Statistical Analysis of Kinetic Friction Coefficient for Dry Sliding Plain Bearing on Shaft Test of Polytetrafluoroethylene 2014-36-0145
This paper discusses the behavior of kinetic friction coefficient and temperature on contact of Polytetrafluoroethylene (PTFE) in a dry sliding test against stainless steel. This polymer is widely used in industry for many tribological applications without lubrication. It was performed essential tribological evaluations: the overall shape analysis of kinetic friction coefficient and temperature on contact curves, regions identification with distinct behavior and the mean and the standard deviation of the values obtained. For this purpose, long duration tests were performed (120 minutes) in a kinetic friction machine, developed and built at the UTFPR's Laboratory of Contact Surfaces, in which a PTFE plain bearing slides without lubrication over a stainless steel shaft with monitoring of kinetic friction coefficient and temperature on contact. The test condition simulates the polymer real application as plain bearing. Four normal loading levels were performed, the PV condition, however, was kept constant and within the material application range. It was determined for kinetic friction coefficient curves: running-in period and, through statistical inferences, periods of transition and stabilization. It was verified that the running-in period lasted about ten minutes, followed by a transition period lasting up to 70 minutes, from which the tribological system has stabilized. It was concluded that the beginning of kinetic friction coefficient stabilization period was dependent on variations of temperature on contact and contact area. The last one evolved, for the case studied, from non-conforming, at the initial condition, to conforming contact due to material wear.