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

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.; Simpson, John

2010-01-01

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

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

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.

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.

Eddy current testing probe with dual half-cylindrical coils

NASA Astrophysics Data System (ADS)

Bae, Byung-Hoon; Choi, Jung-Mi; Kim, Soo-Yong

2000-02-01

We have developed a new eddy current probe composed of a dual half-cylindrical (2HC) coil as an exciting coil and a sensing coil that is placed in the small gap of the 2HC coil. The 2HC coil induces a linear eddy current on the narrow region within the target medium. The magnitude of eddy current has a maximum peak with the narrow width, underneath the center of the exciting 2HC coil. Because of the linear eddy current, the probe can be used to detect not only the existence of a crack but also its direction in conducting materials. Using specimen with a machined crack, and varying the exciting frequency from 0.5 to 100 kHz, we investigated the relationships between the direction of crack and the output voltage of the sensing coil.

Eddy Current Sensing of Torque in Rotating Shafts

NASA Astrophysics Data System (ADS)

Varonis, Orestes J.; Ida, Nathan

2013-12-01

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

Theory and application of high temperature superconducting eddy current probes for nondestructive evaluation

NASA Astrophysics Data System (ADS)

Claycomb, James Ronald

1998-10-01

Several High-T c Superconducting (HTS) eddy current probes have been developed for applications in electromagnetic nondestructive evaluation (NDE) of conducting materials. The probes utilize high-T c SUperconducting Quantum Interference Device (SQUID) magnetometers to detect the fields produced by the perturbation of induced eddy currents resulting from subsurface flaws. Localized HTS shields are incorporated to selectively screen out environmental electromagnetic interference and enable movement of the instrument in the Earth's magnetic field. High permeability magnetic shields are employed to focus flux into, and thereby increase the eddy current density in the metallic test samples. NDE test results are presented, in which machined flaws in aluminum alloy are detected by probes of different design. A novel current injection technique performing NDE of wires using SQUIDs is also discussed. The HTS and high permeability shields are designed based on analytical and numerical finite element method (FEM) calculations presented here. Superconducting and high permeability magnetic shields are modeled in uniform noise fields and in the presence of dipole fields characteristic of flaw signals. Several shield designs are characterized in terms of (1) their ability to screen out uniform background noise fields; (2) the resultant improvement in signal-to-noise ratio and (3) the extent to which dipole source fields are distorted. An analysis of eddy current induction is then presented for low frequency SQUID NDE. Analytical expressions are developed for the induced eddy currents and resulting magnetic fields produced by excitation sources above conducting plates of varying thickness. The expressions derived here are used to model the SQUID's response to material thinning. An analytical defect model is also developed, taking into account the attenuation of the defect field through the conducting material, as well as the current flow around the edges of the flaw. Time harmonic FEM calculations are then used to model the electromagnetic response of eight probe designs, consisting of an eddy current drive coil coupled to a SQUID surrounded by superconducting and/or high permeability magnetic shielding. Simulations are carried out with the eddy current probes located a finite distance above a conducting surface. Results are quantified in terms of shielding and focus factors for each probe design.

Eddy-Current Probes For Inspecting Graphite-Fiber Composites

NASA Technical Reports Server (NTRS)

Workman, Gary L.; Wang, Morgan

1992-01-01

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

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

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Determining Confounding Sensitivities In Eddy Current Thin Film Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

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.

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.

Development of eddy current probe for fiber orientation assessment in carbon fiber composites

NASA Astrophysics Data System (ADS)

Wincheski, Russell A.; Zhao, Selina

2018-04-01

Measurement of the fiber orientation in a carbon fiber composite material is crucial in understanding the load carrying capability of the structure. As manufacturing conditions including resin flow and molding pressures can alter fiber orientation, verification of the as-designed fiber layup is necessary to ensure optimal performance of the structure. In this work, the development of an eddy current probe and data processing technique for analysis of fiber orientation in carbon fiber composites is presented. A proposed directional eddy current probe is modeled and its response to an anisotropic multi-layer conductor simulated. The modeling results are then used to finalize specifications of the eddy current probe. Experimental testing of the fabricated probe is presented for several samples including a truncated pyramid part with complex fiber orientation draped to the geometry for resin transfer molding. The inductively coupled single sided measurement enables fiber orientation characterization through the thickness of the part. The fast and cost-effective technique can be applied as a spot check or as a surface map of the fiber orientations across the structure. This paper will detail the results of the probe design, computer simulations, and experimental results.

Noncontact Measurement Of Sizes And Eccentricities Of Holes

NASA Technical Reports Server (NTRS)

Chern, Engmin J.

1993-01-01

Semiautomatic eddy-current-probe apparatus makes noncontact measurements of nominally round holes in electrically conductive specimens and processes measurement data into diameters and eccentricities of holes. Includes x-y translation platform, which holds specimen and moves it horizontally. Probe mounted on probe scanner, positioning probe along vertical (z) direction and rotates probe about vertical axis at preset low speed. Eddy-current sensing coil mounted in side of probe near tip. As probe rotates, impedance analyzer measures electrical impedance (Z) of coil as function of instantaneous rotation angle. Translation and rotation mechanisms and impedance analyzer controlled by computer, which also processes impedance-measurement data.

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.

Enhanced Eddy-Current Detection Of Weld Flaws

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

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.

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.

Analysis of Eddy Current Capabilities for the Detection of Outer Diameter Stress Corrosion Cracking in Small Bore Metallic Structures

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Williams, Phillip; Simpson, John

2007-01-01

The use of eddy current 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 eddy current 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 eddy current 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.

Electromechanical Apparatus Measures Residual Stress

NASA Technical Reports Server (NTRS)

Chern, Engmin J.; Flom, Yury

1993-01-01

Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.

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.

Determination of plasma displacement based on eddy current diagnostics for the Keda Torus eXperiment

NASA Astrophysics Data System (ADS)

Tu, Cui; Li, Hong; Liu, Adi; Li, Zichao; Zhang, Yuan; You, Wei; Tan, Mingsheng; Luo, Bing; Adil, Yolbarsop; Hu, Jintong; Wu, Yanqi; Yan, Wentan; Xie, Jinlin; Lan, Tao; Mao, Wenzhe; Ding, Weixing; Xiao, Chijin; Zhuang, Ge; Liu, Wandong

2017-10-01

The measurement of plasma displacement is one of the most basic diagnostic tools in the study of plasma equilibrium and control in a toroidal magnetic confinement configuration. During pulse discharge, the eddy current induced in the vacuum vessel and shell will produce an additional magnetic field at the plasma boundary, which will have a significant impact on the measurement of plasma displacement using magnetic probes. In the newly built Keda Torus eXperiment (KTX) reversed field pinch device, the eddy current in the composite shell can be obtained at a high spatial resolution. This device offers a new way to determine the plasma displacement for KTX through the multipole moment expansion of the eddy current, which can be obtained by unique probe arrays installed on the inner and outer surfaces of the composite shell. In an ideal conductor shell approximation, the method of multipole moment expansion of the poloidal eddy current for measuring the plasma displacement in toroidal coordinates, is more accurate than the previous method based on symmetrical magnetic probes, which yielded results in cylindrical coordinates. Through an analytical analysis of many current filaments and numerical simulations of the current distribution in toroidal coordinates, the scaling relation between the first moment of the eddy current and the center of gravity of the plasma current is obtained. In addition, the origin of the multipole moment expansion of the eddy current in KTX is retrieved simultaneously. Preliminary data on the plasma displacement have been collected using these two methods during short pulse discharges in the KTX device, and the results of the two methods are in reasonable agreement.

Detection of Fatigue Cracks at Rivets with Self-Nulling Probe

NASA Technical Reports Server (NTRS)

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

1994-01-01

A new eddy current probe developed at NASA Langley Research Center has been used to detect small cracks at rivets in aircraft lap splices [1]. The device has earlier been used to detect isolated fatigue cracks with a minimum detectable flaw size of roughly 1/2 to 1/3 the diameter of the probe [2]. The present work shows that the detectable flaw size for cracks originating at rivets can be greatly improved upon from that of isolated flaws. The use of a rotating probe method combined with spatial filtering has been used to detect 0.18 cm EDM notches, as measured from the rivet shank, with a 1.27 cm diameter probe and to detect flaws buried under the rivet head, down to a length of 0.076 cm, using a 0.32 cm diameter probe. The Self-Nulling Electromagnetic Flaw Detector induces a high density eddy current ring in the sample under test. A ferromagnetic flux focusing lens is incorporated such that in the absence of any inhomogeneities in the material under test only a minimal magnetic field will reach the interior of the probe. A magnetometer (pickup coil) located in the center of the probe therefore registers a null voltage in the absence of material defects. When a fatigue crack or other discontinuity is present in the test article the path of the eddy currents in the material is changed. The magnetic field associated with these eddy currents then enter into the interior of the probe, producing a large output voltage across the pickup coil leads. Further

A Steel Ball Surface Quality Inspection Method Based on a Circumferential Eddy Current Array Sensor.

PubMed

Zhang, Huayu; Xie, Fengqin; Cao, Maoyong; Zhong, Mingming

2017-07-01

To efficiently inspect surface defects on steel ball bearings, a new method based on a circumferential eddy current array (CECA) sensor was proposed here. The best probe configuration, in terms of the coil quality factor (Q-factor), magnetic field intensity, and induced eddy current density on the surface of a sample steel ball, was determined using 3-, 4-, 5-, and 6-coil probes, for analysis and comparison. The optimal lift-off from the measured steel ball, the number of probe coils, and the frequency of excitation current suitable for steel ball inspection were obtained. Using the resulting CECA sensor to inspect 46,126 steel balls showed a miss rate of ~0.02%. The sensor was inspected for surface defects as small as 0.05 mm in width and 0.1 mm in depth.

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.

Eddy Current Assessment of Engineered Components Containing Nanofibers

NASA Astrophysics Data System (ADS)

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

2009-03-01

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

Eddy current probe response to open and closed surface flaws

NASA Technical Reports Server (NTRS)

Auld, B. A.; Muennemann, F.; Winslow, D. K.

1981-01-01

A general analysis of eddy current response to certain types of open and closed surface flaws is presented for both standard low-frequency and ferromagnetic-resonance (FMR) probes. It is shown analytically that for two-dimensional and three-dimensional surface flaws interrogated by a uniform probe field, the crack opening sensitivity increases with the operating frequency of the probe, this behavior being due to the Faraday induction effect. Experiments with low-frequency probes operating at or below 1 MHz and with the FMR probe operating at approximately 1000 MHz confirm this increase of the crack mouth opening displacement for practical situations where the probe field is not uniform in the vicinity of the flaw.

Eddy-Current Measurement Of Turning Or Curvature

NASA Technical Reports Server (NTRS)

Chern, Engmin J.

1993-01-01

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

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.

Pulsed Eddy Current Probe Design Based on Transient Circuit Analysis

NASA Astrophysics Data System (ADS)

Cadeau, Trevor J.; Krause, Thomas W.

2009-03-01

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

Eddy current position indicating apparatus for measuring displacements of core components of a liquid metal nuclear reactor

DOEpatents

Day, Clifford K.; Stringer, James L.

1977-01-01

Apparatus for measuring displacements of core components of a liquid metal fast breeder reactor by means of an eddy current 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.

Rotating concave eddy current probe

DOEpatents

Roach, Dennis P [Albuquerque, NM; Walkington, Phil [Albuquerque, NM; Rackow, Kirk A [Albuquerque, NM; Hohman, Ed [Albuquerque, NM

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.

Self-Nulling Eddy Current Probe for Surface and Subsurface Flaw Detection

NASA Technical Reports Server (NTRS)

Wincheski, B.; Fulton, J. P.; Nath, S.; Namkung, M.; Simpson, J. W.

1994-01-01

An eddy current probe which provides a null-signal in the presence of unflawed material without the need for any balancing circuitry has been developed at NASA Langley Research Center. Such a unique capability of the probe reduces set-up time, eliminates tester configuration errors, and decreases instrumentation requirements. The probe is highly sensitive to surface breaking fatigue cracks, and shows excellent resolution for the measurement of material thickness, including material loss due to corrosion damage. The presence of flaws in the material under test causes an increase in the extremely stable and reproducible output voltage of the probe. The design of the probe and some examples illustrating its flaw detection capabilities are presented.

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.

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.

Eddy-Current Detection of Cracks in Tubes

NASA Technical Reports Server (NTRS)

Parent, R.; Kettering, D.

1987-01-01

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

Characteristics of Ferromagnetic Flux Focusing Lens in the Development of Surface/Subsurface Flaw Detector

NASA Technical Reports Server (NTRS)

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

1993-01-01

Electromagnetic NDE techniques have in the past steered away from the use of ferromagnetic materials. Although their high permeabilities lead to increased field levels, the properties of ferrous elements in the presence of alternating magnetic fields are difficult to determine. In addition, their use leads to losses which can be minimized through the use of low conductivity ferrites. In fact, the eddy current probes which do incorporate ferromagnetic materials have focused on these losses and the shielding which can be obtained by surrounding a probe with a high permeability, conducting material. Eddy current probes enclosed in conducting and magnetic shields have been used to prevent the generated fields from interacting with materials in the vicinity of the probe, such as when testing near material boundaries. A recent invention has used ferromagnetic shielding to magnetically separate individual concentric eddy current probes in order to eliminate cross-talk between the probes so that simultaneous detection of different types of flaws at different depths can be achieved. In contrast to the previous uses of ferromagnetic materials purely as magnetic shields, an electromagnetic flaw detector recently developed at NASA Langley Research Center takes advantage of the flux focusing properties of a ferromagnetic mild steel in order to produce a simple, effective device for the non-destructive evaluation of conducting materials. The Flux Focusing Eddy Current Probe has been shown to accurately measure material thickness and fatigue damage. The straight forward flaw response of the probe makes the device ideal for rapid inspection of large structures, and has lead to its incorporation in a computer controlled search routine to locate fatigue crack tips and monitor experimental fatigue crack growth experiments.

Determination of eddy current response with magnetic measurements.

PubMed

Jiang, Y Z; Tan, Y; Gao, Z; Nakamura, K; Liu, W B; Wang, S Z; Zhong, H; Wang, B B

2017-09-01

Accurate mutual inductances between magnetic diagnostics and poloidal field coils are an essential requirement for determining the poloidal flux for plasma equilibrium reconstruction. The mutual inductance calibration of the flux loops and magnetic probes requires time-varying coil currents, which also simultaneously drive eddy currents in electrically conducting structures. The eddy current-induced field appearing in the magnetic measurements can substantially increase the calibration error in the model if the eddy currents are neglected. In this paper, an expression of the magnetic diagnostic response to the coil currents is used to calibrate the mutual inductances, estimate the conductor time constant, and predict the eddy currents response. It is found that the eddy current effects in magnetic signals can be well-explained by the eddy current response determination. A set of experiments using a specially shaped saddle coil diagnostic are conducted to measure the SUNIST-like eddy current response and to examine the accuracy of this method. In shots that include plasmas, this approach can more accurately determine the plasma-related response in the magnetic signals by eliminating the field due to the eddy currents produced by the external field.

A wide linear range Eddy Current Displacement Sensor equipped with dual-coil probe applied in the Magnetic Suspension Flywheel.

PubMed

Fang, Jiancheng; Wen, Tong

2012-01-01

The Eddy Current 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 eddy current 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.

Detection of Cracks at Welds in Steel Tubing Using Flux Focusing Electromagnetic Probe

NASA Technical Reports Server (NTRS)

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

1994-01-01

The inspection of weldments in critical pressure vessel joints is a major concern in the nuclear power industry. Corrosive environments can speed the fatigue process and access to the critical area is often limited. Eddy current techniques have begun to be used to help overcome these obstacles [1]. As direct contact and couplants are not required, remote areas can be inspected by simply snaking an eddy current coil into the intake tube of the vessel. The drawback of the eddy current method has been the high sensitivity to small changes in the conductivity and permeability of the test piece which are known to vary at weldments [1]. The flaw detection mechanism of the flux focusing electromagnetic probe can help alleviate these difficulties and provide a unique capability for detecting longitudinal fatigue cracks in critical tube structures. The Flux Focusing Electromagnetic Flaw Detector, originally invented for the detection of fatigue and corrosion damage in aluminum plates [2-3], has been adapted for use in testing steel tubing for longitudinal fatigue cracks. The modified design allows for the probe to be placed axisymmetrically into the tubing, inducing eddy currents in the tube wall. The pickup coil of the probe is fixed slightly below the primary windings and is rotated 90 so that its axis is normal to the tube wall. The magnetic flux of the primary coil is focused through the use of ferromagnetic material so that in the absence of fatigue damage there will be no flux linkage with the pickup coil. The presence of a longitudinal fatigue crack will cause the eddy currents induced in the tube wall to flow around the flaw and directly under the pickup coil. The magnetic field associated with these currents will then link the pickup coil and an unambiguous increase in the output voltage of the probe will be measured. The use of the flux focusing electromagnetic probe is especially suited for the detection of flaws originating at or near tube welds. The probe is shown to discriminate against signals due solely to the weld joint so that flaw signals are not hidden in the background in these locations. Experimental and finite element modeling results are presented for the flaw detection capabilities of the probe in stainless steel tubes.

Temperature sensitivity study of eddy current and digital gauge probes for nuclear fuel rod oxide measurement

NASA Astrophysics Data System (ADS)

Beck, Faith R.; Lind, R. Paul; Smith, James A.

2018-04-01

Novel fuels are part of the nationwide effort to reduce the enrichment of Uranium for energy production. Performance of such fuels is determined by irradiating their surfaces. To test irradiated samples, the instrumentation must operate remotely. The plate checker used in this experiment at Idaho National Lab (INL) performs non-destructive testing on fuel rod and plate geometries with two different types of sensors: eddy current and digital thickness gauges. The sensors measure oxide growth and total sample thickness on research fuels, respectively. Sensor measurement accuracy is crucial because even 10 microns of error is significant when determining the viability of an experimental fuel. One parameter known to affect the eddy current and thickness gauge sensors is temperature. Since both sensor accuracies depend on the ambient temperature of the system, the plate checker has been characterized for these sensitivities. The manufacturer of the digital gauge probes has noted a rather large coefficient of thermal expansion for their linear scale. It should also be noted that the accuracy of the digital gauge probes are specified at 20°C, which is approximately 7°C cooler than the average hot-cell temperature. In this work, the effect of temperature on the eddy current and digital gauge probes is studied, and thickness measurements are given as empirical functions of temperature.

Simplified Numerical Analysis of ECT Probe - Eddy Current Benchmark Problem 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sikora, R.; Chady, T.; Gratkowski, S.

2005-04-09

In this paper a third eddy current benchmark problem is considered. The objective of the benchmark is to determine optimal operating frequency and size of the pancake coil designated for testing tubes made of Inconel. It can be achieved by maximization of the change in impedance of the coil due to a flaw. Approximation functions of the probe (coil) characteristic were developed and used in order to reduce number of required calculations. It results in significant speed up of the optimization process. An optimal testing frequency and size of the probe were achieved as a final result of the calculation.

Computer programs for eddy-current defect studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 aremore » 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.« less

Comprehensive characterization of measurement data gathered by the pressure tube to calandria tube gap probe

NASA Astrophysics Data System (ADS)

Shokralla, Shaddy Samir Zaki

Multi-frequency eddy current measurements are employed in estimating pressure tube (PT) to calandria tube (CT) gap in CANDU fuel channels, a critical inspection activity required to ensure fitness for service of fuel channels. In this thesis, a comprehensive characterization of eddy current gap data is laid out, in order to extract further information on fuel channel condition, and to identify generalized applications for multi-frequency eddy current data. A surface profiling technique, generalizable to multiple probe and conductive material configurations has been developed. This technique has allowed for identification of various pressure tube artefacts, has been independently validated (using ultrasonic measurements), and has been deployed and commissioned at Ontario Power Generation. Dodd and Deeds solutions to the electromagnetic boundary value problem associated with the PT to CT gap probe configuration were experimentally validated for amplitude response to changes in gap. Using the validated Dodd and Deeds solutions, principal components analysis (PCA) has been employed to identify independence and redundancies in multi-frequency eddy current data. This has allowed for an enhanced visualization of factors affecting gap measurement. Results of the PCA of simulation data are consistent with the skin depth equation, and are validated against PCA of physical experiments. Finally, compressed data acquisition has been realized, allowing faster data acquisition for multi-frequency eddy current systems with hardware limitations, and is generalizable to other applications where real time acquisition of large data sets is prohibitive.

Development of Eddy Current Techniques for Detection of Deep Fatigue Cracks in Multi-Layer Airframe Components

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.

2008-01-01

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 Eddy current techniques can be applied on in-service aircraft from the exterior of the skin without knowing sealant condition, the current eddy current techniques are not able to detect defects with wanted sensitivity. In this work a series of low frequency eddy current 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.

Eddy-Current Monitoring Of Composite Layups

NASA Technical Reports Server (NTRS)

Fox, Robert L.; Buckley, John D.

1993-01-01

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

Probing of multiple magnetic responses in magnetic inductors using atomic force microscopy.

PubMed

Park, Seongjae; Seo, Hosung; Seol, Daehee; Yoon, Young-Hwan; Kim, Mi Yang; Kim, Yunseok

2016-02-08

Even though nanoscale analysis of magnetic properties is of significant interest, probing methods are relatively less developed compared to the significance of the technique, which has multiple potential applications. Here, we demonstrate an approach for probing various magnetic properties associated with eddy current, coil current and magnetic domains in magnetic inductors using multidimensional magnetic force microscopy (MMFM). The MMFM images provide combined magnetic responses from the three different origins, however, each contribution to the MMFM response can be differentiated through analysis based on the bias dependence of the response. In particular, the bias dependent MMFM images show locally different eddy current behavior with values dependent on the type of materials that comprise the MI. This approach for probing magnetic responses can be further extended to the analysis of local physical features.

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..

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.

New type of eddy current sensor for large-displacement test

NASA Astrophysics Data System (ADS)

Pan, Haifeng; Zhu, Huizhong; Fu, Zhibin; Xu, Yuzheng; Feng, Guanping

2001-09-01

In this paper a new type of large displacement eddy current sensor is developed to overcome the three main disadvantages of the traditional eddy current senor. For a traditional sensor, the measurement range is limited and less than one half of the diameter of the measuring coil. The output is high sensitivity to the changes of the target material and the cable length connected between the probe and the preamplifier. When the material or the cable length changed, it is necessary to readjust the preamplifier. The probe of the new eddy current sensor has three coaxial measuring coils, one is an exciting coil and the other two are receiving coils. The diameter of measuring coils is (Phi) 11 mm. The measurement range of this sensor is 40mm and almost four times of the diameter of the coil. The form of differential input and feedback amplification is used in signal amplifier. Thus the effect of the common modules, such as the changes of the target material and the cable length, can be counteracted well.

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.

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.

Correlation of eddy current responses between fatigue cracks and electrical-discharge-machining notches

NASA Astrophysics Data System (ADS)

Seo, Sukho; Choi, Gyudong; Eom, Tae Jhoun; Lee, Bokwon; Lee, Soo Yeol

2017-07-01

The eddy current responses of Electrical Discharge Machining (EDM) notches and fatigue cracks are directly compared to verify the reliability of eddy current inspection. The fatigue crack growth tests using a constant load range control mode were conducted to obtain a variety of edge crack sizes, ranging from 0.9 to 6.6 mm for Al alloy and from 0.1 to 3 mm for Ti alloy. EDM notch specimens of Al and Ti alloys were accordingly prepared in lengths similar to that of the fatigued specimen. The crack length was determined by optical microscope and scanning electron microscope. The eddy current responses between the EDM and fatigued specimens with varying notch/crack length were examined using probe sensors at (100-500) kHz and (1-2) MHz for Al and Ti alloys, respectively. The results show a significant difference in the eddy current signal between the two specimens, based on the correlation between the eddy current response and notch/crack length. This suggests that eddy current inspection using the EDM reference specimen is inaccurate in determining the precise crack size, unless the eddy current response data base is obtained from a fatigue-cracked specimen.

Measurement of eddy-current distribution in the vacuum vessel of the Sino-UNIted Spherical Tokamak.

PubMed

Li, G; Tan, Y; Liu, Y Q

2015-08-01

Eddy currents 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 eddy currents are more complex than those found in a standard tokamak. Thus, it is necessary to measure and analyze the eddy-current distribution. In this study, we propose an experimental method for measuring the eddy-current 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 eddy current 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 eddy-current distribution despite the presence of the magnetic field generated by the external coils.

Transmit-receive eddy current probes for defect detection and sizing in steam generator tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obrutsky, L.S.; Cecco, V.S.; Sullivan, S.P.

