Complex Magnetic Permeability Evaluation of Steel Fibers Using Eddy Current NDE and Inverse Problem Methods

This paper presents a simple approach for evaluating the complex magnetic permeability of the steel fibers used in concrete according to frequency.The approach utilises the eddy current non-destructive evaluation method, where the electrical impedance is measured using a precision LCR meter and computed using a magneto-harmonic model solved in Py-FEMM software.Initially, the electrical conductivity of the steel fiber is measured using a two-contact DC method.Then, the inverse problem method is applied to identify the complex magnetic permeability.This is achieved by iteratively minimising the difference between the calculated and measured impedances using a simplex optimization algorithm.The proposed approach offers a non-contact, non-destructive, fast, and efficient procedure to evaluate the complex permeability.The obtained results provide valuable insights into evaluating the distribution of steel fibers in concrete.