FOCUSSED PROBES ULTRASONIC FOLLOW-UP OF ACTUAL FLAW GROWTH DURING FATIGUE TESTING

Ultrasonic follow-up of fatigue cracks growth during laboratory experiment on two welded test specimens with embedded defects was carried out using focussed probes. It has been shown that the correlation between the C-Scans and the actual defect was good. The use of immersion testing technique as well as the good resolution of the focussed probes allowed excellent reproducibility of the results. This experiment has also shown that the sizing of such fatigue cracks (having a relatively well defined and known orientation), is only possible when using at least two directions of incidence opposite to each other.