| A pin on disk type apparatus was used to test multiple configurations of a polyoxymethylene/steel interface to examine the effect of normal external load, sliding velocity, polymer resin type, and lubrication on the development of kinetic friction. Both lubricated and dry samples were tested in each configuration. The normal load was varied from 3 to 100 N, and the force of friction was measured in situ via a miniature load cell. The coefficient of friction displayed Hertzian contact behavior and for the steel pin on polymer disk experimental configuration, the effects of the sliding velocity, temperature, and time were secondary. Further testing was conducted where the type of polyoxymethylene resin used varied. The sliding velocity was held constant as the effect of normal load was investigated. Each of the resin types indicated Hertzian contact behavior as the friction force followed a linear dependence on the normal external load. However, analyzing the coefficient of friction as a function of applied load showed that the frictional behavior was unclear and hidden adhesive effects may be present. Notably all three resins behaved similarly. While each resin type varied in molecular weight, each gave a similar measurement for its lamellar size. |
