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The constant engine development requirements of increased durability with lower cost, size and power loss need innovations in technology from designers and manufacturers of critical components such an engine bearings. A detailed experimental program has shown that a connecting rod bearing with “end-relief” grooves can give surprising and unexpected benefits in reducing bearing temperature. Bearing shells with “end-relief” resulted in an effective bearing width reduced by 6mm or 30%, yet still gave benefits in temperature reduction. The depth of the “end-relief” was too large for any hydrodynamic oil film to generate pressure to support the applied load.

The influence of big-end bore fretting on connecting rod fatigue fracture is investigated. A finite element model, including rod-bearing contact interaction, is developed to simulate a fatigue test rig where the connecting rod is subjected to an alternating uniaxial load. Comparison of the model results with a rod fracture from the fatigue rig shows good correlation between the fracture location and the peak ‘Ruiz’ criterion, rather than the peak tensile stress location, indicating the potential of fretting to initiate a fatigue fracture and the usefulness of the ‘Ruiz’ criterion as a measure of location and severity. The model is extended to simulate a full engine cycle using pressure loads from a bearing EHL analysis. A fretting map and a ‘Ruiz’ criterion map are developed for the full engine cycle, giving an indication of a safe ‘Ruiz’ level from an existing engine which has been in service for more than 5 years.

An elasto-hydrodynamic lubrication model is used to study the effects of multi-order journal lobing on the performance of a big-end bearing in a turbo-charged diesel engine. The journal has 5 lobes superimposed with 50 lobes of chatter. Results show that any form of lobing has adverse effects on bearing performance, reducing film thickness and increasing oil film pressure. The effects of low and high order lobing are additive, but the bearing system is more sensitive to high order lobing, i.e. chatter. To improve the reliability of big-end bearing systems lobing on the journal should be minimised especially chatter.

This paper reports attempts to gain better understanding of the influence of bearing wear on the performance of hydrodynamically lubricated bearings. An analysis was carried out on bearings from a Sapphire bearing test rig using an elastohydrodynamic model. This involved the use of both the original and worn bearing surface profiles. The results indicated that bearing wear could improve the lubrication conditions. Also the progress of wear in the bearing was simulated using a simple model of the wear process. This model predicted that the wear would progress at a reducing rate. The predicted wear agreed well with measurements both in terms of the wear profile and the location of wear.