Science.gov

Sample records for eddy current couplings

  1. Silent Flange Coupling Design Used for the Schenck Eddy Current Dynamometer

    NASA Astrophysics Data System (ADS)

    Schinteie, D.; Croitorescu, V.

    2016-11-01

    The silent flange used for coupling different machines/systems to an eddy current dynamometer represents one of the modular components each test-bench should use. By introducing a silent flange into a dynamometer, the coupling steps are easier and faster. For an appropriate design, the silent flange was analyzed using dedicated software during different operation procedures and scenarios, for materials that allow easy manufacturing. This study shows that the design for this silent flange model has no danger of failure due to the small deformation and the values for the equivalent stresses. The silent flange coupling is suitable for the dynamometer for his high positioning accuracy, the zero backlash and the fact that there is no motion between the shafts.

  2. Fully-coupled magnetoelastic model for Galfenol alloys incorporating eddy current losses and thermal relaxation

    NASA Astrophysics Data System (ADS)

    Evans, Phillip G.; Dapino, Marcelo J.

    2008-03-01

    A general framework is developed to model the nonlinear magnetization and strain response of cubic magnetostrictive materials to 3-D dynamic magnetic fields and 3-D stresses. Dynamic eddy current losses and inertial stresses are modeled by coupling Maxwell's equations to Newton's second law through a nonlinear constitutive model. The constitutive model is derived from continuum thermodynamics and incorporates rate-dependent thermal effects. The framework is implemented in 1-D to describe a Tonpilz transducer in both dynamic actuation and sensing modes. The model is shown to qualitatively describe the effect of increase in magnetic hysteresis with increasing frequency, the shearing of the magnetization loops with increasing stress, and the decrease in the magnetostriction with increasing load stiffness.

  3. Testing of inductively coupled Eddy current position sensor of diverse safety rod in sodium

    SciTech Connect

    Vijayashree, R.; Veeraswamy, R.; Nashine, B. K.; Dash, S. K.; Sharma, P.; Rajan, K. K.; Vijayakumar, G.; Rao, C. B.; Sosamma, S.; Kalyanasundaram, P.

    2011-07-01

    Prototype Fast Breeder Reactor (PFBR) is 500 MWe sodium cooled reactor under construction at Kalpakkam (India)). To improve the reliability of shutdown, Diverse Safety Rods (DSRs) are used in-addition to normal Control and Safety rods. During reactor operating condition, the DSR is parked above the active core and held in its top position by an electromagnet. In the event of a scram signal from the safety logic, the electromagnet holding the DSR is de-energised. Hence the DSR is released into the active core and at the end of travel DSR gets deposited in its bottom position. Because of the mechanical constraints, hard wired connectivity is not permitted from the DSR subassembly to the instrumentation outside the reactor. Hence an inductively coupled Eddy Current Position Sensor (ECPS) has been conceptualized to detect that the DSR has reached its bottom most position and to measure the drop time. Results of feasibility study on laboratory model have been reported earlier. Testing of a 1:1 scale engineering model of ECPS is reported in this paper. Results obtained from the high temperature sodium testing of ECPS indicate a clearly measurable change in pick up voltage with sensitivity of 11 % at 675 Hz. The ECPS is in advanced stage of implementation in DSRDM of PFBR. (authors)

  4. Application of coupled electric field method for eddy current non-destructive inspection of multilayer structures

    NASA Astrophysics Data System (ADS)

    Bouchala, T.; Abdelhadi, B.; Benoudjit, A.

    2015-04-01

    The development of fast and accurate method describing the electromagnetic phenomena intervening in eddy current non-destructive systems is very interesting, since it permits the design of reliable systems permitting the detection and the characterisation of defect in conductive materials. The coupled electric field method presented in this article can assume a large part of these objectives, because it is fast in comparison to the finite element method and easily invertible since the sensor impedance variation is an explicit function of target physical and geometrical characteristics. These advantages have motivated us to extend this method for multilayered structures, very interesting in aeronautic industry, by superposing the inductive effects in different layers. The impedance of an absolute sensor operating above three conducting layers will be calculated and compared to those obtained with finite element method. Afterwards, we shall exploit the model to study the effect of defect characteristics on the sensor impedance. Furthermore, regarding to the depth penetration effect, we shall make into evidence the necessity of accomplishing an optimal choice of the exciting field frequency during the inspection of multilayered materials. The essential importance of this method, besides of its rapidity, resides in its possibility to be extended to 2D irregular and 3D asymmetric configurations.

  5. 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.

  6. Eddy current enhancement for EMATs

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  7. 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.

  8. Mesoscale Eddy - Internal Wave Coupling:

    NASA Astrophysics Data System (ADS)

    Polzin, K. L.

    2012-12-01

    The issue of internal wave--mesoscale eddy interactions is revisited. Direct estimates of energy transfer from the Local Dynamics Experiment of the PolyMode field program (Polzin, 2010 JPO) return viscosity estimates of ν h \\cong 50 m2 s-1 and ν v + (f2)/(N^2) Kh \\cong 2.5×10-3 m2 s-1. These estimates indicate that mesoscale eddy-internal wave interactions may play an O(1) role in the mesoscale eddy energy budget as dissipation and the internal wave budget as a source. Radiation balance equation formulations for this coupling (Müller 1976, JFM) are examined. In these formulations permanent transfer of energy and internal wave pseudomomentum for mesoscale eddy potential vorticity is enabled by nonlinearity in the wavefield. Revision of radiation balance equation formulations to account for non-local effects returns predictions of ν h \\cong 50-100 m2 s-1 and ν v + (f2)/(N^2) Kh \\cong -1×10-3 to 4×10-3 m2 s-1. The prediction for the effective vertical viscosity is sensitive to how internal wave energy is distributed in the spectral domain with negative values appropriate to the Garrett and Munk spectrum and positive values appropriate to the background spectrum in the LDE area. Geographic scalings in terms of latitude, stratification and mesoscale eddy variability will be described. The process described here is best interpreted as an amplifier of a pre-existing or externally forced finite amplitude wavefield rather than the spontaneous imbalance of a linear field. Energy, pseudomomentum and vorticity can be transfered from the slow manifold (geostrophically balanced motions) to the fast manifold (internal gravity waves) via linear wave propagation in asymmetric background flows, but that transfer is reversible. The permanent transfer is accomplished by nonlinearity on the fast manifold.

  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. 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.

  11. 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.

  12. Observed eddy dissipation in the Agulhas Current

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  13. Loop Current Eddy formation and baroclinic instability

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  14. 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.

  15. 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.

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

    SciTech Connect

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

    1986-11-01

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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. A western boundary current eddy characterisation study

    NASA Astrophysics Data System (ADS)

    Ribbe, Joachim; Brieva, Daniel

    2016-12-01

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

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

    SciTech Connect

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

    1986-01-01

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

  4. 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,…

  5. 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.

  6. Development of magnetic eddy current testing techniques

    NASA Astrophysics Data System (ADS)

    Tada, Toyokazu; Suetsugu, Hidehiko

    2017-02-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Eddy Current Assessment of Duplex Metallic Coatings

    NASA Astrophysics Data System (ADS)

    Krzywosz, K. J.

    2004-02-01

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

  20. An electromagnetic microscope for eddy current evaluation of materials

    SciTech Connect

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

    1991-03-01

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

  1. 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.

  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. 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.

  4. 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).

  5. 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).

  6. 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)

  7. 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.

  8. 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.

  9. 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.

  10. 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).

  11. 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.

  12. 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.

  13. Conjugate spectrum filters for eddy current signal processing

    SciTech Connect

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

    1993-07-01

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

  14. 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.

  15. 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.

  16. 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.

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

    SciTech Connect

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

    1985-07-01

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

  18. Biogeochemical Properties of Eddies in the California Current System

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  19. 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.

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

    Swiderski, W

    2016-12-01

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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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…

  11. 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.

  12. 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.

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

    SciTech Connect

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

    1989-06-22

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

  14. Vibration attenuation of conductive beams by inducing eddy currents

    NASA Astrophysics Data System (ADS)

    Irazu, L.; Elejabarrieta, M. J.

    2016-09-01

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

  15. 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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Desjardins, Daniel

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

  18. 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.

  19. Current induced interlayer coupling

    NASA Astrophysics Data System (ADS)

    Levy, Peter M.; Heide, Carsten; Zhang, Shufeng; Fert, Albert

    2001-03-01

    It has recently been shown that a perpendicular current in a magnetically multilayered structures induces an unusual bilinear coupling between the magnetizations of the layers [1]. While this was demonstrated in the ballistic regime, transport is likely to be diffusive in the structures where this may be relevant to the role of currents in switching the magnetization of the layers. We have derived the current induced coupling by using the Boltzmann equation in terms of the parameters used to describe the giant magnetoresistance of magnetically layered structures, and thereby estimate the strength of this coupling. Work supported in part by DARPA and ONR. [1] C.Heide and R.J.Elliott, Europhys. Lett. 50, 271 (2000).

  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. 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.

  2. 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.

  3. a Macroscopic Analysis of Eddy Currents in Nonferrous Metals

    NASA Astrophysics Data System (ADS)

    Holder, Morris Eugene

    1992-01-01

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

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  7. Solar wind eddies and the heliospheric current sheet

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  8. 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.

  9. Eddy current analysis of thin film recording heads

    NASA Astrophysics Data System (ADS)

    Shenton, D.; Cendes, Z. J.

    1984-03-01

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

  10. 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).

  11. 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.

  12. 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.

  13. Coupling between SST and wind speed over mesoscale eddies in the South China Sea

    NASA Astrophysics Data System (ADS)

    Sun, Shuangwen; Fang, Yue; Liu, Baochao; ᅟ, Tana

    2016-11-01

    The coupling between sea surface temperature (SST) and sea surface wind speed over mesoscale eddies in the South China Sea (SCS) was studied using satellite measurements. Positive correlations between SST anomalies (SSTA) and wind speed anomalies were found over both cyclonic and anticyclonic eddies. In contrast to the open oceans, the spatial patterns of the coupling over mesoscale eddies in the SCS depend largely on the seasonal variations of the background SST gradient, wind speed, and wind directional steadiness. In summer, the maximum SSTA location coincides with the center of eddy-induced sea surface height anomalies. In winter, the eddy-induced SSTA show a clear dipole pattern. The spatial patterns of wind speed anomalies over eddies are similar to those of the SSTA in both seasons. Wind speed anomalies are linearly correlated with SSTA over anticyclonic and cyclonic eddies. The coupling coefficients between SSTA and wind speed anomalies in the SCS are comparable to those in the open oceans.

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

    SciTech Connect

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

    1992-10-01

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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  20. 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,…

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  2. Determining confounding sensitivities in eddy current thin film measurements

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  3. 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.

  4. 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.

  5. 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.

  6. A Lagrangian approach to the Loop Current eddy separation

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  7. A Lagrangian approach to the Loop Current eddy separation

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. A Model for Axial Magnetic Bearings Including Eddy Currents

    NASA Technical Reports Server (NTRS)

    Kucera, Ladislav; Ahrens, Markus

    1996-01-01

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

  12. Assessing thermal barrier coatings by eddy-current inversion

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

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

  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 system for inspection of train hollow axles

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  15. Eddy-current transducer based on flat spiral coils

    SciTech Connect

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

    1988-12-01

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

  16. 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.

  17. Mesoscale Eddy - Internal Wave Coupling and Closure of the Thermocline Circulation

    NASA Astrophysics Data System (ADS)

    Polzin, K. L.

    2006-12-01

    The standard dynamical paradigm for oceanic dynamics is to consider the stratified interior as an ideal fluid and place all dissipative processes in either the bottom boundary layer or associate them with eddy/mixed layer interactions. This conceptual framework is consistent with an absence of mean interior potential vorticity gradients. On the other hand, background potential vorticity gradients are clearly documented in hydrographic data, e.g. [1]. Moreover, current meter data [2] also document the presence of downgradient eddy fluxes of potential vorticity. Thus we arrive at an essential conundrum: what is the frictional or diabatic process that permits the material modification of potential vorticity within the stratified oceanic interior associated with the downgradient fluxes? It is clear that diabatic processes are far too weak. A case will be made here that a coupling between mesoscale eddies and the internal wavefield acts as a frictional process. The case to be presented will focus on the interpretation of observations. These include current meter array data obtained as part of the POLYMODE Local Dynamics Experiment (LDE). [3] found correlations between internal wave momentum fluxes (stresses) and eddy rate of strain estimates that they interpreted in terms of a horizontal viscosity ν_h=200-400 m2 s-1. A revised estimate of this horizontal viscosity (ν_h=50 m2 s-1) and a vertical viscosity (ν_v=3×10-3 m2 s-1) estimate will be presented. Viscosity coefficients of this magnitude indicate that transfers of energy, momentum and potential vorticity between internal waves and mesoscale eddies are a significant part of the eddy energy^{[4]} and eddy enstrophy (potential vorticity squared) budgets. Finally, an attempt will be made to relate such coupling coefficients to recent satellite altimetry based estimates of mesoscale eddy kinetic energy cascades^{[5]} (see also Scott et al., this session), which, according to a preliminary numerical study (Arbic et al

  18. 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.

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

    PubMed

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

    2010-10-01

    The lithium tokamak experiment (LTX) is a modest-sized spherical tokamak (R(0)=0.4 m and a=0.26 m) designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 °C. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.

  20. Magnetic Diagnostics for Equilibrium Reconstructions in the Presence of Nonaxisymmetric Eddy Current Distributions in Tokamaks

    SciTech Connect

    Kaita, R.; Kozub, T.; Logan, N.; Majeski, R.; Menard, J.; Zakharov, L.

    2010-12-10

    The lithium tokamak experiment LTX is a modest-sized spherical tokamak R0=0.4 m and a =0.26 m designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 oC. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.

  1. 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.

  2. 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.

  3. Anomalous diffusion of electromagnetic eddy currents in geological formations

    NASA Astrophysics Data System (ADS)

    Weiss, Chester J.; Everett, Mark E.

    2007-08-01

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Swiderski, Waldemar

    2016-10-01

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

  12. 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.

  13. 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.

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

    PubMed

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

    2016-11-01

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

  15. The eddy current probe array for Keda Torus eXperiment

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  16. Research Initiatives for Materials State Sensing (RIMSS) Task Order 0020: High Frequency Eddy Current NDE

    DTIC Science & Technology

    2014-10-01

    Approved for public release; distribution unlimited.  Between single sweep measurements Eddy Current excitation will not run, to prevent heating the...AFRL-RX-WP-TR-2015-0004 RESEARCH INITIATIVES FOR MATERIALS STATE SENSING (RIMSS) Task Order 0020: High Frequency Eddy Current NDE...Frequency Eddy Current NDE 5a. CONTRACT NUMBER FA8650-10-D-5210-0020 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR(S) See

  17. Gas turbine coatings eddy current quantitative and qualitative evaluation

    NASA Astrophysics Data System (ADS)

    Ribichini, Remo; Giolli, Carlo; Scrinzi, Erica

    2017-02-01

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

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Solution to the Eddy-Current Problem for Type-II Superconductors by Relaxation Method

    NASA Astrophysics Data System (ADS)

    Janíková, Edita; Slodička, Marián

    2008-09-01

    The fast developing industrial applications of superconductors require rigorous mathematical models of their physical behaviour and efficient numerical methods to solve them. We propose and study theoretically a new approximation scheme to solve the 3D eddy-current problem of diffusion of the electric field in type-II superconductors. The method is based on the relaxation principle, where the nonlinear time- and space-dependent partial differential equation (PDE) is split into a linear time-independent PDE coupled with a nonlinear equation involving no partial derivatives.

  6. 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.

  7. Observed air-sea interactions in tropical cyclone Isaac over Loop Current mesoscale eddy features

    NASA Astrophysics Data System (ADS)

    Jaimes, Benjamin; Shay, Lynn K.; Brewster, Jodi K.

    2016-12-01

    Air-sea interactions during the intensification of tropical storm Isaac (2012) into a hurricane, over warm oceanic mesoscale eddy features, are investigated using airborne oceanographic and atmospheric profilers. Understanding these complex interactions is critical to correctly evaluating and predicting storm effects on marine and coastal facilities in the Gulf of Mexico, wind-driven mixing and transport of suspended matter throughout the water column, and oceanic feedbacks on storm intensity. Isaac strengthened as it moved over a Loop Current warm-core eddy (WCE) where sea surface warming (positive feedback mechanism) of ∼0.5 °C was measured over a 12-h interval. Enhanced bulk enthalpy fluxes were estimated during this intensification stage due to an increase in moisture disequilibrium between the ocean and atmosphere. These results support the hypothesis that enhanced buoyant forcing from the ocean is an important intensification mechanism in tropical cyclones over warm oceanic mesoscale eddy features. Larger values in equivalent potential temperature (θE = 365   ∘K) were measured inside the hurricane boundary layer (HBL) over the WCE, where the vertical shear in horizontal currents (δV) remained stable and the ensuing cooling vertical mixing was negligible; smaller values in θE (355   ∘K) were measured over an oceanic frontal cyclone, where vertical mixing and upper-ocean cooling were more intense due to instability development in δV . Thus, correctly representing oceanic mesoscale eddy features in coupled numerical models is important to accurately reproduce oceanic responses to tropical cyclone forcing, as well as the contrasting thermodynamic forcing of the HBL that often causes storm intensity fluctuations over these warm oceanic regimes.

  8. 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

  9. 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.

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

    PubMed

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

    2016-02-26

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

  11. 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

  12. 3-D residual eddy current field characterisation: applied to diffusion weighted magnetic resonance imaging.

    PubMed

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

    2013-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Svatoš, J.

    2016-11-01

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

  14. 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

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

    DTIC Science & Technology

    2008-12-01

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

  16. 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. __________________________________________________

  17. 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.

  18. 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.

  19. Eddy-Current Sensors with Asymmetrical Point Spread Function

    PubMed Central

    Gajda, Janusz; Stencel, Marek

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Chen, Xing-Le; Lei, Yin-Zhao

    2015-03-01

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

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

    SciTech Connect

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    PubMed

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

    2017-02-01

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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    SciTech Connect

    Ward, R.C.; LaBoissonniere, A.

    1995-12-31

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

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

    NASA Astrophysics Data System (ADS)

    Fukutomi, H.; Ogata, T.

    2004-02-01

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Lepage, B.

    2012-05-01

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

  10. 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.

  11. 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.

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

    SciTech Connect

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

    2016-01-15

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

  13. 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.

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

    PubMed Central

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

    2017-01-01

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

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

    PubMed

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

    2017-03-13

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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Ozkaya, Efe; Yilmaz, Cetin

    2017-02-01

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

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

    SciTech Connect

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

    2015-07-01

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

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

    SciTech Connect

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

    2015-07-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  2. 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.

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

    DTIC Science & Technology

    2014-12-23

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

  4. Precise on-machine extraction of the surface normal vector using an eddy current sensor array

    NASA Astrophysics Data System (ADS)

    Wang, Yongqing; Lian, Meng; Liu, Haibo; Ying, Yangwei; Sheng, Xianjun

    2016-11-01

    To satisfy the requirements of on-machine measurement of the surface normal during complex surface manufacturing, a highly robust normal vector extraction method using an Eddy current (EC) displacement sensor array is developed, the output of which is almost unaffected by surface brightness, machining coolant and environmental noise. A precise normal vector extraction model based on a triangular-distributed EC sensor array is first established. Calibration of the effects of object surface inclination and coupling interference on measurement results, and the relative position of EC sensors, is involved. A novel apparatus employing three EC sensors and a force transducer was designed, which can be easily integrated into the computer numerical control (CNC) machine tool spindle and/or robot terminal execution. Finally, to test the validity and practicability of the proposed method, typical experiments were conducted with specified testing pieces using the developed approach and system, such as an inclined plane and cylindrical and spherical surfaces.

  5. Eddy Current Minimizing Flow Plug for Use in Flow Conditioning and Flow Metering

    NASA Technical Reports Server (NTRS)

    England, John Dwight (Inventor); Kelley, Anthony R. (Inventor)

    2015-01-01

    An eddy-current-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.

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

    NASA Astrophysics Data System (ADS)

    Rowland, Roderick

    1996-11-01

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

  7. The coupling of mechanical dynamics and induced currents in plates and surfaces

    SciTech Connect

    Weissenburger, D.W.; Bialek, J.M.

    1986-10-01

    Significant mechanical reactions and deflections may be produced when electrical eddy currents induced in a conducting structure by transformer-like electromotive forces interact with background magnetic fields. Additional eddy currents induced by structural motion through the background fields modify both the mechanical and electrical dynamic behavior of the system. The observed effects of these motional eddy currents are sometimes referred to as magnetic damping and magnetic stiffness. This paper addresses the coupled structural deformation and eddy currents in flat plates and simple two-dimensional surfaces in three-space. A coupled system of equations has been formulated using finite element techniques for the mechanical aspects and a mesh network method for the electrical aspects of the problem.

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

    SciTech Connect

    DeLucia, J.

    1985-12-01

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

  9. 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.

  10. 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

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1987-11-01

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

  13. 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Brown, Alexander; Eviston, Connor

    2017-02-01

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

  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. 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.

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

    PubMed

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

    2005-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Li, Rongfeng; Zeng, Qingcun; Ji, Zhongzhen

    1992-09-01

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

  2. Scanning tone burst eddy-current thermography (S-TBET) for NDT of carbon fiber reinforced plastic (CFRP) components

    SciTech Connect

    Libin, M. N.; Maxfield, B. W.; Balasubramanian, Krishnan

    2014-02-18

    Tone Burst Eddy Current technique uses eddy current to apply transient heating inside a component and uses a conventional IR camera for visualization of the response to the transient heating. This technique has been earliest demonstrated for metallic components made of AL, Steel, Stainless Steel, etc., and for detection of cracks, corrosion and adhesive dis-bonds. Although, not nearly as conducting as metals, the Carbon Fibre Reinforced Plastic (CFRP) material absorbs measurable electromagnetic radiation in the frequency range above 10 kHz. When the surface temperature is observed on the surface that is being heated (defined as the surface just beneath and slightly to one side of the heating coil), the surface temperature increases with increasing frequency because the internal heating increases with frequency. A 2-D anisotropic transient Eddy current heating and thermal conduction model has been developed that provides a reasonable description of the processes described above. The inherent anisotropy of CFRP laminates is included in this model by calculating the heating due to three superimposed, tightly coupled isotropic layers having a specified ply-layup. The experimental apparatus consists of an induction heating coil and an IR camera with low NETD and high frame rates. The coil is moved over the sample using a stepper motor controlled manipulator. The IR data recording is synchronized with the motion control to provide a movie of the surface temperature over time. Several components were evaluated for detection of impact damage, location of stiffeners, etc. on CFRP components.

  3. Scanning tone burst eddy-current thermography (S-TBET) for NDT of carbon fiber reinforced plastic (CFRP) components

    NASA Astrophysics Data System (ADS)

    Libin, M. N.; Maxfield, B. W.; Balasubramanian, Krishnan

    2014-02-01

    Tone Burst Eddy Current technique uses eddy current to apply transient heating inside a component and uses a conventional IR camera for visualization of the response to the transient heating. This technique has been earliest demonstrated for metallic components made of AL, Steel, Stainless Steel, etc., and for detection of cracks, corrosion and adhesive dis-bonds. Although, not nearly as conducting as metals, the Carbon Fibre Reinforced Plastic (CFRP) material absorbs measurable electromagnetic radiation in the frequency range above 10 kHz. When the surface temperature is observed on the surface that is being heated (defined as the surface just beneath and slightly to one side of the heating coil), the surface temperature increases with increasing frequency because the internal heating increases with frequency. A 2-D anisotropic transient Eddy current heating and thermal conduction model has been developed that provides a reasonable description of the processes described above. The inherent anisotropy of CFRP laminates is included in this model by calculating the heating due to three superimposed, tightly coupled isotropic layers having a specified ply-layup. The experimental apparatus consists of an induction heating coil and an IR camera with low NETD and high frame rates. The coil is moved over the sample using a stepper motor controlled manipulator. The IR data recording is synchronized with the motion control to provide a movie of the surface temperature over time. Several components were evaluated for detection of impact damage, location of stiffeners, etc. on CFRP components.

  4. Advances in transient (pulsed) eddy current for inspection of multi-layer aluminum structures in the presence of ferrous fasteners

    NASA Astrophysics Data System (ADS)

    Desjardins, D. R.; Vallières, G.; Whalen, P. P.; Krause, T. W.

    2012-05-01

    An experimental investigation of the electromagnetic processes underlying transient (pulsed) eddy current inspection of aircraft wing structures in the vicinity of ferrous fasteners is performed. The separate effects of transient excitation of ferrous fastener and eddy currents induced in the surrounding aluminum structure are explored using a transmit-receive configuration with transient excitation of a steel rod, an aluminum plate with a bore hole and a steel rod through the bore hole. Observations are used to interpret results from a coupled driving and differential coil sensing unit applied to detect fatigue cracks emanating from bolt holes in aluminum structures with ferrous fasteners present. In particular, it is noted that abrupt magnetization of the fastener, by the probe's central driving unit, can transfer flux and consequently, induce strong eddy current responses deep within the aluminum structure in the vicinity of the bore hole. Rotation of the probe, centered over the fastener, permits detection of subsurface discontinuities, such as cracks, by the pair of differentially connected pickup coils.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Hall, Cody A.; Leben, Robert R.

    2016-12-01

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

  7. 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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

    Yakimov, Evgeny; Galtseva, Olga; Ustyugov, Daniil

    2017-01-01

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

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

    SciTech Connect

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

    1985-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    PubMed

    Thompson, Andrew F

    2008-12-28

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

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

    SciTech Connect

    Fu, Fangwei

    2006-01-01

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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

    Hano, Mitsuo; Hotta, Masashi

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  9. 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…

  10. 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.

  11. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Wu, Tao; Bowler, John R.

    2017-02-01

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

  14. 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…

  15. Eddy Effects in the General Circulation, Spanning Mean Currents, Mesoscale Eddies, and Topographic Generation, Including Submesoscale Nests

    DTIC Science & Technology

    2013-09-30

    Eddies, and Topographic Generation, Including Submesoscale Nests Alexander F. Shchepetkin (PI) James C. McWilliams and Maarten J. Molemaker (co-PIs... submesoscale phenomena; analysis and understanding the underlying physical processes; improving parameterizations of unresolved processes...mesoscale and submesoscale eddies generated by instability and bottom topography effects. This is accompanied by development of modeling codes

  16. Development of a resonant repeater tag for the enhancement of sensitivity and specificity in a wireless eddy current sensing scheme

    NASA Astrophysics Data System (ADS)

    Woo, Byungki; Andringa, Matthew; Wood, Sharon; Neikirk, Dean P.

    2006-03-01

    Eddy current sensing has been successfully used in various applications from testing heat exchange tubes for nuclear power plants to assessing dielectric thickness on printed circuit boards. However, in civil infrastructures cosmetic or cementitious surface material often keeps the probe or reader coil from accessing conductive medium inside the structure, resulting in reduced coupling as the distance increases between the DUT (device under test) and probe. Thus, the direct application of existing eddy current sensing technique is not very useful to detect flaws in civil infrastructures. To address this weak coupling problem, a simple scheme is proposed in which a resonant passive repeater tag is placed between the reader coil and the conducting test target. In this paper, the feasibility of detecting defects like cracks or fractures in conductive medium using a passive resonant tag and remote inductive pick-up as a method of interrogation is shown. Experimental data taken from simple setups to demonstrate the advantage of the proposed scheme are presented.

  17. 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.

  18. 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.

  19. Simultaneous absolute and differential operation of eddy current bobbin probes for heat exchanger tube inspection

    SciTech Connect

    Sullivan, S.P.; Smith, S.P.; Sharp, F.L.

    2000-05-01

    Here the authors try to dissolve some commonly held misconceptions about the operation of eddy current probes used for inspecting heat exchanger tubes. With the help of computer model results, the authors demonstrate that, for optimized operation, absolute/differential probes should be operated with coil current flowing in phase with another. This month's feature should be of interest to researchers as well as for NDT field personnel.

  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. Finite element solution of nonlinear eddy current problems with periodic excitation and its industrial applications☆

    PubMed Central

    Bíró, Oszkár; Koczka, Gergely; Preis, Kurt

    2014-01-01

    An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer. PMID

  2. Finite element solution of nonlinear eddy current problems with periodic excitation and its industrial applications.

    PubMed

    Bíró, Oszkár; Koczka, Gergely; Preis, Kurt

    2014-05-01

    An efficient finite element method to take account of the nonlinearity of the magnetic materials when analyzing three-dimensional eddy current problems is presented in this paper. The problem is formulated in terms of vector and scalar potentials approximated by edge and node based finite element basis functions. The application of Galerkin techniques leads to a large, nonlinear system of ordinary differential equations in the time domain. The excitations are assumed to be time-periodic and the steady-state periodic solution is of interest only. This is represented either in the frequency domain as a finite Fourier series or in the time domain as a set of discrete time values within one period for each finite element degree of freedom. The former approach is the (continuous) harmonic balance method and, in the latter one, discrete Fourier transformation will be shown to lead to a discrete harmonic balance method. Due to the nonlinearity, all harmonics, both continuous and discrete, are coupled to each other. The harmonics would be decoupled if the problem were linear, therefore, a special nonlinear iteration technique, the fixed-point method is used to linearize the equations by selecting a time-independent permeability distribution, the so-called fixed-point permeability in each nonlinear iteration step. This leads to uncoupled harmonics within these steps. As industrial applications, analyses of large power transformers are presented. The first example is the computation of the electromagnetic field of a single-phase transformer in the time domain with the results compared to those obtained by traditional time-stepping techniques. In the second application, an advanced model of the same transformer is analyzed in the frequency domain by the harmonic balance method with the effect of the presence of higher harmonics on the losses investigated. Finally a third example tackles the case of direct current (DC) bias in the coils of a single-phase transformer.

  3. Comparison of Firebrand Propagation Prediction by a Plume Model and a Coupled-Fire/Atmosphere Large-Eddy Simulator

    NASA Astrophysics Data System (ADS)

    Bhutia, Sangay; Ann Jenkins, Mary; Sun, Ruiyu

    2010-01-01

    Firebrand spotting is one of the most vexing problems associated with wildland fires, challenging the lives and efforts of fire-fighting planners. This work is an effort to model numerically the event of firebrand spotting for the purposes of reviewing past modelling approaches and of demonstrating a more current coupled fire/atmosphere approach. A simple, two-dimensional treatment of the process of firebrand lofting is examined under the restrictive conditions typical of a classical plume modelling approach. Using this approach, the differences in trajectories of combusting and non-combusting particles are investigated. Next, firebrand spotting is examined using a coupled fire/atmosphere LES (Large Eddy Simulator) in which the processes of firebrand lofting, propagation, and deposition are connected. The behaviour of combusting and non-combusting firebrands released from a moving grassfire into three-dimensional time-varying coupled atmosphere-wildfire induced circulations is examined. When these results are compared to the results of a classical plume model for firebrand spotting, it is found that firebrand propagation in the coupled LES simulated flow is significantly different from that obtained by the two-dimensional empirically-derived plume model approach. The coupled atmosphere-wildfire LES results are explorative and need to be subjected to direct testing.

  4. 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.

  5. 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.

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

    SciTech Connect

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

    2000-01-01

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

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Fukuoka, Katsuhiro; Hashimoto, Mitsuo

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

  10. 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.

  11. Eddy Current Pulsed Thermography with Different Excitation Configurations for Metallic Material and Defect Characterization.

    PubMed

    Tian, Gui Yun; Gao, Yunlai; Li, Kongjing; Wang, Yizhe; Gao, Bin; He, Yunze

    2016-06-08

    This paper reviews recent developments of eddy current pulsed thermography (ECPT) for material characterization and nondestructive evaluation (NDE). Due to the fact that line-coil-based ECPT, with the limitation of non-uniform heating and a restricted view, is not suitable for complex geometry structures evaluation, Helmholtz coils and ferrite-yoke-based excitation configurations of ECPT are proposed and compared. Simulations and experiments of new ECPT configurations considering the multi-physical-phenomenon of hysteresis losses, stray losses, and eddy current heating in conjunction with uniform induction magnetic field have been conducted and implemented for ferromagnetic and non-ferromagnetic materials. These configurations of ECPT for metallic material and defect characterization are discussed and compared with conventional line-coil configuration. The results indicate that the proposed ECPT excitation configurations can be applied for different shapes of samples such as turbine blade edges and rail tracks.

  12. 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

  13. 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.

  14. Magnetic, eddy-current, and electrical methods. Electromagnetic quality control of carburization of steel products

    SciTech Connect

    Gorkunov, E.S.; Kogan, L.Kh.; Baraz, E.M.; Korolev, A.L.

    1994-08-01

    We have studied the effect that the casehardening (carburizing) temperature and time, carburizer activity, and variation of the conditions of subsequent heat treatment has on the electromagnetic properties of carburized specimens of 12Kh2N4A steel. The possibilities of nondestructive testing for the main parameters that determine the quality of carburization of 12Kh2N4A steel products, using coercimetric and eddy-current methods, are considered. The optimal depth of penetration of the magnetic flux in the portion of the inspected carburized product for greater inspection reliability is determined. The joint use of coercimetric and eddy-current methods makes it possible to monitor the depth and wear resistance of the carburized case and also to estimate the amount of retained austenite in the layer and reveal the effect of the decarburized surface zone.

  15. Design of permanent magnet eddy current brake for a small scaled electromagnetic launch model

    NASA Astrophysics Data System (ADS)

    Zhou, Shigui; Yu, Haitao; Hu, Minqiang; Huang, Lei

    2012-04-01

    A variable pole-pitch double-sided permanent magnet (PM) linear eddy current brake (LECB) is proposed for a small scaled electromagnetic launch model. A two-dimensional (2D) analytical steady state model is presented for the double-sided PM-LECB, and the expression for the braking force is derived. Based on the analytical model, the material and eddy current skin effect of the conducting plate are analyzed. Moreover, a variable pole-pitch double-sided PM-LECB is proposed for the effective braking of the moving plate. In addition, the braking force is predicted by finite element (FE) analysis, and the simulated results are in good agreement with the analytical model. Finally, a prototype is presented to test the braking profile for validation of the proposed design.

  16. 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.

  17. Reliability assessment at airline inspection facilities. Volume 2: Protocol for an eddy current inspection reliability experiment

    NASA Astrophysics Data System (ADS)

    Spencer, Floyd; Borgonovi, Giancarlo; Roach, Dennis; Schurman, Don; Smith, Ron

    1993-05-01

    The Aging Aircraft NDI Development and Demonstration Center (AANC) at Sandia National Laboratories is charged by the FAA to support technology transfer, technology assessment, and technology validation. A key task facing the center is the establishment of a consistent and systematic methodology to assess the reliability of inspections through field experiments. This task is divided into three major areas: reliability of eddy current lap splice inspections at transport aircraft maintenance facilities; reliability of inspection at commuter aircraft maintenance facilities; and reliability of inspection associated with visual inspection of aircraft structural parts. Volume 2 is the second document in a series of three describing the planning, execution, and results of an eddy current inspection field experiment. This document provides a detailed description of the experimental hardware and protocols. It also describes the methodology to be used in the analysis of the data.

  18. 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.

  19. Analysis and experiment of eddy current loss in Homopolar magnetic bearings with laminated rotor cores

    NASA Astrophysics Data System (ADS)

    Jinji, Sun; Dong, Chen

    2013-08-01

    This paper analyses the eddy current loss in Homopolar magnetic bearings with laminated rotor cores produced by the high speed rotation in order to reduce the power loss for the aerospace applications. The analytical model of rotational power loss is proposed in Homopolar magnetic bearings with laminated rotor cores considering the magnetic circuit difference between Homopolar and Heteropolar magnetic bearings. Therefore, the eddy current power loss can be calculated accurately using the analytical model by magnetic field solutions according to the distribution of magnetic fields around the pole surface and boundary conditions at the surface of the rotor cores. The measurement method of rotational power loss in Homopolar magnetic bearing is proposed, and the results of the theoretical analysis are verified by experiments in the prototype MSCMG. The experimental results show the correctness of calculation results.

  20. Mesoscale Coupled Ocean-Atmosphere Feedbacks in Boundary Current Systems

    NASA Astrophysics Data System (ADS)

    Putrasahan, Dian Ariyani

    The focus of this dissertation is on studying ocean-atmosphere (OA) interactions in the Humboldt Current System (HCS) and Kuroshio Extension (KE) region using satellite observations and the Scripps Coupled Ocean-Atmosphere Regional (SCOAR) model. Within SCOAR, a new technique is introduced by implementing an interactive 2-D spatial smoother within the SST-flux coupler to remove the mesoscale SST field felt by the atmosphere. This procedure allows large-scale SST coupling to be preserved while extinguishing the mesoscale eddy impacts on the atmospheric boundary layer (ABL). This technique provides insights to spatial-scale dependence of OA coupling, and the impact of mesoscale features on both the ABL and the surface ocean. For the HCS, the use of downscaled forcing from SCOAR, as compared to NCEP Reanalysis 2, proves to be more appropriate in quantifying wind-driven upwelling indices along the coast of Peru and Chile. The difference in their wind stress distribution has significant impact on the wind-driven upwelling processes and total upwelling transport along the coast. Although upwelling induced by coastal Ekman transport dominates the wind-driven upwelling along coastal areas, Ekman pumping can account for 30% of the wind-driven upwelling in several coastal locations. Control SCOAR shows significant SST-wind stress coupling during fall and winter, while Smoothed SCOAR shows insignificant coupling throughout, indicating the important role of ocean mesoscale eddies on air-sea coupling in HCS. The SST-wind stress coupling however, did not produce any rectified response on the ocean eddies. Coupling between SST, wind speed and latent heat flux is insignificant on large-scale coupling and full coupling mode. On the other hand, coupling between these three variables are significant on the mesoscale for most of the model run, which suggests that mesoscale SST affects latent heat through direct flux anomalies as well as indirectly through stability changes on the

  1. Numerical study on the interactions between the Kuroshio current in the Luzon Strait and a mesoscale eddy

    NASA Astrophysics Data System (ADS)

    Kuo, Yi-Chun; Chern, Ching-Sheng; Zheng, Zhe-Wen

    2017-02-01

    The Luzon Strait (LS) connects the northwestern Pacific Ocean and the South China Sea (SCS) and is the western boundary gap for the Kuroshio current (KC). Satellite observations indicate that a cyclonic mesoscale eddy can trigger westward extension of the KC into the SCS and shed a smaller anticyclonic eddy to the west of the LS. We used a nonlinear reduced-gravity (primitive equation) model to study this phenomenon and analyzed the dynamic process. The location of the collision between the eddy and the KC could be critical for varying the circulation in the LS. The eddy's deformation rate, associated with its decaying speed, is also closely related to the location of the eddy during collision. When a cyclonic eddy moved from a region to the east of the Luzon Island toward the LS, the KC intruded into the SCS with growing negative vorticity during the collision of the eddy and KC. This tendency for negative vorticity is attributed to the beta effect and squeezing of the planetary vorticity caused by the flow divergence. As the eddy dissipated, the KC in the LS recovered its original pattern. When the collision of the eddy occurred at the center of the LS, the momentum balance of the KC loop was dominated by the inertial term, and the circulation in the LS remained in a leaping state.

