-time1/2 curve can be used to detect the subsurface defects. Separation time was defined and extracted from temperature responses as characteristic feature. Experiment studies with mild steel sample were conducted, and the experimental results showed that two features representing separation time can be used to measure the defect's depth based on their linear relationships.

  15. 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.

  16. Enhanced Eddy-Current Detection Of Weld Flaws

    NASA Technical Reports Server (NTRS)

    Van Wyk, Lisa M.; Willenberg, James D.

    1992-01-01

    Mixing of impedances measured at different frequencies reduces noise and helps reveal flaws. In new method, one excites eddy-current probe simultaneously at two different frequencies; usually, one of which integral multiple of other. Resistive and reactive components of impedance of eddy-current probe measured at two frequencies, mixed in computer, and displayed in real time on video terminal of computer. Mixing of measurements obtained at two different frequencies often "cleans up" displayed signal in situations in which band-pass filtering alone cannot: mixing removes most noise, and displayed signal resolves flaws well.

  17. Characterization of Magnetron Sputtered Coatings by Pulsed Eddy Current Techniques

    SciTech Connect

    Mulligan, Chris; Lee Changqing; Danon, Yaron

    2005-04-09

    A method that uses induced pulsed eddy currents for characterization of thick magnetron sputtered Nb coatings on steel is presented in this paper. The objectives of this work are to develop a system for rapid quantitative nondestructive inspection of coatings as well as to determine the correlation between coating properties, such as density and purity, and eddy current measured resistivity of coatings. A two-probe differential system having higher sensitivity and less noise than a one-probe system with 2-D scanning ability was developed.

  18. Low frequency eddy current benchmark study for model validation

    SciTech Connect

    Mooers, R. D.; Boehnlein, T. R.; Cherry, M. R.; Knopp, J. S.; Aldrin, J. C.; Sabbagh, H. A.

    2011-06-23

    This paper presents results of an eddy current model validation study. Precise measurements were made using an impedance analyzer to investigate changes in impedance due to Electrical Discharge Machining (EDM) notches in aluminum plates. Each plate contained one EDM notch at an angle of 0, 10, 20, or 30 degrees from the normal of the plate surface. Measurements were made with the eddy current probe both scanning parallel and perpendicular to the notch length. The experimental response from the vertical and oblique notches will be reported and compared to results from different numerical simulation codes.

  19. Eddy current NDE performance demonstrations using simulation tools

    SciTech Connect

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

    2013-01-25

    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{sub C}armel3D 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.

  20. Eddy-resolving simulation of lofting turbidity currents

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, S.; Lenk, E.; Meiburg, E. H.

    2012-12-01

    Turbidity currents originate due to horizontal pressure gradient created by differences in sediment concentration. Often turbidity currents propagate as a ground hugging underflow because its bulk density is higher than the density of the ambient fluid. If the density of the interstitial fluid in turbidity current is smaller than the density of the ambient fluid, then turbidity current can become positively buoyant after sufficient sand grains have settled. The current then lifts off from the bottom surface and travels as a surface gravity current over the heavier ambient fluid. These types of lofting currents, where the buoyancy reverses its direction, have been observed when sediment laden fresh water enters the sea or during volcanic eruption that creates a pyroclastic flow. We use a lock-exchange configuration with mono-disperse and bi-disperse grains to study the lofting characteristics of turbidity currents. Most of the Reynolds-stress carrying eddies are resolved in Large-eddy simulation (LES) and their predictions are more accurate than Reynolds-averaged models where none of the eddies are resolved. We use LES to study lofting turbidity currents at high Reynolds numbers that are comparable to laboratory and field scale flows. Dynamic Smagorinsky model is used to parameterize the sub-grid scale stresses that are not resolved by the grid. Results show that the deposit profiles has a sharp decay at the lift-off point unlike a ground hugging turbidity current whose deposit profile has a slow monotonic decay from the lock region.

  1. Apparatus For Eddy-Current Inspection Of Bolts

    NASA Technical Reports Server (NTRS)

    Amos, Jay M.

    1994-01-01

    Eddy-current apparatus for inspection of bolts, studs, and other threaded fasteners detects flaws in threads, shanks, and head fillets. With help of apparatus, technician quickly inspects fasteners of various dimensions. Accommodates fasteners with diameters from 0.190 in. to 1 in. and with lengths up to 5 in. Basic design modified to accommodate fasteners of other sizes.

  2. 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

  3. Eddy Current Rail Inspection Using AC Bridge Techniques.

    PubMed

    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

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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…

  9. Remote field eddy current detection of stress-corrosion cracks

    SciTech Connect

    Nestleroth, J.B.

    1990-02-01

    The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode that examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.

  10. 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.

  11. Application of torque margin ratios for Eddy Current Dampers

    NASA Astrophysics Data System (ADS)

    Starin, Scott; Rodriguez, Tony

    2003-09-01

    Eddy Current Dampers (ECDs) offer higher robustness, torque capacity and linearity than Fluid Dampers. One of the perceived disadvantages of ECDs when compared to Fluid Dampers is the magnitude of zero speed Coulomb torque. However, the magnitude of total Coulomb torque must be analyzed and considered when applying torque margin ratios, depending on the construction of the ECD and method of reaction torque generation.

  12. Technique for temperature compensation of eddy-current proximity probes

    NASA Technical Reports Server (NTRS)

    Masters, Robert M.

    1989-01-01

    Eddy-current proximity probes are used in turbomachinery evaluation testing and operation to measure distances, primarily vibration, deflection, or displacment of shafts, bearings and seals. Measurements of steady-state conditions made with standard eddy-current proximity probes are susceptible to error caused by temperature variations during normal operation of the component under investigation. Errors resulting from temperature effects for the specific probes used in this study were approximately 1.016 x 10 to the -3 mm/deg C over the temperature range of -252 to 100 C. This report examines temperature caused changes on the eddy-current proximity probe measurement system, establishes their origin, and discusses what may be done to minimize their effect on the output signal. In addition, recommendations are made for the installation and operation of the electronic components associated with an eddy-current proximity probe. Several techniques are described that provide active on-line error compensation for over 95 percent of the temperature effects.

  13. Eddy current array probe for corrosion mapping on ageing aircraft

    NASA Astrophysics Data System (ADS)

    Leclerc, Rémi; Samson, Rock

    2000-05-01

    The life of an airplane in the civil and military fleet is expanding by many years. The corrosion on aircraft is becoming a serious problem. The corrosion can also lead to the development of "multi-site damage" (MSD) and catastrophic failure. The need for a fast and reliable nondestructive technique for the detection of corrosion is a prime concern. A simple eddy current or ultrasonic probe can be very time consuming in the inspection because of the small area covered by the probe. The use of an eddy current array probe can cut the time use for an inspection or increase the surface scanned. Because it is an eddy current technology, the surface preparation is minimal compared to other techniques like ultrasound. It is also possible to detect defects beyond the first layer in a multiple layer panel. A flexible probe was employed to demonstrate the capacities of an eddy current array probe. This flexible probe can also match the profile of the structure to inspect limiting the lift-off. The C-scan technique is used in the display to see all the data on the same screen. The interpretation is also simplified.

  14. 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.

  15. 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.

  16. Aeroacoustic flowmeter

    NASA Technical Reports Server (NTRS)

    Shakkottai, Parthasarathy (Inventor); Kwack, Eug Y. (Inventor)

    1990-01-01

    The flowmeter is based on a measurement of phase difference between two points on the circumference of a pipe separated axially by an integral multiple of sound wavelength. Plane sound waves are generated aeroacoustically by a non-protruding ring cavity energized either directly by the flow or by a subsidiary flow of the same medium. The frequency of the aeroacoustic source varies with temperature and therefore the temperature can be obtained. In the case of steam flow, temperature can be measured independently and therefore from the measured frequency (or speed of sound), the quality of wet steam can be measured. The flowmeter is linear in velocity and no calibrations are required.

  17. 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.

  18. Eddy current mapping inside a plane conductor with flaws

    NASA Astrophysics Data System (ADS)

    Ribeiro, A. Lopes; Ramos, H. Geirinhas; Pasadas, D. J.; Rocha, T. J.

    2013-01-01

    When a constant field probe with sinusoidal excitation is used to detect flaws inside a conductor, the lines of current must be uniform in a limited area under the influence of the constant excitation field. The existence of flaws inside the metallic material forces the current to deviate from the uniform previous configuration. A magnetic field sensor may be used to measure one component of the magnetic field perturbation due to the eddy current anomalies. In this paper a giant magnetoresistor sensor is used to measure the magnetic field perturbation. The measured field is used to infer about the current perturbation, and a final current density map is obtained. The inversion algorithms are based on a deconvolution process with regularization. The kernel is precisely the field of a single eddy as detected by the magnetic sensor.

  19. Flowmeters and reciprocity

    NASA Astrophysics Data System (ADS)

    Hemp, J.

    1988-11-01

    A general method is given for developing the basic theory of any kind of 'interrogating field' flowmeter. These include electromagnetic flowmeters, transit-time ultrasonic flowmeters, and Coriolis mass flowmeters. The general expression for the weight vector for the Coriolis mass flowmeter is derived and calculated in one configuration.

  20. 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.

    2015-02-01

    Oceanic eddies occur in all world oceans, but are more energetic when associated to western boundary currents (WBC) systems. In these regions, eddies play an important role on mixing and energy exchange. Therefore, it is important to quantify and qualify eddies occurring within these systems. Previous studies performed eddy censuses in Southern Hemisphere WBC systems. However, important aspects of local eddy population are still unknown. Main questions to be answered relate to eddies' spatial distribution, propagation and lifetime within each system. Here, we use a global eddy dataset to qualify eddies based on their surface characteristics at the Agulhas Current (AC), the Brazil Current (BC) and the East Australian Current (EAC) Systems. We show that eddy propagation within each system is highly forced by the local mean flow and bathymetry. In the AC System, eddy polarity dictates its 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 anticyclonics reach the Great Australian Bight. Eddies in all systems and from both polarities presented a geographical segregation according to size. Large eddies occur along the Agulhas Retroflection, the Agulhas Return Current, the Brazil-Malvinas Confluence and the Coral Sea. Small eddies occur in the systems southernmost domains. Understanding eddies' propagation helps to establish monitoring programs, and to better understand how these features would affect local mixing.

  1. 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.

  2. 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.

  3. Modeling and strain gauging of eddy current repulsion deicing systems

    NASA Technical Reports Server (NTRS)

    Smith, Samuel O.

    1993-01-01

    Work described in this paper confirms and extends work done by Zumwalt, et al., on a variety of in-flight deicing systems that use eddy current repulsion for repelling ice. Two such systems are known as electro-impulse deicing (EIDI) and the eddy current repulsion deicing strip (EDS). Mathematical models for these systems are discussed for their capabilities and limitations. The author duplicates a particular model of the EDS. Theoretical voltage, current, and force results are compared directly to experimental results. Dynamic strain measurements results are presented for the EDS system. Dynamic strain measurements near EDS or EIDI coils are complicated by the high magnetic fields in the vicinity of the coils. High magnetic fields induce false voltage signals out of the gages.

  4. 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.

  5. 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.

  6. 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.

  7. Analytical Modeling for the Grating Eddy Current Displacement Sensors

    NASA Astrophysics Data System (ADS)

    Lv, Chunfeng; Tao, Wei; Lei, Huaming; Jiang, Yingying; Zhao, Hui

    2015-02-01

    As a new type of displacement sensor, grating eddy current displacement sensor (GECDS) combines traditional eddy current sensors and grating structure in one. The GECDS performs a wide range displacement measurement without precision reduction. This paper proposes an analytical modeling approach for the GECDS. The solution model is established in the Cartesian coordinate system, and the solving domain is limited to finite extents by using the truncated region eigenfunction expansion method. Based on the second order vector potential, expressions for the electromagnetic field as well as coil impedance related to the displacement can be expressed in closed-form. Theoretical results are then confirmed by experiments, which prove the suitability and effectiveness of the analytical modeling approach.

  8. 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).

  9. Remote field eddy current technique - Phantom exciter model calculations

    NASA Astrophysics Data System (ADS)

    Atherton, D. L.; Czura, W.

    1993-03-01

    High resolution results of finite element calculations for remote field eddy current 'phantom exciter' simulations of slit defect interactions using single through wall transit are presented. These show that fine circumferential slits cause almost no field perturbations in the case of nonferromagnetic tubes but big perturbations in ferromagnetic tubes where high magnetic H fields occur in the slits. Defect-induced magnetic field perturbations must therefore be considered in addition to eddy current perturbations when ferromagnetic materials are inspected, particularly in the case of fine slits orthogonal to the magnetic field direction. Additional details seen are the funnelling of energy into slits in ferromagnetic pipes and precursor disturbances of fields approaching defects. It is suggested that these are due to the reflection of the electromagnetic waves dictated by boundary conditions at the near-side defect boundary.

  10. Eddy-current crack detection at frequencies approaching electrical resonance

    NASA Astrophysics Data System (ADS)

    Hughes, Robert R.; Dixon, Steve

    2014-02-01

    The effect of operating an absolute eddy-current (EC) probe at frequencies around its electrical resonance was investigated. A defect signal enhancement phenomenon was observed and characterised. Experimental tests were performed on notch defects in typical aerospace superalloys. An absolute mode EC probe was operated by sweeping through a range of frequencies, in the MHz range, encompassing the electrical resonance of the system. Resonance decoupling above defects results in a signal-to-noise ratio (SNR) peak, within a band of frequencies approaching resonance, of up to 3.7 times that measured at 1MHz. This near electrical resonance signal enhancement (NERSE) phenomenon poses the possibility for a simple operational approach method for improving the sensitivity of conventional eddy-current testing.

  11. 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.

  12. Eddy-Current Detection of Weak Bolt Heads

    NASA Technical Reports Server (NTRS)

    Messina, C. P.

    1987-01-01

    Electronic test identifies flawed units passing hardness tests. Eddy-current test detects weakness in head-to-shank junctions of 1/4-28 cup-washer lock bolts. Developed for alloy A286 steel bolts in Space Shuttle main engine fuel turbo-pump. Test examines full volume of head, including head-to-shank transition and nondestructively screens out potentially defective units. Test adapts to any other alloys.

  13. 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.

  14. Eddy-Current Inspection of Narrow Metal Tubes

    NASA Technical Reports Server (NTRS)

    Ambrose, H. H.; Kleint, R. E.; Kirkham, K. E.

    1984-01-01

    Inspection technique for narrow-bore metal tubing involves use of small internal eddy-current probe. Probe consists of thin copper wire wrapped on bobbin. Probe small enough to pass through bends in tube being measured. Technique useful for strain measurements where operating conditions or inaccessibility prevent use of such conventional methods as X-ray diffraction, electrical-resistance measurements, strain gages, or holography.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Eddy current inspection of bonded composite crack repair

    NASA Astrophysics Data System (ADS)

    Smith, Thomas K., Jr.; Guijt, Cornelius; Fredell, Robert

    1996-11-01

    The aging of the US aircraft fleet poses serious economic and safety challenges. Fatigue cracks in the 7079-T6 aluminum fuselage skin of aging transports have presented zn opportunity to test a prototype repair. GLARE, a fiber metal laminate, has been applied to repair fuselage cracks in the fuselage skin of a US transport aircraft. This affordable prototype solution to extend the life of aging aircraft requires an inspection method to track crack growth and monitor the effectiveness of the patch on repaired fuselage skin. The fiber metal laminate patch is opaque and the fuselage skin at the damage location generally can only be accessed from the outside surface requiring the use of a non-destructive means to monitor crack length. Advances in eddy current inspection technology have provided a means to detect and track crack growth beneath patches on fuselage skins. This paper describes the development of low-frequency eddy current techniques to monitor cracks under bonded composite repair patches applied to stiffened fuselage structures. The development involved the use of a rugged portable eddy current inspection unit. The results show crack growth can be monitored to ensure the continued structural integrity of repaired flawed structures; however, the influence of substructure present a challenge to the inspector in detecting crack growth.

  1. 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,…

  2. Video flowmeter

    DOEpatents

    Lord, D.E.; Carter, G.W.; Petrini, R.R.

    1983-08-02

    A video flowmeter is described that is capable of specifying flow nature and pattern and, at the same time, the quantitative value of the rate of volumetric flow. An image of a determinable volumetric region within a fluid containing entrained particles is formed and positioned by a rod optic lens assembly on the raster area of a low-light level television camera. The particles are illuminated by light transmitted through a bundle of glass fibers surrounding the rod optic lens assembly. Only particle images having speeds on the raster area below the raster line scanning speed may be used to form a video picture which is displayed on a video screen. The flowmeter is calibrated so that the locus of positions of origin of the video picture gives a determination of the volumetric flow rate of the fluid. 4 figs.

  3. Video flowmeter

    DOEpatents

    Lord, D.E.; Carter, G.W.; Petrini, R.R.

    1981-06-10

    A video flowmeter is described that is capable of specifying flow nature and pattern and, at the same time, the quantitative value of the rate of volumetric flow. An image of a determinable volumetric region within a fluid containing entrained particles is formed and positioned by a rod optic lens assembly on the raster area of a low-light level television camera. The particles are illuminated by light transmitted through a bundle of glass fibers surrounding the rod optic lens assembly. Only particle images having speeds on the raster area below the raster line scanning speed may be used to form a video picture which is displayed on a video screen. The flowmeter is calibrated so that the locus of positions of origin of the video picture gives a determination of the volumetric flow rate of the fluid.

  4. Video flowmeter

    DOEpatents

    Lord, David E.; Carter, Gary W.; Petrini, Richard R.

    1983-01-01

    A video flowmeter is described that is capable of specifying flow nature and pattern and, at the same time, the quantitative value of the rate of volumetric flow. An image of a determinable volumetric region within a fluid (10) containing entrained particles (12) is formed and positioned by a rod optic lens assembly (31) on the raster area of a low-light level television camera (20). The particles (12) are illuminated by light transmitted through a bundle of glass fibers (32) surrounding the rod optic lens assembly (31). Only particle images having speeds on the raster area below the raster line scanning speed may be used to form a video picture which is displayed on a video screen (40). The flowmeter is calibrated so that the locus of positions of origin of the video picture gives a determination of the volumetric flow rate of the fluid (10).

  5. Determination of linear defect depths from eddy currents disturbances

    NASA Astrophysics Data System (ADS)

    Ramos, Helena Geirinhas; Rocha, Tiago; Pasadas, Dário; Ribeiro, Artur Lopes

    2014-02-01

    One of the still open problems in the inspection research concerns the determination of the maximum depth to which a surface defect goes. Eddy current testing being one of the most sensitive well established inspection methods, able to detect and characterize different type of defects in conductive materials, is an adequate technique to solve this problem. This paper reports a study concerning the disturbances in the magnetic field and in the lines of current due to a machined linear defect having different depths in order to extract relevant information that allows the determination of the defect characteristics. The image of the eddy currents (EC) is paramount to understand the physical phenomena involved. The EC images for this study are generated using a commercial finite element model (FLUX). The excitation used produces a uniform magnetic field on the plate under test in the absence of defects and the disturbances due to the defects are compared with those obtained from experimental measurements. In order to increase the limited penetration depth of the method giant magnetoresistors (GMR) are used to lower the working frequency. The geometry of the excitation planar coil produces a uniform magnetic field on an area of around the GMR sensor, inducing a uniform eddy current distribution on the plate. In the presence of defects in the material surface, the lines of currents inside the material are deviated from their uniform direction and the magnetic field produced by these currents is sensed by the GMR sensor. Besides the theoretical study of the electromagnetic system, the paper describes the experiments that have been carried out to support the theory and conclusions are drawn for cracks having different depths.

  6. Micromagnetic modeling with eddy current and current-induced spin torque effect

    NASA Astrophysics Data System (ADS)

    Wadhwa, P.; Jalil, M. B. A.; Tan, S. G.

    2005-12-01

    We present a micromagnetic model which incorporates eddy current and spin transfer torque effects due to the passage of a spin-polarized current in the current-perpendicular-to-plane (CPP) geometry. Eddy current effects are modeled by solving Faraday's and Poisson's equations self-consistently with the Landau-Lifshitz-Gilbert (LLG) equation, whereas spin transfer torque is modeled by including the Slonczewski spin torque term in the LLG equation. We consider a 50 nm cubic Co element, which forms the free layer of a pseudo-spin-valve structure. With a typical damping parameter of α =0.5, the eddy currents act to accelerate the magnetic reversal process. The spin torque effect can also assist the reversal process but at high current densities exceeding Jext=108A/cm2 onwards. At these current densities, spin transfer torque also causes a substantial reduction in the coercivity.

  7. Eddy current calculations using half-space Green's functions

    NASA Astrophysics Data System (ADS)

    Bowler, J. R.

    1987-02-01

    A simple scalar representation is used to describe the electromagnetic field in the quasi-static limit for an arbitrary time-harmonic source current above an imperfectly conducting half-space. Solutions are given in terms of half-space scalar and dyadic Green's functions. The general results are then used to derive analytical expressions for the fields arising from circular filaments and extended sources whose axes of symmetry are parallel to the surface of the conductor. These tangent coil solutions have applications in the theory of inductive sensors, particularly for eddy current nondestructive testing.

  8. 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.

  9. 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.

  10. 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. PMID:21106418

  11. Characterization of small cracks in eddy current testing

    NASA Astrophysics Data System (ADS)

    Le Bihan, Y.; Pávó, J.; Marchand, C.

    2008-08-01

    A study on the characterization of small cracks by using eddy current testing (ECT) signal is presented. The significant parameters of the ECT data are selected using principal component analysis according to two approaches. The ECT signal inversion is then achieved using a parametric model trained with synthetic data obtained with a fast numerical simulation tool. The characterization procedure is then tested using experimental data. Results show that information can be obtained concerning the area of the cracks. This article has been submitted as part of “IET Colloquium on Reliability in Electromagnetic Systems”, 24 and 25 May 2007, Paris

  12. 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.

  13. 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.

  14. 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.

  15. Solving time-dependent two-dimensional eddy current problems

    NASA Technical Reports Server (NTRS)

    Lee, Min Eig; Hariharan, S. I.; Ida, Nathan

    1990-01-01

    Transient eddy current calculations are presented for an EM wave-scattering and field-penetrating case in which a two-dimensional transverse magnetic field is incident on a good (i.e., not perfect) and infinitely long conductor. The problem thus posed is of initial boundary-value interface type, where the boundary of the conductor constitutes the interface. A potential function is used for time-domain modeling of the situation, and finite difference-time domain techniques are used to march the potential function explicitly in time. Attention is given to the case of LF radiation conditions.

  16. 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.

  17. 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.

  18. 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.

  19. 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%.

  20. Note: Eddy current displacement sensors independent of target conductivity

    NASA Astrophysics Data System (ADS)

    Wang, Hongbo; Li, Wei; Feng, Zhihua

    2015-01-01

    Eddy current sensors (ECSs) are widely used for non-contact displacement measurement. In this note, the quantitative error of an ECS caused by target conductivity was analyzed using a complex image method. The response curves (L-x) of the ECS with different targets were similar and could be overlapped by shifting the curves on x direction with √2δ/2. Both finite element analysis and experiments match well with the theoretical analysis, which indicates that the measured error of high precision ECSs caused by target conductivity can be completely eliminated, and the ECSs can measure different materials precisely without calibration.

  1. Solving time-dependent two-dimensional eddy current problems

    NASA Technical Reports Server (NTRS)

    Lee, Min Eig; Hariharan, S. I.; Ida, Nathan

    1988-01-01

    Results of transient eddy current calculations are reported. For simplicity, a two-dimensional transverse magnetic field which is incident on an infinitely long conductor is considered. The conductor is assumed to be a good but not perfect conductor. The resulting problem is an interface initial boundary value problem with the boundary of the conductor being the interface. A finite difference method is used to march the solution explicitly in time. The method is shown. Treatment of appropriate radiation conditions is given special consideration. Results are validated with approximate analytic solutions. Two stringent test cases of high and low frequency incident waves are considered to validate the results.

  2. Numerical results for the WFNDEC 2012 eddy current benchmark problem

    NASA Astrophysics Data System (ADS)

    Theodoulidis, T. P.; Martinos, J.; Poulakis, N.

    2013-01-01

    We present numerical results for the World Federation of NDE Centers (WFNDEC) 2012 eddy current benchmark problem obtained with a commercial FEM package (Comsol Multiphysics). The measurements of the benchmark problem consist of coil impedance values acquired when an inspection probe coil is moved inside an Inconel tube along an axial through-wall notch. The simulation runs smoothly with minimal user interference (default settings used for mesh and solver) and agreement between numerical and experimental results is excellent for all five inspection frequencies. Comments are made for the pros and cons of FEM and also some good practice rules are presented when using such numerical tools.

  3. Pulsed Eddy Current Probe Design Based on Transient Circuit Analysis

    NASA Astrophysics Data System (ADS)

    Cadeau, Trevor J.; Krause, Thomas W.

    2009-03-01

    Probe design parameters affecting depth of penetration of pulsed eddy currents in multi-layer aluminum 2024-T3 were examined. Several probe designs were evaluated for their ability to detect a discontinuity at the bottom of a stack of aluminum plates. The reflection type probes, consisting of pick-up coil and encircling drive coil, were characterized based on their transient response to a square pulse excitation. Probes with longer fundamental time constants, equivalent to a lower driving frequency, generated greater depth of penetration. However, additional factors such as inductive and resistive load, and excessive coil heating were also factors that limited signal-to-noise response with increasing layer thickness.

