Page 207 - The Tribology Handbook

Brakes B8

Table 8.10 Performance and allowable operating conditions for various materials

Temperatures, "C Working pressures Maximum pressure
Malerzals P,
Maximum Maximum operating kN1m' MNIm2
LININGS
Woven cotton 0.50 150 100 70-700 1.5
Woven asbesto:n 0.40 250 125 70-700 2.1
Nos-asbestos
light duty (flexible) 0.38 350 175 70-700 2.1
medium duty (semi-flexible) 0.35 400 200 70-700 2.8
heavy duty (rigid) 0.35 500 225 70-700 3.8
PADS
Resin based 0.32 650 300 350-1750 5.5
Sintered 0.30 650 300 350-3500 5.5
Cermet 0.32 800 400 350-1050 5.9

Table 8.11 Typical mechanical properties
-
Ultiniate strength

Materials Tensile Shear Compressiue Rivet-holding capaci& Specijc Graoity

LINING
Woven cotton 20.7 12.4 96.5 69 1 .0
Woven asbestos 24.1 13.8 103.4 83 1.5-2.0
Non-asbestos
light duty 8.2 8.2 41.3 103 1.7
medium duty 10.3 8.2 96.5 152 1.7
heavy duty 13.8 9.0 103.4 172 2.0
PAD
Resin-based _- 9.0 103.4 - 2.0
Sintered metals 48.2 68.9 151.6 - 6.0

Mating surfaces

Woven cotton or asbestos linings, and those with steel and Sintered metals should run against fine-grained pearlitic
inorganic or organic fibre reinforcement, should run cast iron or alloy irons, Brinell Hardness 180-250. High
against fine-grained pearlitic cast-iron or alloy cast-iron of carbon steel such as EN6 for moderately loaded, and
Brinell Hardness 180-240 or steel cold-rolled or forged EN42 for heavy-duty thin counterplates in multidisc
with a Brinell Hardness greater than 200. The surface clutches. Minimum Brinell Hardness 200 for heavy duty.
should be fine-turned or ground to a finish of at least The surface finish should be 0.9-1.5 pm CLA.
2.5 pm CLA. (Cast steel and non-ferrous materials are not Cermets should run against similar cast irons with
recommended. Some friction materials are very sensitive Brinell Hardness greater than 200. High carbon steels
to trace amounts of titanium (and some other elements) in with a hardness between 200 and 300 are acceptable. The
the cast iron rotor, and these trace elements can consid- surface finish should again be 0.9-1.5 pm @LA.
erably reduce p, though they also tend to increase the life
of the friction material.

B8.8