  2. Emergent eddy saturation from an energy constrained eddy parameterisation

    NASA Astrophysics Data System (ADS)

    Mak, J.; Marshall, D. P.; Maddison, J. R.; Bachman, S. D.

    2017-04-01

    The large-scale features of the global ocean circulation and the sensitivity of these features with respect to forcing changes are critically dependent upon the influence of the mesoscale eddy field. One such feature, observed in numerical simulations whereby the mesoscale eddy field is at least partially resolved, is the phenomenon of eddy saturation, where the time-mean circumpolar transport of the Antarctic Circumpolar Current displays relative insensitivity to wind forcing changes. Coarse-resolution models employing the Gent-McWilliams parameterisation with a constant Gent-McWilliams eddy transfer coefficient seem unable to reproduce this phenomenon. In this article, an idealised model for a wind-forced, zonally symmetric flow in a channel is used to investigate the sensitivity of the circumpolar transport to changes in wind forcing under different eddy closures. It is shown that, when coupled to a simple parameterised eddy energy budget, the Gent-McWilliams eddy transfer coefficient of the form described in Marshall et al. (2012) [A framework for parameterizing eddy potential vorticity fluxes, J. Phys. Oceanogr., vol. 42, 539-557], which includes a linear eddy energy dependence, produces eddy saturation as an emergent property.

  3. 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..

  4. 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

  5. a Parametric Study of Eddy Current Response for Probability of Detection Estimation

    NASA Astrophysics Data System (ADS)

    Hoppe, W. C.

    2010-02-01

    In the study reported here, historical Probability of Detection (POD) data for eddy current inspections were analyzed using an extension of the "a-hat versus a" model in order to better account for known crack variables and thereby better separate system and crack factors influencing the POD parameters. Intriguing insights have been gained in the process suggesting a simple model for POD estimation. The parametric model will be presented including results of the study and suggestions for further research.

  6. 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.

  7. Calculation of eddy currents and associated losses in electrical steel laminations

    SciTech Connect

    Gyselinck, J.; Vandevelde, L.; Melkebeek, J. . Lab. for Electrical Machines and Power Electronics); Dular, P.; Henrotte, F.; Legros, W. . Dept. of Electrical Engineering)

    1999-05-01

    Starting from the well known analytical formula for the eddy current losses in electrical steel laminations, saturation and edge effects are studied by means of 1D and 2D finite element models of a single lamination. A novel method for directly including the laminated core energy dissipation in a time stepped 2D model of a complete (rotating) machine is proposed. By way of example the method is applied to a tooth model enforced flux waveforms.

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

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

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

  10. 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.

  11. Investigation of Acoustic Fields Generated by Eddy Currents Using an Atomic Force Microscope (Postprint)

    DTIC Science & Technology

    2012-08-01

    AFRL-RX-WP-JA-2014-0230 INVESTIGATION OF ACOUSTIC FIELDS GENERATED BY EDDY CURRENTS USING AN ATOMIC FORCE MICROSCOPE (POSTPRINT) V...Institute of Physics AIR FORCE RESEARCH LABORATORY MATERIALS AND MANUFACTURING DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750 AIR... FORCE MATERIEL COMMAND UNITED STATES AIR FORCE NOTICE AND SIGNATURE PAGE Using Government drawings, specifications, or other data included in

  12. Fundamental Feature Extraction Methods for the Analysis of Eddy Current Data (Preprint)

    DTIC Science & Technology

    2006-12-01

    5d. PROJECT NUMBER 4349 5e. TASK NUMBER RG 6. AUTHOR(S) Jeremy S. Knopp (AFRL/RXLP) John C. Aldrin (Computational Tools ) 5f. WORK UNIT...NUMBER M04R1000 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Computational Tools Gurnee...1 and John C. ALDRINb a Air Force Research Laboratory, USA b Computational Tools ,USA Abstract. Features are investigated in eddy current

  13. Analytical model development of an eddy-current-based non-contacting steel plate conveyance system

    NASA Astrophysics Data System (ADS)

    Liu, Cheng-Tsung; Lin, Sheng-Yang; Yang, Yung-Yi; Hwang, Chang-Chou

    A concise model for analyzing and predicting the quasi-static electromagnetic characteristics of an eddy-current-based non-contacting steel plate conveyance system has been developed. Confirmed by three-dimensional (3-D) finite element analysis (FEA), adequacy of the analytical model can be demonstrated. Such an effective approach, which can be conveniently used by the potential industries for preliminary system operational performance evaluations, will be essential for designers and on-site engineers.

  14. Progress and Pitfalls in Satellite Surveillance of Loop Current Frontal Eddy Cyclones

    NASA Astrophysics Data System (ADS)

    Walker, N. D.; Leben, R. R.; Anderson, S. P.; Balasubramanian, S.

    2007-05-01

    In the last decade, significant advances in active and passive remote sensing have transpired that are enabling researchers to better quantify and model time and space scales of ocean processes. This paper presents recent attempts to track the motion and development of rapidly propagating cyclonic mesoscale eddies along the outer margin of the Loop Current in the Gulf of Mexico. Recent research has shown the critical role that these features play in the intensification of surface currents and as trigger mechanisms for deep flows in oil and gas producing areas in the northern Gulf of Mexico. The rapid motion of these cyclonic frontal features (35 km/day) has made their study problematic. In this paper, we discuss the use of several remote sensing systems and the integration of data from these systems to better understand the behavior and impacts of the frontal eddy cyclones on Gulf circulation processes. Mid-infrared (3.5-3.9 micron) measurements from GOES GVAR, available in real-time every 15 minutes over the Gulf, provide an excellent source of "de-clouded" night-time surface temperature information, from which sea surface temperatures (SST) are estimated with daily updates (http:www.esl.lsu.edu). Measurements in this atmospheric window maximize the sampling frequency of ocean information in cloudy and humid ocean regions such as the Gulf of Mexico. On the other hand, satellite altimetry measurements provide the only remote sensing technique that directly measures a dynamical variable of ocean state - the sea surface height (SSH). Detection of mesoscale eddies has been improved by combining multi-mission measurements from TOPEX-Poseidon, ERS- 2, GFO, Jason-1 and Envisat into a gridded product, updated daily (http:argo.colorado.edu/~realtime/welcome). Ocean color sensors (SeaWiFS, MODIS, Oceansat-1 OCM) provide surface pigment information (chlorophyll a, CDOM) that can aid in the discrimination of Gulf features as cold core eddies contain more chlorophyll a, due to

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Approximate expressions of mean eddy current torque acted on space debris

    NASA Astrophysics Data System (ADS)

    Lin, Hou-yuan; Zhao, Chang-yin

    2017-02-01

    Rotational state of space debris will be influenced by eddy current torque which is produced by the conducting body rotating within the geomagnetic field. Former expressions of instantaneous torque established in body-fixed coordinate system will change in space during rotation due to the variation of the coordinate system. In order to further investigate the evolution of the rotation of space debris subjected to the eddy current torque, approximate expressions of mean eddy current torque in inertial coordinate system are obtained from the average of the Euler dynamics equations under the assumption that two of the principal moments of inertia of the space debris are similar. Then the expressions are verified through numerical simulation, in which the orientation of the averaged variation of angular momentum is in agreement with the torque from the expressions, which is on an identical plane with magnetic field and the angular momentum. The torque and the averaged variation of the angular momentum have the same evolution trend during rotation in spite of minor deviations of their values.

