Paper 19: Unlubricated Sliding at High Speeds between Copper and Steel Surfaces

Abstract

Experiments are described in which stationary copper specimens are rubbed in a normal atmosphere against a rotating S62 steel disc under normal loads up to 4·5 lbf. The coefficient of friction is measured at sliding speeds of 93, 220, 328, and 490 ft/s using ⅛-in diameter specimens. Except at the lowest speed a gradual buildup of a continuous copper oxide layer on the disc track is observed with increasing normal load together with a corresponding decrease in the coefficient of friction. Having established an oxide layer on the track the coefficient of friction observed is low for all normal loads. The coefficient of friction is shown to decrease with normal load N and sliding speed U, to be a function of N1/2 U, and to depend on the state of the disc surface. Wear of -in diameter specimens is measured by weighing before and after a test. The wear rate is shown to decrease with sliding speed and increase with load, and for speeds of 220 and 328 ft/s to be a function of N/U. The wear rates measured at 93 ft/s are the same function of N/U for low values of N/U.

Modeling of twist drills wear by a temperature-dependent friction law

“…Experiments (using, for example, a high speed pin-on-disk test device) have shown that at large sliding velocities a reduction of the friction coefficient is obtained when the normal pressure or the sliding velocity is increased (Williams and Griffen, 1964;Kadhim andPowell, 1966-1967;Montgomery, 1976;Lim et al, 1989).…”

Formation of molten metal films during metal-on-metal slip under extreme interfacial conditions

“…By post examination of the tips of the projectile he studied the evolution of the melt process during the penetration event. Williams and Gri en (1964), Montgomery (1976b), Kadhim and, Powell (1966-1967) and Lim et al (1989) conducted high speed sliding experiments using a high-speed pin-on-disk test device. The results of these studies indicate a reduction in the coe cient of friction when the normal pressure and/or the sliding velocity were increased.…”