Study and Development of Inspection Technique for Wire Strand Damages based on Magnetic Flux Leakage Detection

This paper presents the development of a nondestructive testing technique for detecting wire strand damages, which are often installed in large structures such as broadcast towers, cable-stayed bridges, and external post-tensioning. By inducing high magnetic field strength, the induced magnetic field is changed due to leakage flux around the area of wire strand damage. In order to study the features of these flux leakages, a 3-dimensional numerical model was created using a 15.2 mmdiameter wire strand with different artificial notches. Then the model was calculated by using Finite Element Method (FEM). The computation results showed the different patterns of magnetic flux leakage in relation to the degree of wire strand damage. Moreover, the numerical calculation results were validated by setting up the experiment similar to computation modeling to detect the magnetic field leakage by using a high sensitivity magnetic field sensor. The experimental results confirmed that flux leakage patterns had similar trends compared with the numerical results. Consequently, the outcome of this research can be used for designing and improving the inspection technique of in-serviced wire strand in large structures based on magnetic field detection.