Effect of normal load on friction characteristics (part 1): friction between a hard conical projection and a soft rubbing surface having triangular prismatic projections

摘要

In this work, friction mechanisms were theoretically considered using a model of macroscopic contact between surface protrusions that took into account the surface asperities of two solids with a sufficient hardness difference and the flow of protrusion periphery; the effect of normal load on friction characteristics were also determined. It was assumed that after machining by grinding, surface asperities of hard materials would have the form of right circular cones with semivertical angles α. On the other hand, it was supposed that the surface of soft material used as a sliding surface was machined by cutting. Also, it was supposed that sliding surfaces were smooth or had triangular prismatic projections with semivertical angle θ oriented either parallel to or vertical to the direction of sliding. When projections on the surface of hard material had the form of right circular cones, the friction obeyed the Amonton-Coulomb friction laws in a wide range of normal loads. However, in the range of low loads, the coefficient of friction, in general, changed with the position of contact and with a change of the shape and the size of projections on sliding surfaces and results obtained by numerical calculations using theoretical analysis data showed that in this case, the above friction laws were inapplicable.