EMAT pipe inspection with guided waves

摘要

Electro Magnetic Acoustic Transducers (EMATs) are a well-known type of ultrasonic probes used for non-destructive evaluation (NDE) of electrically conductive materials. Con-ventional Ultrasonic Testing (UT) is performed by longi-tudinal waves and mode converted shear waves generated by piezoelectric probes. EMATs 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 ofnearly ali types ofguided 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 toler-ate liquids (e.g. natural-gas pipelines) or on sensitive and coated surfaces of blanks used for car bodies in the auto-motive industry etc.