1997-02-01

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 eddy current bobbin probes, is ineffectual inmore » 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 eddy current 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.« less

NONDESTRUCTIVE EDDY CURRENT TESTING

DOEpatents

Renken, C.J. Jr.

1961-05-23

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

Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Endo, H.; Uchimoto, T.; Takagi, T.

2006-03-06

An eddy current testing (ECT) system with multi-coil type probes is applied to size up cracks fabricated on austenite stainless plates. We have developed muti-channel ECT system to produce data as digital images. The probes consist of transmit-receive type sensors as elements to classify crack directions, working as two scan direction modes simultaneously. Template matching applied to the ECT images determines regions of interest in sizing up cracks. Finite element based inversion sizes up the crack depth from the measured ECT signal. The present paper demonstrates this approach for fatigue crack and stress corrosion cracking.

Eddy current sensing of intermetallic composite consolidation

NASA Technical Reports Server (NTRS)

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

1991-01-01

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

Development of Eddy Current Techniques for the Detection of Cracking in Space Shuttle Primary Reaction Control Thrusters

NASA Technical Reports Server (NTRS)

Wincheski, Buzz A.; Simpson, John W.; Koshti, Ajay

2007-01-01

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 eddy current 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 eddy current 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 eddy current 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.

Development of Eddy Current Technique for the Detection of Stress Corrosion Cracking in Space Shuttle Primary Reaction Control Thrusters

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Simpson, John; Koshti, Ajay

2006-01-01

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 eddy current 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 eddy current 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 eddy current 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.

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

NASA Astrophysics Data System (ADS)

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

2011-04-01

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

Analytical model of tilted driver–pickup coils for eddy current nondestructive evaluation

NASA Astrophysics Data System (ADS)

Cao, Bing-Hua; Li, Chao; Fan, Meng-Bao; Ye, Bo; Tian, Gui-Yun

2018-03-01

A driver-pickup probe possesses better sensitivity and flexibility due to individual optimization of a coil. It is frequently observed in an eddy current (EC) array probe. In this work, a tilted non-coaxial driver-pickup probe above a multilayered conducting plate is analytically modeled with spatial transformation for eddy current nondestructive evaluation. Basically, the core of the formulation is to obtain the projection of magnetic vector potential (MVP) from the driver coil onto the vector along the tilted pickup coil, which is divided into two key steps. The first step is to make a projection of MVP along the pickup coil onto a horizontal plane, and the second one is to build the relationship between the projected MVP and the MVP along the driver coil. Afterwards, an analytical model for the case of a layered plate is established with the reflection and transmission theory of electromagnetic fields. The calculated values from the resulting model indicate good agreement with those from the finite element model (FEM) and experiments, which validates the developed analytical model. Project supported by the National Natural Science Foundation of China (Grant Nos. 61701500, 51677187, and 51465024).

Electromagnetic Detection of Fatigue Cracks under Protruding Head Ferromagnetic Fasteners

NASA Technical Reports Server (NTRS)

Wincheski, Buzz; Namkung, Min

2004-01-01

The detection of fatigue cracks under installed fasteners has been a major goal of the aging aircraft NDE community. The Sliding Probe, Magneto-Optic Imager, Rotating Self-Nulling Probe, Low Frequency Eddy Current Array, and Eddyscan systems are among the instruments developed for this inspection. It has been verified that the detection of fatigue cracks under flush head aluminum and titanium fasteners can be accomplished with a high resolution by the above techniques. The detection of fatigue cracks under ferromagnetic and protruding head fasteners, however, has been found to be much more difficult. For the present work, the inspection for fatigue cracks under SAE 4340 Steel Hi-Lok fasteners is explored. Modifications to the Rotating Self-Nulling Eddy Current Probe System are presented which enable the detection of fatigue cracks hidden under the protruding head of the ferromagnetic fastener. Inspection results for samples with varying length EDM notches are shown, as well as a comparison between the signature from an EDM notch and an actual fatigue crack. Finite Element Modeling is used to investigate the effect of the ferromagnetic fastener on the induced eddy current distribution in order to help explain the detection characteristics of the system. This paper will also introduce a modification to the Rotating Probe System designed specifically for the detection of deeply buried flaws in multilayer conductors. The design change incorporates a giant magnetoresistive (GMR) sensor as the pickup device to improve the low frequency performance of the probe. The flaw detection capabilities of the GMR based Self- Nulling Probe are presented along with the status of the GMR based Rotating Probe System for detection of deeply buried flaws under installed fasteners.

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Eddy current analysis of cracks grown from surface defects and non-metallic particles

NASA Astrophysics Data System (ADS)

Cherry, Matthew R.; Hutson, Alisha; Aldrin, John C.; Shank, Jared

2018-04-01

Eddy current methods are sensitive to any discrete change in conductivity. Traditionally this has been used to determine the presence of a crack. However, other features that are not cracks such as non-metallic inclusions, carbide stringers and surface voids can cause an eddy current indication that could potentially lead to a reject of an in-service component. These features may not actually be lifelimiting, meaning NDE methods could reject components with remaining useful life. In-depth analysis of signals from eddy current sensors could provide a means of sorting between rejectable indications and false-calls from geometric and non-conductive features. In this project, cracks were grown from voids and non-metallic inclusions in a nickel-based super-alloy and eddy current analysis was performed on multiple intermediate steps of fatigue. Data were collected with multiple different ECT probes and at multiple frequencies, and the results were analyzed. The results show how cracks growing from non-metallic features can skew eddy current signals and make characterization a challenge. Modeling and simulation was performed with multiple analysis codes, and the models were found to be in good agreement with the data for cracks growing away from voids and non-metallic inclusions.

Eddy current proximity measurement of perpendicular tubes from within pressure tubes in CANDU nuclear reactors

NASA Astrophysics Data System (ADS)

Bennett, P. F. D.; Underhill, P. R.; Morelli, J.; Krause, T. W.

2018-04-01

Fuel channels in CANDU® (CANada Deuterium Uranium) nuclear reactors consist of two non-concentric tubes; an inner pressure tube (PT) and a larger diameter calandria tube (CT). Up to 400 horizontally mounted fuel channels are contained within a calandria vessel, which also holds the heavy water moderator. Certain fuel channels pass perpendicularly over horizontally oriented tubes (nozzles) that are part of the reactor's liquid injection shutdown system (LISS). Due to sag, these fuel channels are at risk of coming into contact with the LISS nozzles. In the event of contact between the LISS nozzle and CT, flow-induced vibrations from within the moderator could lead to fretting and deformation of the CT. LISS nozzle proximity to CTs is currently measured optically from within the calandria vessel, but from outside the fuel channels. Measurement by an independent means would provide confidence in optical results and supplement cases where optical observations are not possible. Separation of PT and CT, known as gap, is monitored from within the PT using a transmit-receive eddy current probe. Investigation of the eddy current based gap probe as a tool to also measure proximity of LISS nozzles was carried out experimentally in this work. Eddy current response as a function of LISS-PT proximity was recorded. When PT-CT gap, PT wall thickness, PT resistivity and probe lift-off variations were not present this dependence could be used to determine the LISS-PT proximity. This method has the potential to provide LISS-CT proximity using existing gap measurement data. Obtaining LISS nozzle proximity at multiple inspection intervals could be used to provide an estimate of the time to LISS-CT contact, and thereby provide a means of optimizing maintenance schedules.

Eddy Current Testing for Detecting Small Defects in Thin Films

NASA Astrophysics Data System (ADS)

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

2007-03-01

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

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.

Electromagnetic microscope compared with a conventional pulsed eddy-current probe

NASA Astrophysics Data System (ADS)

Podney, Walter N.

1998-03-01

A superconductive probe presently can detect a crack at a rivet hole that is two to three times smaller than the smallest crack detectable by a conventional probe. As the technology matures and noise resolution approaches a limit set by SQUIDS, approximately 1 fH, it will enable detecting submillimeter cracks down to approximately 15 mm.

Subminiature eddy current transducers for studying metal- dielectric junctions

NASA Astrophysics Data System (ADS)

Dmitriev, S.; Katasonov, A.; Malikov, V.; Sagalakov, A.; Davydchenko, M.; Shevtsova, L.; Ishkov, A.

2016-11-01

Based on an eddy current transducer (ECT), a probe has been designed to research metal-dielectric structures. The measurement procedure allowing one to detect defects in laminate composites with a high accuracy is described. The transducer was tested on the layered structure consisting of paper and aluminum layers with a thickness of 100 μm each in which the model defect was placed. The dependences of the ECT signal on the defect in this structure are given.

Evaluation of the Self-Nulling Rotating Eddy Current Probe System

NASA Technical Reports Server (NTRS)

Hagemaier, Don; Rengel, Kent; Wincheski, Buzz; Namkung, Min

1999-01-01

In order to detect multi-site fatigue cracks located under flush-head rivets, automated eddy current equipment is required. To assure a reliable system, the eddy current probe must be centered easily over the installed rivets. To meet these requirements, the NDE Group at NASA LaRC developed the Self-Nulling Rotating Eddy Current Probe System (SNRECPS) which will be referred to as RPS in this document. The system was evaluated at the FAA, NDI Validation Center, in Albuquerque, New Mexico. The system was capable of detecting a 0.032 inch long crack with a 90/95% PoD. Further evaluations were conducted at Boeing in Long Beach, California. These evaluations included fatigue cracks and notches in a range from 0.025 to 0.100 inch long under flush-head aluminum rivets, and titanium or steel flush-head fasteners. The results of these tests are reported herein. Subsequently, the system was loaned to the USAF Structures Laboratory for the purpose of detecting and measuring short cracks under flush-head rivets in a variety of fatigue test specimens. The inspection task was to detect and plot crack growth from numbered fasteners in lettered rows. In January, 1998, the system was taken to Northwest Airlines Maintenance Base, in Atlanta, to inspect a DC-9, for multi-site cracks in three circumferential splices. The aircraft had 83,000 cycles. The inspection was conducted at 30 kHz from longeron 5 left to longeron 5 right. The system was calibrated using a 0,030 EDM first layer notch. The instrument gain was set to 19 mV from the notch. The reject level was set at 10 mV and the unflawed fasteners yielded a signal amplitude of 2 to 3 mV. Only one fastener location, out of about 2,500 tested, yielded a signal of 58 mV. The rivet was removed and visually evaluated. It appeared to be a slight gouge in the counter-sink zone. No fatigue cracks were detected. The same fastener locations were also inspected using the Boeing MAUS system at 60 kHz. No cracks were detected. Thus far, the rotating probe eddy current system has been found to be very user friendly and capable of detecting first layer cracks on the order of 0.030 inch long or longer.

An Effective Electrical Resonance-Based Method to Detect Delamination in Thermal Barrier Coating

NASA Astrophysics Data System (ADS)

Kim, Jong Min; Park, Jae-Ha; Lee, Ho Girl; Kim, Hak-Joon; Song, Sung-Jin; Seok, Chang-Sung; Lee, Young-Ze

2017-12-01

This research proposes a simple yet highly sensitive method based on electrical resonance of an eddy-current probe to detect delamination of thermal barrier coating (TBC). This method can directly measure the mechanical characteristics of TBC compared to conventional ultrasonic testing and infrared thermography methods. The electrical resonance-based method can detect the delamination of TBC from the metallic bond coat by shifting the electrical impedance of eddy current testing (ECT) probe coupling with degraded TBC, and, due to this shift, the resonant frequencies near the peak impedance of ECT probe revealed high sensitivity to the delamination. In order to verify the performance of the proposed method, a simple experiment is performed with degraded TBC specimens by thermal cyclic exposure. Consequently, the delamination with growth of thermally grown oxide in a TBC system is experimentally identified. Additionally, the results are in good agreement with the results obtained from ultrasonic C-scanning.

An Effective Electrical Resonance-Based Method to Detect Delamination in Thermal Barrier Coating

NASA Astrophysics Data System (ADS)

Kim, Jong Min; Park, Jae-Ha; Lee, Ho Girl; Kim, Hak-Joon; Song, Sung-Jin; Seok, Chang-Sung; Lee, Young-Ze

2018-02-01

This research proposes a simple yet highly sensitive method based on electrical resonance of an eddy-current probe to detect delamination of thermal barrier coating (TBC). This method can directly measure the mechanical characteristics of TBC compared to conventional ultrasonic testing and infrared thermography methods. The electrical resonance-based method can detect the delamination of TBC from the metallic bond coat by shifting the electrical impedance of eddy current testing (ECT) probe coupling with degraded TBC, and, due to this shift, the resonant frequencies near the peak impedance of ECT probe revealed high sensitivity to the delamination. In order to verify the performance of the proposed method, a simple experiment is performed with degraded TBC specimens by thermal cyclic exposure. Consequently, the delamination with growth of thermally grown oxide in a TBC system is experimentally identified. Additionally, the results are in good agreement with the results obtained from ultrasonic C-scanning.

Validation Test Results for Orthogonal Probe Eddy Current Thruster Inspection System

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.

2007-01-01

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 Eddy Current (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.

A Tool Measuring Remaining Thickness of Notched Acoustic Cavities in Primary Reaction Control Thruster NDI Standards

NASA Technical Reports Server (NTRS)

Sun, Yushi; Sun, Changhong; Zhu, Harry; Wincheski, Buzz

2006-01-01

Stress corrosion cracking in the relief radius area of a space shuttle primary reaction control thruster is an issue of concern. The current approach for monitoring of potential crack growth is nondestructive inspection (NDI) of remaining thickness (RT) to the acoustic cavities using an eddy current or remote field eddy current probe. EDM manufacturers have difficulty in providing accurate RT calibration standards. Significant error in the RT values of NDI calibration standards could lead to a mistaken judgment of cracking condition of a thruster under inspection. A tool based on eddy current principle has been developed to measure the RT at each acoustic cavity of a calibration standard in order to validate that the standard meets the sample design criteria.

Numerical modelling as a cost-reduction tool for probability of detection of bolt hole eddy current testing

NASA Astrophysics Data System (ADS)

Mandache, C.; Khan, M.; Fahr, A.; Yanishevsky, M.

2011-03-01

Probability of detection (PoD) studies are broadly used to determine the reliability of specific nondestructive inspection procedures, as well as to provide data for damage tolerance life estimations and calculation of inspection intervals for critical components. They require inspections on a large set of samples, a fact that makes these statistical assessments time- and cost-consuming. Physics-based numerical simulations of nondestructive testing inspections could be used as a cost-effective alternative to empirical investigations. They realistically predict the inspection outputs as functions of the input characteristics related to the test piece, transducer and instrument settings, which are subsequently used to partially substitute and/or complement inspection data in PoD analysis. This work focuses on the numerical modelling aspects of eddy current testing for the bolt hole inspections of wing box structures typical of the Lockheed Martin C-130 Hercules and P-3 Orion aircraft, found in the air force inventory of many countries. Boundary element-based numerical modelling software was employed to predict the eddy current signal responses when varying inspection parameters related to probe characteristics, crack geometry and test piece properties. Two demonstrator exercises were used for eddy current signal prediction when lowering the driver probe frequency and changing the material's electrical conductivity, followed by subsequent discussions and examination of the implications on using simulated data in the PoD analysis. Despite some simplifying assumptions, the modelled eddy current signals were found to provide similar results to the actual inspections. It is concluded that physics-based numerical simulations have the potential to partially substitute or complement inspection data required for PoD studies, reducing the cost, time, effort and resources necessary for a full empirical PoD assessment.

Three-axis orthogonal transceiver coil for eddy current sounding

NASA Astrophysics Data System (ADS)

Sukhanov, D.; Zavyalova, K.; Goncharik, M.

2017-08-01

We propose the new structure of three-axis transceiver magnetic-induction coil for eddy current probing. Due to the orientation of the coils, the direct signal from the transmitting coil to the receiving coil is minimized, which provided a high dynamic range. Sensitivity in all directions is provided by combining coils of different orientations. Numerical simulation and experimental studies of such a system have been carried out and confirmed the applicability of the proposed method and the mathematical model.

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

Differential geometry based model for eddy current inspection of U-bend sections in steam generator tubes

NASA Astrophysics Data System (ADS)

Mukherjee, Saptarshi; Rosell, Anders; Udpa, Lalita; Udpa, Satish; Tamburrino, Antonello

2017-02-01

The modeling of U-Bend segment in steam generator tubes for predicting eddy current probe signals from cracks, wear and pitting in this region poses challenges and is non-trivial. Meshing the geometry in the cartesian coordinate system might require a large number of elements to model the U-bend region. Also, since the lift-off distance between the probe and tube wall is usually very small, a very fine mesh is required near the probe region to accurately describe the eddy current field. This paper presents a U-bend model using differential geometry principles that exploit the result that Maxwell's equations are covariant with respect to changes of coordinates and independent of metrics. The equations remain unaltered in their form, regardless of the choice of the coordinates system, provided the field quantities are represented in the proper covariant and contravariant form. The complex shapes are mapped into simple straight sections, while small lift-off is mapped to larger values, thus reducing the intrinsic dimension of the mesh and stiffness matrix. In this contribution, the numerical implementation of the above approach will be discussed with regard to field and current distributions within the U-bend tube wall. For the sake of simplicity, a two dimensional test case will be considered. The approach is evaluated in terms of efficiency and accuracy by comparing the results with that obtained using a conventional FE model in cartesian coordinates.

Magnetoresistive flux focusing eddy current flaw detection

NASA Technical Reports Server (NTRS)

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

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.

Near DC eddy current measurement of aluminum multilayers using MR sensors and commodity low-cost computer technology

NASA Astrophysics Data System (ADS)

Perry, Alexander R.

2002-06-01

Low Frequency Eddy Current (EC) probes are capable of measurement from 5 MHz down to DC through the use of Magnetoresistive (MR) sensors. Choosing components with appropriate electrical specifications allows them to be matched to the power and impedance characteristics of standard computer connectors. This permits direct attachment of the probe to inexpensive computers, thereby eliminating external power supplies, amplifiers and modulators that have heretofore precluded very low system purchase prices. Such price reduction is key to increased market penetration in General Aviation maintenance and consequent reduction in recurring costs. This paper examines our computer software CANDETECT, which implements this approach and permits effective probe operation. Results are presented to show the intrinsic sensitivity of the software and demonstrate its practical performance when seeking cracks in the underside of a thick aluminum multilayer structure. The majority of the General Aviation light aircraft fleet uses rivets and screws to attach sheet aluminum skin to the airframe, resulting in similar multilayer lap joints.

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.

Models in the Design and Validation of Eddy Current Inspection for Cracking in the Shuttle Reaction Control System Thruster

NASA Technical Reports Server (NTRS)

Aldrin, John C.; Williams, Phillip A.; Wincheski, Russell (Buzz) A.

2008-01-01

A case study is presented for using models in eddy current 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.

Evaluation of eddy-current proximity devices for measuring thin potassium film thicknesses

NASA Technical Reports Server (NTRS)

Asadourian, A. S.

1972-01-01

Two eddy current 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.

Recent Advances in Simulation of Eddy Current Testing of Tubes and Experimental Validations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reboud, C.; Premel, D.; Lesselier, D.

2007-03-21

Eddy current testing (ECT) is widely used in iron and steel industry for the inspection of tubes during manufacturing. A collaboration between CEA and the Vallourec Research Center led to the development of new numerical functionalities dedicated to the simulation of ECT of non-magnetic tubes by external probes. The achievement of experimental validations led us to the integration of these models into the CIVA platform. Modeling approach and validation results are discussed here. A new numerical scheme is also proposed in order to improve the accuracy of the model.

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.

Recent Advances in Simulation of Eddy Current Testing of Tubes and Experimental Validations

NASA Astrophysics Data System (ADS)

Reboud, C.; Prémel, D.; Lesselier, D.; Bisiaux, B.

2007-03-01

Eddy current testing (ECT) is widely used in iron and steel industry for the inspection of tubes during manufacturing. A collaboration between CEA and the Vallourec Research Center led to the development of new numerical functionalities dedicated to the simulation of ECT of non-magnetic tubes by external probes. The achievement of experimental validations led us to the integration of these models into the CIVA platform. Modeling approach and validation results are discussed here. A new numerical scheme is also proposed in order to improve the accuracy of the model.

Low-frequency nondestructive analysis of cracks in multilayer structures using a scanning magnetic microscope

NASA Astrophysics Data System (ADS)

Adamo, M.; Nappi, C.; Sarnelli, E.

2010-09-01

The use of a scanning magnetic microscope (SMM) with a high temperature superconducting quantum interference device (SQUID) for quantitative measurements in eddy current nondestructive analysis (NDA) is presented. The SQUID has been used to detect the weak magnetic field variations around a small defect, close to a structural part generating an intensive magnetic field. The experimental data for a deep crack close to a rivet in a multilayer conducting plate have been taken in a RF-shielded environment and discussed in the light of the theoretical predictions. The results show that eddy current NDA can distinguish subsurface crack signals from wider structural signals, with defects located 10 mm below the surface. Moreover, in order to visualize the structure of the probing current when a circular induction coil is used, the simulation of eddy currents in a thick unflawed conducting plate has been carried out.

A versatile nondestructive evaluation imaging workstation

NASA Technical Reports Server (NTRS)

Chern, E. James; Butler, David W.

1994-01-01

Ultrasonic C-scan and eddy current imaging systems are of the pointwise type evaluation systems that rely on a mechanical scanner to physically maneuver a probe relative to the specimen point by point in order to acquire data and generate images. Since the ultrasonic C-scan and eddy current imaging systems are based on the same mechanical scanning mechanisms, the two systems can be combined using the same PC platform with a common mechanical manipulation subsystem and integrated data acquisition software. Based on this concept, we have developed an IBM PC-based combined ultrasonic C-scan and eddy current imaging system. The system is modularized and provides capacity for future hardware and software expansions. Advantages associated with the combined system are: (1) eliminated duplication of the computer and mechanical hardware, (2) unified data acquisition, processing and storage software, (3) reduced setup time for repetitious ultrasonic and eddy current scans, and (4) improved system efficiency. The concept can be adapted to many engineering systems by integrating related PC-based instruments into one multipurpose workstation such as dispensing, machining, packaging, sorting, and other industrial applications.

A versatile nondestructive evaluation imaging workstation

NASA Astrophysics Data System (ADS)

Chern, E. James; Butler, David W.

1994-02-01

Ultrasonic C-scan and eddy current imaging systems are of the pointwise type evaluation systems that rely on a mechanical scanner to physically maneuver a probe relative to the specimen point by point in order to acquire data and generate images. Since the ultrasonic C-scan and eddy current imaging systems are based on the same mechanical scanning mechanisms, the two systems can be combined using the same PC platform with a common mechanical manipulation subsystem and integrated data acquisition software. Based on this concept, we have developed an IBM PC-based combined ultrasonic C-scan and eddy current imaging system. The system is modularized and provides capacity for future hardware and software expansions. Advantages associated with the combined system are: (1) eliminated duplication of the computer and mechanical hardware, (2) unified data acquisition, processing and storage software, (3) reduced setup time for repetitious ultrasonic and eddy current scans, and (4) improved system efficiency. The concept can be adapted to many engineering systems by integrating related PC-based instruments into one multipurpose workstation such as dispensing, machining, packaging, sorting, and other industrial applications.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2014-01-01

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

Eddy Current COPV Overwrap and Liner Thickness Measurement System and Data Analysis for 40-Inch Kevlar COPVs SN002 and SN027

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.

2008-01-01

As part of the health assessment of flight spare 40in diameter Kevlar composite overwrapped pressure vessels (COPVs) SN002 and SN027 an eddy current characterization of the composite and liner thickness change during pressurization was requested under WSTF-TP-1085-07.A, "Space Shuttle Orbiter Main Propulsion System P/N MC282-0082-0101 S/N 002 and Orbital Maneuvering System P/N MC282-0082-001 S/N 027 COPV Health Assessment." The through the thickness strains have been determined to be an important parameter in the analysis of the reliability and likelihood of stress rupture failure. Eddy current techniques provide a means to measure these thicknesses changes based upon the change in impedance of an eddy current sensor mounted on the exterior of the vessel. Careful probe and technique design have resulted in the capability to independently measure the liner and overwrap thickness changes to better than +/- 0.0005 in. at each sensor location. Descriptions of the inspection system and test results are discussed.

Investigation of eddy current examination on OD fatigue crack for steam generator tubes

NASA Astrophysics Data System (ADS)

Kong, Yuying; Ding, Boyuan; Li, Ming; Liu, Jinhong; Chen, Huaidong; Meyendorf, Norbert G.

