Measurement of conductivity and diameter of metallic rods using eddy current testing.

• The self-inductance variation of coil is linear to the of logarithm of rod diameter under high-frequency. • The peak frequency ω peak has the inverse relationship with conductivity. • The coefficient of peak frequency regarding diameter can be corrected by high-frequency response. • The radius and conductivity of rods is deduced using the peak-frequency and self-inductance of coil under high-frequency. The conductivity and radius are significant parameters for metallic rods, which are associated with metal composition, hardness and microstructure. Accurate conductivity and radius measurement can reflect internal structure status of metallic rod, so as to prevent accidents. The method in this paper aims at simultaneously estimating the conductivity and diameter using sweep-frequency eddy current testing (ECT). This method is an extension of the analytical solution we proposed previously. Specifically, the peak frequency of the imaginary part of the self-inductance variation has the inverse relationship with conductivity. However, the peak frequency is also affected by rod diameter. In order to decouple the conductivity and diameter of metallic, the real part of self-inductance variation have been proved to be only related to the diameter of the metallic rod under high frequency. Combining the peak frequency and real part of self-inductance variation under high frequency, the conductivity and radius can be simultaneously obtained. The experiments using standard specimen are implemented to- verify the feasibility of the method. Results illustrate the average relative errors are within 1.4%. [ABSTRACT FROM AUTHOR]