13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- (a) Steel A: RH 25%; RH 85% (b) Steel C: RH 25%; RH 85% Figure 8. Crack morphology observed in (a) Steel A and (b) Steel C (Blank and solid arrows indicate origin of crack initiation and crack tips, respectively. Axial stresses applied in the horizontal direction) Figure 9. SEM micrographs showing fracture surfaces in RH25% (left) and RH85% (right) in Steel C 3.2 Effect of reverted austenite on fatigue properties in high humidity Figure 10 shows the effect of reverted austenite on fatigue strength in different humidity by comparing the results of Steel B that had 10% reverted austenite with those of Steel A, which had the same hardness as Steel B but did not include any reverted austenite. Much different from that in Steel A, the fatigue strength of Steel B remains less affected by high humidity. Figure 10. S-N curves of Steel B 10 5 10 6 10 7 0 100 200 300 400 500 600 700 800 Steel A (γ = 0%) RH25% RH65% RH85% Steel B (γ = 10%) RH25% RH65% RH85% Stress amplitude, σ a MPa Number of cycles to failure, N f cycle
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