Invariance transformations for magnetic flux leakage signals

Mandayam, Shreekanth; Удпа, Лалита; Удпа, Сатиш С.; Lord, W.

doi:10.1109/20.497553

Cited by 47 publications

(14 citation statements)

References 2 publications

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“…Inspection systems based on the simultaneous use of conventional ultrasonic transducers with magnetic flux leakage (MFL) sensors have a higher probability of detecting smaller near-surface and surfacebreaking defects in the rail head. However, as inspection speed increases, the performance of MFL sensors tends to deteriorate rapidly due to a reduction in the magnetic flux density arising from the eddy current excitation [1][2][3]. The use of higher magnetic fields to compensate for the reduction in magnetic flux density may not be straight forward due to the potential interference with the electronic equipment installed on rail tracks.…”

Section: Introductionmentioning

confidence: 99%

High-speed inspection of rails using ACFM techniques

Papaelias

Lugg

Roberts

et al. 2009

NDT & E International

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Section: Introductionmentioning

confidence: 99%

High-speed inspection of rails using ACFM techniques

Papaelias

Lugg

Roberts

et al. 2009

NDT & E International

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“…In addition, the statistical features invariant to sensor-tilt are studied for detection classifications regarding different crack cases. The presented scheme has no requirement of signal trainings that are time-consuming and used by radial basis functions and neural network in [15,16].…”

Section: Introductionmentioning

confidence: 99%

“…However, irregularities due to the poor drilling around fastener hole sites and variations in the experimental operation, the probe and sensor-tilt diversion particularly are able to produce asymmetric signals, because they disturb induced current patterns same as the crack behavior [17]. The invariant feature analysis using signal processing techniques and invariance transformations have been reported to remove the asymmetry noise and probe lift-off effects which hinder crack identifications and ascend false calls [14][15][16][17]. Since the GMR sensor is placed at the center of multi-line EC probe, the lift-off changes might yield tilt sensor.…”

Section: Introductionmentioning

confidence: 99%

Sensor-tilt invariance analysis for eddy current signals

Yang

Zeng

Deng

et al. 2012

NDT & E International

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“…One example is Steam Generator tube inspection in nuclear power plants, where the measurements are taken at 4 frequencies with the same probe coil in a single scan using time multiplexing. Advanced signal processing algorithms based on invariance transformation can be used to make the data insensitive to unwanted parameters such as base conductivity, temperature and surface roughness, while retaining sensitivity to parameters of interest which is the oxide layer thickness [7,8]. The ability to use the same coil for the multiple frequencies will minimize the scanning time of a measurement bench.…”

Section: Future Workmentioning

confidence: 99%

Determining confounding sensitivities in eddy current thin film measurements

Gros

Удпа²,

Smith

et al. 2017

AIP Conference Proceedings

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Abstract. 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.

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Invariance transformations for magnetic flux leakage signals

Cited by 47 publications

References 2 publications

High-speed inspection of rails using ACFM techniques

High-speed inspection of rails using ACFM techniques

Sensor-tilt invariance analysis for eddy current signals

Determining confounding sensitivities in eddy current thin film measurements

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