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© The University of Sheffield

Matthew Brown

Project Title: Developing a non-destructive evaluation technique for the examination of machined surfaces

Academic Supervisor: Dr Hassan Ghadbeigi

AMRC Supervisor: Dr Pete Crawforth

Industrial sponsor: Rolls-Royce and Seco Tools

The surface integrity of machined components is typically assessed through destructive evaluation. This process is expensive, time-consuming and destroys the component. Thus there is no current method for carrying out a comprehensive surface integrity inspection in-service. Non-destructive testing could provide an alternative method for surface integrity inspection and may offer cost/time benefits in addition to allowing the part to be used following inspection. 

 

Machined surfaces can contain a wide variety of defects but one of the most feared by materials engineers is white layer. This is due to the lack of understanding around the formation of the defect and its detrimental effect on the fatigue life of a component. Machining induced white layer is found in high strength aero-engine materials such as titanium alloys, nickel superalloys and steels and these materials are the focus of the EngD.

  

Currently, in the second year of the EngD programme, my research is focusing on characterizing the physical properties of machining-induced white layer in Ti-6Al-4V. Characterization methods employed include XRD, EBSD, FEG-SEM, nanoindentation and optical microscopy. This characterization is necessary so that a non-destructive evaluation method can be designed to detect a change in a key physical property associated with white layer. Non-destructive tests I will be investigating include ultrasound surface acoustic wave inspection, high-frequency eddy current testing, Barkhausen noise testing and acoustic emission testing.

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