الفهرس 
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Abstract
The thesis presents the results of experimemental tests of four
different standard size samples of friction materials used in automotive clutch and brake shoe linings. A description of a test machine interfaced with a PC computer for data collection in terms of friction force and sample temperature is given. The applied force and speed are held constant during a 90 minutes test run.
The tests coverd 16 tests for each sample at four different bearing pressures and four different rubbing speeds. The test results show varaitions in the coefficient of friction and specific wear rate depending upon the sample composition and test conditions. The variation in the coefficient of friction during the test run is calculated to rpresent the sensitivity of the sample material. Further, the relation between the average coefficient of friction and wear rate and the test conditions are examined and related for each sample.
The percentage change in the coefficient of friction reached about
39.5% in some cases, while the order of magnitudes of the coefficient
of friction and specific wear rate are from 0.2473 to 0.3453 and 2.171x
10”8 to 8.75xl0”8 gr/(N.m), respectively.
Marterial type no. 4 has the best stability in the coefficient of friction and wear resistance compared with the other three types, while material type no 3 has the lowest values at correspondind values of rubbing speed or bearing •pressure. This can be attributed to the fact that material type no.4 has the highest tensile and shear strength
( 19.land 10.2 MN/m2
and the highest hardness of28 HB. In addetion
it has 35% woven asbestos and 20% metalic fibber which reinforces the wear resistance. Moreover, material type no. 4 has 35o/o woven asbestos and 20% metalic fibers which improve the wear resistance. On the other hand, the other three materials contain fiber asbestos and
have no metalic fibers. Further, the reason for material no. 3 has the
the lowest wear resistance and stability in the coefficient of friction can be attributed to the fact that it has the highest rubber contents.