THE USE OF VIBRATION MONITORING IN DETECTING THE INITIATION AND PREDICTION OF CORRUGATIONS IN ROLLING-SLIDING CONTACT WEAR

Vibration displacements and accelerations have been monitored on a modified Amsler machine during the dry rolling-sliding wear testing of rail steels. Certain combinations of contact stress and creepage lead to periodic circumferential surface deformations of the test discs, termed corrugations. The low frequency corrugations are defined as facets. Dramatic facets have occurred at 500 MPa maximum Hertzian contact stress and 10% creepage, in the frequency band ranging from 1-100 Hz, with a typical facet frequency initiated at 58.25 Hz. No higher frequency corrugations occurred during the test run, unlike previous tests (J.E. Garnham, J.R. Brightling and J.H. Beynon, Wear, 124 (1988) 45-63). The evolution of the surface deformation was observed by surface profilometry, as well as by monitoring the facet vibration component trend, and a good correlation between the two has been found. Aslo, a significant correlation between the predominant peaks of the displacement spectra and the higher harmonics of the rotation frequency have been detected, leading to conclusions concerning the mechanism of facet initiation. At the end of the test the facets degenerated into pronounced eccentricities causing a high level component of the rotation frequency that could easily be detected by following the evolution of the characteristic component. The tests highlighted that the vibration displacement is more suitable for the monitoring of rolling-sliding contact defects than is the acceleration, which tends to emphasise the high frequency components. Vibration monitoring is shown to be a proper and powerful tool for the early detection of facet initiation.