  20. 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> </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_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" 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_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</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="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1511.1278S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1511.1278S"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> measurement system evaluation for corrosion depth determination on cast aluminum aircraft structure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, Surendra; Greving, Dan; Kinney, Andy; Vensel, Fred; Ohm, Jim; Peeler, Mike</p> <p>2013-01-01</p> <p>An <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) technique was developed to determine the corrosion depth on a bare flange face of a cast aluminum A356-T6 aircraft engine structure. The EC response and the corrosion depths determined through metallurgical cross sections were used to develop an empirical relation between EC response and depth. The EC technique and depth determination are used to inspect the engine structures during overhaul to determine if they are fit for continued service. An accurate and reliable Non-Destructive Inspection is required to ensure that structures returned to service are safe for continued operation. NDE system reliability demonstrations of the <span class="hlt">eddy</span> <span class="hlt">current</span> technique are traditionally reported in terms of Probability of Detection (POD) data using MIL-HDBK-1823A. However, the calculation of POD data is based on a simple linear predictive model that is valid only if certain criteria are met. These are: 1) NDE system response is measurable (i.e. continuous data), 2) Flaw size is known and measurable (i.e. continuous data), 3) relationship between the NDE system response and flaw size is linear (or linear on a log scale), 4) variation in measured responseresponse around a predicted response for a given flaw size is normally distributed, 5) the variation around the predicted response is constant (i.e. variation does not change with flaw size), and 6) inherent variability in the NDE system is known and fully understood. In this work, a Measurement System Evaluation (MSE) of the <span class="hlt">Eddy</span> <span class="hlt">Current</span> System was used to address some of these concerns. This work was completed on two aircraft structures having varying corrosion depths. The data were acquired in a random manner at fifty regions of interests (ROIs). Three operators participated in this study, and each operator measured <span class="hlt">Eddy</span> <span class="hlt">Current</span> response three times in each ROI. In total, there were four hundred and fifty data points collected. Following this, the two structures were sectioned for measuring corrosion depth. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........82P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........82P"><span>Dynamic suspension modeling of an <span class="hlt">eddy-current</span> device: An application to Maglev</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paudel, Nirmal</p> <p></p> <p>When a magnetic source is simultaneously oscillated and translationally moved above a linear conductive passive guideway such as aluminum, <span class="hlt">eddy-currents</span> are induced that give rise to a time-varying opposing field in the air-gap. This time-varying opposing field interacts with the source field, creating simultaneously suspension, propulsion or braking and lateral forces that are required for a Maglev system. In this thesis, a two-dimensional (2-D) analytic based steady-state <span class="hlt">eddy-current</span> model has been derived for the case when an arbitrary magnetic source is oscillated and moved in two directions above a conductive guideway using a spatial Fourier transform technique. The problem is formulated using both the magnetic vector potential, A, and scalar potential, o.Using this novel A-o approach the magnetic source needs to be incorporated only into the boundary conditions of the guideway and only the magnitude of the source field along the guideway surface is required in order to compute the forces and power loss. The performance of this analytic based steady-state <span class="hlt">eddy-current</span> model has been validated by comparing it with a 2-D finite-element model. The magnetic source used for the validation is a radially magnetized Halbach rotor, called an electrodynamic wheel (EDW). The 2-D analytic based transient <span class="hlt">eddy-current</span> force and power loss equations are derived for the case when an arbitrary magnetic source is moving and oscillating above a conductive guideway. These general equations for force and power loss are derived using a spatial Fourier transform and temporal Laplace transform technique. The derived equations are capable of accounting for step changes in the input parameters, in addition to arbitrary continuous changes in the input conditions. The equations have been validated for both step changes as well as continuous changes in the input conditions using a 2-D transient finite-element model. The dynamics of an EDW Maglev is investigated by using both steady</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20632898','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20632898"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/15616560','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15616560"><span>Break-up of the Atlantic deep western boundary <span class="hlt">current</span> into <span class="hlt">eddies</span> at 8 degrees S.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dengler, M; Schott, F A; Eden, C; Brandt, P; Fischer, J; Zantopp, R J</p> <p>2004-12-23</p> <p>The existence in the ocean of deep western boundary <span class="hlt">currents</span>, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago. These ocean <span class="hlt">currents</span> have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary <span class="hlt">current</span> is estimated to carry (10-40) x 10(6) m3 s(-1) of water, transporting North Atlantic Deep Water--from the overflow regions between Greenland and Scotland and from the Labrador Sea--into the South Atlantic and the Antarctic circumpolar <span class="hlt">current</span>. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary <span class="hlt">current</span> breaks up at 8 degrees S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating <span class="hlt">eddies</span>, rather than by a continuous flow. Our model simulation indicates that the deep western boundary <span class="hlt">current</span> breaks up into <span class="hlt">eddies</span> at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26329187','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26329187"><span>Measurement of <span class="hlt">eddy-current</span> distribution in the vacuum vessel of the Sino-UNIted Spherical Tokamak.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, G; Tan, Y; Liu, Y Q</p> <p>2015-08-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">currents</span> have an important effect on tokamak plasma equilibrium and control of magneto hydrodynamic activity. The vacuum vessel of the Sino-UNIted Spherical Tokamak is separated into two hemispherical sections by a toroidal insulating barrier. Consequently, the characteristics of <span class="hlt">eddy</span> <span class="hlt">currents</span> are more complex than those found in a standard tokamak. Thus, it is necessary to measure and analyze the <span class="hlt">eddy-current</span> distribution. In this study, we propose an experimental method for measuring the <span class="hlt">eddy-current</span> distribution in a vacuum vessel. By placing a flexible printed circuit board with magnetic probes onto the external surface of the vacuum vessel to measure the magnetic field parallel to the surface and then subtracting the magnetic field generated by the vertical-field coils, the magnetic field due to the <span class="hlt">eddy</span> <span class="hlt">current</span> can be obtained, and its distribution can be determined. We successfully applied this method to the Sino-UNIted Spherical Tokamak, and thus, we obtained the <span class="hlt">eddy-current</span> distribution despite the presence of the magnetic field generated by the external coils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSA21C..07B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSA21C..07B"><span>Stratosphere-troposphere <span class="hlt">coupling</span>, downward control, <span class="hlt">eddy</span> feedbacks, and all that (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Birner, T.; Baldwin, M. P.; Thompson, D. W.</p> <p>2013-12-01</p> <p>Stratospheric variability, e.g. associated with sudden stratospheric warmings, can have substantial effects on surface weather and climate, especially at middle to high latitudes. Despite clear evidence of these impacts, the primary dynamics of such stratosphere-troposphere <span class="hlt">coupling</span> are not yet well understood. A range of theories and proposed mechanisms exists, but none is fully conclusive. Here we show that the stratospheric meridional circulation forces the column of air above the Arctic downwards into the troposphere, acting like a mechanical plunger that controls the day-to-day thickness of the troposphere. Concurrently, isentropic surfaces undergo large coherent associated changes in the lower stratosphere and upper troposphere, in particular in their meridional slope, affecting tropopause-level baroclinicity. Furthermore, polar cap tropopause height and temperature show large associated changes. Raising and lowering of the Arctic tropopause layer leads to stretching and compression of the tropospheric column and a north-south dipole in surface pressure similar to the Northern Annular Mode. However, vortex stretching is found to severely overestimate the surface pressure response highlighting the importance of internal tropospheric <span class="hlt">eddy</span> feedbacks. The response in tropopause potential temperature is found to be consistent with these tropospheric <span class="hlt">eddy</span> feedbacks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRC..119.4351C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRC..119.4351C"><span>Long-term trends in the East Australian <span class="hlt">Current</span> separation latitude and <span class="hlt">eddy</span> driven transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cetina-Heredia, P.; Roughan, M.; van Sebille, E.; Coleman, M. A.</p> <p>2014-07-01</p> <p>An observed warming of the Tasman Sea in recent decades has been linked to a poleward shift of the maximum wind stress curl, and a strengthening of the poleward flow along the coast of southeastern Australia. However, changes in the East Australian <span class="hlt">Current</span> (EAC) separation latitude, as well as in the contribution of the EAC, the EAC extension and its <span class="hlt">eddy</span> field to the total southward transport due to such a strengthening remain unknown. This study uses 30 years (1980-2010) of the Ocean Forecast for the Earth Simulator (OFES) sea surface height and velocity outputs to obtain a three decade long-time series of (i) the EAC separation latitude, (ii) the southward transport along the coast of southeastern Australia (28°S-39°S), and (iii) the southward transport across the EAC separation latitude. A Lagrangian approach is implemented and the spin parameter Ω is used to provide a quantitative distinction between the transports occurring outside and inside (cyclonic and anticyclonic) <span class="hlt">eddies</span>. Significant positive trends of the low pass southward transports indicate that the intensification of the poleward flow has occurred both within the EAC and in the EAC extension. In addition, a significant increase in southward transport inside and outside <span class="hlt">eddies</span> is found. Importantly, the contribution of <span class="hlt">eddy</span> driven transport has a large temporal variability and shows a sharp increase from 2005 onward. Finally our results show that the EAC has not penetrated further south but it has separated more frequently at the southernmost latitudes within the region where it typically turns eastward.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712816A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712816A"><span>A description of <span class="hlt">eddy</span>-mean flow feedbacks in equatorial and boundary <span class="hlt">current</span> systems of the South Indian Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aguiar-González, Borja; Ponsoni, Leandro; Maas, Leo R. M.; Ridderinkhof, Herman; van Aken, Hendrik</p> <p>2015-04-01</p> <p>While many observational and modeling efforts have addressed <span class="hlt">eddy</span>-mean flow interactions acting over nearly idealized zonal jets, little is know about whether findings in those studies can be extended to <span class="hlt">current</span> systems with different configurations in the real ocean. This topic is of special interest for ocean-climate models where <span class="hlt">eddy</span> interactions with the mean flow may be unresolved, demanding further insight on the mechanism by which the <span class="hlt">eddy</span> field and the mean circulation should feed back in a realistic representation of future climate change scenarios. Following this motivation, we investigate local exchange of momentum and kinetic energy operating in a variety of <span class="hlt">eddy</span>-mean flow systems of the South Indian Ocean (SIO). To this aim we use 21 years (1993-2013) of newly processed satellite altimetry observations, and adopt a definition of the mean flow as a seasonally-dependent temporal mean where the <span class="hlt">eddy</span> field encompasses the daily instantaneous deviation from the altimeter-derived velocities. This approach allows time-varying feedbacks to evolve throughout the year. We find that the <span class="hlt">eddy</span> field feeds back on the mean circulation, contributing importantly to the overall seasonal strengthening and weakening of all <span class="hlt">current</span> systems involved in the tropical and subtropical gyre of the SIO. Although significant contributions to the momentum and energy balances were also obtained along the Agulhas (Return) <span class="hlt">Current</span> and the Antarctic Circumpolar <span class="hlt">Current</span> (ACC), they exhibit a weak/absent seasonal cycle, suggesting that the strength of these dynamical processes is mostly persistent throughout the year. Spatial distribution of the <span class="hlt">eddy</span> kinetic energy conversion rates and the convergence of horizontal <span class="hlt">eddy</span> momentum fluxes indicate that over regions where the <span class="hlt">eddy</span> field draws energy from the mean flow through barotropic instabilities, the <span class="hlt">current</span> is importantly decelerated by alongstream <span class="hlt">eddy</span> forces on its upstream side, while further downstream the situation reverses with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862838','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862838"><span><span class="hlt">Eddy-current</span> system for the vibration-testing of blades</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Jacobs, Martin E.</p> <p>1977-01-01</p> <p>This invention is an improved system for the vibration-testing of cantilevered non-ferrous articles by inducing <span class="hlt">eddy</span> <span class="hlt">currents</span> therein. The principal advantage of the system is that relatively little heat is generated in the article being vibrated. Thus, a more accurate measurement of the fatigue characteristics of the article is obtained. Furthermore, the generation of relatively little heat in the blade permits tests to be conducted in low-pressure atmospheres simulating certain actual processes environments. Heat-generation in the vibrated article is minimized by utilizing <span class="hlt">eddy</span> <span class="hlt">currents</span> which are generated by an electromagnet whose magnetic field varies but does not change polarity. The typical winding for the electromagnet is excited with pulsating d.c. That is, the winding is alternately charged by connecting it across a d.c. power supply and then discharged by connecting it across a circuit for receiving <span class="hlt">current</span> generated in the winding by self-induction. Preferably, the discharge circuit is designed so that the waveform of the discharging <span class="hlt">current</span> approximates that of the charging <span class="hlt">current</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19272885','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19272885"><span>A new method for electric impedance imaging using an <span class="hlt">eddy</span> <span class="hlt">current</span> with a tetrapolar circuit.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahsan-Ul-Ambia; Toda, Shogo; Takemae, Tadashi; Kosugi, Yukio; Hongo, Minoru</p> <p>2009-02-01</p> <p>A new contactless technique for electrical impedance imaging, using an <span class="hlt">eddy</span> <span class="hlt">current</span> managed along with the tetrapolar circuit method, is proposed. The <span class="hlt">eddy</span> <span class="hlt">current</span> produced by a magnetic field is superimposed on a constant <span class="hlt">current</span> that is normally used in the tetrapolar circuit method, and thus is used to control the <span class="hlt">current</span> distribution in the body. By changing the <span class="hlt">current</span> distribution, a set of voltage differences is measured with a pair of electrodes. This set of voltage differences is used in the image reconstruction of the resistivity distribution. The least square error minimization method is used in the reconstruction algorithm. The principle of this method is explained theoretically. A backprojection algorithm was used to get 2-D images. Based on this principle, a measurement system was developed and model experiments were conducted with a saline-filled phantom. The estimated shape of each model in the reconstructed image was similar to that of the corresponding model. From the results of these experiments, it is confirmed that the proposed method is applicable to the realization of electrical conductivity imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DContinental%2Bshelf','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840030371&hterms=Continental+shelf&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DContinental%2Bshelf"><span>Observations of a loop <span class="hlt">current</span> frontal <span class="hlt">eddy</span> intrusion onto the west Florida shelf</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paluszkiewicz, T.; Atkinson, L. P.; Posmentier, E. S.; Mcclain, C. R.</p> <p>1983-01-01</p> <p>Data were examined to determine the structure of this intrusion (April 1-7, 1982) and to investigate its effects on water masses in the outer shelf region. A frontal <span class="hlt">eddy</span>, made up of a warm filament separated from the main <span class="hlt">current</span> by a region of cooler water, propagated southeastward at 30 cm/s, intruding onto the shelf near 26 deg N between April 4 and 6. It was found from temperature-salinity (T-S) properties that water in the filament was Loop <span class="hlt">Current</span> water that had been contiguous with Loop <span class="hlt">Current</span> water 80 m deeper in the main body of the <span class="hlt">current</span>. It is noted that water in the cold region was Continental Edge water, a transitional water mass with cooler, fresher T-S characteristics. Under this region, upwelling of deeper Loop <span class="hlt">Current</span> water occurred, and elevated nutrient concentrations were found in the upwelled dome under the cold region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/496665','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/496665"><span>Wavelets in the solution of the volume integral equation: Application to <span class="hlt">eddy</span> <span class="hlt">current</span> modeling</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wang, B.; Moulder, J.C.; Basart, J.P.</p> <p>1997-05-01</p> <p>There is growing interest in the applications of wavelets as basis functions in solutions of integral equations, especially in the area of electromagnetic field problems. In this article we apply a wavelet expansion to the solution of the three-dimensional <span class="hlt">eddy</span> <span class="hlt">current</span> modeling problem based on the volume integral method. Although this method shows promise for <span class="hlt">eddy</span> <span class="hlt">current</span> modeling of three-dimensional flaws, it is restricted by the computing power required to solve a large linear system. In this article we show that applying a wavelet basis to the volume integral method can dramatically reduce the size of the linear system to be solved. In our approach, the unknown total field is expressed as a twofold summation of shifted and dilated forms of a properly chosen basis function that is often referred to as the mother wavelet. The wavelet expansion can adaptively fit itself to the total field distribution by distributing the localized functions near the flaw boundary, where the field change is large, and the more spatially diffused functions over the interior of the flaw where the total field tends to be smooth. The approach is thus best suited to modeling large three-dimensional flaws where the large number of elements used in the volume integral method requires extremely large memory space and computational capacity. The feasibility of the wavelet method is discussed in the context of the physical nature of <span class="hlt">eddy-current</span> modeling problems. Numerical examples using both Haar wavelets and Daubechies compactly supported wavelets with periodic extension are given. The results of the wavelet method are also compared with experimental results from a cylindrical flat-bottom hole in an aluminum plate. These numerical examples and comparisons indicate that the wavelet method can greatly reduce the numerical complexity of the problem with negligible loss in accuracy. {copyright} {ital 1997 American Institute of Physics.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JAP....81.6397W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JAP....81.6397W"><span>Wavelets in the solution of the volume integral equation: Application to <span class="hlt">eddy</span> <span class="hlt">current</span> modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Bing; Moulder, John C.; Basart, John P.</p> <p>1997-05-01</p> <p>There is growing interest in the applications of wavelets as basis functions in solutions of integral equations, especially in the area of electromagnetic field problems. In this article we apply a wavelet expansion to the solution of the three-dimensional <span class="hlt">eddy</span> <span class="hlt">current</span> modeling problem based on the volume integral method. Although this method shows promise for <span class="hlt">eddy</span> <span class="hlt">current</span> modeling of three-dimensional flaws, it is restricted by the computing power required to solve a large linear system. In this article we show that applying a wavelet basis to the volume integral method can dramatically reduce the size of the linear system to be solved. In our approach, the unknown total field is expressed as a twofold summation of shifted and dilated forms of a properly chosen basis function that is often referred to as the mother wavelet. The wavelet expansion can adaptively fit itself to the total field distribution by distributing the localized functions near the flaw boundary, where the field change is large, and the more spatially diffused functions over the interior of the flaw where the total field tends to be smooth. The approach is thus best suited to modeling large three-dimensional flaws where the large number of elements used in the volume integral method requires extremely large memory space and computational capacity. The feasibility of the wavelet method is discussed in the context of the physical nature of <span class="hlt">eddy-current</span> modeling problems. Numerical examples using both Haar wavelets and Daubechies compactly supported wavelets with periodic extension are given. The results of the wavelet method are also compared with experimental results from a cylindrical flat-bottom hole in an aluminum plate. These numerical examples and comparisons indicate that the wavelet method can greatly reduce the numerical complexity of the problem with negligible loss in accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NTE....31..191Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NTE....31..191Z"><span>Thickness measurement of multi-layer conductive coatings using multifrequency <span class="hlt">eddy</span> <span class="hlt">current</span> techniques</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Dejun; Yu, Yating; Lai, Chao; Tian, Guiyun</p> <p>2016-07-01</p> <p>To ensure the key structural performance in high-temperature and high-stress environments, thermal barrier coatings (TBCs) are often adopted in engineering. The thickness of these multi-layer conductive coatings is an important quality indicator. In order to measure the thickness of multi-layer conductive coatings, a new measurement approach is presented using <span class="hlt">eddy</span> <span class="hlt">current</span> testing techniques, and then, an inversion algorithm is proposed and proved efficient and applicable, of which the maximum experimental relative error is within 10%. Therefore, the new approach can be effectively applied to thickness measurement of multi-layer conductive coatings such as TBCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA033376','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA033376"><span>Non-Destructive Inspection and Volume Fraction Determination of CFRP Using an <span class="hlt">Eddy</span> <span class="hlt">Current</span> Method</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1976-06-01</p> <p>thickness 9 4.3 Edge effect 11 4.4 Response to volume fraction 12 5 RESULTS FROM DIRECTIONAL PROBE 13 6 DISCUSSION 14 7 CONCLUSIONS 15 Acknowledgment...use of one unique probe. 4.3 Edge effect It has been demonstrated in section 4.1 that the important part of the <span class="hlt">eddy</span> <span class="hlt">current</span> path covers an area 7.5mm...in diameter on cross ply and 15 x 7.5mm on unidirectional CFRP. As might be expected, this results in an edge effect which arises when part of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..177a2111D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..177a2111D"><span>Non-destructive testing of nanomaterials by using subminiature <span class="hlt">eddy</span> <span class="hlt">current</span> transducers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dmitriev, S. F.; Ishkov, A. V.; Katasonov, A. O.; Malikov, V. N.; Sagalakov, A. M.; Shevtsova, L. I.</p> <p>2017-02-01</p> <p>A sensor for studying nanomaterials has been developed on the basis of a transformer-type <span class="hlt">eddy-current</span> transducer. The basic technical data are stated (the number of windings is 100-400 turns, and the value of the initial permeability of the core is µmax = 36000). Measurements technique which allows high-precision measuring the electrical conductivity in thin film Ce-Nb. The electrical conductivity of Niobium-Selenium varies from 3.3·105 to 3.7·105 MS/m in the ratio of four from 4 to 60 nm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4634459"><span>Research on Defects Inspection of Solder Balls Based on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Pulsed Thermography</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Xiuyun; Zhou, Jinlong; Tian, Guiyun; Wang, Yizhe</p> <p>2015-01-01</p> <p>In order to solve tiny defect detection for solder balls in high-density flip-chip, this paper proposed feasibility study on the effect of detectability as well as classification based on <span class="hlt">eddy</span> <span class="hlt">current</span> pulsed thermography (ECPT). Specifically, numerical analysis of 3D finite element inductive heat model is generated to investigate disturbance on the temperature field for different kind of defects such as cracks, voids, etc. The temperature variation between defective and non-defective solder balls is monitored for defects identification and classification. Finally, experimental study is carried on the diameter 1mm tiny solder balls by using ECPT and verify the efficacy of the technique. PMID:26473871</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150012191','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150012191"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> Minimizing Flow Plug for Use in Flow Conditioning and Flow Metering</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>England, John Dwight (Inventor); Kelley, Anthony R. (Inventor)</p> <p>2015-01-01</p> <p>An <span class="hlt">eddy-current</span>-minimizing flow plug has open flow channels formed between the plug's inlet and outlet. Each open flow channel includes (i) a first portion that originates at the inlet face and converges to a location within the plug that is downstream of the inlet, and (ii) a second portion that originates within the plug and diverges to the outlet. The diverging second portion is approximately twice the length of the converging first portion. The plug is devoid of planar surface regions at its inlet and outlet, and in fluid flow planes of the plug that are perpendicular to the given direction of a fluid flowing therethrough.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/993215','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/993215"><span>The RF performance of cavity made from defective niobium material determined by <span class="hlt">Eddy</span> <span class="hlt">Current</span> Scanning</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, G.; Cooley, L.; Sergatskov, D.; Ozelis, J.; Brinkmann, A.; Singer, W.; Singer, X.; Pekeler, M.</p> <p>2010-10-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> scanning (ECS) has been used to screen niobium sheets to avoid defective material being used in costly cavity fabrication. The evaluation criterion of this quality control tool is not well understood. Past surface studies showed some features were shallow enough to be removed by chemical etching. The remaining features were identified to be small number of deeper inclusions, but mostly unidentifiable features (by chemical analysis). A real cavity made of defective niobium material has been tested. The cavity achieved high performance with comparable results to the cavities made from defect free cavities. Temperature mapping could help to define the control standard clearly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21260289','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21260289"><span><span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> SYSTEM FOR DETECTION OF CRACKING BENEATH BRAIDING IN CORRUGATED METAL HOSE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wincheski, Buzz; Simpson, John; Hall, George</p> <p>2009-03-03</p> <p>In this paper an <span class="hlt">eddy</span> <span class="hlt">current</span> system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.</p> </li> </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_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" 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_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</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="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AmJPh..80..800T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AmJPh..80..800T"><span>Rolling magnets down a conductive hill: Revisiting a classic demonstration of the effects of <span class="hlt">eddy</span> <span class="hlt">currents</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomasel, Fernando G.; Marconi, Mario C.</p> <p>2012-09-01</p> <p>We re-examine the case of rare-earth magnets rolling down an inclined plane, presenting an approach to conducting quantitative investigations that results in high-quality experimental data connecting simple experiments to a handful of important applications of <span class="hlt">eddy</span> <span class="hlt">currents</span>. These include not only magnetic braking but also the characterization of conductive materials, measurement of the thickness of dielectric coatings, and nondestructive evaluation of conductive objects. The simplicity of the proposed experimental setups, which include the use of widely available smart phones to record video that can be post-processed with free software, makes these experiments appealing to high school and college physics students.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090009966','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090009966"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> System for Detection of Cracking Beneath Braiding in Corrugated Metal Hose</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Buzz; Simpson, John; Hall, George</p> <p>2008-01-01</p> <p>In this paper an <span class="hlt">eddy</span> <span class="hlt">current</span> system for the detection of partially-through-the-thickness cracks in corrugated metal hose is presented. Design criteria based upon the geometry and conductivity of the part are developed and applied to the fabrication of a prototype inspection system. Experimental data are used to highlight the capabilities of the system and an image processing technique is presented to improve flaw detection capabilities. A case study for detection of cracking damage in a space shuttle radiator retract flex hoses is also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009MaCom..78.1929A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009MaCom..78.1929A"><span>An boldsymbol{E} -based mixed formulation for a time-dependent <span class="hlt">eddy</span> <span class="hlt">current</span> problem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acevedo, Ramiro; Meddahi, Salim; Rodriguez, Rodolfo</p> <p>2009-12-01</p> <p>In this paper, we analyze a mixed form of a time-dependent <span class="hlt">eddy</span> <span class="hlt">current</span> problem formulated in terms of the electric field boldsymbol{E} . We show that this formulation admits a well-posed saddle point structure when the constraints satisfied by the primary unknown in the dielectric material are handled by means of a Lagrange multiplier. We use Nedelec edge elements and standard nodal finite elements to define a semi-discrete Galerkin scheme. Furthermore, we introduce the corresponding backward-Euler fully-discrete formulation and prove error estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720008638','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720008638"><span>Evaluation of <span class="hlt">eddy-current</span> proximity devices for measuring thin potassium film thicknesses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Asadourian, A. S.</p> <p>1972-01-01</p> <p>Two <span class="hlt">eddy</span> <span class="hlt">current</span> proximity probe systems were tested over a range of 0 to 508 micrometers (0 to 20 mils) of simulated potassium film thicknesses for simulated temperatures of 66 C (150 F), 232 C (450 F), and 666 C (1230 F). The results of short time calibration tests are presented. Instrument drift was a problem throughout the testing and, without correction, may limit the use of such systems to short periods of time. Additional development will be required prior to their being usable as practical instrumentation systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840008494','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840008494"><span>Design study of magnetic <span class="hlt">eddy-current</span> vibration suppression dampers for application to cryogenic turbomachinery</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gunter, E. J.; Humphris, R. R.; Severson, S. J.</p> <p>1983-01-01</p> <p>Cryogenic turbomachinery used to pump high pressure fuel (liquid H2) and oxidizer (liquid O2) to the main engines of the Space Shuttle have experienced rotor instabilities. Subsynchronous whirl, an extremely destructive instability, has caused bearing failures and severe rubs in the seals. These failures have resulted in premature engine shutdowns or, in many instances, have limited the power level to which the turbopumps could be operated. The feasibility of using an <span class="hlt">eddy</span> <span class="hlt">current</span> type of damping mechanism for the Space Shuttle Main Engine is outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/634112','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/634112"><span>Crack detection on HC-130H aircraft using low frequency <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moore, D.G.; Mihelic, J.E.; Barnes, J.D.</p> <p>1998-02-01</p> <p>An <span class="hlt">eddy</span> <span class="hlt">current</span> inspection method was developed at the Federal Aviation Administration`s Airworthiness Assurance NDI Validation Center (AANC) to easily and rapidly detect subsurface fatigue cracks in the wheel well fairing on the US Coast Guard (USCG) HC-130H aircraft caused by fatigue. The inspection procedure locates cracks as small as 10.2 millimeters in length at 2.54 mm below the skin surface at raised fastener sites. The test procedure developed baseline three USCG aircraft. Inspection results on the three aircraft reveals good correlation with results made during subsequent structural disassembly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20798265','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20798265"><span>Flaws Identification Using <span class="hlt">Eddy</span> <span class="hlt">Current</span> Differential Transducer and Artificial Neural Networks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chady, T.; Lopato, P.</p> <p>2006-03-06</p> <p>In this paper we present a multi-frequency excitation <span class="hlt">eddy</span> <span class="hlt">current</span> differential transducer and dynamic neural models which were used to detect and identify artificial flaws in thin conducting plates. Plates are made of Inconel600. EDM notches have relative depth from 10% to 80% and length from 2 mm to 7 mm. All flaws were located on the opposite surface of the examined specimen. Measured signals were used as input for training and verifying dynamic neural networks with a moving window. Wide range of ANN (Artificial Neural Network) structures are examined for different window length and different number of frequency components in excitation signal. Observed trends are presented in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21511638','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21511638"><span>Simulation for the assessment of wall thinning using <span class="hlt">eddy</span> <span class="hlt">current</span> method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cheng, W.; Komura, I.</p> <p>2011-06-23</p> <p>A pipe with protective cladding and insulation was simplified to a four-layered structure when the diameter of a pipe is large enough, and analytical solutions for sinusoidal and pulsed wave excitation were derived. Simulation implemented by using the analytical solutions showed that sinusoidal excitation is not appropriate for the monitoring of inner thinning, while pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> method can be used to measure wall-thickness regardless of inner or outer thinning by using the decay rate of log(Bz) as a particular parameter to evaluate wall thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21371028','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21371028"><span>PULSED <span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> THICKNESS MEASUREMENT OF SELECTIVE PHASE CORROSION ON NICKEL ALUMINUM BRONZE VALVES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krause, T. W.; Harlley, D.; Babbar, V. K.; Wannamaker, K.</p> <p>2010-02-22</p> <p>Nickel Aluminum Bronze (NAB) is a material with marine environment applications that under certain conditions can undergo selective phase corrosion (SPC). SPC involves the removal of minority elements while leaving behind a copper matrix. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) was evaluated for determination of SPC thickness on a NAB valve section with access from the surface corroded side. A primarily linear response of PEC amplitude, up to the maximum available SPC thickness of 4 mm was observed. The combination of reduced conductivity and permeability in the SPC phase relative to the base NAB was used to explain the observed sensitivity of PEC to SPC thickness variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003AIPC..657..359K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003AIPC..657..359K"><span>Simulation of <span class="hlt">Eddy-Current</span> Corrosion Detection Using a Sensor Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Katyal, V.; Bowler, J. R.</p> <p>2003-03-01</p> <p>A computer simulation has been developed to evaluate <span class="hlt">eddy-current</span> probes containing magnetic field sensor arrays for the detection and evaluation of hidden corrosion. The simulation is used to assess probes that incorporate magneto-resistive or Hall devices in a closely-spaced, linear array. These probes will allow rapid data acquisition over a track width determined by the length of the array. The benefit of the simulation is that adjustments to the virtual probe parameters are easily made allowing improvements in sensitivity, imaging capability and resolution. A number of probe designs have been studied in this way including the "racetrack" probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706b0025P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706b0025P"><span>Experimental validation of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe for defect detection in thick conducting specimen</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahesh Raja, P.; Arunachalam, Kavitha; Balasubramanian, Krishnan</p> <p>2016-02-01</p> <p>This paper presents numerical modeling and experimental measurements of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) probe for detecting subsurface defects in 10 mm to 15 mm thick conducting specimen. Measurements are presented for a pancake air core coil to detect subsurface defect in 10 mm thick aluminum slab. EC coil parameters namely inner radius(r1), and outer radius(r2), and operating frequency (f) are optimized for deeper penetration in the conducting plate (35 MS/m) for a given coil height(h), and lift off distance (d). Preliminary simulation results are presented for a subsurface defect in 15 mm thick aluminium plate for the optimized EC coil parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDKP1110T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDKP1110T"><span>Unsteady adjoint for large <span class="hlt">eddy</span> simulation of a <span class="hlt">coupled</span> turbine stator-rotor system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Talnikar, Chaitanya; Wang, Qiqi; Laskowski, Gregory</p> <p>2016-11-01</p> <p>Unsteady fluid flow simulations like large <span class="hlt">eddy</span> simulation are crucial in capturing key physics in turbomachinery applications like separation and wake formation in flow over a turbine vane with a downstream blade. To determine how sensitive the design objectives of the <span class="hlt">coupled</span> system are to control parameters, an unsteady adjoint is needed. It enables the computation of the gradient of an objective with respect to a large number of inputs in a computationally efficient manner. In this paper we present unsteady adjoint solutions for a <span class="hlt">coupled</span> turbine stator-rotor system. As the transonic fluid flows over the stator vane, the boundary layer transitions to turbulence. The turbulent wake then impinges on the rotor blades, causing early separation. This <span class="hlt">coupled</span> system exhibits chaotic dynamics which causes conventional adjoint solutions to diverge exponentially, resulting in the corruption of the sensitivities obtained from the adjoint solutions for long-time simulations. In this presentation, adjoint solutions for aerothermal objectives are obtained through a localized adjoint viscosity injection method which aims to stabilize the adjoint solution and maintain accurate sensitivities. Preliminary results obtained from the supercomputer Mira will be shown in the presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ChJME..27..768Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ChJME..27..768Y"><span>Transient-spatial pattern mining of <span class="hlt">eddy</span> <span class="hlt">current</span> pulsed thermography using wavelet transform</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Hailong; Gao, Bin; Tian, Guiyun; Ren, Wenwei; Woo, Wai Lok</p> <p>2014-07-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> pulsed thermography(ECPT) is an emerging Non-destructive testing and evaluation(NDT & E) technique, which uses hybrid <span class="hlt">eddy</span> <span class="hlt">current</span> and thermography NDT & E techniques that enhances the detectability from their compensation. <span class="hlt">Currently</span>, this technique is limited by the manual selection of proper contrast frames and the issue of improving the efficiency of defect detection of complex structure samples remains a challenge. In order to select a specific frame from transient thermal image sequences to maximize the contrast of thermal variation and defect pattern from complex structure samples, an energy driven approach to compute the coefficient energy of wavelet transform is proposed which has the potential of automatically selecting both optimal transient frame and spatial scale for defect detection using ECPT. According to analysis of the variation of different frequency component and the comparison study of the detection performance of different scale and wavelets, the frame at the end of heating phase is automatically selected as an optimal transient frame for defect detection. In addition, the detection capabilities of the complex structure samples can be enhanced through proper spatial scale and wavelet selection. The proposed method has successfully been applied to low speed impact damage detection of carbon fibre reinforced polymer(CFRP) composite as well as providing the guidance to improve the detectability of ECPT technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...117o4104M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...117o4104M"><span><span class="hlt">Eddy</span> <span class="hlt">currents</span>: A misleading contribution when measuring magnetoelectric voltage coefficients of thin film devices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>More-Chevalier, J.; Cibert, C.; Bouregba, R.; Poullain, G.</p> <p>2015-04-01</p> <p>Tb0.3Dy0.7Fe2/Pt/PbZr0.56Ti0.44O3 (Terfenol-D/Pt/PZT) magnetoelectric (ME) thin films were deposited on Pt/TiO2/SiO2/Si substrate. The ME voltage coefficient αHME was determined at room temperature using a lock-in amplifier and by applying to the sample an alternating magnetic field of a few mT. Surprisingly, very similar responses were obtained from a simple commercial capacitor set in series with a small loop of wire. This allowed us first to accurately model and reproduce the frequency response of the ferroelectric PZT layer alone. We also observed that, at low frequency, the voltage across the ferroelectric capacitor and the <span class="hlt">current</span> in the circuit did not decrease significantly when diminishing then removing, the area of the conductive loop. One major conclusion is that <span class="hlt">eddy</span> <span class="hlt">currents</span> in the lead wires, rather than the classical electromotive force across conductive loops, contribute significantly to the total voltage response, at least for thin film ME devices. A model taking into account <span class="hlt">eddy</span> <span class="hlt">currents</span> was then developed for the extraction of the true αHME. A large αHME of 4.6 V/cm.Oe was thus obtained for the Terfenol-D/Pt/PZT thin film device, without DC magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA527308','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA527308"><span>Inter-annual Variability and Prediction of <span class="hlt">Eddies</span> in the Gulf of Aden and the Somali <span class="hlt">Current</span> Region</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2009-01-01</p> <p>in the Gulf of Aden and the Somali <span class="hlt">Current</span> Region Julian P. McCreary , Jr. International Pacific Research Center University of Hawaii at Manoa...and Indian Ocean Dipole years. Manuscript in progress. Jensen, T.G, Z. Yu and J. P. McCreary : <span class="hlt">Eddies</span> in the Gulf of Aden – an overview. Manuscript...Z., T. G. Jensen, A. Ishida, R. Furue and J. P. McCreary (2009): Mesoscale <span class="hlt">Eddies</span> in the Gulf of Aden. Powerpoint presentation IMPACT</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25430380','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25430380"><span>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="https://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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcScD..11.1949A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcScD..11.1949A"><span>Influence of frontal cyclones evolution on the 2009 (Ekman) and 2010 (Franklin) Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> detachment events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Androulidakis, Y. S.; Kourafalou, V. H.; Le Hénaff, M.</p> <p>2014-07-01</p> <p>The anticyclonic Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> (LCE) shedding events are strongly associated with the evolution of Loop <span class="hlt">Current</span> Frontal <span class="hlt">Eddies</span> (LCFEs) over the eastern Gulf of Mexico (GoM). A numerical simulation, in tandem with in situ measurements and satellite data, was used to investigate the Loop <span class="hlt">Current</span> (LC) evolution and the surrounding LCFEs formation, structure, growth and migration during the <span class="hlt">Eddy</span> Ekman and <span class="hlt">Eddy</span> Franklin shedding events in the summers of 2009 and 2010, respectively. During both events, Northern GoM LCFEs appeared vertically coherent to at least 1500 m in temperature observations. They propagated towards the base of the LC where, together with the migration of Campeche Bank <span class="hlt">eddies</span> from south of the LC, contributed to its "necking down". Growth of Campeche Bank LCFEs involved in <span class="hlt">Eddy</span> Franklin was partially attributed to Campeche Bank waters following upwelling events. Slope processes associated with such upwelling include offshore exports of high positive vorticity that may trigger cyclone formation and growth. The advection and growth of LCFEs, originating from the northern and southern GoM, and their interaction with the LC over the LCE detachment area favor shedding conditions and may lead to the final separation of the LCE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcSci..10..947A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcSci..10..947A"><span>Influence of frontal cyclone evolution on the 2009 (Ekman) and 2010 (Franklin) Loop <span class="hlt">Current</span> <span class="hlt">eddy</span> detachment events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Androulidakis, Y. S.; Kourafalou, V. H.; Le Hénaff, M.</p> <p>2014-11-01</p> <p>The anticyclonic Loop <span class="hlt">Current</span> <span class="hlt">Eddy</span> (LCE) shedding events are strongly associated with the evolution of Loop <span class="hlt">Current</span> Frontal <span class="hlt">Eddies</span> (LCFEs) over the eastern Gulf of Mexico (GoM). A numerical simulation, in tandem with in situ measurements and satellite data, was used to investigate the Loop <span class="hlt">Current</span> (LC) evolution and the surrounding LCFE formation, structure, growth and migration during the <span class="hlt">Eddy</span> Ekman and <span class="hlt">Eddy</span> Franklin shedding events in the summers of 2009 and 2010, respectively. During both events, northern GoM LCFEs appeared vertically coherent to at least 1500 m in temperature observations. They propagated towards the base of the LC, where, together with the migration of Campeche Bank (southwest GoM shelf) <span class="hlt">eddies</span> from south of the LC, contributed to its "necking-down". Growth of Campeche Bank LCFEs involved in <span class="hlt">Eddy</span> Franklin was partially attributed to Campeche Bank waters following upwelling events. Slope processes associated with such upwelling included offshore exports of high positive potential vorticity that may trigger cyclone formation and growth. The advection and growth of LCFEs, originating from the northern and southern GoM, and their interaction with the LC over the LCE detachment area favor shedding conditions and may contribute to the final separation of the LCE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..369Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..369Z"><span>The <span class="hlt">eddy</span>-mean flow interaction and the intrusion of western boundary <span class="hlt">current</span> into the South China Sea type basin in an idealized model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Linhao</p> <p>2016-04-01</p> <p>In this paper, an ideal model on the role of mesoscale <span class="hlt">eddies</span> in the Kuroshio intruding into the South China Sea (SCS) is developed, which represents the northwestern Pacific and the SCS by two rectangle basins connected by a gap. In the case of only considering intrinsic ocean variability, a time-dependent western boundary <span class="hlt">current</span> (WBC) driven by steady wind is modeled under both <span class="hlt">eddy</span>-resolving and non-<span class="hlt">eddy</span>-resolving resolutions. Almost all simulated WBC intrudes into the adjacent sea in the form of loop <span class="hlt">current</span> with multiple-state transitions and <span class="hlt">eddy</span>-shedding process, which has aperiodic variations on intraseasonal or interannual scales, determined by the <span class="hlt">eddy</span>-induced WBC variation. For the parameters considered in this paper, the WBC intrusion exhibits a 30~90-day cycle in the presence of the subgrid-scale <span class="hlt">eddy</span> forcing (SSEF), but a 300~500-day cycle in the absence of SSEF. Moreover, the roles of the resolved (grid-scale) and unresolved (subgrid-scale) <span class="hlt">eddies</span> in the WBC intrusion are studied. It is found that the unresolved <span class="hlt">eddy</span>-flow interaction strongly regulates the WBC intrusion through the PV forcing induced by shear flows and baroclinic processes. But the resolved <span class="hlt">eddy</span> forcing, which is dominated by the <span class="hlt">eddy-eddy</span> interaction solely through baroclinic processes, shows weak correlation to the WBC intrusion. The associated <span class="hlt">eddy</span>-induced PV exchange between the two basins is mainly accomplished by isopycnal-thickness <span class="hlt">eddy</span> fluxes, particularly by the cross-front PV fluxes due to the unresolved <span class="hlt">eddy</span>. And the unresolved <span class="hlt">eddy</span>-flow interaction, as well as resolved and unresolved <span class="hlt">eddy-eddy</span> interactions, mainly governs the PV transport for the WBC intrusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NTE....28..145W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NTE....28..145W"><span>Reconstruction of stress corrosion cracks using signals of pulsed <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>Wang, Li; Xie, Shejuan; Chen, Zhenmao; Li, Yong; Wang, Xiaowei; Takagi, Toshiyuki</p> <p>2013-06-01</p> <p>A scheme to apply signals of pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> testing (PECT) to reconstruct a deep stress corrosion crack (SCC) is proposed on the basis of a multi-layer and multi-frequency reconstruction strategy. First, a numerical method is introduced to extract conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ECT) signals of different frequencies from the PECT responses at different scanning points, which are necessary for multi-frequency ECT inversion. Second, the conventional fast forward solver for ECT signal simulation is upgraded to calculate the single-frequency pickup signal of a magnetic field by introducing a strategy that employs a tiny search coil. Using the multiple-frequency ECT signals and the upgraded fast signal simulator, we reconstructed the shape profiles and conductivity of an SCC at different depths layer-by-layer with a hybrid inversion scheme of the conjugate gradient and particle swarm optimisation. Several modelled SCCs of rectangular or stepwise shape in an SUS304 plate are reconstructed from simulated PECT signals with artificial noise. The reconstruction results show better precision in crack depth than the conventional ECT inversion method, which demonstrates the validity and efficiency of the proposed PECT inversion scheme.