Small turbine blade inspection using laser strain techniques
High-pressure turbine blades in a gas turbine engine are constantly exposed to extremely hostile operating conditions, where temperatures can regularly exceed the melting point of the parent material. These conditions make the blades susceptible to thermal fatigue cracking, corrosion
and, in some cases, damage due to particle impact. The required inspection method in aerospace for finding surface-breaking defects is Fluorescent Penetrant Inspection (FPI). However, the blade must be extensively cleaned prior to FPI and this represents a considerable cost in terms of time
and resource, particularly if the blade is subsequently found to be unserviceable. Therefore, the ability to inspect such components prior to the cleaning stage is an attractive proposition. This paper describes the use of laser strain techniques to identify cracks in high-pressure turbine
blades as a means of conducting inspections in the engine-ran condition. A set of nine blades were cleaned and inspected in the conventional manner using FPI, with all highlighted defects recorded photographically. Next, laser shearography techniques were applied to the test set using a bespoke
laboratory system. Distortions in the resultant fringe patterns caused by defects in the material were then used to identify the cracks. All cracks highlighted by FPI were also found using the shearography method. In addition, the laser shearography technique highlighted a region of impact
damage on the aerofoil of one blade, not identified at the first inspection.
Document Type: Research Article
Affiliations: 1 Rolls-Royce plc, Mavor Ave, Nerston, East Kilbride, Glasgow G74 4PY. gerry.harveyrolls-royce.com, Tel: 013552 78649
Publication date: 01 March 2009
- Official Journal of The British Institute of Non-Destructive Testing - includes original research and development papers, technical and scientific reviews and case studies in the fields of NDT and CM.
- Information for Authors
- Submit a Paper
- Subscribe to this Title
- Information for Advertisers
- Terms & Conditions
- Ingenta Connect is not responsible for the content or availability of external websites
- Access Key
- Free content
- Partial Free content
- New content
- Open access content
- Partial Open access content
- Subscribed content
- Partial Subscribed content
- Free trial content