Page 199 - The Tribology Handbook

Friction clutches 57

Table 7.5 Typical physical and mechanical properties of clutch facings
Resin-bared materials Sintered metals

Thermal conductivity 0.80 W/m"C 16 W/m"C
Specific heat 1.25 kJ/kg"C 0.42 kJ/kg"C
-
Thermal expansion 0.5 x IO-~PC 0.13 x 10-~/"c
Specific gravity 1.6 for woven/wound 6.0
2.8 for moulded
Brinell hardness number 6-15 13
-
MN/m2 MN/m2
~
Ultimate tensile strength 20 45
Ultimate shear strength 12 35
Ultimate compressive strength 100 150

If the maximum temperatures in the tables are exceeded
the p may fa11 badly. Any increase in temperature will
increase the wear rate. Figure 7.20 shows how the wear of
resin-based materials typically increases with tempera-
ture, taking the wear at 100°C as unity.

100 200 300 400
TEMPERATURE, 'C

Figure 7.20 The effect of temperature on the wear
rate of clutch facing materials

B7.9