2015-03-01

The opening width of fatigue crack was very small, and conventional Bobbin probe was very difficult to detect it in steam generator tubes. Different sizes of 8 fatigue cracks were inspected using bobbin probe rotating probe. The analysis results showed that, bobbin probe was not sensitive for fatigue crack even for small through wall crack mixed with denting signal. On the other hand, the rotating probe was easily to detect all cracks. Finally, the OD phase to depth curve for fatigue crack using rotating probe was established and the results agreed very well with the true crack size.

Magnetic Diagnosis Upgrade and Analysis for MHD Instabilities on the J-TEXT

NASA Astrophysics Data System (ADS)

Guo, Daojing; Hu, Qiming; Zhuang, Ge; Wang, Nengchao; Ding, Yonghua; Tang, Yuejin; Yu, Qingquan; Huazhong University of Science; Technology Team; Max-Planck-Institut für Plasmaphysik Collaboration

2017-10-01

The magnetic diagnostic system on the J-TEXT tokamak has been upgraded to measure the magnetohydrodynamic (MHD) instabilities with diverse bands of frequencies. 12 saddle loop probes and 73 Mirnov probes are newly developed. The fabrication and installment of the new probes are elaborately designed, in consideration of higher spatial resolution and better amplitude-frequency characteristic. In this case, the probes utilize two kinds of novel fabrication craft, one of which is low temperature co-fired ceramics (LTCC), the other is flexible printed circuit (FPC). A great deal of experiments on the J-TEXT have validated the stability of the new system. Some typical discharges observed by the new diagnostic system are reviewed. In order to extract useful information from raw signals, several efficient signal processing methods are reviewed. An analytical model based on lumped eddy current circuits is used to compensate equilibrium flux and the corresponding eddy current fluxes, a visualization processing based on singular value decomposition (SVD) and cross-power spectrum are applied to detect the mode number. Fusion Science Program of China (Contract Nos. 2015GB111001 and 2014GB108000) and the National Natural Science Foundation of China (Contract Nos. 11505069 and 11405068).

Model based optimization of driver-pickup separation for eddy current measurement of gap

NASA Astrophysics Data System (ADS)

Klein, G.; Morelli, J.; Krause, T. W.

2018-04-01

The fuel channels in CANDU® (CANada Deuterium Uranium) nuclear reactors consist of a pressure tube (PT) contained within a larger diameter calandria tube (CT). The separation between the tubes, known as the PT-CT gap, ensures PT hydride blisters, which could lead to potential cracking of the PT, do not develop. Therefore, accurate measurements are required to confirm that contact between PT and CT is not imminent. Gap measurement uses an eddy current probe. However this probe is sensitive to lift-off variations, which can adversely affect estimated gap. A validated analytical flat plate model of eddy current response to gap was used to examine the effect of driver-pickup spacing on lift-off and response to gap at a frequency of 4 kHz, which is used for in-reactor measurements. This model was compared against, and shown to have good agreement with, a COMSOL® finite element method (FEM) model. The optimum coil separation, which included the constraint of coil size, was found to be 11 mm, resulting in a phase response between lift-off and response to change in gap of 66°. This work demonstrates the advantages of using analytical models for optimizing coil designs for measurement of parameters that may negatively influence the outcome of an inspection measurement.

Flowpath evaluation and reconnaissance by remote field Eddy current testing (FERRET)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smoak, A.E.; Zollinger, W.T.

1993-12-31

This document describes the design and development of FERRET (Flowpath Evaluation and Reconnaisance by Remote-field Eddy current Testing). FERRET is a system for inspecting the steel pipes which carry cooling water to underground nuclear waste storage tanks. The FERRET system has been tested in a small scale cooling pipe mock-up, an improved full scale mock-up, and in flaw detection experiments. Early prototype designs of FERRET and the FERRET launcher (a device which inserts, moves, and retrieves probes from a piping system) as well as the field-ready design are discussed.

Eddy current signal comparison for tube identification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glass, S. W., E-mail: Bill.Glass@areva.com, E-mail: Ratko.Vojvodic@areva.com; Vojvodic, R., E-mail: Bill.Glass@areva.com, 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 somemore » 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.« less

GMR-based eddy current probe for weld seam inspection and its non-scanning detection study

NASA Astrophysics Data System (ADS)

Gao, Peng; Wang, Chao; Li, Yang; Wang, Libin; Cong, Zheng; Zhi, Ya

2017-04-01

Eddy current testing is one of the most important non-destructive testing methods for welding defects detection. This paper presents the use of a probe consisting of 4 giant magneto-resistive (GMR) sensors to detect weld defects. Information from four measuring points above and on both sides of the weld seam is collected at the same time. By setting the GMR sensors' sensing axes perpendicular to the direction of the excitation magnetic field, the information collected mainly reflects the change in the eddy current which is caused by defects. Digital demodulation technology is applied to extract the real part and imaginary part of the GMR sensors' output signals. The variables containing directional information of the magnetic field are introduced. Based on the data from the four GMR (4-GMR) sensors' output signals, four values, Ran, Mean, Var and k are selected as the feature quantities for defect recognition. Experiments are carried out on weld seams with and without defects, and the detection outputs are given in this paper. The 4-GMR probe is also employed to investigate non-scanning weld defect detection and the four feature quantities (Ran, Mean, Var and k) are studied to evaluate weld quality. The non-scanning weld defect detection is presented. A support vector machine is used to classify and discriminate welds with and without defects. Experiments carried out show that through the method in this paper, the recognition rate is 92% for welds without defects and 90% for welds with defects, with an overall recognition rate of 90.9%, indicating that this method could effectively detect weld defects.

Effects of Induced Electric Fields on Tissues and Cells

NASA Astrophysics Data System (ADS)

Sequin, Emily Katherine

Cancer remains a substantial health burden in the United States. Traditional treatments for solid malignancies may include chemotherapy, radiation therapy, targeted therapies, or surgical resection. Improved surgical outcomes coincide with increased information regarding the tumor extent in the operating room. Furthermore, pathological examination and diagnosis is bettered when the pathologist has additional information about lesion locations on the large resected specimens from which they take a small sample for microscopic evaluation. Likewise, cancer metastasis is a leading cause of cancer death. Fully understanding why a particular tumor becomes metastatic as well as the mechanisms of cell migration are critical to both preventing metastasis and treating it. This dissertation utilizes the complex interactions of induced electric fields with tissues and cells to meet two complementary research goals. First, eddy currents are induced in tissues using a coaxial eddy current probe (8mm diameter) in order to distinguish tumor tissue from surrounding normal tissue to address the needs of surgeons performing curative cancer resections. Measurements on animal tissue phantoms characterize the eddy current measurement finding that the effective probing area corresponds to about twice the diameter of the probe and that the specimen temperature must be constant for reliable measurements. Measurements on ten fresh tissue specimens from human patients undergoing surgical resection for liver metastases from colorectal cancer showed that the eddy current measurement technique can be used to differentiate tumors from surrounding liver tissue in a non-destructive, non-invasive manner. Furthermore, the differentiation between the tumor and normal tissues required no use of contrast agents. Statistically significant differences between eddy current measurements in three tissue categories, tumor, normal, and interface, were found across patients using a Tukey's pairwise comparison. Moreover, the first eddy current image of the interface region between tumor and normal tissues is presented. Secondly, the effects of induced electric fields on cell motility are explored as cell motility plays an important role in both cancer metastasis and the healing of chronic wounds. Human keratinocyte migration in a wound healing assay was reduced by about 50% under the influence of a 1 Hz induced electric field with a maximum field strength of approximately 34.3 microV/cm. A modified Transwell migration assay was developed to study to migration of metastatic breast cancer cells under the influence of an induced electric field at 100 kHz and maximum field strength of 11.2 microV/cm. It was shown that low frequency, low magnitude, noncontact electric fields can overcome the effects of the chemoattractants SDF1aalpha and EGF. This suggests a possible therapeutic benefit for the treatment of metastatic cancer with non-invasive, induced electric fields. In essence, this work has laid the foundation for exploring the use of non-contact, induced electric fields to study the properties of tissues and cells. These findings support the further development of eddy current technology into a tool useful in the operating room for surgeons seeking information on surgical margin quality. Furthermore, the modifications to standard migration assays offer new ways to study cell motility.

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.

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

PubMed

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

2014-08-01

We performed a new coupled circuit numerical simulation of eddy currents in an open compact magnetic resonance imaging (MRI) system. Following the coupled circuit approach, the conducting structures were divided into subdomains along the length (or width) and the thickness, and by implementing coupled circuit concepts we have simulated transient responses of eddy currents for subdomains in different locations. We implemented the Eigen matrix technique to solve the network of coupled differential equations to speed up our simulation program. On the other hand, to compute the coupling relations between the biplanar gradient coil and any other conducting structure, we implemented the solid angle form of Ampere's law. We have also calculated the solid angle for three dimensions to compute inductive couplings in any subdomain of the conducting structures. Details of the temporal and spatial distribution of the eddy currents were then implemented in the secondary magnetic field calculation by the Biot-Savart law. In a desktop computer (Programming platform: Wolfram Mathematica 8.0®, Processor: Intel(R) Core(TM)2 Duo E7500 @ 2.93GHz; OS: Windows 7 Professional; Memory (RAM): 4.00GB), it took less than 3min to simulate the entire calculation of eddy currents and fields, and approximately 6min for X-gradient coil. The results are given in the time-space domain for both the direct and the cross-terms of the eddy current magnetic fields generated by the Z-gradient coil. We have also conducted free induction decay (FID) experiments of eddy fields using a nuclear magnetic resonance (NMR) probe to verify our simulation results. The simulation results were found to be in good agreement with the experimental results. In this study we have also conducted simulations for transient and spatial responses of secondary magnetic field induced by X-gradient coil. Our approach is fast and has much less computational complexity than the conventional electromagnetic numerical simulation methods. Copyright © 2014 Elsevier Inc. All rights reserved.

Metallic Bead Detection by Using Eddy-Current Probe with SV-GMR Sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamada, S.; Chomsuwan, K.; Hagino, T.

2005-04-09

The progress of the ECT probe with micro magnetic sensor becomes possible to apply to various applications. The detection of micro metallic bead used for electric packaging has been reported in this paper. We proposed micro ECT probes with meander coil as exciter and spin-valve giant magneto-resistance (SV-GMR) as receiver. Micro metallic bead(solder ball) with the diameter of 0.25 to 0.76 mm is used as a measuring object. We discuss the detection and alignment of metallic bead by using ECT technique.

Device Rotates Bearing Balls For Inspection

NASA Technical Reports Server (NTRS)

Burley, R. K.

1988-01-01

Entire surface of ball inspected automatically and quickly. Device holds and rotates bearing ball for inspection by optical or mechanical surface-quality probe, eddy-current probe for detection of surface or subsurface defects, or circumference-measuring tool. Ensures entire surface of ball moves past inspection head quickly. New device saves time and increases reliability of inspections of spherical surfaces. Simple to operate and provides quick and easy access for loading and unloading of balls during inspection.

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

DOEpatents

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

1983-01-01

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

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

DOEpatents

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

1983-10-25

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

OTVE turbopump condition monitoring, task E.5

NASA Technical Reports Server (NTRS)

Coleman, Paul T.; Collins, J. J.

1989-01-01

Recent work has been carried out on development of isotope wear analysis and optical and eddy current technologies to provide bearing wear measurements and real time monitoring of shaft speed, shaft axial displacement and shaft orbit of the Orbit Transfer Vehicle hydrostatic bearing tester. Results show shaft axial displacement can be optically measured (at the same time as shaft orbital motion and speed) to within 0.3 mils by two fiberoptic deflectometers. Evaluation of eddy current probes showed that, in addition to measuring shaft orbital motion, they can be used to measure shaft speed without having to machine grooves on the shaft surface as is the usual practice for turbomachinery. The interim results of this condition monitoring effort are presented.

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.

Study on quantitative detection technology of special position defects in heat transfer tubes of nuclear power plants

NASA Astrophysics Data System (ADS)

Qi, Pan; Cui, Hongyan; Shao, Wenbin; Feng, Meiming; Liao, Shusheng

2018-04-01

This study was conducted analyzing eddy current signals from a rotary probe and an array probe to detect artificial cracks and flat bottom holes (FBH) located in selected positions in a steam generator heat transfer tube of a nuclear power plant. In particular, the study examined the expanded transition section, and the detection sensitivity and the variation characteristics of the unilateral signal to provide guidance for in-service inspections.

Eddy Current Testing and Sizing of Deep Cracks in a Thick Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.; Endo, H.; Uchimoto, T.

2004-02-26

Due to the skin effect of eddy current testing, target of ECT restricts to thin structure such as steam generator tubes with 1.27mm thickness. Detecting and sizing of a deep crack in a thick structure remains a problem. In this paper, an ECT probe is presented to solve this problem with the help of numerical analysis. The parameters such as frequency, coil size etc. are discussed. The inverse problem of crack sizing is solved by applying a fast simulator of ECT based on an edge based finite element method and steepest descent method, and reconstructed results of 5, 10 andmore » 15mm depth cracks from experimental signals are shown.« less

Thickness Gauging of Single-Layer Conductive Materials with Two-Point Non Linear Calibration Algorithm

NASA Technical Reports Server (NTRS)

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

1998-01-01

A thickness gauging instrument uses a flux focusing eddy current probe and two-point nonlinear calibration algorithm. The instrument is small and portable due to the simple interpretation and operational characteristics of the probe. A nonlinear interpolation scheme incorporated into the instrument enables a user to make highly accurate thickness measurements over a fairly wide calibration range from a single side of nonferromagnetic conductive metals. The instrument is very easy to use and can be calibrated quickly.

A Gradient-Field Pulsed Eddy Current Probe for Evaluation of Hidden Material Degradation in Conductive Structures Based on Lift-Off Invariance

PubMed Central

Li, Yong; Jing, Haoqing; Zainal Abidin, Ilham Mukriz; Yan, Bei

2017-01-01

Coated conductive structures are widely adopted in such engineering fields as aerospace, nuclear energy, etc. The hostile and corrosive environment leaves in-service coated conductive structures vulnerable to Hidden Material Degradation (HMD) occurring under the protection coating. It is highly demanded that HMD can be non-intrusively assessed using non-destructive evaluation techniques. In light of the advantages of Gradient-field Pulsed Eddy Current technique (GPEC) over other non-destructive evaluation methods in corrosion evaluation, in this paper the GPEC probe for quantitative evaluation of HMD is intensively investigated. Closed-form expressions of GPEC responses to HMD are formulated via analytical modeling. The Lift-off Invariance (LOI) in GPEC signals, which makes the HMD evaluation immune to the variation in thickness of the protection coating, is introduced and analyzed through simulations involving HMD with variable depths and conductivities. A fast inverse method employing magnitude and time of the LOI point in GPEC signals for simultaneously evaluating the conductivity and thickness of HMD region is proposed, and subsequently verified by finite element modeling and experiments. It has been found from the results that along with the proposed inverse method the GPEC probe is applicable to evaluation of HMD in coated conductive structures without much loss in accuracy. PMID:28441328

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation

PubMed Central

Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-01-01

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size. PMID:28758985

A Gradient-Field Pulsed Eddy Current Probe for Evaluation of Hidden Material Degradation in Conductive Structures Based on Lift-Off Invariance.

PubMed

Li, Yong; Jing, Haoqing; Zainal Abidin, Ilham Mukriz; Yan, Bei

2017-04-25

Coated conductive structures are widely adopted in such engineering fields as aerospace, nuclear energy, etc. The hostile and corrosive environment leaves in-service coated conductive structures vulnerable to Hidden Material Degradation (HMD) occurring under the protection coating. It is highly demanded that HMD can be non-intrusively assessed using non-destructive evaluation techniques. In light of the advantages of Gradient-field Pulsed Eddy Current technique (GPEC) over other non-destructive evaluation methods in corrosion evaluation, in this paper the GPEC probe for quantitative evaluation of HMD is intensively investigated. Closed-form expressions of GPEC responses to HMD are formulated via analytical modeling. The Lift-off Invariance (LOI) in GPEC signals, which makes the HMD evaluation immune to the variation in thickness of the protection coating, is introduced and analyzed through simulations involving HMD with variable depths and conductivities. A fast inverse method employing magnitude and time of the LOI point in GPEC signals for simultaneously evaluating the conductivity and thickness of HMD region is proposed, and subsequently verified by finite element modeling and experiments. It has been found from the results that along with the proposed inverse method the GPEC probe is applicable to evaluation of HMD in coated conductive structures without much loss in accuracy.

Imaging of Subsurface Corrosion Using Gradient-Field Pulsed Eddy Current Probes with Uniform Field Excitation.

PubMed

Li, Yong; Ren, Shuting; Yan, Bei; Zainal Abidin, Ilham Mukriz; Wang, Yi

2017-07-31

A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size.

A pulsed eddy current probe for inspection of support plates from within Alloy-800 steam generator tubes

NASA Astrophysics Data System (ADS)

Krause, T. W.; Babbar, V. K.; Underhill, P. R.

2014-02-01

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 eddy current (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.

Aluminum hydroxide coating thickness measurements and brushing tests on K West Basin fuel elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pitner, A.L.

1998-09-11

Aluminum hydroxide coating thicknesses were measured on fuel elements stored in aluminum canisters in K West Basin using specially developed eddy current probes . The results were used to estimate coating inventories for MCO fuel,loading. Brushing tests successfully demonstrated the ability to remove the coating if deemed necessary prior to MCO loading.

Quantitative impedance measurements for eddy current model validation

NASA Astrophysics Data System (ADS)

Khan, T. A.; Nakagawa, N.

2000-05-01

This paper reports on a series of laboratory-based impedance measurement data, collected by the use of a quantitatively accurate, mechanically controlled measurement station. The purpose of the measurement is to validate a BEM-based eddy current model against experiment. We have therefore selected two "validation probes," which are both split-D differential probes. Their internal structures and dimensions are extracted from x-ray CT scan data, and thus known within the measurement tolerance. A series of measurements was carried out, using the validation probes and two Ti-6Al-4V block specimens, one containing two 1-mm long fatigue cracks, and the other containing six EDM notches of a range of sizes. Motor-controlled XY scanner performed raster scans over the cracks, with the probe riding on the surface with a spring-loaded mechanism to maintain the lift off. Both an impedance analyzer and a commercial EC instrument were used in the measurement. The probes were driven in both differential and single-coil modes for the specific purpose of model validation. The differential measurements were done exclusively by the eddyscope, while the single-coil data were taken with both the impedance analyzer and the eddyscope. From the single-coil measurements, we obtained the transfer function to translate the voltage output of the eddyscope into impedance values, and then used it to translate the differential measurement data into impedance results. The presentation will highlight the schematics of the measurement procedure, a representative of raw data, explanation of the post data-processing procedure, and then a series of resulting 2D flaw impedance results. A noise estimation will be given also, in order to quantify the accuracy of these measurements, and to be used in probability-of-detection estimation.—This work was supported by the NSF Industry/University Cooperative Research Program.

An Application of a New Electromagnetic Sensor to Real-Time Monitoring of Fatigue Crack Growth in Thin Metal Plates

NASA Technical Reports Server (NTRS)

Namkung, M.; Fulton, J. P.; Wincheski, B.; Clendenin, C. G.

1993-01-01

A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles which necessitates automation of the whole process. If the rate of crack growth can be determined the experimenter can vary externally controlled parameters such as load level, load cycle frequency and so on. Hence, knowledge of the precise location of the crack tip at any given time is very valuable. One technique currently available for measuring fatigue crack length is the DC potential drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another approach is to digitize an optical image of the test specimen surface and then apply a pattern recognition technique to locate the crack tip, but this method is still under development. The present work is an initial study on applying eddy current-type probes to monitoring fatigue crack growth. The performance of two types of electromagnetic probes, a conventional eddy current probe and a newly developed self-nulling probe, was evaluated for the detection characteristics at and near the tips of fatigue cracks. The scan results show that the latter probe provides a very well defined local maximum in its output in the crack tip region suggesting the definite possibility of precisely locating the tip, while the former provides a somewhat ambiguous distribution of the sensor output in the same region. The paper is organized as follows: We start by reviewing the design and performance characteristics of the self-nulling probe and then describe the scan results which demonstrate the basic properties of the self-nulling probe. Next, we provide a brief description of the software developed for tracing a simulated crack and give a brief discussion of the main results of the test. The final section summarizes the major accomplishments of the present work and the elements of the future R&D needs.

Development and Application of Eddy Current Sensor Arrays for Process Integrated Inspection of Carbon Fibre Preforms.

PubMed

Berger, Dietrich; Lanza, Gisela

2017-12-21

This publication presents the realisation of a sensor concept, which is based on eddy current testing, to detect textile defects during preforming of semi-finished carbon fibre parts. The presented system has the potential for 100% control of manufactured carbon fibre based components, allowing the immediate exclusion of defective parts from further process steps. The core innovation of this system is given by the high degree of process integration, which has not been implemented in the state of the art. The publication presents the functional principle of the sensor that is based on half-transmission probes as well as the signals that can be gained by its application. Furthermore, a method to determine the optimum sensor resolution is presented as well as the sensor housing and its integration in the preforming process.

METAL RESISTIVITY MEASURING DEVICE

DOEpatents

Renken, J. Jr.; Myers, R.G.

1960-12-20

An eddy current device is offered for detecting discontinuities in metal samples. Alternate short and long duration pulses are inductively applied to a metal sample via the outer coil of a probe. The long pulses give a resultant signal from the metal sample responsive to probe-tosample spacing and discontinuities within the sample and the shont pulses give a resultant signal responsive only to probe -to-sample spacing. The inner coil of the probe detects the two resultant signals and transmits them to a separation network where the two signals are separated. The two separated signals are then transmitted to a compensation network where the detected signals due to the short pulses are used to compensate for variations due to probe-to-sample spacing contained in the detected signals from the long pulses. Thus, a resultant signal is obtained responsive to discontinuities within the sample and independent of probe-to- sample spacing.

Results of rocket measurements of D-region ionization over Thumba in MAP

NASA Technical Reports Server (NTRS)

Chakrabarty, D. K.; Beig, G.; Garg, S. C.; Subrahmanyam, P.; Zalpuri, K. S.; Somayajulu, Y. V.; Rao, M. N. M.; Tandel, C. B.; Murlikrishna, T. R.

1989-01-01

Under MAP, two rockets were launched from Thumba (8.5 N, 76.8 E) around 1030 hrs Lt with identical payloads on 7 and 10 March 1986 for D region studies. Positive ion densities were measured by spherical probe and Gerdien condenser and electron densities were measured by Langmuir probe and propagation experiments. In both flights a valley in ionization height profile was noticed around 83 km. The density of ionization at this altitude was about 4 x 10(2) cu cm. A detailed positive ion-chemical scheme was used to reproduce the measured ionization height profiles. The density of NO needed to reproduce the valley in ionization at 83 km came around 5 x 10(5) cu cm. A photochemical treatment without diffusion process was found inadequate to explain this value of NO. Calculations showed that the value of vertical eddy diffusion needed to reproduce the value of NO was around 10(6)sq cm/s. Interestingly, the same value of eddy diffusion coefficient was obtained when derived in the manner described by Thrane and his coworkers using only the positive ion current data of spherical probes.

Application of Self Nulling Eddy Current Probe Technique to the Detection of Fatigue Crack Initiation and Control of Test Procedures

NASA Technical Reports Server (NTRS)

Namkung, M.; Nath, S.; Wincheski, B.; Fulton, J. P.

1994-01-01

A major part of fracture mechanics is concerned with studying the initiation and propagation of fatigue cracks. This typically requires constant monitoring of crack growth during fatigue cycles and the knowledge of the precise location of the crack tip at any given time. One technique currently available for measuring fatigue crack length is the Potential Drop method. The method, however, may be inaccurate if the direction of crack growth deviates considerably from what was assumed initially or the curvature of the crack becomes significant. Another popular approach is to optically view the crack using a high magnification microscope, but this entails a person constantly monitoring it. The present proposed technique uses an automated scheme, in order to eliminate the need for a person to constantly monitor the experiment. Another technique under development elsewhere is to digitize an optical image of the test specimen surface and then apply a pattern recognition algorithm to locate the crack tip. A previous publication showed that the self nulling eddy current probe successfully tracked a simulated crack in an aluminum sample. This was the impetus to develop an online real time crack monitoring system. An automated system has been developed which includes a two axis scanner mounted on the tensile testing machine, the probe and its instrumentation and a personal computer (PC) to communicate and control all the parameters. The system software controls the testing parameters as well as monitoring the fatigue crack as it propagates. This paper will discuss the experimental setup in detail and demonstrate its capabilities. A three dimensional finite element model is utilized to model the magnetic field distribution due to the probe and how the probe voltage changes as it scans the crack. Experimental data of the probe for different samples under zero load, static load and high cycle fatigue load will be discussed. The final section summarizes the major accomplishments of the present work, the elements of the future R&D needs and the advantages and disadvantages of using this system in the laboratory and field.