  4. 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.

  5. 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.

  6. Analysis techniques for eddy current imaging of carbon fiber materials

    NASA Astrophysics Data System (ADS)

    Schulze, Martin H.; Meyendorf, Norbert; Heuer, Henning

    2010-04-01

    Carbon fiber materials become more and more important for many applications. Unlike metal the technological parameters and certified quality control mechanisms for Raw Carbon Fiber Materials (RCF) have not yet been developed. There is no efficient and reliable testing system for in-line inspections and consecutive manual inspections of RCF and post laminated Carbon Fiber Reinforced Plastics (CFRP). Based upon the multi-frequency Eddy Current system developed at Fraunhofer IZFP, structural and hidden defects such as missing carbon fiber bundles, lanes, suspensions, fringes, missing sewing threads and angle errors can be detected. Using an optimized sensor array and intelligent image pre-processing algorithms, the complex impedance signal can be allocated to different carbon fiber layers. This technique enables the detection of defects in depths of up to 5 layers, including the option of free scale measuring resolution and testing frequency. Appropriate parameter lists for optimal error classifications are available. The dimensions of the smallest detectable flaws are in the range of a few millimeters. Algorithms and basic Eddy Current C-Scan processing techniques for carbon fiber material testing are described in this paper.

  7. 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.

  8. 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.

  9. Eddy-current steam generator data analysis performance. Final report

    SciTech Connect

    Harris, D.H.

    1993-06-01

    This study assessed the accuracy of eddy current, bobbin coil data analysis of steam generator tubes conducted under the structure of the PWR Steam Generator Examination Guidelines, Individual and team performance measures were obtained from independent analyses of data from 1619 locations in a sample of 199 steam generator tubes. The 92 reportable indications contained in the tube sample, including 64 repairable indications, were attributable to: wear at anti-vibration bars, intergranular attack/stress-corrosion cracking (IGA/SCC) within tube sheet crevice regions, primary-water stress-corrosion cracking (PWSCC) at tube roll transitions, or thinning at cold-leg tube supports. Analyses were conducted by 20 analysts, four each from five vendors of eddy current steam generator examination services. In accordance with the guidelines, site orientation was provided with plant-specific guidelines; preanalysis practice was completed on plant-specific data; analysts were qualified by performance testing; and independent primary-secondary analyses were conducted with resolution of discrepancies (team analyses). Measures of analysis performance included percentages of indications correctly reported, percentages of false reports, and relative operating characteristic (ROC) curves. ROC curves presented comprehensive pictures of analysis accuracy generalizable beyond the specific conditions of this study. They also provided single-value measures of analysis accuracy. Conclusions and recommendations were provided relative to analysis accuracy, effect of primary-secondary analyses, analyses of tube sheet crevice regions, establishment of reporting criteria, improvement of examination guidelines, and needed research.

  10. 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).

  11. Eddy current techniques for super duplex stainless steel characterization

    NASA Astrophysics Data System (ADS)

    Camerini, C.; Sacramento, R.; Areiza, M. C.; Rocha, A.; Santos, R.; Rebello, J. M.; Pereira, G.

    2015-08-01

    Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content.

  12. Modeling of eddy current NDE probe for steam generator tubes.

    SciTech Connect

    Chang, F. C.; Bakhtiari, S.; Kupperman, D.

    2003-01-29

    Calculations were performed with a three-dimensional (3-D) finite-element model to describe the response of an eddy current (EC) probe to defects in steam generator (SG) tubing of a nuclear reactor. Such calculations could be very helpful in understanding and interpreting the EC probe response to complex tube/defect geometries associated with longitudinal inner/outer notches, roll transitions, sludge, and through-wall holes in SG tubes. The governing field equations are derived in terms of coupled magnetic vector and electric scalar potentials in the conducting media and total or reduced scalar potentials in the non-conducting regions. To assess the validity of the model, we compared the signal responses for two numerical approaches, stored-energy-and-power-loss approach and magnetic-flux approach for various tube/defect geometries. Simulation results are also presented on the tube/defect geometries for the pancake coil response and the transmitter/receiver (T/R) probe response. The results indicate that the eddy-current NDE modeling is capable of predicting EC probe response to flaws in steam generator tubes.

  13. 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.

  14. Inverse Problem in Nondestructive Testing Using Arrayed Eddy Current Sensors

    PubMed Central

    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. PMID:22163680

  15. 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. PMID:22163680

  16. 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.

  17. 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.

  18. 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.

  19. Electrical Circuit Model of an Eddy Current System for Computing Multiple Parameters

    NASA Astrophysics Data System (ADS)

    Siddoju, A.; Sathish, S.; Ko, R.; Blodgett, M.

    2006-03-01

    An electrical circuit based model for eddy current system has been developed using commercial electrical engineering software. The model allows incorporation of individual characteristics of the signal generator, the cable, the eddy current sensor and the sample under test. Computational results of the characteristics of the system, obtained by sweeping the frequency, under normal and varying test conditions are presented. The sensitivity of the eddy current system response due to changes in different parameters during test conditions is discussed.

  20. 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.

  1. 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.

  2. 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.

  3. Eddy current characterization of magnetic treatment of nickel 200

    NASA Technical Reports Server (NTRS)

    Chern, E. J.

    1993-01-01

    Eddy current methods have been applied to characterize the effect of magnetic treatments on component service-life extension. Coil impedance measurements were acquired and analyzed 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 electromagnetic properties of nickel 200 that then 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.

  4. Eddy current jet engine disk-crack monitor

    NASA Technical Reports Server (NTRS)

    Barranger, J. P.

    1984-01-01

    A disk-crack monitor is described that is suitable for use on the ground or in flight. The system consists of an engine-mounted eddy current sensor, a series capacitance in each leg of the sensor circuit, and a capacitance-conductance bridge followed by an oscilloscope capable of advanced signal processing. It was applied to the detection of service-induced cracks in the first-stage turbine wheel of a helicopter engine. A 3.5 mm long radial fatigue crack plus smaller cracks, all located in the blade root region of the wheel, were detected during engine test stand operation at ground idle speed and temperature. The calculation of the value of series capacitance is also presented.

  5. 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.

  6. 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.

  7. Eddy current inspection of weld defects in tubing

    NASA Astrophysics Data System (ADS)

    Katragadda, G.; Lord, W.

    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.

  8. 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.

  9. Method and apparatus for deflection measurements using eddy current effects

    NASA Technical Reports Server (NTRS)

    Chern, Engmin J. (Inventor)

    1993-01-01

    A method and apparatus for inserting and moving a sensing assembly with a mechanical positioning assembly to a desired remote location of a surface of a specimen under test and measuring angle and/or deflection by sensing the change in the impedance of at least one sensor coil located in a base plate which has a rotatable conductive plate pivotally mounted thereon so as to uncover the sensor coil(s) whose impedance changes as a function of deflection away from the center line of the base plate in response to the movement of the rotator plate when contacting the surface of the specimen under test is presented. The apparatus includes the combination of a system controller, a sensing assembly, an eddy current impedance measuring apparatus, and a mechanical positioning assembly driven by the impedance measuring apparatus to position the sensing assembly at a desired location of the specimen.

  10. Groove dimensioning using remote field eddy current inspection

    NASA Astrophysics Data System (ADS)

    Davoust, M.-E.; Fleury, G.

    2000-09-01

    The remote field eddy current technique is used for dimensioning the grooves that may occur in the ferromagnetic pipes. We propose a method to estimate the depth and the length of corrosion grooves from measurement of a pick-up coil signal phase at different positions close to the defect. Groove dimensioning requires the knowledge of the physical relation between measurements and defect dimensions; therefore finite-element calculations are performed to design parametric algebraic functions for modeling the physical phenomena. Different models are possible; the choice of this algebraic function is discussed from identification criteria. By means of new measurement formalism and two previously defined measurement relations, estimates of groove sizes may be given. In the first approach, algebraic function parameters and groove dimensions are linked through a polynomial function; this approach is proved to be better than a second one which tries to take advantage of more physical considerations.

  11. 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.

  12. Support of gas flowmeter upgrade

    NASA Technical Reports Server (NTRS)

    Waugaman, Dennis

    1996-01-01

    A project history review, literature review, and vendor search were conducted to identify a flowmeter that would improve the accuracy of gaseous flow measurements in the White Sands Test Facility (WSTF) Calibration Laboratory and the Hydrogen High Flow Facility. Both facilities currently use sonic flow nozzles to measure flowrates. The flow nozzle pressure drops combined with corresponding pressure and temperature measurements have been estimated to produce uncertainties in flowrate measurements of 2 to 5 percent. This study investigated the state of flowmeter technology to make recommendations that would reduce those uncertainties. Most flowmeters measure velocity and volume, therefore mass flow measurement must be calculated based on additional pressures and temperature measurement which contribute to the error. The two exceptions are thermal dispersion meters and Coriolis mass flowmeters. The thermal dispersion meters are accurate to 1 to 5 percent. The Coriolis meters are significantly more accurate, at least for liquids. For gases, there is evidence they may be accurate to within 0.5 percent or better of the flowrate, but there may be limitations due to inappropriate velocity, pressure, Mach number and vibration disturbances. In this report, a comparison of flowmeters is presented. Candidate Coriolis meters and a methodology to qualify the meter with tests both at WSTF and Southwest Research Institute are recommended and outlined.

  13. 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.

  14. 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

  15. 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

  16. Eddy current in a rotating cylinder in a static field by a stochastic method

    NASA Astrophysics Data System (ADS)

    Lévêque, J.; Lubin, T.; Mezani, S.; Rezzoug, A.

    2012-02-01

    This paper deals with the calculation of eddy current in a copper cylinder. This cylinder rotates in an applied static magnetic field. The electromagnetic problem is solved in two-dimension by considering transient motion. Two methods for eddy current computation are compared: stochastic method and classical finite element method. The main goal of this paper is to compare these methods.

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

    PubMed

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

    2016-01-01

    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

  18. 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.

  19. 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.

  20. Large-eddy simulation of density currents on inclined beds

    NASA Astrophysics Data System (ADS)

    Chawdhary, Saurabh; Khosronejad, Ali; Christodoulou, George; Sotiropoulos, Fotis

    2013-11-01

    Density currents are stratified flow in presence of density differential and gravity field. We carry out Large-Eddy Simulation (LES) to simulate the flow of a density current formed over sloped bed due to an incoming jet of heavy density salty water for two different cases of bed slope: (a) 5 degrees and (b) 15 degrees. The Reynolds and Richardson numbers based on inlet height and inlet velocity were (a) 1100 and 0.471, and (b) 2000 and 0.0355, respectively. The Schmidt number is set equal to 620, which corresponds to the value for salt-water. The computed results are compared with laboratory experiments in terms of overall shape of the heavy-density plume and its spreading rate and are shown to be in reasonable agreement. The instantaneous LES flow fields are further analyzed to gain novel insights into the rich dynamics of coherent vortical structures in the flow. The half-width of the plume is plotted as a function of downstream length and found to exhibit three different regions on a log scale, in agreement with previous experimental findings. We acknowledge computational support from the Minnesota Supercomputing Institute.

  1. Three dimensional boundary element solutions for eddy current nondestructive evaluation

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Song, Jiming; Nakagawa, Norio

    2014-02-01

    The boundary integral equations (BIE) method is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations. It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, and fracture mechanics. The eddy current problem is formulated by the BIE and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The three dimensional arbitrarily shaped objects are described by a number of triangular patches. The Stratton-Chu formulation is specialized for the conductive medium. The equivalent electric and magnetic surface currents are expanded in terms of Rao-Wilton-Glisson (RWG) vector basis function while the normal component of magnetic field is expanded in terms of the pulse basis function. Also, a low frequency approximation is applied in the external medium. Additionally, we introduce Auld's impedance formulas to calculate impedance variation. There are very good agreements between numerical results and those from theory and/or experiments for a finite cross-section above a wedge.

  2. 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

  3. 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. __________________________________________________

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    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 (˜350 μm) and larger (˜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.

  6. An analytical model of eddy current ferrite-core probes

    NASA Astrophysics Data System (ADS)

    Lu, Y.; Bowler, J. R.

    2012-05-01

    An analytical model of an axisymmetric eddy current probe with a cylindrical ferrite core above a layered conductive half-space is developed. Initially we consider the magnetic vector potential of a circular filament coaxial with a ferrite core over a layered conducting half-space. The principle of superposition is then used to derive close-form expressions for both the electromagnetic field and the impedance of a coil from the filament field. Rather than locating the probe in infinite space, it is confined coaxially within a circularly cylindrical boundary on which the vector potential field is zero. The radius of this artificial boundary is large in order to ensure that does not interfere substantially with the field near the probe. By using a truncated region in this way, the vector potential in the probe region can be expanded as a series rather than an integral form. Thus the solution of the problem amounts to finding the expansion coeefficients in the series. The numerical predictions of probe impedance have been compared with experimental data showing good agreement.

  7. Transient Eddy Current Response Due to a Conductive Cylindrical Rod

    NASA Astrophysics Data System (ADS)

    Fu, Fangwei; Bowler, J. R.

    2007-03-01

    Transient eddy current test systems have been developed for the inspection of aircraft structures and for oil and gas pipelines. This work is supported by theoretical developments in which transient fields and time domain signals are determined for the geometry of interest. However most of the models to date have been aimed at structures that are planar, relatively little attention being paid to the corresponding problems in cylindrical geometries. In order to rectify this deficiency, we have examined theoretically the transient probe signal response due to a cylindrical conductive rod excited by an encircling coil. The transient fields can be calculated from a Fourier transform of the frequency domain solutions for infinite rods or tubes but, as with planar structures, we have found that it is better to use series solutions in the time domain since these provide more accurate and flexible representations of transient fields. Two types of series are used; one which converges faster at short times and one which converges faster at longer times. Calculations using these series show that they are in mutual agreement and agree with results computed using the fast Fourier transform.

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

    PubMed

    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

  9. 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.

  10. Eddy current nondestructive material evaluation based on HTS SQUIDs

    NASA Astrophysics Data System (ADS)

    Mück, M.; Kreutzbruck, M. v.; Baby, U.; Tröll, J.; Heiden, C.

    1997-08-01

    High Temperature Superconductor (HTS) Superconducting Quantum Interference Devices (SQUIDs) are promising sensors for applications in eddy current nondestructive evaluation (NDE). Due to their high field sensitivity at low frequencies, they are especially suitable for applications, where a large penetration depth is required. We have investigated two different SQUID-based NDE systems, one of which is optimised for testing felloes of aircraft wheels. The second system allows for testing planar structures using a motorised x-y-stage, which moves the cryostat above the planar samples. As sensors 3 GHz rf SQUIDs made from YBCO were used, having a field noise of about 1 pT/√Hz. This results in a dynamic range of our SQUID system of about 155 dB/√Hz. In most cases, the SQUIDs have been cooled by immersing them in liquid nitrogen. We have however also developed a cryosystem, which allows for cooling the sensors by a Ne-gas flow. In planar test structures we could detect flaws with lengths of 10 mm, having a height of 0.6 mm in a depth of 13 mm. In aircraft felloes, flaws located at the inner surface of the felloe (thickness 8 mm) were easily detectable despite a high static background field of up to 0.5 G caused by ferromagnetic structures inside the felloe. For flaws in a depth of 5 mm, the spatial resolution of both systems was about 8 mm without applying image postprocessing.

  11. 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

  12. Cleavage of a Gulf of Mexico Loop Current eddy by a deep water cyclone

    NASA Astrophysics Data System (ADS)

    Biggs, D. C.; Fargion, G. S.; Hamilton, P.; Leben, R. R.

    1996-09-01

    Eddy Triton, an anticyclonic eddy shed by the Loop Current in late June 1991, drifted SW across the central Gulf of Mexico in the first 6 months of 1992, along the ``southern'' of the three characteristic drift paths described by Vukovich and Crissman [1986] from their analyses of 13 years of advanced very high resolution radiometer sea surface temperature data. An expendable bathythermograph (XBT) and conductivity-temperature-depth (CTD) transect of opportunity through Triton at eddy age 7 months in January 1992 found that eddy interior stood 23 dyn. cm higher than periphery; this gradient drove an anticyclonic swirl transport of 9-10 Sv relative to 800 dbar. At eddy age 9-10 months and while this eddy was in deep water near 94°W, it interacted with a mesoscale cyclonic circulation and was cleaved into two parts. The major (greater dynamic centimeters) piece drifted NW to end up in the ``eddy graveyard'' in the NW corner of the gulf, while the minor piece drifted SW and reached the continental margin of the western gulf off Tuxpan. This southern piece of Eddy Triton then turned north to follow the 2000-m isobath to about 24°N and later coalesced with what remained of the major fragment. Because Eddy Triton's cleavage took place just before the start of marine mammals (GulfCet) and Louisiana-Texas physical oceanography (LATEX) field programs, the closely spaced CTD, XBT, and air dropped XBT (AXBT) data that were gathered on the continental margin north of 26°N in support of these programs allow a detailed look at the northern margin of the larger fragment of this eddy. Supporting data from the space-borne altimeters on ERS 1 and TOPEX/POSEIDON allow us to track both pieces of Eddy Triton in the western Gulf and follow their spin down in dynamic height, coalescence, and ultimate entrainment in January 1993 into another anticyclonic eddy (Eddy U).

  13. Analysis of eddy current losses during discharging period in a 600 kJ SMES

    NASA Astrophysics Data System (ADS)

    Park, M. J.; Kwak, S. Y.; Lee, S. Y.; Kim, W. S.; Lee, J. K.; Park, C.; Choi, K.; Bae, J. H.; Kim, S. H.; Sim, K. D.; Seong, K. C.; Jung, H. K.; Hahn, S.

    2008-09-01

    The operation of the SMES system can be divided into three modes such as charging, operating and discharging. During the charging and the discharging modes, a magnetic field variation due to the current increase and decrease generate eddy current losses in the SMES system. The eddy current loss in discharging mode is the major factor to be considered because the operating time in the mode is fixed, whereas the charging mode has the arbitrary operating time which is not fixed. In this paper, we present the analysis results of the eddy current losses which are generated in the 600 kJ class HTS SMES system during the discharging mode.

  14. Analytical model for estimation of eddy current and power loss in conducting plate and its application

    NASA Astrophysics Data System (ADS)

    Sinha, Gautam; Prabhu, S. S.

    2011-06-01

    A model is developed to study the eddy current induced in a thin conducting but nonmagnetic plate of finite size when exposed to a time varying magnetic field. The applied field may be uniform or vary in space. This model can accurately estimate the eddy current contour in the plate and loss due to eddy current. Power losses for plates of various dimensions and at different frequencies are calculated to establish the accuracy of the model. We have also calculated the magnetic field generated by the induced eddy current when the plate of finite size is placed between the two parallel poles of a dipole magnet made of magnetic material of very high permeability. The force acting on the plate due to the interaction of the induced eddy current and the applied external field is also calculated. The model can predict the time variation of force and eddy current. The model may be applicable to understand the effect of eddy current on the vacuum chamber of an accelerator. Various other applications, where this model is useful, are also reported. The results are compared against the results obtained by a simulation using a finite element based code. Here the rectangular plate is considered but the model can be applicable for other geometries as well.

  15. 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.

  16. 3D analysis of eddy current loss in the permanent magnet coupling

    NASA Astrophysics Data System (ADS)

    Zhu, Zina; Meng, Zhuo

    2016-07-01

    This paper first presents a 3D analytical model for analyzing the radial air-gap magnetic field between the inner and outer magnetic rotors of the permanent magnet couplings by using the Amperian current model. Based on the air-gap field analysis, the eddy current loss in the isolation cover is predicted according to the Maxwell's equations. A 3D finite element analysis model is constructed to analyze the magnetic field spatial distributions and vector eddy currents, and then the simulation results obtained are analyzed and compared with the analytical method. Finally, the current losses of two types of practical magnet couplings are measured in the experiment to compare with the theoretical results. It is concluded that the 3D analytical method of eddy current loss in the magnet coupling is viable and could be used for the eddy current loss prediction of magnet couplings.

  17. 3D analysis of eddy current loss in the permanent magnet coupling.

    PubMed

    Zhu, Zina; Meng, Zhuo

    2016-07-01

    This paper first presents a 3D analytical model for analyzing the radial air-gap magnetic field between the inner and outer magnetic rotors of the permanent magnet couplings by using the Amperian current model. Based on the air-gap field analysis, the eddy current loss in the isolation cover is predicted according to the Maxwell's equations. A 3D finite element analysis model is constructed to analyze the magnetic field spatial distributions and vector eddy currents, and then the simulation results obtained are analyzed and compared with the analytical method. Finally, the current losses of two types of practical magnet couplings are measured in the experiment to compare with the theoretical results. It is concluded that the 3D analytical method of eddy current loss in the magnet coupling is viable and could be used for the eddy current loss prediction of magnet couplings. PMID:27475575

  18. Eddy current distributions in cylindrical samples: effect on equivalent sample resistance.

    PubMed

    Harpen, M D

    1989-09-01

    We present a general technique for the determination of eddy current distributions within an irregularly shaped conducting sample in the uniform field of an NMR RF coil. Also presented is a general expression for the sample-induced coil resistance. The technique is applied specifically to a conducting cylindrical solid. Unlike previous descriptions of cylindrical samples in solenoidal coils where the induction is parallel to the axis of the cylinder and eddy current streamlines are circular, we treat the case where the induction is perpendicular to the cylindrical axis and where consequently eddy current streamlines take on an irregular shape. PMID:2798558

  19. Development of Interior Permanent Magnet Motors with Concentrated Windings for Reducing Magnet Eddy Current Loss

    NASA Astrophysics Data System (ADS)

    Yamazaki, Katsumi; Kanou, Yuji; Fukushima, Yu; Ohki, Shunji; Nezu, Akira; Ikemi, Takeshi; Mizokami, Ryoichi

    In this paper, we present the development of interior magnet motors with concentrated windings, which reduce the eddy current loss of the magnets. First, the mechanism of the magnet eddy current loss generation is investigated by a simple linear magnetic circuit. Due to the consideration, an automatic optimization method using an adaptive finite element method is carried out to determine the stator and rotor shapes, which decrease the eddy current loss of the magnet. The determined stator and rotor are manufactured in order to proof the effectiveness by the measurement.

  20. 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.

  1. Discontinuity interaction and anomalous source models in through transmission eddy current testing

    SciTech Connect

    Mergelas, B.J.; Atherton, D.L.

    1996-01-01

    Growing interest in the detection of external, axially aligned stress corrosion cracks in ferromagnetic oil and gas transmission pipelines, has prompted a detailed investigation of discontinuity interactions in remote field eddy current (RFEC) testing. Experimental measurements and numerical modeling were undertaken to study discontinuity interactions in a single through-wall transmission geometry for ferromagnetic and nonferromagnetic pipes. Anomalous source models have been introduced in order to explain the responses of axial discontinuities to circumferential eddy currents or circumferential AC magnetic fields. In nonferromagnetic material, discontinuity responses may be modeled by two types of anomalous eddy current sources. In ferromagnetic materials, an anomalous magnetization source is useful for explaining discontinuity response.

  2. Finite element modeling of magnetic bias eddy current probe interaction with ferromagnetic materials

    NASA Astrophysics Data System (ADS)

    Lei, J.

    2013-01-01

    Requirements to demonstrate eddy current inspection capabilities for inspection of steam generator tubes in nuclear power generation stations are becoming more rigorous. One method to support qualification of an existing, modified, or new eddy current probe design is to model the probe response to various degradation modes and tube artifacts with a finite element approach. Magnetic-bias probes are used to inspect for defects in conditions where material magnetic permeability effects are a concern, such as in the presence of ferromagnetic tubes, deposits, or supports. In this paper, a transient finite element modeling approach was used to model the interaction of magnetic-bias eddy current probes with ferromagnetic materials.

  3. RESONANT FREQUENCY EDDY CURRENT LIFTOFF MEASUREMENTS FOR SHOT PEENING INTENSITY ASSESSMENT IN MATERIALS

    SciTech Connect

    Ko, Ray T.; Blodgett, Mark P.; Sathish, Shamachary; Boehnlein, Thomas R.

    2008-02-28

    The shot peening intensity of nickel base materials has been examined with an innovative eddy current measurement. The goal is to provide a nondestructive tool to quantitatively evaluate the surface conditions after shot peening. Traditionally, the residual stress caused by the shot peening process can be examined by X-ray diffraction. Recent eddy current works have shown promising results in evaluating the small conductivity variation due to the residual stress. This study explores the feasibility of utilizing the cable which connects to a network analyzer and a conventional eddy current probe to monitor the surface conditions due to the shot peening.

  4. Eddy Current Testing and Four-Point Probe Measurement of - and Macromaterials Enhanced Polymeric Composites

    NASA Astrophysics Data System (ADS)

    Ko, Ray T.; Gibson, Thao; Fielding, Jennifer

    2010-02-01

    Nano- and macromaterials are being engineered into polymeric composites to enhance the electrical conductivity for lightning strike protection purposes. Electrical conductivity can be measured using a four-point probe method. Eddy current methods can provide a more localized measure of conductivity on the surface of a component. In this study, engineered composites containing both macro- and nanomaterials have been fabricated. Eddy current measurements were made on these specimens to quantify the sensitivity of this method to the relevant variables. Eddy current results in the sub-MHz frequency range agreed well with the electrical conductivity data from four-point probe measurements.

