PSI - Issue 35

Martin Ferreira Fernandes et al. / Procedia Structural Integrity 35 (2022) 141–149 Martin Ferreira Fernandes et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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Fig. 6. Fracture surfaces of fatigue (23415 cycles) and (b) dwell-fatigue (2311 cycles) tests at 975 MPa.

Fig. 7. Fracture surfaces of (a) fatigue (83281 cycles) and (b) dwell-fatigue (18630 cycles) tests at 950 MPa.

Fig. 8 shows SEM images of the fracture surface of a dwell-fatigue test at a maximum stress level of 1000 MPa (1821 cycles). The overview of the fracture (Fig. 8a) had an appearance of cup-and-cone, characteristic of a ductile fracture. The fracture surface is composed of dimples near the surface (Fig. 8b) and in the center of the specimen (Fig. 8c). The fracture surface is also composed of large voids (Fig. 8d). Fig. 9 displays the fracture surface of a dwell-fatigue test at the stress level of 950 MPa (18630 cycles). The fracture morphology was similar to a fatigue fracture with the crack nucleation at the surface (Fig. 9b). Figs. 9c and 9d show the dimples present in regions “B” and “C”.

Fig. 8. Fracture surface of dwell-fatigue test at 1000 MPa (1821 cycles). (a) Overview and details of regio ns (b) “A”, (b) “B” and (d) “C” .