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

Advanced high-pressure turbine blades of jet engines are hollow and monocry stalline. The external wall thickness of these blades has to be checked sys tematically and quickly after manufacturing in order to guarantee the blade strength. Thickness evaluation is made difficult by the presence of intern al partitions and by the crystalline anisotropy of the superalloy used in b lade manufacturing. In this paper, the authors present the advantages of th e eddy current (EC) technique in comparison to other non-destructive evalua tion (NDE) techniques for wall thickness evaluation. A dedicated EC sensor was developed and implemented. The thickness evaluation was carried out wit h a neural network inverse model, and the results show the high accuracy an d reliability of the proposed method. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.