Flux-focusing eddy current probe and rotating probe method for flaw detection

NASA Astrophysics Data System (ADS)

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

1994-11-01

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.

Flux-focusing eddy current probe and rotating probe method for flaw detection

NASA Technical Reports Server (NTRS)

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

1994-01-01

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.

Pulsed eddy current inspection of broach support plates in steam generators

NASA Astrophysics Data System (ADS)

Mokros, Sarah Gwendolyn

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

Variables Affecting Probability of Detection in Bolt Hole Eddy Current Inspection

NASA Astrophysics Data System (ADS)

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

2009-03-01

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

Frequency optimization in the eddy current test for high purity niobium

NASA Astrophysics Data System (ADS)

Joung, Mijoung; Jung, Yoochul; Kim, Hyungjin

2017-01-01

The eddy current test (ECT) is frequently used as a non-destructive method to check for the defects of high purity niobium (RRR300, Residual Resistivity Ratio) in a superconducting radio frequency (SRF) cavity. Determining an optimal frequency corresponding to specific material properties and probe specification is a very important step. The ECT experiments for high purity Nb were performed to determine the optimal frequency using the standard sample of high purity Nb having artificial defects. The target depth was considered with the treatment step that the niobium receives as the SRF cavity material. The results were analysed via the selectivity that led to a specific result, depending on the size of the defects. According to the results, the optimal frequency was determined to be 200 kHz, and a few features of the ECT for the high purity Nb were observed.

Metal Resistivity Measuring Device

DOEpatents

Renken, Jr, C. J.; Myers, R. G.

1960-12-20

An eddy current device is designed for detecting discontinuities in metal samples. Alternate short and long duration pulses are inductively applied to a metal sample via the outer coil of a probe. The lorg pulses give a resultant signal from the metal sample responsive to probe-tosample spacing and discontinuities with the sample, and the short pulses give a resultant signal responsive only to probe-to-sample spacing. The inner coil of the probe detects the two resultant signals and transmits them to a separation network where the two signals are separated. The two separated signals are then transmitted to a compensation network where the detected signals due to the short pulses are used to compensate for variations due to probeto-sample spacing contained in the detected signals from the long pulses. Thus a resultant signal is obtained responsive to discontinuities within the sample and independent of probe-to- sample spacing.

Foucault pendulum with eddy-current damping of the elliptical motion

NASA Astrophysics Data System (ADS)

Mastner, G.; Vokurka, V.; Maschek, M.; Vogt, E.; Kaufmann, H. P.

1984-10-01

A newly designed Foucault pendulum is described in which the mechanical Charron ring, used throughout in previous designs for damping of the elliptical motion of the pendulum, is replaced by an electromagnetic eddy-current brake, consisting of a permanent magnet attached to the bottom of the bob and a metallic ring. This damping device is very efficient, as it is self-aligning, symmetrical in the damping effect, and never wears out. The permanent magnet is also used, together with a coil assembly and an electronic circuitry, for the dipole-torque drive of the pendulum as well as for accurate stabilization of the amplitude of the swing. A latched time display, controlled by Hall probes activated by the magnet, is used to visualize the Foucault rotation. The pendulum system and its associated electronic circuitry are described in detail. The optimizing of the drive mode is discussed. Measurements of deviations from theoretical value of the Foucault rotation velocity made automatically in a continuous run show a reproducible accuracy of ±1% or better in individual 360° rotations during the summer months. The quality factor of the pendulum as mechanical resonator was measured as a function of the amplitude in the presence of the eddy-current damping ring.

NDE of copper canisters for long-term storage of spent nuclear fuel from the Swedish nuclear power plants

NASA Astrophysics Data System (ADS)

Stepinski, Tadeusz

2003-07-01

Sweden has been intensively developing methods for long term storage of spent fuel from the nuclear power plants for twenty-five years. A dedicated research program has been initiated and conducted by the Swedish company SKB (Swedish Nuclear Fuels and Waste Management Co.). After the interim storage SKB plans to encapsulate spent nuclear fuel in copper canisters that will be placed at a deep repository located in bedrock. The canisters filled with fuel rods will be sealed by an electron beam weld. This paper presents three complementary NDE techniques used for assessing the sealing weld in copper canisters, radiography, ultrasound, and eddy current. A powerful X-ray source and a digital detector are used for the radiography. An ultrasonic array system consisting of a phased ultrasonic array and a multi-channel electronics is used for the ultrasonic examination. The array system enables electronic focusing and rapid electronic scanning eliminating the use of a complicated mechanical scanner. A specially designed eddy current probe capable of detecting small voids at the depth up to 4 mm in copper is used for the eddy current inspection. Presently, all the NDE techniques are verified in SKB's Canister Laboratory where full scale canisters are welded and examined.

Fatigue Crack Length Sizing Using a Novel Flexible Eddy Current Sensor Array.

PubMed

Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying

2015-12-21

The eddy current 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 eddy current 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.

Fatigue Crack Length Sizing Using a Novel Flexible Eddy Current Sensor Array

PubMed Central

Xie, Ruifang; Chen, Dixiang; Pan, Mengchun; Tian, Wugang; Wu, Xuezhong; Zhou, Weihong; Tang, Ying

2015-01-01

The eddy current 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 eddy current 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

Steam generator tube inspection in Japan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fukui, Shigetaka

1997-02-01

Steam generator tube inspection was first carried out in 1971 at Mihama Unit-1 that is first PWR plant in Japan, when the plant was brought into the first annual inspection. At that time, inspection was made on sampling basis, and only bobbin coil probe was used. After experiencing various kinds of tube degradations, inspection method was changed from sampling to all number of tubes, and various kinds of probes were used to get higher detectability of flaw. At present, it is required that all the tubes shall be inspected in their full length at each annual inspection using standard bobbinmore » coil probe, and some special probes for certain plants that have susceptibility of occurrence of flaw. Sleeve repaired portion is included in this inspection. As a result of analyses of eddy current testing data, all indications that have been evaluated to be 20% wall thickness or deeper shall be repaired by either plugging or sleeving, where flaw morphology is to be a wastage or wear. Other types of flaw such as IGA/SCC are not allowed to be left inservice when those indications are detected. These inspections are performed according to inspection procedures that are approved by regulatory authority. Actual inspections are witnessed by the Japan Power engineering and inspection corporation (JAPEIC)`s inspectors during data acquisition and analysis, and they issue inspection report to authority for review and approval. It is achieved high safety performance of steam generator through this method of inspections, however. some tube leakage problems were experienced in the past. To prevent recurrence of such events, government is conducting development and verification test program for new eddy current testing technology.« less

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.

Piping inspection instrument carriage with precise and repeatable position control and location determination

DOEpatents

Hapstack, M.; Talarek, T.R.; Zollinger, W.T.; Heckendorn, F.M. II; Park, L.R.

1994-02-15

An instrument carriage for inspection of piping comprises front and rear leg assemblies for engaging the interior of the piping and supporting and centering the carriage therein, and an instrumentation arm carried by a shaft system running from the front to rear leg assemblies. The shaft system has a screw shaft for moving the arm axially and a spline gear for moving the arm azimuthally. The arm has a pair of air cylinders that raise and lower a plate in the radial direction. On the plate are probes including an eddy current probe and an ultrasonic testing probe. The ultrasonic testing probe is capable of spinning 360[degree] about its axis. The instrument carriage uses servo motors and pressurized air cylinders for precise actuation of instrument components and precise, repeatable actuation of position control mechanisms. 8 figures.

Piping inspection instrument carriage with precise and repeatable position control and location determination

DOEpatents

Hapstack, Mark; Talarek, Ted R.; Zollinger, W. Thor; Heckendorn, II, Frank M.; Park, Larry R.

1994-01-01

An instrument carriage for inspection of piping comprises front and rear leg assemblies for engaging the interior of the piping and supporting and centering the carriage therein, and an instrumentation arm carried by a shaft system running from the front to rear leg assemblies. The shaft system has a screw shaft for moving the arm axially and a spline gear for moving the arm azimuthally. The arm has a pair of air cylinders that raise and lower a plate in the radial direction. On the plate are probes including an eddy current probe and an ultrasonic testing probe. The ultrasonic testing probe is capable of spinning 360.degree. about its axis. The instrument carriage uses servo motors and pressurized air cylinders for precise actuation of instrument components and precise, repeatable actuation of position control mechanisms.

Inspecting Friction Stir Welding using Electromagnetic Probes

NASA Technical Reports Server (NTRS)

Kinchen, David G.

2004-01-01

A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

Tube cutter tool and method of use for coupon removal

DOEpatents

Nachbar, H.D.; Etten, M.P. Jr.; Kurowski, P.A.

1997-05-06

A tube cutter tool is insertable into a tube for cutting a coupon from a damaged site on the exterior of the tube. Prior to using the tool, the damaged site is first located from the interior of the tube using a multi-coil pancake eddy current test probe. The damaged site is then marked. A fiber optic probe is used to monitor the subsequent cutting procedure which is performed using a hole saw mounted on the tube cutter tool. Prior to completion of the cutting procedure, a drill in the center of the hole saw is drilled into the coupon to hold it in place. 4 figs.

Tube cutter tool and method of use for coupon removal

DOEpatents

Nachbar, Henry D.; Etten, Jr., Marvin P.; Kurowski, Paul A.

1997-01-01

A tube cutter tool is insertable into a tube for cutting a coupon from a damaged site on the exterior of the tube. Prior to using the tool, the damaged site is first located from the interior of the tube using a multi-coil pancake eddy current test probe. The damaged site is then marked. A fiber optic probe is used to monitor the subsequent cutting procedure which is performed using a hole saw mounted on the tube cutter tool. Prior to completion of the cutting procedure, a drill in the center of the hole saw is drilled into the coupon to hold it in place.

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,…

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

PubMed

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

2016-05-01

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

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.

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

NASA Astrophysics Data System (ADS)

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

2015-10-01

This paper deals with the problem of imaging defects in metallic structures through eddy current (EC) inspections, and proposes an original process for a possible tomographical crack evaluation. This process is based on a semi analytical modeling, called "distributed point source method" (DPSM) which is used to describe and equate the interactions between the implemented EC probes and the structure under test. Several steps will be successively described, illustrating the feasibility of this new imaging process dedicated to the quantitative evaluation of defects. The basic principles of this imaging process firstly consist in creating a 3D grid by meshing the volume potentially inspected by the sensor. As a result, a given number of elemental volumes (called voxels) are obtained. Secondly, the DPSM modeling is used to compute an image for all occurrences in which only one of the voxels has a different conductivity among all the other ones. The assumption consists to consider that a real defect may be truly represented by a superimposition of elemental voxels: the resulting accuracy will naturally depend on the density of space sampling. On other hand, the excitation device of the EC imager has the capability to be oriented in several directions, and driven by an excitation current at variable frequency. So, the simulation will be performed for several frequencies and directions of the eddy currents induced in the structure, which increases the signal entropy. All these results are merged in a so-called "observation matrix" containing all the probe/structure interaction configurations. This matrix is then used in an inversion scheme in order to perform the evaluation of the defect location and geometry. The modeled EC data provided by the DPSM are compared to the experimental images provided by an eddy current imager (ECI), implemented on aluminum plates containing some buried defects. In order to validate the proposed inversion process, we feed it with computed images of various acquisition configurations. Additive noise was added to the images so that they are more representative of actual EC data. In the case of simple notch type defects, for which the relative conductivity may only take two extreme values (1 or 0), a threshold was introduced on the inverted images, in a post processing step, taking advantage of a priori knowledge of the statistical properties of the restored images. This threshold allowed to enhance the image contrast and has contributed to eliminate both the residual noise and the pixels showing non-realistic values.

49 CFR 180.209 - Requirements for requalification of specification cylinders.

Code of Federal Regulations, 2012 CFR

2012-10-01

... Requalification period (years) Eddy current examination combined with visual inspection Eddy current—In accordance... performing eddy current must be familiar with the eddy current equipment and must standardize (calibrate) the system in accordance with the requirements provided in Appendix C to this part. 2 The eddy current must...

49 CFR 180.209 - Requirements for requalification of specification cylinders.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Requalification period (years) Eddy current examination combined with visual inspection Eddy current—In accordance... performing eddy current must be familiar with the eddy current equipment and must standardize (calibrate) the system in accordance with the requirements provided in Appendix C to this part. 2 The eddy current must...

49 CFR 180.209 - Requirements for requalification of specification cylinders.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Requalification period (years) Eddy current examination combined with visual inspection Eddy current—In accordance... performing eddy current must be familiar with the eddy current equipment and must standardize (calibrate) the system in accordance with the requirements provided in Appendix C to this part. 2 The eddy current must...

Improved Imaging With Laser-Induced Eddy Currents

NASA Technical Reports Server (NTRS)

Chern, Engmin J.

1993-01-01

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

Influence of magnet eddy current on magnetization characteristics of variable flux memory machine

NASA Astrophysics Data System (ADS)

Yang, Hui; Lin, Heyun; Zhu, Z. Q.; Lyu, Shukang

2018-05-01

In this paper, the magnet eddy current characteristics of a newly developed variable flux memory machine (VFMM) is investigated. Firstly, the machine structure, non-linear hysteresis characteristics and eddy current modeling of low coercive force magnet are described, respectively. Besides, the PM eddy current behaviors when applying the demagnetizing current pulses are unveiled and investigated. The mismatch of the required demagnetization currents between the cases with or without considering the magnet eddy current is identified. In addition, the influences of the magnet eddy current on the demagnetization effect of VFMM are analyzed. Finally, a prototype is manufactured and tested to verify the theoretical analyses.

Proceedings of the DARPA/AFML Review of Progress in Quantitative Nondestructive Evaluation, 8-13 July, La Jolla, California.

DTIC Science & Technology

1980-07-01

Solution of the Nonlinear Eddy Current and Loss Problems in Quasilinear Poisson Equation in a Nonuniform the Solid Rotors of Large Turbogenerators...stable probe support and aiid possibly also for the effect of a nonuniform Scanning mechanisms, especially for test pieces of magnetic field...without specimen): defects such as inclusions, voids, delaminations, 55 db and nonuniform particle distribution. Due to im- Dynamic range: 50 to 70

78 FR 27001 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-09

... one-time mid- frequency eddy current (MFEC) inspection, a low-frequency eddy current (LFEC) inspection... new AD instead requires repetitive external eddy current inspections for cracking of certain fuselage crown lap joints, and corrective actions if necessary; internal eddy current and detailed inspections...

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. Copyright © 2010 Elsevier Inc. All rights reserved.

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.

Surface Profiling and Core Evaluation of Aluminum Honeycomb Sandwich Aircraft Panels Using Multi-Frequency Eddy Current Testing

PubMed Central

Reyno, Tyler; Underhill, P. Ross; Krause, Thomas W.; Marsden, Catharine; Wowk, Diane

2017-01-01

Surface damage on honeycomb aircraft panels is often measured manually, and is therefore subject to variation based on inspection personnel. Eddy current testing (ECT) is sensitive to variations in probe-to-specimen spacing, or lift-off, and is thus promising for high-resolution profiling of surface damage on aluminum panels. Lower frequency testing also allows inspection through the face sheet, an advantage over optical 3D scanning methods. This paper presents results from the ECT inspection of surface damage on an approximately flat aluminum honeycomb aircraft panel, and compares the measurements to those taken using optical 3D scanning technology. An ECT C-Scan of the dented panel surface was obtained by attaching the probe to a robotic scanning apparatus. Data was taken simultaneously at four frequencies of 25, 100, 400 and 1600 kHz. A reference surface was then defined that approximated the original, undamaged panel surface, which also compensated for the effects of specimen tilt and thermal drift within the ECT instrument. Data was converted to lift-off using height calibration curves developed for each probe frequency. A damage region of 22,550 mm2 area with dents ranging in depth from 0.13–1.01 mm was analyzed. The method was accurate at 1600 kHz to within 0.05 mm (2σ) when compared with 231 measurements taken via optical 3D scanning. Testing at 25 kHz revealed a 3.2 mm cell size within the honeycomb core, which was confirmed via destructive evaluation. As a result, ECT demonstrates potential for implementation as a method for rapid in-field aircraft panel surface damage assessment. PMID:28906434

Surface Profiling and Core Evaluation of Aluminum Honeycomb Sandwich Aircraft Panels Using Multi-Frequency Eddy Current Testing.

PubMed

Reyno, Tyler; Underhill, P Ross; Krause, Thomas W; Marsden, Catharine; Wowk, Diane

2017-09-14

Surface damage on honeycomb aircraft panels is often measured manually, and is therefore subject to variation based on inspection personnel. Eddy current testing (ECT) is sensitive to variations in probe-to-specimen spacing, or lift-off, and is thus promising for high-resolution profiling of surface damage on aluminum panels. Lower frequency testing also allows inspection through the face sheet, an advantage over optical 3D scanning methods. This paper presents results from the ECT inspection of surface damage on an approximately flat aluminum honeycomb aircraft panel, and compares the measurements to those taken using optical 3D scanning technology. An ECT C-Scan of the dented panel surface was obtained by attaching the probe to a robotic scanning apparatus. Data was taken simultaneously at four frequencies of 25, 100, 400 and 1600 kHz. A reference surface was then defined that approximated the original, undamaged panel surface, which also compensated for the effects of specimen tilt and thermal drift within the ECT instrument. Data was converted to lift-off using height calibration curves developed for each probe frequency. A damage region of 22,550 mm² area with dents ranging in depth from 0.13-1.01 mm was analyzed. The method was accurate at 1600 kHz to within 0.05 mm (2σ) when compared with 231 measurements taken via optical 3D scanning. Testing at 25 kHz revealed a 3.2 mm cell size within the honeycomb core, which was confirmed via destructive evaluation. As a result, ECT demonstrates potential for implementation as a method for rapid in-field aircraft panel surface damage assessment.

The Complex Behaviour of High-Frequency Currents in Simple Circuits

PubMed Central

Bauwens, P.

1947-01-01

The fact that standing wave phenomena exist along transmission lines and loops conducting high-frequency electrical energy is responsible for effects of which therapeutic use can be made. A. Power measurements are made possible because parallel transmission lines behave as power transformers of which the ratio varies with the length of these lines. In a generator designed by the G.E.C. the dimensions of the lines are such that after a preliminary estimation of the impedance of the load in the treatment field, the sensitivity of the meter can be adjusted so that the meter subsequently registers in watts the power absorbed in this load. B. When using cable electrodes, in practice, the presence of strong electric fields between the antinodal portions of the loop as well as strong oscillating magnetic fields around the nodal portion gives rise to two distinct phenomena (fig. 6). Search for currents resulting from the electric field on the one hand, and for eddy currents due to the magnetic field on the other, was carried out at St. Thomas's Hospital, in liquid phantoms by means of a probe (fig. 5a) incorporating a small lamp capable of being rotated in every direction. Voltage measurements were recorded by matching its light intensity with that of a similar lamp in circuit with a variable resistance and a voltmeter (fig. 5b). When a portion of a cable electrode was coiled around a cylindrical vessel containing an electrolyte, the effects due to the two conditions could be dissociated. The following observations were made (fig. 7): (a) By using the nodal portions of the loop only, it was shown that only eddy currents are produced and that the lower the resistance of the electrolyte the more easily they are produced. They are strongest at the periphery and rapidly fall off away from it, as shown by the curves of the graph in fig. 8. (b) By using only the antinodal portions of the loop, coiled around the same vessel, coaxial or longitudinal currents can be demonstrated. It is interesting to note that these exist both at the periphery and at the centre. (c) When the whole cable is wound around the vessel, the concentration of the electrolyte becomes the factor determining the way in which the energy will be dissipated: (1) with tap-water, it is found that no eddy currents can be demonstrated whereas coaxial currents exist; (2) with strong saline solutions the converse holds good; (3) with electrolytes of intermediate concentration both types of currents can be shown to coexist at the periphery while at the centre only coaxial currents can be demonstrated. The fact that eddy currents and coaxial currents could be detected simultaneously and did not, as might be expected, give rise to a resultant, could only be explained by assuming that although eddy currents and coaxial currents coexisted as far as their effects on the pilot lamp were concerned, these two phenomena were not coincident as regards their phase relations. On examining the system more closely it became clear that the coaxial currents must be approximately 90 degrees out of phase with the eddy currents. By means of another type of probe (fig. 5c) for surface work, consisting of two metallic buttons mounted on an insulating strip and bridged by a small lamp, P3, similar to the one used throughout the investigations, it was possible to show that the same conditions existed in the body. It could be demonstrated that both coaxial and eddy currents occurred and that the predominance of one or the other type was dictated by conditions related to impedance. In the thigh just above the knee-joint, in most cases both currents could be demonstrated. It could also be shown that when half the cable was wound clockwise and the other half anticlockwise, so as to cancel the magnetic field between the two halves, no eddy currents existed. C. Present therapeutic applications of high-frequency currents involve the continuous dissipation of electrical energy in the load under treatment. Under these conditions the only detectable effect to which therapeutic value may be ascribed is the rise in temperature which results from heat production. This rise in temperature sets a limit to the power which can be used without risk of burns. Consequently effects other than thermal ones which might manifest themselves under higher intensities remain undetected. It is not possible to predict what would happen if, instead of treating tissues by means of sustained high-frequency electrical energy, tissues were subjected to intermittent radio-frequency pulses of very high intensity separated by silent periods of sufficient length to allow for the dissipation of heat. Those who have some technical knowledge of such matters will readily recognize an application of “Radar” technique in this. ImagesFig. 5 a, b, cFig. 9Fig. 10 PMID:19993665

The Complex Behaviour of High-Frequency Currents in Simple Circuits.

PubMed

Bauwens, P

1947-10-01

The fact that standing wave phenomena exist along transmission lines and loops conducting high-frequency electrical energy is responsible for effects of which therapeutic use can be made.A. Power measurements are made possible because parallel transmission lines behave as power transformers of which the ratio varies with the length of these lines. In a generator designed by the G.E.C. the dimensions of the lines are such that after a preliminary estimation of the impedance of the load in the treatment field, the sensitivity of the meter can be adjusted so that the meter subsequently registers in watts the power absorbed in this load.B. When using cable electrodes, in practice, the presence of strong electric fields between the antinodal portions of the loop as well as strong oscillating magnetic fields around the nodal portion gives rise to two distinct phenomena (fig. 6).Search for currents resulting from the electric field on the one hand, and for eddy currents due to the magnetic field on the other, was carried out at St. Thomas's Hospital, in liquid phantoms by means of a probe (fig. 5a) incorporating a small lamp capable of being rotated in every direction. Voltage measurements were recorded by matching its light intensity with that of a similar lamp in circuit with a variable resistance and a voltmeter (fig. 5b).When a portion of a cable electrode was coiled around a cylindrical vessel containing an electrolyte, the effects due to the two conditions could be dissociated. The following observations were made (fig. 7):(a) By using the nodal portions of the loop only, it was shown that only eddy currents are produced and that the lower the resistance of the electrolyte the more easily they are produced. They are strongest at the periphery and rapidly fall off away from it, as shown by the curves of the graph in fig. 8.(b) By using only the antinodal portions of the loop, coiled around the same vessel, coaxial or longitudinal currents can be demonstrated. It is interesting to note that these exist both at the periphery and at the centre.(c) When the whole cable is wound around the vessel, the concentration of the electrolyte becomes the factor determining the way in which the energy will be dissipated: (1) with tap-water, it is found that no eddy currents can be demonstrated whereas coaxial currents exist; (2) with strong saline solutions the converse holds good; (3) with electrolytes of intermediate concentration both types of currents can be shown to coexist at the periphery while at the centre only coaxial currents can be demonstrated.The fact that eddy currents and coaxial currents could be detected simultaneously and did not, as might be expected, give rise to a resultant, could only be explained by assuming that although eddy currents and coaxial currents coexisted as far as their effects on the pilot lamp were concerned, these two phenomena were not coincident as regards their phase relations. On examining the system more closely it became clear that the coaxial currents must be approximately 90 degrees out of phase with the eddy currents.By means of another type of probe (fig. 5c) for surface work, consisting of two metallic buttons mounted on an insulating strip and bridged by a small lamp, P(3), similar to the one used throughout the investigations, it was possible to show that the same conditions existed in the body. It could be demonstrated that both coaxial and eddy currents occurred and that the predominance of one or the other type was dictated by conditions related to impedance. In the thigh just above the knee-joint, in most cases both currents could be demonstrated. It could also be shown that when half the cable was wound clockwise and the other half anticlockwise, so as to cancel the magnetic field between the two halves, no eddy currents existed.C. Present therapeutic applications of high-frequency currents involve the continuous dissipation of electrical energy in the load under treatment. Under these conditions the only detectable effect to which therapeutic value may be ascribed is the rise in temperature which results from heat production. This rise in temperature sets a limit to the power which can be used without risk of burns. Consequently effects other than thermal ones which might manifest themselves under higher intensities remain undetected.It is not possible to predict what would happen if, instead of treating tissues by means of sustained high-frequency electrical energy, tissues were subjected to intermittent radio-frequency pulses of very high intensity separated by silent periods of sufficient length to allow for the dissipation of heat. Those who have some technical knowledge of such matters will readily recognize an application of "Radar" technique in this.

