The limiting pressure-velocity (PV) of plastics under unlubricated sliding

The limiting pressure‐velocity (PV) of plastics materials under normal contacting pressure P and sliding velocity V when the sliding goes on continuously unlubricated has been discussed theoretically in this study. The sliding friction tests between the rotating edge of a hollow cylinder against a stationary metal surface were carried out in room air and when the metals were cooled with circulating water. The results obtained were as follows: The relation between PVmax and the critical temperature τbmax of the surface above which ordinary frictional conditions are not maintained may be represented by the following formula, \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm PV}_{max} = C(\tau _{bmax } - \tau _a)} & {(1)} \\ \end{array} $$\end{document} Where C = Hn/μk, and H is the mean total heat conductivity between materials and environment in cal/cm2. °C · s, n the area ratio of heat radiation surface to frictional surface, μ the kinetic frictional coefficient, k the thermal equivalent of frictional work in cal/kg · cm · s, and τa the cooling or environment temperature. The value of C ranges from 1 to 10 in cal/kg · cm s · °C, and the value of PVmax from 45 to 750 in kg/cm2 · cm/s under prevailing room temperature air cooling in this experiment, however, the value of C has been increased about 2.3 times as much as those values by circulating water of 2°C around the lower side of the test piece.