PSI - Issue 19

Fumiyosi Yoshinaka et al. / Procedia Structural Integrity 19 (2019) 214–223 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. Normal probability distribution of the fatigue lives N f at the total strain range Δ ε t of 2%.

The total strain range Δ ε t can be divided into inelastic strain range Δ ε in and elastic strain range Δ ε e : ∆ t = ∆ in + ∆ e Figure 3 shows the (a) Δ ε in - N f and (b) Δ ε e - N f relationships. It is widely accepted that the Δ ε in - N f and Δ ε e - N f relationships can be respectively fitted using the Coffin – Manson (Eq.2) and Basquin (Eq.3) laws (Brechet et al. (1992)) as follows: ∆ in ・ f in = in (2) ∆ e ・ f e = e (3) The fitting lines according to the Coffin – Manson and Basquin laws are illustrated in Fig. 3, while the coefficients of Eqs. 2 and 3 are listed in Table 2. Fe-15Mn-10Cr-8Ni demonstrated a longer N f against Δ ε in compared to that of the other materials. On the other hand, for Δ ε e - N f , N f of Fe-15Mn-10Cr-8Ni-4Si took a value similar to that of austenitic steels, namely, Fe-28Mn-5Cr-6Si and SUS304, in the lower strain level, where significantly long N f values were recognized for Δ ε in - N f . Based on these results, it is considered that the superior fatigue life of Fe-15Mn 10Cr-8Ni can be attributed mainly to the response of the inelastic strain component, and the prolonged N f can be obtained for a relatively lower strain level. (1)

Fig. 3. (a) R elationship between the inelastic strain range Δ ε t and the number of cycles to failure N f ; (b) relationship between the elastic strain range Δ ε t and the number of cycles to failure N f .