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Technical Paper

Surface and Engine Oil Effects on Journal Bearing Lubrication

Lubrication conditions in journal bearings lubricated with low friction engine oils have been investigated using two complementary experimental techniques. Load supporting capacity under conditions ranging from fully flooded to mixed lubrication was measured for several candidate oils using a bench test that simulates the dynamic motion of a journal bearing at fixed, measurable eccentricities. The performance of these oils was also assessed using a bearing test rig in which journal friction is measured under typical engine conditions of speed, load and temperature. Significant mixed lubrication conditions were shown to exist at low speeds in heavily loaded journal bearings. Under such conditions, oil with friction reducing additives exhibit higher load supporting capacity, distinct separation of moving parts, and reduced friction relative to oils without such additives.
Journal Article

Stress-Strain Relations for Nodular Cast Irons with Different Graphite Volume Fractions under Tension and Compression

In this paper, the results of finite element analyses for nodular cast irons with different volume fractions of graphite particles based on an axisymmetric unit cell model under uniaxial compression and tension are presented. The experimental compressive stress-strain data for a nodular cast iron with the volume fraction of graphite particles of 4.5% are available for use as the baseline material data. The elastic-plastic stress-strain relation for the matrix of the cast iron is estimated based on the experimental compressive stress-strain curve of the cast iron with the rule of mixture. The elastic-plastic stress-strain relation for graphite particles is obtained from the literature. The compressive stress-strain curve for the cast iron based on the axisymmetric unit cell model with the use of the von Mises yield function was then obtained computationally and compared well with the compressive stress-strain relation obtained from the experiment.
Technical Paper

Fuel Economy Improvement Through Frictional Loss Reduction in Light Duty Truck Rear Axle

In an effort to improve fuel economy for light duty trucks, an initiative was undertaken to reduce frictional losses in rear axle through use of low friction lubricants and novel surface finish on gears while maintaining durability. This paper describes the effect of rear axle lubricants on fuel economy. A laboratory rig was set up using a full size pick-up truck rear axle to measure axle efficiency and lubricant temperature with various SAE 75W-90 and SAE 75W-140 viscosity grade lubricants. Traction coefficients of lubricants were also measured at various temperatures using a laboratory ball and disk contact geometry. An improvement in axle efficiency up to 4.3% was observed over current Ford factory fill SAE 75W-140 lubricant depending on speed, torque and the type of lubricant used. The temperature of the lubricants was also lower than that with the current factory fill. This is important for maintaining bearing life and overall durability of the rear axle.