A General Approach to the Analysis of Fatigue Cracks in Lubricated Contacts

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In recent years there has been noticeable appreciation of the importance of failure mechanisms which affect the performance of the most critical assemblies, whose components undergo mutual contact interactions. In particular, most of the complex engineering products such as bearings, gas turbine blades/shafts, gears, railways, bolted flanges, car engines, etc. could not operate without contact and frictional interfaces. Therefore the assessment of tribological performance (i.e. how the material strength of couplings if affected by the presence lubricants, friction and wear) of these assemblies is a must for any industrial setting.Let us consider bearings as an example application. They are mechanical components used to reduce friction and provide load support for rotary or linear equipment. A single bearing failure can cause hours of downtime, including the identification and replacement of the failed component. For this reason, companies around the world have spent a vast amount of money and resources on different types of predictive maintenance technology. This suggests that fundamental research on the main phenomena responsible for such failures needs to be carried out.The proposed work will attempt to address the root causes of material failures in the presence of lubricated contacts. The role of fluid, according to some experimental observations, experience gathered from engineering practice, and the results of the theoretical analyses, is often regarded as the main contributor to catastrophic crack growth. The origin of cracks induced by the rolling/rubbing of contacting pairs will be studied and the fluid/solid interaction which is deemed as responsible for the propagation of such cracks will be investigated. Furthermore, robust experimental techniques will allow monitoring and measuring the presence of fluid within cracks generated during rolling contacts and subsequent crack growth to failure.A properly managed research programme will provide valuable feedback about how a component performs when subjected to contact loading under different working conditions. It will uncover information for improvements that prevent future failure. Rigorous root cause determination might lead to improvements that yield:(a) Greater safety(b) Improved design and reliability(c) Greater efficiency(d) Reduced maintenance(e) Reduced life-cycle costs