Surface damage resulting from rolling contact operating in magnetic field

摘要

This paper describes the effects of magnetic field on rolling contact performance of steel discs and presents an investigation into the mechanisms governing these effects by applying contact mechanics and magnetism theory. The tests were carried out in disc-on-disc contact configuration using two contact conditions, i.e. pure rolling and rolling with 10% sliding. Also two horizontal static magnetic fields of 0.4 and 1.1 T created by permanent magnets were applied. The results of scanning electron microscopy observations reveal that finer wear particles and smoother worn surfaces are produced in the presence of a magnetic field. The smoother surfaces are also confirmed by surface roughness measurements. For generation of the finer wear particles, it is considered that the subsurface crack initiation point is moved towards the surface due to the magnetic field. Wear amounts are decreased in the magnetic fields under pure rolling conditions. However, at rolling with 10% sliding, the wear amounts are increased in the magnetic fields, even though finer particles and smoother surfaces are observed. Both tendencies are explained by calculating the number of cycles required to generate wear particles, which were reduced due to the magnetic field presence. It is considered, therefore, that domain walls near the contact region are caught by dislocations when the specimen is magnetized and part of the energy for magnetization activates the dislocation movement resulting in crack initiation.