</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_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" 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_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</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="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26817456','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26817456"><span>A Novel Application of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Braking for Functional Strength Training During Gait.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Washabaugh, Edward P; Claflin, Edward S; Gillespie, R Brent; Krishnan, Chandramouli</p> <p>2016-09-01</p> <p>Functional strength training is becoming increasingly popular when rehabilitating individuals with neurological injury such as stroke or cerebral palsy. Typically, resistance during walking is provided using cable robots or weights that are secured to the distal shank of the subject. However, there exists no device that is wearable and capable of providing resistance across the joint, allowing over ground gait training. In this study, we created a lightweight and wearable device using <span class="hlt">eddy</span> <span class="hlt">current</span> braking to provide resistance to the knee. We then validated the device by having subjects wear it during a walking task through varying resistance levels. Electromyography and kinematics were collected to assess the biomechanical effects of the device on the wearer. We found that <span class="hlt">eddy</span> <span class="hlt">current</span> braking provided resistance levels suitable for functional strength training of leg muscles in a package that is both lightweight and wearable. Applying resistive forces at the knee joint during gait resulted in significant increases in muscle activation of many of the muscles tested. A brief period of training also resulted in significant aftereffects once the resistance was removed. These results support the feasibility of the device for functional strength training during gait. Future research is warranted to test the clinical potential of the device in an injured population.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706i0005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706i0005B"><span>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/2017AIPC.1806k0013A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0013A"><span>Model-based probe state estimation and crack inverse methods addressing <span class="hlt">eddy</span> <span class="hlt">current</span> probe variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aldrin, John C.; Oneida, Erin K.; Shell, Eric B.; Sabbagh, Harold A.; Sabbagh, Elias; Murphy, R. Kim; Mazdiyasni, Siamack; Lindgren, Eric A.; Mooers, Ryan D.</p> <p>2017-02-01</p> <p>A model-based calibration process is introduced that estimates the state of the <span class="hlt">eddy</span> <span class="hlt">current</span> probe. First, a carefully designed surrogate model was built using VIC-3D® simulations covering the critical range of probe rotation angles, tilt in two directions, and probe offset (liftoff) for both transverse and longitudinal flaw orientations. Some approximations and numerical compromises in the model were made to represent tilt in two directions and reduce simulation time; however, this surrogate model was found to represent the key trends in the <span class="hlt">eddy</span> <span class="hlt">current</span> response for each of the four probe properties in experimental verification studies well. Next, this model was incorporated into an iterative inversion scheme during the calibration process, to estimate the probe state while also addressing the amplitude/phase fit and centering the calibration notch indication. Results are presented showing several examples of the blind estimation of tilt and rotation angle for known experimental cases with reasonable agreement. Once the probe state is estimated, the final step is to transform the base crack inversion surrogate model and apply it for crack characterization. Using this process, results are presented demonstrating improved crack inversion performance for extreme probe states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JPhD...37..501S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JPhD...37..501S"><span>Calibration of <span class="hlt">eddy</span> <span class="hlt">current</span> carburization measurements in ethylene production tubes using ion beam analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stevens, K. J.; Trompetter, W. J.</p> <p>2004-02-01</p> <p>Nuclear reaction analysis using a 12C(d, p0)13C reaction and a 16O(d, p1)17O reaction, with 1.02 MeV deuterons in an accelerator microprobe, has been used to produce quantitative linescans of the carbon and oxygen levels in ex-service ethylene pyrolysis tubes of HPM, HK40 and Manaurite XM alloy. Particle induced x-ray emission in the ion beam microprobe and energy dispersive analysis of x-rays in a scanning electron microscope were used for linescans of the heavier elements (Cr, Ni, Fe, Si and Ti). The composition linescans were used to calibrate the response and accuracy of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe system for measuring carburization near the inner surface of the tubes. The influence of the ferromagnetic outer oxide surface layers has been clarified. A two-dimensional ANSYS finite element model (FEM) was used for interpretation of the <span class="hlt">eddy</span> <span class="hlt">current</span> scans. Good correlation was obtained between the ion beam analysis results, the impedance scans and the FEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MSSP...44..211R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MSSP...44..211R"><span>Angular approach combined to mechanical model for tool breakage detection by <span class="hlt">eddy</span> <span class="hlt">current</span> sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ritou, M.; Garnier, S.; Furet, B.; Hascoet, J. Y.</p> <p>2014-02-01</p> <p>The paper presents a new complete approach for Tool Condition Monitoring (TCM) in milling. The aim is the early detection of small damages so that catastrophic tool failures are prevented. A versatile in-process monitoring system is introduced for reliability concerns. The tool condition is determined by estimates of the radial eccentricity of the teeth. An adequate criterion is proposed combining mechanical model of milling and angular approach.Then, a new solution is proposed for the estimate of cutting force using <span class="hlt">eddy</span> <span class="hlt">current</span> sensors implemented close to spindle nose. Signals are analysed in the angular domain, notably by synchronous averaging technique. Phase shifts induced by changes of machining direction are compensated. Results are compared with cutting forces measured with a dynamometer table.The proposed method is implemented in an industrial case of pocket machining operation. One of the cutting edges has been slightly damaged during the machining, as shown by a direct measurement of the tool. A control chart is established with the estimates of cutter eccentricity obtained during the machining from the <span class="hlt">eddy</span> <span class="hlt">current</span> sensors signals. Efficiency and reliability of the method is demonstrated by a successful detection of the damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26703608','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26703608"><span>Fatigue Crack Length Sizing Using a Novel Flexible <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Array.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying</p> <p>2015-12-21</p> <p>The <span class="hlt">eddy</span> <span class="hlt">current</span> probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar <span class="hlt">eddy</span> <span class="hlt">current</span> sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AIPC..509..457K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..509..457K"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> monitoring of fatigue crack growth in Zr-2.5% Nb pressure tube</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krause, T. W.; Martin, A. E.; Sheppard, R. R.; Schankula, J. J.</p> <p>2000-05-01</p> <p>Zr-2.5% wt. Nb pressure tubes (PTs) form the core of the heat transport system in CANDU nuclear reactors. These 6 m long, 100 mm diameter tubes are operated at elevated temperatures (nominally 300 °C) and at pressures that produce hoop stresses that are 25% of the ultimate tensile strength of the PT (120 Mpa). Therefore, detection and characterization of flaws in these components becomes crucial for their continued pressure retaining integrity. If a flaw is detected, however, the cost of PT replacement is expensive. Periodic in-service inspection of a flaw that demonstrates no change in flaw characteristics can be used to allow a pressure tube to remain in-service. This requires confidence in the accuracy and reliability of methods used to inter flaw characteristics. Such confidence can only be developed by comparing nondestructive predictions with results from destructive examinations. In this work, <span class="hlt">eddy</span> <span class="hlt">current</span> testing was used to monitor the progressive stages of a fatigue crack, grown through pressure cycling from a notch on the inner surface of a PT. Results from a differential lift-off compensated <span class="hlt">eddy</span> <span class="hlt">current</span> probe were used to produce sizing estimates of the crack grown between 35% (base of notch) and 74% of the PT wall. A comparison with a destructive examination of the crack demonstrated sensitivity too changes in crack depth accurate to 5% of the tube wall thickness. Such results, combined with similar information obtained from ultrasonics will increase confidence in interpretation of PT inspection data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..MAR.K1177Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..MAR.K1177Y"><span>Suppressing local hot spots due to <span class="hlt">eddy</span> <span class="hlt">currents</span> in magnetic coil systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yao, Zhen; Shojinaga, Aaron; Wu, Yong; Shvartsman, Shmaryu; Eagan, Timothy; Chmielewski, Thomas; Brown, Robert</p> <p>2011-03-01</p> <p>A particular goal in magnetic field applications is to avoid <span class="hlt">eddy</span> <span class="hlt">current</span> heating in coils and shields. It is important, in MRI, for example, to avoid hot spots near the patient to be imaged as well as in the vicinity of soldering joints. We develop effective analytical formulas for the <span class="hlt">eddy</span> <span class="hlt">current</span> behavior of sources close to surrounding conductors, we verify these via numerical simulations, and we make successful comparisons to corresponding experimental temperature distributions. Optimized patterns of incisions made in the conductors are discovered for addressing particularly troublesome heating locations. The criteria include the need to minimize the number and length of the cuts. Theory and experiment are in agreement on the efficacy of this method for reducing steady-state temperatures. An example of results in the practical design of commercial coils and shields is that a single cut parallel to the long edge of rectangular conductors reduces the temperatures much more than making multiple cuts parallel to the short edge. Supported by Ohio Third Frontier Program</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007IJTPE.127..929F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007IJTPE.127..929F"><span><span class="hlt">Eddy</span> <span class="hlt">Current</span> Analysis of Thin Metal Container in Induction Heating by Line Integral Equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fujita, Hagino; Ishibashi, Kazuhisa</p> <p></p> <p>In recent years, induction-heating cookers have been disseminated explosively. It is wished to commercialize flexible and disposable food containers that are available for induction heating. In order to develop a good quality food container that is heated moderately, it is necessary to analyze accurately <span class="hlt">eddy</span> <span class="hlt">currents</span> induced in a thin metal plate. The integral equation method is widely used for solving induction-heating problems. If the plate thickness approaches zero, the surface integral equations on the upper and lower plate surfaces tend to become the same and the equations become ill conditioned. In this paper, firstly, we derive line integral equations from the boundary integral equations on the assumption that the electromagnetic fields in metal are attenuated rapidly compared with those along the metal surface. Next, so as to test validity of the line integral equations, we solve the <span class="hlt">eddy</span> <span class="hlt">current</span> induced in a thin metal container in induction heating and obtain power density given to the container and impedance characteristics of the heating coil. We compare computed results with those by FEM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706i0017B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706i0017B"><span>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('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4721828"><span>Fatigue Crack Length Sizing Using a Novel Flexible <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor Array</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying</p> <p>2015-01-01</p> <p>The <span class="hlt">eddy</span> <span class="hlt">current</span> probe, which is flexible, array typed, highly sensitive and capable of quantitative inspection is one practical requirement in nondestructive testing and also a research hotspot. A novel flexible planar <span class="hlt">eddy</span> <span class="hlt">current</span> sensor array for the inspection of microcrack presentation in critical parts of airplanes is developed in this paper. Both exciting and sensing coils are etched on polyimide films using a flexible printed circuit board technique, thus conforming the sensor to complex geometric structures. In order to serve the needs of condition-based maintenance (CBM), the proposed sensor array is comprised of 64 elements. Its spatial resolution is only 0.8 mm, and it is not only sensitive to shallow microcracks, but also capable of sizing the length of fatigue cracks. The details and advantages of our sensor design are introduced. The working principal and the crack responses are analyzed by finite element simulation, with which a crack length sizing algorithm is proposed. Experiments based on standard specimens are implemented to verify the validity of our simulation and the efficiency of the crack length sizing algorithm. Experimental results show that the sensor array is sensitive to microcracks, and is capable of crack length sizing with an accuracy within ±0.2 mm. PMID:26703608</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NTE....28..354Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NTE....28..354Y"><span>Pulsed remote field <span class="hlt">eddy</span> <span class="hlt">current</span> technique applied to non-magnetic flat conductive plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Binfeng; Zhang, Hui; Zhang, Chao; Zhang, Zhanbin</p> <p>2013-12-01</p> <p>Non-magnetic metal plates are widely used in aviation and industrial applications. The detection of cracks in thick plate structures, such as multilayered structures of aircraft fuselage, has been challenging in nondestructive evaluation societies. The remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (RFEC) technique has shown advantages of deep penetration and high sensitivity to deeply buried anomalies. However, the RFEC technique is mainly used to evaluate ferromagnetic tubes. There are many problems that should be fixed before the expansion and application of this technique for the inspection of non-magnetic conductive plates. In this article, the pulsed remote field <span class="hlt">eddy</span> <span class="hlt">current</span> (PRFEC) technique for the detection of defects in non-magnetic conducting plates was investigated. First, the principle of the PRFEC technique was analysed, followed by the analysis of the differences between the detection of defects in ferromagnetic and non-magnetic plain structures. Three different models of the PRFEC probe were simulated using ANSYS. The location of the transition zone, defect detection sensitivity and the ability to detect defects in thick plates using three probes were analysed and compared. The simulation results showed that the probe with a ferrite core had the highest detecting ability. The conclusions derived from the simulation study were also validated by conducting experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5551909','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5551909"><span>Calculation of <span class="hlt">eddy-currents</span> induced in a compact synchrotron superconducting magnet structure during a <span class="hlt">current</span> ramp</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalsi, S. . Space and Electronics Systems Div.); Heese, R. )</p> <p>1991-01-01</p> <p>Under DARPA sponsorship, a compact Superconducting X-Ray Light Source (SXSL) is being designed and built by the Brookhaven National Laboratory (BNL) with industry participation from Grumman Corporation and General Dynamics. The SXLS machine employs two 180{degrees} curved 4 telsa superconducting dipole magnets. These magnets are required to produce a dipole field for bending the beam but at the same time they must produce finite amounts of higher multipoles which are required for conditioning the beam. In fact uniformity of the field to less than 1 part in 10,000 must be maintained under all operating conditions. When a superconducting magnet is ramped from zero to full field, the changing magnetic field produces <span class="hlt">eddy-currents</span> in the magnet structure which in turn can produce undesirable multipoles. This paper discusses a simple method for estimating these <span class="hlt">eddy-currents</span> and their effect on the field harmonics. The paper present the analysis basis and its application to the SXLS magnet support structure and to the beam chamber components. 5 figs., 1 tab.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19860038376&hterms=Hakkinen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DHakkinen','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19860038376&hterms=Hakkinen&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DHakkinen"><span><span class="hlt">Coupled</span> ice-ocean dynamics in the marginal ice zones Upwelling/downwelling and <span class="hlt">eddy</span> generation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, S.</p> <p>1986-01-01</p> <p>This study is aimed at modeling mesoscale processes such as upwelling/downwelling and ice edge <span class="hlt">eddies</span> in the marginal ice zones. A two-dimensional <span class="hlt">coupled</span> ice-ocean model is used for the study. The ice model is <span class="hlt">coupled</span> to the reduced gravity ocean model through interfacial stresses. The parameters of the ocean model were chosen so that the dynamics would be nonlinear. The model was tested by studying the dynamics of upwelling. Wings parallel to the ice edge with the ice on the right produce upwelling because the air-ice momentum flux is much greater than air-ocean momentum flux; thus the Ekman transport is greater than the ice than in the open water. The stability of the upwelling and downwelling jets is discussed. The downwelling jet is found to be far more unstable than the upwelling jet because the upwelling jet is stabilized by the divergence. The constant wind field exerted on a varying ice cover will generate vorticity leading to enhanced upwelling/downwelling regions, i.e., wind-forced vortices. Steepening and strengthening of vortices are provided by the nonlinear terms. When forcing is time-varying, the advection terms will also redistribute the vorticity. The wind reversals will separate the vortices from the ice edge, so that the upwelling enhancements are pushed to the open ocean and the downwelling enhancements are pushed underneath the ice.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......235H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......235H"><span>Parallel distributed, reciprocal Monte Carlo radiation in <span class="hlt">coupled</span>, large <span class="hlt">eddy</span> combustion simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hunsaker, Isaac L.</p> <p></p> <p>Radiation is the dominant mode of heat transfer in high temperature combustion environments. Radiative heat transfer affects the gas and particle phases, including all the associated combustion chemistry. The radiative properties are in turn affected by the turbulent flow field. This bi-directional <span class="hlt">coupling</span> of radiation turbulence interactions poses a major challenge in creating parallel-capable, high-fidelity combustion simulations. In this work, a new model was developed in which reciprocal monte carlo radiation was <span class="hlt">coupled</span> with a turbulent, large-<span class="hlt">eddy</span> simulation combustion model. A technique wherein domain patches are stitched together was implemented to allow for scalable parallelism. The combustion model runs in parallel on a decomposed domain. The radiation model runs in parallel on a recomposed domain. The recomposed domain is stored on each processor after information sharing of the decomposed domain is handled via the message passing interface. Verification and validation testing of the new radiation model were favorable. Strong scaling analyses were performed on the Ember cluster and the Titan cluster for the CPU-radiation model and GPU-radiation model, respectively. The model demonstrated strong scaling to over 1,700 and 16,000 processing cores on Ember and Titan, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20959261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20959261"><span>An efficient 3-D <span class="hlt">eddy-current</span> solver using an independent impedance method for transcranial magnetic stimulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Geeter, Nele; Crevecoeur, Guillaume; Dupre, Luc</p> <p>2011-02-01</p> <p>In many important bioelectromagnetic problem settings, <span class="hlt">eddy-current</span> simulations are required. Examples are the reduction of <span class="hlt">eddy-current</span> artifacts in magnetic resonance imaging and techniques, whereby the <span class="hlt">eddy</span> <span class="hlt">currents</span> interact with the biological system, like the alteration of the neurophysiology due to transcranial magnetic stimulation (TMS). TMS has become an important tool for the diagnosis and treatment of neurological diseases and psychiatric disorders. A widely applied method for simulating the <span class="hlt">eddy</span> <span class="hlt">currents</span> is the impedance method (IM). However, this method has to contend with an ill conditioned problem and consequently a long convergence time. When dealing with optimal design problems and sensitivity control, the convergence rate becomes even more crucial since the <span class="hlt">eddy-current</span> solver needs to be evaluated in an iterative loop. Therefore, we introduce an independent IM (IIM), which improves the conditionality and speeds up the numerical convergence. This paper shows how IIM is based on IM and what are the advantages. Moreover, the method is applied to the efficient simulation of TMS. The proposed IIM achieves superior convergence properties with high time efficiency, compared to the traditional IM and is therefore a useful tool for accurate and fast TMS simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......314B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......314B"><span>Inspection of ferromagnetic support structures from within alloy 800 steam generator tubes using pulsed <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buck, Jeremy Andrew</p> <p></p> <p>Nondestructive testing is a critical aspect of component lifetime management. Nuclear steam generator (SG) tubes are the thinnest barrier between irradiated primary heat transport system and the secondary heat transport system, whose components are not rated for large radiation fields. Conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ECT) and ultrasonic testing are <span class="hlt">currently</span> employed for inspecting SG tubes, with the former doing most inspections due to speed and reliability based on an understanding of how flaws affect coil impedance parameters when conductors are subjected to harmonically induced <span class="hlt">currents</span>. However, when multiple degradation modes are present simultaneously near ferromagnetic materials, such as tube fretting, support structure corrosion, and magnetite fouling, ECT reliability decreases. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC), which induces transient <span class="hlt">eddy</span> <span class="hlt">currents</span> via square wave excitation, has been considered in this thesis to simultaneously examine SG tube and support structure conditions. An array probe consisting of a central driver, coaxial with the tube, and an array of 8 sensing coils, was used in this thesis to perform laboratory measurements. The probe was delivered from the inner diameter (ID) of the SG tube, where support hole diameter, tube frets, and 2D off-centering were varied. When considering two variables simultaneously, scores obtained from a modified principal components analysis (MPCA) were sufficient for parameter extraction. In the case of hole ID variation with two dimensional tube off-centering (three parameters), multiple linear regression (MLR) of the MPCA scores provided good estimates of parameters. However, once a fourth variable, outer diameter tube frets, was introduced, MLR proved insufficient. Artificial neural networks (ANNs) were investigated in order to perform pattern recognition on the MPCA scores to simultaneously extract the four measurement parameters from the data. All models throughout this thesis were created and validated using</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DSRII..58..538S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DSRII..58..538S"><span>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://hdl.handle.net/2060/20090027875','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090027875"><span>Large-<span class="hlt">Eddy</span> Simulation: <span class="hlt">Current</span> Capabilities, Recommended Practices, and Future Research</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Georgiadis, Nicholas J.; Rizzetta, Donald P.; Fureby, Christer</p> <p>2009-01-01</p> <p>This paper presents the results of an activity by the Large <span class="hlt">Eddy</span> Simulation (LES) Working Group of the AIAA Fluid Dynamics Technical Committee to (1) address the <span class="hlt">current</span> capabilities of LES, (2) outline recommended practices and key considerations for using LES, and (3) identify future research needs to advance the capabilities and reliability of LES for analysis of turbulent flows. To address the <span class="hlt">current</span> capabilities and future needs, a survey comprised of eleven questions was posed to LES Working Group members to assemble a broad range of perspectives on important topics related to LES. The responses to these survey questions are summarized with the intent not to be a comprehensive dictate on LES, but rather the perspective of one group on some important issues. A list of recommended practices is also provided, which does not treat all aspects of a LES, but provides guidance on some of the key areas that should be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAG....92..137S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAG....92..137S"><span>Simple wideband models for disks and wires in the <span class="hlt">eddy</span> <span class="hlt">current</span> approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, Waymond R.; McFadden, Michael</p> <p>2013-05-01</p> <p>Wideband electromagnetic induction systems have shown improved false alarm rates when compared with traditional metal detectors. Calibration of these sensors and the development of algorithms for target discrimination could be assisted by a set of models for common targets. In this paper, simple wideband models of the <span class="hlt">eddy</span> <span class="hlt">current</span> response for a wire and disk are provided. These are provided in the form of a singularity expansion of the polarizability dyadic. In an effort to make this form more concrete, a major focus of the paper is on relating the terms of the expansion to graphs of the <span class="hlt">currents</span> present on the disk. The models provided in the paper are based on limiting forms of a cylinder as computed using the body-of-revolutions finite element method. Measured polarizability dyadics are also shown to fit the forms provided reasonably well.</p> </li> </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_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" 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_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</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="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/712807','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/712807"><span><span class="hlt">Eddy-current</span> inspection of ferromagnetic tubing using pulsed magnetic saturation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dodd, C V; Deeds, W E</p> <p>1986-07-01</p> <p>A pulsed <span class="hlt">eddy-current</span> system has been designed and developed for nondestructive evaluation of 2.25Cr-1Mo steam generator tubing from the bore side. Since the tubing is ferromagnetic, a large <span class="hlt">current</span> pulse is sent through a driver coil to produce magnetic saturation all the way through the tube wall. A pickup coil produces an output pulse that is dependent upon the tube properties as well as the driving pulse. The output pulse heights at selected times are used as data that are computer-correlated with calibration data taken from machined standards. Performance data, circuit diagrams, and computer programs are given for the system, which has been demonstrated to detect small flaws located near the outside of a thick ferromagnetic tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0025W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0025W"><span>Electromagnetic modeling of an <span class="hlt">eddy-current</span> position sensor for use in a fast reactor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Tao; Bowler, John R.</p> <p>2017-02-01</p> <p>In this article, we proposed a novel theoretical electromagnetic model of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe used as a position sensor with respect to a tube in a fast reactor under standby conditions. In these circumstances the coil position cannot be guided by optical aids but electromagnetic sensing can be used. Initially, we derived analytical expressions for the quasi-static time-harmonic electromagnetic field of a circular <span class="hlt">current</span> filament via the transverse magnetic potential expressed in terms of a single layer potential. This is then used to deduce the field of a circular sensor coil near a conductive tube, the axis of the coil having an arbitrary direction with respect to that of the tube. The fields for an external coil have been determined and can be used to deduce coil impedance variations with frequency, location and orientation. The model predictions can be used to guide the probe to a desire position with respect to the tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJAP..7210701P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJAP..7210701P"><span>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://adsabs.harvard.edu/abs/2005AIPC..760..425J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..760..425J"><span>Studies into the Effects of Surface Roughness on Spatial <span class="hlt">Eddy-Current</span> Data from Nickel-Based Engine Alloys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, M. J.; Nakagawa, N.; Wendt, S. E.; Hentscher, S. R.; Nelson, D. L.; Buhr, K. T.; Kilbugh, B. A.; Raithel, D. C.</p> <p>2005-04-01</p> <p><span class="hlt">Eddy-current</span> scans have been carried out on two Inconel-718 specimens following the application of various levels of shot peening and heat treatments. The conventional analysis of roughened or shot peened surfaces looks at multi-frequency impedance measurements and interprets the data as a change in conductivity or liftoff. An approach involving the statistical analysis of scanned <span class="hlt">eddy-current</span> impedance data is suggested as an alternative that may provide a more sensitive way of determining the treatment history of a component. It is possible that an analysis of these statistical distributions in spatial <span class="hlt">eddy-current</span> data could be used to determine the level of remaining residual stress in engine components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/876522','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/876522"><span>On the modeling, design and validation of two dimensional quasi-static <span class="hlt">eddy</span> <span class="hlt">current</span> forces in a mechanical oscillator.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mitchell, John Anthony; Epp, David S.; Wittwer, Jonathan W.</p> <p>2005-10-01</p> <p>Damping vibrations is important in the design of some types of inertial sensing devices. One method for adding damping to a device is to use magnetic forces generated by a static magnetic field interacting with <span class="hlt">eddy</span> <span class="hlt">currents</span>. In this report, we develop a 2-dimensional finite element model for the analysis of quasistatic <span class="hlt">eddy</span> <span class="hlt">currents</span> in a thin sheet of conducting material. The model was used for design and sensitivity analyses of a novel mechanical oscillator that consists of a shuttle mass (thin sheet of conducting material) and a set of folded spring elements. The oscillator is damped through the interaction of a static magnetic field and <span class="hlt">eddy</span> <span class="hlt">currents</span> in the shuttle mass. Using a prototype device and Laser Dopler Velocimetry (LDV), measurements were compared to the model in a validation study using simulation based uncertainty analyses. Measurements were found to follow the trends predicted by the model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......410M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......410M"><span>Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of broach support plates in steam generators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mokros, Sarah Gwendolyn</p> <p></p> <p>Steam Generators (SGs) are a critical component of nuclear reactors, employing thousands of SG tubes to convert heat generated in the reactor core into useable energy. SG tubes are supported at numerous locations by Broach Support Plates (BSPs) that have trefoil shaped holes, which prevent excessive tube vibrations, while allowing water to easily flow through the support structures. A number of degradation modes occur in SGs, such as SG tube fretting, cracking or denting, requiring periodic inspection. <span class="hlt">Currently</span>, conventional <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing (ECT) is used to non-destructively assess the condition of SG tubes and components. However, as reactors age, new modes of degradation will likely appear that may be difficult to detect and characterize using conventional ECT, such as wall loss in BSPs and build-up of corrosion products, which typically form as a hard sludge called magnetite. Pulsed <span class="hlt">Eddy</span> <span class="hlt">Current</span> (PEC) technologies are an emerging technique that is presented in this work as a method to further advance inspection techniques used in CANDURTM nuclear reactors. A PEC probe was designed to inspect the unique shape of the trefoil shaped hole to detect and characterize wall loss and the presence of magnetite in A516 carbon steel BSPs with trefoil shaped holes from within 15.9 mm (5/8") Alloy-800 SG tubes. PEC was also used to observe how measurements of wall loss were affected by the presence of magnetite. This work presents Finite Element Method (FEM) simulations and experimental results collected to observe these degradation modes. The probe was demonstrated to be capable of detecting far side wall loss as low as 20%, locating and characterizing the relative permeability of magnetite, and of detecting wall loss when magnetite was present. FEM simulations and experimental results were found to be in good agreement, suggesting that additional investigations of the effects of BSP degradation on PEC signal response may also be performed using FEM models.</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>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('https://www.osti.gov/scitech/biblio/20632918','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20632918"><span>Development of a 3D Electromagnetic Model for <span class="hlt">Eddy</span> <span class="hlt">Current</span> Tubing Inspection: Application to Steam Generator Tubing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pichenot, G.; Premel, D.; Sollier, T.; Maillot, V.</p> <p>2004-02-26</p> <p>In nuclear plants, the inspection of heat exchanger tubes is usually carried out by using <span class="hlt">eddy</span> <span class="hlt">current</span> nondestructive testing. A numerical model, based on a volume integral approach using the Green's dyadic formalism, has been developed, with support from the French Institute for Radiological Protection and Nuclear Safety, to predict the response of an <span class="hlt">eddy</span> <span class="hlt">current</span> bobbin coil to 3D flaws located in the tube's wall. With an aim of integrating this model into the NDE multi techniques platform CIVA, it has been validated with experimental data for 2D and 3D flaws.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21054941','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21054941"><span>Multifrequency <span class="hlt">Eddy</span> <span class="hlt">Current</span> Inspection of Corrosion in Clad Aluminum Riveted Lap Joints and Its Effect on Fatigue Life</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Okafor, A. C.; Natarajan, S.</p> <p>2007-03-21</p> <p>Aging aircraft are prone to corrosion damage and fatigue cracks in riveted lap joints of fuselage skin panels. This can cause catastrophic failure if not detected and repaired. Hence detection of corrosion damage and monitoring its effect on structural integrity are essential. This paper presents multifrequency <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) inspection of corrosion damage and machined material loss defect in clad A1 2024-T3 riveted lap joints and its effect on fatigue life. Results of <span class="hlt">eddy</span> <span class="hlt">current</span> inspection, corrosion product removal and fatigue testing are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/899424','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/899424"><span>Computer Calculations of <span class="hlt">Eddy-Current</span> Power Loss in Rotating Titanium Wheels and Rims in Localized Axial Magnetic Fields</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mayhall, D J; Stein, W; Gronberg, J B</p> <p>2006-05-15</p> <p>We have performed preliminary computer-based, transient, magnetostatic calculations of the <span class="hlt">eddy-current</span> power loss in rotating titanium-alloy and aluminum wheels and wheel rims in the predominantly axially-directed, steady magnetic fields of two small, solenoidal coils. These calculations have been undertaken to assess the <span class="hlt">eddy-current</span> power loss in various possible International Linear Collider (ILC) positron target wheels. They have also been done to validate the simulation code module against known results published in the literature. The commercially available software package used in these calculations is the Maxwell 3D, Version 10, Transient Module from the Ansoft Corporation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JAP....67.4741F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JAP....67.4741F"><span><span class="hlt">Eddy-current</span> analysis of isolated permanent-magnet drives using two- and three-dimensional finite-element methods (abstract)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferreira, C. A.</p> <p>1990-05-01</p> <p>Present drive systems which rely on mechanical devices for torque transmission have some negative features: the driven component cannot be isolated from the drive motor, rotating seals have inherent leakage and friction problems, and mechanical failures often occur due to torque overloads. Magnetic <span class="hlt">couplings</span> are especially well suited for use in isolated-drive systems. This is often the case in military and aerospace applications where pumps and compressors are vital parts of the thermal and fuel operating systems. The application of permanent-magnet <span class="hlt">couplings</span> in isolated drives requires accurate calculation of the <span class="hlt">eddy-current</span> losses induced on the hermetic vessel. This is because the losses along with the required output torque dictate the size and efficiency of the permanent-magnet <span class="hlt">coupling</span>. The vessel isolates the drive member from the driven member of the turbocompressor. The paper will show the formulation of the computational method based on the Poynting-vector theorem and the concept of motional electric field intensity. The <span class="hlt">eddy-current</span> losses are calculated using two- and three-dimensional magnetostatic finite-element (FE) analysis. A comparison of the results obtained by two- and three-dimensional FE analysis is made. The results of the analysis will be compared to test data for verification. The test-facility setup and procedure will also be described. This state-of-the-art technique for computation of <span class="hlt">eddy-current</span> losses has several advantages over conventional analysis methods: the nonlinearities of the magnetic circuit are taken into account, magnetic field fringing and end-leakage effects are not neglected, and the method does not rely on the use of empirical factors. The significant benefits of this approach are that trial-and-error experimental design approaches are eliminated and test data provide validation of analytical results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080001613','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080001613"><span>Validation Test Results for Orthogonal Probe <span class="hlt">Eddy</span> <span class="hlt">Current</span> Thruster Inspection System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Russell A.</p> <p>2007-01-01</p> <p>Recent nondestructive evaluation efforts within NASA have focused on an inspection system for the detection of intergranular cracking originating in the relief radius of Primary Reaction Control System (PCRS) Thrusters. Of particular concern is deep cracking in this area which could lead to combustion leakage in the event of through wall cracking from the relief radius into an acoustic cavity of the combustion chamber. In order to reliably detect such defects while ensuring minimal false positives during inspection, the Orthogonal Probe <span class="hlt">Eddy</span> <span class="hlt">Current</span> (OPEC) system has been developed and an extensive validation study performed. This report describes the validation procedure, sample set, and inspection results as well as comparing validation flaws with the response from naturally occuring damage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/257304','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/257304"><span>Performance demonstration tests for <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of steam generator tubing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kurtz, R.J.; Heasler, P.G.; Anderson, C.M.</p> <p>1996-05-01</p> <p>This report describes the methodology and results for development of performance demonstration tests for <span class="hlt">eddy</span> <span class="hlt">current</span> (ET) inspection of steam generator tubes. Statistical test design principles were used to develop the performance demonstration tests. Thresholds on ET system inspection performance were selected to ensure that field inspection systems would have a high probability of detecting and and correctly sizing tube degradation. The technical basis for the ET system performance thresholds is presented in detail. Statistical test design calculations for probability of detection and flaw sizing tests are described. A recommended performance demonstration test based on the design calculations is presented. A computer program for grading the probability of detection portion of the performance demonstration test is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ChPhy..15.1903Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ChPhy..15.1903Z"><span>High-Tc planar SQUID gradiometer for <span class="hlt">eddy</span> <span class="hlt">current</span> non-destructive evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Ming-Jian; Lang, Pei-Lin; Peng, Zhi-Hui; Chen, Ying-Fei; Chen, Ke; Zheng, Dong-Ning</p> <p>2006-08-01</p> <p>This paper reports the fabrication and test of a high-Tc SQUID planar gradiometer which is patterned from YBCO thin film deposited on a SrTiO3 bicrystal substrate. The measurement of noise spectrum at 77K shows that the white noise at 200 Hz is about 1×10-4Φ0/(Hz)1/2. The minimal magnetic gradient is measured and the results suggest that the minimal magnetic gradient is 94 pT/m. The planar gradiometer is used in non-destructive evaluation (NDE) experiments to detect the artifacts in conducting aluminium plates by performing <span class="hlt">eddy</span> <span class="hlt">current</span> testing in an unshielded environment. The effect of the exciting coil dimension on the NDE results is investigated. By mapping out the induced field distribution, flaws about 10mm below the plate surface can be clearly identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096.1808L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096.1808L"><span>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://hdl.handle.net/2060/20120015904','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120015904"><span>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>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://www.osti.gov/scitech/servlets/purl/572689','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/572689"><span>Nondestructive inspection assessment of <span class="hlt">eddy</span> <span class="hlt">current</span> and electrochemical analysis to separate inconel and stainless steel alloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moore, D.G.; Sorensen, N.R.</p> <p>1998-02-01</p> <p>This report presents a nondestructive inspection assessment of <span class="hlt">eddy</span> <span class="hlt">current</span> and electrochemical analysis to separate inconel alloys from stainless steel alloys as well as an evaluation of cleaning techniques to remove a thermal oxide layer on aircraft exhaust components. The results of this assessment are presented in terms of how effective each technique classifies a known exhaust material. Results indicate that either inspection technique can separate inconel and stainless steel alloys. Based on the experiments conducted, the electrochemical spot test is the optimum for use by airframe and powerplant mechanics. A spot test procedure is proposed for incorporation into the Federal Aviation Administration Advisory Circular 65-9A Airframe & Powerplant Mechanic - General Handbook. 3 refs., 70 figs., 7 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016mecs.conf..371Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016mecs.conf..371Z"><span>Analysis of Dissimilar Material Defect Based on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Conductivity Testing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xiaofan; Li, Lifu</p> <p></p> <p>In this experiment, the conductivity distribution of lack of penetration (LOP) in friction stir welding (FSW) of dissimilar materials has been tested, and has been compared with the conductivity distribution of the same kind of material, by using <span class="hlt">eddy</span> <span class="hlt">current</span> conductivity meter. CZ state and M state LY12 aluminum alloy has been studied. The results show that when the depth of LOP is small, the conductivity of M state is the highest, the conductivity decreases gradually to the weld center, reduce to the minimum until reach the CZ state base metal. When the depth of LOP is larger, the conductivity of the weld center decreases sharply with the depth of LOP increases gradually. Scilicet, the larger the depth of LOP, the lower the conductivity. The conductivity distribution of other areas is similar to the distribution when the depth of LOP is small.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21054940','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21054940"><span>Application of Millimeter Wave, <span class="hlt">Eddy</span> <span class="hlt">Current</span> and Thermographic Methods for Detection of Corrosion in Aluminum Substrate</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ryley, A. C.; Ghasr, M. T.; Kharkovsky, S.; Zoughi, R.; Steffes, Gary</p> <p>2007-03-21</p> <p>Aluminum structures exposed to the elements are susceptible to corrosion. Corrosion may cause various mechanical and structural deficiencies such as material thinning. It is desirable to rapidly detect and evaluate the properties of an aluminum substrate early in the corrosion process to avoid costly maintenance actions later. There are several nondestructive testing methods for this purpose. To investigate capabilities of millimeter wave, conventional <span class="hlt">eddy</span> <span class="hlt">current</span>, and flash thermography techniques for detection of large corrosion areas in aluminum substrates, two corroded samples were inspected with and without dielectric coating (applique). This paper presents the results of the c-scan imaging of these samples using the methods mentioned above. The attributes of these methods for detection and evaluation of large, severe and non-uniform corrosion areas with and without a dielectric coating are discussed.</p> </li> </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_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" 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_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> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/467901','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/467901"><span>Transmit-receive <span class="hlt">eddy</span> <span class="hlt">current</span> probes for defect detection and sizing in steam generator tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Obrutsky, L.S.; Cecco, V.S.; Sullivan, S.P.</p> <p>1997-02-01</p> <p>Inspection of steam generator tubes in aging Nuclear Generating Stations is increasingly important. Defect detection and sizing, especially in defect prone areas such as the tubesheet, support plates and U-bend regions, are required to assess the fitness-for-service of the steam generators. Information about defect morphology is required to address operational integrity issues, i.e., risk of tube rupture, number of tubes at risk, consequential leakage. A major challenge continues to be the detection and sizing of circumferential cracks. Utilities around the world have experienced this type of tube failure. Conventional in-service inspection, performed with <span class="hlt">eddy</span> <span class="hlt">current</span> bobbin probes, is ineffectual in detecting circumferential cracks in tubing. It has been demonstrated in CANDU steam generators, with deformation, magnetite and copper deposits that multi-channel probes with transmit-receive <span class="hlt">eddy</span> <span class="hlt">current</span> coils are superior to those using surface impedance coils. Transmit-receive probes have strong directional properties, permitting probe optimization according to crack orientation. They are less sensitive to lift-off noise and magnetite deposits and possess good discrimination to internal defects. A single pass C3 array transmit-receive probe developed by AECL can detect and size circumferential stress corrosion cracks as shallow as 40% through-wall. Since its first trial in 1992, it has been used routinely for steam generator in-service inspection of four CANDU plants, preventing unscheduled shutdowns due to leaking steam generator tubes. More recently, a need has surfaced for simultaneous detection of both circumferential and axial cracks. The C5 probe was designed to address this concern. It combines transmit-receive array probe technology for equal sensitivity to axial and circumferential cracks with a bobbin probe for historical reference. This paper will discuss the operating principles of transmit-receive probes, along with inspection results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0005B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0005B"><span>Evaluation of machine learning tools for inspection of steam generator tube structures using pulsed <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buck, J. A.; Underhill, P. R.; Morelli, J.; Krause, T. W.</p> <p>2017-02-01</p> <p>Degradation of nuclear steam generator (SG) tubes and support structures can result in a loss of reactor efficiency. Regular in-service inspection, by conventional <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ECT), permits detection of cracks, measurement of wall loss, and identification of other SG tube degradation modes. However, ECT is challenged by overlapping degradation modes such as might occur for SG tube fretting accompanied by tube off-set within a corroding ferromagnetic support structure. Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) is an emerging technology examined here for inspection of Alloy-800 SG tubes and associated carbon steel drilled support structures. Support structure hole size was varied to simulate uniform corrosion, while SG tube was off-set relative to hole axis. PEC measurements were performed using a single driver with an 8 pick-up coil configuration in the presence of flat-bottom rectangular frets as an overlapping degradation mode. A modified principal component analysis (MPCA) was performed on the time-voltage data in order to reduce data dimensionality. The MPCA scores were then used to train a support vector machine (SVM) that simultaneously targeted four independent parameters associated with; support structure hole size, tube off-centering in two dimensions and fret depth. The support vector machine was trained, tested, and validated on experimental data. Results were compared with a previously developed artificial neural network (ANN) trained on the same data. Estimates of tube position showed comparable results between the two machine learning tools. However, the ANN produced better estimates of hole inner diameter and fret depth. The better results from ANN analysis was attributed to challenges associated with the SVM when non-constant variance is present in the data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006DSRI...53.1483G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006DSRI...53.1483G"><span><span class="hlt">Eddy</span>-resolving simulation of plankton ecosystem dynamics in the California <span class="hlt">Current</span> System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gruber, Nicolas; Frenzel, Hartmut; Doney, Scott C.; Marchesiello, Patrick; McWilliams, James C.; Moisan, John R.; Oram, John J.; Plattner, Gian-Kasper; Stolzenbach, Keith D.