A novel high pressure shear cell has been used to study friction phenomena
between crushed silica and Ni-Hard 4 at surface stresses commonly experienc
ed in ore crushers. Surface normal loads of more than 300 MPa were used, to
gether with tangential loads sufficient to initiate and maintain slip at th
e crushing surface. Under these load conditions, the friction coefficient i
ncreased with sliding distance, rising from an initial value of less than 0
.1 and leveling off to a plateau value of about 0.4-0.6 in the first few mi
llimeters of shear displacement. The variation of friction coefficient with
shear displacement could be divided into three stages: the first dominated
by particle rearrangement in the abrasive bed, a second transition stage w
here particle rearrangement and particle crushing occurred together, and a
third dominated by a slowly evolving layer of fine powder adjacent to the c
rushing surface. This last stage was characterized by a relatively stable (
plateau) value for the friction coefficient. This plateau was a weak functi
on of the normal load.
Analytical and experimental results showed that larger abrasive particles p
referentially penetrate the surface and, as a result, cause the most extens
ive ploughing damage. Thus, if fine particles are concentrated at the crush
ing surface they can protect that surface from penetration and ploughing by
larger particles. a feature also observed experimentally.
An energy analysis of the crushing and wear event revealed that interpartic
le friction and particle fracture occurring within the bed of abrasive mate
rial contributes significantly to the energy consumed as a result of shear
displacement. (C) 2001 Elsevier Science B.V. All rights reserved.