Time-domain approximate expressions for voltage induced by pulsed eddy current field of ferromagnetic plate

Pulsed eddy current testing is one of the electromagnetic nondestructive testing technologies, which is able to detect the ferromagnetic plate thickness by using the transient response signal of the voltage induced by pulsed eddy current field. Based on the time-domain analytic expressions for pulsed eddy current field of conductive plate, this paper study the way to simplify the expressions of the induced voltage. By calculating the order of magnitude of each variable in the analytic expressions, and combining with the diffusion process of the pulsed eddy current in the ferromagnetic plate, the time-domain expressions of voltage induced by pulsed eddy current field in ferromagnetic plate is simplified into two approximate expressions. Through coordinate transformation, the approximate curves become two straight lines in the log-log and semi-log coordinates respectively. The approximate expressions of the induced voltage are verified through the theoretical calculation and experiments.