The capability and application of horizontally polarised shear waves for the ultrasonic inspection of austenitic welds

Nuclear electric's NDT applications Centre, in collaboration with IzfP, Germany, has evaluated Electromagnetic Acoustic Trasnducers (EMATs) for the generation of horizontally polarized shear (SH) waves for ultrasonic inspection of austenitic welds. A range of austenitic weld blocks containing both realistic and artificial defects have been inspected using both angle compression wave probes and EMATs. The comparison shows that SH wave results have good signal to noise ratio for the detection of defects and the SH wave images are much "cleaner" than those for angel compression waves simplifying data interpretation. Modelling is used to explain the observed phenomena and to predict cases where SH waves might be best employed and where SH waves offer no significant benfit over compression waves. The paper discusses the benefits and drawbacks of using EMATs compared with angle compression wave probes and proposes inspection strategies incorporating both probe types.