13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- pearlitic steel [15] and it can be considered a slow propagation mode in hydrogen-assisted fracture processes linked with subcritical cracking at one micrometer per second or less [16]. Figure 8. Fractograph corresponding to fatigue initiation phase: hot rolled bar (left) and prestressing steel wire (right). In both images the fatigue crack growth direction is from left to right Figure 9. Fractograph corresponding to fatigue propagation phase: hot rolled bar (left) and prestressing steel wire (right). In both images the fatigue crack growth direction is from left to right 4. Simulations In the Whöler tests, a smooth specimen (samples of the as-supplied wire) was subjected to fatigue loading under constant amplitude, stress level of about half of the yield strength (Δσ=σY/2), up to fracture due to initiation and propagation of a fatigue crack reaching its critical value (Fig. 10). Figure 10. Fracture surface in the specimens after the Whöler tests: hot rolled bar (left) and prestressing steel wire (right). In both images the fatigue crack growth direction is from left to right
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