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Ultrasonic inspectability of austenitic stainless steel and dissimilar metal weld joints

 
: Pudovikov, S.

Kompetenzverbund Kerntechnik; Staatliche Materialprüfungsanstalt -MPA-, Stuttgart:
5. Workshop Kompetenzverbund Kerntechnik "Komponentensicherheit und Werkstoffverhalten" : 08.10.2008, Stuttgart
Stuttgart: MPA, 2008
S.8.1-8.13
Workshop "Komponentensicherheit und Werkstoffverhalten" <5, 2008, Stuttgart>
Englisch
Konferenzbeitrag
Fraunhofer IZFP ()
phased array

Abstract
Since their invention in 1912, austenitic stainless steel materials are widely used in a variety of industry sectors. In particular, austenitic stainless steel material is qualified to meet the design criteria of high quality, safety related applications, for example, the primary loop of the most of the nuclear power plants in the world, due to
high durability and corrosion resistance.
Certain operating conditions may cause a range of changes in the integrity of the component, and therefore require nondestructive testing at reasonable intervals. These in-service inspections are often performed using ultrasonic techniques, in particular when cracking is of specific concern. However, the coarse, dendritic grain structure of the weld material, formed during the welding process, is extreme and unpredictably anisotropic. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of ultrasonic Phased Array techniques becomes desirable.
The "Sampling Phased Array" technique, invented and developed by Fraunhofer IZFP, allows the acquisition of time signals (A-scans) for each individual transducer element of the array along with image reconstruction techniques using "SynFoc" algorithms. The reconstruction considers the sound propagation from each image pixel to the individual sensor element. For anisotropic media, where the sound beam is deflected and the sound path is not known a-priory, we implement a new phase adjustment called "Reverse Phase Matching" technique. This algorithm
permits the acquisition of phase-corrected A-scans that represent the actual sound propagation in the anisotropic structure; this technique can be utilized for image reconstruction.

: http://publica.fraunhofer.de/dokumente/N-88505.html