The article deals with the problem of detecting hidden defects in metal parts using magnetometry methods. As the object of study, the axes of wheel pairs of railway cars are chosen. The subject of the study is latent defects and fatigue cracks in the developmental stage. It is shown that the latent cracks that develop in the case of fatigue failure are the most dangerous defect that leads to accidents of technical objects and catastrophes. It is established that modern methods of nondestructive testing do not provide reliable detection of such defects. Two methods of flaw detection, a ferro-probe and based on the magnetic memory of a metal are considered. Approaches to the improvement of the ferrosonde method are proposed. The reliability of defect detection by ferro-probes can be increased by transferring them to resonant mode and by using software signal processing. The use of the resonant mode makes it possible to increase the sensitivity of the ferro-probe by a factor of 8-10. As a mathematical basis for signal processing, it is proposed to use methods of nonlinear mechanics, the theory of chaos, and a multiplex method of recording a useful signal. As an alternative method of diagnostics, it is proposed to use the method of magnetic memory of metal. The essence of the method is briefly considered. As the main objects for detection, concentrators of mechanical stresses, traces of plastic deformation and defects in the form of discontinuity of the metal are determined. The device implementing this method is described. The results of testing the device on samples with different defects are given. Prospects and directions for further improvement of the proposed methods for nondestructive testing of the state of technical objects are outlined.
Keyword: non-destructive testing, hidden defect, magnetometry, ferrozond, metal magnetic memory method.