Figure 1
Film thickness measurements. (a) Schematic of the custom-built UTFI apparatus, which consisted of spectroscopy measurement system and pure rolling reciprocating rig for measuring the film thickness of the test lubricant under pure-rolling contact (U1 = U2); DS: displacement sensor and HM: half mirror; (b) Experimental protocol—A: after loading from the non-contact state without any lubricants, the film thickness was measured under static contact conditions; B: after injecting a test lubricant into the contact point, the film thickness was measured under static contact conditions; C: after unloading and reloading, the film thickness was measured under static contact conditions, and then the plate and ball were moved with the pure rolling motion for half a stroke back from the origin; D: during the pure rolling motion for a forward stroke, the film thickness was measured at the origin; E: during the pure rolling motion for a backward stroke, the film thickness was measured at the origin; F: after the plate and ball were moved with the pure rolling motion for half a stroke back to the origin, the film thickness was measured static contact; (c) Temporal changes in the film thickness of the HD and SA/HD lubricant films according to the protocol; black plots and error bars: the mean and standard deviation of the three-time measurements of the HD; red plots and error bars: the mean and standard deviation of the five-time measurements of the SA/HD.
