Progress in UT of austenitic and dissimilar metal welds using Shear Horizontal Waves and Electromagnetic US -EMUS- probes

Among the different ultrsonic wave modes - Longitudinal (L-) waves, Shear waves with polarization in the plane of incidence (SV-waves), L-waves with a high beam angle of 70 (TRL 70) and SH-waves show most promising advantages for the inspection of austenitic and dissimilar metal welds. Whereas high beam angle L-waves excited and detected by conventional piezoelectric probe-technology and equipments have been used for some years, for the application of SH-waves appropriate EMUS-probes and instrumentations had to be developed. The contribution will describe the basic physical features of SH-waves contributing to the improvement of the inspectability of welds with dendritic grain structure. The experimental verification of their theoretically predicted capability to penetrate into the weld and to pass trough the wild will be demonstrated by results of automated test specimen-measurements. Apart from this, the design of the EMUS-probes and -instrumentations will be presented. Phased-Array probes with up to 8 array elements and electronically steerable beam angles from 90 to 40 angle were developed; the realization of the instrumentation for in-field applications will be described.