chapter
HANDS AND HOLDING
Pages 13

Ff = M c ,A r ‘ F ' .................................................................................................................(2) in which A t stands for the contact area and q for some dimensionless exponent smaller than 1. M is a proportional factor. It has a dimension of [(MPa)l q] in case the forces are expressed in [N] and the area in [mm2]. The factor cp is the pressure distribution factor, dimensionless and dependent on q. It expresses the number of times the pressure p in a point is bigger or smaller than the average pressure p m on the contact surface. This formula can be seen as a refinement of the equation of Comaish and Bottoms (1971). It can be derived from the equations of Hertz (1895) and the supposition that the frictional stress r is proportional to the pressure p according to r = Mpq.