Effects of sliding surface profile on friction characteristics of viscoelastic material

Abstract

In order to clarify the effect of surface profile on friction characteristics of viscoelastic material used for oil seal, sliding test was conducted under oil lubrication with the NBR (Nitrile Butadiene Rubber) specimen in combination with steel specimen. The sliding surface profiles with different feature in the steel specimens were introduced by polish process and blast process. The NBR specimens with different surface feature were also employed. Under a low load condition, steel specimens with plateau surface showed the lower friction coefficient. The reduction of contact area and pocket effect could lead to the lower friction coefficient. Similar effect was provided by the NBR specimens with rough surface or dimples. Friction behavior under a low load condition was influenced by adhesion force. The adhesion force decreased with increasing surface roughness, that is with decreasing contact area. Therefore, the friction coefficient decreased with increasing surface roughness in NBR specimen. The friction coefficient of the NBR specimen with dimples which had small asperity and large concave portion was remarkably small under a low load condition. On the other hand, under a high load condition, where the deformation of NBR specimen was rather large, the effect of surface profile on friction coefficient was small.