Time-domain analytic expressions for pulsed eddy current field of conductive plate and characteristic quantity for thickness measurement

This paper solves the pulsed eddy current field in time-domain of the conductive plate induced by falling current, and puts forward a way to obtain the signal characteristic quantity for thickness measurement. Through Laplace transformation and finite Hankel transformation, the series expansions for truncated eddy current field are attained in complex frequency-domain. The inverse Laplace transformation is figured out via residue theorem, and a new method is developed to calculate the eddy current field induced by falling current through the convolution between the time derivative of current and the unit step response of the model. The variations of the eddy current density in the conductor are studied and its relationship with induced voltage is presented. The thickness of the plate can be measured by using the peak time of the differential induced voltage between conductive plate and conducting half-space. Analytic expressions and characteristic quantity are verified through the experiments on aluminium plates.