  5. High accuracy fuel flowmeter

    NASA Technical Reports Server (NTRS)

    1986-01-01

    All three flowmeter concepts (vortex, dual turbine, and angular momentum) were subjected to experimental and analytical investigation to determine the potential portotype performance. The three concepts were subjected to a comprehensive rating. Eight parameters of performance were evaluated on a zero-to-ten scale, weighted, and summed. The relative ratings of the vortex, dual turbine, and angular momentum flowmeters are 0.71, 1.00, and 0.95, respectively. The dual turbine flowmeter concept was selected as the primary candidate and the angular momentum flowmeter as the secondary candidate for prototype development and evaluation.

  6. Software compensation of eddy current fields in multislice high order dynamic shimming

    PubMed Central

    Sengupta, Saikat; Avison, Malcolm J.; Gore, John C.; Welch, E. Brian

    2011-01-01

    Dynamic B0 shimming (DS) can produce better field homogeneity than static global shimming by dynamically updating slicewise shim values in a multislice acquisition. The performance of DS however is limited by eddy current fields produced by the switching of 2nd and 3rd order unshielded shims. In this work, we present a novel method of eddy field compensation (EFC) applied to higher order shim induced eddy current fields in multislice DS. This method does not require shim shielding, extra hardware for eddy current compensation or subject specific prescanning. The interactions between shim harmonics are modeled assuming steady state of the medium and long time constant, cross and self term eddy fields in a DS experiment and ‘correction factors’ characterizing the entire set of shim interactions are derived. The correction factors for a given time between shim switches are shown to be invariable with object scanned, shim switching pattern and actual shim values, allowing for their generalized prospective use. Phantom and human head, 2nd and 3rd order DS experiments performed without any hardware eddy current compensation using the technique show large reductions in field gradients and offsets leading to significant improvements in image quality. This method holds promise as an alternative to expensive hardware based eddy current compensation required in 2nd and 3rd order DS. PMID:21458339

  7. 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.

  8. 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. PMID:26827315

  9. 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.

  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. The eddy-current technique for nondestructive evaluation of generator retaining rings: Feasibility study: Interim report

    SciTech Connect

    Elmo, P.M.; Nottingham, L.D.

    1988-05-01

    An evaluation of the feasibility of using eddy current nondestructive inspection techniques to detect intergranular stress corrosion in generator rotor retaining rings was conducted by the EPRI NDE Center. Experiments were conducted using a bend-bar containing representative stress corrosion damage, a calibration block containing electrical discharge machined (EDM) notches, and four retired retaining rings containing EDM notches and stress corrosion damage. An eddy current transducer transport was designed and fabricated to interface with an existing computer-controlled, two-axis positioner and digital eddy current data acquisition system. Test results of experiments performed with this equipment on the retaining ring test-bed provided experimental validation of the eddy current method's feasibility as a retaining ring inspection method. Details are given of the system and its performance under laboratory and simulated service-inspection conditions. 9 refs., 47 figs.

  12. Eddy current signal deconvolution technique for the improvement of steam generator tubing burst pressure predictions.

    SciTech Connect

    Petri, M. C.; Wei, T. Y. C.; Kupperman, D. S.; Reifman, J.; Morman, J. A.

    2000-01-01

    Eddy current techniques are extremely sensitive to the presence of axial cracks in nuclear power plant steam generator tube walls, but they are equally sensitive to the presence of dents, fretting, support structures, corrosion products, and other artifacts. Eddy current signal interpretation is further complicated by cracking geometries more complex than a single axial crack. Although there has been limited success in classifying and sizing defects through artificial neural networks, the ability to predict tubing integrity has, so far, eluded modelers. In large part, this lack of success stems from an inability to distinguish crack signals from those arising from artifacts. We present here a new signal processing technique that deconvolves raw eddy current voltage signals into separate signal contributions from different sources, which allows signals associated with a dominant crack to be identified. The signal deconvolution technique, combined with artificial neural network modeling, significantly improves the prediction of tube burst pressure from bobbin-coil eddy current measurements of steam generator tubing.

  13. 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.

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

    SciTech Connect

    Kustra, T.A.; Huntingdon, N.; Caffarel, A.J.

    1990-01-09

    This patent describes an apparatus for measuring physical characteristics of an electrically conductive material in a heated environment. It comprises: eddy current probe means including a primary coil and a reference coil for producing an eddy current signal in response to the probe means coming in contact with the material; resistance measuring means including a digital ohm meter for measuring the resistances of the primary coil and the reference coil; output means for outputting the eddy current signal; and switch means connected between the probe means, the resistance measuring means, and the output means, for connecting the probe means to the resistance measuring means to measure the resistances of the coils, and for connecting the probe means to the output means to obtain the eddy current signal.

  15. Eddy-current effects on ferromagnetic resonance: Spin wave excitations and microwave screening effects

    NASA Astrophysics Data System (ADS)

    Flovik, Vegard; Pettersen, Bjørn Holst; Wahlström, Erik

    2016-04-01

    We investigate how controlling induced eddy currents in thin film ferromagnet-normal metal (FM/NM) structures can be used to tailor the local microwave (MW) fields in ferromagnetic resonance (FMR) experiments. The MW fields produced by eddy currents will in general have a relative phase shift with respect to the applied MW field which depends on the sample geometry. The induced fields can thus partially compensate the applied MW field, effectively screening the FM in selected parts of the sample. The highly localized fields produced by eddy currents enable the excitation of spin wave modes with non-zero wave vectors ( k ≠ 0 ), in contrast to the uniform k = 0 mode normally excited in FMR experiments. We find that the orientation of the applied MW field is one of the key parameters controlling the eddy-current effects. The induced currents are maximized when the applied MW field is oriented perpendicular to the sample plane. Increasing the magnitude of the eddy currents results in a stronger induced MW field, enabling a more effective screening of the applied MW field as well as an enhanced excitation of spin wave modes. This investigation underlines that eddy currents can be used to control the magnitude and phase of the local MW fields in thin film structures.

  16. Coupling between angular deflection and eddy currents in the FELIX plate experiment

    SciTech Connect

    Turner, L.R.; Cuthbertson, J.W.

    1983-08-01

    For a conducting body experiencing superimposed changing and steady magnetic field, for example a limiter in a tokamak during plasma quench, the induced eddy currents and the deflections resulting from those eddy currents are coupled. Experimental study of these coupled deflections and currents can be performed with the FELIX (Fusion Electromagnetic Induction Experiment) facility nearing completion at ANL. Predictions of the coupling are described, as computed with the code EDDYNET, which has been modified for this purpose. Effects of the coupling will be readily observable experimentally. In the FELIX plate experiment, the coupling between deflection and eddy currents was readily calculated because the rigid-body rotation of the plate is equivalent to a contrarotation of the applied magnetic fields. For a geometry such as a plasma limiter, in which the eddy currents would cause a deformation of the conducting body, an analysis of the coupling between eddy currents and deformation would require a structural-analysis code and an eddy current code to be simultaneously computing from the same mesh.

  17. Study on classical and excess eddy currents losses of Terfenol-D

    NASA Astrophysics Data System (ADS)

    Talebian, Soheil; Hojjat, Yousef; Ghodsi, Mojtaba; Karafi, Mohammad Reza

    2015-08-01

    In the present paper, classical and excess eddy currents losses of Terfenol-D are studied and effects of magnetic field frequency, peak of magnetic flux density and diameter of Terfenol-D on the eddy currents losses are investigated. To provide reliable data for the purpose of the paper, an experimental laboratory is fabricated and used to obtain major and minor hysteresis loops of Terfenol-D at different frequencies. In theoretical study, initially an analytical model based on uniform distribution of magnetic flux is developed which yields to calculation of classical eddy currents losses. Then, another eddy currents model based on non-uniform distribution of magnetic flux and nonlinear diffusion of electromagnetic fields is presented. The difference between output values of the two models is identified as excess eddy currents losses. Obtained results show that the values of excess losses are generally larger than classical losses and applying just classical model leads to wrong calculation of actual value of eddy currents losses. For the results obtained from two above models, empirical models with respect to the magnetic field frequency and the peak value of magnetic flux density are achieved which can predict the eddy currents losses precisely. To validate the empirical relations, experiments are repeated at a new frequency and values of power losses calculated from analytical equations are compared with the predicted values of the empirical models. The results point towards possibility to use the obtained empirical relations in order to calculate the classical and excess eddy currents losses of Terfenol-D at the frequencies below 200 Hz and different values of magnetic flux density.

  18. 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.

  19. Modelling of eddy currents related to large angle magnetic suspension test fixture

    NASA Technical Reports Server (NTRS)

    Britcher, Colin P.; Foster, Lucas E.

    1994-01-01

    This report presents a preliminary analysis of the mathematical modelling of eddy current effects in a large-gap magnetic suspension system. It is shown that eddy currents can significantly affect the dynamic behavior and control of these systems, but are amenable to measurement and modelling. A theoretical framework is presented, together with a comparison of computed and experimental data related to the Large Angle Magnetic Suspension Test Fixture at NASA Langley Research Center.

  20. EDDY CURRENT INVERSION AND ESTIMATION METRICS FOR EVALUATING THERMAL BARRIER COATINGS

    SciTech Connect

    Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.; Knopp, Jeremy S.; Aldrin, John C.; Nyenhuis, John

    2010-02-22

    In this paper, sophisticated eddy-current techniques incorporating model-based inverse methods were successfully demonstrated to measure the thickness and remaining-life of high-temperature coatings. To further assure the performance of these inverse methods, several estimation metrics including Fisher Information, Cramer-Rao Lower Bound (CRLB), covariance, and singular value decomposition (SVD) are introduced. The connections and utility of these metrics are illustrated in the design of eddy current methods for estimating layer thickness, conductivity and probe liftoff.

  1. Parametric Studies and Optimization of Eddy Current Techniques through Computer Modeling

    SciTech Connect

    Todorov, E. I.

    2007-03-21

    The paper demonstrates the use of computer models for parametric studies and optimization of surface and subsurface eddy current techniques. The study with high-frequency probe investigates the effect of eddy current frequency and probe shape on the detectability of flaws in the steel substrate. The low-frequency sliding probe study addresses the effect of conductivity between the fastener and the hole, frequency and coil separation distance on detectability of flaws in subsurface layers.

  2. Finite Element Modeling of Pulsed Eddy Current Signals from Aluminum Plates Having Defects

    NASA Astrophysics Data System (ADS)

    Babbar, V. K.; Harlley, D.; Krause, T. W.

    2010-02-01

    The pulsed eddy current technique is being developed for detection of flaws located at depth within conducting structures. The present work investigates the pulsed eddy current response from flat-plate conductors having defects by using finite element modeling. Modeling revealed the optimum probe position with respect to a multilayer defect geometry. Models were also produced to investigate the effect of changing some probe parameters on pickup signal and penetration depth.

  3. Eddy Current Inversion and Estimation Metrics for Evaluating Thermal Barrier Coatings

    NASA Astrophysics Data System (ADS)

    Sabbagh, Harold A.; Knopp, Jeremy S.; Aldrin, John C.; Murphy, R. Kim; Sabbagh, Elias H.; Nyenhuis, John

    2010-02-01

    In this paper, sophisticated eddy-current techniques incorporating model-based inverse methods were successfully demonstrated to measure the thickness and remaining-life of high-temperature coatings. To further assure the performance of these inverse methods, several estimation metrics including Fisher Information, Cramer-Rao Lower Bound (CRLB), covariance, and singular value decomposition (SVD) are introduced. The connections and utility of these metrics are illustrated in the design of eddy current methods for estimating layer thickness, conductivity and probe liftoff.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. In situ measured current structures of the eddy field in the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    Ternon, J. F.; Roberts, M. J.; Morris, T.; Hancke, L.; Backeberg, B.

    2014-02-01

    Circulation and the related biological production have been studied during five cruises conducted in the Mozambique Channel (MZC) between 2005 and 2010. The circulation in the MZC is known to be highly turbulent, favouring enhanced primary production as a result of mesoscale eddy dynamics, and connectivity throughout the Channel due to the variable currents associated with migrating eddies. This paper presents the results of in situ measurements that characterize the horizontal and vertical currents in the surface and subsurface layers (0-500 m). The in situ data were analysed together with the geostrophic eddy field observed from satellite altimeter measurements. Different circulation regimes were investigated, including the "classical" anticyclonic eddy generated at the Channel narrows (16°S), the enhancement of southward migrating eddies by merging with structures (both cyclonic and anticyclonic) formed in the east of the Channel, and the presence of a fully developed cyclonic eddy at the Channel narrows. Comparison between in situ measurements (S-ADCP and velocities derived from surface drifters) and the geostrophic current derived from sea surface height measurements indicated that the latter can provide a reliable, quantitative description of eddy driven circulation in the MZC, with the exception that these currents are weaker by as much 30%. It is also suggested from in situ observation (drifters) that the departure from geostrophy of the surface circulation might be linked to strong wind conditions. Finally, our observations highlight that a-geostrophic currents need to be considered in future research to facilitate a more comprehensive description of the circulation in this area.

  10. 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.

  11. Quantification and compensation of eddy-current-induced magnetic-field gradients.

    PubMed

    Spees, William M; Buhl, Niels; Sun, Peng; Ackerman, Joseph J H; Neil, Jeffrey J; Garbow, Joel R

    2011-09-01

    Two robust techniques for quantification and compensation of eddy-current-induced magnetic-field gradients and static magnetic-field shifts (ΔB0) in MRI systems are described. Purpose-built 1-D or six-point phantoms are employed. Both procedures involve measuring the effects of a prior magnetic-field-gradient test pulse on the phantom's free induction decay (FID). Phantom-specific analysis of the resulting FID data produces estimates of the time-dependent, eddy-current-induced magnetic field gradient(s) and ΔB0 shift. Using Bayesian methods, the time dependencies of the eddy-current-induced decays are modeled as sums of exponentially decaying components, each defined by an amplitude and time constant. These amplitudes and time constants are employed to adjust the scanner's gradient pre-emphasis unit and eliminate undesirable eddy-current effects. Measurement with the six-point sample phantom allows for simultaneous, direct estimation of both on-axis and cross-term eddy-current-induced gradients. The two methods are demonstrated and validated on several MRI systems with actively-shielded gradient coil sets. PMID:21764614

  12. 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.

  13. 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.

  14. Ferromagnetic eddy current probe having eccentric magnetization for detecting anomalies in a tube

    SciTech Connect

    Cecco, V.S.; Carter, J.R.

    1993-08-17

    An eddy current probe is described for detecting anomalies in a tube made of a ferromagnetic material, comprising: a probe housing made of a non-ferromagnetic material and shaped to be introduced into the tube for inspection, said housing having a central axis substantially coinciding with the axis of the tube to be inspected when the probe is in use; at least two eddy current measuring assemblies provided in said housing, each said assembly including magnetization means for generating a magnetic field in the tube under inspection to magnetize said tube, said magnetization means producing a maximum magnetization at an area of said tube and a minimum magnetization at a diametrically opposite area of said tube and at least one eddy current measuring coil associated with said magnetization means to measure the eddy current generated in the said tube and which has a relatively high sensitivity to an anomaly at said maximum magnetization area; and said eddy current measuring assemblies being spaced apart axially within said housing and rotated about said central axis from each other by a predetermined angle so that each assembly is sensitive to anomalies differently depending upon their location in said housing.

  15. 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. PMID:25430382

  16. Determination of crack depth in aluminum using eddy currents and GMR sensors

    NASA Astrophysics Data System (ADS)

    Lopes Ribeiro, A.; Pasadas, D.; Ramos, H. G.; Rocha, T.

    2015-03-01

    In this paper we use eddy currents to determine the depth of linear cracks in aluminum plates. A constant field probe is used to generate the spatially uniform excitation field and a single axis giant magneto-resistor (GMR) sensor is used to measure the eddy currents magnetic field. Different depths were machined in one aluminum plate with 4 mm of thickness. By scanning those cracks the magnetic field components parallel and perpendicular to the crack's line were measured when the eddy currents were launched perpendicularly to the crack's line. To characterize one crack in a plate of a given thickness and material, the experimental procedure was defined. The plate surface is scanned to detect and locate one crack. The acquired data enables the determination of the crack's length and orientation. A second scanning is performed with the excitation current perpendicular to the crack and the GMR sensing axis perpendicular and parallel to the crack's line.

  17. 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.

  18. 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.

  19. Application of CFD to Explain Anomalous Stall Behavior of the SSME Flowmeter

    NASA Technical Reports Server (NTRS)

    Ascoli, E.; Clever, W.; Hadid, A.; Lynch, E. D.; Stewart, M.; Lee, K.

    1999-01-01

    The Space Shuttle Main Engine (SSME) Fuel Flowmeter is located in the duct between the low and high pressure fuel turbopumps. In the flowmeter the rotation rate of a 4-blade rotor positioned downstream of two flow straighteners is employed to measure the engine fuel flow rate and thereby control the engine mixture ratio via the engine controller. Hence, inaccurate operation of the flowmeter could have serious consequences for SSME engine operation and performance, forcing, for example, tanking of extra fuel to allow for inaccurate flowmeter measurement. Since the current flight flowmeter configuration was incorporated into the SSME in the early eighties, some anomalies in flowmeter behavior have been observed. The initial flowmeter incorporated an "egg crate" design for the two flow straighteners which turn the duct flow to make it more uniform and parallel after it has come out of the 90 degree bend just upstream of the flowmeter.

  20. Eddy-current non-inertial displacement sensing for underwater infrasound measurements.

    PubMed

    Donskoy, Dimitri M; Cray, Benjamin A

    2011-06-01

    A non-inertial sensing approach for an Acoustic Vector Sensor (AVS), which utilizes eddy-current displacement sensors and operates well at Ultra-Low Frequencies (ULF), is described here. In the past, most ULF measurements (from mHertz to approximately 10 Hertz) have been conducted using heavy geophones or seismometers that must be installed on the seafloor; these sensors are not suitable for water column measurements. Currently, there are no readily available compact and affordable underwater AVS that operate within this frequency region. Test results have confirmed the validity of the proposed eddy-current AVS design and have demonstrated high acoustic sensitivity. PMID:21682361

  1. Vessel Eddy Current Measurement for the National Spherical Torus Experiment (NSTX)

    SciTech Connect

    D.A. Gates; J. Menard; R. Marsala

    2004-11-19

    A simple analog circuit that measures the NSTX axisymmetric eddy current distribution has been designed and constructed. It is based on simple circuit model of the NSTX vacuum vessel that was calibrated using a special axisymmetric eddy current code which was written so that accuracy was maintained in the vicinity of the current filaments. The measurement and the model have been benchmarked against data from numerous vacuum shots and they are in excellent agreement. This is an important measurement that helps give more accurate equilibrium reconstructions.

  2. Apparatus and method for non-destructive testing using multi-frequency eddy currents

    SciTech Connect

    Hedengren, K.H.V.

    1993-08-17

    A method is described of improving eddy current flaw detection and resolution comprising the steps of: providing a plurality of probe elements; providing an alternating source of current capable of oscillating at a multiplicity of discrete frequencies; simultaneously driving said plurality of probe elements with said multiplicity of frequencies to excite discrete frequency responsive signals therefrom; scanning to acquire a corresponding multiplicity of discrete frequency responsive signals from each probe element of said plurality of probe elements; and resolving a corresponding multiplicity of eddy current images from said scan responsive multiplicity of frequency responsive signals.

  3. Analysis and comparison for rotor eddy current losses of permanent magnet synchronous generator according to dc and ac load conditions

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Kim, Hyun-Kyu; Choi, Jang-Young; Ko, Kyoung-Jin

    2009-04-01

    This paper presents an analytical procedure for the calculation of the eddy current losses of permanent magnet synchronous generator (PMSG). The dc and ac loading effects on the eddy current is examined through the suggested analytical procedure that considers the radial and tangential flux density waveform through a phase current harmonic analysis. The corresponding test results are also presented to quantify and compare those loading effects on the eddy current. The results verified the suggested analytical procedures and show that the rotor eddy current losses for PMSG with the dc loads turned out to be more significant than those with the ac loads.

  4. 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.

  5. 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

  6. Application of finite element models to eddy current probe design for aircraft inspection

    NASA Astrophysics Data System (ADS)

    Sharma, Sarit

    Eddy current nondestructive testing (NDT) methods are used extensively in the inspection of aircraft structures. Improvements and innovations in probe design are constantly required for detection of flaws in complex multilayer aircraft structures. This thesis investigates alternate designs of eddy current probes for addressing some of these problems. An important aspect of probe design is the capability to simulate probe performance. Numerical computation and visualization of the electromagnetic fields can provide valuable insight into the design of new probes. Finite element methods have been used in this dissertation to numerically compute the electromagnetic fields associated with the probe coils, and the eddy current probe signals. A major contribution of this thesis is development of techniques to reduce the computer resource requirement in the finite element modeling: of the eddy current phenomenon. The first flaw detection problem is addressed by focusing the flux of the probe using active compensation techniques. A novel eddy current probe using a combination of coils is proposed and studied using: the 3D model simulation. The probe consists of two current carrying concentric coils to detect flaws closer to the sample edges. Detection of defects in second and third layer of samples has been demonstrated using: the remote field eddy current (RFEC) method. In the RFEC method the pickup coils are located in the far field region which leads to a large volume to be modeled numerically with large number of elements. A method involving partitioning the volume in the 3D finite element model is demonstrated for the RFEC detection of defects. Magneto-optic/eddy current imaging (MOI) techniques have shown considerable promise in the detection of corrosion in the second layer. MOI is a nondestructive testing method currently in use in aircraft frame inspection and it involves optically sensing the magnetic field induced by the eddy currents in the test sample. A

  7. Double half RF pulses for reduced sensitivity to eddy currents in UTE imaging.

    PubMed

    Josan, Sonal; Pauly, John M; Daniel, Bruce L; Pauly, Kim Butts

    2009-05-01

    Ultrashort echo time imaging with half RF pulse excitation is challenging as eddy currents induced by the slice-select gradient distort the half pulse slice profile. This work presents two pulses with T(2)-dependent slice profiles that are less sensitive to eddy currents. The double half pulse improves the slice selectivity for long T(2) components, while the inverted double half pulse suppresses the unwanted long T(2) signal. Thus, both approaches prevent imperfect cancellation of out-of-slice signal from contaminating the desired slice. Experimental results demonstrate substantially improved slice selectivity and R(2)* quantitation accuracy with these pulses. These pulses are effective in making short T(2) imaging and quantitation less sensitive to eddy currents and provide an alternative to time-consuming gradient characterization. PMID:19235919

  8. An active sensor for monitoring bearing wear by means of an eddy current displacement sensor

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Toshihiko; Ueda, Masahiro

    2007-01-01

    A new and simple sensor for directly monitoring bearing wear has been developed by improving an eddy current displacement sensor. The sensor can be applied for non-metal shafts as well as metal shafts, and in this sense, we call it an 'active sensor'. In this sensor, an aluminium foil, used as a target metal for the eddy current sensor, has been sandwiched between two wedge-shaped acrylic plates and combined with an eddy current displacement sensor as a unit. The whole system consists of this new sensor, a data processing system including an amplifier, a 14-bit A/D converter, a personal computer and a display. The error of this system was about 20 µm, which was sufficiently small for use in a practical plant.

  9. A connection between the South Equatorial Current north of Madagascar and Mozambique Channel Eddies

    NASA Astrophysics Data System (ADS)

    Backeberg, B. C.; Reason, C. J. C.

    2010-02-01

    Combining high resolution model output and geostrophic currents derived from satellite altimeter data, it is shown that the formation of mesoscale eddies in the Mozambique Channel (MZC) is connected to variability in the transport of the South Equatorial Current (SEC). Lagged cross-correlations of the currents north of Madagascar and vorticities in the MZC, combined with a composite analysis of the model output, show that eddies form in the narrows of the channel approximately 20 weeks following a westward transport pulse in the SEC. A relationship between MZC eddies and the large-scale variability of the South Indian Ocean may have downstream impacts on the Agulhas leakage, the Atlantic Meridional overturning circulation, and thus climate.

  10. 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.

  11. Axisymmetric eddy current inspection of highly conducting thin layers via asymptotic models

    NASA Astrophysics Data System (ADS)

    Haddar, Houssem; Jiang, Zixian

    2015-11-01

    Thin copper deposits covering the steam generator tubes can blind eddy current probes in non-destructive testings of problematic faults and it is therefore important that they are identified. Existing methods based on shape reconstruction using eddy current signals encounter difficulties of high numerical costs due to the layer’s small thickness and high conductivity. In this article, we approximate the axisymmetric eddy current problem with some appropriate asymptotic models using effective transmission conditions representing the thin deposits. In these models, the geometrical information related to the deposit is transformed into parameter coefficients on a fictitious interface. A standard iterative inversion algorithm is then applied to the asymptotic models to reconstruct the thickness of the thin copper layers. Numerical tests both validating the asymptotic model and showing the benefits of the inversion procedure are provided.

  12. Development and Application of Wide Bandwidth Magneto-Resistive Sensor Based Eddy Current Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Russell A.; Simpson, John

    2010-01-01

    The integration of magneto-resistive sensors into eddy current probes can significantly expand the capabilities of conventional eddy current nondestructive evaluation techniques. The room temperature solid-state sensors have typical bandwidths in the megahertz range and resolutions of tens of microgauss. The low frequency sensitivity of magneto-resistive sensors has been capitalized upon in previous research to fabricate very low frequency eddy current sensors for deep flaw detection in multilayer conductors. In this work a modified probe design is presented to expand the capabilities of the device. The new probe design incorporates a dual induction source enabling operation from low frequency deep flaw detection to high frequency high resolution near surface material characterization. Applications of the probe for the detection of localized near surface conductivity anomalies are presented. Finite element modeling of the probe is shown to be in good agreement with experimental measurements.

