Fan Blade Titanium Alloys
Two main topics of titanium research have developed International renown at Swansea UTC; fundamental understanding of “cold dwell sensitivity” in near-alpha titanium alloys and advanced lifing correlations supporting component design and operation.
Cold dwell behaviour was first acknowledged from the in-service failure of RB211 fan discs in the 1970s. Work based at Swansea UTC demonstrated that the combination of anisotropic crystal plasticity and stress redistribution was a pre-requisite for “quasi-cleavage facet formation” and dwell induced failures. A series of seminal academic papers, keynote presentations at International conferences resulted describing the “Evans-Bache” model. The application of electron back scattered diffraction for measuring facet inclination on fracture surfaces was pioneered at Swansea UTC and recent codes have endorsed automated quantitative tilt fractography. Ultimately, this led to the award of the IoM3 Harvey Flower Titanium Prize for “contribution to an improved understanding of titanium metallurgy or alloy development” to Prof WJ Evans in 2007 and Prof MR Bache in 2013.
Unrivalled testing facilities for the characterisation of constitutive behaviour have underpinned the development of advanced lifing algorithms applied to “Class A” safety critical titanium components. Research conducted under EPSRC grants along with Rolls-Royce private venture funding has married fundamental materials knowledge to non-linear, strain based lifing procedures applied to Ti6/4 fan disc materials employed across the fleet of Rolls-Royce Trent engines. Similar studies were completed on Ti 6246 compressor disc alloy. Such techniques encompassed intimate knowledge of creep-fatigue-environmental interactions gathered from precise, empirical experimentation in the Swansea laboratories. Fatigue crack initiation and crack propagation were predicted based only on deformation characteristics in the alloy.
- M.R. Bache, “A review of dwell sensitive fatigue in titanium alloys: the role of microstructure, texture and operating conditions”, Int. J. Fatigue, 25, pp.1079-1087, 2003. 10.1016/S0142-1123(03)00145-2
- W.J. Evans and M.R. Bache, “Dwell-sensitive fatigue under biaxial loads in the near alpha titanium alloy IMI685”, Int. J. Fatigue, 16, pp.443-452, 1994. 10.1016/0142-1123(94)90194-5
- M.R. Bache, M. Cope, H.M. Davies, W.J. Evans and G. Harrison, “Dwell sensitive fatigue in a near alpha titanium alloy at ambient temperature”, Int. J. Fatigue, 19, Supp. 1, pp. S83-S88, 1997. 10.1016/S0142-1123(97)00020-0
- M.T. Whittaker, W.J. Evans, R.J. Lancaster, W. Harrison, P.S. Webster. “The effect of microstructure and texture on mechanical properties of Ti6-4”. International Journal of Fatigue 31, Issues 11-12 (2009) 2022-2030. 10.1016/j.ijfatigue.2009.02.014
- M.T. Whittaker, W. Harrison, R.J. Lancaster, S. Williams "An analysis of modern creep lifing methodologies in the titanium alloy Ti6-4". Materials Science & Engineering A 577 (2013) 114-119. /10.1016/j.msea.2013.03.030,
- W.J. Harrison, M.T. Whittaker, R.J. Lancaster “A Model for Time Dependent Strain Accumulation and Damage at Low Temperatures in Ti-6Al-4V”. Materials Science & Engineering A 574 (2013) 130-136. /10.1016/j.msea.2013.02.070,