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EMAT's and its potential for modern NDE - state of the art and latest applications

: Salzburger, H.-J.


Ultrasonics Ferroelectric and Frequency Control Society; Institute of Electrical and Electronics Engineers -IEEE-:
IEEE International Ultrasonics Symposium 2009. Proceedings. Vol.1 : Rome, Italy, 20 - 23 September 2009
New York, NY: IEEE, 2009
ISBN: 978-1-4244-4389-5
ISBN: 978-1-4244-4390-1
International Ultrasonics Symposium (IUS) <2009, Rom>
Conference Paper
Fraunhofer IZFP ()
NDE; ultrasound; EMAT; polarization; dispersion; propagnation velocity; straight beam; angled beam; phased array

Electro Magnetic Acoustic Transducers (EMAT) are a well known type of ultrasonic probes used for non-destructive evaluation (NDE) of electrically conductive materials. Conventional Ultrasonic Testing (UT) is performed by longitudinal waves and mode converted shear-waves generated by piezoelectric probes. EMAT's are broadening the range of usable wave modes by the direct conversion of polarized shear waves with normal and angle beams and the selective generation and detection of nearly all types of guided waves. Despite their limitations (low efficiency, lift-off sensitivity, limited frequency range etc.) they have the big advantage to perform UT without couplants. The dry coupling allows UT at elevated temperatures, in media which do not tolerate liquids (e.g. natural-gas pipelines) or on sensitive and coated surfaces of blanks used for car bodies in the automotive industry etc. NDE is not only related to defect detection but more and more to material state and condition analysis and monitoring. To this end, polarization, dispersion, propagation velocity, and mode conversion are physical parameters usable for improved and high sophisticated nondestructive measurements.