The global cost of corrosion-related damage is estimated to be £1.9tn annually (3.4% of GDP) and corrosion costs the UK ~£80bn per annum. Hydrogen-associated stress corrosion embrittlement is an important class of environmental degradation. Titanium alloys were until the late 60s considered immune to stress corrosion embrittlement by reacting with water vapour, but subsequent experience has falsified this hypothesis. Therefore, substantial industrial and safety benefit to the UK can be obtained if H-associated degradation in Ti alloys can be understood and mitigated by material design. Because of its ubiquity in the world, hydrogen related cracking is a grand challenge in materials science; from ceramics to perovskite solar cells H-associated degradation mechanisms are critical to the in-service viability of many materials, including metals. Our strategy will be to provide H-tolerance to a material, either by limiting the ingress of embrittling species or by providing traps within the material, where such species can be somehow deactivated. Hydrogen is highly mobile and therefore can concentrate and embrittle critical micro- and nano-scopic features in materials, this can happen over the course of minutes or hours. A main challenge however has been the detection of H inside metallic systems. Lacking an electron shell to excite, H cannot be measured in electron microscopy and vacuum systems often contain H, and so even mass spectrometry techniques struggle to sensitively measure H in a sample. Therefore, our understanding of how hydrogen leads to cracking in different materials systems is much more limited than we might like to concede. We will develop new methods for atomic-scale experimental measurements to identify where Hydrogen locates within a material. Small samples will be prepared and handled at cryogenic temperatures to limit H mobility and elemental "atom-by-atom" mapping will be conducted to understand how the mobility of H changes by trapping at different material phases, interfaces and crystal defects. Some Ti alloys are more resistant to Hydrogen embrittlement and corrosion than others, but the physical mechanisms behind are not well understood. For instance, highly pure titanium is nearly immune to H, but its corrosion performance drastically changes if small impurities are present; some elements, such as Fe, are known to reduce corrosion performance, whereas others, including Mo and Pd, dramatically improve corrosion. We will then carefully examine the effect of typical alloy additions on the cracking propensity using bend tests under H exposure in alloys with different compositions. Detailed microscopic inspection at several length-scales will be conducted to understand the mechanisms of H-induced failure. The prediction of H mobility and H-related damage in engineering alloys is complicated, as these materials contain several phases, crystal defects and alloying elements, which all influence H behaviour. With so many interacting effects, the use of physically-faithful models and simulations will be vital to disentangling them fully from each other. Therefore, we will develop new computational models for hydrogen diffusion within a material to elucidate how different features affect local H transport and trapping. In addition, we will adopt and improve micro-mechanics modelling techniques, via incorporating equations for the newly-unravelled embrittlement mechanisms in Ti, and compare the mechanical performance of H-containing alloys against their H-free version. Based on these outcomes, we will develop optimal material guidelines for the alloy and process designer, highlighting what phase/alloy combinations are more resistant against H-induced failure. In addition, optimal materials will be designed, manufactured and tested in order to provide final validation of our concepts.

The design of complex couplings and connections against failure is a key topic for the optimisation of key aeroengine components, which represents a vital challenge for the sustained competitiveness of the British aeroengine industry. The difficulties associated with gaining access to the intimate contacting regions of such components provides an opportunity for computational modelling and predictive techniques. This project will bring about a quantum leap in the application of modelling techniques to the design of engineering contact connections through the consolidation of a number of different techniques. The key techniques that will be incorporated in the tool to be developed are: (i) finite element based modelling of material removal due to fretting wear action, (ii) asymptotic solutions for characterising the multiaxial stress states for cracking prediction at sharp contact edges and steep contact stress gradients, (iii) the use of multiaxial representative testing techniques for obtaining cycle-dependent frictional contact data(iv) a combined wear-fatigue prediction technique to provide a fretting fatigue damage parameter that captures the effects of slip amplitude.The tool will be applied to realistic three-dimensional aeroengine demonstrator components and validated against existing test data from previous EPSRC-funded work.

