On the role of varying normal load and of randomly distributed relative velocities in the wavelength selection process of wear-pattern generation

In systems with moving contacts, as e.g. automotive vehicles on dirt-roads, friction brakes, and of course railway vehicles moving on railway tracks, spatially periodic wear patterns may appear on the contact partners’ surfaces. There is general agreement that the patterns are related to structural resonances. Using simple models with a moving point contact and an idealized wear model the present work first reviews some of the present understanding of wear-pattern generation. Then additional intuitively accessible explanations for the phenomena observed are developed and the effect of randomly specified relative velocities on the wavelength selection process is investigated. For this purpose the stability analysis of the surface evolution equation is pursued with the full, as well as with a reduced system, and a simple linear approach to deal with distributions of relative velocities is introduced. For fixed relative velocity the analysis yields an intuitively accessible picture of wear-pattern appearance or evanescence, as well as of wear-pattern motion. Based on these results it is shown, how dominant wavelengths are selected as a consequence of randomly distributed relative velocities.