Study on electromagnetic characteristics of cylindrical hole defect in variable parameter traction motor shaft based on eddy current effect

Detecting common cylindrical hole defects (corrosion defects) in locomotive traction motor shafts is essential to ensure equipment reliability and safety. This paper conducts an in-depth study of rotating shafts with a rich magnetic field surrounding them, with the goal of identifying cylindrical hole defects and diagnosing corrosion defects. During eddy current testing, to investigate the influence of variable-parameter (bottom diameter and depth) cylindrical hole defects on the electromagnetic properties of traction motor shafts, an equivalent model of a variable-parameter defect detection system for cylindrical hole defects (corrosion defects) was established using COMSOL software, based on eddy current testing theory, and simulation analysis was performed. By studying the horizontal and vertical magnetic induction intensities(HMII, VMII) and their respective phases(PHMII, PVMII), the magnetic field distribution around the cylindrical hole defect under variable parameters was analyzed. The results show that HMII and its phase have a significant geometric correspondence, allowing for quantitative assessment of the defect bottom diameter through characteristic peak spacing or phase lag width. Simultaneously, the amplitude variations of HMII and VMII can qualitatively determine the presence of defects and evaluate their relative depth (limited by the saturation threshold). Furthermore, PVMII is insensitive to the defect's geometric parameters.