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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.

In this paper, the evolution equation for the active yield surface during the unloading/reloading process based on the pressure-sensitive Drucker-Prager yield function and a recently developed anisotropic hardening rule with a non-associated flow rule is first presented. A user material subroutine based on the anisotropic hardening rule and the constitutive relation was written and implemented into the commercial finite element program ABAQUS. A two-dimensional plane strain finite element analysis of a crankshaft section under fillet rolling was conducted. After the release of the roller, the magnitude of the compressive residual hoop stress for the material with consideration of pressure sensitivity typically for cast irons is smaller than that without consideration of pressure sensitivity. In addition, the magnitude of the compressive residual hoop stress for the pressure-sensitive material with the non-associated flow rule is smaller than that with the associated flow rule.

A number of spark ignition engines from 1997 to 2003 are analyzed for their overall friction characteristics using the Willans line approach. This methodology appears to be quite robust across many different types of engines. Using a variety of partial and complete engine maps from multiple manufacturers, it is confirmed that engine friction has been decreasing over the decades (compared to past studies). Overall there has been a 25% reduction over 30 years. It is also demonstrated that thermal efficiency (defined here as the slope of fuel mep and bmep excluding enrichment) has been remaining steady during the same period. The application to aggregate engine models is discussed.

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.

Improvement of engine fuel efficiency through the use of low friction engine oils is a major task in engine lubrication research. This friction reduction can be achieved by improving the rheological characteristics and elastohydrodynamic (EHD) properties of engine oils, and by controlling boundary chemical interactions between oil-based additives and lubricated components in the engine. In order to achieve minimal frictional power loss under all lubrication regimes, engine tribological systems must be designed to effectively use advanced lubricant technology, material and surface modifications. This paper presents results of cooperative research addressing opportunities for minimizing friction through extension of hydrodynamic lubrication regime in lubricated components using various formulation approaches. A set of experimental oils has been evaluated using laboratory test rigs that simulate hydrodynamic, EHD, mixed and boundary lubrication.

The newly developed Sequence VIB engine dynamometer test for measuring the ability of engine oils to improve engine fuel efficiency was designed as an improvement on its predecessor, the Sequence VIA test. The Sequence VIB test features an additional, extended oil aging to correspond to aging of engine oils in certification vehicles and in customer use, and a new set of boundary/mixed and hydrodynamic lubrication stages to better represent a wider range of engines. Five fuel economy measurement stages were chosen for the Sequence VIB test from a larger set of prototype stages, based on extensive friction modeling of engines, analysis of Sequence VIA data on reference oils, and operational considerations. Time factors for these stages were derived based on a mini-mapping of engines considering engine operating conditions in the Metro/Highway Federal fuel economy test procedure (FTP M/H) and the estimated market volume of each engine-vehicle.

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.

Experimental forms of two different types of engine oil viscosity sensors have been tested that use uniformly poled disks of piezoelectric PZT ceramic. In both cases, the disks were used to form electromechanical resonators functioning as the frequency-controlling element in a transistor oscillator circuit. The simpler type of sensor used only one disk, vibrating in a radial-longitudinal mode of vibration. In this mode, a disk 2.54 cm in diameter and 0.127 cm thick had a resonant frequency of approximately 90 kHz. The second type of sensor used two such disks bonded together by a conducting epoxy, with poling directions oriented in opposite directions. This composite resonator vibrated in a radially-symmetrical, flexural mode of vibration, with the lowest resonant frequency at approximately 20 kHz. The presence of tangential components of motion on the major faces of both resonators made them sensitive to the viscosity of fluids in which they were immersed.

The friction reducing potential of low viscosity engine oils in bearings has been investigated using a journal bearing test rig. Friction was measured on both the journal and bearing of a production connecting rod and compared to results from a simple analytical model over a range of speeds and loads. Hydrodynamic lubrication conditions existed over most test conditions, but mixed lubrication conditions were shown to exist at low speeds in heavily loaded journal bearings. Results indicate significant friction reduction through the use of low viscosity oils under hydrodynamic lubrication conditions. In mixed lubrication conditions, oils with friction reducing additives exhibit lower friction than those without such additives. These findings suggest the possibility that a low viscosity oil with effective friction reducing additives can extend low friction benefits over the entire range of operation of engine bearings.

A laboratory wear test is used to evaluate the wear protection properties of new and used engine oils formulated for FFV service. Laboratory-blended mixtures of these oils with methanol and water have also been tested. The test consists of a steel ball rotating against three polished cast iron discs. Oil samples are obtained at periodic intervals from a fleet of 3.0L Taurus vehicles operating under controlled go-stop conditions. To account for the effects of fuel dilution, some oils are tested before and after a stripping procedure to eliminate gasoline, methanol and other volatile components. In addition to TAN and TBN measurements, a capillary electrophoresis technique is used to evaluate the formate content in the oils. The results suggest that wear properties of used FFV lubricants change significantly with their degree of usage.

A short engine sequence test, based on the Sequence VD procedure, was used to screen FFV oil candidates more rapidly. Since only one engine is needed to compare the wear-protection performance of several lubricants, engine hardware variability is not a significant issue in this test procedure. Several lubricants, some specially formulated for FFV engines, were tested using standard Sequence VD engine hardware which includes molybdenum top piston-rings. Results showed clear discrimination of the performance of oil candidates. These lubricants were also tested using an engine with chromium-faced top rings and exhibited similar performance ranking.

The variation of viscosity with temperature and shear rate plays an important role in the analysis of lubrication of automotive systems. In this paper, a method for predicting the viscosity of non-Newtonian fluids, such as multigrade engine oils, over a wide range of temperatures and shear rates is outlined. This expression determines viscosity parameters for shear thinning fluids in terms of easily measured viscosity values at some reference state. A comparison of predictions with experimental data suggests that viscosity for multigrade engine oils can be predicted to within experimental uncertainty. The proposed method can be used in assessing lubricant viscosity at shear rates greater than 106 s-1, which are beyond the capability of current laboratory instruments. A comparative study with multigrade oils shows that performance at very high shear rates cannot be accurately gauged from high temperature, high shear (HTHS) viscosity measurements.

Rheological measurements were performed on a series of lubricants for flexible fuel vehicles, and blends of water or methanol in these oils. A series of measurements, including kinematic viscosity, viscosity at low and high shear rates, low shear viscosity under borderline pumping conditions, and density were performed on all oils and blends. The effects of mixing conditions, such as mixing speed and temperature on these properties were also studied. Viscosity increases when water emulsifies in oils. Methanol exhibits limited solubility in all oils, but more so in synthetic base oils. Viscosity tests at 248 K (-25°C) do not indicate the onset of critical pumping conditions, even at high concentrations of water or methanol. Tests at high shear rates at 323 K (50°C) suggest that water-oil emulsions are quite stable, while methanol-oil blends lose their methanol content either due to evaporation or shear-induced separation.

The pressure drop in turbulent pipe flow is suggested as a technique for monitoring the condition of oils during use in an engine. Several new and used oils are tested in a flow loop designed to simulate operating temperatures in an internal combustion engine. The used oils are obtained from four and six cylinder fuel injected gasoline engines typically used in city driving conditions. Changes in viscosity and composition are measured directly using a viscometer and gel permeation chromatography equipment. The proposed monitoring technique provides a sensitive measure of these changes.