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Details of Grant 

EPSRC Reference: EP/T026529/2
Title: Fatigue Testing beyond Extremes
Principal Investigator: Gong, Dr J
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Culham Centre for Fusion Energy Daido Metal Europe Limited Rolls-Royce Plc (UK)
Rutherford Appleton Laboratory
Department: Engineering
Organisation: Kings College London
Scheme: EPSRC Fellowship
Starts: 16 October 2023 Ends: 28 February 2026 Value (£): 699,475
EPSRC Research Topic Classifications:
Materials testing & eng.
EPSRC Industrial Sector Classifications:
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Summary on Grant Application Form
Fatigue is the most pervasive failure mode that affects nearly all industrial sectors - including energy industries involving power plants, anemo-electric and tidal stream generators; transport vehicles and aircraft; national infrastructure such railway and bridges; military equipment from a blade in an engine to a whole ship; medical devices and human body implants. The economic cost of fracture has been enormous, approaching 4% of GDP, whereas 50-90% of all these mechanical failures are due to fatigue. Most fatigue failures are unexpected, and can lead to catastrophic consequences. In safety-critical sectors such as the aero-space and nuclear industries, there are ever increasing demands for better understanding of fatigue with respect to the microstructure of metallic components and the demanding environments that they are placed in.

The ultra-small, ultra fast fatigue testing techniques I have created are able to make a breakthrough by addressing the classic needle in haystack problem in fatigue crack initiation (FCI) and short crack growth (SCG). Fatigue at these early stages is localized within a few hundred micro-meters. However, they account for more than 50% life in low cycle fatigue (LCF) and approximately 90% in the high cycle fatigue (HCF) regime, and contribute to the largest portion of scatter. My micro- and meso- cantilever techniques are capable of isolating FCI and SCG in selected microstructure features, allowing for the systematic exploration of slip evolution, slip band decohesion and short crack propagation in the context of an exquisitely well characterised volume of material. The ultra-fast testing rate up to 20 kHz means robust exploration can be achieved to 10^9 cycles and beyond, in hours in contrast to months or years demanded by the conventional method.

This proposal, through further development of state-of-the-art extremely small and fast fatigue testing techniques, looks to radically change the technical scope of fatigue analysis by allowing environmental effects to be systematically explored at the levels of FCI and SCG and across the HCF and LCF regimes. In-situ ultrasonic fatigue testing rig will be installed in an advanced scanning electron microscope, enabling in-situ observation of the progression of HCF FCI and SCG at the resolution of ~ 1 nm. I will apply these cutting edge techniques to underpinning major fatigue issues in Ti and Ni alloys of technologically importance to the aero-engine industry and proton accelerators, specifically:

(i) To achieve a breakthrough in mechanistic understanding of HCF FCI and SCG in titanium alloys with respect to the environments and deliver essential HCF FCI and SCG properties;

(ii) To make groundbreaking study of fatigue in Alpha Case and dwelling fatigue in titanium alloys, which are major issues in aero-engine industry;

(iii) To determine the effect of the heavy irradiation on HCF performance of Ti-alloys that will be used in the next generation proton accelerators;

(iv) To achieve comprehensively understanding of the environmental effect on fatigue in single-crystal nickel superalloys that have the heterogeneous distribution of gamma' phase and element segregation;

(v) To determine the HCF and LCF performance of the multi-functional coatings on the surface of a nickel turbo blade in the context of atmosphere, temperature and pre-corrosion treatment.

A Ultrasonic Fatigue Testing Centre will be established to satisfy the frequent HCF assessment requests from the industry. The new functions developed on the ultrasonic fatigue testing rig in this project will be transferred to the national lab at Culham to update the bespoke rig in a 'hot cell', for study of active materials in support of fission and fusion innovation.

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