  13. 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.

  14. 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.

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

    SciTech Connect

    Fangwei Fu

    2006-08-09

    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

  16. Characterization of eddy current distortion effects on magnetic resonance axonography of human brain

    NASA Astrophysics Data System (ADS)

    Elshafiey, Ibrahim; Narayana, Ponnada A.

    2002-05-01

    Axonography of human brain, based on diffusion tensor magnetic resonance imaging (DT-MRI), has recently gained popularity because of its potential in providing crucial information about intercommunication between different regions of brain. This technique exploits the sensitivity of MRI to random water diffusion in tissues in the presence of diffusion gradient pulses incorporated into the imaging sequence. Large diffusion weighting that is necessary for the generation of axonography with high SNR is achieved by increasing the magnitude of diffusion pulses. However large diffusion gradients induce strong eddy currents in the metallic structure of the cryostat that houses the superconducting coil of the scanner magnet, resulting in distortion of magnetic resonance images. The purpose of this study was to characterize the effect of eddy currents on images obtained using the DT-MRI of human brain. Characterization of eddy current effects is essential for optimizing the scanning parameters and improving image quality. All MRI studies were performed on 1.5-T GE scanner, using single shot diffusion weighed echo planar imaging sequence. All acquisitions were cardiac gated for minimizing the pulsation effect of cerebrospinal fluid (CSF) on the images. Diffusion gradient- or b-space was explored using a set of 62 directions along the two poles, and 60 other directions. Total scan time was less than three minutes. The exploration of the b-space helps quantify the relationship between the orientation of diffusion gradients and eddy current levels. Experimental results demonstrate that certain directions are more prone to eddy current-induced image distortions. Determining the optimum gradient directions should present a powerful technique for reducing eddy current distortion, and thus enhance the use of MRI axonography for a noninvasive assessment of human brain.

  17. 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.

  18. Eddy current effects in the magnetization dynamics of ferromagnetic metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Denisov, S. I.; Lyutyy, T. V.; Pedchenko, B. O.; Babych, H. V.

    2014-07-01

    We develop an analytical model for describing the magnetization dynamics in ferromagnetic metal nanoparticles, which is based on the coupled system of the Landau-Lifshitz-Gilbert (LLG) and Maxwell equations. By solving Maxwell's equations in the quasi-static approximation and finding the magnetic field of eddy currents, we derive the closed LLG equation for the magnetization that fully accounts for the effects of conductivity. We analyze the difference between the LLG equations in metallic and dielectric nanoparticles and show that these effects can strongly influence the magnetization dynamics. As an example illustrating the importance of eddy currents, the phenomenon of precessional switching of magnetization is considered.

  19. 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.

  20. Finite Element Modeling of Pulsed Eddy Current Signals from Conducting Cylinders and Plates

    NASA Astrophysics Data System (ADS)

    Babbar, V. K.; Kooten, P. V.; Cadeau, T. J.; Krause, T. W.

    2009-03-01

    Pulsed eddy current technique is being developed for detection of flaws located at depth within conducting structures. The present work investigates the pulsed eddy current response from cylindrical and flat-plate conductors by using finite element modeling employing COMSOL Multiphysics commercial package. The benchmark case of a driver/pick-up coil configuration encircling a solid conducting cylinder is used to model the transient electromagnetic response of cylinders of different diameters and lengths. A good comparison with experimental results validates the model. The work was extended to model a planar coil response to flat-plate aluminum structures.

  1. 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.

  2. 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.

  3. Submerged Eddy Current Method of Hydrogen Content Evaluation of ZIRCALOY-4 Fuel Cladding

    NASA Astrophysics Data System (ADS)

    Pfeif, E. A.; Jones, Z.; Lasseigne, A. N.; Koenig, K.; Krzywosz, K.; Mader, E. V.; Yagnik, S.; Mishra, B.; Olson, D. L.

    2011-06-01

    Submerged eddy current testing of zircaloy-4 fuel cladding has been developed as a method of characterizing the hydrogen evolution within zircaloy-4 fuel cladding in spent fuel pools. The parameters associated with storage in spent fuel pools must be incorporated and accounted for within the hydrogen content measurements. A focus on the effects of water and temperature must be incorporated and separated out of the hydrogen measurements. The use of submerged eddy current measurements to identify hydrogen content and hydride phases present in zircaloy-4 fuel cladding will be presented.

  4. 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.

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

    PubMed

    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. PMID:26521001

  6. 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.

  7. Hidden Crack Detection with GMR Sensing of Magnetic Fields from Eddy Currents

    SciTech Connect

    Ko, Ray T.; Sathish, Shamachary; Knopp, Jeremy S.; Blodgett, Mark P.

    2007-03-21

    A giant magneto-resistive (GMR) sensor placed inside a coil has been used for same side eddy current measurements on metallic plates. Magnetic fields from eddy currents generated in these metallic plates by excitation of the coil, are detected by the GMR sensor. The signal excitation and detection is accomplished using a lock-in amplifier which allows independent measurement of the phase and magnitude. The sensor configuration has been used to detect notches. Phase and magnitude images acquired with this sensor configuration are compared with the images obtained using the coil only.

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

    NASA Astrophysics Data System (ADS)

    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 @ 2.93 GHz; OS: Windows 7 Professional; Memory (RAM): 4.00 GB), it took less than 3 min to simulate the entire calculation of eddy currents and fields, and approximately 6 min 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

  9. 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

  10. 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. PMID:27466126

  11. 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.

  12. 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.

  13. 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.

  14. The formation of a cold-core eddy in the East Australian Current

    NASA Astrophysics Data System (ADS)

    Macdonald, H. S.; Roughan, M.; Baird, M. E.; Wilkin, J.

    2016-02-01

    Cold-core eddies (CCEs) frequently form in western boundary currents and can affect continental shelf processes. It is not always clear, however, if baroclinic or barotropic instabilities contribute more to their formation. The Regional Ocean Modelling System (ROMS) is used to investigate the ocean state during the formation of a CCE in the East Australian Current (EAC) during October 2009. The observed eddy initially appeared as a small billow (approx. 50 km in length) that perturbed the landward edge of the EAC. The billow grew into a mesoscale CCE (approx. 100 km in diameter), diverting the EAC around it. A ROMS simulation with a realistic wind field reproduced a similar eddy. This eddy formed from negative vorticity waters found on the continental shelf south of the EAC separation point. A sensitivity analysis is performed whereby the impact of 3 different wind forcing scenarios, upwelling, downwelling, and no winds, are investigated. A CCE formed in all wind scenarios despite the wind induced changes in hydrographic conditions in the continental shelf and slope waters. As such, the source of energy for eddy formation did not come from the interactions of wind with the continental shelf waters. Analysis of strain and energy transformation confirms this by showing that the prevailing source of CCE energy was kinetic energy of the offshore EAC. These results clearly link the formation of the CCE to the swift flowing EAC and barotropic instabilities.

  15. Laser double Doppler flowmeter

    NASA Astrophysics Data System (ADS)

    Poffo, L.; Goujon, J.-M.; Le Page, R.; Lemaitre, J.; Guendouz, M.; Lorrain, N.; Bosc, D.

    2014-05-01

    The Laser Doppler flowmetry (LDF) is a non-invasive method for estimating the tissular blood flow and speed at a microscopic scale (microcirculation). It is used for medical research as well as for the diagnosis of diseases related to circulatory system tissues and organs including the issues of microvascular flow (perfusion). It is based on the Doppler effect, created by the interaction between the laser light and tissues. LDF measures the mean blood flow in a volume formed by the single laser beam, that penetrate into the skin. The size of this measurement volume is crucial and depends on skin absorption, and is not directly reachable. Therefore, current developments of the LDF are focused on the use of always more complex and sophisticated signal processing methods. On the other hand, laser Double Doppler Flowmeter (FL2D) proposes to use two laser beams to generate the measurement volume. This volume would be perfectly stable and localized at the intersection of the two laser beams. With FL2D we will be able to determine the absolute blood flow of a specific artery. One aimed application would be to help clinical physicians in health care units.

  16. 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…

  17. 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.

  18. 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.

  19. 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…

  20. Numerical upscaling for the eddy-current model with stochastic magnetic materials

    NASA Astrophysics Data System (ADS)

    Eberhard, Jens P.; Popović, Dan; Wittum, Gabriel

    2008-04-01

    This paper deals with the upscaling of the time-harmonic Maxwell equations for heterogeneous media. We analyze the eddy-current approximation of Maxwell's equations to describe the electric field for heterogeneous, isotropic magnetic materials. The magnetic permeability of the materials is assumed to have random heterogeneities described by a Gaussian random field. We apply the so-called Coarse Graining method to develop a numerical upscaling of the eddy-current model. The upscaling uses filtering and averaging procedures in Fourier space which results in a formulation of the eddy-current model on coarser resolution scales where the influence of sub-scale fluctuations is modeled by effective scale- and space-dependent reluctivity tensors. The effective reluctivity tensors can be obtained by solving local partial differential equations which contain a Laplacian as well as a curl-curl operator. We present a computational method how the equation of the combined operators can be discretized and solved numerically using an extended variational formulation compared to standard discretizations. We compare the results of the numerical upscaling of the eddy-current model with theoretical results of Eberhard [J.P. Eberhard, Upscaling for the time-harmonic Maxwell equations with heterogeneous magnetic materials, Physical Review E 72 (3), (2005)] and obtain a very good agreement.

  1. Exploring the eddy current excitation invariance to infer about defect characteristics

    SciTech Connect

    Ribeiro, A. Lopes; Ramos, H. G.

    2011-06-23

    This paper explores the excitation probe excitation field invariance when the eddy current method is applied to detect, localize and characterize material defects in conductive nonmagnetic media. The cases relative to rotational symmetry in circular solenoidal probes and translation symmetry in constant field probes are presented. The experimental data shows that this theoretical treatment is useful to preview the behavior of these probes.

  2. 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.

  3. Remote field eddy current detection of stress-corrosion cracks. Final report

    SciTech Connect

    Nestleroth, J.B.

    1990-02-01

    The feasibility of detecting stress-corrosion cracks (SSC) using the Remote Field Eddy Current (RFEC) technique was demonstrated. The RFEC technique interrogates the entire thickness of the pipe and is applicable for in-line inspection. If it can be shown that the RFEC technique is effective in detecting SSC, then the technique is an ideal method for detecting the defects of interest. A defect detection model is proposed for explaining the mechanism for crack detection. For axially oriented, closed cracks, such as SCC, the conventional defect detection model proved to be too simplistic and not applicable. Therefore, a new detection mode that examines the flow of circumferential eddy currents was developed based on experimental results. This model, though not rigorous, provides a general understanding of the applicability of the RFEC technique for finding SSC. The data from the cracks and various artificial defects is presented in three formats: isometric projections, pseudocolor images and line-of-sight data. Though only two cracks were found, the experimental results correlate well with the circumferential eddy current theory. A theoretical analysis of the effects of motion on the output signal of the receiver is presented. This analysis indicates that inspection speed of simple implementations may be limited to a few miles per hour. Remote field eddy current inspection has excellent potential for inspection of gas transmission lines for detecting stress corrosion cracks that should be further developed.

  4. A feature-based eddy-current imaging system for personal computers: Final report

    SciTech Connect

    Elmo, P.M.; Shankar, R.

    1989-03-01

    Imaging eddy current nondestructive evaluation (NDE) data on low-cost, field-deployable personal computer (PC) systems is now possible. This report describes the modification of a previously developed feature-based ultrasonic (UT) testing system for automatic eddy current (EC) inspection. This EC system was applied to flat plate and circular geometries. The PC system manipulates the eddy current probe around the part to be inspected; acquires multi-frequency, dual-channel digital data and displays images of an operator-selected channel; and utilizes advanced signal processing software to generate and display impedance-plane trajectories for all frequencies. Laboratory experiments using this eddy current test system on flaw calibration standards, induced intergranular-stress-corrosion-cracking (IGSCC) in retaining ring material coupons, and induced cracks in full size retaining rings have demonstrated the system's capability to detect surface damage. Future efforts will incorporate other problem-relevant signal processing algorithms to aid in detecting and characterizing surface-damage, such as pitting and cracking. 6 refs., 20 figs.

  5. Evaluation of Outer Flaws in Titanium Alloys Using Eddy Current Measuring System

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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.

  6. Theoretical prediction of remote-field eddy current response for the nondestructive evaluation of metallic tubes

    NASA Astrophysics Data System (ADS)

    Palanisamy, R.

    1987-04-01

    The remote-field eddy current effect refers to low-frequency eddy current nondestructive testing (NDT) phenomenon in tubular conductors in which the behavior of both amplitude and phase of induced magnetic field are in apparent contradiction to the well-known ``skin-effect'' theory. Near-equal detection sensitivity across the wall thickness, the ability to measure wall thickness, and the absence of lift-off problems are some of the attractive features of this technique. Despite its early recognition and useful application in down-hole inspection of oil-well casing, no development of adequate scientific basis that could explain this phenomenon has been reported in the open literature. Modeling of the remote-field eddy current phenomenon using the axisymmetric finite element computer code is described in this paper. The results presented show that the finite element numerical technique originally developed for the computation of fields in electrical and magnetic devices can be used as well for the modeling of remote-field eddy current NDT problems.

  7. 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.

  8. Development of an ultralow frequency eddy current instrument for the detection and sizing of stress corrosion cracks

    SciTech Connect

    Hayford, D.T.

    1988-01-01

    This book describes an investigation of the potential to use remote field eddy currents at low frequencies that would permit penetration of pipeline steels and use this technique to detect stress corrosion cracking on coated pipelines without requiring coating to be removed. The report describes development of a prototype eddy current instrument.

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

    NASA Astrophysics Data System (ADS)

    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

    2016-07-01

    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.

  10. Sidetone generator flowmeter

    DOEpatents

    Fritz, R.J.

    1983-11-03

    A flowmeter is provided which uses the sidetones generated in a cavity formed in the wall of a flowpipe or the like in response to fluid flowing past the cavity to provide a measure of the flow velocity of that fluid. The dimensions of the cavity are such as to provide a dominant vibratory frequency which is sensed by a pressure sensor. The flowmeter is adapted for use for a range of frequencies in which the Strouhal number is constant and under these conditions the vibratory frequency is directly related to the flow rate. The tone generator cavity and pressure transducer form a unit which is connected in-line in the flowpipe.

  11. 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.

  12. 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.

  13. Fast solver for large scale eddy current non-destructive evaluation problems

    NASA Astrophysics Data System (ADS)

    Lei, Naiguang

    Eddy current testing plays a very important role in non-destructive evaluations of conducting test samples. Based on Faraday's law, an alternating magnetic field source generates induced currents, called eddy currents, in an electrically conducting test specimen. The eddy currents generate induced magnetic fields that oppose the direction of the inducing magnetic field in accordance with Lenz's law. In the presence of discontinuities in material property or defects in the test specimen, the induced eddy current paths are perturbed and the associated magnetic fields can be detected by coils or magnetic field sensors, such as Hall elements or magneto-resistance sensors. Due to the complexity of the test specimen and the inspection environments, the availability of theoretical simulation models is extremely valuable for studying the basic field/flaw interactions in order to obtain a fuller understanding of non-destructive testing phenomena. Theoretical models of the forward problem are also useful for training and validation of automated defect detection systems. Theoretical models generate defect signatures that are expensive to replicate experimentally. In general, modelling methods can be classified into two categories: analytical and numerical. Although analytical approaches offer closed form solution, it is generally not possible to obtain largely due to the complex sample and defect geometries, especially in three-dimensional space. Numerical modelling has become popular with advances in computer technology and computational methods. However, due to the huge time consumption in the case of large scale problems, accelerations/fast solvers are needed to enhance numerical models. This dissertation describes a numerical simulation model for eddy current problems using finite element analysis. Validation of the accuracy of this model is demonstrated via comparison with experimental measurements of steam generator tube wall defects. These simulations generating two

  14. 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.

  15. Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers

    DOEpatents

    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.

  16. The in-service inspection of coated steel welds using Eddy-Current Techniques

    NASA Astrophysics Data System (ADS)

    Brown, B. J.; Zaid, M.; Picton, P. D.; Mabbutt, S. J.

    2012-05-01

    Traditionally surface crack detection in coated Ferritic Steel Welds with Eddy-Current Techniques has been difficult due to the change in material properties in the Heat Affected Zone. These typically produce signals larger than crack signals. Sophisticated probe design and construction, combined with modern electronic equipment, have largely overcome the traditional problems and now enable the advantages of Eddy-Current Techniques to be applied to In-Service Inspection of Coated Ferritic Steel Structures in the as-we!ded conditions. Specifically, the advantage of the technique is that under quantifiable conditions an inspection may now be carried out through corrosion protection systems. It is the intention of this paper to review the current information available, establish the limiting parameters of the technique and detail the practical experiments conducted to determine the extent of the limiting parameters. The results of these experiments are detailed. Having determined the limiting factors, outline testing procedures have been established together with relative sensitivity settings.

  17. Corrosion Detection in Airframes Using a New Flux-Focusing Eddy Current Probe

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    A new flux-focusing eddy current probe was recently developed at NASA Langley Research Center. The new probe is similar in design to a reflection type eddy current probe, but is unique in that it does not require the use of an impedance bridge for balancing. The device monitors the RMS output voltage of a pickup coil and, as a result, is easier to operate and interpret than traditional eddy current instruments. The unique design feature of the probe is a ferromagnetic cylinder, typically 1020 steel, which separates a concentrically positioned drive and pickup coil. The increased permeability of the steel causes the magnetic flux produced by the drive coil to be focused in a ring around the pickup coil. At high frequencies the eddy currents induced in both the sample and the cylinder allow little or no flux to link with the pickup coil. This results in a self-nulling condition which has been shown to be useful for the unambiguous detection of cracks in conducting materials. As the frequency is lowered the flux produced by the drive coil begins to link with the pickup coil causing an output which, among other things, is proportional to the thickness of the test specimen. This enables highly accurate measurements of the thickness of conducting materials and helps to facilitate the monitoring of thickness variations in a conducting structure such as an aircraft fuselage. Under ideal laboratory conditions the probe can sense thickness changes on the order of 1% as illustrated. However, this is highly dependent upon the thickness, and the geometric complexity of the sample being tested and for practical problems the sensitivity is usually much less. In this presentation we highlight some of the advantages and limitations in using the probe to inspect aircraft panels for corrosion and other types of material nonuniformities. In particular, we present preliminary results which illustrate the probes capabilities for detecting first and second layer corrosion in aircraft

  18. Superconductive microprobes for eddy current evaluation of materials

    NASA Astrophysics Data System (ADS)

    Podney, Walter N.

    1989-07-01

    Superconductive quantum interference devices (SQUIDS) offer new technology for locating materials flaws electromagnetically that promises to increase sensitivity, depth of magnetic flux enables use of microscopic pickup loops in a gradiometer configuration to give high resolution. A cryogenic umbilical connects pickup loops to a remote cryostat housing SQUID sensors to ease scanning. A pair of drive coils a few millimeters in radius that encircle pickup loops forming a coplanar gradiometer 1 mm or less in radius comprise a superconductive microprobe. It provides a depth of field of several millimeters to a 0.1 mm flaw in an aluminum plate, when operating with a drive current a 1 A oscillating at a frequency of 1kHz. Its field of view ranges to several millimeters, for flaws a few millimeters deep, and its horizontal resolution is 1 mm or so, for flaw depths out to its depth of field. An array of microprobes form receptors much like rods in the retina of a magnetic eye. The eye leads to an electromagnetic microscope for imaging internal flaws in aluminum plates. It gives multiple images that enable resolving depth of a 0.1 mm flaw to a few tenths of a millimeter with a horizontal resolution of one millimeter or so.

  19. Conductivity Profile Determination by Eddy Current for Shot Peened Superalloy Surfaces Toward Residual Stress Assessment

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    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.

  20. 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.

  1. Swept frequency eddy current material profiling using radial basis function neural networks for inversion

    SciTech Connect

    Katragadda, G.; Lewis, D.; Wallace, J.; Si, J.

    2000-01-01

    Traditional methods for inverting swept frequency or pulsed eddy current signals to get material information involve iterating with a forward model until the response from the model under the same excitation condition is as close to the measured signal as possible. Although the feasibility of the model based inversion has been demonstrated, the complexity of such procedures and the computational resources that this technique requires has hampered its widespread acceptance in industry. Recent approaches include using the look up tables for features extracted from the signals. The performance of look up table approach depends on the choice of the features extracted. The authors propose an innovative approach of using a neural network (NN) to solve this inversion problem. Although the use of NN for inverting uniform field eddy current data has been demonstrated, this is the first effort to investigate the feasibility of NN inversion of swept frequency and pulsed eddy current data for thickness measurements of metallic coatings of metal substrates. The authors previously reported initial results from this research. The current paper focuses on the PC based instrumentation and software developed for the swept frequency material profiler. Results of the NN based classification are summarized, and potential applications discussed.

  2. 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.

  3. Magnetic diagnostics for equilibrium reconstructions in the presence of nonaxisymmetric eddy current distributions in tokamaks (invited)

    SciTech Connect

    Berzak, L.; Jones, A. D.; Kaita, R.; Kozub, T.; Logan, N.; Majeski, R.; Menard, J.; Zakharov, L.

    2010-10-15

    The lithium tokamak experiment (LTX) is a modest-sized spherical tokamak (R{sub 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 deg. 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.

  4. Magnetic and transport eddy-current anomalies in cylinders owing to magnetization rotations

    NASA Astrophysics Data System (ADS)

    Chen, D.-X.; Pascual, L.

    2001-06-01

    For a magnetic conducting cylinder with a coaxial core, where the spontaneous magnetization Ms is helical, the technical magnetization under an axial AC magnetic field or AC transport current is carried out by Ms rotations, which induce normal and lateral eddy currents. The low-frequency eddy-current anomaly factors for the magnetic and the transport case, η, are calculated as functions of the radius ratio of the core to the cylinder, p= rb/ r0, the scalar susceptibility of the shell normalized to the normal susceptibility of the core, q= χs/ χzz or χs/ χφφ, and the helical angle with respect to the z-axis, α. It is shown that for the typical case of α= π/4, the lateral-eddy-current loss is appreciably less and greater than the normal one in the magnetic and transport case, respectively, which is in contrast to the situation of a slab where both losses are equal.

  5. Rotating field eddy current probe for characterization of cracking in non-magnetic tubing

    SciTech Connect

    Capobianco, T.E.

    1998-07-01

    A rotating field eddy current probe was built and tested for use in small diameter, non-magnetic tubing. The rotating field probe is a driver/pickup style with two orthogonally wound drive coils and a pancake pickup coil. The driver coils are excited by two sine waves 90{degree} out of phase with each other. The physical arrangement of the drive coils and the 90{degree} phase shift of the excitation waveforms creates a field which rotates in the test piece under the drive coils. Preliminary tests on electrical discharge machined (EDM) notches show that phased based estimates of notch depth are possible. Probes currently used for detection of cracks in tubing produce responses that have proven unreliable for estimating defect depths. This recently developed version of the rotating field eddy current probe produces a bipolar response in the presence of a crack or a notch. Typically, the phase angle of a bipolar eddy current response is easily identified and measured and is used extensively for estimating depths of volumetric defects. Data are shown relating the phase angle of the rotating field probe`s bipolar response to the depth of circumferential EDM notches.

  6. 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.

  7. 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.

  8. 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

  9. Preliminary results on passive eddy current damper technology for SSME turbomachinery

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1985-01-01

    Some preliminary results have been obtained for the dynamic response of a rotor operating over a speed range of 800 to 10,000 rpm. Amplitude frequency plots show the lateral vibratory response of an unbalanced rotor with and without external damping. The mode of damping is by means of eddy currents generated with 4 c shaped permanent magnets installed at the lower bearing of a vertically oriented rotor. The lower ball bearing and its damper assembly are totally immersed in liquid nitrogen at a temperature of -197 deg C (-320 deg F). These preliminary results for a referenced or base line passive eddy current damper assembly show that the amplitude of synchronous vibration is reduced at the resonant frequency. Measured damping coefficients were calculated to phi = .086; this compares with a theoretically calculated value of phi = .079.

  10. 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

  11. 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.

  12. 3-D Magnetic Field Analysis of Permanent Magnet Motor Considering Magnetizing, Demagnetizing and Eddy Current Loss

    NASA Astrophysics Data System (ADS)

    Miyata, Koji; Aoyama, Yasuaki; Yokoyama, Tomonori; Ohashi, Ken; Kondo, Minoru; Matsuoka, Koichi

    Rare-earth magnets, which have high energy product, have been widely used in several industrial applications such as voice coil motors for hard disk drives, MRI for medical devices and motors for electric vehicle. In order to realize a small and high performance device, the magnetic field analysis techniques are required. In this paper, we applied the magnetic field analysis to design the permanent magnet synchronous motors into the rail traction system. In the inverter fed motor drive, the eddy current loss in the permanent magnet increased. We simulated the effect that eddy current was decreased by using a divided permanent magnet. Furthermore, the permanent magnet tends to be demagnetized due to the effect of a demagnetizing field formed at high temperatures. However, according to our analysis, demagnetization does not occur within the range of our design specifications. Also, we performed magnetic field analysis assuming a pulse-type magnetization process and designed an optimal magnetizing coil.

