Development of a Reciprocating Test Rig for Tribological Studies of Piston Engine Moving Components - Part II: Measurements of Piston Ring Friction Coefficients and Rig Test Confirmation

Piston ring friction coefficients were measured using a slider-crank mechanism driven long-stroke reciprocating test rig under various load, speed, and lubrication conditions. Ring and liner specimens were prepared from either new or used engines to ensure that the surface finish and material metallurgy are realistic. Consistent four-branch looping type Stribeck relations have been generated. Measured rig friction force profiles and friction coefficient values correlate well with engine/simulator tests reported in the literature. Good comparison of aluminum bore surface scuffing failure patterns with engine cold scuffing test offers added evidence confirming that the test rig is capable and acceptable for performing simulated piston/piston ring tribological studies, including scuffing investigations.