Adaptive Inspection of Component of Complex Geometry with a Flexible Phased Array Probe

摘要

Ultrasonic in service inspections of primary and auxiliary circuits ofrnpressurized water reactors are mainly performed with contact transducers.rnSuch components may have a complex geometry and irregular state of surface,rnwhich leads to degraded defect detection and characterization performances.rnFor irregular profiles, unmatched contact between the specimen and the wedgernwould occur (and vary according to the inspection position) thus resultingrnin a poor detection sensitivity and distortion of the ultrasonic beam.rnSmooth profiles variations, however, may also be hardly assessed if the beamrnaxis is disoriented, which would obviously give rise to a mistaken defectrnlocalization. At last, the transducer scanning may be limited, and the scanrnarea partially covered. To overcome such difficulties, a smart flexiblernphased array concept has been developed : the flexible radiating surface ofrnthe transducer allows to fit the inspected profile, while phased arrayrntechniques are used to preserve the ultrasonic beam characteristics throughrnthe whole inspection. A specific instrumentation inserted in the transducerrnhousing allows to measure its own deformation and to compute optimised delayrnlaws according to the profile. Experiments and modelling tests have beenrncarried out in transmission mode to validate the transducer's ability torncompensate the distortions encountered on various complex profiles. Otherrnexperiments in pulse-echo mode and beam-steering performed on an irregularrnprofile specimen containing artificial reflectors show the defect detectionrnand characterization efficiency of the system.