</p> <p>2006-09-01</p> <p>We study the dynamics of the planktonic ecosystem in the coastal upwelling zone within the California <span class="hlt">Current</span> System using a three-dimensional (3-D), <span class="hlt">eddy</span>-resolving circulation model <span class="hlt">coupled</span> to an ecosystem/biogeochemistry model. The physical model is based on the Regional Oceanic Modeling System (ROMS), configured at a resolution of 15 km for a domain covering the entire US West Coast, with an embedded child grid covering the central California upwelling region at a resolution of 5 km. The model is forced with monthly mean boundary conditions at the open lateral boundaries as well as at the surface. The ecological/biogeochemical model is nitrogen based, includes single classes for phytoplankton and zooplankton, and considers two detrital pools with different sinking speeds. The model also explicitly simulates a variable chlorophyll-to-carbon ratio. Comparisons of model results with either remote sensing observations (AVHRR, SeaWiFS) or in-situ measurements from the CalCOFI program indicate that our model is capable of replicating many of the large-scale, time-averaged features of the coastal upwelling system. An exception is the underestimation of the chlorophyll levels in the northern part of the domain, perhaps because of the lack of short-term variations in the atmospheric forcing. Another shortcoming is that the modeled thermocline is too diffuse, and that the upward slope of the isolines toward the coast is too small. Detailed time-series comparisons with observations from Monterey Bay reveal similar agreements and discrepancies. We attribute the good agreement between the modeled and observed ecological properties in large part to the accuracy of the physical fields. In turn, many of the discrepancies can be traced back to our use of monthly mean forcing. Analysis of the ecosystem structure and dynamics reveal that the magnitude and pattern of phytoplankton biomass in the nearshore region are determined largely by the balance of growth and zooplankton</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title49-vol2/pdf/CFR-2010-title49-vol2-part180-appC.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title49-vol2/pdf/CFR-2010-title49-vol2-part180-appC.pdf"><span>49 CFR Appendix C to Part 180 - <span class="hlt">Eddy</span> <span class="hlt">Current</span> Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-10-01</p> <p>... 49 Transportation 2 2010-10-01 2010-10-01 false <span class="hlt">Eddy</span> <span class="hlt">Current</span> Examination With Visual Inspection... PACKAGINGS Pt. 180, App. C Appendix C to Part 180—<span class="hlt">Eddy</span> <span class="hlt">Current</span> Examination With Visual Inspection for DOT 3AL... <span class="hlt">current</span> examination with visual inspection must develop, update, and maintain a written...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712767C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712767C"><span>On the <span class="hlt">coupled</span> use of sapflow and <span class="hlt">eddy</span> covariance measurements: environmental impacts on the evapotranspiration of an heterogeneous - wild olives based - Sardinian ecosystem.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Curreli, Matteo; Corona, Roberto; Montaldo, Nicola; Oren, Ram</p> <p>2015-04-01</p> <p>Sapflow and <span class="hlt">eddy</span> covariance techniques are attractive methods for evapotranspiration (ET) estimates. We demonstrated that in Mediterranean ecosystems, characterized by an heterogeneous spatial distribution of different plant functional types (PFT) such as grass and trees, the combined use of these techniques becomes essential for the actual ET estimates. Indeed, during the dry summers these water-limited heterogeneous ecosystems are typically characterized by a simple dual PFT system with strong-resistant woody vegetation and bare soil, since grass died. An <span class="hlt">eddy</span> covariance - micrometeorological tower has been installed over an heterogeneous ecosystem at the Orroli site in Sardinia (Italy) from 2003. The site landscape is a mixture of Mediterranean patchy vegetation types: wild olives, different shrubs and herbaceous species, which died during the summer. Where patchy land cover leads and the surface fluxes from different cover are largely different, ET evaluation may be not robust enough and <span class="hlt">eddy</span> covariance method hypothesis are not anymore preserved. In these conditions the sapflow measurements, performed by thermodissipation probes, provide robust estimates of the transpiration from woody vegetation. Through the <span class="hlt">coupled</span> use of the sapflow sensor observations, a 2D footprint model of the <span class="hlt">eddy</span> covariance tower and high resolution satellite images for the estimate of the foot print land cover map, the <span class="hlt">eddy</span> covariance measurements can be correctly interpreted, and ET components (bare soil evaporation and woody vegetation transpiration) can be separated. Based on the Granier technique, 33 thermo-dissipation probes have been built and 6 power regulators have been assembled to provide a constant <span class="hlt">current</span> of 3V to the sensors. The sensors have been installed at the Orroli site into 15 wild olives clumps with different characteristics in terms of tree size, exposition to wind and solar radiation and soil depth. The sap flow sensors outputs are analyzed to estimate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ChJOL..28..364H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ChJOL..28..364H"><span>Path transition of the western boundary <span class="hlt">current</span> with a gap due to mesoscale <span class="hlt">eddies</span>: a 1.5-layer, wind-driven experiment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hu, Po; Hou, Yijun</p> <p>2010-03-01</p> <p>Using a 1.5 layer nonlinear shallow-water reduced-gravity model, we executed numerical simulations to investigate the possibility of a western boundary <span class="hlt">current</span> (WBC) path transition due to mesoscale <span class="hlt">eddies</span> based on the background of the Kuroshio intrusion into the South China Sea (SCS) from the Luzon Strait. Because the WBC existed different <span class="hlt">current</span> states with respect to different wind stress control parameters, we chose three steady WBC states (loop <span class="hlt">current</span>, <span class="hlt">eddy</span> shedding and leaping) as the background flow field and simulated the path transition of the WBC due to mesoscale <span class="hlt">eddies</span>. Our simulations indicated that either an anticyclonic or cyclonic <span class="hlt">eddy</span> can lead to path transition of the WBC with different modes. The simulation results also show that the mesoscale <span class="hlt">eddies</span> can lead to path transition of the WBC from loop and <span class="hlt">eddy</span> shedding state to leaping state because of the hysteresis effect. The leaping state is relatively stable compared with the mesoscale <span class="hlt">eddies</span>. Moreover, an anticyclonic <span class="hlt">eddy</span> is more effective in producing the WBC path transition for the path transition than a cyclonic <span class="hlt">eddy</span>. Our results may help to explain some phenomena observed regarding the path transition of the Kuroshio due to the mesoscale <span class="hlt">eddies</span> at the Luzon Strait.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006MeScT..17..393Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006MeScT..17..393Y"><span>A multi-frequency impedance analysing instrument for <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>Yin, W.; Dickinson, S. J.; Peyton, A. J.</p> <p>2006-02-01</p> <p>This paper presents the design of a high-performance multi-frequency impedance analysing instrument (MFIA) for <span class="hlt">eddy</span> <span class="hlt">current</span> testing which has been developed primarily for monitoring a steel production process using an inductive sensor. The system consists of a flexible multi-frequency waveform generator and a voltage/<span class="hlt">current</span> measurement unit. The impedance of the sensor is obtained by cross-spectral analysis of the <span class="hlt">current</span> and voltage signals. The system contains high-speed digital-to-analogue, analogue-to-digital converters and dual DSPs with one for control and interface and one dedicated to frequency-spectra analysis using fast Fourier transformation (FFT). The frequency span of the signal that can be analysed ranges from 1 kHz to 8 MHz. The system also employs a high-speed serial port interface (USB) to communicate with a personal computer (PC) and to allow for fast transmission of data and control commands. Overall, the system is capable of delivering over 250 impedance spectra per second. Although the instrument has been developed mainly for use with an inductive sensor, the system is not restricted to inductive measurement. The flexibility of the design architecture is demonstrated with capacitive and resistive measurements by using appropriate input circuitry. Issues relating to optimizing the phase of the spectra components in the excitation waveform are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26413505','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26413505"><span>Correction for <span class="hlt">Eddy</span> <span class="hlt">Current</span>-Induced Echo-Shifting Effect in Partial-Fourier Diffusion Tensor Imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Truong, Trong-Kha; Song, Allen W; Chen, Nan-Kuei</p> <p>2015-01-01</p> <p>In most diffusion tensor imaging (DTI) studies, images are acquired with either a partial-Fourier or a parallel partial-Fourier echo-planar imaging (EPI) sequence, in order to shorten the echo time and increase the signal-to-noise ratio (SNR). However, <span class="hlt">eddy</span> <span class="hlt">currents</span> induced by the diffusion-sensitizing gradients can often lead to a shift of the echo in k-space, resulting in three distinct types of artifacts in partial-Fourier DTI. Here, we present an improved DTI acquisition and reconstruction scheme, capable of generating high-quality and high-SNR DTI data without <span class="hlt">eddy</span> <span class="hlt">current</span>-induced artifacts. This new scheme consists of three components, respectively, addressing the three distinct types of artifacts. First, a k-space energy-anchored DTI sequence is designed to recover <span class="hlt">eddy</span> <span class="hlt">current</span>-induced signal loss (i.e., Type 1 artifact). Second, a multischeme partial-Fourier reconstruction is used to eliminate artificial signal elevation (i.e., Type 2 artifact) associated with the conventional partial-Fourier reconstruction. Third, a signal intensity correction is applied to remove artificial signal modulations due to <span class="hlt">eddy</span> <span class="hlt">current</span>-induced erroneous T2(∗) -weighting (i.e., Type 3 artifact). These systematic improvements will greatly increase the consistency and accuracy of DTI measurements, expanding the utility of DTI in translational applications where quantitative robustness is much needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/538795','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/538795"><span>Advanced flux leakage and <span class="hlt">eddy</span> <span class="hlt">current</span> signal analysis for casing and pipe inspection. Final report, September 1994-October 1996</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Merchant, G.A.</p> <p>1997-01-01</p> <p>The objective of the project was to develop signal analysis methods and algorithms which will extract from the magnetic flux leakage and <span class="hlt">eddy</span> <span class="hlt">current</span> (FLEC) signals all the quantitative information they inherently contain and format that information in a manner which facilitates its interpretation in terms of casing condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MS%26E..150a2026C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MS%26E..150a2026C"><span>Detection of cold cracks in the cast-steels by the methods of ultrasonic and <span class="hlt">eddy-current</span> infrared thermography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheprasov, A. I.; Knyazev, S. V.; Usoltsev, A. A.; Dolgopolov, A. E.; Mamedov, R. O.</p> <p>2016-09-01</p> <p>The aim of this study was to investigate the possibility of detection of cold cracks in the massive steel products using ultrasonic and <span class="hlt">eddy-current</span> excitation, as well as the thermal imaging method of temperature recording, that in the perspective should be completed by the development of requirements for the monitoring equipment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JPhD...46.5001M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JPhD...46.5001M"><span>Impact of <span class="hlt">eddy</span> <span class="hlt">currents</span> on the dispersion relation of surface spin waves in thin conducting magnetic films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maksymov, I. S.; Kostylev, M.</p> <p>2013-12-01</p> <p>We propose a rigorous solution to a long-standing problem of the impact of <span class="hlt">eddy</span> <span class="hlt">currents</span> on the dispersion relation of surface spin waves propagating in thin conducting magnetic films. Our results confirm the prediction of the Almeida-Mill's exchange-free theory that the inclusion of the <span class="hlt">eddy-current</span> contribution results in a deviation of the dispersion curve for the fundamental mode from the Damon-Eshbach law and a substantial linewidth broadening in a large wave vector range. We show that the decrease in the spin-wave frequency is due to an increase in the in-plane component of the dynamic magnetic field within the conducting film. The decrease in the frequency is accompanied by a drastic change in the asymmetry of the modal profiles for the waves. This effect is not observable in magneto-insulating films and therefore it is unambiguously attributed to <span class="hlt">eddy</span> <span class="hlt">currents</span> that appear in conducting films only. We also show that the wave vector range in which <span class="hlt">eddy</span> <span class="hlt">currents</span> affect the dispersion curve is strongly correlated with the value of the film conductivity. This result holds for conducting films with the thickness 10-100 nm, which are considered promising for future magnonic and spintronic applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA206627','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA206627"><span>Computer Algorithms and Architectures for Three-Dimensional <span class="hlt">Eddy-Current</span> Nondestructive Evaluation. Volume 1. Executive Summary</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1989-01-20</p> <p>LLAA6 .l iI -SA/TR-2/89 A003: FINAL REPORT * COMPUTER ALGORITHMS AND ARCHITECTURES N FOR THREE-DIMENSIONAL <span class="hlt">EDDY-CURRENT</span> NONDESTRUCTIVE EVALUATION...Ciasuication) COMPUTER ALGORITHMS AND ARCHITECTURES FOR THREE-DIMENSIONAL EDD~j~~JRRN iv ummary Q PERSONAL AUTriOR(S) SBAHASCAE 1 3a. TYPE Of REPORT</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=currents+AND+eddy&pg=2&id=ED182612','ERIC'); return false;" href="http://eric.ed.gov/?q=currents+AND+eddy&pg=2&id=ED182612"><span>Nuclear Technology. Course 32: Nondestructive Examination (NDE) Techniques II. Module 32-5, Fundamentals of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Espy, John</p> <p></p> <p>This fifth in a series of six modules for a course titled Nondestructive Examination (NDE) Techniques II describes the fundamental concepts applicable to <span class="hlt">eddy</span> <span class="hlt">current</span> testing in general. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED086443.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED086443.pdf"><span>Nondestructive Testing <span class="hlt">Eddy</span> <span class="hlt">Current</span> Equipment, Methods and Applications RQA/M1-5330.12 (V-II).</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>National Aeronautics and Space Administration, Huntsville, AL. George C. Marshall Space Flight Center.</p> <p></p> <p>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 <span class="hlt">eddy</span> <span class="hlt">current</span> testing. The subject is presented under the following headings: Test Coils, Methods and Indications, and Applications. High product quality and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=currents+AND+eddy&pg=2&id=ED182613','ERIC'); return false;" href="http://eric.ed.gov/?q=currents+AND+eddy&pg=2&id=ED182613"><span>Nuclear Technology. Course 32: Nondestructive Examination (NDE) Techniques II. Module 32-6, Operation of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Test Equipment.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Espy, John; Selleck, Ben</p> <p></p> <p>This sixth in a series of six modules for a course titled Nondestructive Examination (NDE) Techniques II details <span class="hlt">eddy</span> <span class="hlt">current</span> examination of steam generator tubing. The module follows a typical format that includes the following sections: (1) introduction, (2) module prerequisites, (3) objectives, (4) notes to instructor/student, (5) subject…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1027456','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1027456"><span>Mountable <span class="hlt">eddy</span> <span class="hlt">current</span> sensor for in-situ remote detection of surface and sub-surface fatigue cracks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Yepez, III, Esteban; Roach, Dennis P.; Rackow, Kirk A.; DeLong, Waylon A.</p> <p>2011-09-06</p> <p>A wireless, integrated, mountable, portable, battery-operated, non-contact <span class="hlt">eddy</span> <span class="hlt">current</span> sensor that provides similar accuracy to 1970's laboratory scale equipment (e.g., a Hewlett-Packard GP4194A Impedance Analyzer) at a fraction of the size and cost.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhFl...28b1301S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhFl...28b1301S"><span>Sand waves in environmental flows: Insights gained by <span class="hlt">coupling</span> large-<span class="hlt">eddy</span> simulation with morphodynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sotiropoulos, Fotis; Khosronejad, Ali</p> <p>2016-02-01</p> <p>Sand waves arise in subaqueous and Aeolian environments as the result of the complex interaction between turbulent flows and mobile sand beds. They occur across a wide range of spatial scales, evolve at temporal scales much slower than the integral scale of the transporting turbulent flow, dominate river morphodynamics, undermine streambank stability and infrastructure during flooding, and sculpt terrestrial and extraterrestrial landscapes. In this paper, we present the vision for our work over the last ten years, which has sought to develop computational tools capable of simulating the <span class="hlt">coupled</span> interactions of sand waves with turbulence across the broad range of relevant scales: from small-scale ripples in laboratory flumes to mega-dunes in large rivers. We review the computational advances that have enabled us to simulate the genesis and long-term evolution of arbitrarily large and complex sand dunes in turbulent flows using large-<span class="hlt">eddy</span> simulation and summarize numerous novel physical insights derived from our simulations. Our findings explain the role of turbulent sweeps in the near-bed region as the primary mechanism for destabilizing the sand bed, show that the seeds of the emergent structure in dune fields lie in the heterogeneity of the turbulence and bed shear stress fluctuations over the initially flatbed, and elucidate how large dunes at equilibrium give rise to energetic coherent structures and modify the spectra of turbulence. We also discuss future challenges and our vision for advancing a data-driven simulation-based engineering science approach for site-specific simulations of river flooding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/203815','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/203815"><span>Effect of the surface film electric resistance on <span class="hlt">eddy</span> <span class="hlt">current</span> detectability of surface cracks in Alloy 600 tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Saario, T.; Paine, J.P.N.</p> <p>1995-12-31</p> <p>The most widely used technique for NDE of steam generator tubing is <span class="hlt">eddy</span> <span class="hlt">current</span>. This technique can reliably detect cracks grown in sodium hydroxide environment only at depths greater than 50% through wall. However, cracking caused by thiosulphate solutions have been detected and sized at shallower depths. The disparity has been proposed to be caused by the different electric resistance of the crack wall surface films and corrosion products in the cracks formed in different environments. This work was undertaken to clarify the role of surface film electric resistance on the disparity found in <span class="hlt">eddy</span> <span class="hlt">current</span> detectability of surface cracks in alloy 600 tubes. The proposed model explaining the above mentioned disparity is the following. The detectability of tightly closed cracks by the <span class="hlt">eddy</span> <span class="hlt">current</span> technique depends on the electric resistance of the surface films of the crack walls. The nature and resistance of the films which form on the crack walls during operation depends on the composition of the solution inside the crack and close to the crack location. During cooling down of the steam generator, because of contraction and loss of internal pressurization, the cracks are rather tightly closed so that exchange of electrolyte and thus changes in the film properties become difficult. As a result, the surface condition prevailing at high temperature is preserved. If the environment is such that the films formed on the crack walls under operating conditions have low electric resistance, <span class="hlt">eddy</span> <span class="hlt">current</span> technique will fail to indicate these cracks or will underestimate the size of these cracks. However, if the electric resistance of the films is high, a tightly closed crack will resemble an open crack and will be easily indicated and correctly sized by <span class="hlt">eddy</span> <span class="hlt">current</span> technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JAP...109gD348A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JAP...109gD348A"><span>Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> differential probe to detect the defects in a stainless steel pipe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Angani, C. S.; Park, D. G.; Kim, C. G.; Leela, P.; Kishore, M.; Cheong, Y. M.</p> <p>2011-04-01</p> <p>Pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) is an electromagnetic nondestructive technique widely used to detect and quantify the flaws in conducting materials. In the present study a differential Hall-sensor probe which is used in the PEC system has been fabricated for the detection of defects in stainless steel pipelines. The differential probe has an exciting coil with two Hall-sensors. A stainless steel test sample with electrical discharge machining (EDM) notches under different depths of 1-5 mm was made and the sample was laminated by plastic insulation having uniform thickness to simulate the pipelines in nuclear power plants (NPPs). The driving coil in the probe is excited by a rectangular <span class="hlt">current</span> pulse and the resultant response, which is the difference of the two Hall-sensors, has been detected as the PEC probe signal. The discriminating time domain features of the detected pulse such as peak value and time to zero are used to interpret the experimental results with the defects in the test sample. A feature extraction technique such as spectral power density has been devised to infer the PEC response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JTePh..60.1697K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JTePh..60.1697K"><span>Measurements of the transverse resistance and <span class="hlt">eddy</span> <span class="hlt">current</span> losses in a cable-in-conduit conductor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keilin, V. E.; Kovalev, I. A.; Kruglov, S. L.; Lelekhov, S. A.; Il'in, A. A.; Naumov, A. V.; Shcherbakov, V. I.; Shutov, K. A.</p> <p>2015-11-01</p> <p>In the case of plasma <span class="hlt">current</span> interruption in tokamaks, the conductor of toroidial field (TF) coils experiences the action of a pulsed decreasing magnetic field (PDMF) parallel to the conductor's axis. To estimate the stability of a cable-in-conduit conductor against the PDMF, a new experimental method to study different types of losses is applied. This method exploits a high sensitivity of temperature and gas pressure to input energy in a closed volume. It allows one to measure hysteresis losses with a rather high accuracy (provided that the rate of change of the PDMF is low) and a sum of hysteresis losses and <span class="hlt">eddy</span> <span class="hlt">current</span> losses (when the rate of change of the PDMF is high). An experimental setup to measure the transverse (circumferential) resistance and losses has been developed at the National Research Centre Kurchatov Institute. A Russianmade Nb3Sn conductor intended for the TF coils of the International Thermonuclear Experimental Reactor is subjected to a PDMF with different amplitudes and characteristic times. The electromagnetic time constant and the transverse resistivity of the conductor are experimentally determined. The maximum temperature of strands under the action of the PDMF is calculated.</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('https://www.osti.gov/scitech/biblio/1244185','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1244185"><span>Fast Acting <span class="hlt">Eddy</span> <span class="hlt">Current</span> Driven Valve for Massive Gas Injection on ITER</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lyttle, Mark S; Baylor, Larry R; Carmichael, Justin R; Combs, Stephen Kirk; Ericson, Milton Nance; Ezell, N Dianne Bull; Meitner, S. J.; Rasmussen, David A; Warmack, Robert J Bruce; Maruyama, So; Kiss, Gabor</p> <p>2015-01-01</p> <p>Tokamak plasma disruptions present a significant challenge to ITER as they can result in intense heat flux, large forces from halo and <span class="hlt">eddy</span> <span class="hlt">currents</span>, and potential first-wall damage from the generation of multi-MeV runaway electrons. Massive gas injection (MGI) of high Z material using fast acting valves is being explored on existing tokamaks and is planned for ITER as a method to evenly distribute the thermal load of the plasma to prevent melting, control the rate of the <span class="hlt">current</span> decay to minimize mechanical loads, and to suppress the generation of runaway electrons. A fast acting valve and accompanying power supply have been designed and first test articles produced to meet the requirements for a disruption mitigation system on ITER. The test valve incorporates a flyer plate actuator similar to designs deployed on TEXTOR, ASDEX upgrade, and JET [1 3] of a size useful for ITER with special considerations to mitigate the high mechanical forces developed during actuation due to high background magnetic fields. The valve includes a tip design and all-metal valve stem sealing for compatibility with tritium and high neutron and gamma fluxes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4732048','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4732048"><span>Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>de Alcantara, Naasson P.; da Silva, Felipe M.; Guimarães, Mateus T.; Pereira, Matheus D.</p> <p>2015-01-01</p> <p>This paper presents a theoretical and experimental study on the use of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed <span class="hlt">current</span> technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works. PMID:26712754</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26712754','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26712754"><span>Corrosion Assessment of Steel Bars Used in Reinforced Concrete Structures by Means of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Alcantara, Naasson P; da Silva, Felipe M; Guimarães, Mateus T; Pereira, Matheus D</p> <p>2015-12-24</p> <p>This paper presents a theoretical and experimental study on the use of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Testing (ECT) to evaluate corrosion processes in steel bars used in reinforced concrete structures. The paper presents the mathematical basis of the ECT sensor built by the authors; followed by a finite element analysis. The results obtained in the simulations are compared with those obtained in experimental tests performed by the authors. Effective resistances and inductances; voltage drops and phase angles of wound coil are calculated using both; simulated and experimental data; and demonstrate a strong correlation. The production of samples of corroded steel bars; by using an impressed <span class="hlt">current</span> technique is also presented. The authors performed experimental tests in the laboratory using handmade sensors; and the corroded samples. In the tests four gauges; with five levels of loss-of-mass references for each one were used. The results are analyzed in the light of the loss-of-mass and show a strong linear behavior for the analyzed parameters. The conclusions emphasize the feasibility of the proposed technique and highlight opportunities for future works.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA511959','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA511959"><span><span class="hlt">Eddies</span> and Filaments of the Western Adriatic <span class="hlt">Current</span> near Cape Gargano: Analysis and Prediction</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2008-10-21</p> <p>used. The Po discharge was spread over 5 discharge locations spanning the delta to simulate the river’s actual distributaries. During the period Feb 1...The vertical sections follow transects A1 and A2, which parallel the actual Aquashuttle transect A (Fig. 9c), but are displaced progressively to its...west at intervals of 4 km and aligned closely with the predicted <span class="hlt">eddy</span> locations (Fig. 11d–f). The model does not show <span class="hlt">eddies</span> along the actual</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19740028957&hterms=electromagnetic+induction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Delectromagnetic%2Binduction','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19740028957&hterms=electromagnetic+induction&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Delectromagnetic%2Binduction"><span>Global electromagnetic induction in the moon and planets. [poloidal <span class="hlt">eddy</span> <span class="hlt">current</span> transient response</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dyal, P.; Parkin, C. W.</p> <p>1973-01-01</p> <p>Experiments and analyses concerning electromagnetic induction in the moon and other extraterrestrial bodies are summarized. The theory of classical electromagnetic induction in a sphere is first considered, and this treatment is extended to the case of the moon, where poloidal <span class="hlt">eddy-current</span> response has been found experimentally to dominate other induction modes. Analysis of lunar poloidal induction yields lunar internal electrical conductivity and temperature profiles. Two poloidal-induction analytical techniques are discussed: a transient-response method applied to time-series magnetometer data, and a harmonic-analysis method applied to data numerically Fourier-transformed to the frequency domain, with emphasis on the former technique. Attention is given to complicating effects of the solar wind interaction with both induced poloidal fields and remanent steady fields. The static magnetization field induction mode is described, from which are calculated bulk magnetic permeability profiles. Magnetic field measurements obtained from the moon and from fly-bys of Venus and Mars are studied to determine the feasibility of extending theoretical and experimental induction techniques to other bodies in the solar system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhD...49o5303C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhD...49o5303C"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> characterization of small cracks using least square support vector machine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chelabi, M.; Hacib, T.; Le Bihan, Y.; Ikhlef, N.; Boughedda, H.; Mekideche, M. R.</p> <p>2016-04-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> (EC) sensors are used for non-destructive testing since they are able to probe conductive materials. Despite being a conventional technique for defect detection and localization, the main weakness of this technique is that defect characterization, of the exact determination of the shape and dimension, is still a question to be answered. In this work, we demonstrate the capability of small crack sizing using signals acquired from an EC sensor. We report our effort to develop a systematic approach to estimate the size of rectangular and thin defects (length and depth) in a conductive plate. The achieved approach by the novel combination of a finite element method (FEM) with a statistical learning method is called least square support vector machines (LS-SVM). First, we use the FEM to design the forward problem. Next, an algorithm is used to find an adaptive database. Finally, the LS-SVM is used to solve the inverse problems, creating polynomial functions able to approximate the correlation between the crack dimension and the signal picked up from the EC sensor. Several methods are used to find the parameters of the LS-SVM. In this study, the particle swarm optimization (PSO) and genetic algorithm (GA) are proposed for tuning the LS-SVM. The results of the design and the inversions were compared to both simulated and experimental data, with accuracy experimentally verified. These suggested results prove the applicability of the presented approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22571825','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22571825"><span>Approaches to improve separation efficiency of <span class="hlt">eddy</span> <span class="hlt">current</span> separation for recovering aluminum from waste toner cartridges.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruan, Jujun; Xu, Zhenming</p> <p>2012-06-05</p> <p>Separation efficiency of <span class="hlt">eddy</span> <span class="hlt">current</span> separation (ECS) is low (about 85%) in industrial application for recovering aluminum from crushed waste toner cartridges. Influencing factors of ECS were studied to improve the separation efficiency. Operation factors were researched by orthogonal experiment of ECS on investigating the separation distance between aluminum and plastic flakes. The results indicated the difference (ωR-v) between feeding speed (v) and rotation speed (ω) of magnetic drum (radius: R) was critical factor of influencing the separation efficiency, feeding speed (v) was general factor, and collecting position (H) was subordinate factor. Separation efficiency decreased as the increasing of v, and increased as the increasing of (ωR-v). 0.9 m was the optimal value of H in the orthogonal experiment. Influencing factors of particle characteristics and machine structure were studied by newly established models for computing the separation distance between aluminum and plastic flake in ECS. The results indicated changing of particle size would influence the separation efficiency greater than ω and particle shape. Separation efficiency will increase as the increasing of particle size and ω. Shape of circle is beneficial to improve separation efficiency. Finally, approaches to improve separation efficiency of ECS were presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6636428','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6636428"><span>3-D transient <span class="hlt">eddy</span> <span class="hlt">current</span> calculations for the FELIX cylinder experiments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Davey, K.R.; Turner, L.R.</p> <p>1986-12-01</p> <p>The three-dimensional <span class="hlt">eddy</span> <span class="hlt">current</span> transient field problem is formulated first using the U-V method. This method breaks the vector Helmholtz equation into two scalar Helmholtz equations. Null field integral equations and the appropriate boundary conditions are used to set up an identification matrix which is independent of null field point locations. Embedded in the identification matrix are the unknown eigenvalues of the problem representing its impulse response in time. These eigenvalues are found by equating the determinant of the identification matrix to zero. When this initial forcing function is Fourier decomposed into its spatial harmonics, each Fourier component can be associated with a unique eigenvalue by this technique. The true transient solution comes through a convolution of the impulse response so obtained with the particular external field decay governing the problem at hand. The technique is applied to the FELIX cylinder experiments; computed results are compared to data. A pseudoanalytic confirmation of the eigenvalues so obtained is formulated to validate the procedure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RScI...87j4707L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RScI...87j4707L"><span>Approach for removing ghost-images in remote field <span class="hlt">eddy</span> <span class="hlt">current</span> testing of ferromagnetic pipes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luo, Q. W.; Shi, Y. B.; Wang, Z. G.; Zhang, W.; Zhang, Y.</p> <p>2016-10-01</p> <p>In the non-destructive testing of ferromagnetic pipes based on remote field <span class="hlt">eddy</span> <span class="hlt">currents</span>, an array of sensing coils is often used to detect local defects. While testing, the image that is obtained by sensing coils exhibits a ghost-image, which originates from both the transmitter and sensing coils passing over the same defects in pipes. Ghost-images are caused by transmitters and lead to undesirable assessments of defects. In order to remove ghost-images, two pickup coils are coaxially set to each other in remote field. Due to the time delay between differential signals tested by the two pickup coils, a Wiener deconvolution filter is used to identify the artificial peaks that lead to ghost-images. Because the sensing coils and two pickup coils all receive the same signal from one transmitter, they all contain the same artificial peaks. By subtracting the artificial peak values obtained by the two pickup coils from the imaging data, the ghost-image caused by the transmitter is eliminated. Finally, a relatively highly accurate image of local defects is obtained by these sensing coils. With proposed method, there is no need to subtract the average value of the sensing coils, and it is sensitive to ringed defects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AIPC..615..520G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AIPC..615..520G"><span>Multiplexed HTS rf SQUID magnetometer array for <span class="hlt">eddy</span> <span class="hlt">current</span> testing of aircraft rivet joints</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gärtner, S.; Krause, H.-J.; Wolters, N.; Lomparski, D.; Wolf, W.; Schubert, J.; Kreutzbruck, M. v.; Allweins, K.</p> <p>2002-05-01</p> <p>Using three rf SQUID magnetometers, a multiplexed SQUID array was implemented. The SQUIDs are positioned in line with 7 mm spacing and operated using one feedback electronics with sequential read out demodulation at different radio frequencies (rf). The cross-talk between SQUID channels was determined to be negligible. To show the performance of the SQUID array, <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) measurements of aluminum aircraft samples in conjunction with a differential (double-D) EC excitation and lock-in readout were carried out. With computer-controlled continuous switching of the SQUIDs during the scan, three EC signal traces of the sample are obtained simultaneously. We performed measurements with an EC excitation frequency of 135 Hz to localize an artificial crack (sawcut flaw) of 20 mm length in an aluminum sheet with 0.6 mm thickness. The flaw was still detected when covered with aluminum of up to 10 mm thickness. In addition, measurements with varying angles between scanning direction and flaw orientation are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004JaJAP..43.1488H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004JaJAP..43.1488H"><span><span class="hlt">Eddy-Current</span>-Based Nondestructive Inspection System Using Superconducting Quantum Interference Device for Thin Copper Tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hatsukade, Yoshimi; Kosugi, Akifumi; Mori, Kazuaki; Tanaka, Saburo</p> <p>2004-11-01</p> <p>An <span class="hlt">eddy-current</span>-based nondestructive inspection (NDI) system using superconducting quantum interference device (SQUID) cooled using a coaxial pulse tube cryocooler was constructed for the inspection of microflaws on copper tubes employing a high-Tc SQUID gradiometer and a Helmholtz-like coil inducer. The detection of artificial flaws several tens of μm in depth on copper tubes 6.35 mm in outer diameter and 0.825 mm in thickness was demonstrated using the SQUID-NDI system. With an excitation field of 1.6 μT at 5 kHz, a 30-μm-depth flaw was successfully detected by the system at an SN ratio of at least 20. The magnetic signal amplitude due to the flaw was proportional to both excitation frequency and the square of flaw depth. With consideration of the system’s sensitivity, the results indicate that sub-10-μm-depth flaws are detectable by the SQUID-NDI system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NTE....30..233L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NTE....30..233L"><span>Application of Hilbert-Huang transform for defect recognition in pulsed <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>Liu, Baoling; Huang, Pingjie; Hou, Dibo; Chen, Xiao; Zhang, Guangxin</p> <p>2015-07-01</p> <p>Defect recognition plays an important role in the structure integrity and health monitor of in-service equipment. However, it is difficult to recognise deep-layer defect or small-size defect in conductive structure during pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) testing. Aiming at the issue, this article proposes a method based on Hilbert-Huang transform which consists of two modules: data processing and defect recognition. In the data processing module, the PEC response signal is decomposed into a few of intrinsic mode functions (IMFs) using ensemble empirical mode decomposition method. The IMFs whose variance contribution rates are bigger than 1% are chosen to reconstruct signal in order to remove noise. In the defect recognition module, the features based on specific frequency components of marginal spectrum (MS) of the reconstructed signals are extracted to discriminate those defects in surface and subsurface. Furthermore, the normalisation MS energy ratio is proposed to quantify defects which cannot be distinguished using peak value in time domain. Experiments show that the proposed method can achieve better de-noising effect and defect evaluation, which contributes to the recognition of those complicated defects such as deep-layered and small-sized defect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JSV...373...52D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JSV...373...52D"><span>Modeling and evaluation of damping coefficient of <span class="hlt">eddy</span> <span class="hlt">current</span> dampers in rotordynamic applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Detoni, J. G.; Cui, Q.; Amati, N.; Tonoli, A.</p> <p>2016-07-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> dampers (ECD) can be used to introduce damping in rotordynamic applications. ECDs are contactless in nature and can be made to introduce negligible drag force, thus being a perfect match for passive magnetic bearings such as permanent magnet bearings and superconducting bearings. However, modeling and estimating the amount of damping introduced by an ECD is a difficult task due to complicated geometry and working conditions. The present study presents a novel method for modeling and identification of the damping characteristics of ECDs for rotordynamic applications. The proposed method employs an analytical dynamic model of the ECD and curve fitting with results of electromagnetic finite element (FE) models to obtain the parameters characterizing the ECD's mechanical impedance. The damping coefficient can be obtained with great accuracy from a single FE solution in quasistatic conditions. The validity of the proposed method is limited to the case of ECDs employing an axisymmetric conductor, such as a disc or a cylinder, thus covering most cases in rotordynamic applications. Finally, the accuracy of the identification procedure is verified experimentally by comparing the model's results with experimental tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920046038&hterms=gas+turbine+blade+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgas%2Bturbine%2Bblade%2Btest','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920046038&hterms=gas+turbine+blade+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dgas%2Bturbine%2Bblade%2Btest"><span>Automated <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of Space Shuttle APU turbine wheel blades</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fisher, Jay L.; Rowland, Stephen N.; Stolte, Jeffrey S.; Salkowski, Charles</p> <p>1991-01-01</p> <p>An automated inspection system based on <span class="hlt">eddy</span> <span class="hlt">current</span> testing (ET) techniques has been developed to inspect turbine wheel blades on the APU used in NASA's Space Transportation system. The APU is a hydrazine-powered gas turbine with a 15-cm diameter Rene 41 turbine wheel, which has 123 first-stage blades and 123 second-stage blades. The flaw detection capability of the ET system is verified through comparison with fluorescent penetrant test results. Results of the comparison indicate that ET is capable of inspecting surfaces with very restrictive geometries. The ET capability requires development of probes with extremely small coils to allow inspection within 0.4 mm of the blade root and the leading and trailing edges of the blade and within a height restriction of less than 1 mm. The color 2D presentation of the ET data provided crack-growth pattern and length information similar to those found with visual techniques. It also provided visual clues to minimize geometry effects such as generated from blade edges, a neighoring blade, and changes in the blade thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3472811','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3472811"><span>Experimental Estimating Deflection of a Simple Beam Bridge Model Using Grating <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensors</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lü, Chunfeng; Liu, Weiwen; Zhang, Yongjie; Zhao, Hui</p> <p>2012-01-01</p> <p>A novel three-point method using a grating <span class="hlt">eddy</span> <span class="hlt">current</span> absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each other rather than using any other auxiliary static reference points for measuring devices in a conventional method. Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints. In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection. Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches. Principles of the three-point method and displacement measurement of the GECS are introduced in detail. Both static and dynamic experiments have been carried out on a simple beam bridge model, which demonstrate that the three-point deflection estimation method using the GECS is effective and offers a reliable way for bridge deflection estimation, especially for long-term monitoring. PMID:23112583</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11336983','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11336983"><span>Involvement of <span class="hlt">eddy</span> <span class="hlt">currents</span> in the mutagenicity of ELF magnetic fields.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Koana, T; Okada, M O; Takashima, Y; Ikehata, M; Miyakoshi, J</p> <p>2001-05-09</p> <p>Possible carcinogenic and/or mutagenic activity of extremely low frequency magnetic fields was examined using somatic mutation and recombination test system of Drosophila melanogaster. An X-linked semi-dominant DNA repair defective mutation mei-41(D5) was introduced into the conventional mwh/flr test system to enhance mutant spot frequency. Virgin females of w mei-41(D5)/FM6; flr/TM6 were crossed with w mei-41(D5)/Y; mwh jv; spa(pol) males. The F(1) third instar larvae were exposed to a 50Hz, 20mT sinusoidal AC magnetic field for 24h. After moulting from pupal cases, their wings were examined under a bright field microscope to detect hair spots with mwh or flr mutant morphology. The exposure caused a statistically significant enhancement in somatic recombination spot frequency. Mutant spots arising due to chromosomal non-disjunction or terminal deletion also increased but the frequency of spots resulting from point mutation was not altered. The enhancement in the recombination spot frequency was suppressed to the control level when a culture medium without electrolytes was used during exposure. When larvae were exposed to a magnetic field in an annular dish, flies from the outer ring showed more mutant spots compared to those from the inner ring. These results suggest that the detected mutagenic activity was that of the induced <span class="hlt">eddy</span> <span class="hlt">current</span>, rather than that of the magnetic field itself.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27164112','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27164112"><span>Frequency Optimization for Enhancement of Surface Defect Classification Using the <span class="hlt">Eddy</span> <span class="hlt">Current</span> Technique.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun</p> <p>2016-05-07</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0027Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0027Z"><span>Advanced model of <span class="hlt">eddy-current</span> NDE inverse problem with sparse grid algorithm</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Liming; Sabbagh, Harold A.; Sabbagh, Elias H.; Murphy, R. Kim; Bernacchi, William</p> <p>2017-02-01</p> <p>In model-based inverse problem, some unknown parameters need to be estimated. These parameters are used not only to characterize the physical properties of cracks, but also to describe the position of the probes (such as lift off and angles) in the calibration. After considering the effect of the position of the probes in the inverse problem, the accuracy of the inverse result will be improved. With increasing the number of the parameters in the inverse problems, the burden of calculations will increase exponentially in the traditional full grid method. The sparse grid algorithm, which was introduced by Sergey A. Smolyak, was used in our work. With this algorithm, we obtain a powerful interpolation method that requires significantly fewer support nodes than conventional interpolation on a full grid. In this work, we combined sparse grid toolbox TASMANIAN, which is produced by Oak Ridge National Laboratory, and professional <span class="hlt">eddy-current</span> NDE software, VIC-3D R◯, to solve a specific inverse problem. An advanced model based on our previous one is used to estimate length and depth of the crack, lift off and two angles of the position of probes. Considering the calibration process, pseudorandom noise is considered in the model and statistical behavior is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4970006','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4970006"><span>A Flexible Arrayed <span class="hlt">Eddy</span> <span class="hlt">Current</span> Sensor for Inspection of Hollow Axle Inner Surfaces</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sun, Zhenguo; Cai, Dong; Zou, Cheng; Zhang, Wenzeng; Chen, Qiang</p> <p>2016-01-01</p> <p>A reliable and accurate inspection of the hollow axle inner surface is important for the safe operation of high-speed trains. In order to improve the reliability of the inspection, a flexible arrayed <span class="hlt">eddy</span> <span class="hlt">current</span> sensor for non-destructive testing of the hollow axle inner surface was designed, fabricated and characterized. The sensor, consisting of two excitation traces and 28 sensing traces, was developed by using the flexible printed circuit board (FPCB) technique to conform the geometric features of the inner surfaces of the hollow axles. The main innovative aspect of the sensor was the new arrangement of excitation/sensing traces to achieve a differential configuration. Finite element model was established to analyze sensor responses and to determine the optimal excitation frequency. Experimental validations were conducted on a specimen with several artificial defects. Results from experiments and simulations were consistent with each other, with the maximum relative error less than 4%. Both results proved that the sensor was capable of detecting longitudinal and transverse defects with the depth of 0.5 mm under the optimal excitation frequency of 0.9 MHz. PMID:27347952</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4883340','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4883340"><span>Frequency Optimization for Enhancement of Surface Defect Classification Using the <span class="hlt">Eddy</span> <span class="hlt">Current</span> Technique</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fan, Mengbao; Wang, Qi; Cao, Binghua; Ye, Bo; Sunny, Ali Imam; Tian, Guiyun</p> <p>2016-01-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> testing is quite a popular non-contact and cost-effective method for nondestructive evaluation of product quality and structural integrity. Excitation frequency is one of the key performance factors for defect characterization. In the literature, there are many interesting papers dealing with wide spectral content and optimal frequency in terms of detection sensitivity. However, research activity on frequency optimization with respect to characterization performances is lacking. In this paper, an investigation into optimum excitation frequency has been conducted to enhance surface defect classification performance. The influences of excitation frequency for a group of defects were revealed in terms of detection sensitivity, contrast between defect features, and classification accuracy using kernel principal component analysis (KPCA) and a support vector machine (SVM). It is observed that probe signals are the most sensitive on the whole for a group of defects when excitation frequency is set near the frequency at which maximum probe signals are retrieved for the largest defect. After the use of KPCA, the margins between the defect features are optimum from the perspective of the SVM, which adopts optimal hyperplanes for structure risk minimization. As a result, the best classification accuracy is obtained. The main contribution is that the influences of excitation frequency on defect characterization are interpreted, and experiment-based procedures are proposed to determine the optimal excitation frequency for a group of defects rather than a single defect with respect to optimal characterization performances. PMID:27164112</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/1996SPIE.2947..211B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996SPIE.2947..211B"><span>Validation of a pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> system for measuring wall thinning through insulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brett, Colin R.; de Raad, Jan A.