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

Written records of the quenching of steel exist as early as the first century of the European Iron Age. In Homer we find "... As when the smith an hatchet or a large axe ... plunges the hissing blade deep in cold water: whence the strength of steel ..." Archeological evidence for quenched and tempered steel exists from several centuries earlier. Tempering has been regarded as essential in order to mitigate the extreme hardness and brittleness of as-quenched steel. On the other hand the strength limit has been reached in low cost hardened martensitic and hard-drawn pearlitic steels. We propose to push the envelope making the radical move of dispensing with the tempering step and designing new multiphase, as quenched, tough, lean (low cost, resource efficient) steel (MATLeS). The key is to exploit recently acquired understanding of the plasticity of body centered cubic metals; work hardening; and interplay between dissolved carbon, dislocations and metal carbonitrides. This will be put together with novel state-of-the-art experimental techniques: in particular precession electron microscopy and tensile stress relaxation. In powerful combination these will furnish us with the means to manipulate and exploit the hierarchical lath martensite microstructure (HiLaMM). The new steels we design will have excellent green credentials: resource efficiency, recyclability, high strength-to-weight ratio. Our vision is toward the electric vehicle economy, light-weighting of structural offshore wind farm components and super-strong cables for undersea and civil engineering projects. Making full-circle, our outcomes will inform modern theories in materials science, advancing solutions to one of the world's outstanding scientific questions: what is the nature of work hardening? (Why can I not straighten the poker you have just bent?)

Improvements in lubricant technology are needed to reduce friction in machines and thus save energy and control global warming. Lubricants consist of a mineral or synthetic oil in which are dissolved up to ten or so chemical additives. The most important of these additives are friction and wear-reducing agents. These react with rubbing metal surfaces to form thin protective films that, as their names suggest, give low friction and wear. These films form only when surfaces rub together so they are often called "tribofilms". Until recently we had very little idea of what caused tribofilms to form - was it the high temperature or pressure in rubbing contacts, or the metals becoming activated in some way by rubbing? This ignorance made it almost impossible to design additives except by trial and error or to build models their behaviour. However earlier this year it was shown conclusively that the most widely-used antiwear additive reacts in rubbing contacts because of the high shear forces present. These forces stretch the bonds in the molecules until they break, which leads to chemical reaction to form a tribofilm. This concept, of applied forces driving chemical reactions, is quite well known in modern chemistry and is called mechanochemistry. But this is the first time it has been shown indubitably to control tribofilm formation in the field of lubrication. It is very important insight since it points the way to us being able to predict how particular additive molecular structures will behave in rubbing contacts and thus design better additives to give lower friction and less wear. The current project will explore the full significance of mechanochemistry to lubricant design and use. It will test which types of lubricant additive reaction are driven by shear forces and develop quantitative relations between reaction rate, applied shear force and temperature so as to enable modelling to proceed. It will look at a range of model antiwear additives with different but related structures to identify which bonds break to precipitate tribofilm formation - thereby enabling molecular structure to be optimised. It will also follow the reaction sequence that results from initial bond breaking to tribofilm formation by looking into rubbing contacts (with one transparent surface transparent) using chemical spectroscopy. All of this will be done in specially-designed test equipment that is able to reach the very high contact shear forces normally present in solid-solid rubbing contact conditions and that drive the chemical reactions involved. The overall goal is to understand, for the first time and through the use of advanced experimental and modelling techniques, how lubricant additives react in rubbing contacts to form low friction and low wear films, and so to enable new and more energy-saving lubricants to be designed in future.

Almost all engineering systems and many biological ones contain components that are loaded and rub against one another, such as gears and bearings in machines and hip and knee joints in humans. This rubbing results both in friction, that wastes energy, and in wear and other forms of surface damage that lead to machine (and human) downtime, and the need for expensive repair and replacement. This whole field of research is called Tribology and is pivotal both in the quest for sustainability, including reducing CO2 emissions, and in improving the quality of our lives. In Tribology the effects of rubbing, such as frictional dissipation and wear, are perceived as macroscale phenomena and are traditionally studied by macroscale experiments and analysis. However they actually originate at the atomic and molecular scale, where the severe local stresses produced by rubbing cause restructuring of surface layers, while the molecules of lubricant in rubbing contacts interact with and protect surfaces. Thus to understand and so improve tribological systems we need an approach that spans the molecular, meso- and macro-scales. This will yield both information as to the origins of friction and surface damage - and unwanted phenomena are best tackled at their roots - as well as the ability to design macro-scale components such as lubricants, bearings, gears, engines and replacement joints that operate reliably and efficiently for as long as required. To meet this need, the proposed research will develop and apply advanced techniques to model rubbing contacts at all the necessary scales - atomic/molecular simulations of surfaces and lubricants, meso-scale modelling looking at structural evolution of surfaces due to rubbing, and macro-scale simulations of actual rubbing components such as bearings and engines. These simulations will be validated by experiments that also span the same range of scales, including direct observation of molecules in rubbing contacts. The most critical and innovative stage of this project, however, will be to link all these models together in to a single computer-based package. The result will be a set of modelling programs that can be used in many different ways; for example to explore the origins of tribological phenomena; to optimise lubricant surface and materials design; to predict performance of machines based on a combination of design and underlying atomic/molecular processes. Such an approach will give us tools both to understand in full tribological phenomena such as friction and wear and to enable effective "virtual testing", where new and novel designs, lubricants and surfaces can be combined and their effectiveness tested prior to recourse to time-consuming and expensive experimental development.