Computational methods in eddy current crack detection at fastener sites in multi-layer structures

Knopp, Jeremy S.; Aldrin, John C.; Jata, Kumar V.

doi:10.1080/10589750802195519

Cited by 27 publications

(13 citation statements)

References 40 publications

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“…Conventional eddy current (EC) techniques such as sliding EC probes, self-nulling EC probes, and low frequency EC methods have been commonly used for detecting fatigue cracks in riveted structures [1], [2]. However, conventional EC methods are limited in their ability to detect subsurface cracks due to the penetration depth of electromagnetic fields [3]. Reliable inspection of hidden cracks under fastener heads in layered components still poses a major challenge in NDE.…”

Section: Introductionmentioning

confidence: 99%

Rotating Field EC-GMR Sensor for Crack Detection at Fastener Site in Layered Structures

et al. 2015

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Eddy current-based techniques have been investigated for the inspection of embedded cracks under fastener heads in riveted structures. However, these techniques are limited in their ability to detect cracks that are not perpendicular to induced current flows. Further, the presence of a steel fastener of high permeability produces a strong signal that masks relatively smaller indication from a crack. In this paper, a rotating electromagnetic field is designed to rotate the applied magnetic fields and related eddy currents electrically so that the sensor shows uniform sensitivity in detecting cracks in all radial directions around fastener sites. Giant magnetoresistive sensors are employed to image the normal component of this rotating field, to detect different crack orientations at aluminum and ferromagnetic fastener sites. Numerical model-based studies and experimental validation are presented.Index Terms-Eddy current, giant magnetoresistive sensor, rotating electromagnetic field, fastener hole inspection, NDE.

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Section: Introductionmentioning

confidence: 99%

Rotating Field EC-GMR Sensor for Crack Detection at Fastener Site in Layered Structures

et al. 2015

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“…Examples of aging aircraft eddy current inspections are the detection of cracks around fastener holes and the detection of corrosion in multi-layered structures [1]. For these inspections, it is also advantageous to ascertain the crack size or percent material loss due to corrosion in order to prescribe the most appropriate maintenance action.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty Propagation in Eddy Current Nde Inverse Problems

Aldrin¹,

Knopp²,

Blodgett³

et al. 2011

AIP Conference Proceedings

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The probabilistic collocation method (PCM) was introduced to efficiently propagate the distributions of input parameters for eddy current NDE inverse problems. A multilevel approach was also considered to simultaneously address input parameter variability and the uniqueness of the inversion result. A case study is presented for the problem of characterizing material loss in a multi-layer structure with varying liftoff and material properties. The performance and sensitivity of the uncertainty propagation method using PCM was evaluated under varying conditions.

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“…This is the basis of crack and fissure detection in otherwise conductive media by the eddy current method. A review of models used to support crack detection via the eddy current approach is given in [18].…”

Section: Appendix -Vessel Conductivitymentioning

confidence: 99%

Auto-Tuned Induction Coil Conductivity Sensor for In-Vivo Human Tissue Measurements

Heller¹,

Feldkamp²

2009

Measurement Science Review

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Auto-tuned induction coil technology, based upon phase-locked loop circuitry (PLL), was developed and shown to be an effective tool for in-vivo measurement of electrical conductivity of human tissues. Because electrical contact is not required, several disadvantages of the electrode method for conductivity determination are avoided, such as electrode polarization and variable conductivity associated with the stratum corneum of the epidermis. Fixed frequency excitation is supplied to a parallel tuned RLC circuit, or "sensor", while bias applied to a varactor diode is automatically adjusted via PLL circuitry to maintain the RLC sensor at resonance. Since resonant impedance of a coil positioned near a conductive object is known to be frequency dependent, such an arrangement permits precise calibration of the sensor against a set of standard Potassium Chloride solutions. In our experiments, a two-layer spiral coil is used with upper and lower spiral arms staggered so as to reduce inter-winding coil capacitance. Preliminary in-vivo testing was done on the forearms of a single male subject as a prelude to more extensive use in a clinical setting. In that instance, electrical conductivity at the proximal volar forearm location was shown to depend on forearm elevation. Clinical studies using our prototype, as well as further consideration of the "elevation effect", are discussed in a companion paper.

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Computational methods in eddy current crack detection at fastener sites in multi-layer structures

Cited by 27 publications

References 40 publications

Rotating Field EC-GMR Sensor for Crack Detection at Fastener Site in Layered Structures

Rotating Field EC-GMR Sensor for Crack Detection at Fastener Site in Layered Structures

Uncertainty Propagation in Eddy Current Nde Inverse Problems

Auto-Tuned Induction Coil Conductivity Sensor for In-Vivo Human Tissue Measurements

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