A Novel Pulsed Eddy Current Criterion for Non-Ferromagnetic Metal Thickness Quantifications under Large Liftoff

• Published in: Sensors (Basel, Switzerland) Vol. 22; no. 2; p. 614
• Main Authors: Wang, Haowen, Huang, Jiangbo, Liu, Longhuan, Qin, Shanqiang, Fu, Zhihong
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.01.2022; MDPI
• Subjects: Aluminum; Analysis; Conductors; dynamic apparent time constant; Eddy currents; Ferromagnetism; Inspection; Insulating layers; Investigations; lift-off variations; Noise; Nondestructive testing; Permeability; pulsed eddy current; Structural health monitoring; Thickness; thickness quantifications; Time constant; dynamic apparent time constant; lift-off variations; pulsed eddy current; thickness quantifications
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s22020614

The pulsed eddy current (PEC) inspection is considered a versatile non-destructive evaluation technique, and it is widely used in metal thickness quantifications for structural health monitoring and target recognition. However, for non-ferromagnetic conductors covered with non-uniform thick insulating layers, there are still deficiencies in the current schemes. The main purpose of this study is to find an effective feature, to measure wall thinning under the large lift-off variations, and further expand application of the PEC technology. Therefore, a novel method named the dynamic apparent time constant (D-ATC) is proposed based on the coil-coupling model. It associates the dynamic behavior of the induced eddy current with the geometric dimensions of the non-ferromagnetic metallic component by the time and amplitude features of the D-ATC curve. Numeral calculations and experiments show that the time signature is immune to large lift-off variations.