The hysteretic part of the friction coefficient for rubber sliding on an ideal rigid, rough surface has been investigated by FE technique. The FE models were created by using two different FE softwares, ABAQUS and MSC.MARC. The surface roughness has been considered by using two different sine waves having a wavelength of 100？μm and 11.11？μm, as well as their superposition. Parameters of the viscoelastic material models of the rubber were gained, firstly from a fit to the measured storage modulus, secondly from a fit to the measured loss factor master curve of the rubber. The effect of viscoelastic material models, comparing 10-term and 40-term generalized Maxwell models was also considered together with the temperature effect between ？50 and C. According to the results, both postprocessing methods, namely, the reaction force and the energy-based approach, show very similar coefficients of friction. The 40-term Maxwell model fitted to both the storage modulus and loss factor curve provided the most realistic results. The tendency of the FE results has been explained by semianalytical theory. 1. Introduction It is important to characterize the friction behaviour of rubber components sliding on rough counterpart in a number of applications, such as seals, wiper blades, and tires. Many papers found in the literature deal with improving the tribological properties of sliding pairs and decreasing the friction. In the absence of lubricant when contacting surfaces are dry and clean, the rubber friction is mainly due to adhesion (especially at low sliding speeds) and hysteresis [1–4]. The hysteretic friction comes into being when the rubber is subjected to cyclic deformation by the macro- and/or microgeometry (surface roughness) of the hard, rough substrate [2, 4]. When a rubber component slides on a hard, rough substrate, the surface asperities of the substrate exert oscillating forces on the rubber surface leading to energy “dissipation” via the internal friction of the rubber. In the most engineering applications, rubber/metal sliding pairs are lubricated in order to decrease the friction force arising in dry case. In presence of lubricant, rubber friction is due to hysteretic losses in the rubber, boundary lubrication, and fluid friction. The lubrication decreases the contribution of nanoroughness to hysteretic friction because lubricant fills out the nanovalleys, which makes the penetration of the rubber impossible into these regions. In the case of fluid friction, friction force comes from the shearing of a continuous, relatively thick fluid film. At the
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