  13. 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.

  14. Analysis of eddy current distributions in the CMS magnet yoke during the solenoid discharge

    SciTech Connect

    Klyukhin, V.I.; Campi, D.; Cure, B.; Gaddi, A.; Gerwig, H.; Grillet, J.P.; Herve, A.; Loveless, R.; Smith, R.P.; /Fermilab

    2005-01-01

    Flux loops have been installed on selected segments of the magnetic flux return yoke of the 4 T superconducting coil of the Compact Muon Solenoid (CMS) detector under construction at CERN. Voltages induced in the loops during discharge of the solenoid will be sampled on-line during the entire discharge and integrated off-line to provide a measurement of the initial magnetic flux density in steel at the maximum field to an accuracy of a few percent. Although the discharge of the solenoid is rather slow (190 s time constant), the influence of eddy currents induced in the yoke elements should be estimated. The calculation of eddy currents is performed with Vector Fields program ELEKTRA. The results of calculations are reported.

  15. 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

    2016-01-01

    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

  16. Comparison of two modeling approaches of eddy current industrial non-destructive testing of steel pipes

    NASA Astrophysics Data System (ADS)

    Trillon, Adrien; Deneuville, François; Reboud, Christophe; Foucher, Fabrice; Lesselier, Dominique; Maurice, Lea

    2014-02-01

    In the framework of the COFREND working group "Eddy current modeling", a benchmark has been proposed by the Vallourec research center. This case corresponds to the modeling of an industrial online testing of seamless steel pipes by eddy current method with encircling coils. The centering of the steel pipe in the coil is not considered as perfect and a shift is imposed to the pipe. For this benchmark, the Vallourec research center (VRA, Vallourec Research Aulnoye) has compared two solutions with different approaches: the first one is based on semi-analytical methods through the CIVA software developed by the CEA, the second one on finite element method through the software Flux. Results for these two approaches are very similar between them and coherent to experimental data. It proves that these two simulations methods are valid and could be used as a complementary approach.

  17. Pulsed eddy-current inspection of thin-walled stainless steel tubing

    SciTech Connect

    Dodd, C.V.; Koerner, D.W.; Deeds, W.E.; Pickett, C.A.

    1987-09-01

    A pulsed eddy-current system has been developed for production inspection of small, thin-wall, non-ferromagnetic tubing. To detect and accurately size both outer and bore-side flaws required an operating frequency higher than available from present commercial equipment. A pulsed eddy-current instrument was designed and constructed that used 3.2 MHz square waves, with a bandwidth of 20 MHz. The system is able to reliably detect flaws as small as 0.015 mm (0.6 mils) on either the inner or outer surface of the tube. A computer controls the scanning of the tube, as recording, analyzing, and plotting the data. The computer programs and instrument details are given in the report.

  18. Anisotropic grain noise in eddy current inspection of noncubic polycrystalline metals

    NASA Astrophysics Data System (ADS)

    Blodgett, Mark; Nagy, Peter B.

    1998-03-01

    This letter discusses the role electrical anisotropy plays in the structural integrity assessment of polycrystalline titanium alloys from the standpoint of fatigue crack detection and the related issue of microstructural noise. In eddy current inspection of noncubic crystallographic classes of polycrystalline metals the electric anisotropy of individual grains produces an inherent microstructural variation or noise that is very similar to the well-known acoustic noise produced by the elastic anisotropy of both cubic and noncubic materials in ultrasonic characterization. The presented results demonstrate that although the electrical grain noise is clearly detrimental in eddy current nondestructive testing for small flaws, it can be also exploited for characterization of the microstructure in noncubic polycrystalline materials such as titanium alloys in the same way acoustic grain noise is used for ultrasonic characterization of the microstructure in different materials.

  19. Design of Diaphragm and Coil for Stable Performance of an Eddy Current Type Pressure Sensor.

    PubMed

    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

  20. Logarithmic analysis of eddy current thermography based on longitudinal heat conduction for subsurface defect evaluation

    NASA Astrophysics Data System (ADS)

    Yang, Ruizhen; He, Yunze

    2014-11-01

    Longitudinal heat conduction from surface to inside of solid material could be used to evaluate the subsurface defects. Considering that the skin depth of high frequency eddy current in metal is quite small, this paper proposed logarithmic analysis of eddy current thermography (ECT) to quantify the depth of subsurface defects. The proposed method was verified through numerical and experimental studies. In numerical study, ferromagnetic material and non-ferromagnetic material were both considered. Results showed that the temperature-time curve in the logarithm domain could be used to detect subsurface defects. Separation time was defined as the characteristic feature to measure the defect's depth based on their linear relationships. The thermograms reconstructed by logarithm of temperature can improve defect detectability.

  1. 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. PMID:23387673

  2. Pulsed remote eddy current field array technique for nondestructive inspection of ferromagnetic tube

    NASA Astrophysics Data System (ADS)

    Yang, Binfeng; Li, Xuechao

    2010-03-01

    One pick-up coil with a large inner diameter is usually used in pulsed remote field eddy current technique, which decreases the identification ability to defect. With the purpose of overcoming this problem, array pulsed remote field eddy current technique is proposed to enhance the precision in quantification of defect. The finite element method is used to optimise the structure of probe and analyse of the influence effect of response signal with the variation of the defect depths. The results of experimental work confirm that the array pulsed remote field technique has the advantages of high precision and sensitivity, which can be used as an effective method for quantification of defect in tube.

  3. Modeling of thin structures in eddy current testing with shell elements

    NASA Astrophysics Data System (ADS)

    Ospina, A.; Santandrea, L.; Le Bihan, Y.; Marchand, C.

    2010-11-01

    The modeling and design of eddy currents sensors for non-destructive testing applications, generally, requires numerical methods. Among these methods, the finite element method is one of the most used. Indeed, it presents a great capability to treat a large variety of configurations. However, in the study of eddy current testing problems, the existence of structures that have a geometrical dimension smaller than the others (thin air gaps, coatings...) will lead to difficulties related to the meshing process. The introduction of particular elements such as shell elements allows to simplify the modeling of these problems. In this paper, the shell elements are used in two different 2D axisymmetric formulations, the electric formulation a* and the magnetic formulation t-ϕ in order to simulate the behaviour of the electromagnetic fields. The results obtained with the two formulations are compared with analytical solutions.

  4. 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.

  5. 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.

  6. 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.

  7. Iron yoke eddy current induced losses with application to the ALS septum magnets

    SciTech Connect

    Schlueter, R.D.

    1991-08-16

    The theoretical development of relations governing the eddy current induced losses in iron electromagnet yokes is reviewed. A baseline laminated electromagnet design is analyzed and a parametric study illustrates the sensitivity of core losses to perturbations of various geometrical, material, and excitation parameters. Core losses and field gradients for the ALS septum magnets are calculated. Design modifications capable of eliminating transverse and longitudinal field gradients are discussed.

  8. 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.

  9. [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. PMID:17598478

  10. Quality Assessment of Refractory Protective Coatings Using Multi-Frequency Eddy Current MWM-Arrays

    SciTech Connect

    Zilberstein, Vladimir; Evans, Leslie; Huguenin, Carolene; Grundy, David; Lyons, Robert; Goldfine, Neil; Mulligan, Christopher

    2006-03-06

    Demands for increased range, rate of fire, and muzzle velocity have prompted development of new refractory metal coatings. Nondestructive measurement of coating electrical conductivity and thickness is crucial to the process development and statistical process control. This paper presents absolute property coating characterization results for Ta coatings obtained with a Meandering Winding Magnetometer (MWM registered ) eddy-current sensor and MWM-Array sensor. The measured coating conductivity indicates the ratio of the intended {alpha}-Ta to the undesirable {beta}-Ta.

  11. 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

  12. Compensation for the eddy current effect in the APS storage ring vacuum chamber

    SciTech Connect

    Chung, Y.

    1990-05-30

    The amplitude attenuation and the phase shift of the correction magnet field inside the APS storage ring vacuum chamber due to the eddy current effect were measured. A circuit to compensate for this effect was then inserted between the signal source and the magnet power supply. The amplitude was restored with an error of less than 20% of the source signal amplitude and the phase shift was reduced from 80{degrees} to 12{degrees} at 10 Hz.

  13. 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.

  14. 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.

  15. Recent advances in modeling discontinuities in anisotropic and heterogeneous materials in eddy current NDE

    SciTech Connect

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

    2011-06-23

    Recent advances are presented to model discontinuities in random anisotropies that arise in certain materials, such as titanium alloys. A numerical model is developed to provide a full anisotropic representation of each crystalline in a gridded region of the material. Several simulated and experimental demonstrations are presented highlighting the effect of grain noise on eddy current measurements. Agreement between VIC-3D(c) model calculations and experimental data in titanium alloy specimens with known flaws is demonstrated.

  16. Effects of bending stresses and tube curvature on remote field eddy current signals

    SciTech Connect

    Sutherland, J.; Atherton, D.L.

    1997-01-01

    The effects of bending stresses and tube curvature on remote field eddy current signals were investigated. This technique is a recognized method for the nondestructive evaluation of ferromagnetic tubing, as used in heat exchangers and boiler systems. Different stress states were examined (elastic stress, plastic deformation, and residual stress) and found to give distinctive behavior. Elastic and residual stresses can appear as wall loss, depending on the operating frequency and baseline used for inspection and interpretation.

  17. Model Development for Broadband Spiral-Coil Eddy-Current Probes

    NASA Astrophysics Data System (ADS)

    Murphy, R. Kim; Sabbagh, Harold A.; Sabbagh, Elias H.; Blodgett, Mark P.; Knopp, Jeremy; Aldrin, John C.

    2009-03-01

    In this paper we demonstrate how the volume-integral algorithm of VIC-3D© can be applied to develop a computer code to design spiral-coil eddy-current probes for optimal broadband performance. This code will allow the designer to predict probe performance as a function of frequency, and is applied to model problems covering the frequency range of 107 to 1012 Hz.

  18. Comparative Analysis of Selected Eddy Current Transducers for Titanium Alloy Evaluation

    NASA Astrophysics Data System (ADS)

    Chady, T.; Sikora, R.; Baniukiewicz, P.; Lopato, P.; Kowalczyk, J.; Psuj, G.; Caryk, M.

    2010-02-01

    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.

  19. 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..

  20. FIONDA (Filtering Images of Niobium Disks Application): Filter application for Eddy Current Scanner data analysis

    SciTech Connect

    Boffo, C.; Bauer, P.; /Fermilab

    2005-05-01

    As part of the material QC process, each Niobium disk from which a superconducting RF cavity is built must undergo an eddy current scan [1]. This process allows to discover embedded defects in the material that are not visible to the naked eye because too small or under the surface. Moreover, during the production process of SC cavities the outer layer of Nb is removed via chemical or electro-chemical etching, thus it is important to evaluate the quality of the subsurface layer (in the order of 100nm) where superconductivity will happen. The reference eddy current scanning machine is operated at DESY; at Fermilab we are using the SNS eddy current scanner on loan, courtesy of SNS. In the past year, several upgrades were implemented aiming at raising the SNS machine performance to that of the DESY reference machine [2]. As part of this effort an algorithm that enables the filtering of the results of the scans and thus improves the resolution of the process was developed. The description of the algorithm and of the software used to filter the scan results is presented in this note.

  1. Eddy Current for Sizing Cracks in Canisters for Dry Storage of Used Nuclear Fuel

    SciTech Connect

    Meyer, Ryan M.; Jones, Anthony M.; Pardini, Allan F.

    2014-01-01

    The storage of used nuclear fuel (UNF) in dry canister storage systems (DCSSs) at Independent Spent Fuel Storage Installations (ISFSI) sites is a temporary measure to accommodate UNF inventory until it can be reprocessed or transferred to a repository for permanent disposal. Policy uncertainty surrounding the long-term management of UNF indicates that DCSSs will need to store UNF for much longer periods than originally envisioned. Meanwhile, the structural and leak-tight integrity of DCSSs must not be compromised. The eddy current technique is presented as a potential tool for inspecting the outer surfaces of DCSS canisters for degradation, particularly atmospheric stress corrosion cracking (SCC). Results are presented that demonstrate that eddy current can detect flaws that cannot be detected reliably using standard visual techniques. In addition, simulations are performed to explore the best parameters of a pancake coil probe for sizing of SCC flaws in DCSS canisters and to identify features in frequency sweep curves that may potentially be useful for facilitating accurate depth sizing of atmospheric SCC flaws from eddy current measurements.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Piezoresistive Effect for Near-Surface Eddy Current Residual Stress Assessment

    SciTech Connect

    Yu, F.; Nagy, P.B.

    2005-04-09

    This paper discusses the relationship between isothermal and adiabatic piezoresistive properties of metals. The piezoresistive effect, i.e., stress-dependence of the electrical resistivity, can be exploited for nondestructive residual stress assessment using eddy current measurements. First, the paper establishes the relationship between the familiar isothermal piezoresistivity coefficients measured under uniaxial tension and hydrostatic pressure and the relevant isothermal electroelastic coefficients measured under uniaxial and biaxial stress conditions either by non-directional circular or directional elliptical eddy current coils. In order to quantitatively assess the prevailing residual stress from eddy current conductivity measurements, the electroelastic coefficients must be first determined. These calibration measurements are usually conducted on a reference specimen of the material to be tested using cyclic uniaxial loads between 0.1 and 10 Hz, which is fast enough to produce adiabatic conditions. It is demonstrated that in high-conductivity metals such calibration measurements must be corrected for the thermoelastic effect, which is always positive, i.e., it increases the conductivity in tension, when the material cools down, and reduces it in compression, when the material heats up.

  7. 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.

  8. Application of Resonant Frequency Eddy Current Technique on a Shot-Peened Nickel-Based Engine-Grade Material

    SciTech Connect

    Ko, Ray T.; Sathish, Shamachary; Boehnlein, Thomas R.; Blodgett, Mark P.

    2007-03-21

    The shot peening conditions of a nickel-based engine-grade material were evaluated using a novel eddy current measurement technique. With this technique, the shift of a resonant frequency was found to be dependent on variables which also affect conventional eddy current testing. The cable effect is another important variable, which is often neglected in a routine eddy current testing, is also discussed. Experimental results showed that at high frequencies, the shot peening conditions were easily distinguishable using this frequency shift technique.

  9. Detecting second-layer fatigue cracks under installed skins and fasteners with low-frequency eddy current array

    NASA Astrophysics Data System (ADS)

    Hill, Brian; Sheppard, William

    1992-12-01

    A low-frequency eddy current array (LFECA) inspection system has been developed for the F/A-18 Hornet program. The LFECA system is designed for use on composite or titanium first layer skins installed over aluminum substructures and differs substantially from conventional eddy current equipment. The discussion covers a general description of the current F/A-18 LFECA system, compensation algorithms, and LFECA response to second-layer fatigue cracks.

  10. Ultrasonic flowmetering with reflected pulses

    NASA Astrophysics Data System (ADS)

    Hoyle, D. C.; Glicksman, L. R.; Peterson, C. R.

    1984-09-01

    Consolidated Edison of New York City has expressed the need for a new gasmeter for accurately monitoring large diameter interdistrict gas transmission lines for loss due to theft or leakage. A research effort aimed at developing a new flowmeter for Con Edison is described. The new flowmeter uses ultrasonic flowmetering technology in a novel way to meet Con Edison's four major design specifications: the flowmeter should be accurate to 0.5 percent of totalized flow over one year, it should be much simpler to install than a conventional flowmeter, essentially meaning that excavation be limited to that necessary to expose the upper surface of a buried main; its installation must not require service shutdown; and, the flowmeter should not require zero-flow calibration once installed in the gas main.

