Quantitative measurements of sliding friction coefficients of tribological interfaces with a new differential infrared radiometric instrument

Experimental sliding friction coefficient (SFC) measurements using a mechanical friction rig and infrared radiometric emission data from a novel instrument monitoring radiant heat generation at the tribological interface of the rig are described. The infrared radiometric (IRM) system features thermal-emission-intensity harmonic modulation with background-radiation-compensating wave forms, leading to differential signal operation mode and suppression of ambient radiation. The mechanical friction rig was used to generate friction between pairs of moving and stationary samples and to provide reference normal-force and friction-force measurements. Correlations between the lock-in amplifier readouts and the SFC data obtained simultaneously from the mechanical system have been established. The ratio of SFCs from adjacent steel surfaces with and without a lubricant film was accurately measured by the IRM instrument.