My fellowship will lead a research programme employing state of the art experimental and computational techniques to provide new, fundamental insight into the environmental degradation of nickel superalloys and steels that occur as a result of interactions with the corrosive gaseous species they encounter in-service. I have published some preliminary work from my corrosion and oxidation research program, though the full potential benefits for the development of corrosion resistant high temperature materials, have barely been explored. I plan to address these questions through advanced characterisation of samples exposed to corrosive environments in laboratory furnaces, during high temperature mechanical tests and a study of ex-service components provided by my industrial collaborators. The results will then be used to design a new generation of alloys, whose corrosion resistance will be tailored to their specific applications. To maximise the impact of my research, I will work closely with my industrial collaborators such as Rolls-Royce plc, as well as my academic collaborators, including Prof Michael Moody (Atom probe Tomography Group, University of Oxford), to characterise the samples, inform alloy design and produce new superalloys with improved corrosion resistance. Corrosion research is extremely timely and globally important with potential for substantial future savings and component lifetime extension.

The global appetite for power and for efficient transportation can only increase as nations industrialise and the world's population grows. This application is about making engines more efficient using game changing technology that enables sophisticated computer control of engine thermodynamic cycles. This research will address the technological building blocks required for computer controlled manipulation of power generating fluid flows. The technical difficulties of modulating engine flows can be immense but the prize for control substantial. For example, the leakage flows at the tip of a gas turbine blade and the cooling airflows in a combustion chamber contribute significantly to engine fuel burn and emissions respectively. Many such engine flows are high speed, high pressures (20bar+) and at high temperatures (500 degC+) and reside in difficult to access parts of the engine. This means that conventional valves and actuators that have moving parts are not viable due to inadequate life and slow response time. We shall consider here a novel concept of a valve that has no moving parts and works at the pressures and temperatures normally found in gas turbines or diesel engines. The Electro-fluidic-transistor-valves to be studied in this research use small plasma discharges in combination with fundamental fluidic effects to inject or switch off jets of air when commanded. One of the goals in this research is to understand the fundamental parameters that influence the operation and performance of such devices. How fast can such devices be made to operate? And how can control engineering be used to directly manipulate on the micro scale the flow past the turbine blade tip that is the single biggest contributor aero-engine inefficiency? To answer these questions, this ambitious proposal uses an integrated approach that will research the science of the plasma switched fluidic valves, identify the key control laws and architectures for high bandwidth flow control and then demonstrate the concept experimentally in a challenging high speed turbine application. This will require close research collaboration between control engineers and thermo-fluid specialists, a direction well aligned with EPSRC strategy for both Control Engineering and Aerodynamics disciplines. The applicants are convinced that this multi-channel approach is the best way to propel this potentially disruptive technology into CO2 saving applications.

Aero-engine compressors deliver a large quantity of air at high pressure. From an efficiency viewpoint, it is desirable to operate them at the highest possible pressure ratios but such operating points are inherently unstable because of their close proximity to undesirable aerodynamic phenomena of stall and surge. Rotating stall is a local instability where reduced flow rate gives rise to flow separation and results in the formation of stall cells. These cells begin to rotate around the annulus and hit the blades, thus causing high vibratory loads. Surge is a global instability in which flow reversal occurs throughout the machine, causing high transient stresses in the blading. Deficiencies in understanding the exact mechanisms and a lack of modelling methodology prevent the determination of the dynamic loads and the ensuing blade response. Therefore, current designs are based on safe margins where the bladerow spacing is not optimum. Using an advanced computational method, it is proposed to build a large-scale model of a typical industrial core-compressor which has been the subject of previous studies by the proposers and for which experimental data are available. The aim of the project is not only to understand the rotating stall and surge mechanisms and the links between them, but also to prove the feasibility of the large-scale modelling approach as a design tool. A further objective is the investigation of recovery mechanisms from rotating stall and surge..