Geometrically anisotropic probes: an improved eddy current technique

Mayos, M.; Müller, Jan

doi:10.1007/bf00568889

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…The pancake coil geometry (System I) is perhaps the most widely used in practice. As all the configurations are 'geometrically anisotropic' they are well suited to detection of directional defects, such as fatigue cracks (Mayos and Muller 1987). Coil configurations such as Systems V and VI, for which Z 12 = 0 irrespective of frequency, separation and liftoff, are significant because any change in mutual impedance must, in principle, be due to the presence of a defect.…”

Section: Discussionmentioning

confidence: 99%

“…The response of driver-pickup coil systems is dictated by the change in mutual impedance due to the defect, and the coil configuration is designed to minimize the effects of coil liftoff, temperature fluctuations and other sources of unwanted signals while maximizing the defect response. Practical applications of driver-pickup coil arrangements include axisymmetric reflection probes for measurement of conductivity and coating thickness (Deeds et al 1979), through-transmission systems for characterization of metallic sheets (Dodd and Deeds 1982), circular-driver/differential-pickup coils for surface crack detection (Auld et al 1989), remote-field eddy-current systems for pipe inspection (Schmidt 1989, Haugland 1996 and sliding coils for detection and sizing of cracks in lap joints and heat-exchanger tubing (Mayos and Muller 1987, Cecco et al 1993, Obrutsky et al 1996. More complex configurations, which rely on orthogonal driver-pickup coils, have also been proposed for detecting and sizing defects in other specialized applications (Beissner and Sablik 1984, Popa et al 1997, Grimberg et al 2000, Hoshikawa et al 2001.…”

Section: Introductionmentioning

confidence: 99%

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Mutual impedance of air-cored coils above a conducting plate

Burke

Ibrahim

2004

J. Phys. D: Appl. Phys.

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The change in mutual impedance ΔZ12 due to eddy-current induction is considered for an arbitrary pair of air-cored coils located above a conducting plate. A general expression is derived for ΔZ12 and applied to the specific case of cylindrical coils with rectangular cross-section. A series of closed-form expressions for ΔZ12 is presented for the geometries that cover all of the possible coil configurations for which the orientation of the individual coils is either normal or tangential to the plate. Expressions are also obtained for ΔZ12 in the dipole limit and the results are compared with earlier work for dipole loops. The validity of the theory is tested against experimental measurements for representative high-symmetry coil systems above an aluminium-alloy plate. The theoretical calculations and experimental results are in excellent agreement over the experimental frequency range 100 Hz–50 kHz. The significance of the results for eddy-current non-destructive inspection using driver–pickup coils is discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mutual impedance of air-cored coils above a conducting plate

Burke

Ibrahim

2004

J. Phys. D: Appl. Phys.

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“…these results explain the advantages of eC probes in which the sensing (receive) and the drive (transmit) coils are spaced apart. eddy current probes with spaced coils were named transmit-receive or anaxial eC probes and investigated in detail in a few publications [19][20][21]. In these studies, the specific useful peculiarities of these probes, such as high penetration and noise tolerance, were shown.…”

Section: General Considerations On the Penetration Of Eddy Currents I...mentioning

confidence: 99%

Eddy Current Techniques for Detecting Hidden Subsurface Defects in Multilayer Aircraft Structures

Uchanin

2022

Transactions on Aerospace Research

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In-service non-destructive inspection (NDI) is a very important part of the aircraft maintenance program that minimizes aircraft breakdowns due to the fracture of critical components. The eddy current (EC) NDI method is one of the most applicable methods for this purpose, due to its high sensitivity to fatigue cracks and corrosion damage in the main structural materials. In this paper, selective double differential type EC probes characterized by the enhanced possibility of detecting subsurface cracks initiated by fatigue or stress corrosion phenomena are presented. For different applications, a family of double differential type EC probes was developed with different sizes (from 5 to 33 mm) and different spatial resolutions. These types of probes are characterized by different operational frequencies in a wide frequency range (from 0.2 kHz to 1.0 MHz), high penetration depth and unique sensitivity to subsurface defects of different types (like elongated fatigue cracks or local corrosive pitting), and a high level of specific noise suppression concerned with the scanning inspection procedures. The EC probes proposed were investigated as effective tools for characteristic aircraft applications concerned with subsurface defect detection in multilayer structures, such as the detection of cracks in the second layer of a riveted two-layer structure or cracks initiated on the side surface of a multilayer structure with the suppression of the reinforcing hoop influence; the detection of subsurface defects in arc welding with a rough surface; the detection of cracks through repair patches fabricated from aluminum alloy or carbon fiber reinforced plastic, etc. These techniques create remarkable possibilities for the well-timed detection of dangerous damage without disassembling the aircraft structure or removing protective coating.

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Mutual Impedance of Planar Eddy-Current Driver–pickup Spiral Coils

Burke

Ditchburn

2008

Research in Nondestructive Evaluation

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Geometrically anisotropic probes: an improved eddy current technique

Cited by 3 publications

References 2 publications

Mutual impedance of air-cored coils above a conducting plate

Mutual impedance of air-cored coils above a conducting plate

Eddy Current Techniques for Detecting Hidden Subsurface Defects in Multilayer Aircraft Structures

Mutual Impedance of Planar Eddy-Current Driver–pickup Spiral Coils

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