The non-destructive detection of creep and creep-fatigue damages was studied by employing an ultrasonic technique, taking account of the applicability to welded joints. Particular attention was paid to the change of ultrasonic wave attenuation and that of the anisotropy during the creep and creep-fatigue failures. The experimental results, using the welded joint of 2.25 Cr-1 Mo steel and the dissimilar metal welded joint between 2.25 G-1 Mo and Type 316 steels, showed that the development process of creep damage and that of creep-fatigue one were successfully reflected on the change of the ultrasonic attenuation as follows: the ultrasonic wave attenuation remarkably increased with the creep and the creep-fatigue damages, especially at the final rupture zone, while the change was not noticeable at the other zones accompanying with negligible damage. In addition, the attenuation exhibited a comparable change to the other useful engineering parameters, such as the A-parameter; i.e., the change was satisfied, or competent for detection. These results indicate that the ultrasonic attenuation properties provide the useful information to detect the creep and creep-fatigue damages nondestructively, as well as to find out the dangerous sites to failure, in welded joints.
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