Research on the stress-magnetism effect of ferromagnetic materials based on three-dimensional magnetic flux leakage testing

• Three-dimensional system to measure x, y, and z components of magnetic field.
• Distribution of two-dimensional spectrum entropy extracted from magnetic signals by Fourier transform.
• Method for estimating stress concentration with support vector machines model (SVM).

Metal magnetic memory is a non-destructive testing technique in which the stress-magnetism effect of ferromagnetic materials is applied to evaluate the stress-concentration zone. A test platform was developed to measure the three-dimensional magnetic flux, based on leakage flux theory, in order to realize real-time display, processing, and storage of magnetic signals by using LabVIEW programs. The distribution of the two-dimensional spectrum entropy of detection signals is intuitively displayed by Fourier transform and support vector machines model. Our results demonstrate that data acquisition can be realized accurately using magnetic flux leakage inspection technology based on LabVIEW and that the distribution of the spectrum entropy can provide a method for monitoring crack growth through diagnosis of internal stress concentrations in materials.