PROJECT TITLE :

Thickness Measurement of an Iron Plate Using Low-Frequency Eddy Current Testing With an HTS Coil

ABSTRACT:

We applied low-frequency eddy current testing (ECT) using a high-temperature superconducting (HTS) coil so as to measure the thickness of an iron plate. Using this method, we have a tendency to measured changes in coil impedance when the iron plate was placed below the coil. Although low-frequency measurements were necessary to avoid the skin effect, changes in coil impedance became terribly tiny at low frequencies. For this reason, an HTS coil was used in order to sensitively live these little changes. First, changes within the inductance L and also the resistance R of the coil were measured when the iron plate was positioned 18 mm below the HTS coil, and also the thickness of the plate was changed in increments from half-dozen to 22 mm. The results show that we have a tendency to were ready to estimate the thickness of the plate up to 22 mm based on the changes in R when an excitation frequency of four Hz was used. Next, the effect of the liftoff between the iron plate and the HTS coil on the changes in Land R was studied whereas the liftoff was changed from eighteen to twenty-eight mm. The results show that the liftoff may be estimated from the changes in L. We were therefore ready to see the liftoff and the thickness of the iron plate by measuring changes in L and R, respectively. Results obtained from numerical simulation using the finite element technique were in agreement with the experimental results.