A scratch deformation procedure is described which has been adopted in order to characterise the surface mechanical damage mechanisms of two polymers; a poly(methylmethacrylate) (PMMA) and an ultra high molecular weight poly(ethylene) (UHMWPE) under dry and lubricated conditions. The variation of the evaluated friction coefficient under a range of experimental conditions, such as the scratching velocity, the imposed strain of the deformation and the state of the interfacial lubrication is described. The results show a marked dependence of the friction coefficient upon the computed contact strain for both materials. The dependence of the friction upon the velocity was found to be evident at the lower velocities when the contact is realised in dry conditions and using the sharper indenters. A subjective assessment of the surface damage was also made for the PMMA system using SEM imaging.
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