</p> <p>1996-11-01</p> <p>There have been several failures in power plant feedwater piping systems due to wall thinning caused by flow- accelerated corrosion of the inner surface. Detection of wastage in susceptible pipes is costly as traditional NDE methods such as ultrasonic testing entail removal and reinstallation of insulation over many meters of pipework. Radiography is one solution to this problem, but it is slow to apply and requires careful attention to safety. The RTD Incotest system uses pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> technology to measure pipewall thickness through insulation and external cladding. The technology has been licensed from Arco, Inc., who originally developed the technique for large diameter pipelines and storage tanks where the area interrogated was made deliberately large. This paper describes an optimized Incotest systems which can detect and measure internal or external wall wastage which is more localized and typical of flow-accelerated corrosion. Improvements have also been made to the inspection and data acquisition in order to increase the inspection rate and overall productivity. Ultimately the performance of the optimized Incotest system has been verified on samples which contain artificial and real corrosion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096..355L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096..355L"><span>Effects of Dynamic and Static Loading on <span class="hlt">Eddy</span> <span class="hlt">Current</span> Nde of Fatigue Cracks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lo, C. C. H.; Nakagawa, N.</p> <p>2009-03-01</p> <p>This paper reports on a study of the effects of dynamic and static loading on <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) crack signals in aerospace materials. In situ EC measurements were performed on a series of fatigue crack samples grown in Al 6061 bars under dynamic loading. The EC signals detected at a fixed location on the fatigue cracks were found to vary periodically with cyclic loading. Under dynamic tension, the amplitude of the vertical component of the crack signal, which is perpendicular to the lift off direction, increases with the load amplitude and the effect is stronger for longer cracks. Such changes in EC signals are attributable to crack morphology changes (i.e. crack opening) under tension. In contrast, the amplitude of crack signal remains relatively unchanged under compression, possibly due to the insulation effect of the oxidation layer on the crack face. The loading effects on crack signals in the Al samples were confirmed by obtaining c-scan images of the fatigue cracks under static loads. C-scans conducted on a series of Ti 64 fatigue crack samples under static loads revealed significantly stronger stress-induced changes of crack signal for Ti 64 than for the Al samples. The results are interpreted in terms of load-induced crack morphology changes, taking into account of likely differences between the Al and Ti alloy samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DSRII.122....6Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DSRII.122....6Z"><span>Effect of surface mesoscale <span class="hlt">eddies</span> on deep-sea <span class="hlt">currents</span> and mixing in the northeastern South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Li, Jianru; Liang, Xinfeng</p> <p>2015-12-01</p> <p>Recent studies suggest that deep-reaching surface-generated <span class="hlt">eddies</span> result in anomalous <span class="hlt">current</span> velocities in the deep sea, and ultimately lead to energy transfer from mesoscale to small-scale motions. Here we examine the influence of mesoscale <span class="hlt">eddies</span> on deep-sea subinertial and near-inertial <span class="hlt">currents</span>, and on possible enhanced oceanic mixing in the deep South China Sea (SCS). We analyzed <span class="hlt">current</span> velocity data for nearly a full water column. Data were obtained using acoustic Doppler <span class="hlt">current</span> profilers and recording <span class="hlt">current</span> meters on a deep-sea mooring system at a depth of 2100 m in the northeastern SCS from October 2012 to May 2013. A highly nonlinear southwestward-propagating anticyclonic <span class="hlt">eddy</span> was detected via a resolved sea-surface-level anomaly. This <span class="hlt">eddy</span> induced pronounced subinertial <span class="hlt">currents</span> with a characteristic time scale of 1-2 months and a maximum velocity of up to 0.2 m s-1 at the subsurface and 0.1 m s-1 at great depth. Near-inertial energy co-occurring with subinertial flows showed a distinctive vertical propagation trend during strong subinertial oscillations in the deep sea. During periods of strong subinertial and near-inertial kinetic energy, estimates of diapycnal diffusivity in the deep ocean showed approximately 10-fold enhancement, with a mean value of 1.2×10-3 m2 s-1 compared to the background value of 1.4×10-4 m2 s-1. The results provide observational evidence of the effect of surface-observed mesoscale motions on benthic <span class="hlt">currents</span> and ocean mixing in the deep SCS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960000294','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960000294"><span>Non-destructive Testing (NDT) of metal cracks using a high Tc rf-SQUID and <span class="hlt">eddy</span> <span class="hlt">current</span> method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lu, D. F.; Fan, Chang-Xin; Ruan, J. Z.; Han, S. G.; Wong, K. W.; Sun, G. F.</p> <p>1995-01-01</p> <p>A SQUID is the most sensitive device to detect change in magnetic field. A nondestructive testing (NDT) device using high temperature SQUID's and <span class="hlt">eddy</span> <span class="hlt">current</span> method will be much more sensitive than those <span class="hlt">currently</span> used <span class="hlt">eddy</span> <span class="hlt">current</span> systems, yet much cheaper than one with low temperature SQUID's. In this paper, we present our study of such a NDT device using a high temperature superconducting rf-SQUID as a gradiometer sensor. The result clearly demonstrates the expected sensitivity of the system, and indicates the feasibility of building a portable HTS SQUID NDT device with the help from cryocooler industry. Such a NDT device will have a significant impact on metal corrosion or crack detection technology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/135390','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/135390"><span>Non-destructive Testing (NDT) of metal cracks using a high Tc rf-SQUID and <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>Lu, D.F.; Fan, C.; Ruan, J.Z.; Han, S.G.; Wong, K.W.; Sun, G.F.</p> <p>1995-04-01</p> <p>A SQUID is the most sensitive device to detect change in magnetic field. A nondestructive testing (NDT) device using high temperature SQUID`s and <span class="hlt">eddy</span> <span class="hlt">current</span> method will be much more sensitive than those <span class="hlt">currently</span> used <span class="hlt">eddy</span> <span class="hlt">current</span> systems, yet much cheaper than one with low temperature SQUID`s. In this paper, the authors present their study of such a NDT device using a high temperature superconducting rf-SQUID as a gradiometer sensor. The result clearly demonstrates the expected sensitivity of the system, and indicates the feasibility of building a portable HTS SQUID NDT device with the help from cryocooler industry. Such a NDT device will have a significant impact on metal corrosion or crack detection technology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/121649','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/121649"><span>Non-destructive testing (NDT) of metal cracks using a high Tc rf-SQUID and <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>Lu, D.F.; Fan, C.; Ruan, J.Z.</p> <p>1994-12-31</p> <p>A SQUID is the most sensitive device to detect change in magnetic field. A non-destructive testing (NDT) device using high temperature SQUIDs and <span class="hlt">eddy</span> <span class="hlt">current</span> method will be much more sensitive than those <span class="hlt">currently</span> used <span class="hlt">eddy</span> <span class="hlt">current</span> systems, yet much cheaper than one with low temperature SQUIDs. In this paper, we present our study of such a NDT device using a high temperature superconducting rf-SQUID as a gradiometer sensor. The result clearly demonstrates the expected sensitivity of the system, and indicates the feasibility of building a portable HTS SQUID NDT device with the help from cryocooler industry. Such a NDT device will have a significant impact on metal corrosion or crack detection technology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19541518','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19541518"><span>Experimental and numerical examination of <span class="hlt">eddy</span> (Foucault) <span class="hlt">currents</span> in rotating micro-coils: Generation of heat and its impact on sample temperature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Aguiar, Pedro M; Jacquinot, Jacques-François; Sakellariou, Dimitris</p> <p>2009-09-01</p> <p>The application of nuclear magnetic resonance (NMR) to systems of limited quantity has stimulated the use of micro-coils (diameter <1mm). One method recently proposed for the union of micro-coils with Magic Angle sample Spinning (MAS), involves the integration of a tuned micro-coil circuit within standard MAS rotors inductively <span class="hlt">coupled</span> to the MAS probe coil, termed "magic-angle coil spinning" (MACS). The spinning of conductive materials results in the creation of circulating Foucault (<span class="hlt">eddy</span>) <span class="hlt">currents</span>, which generate heat. We report the first data acquired with a 4mm MACS system and spinning up to 10kHz. The need to spin faster necessitates improved methods to control heating. We propose an approximate solution to calculate the power losses (heat) from the <span class="hlt">eddy</span> <span class="hlt">currents</span> for a solenoidal coil, in order to provide insight into the functional dependencies of Foucault <span class="hlt">currents</span>. Experimental tests of the dependencies reveal conditions which result in reduced sample heating and negligible temperature distributions over the sample volume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AIPC..509.1923S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..509.1923S"><span>Thermal <span class="hlt">eddy</span> <span class="hlt">current</span> testing of metallization quality of printed circuit boards (PCB)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Savushkin, D. G.; Polyahov, M. Y.; Chernov, L. A.</p> <p>2000-05-01</p> <p>Today the fissile thermal control methods are used often enough to evaluate the metallization quality of printed circuit boards. However, it is necessary to note that the existing difficulties while exciting a non-steady thermal wave. There was offered the thermal input, which allows us to supply heat through the upper edge of a metallizing tube and to register parameters of thermal disturbance from the opposite side. The thermal input represents a hollow metal cone where the thermal disturbance is suggested to be effectuated by <span class="hlt">eddy</span> <span class="hlt">currents</span> induced by a coil situated above the thermal input. The agitating <span class="hlt">current</span> is a kind of radio pulse with a high frequency filling. The field frequency, thickness and the electromagnetic characteristics of the thermal input were selected so that the field couldn't propagate into space beneath the thermal input. It is possible to evaluate some parameters of the metallizing tube registering from the other side of the printed circuit board the thermal disturbance parameters (e.g. the arrival time of maximum and amplitude). The numerical calculations were made with a specially developed software with the purpose of obtaining the dependence of the arrival time of maximum and the thermal disturbance amplitude upon a printed circuit board metallization layer, the hole diameter, the board thickness, the metallization tube conductivity, the contact pad diameter. The heat exchange with the board material was not taken into account when making calculations because the thermal disturbance propagation time along the metallization tube is too short and this assumption does not make a considerable error.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650..434P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650..434P"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> sensor for in-situ monitoring of swelling of Li-ion prismatic cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plotnikov, Yuri; Karp, Jason; Knobloch, Aaron; Kapusta, Chris; Lin, David</p> <p>2015-03-01</p> <p>In-situ monitoring an on-board rechargeable battery in hybrid cars can be used to ensure a long operating life of the battery and safe operation of the vehicle. Intercalations of ions in the electrode material during charge and discharge of a Lithium Ion battery cause periodic stress and strain of the electrode materials that can ultimately lead to fatigue resulting in capacity loss and potential battery failure. <span class="hlt">Currently</span> this process is not monitored directly on the cells. This work is focused on development technologies that would quantify battery swelling and provide in-situ monitoring for onboard vehicle applications. Several rounds of tests have been performed to spatially characterize cell expansion of a 5 Ah cell with a nickel/manganese/cobalt-oxide cathode (Sanyo, Japan) used by Ford in their Fusion HEV battery pack. A collaborative team of researchers from GE and the University of Michigan has characterized the free expansion of these cells to be in the range of 100×125 microns (1% of total cell thickness) at the center point of the cell. GE proposed to use a thin <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) coil to monitor these expansions on the cells while inside the package. The photolithography manufacturing process previously developed for EC arrays for detecting cracks in aircraft engine components was used to build test coils for gap monitoring. These sensors are thin enough to be placed safely between neighboring cells and capable of monitoring small variations in the gap between the cells. Preliminary investigations showed that these coils can be less than 100 micron thick and have sufficient sensitivity in a range from 0 to 2 mm. Laboratory tests revealed good correlation between EC and optical gap measurements in the desired range. Further technology development could lead to establishing a sensor network for a low cost solution for the in-situ monitoring of cell swelling during battery operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22391248','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22391248"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> sensor for in-situ monitoring of swelling of Li-ion prismatic cells</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Plotnikov, Yuri Karp, Jason Knobloch, Aaron Kapusta, Chris Lin, David</p> <p>2015-03-31</p> <p>In-situ monitoring an on-board rechargeable battery in hybrid cars can be used to ensure a long operating life of the battery and safe operation of the vehicle. Intercalations of ions in the electrode material during charge and discharge of a Lithium Ion battery cause periodic stress and strain of the electrode materials that can ultimately lead to fatigue resulting in capacity loss and potential battery failure. <span class="hlt">Currently</span> this process is not monitored directly on the cells. This work is focused on development technologies that would quantify battery swelling and provide in-situ monitoring for onboard vehicle applications. Several rounds of tests have been performed to spatially characterize cell expansion of a 5 Ah cell with a nickel/manganese/cobalt-oxide cathode (Sanyo, Japan) used by Ford in their Fusion HEV battery pack. A collaborative team of researchers from GE and the University of Michigan has characterized the free expansion of these cells to be in the range of 100×125 microns (1% of total cell thickness) at the center point of the cell. GE proposed to use a thin <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) coil to monitor these expansions on the cells while inside the package. The photolithography manufacturing process previously developed for EC arrays for detecting cracks in aircraft engine components was used to build test coils for gap monitoring. These sensors are thin enough to be placed safely between neighboring cells and capable of monitoring small variations in the gap between the cells. Preliminary investigations showed that these coils can be less than 100 micron thick and have sufficient sensitivity in a range from 0 to 2 mm. Laboratory tests revealed good correlation between EC and optical gap measurements in the desired range. Further technology development could lead to establishing a sensor network for a low cost solution for the in-situ monitoring of cell swelling during battery operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045524&hterms=Current+cost&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20000101%2B20170414%26N%3D0%26No%3D30%26Ntt%3DCurrent%2Bcost','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045524&hterms=Current+cost&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20000101%2B20170414%26N%3D0%26No%3D30%26Ntt%3DCurrent%2Bcost"><span>Development of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Techniques for Detection of Deep Fatigue Cracks in Multi-Layer Airframe Components</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>2008-01-01</p> <p>Thick, multi-layer aluminum structure has been widely used in aircraft design in critical wing splice areas. The multi-layer structure generally consists of three or four aluminum layers with different geometry and varying thickness, which are held together with fasteners. The detection of cracks under fasteners with ultrasonic techniques in subsurface layers away from the skin is impeded primarily by interlayer bonds and faying sealant condition. Further, assessment of such sealant condition is extremely challenging in terms of complexity of structure, limited access, and inspection cost. Although <span class="hlt">Eddy</span> <span class="hlt">current</span> techniques can be applied on in-service aircraft from the exterior of the skin without knowing sealant condition, the <span class="hlt">current</span> <span class="hlt">eddy</span> <span class="hlt">current</span> techniques are not able to detect defects with wanted sensitivity. In this work a series of low frequency <span class="hlt">eddy</span> <span class="hlt">current</span> probes have been designed, fabricated and tested for this application. A probe design incorporating a shielded magnetic field sensor concentrically located in the interior of a drive coil has been employed to enable a localized deep diffusion of the electromagnetic field into the part under test. Due to the required low frequency inspections, probes have been testing using a variety of magnetic field sensors (pickup coil, giant magneto-resistive, anisotropic magneto-resistive, and spin-dependent tunneling). The probe designs as well as capabilities based upon a target inspection for sub-layer cracking in an airframe wing spar joint is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1650..414P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1650..414P"><span>High-frequency <span class="hlt">eddy</span> <span class="hlt">current</span> based impedance spectroscopy for characterization of the percolation process of wet conductive coatings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patsora, Iryna; Hillmann, Susanne; Heuer, Henning; Foos, Bryan C.; Calzada, Juan G.</p> <p>2015-03-01</p> <p>Coatings based on wet particles containing pastes are <span class="hlt">currently</span> used in many industries, such as automotive, aircraft and/or wind-power plants, to protect carbon-fiber reinforced plastic against damages caused by electrical effects, such as a lightning strike. In order to understand and control the percolation behavior during the drying, a non-contact <span class="hlt">Eddy</span> <span class="hlt">Current</span> based Impedance Spectroscopy can be used. This technique can be applied in the wet state of the coating and it works non-destructively. Percolation behaviors of the wet conductive coatings are strongly affected by the type of particles used as a filling and the thickness of the coating. Experimental results of <span class="hlt">Eddy</span> <span class="hlt">Current</span> measurements on wet conductive coatings based on different conductive particles and deposited with different thicknesses are discussed. Based on High-Frequency <span class="hlt">Eddy</span> <span class="hlt">Current</span> measurements, a prognosis of the coating parameters after final curing during the wet state becomes conceivable. This, for example, offers a wide opportunity for process control and repairs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4515214','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4515214"><span>Dual Optimization Method of RF and Quasi-Static Field Simulations for Reduction of <span class="hlt">Eddy</span> <span class="hlt">Currents</span> Generated on 7T RF Coil Shielding</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhao, Yujuan; Zhao, Tiejun; Raval, Shailesh B.; Krishnamurthy, Narayanan; Zheng, Hai; Harris, Chad T.; Handler, William B.; Chronik, Blaine A.; Ibrahim, Tamer S.</p> <p>2015-01-01</p> <p>Purpose To optimize the design of radiofrequency (RF) shielding of transmit coils at 7T and reduce <span class="hlt">eddy</span> <span class="hlt">currents</span> generated on the RF shielding when imaging with rapid gradient waveforms. Methods One set of a four-element, 2×2 Tic-Tac-Toe (TTT) head coil structure is selected and constructed to study <span class="hlt">eddy</span> <span class="hlt">currents</span> on the RF coil shielding. The generated <span class="hlt">eddy</span> <span class="hlt">currents</span> are quantitatively studied in the time and frequency domains. The RF characteristics are studied using the finite-difference time-domain (FDTD) method. Five different kinds of RF shielding were tested on a 7T MRI scanner with phantoms and in-vivo human subjects. Results The <span class="hlt">eddy</span> <span class="hlt">current</span> simulation method is verified by the measurement results. <span class="hlt">Eddy</span> <span class="hlt">currents</span> induced by solid/intact and simple-structured slotted RF shielding can significantly distort the gradient fields. EPI images, B1+ maps and S matrix measurements verified that the proposed slot pattern can suppress the <span class="hlt">eddy</span> <span class="hlt">currents</span> while maintaining the RF characteristics of the transmit coil. Conclusion The presented dual-optimization method could be used to design the RF shielding and reduce the gradient field-induced <span class="hlt">eddy</span> <span class="hlt">currents</span> while maintaining the RF characteristics of the transmit coil. PMID:25367703</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26026520','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26026520"><span>Fast valve based on double-layer <span class="hlt">eddy-current</span> repulsion for disruption mitigation in Experimental Advanced Superconducting Tokamak.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhuang, H D; Zhang, X D</p> <p>2015-05-01</p> <p>A fast valve based on the double-layer <span class="hlt">eddy-current</span> repulsion mechanism has been developed on Experimental Advanced Superconducting Tokamak (EAST). In addition to a double-layer <span class="hlt">eddy-current</span> coil, a preload system was added to improve the security of the valve, whereby the valve opens more quickly and the open-valve time becomes shorter, making it much safer than before. In this contribution, testing platforms, open-valve characteristics, and throughput of the fast valve are discussed. Tests revealed that by choosing appropriate parameters the valve opened within 0.15 ms, and open-valve times were no longer than 2 ms. By adjusting working parameter values, the maximum number of particles injected during this open-valve time was estimated at 7 × 10(22). The fast valve will become a useful tool to further explore disruption mitigation experiments on EAST in 2015.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20798226','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20798226"><span>Finite Element Analysis for Imaging Steel Bars Placed Under a Mild Steel Boundary Using <span class="hlt">Eddy</span> <span class="hlt">Current</span> Techniques</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hussin, H.; Zaid, M.; Gaydecki, P.; El-Madaani, F.; Fernandes, B.</p> <p>2006-03-06</p> <p>This paper reports on recent modelling results obtained using finite-element analysis for penetrating a magnetic field through a 2 mm steel boundary. The object is to detect 16 mm steel bars placed under mild steel boundaries at different operating frequencies. To penetrate thicker steel boundaries and increase the depth penetration, a different configuration based on remote field <span class="hlt">eddy</span> <span class="hlt">currents</span> (RFEC) has been modelled.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25459883','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25459883"><span>Mapping B(1)-induced <span class="hlt">eddy</span> <span class="hlt">current</span> effects near metallic structures in MR images: a comparison of simulation and experiment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vashaee, S; Goora, F; Britton, M M; Newling, B; Balcom, B J</p> <p>2015-01-01</p> <p>Magnetic resonance imaging (MRI) in the presence of metallic structures is very common in medical and non-medical fields. Metallic structures cause MRI image distortions by three mechanisms: (1) static field distortion through magnetic susceptibility mismatch, (2) <span class="hlt">eddy</span> <span class="hlt">currents</span> induced by switched magnetic field gradients and (3) radio frequency (RF) induced <span class="hlt">eddy</span> <span class="hlt">currents</span>. Single point ramped imaging with T1 enhancement (SPRITE) MRI measurements are largely immune to susceptibility and gradient induced <span class="hlt">eddy</span> <span class="hlt">current</span> artifacts. As a result, one can isolate the effects of metal objects on the RF field. The RF field affects both the excitation and detection of the magnetic resonance (MR) signal. This is challenging with conventional MRI methods, which cannot readily separate the three effects. RF induced MRI artifacts were investigated experimentally at 2.4 T by analyzing image distortions surrounding two geometrically identical metallic strips of aluminum and lead. The strips were immersed in agar gel doped with contrast agent and imaged employing the conical SPRITE sequence. B1 mapping with pure phase encode SPRITE was employed to measure the B1 field around the strips of metal. The strip geometry was chosen to mimic metal electrodes employed in electrochemistry studies. Simulations are employed to investigate the RF field induced <span class="hlt">eddy</span> <span class="hlt">currents</span> in the two metallic strips. The RF simulation results are in good agreement with experimental results. Experimental and simulation results show that the metal has a pronounced effect on the B1 distribution and B1 amplitude in the surrounding space. The electrical conductivity of the metal has a minimal effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080031115','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080031115"><span>Models in the Design and Validation of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Inspection for Cracking in the Shuttle Reaction Control System Thruster</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Aldrin, John C.; Williams, Phillip A.; Wincheski, Russell (Buzz) A.</p> <p>2008-01-01</p> <p>A case study is presented for using models in <span class="hlt">eddy</span> <span class="hlt">current</span> NDE design for crack detection in Shuttle Reaction Control System thruster components. Numerical methods were used to address the complex geometry of the part and perform parametric studies of potential transducer designs. Simulations were found to show agreement with experimental results. Accurate representation of the coherent noise associated with the measurement and part geometry was found to be critical to properly evaluate the best probe designs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA206629','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA206629"><span>Computer Algorithms and Architectures for Three-Dimensional <span class="hlt">Eddy-Current</span> Nondestructive Evaluation. Volume 3. Chapters 6-11</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1989-01-20</p> <p>mflC FILE. OOR SA/TR-2/89 A003: FINAL REPORT COMPUTER ALGORITHMS AND ARCHITECTURES FOR THREE-DIMENSIONAL <span class="hlt">EDDY-CURRENT</span> NONDESTRUCTIVE EVALUATION CD...J., Ullman, J., The Design and Analysis of Computer Algorithms , Addison-Wesley Publishing Company, 1974. [A2] Anderson, B., Moore, J., Optimal...actual data. DC- 17 I I I I [All Aho, A., Hopcroft, J., Ullman, J., The Design and Analysis of Computer Algorithms , Addison-Wesley Publishing Company</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1637.1406H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1637.1406H"><span>Non destructive technique for cracks detection by an <span class="hlt">eddy</span> <span class="hlt">current</span> in differential mode for steel frames</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harzalla, S.; Belgacem, F. Bin Muhammad; Chabaat, M.</p> <p>2014-12-01</p> <p>In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. <span class="hlt">Eddy</span> <span class="hlt">current</span> testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental signals, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22390775','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22390775"><span>Non destructive technique for cracks detection by an <span class="hlt">eddy</span> <span class="hlt">current</span> in differential mode for steel frames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harzalla, S. Chabaat, M.; Belgacem, F. Bin Muhammad</p> <p>2014-12-10</p> <p>In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material. <span class="hlt">Eddy</span> <span class="hlt">current</span> testing (ECT) is a standard technique in industry for the detection of surface breaking flaws in magnetic materials such as steels. In this context, simulation tools can be used to improve the understanding of experimental signals, optimize the design of sensors or evaluate the performance of ECT procedures. CEA-LIST has developed for many years semi-analytical models embedded into the simulation platform CIVA dedicated to non-destructive testing. The developments presented herein address the case of flaws located inside a planar and magnetic medium. Simulation results are obtained through the application of the Volume Integral Method (VIM). When considering the ECT of a single flaw, a system of two differential equations is derived from Maxwell equations. The numerical resolution of the system is carried out using the classical Galerkin variant of the Method of Moments. Besides, a probe response is calculated by application of the Lorentz reciprocity theorem. Finally, the approach itself as well as comparisons between simulation results and measured data are presented.</p> </li> </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.osti.gov/scitech/servlets/purl/915813','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/915813"><span>Reduced Mandated Inspection by Remote Field <span class="hlt">Eddy</span> <span class="hlt">Current</span> Inspection of Unpiggable Pipelines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Albert Teitsma; Julie Maupin</p> <p>2006-09-29</p> <p>The Remote Field <span class="hlt">Eddy</span> <span class="hlt">Current</span> (RFEC) technique is ideal for inspecting unpiggable pipelines because all of its components can be made much smaller than the diameter of the pipe to be inspected. For this reason, RFEC was chosen as a technology for unpiggable pipeline inspections by DOE-NETL with the support of OTD and PRCI, to be integrated with platforms selected by DOENETL. As part of the project, the RFEC laboratory facilities were upgraded and data collection was made nearly autonomous. The resulting improved data collection speeds allowed GTI to test more variables to improve the performance of the combined RFEC and platform technologies. Tests were conducted on 6-, 8-, and 12-inch seamless and seam-welded pipes. Testing on the 6-inch pipes included using seven exciter coils, each of different geometry with an initial focus on preparing the technology for use on an autonomous robotic platform with limited battery capacity. Reductions in power consumption proved successful. Tests with metal components similar to the Explorer II modules were performed to check for interference with the electromagnetic fields. The results of these tests indicated RFEC would be able to produce quality inspections while on the robot. Mechanical constraints imposed by the platform, power requirements, control and communication protocols, and potential busses and connectors were addressed. Much work went into sensor module design including the mechanics and electronic diagrams and schematics. GTI participated in two Technology Demonstrations for inspection technologies held at Battelle Laboratories. GTI showed excellent detection and sizing abilities for natural corrosion. Following the demonstration, module building commenced but was stopped when funding reductions did not permit continued development for the selected robotic platform. Conference calls were held between GTI and its sponsors to resolve the issue of how to proceed with reduced funding. The project was rescoped for 10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23490354','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23490354"><span>Sensor-based control in <span class="hlt">eddy</span> <span class="hlt">current</span> separation of incinerator bottom ash.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rahman, Md Abdur; Bakker, M C M</p> <p>2013-06-01</p> <p>A sensor unit was placed online in the particle stream produced by an <span class="hlt">eddy</span> <span class="hlt">current</span> separator (ECS) to investigate its functionality in non-ferrous metals recovery. The targeted feed was the 1-6mm size fraction bottom ash from a municipal waste incinerator. The sensor unit was attached to the ECS splitter, where it counted in real-time metal and mineral particles and accurately measured the grade of the stream in the metals product. Influence of segregation (e.g. due to particle size or density) on the metals concentrate were detected and studied using the sensor data collected at different splitter distances. Tests were performed in the laboratory and in a bottom ash processing plant with two different types of ECS and two sources of bottom ash with different moisture content. The measured metal grades matched the manual analyses with errors 0%, 1.5% and 3.1% for moist, dry and very wet feed, respectively. For very wet feed the ECS metals recovery dropped, which was observed from the strongly reduced particle counts and the large changes in cumulative particle properties. The measured sample proved representative for the whole metals concentrate if it is collected at a representative position within the metals particle trajectory fan produced by the ECS. ECS-performance proved sensitively dependent on splitter distance, since a 10mm shift may result in 10% change in metal recovery and 18% change in grade. The main functionalities of the sensor unit are determined as online quality control and facilitation of automatic control over the ECS splitter distance. These functionalities translate in significant improvements in ECS metals recovery which in turn is linked to economic benefits, increased recycling rate of scrap metals and a further reduction of the ecological drawbacks of incinerator bottom ash.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AIPC.1096.1356N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AIPC.1096.1356N"><span>Shot-Peening Intensities VS. <span class="hlt">Eddy</span> <span class="hlt">Current</span> Signals as Seen in Iterative Treatment-Measurement Experiment</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.; Frishman, A. M.; Shen, Y.; Lo, C. C. H.</p> <p>2009-03-01</p> <p>We report on progress in a swept high frequency <span class="hlt">eddy</span> <span class="hlt">current</span> (SHFEC) technique for characterization of surface residual stress on shot-peened superalloy surfaces. Our aim here is to demonstrate the sensitivity of our measurement for practical shot peening intensities, i.e. at 4˜6 A. First, we present our improved probe and instrumentation being sufficiently sensitive to resolve the surface conditions at these low Almen intensities, where our earlier measurements encountered noise problems. The previous coil was also larger (18 mm in diameter) than desirable. Our new probe integrates smaller coils (12 mm in diameter, forming an AC bridge) and on-board electronics on a common printed circuit board, mutually connected at the shortest possible distance. The operational-amplifier-based electronics acts as impedance buffers, and maintains the cabling impedance at the characteristic 50 Ω between the probe board and the instruments. We have thus reduced the instrumentation noises. Second, we present the result of an iterative treatment-measurement experiment, performed on a 2"-by-3" Inconel 718 block specimen, initially polished to a mirror finish. After an initial baseline SHFEC measurement, we performed shot peening, an Almen strip deflection measurement, and a SHFEC measurement as one iteration cycle, and repeated the cycles multiple times at predetermined intervals. We will show the resulting SHFEC signals (i.e. lift-off normalized vertical-component signals) plotted against the Almen intensities. We then draw several conclusions from the experimental data, including a) the SHFEC signals increase monotonically in correlation with the Almen intensity increase, and b) the SHFEC signals exhibit sufficient deviations to resolve 4˜6 A intensities, while c) the SHFEC signals indicate saturation of the Inconel 718 response against peening, but the saturation occurs later in the iteration than indicated by the A-series Almen strip.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24831111','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24831111"><span>A combined experimental and finite element analysis method for the estimation of <span class="hlt">eddy-current</span> loss in NdFeB magnets.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaïm; Mipo, Jean-Claude</p> <p>2014-05-14</p> <p>NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to <span class="hlt">eddy</span> <span class="hlt">current</span> losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the <span class="hlt">eddy</span> <span class="hlt">current</span> loss of PMs, but it remains quite difficult to validate the accuracy of the results with complex devices. In this paper, an experimental test device is used in order to extract the <span class="hlt">eddy</span> <span class="hlt">current</span> losses that are then compared with those of a 3D FE model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060052518','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060052518"><span>Development of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Technique for the Detection of Stress Corrosion Cracking in Space Shuttle Primary Reaction Control Thrusters</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; Koshti, Ajay</p> <p>2006-01-01</p> <p>A recent identification of stress corrosion cracking in the Space Shuttle Primary Reaction Control System (PRCS) thrusters triggered an extensive nondestructive evaluation effort to develop techniques capable of identifying such damage on installed shuttle hardware. As a part of this effort, specially designed <span class="hlt">eddy</span> <span class="hlt">current</span> probes inserted into the acoustic cavity were explored for the detection of such flaws and for evaluation of the remaining material between the crack tip and acoustic cavity. The technique utilizes two orthogonal <span class="hlt">eddy</span> <span class="hlt">current</span> probes which are scanned under stepper motor control in the acoustic cavity to identify cracks hidden with as much as 0.060 remaining wall thickness to the cavity. As crack growth rates in this area have been determined to be very slow, such an inspection provides a large safety margin for continued operation of the critical shuttle hardware. Testing has been performed on thruster components with both actual and fabricated defects. This paper will review the design and performance of the developed <span class="hlt">eddy</span> <span class="hlt">current</span> inspection system. Detection of flaws as a function of remaining wall thickness will be presented along with the proposed system configuration for depot level or on-vehicle inspection capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070022419','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070022419"><span>Development of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Techniques for the Detection of Cracking in Space Shuttle Primary Reaction Control Thrusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Buzz A.; Simpson, John W.; Koshti, Ajay</p> <p>2007-01-01</p> <p>A recent identification of cracking in the Space Shuttle Primary Reaction Control System (PRCS) thrusters triggered an extensive nondestructive evaluation effort to develop techniques capable of identifying such damage on installed shuttle hardware. As a part of this effort, specially designed <span class="hlt">eddy</span> <span class="hlt">current</span> probes inserted into the acoustic cavity were explored for the detection of such flaws and for evaluation of the remaining material between the crack tip and acoustic cavity. The technique utilizes two orthogonal <span class="hlt">eddy</span> <span class="hlt">current</span> probes which are scanned under stepper motor control in the acoustic cavity to identify cracks hidden with as much as 0.060 remaining wall thickness to the cavity. As crack growth rates in this area have been determined to be very slow, such an inspection provides a large safety margin for continued operation of the critical shuttle hardware. Testing has been performed on thruster components with both actual and fabricated defects. This paper will review the design and performance of the developed <span class="hlt">eddy</span> <span class="hlt">current</span> inspection system. Detection of flaws as a function of remaining wall thickness will be presented along with the proposed system configuration for depot level or on-vehicle inspection capabilities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070031760','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070031760"><span>Analysis of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Capabilities for the Detection of Outer Diameter Stress Corrosion Cracking in Small Bore Metallic Structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wincheski, Buzz; Williams, Phillip; Simpson, John</p> <p>2007-01-01</p> <p>The use of <span class="hlt">eddy</span> <span class="hlt">current</span> techniques for the detection of outer diameter damage in tubing and many complex aerospace structures often requires the use of an inner diameter probe due to a lack of access to the outside of the part. In small bore structures the probe size and orientation are constrained by the inner diameter of the part, complicating the optimization of the inspection technique. Detection of flaws through a significant remaining wall thickness becomes limited not only by the standard depth of penetration, but also geometrical aspects of the probe. Recently, an orthogonal <span class="hlt">eddy</span> <span class="hlt">current</span> probe was developed for detection of such flaws in Space Shuttle Primary Reaction Control System (PRCS) Thrusters. In this case, the detection of deeply buried stress corrosion cracking by an inner diameter <span class="hlt">eddy</span> <span class="hlt">current</span> probe was sought. Probe optimization was performed based upon the limiting spatial dimensions, flaw orientation, and required detection sensitivity. Analysis of the probe/flaw interaction was performed through the use of finite and boundary element modeling techniques. Experimental data for the flaw detection capabilities, including a probability of detection study, will be presented along with the simulation data. The results of this work have led to the successful deployment of an inspection system for the detection of stress corrosion cracking in Space Shuttle Primary Reaction Control System (PRCS) Thrusters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21371012','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21371012"><span>LIMITATIONS OF <span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> RESIDUAL STRESS PROFILING IN SURFACE-TREATED ENGINE ALLOYS OF VARIOUS HARDNESS LEVELS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Abu-Nabah, B. A.; Hassan, W. T.; Blodgett, M. P.; Nagy, P. B.</p> <p>2010-02-22</p> <p>Recent research results indicated that <span class="hlt">eddy</span> <span class="hlt">current</span> conductivity measurements might be exploited for nondestructive evaluation of subsurface residual stresses in surface-treated nickel-base superalloy components. This paper presents new results that indicate that in some popular nickel-base superalloys the relationship between the electric conductivity profile and the sought residual stress profile is more tenuous than previously thought. It is shown that in IN718 the relationship is very sensitive to the state of precipitation hardening and, if left uncorrected, could render the <span class="hlt">eddy</span> <span class="hlt">current</span> technique unsuitable for residual stress profiling in components of 36 HRC or harder, i.e., in most critical engine applications. The presented experimental results show that the observed dramatic change in the <span class="hlt">eddy</span> <span class="hlt">current</span> response of hardened IN718 to surface treatment is caused by very fine nanometer-scale features of the microstructure, such as gamma' and gamma'' precipitates, rather than micrometer-scale features, such as changing grain size or carbide precipitates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JMagR.159..151S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JMagR.159..151S"><span>Automated correction of unwanted phase jumps in reference signals which corrupt MRSI spectra after <span class="hlt">eddy</span> <span class="hlt">current</span> correction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simonetti, A. W.; Melssen, W. J.; van der Graaf, M.; Heerschap, A.; Buydens, L. M. C.</p> <p>2002-12-01</p> <p>A commonly applied step in the postprocessing of gradient localized proton MR spectroscopy, is correction for <span class="hlt">eddy</span> <span class="hlt">current</span> effects using the water signal as a reference. However, this method can degrade some of the metabolite signals, in particular if applied on proton MR spectroscopic imaging data. This artifact arises from the water reference signal in the presence of a second signal which resonates close to the main water resonance. The interference of both resonances will introduce jumps in the phase of the reference time domain signal. Using this phase for <span class="hlt">eddy</span> <span class="hlt">current</span> correction will result in a ringing artifact in the frequency domain of the metabolite signal over the whole frequency range. We propose a moving window correction algorithm, which screens the phase of reference signals and removes phase jumps in time domain caused by interference of signals from multiple spin systems. The phase jumps may be abrupt or gradually distributed over several time data points. Because the correction algorithm only corrects time data points which contain phase jumps, the phase is minimally disrupted. Furthermore, the algorithm is automated for large datasets, correcting only those water reference signals which are corrupted. After correction of the corrupted reference signals, normal <span class="hlt">eddy</span> <span class="hlt">current</span> correction may be performed. The algorithm is compared with a method which uses a low-pass filter and tested on simulated data as well as on in vivo proton spectroscopic imaging data from a healthy volunteer and from patients with a brain tumor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/7003172','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/7003172"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Petrini, R.R.; Van Lue, D.F.</p> <p>1983-10-25</p> <p>A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises <span class="hlt">eddy</span> <span class="hlt">current</span> sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced <span class="hlt">eddy</span> <span class="hlt">currents</span> in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The <span class="hlt">eddy</span> <span class="hlt">current</span> sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/864755','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/864755"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Petrini, Richard R.; Van Lue, Dorin F.</p> <p>1983-01-01</p> <p>A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises <span class="hlt">eddy</span> <span class="hlt">current</span> sensing equipment (12) with a probe coil (11), and associated coaxial coil cable (13), coil energizing means (21), and circuit means (21, 12) responsive to impedance changes in the coil as effected by induced <span class="hlt">eddy</span> <span class="hlt">currents</span> in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube 17 of fiberoptic scope 10. The scope 10 is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means (19, 20) for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The <span class="hlt">eddy</span> <span class="hlt">current</span> sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/449553','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/449553"><span>A quantitative analysis of the separation of aluminum cans out of a waste stream based on <span class="hlt">eddy</span> <span class="hlt">current</span> induced levitation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Woltereck, M.; Ludwig, R.; Michalson, W.</p> <p>1997-01-01</p> <p><span class="hlt">Eddy</span> <span class="hlt">current</span> induced levitation can be employed to separate conducting from nonconducting materials as in the recycling of aluminum products. To investigate magnetic fields, <span class="hlt">eddy</span> <span class="hlt">currents</span>, and forces, a multiple strategy involving analytical, numerical, and experimental analysis techniques is implemented. In particular, the configuration of an aluminum can over an arrangement of multiple coils is investigated with a two-dimensional parametric finite element model. The results from these simulations are compared to measurements of a practical levitation device. To establish the fidelity of the finite element model, the authors applied the method to two simplified geometries of a thick and a thin slab extended over a conducting wire. For the first case, an analytical inverse Laplace-transform model for the <span class="hlt">eddy</span> <span class="hlt">current</span> density is developed. For the second case, Lorentz forces exerted on the thin slab are analytically obtained by employing Maxwell`s moving image method. In addition, an approximation to the moving image method is derived which can be described by an equivalent resonance circuit.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15016646','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15016646"><span><span class="hlt">EDDY</span> <span class="hlt">CURRENT</span> EFFECT OF THE BNL-AGS VACUUM CHAMBER ON THE OPTICS OF THE BNL-AGS SYNCHROTRON.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>TSOUPAS,N.; AHRENS,L.; BROWN,K.A.; GLENN,J.W.; GARDNER,K.</p> <p>1999-03-29</p> <p>During the acceleration cycle of the AGS synchrotron, <span class="hlt">eddy</span> <span class="hlt">currents</span> are generated within the walls of the vacuum chambers of the AGS main magnets. The vacuum chambers have elliptical cross section, are made of inconel material with a wall thickness of 2 mm and are placed within the gap of the combined-function main magnets of the AGS synchrotron. The generation of the <span class="hlt">eddy</span> <span class="hlt">currents</span> in the walls of the vacuum chambers, creates various magnetic multipoles, which affect the optics of the AGS machine. In this report these magnetic multipoles are calculated for various time interval starting at the acceleration cycle, where the magnetic field of the main magnet is {approx}0.1 T, and ending before the beam extraction process, where the magnetic field of the main magnet is almost constant at {approx}1.1 T. The calculations show that the magnetic multipoles generated by the <span class="hlt">eddy-currents</span> affect the optics of the AGS synchrotron during the acceleration cycle and in particular at low magnetic fields of the main magnet. Their effect is too weak to affect the optics of the AGS machine during beam extraction at the nominal energies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720018592','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720018592"><span>Effect of <span class="hlt">eddy</span> diffusivity on wind-driven <span class="hlt">currents</span> in a two-layer stratified lake</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gedney, R. T.; Lick, W.; Molls, F. B.</p> <p>1972-01-01</p> <p>The steady state wind-driven circulation was numerically calculated in a rectangular stratified lake. The lake is composed of two layers having uniform but unequal densities and <span class="hlt">eddy</span> diffusivities. The position in thermocline and the three-dimensional velocities in both layers calculated using shallow lake equations. The results show that, as the <span class="hlt">eddy</span> diffusivity in the hypolimnion is increased, the thermocline tilt and hypolimnetic velocities increase. The effect of the other variables such as wind stress, density, basin length, and mean thermocline depth are also shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H33F1384L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H33F1384L"><span>Evaluation of a fully <span class="hlt">coupled</span> large-<span class="hlt">eddy</span> atmosphere and land surface simulation model over heterogeneous surfaces</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, S.; Shao, Y.; Hintz, M.