High Cycle Fatigue of Additive Metal Structures

Mechanical and microstructural characterisations of additive materials are essential pre-cursors to design, processing and engineering application. Mechanical assessments of model structures are unreliable unless the precise microstructure and micro-texture of the final part are replicated in standard test specimen types. Complex and thin section components may not allow the extraction of standard test specimens. This necessitates a drive to explore methodologies for miniature scale testing on coupons extracted from the final repaired part or the need to test the full-scale repaired components during the development stage of the repair process. The integrity of repairs on nickel-based components has successfully demonstrated the advantages of using this approach. The PhD will use novel small-scale testing techniques, such as small punch testing, and full-scale aerofoil testing to understanding of the role of microstructure and texture on the mechanical properties, including crack initiation and growth, tensile and creep, in the titanium alloys of interest. Since the additive materials are destined for use in compressor aerofoils, either as part of a localised repair or as complete aerofoil builds, an understanding of the repaired materials under HCF loading is required. Test rigs for such understanding are being developed as part of the Clean Sky 2 programme of research. It is expected that the student will be able to work collaboratively alongside the Clean Sky 2 programme to understand the primary excitation modes that are required in the HCF testing of repaired aerofoils in order to correlate the results of testing with microstructural observations across the repaired aerofoils. The project will provide a thorough understanding of the role of microstructure and texture on fatigue crack initiation and growth in the alloys of interest as well as a correlation with other local mechanical properties in the repaired aerofoil.