UT with SH-waves and electromagnetic ultrasonic -EMUS-transducers
Abstract
In the ultrasonic testing practice of today SV- and longitudinal waves are exclusively used becuse these wave types can be excited by piezoelectric ultrasonic transducers introduced a long, time ago. SH-waves offer a number of advantages compared to SV- and longitudinal waves as for example: - reflection, refraction and diffraction without mode conversion, - complete corner reflection independent of the angle of incidence, - propagation in thick-walled components (d bigger than lambda) as a bulk wave even along the surface, - propagation in thin-walled components (d smaller or equal than lambda) as a guided wave (SH-mode), - no radiation of energy into fluids of small viscosity. In principle it is possible to excite SH-waves by piezoelectric transducers, but in practice these transducers are not applicable due to coupling problems.