Measurements in a synthetic turbulent boundary layer

NASA Astrophysics Data System (ADS)

Arakeri, J. H.; Coles, D. E.

Some measurements in a synthetic turbulent boundary layer (SBL) are reported. The main diagnostic tool is an X-wire probe. The velocity of the large eddies is determined to be 0.842 times the freestream velocity. The mean properties of the SBL are reasonably close to those of a natural turbulent boundary layer. The large eddy in the SBL appears to be a pair of counterrotating eddies in the stream direction, inclined at a shallow angle and occupying much of the boundary-layer thickness.

Electromagnetic Characterization Of Metallic Sensory Alloy

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.; Simpson, John; Wallace, Terryl A.; Newman, John A.; Leser, Paul; Lahue, Rob

2012-01-01

Ferromagnetic shape-memory alloy (FSMA) particles undergo changes in both electromagnetic properties and crystallographic structure when strained. When embedded in a structural material, these attributes can provide sensory output of the strain state of the structure. In this work, a detailed characterization of the electromagnetic properties of a FSMA under development for sensory applications is performed. In addition, a new eddy current probe is used to interrogate the electromagnetic properties of individual FSMA particles embedded in the sensory alloy during controlled fatigue tests on the multifunctional material.

Electromagnetic characterization of metallic sensory alloy

NASA Astrophysics Data System (ADS)

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

2013-01-01

Ferromagnetic shape-memory alloy (FSMA) particles undergo changes in both electromagnetic properties and crystallographic structure when strained. When embedded in a structural material, these attributes can provide sensory output of the strain state of the structure. In this work, a detailed characterization of the electromagnetic properties of a FSMA under development for sensory applications is performed. In addition, a new eddy current probe is used to interrogate the electromagnetic properties of individual FSMA particles embedded in the sensory alloy during controlled fatigue tests on the multifunctional material.

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.

76 FR 28632 - Airworthiness Directives; The Boeing Company Model 737-300, -400, and -500 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-18

... doing internal eddy current inspections, or repairing the crack. As an alternative to the external eddy current inspections, the AD provides for internal eddy current and detailed inspections for cracks in the... 5, 2011, we issued Emergency AD 2011-08-51, which requires repetitive external eddy current...

A novel eddy current damper: theory and experiment

NASA Astrophysics Data System (ADS)

Ebrahimi, Babak; Khamesee, Mir Behrad; Golnaraghi, Farid

2009-04-01

A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s-2 (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m-1 is achievable with the fabricated prototype. This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.

Working session 2: Tubing inspection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guerra, J.; Tapping, R.L.

1997-02-01

This session was attended by delegates from 10 countries, and four papers were presented. A wide range of issues was tabled for discussion. Realizing that there was limited time available for more detailed discussion, three topics were chosen for the more detailed discussion: circumferential cracking, performance demonstration (to focus on POD and sizing), and limits of methods. Two other subsessions were organized: one dealt with some challenges related to the robustness of current inspection methods, especially with respect to leaving cracked tubes in service, and the other with developing a chart of current NDE technology with recommendations for future development.more » These three areas are summarized in turn, along with conclusions and/or recommendations. During the discussions there were four presentations. There were two (Canada, Japan) on eddy current probe developments, both of which addressed multiarray probes that would detect a range of flaws, one (Spain) on circumferential crack detection, and one (JRC, Petten) on the recent PISC III results.« less

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

NASA Astrophysics Data System (ADS)

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

2017-06-01

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

A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments

NASA Astrophysics Data System (ADS)

Smith, Doran D.; Alexson, Dimitri A.; Garbini, Joseph L.

2013-09-01

The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 μm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

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.

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,…

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 usedmore » 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. __________________________________________________« less

Role of eddy pumping in enhancing primary production in the ocean

NASA Technical Reports Server (NTRS)

Falkowski, Paul G.; Kolber, Zbigniew; Ziemann, David; Bienfang, Paul K.

1991-01-01

Eddy pumping is considered to explain the disparity between geochemical estimates and biological measurements of exported production. Episodic nutrient injections from the ocean into the photic zone can be generated by eddy pumping, which biological measurements cannot sample accurately. The enhancement of production is studied with respect to a cyclonic eddy in the subtropical Pacific. A pump-and-probe fluorimeter generates continuous vertical profiles of primary productivity from which the contributions of photochemical and nonphotochemical processes to fluorescence are derived. A significant correlation is observed between the fluorescence measurements and radiocarbon measurements. The results indicate that eddy pumping has an important effect on phytoplankton production and that this production is near the maximum relative specific growth rates. Based on the production enhancement observed in this case, eddy pumping increases total primary production by only 20 percent and does not account for all enhancement.

The influence of eddy currents on magnetic actuator performance

NASA Technical Reports Server (NTRS)

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

1987-01-01

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

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.

Effect of mesoscale eddies on the Taiwan Strait Current

NASA Astrophysics Data System (ADS)

Chang, Y. L.; Miyazawa, Y.; Guo, X.

2016-02-01

This study shows that mesoscale eddies can alter the Taiwan Strait current. The 20-year data-assimilated Japan Coastal Ocean Predictability Experiment 2 (JCOPE2) reanalysis data are analyzed, and the results are confirmed with idealized experiments. The leading wind-forced seasonal cycle is excluded to focus on the effect of the eddy. The warm eddy southwest of Taiwan is shown to generate a northward flow, whereas the cold eddy produces a southward current. The effect of the eddy penetrates onto the shelf through the Joint Effect of Baroclinicity and Relief (JEBAR). The cross-isobath fluxes lead to shelfward convergence and divergence, setting up the modulation of the sea level slope. The resulting along-strait current anomaly eventually affects a wide area of the Taiwan Strait. The stronger eddy leads to larger modification of the cross-shelf flows and sea level slope, producing a greater transport anomaly. The composite Sea-Viewing Wide Field-of-view Sensor chlorophyll-a (Chl-a) serves as an indicator to show the change in Chl-a concentration in the strait in response to the eddy-induced current. During the warm eddy period, the current carries the southern water of lower concentration northward, reducing Chl-a concentration in the strait. In contrast, Chl-a is enhanced because the cold eddy-induced southward current carries the northern water of higher concentration southward into the strait.

Dual optimization method of radiofrequency and quasistatic field simulations for reduction of eddy currents generated on 7T radiofrequency coil shielding.

PubMed

Zhao, Yujuan; Zhao, Tiejun; Raval, Shailesh B; Krishnamurthy, Narayanan; Zheng, Hai; Harris, Chad T; Handler, William B; Chronik, Blaine A; Ibrahim, Tamer S

2015-11-01

To optimize the design of radiofrequency (RF) shielding of transmit coils at 7T and reduce eddy currents generated on the RF shielding when imaging with rapid gradient waveforms. One set of a four-element, 2 × 2 Tic-Tac-Toe head coil structure was selected and constructed to study eddy currents on the RF coil shielding. The generated eddy currents were quantitatively studied in the time and frequency domains. The RF characteristics were studied using the finite difference time domain method. Five different kinds of RF shielding were tested on a 7T MRI scanner with phantoms and in vivo human subjects. The eddy current simulation method was verified by the measurement results. Eddy currents induced by solid/intact and simple-structured slotted RF shielding significantly distorted the gradient fields. Echo-planar images, B1+ maps, and S matrix measurements verified that the proposed slot pattern suppressed the eddy currents while maintaining the RF characteristics of the transmit coil. The presented dual-optimization method could be used to design RF shielding and reduce the gradient field-induced eddy currents while maintaining the RF characteristics of the transmit coil. © 2014 Wiley Periodicals, Inc.

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

PubMed Central

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

2016-01-01

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

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

PubMed

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

2016-05-07

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

Integral electrical characteristics and local plasma parameters of a RF ion thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masherov, P. E.; Riaby, V. A., E-mail: riaby2001@yahoo.com; Godyak, V. A.

2016-02-15

Comprehensive diagnostics has been carried out for a RF ion thruster based on inductively coupled plasma (ICP) source with an external flat antenna coil enhanced by ferrite core. The ICP was confined within a cylindrical chamber with low aspect ratio to minimize plasma loss to the chamber wall. Integral diagnostics of the ICP electrical parameters (RF power balance and coil current) allowed for evaluation of the antenna coils, matching networks, and eddy current loss and the true RF power deposited to plasma. Spatially resolved electron energy distribution functions, plasma density, electron temperatures, and plasma potentials were measured with movable Langmuirmore » probes.« less

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 2 2010-10-01 2010-10-01 false Eddy Current Examination With Visual Inspection... PACKAGINGS Pt. 180, App. C Appendix C to Part 180—Eddy Current Examination With Visual Inspection for DOT 3AL... procedure applicable to the test equipment it uses to perform eddy current examinations. 2. Visual...

High Tc SQUIDs and eddy-current NDE: a comprehensive investigation from real data to modelling

NASA Astrophysics Data System (ADS)

Ruosi, A.; Valentino, M.; Pepe, G.; Monebhurrun, V.; Lesselier, D.; Duchêne, B.

2000-11-01

The interest in magnetometry for eddy-current non-destructive testing, e.g. of planar conductive structures encountered in the aircraft industry, using high-temperature superconducting quantum interference devices (SQUIDs) is primarily due to their high sensitivity to magnetic flux even at very low frequencies. Here it is shown how theoretical, numerical and measurement machineries are combined to get reasonable synthetic and experimental data and to reach a good understanding of the interaction of diffusive wavefields with a damaged non-magnetic metal plate (as a first step towards the retrieval of pertinent features of the defects). The measurement modalities are considered first. It is illustrated in some detail how laboratory-controlled experiments are performed by a SQUID-based probe displaced above artificially damaged plates. Experimental data are then confronted with simulation results in order to evaluate the accuracy and reliability of this measurement system. Simulations are carried out by a computationally fast vector volume integral method dedicated to a planar layering affected by a volumetric defect, which involves the construction of the dyadic Green system of the layering.

Detection of Anomalous Machining Damages in Inconel 718 and TI 6-4 by Eddy Current Techniques

NASA Astrophysics Data System (ADS)

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

2010-02-01

This paper reports on an eddy current (EC) study aimed at detecting anomalous machining damages in Inconel 718 and Ti 6-4 samples, including (i) surface discontinuities such as re-depositing of chips onto the machined surface, and (ii) microstructural damages manifested as a white surface layer and a subsurface layer of distorted grains, typically tens of microns thick. A series of pristine and machine-damaged coupons were studied by EC scans using a differential probe operated at 2 MHz to detect discontinuous surface anomalies, and by swept high frequency EC (SHFEC) measurements from 0.5 MHz to 65.5 MHz using proprietary detection coils to detect surface microstructural damages. In general, the EC c-scan data from machine-damaged surfaces show spatial variations with larger standard deviations than those from the undamaged surfaces. In some cases, the c-scan images exhibit characteristic bipolar indications in good spatial correlation with surface anomalies revealed by optical microscopy and laser profilometry. Results of the SHFEC measurements indicate a reduced near-surface conductivity of the damaged surfaces compared to the undamaged surfaces.

Automated eddy current inspection of Space Shuttle APU turbine wheel blades

NASA Technical Reports Server (NTRS)

Fisher, Jay L.; Rowland, Stephen N.; Stolte, Jeffrey S.; Salkowski, Charles

1991-01-01

An automated inspection system based on eddy current 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.

Mitigation of eddy current heating during magnetic nanoparticle hyperthermia therapy.

PubMed

Stigliano, Robert V; Shubitidze, Fridon; Petryk, James D; Shoshiashvili, Levan; Petryk, Alicia A; Hoopes, P Jack

2016-11-01

Magnetic nanoparticle hyperthermia therapy is a promising technology for cancer treatment, involving delivering magnetic nanoparticles (MNPs) into tumours then activating them using an alternating magnetic field (AMF). The system produces not only a magnetic field, but also an electric field which penetrates normal tissue and induces eddy currents, resulting in unwanted heating of normal tissues. Magnitude of the eddy current depends, in part, on the AMF source and the size of the tissue exposed to the field. The majority of in vivo MNP hyperthermia therapy studies have been performed in small animals, which, due to the spatial distribution of the AMF relative to the size of the animals, do not reveal the potential toxicity of eddy current heating in larger tissues. This has posed a non-trivial challenge for researchers attempting to scale up to clinically relevant volumes of tissue. There is a relative dearth of studies focused on decreasing the maximum temperature resulting from eddy current heating to increase therapeutic ratio. This paper presents two simple, clinically applicable techniques for decreasing maximum temperature induced by eddy currents. Computational and experimental results are presented to understand the underlying physics of eddy currents induced in conducting, biological tissues and leverage these insights to mitigate eddy current heating during MNP hyperthermia therapy. Phantom studies show that the displacement and motion techniques reduce maximum temperature due to eddy currents by 74% and 19% in simulation, and by 77% and 33% experimentally. Further study is required to optimise these methods for particular scenarios; however, these results suggest larger volumes of tissue could be treated, and/or higher field strengths and frequencies could be used to attain increased MNP heating when these eddy current mitigation techniques are employed.

Development of eddy current microscopy for high resolution electrical conductivity imaging using atomic force microscopy.

PubMed

Nalladega, V; Sathish, S; Jata, K V; Blodgett, M P

2008-07-01

We present a high resolution electrical conductivity imaging technique based on the principles of eddy current and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents generated in the conducting sample are detected and measured with a magnetic tip attached to a flexible cantilever of an AFM. The eddy current generation and its interaction with the magnetic tip cantilever are theoretically modeled using monopole approximation. The model is used to estimate the eddy current force between the magnetic tip and the electrically conducting sample. The theoretical model is also used to choose a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the design of a high resolution electrical conductivity imaging system. The force between the tip and the sample due to eddy currents is measured as a function of the separation distance and compared to the model in a single crystal copper. Images of electrical conductivity variations in a polycrystalline dual phase titanium alloy (Ti-6Al-4V) sample are obtained by scanning the magnetic tip-cantilever held at a standoff distance from the sample surface. The contrast in the image is explained based on the electrical conductivity and eddy current force between the magnetic tip and the sample. The spatial resolution of the eddy current imaging system is determined by imaging carbon nanofibers in a polymer matrix. The advantages, limitations, and applications of the technique are discussed.

Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Computational and Experimental Analysis of Coaxial Intercapillary Positioning Effects on Sample Manipulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

ElNaggar, Mariam S; Barbier, Charlotte N; Van Berkel, Gary J

A coaxial geometry liquid microjunction surface sampling probe (LMJ-SSP) enables direct extraction of analytes from surfaces for subsequent analysis by techniques like mass spectrometry. Solution dynamics at the probe-to-sample surface interface in the LMJ-SSP has been suspected to influence sampling efficiency and dispersion but has not been rigorously investigated. The effect on flow dynamics and analyte transport to the mass spectrometer caused by coaxial retraction of the inner and outer capillaries from each other and the surface during sampling with a LMJ-SSP was investigated using computational fluid dynamics and experimentation. A transparent LMJ-SSP was constructed to provide the means formore » visual observation of the dynamics of the surface sampling process. Visual observation, computational fluid dynamics (CFD) analysis, and experimental results revealed that inner capillary axial retraction from the flush position relative to the outer capillary transitioned the probe from a continuous sampling and injection mode through an intermediate regime to sample plug formationmode caused by eddy currents at the sampling end of the probe. The potential for analytical implementation of these newly discovered probe operational modes is discussed.« less

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

PubMed

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

2015-03-01

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

Mesoscale Eddy Activity and Transport in the Atlantic Water Inflow Region North of Svalbard

NASA Astrophysics Data System (ADS)

Crews, L.; Sundfjord, A.; Albretsen, J.; Hattermann, T.

2018-01-01

Mesoscale eddies are known to transport heat and biogeochemical properties from Arctic Ocean boundary currents to basin interiors. Previous hydrographic surveys and model results suggest that eddy formation may be common in the Atlantic Water (AW) inflow area north of Svalbard, but no quantitative eddy survey has yet been done for the region. Here vorticity and water property signatures are used to identify and track AW eddies in an eddy-resolving sea ice-ocean model. The boundary current sheds AW eddies along most of the length of the continental slope considered, from the western Yermak Plateau to 40°E, though eddies forming east of 20°E are likely more important for slope-to-basin transport. Eddy formation seasonality reflects seasonal stability properties of the boundary current in the eastern portion of the study domain, but on and immediately east of the Yermak Plateau enhanced eddy formation during summer merits further investigation. AW eddies tend to be anticyclonic, have radii close to the local deformation radius, and be centered in the halocline. They transport roughly 0.16 Sv of AW and, due to their warm cores, 1.0 TW away from the boundary current. These findings suggest eddies may be important for halocline ventilation in the Eurasian Basin, as has been shown for Pacific Water eddies in the Canadian Basin.

3D Magnetic Field Analysis of a Turbine Generator Stator Core-end Region

NASA Astrophysics Data System (ADS)

Wakui, Shinichi; Takahashi, Kazuhiko; Ide, Kazumasa; Takahashi, Miyoshi; Watanabe, Takashi

In this paper we calculated magnetic flux density and eddy current distributions of a 71MVA turbine generator stator core-end using three-dimensional numerical magnetic field analysis. Subsequently, the magnetic flux densities and eddy current densities in the stator core-end region on the no-load and three-phase short circuit conditions obtained by the analysis have good agreements with the measurements. Furthermore, the differences of eddy current and eddy current loss in the stator core-end region for various load conditions are shown numerically. As a result, the facing had an effect that decrease the eddy current loss of the end plate about 84%.

Analysis and numerical modelling of eddy current damper for vibration problems

NASA Astrophysics Data System (ADS)

Irazu, L.; Elejabarrieta, M. J.

2018-07-01

This work discusses a contactless eddy current damper, which is used to attenuate structural vibration. Eddy currents can remove energy from dynamic systems without any contact and, thus, without adding mass or modifying the rigidity of the structure. An experimental modal analysis of a cantilever beam in the absence of and under a partial magnetic field is conducted in the bandwidth of 01 kHz. The results show that the eddy current phenomenon can attenuate the vibration of the entire structure without modifying the natural frequencies or the mode shapes of the structure itself. In this study, a new inverse method to numerically determine the dynamic properties of the contactless eddy current damper is proposed. The proposed inverse method and the eddy current model based on a lineal viscous force are validated by a practical application. The numerically obtained transfer function correlates with the experimental one, thus showing good agreement in the entire bandwidth of 01 kHz. The proposed method provides an easy and quick tool to model and predict the dynamic behaviour of the contactless eddy current damper, thereby avoiding the use of complex analytical models.

Eddies on the boundary between the Kuroshio current and coastal waters observed by HF ocean surface radar

NASA Astrophysics Data System (ADS)

Nadai, A.

2016-02-01

The HF ocean surface radar (HFOSR) is one of the powerful tools to measure the ocean current parameters like surface currents. Three observations of the Kuroshio current in the Tokara straight using HFOSR had done by the National Institute of Information and Comunications Technology (NICT: the former name is the Communications Research Laboratory). The first-order echoes on Doppler spectra of HFOSR shows broaden and splitting shape in the region of the border between the Kuroshio currents and coastal waters. The surface velocity maps show the existence of eddy on the border. The investigation of the mechanism of broadening first order-echoes by Nadai (2006) revealed that the modulation of wave fields from surface currents like eddy is the cause of broadening and the measured current fields also influenced the modulated wave fields. Moreover, Nadai (2006) also suggested that the influence is able to reduce using the average of two radial velocities extracted by the first-order echoes. In this paper, the results of current field observation around the border between the Kuroshio current and coastal waters are presented. Many small scale eddies are observed at the border of the Kuroshio current and coastal waters. The typical radius of the eddies is about 10km. Usury the observation of such a small scale eddy is difficult, but the eddies with same scale are observed by airborne synthetic aperture radar in the same area at different time. The eddies shows strong rotation as the typical tangential speed is about 1m/s. While the typical speed of the Kuroshio current is about 1.5m/s, the typical speed of the eddy movements is about 0.7m/s. No eddies generated in the radar coverage, but one or two eddies entered in the radar coverage a day. Therefore the origin of these eddies will exist in the upstream area of the radar coverage. Using the compensation method for the influence of the modulated wave field suggested by Nadai (2006), the eddies shows weak divergence. It is important to consider the mixing between the water of Kuroshio region and East China Sea. However the vertical structure is needed for more precise discussion.

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)

Automation for nondestructive inspection of aircraft

NASA Technical Reports Server (NTRS)

Siegel, M. W.

1994-01-01

We discuss the motivation and an architectural framework for using small mobile robots as automated aids to operators of nondestructive inspection (NDI) equipment. We review the need for aircraft skin inspection, and identify the constraints in commercial airlines operations that make small mobile robots the most attractive alternative for automated aids for NDI procedures. We describe the design and performance of the robot (ANDI) that we designed, built, and are testing for deployment of eddy current probes in prescribed commercial aircraft inspections. We discuss recent work aimed at also providing robotic aids for visual inspection.

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

PubMed Central

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

2016-01-01

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

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

PubMed

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

2016-07-29

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

The numeric calculation of eddy current distributions in transcranial magnetic stimulation.

PubMed

Tsuyama, Seichi; Hyodo, Akira; Sekino, Masaki; Hayami, Takehito; Ueno, Shoogo; Iramina, Keiji

2008-01-01

Transcranial magnetic stimulation (TMS) is a method to stimulate neurons in the brain. It is necessary to obtain eddy current distributions and determine parameters such as position, radius and bend-angle of the coil to stimulate target area exactly. In this study, we performed FEM-based numerical simulations of eddy current induced by TMS using three-dimentional human head model with inhomogeneous conductivity. We used double-cone coil and changed the coil radius and bend-angle of coil. The result of computer simulation showed that as coil radius increases, the eddy current became stronger everywhere. And coil with bend-angle of 22.5 degrees induced stronger eddy current than the coil with bendangle of 0 degrees. Meanwhile, when the bend-angle was 45 degrees, eddy current became weaker than these two cases. This simulation allowed us to determine appropriate parameter easier.

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

DOE PAGES

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

2017-04-18

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

Development of and Improved Magneto-Optic/Eddy-Current Imager

DOT National Transportation Integrated Search

1997-04-01

Magneto-optic/eddy-current imaging technology has been developed and approved for inspection of cracks in aging aircraft. This relatively new nondestructive test method gives the inspector the ability to quickly generate real-time eddy-current images...

Birth of a Loop Current Eddy

NASA Image and Video Library

2010-05-24

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

On the coupled use of sapflow and eddy covariance measurements: environmental impacts on the evapotranspiration of an heterogeneous - wild olives based - Sardinian ecosystem.

NASA Astrophysics Data System (ADS)

Curreli, Matteo; Corona, Roberto; Montaldo, Nicola; Oren, Ram

2015-04-01

Sapflow and eddy 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 eddy 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 eddy 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 coupled use of the sapflow sensor observations, a 2D footprint model of the eddy covariance tower and high resolution satellite images for the estimate of the foot print land cover map, the eddy 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 current 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 innovative allometric relationships between sapwood area, diameter, canopy cover area, which are needed for the correct upscale of the local tree measurements to the site plot larger scale. Results show the response of wild olives stomatal conductance to vapor pressure deficit that follow an exponential decrease. Interestingly the tree exposure impacts transpiration significantly, showing double rates for the trees in the south part of the wild olive clumps. The soil depth also affects ET dynamics due to the influence on water absorption of the root tree system. Finally using an innovative scaling procedure, the sap-flow transpiration at field scale have been compared to the eddy covariance ET, showing the impact of climate dynamics on the ET estimates with the two tecniques.

