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Title: Creep-fatigue-environment interactions in titanium 6246 for compressor disc applications
Author: Ford, B. P.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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The need for increased efficiency in aero engines is pushing many alloys to the limits of their design envelope and there is a desire to expand into the creep-fatigue regime. The current program of research addresses this need for the compressor disc titanium alloy Ti6246. A number of environmental tests were carried out to develop the current understanding of stress-life, strain-life and deformation behaviour. However the bulk of this work focuses on crack growth behaviour under vacuum with particular reference to crack closure and its interaction with creep and fatigue. Closure data were obtained using the Direct Current Potential Drop (DCPD) method. These were extensively analysed, and refined methods of obtaining closure loads from the data were developed and assessed. Additional information about behaviour at the crack tip was also inferred. A study of crack path under dwell revealed substantial activity of interface failure and void forming mechanisms, it also demonstrated that crack growth is highly sensitive to microstructure. In conjunction with crack profiling this allowed an assessment of the effect of stress state on the creep - fatigue - closure interaction. A transition to interface failure dominated crack growth was associated with a Kmax in excess of 17 MPam0.5. This was attributed to void formation, an impingement mechanism at platelet surfaces or some combination of the two.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available