PSI - Issue 71

T. Vivekananda Swamy et al. / Procedia Structural Integrity 71 (2025) 111–117

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Fig. 5 Fatigue fractographs of 150 ℃ Tests (a), (b) and (c), Maximum stress of 1000 MPa. (d), (e) and (f) Maximum stress of 900 MPa. The crack initiation started from the interior of the surface, as shown in Fig. 5 (a), (d), subsequently propagated and experienced a final fracture. Fig. 5 (d) clearly shows two internal crack initiation sites. No Major secondary cracks and fatigue striations were observed in the crack initiation and propagation regions in Fig. 5 (b). This is one of the images of the fractured specimen where the fatigue striations and secondary cracks were absent, even after looking at the higher magnification images. This is owing to the failure of the specimen at a very low number of cycles due to higher maximum stress. No apparent striations are observed in Fig. 5 (e) as in RT. The final fracture region is shown in Fig. 4 (c), (f), 5 (c) and (f). These images show equiaxed dimples indicating the ductile failure mode at the time of the final fracture.