Quantitative evaluation of defects based on the characteristics of the induced eddy current field

Abstract

A quantitative evaluation method for determining the shape, length and depth of surface defects is proposed for the purpose of non-destructive testing (NDT) and evaluation of metal materials. The COMSOL Multiphysics finite element software is used to calculate and analyse the eddy current magnetic field and the influence of the geometric parameters of defects on the spatial three-dimensional magnetic field distributions are studied. The results show that the shape of the surface defect can be judged from the measurement result of the x-Bx curve. The quantitative analysis of the crack length is realised according to the corresponding position of the peak (trough) of surface magnetic field Bz . The depth of the crack can be inversely calculated by the quantitative relationship between the trough depth of Bx (or the peak value of Bz) and the crack depth. Therefore, this method provides convenient and contactless detection technology in which the characteristic quantities corresponding to the defect parameters are independent from each other to improve the accuracy of defect evaluation.