PSI - Issue 42

Jan Klusák et al. / Procedia Structural Integrity 42 (2022) 1369–1375 Jan Klusák et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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initiation and propagation are shown in Fig. 6 The river patterns of crack propagation are apparent in the left micrograph, and a detail of the crack initiation site is in the right-hand side micrograph. The micrographs correspond to stainless steel 1.4306, specimen No. 4, loaded by  a = 260 MPa, N f = 1.87×10 8 cycles.

Fig. 6. Crack initiation and propagation in stainless steel 1.4306 (specimen No. 4,  a = 260 MPa, N f = 1.87e8 cycles)

A slip activity on the surface of the 1.4306 steel is shown in Fig. 7. The figure corresponds to the specimen No. 13, loaded by  a = 270 MPa, and reaching N f = 4.8×10 5 cycles. Expressive slip activity was observed near the crack initiation places.

Fig. 7. Slip markings on the surface of the specimen of 1.4306 stainless steel (specimen No. 13,  a = 270 MPa, N f = 4.8×10 5 cycles) 6. Conclusions Fatigue tests of 1.4306 and 1.4307 stainless steels were performed using the ultrasonic fatigue testing device. Fatigue lifetime expressed by S-N curves was analyzed, where slightly higher number of cycles to fracture was observed for 1.4306 steel. The same steel exhibited a higher fatigue limit; however, the difference was only minor.