Ultrasonic non-destructive testing of pieces of complex geometry with a flexible phased array transducer

Ultrasonic non-destructive testing of components of complex geometry in the nuclear industry faces several difficulties: sensitivity variations due to unmatched contact, inaccurate localization of defects due to variations of transducer orientation, and uncovered area of the component. To improve th e performances of such testing and defect characterization, we propose a ne w concept of ultrasonic contact phased array transducer. The phased array transducer has a flexible radiating surface able to fit th e actual surface of the piece to optimize the contact and thus the sensitiv ity of the test. To control the transmitted field, and therefore to improve the defect characterization, a delay law optimizing algorithm is developed . To assess the capability of such a transducer, the Champ-Sons model, deve loped at the French Atomic Energy Commission for predicting held radiated b y arbitrary transducers into pieces, has to be extended to sources directly in contact with pieces of complex geometry. The good behavior of this new type of probe predicted by computations is experimentally validated with a jointed transducer positioned on pieces of various profiles. (C) 2000 Elsev ier Science B.V. All rights reserved.