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Friction and scuffing resistance characteristics of two piston alloy materials have been investigated by using a long-stroke reciprocating test rig. Tests were conducted under the same load, speed, and starved changing to dry lubrication conditions until the scuffing failure occurred, as indicated by a sudden change of the frictional force signal which was monitored continuously. Measured friction coefficient and scuffing threshold and life results were obtained, and the piston alloy with the better scuffing resistance capability has been identified. Surface texture of new and scuffed piston and cylinder bore specimen surfaces have been measured and characterized by a combination of amplitude and spacing parameters.

A reciprocating test rig driven by a slider-crank mechanism has been developed for the purposes of generating piston ring friction coefficient data needed for engine modeling friction loss computations, and for performing basic tribological studies of piston engine moving components, including the piston skirt, in matters of quantity and detail. The ring friction coefficients were measured along a realistic stroke length with the ring in a compressed state and motion in the groove preserved. Ring and liner specimens were prepared from actual engines to ensure that the surface finish and material metallurgy are realistic. A data acquisition and analysis system was also developed. Results are presented in looping type Stribeck friction coefficient vs. Sommerfeld number relations directly applicable for engine modeling friction loss predictions. Such relations can also be used to examine the basic ring friction behavior quantitatively.

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.

A selected number of papers published within the last five years relating to piston ring tribology research in the areas of friction determination, friction reduction, lubrication, and oil consumption, have been reviewed. Improved ring lubrication models and friction measurement techniques have been developed by various authors. Their efforts have enlarged considerably on our understanding of the main features of ring-cylinder interface friction and lubrication behavior, and the mechanism of engine oil consumption. However, there is still a lack of understanding in matters of quantity and detail. Recommendations for future work are presented.

Applying hydrodynamic lubrication theory for porous bearings and boundary lubrication theory, this paper presents a method of analyzing the performance of a water-lubricated sleeve type porous bushing in an automotive water pump design. Relations of bearing load capacity versus shaft speed have been obtained and compared for sintered iron-graphite bushings (a cermet material developed by the Ford Motor Co.), sintered iron or sintered bronze bushings, and steel bushings. The load capacity was computed, based on a minimum allowable film thickness during hydrodynamic operation, and on a maximum allowable temperature during boundary lubrication operation. The results show that sintered iron-graphite bushings are superior to sintered iron or sintered bronze bushings, as well as steel bushings, in this application, due to the lower coefficient of friction.