Wall thickness evaluation of single-crystal hollow blades by eddy current sensor

Advanced high-pressure turbine blades of jet engines are hollow and monocrystalline. The external wall thickness of these blades has to be checked systematically and quickly after manufacturing in order to guarantee the blade strength. Thickness evaluation is made difficult by the presence of internal partitions and by the crystalline anisotropy of the superalloy used in blade manufacturing. In this paper, the authors present the advantages of the eddy current (EC) technique in comparison to other non-destructive evaluation (NDE) techniques for wall thickness evaluation. A dedicated EC sensor was developed and implemented. The thickness evaluation was carried out with a neural network inverse model, and the results show the high accuracy and reliability of the proposed method. (C) 2001 Elsevier Science Ltd. All rights reserved.