Laser peening extends the lifetime of Rolls-Royce fan blades
To ensure the safe lifetime of Trent engine fan blades, Rolls-Royce adopted a process known as laser shock peening (LSP). It is now used to treat all Trent 500, Trent 800, Trent 1000 and XWB blades. Sales of 1,200 treated Trent XWB engines alone are worth more than £60 billion.
Fan blades in aircraft engines suffer large loads and high frequency vibrations. Over time these stresses can create microscopic cracks in the blades which could eventually cause potentially catastrophic and life threatening engine failure.
The traditional method for stopping cracks is to fire 'shot' at the blades; the shallow indentations create compressive residual stresses that stop cracks growing. But when two Trent 800 blades failed testing, Rolls-Royce decided to explore laser shock peening (LSP), an alternative approach which introduces compressive stresses to a much greater depth via a plasma created by a powerful pulsed laser.
Guaranteed safe lives with LSP
Researchers from the Department of Materials analysed the potential of LSP to strengthen blades. Using penetrating synchrotron X-ray beams they discovered that the laser method generates deep compressive stresses which remain stable under the fatigue loading of air travel.
Following our comprehensive evaluation of the safety and benefits of LSP-treated blades, Rolls-Royce’s adopted LSP to treat its Trent 800 engine. Since then, the company has applied LSP to Trent 500, Trent 800, Trent 1000 and XWB engines. So far, Rolls-Royce has sold more than 1,200 of its latest XWB engines – worth over £60 billion in total.
LSP treatment is contracted by Rolls-Royce to Curtiss-Wright Surface Technologies (formerly The Metal Improvement Company) which has received training and expert support from our research team. Curtiss-Wright runs a dedicated facility near to Rolls-Royce’s blade production centre, employing 30 people. Curtiss-Wright recently won a contract to set up a similar facility inside Rolls-Royce’s Singapore plant, which will produce a further 6,000 blades annually.
- Curtiss-Wright awarded laser peening contract from Rolls-Royce to provide services on Trent turbine engine fan blades
- Increasing the fatigue resistance of fan blades
Materials Testing and Analysis Unit
6,000 blades manufactured in Rolls-Royce's Singapore plant annually.
As part of our partnership with Rolls-Royce, we established a Materials Testing and Analysis Unit to routinely test LSP-treated fan blade components using X-ray diffraction residual stress measurement. Today the Unit confirms the integrity of the LSP-based manufacturing process each and every month; this work is integral to Rolls-Royce’s quality assurance and contributes to Civil Aviation Authority accreditation of Trent aero-engines.
The MTA Unit generates a turnover of £100,000 from Rolls-Royce alone.
£60 billion orders for Rolls-Royce LSP-treated Trent XWB engines.
£8.6 billion annual revenue for Rolls-Royce's aeroengine business.
Researchers in the Department of Materials, led by Professor Philip Withers, have studied the fundamental nature of LSP-induced compressive residual stress. They found that LSP is preferable to more established shallow peening for fan blades' roots which experience contact fatigue.
Key research achievements:
- New methods to measure residual stress in materials
- Demonstration that LSP introduces deep and long-lasting 'protective' stresses into fan blades
- Exploitation of penetrating synchrotron X-ray beams at the European Synchrotron X-ray Facility to map the residual stresses non-destructively.
- Identification of the origins of residual stress and how to manage stresses
- Comparison of four peening surface treatments, with LSP showing greatest benefits for fan blades
In recognition of his use of neutron and hard X-ray beams to map stresses and image defects, the Royal Society awarded Professor Withers its Armourers and Brasiers' Company Prize in 2010.
- P. J. Withers, H. K. D. H. Bhadeshia (2001) "Residual Stress, Part 1 - Measurement techniques" and "Residual Stress, Part 2 - Nature and origins" Mat. Sci and Tech, 17:355-374 doi:10.1179/026708301101509980 and doi:10.1179/026708301101510087
- A. King, A. Steuwer, C. Woodward, and P. J. Withers (2006) "Effects of fatigue and fretting on residual stresses introduced by laser shock peening" Mat. Sci. and Eng., 435(6):12-18 doi:10.1016/j.msea.2006.07.020
- P. J. Withers (2007) "Residual stress and its role in failure" Rep. Prog. Phys., 70:2211-2264 doi:10.1088/0034-4885/70/12/R04