الفهرس 
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Abstract
The present experimental work aimed to establish relationships between different operating parameters and the tribological behavior of the frictional material during the slippage phenomenon occurs throughout transmitting power and torque.
A commercially produced lining materials have been used in this investigation. Three configurations of test specimens have been adopted, one with flat surface and the others with either lateral or longitudinal grooves. A pure slip apparatus available at the Automotive and Tractor Engineering Tribology Laboratory, Faculty of Engineering, El - Minia University has been modified and equipped with a friction force measuring transducer and a system to measure the interface contact temperature directly at the slip surface . Loads were supplied through a simple leverage system .
The study showed that the friction coefficient decreased as contact pressure increased . Furthermore ,the friction coefficient has been observed to increase as the slippage speed increased . However, at higher contact loads a DROP in friction coefficients have been observed. Although the increase in these parameters increased the contact temperature which increased both of junctions adhesion and creep , but adversely affect the junctions yield strength characteristics and hence the tangential stresses required to rupture the junctions .
The frictional heat dissipated during slippage has been observed to have an impressive effect on friction coefficient. Friction coefficient was observed to increase as frictional heat increased up to a certain limit, but as the frictional heat began to increase further, the friction coefficient start to decrease .
The interface contact temperature was observed to decrease for specimens with lateral or longitudinal grooves. This may be related to some sort of air ventilation generated because of the presence of these grooves.
The counterface surface roughness was found to affect strongly the friction coefficient of the lining material . At low value of surface roughness of 2.34 µm Ra low values of friction coefficient were recorded , however as surface roughness increased to 4.68 µm Ra friction coefficient showed its higher values . The further increase of surface roughness to 9.33 and 51 µm Ra showed low values of friction coefficients .