Chapter 2. Prehension

212 THE PHASES OF PREHENSION
FtiYsT. I
DEFORMATION
OR
HYST~ES I s
\ RIGID BASE
\
ADHESION
Figure 6.2 The contact area between an elastomer (like skin) and
a rough support surface is characterized by the draping of the
elastomer about individual asperities. The total friction force
developed in sliding over a single asperity may be separated into
an adhesion and a deformation term. F= total friction, FHYST.=
hysteresis friction, FADH.= adhesion friction, V=velocity of
sliding, W=applied load, p=pressure (from Moore, 1972; adapted by
permission).
Ftotal= Fadhesion + Fhysteresis (2)
The adhesion component is believed to be a molecular stick-slip
process (the bonding of the exposed surface atoms in both surfaces,
according to a stretch, break and relaxation cycle of thermal events).
The hysteresis or deformation term is due to a delayed recovery of the
elastomer after indentation by a particular asperity, and gives rise to