Using contact measurements, experimental evidence was obtained for the existence of the rolling resistance moment. The critical rolling distance prior to detachment is reported. Previously it has been argued that the critical rolling distance should be related to the lattice size and/or the molecular length of the particle and surface materials. However, there has been no theoretical prediction...

Mali is located in the Sahel region of West Africa, to the south-west of Algeria and north of Burkina Faso and Niger (Figure 1). It has a large area of some 1.24 million square kilometres. The terrain is dominated by flat or rolling sand-capped plains in the north and savannah in the south, although rugged hills occur in the north-east. Elevation varies from the highest point at Hombori Tondo (...

We study the lubricated (wet) contact mechanics of a smooth hard cylinder sliding on a randomly rough nominally flat surface of a linear viscoelastic solid. We calculate the rolling and sliding friction, and study the transition from the boundary lubrication to the elasto-hydrodynamic lubrication regime. For the viscoelastic contact the minimum (average) separation does not monotonically increa...