2.2.3. Contact Mechanism and Friction Parameters

The wear of the samples was characterized in a wear test in which the textured sample was exposed to a polyehtylene (PE) ball (diameter of 9.5 mm) sliding over the surface in BCS as lubricant, in order to simulate the human body environment. The sample discs are clamped in a Universal Mechanical Tester (UMT, Bruker, Billerica, MA, United States). The PE ball was pressed against the sample surface and moved in a reciprocate fashion for 104 min with 11 mm/s and a normal load of 0.5 N (18 MPa contact pressure) [21]. The normal force and the shear force are measured and the coefficient of friction during steady state of the wear test was calculated. The wear of the PE ball surface is analyzed by observing the wear diameter with a confocal microscope (S Neox, Sensofar, Terassa, Spain). The wear of the textures is investigated with a SEM (see Section 2.2.2) and energy-dispersive X-ray spectroscopy (EDS) analysis in the same SEM system.
