Influence of Crack Networks on the Ultrasonic Inspection of a Propagated Defect

Thermal fatigue in the mixing zones of pressurized water reactor pipings can potentially lead to the appearance of crack networks. Ultrasonic detection and characterization of a propagated defect in such a network is then a challenge. To study the influence of these secondary crack networks on the ultrasonic inspection of a propagated defect, a mock-up was produced. The innovative manufacturing process must allow, according to the supplier, to propagate cracks with realistic and controlled characteristics, in terms of position, sizing, opening, residual stresses and fracture surface roughness. The selected configuration deals with the inspection of various crack networks of 2 millimetres depth, with various inter-crack spaces (from 1 to 4 millimetres), propagated in a mock-up thickness of 38 millimetres. Two deeper notches were established afterwards in these crack networks. Experimental tests were then carried out and we present and discuss here the various results obtained.