  11. 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/2012PhDT........82P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........82P"><span id="translatedtitle">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://hdl.handle.net/2060/19810017865','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810017865"><span id="translatedtitle">Automatic <span class="hlt">flowmeter</span> calibration system</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lisle, R. V.; Wilson, T. L. (Inventor)</p> <p>1981-01-01</p> <p>A system for automatically calibrating the accuracy of a <span class="hlt">flowmeter</span> is described. The system includes a calculator capable of performing mathematical functions responsive to receiving data signals and function command signals. A prover cylinder is provided for measuring the temperature, pressure, and time required for accumulating a predetermined volume of fluid. Along with these signals, signals representing the temperature and pressure of the fluid going into the meter are fed to a plurality of data registers. Under control of a progress controller, the data registers are read out and the information is fed through a data select circuit to the calculator. Command signals are also produced by a function select circuit and are fed to the calculator set indicating the desired function to be performed. The reading is then compared with the reading produced by the <span class="hlt">flowmeter</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1211..361G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1211..361G"><span id="translatedtitle">Development of a Field Concentrator Coil by Finite Element Modeling for Power Efficiency Optimization in <span class="hlt">Eddy</span> <span class="hlt">Current</span> Thermography Inspection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grenier, M.; Ibarra-Castanedo, C.; Luneau, F.; Bendada, H.; Maldague, X.</p> <p>2010-02-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> thermography is a relatively new inspection technique that takes advantage of the electromagnetic induction phenomenon to generate heat in electro conductive materials during inspection. An interesting advantage of <span class="hlt">eddy</span> <span class="hlt">current</span> heating compared to classical optical or ultrasonic heating is that the excitation source is smaller and can be conveniently shaped in order to provide energy efficient localized heating. Such excitation source is more suitable for the development of portable instruments and to perform field inspections. In this paper, finite element modeling (FEM) is used to optimize the <span class="hlt">eddy</span> <span class="hlt">current</span> coil configuration in terms of heating power efficiency. The performances of air-core coils, normally used in <span class="hlt">eddy</span> <span class="hlt">current</span> thermography, and a new field concentrator coil are compared and discussed. FEM results demonstrate that the proposed field concentrator coil improves the magnetic coupling with the inspected material and requires less energy than air-core coils to generate the same temperature variation.</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 id="translatedtitle">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('http://adsabs.harvard.edu/abs/2016AIPC.1706i0015H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706i0015H"><span id="translatedtitle">Numerical study on distribution law of magnetic field and temperature field around the crack induced by <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>He, Min; Zheng, Wenpei; Zhang, Laibin; Zhou, Fan</p> <p>2016-02-01</p> <p>Alternative <span class="hlt">current</span> field measurement (ACFM) and <span class="hlt">eddy</span> <span class="hlt">current</span> thermography are both induced by <span class="hlt">eddy</span> <span class="hlt">currents</span>, and it is a commonality between them. The commonality has laid a good foundation for the combination of the two testing techniques. In this paper, a numerical study on distribution law of magnetic field and temperature field around the crack using <span class="hlt">eddy</span> <span class="hlt">current</span> excitation is carried out. The feasibility of the combination of ACFM and <span class="hlt">eddy</span> <span class="hlt">current</span> thermography is discussed as well. A specimen made of ferromagnetic material is tested by a U-shaped inducer, and a semielliptical crack is built on the specimen. The distribution law of magnetic field and temperature field is both studied using the same <span class="hlt">eddy</span> <span class="hlt">current</span> excitation. The relationship between the crack size and distribution of magnetic field and temperature field is identified by altering the length and depth of the crack. Through comparisons, the magnetic distribution law around the crack in this paper is consistent with that of ACFM, and the maximum temperature difference around the crack meets the inspection requirement of a thermal imager. These findings might make it possible to eventually combine ACFM and <span class="hlt">eddy</span> <span class="hlt">current</span> thermography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009OcSci...5..173B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009OcSci...5..173B"><span id="translatedtitle">Evaluating two numerical advection schemes in HYCOM for <span class="hlt">eddy</span>-resolving modelling of the Agulhas <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>Backeberg, B. C.; Bertino, L.; Johannessen, J. A.</p> <p>2009-06-01</p> <p>A 4th order advection scheme is applied in a nested <span class="hlt">eddy</span>-resolving Hybrid Coordinate Ocean Model (HYCOM) of the greater Agulhas <span class="hlt">Current</span> system for the purpose of testing advanced numerics as a means for improving the model simulation for eventual operational implementation. Model validation techniques comparing sea surface height variations, sea level skewness and variogram analyses to satellite altimetry measurements quantify that generally the 4th order advection scheme improves the realism of the model simulation. The most striking improvement over the standard 2nd order momentum advection scheme, is that the southern Agulhas <span class="hlt">Current</span> is simulated as a well-defined meandering <span class="hlt">current</span>, rather than a train of successive <span class="hlt">eddies</span>. A better vertical structure and stronger poleward transports in the Agulhas <span class="hlt">Current</span> core contribute toward a better southwestward penetration of the <span class="hlt">current</span>, and its temperature field, implying a stronger Indo-Atlantic inter-ocean exchange. It is found that the transport, and hence this exchange, is sensitive to the occurrences of mesoscale features originating upstream in the Mozambique Channel and southern East Madagascar <span class="hlt">Current</span>, and that the improved HYCOM simulation is well suited for further studies of these inter-actions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009OcScD...6..429B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009OcScD...6..429B"><span id="translatedtitle">Evaluating two numerical advection schemes in HYCOM for <span class="hlt">eddy</span>-resolving modelling of the Agulhas <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>Backeberg, B. C.; Bertino, L.; Johannessen, J. A.</p> <p>2009-02-01</p> <p>A 4th order advection scheme is applied in a nested <span class="hlt">eddy</span>-resolving Hybrid Coordinate Ocean Model (HYCOM) of the greater Agulhas <span class="hlt">Current</span> system for the purpose of testing advanced numerics as a means for improving the model simulation for eventual operational implementation. Model validation techniques comparing sea surface height variations, sea level skewness and variogram analyses to satellite altimetry measurements quantify that generally the 4th order advection scheme improves the realism of the model simulation. The most striking improvement over the standard 2nd order momentum advection scheme, is that the Southern Agulhas <span class="hlt">Current</span> is simulated as a well-defined meandering <span class="hlt">current</span>, rather than a train of successive <span class="hlt">eddies</span>. A better vertical structure and stronger poleward transports in the Agulhas <span class="hlt">Current</span> core contribute toward a better southwestward penetration of the <span class="hlt">current</span>, and its temperature field, implying a stronger Indo-Atlantic inter-ocean exchange. It is found that the transport, and hence this exchange, is sensitive to the occurrences of mesoscale features originating upstream in the Mozambique Channel and Southern East Madagascar <span class="hlt">Current</span>, and that the improved HYCOM simulation is well suited for further studies of these inter-actions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890004389','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890004389"><span id="translatedtitle"><span class="hlt">Flowmeter</span> evaluation for on-orbit operations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baird, R. S.</p> <p>1988-01-01</p> <p>Various <span class="hlt">flowmetering</span> concepts were flow tested to characterize the relative capabilities and limitations for on-orbit fluid-transfer operations. Performance results and basic operating principles of each <span class="hlt">flowmetering</span> concept tested are summarized, and basic considerations required to select the best <span class="hlt">flowmeter(s</span>) for fluid system application are discussed. Concepts tested were clamp-on ultrasonic, area averaging ultrasonic, offset ultrasonic, coriolis mass, vortex shedding, universal venturi tube, turbine, bearingless turbine, turbine/turbine differential-pressure hybrid, dragbody, and dragbody/turbine hybrid <span class="hlt">flowmeters</span>. Fluid system <span class="hlt">flowmeter</span> selection considerations discussed are <span class="hlt">flowmeter</span> performance, fluid operating conditions, systems operating environments, <span class="hlt">flowmeter</span> packaging, <span class="hlt">flowmeter</span> maintenance, and <span class="hlt">flowmeter</span> technology. No one <span class="hlt">flowmetering</span> concept tested was shown to be best for all on-orbit fluid systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988STIN...8913760B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988STIN...8913760B&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Flowmeter</span> evaluation for on-orbit operations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baird, R. S.</p> <p>1988-08-01</p> <p>Various <span class="hlt">flowmetering</span> concepts were flow tested to characterize the relative capabilities and limitations for on-orbit fluid-transfer operations. Performance results and basic operating principles of each <span class="hlt">flowmetering</span> concept tested are summarized, and basic considerations required to select the best <span class="hlt">flowmeter(s</span>) for fluid system application are discussed. Concepts tested were clamp-on ultrasonic, area averaging ultrasonic, offset ultrasonic, coriolis mass, vortex shedding, universal venturi tube, turbine, bearingless turbine, turbine/turbine differential-pressure hybrid, dragbody, and dragbody/turbine hybrid <span class="hlt">flowmeters</span>. Fluid system <span class="hlt">flowmeter</span> selection considerations discussed are <span class="hlt">flowmeter</span> performance, fluid operating conditions, systems operating environments, <span class="hlt">flowmeter</span> packaging, <span class="hlt">flowmeter</span> maintenance, and <span class="hlt">flowmeter</span> technology. No one <span class="hlt">flowmetering</span> concept tested was shown to be best for all on-orbit fluid systems.</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_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" 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_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> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20632898','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20632898"><span id="translatedtitle">Characterization of Retrogression and Re-Aging Heat Treatment of AA7075-T6 Using Nonlinear Acoustics and <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>Ananthula, Rajeshwar; Ko, Ray T.; Sathish, Shamachary; Blodgett, Mark</p> <p>2004-02-26</p> <p>Nonlinear acoustic parameter and <span class="hlt">eddy</span> <span class="hlt">current</span> 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 <span class="hlt">eddy</span> <span class="hlt">current</span> signal shows a minimum at 42 minutes of retrogression time. Application of combined methods for identifying the optimized properties in the material is discussed.</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 id="translatedtitle">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('http://www.ncbi.nlm.nih.gov/pubmed/26329187','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26329187"><span id="translatedtitle">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="http://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. PMID:26329187</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RScI...86h3502L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RScI...86h3502L"><span id="translatedtitle">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="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</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://www.osti.gov/scitech/servlets/purl/862838','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862838"><span id="translatedtitle"><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/2015EGUGA..1712816A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712816A"><span id="translatedtitle">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('http://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2528Continental%2Bshelf%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3D%2528Continental%2Bshelf%2529"><span id="translatedtitle">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/2008PPCF...50h5004P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PPCF...50h5004P"><span id="translatedtitle">Linearly perturbed MHD equilibria and 3D <span class="hlt">eddy</span> <span class="hlt">current</span> coupling via the control surface method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Portone, A.; Villone, F.; Liu, Y.; Albanese, R.; Rubinacci, G.</p> <p>2008-08-01</p> <p>In this paper, a coupling strategy based on the control surface concept is used to self-consistently couple linear MHD solvers to 3D codes for the <span class="hlt">eddy</span> <span class="hlt">current</span> computation of <span class="hlt">eddy</span> <span class="hlt">currents</span> in the metallic structures surrounding the plasma. The coupling is performed by assuming that the plasma inertia (and, with it, all Alfven wave-like phenomena) can be neglected on the time scale of interest, which is dictated by the relevant electromagnetic time of the metallic structures. As is shown, plasma coupling with the metallic structures results in perturbations to the inductance matrix operator. In particular, by adopting the Fourier decomposition in poloidal and toroidal modes, it turns out that each toroidal mode can be associated with a matrix (additively) perturbing the inductance matrix that commonly describes the magnetic coupling of <span class="hlt">currents</span> in vacuum. In this way, the treatment of resistive wall modes instabilities of various toroidal mode numbers and their possible cross-talk through the <span class="hlt">currents</span> induced in the metallic structures can be easily studied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1511..761L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1511..761L"><span id="translatedtitle">Numerical analysis of angular defects in bent plates using tone burst <span class="hlt">eddy-current</span> thermography (TBET)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Libin, M. N.; Balasubramaniam, Krishnan; Maxfield, B. W.</p> <p>2013-01-01</p> <p>Tone Burst <span class="hlt">Eddy</span> <span class="hlt">current</span> Thermography (TBET) is a new hybrid, non-contacting, Non-Destructive Evaluation (NDT) method which employs a combination of Pulsed <span class="hlt">Eddy</span> <span class="hlt">current</span> Thermography (PEC) and Thermographic Non-Destructive Evaluation (TNDE). For understanding angular cracks, fundamental knowledge about the induced <span class="hlt">current</span> density distribution in the component under test is required. Further, this information enables us to find the amount of heat produced at those locations and how it diffuses to the surface. This paper describes simulation work done for cracks set at an angle to the surface in flat and bent aluminum plates. The investigation is implemented by the simulating transient thermal distribution for 2D angular cracks via finite element package COMSOL multi-physics with AC/DC module and general heat transfer. At crack edges, induced <span class="hlt">current</span> is seen concentrated thus indicating a localized high heating in those areas relative to other regions. A numerical study was also carried out by varying parameters like crack angle (0°, 22.5°, 45°, 67.5°) and crack length (0.6mm, 1.2mm, 1.8mm) the transient thermal distributions were compared for different plate bend angles (180°, 120°, 90°, 60°, 30°). TBET method was found well suited for the detection of service induced cracks, usually caused by either rolling contact fatigue or stress corrosion, with a high degree of sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/496665','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/496665"><span id="translatedtitle">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/634112','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/634112"><span id="translatedtitle">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('http://www.ncbi.nlm.nih.gov/pubmed/2811760','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/2811760"><span id="translatedtitle"><span class="hlt">Eddy</span> <span class="hlt">current</span> disruption: effect on nuclear magnetic resonance coil impedance and power loss.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harpen, M D</p> <p>1989-01-01</p> <p>We present a theoretical development and experimental verification of a description of power loss and sample resistance for a lossy sample in a nuclear magnetic resonance radio frequency coil for a sample geometry where the <span class="hlt">eddy</span> <span class="hlt">current</span> streamlines are disrupted from their usually assumed circular paths. Specifically treated is the case of a lossy hemisphere. The problem is solved for two orientations; with the induction parallel and perpendicular to the flat surface of the hemisphere. Results of this analysis as well as those for the full sphere as presented by Hoult and Lauterbur are compared with observation for a variety of sample conductivities and orientation. PMID:2811760</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AmJPh..80..804M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AmJPh..80..804M"><span id="translatedtitle">Quantitative analysis of the damping of magnet oscillations by <span class="hlt">eddy</span> <span class="hlt">currents</span> in aluminum foil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muiznieks, Andris; Dudareva, Inese</p> <p>2012-09-01</p> <p>This paper considers damped rotational oscillations about the vertical axis of a cylindrical permanent magnet that is horizontally suspended by a vertical inelastic thread. The damping of the oscillations is caused by <span class="hlt">eddy</span> <span class="hlt">currents</span> induced in aluminum foil that is placed horizontally below the magnet. A simplified mathematical model of the damped oscillations is proposed and verified by experiment qualitatively and quantitatively. It is shown that the relative energy loss during one oscillation depends linearly on the number of layers of aluminum foil and on the oscillation period. To measure the relative changes of the oscillation amplitude, a magnetic field sensor and data collection interface are used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/18003302','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/18003302"><span id="translatedtitle">In vitro investigation of <span class="hlt">eddy</span> <span class="hlt">current</span> effect on pacemaker operation generated by low frequency magnetic field.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Babouri, A; Hedjeidj, A</p> <p>2007-01-01</p> <p>This paper presents in vitro investigation of the <span class="hlt">eddy</span> <span class="hlt">current</span> induction effects to the cardiac pacemaker exposed to low frequency magnetic fields. The method used in this study is based to the interaction by inductive coupling through the loop formed by the pacemaker and its leads and the surrounding medium. This interaction results in an induced electromotive force between the terminals of the pacemaker which can potentially disturb the operation of this last. In this article we present experimental results, analytical calculations and numerical simulations using the finite element method. PMID:18003302</p> </li> <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 id="translatedtitle"><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://hdl.handle.net/2060/20150012191','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150012191"><span id="translatedtitle"><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://hdl.handle.net/2060/19840008494','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008494"><span id="translatedtitle">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.osti.gov/scitech/servlets/purl/10123845','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10123845"><span id="translatedtitle">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://adsabs.harvard.edu/abs/2016AIPC.1706b0025P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706b0025P"><span id="translatedtitle">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/2012AmJPh..80..800T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AmJPh..80..800T"><span id="translatedtitle">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> </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/2009AIPC.1096..766C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096..766C"><span id="translatedtitle">Tube Support Plate Blockage Evaluation with Televisual Examination and <span class="hlt">Eddy</span> <span class="hlt">Current</span> Analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Châtellier, L.; Stindel, M.; Devinck, J. M.; Chavigny, F.; De Bouvier, O.</p> <p>2009-03-01</p> <p>In some steam generators with broached tube support plates (TSP), water-holes were observed to be clogged. This phenomenon can cause U-bend instability. The challenge is to estimate the average blockage level for each TSP in order to conduct the safety studies based on thermal-hydraulic models. This estimation is also necessary to plan maintenance operation (chemical cleaning) and follow the phenomenon after cleaning. This paper presents the technique used by EDF so as to estimate TSP blockage. The method relies on the association of visual inspection of the upper TSP and <span class="hlt">eddy</span> <span class="hlt">current</span> signal analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950070376&hterms=Eddy+Current&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEddy%2BCurrent','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950070376&hterms=Eddy+Current&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEddy%2BCurrent"><span id="translatedtitle"><span class="hlt">Eddy-Current</span> Detection Of Cracks In Reinforced Carbon/Carbon</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Christensen, Scott V.; Koshti, Ajay M.</p> <p>1995-01-01</p> <p>Investigations of failures of components made of reinforced carbon/carbon show <span class="hlt">eddy-current</span> flaw-detection techniques applicable to these components. Investigation focused on space shuttle parts, but applicable to other parts made of carbon/carbon materials. Techniques reveal cracks, too small to be detected visually, in carbon/carbon matrix substrates and in silicon carbide coates on substrates. Also reveals delaminations in carbon/carbon matrices. Used to characterize extents and locations of discontinuities in substrates in situations in which ultrasonic techniques and destructive techniques not practical.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19990049275&hterms=EDM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEDM','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19990049275&hterms=EDM&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DEDM"><span id="translatedtitle">Evaluation of the Self-Nulling Rotating <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probe System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hagemaier, Don; Rengel, Kent; Wincheski, Buzz; Namkung, Min</p> <p>1999-01-01</p> <p>In order to detect multi-site fatigue cracks located under flush-head rivets, automated <span class="hlt">eddy</span> <span class="hlt">current</span> equipment is required. To assure a reliable system, the <span class="hlt">eddy</span> <span class="hlt">current</span> probe must be centered easily over the installed rivets. To meet these requirements, the NDE Group at NASA LaRC developed the Self-Nulling Rotating <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probe System (SNRECPS) which will be referred to as RPS in this document. The system was evaluated at the FAA, NDI Validation Center, in Albuquerque, New Mexico. The system was capable of detecting a 0.032 inch long crack with a 90/95% PoD. Further evaluations were conducted at Boeing in Long Beach, California. These evaluations included fatigue cracks and notches in a range from 0.025 to 0.100 inch long under flush-head aluminum rivets, and titanium or steel flush-head fasteners. The results of these tests are reported herein. Subsequently, the system was loaned to the USAF Structures Laboratory for the purpose of detecting and measuring short cracks under flush-head rivets in a variety of fatigue test specimens. The inspection task was to detect and plot crack growth from numbered fasteners in lettered rows. In January, 1998, the system was taken to Northwest Airlines Maintenance Base, in Atlanta, to inspect a DC-9, for multi-site cracks in three circumferential splices. The aircraft had 83,000 cycles. The inspection was conducted at 30 kHz from longeron 5 left to longeron 5 right. The system was calibrated using a 0,030 EDM first layer notch. The instrument gain was set to 19 mV from the notch. The reject level was set at 10 mV and the unflawed fasteners yielded a signal amplitude of 2 to 3 mV. Only one fastener location, out of about 2,500 tested, yielded a signal of 58 mV. The rivet was removed and visually evaluated. It appeared to be a slight gouge in the counter-sink zone. No fatigue cracks were detected. The same fastener locations were also inspected using the Boeing MAUS system at 60 kHz. No cracks were detected. Thus far, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21260289','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21260289"><span id="translatedtitle"><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.ncbi.nlm.nih.gov/pubmed/26473871','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26473871"><span id="translatedtitle">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=pubmed">PubMed</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://www.osti.gov/scitech/biblio/40203853','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/40203853"><span id="translatedtitle">Laminated core modeling under rotational excitations including <span class="hlt">eddy</span> <span class="hlt">currents</span> and hysteresis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bottauscio, Oriano; Chiampi, Mario</p> <p>2001-06-01</p> <p>This article presents a numerical model for the electromagnetic analysis of hysteretic-laminated cores under rotational excitations. The computational approach is based on the finite element solution of a two-dimensional field magnetic problem in a homogeneous structure, where the skin effect due to macroscopic <span class="hlt">eddy</span> <span class="hlt">currents</span> in the lamination depth is included through a generalized dynamic constitutive relationship between B and H. The proposed model, after validation, is applied to the analysis of a laminated disk, evaluating the effects of the supply frequency and distorsion on power losses and B{endash}H loops. {copyright} 2001 American Institute of Physics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19334957','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19334957"><span id="translatedtitle">Highly sensitive anisotropic magnetoresistance magnetometer for <span class="hlt">Eddy-current</span> nondestructive evaluation.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, D F; Tachiki, M; Itozaki, H</p> <p>2009-03-01</p> <p>Using a commercially available anisotropic magnetoresistance (AMR) sensor of HMC1001, we developed a sensitive magnetometer. It could operate in amplifier mode or feedback mode. The magnetic field sensitivity of the AMR sensor was about 3.2 mV/V G. When the AMR sensor was biased by a voltage of 24 V, the magnetic field resolutions of the AMR magnetometer were about 12 pT/square root(Hz) at 1 kHz and 20 pT/square root(Hz) at 100 Hz. We used the AMR magnetometer for <span class="hlt">Eddy-current</span> nondestructive evaluation in unshielded environment. PMID:19334957</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21371028','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21371028"><span id="translatedtitle">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('http://www.osti.gov/scitech/biblio/20655378','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20655378"><span id="translatedtitle">Detecting Weld Zone Over Anticorrosion Painting by Rotating Uniform <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probe</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hoshikawa, H.; Koyama, K.; Naruse, Y.</p> <p>2005-04-09</p> <p>The authors have studied application of rotating uniform <span class="hlt">eddy</span> <span class="hlt">current</span> probe to detecting weld zone in steed material over anticorrosion painting. The probe detects not only weld position by the signal level but also weld direction by the signal phase. The experimental results have indicated that the probe provides a signal almost linear to its position with respect to weld zone center over the full width of weld. The signal of the probe is much less influenced by the painting thickness variation than that of the conventional differential pancake-coils probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21511638','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21511638"><span id="translatedtitle">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('http://hdl.handle.net/2060/19720008638','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720008638"><span id="translatedtitle">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://www.osti.gov/scitech/servlets/purl/993215','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993215"><span id="translatedtitle">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> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JCoPh.294..503A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JCoPh.294..503A"><span id="translatedtitle">Finite element simulation of <span class="hlt">eddy</span> <span class="hlt">current</span> problems using magnetic scalar potentials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alonso Rodríguez, Ana; Bertolazzi, Enrico; Ghiloni, Riccardo; Valli, Alberto</p> <p>2015-08-01</p> <p>We propose a new implementation of the finite element approximation of <span class="hlt">eddy</span> <span class="hlt">current</span> problems using, as the principal unknown, the magnetic field. In the non-conducting region a scalar magnetic potential is introduced. The method can deal automatically with any topological configuration of the conducting region and, being based on the search of a scalar magnetic potential in the non-conducting region, has the advantage of making use of a reduced number of unknowns. Several numerical tests are presented for illustrating the performance of the proposed method; in particular, the numerical simulation of a new type of transformer of complicated topological shape is shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21054963','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21054963"><span id="translatedtitle">Recent Advances in Simulation of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing of Tubes and Experimental Validations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Reboud, C.; Premel, D.; Bisiaux, B.</p> <p>2007-03-21</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> testing (ECT) is widely used in iron and steel industry for the inspection of tubes during manufacturing. A collaboration between CEA and the Vallourec Research Center led to the development of new numerical functionalities dedicated to the simulation of ECT of non-magnetic tubes by external probes. The achievement of experimental validations led us to the integration of these models into the CIVA platform. Modeling approach and validation results are discussed here. A new numerical scheme is also proposed in order to improve the accuracy of the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/14663858','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/14663858"><span id="translatedtitle">Inversion of thicknesses of multi-layered structures from <span class="hlt">eddy</span> <span class="hlt">current</span> testing measurements.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Ping-jie; Wu, Zhao-tong</p> <p>2004-01-01</p> <p>Luquire et al.'s impedance change model of a rectangular cross section probe coil above a structure with an arbitrary number of parallel layers was used to study the principle of measuring thicknesses of multi-layered structures in terms of <span class="hlt">eddy</span> <span class="hlt">current</span> testing voltage measurements. An experimental system for multi-layered thickness measurement was developed and several fitting models to formulate the relationships between detected impedance/voltage measurements and thickness are put forward using least square method. The determination of multi-layered thicknesses was investigated after inversing the voltage outputs of the detecting system. The best fitting and inversion models are presented. PMID:14663858</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MS%26E..116a2013D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MS%26E..116a2013D"><span id="translatedtitle"><span class="hlt">Eddy</span> <span class="hlt">Current</span> Defectoscope for Monitoring the Duralumin and Aluminum-Magnesium Alloys</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.; Dmitrieva, L.; Malikov, V.; Sagalakov, A.</p> <p>2016-02-01</p> <p>The system developed is based on an <span class="hlt">eddy-current</span> transducer of the transformer type, and is capable of inspecting plates made of duralumin and aluminum-magnesium alloys for defects. The measurement system supports absolute and differential control modes. The system was tested on a number of duralumin and aluminum-magnesium plates with internal flaws located as deep as 5 mm under the surface. The article provides data that demonstrates a link between the response time and the presence of defects in similar structures at a signal frequency of 1000 Hz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7033572','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/7033572"><span id="translatedtitle">Remote field <span class="hlt">eddy</span> <span class="hlt">current</span> defect interactions: Effects on the external field</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Atherton, D.L.; Czura, W.M.; Mackintosh, D.D. . Dept. of Physics)</p> <p>1994-11-01</p> <p>Finite element calculations for the remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) through-wall inspection technique show that metal loss on either the inside or the outside affect the exterior field as well as the interior transmitted remote field. In ferromagnetic tubes, wall thinning decreases attenuation and phase lag, as found experimentally. In the nonferromagnetic pipe modeled, attenuation decreased but wall thinning increase the phase lag. The exterior field changes are attributed to inner surface reflections of the field diffusing from the exterior to the interior of the pipe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20655364','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20655364"><span id="translatedtitle">Simplified Numerical Analysis of ECT Probe - <span class="hlt">Eddy</span> <span class="hlt">Current</span> Benchmark Problem 3</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sikora, R.; Chady, T.; Gratkowski, S.; Stawicki, K.</p> <p>2005-04-09</p> <p>In this paper a third <span class="hlt">eddy</span> <span class="hlt">current</span> benchmark problem is considered. The objective of the benchmark is to determine optimal operating frequency and size of the pancake coil designated for testing tubes made of Inconel. It can be achieved by maximization of the change in impedance of the coil due to a flaw. Approximation functions of the probe (coil) characteristic were developed and used in order to reduce number of required calculations. It results in significant speed up of the optimization process. An optimal testing frequency and size of the probe were achieved as a final result of the calculation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20632927','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20632927"><span id="translatedtitle"><span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing and Sizing of Deep Cracks in a Thick Structure</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Huang, H.; Endo, H.; Uchimoto, T.; Takagi, T.; Nishimizu, A.; Koike, M.; Matsui, T.