Full-film hydrodynamic lubrication is an ideal which is rarely achieved in practice. In most practical rolling/sliding contacts such as those in gears, bearings and replacement human joints the roughness of the surfaces plays an important part in their lubrication, wear and surface fatigue. In gears, for example, the combined roughness of even the best quality ground surfaces is usually of the order of the oil film which can be generated hydrodynamically. A similar situation occurs in roller bearings at low speed or high temperature and in replacement human joints because of the low effective viscosity of the lubricant. This leads to a lubrication regime which has been loosely described as mixed (meaning a mixture of hydrodynamic and boundary lubrication), or more specifically as micro-elastohydrodynamic lubrication (micro-EHL) in which high ripple pressures occur and colliding asperities on the two surfaces act as individual, transient elastohydrodynamic/solid contact encounters. This project addresses two important engineering consequences of mixed lubrication: (1) mild wear/wear particle generation, and (2) near-surface rolling contact fatigue/micropitting. Much progress has been made in numerical modelling of micro-EHL, but such analyses, if they are to be of practical use, must now be developed to include the detailed behaviour of solid contact events in terms of a wear model. The project will therefore produce an analysis of contact duration, traction, adhesion, flash temperatures and particle removal. The second major development required, in order to advance the study of near-surface distress due to fatigue, is the effect of initial plastic deformation of asperities during the crucial running-in phase when machine surfaces are brought into heavy contact for the first time. This will include a detailed treatment of plastic deformation, permanent set and residual stress field of asperity features.Our specific objectives are to:1. Develop a consistent mixed hydrodynamic/solid contact treatment for real surfaces which includes the detailed modelling of transient dry asperity contacts.2. Develop a model of mild wear particle generation based on the detailed friction, adhesion, deformation and temperatures occurring at transient contacts.3. Produce a model of near-surface fatigue, relevant to the phenomenon of micropitting and rolling contact fatigue, which includes the permanent set and residual stress field obtained from elastic/plastic contact analysis.4. Carry out controlled experiments under realistic engineering load and speed conditions to validate each of these modelling developments.

Additive Manufacturing (AM) often known by the term three-dimensional printing (3DP) has been acknowledged as a potential manufacturing revolution. AM has many advantages over conventional manufacturing techniques; AM techniques manufacture through the addition of material - rather than traditional machining or moulding methods. AM negates the need for tooling, enabling cost-effective low-volume production in high-wage economies and the design & production of geometries that cannot be made by other means. In addition, the removal of tooling and the potential to grow components and products layer-by-layer means that we can produce more from less in terms of more efficient use of raw materials and energy or by making multifunctional components and products. The proposed Centre for Doctoral Training (CDT) in Additive Manufacturing and 3D Printing has the vision of training the next generation of leaders, scientists and engineers in this diverse and multi-disciplinary field. As AM is so new current training programmes are not aligned with the potential for manufacturing and generally concentrate on the teaching of Rapid Prototyping principles, and whilst this can be useful background knowledge, the skills and requirements of using this concept for manufacturing are very different. This CDT will be training cohorts of students in all of the basic aspects of AM, from design and materials through to processes and the implementation of these systems for manufacturing high value goods and services. The CDT will also offer specialist training on aspects at the forefront of AM research, for example metallic, medical and multi-functional AM considerations. This means that the cohorts graduating from the CDT will have the background knowledge to proliferate throughout industry and the specialist knowledge to become leaders in their fields, broadening out the reach and appeal of AM as a manufacturing technology and embedding this disruptive technology in company thinking. In order to give the cohorts the best view of AM, these students will be taken on study tours in Europe and the USA, the two main research powerhouses of AM, to learn from their international colleagues and see businesses that use AM on a daily basis. One of the aims of the CDT in AM is to educate and attract students from complementary basic science, whether this be chemistry, physics or biology. This is because AM is a fast moving area. The benefits of having a CDT in AM and coupling with students who have a more fundamental science base are essential to ensure innovation & timeliness to maintain the UK's leading position. AM is a disruptive technology to a number of industrial sectors, yet the CDTs industrial supporters, who represent a breadth of industrial end-users, welcome this disruption as the potential business benefits are significant. Growing on this industry foresight, the CDT will work in key markets with our supporters to ensure that AM is positioned to provide a real and lasting contribution & impact to UK manufacturing and provide economic stability and growth. This contribution will provide societal benefits to UK citizens through the generation of wealth and employment from high value manufacturing activities in the UK.