Measurement of finite plate size in pulsed eddy current testing

Abstract

Pulsed eddy current methods have been used to measure thickness and physical properties of metallic materials. These methods are applicable to plates of infinite size or plates much larger than the sensor size (3–5 times). However, existing methods (single-frequency or multi-frequency eddy current method) for solving circular plates of finite size are limited to the frequency domain and cannot satisfy relative thick samples or samples with high magnetic permeability. In this research, a pulsed eddy current (PEC) analytical method for finite radius plates is proposed by extending the finite size Dodd–Deeds model and the truncated region eigenfunction expansion (TREE) to the time domain. Based on the modified analytical solution, a radius measurement method for finite size circular carbon steel plates is introduced. The radius measurement method is experimentally verified and the results show that the average error is less than 1%.