Defect depth estimation using pulsed eddy current with varied pulse width excitation

Abstract

Current industry requirements demand defect quantification rather than simple defect detection. Besides the defect geometrical size, its depth location plays a critical role for the integrity of a structure and the safe life operation of the overall assembly. It has been long known that pulsed eddy current (PEC) non-destructive testing (NDT) for electrically conductive materials has the advantage of gathering different depth information in a single excitation process. This fact is due to the low frequencies found in the pulse spectrum that is used for the excitation of the driving coil; however, quantifying the defect depth still remains a challenge. This study considers different pulse widths and frequency components as a method of defect depth discrimination with direct applications in the evaluation of corrosion defects in multi-layer aircraft structures. Experimental testing and numerical modelling approaches are concomitantly discussed as ways of defect depth quantification.