</p> <p>2011-12-01</p> <p>In this study, we present a fully <span class="hlt">coupled</span> large-<span class="hlt">eddy</span> atmosphere and land-surface simulation model (LES-ALM) which integrates a radiation parameterization, a large-<span class="hlt">eddy</span> flow model for the atmospheric boundary layer with explicit consideration of the canopy drag effect, and a land surface model to investigate the atmosphere and land surface interactions over heterogeneous areas. A 12-hour model simulation is carried out and the model performance is validated with the field measurements collected during the FLUXPAT experiment of the German SFB/TR32 project "Patterns in Soil-Vegetation-Atmosphere System: Monitoring, Modeling and Data Assimilation". The simulated surface fluxes, near-surface atmospheric state variables, soil temperature, and the vertical profiles of atmospheric boundary layer quantities are compared with the data. There is a good agreement between the model simulations and the observation at both footprint- and domain-averaged scales. This suggests that the fully <span class="hlt">coupled</span> model can be used as a tool for studying the complex atmosphere and land-surface interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.B72C..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.B72C..03D"><span>Large <span class="hlt">Eddy</span> Simulation of <span class="hlt">Coupled</span> Water and Carbon Exchange and Transport Through and Above Forest Canopies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drewry, D. T.; Albertson, J. D.</p> <p>2002-12-01</p> <p>There are outstanding questions surrounding the measurement and modeling of carbon and water fluxes over complex landscapes. Typically, forest fluxes are measured with the <span class="hlt">eddy</span> covariance technique from a single tower. A unique study over a loblolly pine stand in the Duke Forest yielded high frequency velocity, temperature, water vapor and carbon dioxide fluxes from a network of six instrumented towers, simultaneously. In this talk we explore the canopy-atmosphere dynamics active during this experiment through the use of a Large <span class="hlt">Eddy</span> Simulation (LES) code. The LES includes a numerical representation of the plant canopy structure, a biophysical process sub-model, and mixes the sources and sinks through the boundary layer with a filtered form of the Navier-Stokes equations. Through this combination of a spatially distributed dataset and a 3D model of canopy flows and processes we investigate the relative influences of canopy structure and meteorological forcing on observed and modeled fluxes. This work has implications for our understanding of the effects of canopy turbulence on <span class="hlt">eddy</span> covariance flux measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E2388O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E2388O"><span><span class="hlt">Eddy</span> <span class="hlt">Currents</span> applied to de-tumbling of space debris: feasibility analysis, design and optimization aspects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ortiz Gómez, Natalia; Walker, Scott J. I.</p> <p></p> <p>Existent studies on the evolution of the space debris population show that both mitigation measures and active debris removal methods are necessary in order to prevent the <span class="hlt">current</span> population from growing. Active debris removal methods, which require contact with the target, show complications if the target is rotating at high speeds. Observed rotations go up to 50 deg/s combined with precession and nutation motions. “Natural” rotational damping in upper stages has been observed for some debris objects. This phenomenon occurs due to the <span class="hlt">eddy</span> <span class="hlt">currents</span> induced by the Earth’s magnetic field in the predominantly conductive materials of these man made rotating objects. The idea presented in this paper is to submit the satellite to an enhanced magnetic field in order to subdue it and damp its rotation, thus allowing for its subsequent de-orbiting phase. The braking method that is proposed has the advantage of avoiding any kind of mechanical contact with the target. A deployable structure with a magnetic coil at its end is used to induce the necessary braking torques on the target. This way, the induced magnetic field is created far away from the chaseŕs main body avoiding undesirable effects on its instruments. This paper focuses on the overall design of the system and the parameters considered are: the braking time, the power required, the mass of the deployable structure and the magnetic coil system, the size of the coil, the materials selection and distance to the target. The different equations that link all these variables together are presented. Nevertheless, these equations lead to several variables which make it possible to approach the engineering design as an optimization problem. Given that only a few variables remain, no sophisticated numerical methods are called for, and a simple graphical approach can be used to display the optimum solutions. Some parameters are open to future refinements as the optimization problem must be contemplated globally in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986DSRA...33.1907G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986DSRA...33.1907G"><span>A synoptic comparison of fishes and crustaceans from a warm-core <span class="hlt">eddy</span>, the East Australian <span class="hlt">Current</span>, the Coral Sea and the Tasman Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Griffiths, F. B.; Wadley, V. A.</p> <p>1986-11-01</p> <p>Mesopelagic fishes and crustaceans inside a newly formed, warm-core <span class="hlt">eddy</span> off eastern Australia were similar in composition and abundance of species to those from the more northerly Coral Sea and East Australian <span class="hlt">Current</span> (EAC) source waters of the <span class="hlt">eddy</span>. The crustaceans inside the <span class="hlt">eddy</span> were a mixture of warm-water and cold-water species and were dissimilar to the crustacean fauna on either the Tasman Sea or the Coral Sea-EAC sampling sites. In contrast, of the fishes collected (all from the family Myctophidae), only warm-water or widespread species were present in the <span class="hlt">eddy</span>. A zoogeographic transect along 155° between 16°S and 32°S showed cold-water crustaceans were present between 24°S and 32°S whereas cold-water fishes were absent. The crustacean fauna of a new <span class="hlt">eddy</span> was distinct from both the fauna of the source region and of the Tasman Sea because sufficient cold-water species were already present in the geographical location where a new <span class="hlt">eddy</span> forms. The myctophid fauna of a new warm-core <span class="hlt">eddy</span> was essentially identical to the Coral Sea fauna because cold-water species do not penetrate into the warmer waters of the source of the <span class="hlt">eddies</span>. A temperature of 15°C at 250 m depth may be a useful oceanographic marker separating subtropical from temperate myctophids in the Coral and Tasman seas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AdSpR..56..494G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AdSpR..56..494G"><span>Earth's gravity gradient and <span class="hlt">eddy</span> <span class="hlt">currents</span> effects on the rotational dynamics of space debris objects: Envisat case study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gómez, Natalia Ortiz; Walker, Scott J. I.</p> <p>2015-08-01</p> <p>The space debris population has grown rapidly over the last few decades with the consequent growth of impact risk between <span class="hlt">current</span> objects in orbit. Active Debris Removal (ADR) has been recommended to be put into practice by several National Agencies in order to remove objects that pose the biggest risk for the space community. The most immediate target that is being considered for ADR by the European Space Agency is the Earth-observing satellite Envisat. In order to safely remove such a massive object from its orbit, a capturing process followed by a controlled reentry is necessary. However, <span class="hlt">current</span> ADR methods that require physical contact with the target have limitations on the maximum angular momentum that can be absorbed and a de-tumbling phase prior to the capturing process may be required. Therefore, it is of utmost importance for the ADR mission design to be able to predict accurately how the target will be rotating at the time of capture. This article analyses two perturbations that affect an object in Low Earth Orbit (LEO), the Earth's gravity gradient and the <span class="hlt">eddy</span> <span class="hlt">currents</span> induced by the Earth's magnetic field. The gravity gradient is analysed using the equation of conservation of total energy and a graphical method is presented to understand the expected behaviour of any object under the effect of this perturbation. The <span class="hlt">eddy</span> <span class="hlt">currents</span> are also analysed by studying the total energy of the system. The induced torque and the characteristic time of decay are presented as a function of the object's magnetic tensor. In addition, simulations were carried out for the Envisat spacecraft including the gravity gradient perturbation as well as the <span class="hlt">eddy</span> <span class="hlt">currents</span> effect using the International Geomagnetic Reference Field IGRF-11 to model the Earth's magnetic field. These simulations show that the combined effect of these two perturbations is a plausible explanation for the rotational speed decay observed between April 2013 and September 2013.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013CSR....70...46S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013CSR....70...46S"><span>The roles of vertical shear and topography on the <span class="hlt">eddy</span> formation near the site of origin of the Brazil <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>Soutelino, R. G.; Gangopadhyay, A.; da Silveira, I. C. A.</p> <p>2013-11-01</p> <p>The site of origin of the Brazil <span class="hlt">Current</span> (BC) is <span class="hlt">currently</span> one of the less explored aspects of regional circulation and mesoscale activity in the west side of the South Atlantic Subtropical gyre. The few studies that are available, based either on in situ data or on numerical modeling, seems to agree that the region is characterized by relatively weak baroclinic flow, with substantial mesoscale activity, which is quite different from other western boundary <span class="hlt">current</span> systems (e.g. Florida <span class="hlt">Current</span>, in the North Atlantic). We present numerical simulations that show that the main realistic mesoscale features in the <span class="hlt">eddy</span>-rich vicinities of the BC site of origin can be successfully modeled through the dynamical interaction between parameterized versions of two opposing mean western boundary <span class="hlt">currents</span> (BC and North Brazil Undercurrent—NBUC) and local topography, with no influence of remote dynamics or atmospheric forcing. Large BC-related anticyclones observed in previous work were reproduced and recurrently formed during the model run. Two additional sensitivity experiments were performed. When NBUC is removed from the physical setting, the BC interaction with topography is not sufficient to generate <span class="hlt">eddies</span> similar to observations. When an idealized flat-bottom and a physiographic configuration with no Abrolhos and Royal Charlotte Banks are considered, the BC-NBUC interaction is also not capable of developing realistic mesoscale structures. Our geophysical instability analyses suggest that BC-NBUC vertical shear is promoting baroclinic energy fluxes from the mean flow to the perturbations, resulting in <span class="hlt">eddy</span> formation and growth in the region.</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/2015JGRC..120.7413F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRC..120.7413F"><span>Southern Ocean <span class="hlt">eddy</span> phenomenology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frenger, I.; Münnich, M.; Gruber, N.; Knutti, R.</p> <p>2015-11-01</p> <p>Mesoscale <span class="hlt">eddies</span> are ubiquitous features in the Southern Ocean, yet their phenomenology is not well quantified. To tackle this task, we use satellite observations of sea level anomalies and sea surface temperature (SST) as well as in situ temperature and salinity measurements from profiling floats. Over the period 1997-2010, we identified over a million mesoscale <span class="hlt">eddy</span> instances and were able to track about 105 of them over 1 month or more. The Antarctic Circumpolar <span class="hlt">Current</span> (ACC), the boundary <span class="hlt">current</span> systems, and the regions where they interact are hot spots of <span class="hlt">eddy</span> presence, representing also the birth places and graveyards of most <span class="hlt">eddies</span>. These hot spots contrast strongly to areas shallower than about 2000 m, where mesoscale <span class="hlt">eddies</span> are essentially absent, likely due to topographical steering. Anticyclones tend to dominate the southern subtropical gyres, and cyclones the northern flank of the ACC. Major causes of regional polarity dominance are larger formation numbers and lifespans, with a contribution of differential propagation pathways of long-lived <span class="hlt">eddies</span>. Areas of dominance of one polarity are generally congruent with the same polarity being longer-lived, bigger, of larger amplitude, and more intense. <span class="hlt">Eddies</span> extend down to at least 2000 m. In the ACC, <span class="hlt">eddies</span> show near surface temperature and salinity maxima, whereas <span class="hlt">eddies</span> in the subtropical areas generally have deeper anomaly maxima, presumably inherited from their origin in the boundary <span class="hlt">currents</span>. The temperature and salinity signatures of the average <span class="hlt">eddy</span> suggest that their tracer anomalies are a result of both trapping in the <span class="hlt">eddy</span> core and stirring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0016S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0016S"><span>Model-based study for evaluating the sensitivity of <span class="hlt">eddy</span> <span class="hlt">current</span> GMR probe inspection of multilayer structures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Su, Zhiyi; Rosell, Anders; Udpa, Lalita; Tamburrino, Antonello</p> <p>2017-02-01</p> <p>In <span class="hlt">eddy</span> <span class="hlt">current</span> nondestructive testing (EC-NDT) of a multilayer riveted structure, rotating <span class="hlt">current</span> excitation, generated by orthogonal coils, is advantageous in providing sensitivity to defects of all orientations. The signal of a defect is not only a function of its size but also of the geometrical features in vicinity to the rivet such as edges, adjacent rivets and properties of the layered structure. Numerical models can be used to provide fast and accurate estimates of defect signals. In this paper the sensitivity of the <span class="hlt">eddy</span> <span class="hlt">current</span> system with rotating <span class="hlt">current</span> excitation and GMR sensors is evaluated by considering the effect of rivet permeability, lift-off, thickness of first layer as well as defect orientation related to adjacent rivets and edges on the signal measured. A numerical model capable of simulating these combinations of defect and test geometry parameters at an acceptable computation time is used. A meta-model is developed based on these simulation results and utilized for sensitivity evaluation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JChPh.137o4201A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JChPh.137o4201A"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> effects in plain and hollow cylinders spinning inside homogeneous magnetic fields: Application to magnetic resonance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aubert, G.; Jacquinot, J.-F.; Sakellariou, D.</p> <p>2012-10-01</p> <p>We present a thorough analysis of <span class="hlt">eddy</span> <span class="hlt">currents</span> that develop in a rectangular cross section toroid rotating in a uniform magnetic field. The slow rotation regime is assumed. Compact expressions for the <span class="hlt">current</span> density, the total dissipated power, and the braking torque are given. Examination of the topology of <span class="hlt">current</span> lines reveals that depending upon the relative dimensions of the side and length of the toroid two different regimes exist. The conditions of existence of the two regimes are analytically established. In view of nuclear magnetic resonance (NMR) applications, we derive the angular variation of the magnetic field created by <span class="hlt">eddy</span> <span class="hlt">currents</span> and lay down the formalism necessary for calculating the effect of this field on the NMR spectra of the conductor itself or of a sample co-rotating with the conductor, a situation encountered when dealing with rotating detectors. Examples of calculations for cases of practical interest are presented. The theory is confronted with available data, and we give guidelines for the design of optimized rotating micro-coils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA114352','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA114352"><span>The Dynamics of the Loop <span class="hlt">Current</span> and Shed <span class="hlt">Eddies</span> in a Numerical Model of the Gulf of Mexico.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1981-10-01</p> <p>some basic dynamical ideas and numerical results concerning the behavior of the Loop <span class="hlt">Current-eddy</span> system. The dynamica ) topics include 1) the nature of...sufficiently slow to consider it in isostatic adjustment with respect to CAV trajectories. In the time a fluid particle in the Loop moves from the west side...primitive equations for a two-layer fluid with a free surface: a wi. f^3- --+ \\vi • V vi + k f fW i = -Vpiat (Ci) + ( i - i+l)/(Phi) + AV2 \\vi !T + V (hl vI</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/862919','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/862919"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> position indicating apparatus for measuring displacements of core components of a liquid metal nuclear reactor</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Day, Clifford K.; Stringer, James L.</p> <p>1977-01-01</p> <p>Apparatus for measuring displacements of core components of a liquid metal fast breeder reactor by means of an <span class="hlt">eddy</span> <span class="hlt">current</span> probe. The active portion of the probe is located within a dry thimble which is supported on a stationary portion of the reactor core support structure. Split rings of metal, having a resistivity significantly different than sodium, are fixedly mounted on the core component to be monitored. The split rings are slidably positioned around, concentric with the probe and symmetrically situated along the axis of the probe so that motion of the ring along the axis of the probe produces a proportional change in the probes electrical output.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5659787','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5659787"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> loss and coil inductance evaluation in DC machines by a PG-based F. E. Code</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Arturi, C.M.; Ubaldini, M. )</p> <p>1991-09-01</p> <p>The present paper deals with the evaluation of both the <span class="hlt">eddy</span> <span class="hlt">current</span> loss and the self and mutual inductances of the commutating coils of a dc machine armature-winding for railway traction by a two-dimension PC-based finite element commercial code. The comparison among several distribution of the conductors occupying a given slot and among slots with different ratio of depth to width is made in this paper in order to determine, for a given dc machine, the best design solution with references to both the loss and the self and mutual inductances of the commutating coils.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PrOce.122..153W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PrOce.122..153W"><span>Fatty acid profiles of phyllosoma larvae of western rock lobster (Panulirus cygnus) in cyclonic and anticyclonic <span class="hlt">eddies</span> of the Leeuwin <span class="hlt">Current</span> off Western Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, M.; O'Rorke, R.; Waite, A. M.; Beckley, L. E.; Thompson, P.; Jeffs, A. G.</p> <p>2014-03-01</p> <p>The recent dramatic decline in settlement in the population of the spiny lobster, Panulirus cygnus, may be due to changes in the oceanographic processes that operate offshore of Western Australia. It has been suggested that this decline could be related to poor nutritional condition of the post-larvae, especially lipid which is accumulated in large quantities during the preceding extensive pelagic larval stage. The <span class="hlt">current</span> study focused on investigations into the lipid content and fatty acid (FA) profiles of lobster phyllosoma larvae from three mid to late stages of larval development (stages VI, VII, VIII) sampled from two cyclonic and two anticyclonic <span class="hlt">eddies</span> of the Leeuwin <span class="hlt">Current</span> off Western Australia. The results showed significant accumulation of lipid and energy storage FAs with larval development regardless of location of capture, however, larvae from cyclonic <span class="hlt">eddies</span> had more lipid and FAs associated with energy storage than larvae from anticyclonic <span class="hlt">eddies</span>. FA food chain markers from the larvae indicated significant differences in the food webs operating in the two types of <span class="hlt">eddy</span>, with a higher level of FA markers for production from flagellates and a lower level from copepod grazing in cyclonic versus anticyclonic <span class="hlt">eddies</span>. The results indicate that the microbial food web operating in cyclonic <span class="hlt">eddies</span> provides better feeding conditions for lobster larvae despite anticyclonic <span class="hlt">eddies</span> being generally more productive and containing greater abundances of zooplankton as potential prey for lobster larvae. Gelatinous zooplankton, such as siphonophores, may play an important role in cyclonic <span class="hlt">eddies</span> by accumulating dispersed microbial nutrients and making them available as larger prey for phyllosoma. The markedly superior nutritional condition of lobster larvae feeding in the microbial food web found in cyclonic <span class="hlt">eddies</span>, could greatly influence their subsequent settlement and recruitment to the coastal fishery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NTE....30...63B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NTE....30...63B"><span>New contactless <span class="hlt">eddy</span> <span class="hlt">current</span> non-destructive methodology for electric conductivity measurement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bouchala, T.; Abdelhadi, B.; Benoudjit, A.</p> <p>2015-01-01</p> <p>In this paper, a new method of contactless electric conductivity measurement is developed. This method is essentially based on the association of the <span class="hlt">coupled</span> electric field forward model, which we have recently developed, with a simple and efficient research algorithm. The proposed method is very fast because 1.3 s are sufficient to calculate electric conductivity, in a CPU of 2 GHz and RAM of 3 GB, for a starting research interval of 1.72-17.2 %IACS and tolerance of 1.72 × 10- 5 %IACS. The study of the calculation time according to mesh density and starting interval width has showed that an optimal choice has to be made in order to improve the rapidity while preserving its precision. Considering its rapidity and its simplicity of implementation, this method is more adapted, in comparison to direct <span class="hlt">current</span> techniques using Van der Pauw geometry, for automated applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcSci..12..977D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcSci..12..977D"><span>Effects of surface <span class="hlt">current</span>-wind interaction in an <span class="hlt">eddy</span>-rich general ocean circulation simulation of the Baltic Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dietze, Heiner; Löptien, Ulrike</p> <p>2016-08-01</p> <p>Deoxygenation in the Baltic Sea endangers fish yields and favours noxious algal blooms. Yet, vertical transport processes ventilating the oxygen-deprived waters at depth and replenishing nutrient-deprived surface waters (thereby fuelling export of organic matter to depth) are not comprehensively understood. Here, we investigate the effects of the interaction between surface <span class="hlt">currents</span> and winds on upwelling in an <span class="hlt">eddy</span>-rich general ocean circulation model of the Baltic Sea. Contrary to expectations we find that accounting for <span class="hlt">current</span>-wind effects inhibits the overall vertical exchange between oxygenated surface waters and oxygen-deprived water at depth. At major upwelling sites, however (e.g. off the southern coast of Sweden and Finland) the reverse holds: the interaction between topographically steered surface <span class="hlt">currents</span> with winds blowing over the sea results in a climatological sea surface temperature cooling of 0.5 K. This implies that <span class="hlt">current</span>-wind effects drive substantial local upwelling of cold and nutrient-replete waters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0023M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0023M"><span>Differential geometry based model for <span class="hlt">eddy</span> <span class="hlt">current</span> inspection of U-bend sections 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>Mukherjee, Saptarshi; Rosell, Anders; Udpa, Lalita; Udpa, Satish; Tamburrino, Antonello</p> <p>2017-02-01</p> <p>The modeling of U-Bend segment in steam generator tubes for predicting <span class="hlt">eddy</span> <span class="hlt">current</span> probe signals from cracks, wear and pitting in this region poses challenges and is non-trivial. Meshing the geometry in the cartesian coordinate system might require a large number of elements to model the U-bend region. Also, since the lift-off distance between the probe and tube wall is usually very small, a very fine mesh is required near the probe region to accurately describe the <span class="hlt">eddy</span> <span class="hlt">current</span> field. This paper presents a U-bend model using differential geometry principles that exploit the result that Maxwell's equations are covariant with respect to changes of coordinates and independent of metrics. The equations remain unaltered in their form, regardless of the choice of the coordinates system, provided the field quantities are represented in the proper covariant and contravariant form. The complex shapes are mapped into simple straight sections, while small lift-off is mapped to larger values, thus reducing the intrinsic dimension of the mesh and stiffness matrix. In this contribution, the numerical implementation of the above approach will be discussed with regard to field and <span class="hlt">current</span> distributions within the U-bend tube wall. For the sake of simplicity, a two dimensional test case will be considered. The approach is evaluated in terms of efficiency and accuracy by comparing the results with that obtained using a conventional FE model in cartesian coordinates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMOS11B1188V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMOS11B1188V"><span>Statistical mechanics explanation for the structure of ocean <span class="hlt">eddies</span> and <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>Venaille, A.; Bouchet, F.</p> <p>2010-12-01</p> <p>The equilibrium statistical mechanics of two dimensional and geostrophic flows predicts the outcome for the large scales of the flow, resulting from the turbulent mixing. This theory has been successfully applied to describe detailed properties of Jupiter's Great Red Spot. We discuss the range of applicability of this theory to ocean dynamics. It is able to reproduce mesoscale structures like ocean rings. It explains, from statistical mechanics, the westward drift of rings at the speed of non dispersive baroclinic waves, and the recently observed (Chelton and col.) slower northward drift of cyclonic <span class="hlt">eddies</span> and southward drift of anticyclonic <span class="hlt">eddies</span>. We also uncover relations between strong eastward mid-basin inertial jets, like the Kuroshio extension and the Gulf Stream, and statistical equilibria. We explain under which conditions such strong mid-basin jets can be understood as statistical equilibria. We claim that these results are complementary to the classical Sverdrup-Munk theory: they explain the inertial part basin dynamics, the jets structure and location, using very simple theoretical arguments. References: A. VENAILLE and F. BOUCHET, Ocean rings and jets as statistical equilibrium states, submitted to JPO F. BOUCHET and A. VENAILLE, Statistical mechanics of two-dimensional and geophysical flows, arxiv ...., submitted to Physics Reports P. BERLOFF, A. M. HOGG, W. DEWAR, The Turbulent Oscillator: A Mechanism of Low- Frequency Variability of the Wind-Driven Ocean Gyres, Journal of Physical Oceanography 37 (2007) 2363-+. D. B. CHELTON, M. G. SCHLAX, R. M. SAMELSON, R. A. de SZOEKE, Global observations of large oceanic <span class="hlt">eddies</span>, Geo. Res. Lett.34 (2007) 15606-+ b) and c) are snapshots of streamfunction and potential vorticity (red: positive values; blue: negative values) in the upper layer of a three layer quasi-geostrophic model of a mid-latitude ocean basin (from Berloff and co.). a) Streamfunction predicted by statistical mechanics. Even in an out</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMEP22A..07F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMEP22A..07F"><span><span class="hlt">Coupled</span> large <span class="hlt">eddy</span> simulation and discrete element model of bedload motion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Furbish, D.; Schmeeckle, M. W.</p> <p>2011-12-01</p> <p>We combine a three-dimensional large <span class="hlt">eddy</span> simulation of turbulence to a three-dimensional discrete element model of turbulence. The large <span class="hlt">eddy</span> simulation of the turbulent fluid is extended into the bed composed of non-moving particles by adding resistance terms to the Navier-Stokes equations in accordance with the Darcy-Forchheimer law. This allows the turbulent velocity and pressure fluctuations to penetrate the bed of discrete particles, and this addition of a porous zone results in turbulence structures above the bed that are similar to previous experimental and numerical results for hydraulically-rough beds. For example, we reproduce low-speed streaks that are less coherent than those over smooth-beds due to the episodic outflow of fluid from the bed. Local resistance terms are also added to the Navier-Stokes equations to account for the drag of individual moving particles. The interaction of the spherical particles utilizes a standard DEM soft-sphere Hertz model. We use only a simple drag model to calculate the fluid forces on the particles. The model reproduces an exponential distribution of bedload particle velocities that we have found experimentally using high-speed video of a flat bed of moving sand in a recirculating water flume. The exponential distribution of velocity results from the motion of many particles that are nearly constantly in contact with other bed particles and come to rest after short distances, in combination with a relatively few particles that are entrained further above the bed and have velocities approaching that of the fluid. Entrainment and motion "hot spots" are evident that are not perfectly correlated with the local, instantaneous fluid velocity. Zones of the bed that have recently experienced motion are more susceptible to motion because of the local configuration of particle contacts. The paradigm of a characteristic saltation hop length in riverine bedload transport has infused many aspects of geomorphic thought, including</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AIPC.1511.1242S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AIPC.1511.1242S"><span>Pre-crack fatigue life assessment of relevant aircraft materials using fractal analysis of <span class="hlt">eddy</span> <span class="hlt">current</span> test data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schreiber, Jürgen; Cikalova, Ulana; Hillmann, Susanne; Meyendorf, Norbert; Hoffmann, Jochen</p> <p>2013-01-01</p> <p>Successful determination of residual fatigue life requires a comprehensive understanding of the fatigue related material deformation mechanism. Neither macroscopic continuum mechanics nor micromechanic observations provide sufficient data to explain subsequent deformation structures occurring during the fatigue life of a metallic structure. Instead mesomechanic deformation on different scaling levels can be studied by applying fractal analysis of various means of nondestructive inspection measurements. The resulting fractal dimension data can be correlated to the actual material damage states, providing an estimation of the remaining residual fatigue life before macroscopic fracture develops. Recent efforts were aimed to apply the fractal concept to aerospace relevant materials AA7075-T6 and Ti-6Al-4V. Proven and newly developed fractal analysis methods were applied to <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) measurements of fatigued specimens, with the potential to transition this approach to an aircraft for an in-situ nondestructive inspection. The occurrence of mesomechanic deformation at the material surface of both AA7075-T6 and Ti-6Al-4V specimens could be established via topography images using confocal microscopy (CM). Furthermore, a pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) approach was developed, combined with a sophisticated new fractal analysis algorithm based on short pulse excitation and evaluation of EC relaxation behavior. This paper presents concept, experimental realization, fractal analysis procedures, and results of this effort.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3472851','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3472851"><span>A Wide Linear Range <span class="hlt">Eddy</span> <span class="hlt">Current</span> Displacement Sensor Equipped with Dual-Coil Probe Applied in the Magnetic Suspension Flywheel</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fang, Jiancheng; Wen, Tong</p> <p>2012-01-01</p> <p>The <span class="hlt">Eddy</span> <span class="hlt">Current</span> Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. Wide clearances must be measured in some new MSFWs recently designed for the different space missions, but the coil diameter is limited by some restrictions. In this paper, a multi-channel ECDS equipped with dual-coil probes is proposed to extend the linear range to satisfy the demands of such MSFWs. In order to determine the best configuration of the dual-coil probe, the quality factors of the potential types of the dual-coil probes, the induced <span class="hlt">eddy</span> <span class="hlt">current</span> and the magnetic intensity on the surface of the measuring object are compared with those of the conventional single-coil probe. The linear range of the ECDS equipped with the selected dual-coil probe is extended from 1.1 mm to 2.4 mm under the restrictions without adding any cost for additional compensation circuits or expensive coil materials. The effectiveness of the linear range extension ability and the dynamic response of the designed ECDS are confirmed by the testing and the applications in the MSFW. PMID:23112623</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.9042A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.9042A"><span>Structure, pathways and dynamics of the East Greenland <span class="hlt">Current</span> in <span class="hlt">eddy</span>-resolving global ocean models and observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aksenov, Yevgeny; Bacon, Sheldon; Nurser, George; Coward, Andrew</p> <p>2013-04-01</p> <p>The fresh and cold East Greenland <span class="hlt">Current</span> (EGC) transports Polar waters from the Arctic Ocean southward in the Nordic Seas and the North Atlantic, affecting deep convection in the Nordic and Labrador Seas with potential impacts on the meridional overturning circulation. The pathways of the EGC in Fram Strait and south of it are well documented by observations and model simulations. However, neither the EGC's pathways upstream of Fram Strait nor its sources in the central Arctic Ocean are known sufficiently well to attribute variability of the Arctic outflow to atmospheric or oceanic mechanisms. A set of <span class="hlt">eddy</span>-permitting and <span class="hlt">eddy</span>-resolving global Ocean General Circulation Models (OGCMs) run with dye tracers and observational data have been used to examine the structure and dynamics of the EGC. The Montgomery function on pseudo-neutral surfaces has been applied to the model results to investigate dynamics of the <span class="hlt">current</span> and its inter-annual variability. The sources of the EGC and the covariance of Arctic fresh water sinks via Fram Strait and the Canadian Arctic Archipelago are investigated. The model results are compared with observations, and mechanisms driving the EGC are suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23112623','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23112623"><span>A wide linear range <span class="hlt">Eddy</span> <span class="hlt">Current</span> Displacement Sensor equipped with dual-coil probe applied in the Magnetic Suspension Flywheel.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fang, Jiancheng; Wen, Tong</p> <p>2012-01-01</p> <p>The <span class="hlt">Eddy</span> <span class="hlt">Current</span> Displacement Sensor (ECDS) is widely used in the Magnetic Suspension Flywheel (MSFW) to measure the tiny clearance between the rotor and the magnetic bearings. The linear range of the ECDS is determined by the diameter of its probe coil. Wide clearances must be measured in some new MSFWs recently designed for the different space missions, but the coil diameter is limited by some restrictions. In this paper, a multi-channel ECDS equipped with dual-coil probes is proposed to extend the linear range to satisfy the demands of such MSFWs. In order to determine the best configuration of the dual-coil probe, the quality factors of the potential types of the dual-coil probes, the induced <span class="hlt">eddy</span> <span class="hlt">current</span> and the magnetic intensity on the surface of the measuring object are compared with those of the conventional single-coil probe. The linear range of the ECDS equipped with the selected dual-coil probe is extended from 1.1 mm to 2.4 mm under the restrictions without adding any cost for additional compensation circuits or expensive coil materials. The effectiveness of the linear range extension ability and the dynamic response of the designed ECDS are confirmed by the testing and the applications in the MSFW.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20632905','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20632905"><span>On the Feasibility of <span class="hlt">Eddy</span> <span class="hlt">Current</span> Characterization of the Near-Surface Residual Stress Distribution in Nickel-Base Superalloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blodgett, Mark P.; Nagy, Peter B.</p> <p>2004-02-26</p> <p>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 shot-peened specimens. This technique is based on the so-called electroelastic effect, i.e., the stress-dependence of the electrical conductivity. Unfortunately, the relatively small ({approx}1%) change in electrical conductivity caused by the presence of compressive residual stresses is often distorted, or even completely overshadowed, by the accompanying conductivity loss caused by cold work and surface roughness effects. Recently, it was observed that, in contrast with most other materials, shot-peened Waspaloy and IN100 specimens exhibit an apparent increase in electrical conductivity at increasing inspection frequencies. This observation by itself indicates that in these materials the measured conductivity change is probably dominated by residual stress effects, since both surface roughness and increased dislocation density are known to decrease rather than increase the conductivity and the presence of crystallographic texture does not affect the electrical conductivity of these materials, which crystallize in cubic symmetry. Our preliminary experiments indicate that probably there exists a unique 'window of opportunity' for <span class="hlt">eddy</span> <span class="hlt">current</span> NDE in nickel-base superalloys. We identified five major effects that contribute to this fortunate constellation of material properties, which will be reviewed in this presentation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.A21C0649L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.A21C0649L"><span>Influence of Loop <span class="hlt">Current</span> on Hurricane Katrina in a High-Resolution <span class="hlt">Coupled</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, C.; Chen, S. S.</p> <p>2007-12-01</p> <p>Recent observational and numerical modeling studies have shown that <span class="hlt">coupled</span> atmosphere-wave-ocean models may lead to substantial improvement in prediction of hurricane intensity. However, forecasting hurricane structure and intensity change is still a real challenge, especially when storm moving over the complex ocean features, such as the Gulf Stream and warm ocean <span class="hlt">eddies</span>, which can result in a rapid intensification in some hurricanes under a favorable atmospheric environment. Uncertainty remains to be high from storm to storm. A lack of understanding of the mechanisms of how these ocean features influence hurricane structure could be one of the reasons. To address this issue, a <span class="hlt">coupled</span> atmospheric-wave-ocean model is adopted in this study to simulate the evolution of Hurricane Katrina (2005), which shows the rapid intensification when moving into the Gulf of Mexico. The <span class="hlt">coupled</span> model is consist of the 5th generation Pennsylvania State University / National Center for Atmospheric Research mesoscale model (MM5), WAVEWATCH III (WW3), and the 3D Price-Weller-Pinkel (3DPWP) upper ocean model. To examine the influence of the Loop <span class="hlt">Current</span> and warm <span class="hlt">eddy</span> on Katrina, <span class="hlt">coupled</span> modeling experiments were conducted with both a simplified and a more realistic upper-ocean initial condition. The latter is based on the full physics Hybrid Coordinate Ocean Model (HYCOM) assimilation fields at 0000UTC 26 August 2005. Furthermore, experiments with and without WW3 are also compared to highlight the influence of the ocean surface waves on hurricane structure and intensity. Preliminary results show that both the surface waves and a better oceanic initial condition improved significantly the storm intensity forecasts compared to the observations. The inclusion of surface waves seems to produce a better wind-pressure relationship. To fully understand the physical processes that affect the hurricane intensity by oceanic initial condition and the surface waves, a comprehensive analysis of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5888327','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5888327"><span>Development of an electromagnetic microscope for <span class="hlt">eddy-current</span> evaluation of materials. Annual technical report</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Podney, W.N.</p> <p>1991-08-01</p> <p>Superconductive quantum interference devices (SQUIDs) offer new technology for locating material flaws electromagnetically that promises to increase sensitivity and depth of field as well as to enhance resolution and imaging. The ultrahigh sensitivity of SQUIDs to magnetic flux allows use of microscopic pickup loops in a gradiometer configuration to give high resolution. To realize the advantages of SQUID technology for Air Force requirements in evaluating the integrity of airframes, SQM Technology, Inc. is developing an electromagnetic microscope that uses an array of microscopic pickup loops for imaging micro flaws in aluminum. The prototype comprises a triangular array of microscopic gradiometers that are <span class="hlt">coupled</span> to SQUID sensors through a flexible, cryogenic umbilical, which enables convenient scanning. Development to date shows three main accomplishments: (1) a planar, azimuthal gradiometer configuration enables suppressing source interference, (2) instrument noise at drive <span class="hlt">currents</span> of 1 A or so at frequencies below a few kilohertz is of the order of SQUID noise, and (3) a cryogenic umbilical can provide adequate cooling over a four to six foot length.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDA13001K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDA13001K"><span><span class="hlt">Coupled</span> large-<span class="hlt">eddy</span> simulation and morphodynamics of a large-scale river under extreme flood conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khosronejad, Ali; Sotiropoulos, Fotis; Stony Brook University Team</p> <p>2016-11-01</p> <p>We present a <span class="hlt">coupled</span> flow and morphodynamic simulations of extreme flooding in 3 km long and 300 m wide reach of the Mississippi River in Minnesota, which includes three islands and hydraulic structures. We employ the large-<span class="hlt">eddy</span> simulation (LES) and bed-morphodynamic modules of the VFS-Geophysics model to investigate the flow and bed evolution of the river during a 500 year flood. The <span class="hlt">coupling</span> of the two modules is carried out via a fluid-structure interaction approach using a nested domain approach to enhance the resolution of bridge scour predictions. The geometrical data of the river, islands and structures are obtained from LiDAR, sub-aqueous sonar and in-situ surveying to construct a digital map of the river bathymetry. Our simulation results for the bed evolution of the river reveal complex sediment dynamics near the hydraulic structures. The numerically captured scour depth near some of the structures reach a maximum of about 10 m. The data-driven simulation strategy we present in this work exemplifies a practical simulation-based-engineering-approach to investigate the resilience of infrastructures to extreme flood events in intricate field-scale riverine systems. This work was funded by a Grant from Minnesota Dept. of Transportation.</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://adsabs.harvard.edu/abs/2004IJTIA.123..762T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004IJTIA.123..762T"><span>Position-and Velocity- Sensorless Control of Cylindrical Brushless DC Motors Driven by Sinusoidal <span class="hlt">Current</span> at Low Speed Using <span class="hlt">Eddy</span> <span class="hlt">Current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takashima, Hiroshi; Tomita, Mutuwo; Chen, Zhiqian; Satoh, Mitsuhiko; Doki, Shinji; Okuma, Shigeru</p> <p></p> <p>This paper proposes to paste non-magnetic materials on the rotor surface of a cylindrical brushless DC motor and to use the model including the extended e.m.f. for sensorless control. In the proposed method, the inductance changes depending on the rotor position because of <span class="hlt">eddy</span> <span class="hlt">currents</span>, which flow on the non-magnetic material at high frequency. The rotor position can be estimated at standstill and at low speeds. The simulation results show that the proposed method is very useful.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008DyAtO..45...71H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008DyAtO..45...71H"><span>The Gulf Stream pathway and the impacts of the <span class="hlt">eddy</span>-driven abyssal circulation and the Deep Western Boundary <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>Hurlburt, Harley E.; Hogan, Patrick J.</p> <p>2008-08-01</p> <p>A hydrodynamic model of the subtropical Atlantic basin and the Intra-Americas Sea (9-47°N) is used to investigate the dynamics of Gulf Stream separation from the western boundary at Cape Hatteras and its mean pathway to the Grand Banks. The model has five isopycnal Lagrangian layers in the vertical and allows realistic boundary geometry, bathymetry, wind forcing, and a meridional overturning circulation (MOC), the latter specified via ports in the northern and southern boundaries. The northward upper ocean branch of the MOC (14 Sv) was always included but the southward Deep Western Boundary <span class="hlt">Current</span> (DWBC) was excluded in some simulations, allowing investigation of the impacts of the DWBC and the <span class="hlt">eddy</span>-driven mean abyssal circulation on Gulf Stream separation from the western boundary. The result is resolution dependent with the DWBC playing a crucial role in Gulf Stream separation at 1/16° resolution but with the <span class="hlt">eddy</span>-driven abyssal circulation alone sufficient to obtain accurate separation at 1/32° resolution and a realistic pathway from Cape Hatteras to the Grand Banks with minimal DWBC impact except southeast of the Grand Banks. The separation from the western boundary is particularly sensitive to the strength of the <span class="hlt">eddy</span>-driven abyssal circulation. Farther to the east, between 68°W and the Grand Banks, all of the 1/16° and 1/32° simulations with realistic topography (with or without a DWBC) gave similar generally realistic mean pathways with clear impacts of the topographically constrained <span class="hlt">eddy</span>-driven abyssal circulation versus very unrealistic Gulf Stream pathways between Cape Hatteras and the Grand Banks from otherwise identical simulations run with a flat bottom, in reduced-gravity mode, or with 1/8° resolution and realistic topography. The model is realistic enough to allow detailed model-data comparisons and a detailed investigation of Gulf Stream dynamics. The corresponding linear solution with a Sverdrup interior and Munk viscous western boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4835056','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4835056"><span>Physical-Biological <span class="hlt">Coupling</span> in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic <span class="hlt">Eddy</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan</p> <p>2016-01-01</p> <p>It is widely recognized that the mesoscale <span class="hlt">eddies</span> play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic <span class="hlt">eddy</span> in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the <span class="hlt">eddy</span> center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the <span class="hlt">eddy</span> center to the surrounding water outside the <span class="hlt">eddy</span>. However the TChl a biomass in the surface layer (at 5 m) in the <span class="hlt">eddy</span> center was promoted 2.6-fold compared to the biomass outside the <span class="hlt">eddy</span> (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the <span class="hlt">eddy</span> was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the <span class="hlt">eddy</span>, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the <span class="hlt">eddy</span> center under the effect of nutrient pumping. The doming isopycnal within the <span class="hlt">eddy</span> supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in <span class="hlt">eddy</span> center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27088991','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27088991"><span>Physical-Biological <span class="hlt">Coupling</span> in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic <span class="hlt">Eddy</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan</p> <p>2016-01-01</p> <p>It is widely recognized that the mesoscale <span class="hlt">eddies</span> play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic <span class="hlt">eddy</span> in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the <span class="hlt">eddy</span> center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the <span class="hlt">eddy</span> center to the surrounding water outside the <span class="hlt">eddy</span>. However the TChl a biomass in the surface layer (at 5 m) in the <span class="hlt">eddy</span> center was promoted 2.6-fold compared to the biomass outside the <span class="hlt">eddy</span> (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the <span class="hlt">eddy</span> was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the <span class="hlt">eddy</span>, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the <span class="hlt">eddy</span> center under the effect of nutrient pumping. The doming isopycnal within the <span class="hlt">eddy</span> supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in <span class="hlt">eddy</span> center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5454348','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5454348"><span><span class="hlt">Eddy-current</span> inspection for steam generator tubing program. Annual progress report for period ending December 31, 1979</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dodd, C.V.; Deeds, W.E.; McClung, R.W.</p> <p>1980-07-01</p> <p><span class="hlt">Eddy-current</span> methods provide the best in-service inspection of steam generator tubing, but present techniques can produce ambiguity because of the many independent variables that affect the signals. The <span class="hlt">current</span> development program has used mathematical models and developed or modified computer programs to design optimum probes, instrumentation, and techniques for multifrequency, multiproperty examinations. Interactive calculations and experimental measurements have been made with the use of modular <span class="hlt">eddy-current</span> instrumentation and a minicomputer. These establish the coefficients for the complex equations that define the values of the desired properties (and the attainable accuracy) despite changes in other significant variables. The computer programs for calculating the accuracy with which various properties can be measured indicate that the tubing wall thickness and the defect size can be measured much more accurately than is <span class="hlt">currently</span> required, even when other properties are varying. Our experimental measurements have confirmed these results, although more testing is needed for all the different combinations of cases and different types of defects. To facilitate the extensive laboratory scanning of the matrix of specimens that are necessary to develop algorithms for detection and analysis for all the possible combinations of positions of flaws, tube supports, and probe coils, we have designed, constructed, and begun operation of a computer-controlled automatic positioner. We have demonstrated the ability to overcome the large signals produced by the edge of the tube supports. An advanced microcomputer has been designed, constructed, and installed in the instrumentation to control the examination and provide real-time calculations of the desired properties for display recording during the scanning of the tube.