Best Practices for Evaluating the Capability of Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM) Techniques for Damage Characterization (Post-Print)

DTIC Science & Technology

2016-02-10

a wide range of part, environmental and damage conditions. Best practices of using models are presented for both an eddy current NDE sizing and...to assess the reliability of NDE and SHM characterization capability. Best practices of using models are presented for both an eddy current NDE... EDDY CURRENT NDE CASE STUDY An eddy current crack sizing case study is presented to highlight examples of some of these complex characteristics of

Computational Analysis of Static and Dynamic Behaviour of Magnetic Suspensions and Magnetic Bearings

NASA Technical Reports Server (NTRS)

Britcher, Colin P. (Editor); Groom, Nelson J.

1996-01-01

Static modelling of magnetic bearings is often carried out using magnetic circuit theory. This theory cannot easily include nonlinear effects such as magnetic saturation or the fringing of flux in air-gaps. Modern computational tools are able to accurately model complex magnetic bearing geometries, provided some care is exercised. In magnetic suspension applications, the magnetic fields are highly three-dimensional and require computational tools for the solution of most problems of interest. The dynamics of a magnetic bearing or magnetic suspension system can be strongly affected by eddy currents. Eddy currents are present whenever a time-varying magnetic flux penetrates a conducting medium. The direction of flow of the eddy current is such as to reduce the rate-of-change of flux. Analytic solutions for eddy currents are available for some simplified geometries, but complex geometries must be solved by computation. It is only in recent years that such computations have been considered truly practical. At NASA Langley Research Center, state-of-the-art finite-element computer codes, 'OPERA', 'TOSCA' and 'ELEKTRA' have recently been installed and applied to the magnetostatic and eddy current problems. This paper reviews results of theoretical analyses which suggest general forms of mathematical models for eddy currents, together with computational results. A simplified circuit-based eddy current model proposed appears to predict the observed trends in the case of large eddy current circuits in conducting non-magnetic material. A much more difficult case is seen to be that of eddy currents in magnetic material, or in non-magnetic material at higher frequencies, due to the lower skin depths. Even here, the dissipative behavior has been shown to yield at least somewhat to linear modelling. Magnetostatic and eddy current computations have been carried out relating to the Annular Suspension and Pointing System, a prototype for a space payload pointing and vibration isolation system, where the magnetic actuator geometry resembles a conventional magnetic bearing. Magnetostatic computations provide estimates of flux density within airgaps and the iron core material, fringing at the pole faces and the net force generated. Eddy current computations provide coil inductance, power dissipation and the phase lag in the magnetic field, all as functions of excitation frequency. Here, the dynamics of the magnetic bearings, notably the rise time of forces with changing currents, are found to be very strongly affected by eddy currents, even at quite low frequencies. Results are also compared to experimental measurements of the performance of a large-gap magnetic suspension system, the Large Angle Magnetic Suspension Test Fixture (LAMSTF). Eddy current effects are again shown to significantly affect the dynamics of the system. Some consideration is given to the ease and accuracy of computation, specifically relating to OPERA/TOSCA/ELEKTRA.

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

PubMed

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

2018-02-01

To design and evaluate eddy current-nulled convex optimized diffusion encoding (EN-CODE) gradient waveforms for efficient diffusion tensor imaging (DTI) that is free of eddy current-induced image distortions. The EN-CODE framework was used to generate diffusion-encoding waveforms that are eddy current-compensated. The EN-CODE DTI waveform was compared with the existing eddy current-nulled twice refocused spin echo (TRSE) sequence as well as monopolar (MONO) and non-eddy current-compensated CODE in terms of echo time (TE) and image distortions. Comparisons were made in simulations, phantom experiments, and neuro imaging in 10 healthy volunteers. The EN-CODE sequence achieved eddy current compensation with a significantly shorter TE than TRSE (78 versus 96 ms) and a slightly shorter TE than MONO (78 versus 80 ms). Intravoxel signal variance was lower in phantoms with EN-CODE than with MONO (13.6 ± 11.6 versus 37.4 ± 25.8) and not different from TRSE (15.1 ± 11.6), indicating good robustness to eddy current-induced image distortions. Mean fractional anisotropy values in brain edges were also significantly lower with EN-CODE than with MONO (0.16 ± 0.01 versus 0.24 ± 0.02, P < 1 x 10 -5 ) and not different from TRSE (0.16 ± 0.01 versus 0.16 ± 0.01, P = nonsignificant). The EN-CODE sequence eliminated eddy current-induced image distortions in DTI with a TE comparable to MONO and substantially shorter than TRSE. Magn Reson Med 79:663-672, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

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

PubMed

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

2014-11-01

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

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

NASA Astrophysics Data System (ADS)

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

2017-06-01

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

Probability of detection for bolt hole eddy current in extracted from service aircraft wing structures

NASA Astrophysics Data System (ADS)

Underhill, P. R.; Uemura, C.; Krause, T. W.

2018-04-01

Fatigue cracks are prone to develop around fasteners found in multi-layer aluminum structures on aging aircraft. Bolt hole eddy current (BHEC) is used for detection of cracks from within bolt holes after fastener removal. In support of qualification towards a target a90/95 (detect 90% of cracks of depth a, 95% of the time) of 0.76 mm (0.030"), a preliminary probability of detection (POD) study was performed to identify those parameters whose variation may keep a bolt hole inspection from attaining its goal. Parameters that were examined included variability in lift-off due to probe type, out-of-round holes, holes with diameters too large to permit surface-contact of the probe and mechanical damage to the holes, including burrs. The study examined the POD for BHEC of corner cracks in unfinished fastener holes extracted from service material. 68 EDM notches were introduced into two specimens of a horizontal stabilizer from a CC-130 Hercules aircraft. The fastener holes were inspected in the unfinished state, simulating potential inspection conditions, by 7 certified inspectors using a manual BHEC setup with an impedance plane display and also with one inspection conducted utilizing a BHEC automated C-Scan apparatus. While the standard detection limit of 1.27 mm (0.050") was achieved, given the a90/95 of 0.97 mm (0.039"), the target 0.76 mm (0.030") was not achieved. The work highlighted a number of areas where there was insufficient information to complete the qualification. Consequently, a number of recommendations were made. These included; development of a specification for minimum probe requirements; criteria for condition of the hole to be inspected, including out-of-roundness and presence of corrosion pits; statement of range of hole sizes; inspection frequency and data display for analysis.

Combined Wave and Current Bottom Boundary Layers: A Review

DTIC Science & Technology

2016-03-01

18 3.2 Wave and currents at arbitrary angles ....................................................................... 19 3.3 Eddy viscosity ...closure ................................................................................................. 22 3.3.1 Eddy viscosity for stratified fluids...23 3.3.2 Time-dependent eddy viscosities

Detection and sizing of cracks in structural steel using the eddy current method

DOT National Transportation Integrated Search

2000-11-01

This report summarizes research pertaining to the application of the Eddy Current method as a means of crack detection in structural steel members of highway bridges. Eddy currents are induced when an energized coil is placed near the surface of a co...

78 FR 15281 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-11

... horizontal stabilizer. This AD requires repetitive high frequency eddy current (HFEC) inspections for... repetitive high frequency eddy current (HFEC) inspections for cracking of the left and right rib hinge... high frequency eddy current (HFEC) inspection for cracking of the left and right rib hinge bearing lugs...

78 FR 46536 - Airworthiness Directives; Airbus Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-01

... eddy current inspection of the fastener holes for defects and repair if necessary. We are proposing... also includes doing a high frequency eddy current inspection of the fastener holes for defects and... frequency eddy current inspection of the fastener holes for defects and all applicable repairs, in...

77 FR 26993 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-08

... high frequency eddy current (HFEC) inspections for cracking in holes common to the splice strap and... tasks required by this paragraph: Before further flight, do a high frequency eddy current (HFEC... approval must specifically refer to this AD. (h) Detailed and High Frequency Eddy Current Inspections...

78 FR 71998 - Airworthiness Directives; Bombardier, Inc. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-02

... initial and repetitive [detailed or eddy current] inspections [for cracking and damage and replacement if... the detailed or eddy current inspection for cracking of the pilot-side rudder pedal tubes, specified... within 600 flight cycles thereafter. (2) If the most recent inspection was an eddy current inspection...

77 FR 61550 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-10

... inspection required by AD 2003-14-06 only terminates the external eddy current inspections required by..., which should not terminate the detailed or eddy current inspection, as specified. We find that... terminating action ``before the effective date of this AD'' terminates the eddy current inspections required...

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.

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

PubMed

Zhu, Zina; Meng, Zhuo

2016-07-01

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

Longitudinal gradient coil optimization in the presence of transient eddy currents.

PubMed

Trakic, A; Liu, F; Lopez, H Sanchez; Wang, H; Crozier, S

2007-06-01

The switching of magnetic field gradient coils in magnetic resonance imaging (MRI) inevitably induces transient eddy currents in conducting system components, such as the cryostat vessel. These secondary currents degrade the spatial and temporal performance of the gradient coils, and compensation methods are commonly employed to correct for these distortions. This theoretical study shows that by incorporating the eddy currents into the coil optimization process, it is possible to modify a gradient coil design so that the fields created by the coil and the eddy currents combine together to generate a spatially homogeneous gradient that follows the input pulse. Shielded and unshielded longitudinal gradient coils are used to exemplify this novel approach. To assist in the evaluation of transient eddy currents induced within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using the total-field scattered-field (TFSF) scheme was performed. The simulations demonstrate the effectiveness of the proposed method for optimizing longitudinal gradient fields while taking into account the spatial and temporal behavior of the eddy currents.

Eddy properties in the Southern California Current System

NASA Astrophysics Data System (ADS)

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

2018-05-01

The California Current System (CCS) is an eastern boundary upwelling system characterized by strong eddies that are often generated at the coast. These eddies contribute to intense, long-distance cross-shelf transport of upwelled water with enhanced biological activity. However, the mechanisms of formation of such coastal eddies, and more importantly their capacity to trap and transport tracers, are poorly understood. Their unpredictability and strong dynamics leave us with an incomplete picture of the physical and biological processes at work, their effects on coastal export, lateral water exchange among eddies and their surrounding waters, and how long and how far these eddies remain coherent structures. Focusing our analysis on the southern part of the CCS, we find a predominance of cyclonic eddies, with a 25-km radius and a SSH amplitude of 6 cm. They are formed near shore and travel slightly northwest offshore for 190 days at 2 km day-1. We then study one particular, representative cyclonic eddy using a combined Lagrangian and Eulerian numerical approach to characterize its kinematics. Formed near shore, this eddy trapped a core made up of 67% California Current waters and 33% California Undercurrent waters. This core was surrounded by other waters while the eddy detached from the coast, leaving the oldest waters at the eddy's core and the younger waters toward the edge. The eddy traveled several months as a coherent structure, with only limited lateral exchange within the eddy.

Test and Evaluation of an Eddy Current Clutch/Brake Propulsion System

DOT National Transportation Integrated Search

1975-01-01

This report covers the Phase II effort of a program to develop and test a 15 hp eddy-current clutch propulsion system. Included in the Phase 2 effort are the test and evaluation of the eddy-current clutch propulsion system on board a test vehicle. Th...

78 FR 4042 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-18

... provides an option for a high frequency eddy current inspection for cracking of the critical fastener holes... for a high frequency eddy current inspection for cracking of the critical fastener holes, and repair..., August 9, 2007)), do a high frequency eddy current (HFEC) inspection for cracking of the four critical...

77 FR 5724 - Airworthiness Directives; Fokker Services B.V. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-06

... proposed AD would require repetitive low frequency eddy current inspections of the forward fuselage butt... repetitive [low frequency eddy current] inspections of the forward fuselage butt joints for cracks and, when... effective date of this AD, whichever occurs later, do a low frequency eddy current inspection of the forward...

76 FR 38072 - Airworthiness Directives; The Boeing Company Model 777 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-29

... above. This proposed AD would require repetitive detailed inspection and high frequency eddy current... high frequency eddy current (HFEC) inspection for cracks in the WCS web pockets of spanwise beams... = 160 frequency eddy current inspection per hour = $4,250 inspection cycle. airplanes x $4,250 of...

77 FR 37788 - Airworthiness Directives; Fokker Services B.V. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-25

... Model F.28 Mark 0100 airplane. This AD requires repetitive low frequency eddy current inspections of the... described above, this [EASA] AD requires repetitive [low frequency eddy current] inspections of the forward... eddy current inspection of the forward fuselage butt-joints for cracks, in accordance with the...

78 FR 40050 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-03

... inspections or high frequency eddy current inspections for cracks of the blended area of the fuselage skin... repetitive external detailed inspections or high frequency eddy current inspections for cracks of the blended..., 2009) is August 3, 2009. (h) Repetitive High Frequency Eddy Current (HFEC) Inspections For airplanes on...

Nondestructive examination of recovery stage during annealing of a cold-rolled low-carbon steel using eddy current testing technique

NASA Astrophysics Data System (ADS)

Seyfpour, M.; Ghanei, S.; Mazinani, M.; Kashefi, M.; Davis, C.

2018-04-01

The recovery process in steel is usually investigated by conventional destructive tests that are expensive, time-consuming and also cumbersome. In this study, an alternative non-destructive test technique (based on eddy current testing) is used to characterise the recovery process during annealing of cold-rolled low-carbon steels. For assessing the reliability of eddy current results corresponding to different levels of recovery, X-ray line broadening analysis is also employed. It is shown that there is a strong relationship between eddy current outputs and the extent to which recovery occurs at different annealing temperatures. Accordingly, the non-destructive eddy current test technique represents the potential to be used as a reliable process for detection of the occurrence of recovery in the steel microstructure.

Mechanical properties and eddy current testing of thermally aged Z3CN20.09M cast duplex stainless steel

NASA Astrophysics Data System (ADS)

Liu, Tonghua; Wang, Wei; Qiang, Wenjiang; Shu, Guogang

2018-04-01

To study the thermal aging embrittlement of Z3CN20.09M duplex stainless steel produced in China, accelerated thermal aging experiments were carried out at 380 °C up to 9000 h. Microhardness measurements, Charpy impact and eddy current tests were performed on aged samples to characterize their thermal aging embrittlement. The results showed that the signal amplitude of eddy current decreased with the increase in aging time. Two quantitative correlations of the eddy current signal amplitude with both the Charpy impact energy, and the Vickers microhardness of the ferrite phase are obtained. The study showed that eddy current testing could be used to non-destructively evaluate the thermal aging embrittlement of cast duplex stainless steels.

Eddy current compensation for delta relaxation enhanced MR by dynamic reference phase modulation.

PubMed

Hoelscher, Uvo Christoph; Jakob, Peter M

2013-04-01

Eddy current compensation by dynamic reference phase modulation (eDREAM) is a compensation method for eddy current fields induced by B 0 field-cycling which occur in delta relaxation enhanced MR (dreMR) imaging. The presented method is based on a dynamic frequency adjustment and prevents eddy current related artifacts. It is easy to implement and can be completely realized in software for any imaging sequence. In this paper, the theory of eDREAM is derived and two applications are demonstrated. The theory describes how to model the behavior of the eddy currents and how to implement the compensation. Phantom and in vivo measurements are carried out and demonstrate the benefits of eDREAM. A comparison of images acquired with and without eDREAM shows a significant improvement in dreMR image quality. Images without eDREAM suffer from severe artifacts and do not allow proper interpretation while images with eDREAM are artifact free. In vivo experiments demonstrate that dreMR imaging without eDREAM is not feasible as artifacts completely change the image contrast. eDREAM is a flexible eddy current compensation for dreMR. It is capable of completely removing the influence of eddy currents such that the dreMR images do not suffer from artifacts.

Magnetic Field of Conductive Objects as Superposition of Elementary Eddy Currents and Eddy Current Tomography

NASA Astrophysics Data System (ADS)

Sukhanov, D. Ya.; Zav'yalova, K. V.

2018-03-01

The paper represents induced currents in an electrically conductive object as a totality of elementary eddy currents. The proposed scanning method includes measurements of only one component of the secondary magnetic field. Reconstruction of the current distribution is performed by deconvolution with regularization. Numerical modeling supported by the field experiments show that this approach is of direct practical relevance.

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

PubMed

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

2011-06-01

Dynamic B(0) shimming (DS) can produce better field homogeneity than static global shimming by dynamically updating slicewise shim values in a multislice acquisition. The performance of DS however is limited by eddy current fields produced by the switching of 2nd and 3rd order unshielded shims. In this work, we present a novel method of eddy field compensation (EFC) applied to higher order shim induced eddy current fields in multislice DS. This method does not require shim shielding, extra hardware for eddy current compensation or subject specific prescanning. The interactions between shim harmonics are modeled assuming steady state of the medium and long time constant, cross and self term eddy fields in a DS experiment and 'correction factors' characterizing the entire set of shim interactions are derived. The correction factors for a given time between shim switches are shown to be invariable with object scanned, shim switching pattern and actual shim values, allowing for their generalized prospective use. Phantom and human head, 2nd and 3rd order DS experiments performed without any hardware eddy current compensation using the technique show large reductions in field gradients and offsets leading to significant improvements in image quality. This method holds promise as an alternative to expensive hardware based eddy current compensation required in 2nd and 3rd order DS. Copyright © 2011 Elsevier Inc. All rights reserved.

Gravity Probe B spacecraft description

NASA Astrophysics Data System (ADS)

Bennett, Norman R.; Burns, Kevin; Katz, Russell; Kirschenbaum, Jon; Mason, Gary; Shehata, Shawky

2015-11-01

The Gravity Probe B spacecraft, developed, integrated, and tested by Lockheed Missiles & Space Company and later Lockheed Martin Corporation, consisted of structures, mechanisms, command and data handling, attitude and translation control, electrical power, thermal control, flight software, and communications. When integrated with the payload elements, the integrated system became the space vehicle. Key requirements shaping the design of the spacecraft were: (1) the tight mission timeline (17 months, 9 days of on-orbit operation), (2) precise attitude and translational control, (3) thermal protection of science hardware, (4) minimizing aerodynamic, magnetic, and eddy current effects, and (5) the need to provide a robust, low risk spacecraft. The spacecraft met all mission requirements, as demonstrated by dewar lifetime meeting specification, positive power and thermal margins, precision attitude control and drag-free performance, reliable communications, and the collection of more than 97% of the available science data.

Observations of the interaction between near-inertial waves and mesoscale eddies

NASA Astrophysics Data System (ADS)

Martínez-Marrero, Antonio; Sangrá, Pablo; Caldeira, Rui; Aguiar-González, Borja; Rodríguez-Santana, Ángel

2014-05-01

Trajectories of eight drifters dragged below the surface mixed layer and current meter data from a mooring are used to analyse the interaction between near-inertial waves and mesoscale eddies. Drifters were deployed within eddies generated downstream of Canary and Madeira islands between 1998 and 2007. The mooring was installed in the passage of cyclonic eddies induced by Gran Canaria island during 2006. Rotatory wavelet analysis of Lagrangian velocities shows a clear relationship between the near-inertial waves' intrinsic frequencies and the eddy angular velocities. The results reveal that near-inertial waves reach a minimum frequency of half the planetary vorticity (f/2) in the inner core of young anticyclonic eddies rotating with its maximum absolute angular speed of f/2. The highest amplitudes of the observed inertial motions are also found within anticyclonic eddies evidencing the trapping of inertial waves. Finally, the analysis of the current meter series show frequency fluctuations of the near-inertial currents in the upper 500 meters that are related to the passage of cyclonic eddies. These fluctuations appear to be consistent with the variation of the background vorticity produced by the eddies.

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 S p . 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. S p /S m of aluminum particles in crushed waste refrigerators ranged from 0.08 to 0.51. Separation efficiency increased as the increase of S p /S m . 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 S p of aluminum particles brought positive impact on separation efficiency. Greater S p could increase critical feeding speed to offer greater throughput of eddy current separation. This paper will guide eddy current separation in production of recovering nonferrous metals from crushed e-waste. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, L. J.; Yu, K. X.; Zhang, M., E-mail: zhangming@hust.edu.cn

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 distributionmore » 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.« less

Observations and Numerical Modeling of Eddy Generation in the Mediterranean Undercurrent

NASA Astrophysics Data System (ADS)

Serra, N.; Ambar, I.; Kaese, R.

2001-12-01

In the frame of the European Union MAST III project CANIGO (Canary Islands Gibraltar Azores Observations), RAFOS floats were deployed in the Mediterranean undercurrent off south Portugal during the period from September 1997 to September 1998. An analysis of this Lagrangian approach complemented with results obtained with XBT probes and current meter data from the same project shows some of the major aspects of the flow associated with the undercurrent as well as the eddy activity related with it. Floats that stayed in the undercurrent featured a downstream deceleration and a steering by bottom topography. Three meddy formations at Cape St. Vincent could be isolated from the float data as well as the generation of dipolar structures in the Portimao Canyon, a feature not previously directly observed. The dynamical coupling of meddies and cyclones was observed for a considerable period of time. High-resolution modeling of the Mediterranean Outflow using a sigma-coordinate primitive equations ocean model (SCRUM) incorporating realistic topography and stratification reveals the adjustment of the salty plume while descending along the continental slope of the Gulf of Cadiz channeled by the topography. The model reproduces the generation of eddies in the two observed sites (cape and canyon) and the splitting of the outflow water into well-defined cores.

Review of progress in quantitative NDE

NASA Astrophysics Data System (ADS)

s of 386 papers and plenary presentations are included. The plenary sessions are related to the national technology initiative. The other sessions covered the following NDE topics: corrosion, electromagnetic arrays, elastic wave scattering and backscattering/noise, civil structures, material properties, holography, shearography, UT wave propagation, eddy currents, coatings, signal processing, radiography, computed tomography, EM imaging, adhesive bonds, NMR, laser ultrasonics, composites, thermal techniques, magnetic measurements, nonlinear acoustics, interface modeling and characterization, UT transducers, new techniques, joined materials, probes and systems, fatigue cracks and fracture, imaging and sizing, NDE in engineering and process control, acoustics of cracks, and sensors. An author index is included.

Corrosion-Indicating Pigment And Probes

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph; Bugga, Ratnakumar V.; Attia, Alan I.

1993-01-01

Proposed hydrogen-sensitive paint for metal structures changes color at onset of corrosion, involving emission of hydrogen as result of electrochemical reactions. Pigment of suitable paint includes rhodium compound RhCl(PPh3)3, known as Wilkinson's catalyst. As coating on critical parts of such structures as bridges and aircraft, paint gives early warning of corrosion, and parts thus repaired or replaced before failing catastrophically. Reveals corrosion before it becomes visible to eye. Inspection for changes in color not ordinarily necessitate removal of structure from service, and costs less than inspection by x-ray or thermal neutron radiography, ultrasonic, eddy-current, or acoustic-emission techniques.

77 FR 64709 - Airworthiness Directives; MD Helicopters, Inc.

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-23

... visual inspection, and if necessary, an eddy current inspection of the main rotor lower hub assembly... specifies an initial 100-hour and recurring 300-hour visual and eddy current inspections of the lower hub... a total cost per helicopter of $85 and a total cost of $1,020 for the fleet. Eddy current inspecting...

77 FR 37332 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-21

... the high frequency eddy current inspection for cracking of the critical fastener holes, and repair if... of the bulkhead, and repair if necessary; and proposed an option to the high frequency eddy current...-15152 (72 FR 44753, August 9, 2007)), do a high frequency eddy current (HFEC) inspection for cracking of...

77 FR 43178 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-24

... eddy current high frequency (ETHF) inspections for cracking on the aft side of the left and right wing... NPRM proposed to require repetitive eddy current high frequency (ETHF) inspections for cracking on the...,000 flight cycles after the effective date of this AD, whichever occurs later, do an eddy current high...

76 FR 14349 - Airworthiness Directives; British Aerospace Regional Aircraft Model HP.137 Jetstream Mk.1...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-16

... (FC). For the reasons described above, this AD requires initial and repetitive eddy current... requires initial and repetitive eddy current inspections, and depending on findings, accomplishment of... (landings) on the MLG after the effective date of this AD, whichever occurs later, eddy current inspect all...

78 FR 73457 - Airworthiness Directives; the Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-06

... frequency eddy current inspections for cracking of the tension tie at BS 760 or 780, as applicable, and do... ties, including doing an open-hole high frequency eddy current inspection for cracks, as applicable...) and paragraph (i) of this AD, but not as AMOCs for the high frequency eddy current inspections...

76 FR 58094 - Airworthiness Directives; 328 Support Services GmbH (Type Certificate Previously Held by AvCraft...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-20

... subsequent Eddy Current inspection (NDI) [non-destructive inspection] of the same area to detect cracks... inspections are eddy current inspections. The modification includes cold expansion of the former lower wing... with consequent loss of control. * * * * * The new inspections are eddy current inspections. The...

