Simulation of ultrasonic defect responses in realistic inspection configurations. Theoretical predictions and experimental validations
16th world conference on Nondestructive Testing, Montreal, August 30 - September 3, 2004,
Rapport DSR 29
A semi-analytical modeling approach of the ultrasonic beam-defect interaction developed by CEA (the French Atomic Energy Commission) has been implemented within the CIVA software since many years. This model is based on Auld’s reciprocity arguments between transmitted and received ultrasonic fields and on the application of suitable approximate theories such as Kirchhoff approximation or geometrical theory of diffraction for the field-to-flaw interaction. The simulations features include prediction of echoes arising from defects (direct specular echoes, corner echoes with reflection at the backwall, account for mode conversions due to reflections at the defect or at the backwall), as well as geometrical echoes due to reflections on the specimen boundaries. With the successive versions of the software this approach is continuously improved in order to extend its applicability to more complex configurations and also, when needed, to enhance its reliability. Widening the scope of applicability has been requiring, in parallel, a multiplication of experimental campaigns of validation supported by the French "Institute for Radiological Protection and Nuclear Safety " (IRSN).
In this communication we recall the theoretical basis of the approach. We present the most recent evolutions of the models which mainly concern inspections of parts showing complex geometries. In such configurations, we show various examples of experimental validation performed on realistic mock-ups containing artificial reflectors (electro-eroded notches, side drilled holes…).