Thickness measurement of metal pipe using swept-frequency eddy current testing

Swept-frequency eddy current measurement of pipe thickness is studied in this paper. First, suitable frequency range of swept-frequency eddy current testing is determined by comparing sensitivities of relative reactance change with respect to pipe thickness and other parameters at different frequencies. Based on analytical solutions to pipe eddy current field, Levenberg-Marquardt algorithm and variable transformation, a method for solving inverse eddy current problem is developed. Finally, several inversion calculations are carried out and the results are close to the truth values. The low errors reveal that the method presented in this paper is appropriate. (C) 2015 Elsevier Ltd. All rights reserved.