Rotating Focused Field Eddy-Current Sensing for Arbitrary Orientation Defects Detection in Carbon Steel

Abstract

This paper presents a rotating focused field eddy-current (EC) sensing technique, which leverages the advantages of magnetic field focusing and rotating magnetic field, for arbitrary orientation defects detection. The sensor consists of four identical excitation coils orthogonally arranged in an upside-down pyramid configuration and a giant magneto-resistive (GMR) detection element. The four coils are connected to form two figure-8-shaped focusing sub-probes, which are fed by two identical harmonic currents with 90 degrees phase difference. A finite element model-based study of arbitrary orientation defects detection was performed to understand the probe operational characteristics and optimize its design parameters. Probe prototyping and experimental validation were also carried out on a carbon steel plate specimen with four prefabricated surface-breaking defects. In-situ spot inspection with the probe rotating above the defect and a manual line-scan inspection were both conducted. Results showed that the probe has the capability of detecting defects with any orientations while maintaining the same sensitivity and the defect depth can be quantitatively evaluated by using the signal amplitude. Compared with the existing rotating field probes, the presented probe does not require additional excitation adjustment or data fusion. Meanwhile, due to its focusing effect, it can generate a strong rotating magnetic field at the defect location with a weak background noise, thus yielding superior signal-to-noise ratio.

Parameter identification of pulsed eddy current testing equivalent circuit model and its application to defect evaluation

“…It should be mentioned that there are usually two types of probes, viz., the absolute probe and the transmitter-receiver (TR) probe, used in practical PECT systems. 22,23 The absolute probe only has a single coil and thus matches with the above equivalent circuit model and the corresponding transfer function. However, for the TR probe which utilizes one coil to transmit the primary magnetic field and the other coil to receive the secondary magnetic field, the presented model need to be modified to take into account the coupling between the transmitter and the receiver.…”

Reduction of Coil-Crack Angle Sensitivity Effect Using a Novel Flux Feature of ACFM Technique

“…The techniques developed for the detection of the crack can effectively prevent unnecessary loss and damage. For example, the eddy current (EC) inspection [1][2][3][4] and the alternating current field measurement (ACFM) technique [5][6][7].…”

“…Various excitation profiles of the EC inspection have been proposed to quantitively determine the position and size of surface cracks [1][2][3]. ACFM technique has been originally used in detections of surface cracks in oil and gas industry in previous decades [8][9].…”

Sparse and Random Sampling Techniques for High-Resolution, Full-Field, BSS-Based Structural Dynamics Identification from Video

“…To date, a wide variety of techniques have been developed for structural health monitoring. These techniques include ultrasonic/acoustic-based techniques [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ], eddy-current-based techniques [ 10 , 11 , 12 ], and microwave-based techniques [ 13 , 14 , 15 ]. These technologies are promising for specific structural health monitoring applications, however, they are not readily suited to being scaled up for applications such as monitoring the structural health of an entire city.…”