</p> <p>2004-02-26</p> <p>Due to the skin effect of <span class="hlt">eddy</span> <span class="hlt">current</span> testing, target of ECT restricts to thin structure such as steam generator tubes with 1.27mm thickness. Detecting and sizing of a deep crack in a thick structure remains a problem. In this paper, an ECT probe is presented to solve this problem with the help of numerical analysis. The parameters such as frequency, coil size etc. are discussed. The inverse problem of crack sizing is solved by applying a fast simulator of ECT based on an edge based finite element method and steepest descent method, and reconstructed results of 5, 10 and 15mm depth cracks from experimental signals are shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1430..351L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1430..351L"><span id="translatedtitle">Modeling of new/commercial <span class="hlt">eddy</span> <span class="hlt">current</span> probe for steam generator inspection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lei, Naiguang; Xin, Junjun; Udpa, Lalita; Udpa, Satish S.</p> <p>2012-05-01</p> <p>Computational models serve an important role in Non-Destructive Evaluation applications for enabling effective use of the technology. The solution of simulation models provide valuable insight into the underlying physics, help visualize the field/flaw interaction and help optimize sensor design and develop algorithms for interpreting the measured signals. This paper presents a simulation model for predicting defect signals in Steam Generator tube inspections using commercial <span class="hlt">eddy</span> <span class="hlt">current</span> probe used in industry. The model, based on finite element analysis, uses reduced vector potential formulation and novel strategies for modeling ferrite core probes. Experimental validations of model predictions for a number of defect geometries are presented.</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://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459"><span id="translatedtitle">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://www.osti.gov/scitech/biblio/21268972','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21268972"><span id="translatedtitle">An analytical demonstration of coupling schemes between magnetohydrodynamic codes and <span class="hlt">eddy</span> <span class="hlt">current</span> codes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Liu Yueqiang</p> <p>2008-07-15</p> <p>In order to model a magnetohydrodynamic (MHD) instability that strongly couples to external conducting structures (walls and/or coils) in a fusion device, it is often necessary to combine a MHD code solving for the plasma response, with an <span class="hlt">eddy</span> <span class="hlt">current</span> code computing the fields and <span class="hlt">currents</span> of conductors. We present a rigorous proof of the coupling schemes between these two types of codes. One of the coupling schemes has been introduced and implemented in the CARMA code [R. Albanese, Y. Q. Liu, A. Portone, G. Rubinacci, and F. Villone, IEEE Trans. Magn. 44, 1654 (2008); A. Portone, F. Villone, Y. Q. Liu, R. Albanese, and G. Rubinacci, Plasma Phys. Controlled Fusion 50, 085004 (2008)] that couples the MHD code MARS-F[Y. Q. Liu, A. Bondeson, C. M. Fransson, B. Lennartson, and C. Breitholtz, Phys. Plasmas 7, 3681 (2000)] and the <span class="hlt">eddy</span> <span class="hlt">current</span> code CARIDDI[R. Albanese and G. Rubinacci, Adv. Imaging Electron Phys. 102, 1 (1998)]. While the coupling schemes are described for a general toroidal geometry, we give the analytical proof for a cylindrical plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20655339','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20655339"><span id="translatedtitle"><span class="hlt">Eddy</span> <span class="hlt">Current</span> Nondestructive Residual Stress Assessment in Shot-Peened Nickel-Base Superalloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blodgett, M.P.; Yu, F.; Nagy, P.B.</p> <p>2005-04-09</p> <p>Shot peening and other mechanical surface enhancement methods improve the fatigue resistance and foreign-object damage tolerance of metallic components by introducing beneficial near-surface compressive residual stresses and hardening the surface. However, the fatigue life improvement gained via surface enhancement is not explicitly accounted for in <span class="hlt">current</span> engine component life prediction models because of the lack of accurate and reliable nondestructive methods that could verify the presence of compressive near-surface residual stresses in shot-peened hardware. In light of its frequency-dependent penetration depth, the measurement of <span class="hlt">eddy</span> <span class="hlt">current</span> conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in surface-treated components. This technique is based on the so-called piezoresistivity effect, i.e., the stress-dependence of electrical resistivity. We found that, in contrast with most other materials, surface-treated nickel-base superalloys exhibit an apparent increase in electrical conductivity at increasing inspection frequencies, i.e., at decreasing penetration depths. Experimental results are presented to illustrate that the excess frequency-dependent apparent <span class="hlt">eddy</span> <span class="hlt">current</span> conductivity of shot-peened nickel-base superalloys can be used to estimate the absolute level and penetration depth of the compressive residual stress layer both before and after partial thermal relaxation.</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 id="translatedtitle"><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.ncbi.nlm.nih.gov/pubmed/25430380','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25430380"><span id="translatedtitle">Effect of asymmetrical <span class="hlt">eddy</span> <span class="hlt">currents</span> on magnetic diagnosis signals for equilibrium reconstruction in the Sino-UNIted Spherical Tokamak.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jiang, Y Z; Tan, Y; Gao, Z; Wang, L</p> <p>2014-11-01</p> <p>The vacuum vessel of Sino-UNIted Spherical Tokamak was split into two insulated hemispheres, both of which were insulated from the central cylinder. The <span class="hlt">eddy</span> <span class="hlt">currents</span> flowing in the vacuum vessel would become asymmetrical due to discontinuity. A 3D finite elements model was applied in order to study the <span class="hlt">eddy</span> <span class="hlt">currents</span>. The modeling results indicated that when the Poloidal Field (PF) was applied, the induced <span class="hlt">eddy</span> <span class="hlt">currents</span> 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 <span class="hlt">eddy</span> <span class="hlt">currents</span> converged on the top and bottom of the vessel, the <span class="hlt">current</span> densities there tended to be much higher than those in the equatorial plane were. Moreover, the <span class="hlt">eddy</span> <span class="hlt">currents</span> on the top and bottom of vacuum vessel had the same direction when the <span class="hlt">current</span> 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. PMID:25430380</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014RScI...85kE815J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014RScI...85kE815J"><span id="translatedtitle">Effect of asymmetrical <span class="hlt">eddy</span> <span class="hlt">currents</span> on magnetic diagnosis signals for equilibrium reconstruction in the Sino-UNIted Spherical Tokamaka)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiang, Y. Z.; Tan, Y.; Gao, Z.; Wang, L.</p> <p>2014-11-01</p> <p>The vacuum vessel of Sino-UNIted Spherical Tokamak was split into two insulated hemispheres, both of which were insulated from the central cylinder. The <span class="hlt">eddy</span> <span class="hlt">currents</span> flowing in the vacuum vessel would become asymmetrical due to discontinuity. A 3D finite elements model was applied in order to study the <span class="hlt">eddy</span> <span class="hlt">currents</span>. The modeling results indicated that when the Poloidal Field (PF) was applied, the induced <span class="hlt">eddy</span> <span class="hlt">currents</span> 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 <span class="hlt">eddy</span> <span class="hlt">currents</span> converged on the top and bottom of the vessel, the <span class="hlt">current</span> densities there tended to be much higher than those in the equatorial plane were. Moreover, the <span class="hlt">eddy</span> <span class="hlt">currents</span> on the top and bottom of vacuum vessel had the same direction when the <span class="hlt">current</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/863096','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/863096"><span id="translatedtitle">Doppler radar <span class="hlt">flowmeter</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Petlevich, Walter J.; Sverdrup, Edward F.</p> <p>1978-01-01</p> <p>A Doppler radar <span class="hlt">flowmeter</span> comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.</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 id="translatedtitle">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 id="translatedtitle">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://www.osti.gov/scitech/biblio/186992','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/186992"><span id="translatedtitle">Calculation of motion induced <span class="hlt">eddy</span> <span class="hlt">current</span> forces in null flux coils</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Davey, K.; Morris, T.; Shaaf, J.; Rote, D.</p> <p>1995-11-01</p> <p>Time dependent motion induced <span class="hlt">eddy</span> <span class="hlt">current</span> forces can be quite difficult to compute. The movement of null flux coils between magnets is approached using a coupled boundary element-circuit approach to compute the forces on the structure. The technique involves treating the magnets as a separate circuit whose <span class="hlt">current</span> is dictated by the product of the magnet thickness and the working coercivity. The mutual inductance between the windows of the moving null flux coil and the stationary equivalent magnet coil hold the key for predicting lift, guidance, and drag forces on the coil. The rate of change of these inductances with respect to position determines the forces and <span class="hlt">currents</span>. A steady state approximation to these forces is derived in addition to a numerical simulation when the steady state assumption is invalid. The results compare favorably to laboratory results from a 4 ft. diameter experimental test wheel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1581.1428R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1581.1428R"><span id="translatedtitle">Regularization methods to assess the <span class="hlt">eddy</span> <span class="hlt">current</span> density inside conductive non-ferromagnetic media</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ribeiro, A. Lopes; Ramos, H. G.; Pasadas, D.; Rocha, T.</p> <p>2014-02-01</p> <p>This presentation describes two regularization methods that were applied to preview the <span class="hlt">current</span> density induced in an aluminum plate. The images that result from the measurement of one magnetic field component by scanning the plate were used to determine the <span class="hlt">current</span> density. The scanning was performed using a constant field <span class="hlt">eddy</span> <span class="hlt">current</span> probe and a rectangular area including the defect was covered. With the constant field probe a sinusoidal excitation was imposed to the plate, being the amplitude and phase invariant under a limited space translation. The obtained data was inverted and two regularization methods were applied, Tikhonov and total variation. The two methods were compared to conclude about their inclusion into nondestructive test and evaluation instrumentation.</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 id="translatedtitle"><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://www.ncbi.nlm.nih.gov/pubmed/26817456','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26817456"><span id="translatedtitle">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=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. PMID:26817456</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828"><span id="translatedtitle">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/2016SMaS...25d5021D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SMaS...25d5021D"><span id="translatedtitle">An <span class="hlt">eddy</span> <span class="hlt">current</span>-induced magnetic plucking for piezoelectric energy harvesting</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Do, Nam Ho; Baek, Yoon Su</p> <p>2016-04-01</p> <p>Frequency up-conversion is a very efficient method of energy harvesting in order to overcome low, non-periodic, or altered ambient vibration. In order to perform frequency up-conversion and transference of mechanical energy without contact, an <span class="hlt">eddy</span> <span class="hlt">current</span>-induced magnetic drag force is used. In this paper, we present a novel configuration of <span class="hlt">eddy</span> <span class="hlt">current</span>-induced magnetic plucking for piezoelectric energy harvesting. Our method consists of two permanent magnets, a piezoelectric beam, and a copper disk piece. We design our harvesting method to achieve loading, sudden release, and free vibration using the actuation of the piezoelectric beam through the magnetic mutual coupling between the magnet and copper disk piece. We present the principle of magnetic drag force-generation, characterize the energy harvesting performance of our harvesting method, and demonstrate our harvesting method’s capability of frequency up-conversion and transference of mechanical energy without contact under low, non-periodic, or altered ambient vibration. To that end, we describe the calculation of magnetic drag force with various geometric dimensions and material properties, model of the piezoelectric cantilever beam, comparison between estimation response and measured experiment response, and the measured voltage and power responses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1706i0005B&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016AIPC.1706i0005B&link_type=ABSTRACT"><span id="translatedtitle">Analysis of pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> data using regression models for steam generator tube support structure inspection</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>2016-02-01</p> <p>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 <span class="hlt">eddy</span> <span class="hlt">current</span> 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 <span class="hlt">eddy</span> <span class="hlt">current</span> (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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706i0017B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706i0017B"><span id="translatedtitle">Enhancing pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> for inspection of P-3 Orion lap-joint structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Butt, D. M.; Underhill, P. R.; Krause, T. W.</p> <p>2016-02-01</p> <p>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 <span class="hlt">Eddy</span> <span class="hlt">Current</span> (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 <span class="hlt">eddy</span> <span class="hlt">current</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/79557','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/79557"><span id="translatedtitle">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://www.osti.gov/scitech">SciTech Connect</a></p> <p>Davis, C.W.; Nath, S.; Fulton, J.P.; Namkung, M.</p> <p>1993-12-31</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://hdl.handle.net/2060/19950020358','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950020358"><span id="translatedtitle">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://www.ncbi.nlm.nih.gov/pubmed/26703608','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26703608"><span id="translatedtitle">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=pubmed">PubMed</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> </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/2000AIPC..509..541F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..509..541F"><span id="translatedtitle">Remote field <span class="hlt">eddy</span> <span class="hlt">current</span> inspection for groove sizing—choice of a direct model structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fleury, G.; Davoust, M.-E.</p> <p>2000-05-01</p> <p>The remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) technique is used to inspect conductive pipes from the inside. This technique is known to be sensitive to internal and external flaws. The RFEC mechanism is now well understood and is particularly convenient for ferromagnetic material testing. Many classical methods may be used to characterize defects by <span class="hlt">eddy</span> <span class="hlt">current</span> measurement, such as Lissajous' curve examinations of impedance plane viewing. Those methods are not suitable for quantitative evaluation because the relation between the measured quantities (coil impedance, induced voltage) and crack dimensions is generally unknown. In that context, a number of parametric inversion methods have been previously developed. Those methods need the knowledge of the relationship between the physical quantities (here, length and depth of grooves) and the observed data. In our case, the output of a finite-element code stands for the observed data. Taking account of the symmetry property and limit variations of the data, several algebraic functions may be considered. For each model structure, several parameterizations are feasible. Some criteria are developed to obtain the best parameterization, regarding an identification purpose. Once the best model is chosen, an estimation of the groove dimensions is eventually proposed.</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 id="translatedtitle">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://www.osti.gov/scitech/biblio/227925','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/227925"><span id="translatedtitle">A remote field <span class="hlt">eddy</span> <span class="hlt">current</span> NDT probe for the inspection of metallic plates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sun, Y.S.; Udpa, S.; Lord, W.; Cooley, D.</p> <p>1996-04-01</p> <p>The remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) technique was invented in 1951 and is widely used as a nondestructive evaluation tool for inspecting metallic pipes and tubing. Essentially, the RFEC phenomenon can be observed when an AC coil is excited inside a conducting tube. The RFEC signal can be sensed by a pick-up coil located two to three diameters away from the excitation coil. The signal is closely related to the tube wall condition, thickness, permeability, and conductivity. For tubing inspection, the RFEC technique is characterized by its equal sensitivity to an inner diameter (ID) or an outer diameter (OD) defect, its insensitivity to probe wobble or lift-off, and for not being limited by the penetration depth, which has traditionally been a major disadvantage for conventional <span class="hlt">eddy</span> <span class="hlt">current</span> techniques, especially in ferromagnetic material inspection. However, RFEC applications have been restricted to inspection of metallic tubing, although there are demands for accurate and fast inspection for some flat-shaped metals, such as tank bottoms and vessel walls. Can the RFEC technique be extended to the inspection of metallic plates? This paper shows that the RFEC phenomenon can also be observed in planar metallic plates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AIPC..557..392S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AIPC..557..392S"><span id="translatedtitle">Remote field <span class="hlt">eddy</span> <span class="hlt">current</span> technique applied to the inspection of nonmagnetic 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>Shin, Young-Kil; Chung, Tae-Eon; Lord, William</p> <p>2001-04-01</p> <p>As steam generator (SG) tubes have aged, new and subtle degradations have appeared. Most of them start growing from outside the tubes. Since outer diameter defects might not be detected by conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing due to skin effect phenomena, this paper studies the feasibility of using the remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) technique, which has shown equal sensitivity to inner diameter (ID) and outer diameter (OD) defects in ferromagnetic pipe inspection. Finite element modeling studies show that the operating frequency needs to be increased up to a few hundred kHz in order for RFEC effects to occur in the nonmagnetic SG tube. The proper distance between exciter and sensor coils is also found to be 1.5 OD, which is half of the distance used in ferromagnetic pipe inspection. The resulting defect signals show equal sensitivity to ID and OD defects. These results demonstrate superior capability of the proposed RFEC probe compared to the differential ECT probe in detecting OD defects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096..287N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096..287N"><span id="translatedtitle">Study of the Effects of Edm Notch Width on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Signal Response</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nakagawa, N.; Yang, M.; Larson, B. F.; Madison, E. M.; Raulerson, D.</p> <p>2009-03-01</p> <p>A sometimes stated rule of thumb is that the <span class="hlt">eddy</span> <span class="hlt">current</span> signal from a fatigue crack can be 60% of the strength produced by a similarly sized, rectangular EDM notch. A study was conducted to explore the effect that the width of a discontinuity has on signal strength when inspecting low conductivity materials for small cracks with <span class="hlt">eddy</span> <span class="hlt">current</span> surface probes. EDM notches of different sizes and shapes were planted in Ti-6246 and IN-100 specimens. Each of the two materials received six 0.020 inch long by 0.010 inch deep notches and six 0.030 inch and 0.015 inch deep notches. Three of the notches of each size were rectangular shaped and three were semicircular shaped. One of the notches in each material size group was 0.005 inch wide, one was 0.003 inch wide and one was 0.001 inch wide. Each of the notches was scanned using absolute and differential pencil probes driven at several different frequencies. The experimental results were compared with numerically generated results, which allowed for a zero width notch to be considered. The results indicated that the signal reduction factor from a 0.005 inch wide, rectangular notch to a theoretical zero-width notch of the same size ranged from 25 to 42%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17839546','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17839546"><span id="translatedtitle">The coalescence of two East Australian <span class="hlt">current</span> warm-core <span class="hlt">eddies</span>.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cresswell, G R</p> <p>1982-01-01</p> <p>Two warm-core <span class="hlt">eddies</span> coalesced in about 20 days as their centers rotated around a point on the contracting line that joined them. In the process of forming the new <span class="hlt">eddy</span>, the subsurface isothermal-isohaline "signature" layer of one <span class="hlt">eddy</span> was uplifted and somewhat depleted while that of the other was depressed. PMID:17839546</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/6035705','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/6035705"><span id="translatedtitle">Soap film gas <span class="hlt">flowmeter</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lalin, H.S.; Bermudez, J.E.; Fleming, W.T.</p> <p>1987-09-08</p> <p>A soap film gas <span class="hlt">flowmeter</span> is described comprising: a flow tube having a hollow body with opposite open ends through which a soap film is propelled and a first closed chamber housing a soap solution. It also includes means for supporting the flow tube in a substantially vertical position with the open bottom end of the flow tube disposed in the first chamber above the soap solution; a second closed chamber into which the open top end of the flow tube extends and gas inlet means for introducing gas into the first chamber at a flow rate to be measured using the <span class="hlt">flowmeters</span>. A gas exit means is included for discharging the gas introduced into the first chamber through the second chamber. Plus there are means for generating a single soap bubble from the soap solution substantially at the bottom end of the flow tube and a relatively large opening in the flowtube for providing an open passageway for inlet gas to pass through the flowtube when the bottom open end of the flowtube is covered by the soap solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985STIN...8629199K&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985STIN...8629199K&link_type=ABSTRACT"><span id="translatedtitle">ANL Doppler <span class="hlt">flowmeter</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karplus, H. B.; Raptis, A. C.; Lee, S.; Simpson, T.</p> <p>1985-10-01</p> <p>A <span class="hlt">flowmeter</span> has been developed for measuring flow velocity in hot slurries. The <span class="hlt">flowmeter</span> works on an ultrasonic Doppler principle in which ultrasound is injected into the flowing fluid through the solid pipe wall. Isolating waveguides separate the hot pipe from conventional ultrasonic transducers. Special clamp-on high-temperature transducers also can be adapted to work well in this application. Typical flows in pilot plants were found to be laminar, giving rise to broad-band Doppler spectra. A special circuit based on a servomechanism sensor was devised to determine the frequency average of such a broad spectrum. The device was tested at different pilot plants. Slurries with particulates greater than 70 microns (0.003 in.) yielded good signals, but slurries with extremely fine particulates were unpredictable. Small bubbles can replace the coarse particles to provide a good signal if there are not too many. Successful operation with very fine particulate slurries may have been enhanced by the presence of microbubbles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011MeScT..22f5401Y&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011MeScT..22f5401Y&link_type=ABSTRACT"><span id="translatedtitle">Concentration measurement systems with stable solutions for binary gas mixtures using two <span class="hlt">flowmeters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Youn, Chongho; Kawashima, Kenji; Kagawa, Toshiharu</p> <p>2011-06-01</p> <p>The previously proposed gas concentration measurement system (Yamazaki et al 2007 Meas. Sci. Technol. 18 2762-8) shows a considerable error for some combinations of gases. The error increases when the system of equations determining mole fractions becomes a mathematically ill-conditioned system. Because the parameters of the equations reflect the material properties of the gases, the <span class="hlt">current</span> paper considers <span class="hlt">flowmeters</span> whose flow rate indication does not involve any gas property. This paper firstly illustrates the ill condition for the combination of venturi meter and laminar <span class="hlt">flowmeters</span>. The paper then discusses the simultaneous measurement of flow rate and mole fractions by <span class="hlt">flowmeter</span> combinations: an ultrasonic <span class="hlt">flowmeter</span> and a venturi meter, an ultrasonic <span class="hlt">flowmeter</span> and a laminar <span class="hlt">flowmeter</span>. Experiments are conducted for a mixture of argon and air. When a venturi meter and a laminar <span class="hlt">flowmeter</span> are used, the equations to evaluate the gas mixture ratio become an ill-conditioned system, and hence the evaluated mixture ratio shows a considerable error. On the other hand, the combination of an ultrasonic <span class="hlt">flowmeter</span> and a laminar <span class="hlt">flowmeter</span> detects the gas mixture ratio with proper accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT........93B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT........93B"><span id="translatedtitle">Transient analysis of electromagnets with emphasis on solid components, <span class="hlt">eddy</span> <span class="hlt">currents</span>, and driving circuitry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batdorff, Mark A.</p> <p></p> <p>Valves are commonly used in fluid power systems to control pressure and flow. The emerging field of digital hydraulics demands high-speed, low cost, on/off valves with improved performance. Electromagnets, or solenoids, are commonly used to actuate valves due to their low cost, high reliability, and moderate performance. This work develops a dynamic model for a solid steel electromagnet that can be used for design and optimization, and unveils design tradeoffs with geometry and driving circuitry that are often overlooked. This work develops an accurate, computationally efficient, nonlinear, coupled, dynamic, axisymmetric, high fidelity magnetic equivalent circuit (HFMEC) electromagnet model capable of predicting force, inductance, dynamic response, and energy consumption. The model is intended for applications where both accuracy and solution time are critical. Axisymmetric magnetic fringing and leakage permeances were derived in order to capture nonlinear magnetic field phenomena that affect force and inductance. The tradeoffs between solid-center and hollow-center electromagnets were investigated. It was shown with both simulation and measurement that a hollow-center electromagnet has a 37.7% shorter useful stroke due to increased magnetic fringing and leakage (from 4.0mm to 2.5mm). However, it was also shown that the hollow-center electromagnet has a 70% improved turn-off response (from 617ms to 362ms). A single objective optimization study was performed demonstrating that hollow-center electromagnets are advantageous and can up to 204% increased dynamic response for systems where dynamics are dominated by <span class="hlt">eddy</span> <span class="hlt">current</span> lag. Electromagnets experience dynamic lag when turning on and off due to inductance and <span class="hlt">eddy</span> <span class="hlt">currents</span>. Coil driving methods, such as peak-and-hold, are often used to minimize turn-on lag by using high initial voltages and <span class="hlt">currents</span>. However, circuits often do not address turn-off lag, which can be significant. This work investigates the effects of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/804540','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/804540"><span id="translatedtitle">Remote Field <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probes for the Detection of Stress Corrosion in Transmission Pipelines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Plamen Alexandroz Ivanov</p> <p>2002-08-27</p> <p>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. <span class="hlt">Currently</span>, 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 <span class="hlt">current</span> inspection technology. A possible solution to this problem is to utilize the remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (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 <span class="hlt">eddy</span> <span class="hlt">current</span> 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 <span class="hlt">eddy</span> <span class="hlt">currents</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DSRII..58..538S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DSRII..58..538S"><span id="translatedtitle">The strengthening East Australian <span class="hlt">Current</span>, its <span class="hlt">eddies</span> and biological effects — an introduction and overview</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>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</p> <p>2011-03-01</p> <p>The poleward flowing East Australian <span class="hlt">Current</span> (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 <span class="hlt">eddy</span> 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 <span class="hlt">current</span> 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; <span class="hlt">eddy</span> formation and structure; fine scale connectivity and larval retention. Comparisons with the poleward-flowing Leeuwin <span class="hlt">Current</span> 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 <span class="hlt">Current</span> relationship. The EAC's <span class="hlt">eddy</span> structure and formation by the EAC are examined. A particular cold-core <span class="hlt">eddy</span> is shown to have a "tilt" towards the coast, and that during a rotation the flow of</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 id="translatedtitle">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('http://adsabs.harvard.edu/abs/2015AIPC.1650..336G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650..336G"><span id="translatedtitle">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/2013JAG....92..137S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAG....92..137S"><span id="translatedtitle">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://hdl.handle.net/2060/20090027875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090027875"><span id="translatedtitle">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/2012JAP...111j3907L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAP...111j3907L"><span id="translatedtitle">An analytical model of a ferrite-cored inductor used as an <span class="hlt">eddy</span> <span class="hlt">current</span> probe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lu, Yi; Bowler, John R.; Theodoulidis, Theodoros P.</p> <p>2012-05-01</p> <p>An analytical model of an axisymmetric <span class="hlt">eddy</span> <span class="hlt">current</span> ferrite-cored probe above a multi-layered conducting half-space has been developed using a procedure in which the domain of the problem is truncated radially. This means that solutions can be expressed in the form of generalized Fourier-Bessel series. The expansion coefficients are found by matching the field across the interfaces between the subregions of the problem. Initially, the magnetic vector potential of a simple circular <span class="hlt">current</span> filament is expanded in a series form. The solution is then modified to accommodate an infinitely long coaxial ferrite core, and the principle of superposition is invoked to derive a coil field from the filament field in the presence of the core. Next, we consider a semi-infinite core and then one of finite length. Finally, the effects of a multi-layered conductor are included. Numerical predictions of probe impedance have been compared with experimental data showing excellent agreement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EPJAP..7210701P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015EPJAP..7210701P&link_type=ABSTRACT"><span id="translatedtitle">Original non-stationary <span class="hlt">eddy</span> <span class="hlt">current</span> imaging process for the evaluation of defects in metallic structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Placko, Dominique; Bore, Thierry; Rivollet, Alain; Joubert, Pierre-Yves</p> <p>2015-10-01</p> <p>This paper deals with the problem of imaging defects in metallic structures through <span class="hlt">eddy</span> <span class="hlt">current</span> (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 <span class="hlt">current</span> at variable frequency. So, the simulation will be performed for several frequencies and directions of the <span class="hlt">eddy</span> <span class="hlt">currents</span> 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 <span class="hlt">eddy</span> <span class="hlt">current</span> imager (ECI), implemented on aluminum plates containing some buried defects. In order to validate the proposed inversion process, we feed it with computed</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 id="translatedtitle">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/2016EPJAP..7320902R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EPJAP..7320902R"><span id="translatedtitle">A 2D finite element study on the role of material properties on <span class="hlt">eddy</span> <span class="hlt">current</span> losses in soft magnetic composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Xiaotao; Corcolle, Romain; Daniel, Laurent</p> <p>2016-02-01</p> <p>The use of soft magnetic composites (SMCs) in electrical engineering applications is growing. SMCs provide an effective alternative to laminated steels because they exhibit a high permeability with low <span class="hlt">eddy</span> <span class="hlt">current</span> losses. Losses are a critical feature in the design of electrical machines, and it is necessary to evaluate the role of microstructure and constitutive properties of SMCs during the predesign stage. In this paper we propose a simplified finite element approach to compute <span class="hlt">eddy</span> <span class="hlt">current</span> losses in these materials. The computations allow to quantify the role of exciting source and material properties on <span class="hlt">eddy</span> <span class="hlt">current</span> losses. This analysis can later be used in the development of homogenization models for SMC. Contribution to the topical issue "Numelec 2015 - Elected submissions", edited by Adel Razek</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('http://www.osti.gov/scitech/biblio/20655374','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20655374"><span id="translatedtitle">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://www.osti.gov/scitech">SciTech Connect</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>2005-04-09</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://www.osti.gov/scitech/biblio/462641','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/462641"><span id="translatedtitle">Finite element modeling of conducting shells for <span class="hlt">eddy</span> <span class="hlt">current</span> NDE problems using ``impedance-type`` interface conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Badics, Z.; Matsumoto, Yoshihiro; Kojima, Sota; Usui, Yoshihiko; Aoki, Kazuhiko; Nakayasu, Fumio</p> <p>1997-03-01</p> <p>A 3D finite element scheme is developed to calculate <span class="hlt">eddy</span> <span class="hlt">current</span> probe responses (impedance or induced emf changes of coils) due to conducting shells in <span class="hlt">eddy</span> <span class="hlt">current</span> NDE (nondestructive evaluation) problems. These problems are related to the <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of copper and magnetite deposit zones of steam generator tubing in PWR atomic power plants. The finite element scheme uses impedance interface conditions to model the deposit shells and calculates the probe responses by performing integrals over the shell surfaces, thereby ensuring high accuracy even if the probe signal is very small. Two benchmark arrangements are investigated. One, which has an analytical solution, is a conducting thin plate with an impedance probe. The other is a stainless steel tube with a copper shell attached to its outer surface and scanned by a transmitter-receiver probe. In both problems, the calculated probe responses show good agreement with the analytical and experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007JaJAP..46.4521S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007JaJAP..46.4521S&link_type=ABSTRACT"><span id="translatedtitle">Theoretical Investigation of Guide Wave <span class="hlt">Flowmeter</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sato, Harumichi; Lebedev, Maxim; Akedo, Jun</p> <p>2007-07-01</p> <p>Cylindrical pipes are widely used in industries such as nuclear power plants and micro total analysis systems (μTAS). Measuring the flow rate of fluid in such pipes is critical. Ultrasonic <span class="hlt">flowmeters</span> are noncontact, nondestructive, and easy-to-use devices, and are therefore widely used. However, typical bulk-wave-based ultrasonic <span class="hlt">flowmeters</span> cannot be used for pipes narrower than the wavelength of bulk waves. For such pipes, we are <span class="hlt">currently</span> developing a “guide wave flowmeter” that uses guide waves instead of bulk waves. Previously, we theoretically and experimentally investigated a pipe filled with quiescent fluid for all modes [Jpn. J. Appl. Phys. 45 (2006) 4573]. In this study, we expanded our theoretical investigation to a cylindrical pipe containing flowing fluid, and then compared the results with experimental results. Both the theoretical and experimental results revealed that the flow rate can be determined by measuring the sound velocity (propagation time) of guide waves. This is the operating principle of our guide wave <span class="hlt">flowmeter</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982JSV....84..133H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982JSV....84..133H&link_type=ABSTRACT"><span id="translatedtitle">Theory of transit time ultrasonic <span class="hlt">flowmeters</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hemp, J.