Apparent contact width modification through deterministic surface texturing: friction and wear response in rolling sliding line contacts

To understand the tribological behaviour of rolling–sliding pairs with textured surfaces, two cylinders in contact were modified to account for the introduction of deterministic patterns. The experimental work developed was applied to study the effect of surface texture on the tribological response of Hertzian line contact tested in a twin-disc machine. Contact conditions used were based around a wheel/rail interface. It was found that the contact semi-width increased in the textured discs, which led to a reduction in the apparent contact pressure and subsequent effects on the stick/slip ratio for each percentage of applied slip. The increases in contact widths and the corresponding reduction in contact pressures were verified through finite element numerical simulations, assuming linear elastic material behaviour and a surface-to-surface contact formulation. The study shows that it is possible to reach a constant friction condition at lower slip percentages in textured surfaces. This could be a benefit in addressing problems associated with friction management, that is, to design the texture for contacts where it is difficult to control friction and also to be able to reduce contact pressures. Quantitatively, the apparent contact width increased by approximately 18% for the diamond-textured configuration, while the calculated load-bearing surface contact area remained nearly constant. At 1% slip, the mean crack length decreased by approximately 18% for both textured configurations, whereas the depth of the heavily deformed layer decreased by approximately 46% and 91% for the diamond and slot textures, respectively, compared with the non-textured surface.