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Proceedings Paper

Eddy current technique applied to the nondestructive evaluation of turbine blade wall thickness
Author(s): Yann Le Bihan; Pierre-Yves Joubert; Dominique Placko
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Paper Abstract

The high pressure turbine blades of jet engines show internal channels designed for air cooling. These recesses define the internal walls (partitions) and external walls of the blade. The external wall thickness is a critical parameter which has to be systematically checked in order to ensure the blade strength. The thickness evaluation is usually lead by ultrasonic technique or by X-ray tomography. Nevertheless, both techniques present some drawbacks related to measurement speed and automation capability. These drawbacks are bypassed by the eddy current (EC) technique, well known for its robustness and reliability. However, the wall thickness evaluation is made difficult because of the complexity of the blade geometry. In particular, some disturbances appear in the thickness evaluation because of the partitions, which exclude the use of classical EC probes such as cup-core probe. In this paper, we show the main advantages of probes creating an uniformly oriented magnetic field in order to reduce the partition disturbances. Furthermore, we propose a measurement process allowing to separate the wall thickness parameter from the EC signals. Finally, we present some experimental results validating the proposed technique.

Paper Details

Date Published: 5 May 2000
PDF: 9 pages
Proc. SPIE 3994, Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware IV, (5 May 2000); doi: 10.1117/12.385028
Show Author Affiliations
Yann Le Bihan, Ecole Normale Superieure de Cachan (France)
Pierre-Yves Joubert, Ecole Normale Superieure de Cachan (France)
Dominique Placko, Ecole Normale Superieure de Cachan (France)

Published in SPIE Proceedings Vol. 3994:
Nondestructive Evaluation of Aging Aircraft, Airports, and Aerospace Hardware IV
Ajit K. Mal, Editor(s)

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