Overcoming skin effect limitations: a novel transmit-receive eddy current probe for high-accuracy quantification of deep cracks.

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Bibliographic Details
Title:	Overcoming skin effect limitations: a novel transmit-receive eddy current probe for high-accuracy quantification of deep cracks.
Authors:	Zhang, Dongli¹, Wu, Meixian¹
Source:	Insight: Non-Destructive Testing & Condition Monitoring. May2026, Vol. 68 Issue 5, p306-318. 7p.
Subjects:	Skin effect, Eddy current testing, Electric impedance, Magnetic permeability, Finite element method, Measurement
Abstract:	To address the signal saturation and poor quantification capability of conventional eddy current (EC) probes in deep crack detection, caused by the skin effect, this paper proposes a novel EC probe for inspection of deep cracks in thick-walled structures. The probe adopts a transmit-receive configuration with the transmitting coil (Tx) and the receiving coil (Rx) on opposing faces of the plate, enabling through-thickness magnetic field penetration, fundamentally altering the eddy current distribution and enhancing sensitivity to deep cracks. Theoretical analysis and finite element simulations demonstrate that this configuration effectively mitigates the dominance of surface currents, making the received signal primarily responsive to subsurface disturbances. Notably, the probe exhibits a highly linear relationship between normalised impedance variation and crack depth over a range of 6-32 mm (R2 = 0.999), in stark contrast to the saturated non-linear response of conventional reflection-type probes. Leveraging this linear depth response, a direct inversion model is established for high-accuracy depth quantification, achieving a root mean square error (RMSE) of 0.23 mm. The results validate that the proposed transmit-receive probe overcomes the depth-sensing limitations of traditional EC testing and provides a reliable solution for quantitative evaluation of deeply buried cracks and surface-breaking deep cracks in thick-walled conductive structures. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	To address the signal saturation and poor quantification capability of conventional eddy current (EC) probes in deep crack detection, caused by the skin effect, this paper proposes a novel EC probe for inspection of deep cracks in thick-walled structures. The probe adopts a transmit-receive configuration with the transmitting coil (Tx) and the receiving coil (Rx) on opposing faces of the plate, enabling through-thickness magnetic field penetration, fundamentally altering the eddy current distribution and enhancing sensitivity to deep cracks. Theoretical analysis and finite element simulations demonstrate that this configuration effectively mitigates the dominance of surface currents, making the received signal primarily responsive to subsurface disturbances. Notably, the probe exhibits a highly linear relationship between normalised impedance variation and crack depth over a range of 6-32 mm (R2 = 0.999), in stark contrast to the saturated non-linear response of conventional reflection-type probes. Leveraging this linear depth response, a direct inversion model is established for high-accuracy depth quantification, achieving a root mean square error (RMSE) of 0.23 mm. The results validate that the proposed transmit-receive probe overcomes the depth-sensing limitations of traditional EC testing and provides a reliable solution for quantitative evaluation of deeply buried cracks and surface-breaking deep cracks in thick-walled conductive structures. [ABSTRACT FROM AUTHOR]
ISSN:	13542575