Elastic and plastic deformation of surface asperities and their load-carrying mechanisms during the formation of a real contact area

M. Kalin, B. Žugelj, M. Lamut, K. Hamouda

Tribology International 178 (2023) 108067 1-9


How the contact behaviours of steel engineering surfaces with different roughnesses (Ra = 0.1, 0.6 and 1.0 μm) are affected by the asperity work-hardening and the deformation regime are described here. Large values of the plasticity index Ψ between 20 and 50 indicate that all the surfaces should undergo a full plastic deformation. However, in the loading range up to the yield stress (on a nominal contact area) the rough surfaces exhibited at least 10% elastic deformation, while for the smooth surfaces the elastic deformation was as much as 44%. During the loading, the work-hardening increased the hardness of the rough surfaces by up to 63%, and that of the smooth surfaces by up to 20%. However, the asperities were able to carry the load that resulted in as much as a 4–10-times-higher contact pressure than the (initial) bulk yield strength. The proposed contact mechanisms for such an increased asperity-load-carrying capacity depend on the surface roughness. For the rough surfaces this is due to the work-hardening, while for the smooth surfaces the dominant mechanisms enhancing the load-carrying capacity are the work-hardening combined with the hydrostatic bulk stresses.

Keywords: in-situ asperity experiment, multi-asperity contacts, real contact area, work-hardening, deformation, steel, roughness

URL: https://doi.org/10.1016/j.triboint.2022.108067

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