Numerical study for development of subsurface crack detection using pulsed eddy current and swept frequency eddy current

Abstract

Root-deck crack, a type of subsurface damage, is one of the most concerning fracture issues on orthotropic steel decks. Therefore, the development of novel and easy-to-use subsurface damage detection technique is crucial to detect damage at an early stage to prevent the occurrence of major damage. In this paper, new methods to process the response signal of the eddy current technique (ECT) using the normalised peak and time to zero crossing of the change in induced voltage, and the peak and frequency at the peak of the normalised change in phase angle, are proposed. Based on these newly proposed methods, a probe configuration optimisation study was carried out using dynamic electromagnetic field analysis. From numerical studies, the cup-core probe promises high capability to detect damage located 10 mm below the surface of a 12 mm steel plate and maintain the sensitivity at an eccentric position. Furthermore, the newly proposed signal processing methods enable users to interpret response signals for subsurface damage detection in a more comprehensive way than conventional methods.