Ph.D. Tezi Görüntüleme

      Bending strength, electrical resistivity, tribological and electrotribological properties of prepared brush specimens were measured using equipments which were especially designed and manufactured in this study. Bending strength and hardness increased and electrial resistivity and voltage drop decreased with increasing copper content.

      The coefficient of friction decreased and specific wear rate increased wih increasing copper content without current (10N, 14.1 m/s). The coefficient of frictionwith currentwas found higher than that of without current but brush service temperatures were relatively higher. Specific wear rate increased wih increasing brush load (1-20 N) without current. During the tests under current specific wear rate increased wih increasing brush load between 3-20 N but below 3 N brush load, specific wear rate sharply increased due to arcing effects. The coefficient of friction and voltage drop decreased wih increasing brush load (5-15 N). Sliding velocity (5-15 m/s)and current (10-40 A) increased voltage drop and decreased friction coefficient of copper-graphite brush specimens.

      Copper-graphite brushes with additives such as Pb, ZnO, and MoS2 were also manufactured to study the effects of additives on brush properties. The test results showed that the voltage drop was the lowest in Pb containing brushes but wear rate was the lowest in ZnO containing brushes. MoS2 addition decreased the wear rate without current but inceased it with current. Based on total brush power loss, the best brush grades were order of CO90, CU80, CU85PB5 and CU85ZNO5.