The Effect of Rubber Deterioration on Static Friction on Metal Surfaces with Different Surface Roughness Characteristics

<p>Many studies on friction of rubber materials revealed the effect of power spectrum of surface roughness on friction. On the other hand, quantitative comparison of the effects of specific surface roughness parameters has not been sufficiently conducted as well as the effects of rubber deterioration on friction. In the present paper, the effect of rubber deterioration on static friction and its variation with surface profile (hard chromium (HCr) treatment, salt-bath nitrocarburizing (SBN) treatment, and gas nitrocarburizing (GN) treatment is clarified. The friction test results showed interesting results that the static friction coefficient of SBN surfaces decreased with rubber degradation, whereas the static friction coefficient of GN surfaces increased. Subsequently, we analyze the main characteristics of surface roughness parameters and explore the mechanism. First, due to the small skewness of the GN surface, the blockage of leakage channels is developed, resulting in the formation of oil reservoirs and a squeeze effect due to micro-slip of the rubber. Second, the surface of SBN has high peaks and the bearing area ratio of the peaks is high, which prevents the occurrence of leak-channel blockage and allows the peaks to penetrate rubber. The present paper specifically clarifies that these surface properties provide the obtained friction results.</p>