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JOM....67g1459L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JOM....67g1459L"><span>Large <span class="hlt">Eddy</span> Simulation of Bubbly Flow and Slag Layer Behavior in Ladle with Discrete Phase Model (DPM)-Volume of Fluid (VOF) <span class="hlt">Coupled</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Linmin; Liu, Zhongqiu; Cao, Maoxue; Li, Baokuan</p> <p>2015-07-01</p> <p>In the ladle metallurgy process, the bubble movement and slag layer behavior is very important to the refining process and steel quality. For the bubble-liquid flow, bubble movement plays a significant role in the phase structure and causes the unsteady complex turbulent flow pattern. This is one of the most crucial shortcomings of the <span class="hlt">current</span> two-fluid models. In the <span class="hlt">current</span> work, a one-third scale water model is established to investigate the bubble movement and the slag open-eye formation. A new mathematical model using the large <span class="hlt">eddy</span> simulation (LES) is developed for the bubble-liquid-slag-air four-phase flow in the ladle. The Eulerian volume of fluid (VOF) model is used for tracking the liquid-slag-air free surfaces and the Lagrangian discrete phase model (DPM) is used for describing the bubble movement. The turbulent liquid flow is induced by bubble-liquid interactions and is solved by LES. The procedure of bubble coming out of the liquid and getting into the air is modeled using a user-defined function. The results show that the present LES-DPM-VOF <span class="hlt">coupled</span> model is good at predicting the unsteady bubble movement, slag eye formation, interface fluctuation, and slag entrainment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.524a2091C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.524a2091C"><span><span class="hlt">Coupled</span> fluid-structure interaction simulation of floating offshore wind turbines and waves: a large <span class="hlt">eddy</span> simulation approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calderer, Antoni; Guo, Xin; Shen, Lian; Sotiropoulos, Fotis</p> <p>2014-06-01</p> <p>We develop a computational framework for simulating the <span class="hlt">coupled</span> interaction of complex floating structures with large-scale ocean waves and atmospheric turbulent winds. The near-field approach features a partitioned fluid-structure interaction model (FSI) combining the curvilinear immersed boundary (CURVIB) method of Borazjani and Sotiropoulos (J. Comput. Phys. 2008) and the two-phase flow level set formulation of Kang and Sotiropoulos (Adv. in Water Res. 2012) and is capable of solving complex free-surface flows interacting non-linearly with complex real life floating structures. The near-field solver is <span class="hlt">coupled</span> with a large-scale wave and wind model based on the two-fluid approach of Yang and Shen (J. Comput. Phys. 2011) which integrates a viscous Navier-Stokes solver with undulatory boundaries for the motion of the air and an efficient potential-flow based wave solver. The large-scale turbulent wind is incorporated from the far-field solver to the near-field solver by feeding into the latter inlet boundary conditions. The wave field is incorporated to the near-field solver by using the pressure-forcing method of Guo and Shen (J. Comput. Phys. 2009) which has been appropriately adapted to the level set method. The algorithm for <span class="hlt">coupling</span> the two codes has been validated for a variety of wave cases including a broadband spectrum showing excellent agreement when compared to theoretical results. Finally, the capabilities of the numerical framework are demonstrated by carrying out large <span class="hlt">eddy</span> simulation (LES) of a floating wind turbine interacting with realistic ocean wind and wave conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H34D..03H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H34D..03H"><span>The <span class="hlt">current</span> California drought through <span class="hlt">EDDI</span>'s eyes: early warning and monitoring of agricultural and hydrologic drought with the new Evaporative Demand Drought Index.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hobbins, M.; McEvoy, D.; Huntington, J. L.; Wood, A. W.; Morton, C.; Verdin, J. P.</p> <p>2015-12-01</p> <p>We have developed a physically based, multi-scalar drought index—the Evaporative Demand Drought Index (<span class="hlt">EDDI</span>)—to improve treatment of evaporative dynamics in drought monitoring. Existing popular drought indices—such as the Palmer Drought Severity Index that informs much of the US Drought Monitor (USDM)—have primarily relyied on precipitation and temperature (T) to represent hydroclimatic anomalies, leaving evaporative demand (E0) most often derived from poorly performing T-based parameterizations then used to derive actual evapotranspiration (ET) from LSMs. Instead, <span class="hlt">EDDI</span> leverages the inter-relations of E0 and ET, measuring E0's physical response to surface drying anomalies due to two distinct land surface/atmosphere interactions: (i) in sustained drought, limited moisture availability forces E0 and ET into a complementary relation, whereby ET declines as E0 increases; and (ii) in "flash" droughts, E0 increases due to increasing advection or radiation. E0's rise in response to both drought types suggests <span class="hlt">EDDI</span>'s robustness as a monitor and leading indicator of drought. To drive <span class="hlt">EDDI</span>, we use for E0 daily reference ET from the ASCE Standardized Reference ET equation forced by North American Land Data Assimilation System drivers. <span class="hlt">EDDI</span> is derived by aggregating E0 anomalies from its long-term mean across a period of interest and normalizing them to a Z-score. Positive <span class="hlt">EDDI</span> indicates drier than normal conditions (and so drought). We use the <span class="hlt">current</span> historic California drought as a test-case in which to examine <span class="hlt">EDDI</span>'s performance in monitoring agricultural and hydrologic drought. We observe drought development and decompose the behavior of drought's evaporative drivers during in-drought intensification periods and wetting events. <span class="hlt">EDDI</span>'s performance as a drought leading indicator with respect to the USDM is tested in important agricultural regions. Comparing streamflow from several USGS gauges in the Sierra Nevada to <span class="hlt">EDDI</span>, we find that <span class="hlt">EDDI</span> tracks most major</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA618009','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA618009"><span>Large-<span class="hlt">Eddy</span> Simulations of Tropical Convective Systems, the Boundary Layer, and Upper Ocean <span class="hlt">Coupling</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2014-09-30</p> <p>the Boundary Layer , and Upper Ocean <span class="hlt">Coupling</span> Eric D. Skyllingstad College of Oceanic and Atmospheric Sciences, Oregon State University 104 COAS...NWP) models to more accurately simulate the interaction of tropical deep convection and atmospheric and oceanic boundary layers . OBJECTIVES...Investigate tropical convection and upper ocean circulations on scales from 100 m to 200 km. Elucidate specifically how the ocean mixed layer responds</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011DyAtO..51..109G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011DyAtO..51..109G"><span>On the interactions between planetary geostrophy and mesoscale <span class="hlt">eddies</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grooms, Ian; Julien, Keith; Fox-Kemper, Baylor</p> <p>2011-04-01</p> <p>Multiscale asymptotics are used to derive three systems of equations connecting the planetary geostrophic (PG) equations for gyre-scale flow to a quasigeostrophic (QG) equation set for mesoscale <span class="hlt">eddies</span>. Pedlosky (1984), following similar analysis, found <span class="hlt">eddy</span> buoyancy fluxes to have only a small effect on the large-scale flow; however, numerical simulations disagree. While the impact of <span class="hlt">eddies</span> is relatively small in most regions, in keeping with Pedlosky's result, <span class="hlt">eddies</span> have a significant effect on the mean flow in the vicinity of strong, narrow <span class="hlt">currents</span>. First, the multiple-scales analysis of Pedlosky is reviewed and amplified. Novel results of this analysis include new multiple-scales models connecting large-scale PG equations to sets of QG <span class="hlt">eddy</span> equations. However, only introducing anisotropic scaling of the large-scale coordinates allows us to derive a model with strong two-way <span class="hlt">coupling</span> between the QG <span class="hlt">eddies</span> and the PG mean flow. This finding reconciles the analysis with simulations, viz. that strong two-way <span class="hlt">coupling</span> is observed in the vicinity of anisotropic features of the mean flow like boundary <span class="hlt">currents</span> and jets. The relevant <span class="hlt">coupling</span> terms are shown to be <span class="hlt">eddy</span> buoyancy fluxes. Using the Gent-McWilliams parameterization to approximate these fluxes allows solution of the PG equations with closed tracer fluxes in a closed domain, which is not possible without mesoscale <span class="hlt">eddy</span> (or other small-scale) effects. The boundary layer width is comparable to an <span class="hlt">eddy</span> mixing length when the typical <span class="hlt">eddy</span> velocity is taken to be the long Rossby wave phase speed, which is the same result found by Fox-Kemper and Ferrari (2009) in a reduced gravity layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1706s0003R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1706s0003R"><span>2015 WFNDEC <span class="hlt">eddy</span> <span class="hlt">current</span> benchmark modeling of impedance variation in coil due to a crack located at the plate edge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rocha, João Vicente; Camerini, Cesar; Pereira, Gabriela</p> <p>2016-02-01</p> <p>The 2015 World Federation of NDE Centers (WFNDEC) <span class="hlt">eddy</span> <span class="hlt">current</span> benchmark problem involves the inspection of two EDM notches placed at the edge of a conducting plate with a pancake coil that runs parallel to the plate's edge line. Experimental data consists of impedance variation measured with a precision LCR bridge as a XY scanner moves the coil. The authors are pleased to present the numerical results obtained with commercial FEM packages (OPERA 3-D). Values of electrical resistance and inductive reactance variation between base material and the region around the notch are plotted as function of the coil displacement over the plate. The calculations were made for frequencies of 1 kHz and 10 kHz and agreement between experimental and numerical results are excellent for all inspection conditions. Explanations are made about how the impedance is calculated as well as pros and cons of the presented methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/940164','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/940164"><span>A QR accelerated volume-to-surface boundary condition for finite element solution of <span class="hlt">eddy</span> <span class="hlt">current</span> problems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>White, D; Fasenfest, B; Rieben, R; Stowell, M</p> <p>2006-09-08</p> <p>We are concerned with the solution of time-dependent electromagnetic <span class="hlt">eddy</span> <span class="hlt">current</span> problems using a finite element formulation on three-dimensional unstructured meshes. We allow for multiple conducting regions, and our goal is to develop an efficient computational method that does not require a computational mesh of the air/vacuum regions. This requires a sophisticated global boundary condition specifying the total fields on the conductor boundaries. We propose a Biot-Savart law based volume-to-surface boundary condition to meet this requirement. This Biot-Savart approach is demonstrated to be very accurate. In addition, this approach can be accelerated via a low-rank QR approximation of the discretized Biot-Savart law.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NTE....29..208S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NTE....29..208S"><span>Comparative study of <span class="hlt">eddy</span> <span class="hlt">current</span> and Barkhausen noise methods in microstructural assessment of heat treated steel parts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sahebalam, Alireza; Kashefi, Mehrdad; Kahrobaee, Saeed</p> <p>2014-07-01</p> <p>The present paper describes details of the comparison on the capability of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) and magnetic Barkhausen noise (MBN) techniques in the assessment of different microstructures in mild steel. To produce various microstructures, AISI 1045 steel samples were subjected to different heat treatment processes including annealing, normalising, quenching and tempering. EC outputs (induced voltage, normalised impedance and phase angle) as well as MBN outputs (peak width, position and amplitude) were evaluated. Comparing the EC/MBN outputs for the microstructures, the MBN peak characteristics show better agreement with changes in the microstructures. Besides, using regression analysis, peak width has been proved to be the optimum output to separate the microstructures with high accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1187928','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1187928"><span>Diamagnetic composite material structure for reducing undesired electromagnetic interference and <span class="hlt">eddy</span> <span class="hlt">currents</span> in dielectric wall accelerators and other devices</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Caporaso, George J.; Poole, Brian R.; Hawkins, Steven A.</p> <p>2015-06-30</p> <p>The devices, systems and techniques disclosed here can be used to reduce undesired effects by magnetic field induced <span class="hlt">eddy</span> <span class="hlt">currents</span> based on a diamagnetic composite material structure including diamagnetic composite sheets that are separated from one another to provide a high impedance composite material structure. In some implementations, each diamagnetic composite sheet includes patterned conductor layers are separated by a dielectric material and each patterned conductor layer includes voids and conductor areas. The voids in the patterned conductor layers of each diamagnetic composite sheet are arranged to be displaced in position from one patterned conductor layer to an adjacent patterned conductor layer while conductor areas of the patterned conductor layers collectively form a contiguous conductor structure in each diamagnetic composite sheet to prevent penetration by a magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A33Q..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A33Q..07M"><span>Winds, Mountains, and Wildland Fire: Improved Understanding of <span class="hlt">Coupled</span> Atmosphere-Topography-Fire Interactions Through Large-<span class="hlt">Eddy</span> Simulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Munoz-Esparza, D.; Sauer, J.; Linn, R.</p> <p>2015-12-01</p> <p>Anomalous and unexpected fire behavior in complex terrain continues to result in substantial loss of property and extremely dangerous conditions for firefighting field personnel. We briefly discuss proposed hypotheses of fire interactions with atmospheric flows over complex terrain that can lead to poorly-understood and potentially catastrophic scenarios. Then, our recent results of numerical investigations via large-<span class="hlt">eddy</span> simulation of <span class="hlt">coupled</span> atmosphere-topography-fire phenomenology with the Los Alamos National Laboratory, HiGrad-Firetec model are presented as an example of the potential for increased understanding of these complex processes. This investigation focuses on the influence of downslope surface wind enhancement through stably stratified flow over an isolated hill, and the resulting dramatic changes in fire behavior including spread rate, and intensity. Implications with respect to counter-intuitive fire behavior and extreme fire events are discussed. This work demonstrates a tremendous opportunity to immediately create safer and more effective policy for field personnel through improved predictability of atmospheric conditions over complex terrain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS23B1199H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS23B1199H"><span>Turbulent Fluxes of Suspended Sediment from <span class="hlt">Coupled</span> Acoustic Doppler <span class="hlt">Current</span> Profilers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hoitink, T.; Sassi, M.; Vermeulen, B.</p> <p>2014-12-01</p> <p>Turbulent diffusion is a cornerstone in geophysical fluid mechanics, controlling the exchange of momentum, heat and mass in surface flows occurring in the atmosphere, in rivers and in the ocean. In fluvial and coastal systems, modeling turbulent diffusion of momentum and suspended sediment requires knowledge about turbulent diffusivities, which is generally derived from parameterizations based on laboratory experiments. Field determinations of momentum and sediment diffusivities are cumbersome, requiring an instrumental array to simultaneously sample turbulence and mean flow quantities in time and in space. Recently, a new technique to analyze geophysical surface flow turbulence was introduced, appropriate for large scale systems, based on <span class="hlt">coupling</span> of acoustic Doppler <span class="hlt">current</span> profilers (ADCPs). Here, we extend this approach to obtain collocated profiles of both the Reynolds stress tensor and <span class="hlt">eddy</span> covariance fluxes, to derive vertical profiles of turbulent momentum and sediment diffusivity in a tidal river. Shear and normal stresses are obtained by combining the variances in radial velocities measured by the ADCP beams. The covariances between radial velocities and calibrated acoustic backscatter allow to determine the three Cartesian components of the turbulent flux of suspended sediment. The main advantage of this new approach is that flow velocity and sediment concentration measurements are exactly collocated, and that it allows to profile over longer ranges, in comparison to existing techniques. Results show that vertical profiles of the inverse turbulent Prandtl-Schmidt number is coherent with corresponding profiles of the sediment diffusivity, rather than with profiles of the <span class="hlt">eddy</span> viscosity. This implies modelling suspended sediment dynamics requires knowledge about the sediment diffusivity, as the Prandtl-Schmidt number cannot be estimated from the <span class="hlt">eddy</span> viscosity alone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005APS..DFD.BR004O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005APS..DFD.BR004O"><span>Large <span class="hlt">Eddy</span> Simulation study of the development of finite-channel lock-release <span class="hlt">currents</span> at high Grashof numbers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ooi, Seng-Keat</p> <p>2005-11-01</p> <p>Lock-exchange gravity <span class="hlt">current</span> flows produced by the instantaneous release of a heavy fluid are investigated using 3-D well resolved Large <span class="hlt">Eddy</span> Simulation simulations at Grashof numbers up to 8*10^9. It is found the 3-D simulations correctly predict a constant front velocity over the initial slumping phase and a front speed decrease proportional to t-1/3 (the time t is measured from the release) over the inviscid phase, in agreement with theory. The evolution of the <span class="hlt">current</span> in the simulations is found to be similar to that observed experimentally by Hacker et al. (1996). The effect of the dynamic LES model on the solutions is discussed. The energy budget of the <span class="hlt">current</span> is discussed and the contribution of the turbulent dissipation to the total dissipation is analyzed. The limitations of less expensive 2D simulations are discussed; in particular their failure to correctly predict the spatio-temporal distributions of the bed shear stresses which is important in determining the amount of sediment the gravity <span class="hlt">current</span> can entrain in the case in advances of a loose bed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007DSRII..54.1129G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007DSRII..54.1129G"><span>Potential mechanisms of influence of the Leeuwin <span class="hlt">Current</span> <span class="hlt">eddy</span> system on teleost recruitment to the Western Australian continental shelf</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaughan, Daniel J.</p> <p>2007-04-01</p> <p>The Leeuwin <span class="hlt">Current</span> (LC), an oligotrophic, warm <span class="hlt">current</span> that flows south (poleward) along the shelf-break off the west coast of Australia and then east along the south coast, is recognized as a key factor affecting fisheries production in the region, but the mechanisms for this influence have not been determined. Recruitment strength of the globally significant western rock lobster ( Panulirus cygnus) stock is correlated to interannual variations in the strength of the LC. While this relationship has been based on a 2-decade time-series of P. cygnus recruitment data, the important teleost species of the region rarely have recruitment data for more than a few years; yet this group is nonetheless economically, socially and politically important. Furthermore, there is little knowledge of the egg- and larval-stage dynamics for the majority of these teleosts. Previous and new information on those aspects of the LC system that could theoretically impact on recruitment of shelf teleosts were identified to provide a basis for developing a conceptual model of how the LC could affect recruitment. The potential impacts of the LC system, which entrains shelf water, were examined with reference to retention/loss of teleost eggs and larvae and positive/negative influences on feeding conditions for larvae. Owing to the lack of early-life-history information for many teleosts in Western Australia, this was undertaken for generalized shelf species whose eggs are spawned on the shelf and whose larvae must settle on the shelf to access favourable nursery habitat. The results indicate that the LC system most likely contributes a net negative impact on success of teleost eggs and larvae. Larvae of shelf teleosts entrained and trapped in the warm-core (WC) <span class="hlt">eddies</span> that form from the LC and then propagate offshore would contribute little to recruitment. Given that larval teleosts predominantly feed on copepods and that these were much less abundant in the WC <span class="hlt">eddy</span> than is typical of shelf</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhyB..406.3576Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhyB..406.3576Z"><span>Domain wall dynamics and Hall effect in <span class="hlt">eddy</span> <span class="hlt">current</span> loop in amorphous ferromagnetic wire with small helical anisotropy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ziman, J.; Onufer, J.; Kladivová, M.</p> <p>2011-10-01</p> <p>Small helical anisotropy was induced in amorphous ferromagnetic Co 68.2Fe 4.3Si 12.5B 15 wire by <span class="hlt">current</span> annealing and simultaneous application of tensile stress and torsion. Presence of helical anisotropy was confirmed by measurement and analysis of the circular magnetic flux versus axial magnetic field hysteresis loops. These measurements also showed that a single domain wall between circular domains can be created by placing the wire in a sufficiently high inhomogeneous magnetic field generated by Helmholtz coils with opposite <span class="hlt">currents</span>. The domain wall velocity versus axial driving field was measured. The results show that the basic dynamic properties (magnitude of the wall mobility, field interval in which linear dependencies between velocity and field are observed, accelerated increase of the velocity for higher fields) are very similar to those obtained for the domain wall between circular domains driven by a constant circular field. The Hall effect was detected in the <span class="hlt">eddy</span> <span class="hlt">current</span> loop generated by the moving domain wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NucFu..56j6010R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NucFu..56j6010R"><span>Asymmetric toroidal <span class="hlt">eddy</span> <span class="hlt">currents</span> (ATEC) to explain sideways forces at JET</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roccella, R.; Roccella, M.; Riccardo, V.; Chiocchio, S.; Contributors, JET</p> <p>2016-10-01</p> <p>During some JET vertical displacement events (VDEs) plasma <span class="hlt">current</span> and position are found to be toroidally asymmetric. When asymmetries lock, the vessel has been observed to move horizontally, consequently strong horizontal forces are expected following plasma asymmetries, whether locked or rotating. The cause of horizontal forces is, as already identified in previous works, the asymmetric circulation of <span class="hlt">current</span> in the structures. The physics mechanism responsible for these asymmetric <span class="hlt">currents</span> is instead an open issue and it is the object of the present analysis. In particular it will be shown that the asymmetry is not due to a direct exchange of <span class="hlt">current</span> between plasma and structure (as in the case of halo <span class="hlt">currents</span>) but to asymmetric conductive paths which arise, in the structures, when the plasma column asymmetrically wets the wall. Simulations of this phenomenon using finite element (FE) models have been conducted to reproduce the JET observation during locked and rotating asymmetric VDEs. Estimated sideways force, asymmetry (I\\text{p}\\text{asym} ) and normalized asymmetry (A\\text{p}\\text{asym} ) of plasma <span class="hlt">current</span>, vertical position at different toroidal locations during the disruption and halo <span class="hlt">current</span> asymmetry have been compared with measurements done at JET during upward AVDEs. The substantial match between experiments and simulations confirms the soundness of the assumptions. Furthermore, the same physical model applied to downward VDEs shows that divertor support and coils, together with the geometry of the limiting surfaces, considerably lessen asymmetric loads as experienced at JET after installing those components.</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.dtic.mil/docs/citations/ADA159228','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA159228"><span>Exploratory Development on Advanced <span class="hlt">Eddy</span> <span class="hlt">Current</span> Coil Excitation and Signal Processing.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1985-04-01</p> <p>Input Voltage Waveform (Bottom Trace) and Output <span class="hlt">Current</span> Waveform (1 Ampere per Division) of the Voltage-to- <span class="hlt">Current</span> Amplifier . . . . . . . 44 27...volts maxism sad 5 amperes maximim with an average power dissipation of less than 2.5 watts. Although the technique of PSC examination has existed for...designed for this project at SwRI. The amplifier is a wideband (approximately 50-MHz) device capable of delivering at least 2.5 Amperes into a load impedance</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AcAau..76..145P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AcAau..76..145P"><span>Study on the <span class="hlt">eddy</span> <span class="hlt">current</span> damping of the spin dynamics of space debris from the Ariane launcher upper stages</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Praly, N.; Hillion, M.; Bonnal, C.; Laurent-Varin, J.; Petit, N.</p> <p>2012-07-01</p> <p>This paper addresses the topic of damping of the spin dynamics of a spatial debris orbiting around the Earth. Such debris, which can consist of parts of heavy launchers such as the Ariane rocket under consideration in this article, are impacted by torques generated by <span class="hlt">eddy</span> <span class="hlt">currents</span> as their conducting non-ferromagnetic body orbits through the Earth magnetosphere. Several previous works have focused on describing this induction phenomenon and have proposed analysis of empirical observations of this particular and important effect which has attracted much attention since the number of spatial debris has emerged as a problem for the future of space programs, especially in low orbits. In this paper, we present a relatively comprehensive modeling of the induction phenomenon, by means of Maxwell's equations inside the conducting and non-ferromagnetic body. Through the generalized Ohm's law, we show how one can obtain a partial differential equation with Neumann's boundary conditions problem that, once solved, e.g. through a finite elements method, yields the values of induced <span class="hlt">currents</span> and braking torques. The case of a depleted upper stage of a heavy launcher, having a cylindrical shape and thin walls is particularly studied. We show a methodology to estimate the decay-rate of the spinning velocity, which is proven to satisfy a first-order asymptotically stable linear dynamics. Special cases consisting of typical orbit of space debris are treated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4299100','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4299100"><span>A Novel High Sensitivity Sensor for Remote Field <span class="hlt">Eddy</span> <span class="hlt">Current</span> Non-Destructive Testing Based on Orthogonal Magnetic Field</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Xiaojie; Liu, Ming; Zhang, Zhanbin; Jia, Yueling</p> <p>2014-01-01</p> <p>Remote field <span class="hlt">eddy</span> <span class="hlt">current</span> is an effective non-destructive testing method for ferromagnetic tubular structures. In view of conventional sensors' disadvantages such as low signal-to-noise ratio and poor sensitivity to axial cracks, a novel high sensitivity sensor based on orthogonal magnetic field excitation is proposed. Firstly, through a three-dimensional finite element simulation, the remote field effect under orthogonal magnetic field excitation is determined, and an appropriate configuration which can generate an orthogonal magnetic field for a tubular structure is developed. Secondly, optimized selection of key parameters such as frequency, exciting <span class="hlt">currents</span> and shielding modes is analyzed in detail, and different types of pick-up coils, including a new self-differential mode pick-up coil, are designed and analyzed. Lastly, the proposed sensor is verified experimentally by various types of defects manufactured on a section of a ferromagnetic tube. Experimental results show that the proposed novel sensor can largely improve the sensitivity of defect detection, especially for axial crack whose depth is less than 40% wall thickness, which are very difficult to detect and identify by conventional sensors. Another noteworthy advantage of the proposed sensor is that it has almost equal sensitivity to various types of defects, when a self-differential mode pick-up coil is adopted. PMID:25615738</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA261087','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA261087"><span><span class="hlt">Eddy</span> Generation at a Convex Corner by a Coastal <span class="hlt">Current</span> in a Rotating System</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1992-03-01</p> <p>Volume flux calculations based on the sur- face velocity revealed vertical shear which increased with gyre size. Hydraulic models were also applied to...Theoretical Studies ............................. 23 1.4. Plan of the Thesis ........ ............................ 30 I 2. Hydraulic Models of...and Kase, Beckmann, and Hinricksen (1989). Their models suggest that meddies are broken off from the Mediterranean Outflow by stronger <span class="hlt">currents</span> above</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002PhDT........72A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002PhDT........72A"><span><span class="hlt">Eddies</span> along western boundaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arruda, Wilton Zumpichiatti</p> <p></p> <p>The Ulleung <span class="hlt">eddy</span> owes its existence to beta and nonlinearities . A nonlinear theory for the Ulleung Warm <span class="hlt">Eddy</span> (UWE) in the Japan/East Sea is proposed. Using the nonlinear reduced gravity (shallow water) equations, it is shown analytically and numerically that the <span class="hlt">eddy</span> is established in order to balance the northward momentum flux exerted by the separating western boundary <span class="hlt">current</span> (WBC). In this scenario the presence of beta produces a southward (<span class="hlt">eddy</span>) force balancing the northward momentum flux of the separating East Korea Warm <span class="hlt">Current</span>. In contrast to the familiar idea attributing the formation of <span class="hlt">eddies</span> to instabilities (i.e., the breakdown of a known steady solution), the UWE is an integral part of the steady stable solution. On an f-plane no <span class="hlt">eddy</span> is produced. To balance the northward momentum force imparted by the nonlinear WBC the f-plane system moves offshore producing a southward Coriolis force. We also found that the observed UWE scale agrees with the analytical and numerical estimates. The Mindanao and Halmahera <span class="hlt">eddies</span> are due to the bending of their parent <span class="hlt">currents</span>, nonlinearities and beta. Starting with the simple case of a northward (southward) WBC flowing along a concave solid boundary with a sharp corner on an beta-plane, it is shown that an anticyclonic (cyclonic) <span class="hlt">eddy</span> is established to balance the upstream momentum flux. (On an f-plane no <span class="hlt">eddy</span> is established because a pressure force which balances the WBC momentum flux is generated.) With the aid of the above analysis we then examine the collision of two opposing WBCs on a beta-plane. It is shown that this problem can be conceptually reduced to the above problem of two WBCs turning in a solid corner on a beta-plane where the streamline separating the two colliding <span class="hlt">currents</span> acts like a "zonal wall." We show that an <span class="hlt">eddy</span> is established (to balance the momentum flux of the respective WBC) on each side of the dividing streamline. Based on the collision problem, an explanation for the Mindanao and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994nasa.reptW....W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994nasa.reptW....W"><span>Flux-focusing <span class="hlt">eddy</span> <span class="hlt">current</span> probe and rotating probe method for flaw detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wincheski, Buzz A.; Fulton, James P.; Nath, Shridhar C.; Simpson, John W.; Namkung, Min</p> <p>1994-11-01</p> <p>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 <span class="hlt">current</span> 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 <span class="hlt">current</span> flow about the rivet can be held constant. Any further changes in the <span class="hlt">current</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OcDyn..66..299C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OcDyn..66..299C"><span>Dynamic links between shape of the <span class="hlt">eddy</span> viscosity profile and the vertical structure of tidal <span class="hlt">current</span> amplitude in bays and estuaries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Wei; de Swart, Huib E.</p> <p>2016-03-01</p> <p>Several field studies in bays and estuaries have revealed pronounced subsurface maxima in the vertical profiles of the <span class="hlt">current</span> amplitude of the principal tidal harmonic, or of its vertical shear, over the water column. To gain fundamental understanding about these phenomena, a semi-analytical model is designed and analysed, with focus on the sensitivity of the vertical structure of the tidal <span class="hlt">current</span> amplitude to formulations of the vertical shape of the <span class="hlt">eddy</span> viscosity. The new analytical solutions for the tidal <span class="hlt">current</span> amplitude are used to explore their dependence on the degree of surface mixing, the vertical shape of <span class="hlt">eddy</span> viscosity in the upper part of the water column and the density stratification. Sources of surface mixing are wind and whitecapping. Results show three types of <span class="hlt">current</span> amplitude profiles of tidal harmonics, characterised by monotonically decreasing shear towards the surface, "surface jumps" (vertical shear of tidal <span class="hlt">current</span> amplitude has a subsurface maximum) and "subsurface jets" (maximum tidal <span class="hlt">current</span> amplitude below the surface), respectively. The "surface jumps" and "subsurface jets" both occur for low turbulence near the surface, whilst additionally the surface jumps only occur if the <span class="hlt">eddy</span> viscosity in the upper part of the water column decreases faster than linearly to the surface. Furthermore, "surface jumps" take place for low density stratification, while and "subsurface jets" occur for high density stratification. The physics causing the presence of surface jumps and subsurface jets is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/460783','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/460783"><span>Effect of conductivity between fasteners and aluminum skin on <span class="hlt">eddy</span> <span class="hlt">current</span> specimens</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Moore, D.G.; Hutchinson, M.C.</p> <p>1997-04-01</p> <p>The Federal Aviation Administration Airworthiness Assurance Nondestructive Inspection Validation Center (FAA-AANC) and Boeing Commercial Airplane Group are <span class="hlt">currently</span> developing a study pertaining to the detection of cracks in multi-layered aluminum sheets. The specimen panels model pertinent aspects of the lap splice joints for Boeing 737 aircraft, Line Numbers 292 - 2565. Upon initial characterization of the specimen panels, it became clear that signals produced from a sliding probe at fastener sites were not representative of an in-service lap splice, and therefore, could not be used in a probability of detection experiment. This paper discusses specimen characterization and steps taken to make the specimens useful for nondestructive technology assessment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JAP....86.6494B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JAP....86.6494B"><span>Time domain half-space dyadic Green's functions for <span class="hlt">eddy-current</span> calculations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bowler, J. R.</p> <p>1999-12-01</p> <p>The field due to an impulsive <span class="hlt">current</span> dipole embedded in a half-space conductor adjoining a nonconducting half space is given by an exact solution of the quasistatic field equations. This solution has been used to construct a half-space dyadic Green's function containing a term for an unbounded conductor plus terms representing the field reflected at the interface between conducting and nonconducting regions. The resulting kernel can be used in the formulation of time-dependent scattering problems to express the electric field in a conductor as an integral over an electric dipole distribution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1581.1352K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1581.1352K"><span>A pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> probe for inspection of support plates from within Alloy-800 steam generator tubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krause, T. W.; Babbar, V. K.; Underhill, P. R.</p> <p>2014-02-01</p> <p>Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhD...48s5002D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhD...48s5002D"><span>A model-based method for the characterisation of stress in magnetic materials using <span class="hlt">eddy</span> <span class="hlt">current</span> non-destructive evaluation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dahia, Abla; Berthelot, Eric; Le Bihan and, Yann; Daniel, Laurent</p> <p>2015-03-01</p> <p>A precise knowledge of the distribution of internal stresses in materials is key to the prediction of magnetic and mechanical performance and lifetime of many industrial devices. This is the reason why many efforts have been made to develop and enhance the techniques for the non-destructive evaluation of stress. In the case of magnetic materials, the use of <span class="hlt">eddy</span> <span class="hlt">current</span> (EC) techniques is a promising pathway to stress evaluation. The principle is based on the significant changes in magnetic permeability of magnetic materials subjected to mechanical stress. These modifications of magnetic permeability affect in turn the signal obtained from an EC probe inspecting the material. From this principle, a numerical tool is proposed in this paper to predict the EC signal obtained from a material subjected to stress. This numerical tool is a combination of a 3D finite element approach with a magneto-mechanical constitutive law describing the effect of stress on the magnetic permeability. The model provides the variations of impedance of an EC probe as a function of stress. An experimental setup in which a magnetic material subjected to a tension stress is inspected using EC techniques is tailored in order to validate the model. A very good agreement is found between experimental and modelling results. For the Iron-Cobalt alloy tested in this study, it is shown that a uniaxial tensile stress can be detected with an error lower than 3 MPa in the range from 0 to 100 MPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007MSSP...21..441D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007MSSP...21..441D"><span>Tool vibration detection with <span class="hlt">eddy</span> <span class="hlt">current</span> sensors in machining process and computation of stability lobes using fuzzy classifiers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Devillez, Arnaud; Dudzinski, Daniel</p> <p>2007-01-01</p> <p>Today the knowledge of a process is very important for engineers to find optimal combination of control parameters warranting productivity, quality and functioning without defects and failures. In our laboratory, we carry out research in the field of high speed machining with modelling, simulation and experimental approaches. The aim of our investigation is to develop a software allowing the cutting conditions optimisation to limit the number of predictive tests, and the process monitoring to prevent any trouble during machining operations. This software is based on models and experimental data sets which constitute the knowledge of the process. In this paper, we deal with the problem of vibrations occurring during a machining operation. These vibrations may cause some failures and defects to the process, like workpiece surface alteration and rapid tool wear. To measure on line the tool micro-movements, we equipped a lathe with a specific instrumentation using <span class="hlt">eddy</span> <span class="hlt">current</span> sensors. Obtained signals were correlated with surface finish and a signal processing algorithm was used to determine if a test is stable or unstable. Then, a fuzzy classification method was proposed to classify the tests in a space defined by the width of cut and the cutting speed. Finally, it was shown that the fuzzy classification takes into account of the measurements incertitude to compute the stability limit or stability lobes of the process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1806k0006U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1806k0006U"><span>Finite element model study of the effect of corner rounding on detectability of corner cracks using bolt hole <span class="hlt">eddy</span> <span class="hlt">current</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Underhill, P. R.; Krause, T. W.</p> <p>2017-02-01</p> <p>Recent work has shown that the detectability of corner cracks in bolt-holes is compromised when rounding of corners arises, as might occur during bolt-hole removal. Probability of Detection (POD) studies normally require a large number of samples of both fatigue cracks and electric discharge machined notches. In the particular instance of rounding of bolt-hole corners the generation of such a large set of samples representing the full spectrum of potential rounding would be prohibitive. In this paper, the application of Finite Element Method (FEM) modeling is used to supplement the study of detection of cracks forming at the rounded corners of bolt-holes. FEM models show that rounding of the corner of the bolt-hole reduces the size of the response to a corner crack to a greater extent than can be accounted for by loss of crack area. This reduced sensitivity can be ascribed to a lower concentration of <span class="hlt">eddy</span> <span class="hlt">currents</span> at the rounded corner surface and greater lift-off of pick-up coils relative to that of a straight-edge corner. A rounding with a radius of 0.4 mm (.016 inch) showed a 20% reduction in the strength of the crack signal. Assuming linearity of the crack signal with crack size, this would suggest an increase in the minimum detectable size by 25%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22263748','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22263748"><span>A pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> probe for inspection of support plates from within Alloy-800 steam generator tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Krause, T. W.; Babbar, V. K.; Underhill, P. R.</p> <p>2014-02-18</p> <p>Support plate degradation and fouling in nuclear steam generators (SGs) can lead to SG tube corrosion and loss of efficiency. Inspection and monitoring of these conditions can be integrated with preventive maintenance programs, thereby advancing station-life management processes. A prototype pulsed <span class="hlt">eddy</span> <span class="hlt">current</span> (PEC) probe, targeting inspection issues associated with SG tubes in SS410 tube support plate structures, has been developed using commercial finite element (FE) software. FE modeling was used to identify appropriate driver and pickup coil configurations for optimum sensitivity to changes in gap and offset for Alloy-800 SG tubes passing through 25 mm thick SS410 support plates. Experimental measurements using a probe that was manufactured based on the modeled configuration, were used to confirm the sensitivity of differential PEC signals to changes in relative position of the tube within the tube support plate holes. Models investigated the effect of shift and tilt of tube with respect to hole centers. Near hole centers and for small shifts, modeled signal amplitudes from the differentially connected coil pairs were observed to change linearly with tube shift. This was in agreement with experimentally measured TEC coil response. The work paves the way for development of a system targeting the inspection and evaluation of support plate structures in steam generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AIPC.1637.1416H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AIPC.1637.1416H"><span><span class="hlt">Eddy</span> <span class="hlt">current</span> modeling by finite element method for evaluation of mechanical properties of the structure cracked in absolute probe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Harzallah, Salaheddine; Chabaat, Mohamed; Belgacem, Fethi Bin Muhammad</p> <p>2014-12-01</p> <p>In this paper, a nondestructive evaluation by sensor <span class="hlt">Eddy</span> <span class="hlt">current</span> is used as a tool to control cracks and micro-cracks in materials. A simulation by a numerical approach based on the finite element method is employed to detect cracks in materials and eventually to study their propagation using a crucial parameter such as a Stress Intensity Factor (SIF). This method has emerged as one of the most efficient techniques for prospecting cracks in materials, evaluating SIFs and analyzing crack's growth in the context of linear elastic fracture mechanics (LEFM). This technique uses extrapolation of displacements from results compared with those obtained by the integral interaction. On the other hand, crack's growth is analyzed as a model by combining the maximum circumferential stress criteria with the critical plane for predicting the direction of crack growth. Moreover, a constant crack growth increment is determined using the modified Paris's model. Furthermore, stress intensity factors needed for these models are calculated using the domain form of the J-integral interactions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22069361','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22069361"><span>Diffusion <span class="hlt">current</span> in a system of <span class="hlt">coupled</span> Josephson junctions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shukrinov, Yu. M. Rahmonov, I. R.</p> <p>2012-08-15</p> <p>The role of a diffusion <span class="hlt">current</span> in the phase dynamics of a system of <span class="hlt">coupled</span> Josephson junctions (JJs) has been analyzed. It is shown that, by studying the temporal dependences of the superconducting, quasi-particle, diffusion, and displacement <span class="hlt">currents</span> and the dependences of average values of these <span class="hlt">currents</span> on the total <span class="hlt">current</span>, it is possible to explain the main features of the <span class="hlt">current</span>-voltage characteristic (CVC) of the system. The effect of a diffusion <span class="hlt">current</span> on the character of CVC branching in the vicinity of a critical <span class="hlt">current</span> and in the region of hysteresis, as well as on the part of CVC branch corresponding to a parametric resonance in the system is demonstrated. A clear interpretation of the differences in the character of CVC branching in a model of capacitively <span class="hlt">coupled</span> JJs (CCJJ model) and a model of capacitive <span class="hlt">coupling</span> with diffusion <span class="hlt">current</span> (CCJJ+DC model) is proposed. It is shown that a decrease in the diffusion <span class="hlt">current</span> in a JJ leads to the switching of this junction to an oscillating state. The results of model calculations are qualitatively consistent with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JETP..115..289S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JETP..115..289S"><span>Diffusion <span class="hlt">current</span> in a system of <span class="hlt">coupled</span> Josephson junctions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shukrinov, Yu. M.; Rahmonov, I. R.</p> <p>2012-08-01</p> <p>The role of a diffusion <span class="hlt">current</span> in the phase dynamics of a system of <span class="hlt">coupled</span> Josephson junctions (JJs) has been analyzed. It is shown that, by studying the temporal dependences of the superconducting, quasi-particle, diffusion, and displacement <span class="hlt">currents</span> and the dependences of average values of these <span class="hlt">currents</span> on the total <span class="hlt">current</span>, it is possible to explain the main features of the <span class="hlt">current</span>-voltage characteristic (CVC) of the system. The effect of a diffusion <span class="hlt">current</span> on the character of CVC branching in the vicinity of a critical <span class="hlt">current</span> and in the region of hysteresis, as well as on the part of CVC branch corresponding to a parametric resonance in the system is demonstrated. A clear interpretation of the differences in the character of CVC branching in a model of capacitively <span class="hlt">coupled</span> JJs (CCJJ model) and a model of capacitive <span class="hlt">coupling</span> with diffusion <span class="hlt">current</span> (CCJJ+DC model) is proposed. It is shown that a decrease in the diffusion <span class="hlt">current</span> in a JJ leads to the switching of this junction to an oscillating state. The results of model calculations are qualitatively consistent with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930000707&hterms=transformer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtransformer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930000707&hterms=transformer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dtransformer"><span>Direct-<span class="hlt">Current</span> Monitor With Flux-Reset Transformer <span class="hlt">Coupling</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Canter, Stanley</p> <p>1993-01-01</p> <p>Circuit measures constant or slowly-varying unidirectional electrical <span class="hlt">current</span> using flux-reset transformer <span class="hlt">coupling</span>. Measurement nonintrusive in sense that no need for direct contact with wire that carries load <span class="hlt">current</span> to be measured, and no need to install series resistive element in load-<span class="hlt">current</span> path. Toroidal magnetic core wrapped with coil of wire placed around load-<span class="hlt">current</span>-carrying wire, acts as transformer core, load-<span class="hlt">current</span>-carrying wire acts as primary winding of transformer, and coil wrapped on core acts as secondary winding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040034113&hterms=large+population&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dlarge%2Bpopulation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040034113&hterms=large+population&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dlarge%2Bpopulation"><span>Large- and Small-Scale Ring <span class="hlt">Current</span> Electrodynamic <span class="hlt">Coupling</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Khazanov, G. V.</p> <p>2003-01-01</p> <p>In this talk we will address the two primary issues of ring <span class="hlt">current</span> (RC) electrodynamic <span class="hlt">coupling</span>: 1. RC self-consistent magnetosphere-ionosphere <span class="hlt">coupling</span> that includes calculation of the magnetospheric electric field (large scale electrodynamic <span class="hlt">coupling</span>); and 2. RC self-consistent <span class="hlt">coupling</span> with electromagnetic ion cyclotron (EMIC) waves (small scale electrodynamic <span class="hlt">coupling</span>). Our study will be based on two RC models that we have recently developed in our group. The first model by Khazanov et al. [2002] <span class="hlt">couples</span> the system of two kinetic equations: one equation which describes the RC ion dynamics and another equation which describes the energy density evolution of EMIC waves. The second model by Khazanov et al. [2003] deals with large scale electrodynamic <span class="hlt">coupling</span> processes and provides a self-consistent simulation of RC ions and the magnetospheric electric field. There is presently no model that addresses both of these issues simultaneously in a self-consistent calculation. However, the need exists for such a model, because these two processes directly influence each other, with the mesoscale <span class="hlt">coupling</span> changing the drift paths of the thermal and energetic particle populations in the inner magnetosphere, thereby changing the wave interactions, and the microscale <span class="hlt">coupling</span> altering the pitch angle distributions and ionospheric conductivities (through increased precipitation), thus changing the field-aligned <span class="hlt">currents</span> and electric potential structure. The initial thrust of the work will be the development of a combined kinetic model of micro- and meso-scale RC electrodynamic <span class="hlt">coupling</span> processes and to examine their interactions with each other on a global scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA587071','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA587071"><span>An <span class="hlt">Eddy</span>-Resolving Ocean Reanalysis using the 1/12 degree Global HYbrid Coordinate Ocean Model (HYCOM) and the Navy <span class="hlt">Coupled</span> Ocean Data Assimilation (NCODA) Scheme</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2013-05-01</p> <p>research opportunities 2 HYbrid Coordinate Ocean Model 3 Tri-pole latitudinal grid resolution (km) Mercator projection : 66°S to 47°N Curvi...Data Assimilation (NCODA) scheme 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER...capable of fully resolving oceanic mesoscale features (<span class="hlt">eddies</span> and <span class="hlt">current</span> meanders) across the globe • This project addresses the need for a long</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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