76 FR 58416 - Airworthiness Directives; Lockheed Martin Corporation/Lockheed Martin Aeronautics Company Model L...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-21

... specifies a bolt hole eddy current inspection to verify the cracking. The corrective actions for cracking... specified in paragraph (k) of this AD, do eddy current non-destructive inspections (NDI) and detailed... secondary eddy current inspection to detect cracking of fastener holes with suspected crack indications; in...

77 FR 18963 - Airworthiness Directives; MD Helicopters, Inc.

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-29

...) Model MD900 helicopters. The existing AD requires a visual inspection, and if necessary, an eddy current... with an airworthy lower hub. If there is no crack as a result of the visual inspection, eddy current... nondestructive eddy current inspection of the lower hub. That AD was prompted by cracks found on four lower hubs...

77 FR 21402 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-10

... option is to conduct an eddy current inspection and the other option is to conduct a visual inspection... blade sanding inspection rather than the eddy current inspection, at an average labor rate of $85 per.... (1) Inspect by using either an eddy current inspection in accordance with paragraphs B.(1)(a) through...

Quantification and Compensation of Eddy-Current-Induced Magnetic Field Gradients

PubMed Central

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

2011-01-01

Two robust techniques for quantification and compensation of eddy-current-induced magnetic-field gradients and static magnetic-field shifts (ΔB0) in MRI systems are described. Purpose-built 1-D or 6-point phantoms are employed. Both procedures involve measuring the effects of a prior magnetic-field-gradient test pulse on the phantom’s free induction decay (FID). Phantom-specific analysis of the resulting FID data produces estimates of the time-dependent, eddy-current-induced magnetic field gradient(s) and ΔB0 shift. Using Bayesian methods, the time dependencies of the eddy-current-induced decays are modeled as sums of exponentially decaying components, each defined by an amplitude and time constant. These amplitudes and time constants are employed to adjust the scanner’s gradient pre-emphasis unit and eliminate undesirable eddy-current effects. Measurement with the six-point sample phantom allows for simultaneous, direct estimation of both on-axis and cross-term eddy-current-induced gradients. The two methods are demonstrated and validated on several MRI systems with actively-shielded gradient coil sets. PMID:21764614

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

PubMed

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

2011-09-01

Two robust techniques for quantification and compensation of eddy-current-induced magnetic-field gradients and static magnetic-field shifts (ΔB0) in MRI systems are described. Purpose-built 1-D or six-point phantoms are employed. Both procedures involve measuring the effects of a prior magnetic-field-gradient test pulse on the phantom's free induction decay (FID). Phantom-specific analysis of the resulting FID data produces estimates of the time-dependent, eddy-current-induced magnetic field gradient(s) and ΔB0 shift. Using Bayesian methods, the time dependencies of the eddy-current-induced decays are modeled as sums of exponentially decaying components, each defined by an amplitude and time constant. These amplitudes and time constants are employed to adjust the scanner's gradient pre-emphasis unit and eliminate undesirable eddy-current effects. Measurement with the six-point sample phantom allows for simultaneous, direct estimation of both on-axis and cross-term eddy-current-induced gradients. The two methods are demonstrated and validated on several MRI systems with actively-shielded gradient coil sets. Copyright © 2011 Elsevier Inc. All rights reserved.

An avenue of eddies: Quantifying the biophysical properties of mesoscale eddies in the Tasman Sea

NASA Astrophysics Data System (ADS)

Everett, J. D.; Baird, M. E.; Oke, P. R.; Suthers, I. M.

2012-08-01

The Tasman Sea is unique - characterised by a strong seasonal western boundary current that breaks down into a complicated field of mesoscale eddies almost immediately after separating from the coast. Through a 16-year analysis of Tasman Sea eddies, we identify a region along the southeast Australian coast which we name ‘Eddy Avenue’ where eddies have higher sea level anomalies, faster rotation and greater sea surface temperature and chlorophyll a anomalies. The density of cyclonic and anticyclonic eddies within Eddy Avenue is 23% and 16% higher respectively than the broader Tasman Sea. We find that Eddy Avenue cyclonic and anticyclonic eddies have more strongly differentiated biological properties than those of the broader Tasman Sea, as a result of larger anticyclonic eddies formed from Coral Sea water depressing chl. a concentrations, and for coastal cyclonic eddies due to the entrainment of nutrient-rich shelf waters. Cyclonic eddies within Eddy Avenue have almost double the chlorophyll a (0.35 mg m-3) of anticyclonic eddies (0.18 mg m-3). The average chlorophyll a concentration for cyclonic eddies is 16% higher in Eddy Avenue and 28% lower for anticyclonic eddies when compared to the Tasman Sea. With a strengthening East Australian Current, the propagation of these eddies will have significant implications for heat transport and the entrainment and connectivity of plankton and larval fish populations.

Impacts of the Mesoscale Ocean-Atmosphere Coupling on the Peru-Chile Ocean Dynamics: The Current-Induced Wind Stress Modulation

NASA Astrophysics Data System (ADS)

Oerder, V.; Colas, F.; Echevin, V.; Masson, S.; Lemarié, F.

2018-02-01

The ocean dynamical responses to the surface current-wind stress interaction at the oceanic mesoscale are investigated in the South-East Pacific using a high-resolution regional ocean-atmosphere coupled model. Two simulations are compared: one includes the surface current in the wind stress computation while the other does not. In the coastal region, absolute wind velocities are different between the two simulations but the wind stress remains very similar. As a consequence, the mean regional oceanic circulation is almost unchanged. On the contrary, the mesoscale activity is strongly reduced when taking into account the effect of the surface current on the wind stress. This is caused by a weakening of the eddy kinetic energy generation near the coast by the wind work and to intensified offshore eddy damping. We show that, above coherent eddies, the current-stress interaction generates eddy damping through Ekman pumping and eddy kinetic energy dissipation through wind work. This alters significantly the coherent eddy vertical structures compared with the control simulation, weakening the temperature and vorticity anomalies and increasing strongly the vertical velocity anomalies associated to eddies.

Use of eddy current mixes to solve a weld examination application

DOE Office of Scientific and Technical Information (OSTI.GOV)

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.

A combined experimental and finite element analysis method for the estimation of eddy-current loss in NdFeB magnets.

PubMed

Fratila, Radu; Benabou, Abdelkader; Tounzi, Abdelmounaïm; Mipo, Jean-Claude

2014-05-14

NdFeB permanent magnets (PMs) are widely used in high performance electrical machines, but their relatively high conductivity subjects them to eddy current losses that can lead to magnetization loss. The Finite Element (FE) method is generally used to quantify the eddy current 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 eddy current losses that are then compared with those of a 3D FE model.

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

NASA Astrophysics Data System (ADS)

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

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

A High-Sensitivity Flexible Eddy Current Array Sensor for Crack Monitoring of Welded Structures under Varying Environment.

PubMed

Chen, Tao; He, Yuting; Du, Jinqiang

2018-06-01

This paper develops a high-sensitivity flexible eddy current array (HS-FECA) sensor for crack monitoring of welded structures under varying environment. Firstly, effects of stress, temperature and crack on output signals of the traditional flexible eddy current array (FECA) sensor were investigated by experiments that show both stress and temperature have great influences on the crack monitoring performance of the sensor. A 3-D finite element model was established using Comsol AC/DC module to analyze the perturbation effects of crack on eddy currents and output signals of the sensor, which showed perturbation effect of cracks on eddy currents is reduced by the current loop when crack propagates. Then, the HS-FECA sensor was proposed to boost the sensitivity to cracks. Simulation results show that perturbation effect of cracks on eddy currents excited by the HS-FECA sensor gradually grows stronger when the crack propagates, resulting in much higher sensitivity to cracks. Experimental result further shows that the sensitivity of the new sensor is at least 19 times that of the original one. In addition, both stress and temperature variations have little effect on signals of the new sensor.

Eddy-current testing of fatigue degradation upon contact fatigue loading of gas powder laser clad NiCrBSi-Cr3C2 composite coating

NASA Astrophysics Data System (ADS)

Savrai, R. A.; Makarov, A. V.; Gorkunov, E. S.; Soboleva, N. N.; Kogan, L. Kh.; Malygina, I. Yu.; Osintseva, A. L.; Davydova, N. A.

2017-12-01

The possibilities of the eddy-current method for testing the fatigue degradation under contact loading of gas powder laser clad NiCrBSi-Cr3C2 composite coating with 15 wt.% of Cr3C2 additive have been investigated. It is shown that the eddy-current testing of the fatigue degradation under contact loading of the NiCrBSi-15%Cr3C2 composite coating can be performed at high excitation frequencies 72-120 kHz of the eddy-current transducer. At that, the dependences of the eddy-current instrument readings on the number of loading cycles have both downward and upward branches, with the boundary between the branches being 3×105 cycles in the given loading conditions. This is caused, on the one hand, by cracking, and, on the other hand, by cohesive spalling and compaction of the composite coating, which affect oppositely the material resistivity and, correspondingly, the eddy-current instrument readings. The downward branch can be used to monitor the processes of crack formation and growth, the upward branch - to monitor the degree of cohesive spalling, while taking into account in the testing methodology an ambiguous character of the dependences of the eddy-current instrument readings on the number of loading cycles.

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.

76 FR 52901 - Airworthiness Directives; The Boeing Company Model 757-200, -200PF, and -200CB Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-24

... if necessary. This proposed AD would also add an option for the high frequency eddy current... also adds an optional ultrasonic inspection for the high frequency eddy current inspection to detect... proposed AD would also add an option for the high frequency eddy current inspection for cracking of the...

77 FR 21395 - Airworthiness Directives; Fokker Services B.V. Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-10

... would require performing a low frequency eddy current inspection for cracks of the lap joint of the rear...-frequency eddy current inspection of the lap joint for cracks and, depending on findings, repair of the lap... AD: Do a low frequency eddy current (LFEC) inspection for cracks of the lap joint of the rear...

76 FR 41662 - Airworthiness Directives; MD Helicopters, Inc. Model MD900 Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-15

... different compliance time; adds an eddy current inspection; retains the requirement to replace a cracked... and recurring 300-hour visual and eddy current inspections of the lower hub for a crack and, if there... AD requires a visual inspection, and if necessary, an eddy current inspection of the lower hub for a...

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

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.

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

PubMed

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

2014-03-14

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.

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

76 FR 9495 - Airworthiness Directives; Air Tractor, Inc. Models AT-802 and AT-802A Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-18

...-18, which requires you to repetitively inspect (using the eddy current method) the two outboard... through 0101 and AT-802A-0092 through 0101: To perform, using the eddy current method, two inspections at... through 0178 and AT-802A-0102 through 0178 to perform using the eddy current method, two inspections at 5...

76 FR 2281 - Airworthiness Directives; BAE SYSTEMS (OPERATIONS) LIMITED Model BAe 146 Airplanes, and Model...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-13

... this AD, perform an external eddy current inspection of the forward fuselage skin to detect cracking... paragraphs (j)(1), (j)(2), and (j)(3) of this AD, do an external eddy current inspection of the forward... this AD, do an external eddy current inspection of the forward fuselage skin to detect cracking, in...

76 FR 66209 - Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Model S-92A Helicopters

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-26

... option is to conduct an eddy current inspection and the other option is to conduct a visual inspection... eddy current inspection, at an average labor rate of $85 per work hour. Required parts would cost about... using either an eddy current inspection in accordance with paragraphs B.(1)(a) through B.(1)(o) or using...

75 FR 5692 - Airworthiness Directives; The Boeing Company Model 747-200C and -200F Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-04

... all Model 747-200C and -200F series airplanes. This AD requires a high frequency eddy current (HFEC... on July 6, 2009 (74 FR 31894). That NPRM proposed to require a high frequency eddy current inspection..., whichever occurs later: Do an open-hole high frequency eddy current (HFEC) inspection of all the fastener...

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.

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

NASA Astrophysics Data System (ADS)

Krauter, N.; Stefani, F.

2017-10-01

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

Eddy current measurement of the thickness of top Cu film of the multilayer interconnects in the integrated circuit (IC) manufacturing process

NASA Astrophysics Data System (ADS)

Qu, Zilian; Meng, Yonggang; Zhao, Qian

2015-03-01

This paper proposes a new eddy current method, named equivalent unit method (EUM), for the thickness measurement of the top copper film of multilayer interconnects in the chemical mechanical polishing (CMP) process, which is an important step in the integrated circuit (IC) manufacturing. The influence of the underneath circuit layers on the eddy current is modeled and treated as an equivalent film thickness. By subtracting this equivalent film component, the accuracy of the thickness measurement of the top copper layer with an eddy current sensor is improved and the absolute error is 3 nm for sampler measurement.

An efficient 3-D eddy-current solver using an independent impedance method for transcranial magnetic stimulation.

PubMed

De Geeter, Nele; Crevecoeur, Guillaume; Dupre, Luc

2011-02-01

In many important bioelectromagnetic problem settings, eddy-current simulations are required. Examples are the reduction of eddy-current artifacts in magnetic resonance imaging and techniques, whereby the eddy currents 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 eddy currents 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 eddy-current 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.

A numerical study of the acoustic radiation due to eddy current-cryostat interactions.

PubMed

Wang, Yaohui; Liu, Feng; Zhou, Xiaorong; Li, Yu; Crozier, Stuart

2017-06-01

To investigate the acoustic radiation due to eddy current-cryostat interactions and perform a qualitative analysis on noise reduction methods. In order to evaluate the sound pressure level (SPL) of the eddy current induced warm bore wall vibration, a Finite Element (FE) model was created to simulate the noises from both the warm bore wall vibration and the gradient coil assembly. For the SPL reduction of the warm bore wall vibration, we first improved the active shielding of the gradient coil, thus reducing the eddy current on the warm bore wall. A damping treatment was then applied to the warm bore wall to control the acoustic radiation. Initial simulations show that the SPL of the warm bore wall is higher than that of the gradient assembly with typical design shielding ratios at many frequencies. Subsequent simulation results of eddy current control and damping treatment application show that the average SPL reduction of the warm bore wall can be as high as 9.6 dB, and even higher in some frequency bands. Combining eddy current control and suggested damping scheme, the noise level in a MRI system can be effectively reduced. © 2017 American Association of Physicists in Medicine.

[Quantitative experiment and analysis of gradient-induced eddy currents on magnetic resonance imaging].

PubMed

He, Wenjing; Zhu, Yuanzhong; Wang, Wenzhou; Zou, Kai; Zhang, Kai; He, Chao

2017-04-01

Pulsed magnetic field gradients generated by gradient coils are widely used in signal location in magnetic resonance imaging (MRI). However, gradient coils can also induce eddy currents in final magnetic field in the nearby conducting structures which lead to distortion and artifact in images, misguiding clinical diagnosis. We tried in our laboratory to measure the magnetic field of gradient-induced eddy current in 1.5 T superconducting magnetic resonance imaging device; and extracted key parameters including amplitude and time constant of exponential terms according to inductance-resistance series mathematical module. These parameters of both self-induced component and crossing component are useful to design digital filters to implement pulse pre-emphasize to reshape the waveform. A measure device that is a basement equipped with phantoms and receiving coils was designed and placed in the isocenter of the magnetic field. By applying testing sequence, contrast experiments were carried out in a superconducting magnet before and after eddy current compensation. Sets of one dimension signal were obtained as raw data to calculate gradient-induced eddy currents. Curve fitting by least squares method was also done to match inductance-resistance series module. The results also illustrated that pulse pre-emphasize measurement with digital filter was correct and effective in reducing eddy current effect. Pre-emphasize waveform was developed based on system function. The usefulness of pre-emphasize measurement in reducing eddy current was confirmed and the improvement was also presented. All these are valuable for reducing artifact in magnetic resonance imaging device.

Eddy current probe and method for flaw detection in metals

DOEpatents

Watjen, J.P.

1987-06-23

A flaw detecting system is shown which includes a probe having a pair of ferrite cores with in-line gaps in close proximity to each other. An insulating, non-magnetic, non-conducting holder fills the gaps and supports the ferrite cores in a manner such that the cores form a generally V-shape. Each core is provided with an excitation winding and a detection winding. The excitation windings are connected in series or parallel with an rf port for connection thereof to a radio frequency source. The detection windings, which are differentially wound, are connected in series circuit to a detector port for connection to a voltage measuring instrument. The ferrite cores at the in-line gaps directly engage the metal surface of a test piece, and the probe is scanned along the test piece. In the presence of a flaw in the metal surface the detection winding voltages are unbalanced, and the unbalance is detected by the voltage measuring instrument. The insulating holder is provided with a profile which conforms to that of a prominent feature of the test piece to facilitate movement of the probe along the feature, typically an edge or a corner. 9 figs.

Eddy current probe and method for flaw detection in metals

DOEpatents

Watjen, John P.

1987-06-23

A flaw detecting system is shown which includes a probe having a pair of ferrite cores with in-line gaps in close proximity to each other. An insulating, non-magnetic, non-conducting holder fills the gaps and supports the ferrite cores in a manner such that the cores form a generally V-shape. Each core is provided with an excitation winding and a detection winding. The excitation windings are connected in series or parallel with an rf port for connection thereof to a radio frequency source. The detection windings, which are differentially wound, are connected in series circuit to a detector port for connection to a voltage measuring instrument. The ferrite cores at the in-line gaps directly engage the metal surface of a test piece, and the probe is scanned along the test piece. In the presence of a flaw in the metal surface the detection winding voltages are unbalanced, and the unbalance is detected by the voltage measuring instrument. The insulating holder is provided with a profile which conforms to that of a prominent feature of the test piece to facilitate movement of the probe along the feature, typically an edge or a corner.

The Dynamics of Cuba Anticyclones (CubANs) and Interaction With the Loop Current/Florida Current System

NASA Astrophysics Data System (ADS)

Kourafalou, Vassiliki; Androulidakis, Yannis; Le Hénaff, Matthieu; Kang, HeeSook

2017-10-01

Mesoscale anticyclonic eddies along the northern Cuban coast (CubANs) have been identified in the Straits of Florida, associated with the northward shift of the Florida Current (FC) and the anticyclonic curvature of the Loop Current (LC) at the western entrance of the Straits. The dynamics of CubAN eddies and their interaction with the LC/FC system are described for the first time using satellite, drifter and buoy data, and a high-resolution model. It is shown that the evolution of CubANs to the south of the FC front complements the evolution of cyclonic eddies to the north of the FC, advancing previous studies on synergy between FC meandering and eddy activity. Two types of CubAN eddies are characterized: (a) a main anticyclonic cell (type "A") within the core of the LC during retracted phase conditions, associated with the process of LC Eddy (LCE) shedding from an extended LC, and (b) an individual, distinct anticyclonic eddy that is released from the main LC core and is advected eastward, along the northern Cuban coast (type "B"). There are also mixed cases, when the process of LCE shedding has started, so a type "A" CubAN is being formed, in the presence of one or more eastward progressing type "B" eddies. CubAN evolution is associated with an increased mixed layer and weaker stratification of the upper ocean along the eddy's track. The cyclonic activity along the Cuban coast and wind-induced upwelling events also contribute to the evolution and fate of the CubAN eddies.

Formation of Maximum Eddy Current Force by Non Ferrous Materials

NASA Astrophysics Data System (ADS)

Kader, M. M. A.; Razali, Z. B.; Yasin, N. S. M.; Daud, M. H.

2018-03-01

This project is concerned with the study of eddy current effects on various materials such as aluminum, copper and magnesium. Two types of magnets used in this study; magnetic ferrite (ZnFe+2O4) and magnetic neodymium (NdFeBN42). Eddy current force will be exerted to these materials due to current flows along the magnet. This force depends on the type of magnet, type of material and the gap between the magnet and the material or between the two magnets. The results show that at constant magnet to material gap, the eddy current force decreases as the magnet to magnet gap increases. Similarly, at constant magnet to magnet gap, the eddy current force decreases as the magnet to material gap increases. The minimum force was achieved when the gap of magnet to material is maximum, similarly to the gap of magnet to magnet. The weakest force was between Copper and Neodymium at a magnet to material gap of 20 mm and magnet to magnet gap of 40 mm; the eddy current force was 0.00048 N. The strongest force (maximum) was between Magnesium and Ferrite and 0.42273 N at a magnet to material gap of 3 mm and magnet to magnet gap of 5 mm.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 themore » equilibrium reconstruction are presented.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmitt, J. C., E-mail: jschmitt@pppl.gov; Lazerson, S.; Majeski, R.

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 themore » equilibrium reconstruction are presented.« less

75 FR 5677 - Airworthiness Directives; The Boeing Company Model 767-200, -300, and -300F Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-04

... detailed and eddy current inspections to detect cracks and corrosion of certain midspar fuse pins, and... addition to longitudinal cracks. In addition, eddy current inspection of the midspar fuse pins in..., 311T3102-3, 311T3102-4, 311T2102-1 or 311T2102-2: Do a detailed inspection and an eddy current inspection...

75 FR 35611 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, and MD-10-10F...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-23

... one-time high frequency eddy current inspection of fastener holes for cracks at the left and right... frequency eddy current inspection of fastener holes for cracks at the left and right side wing rear spar... frequency eddy current inspection for cracking of fastener holes at the left and right side wing rear spar...

75 FR 38061 - Airworthiness Directives; Airbus Model A300 B4-600 Series Airplanes; Model A300 B4-600R Series...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-01

... dimensional measurement of the holes, and doing corrective actions if necessary; doing an eddy current... dimensional measurement of the holes, doing an eddy current inspection of the holes for cracking, doing a cold... the effective date of this AD, prior to doing any cold working process, determine if an eddy current...

75 FR 2831 - Airworthiness Directives; McDonnell Douglas Corporation Model DC-10-10, DC-10-10F, and MD-10-10F...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-19

... proposed AD would require a one-time high frequency eddy current inspection of fastener holes for cracks at... high frequency eddy current inspection of fastener holes for cracking at the left and right side wing... of this AD, do a one-time high frequency eddy current inspection for cracking of fastener holes at...

75 FR 16683 - Airworthiness Directives; The Boeing Company Model 777-200LR and -300ER Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-02

... eddy current inspection for cracking of the keyway of the fuel tank access door cutout on the left and... frequency eddy current (HFEC) inspection for cracking at the keyway of the fuel tank access door cutout on... frequency eddy current (HFEC) inspection for cracking of the keyway of the fuel tank access door cutout on...

76 FR 1990 - Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-6, PC-6-H1, PC-6-H2, PC-6/350, PC-6/350...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-12

... eddy current and visual inspections of the upper wing strut fitting for evidence of cracks, wear and/or... permitted extending the intervals for the repetitive eddy current and visual inspections from 100 Flight... the applicability and to require repetitive eddy current and visual inspections of the upper wing...

75 FR 62005 - Airworthiness Directives; Pilatus Aircraft Ltd. Models PC-6, PC-6-H1, PC-6-H2, PC-6/350, PC-6/350...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-07

... the applicability and to require repetitive eddy current and visual inspections of the upper wing... the applicability and to require repetitive eddy current and visual inspections of the upper wing... Emergency AD 2007-0241-E to extend the applicability and to require repetitive eddy current and visual...

Eddy current spectroscopy for near-surface residual stress profiling in surface treated nonmagnetic engine alloys

NASA Astrophysics Data System (ADS)

Abu-Nabah, Bassam A.

Recent research results indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of near-surface residual stresses in surface-treated nickel-base superalloy components. Most of the previous experimental studies were conducted on highly peened (Almen 10-16A) specimens that exhibit harmful cold work in excess of 30% plastic strain. Such high level of cold work causes thermo-mechanical relaxation at relatively modest operational temperatures; therefore the obtained results were not directly relevant to engine manufacturers and end users. The main reason for choosing peening intensities in excess of recommended normal levels was that in low-conductivity engine alloys the eddy current penetration depth could not be forced below 0.2 mm without expanding the measurements above 10 MHz which is beyond the operational range of most commercial eddy current instruments. As for shot-peened components, it was initially felt that the residual stress effect was more difficult to separate from cold work, texture, and inhomogeneity effects in titanium alloys than in nickel-base superalloys. In addition, titanium alloys have almost 50% lower electric conductivity than nickel-base superalloys; therefore require proportionally higher inspection frequencies, which was not feasible until our recent breakthrough in instrument development. Our work has been focused on six main aspects of this continuing research, namely, (i) the development of an iterative inversion technique to better retrieve the depth-dependent conductivity profile from the measured frequency-dependent apparent eddy current conductivity (AECC), (ii) the extension of the frequency range up to 80 MHz to better capture the peak compressive residual stress in nickel-base superalloys using a new eddy current conductivity measuring system, which offers better reproducibility, accuracy and measurement speed than the previously used conventional systems, (iii) the lift-off effect on high frequency eddy current spectroscopy, (iv) the development of custom-made spiral coils to allow eddy current conductivity characterization over the whole frequency range of interest with reduced coil sensitivity to lift off, (v) the benefits of implementing a semi-quadratic system calibration in reducing the coil sensitivity to lift-off, and (vi) the feasibility of adapting high-frequency eddy current residual stress characterization for shot-peened titanium alloys.

