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Indication of creep embrittlement in low carbon steel components using NDT-methods

: Jansky, J.; Dobmann, G.

Kussmaul, K.F.:
Structural mechanics in reactor technology. Transactions of the 12th International Conference on Structural Mechanics in Reactor Technology. Vol. G. Fracture mechanics and non-destructive evaluation
Amsterdam: Elsevier, 1993
ISBN: 0-444-81515-5
International Conference on Structural Mechanics in Reactor Technology (SMIRT) <12, 1993, Stuttgart>
Conference Paper
Fraunhofer IZFP ()
creep; creep damage; defect analysis; Fehleranalyse; magnetisches Prüfverfahren; nondestructive testing; Ultraschallprüfung

Damage analysis of the piping material revealed hints of creep crack growth during operation in to circumferential weldment adjoined regions loaded with high bending moments and strain induced material embrittlement along the pipe length. Ultrasonic as well as magnetic nondestructive tests (NDT) have been performed in order to characterize the material state of a pipe segment loaded during service with high bending moments. The results were compared to corresponding test resulting obtained from reference material in the "as delivered state". The NDT have been performed prior to Charpy V toughness testing. The pipe segemtn was scanned in the circumferential direction but - depending on the sensor orientation - NDT - data were recorded in both circumferential and axial direction. Compared to the "as delivered state" an anisotropic behaviour of two NDT-parameters is observed which is not symmetrical with respect to the pipe cross section. The Charpy V data measured on the pipe circumfer e nce at ambient temperature 80xC and 150xC revealed different toughness results depending on the circumferential position and therefor on the bending stress. A direct correlation between localy reduced toughness and the NDT-data behaviour is not observed. However, the asymmetry found in the pipe cross section indicates an asymmetric loading.