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

• An accurate method for solving inverse pipe eddy current problem is developed.
• The suitable frequency range is determined.
• The constraints of the inverse problem is eliminated.
• The huge magnitude disparity between the unknown parameters is removed.

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.