Transient tidal eddy motion in the western Gulf of Maine, part 1: Primary structure

NASA Astrophysics Data System (ADS)

Brown, W. S.; Marques, G. M.

2013-07-01

High frequency radar-derived surface current maps of the Great South Channel (GSC) in the western Gulf of Maine in 2005 revealed clockwise (CW) and anticlockwise (ACW) eddy motion associated with the strong regional tidal currents. To better elucidate the kinematics and dynamics of these transient tidal eddy motions, an observational and modeling study was conducted during the weakly stratified conditions of winter 2008-2009. Our moored bottom pressure and ADCP current measurements in 13m depth were augmented by historical current measurements in about 30m in documenting the dominance of highly polarized M2 semidiurnal currents in our nearshore study region. The high-resolution finite element coastal ocean model (QUODDY) - forced by the five principal tidal constituents - produced maps depicting the formation and evolution of the CW and ACW eddy motions that regularly follow maximum ebb and flood flows, respectively. Observation versus model current comparison required that the model bottom current drag coefficient be set to at an unusually high Cd=0.01 - suggesting the importance of form drag in the study region. The observations and model results were consistent in diagnosing CW or ACW eddy motions that (a) form nearshore in the coastal boundary layer (CBL) for about 3h after the respective tidal current maxima and then (b) translate southeastward across the GSC along curved 50m isobath at speeds of about 25m/s. Observation-based and model-based momentum budget estimates were consistent in showing a first order forced semidiurnal standing tidal wave dynamics (like the adjacent Gulf of Maine) which was modulated by adverse pressure gradient/bottom stress forcing to generate the eddy motions. Observation-based estimates of terms in the transport vorticity budget showed that in the shallower Inner Zone subregion (average depth=23m) that the diffusion of nearshore vorticity was dominant in feeding the growth of eddy motion vorticity; while in the somewhat deeper Outer Zone subregion (33m) bottom current lateral shear and water column stretching/squashing was significant in modulating the eddy motion. We conclude that the transient eddy motions in the GSC region are phase eddies that accompany the change of tide across the GSC and are (1) generated by bottom stress gradients in the shallower nearshore - an issue which needs to be better understood for improved future forecasting.

Subregional characterization of mesoscale eddies across the Brazil-Malvinas Confluence

NASA Astrophysics Data System (ADS)

Mason, Evan; Pascual, Ananda; Gaube, Peter; Ruiz, Simón; Pelegrí, Josep L.; Delepoulle, Antoine

2017-04-01

Horizontal and vertical motions associated with coherent mesoscale structures, including eddies and meanders, are responsible for significant global transports of many properties, including heat and mass. Mesoscale vertical fluxes also influence upper ocean biological productivity by mediating the supply of nutrients into the euphotic layer, with potential impacts on the global carbon cycle. The Brazil-Malvinas Confluence (BMC) is a western boundary current region in the South Atlantic with intense mesoscale activity. This region has an active role in the genesis and transformation of water masses and thus is a critical component of the Atlantic meridional overturning circulation. The collision between the Malvinas and Brazil Currents over the Patagonian shelf/slope creates an energetic front that translates offshore to form a vigorous eddy field. Recent improvements in gridded altimetric sea level anomaly fields allow us to track BMC mesoscale eddies with high spatial and temporal resolutions using an automated eddy tracker. We characterize the eddies across fourteen 5° × 5° subregions. Eddy-centric composites of tracers and geostrophic currents diagnosed from a global reanalysis of surface and in situ data reveal substantial subregional heterogeneity. The in situ data are also used to compute the evolving quasi-geostrophic vertical velocity (QG-ω) associated with each instantaneous eddy instance. The QG-ω eddy composites have the expected dipole patterns of alternating upwelling/downwelling, however, the magnitude and sign of azimuthally averaged vertical velocity varies among subregions. Maximum eddy values are found near fronts and sharp topographic gradients. In comparison with regional eddy composites, subregional composites provide refined information about mesoscale eddy heterogeneity.

The Leeuwin Current and its eddies: An introductory overview

NASA Astrophysics Data System (ADS)

Waite, A. M.; Thompson, P. A.; Pesant, S.; Feng, M.; Beckley, L. E.; Domingues, C. M.; Gaughan, D.; Hanson, C. E.; Holl, C. M.; Koslow, T.; Meuleners, M.; Montoya, J. P.; Moore, T.; Muhling, B. A.; Paterson, H.; Rennie, S.; Strzelecki, J.; Twomey, L.

2007-04-01

The Leeuwin Current (LC) is an anomalous poleward-flowing eastern boundary current that carries warm, low-salinity water southward along the coast of Western Australia. We present an introduction to a new body of work on the physical and biological dynamics of the LC and its eddies, collected in this Special Issue of Deep-Sea Research II, including (1) several modelling efforts aimed at understanding LC dynamics and eddy generation, (2) papers from regional surveys of primary productivity and nitrogen uptake patterns in the LC, and (3) the first detailed field investigations of the biological oceanography of LC mesoscale eddies. Key results in papers collected here include insight into the source regions of the LC and the Leeuwin Undercurrent (LUC), the energetic interactions of the LC and LUC, and their roles in the generation of warm-core (WC) and cold-core (CC) eddies, respectively. In near-shore waters, the dynamics of upwelling were found to control the spatio-temporal variability of primary production, and important latitudinal differences were found in the fraction of production driven by nitrate (the f-ratio). The ubiquitous deep chlorophyll maximum within LC was found to be a significant contributor to total water column production within the region. WC eddies including a single large eddy studied in 2000 contained relatively elevated chlorophyll a concentrations thought to originate at least in part from the continental shelf/shelf break region and to have been incorporated during eddy formation. During the Eddies 2003 voyage, a more detailed study comparing the WC and CC eddies illuminated more mechanistic details of the unusual dynamics and ecology of the eddies. Food web analysis suggested that the WC eddy had an enhanced "classic" food web, with more concentrated mesozooplankton and larger diatom populations than in the CC eddy. Finally, implications for fisheries management are addressed.

Eddy currents in a conducting sphere

NASA Technical Reports Server (NTRS)

Bergman, John; Hestenes, David

1986-01-01

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

Analytical modeling and analysis of magnetic field and torque for novel axial flux eddy current couplers with PM excitation

NASA Astrophysics Data System (ADS)

Li, Zhao; Wang, Dazhi; Zheng, Di; Yu, Linxin

2017-10-01

Rotational permanent magnet eddy current couplers are promising devices for torque and speed transmission without any mechanical contact. In this study, flux-concentration disk-type permanent magnet eddy current couplers with double conductor rotor are investigated. Given the drawback of the accurate three-dimensional finite element method, this paper proposes a mixed two-dimensional analytical modeling approach. Based on this approach, the closed-form expressions of magnetic field, eddy current, electromagnetic force and torque for such devices are obtained. Finally, a three-dimensional finite element method is employed to validate the analytical results. Besides, a prototype is manufactured and tested for the torque-speed characteristic.

Quantifying mesoscale eddies in the Lofoten Basin

NASA Astrophysics Data System (ADS)

Raj, R. P.; Johannessen, J. A.; Eldevik, T.; Nilsen, J. E. Ø.; Halo, I.

2016-07-01

The Lofoten Basin is the most eddy rich region in the Norwegian Sea. In this paper, the characteristics of these eddies are investigated from a comprehensive database of nearly two decades of satellite altimeter data (1995-2013) together with Argo profiling floats and surface drifter data. An automated method identified 1695/1666 individual anticyclonic/cyclonic eddies in the Lofoten Basin from more than 10,000 altimeter-based eddy observations. The eddies are found to be predominantly generated and residing locally. The spatial distributions of lifetime, occurrence, generation sites, size, intensity, and drift of the eddies are studied in detail. The anticyclonic eddies in the Lofoten Basin are the most long-lived eddies (>60 days), especially in the western part of the basin. We reveal two hotspots of eddy occurrence on either side of the Lofoten Basin. Furthermore, we infer a cyclonic drift of eddies in the western Lofoten Basin. Barotropic energy conversion rates reveals energy transfer from the slope current to the eddies during winter. An automated colocation of surface drifters trapped inside the altimeter-based eddies are used to corroborate the orbital speed of the anticyclonic and cyclonic eddies. Moreover, the vertical structure of the altimeter-based eddies is examined using colocated Argo profiling float profiles. Combination of altimetry, Argo floats, and surface drifter data is therefore considered to be a promising observation-based approach for further studies of the role of eddies in transport of heat and biomass from the slope current to the Lofoten Basin.

Internal and forced eddy variability in the Labrador Sea

NASA Astrophysics Data System (ADS)

Bracco, A.; Luo, H.; Zhong, Y.; Lilly, J.

2009-04-01

Water mass transformation in the Labrador Sea, widely believed to be one of the key regions in the Atlantic Meridional Overturning Circulation (AMOC), now appears to be strongly impacted by vortex dynamics of the unstable boundary current. Large interannual variations in both eddy shedding and buoyancy transport from the boundary current have been observed but not explained, and are apparently sensitive to the state of the inflowing current. Heat and salinity fluxes associated with the eddies drive ventilation changes not accounted for by changes in local surface forcing, particularly during occasional years of extreme eddy activity, and constitute a predominant source of "internal" oceanic variability. The nature of this variable eddy-driven restratification is one of the outstanding questions along the northern transformation pathway. Here we investigate the eddy generation mechanism and the associated buoyancy fluxes by combining realistic and idealized numerical modeling, data analysis, and theory. Theory, supported by idealized experiments, provides criteria to test hypotheses as to the vortex formation process (by baroclinic instability linked to the bottom topography). Ensembles of numerical experiments with a high-resolution regional model (ROMS) allow for quantifying the sensitivity of eddy generation and property transport to variations in local and external forcing parameters. For the first time, we reproduce with a numerical simulation the observed interannual variability in the eddy kinetic energy in the convective region of the Labrador Basin and along the West Greenland Current.

Inspection of cup-shaped steel parts from the I.D. side using eddy current

NASA Astrophysics Data System (ADS)

Griffiths, Erick W.; Pearson, Lee H.

2018-04-01

An eddy current method was developed to inspect cup-shaped steel parts from the I.D. side. During the manufacturing process of these parts, a thin Al tape foil is applied to the I.D. side of the part. One of the critical process parameters is that only one foil layer can be applied. An eddy current inspection system was developed to reject parts with more than one foil layer. The Al tape foil is cut to length to fit the inner diameter, however, after application of the foil there is a gap created between the beginning and end of the foil. It was found that this gap interfered with the eddy current inspection causing a false positive indication. To solve this problem a sensor design and data analysis process were developed to overcome the effects of these gaps. The developed system incorporates simultaneous measurements from multiple eddy current sensors and signal processing to achieve a reliable inspection.

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.

Double-spin-echo diffusion weighting with a modified eddy current adjustment.

PubMed

Finsterbusch, Jürgen

2010-04-01

Magnetic field inhomogeneities like eddy current-related gradient fields cause geometric distortions in echo-planar imaging (EPI). This in particular affects diffusion-weighted imaging where these distortions vary with the direction of the diffusion weighting and hamper the accurate determination of diffusion parameters. The double-spin-echo preparation often used aims to reduce the cumulative eddy current effect by adjusting the diffusion-weighting gradient pulse durations to the time constant of the dominant eddy current contribution. However, eddy currents with a variety of time constants may be present and cause residual distortions. Here, a modification is proposed where the two bipolar gradient pairs of the preparation are adjusted independently to different time constants. At the expense of a slightly prolonged echo time, residual geometric distortions and correspondingly increased values of the diffusion anisotropy can be reduced as is demonstrated in phantoms and the human brain. Thus, it may help to improve the reliability of diffusion-weighted EPI. Copyright 2010 Elsevier Inc. All rights reserved.

Thin film eddy current impulse deicer

NASA Technical Reports Server (NTRS)

Smith, Samuel O.; Zieve, Peter B.

1990-01-01

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

Rapid Measurement and Correction of Phase Errors from B0 Eddy Currents: Impact on Image Quality for Non-Cartesian Imaging

PubMed Central

Brodsky, Ethan K.; Klaers, Jessica L.; Samsonov, Alexey A.; Kijowski, Richard; Block, Walter F.

2014-01-01

Non-Cartesian imaging sequences and navigational methods can be more sensitive to scanner imperfections that have little impact on conventional clinical sequences, an issue which has repeatedly complicated the commercialization of these techniques by frustrating transitions to multi-center evaluations. One such imperfection is phase errors caused by resonant frequency shifts from eddy currents induced in the cryostat by time-varying gradients, a phenomemon known as B0 eddy currents. These phase errors can have a substantial impact on sequences that use ramp sampling, bipolar gradients, and readouts at varying azimuthal angles. We present a method for measuring and correcting phase errors from B0 eddy currents and examine the results on two different scanner models. This technique yields significant improvements in image quality for high-resolution joint imaging on certain scanners. The results suggest that correction of short time B0 eddy currents in manufacturer provided service routines would simplify adoption of non-Cartesian sampling methods. PMID:22488532

Apparatus and method for inspecting a bearing ball

NASA Technical Reports Server (NTRS)

Bankston, B. F. (Inventor)

1985-01-01

A method and apparatus for inspecting the surface of a ball bearing is disclosed which includes a base having a high friction non-abrasive base scanning surface. A holding device includes a cone-shaped cup recess in which a ball element is received. Air is introduced through a passage to relieve friction between the wall of the recess and the ball element and facilitate rolling of the ball over the high friction base surface. The holding device is moved over the base scanning surface in a predetermined pattern such that the entire surface of the ball element is inspected byan eddy current probe which detects any surface defects.

Apparatus for inspecting piping

DOEpatents

Zollingger, W. Thor; Appel, D. Keith; Park, Larry R.

1995-01-01

An inspection rabbit for inspecting piping systems having severe bends therein. The rabbit consists of a flexible, modular body containing a miniaturized eddy current inspection probe, a self-contained power supply for proper operation of the rabbit, an outer surface that allows ease of movement through piping systems and means for transmitting data generated by the inspection device. The body is preferably made of flexible polyvinyl chloride (PVC) tubing or, alternatively, silicone rubber with a shrink wrapping of polytetrafluoroethylene (TEFLON.RTM.). The body is formed to contain the power supply, preferably a plurality of batteries, and a spool of communication wire that connects to a data processing computer external to the piping system.

Measurement station for interim inspections of Lightbridge metallic fuel rods at the Halden Boiling Water Reactor

NASA Astrophysics Data System (ADS)

Hartmann, C.; Totemeier, A.; Holcombe, S.; Liverud, J.; Limi, M.; Hansen, J. E.; Navestad, E. AB(; )

2018-01-01

Lightbridge Corporation has developed a new Uranium-Zirconium based metallic fuel. The fuel rods aremanufactured via a co-extrusion process, and are characterized by their multi-lobed (cruciform-shaped) cross section. The fuel rods are also helically-twisted in the axial direction. Two experimental fuel assemblies, each containing four Lightbridge fuel rods, are scheduled to be irradiated in the Halden Boiling Water Reactor (HBWR) starting in 2018. In addition to on-line monitoring of fuel rod elongation and critical assembly conditions (e.g. power, flow rates, coolant temperatures, etc.) during the irradiation, several key parameters of the fuel will be measured out-of-core during interim inspections. An inspection measurement station for use in the irradiated fuel handling compartment at the HBWR has therefore been developed for this purpose. The multi-lobed cladding cross section combined with the spiral shape of the Lightbridge metallic fuel rods requires a high-precision guiding system to ensure good position repeatability combined with low-friction guiding. The measurement station is equipped with a combination of instruments and equipment supplied from third-party vendors and instruments and equipment developed at Institute for Energy Technology (IFE). Two sets of floating linear voltage differential transformer (LVDT) pairs are used to measure swelling and diameter changes between the lobes and the valleys over the length of the fuel rods. Eddy current probes are used to measure the thickness of oxide layers in the valleys and on the lobe tips and also to detect possible surface cracks/pores. The measurement station also accommodates gamma scans. Additionally, an eddy-current probe has been developed at IFE specifically to detect potential gaps or discontinuities in the bonding layer between the metallic fuel and the Zirconium alloy cladding. Potential gaps in the bonding layer will be hidden behind a 0.5-1.0 mm thick cladding wall. It has therefore been necessary to perform a careful design study of the probe geometry. For this, finite element analysis (FEA) has been performed in combination with practical validation tests on representative fuel dummies with machined flaws to find the probe geometry that best detects a hidden flaw. Tests performed thus far show that gaps down to 25 μm thickness can be detected with good repeatability and good discrimination from lift-off signals.

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.

76 FR 66620 - Airworthiness Directives; Bombardier, Inc. Model CL-215-1A10, CL-215-6B11 (CL-215T Variant), and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-10-27

... effective date of this AD: Perform an in situ eddy current inspection for cracks on the forward lug of the...-6B11 (CL-415 Variant) airplanes). Thereafter, repeat the in situ eddy current inspection at intervals not to exceed 165 land landings. (2) If no crack is found: Repeat the in situ eddy current inspection...

Development of Ground Coils with Low Eddy Current Loss by Applying the Compression Molding Method after the Coil Winding

NASA Astrophysics Data System (ADS)

Suzuki, Masao; Aiba, Masayuki; Takahashi, Noriyuki; Ota, Satoru; Okada, Shigenori

In a magnetically levitated transportation (MAGLEV) system, a huge number of ground coils will be required because they must be laid for the whole line. Therefore, stable performance and reduced cost are essential requirements for the ground coil development. On the other hand, because the magnetic field changes when the superconducting magnet passes by, an eddy current will be generated in the conductor of the ground coil and will result in energy loss. The loss not only increases the magnetic resistance for the train running but also brings an increase in the ground coil temperature. Therefore, the reduction of the eddy current loss is extremely important. This study examined ground coils in which both the eddy current loss and temperature increase were small. Furthermore, quantitative comparison for the eddy current loss of various magnet wire samples was performed by bench test. On the basis of the comparison, a round twisted wire having low eddy current loss was selected as an effective ground coil material. In addition, the ground coils were manufactured on trial. A favorable outlook to improve the size accuracy of the winding coil and uneven thickness of molded resin was obtained without reducing the insulation strength between the coil layers by applying a compression molding after winding.

A quantitative comparison of two methods to correct eddy current-induced distortions in DT-MRI.

PubMed

Muñoz Maniega, Susana; Bastin, Mark E; Armitage, Paul A

2007-04-01

Eddy current-induced geometric distortions of single-shot, diffusion-weighted, echo-planar (DW-EP) images are a major confounding factor to the accurate determination of water diffusion parameters in diffusion tensor MRI (DT-MRI). Previously, it has been suggested that these geometric distortions can be removed from brain DW-EP images using affine transformations determined from phantom calibration experiments using iterative cross-correlation (ICC). Since this approach was first described, a number of image-based registration methods have become available that can also correct eddy current-induced distortions in DW-EP images. However, as yet no study has investigated whether separate eddy current calibration or image-based registration provides the most accurate way of removing these artefacts from DT-MRI data. Here we compare how ICC phantom calibration and affine FLIRT (http://www.fmrib.ox.ac.uk), a popular image-based multi-modal registration method that can correct both eddy current-induced distortions and bulk subject motion, perform when registering DW-EP images acquired with different slice thicknesses (2.8 and 5 mm) and b-values (1000 and 3000 s/mm(2)). With the use of consistency testing, it was found that ICC was a more robust algorithm for correcting eddy current-induced distortions than affine FLIRT, especially at high b-value and small slice thickness. In addition, principal component analysis demonstrated that the combination of ICC phantom calibration (to remove eddy current-induced distortions) with rigid body FLIRT (to remove bulk subject motion) provided a more accurate registration of DT-MRI data than that achieved by affine FLIRT.

Development of a second generation rolling contact fatigue tester

NASA Astrophysics Data System (ADS)

Deshmukh, Satyam U.

Contact fatigue failure has been in research since the early twentieth century. The need for a second generation sliding-rolling contact fatigue tester was proposed by Gregory Dvorak and Dr. Marcellin Zahui. The first generation RCF tester was used for testing super finishing processes for gear surfaces. The second generation RCF tester was funded by the Advanced Engineering Materials lab of University of North Dakota. Verification of the second generation Rolling Contact Fatigue Tester will be discussed in this thesis including the design details, assembly and testing procedure and to discuss its different parameters. The tester will have the capability of testing hollow specimens using a bobbin eddy current testing probe. This tester will allow a wide range of experiments and is not built for one specific purpose. An eddy current device is used for detecting cracks. The loading force is applied using hydraulic cylinders and a hydraulic power unit. Before testing began, the machine was run for some time at full speed. A lot of minor problems were detected and fixed. Three specimens of AISI 8620 were tested in this tester. All tests gave results matching with some of the other well-known RCF testers. These tests were performed to evaluate mechanical limits of the tester and to evaluate the software performance of the tester.

Sensor Fusion Techniques for Phased-Array Eddy Current and Phased-Array Ultrasound Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arrowood, Lloyd F.

Sensor (or Data) fusion is the process of integrating multiple data sources to produce more consistent, accurate and comprehensive information than is provided by a single data source. Sensor fusion may also be used to combine multiple signals from a single modality to improve the performance of a particular inspection technique. Industrial nondestructive testing may utilize multiple sensors to acquire inspection data depending upon the object under inspection and the anticipated types of defects that can be identified. Sensor fusion can be performed at various levels of signal abstraction with each having its strengths and weaknesses. A multimodal data fusionmore » strategy first proposed by Heideklang and Shokouhi that combines spatially scattered detection locations to improve detection performance of surface-breaking and near-surface cracks in ferromagnetic metals is shown using a surface inspection example and is then extended for volumetric inspections. Utilizing data acquired from an Olympus Omniscan MX2 from both phased array eddy current and ultrasound probes on test phantoms, single and multilevel fusion techniques are employed to integrate signals from the two modalities. Preliminary results demonstrate how confidence in defect identification and interpretation benefit from sensor fusion techniques. Lastly, techniques for integrating data into radiographic and volumetric imagery from computed tomography are described and results are presented.« less

Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique.

PubMed

Li, Wei; Wang, Hongbo; Feng, Zhihua

2016-04-01

This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation.

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

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

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...

Code of Federal Regulations, 2013 CFR

2013-10-01

... for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180 Transportation... Pt. 180, App. C Appendix C to Part 180—Eddy Current Examination With Visual Inspection for DOT 3AL... with CGA pamphlet C-6.1 (IBR; see § 171.7 of this subchapter). 3. Eddy Current Equipment. A reference...

76 FR 26962 - Airworthiness Directives; Airbus Model A300 B2-1C, A300 B2-203, A300 B2K-3C, A300-B4-103, A300 B4...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-10

... repetitive detailed inspections for disbonding and cracking of the fuselage inner doubler; eddy current and... detailed inspections for disbonding and cracking of the fuselage inner doubler; eddy current and ultrasonic... or Modification if Necessary (g) For airplanes on which an eddy current inspection of the ``special...

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

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.

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

PubMed

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

2010-12-01

Eddy currents are inevitably induced when time-varying magnetic field gradients interact with the metallic structures of a magnetic resonance imaging (MRI) scanner. The secondary magnetic field produced by this induced current degrades the spatial and temporal performance of the primary field generated by the gradient coils. Although this undesired effect can be minimized by using actively and/or passively shielded gradient coils and current pre-emphasis techniques, a residual eddy current still remains in the MRI scanner structure. Accurate simulation of these eddy currents is important in the successful design of gradient coils and magnet cryostat vessels. Efficient methods for simulating eddy currents are currently restricted to cylindrical-symmetry. The approach presented in this paper divides thick conducting cylinders into thin layers (thinner than the skin depth) and expresses the current density on each as a Fourier series. The coupling between each mode of the Fourier series with every other is modeled with an inductive network method. In this way, the eddy currents induced in realistic cryostat surfaces by coils of arbitrary geometry can be simulated. The new method was validated by simulating a canonical problem and comparing the results against a commercially available software package. An accurate skin depth of 2.76 mm was calculated in 6 min with the new method. The currents induced by an actively shielded x-gradient coil were simulated assuming a finite length cylindrical cryostat consisting of three different conducting materials. Details of the temporal-spatial induced current diffusion process were simulated through all cryostat layers, which could not be efficiently simulated with any other method. With this data, all quantities that depend on the current density, such as the secondary magnetic field, are simply evaluated. Copyright © 2010 Elsevier Inc. All rights reserved.

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