  In the sliding contact of elastomer on a rigid substrate, the coefficient of
friction may depend on a large number of system and loading parameters,
including normal force, sliding velocity, shape of contacting bodies, surface
roughness and so on. It was argued earlier that the contact configuration is
determined more immediately through the indentation depth than the normal
force, and thus the indentation depth can be considered as one of "robust
governing parameters" of friction. Both models of friction of simple shapes and
fractal surfaces demonstrate that the coefficient of friction of elastomers
should be generally a function of dimensionless combinations of sliding
velocity, surface gradient, relaxation time and size of micro-contacts. The
relaxation time does depend only on temperature and the surface slope and the
size of micro contacts mostly on the indentation depth. Based on this general
structure of the law of friction, we propose a generalized master curve
procedure for elastomer friction where the significant governing parameter -
indentation depth (or normal force) was taken into account. Unlike the
generation of the classical master curve by horizontal shifting of dependence
"friction - logarithm of velocity" for different temperatures, in the case of
various indentation depth the shifting in both horizontal and vertical
direction is required. We experimentally investigated coefficient of friction
of elastomer on sliding velocity for different indentation depths and
temperatures, and generated a master curve according to this hypothesis.
