PSI - Issue 25

Pedro R. da Costa et al. / Procedia Structural Integrity 25 (2020) 445–453 Author name / Structural Integrity Procedia 00 (2019) 000–000

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results the difference is more pronounced with 45 % higher stresses at 20 kHz for no failure specimens. No failure in the VHCF regime was observed for any tested specimen. Tested specimens that nucleated a fatigue crack and lost resonance were led to total failure and studied carefully with the use of SEM. The obtained images were compared to uniaxial ultrasonic specimens machined also from the same railway wheel section, the Rim. SEM analysis to conventional fatigue specimens were also conducted for uniaxial and multiaxial conventional fatigue specimens. Taken and compared SEM images for uniaxial and multiaxial specimens are showed in figure 8 and 9, respectively.

Figure 8. Uniaxial ultrasonic specimen (A) optical microscope general view; (B) SEM general view; (C) fatigue propagation near initiation 500x; (D) fatigue propagation near initiation 1000x. Uniaxial conventional specimen (A) optical microscope general view; (B) SEM general view; (C) fatigue propagation near initiation 500x; (D) fatigue propagation near initiation 1000x .

Figure 9. Multiaxial ultrasonic specimen (A) optical microscope general view; (B) SEM general view; (C) point of fatigue crack initiation 500x; (D) point of fatigue crack initiation 1000x. Conventional ultrasonic specimen (A) optical microscope general view; (B) SEM general view; (C) fatigue propagation near initiation 500x; (D) fatigue propagation near initiation 1000x.