</p> <p>1982-09-01</p> <p>A theory of transit time ultrasonic <span class="hlt">flowmeters</span> for clean fluids is developed from the equations of fluid mechanics applied simultaneously to the fluid and the sound vibrations. These equations are linearized (weak sound) and use is made of the electroacoustic reciprocity theorem to give a relation between the voltages and <span class="hlt">currents</span> at the transducer terminals and the fluid velocity. The technique of "reciprocal operation" of a transit time ultrasonic <span class="hlt">flowmeter</span> is described and the way this technique eliminates zero drift is explained. The theory can be applied to meters with broad sound beams (which provide a better average over velocity profiles) or meters in which the wavelength of sound is not necessarily small compared with the duct diameter. Small modificaition of the sound field (due to flow) is assumed and the resulting phase (or amplitude) shift of the received signal is expressed as an integral throughout the fluid of the dot product of the fluid velocity and a weight vector defined in terms of the sound fields in the stationary fluid. Simple <span class="hlt">flowmeter</span> designs which approach the ideal of complete immunity to velocity distribution are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.9392K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.9392K"><span id="translatedtitle">Evidences on <span class="hlt">eddy</span> variability and density <span class="hlt">currents</span> in the deep flow of the Strait of Otranto</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kovacevic, Vedrana; Ursella, Laura; Gacic, Miroslav</p> <p>2010-05-01</p> <p>The Strait of Otranto is 70 km wide channel connecting the Adriatic and the Ionian Seas (Mediterranean) over the 800 m deep sill. On average, a northward/southward inflow/outflow takes place along the eastern/western coast of the channel. In particular, the outflow of the Adriatic Dense Water (AdDW) occurs as a density-driven <span class="hlt">current</span> in the bottom layer pressed against the western continental margin. In the framework of the Italian national project VECTOR ("VulnErabilità delle Coste e degli ecosistemi marini italiani ai cambiamenti climaTici e loro ruolO nei cicli del caRbonio mediterraneo") the vein of the AdDW was monitored in the period Nov2006-Apr2007. Three moorings (V2, V3 and V4), about 13 km apart, were deployed in the bottom layer along the E-W section at the southernmost and deepest end of the strait. They were equipped with RDI upward-looking ADCPs (Acoustic Doppler <span class="hlt">Current</span> Profiler), bottom RCM <span class="hlt">current</span>-meters and SBE-CT (Conductivity and Temperature) instruments. The <span class="hlt">current</span>-meter at the deepest mooring (V4) mounted also a turbidity sensor. Rotational events at the ten-day time scale are observed in the <span class="hlt">current</span> records. In particular, two strong events are evident on the 8-11 and on the 20-24 December 2006. Cross-correlation and rotary spectral analysis of <span class="hlt">current</span> time-series at the outermost and central mooring reveal the concomitant occurrence of the rotation in the opposite sense. These rotational events have been explained in terms of the passage of mesoscale <span class="hlt">eddies</span> (diameter of few tens of kilometers and velocity propagation of 15 cm/s toward south). The assumption is that the <span class="hlt">eddy</span> formation mechanism is due to the stretching of the high potential vorticity water column over the Strait sill to the north. The footprint of mesoscale <span class="hlt">eddies</span> is also clearly evident both in CT and turbidity records. A detailed look into the two December events, when the <span class="hlt">eddy</span> passage is assumed, shows a number of coincidences: temperature and salinity drop at V3 and V4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17371723','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17371723"><span id="translatedtitle">A quantitative comparison of two methods to correct <span class="hlt">eddy</span> <span class="hlt">current</span>-induced distortions in DT-MRI.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Muñoz Maniega, Susana; Bastin, Mark E; Armitage, Paul A</p> <p>2007-04-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span>-induced geometric distortions of single-shot, diffusion-weighted, echo-planar (DW-EP) images are a major confounding factor to the accurate determination of water diffusion parameters in diffusion tensor MRI (DT-MRI). Previously, it has been suggested that these geometric distortions can be removed from brain DW-EP images using affine transformations determined from phantom calibration experiments using iterative cross-correlation (ICC). Since this approach was first described, a number of image-based registration methods have become available that can also correct <span class="hlt">eddy</span> <span class="hlt">current</span>-induced distortions in DW-EP images. However, as yet no study has investigated whether separate <span class="hlt">eddy</span> <span class="hlt">current</span> calibration or image-based registration provides the most accurate way of removing these artefacts from DT-MRI data. Here we compare how ICC phantom calibration and affine FLIRT (http://www.fmrib.ox.ac.uk), a popular image-based multi-modal registration method that can correct both <span class="hlt">eddy</span> <span class="hlt">current</span>-induced distortions and bulk subject motion, perform when registering DW-EP images acquired with different slice thicknesses (2.8 and 5 mm) and b-values (1000 and 3000 s/mm(2)). With the use of consistency testing, it was found that ICC was a more robust algorithm for correcting <span class="hlt">eddy</span> <span class="hlt">current</span>-induced distortions than affine FLIRT, especially at high b-value and small slice thickness. In addition, principal component analysis demonstrated that the combination of ICC phantom calibration (to remove <span class="hlt">eddy</span> <span class="hlt">current</span>-induced distortions) with rigid body FLIRT (to remove bulk subject motion) provided a more accurate registration of DT-MRI data than that achieved by affine FLIRT. PMID:17371723</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 id="translatedtitle">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('http://www.osti.gov/scitech/biblio/21054941','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21054941"><span id="translatedtitle">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('http://adsabs.harvard.edu/abs/2007AIPC..894.1274O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AIPC..894.1274O"><span id="translatedtitle">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://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okafor, A. C.; Natarajan, S.</p> <p>2007-03-01</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('http://www.osti.gov/scitech/biblio/20798254','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20798254"><span id="translatedtitle">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('http://hdl.handle.net/2060/20150007196','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150007196"><span id="translatedtitle"><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/2001AIPC..557..664S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AIPC..557..664S"><span id="translatedtitle">Neural network inversion of synthetic <span class="hlt">eddy</span> <span class="hlt">current</span> testing signals from flaws in 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>Song, S. J.; Kim, C. H.; Shin, Y. K.; Lee, H. B.; Park, Y. W.; Yim, C. J.</p> <p>2001-04-01</p> <p>This paper reports our recent endeavor to develop automated, systematic inversion tools by the novel combination of neural networks and finite element modeling for <span class="hlt">eddy</span> <span class="hlt">current</span> flaw characterization in steam generator tubes. Specifically, this paper describes 1) development of the finite element models that can simulate synthetic ECT signals from axisymmetric flaws with arbitrary cross-sections, 2) construction of databases with abundant flaw signals, 3) implementation of effective feature extraction software and proposition of feature selection criteria, and finally 4) development of inversion tools by use of two neural networks for flaw classification and sizing. In addition, this paper also presents the performance of the proposed inversion tools for solving two sample problems: classification of flaws with non-symmetric cross-sections, and classification and sizing of flaws with tip variation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706s0002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706s0002D"><span id="translatedtitle">Solution of the WFNDEC 2015 <span class="hlt">eddy</span> <span class="hlt">current</span> benchmark with surface integral equation method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Demaldent, Edouard; Miorelli, Roberto; Reboud, Christophe; Theodoulidis, Theodoros</p> <p>2016-02-01</p> <p>In this paper, a numerical solution of WFNDEC 2015 <span class="hlt">eddy</span> <span class="hlt">current</span> benchmark is presented. In particular, the Surface Integral Equation (SIE) method has been employed for numerically solving the benchmark problem. The SIE method represent an effective and efficient alternative to standard numerical solver like Finite Element Method (FEM) when electromagnetic fields need to be calculated in problems involving homogeneous media. The formulation of SIE method allows to properly solve the electromagnetic problem by meshing the surface of the media instead to the complete media volume as done in FEM. The surface meshing enables to describe the problem with a smaller number of unknowns with respect to FEM. This property is directly translated in an obvious gain in terms of CPU time efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1335.1769M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1335.1769M"><span id="translatedtitle">Developing and Using Benchmarks for <span class="hlt">Eddy</span> <span class="hlt">Current</span> Simulation Codes Validation to Address Industrial Issues</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mayos, M.; Buvat, F.; Costan, V.; Moreau, O.; Gilles-Pascaud, C.; Reboud, C.; Foucher, F.</p> <p>2011-06-01</p> <p>To achieve performance demonstration, which is a legal requirement for the qualification of NDE processes applied on French nuclear power plants, the use of modeling tools is a valuable support, provided that the employed models have been previously validated. To achieve this, in particular for <span class="hlt">eddy</span> <span class="hlt">current</span> modeling, a validation methodology based on the use of specific benchmarks close to the actual industrial issue has to be defined. Nonetheless, considering the high variability in code origin and complexity, the feedback from experience on actual cases has shown that it was critical to define simpler generic and public benchmarks in order to perform a preliminary selection. A specific Working Group has been launched in the frame of COFREND, the French Association for NDE, resulting in the definition of several benchmark problems. This action is now ready for mutualization with similar international approaches.</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 id="translatedtitle">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://www.ncbi.nlm.nih.gov/pubmed/17281087','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17281087"><span id="translatedtitle">Development of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor systems in artificial heart for noncontact gap sensing.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahn, C; Kim, K; Moon, K; Jeong, K; Kim, H; Lee, J; Hwang, C; Sun, K</p> <p>2005-01-01</p> <p>The axial flow pump has been developed in Korea Artificial Organ Center. It consists of an impeller, a motor and a magnetic bearing. The magnetic bearing fully levitates the impeller not to contact with other parts of pump. However, in order to control the gap between the impeller and other parts, continuous gap sensing is necessary. The conventional gap sensors are relatively large to implant in artificial heart. Thus, the compact <span class="hlt">eddy</span> <span class="hlt">current</span> sensor system proper for artificial heart was developed and the performances were evaluated. It showed good results and has small size. However, the dependency of the sensor upon temperature and target material was shown also. Moreover, the output of sensor had nonlinear responses. These must be calibrated in further study. PMID:17281087</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25173300','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25173300"><span id="translatedtitle">Ultrahigh-resolution and non-contact diameter measurement of metallic wire using <span class="hlt">eddy</span> <span class="hlt">current</span> sensor.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Wei; Wang, Hongbo; Feng, Zhihua</p> <p>2014-08-01</p> <p>This paper proposes a new method using <span class="hlt">eddy</span> <span class="hlt">current</span> sensor (ECS) for online non-contact diameter measurement of metallic wires with ultrahigh resolution. A prototype sensor was designed, fabricated, and tested for copper wires with diameters ranging from 1.12 mm to 1.30 mm. A solenoid coil with dimensions of 16 mm long and 2.1 mm in diameter is used as sensing element with a working frequency of 1.3 MHz. With a well-designed bridge, the sensing coil's inductance variation can be detected and the wire's diameter can be calculated. The ECS system demonstrated a dynamic resolution better than 2.2 μm and a static resolution better than 0.42 nm for a wire with a diameter of 1.3 mm. This non-contact method has competitive advantages over other methods in many aspects, especially in terms of measurement resolution. PMID:25173300</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 id="translatedtitle">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://www.osti.gov/scitech/servlets/purl/257304','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/257304"><span id="translatedtitle">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://adsabs.harvard.edu/abs/2015AIPC.1650.1186S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650.1186S"><span id="translatedtitle">An <span class="hlt">eddy-current</span> model for three-dimensional nondestructive evaluation of advanced composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sabbagh, Harold A.; Murphy, R. Kim; Sabbagh, Elias H.</p> <p>2015-03-01</p> <p>We have developed a rigorous electromagnetic model and an inversion algorithm for the three-dimensional NDE of advanced composite materials. This approach extends Victor Technologies' work in <span class="hlt">eddy-current</span> NDE of conventional metals, and allows one to determine in localized regions the fiber-resin ratio in graphite-epoxy, and to determine those anomalies, e.g., delaminations, broken fibers, moisture content, etc., that can be reconstructed by our inversion method. In developing the model, we apply rigorous electromagnetic theory to determine a Green's function for a slab of anisotropic composite material, and then determine the integral relations for the forward and inverse problems using the Green's function. We will give examples of the solution of forward problems using this model.</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://www.osti.gov/scitech/biblio/21054940','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21054940"><span id="translatedtitle">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://hdl.handle.net/2060/20040111997','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040111997"><span id="translatedtitle">Self-Nulling <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probe for Surface and Subsurface Flaw Detection</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, B.; Fulton, J. P.; Nath, S.; Namkung, M.; Simpson, J. W.</p> <p>1994-01-01</p> <p>An <span class="hlt">eddy</span> <span class="hlt">current</span> probe which provides a null-signal in the presence of unflawed material without the need for any balancing circuitry has been developed at NASA Langley Research Center. Such a unique capability of the probe reduces set-up time, eliminates tester configuration errors, and decreases instrumentation requirements. The probe is highly sensitive to surface breaking fatigue cracks, and shows excellent resolution for the measurement of material thickness, including material loss due to corrosion damage. The presence of flaws in the material under test causes an increase in the extremely stable and reproducible output voltage of the probe. The design of the probe and some examples illustrating its flaw detection capabilities are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120015904','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015904"><span id="translatedtitle">Research and Development of Automated <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing for Composite Overwrapped Pressure Vessels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Carver, Kyle L.; Saulsberry, Regor L.; Nichols, Charles T.; Spencer, Paul R.; Lucero, Ralph E.</p> <p>2012-01-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> 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.</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 id="translatedtitle">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('http://adsabs.harvard.edu/abs/2012AIPC.1430..689Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1430..689Y"><span id="translatedtitle">Nonlinear, non-stationary image processing technique for <span class="hlt">eddy</span> <span class="hlt">current</span> NDE</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Guang; Dib, Gerges; Kim, Jaejoon; Zhang, Lu; Xin, Junjun; Udpa, Lalita</p> <p>2012-05-01</p> <p>Automatic analysis of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) data has facilitated the analysis of large volumes of data generated in the inspection of steam generator tubes in nuclear power plants. The traditional procedure for analysis of EC data includes data calibration, pre-processing, region of interest (ROI) detection, feature extraction and classification. Accurate ROI detection has been enhanced by pre-processing, which involves reducing noise and other undesirable components as well as enhancing defect indications in the raw measurement. This paper presents the Hilbert-Huang Transform (HHT) for feature extraction and support vector machine (SVM) for classification. The performance is shown to significantly better than the existing rule based classification approach used in industry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010NTE....25..169D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010NTE....25..169D"><span id="translatedtitle">Detection of graphite balls for the fuel handling system in HTGR using <span class="hlt">eddy</span> <span class="hlt">current</span> testing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dong, Li; ZhenGuo, Sun; Qiang, Chen</p> <p>2010-06-01</p> <p>The spherical graphite fuel elements (graphite balls) are transported into and out of the core in high-temperature gas-cooled pebble bed reactors (HTGR) by a fuel handling system (FHS) during plant operation. In order to control the reactor, it is necessary to have information on the location and movement of the graphite balls at various points of the FHS. In this paper, a new through-transmission <span class="hlt">eddy</span> <span class="hlt">current</span> testing probe has been put forward to detect the graphite balls. The probe's electromagnetic finite element model (FEM) has been established so as to study the factors affecting the performance of the probe. On this basis, electromagnetic detection parameters and probe designs have been optimised. According to the results of analysis, a bidirectional detector for the fuel ball handling system of HTGR has been developed. The experimental results confirm the validity of the FEM, and show that the detector works accurately and reliably, which meets the requirements of application in HTGR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096.1808L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096.1808L"><span id="translatedtitle">Variables Affecting Probability of Detection in Bolt Hole <span class="hlt">Eddy</span> <span class="hlt">Current</span> Inspection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lemire, H.; Krause, T. W.; Bunn, M.; Butcher, D. J.</p> <p>2009-03-01</p> <p>Physical variables affecting probability of detection (POD) in a bolt-hole <span class="hlt">eddy</span> <span class="hlt">current</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20798253','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20798253"><span id="translatedtitle">The Effect of Opening on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probe Response for an Idealized through Crack</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fu Fangwei; Bowler, J. R.; Theodoulidis, T. P.</p> <p>2006-03-06</p> <p>A structure representing an idealized through crack was formed by placing two coplanar aluminum rectangular plates next to one another with their edges separated by a small distance. The coil impedance variation with position was measured as a coil was moved over the adjacent plate edges. An analytical theory is used to evaluate the coil impedance change due to the gap between the plates. This theory is based on the truncated region eigenfunction expansion method. The difference between the <span class="hlt">eddy</span> <span class="hlt">current</span> probe signal due to a notch compared with that of a crack can be partly accounted for by the difference in the opening. We have investigated the effect of varying the opening of the simulated crack and shown theoretically and experimentally how the coil impedance changes with position, opening and frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/20655379','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/20655379"><span id="translatedtitle">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/2010AIPC.1211..393S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1211..393S"><span id="translatedtitle">Performance Evaluation of Several Types of Pulsed <span class="hlt">Eddy</span> <span class="hlt">Current</span> Probes for Detecting Wall Thickness Reduction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shin, Young-Kil; Choi, Dong-Myung; Jung, Hee-Sung; Um, Tae-Gun</p> <p>2010-02-01</p> <p>In this paper, four different types of pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) probe are designed and their performance of detecting wall thickness reduction is compared. By using the backward difference method in time and the finite element method in space, PEC signals from various thickness and materials are numerically calculated and three features of the signal are selected. Since PEC signals and features are obtained by various types and sizes of probe, the comparison is made through the normalized features which reflect the sensitivity of the feature to thickness reduction. The normalized features indicate that the shielded reflection probe provides the best sensitivity to wall thickness reduction for all three signal features. Results show that the best sensitivity to thickness reduction is achieved by the peak value, but also suggest that the time to peak can be a good candidate because of its linear relationship with the thickness variation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/170287','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/170287"><span id="translatedtitle"><span class="hlt">Eddy</span> <span class="hlt">current</span> probe for nondestructive testing using cross-coupled figure-eight coils</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sasada, I.; Watanabe, N.</p> <p>1995-11-01</p> <p>It is shown that the pickup head consisting of cross-coupled figure-eight coils originally developed for the magnetostrictive torque sensor is well suited for the <span class="hlt">eddy</span> <span class="hlt">current</span> probe detecting small defects in a nonmagnetic conductive material. The probe is easily extended to a one dimensional array form, which substantially reduces number of times of scanning the targeted materials. The response of a single unit of the probe to a trough hole defect in an aluminum plate are presented. A half-way hole at the back of an aluminum plate of 1.2 mm in thickness was successfully detected from the front using this probe. A five-channel array was developed in which the excitation coil is shared by all the channel. A small through hole defect in an aluminum plate was detected clearly by a single scan with the array probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1211..353T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1211..353T"><span id="translatedtitle">Analytical and Numerical Modeling of Pulsed <span class="hlt">Eddy</span> <span class="hlt">Current</span> Response to Thin Conducting Plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tetervak, A.; Krause, T. W.; Mandache, C.; Lefebvre, J. H. V.</p> <p>2010-02-01</p> <p>Modeling of transient <span class="hlt">eddy</span> <span class="hlt">current</span> response in planar structures requires incorporation of all elements within the system comprised of exciting and pick-up coils, and the conducting structure being investigated. The combined response includes the feedback processes that in turn modify the time constants within the system. In this work analytical and numerical methods are utilized to solve for those feedback mechanisms within the circuit-conductor system that generates the final pick-up coil response. Further, applying numerical analysis to results of the modeling, we parameterize probe-sample interaction via lumped-circuit analogies justified for thin samples. Results are compared with experimental measurements where these parameters have been characterized.</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 id="translatedtitle">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://www.osti.gov/scitech/biblio/146327','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/146327"><span id="translatedtitle">Proving Coriolis <span class="hlt">flowmeters</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Apple, C.</p> <p>1995-12-01</p> <p>Coriolis meters provide significant advantages for custody transfer measurement of fluids. The most obvious feature is the Coriolis meter`s ability to provide a direct mass flow measurement. This makes Coriolis meters ideally suited to measuring products which are commonly accounted for on a mass basis, such as LPG, NGL, ethylene, liquid CO{sub 2}. Using a single Coriolis meter simplifies the metering system by replacing a volumetric <span class="hlt">flowmeter</span>, densitometer, and flow computer, with a single measurement device. Another unique feature of Coriolis meters is their ability to measure fluid density independently of mass flow rate. The density measurement is determined in the same manner as any vibrating tube densitometer. By measuring both the mass flow rate ({center_dot}m) and density ({rho}), the Coriolis meter can provide a volumetric flow measurement (q) by performing the following calculation: q = {center_dot}m / {rho}. Coriolis meters have no rotating parts such as bearings or gears, that wear with time. This reduces maintenance costs. Since solids can flow through the meters without damage, strainers are generally unnecessary. Also, gas or vapor in the process fluid which can damage turbine meters due to overspin, will not harm Coriolis meters. The measurement accuracy of Coriolis meters, {+-}0.15%, is suitable for custody transfer measurement. The meters are capable of measuring flow bi-directionally. This is particularly advantageous for loading rack and cavern storage applications. <span class="hlt">Flowmeters</span> which are used for custody transfer measurement, generally require some means to prove meter accuracy. The principles of operation of Coriolis meters are fundamentally different than those of turbine or positive displacement meters. In order to properly prove these meters it is important to understand some basics about the meters operation and output signals.</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 id="translatedtitle">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('http://adsabs.harvard.edu/abs/2016CSR...114....1R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CSR...114....1R"><span id="translatedtitle">The Costa Rica Coastal <span class="hlt">Current</span>, <span class="hlt">eddies</span> and wind forcing in the Gulf of Tehuantepec, Southern Mexican Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reyes-Hernández, Cristóbal; Ahumada-Sempoal, Miguel Ángel; Durazo, Reginaldo</p> <p>2016-02-01</p> <p>The hydrographic structure and circulation of the Southern Mexican Pacific, from August 31 to September 24 2004, when tropical atmospheric activity was at its peak, was analyzed based on AVISO absolute dynamic topography and an array of 106 CTD profiles, within an area of about 500 km×500 km between Punta Maldonado and Puerto Chiapas. The surveyed area was occupied by mesoscale anticyclonic and cyclonic <span class="hlt">eddies</span> that determined the path of water with temperature and salinity characteristic of the Costa Rica Coastal <span class="hlt">Current</span>. The origin of each <span class="hlt">eddy</span> was investigated with respect to QuikSCAT wind conditions. The sequence of AVISO images and wind data showed that the largest anticyclonic <span class="hlt">eddies</span> originated outside the Gulf of Tehuantepec through mechanisms distinct from local wind forcing, although two northerly wind events in the Gulf of Tehuantepec possibly had an influence on the smallest anticyclonic and cyclonic <span class="hlt">eddies</span>. The relative position of each <span class="hlt">eddy</span> allowed the flow of relatively low temperature and salinity water (the Costa Rica Coastal <span class="hlt">Current</span>) into and throughout the Gulf of Tehuantepec, converging at about Puerto Angel with relatively high temperature and salinity water moving from the west.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950031117&hterms=recruitment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Drecruitment','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950031117&hterms=recruitment&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Drecruitment"><span id="translatedtitle">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://ntrs.nasa.gov/search.jsp?R=19900000312&hterms=Respiratory+system&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2528Respiratory%2Bsystem%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900000312&hterms=Respiratory+system&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2528Respiratory%2Bsystem%2529"><span id="translatedtitle">Self-Calibrating Respiratory-<span class="hlt">Flowmeter</span> Combination</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Westenskow, Dwayne R.; Orr, Joseph A.</p> <p>1990-01-01</p> <p>Dual <span class="hlt">flowmeters</span> ensure accuracy over full range of human respiratory flow rates. System for measurement of respiratory flow employs two <span class="hlt">flowmeters</span>; one compensates for deficiencies of other. Combination yields easily calibrated system accurate over wide range of gas flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMagR.244...74C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMagR.244...74C"><span id="translatedtitle">Characterization and correction of <span class="hlt">eddy-current</span> artifacts in unipolar and bipolar diffusion sequences using magnetic field monitoring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chan, Rachel W.; von Deuster, Constantin; Giese, Daniel; Stoeck, Christian T.; Harmer, Jack; Aitken, Andrew P.; Atkinson, David; Kozerke, Sebastian</p> <p>2014-07-01</p> <p>Diffusion tensor imaging (DTI) of moving organs is gaining increasing attention but robust performance requires sequence modifications and dedicated correction methods to account for system imperfections. In this study, <span class="hlt">eddy</span> <span class="hlt">currents</span> in the "unipolar" Stejskal-Tanner and the velocity-compensated "bipolar" spin-echo diffusion sequences were investigated and corrected for using a magnetic field monitoring approach in combination with higher-order image reconstruction. From the field-camera measurements, increased levels of second-order <span class="hlt">eddy</span> <span class="hlt">currents</span> were quantified in the unipolar sequence relative to the bipolar diffusion sequence while zeroth and linear orders were found to be similar between both sequences. Second-order image reconstruction based on field-monitoring data resulted in reduced spatial misalignment artifacts and residual displacements of less than 0.43 mm and 0.29 mm (in the unipolar and bipolar sequences, respectively) after second-order <span class="hlt">eddy-current</span> correction. Results demonstrate the need for second-order correction in unipolar encoding schemes but also show that bipolar sequences benefit from second-order reconstruction to correct for incomplete intrinsic cancellation of <span class="hlt">eddy-currents</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/24880880','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/24880880"><span id="translatedtitle">Characterization and correction of <span class="hlt">eddy-current</span> artifacts in unipolar and bipolar diffusion sequences using magnetic field monitoring.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chan, Rachel W; von Deuster, Constantin; Giese, Daniel; Stoeck, Christian T; Harmer, Jack; Aitken, Andrew P; Atkinson, David; Kozerke, Sebastian</p> <p>2014-07-01</p> <p>Diffusion tensor imaging (DTI) of moving organs is gaining increasing attention but robust performance requires sequence modifications and dedicated correction methods to account for system imperfections. In this study, <span class="hlt">eddy</span> <span class="hlt">currents</span> in the "unipolar" Stejskal-Tanner and the velocity-compensated "bipolar" spin-echo diffusion sequences were investigated and corrected for using a magnetic field monitoring approach in combination with higher-order image reconstruction. From the field-camera measurements, increased levels of second-order <span class="hlt">eddy</span> <span class="hlt">currents</span> were quantified in the unipolar sequence relative to the bipolar diffusion sequence while zeroth and linear orders were found to be similar between both sequences. Second-order image reconstruction based on field-monitoring data resulted in reduced spatial misalignment artifacts and residual displacements of less than 0.43 mm and 0.29 mm (in the unipolar and bipolar sequences, respectively) after second-order <span class="hlt">eddy-current</span> correction. Results demonstrate the need for second-order correction in unipolar encoding schemes but also show that bipolar sequences benefit from second-order reconstruction to correct for incomplete intrinsic cancellation of <span class="hlt">eddy-currents</span>. PMID:24880880</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. 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