Detection and Analysis of Magnetic Field Anomalies over Surface Defects of Complex-Profile Parts

This article presents an effective method for detecting surface defects via magnetic field anomalies occurring over cracks, cleavages, and crevices of angular elements of complex-profile parts made of ferromagnetic materials. The method is based on the spectral analysis of the signal of a tangentially oriented vibration–induction transducer (VIT). The amplitude–phase method of analysis and research based on mathematical modeling of the signal of the VIT in the form of a trigonometric series is theoretically substantiated. The results of recording and analyzing the distribution of the magnetic field strength and the amplitude–phase spectrum of the signal of the VIT along a surface with involute and threaded profiles are presented. The results were obtained on control samples of a gear wheel, a threaded rod, and a bolt with artificial defects. The conditions for detecting surface defects based on the results of measuring the amplitude and phase of the first two harmonics of the signal of the VIT are formulated. The parameters of the control scheme of the involute and threaded profiles with module and pitch values of the order of several millimeters, which make the automation of the control process with a satisfactory signal-to-background ratio possible, are determined. The method is designed to control the continuity of parts containing profiled surface areas (i.e., fillet, involute, threaded, and splined profiles).