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EMAT and multifrequency eddy current testing on test block Nr. 81-1192-EMT

: Betzold, K.; Deuster, G.; Hübschen, G.

International journal of pressure vessels and piping 35 (1988), pp.189-199
ISSN: 0308-0161
International Seminar on Non-Destructive Examiniation in Relation to Structural Integrity <5, 1987, Davos>
Conference Paper
Fraunhofer IZFP ()
cladding; creepring wave; eddy current; longitudinal wave; pick-up coil; rayleigh-wave; SH-wave

On a cladded test specimen with 2 mm cylindrical holes in different depths, measurements with SH waves, longitudinal waves (creeping waves) and Rayleigh waves from the clad as well as from the ferritic side were performed. Investigations with the multifrequency eddy current prototype were also carried out. The sensitivity of longitudinal waves of near grazing incidence is higher than of SH waves in depths between 7 and 11 mm. Comparable sensitivities are reached with SH and longitudinal waves for crack-line defects in the austenitic cladding/ferritic base material interface. Surface defects can only be detected with SH waves. From the ferritic side all test reflectors are detected by SH waves. After suppressing disturbing influences, the cylindrical holes between 3 and 5 mm below the surface can be detected with the mulitfrequency equipment. There are no detection problems for surface breaking defects. Lower frequencies will enable us to increase the penetration depth.