Nonlinear FEM-BEM formulation and model-free inversion procedure for reconstruction of cracks using pulse eddy currents

Abstract

Pulse eddy currents are proposed as a nondestructive testing (NDT) technique to detect flaws in conductive structures with large thickness. The harmonic component of a pulse is rich, the pickup signal containing the amount of information corresponding to multifrequency analysis. Due to the short time length of the pulse, the amplitude of the excitation increases up to 100 times of the amplitude for an ac signal. Both direct simulation of pulse eddy-currents phenomena using an A-FEM-BEM code and neural networks-based inversion techniques are performed. Numerical results for the inversion of signals due to outer defects are shown.

Pulse eddy currents using an integral-FEM formulation for cracks detection

“…In the case of AC, the pancake coil is optimized for a certain frequency. In the case of pulse excitation, due to the rich harmonic component of the signal, such a frequency optimisation technique is hampered [4]. The scan path is 20 cm long, in y-direction, centered over the plate; 9 scan points, with scan pitch 2.5 mm are analized.…”

“…The rectangular pulse shape accounts for a multi-frequency analysis, the lower harmonics penetrating deeper in the material; in the same time the heating exposure of the coil-probe system is limited to only the short duration of a signal, allowing thus an increase in the signal power. Multiple industrial applications were reported, such as detection of cracks in multiple layered plates around fasteners for aeronautics industry [3], crack detection and thickness evaluation in structural steels [4]. Current study investigates the possibility to detect defects in conductive plates using simulated pulse eddy currents signals.…”

Shape Mapping Detection of Electric Vehicle Alloy Defects Based on Pulsed Eddy Current Rectangular Sensors

“…The probe in EC testing is usually comprised of excitation and detection units. The excitation unit inducing the eddy current in materials being tested is usually a cylindrical coil [26][27][28][29][30][31][32]. As a comparison, a rectangular coil can induce uniform and unidirectional eddy currents in the detected material, and has been devised particularly for EC testing [33] and alternating current field measurement (ACFM) testing [34].…”

Geometry optimization of solid rotor eddy current brake by using sensitivity analysis and 3D finite elements

“…However, the optimization of the rotor geometry may require laborious and expensive numerical schemes especially when 3D configuration should be considered [4,5]. Although both stochastic [6] and deterministic optimization algorithms can be implemented [7][8][9], the sensitivity analysis technique combined with finite element methods enables robust and fast convergence [1].…”