PSI - Issue 66

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Alfonso Fernández-Canteli et al. / Procedia Structural Integrity 66 (2024) 296–304 A. Fernández-Canteli et al / Structural Integrity Procedia 00 (2025) 000–000

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analytical expression for the curve while ensuring . 50 200

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3 parametric Weibull cdf a-N experimental results

3 parametric Weibull cdf Experimental results

3 parametric Weibull cdf a-N experimental results

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15 a [mm]

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(a) (c) Fig. 3. (a) Fitted curve with experimental data assuming asymptotic definition; (b) Fitted ∗ − curve with experimental data; and (c) Fitted curve from the ∗ − curve along with the original experimental data. Fig. 4 proves that Expr. (5), which represents the analytical definition of the / using the modified expression for given by Expr. (4), points out an upper limit value of the crack size, , for asymptotic crack growth rate, / , as physically expected. (b)

10 -2

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10 -5 da/dN [mm/cycle]

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Fig. 4. / curve obtained through Expr.(4) against the crack length value, , along with the original experimental data. With regard to the calculation of the maximum stress intensity factor, , the analytical definitions proposed in the literature and included in the ASTM E647-11 [10] is implemented. On the one hand, the expression of the stress intensity factor for the particular type of specimen selected, in this case the CT type, is given in Expr.7. On the other hand, the graphical representation of the stress intensity factor versus crack size is shown in Fig. 5, where , , and , are referred to the maximum load applied during the test, the specimen thickness, the specimen width and the / ratio, respectively. Note that despite the monotonic increasing trend of as a function of , in the real test, the phenomenon is limited by the selected critical crack size, , at which an unstable crack growth would occur leading to the collapse of the specimen. [ √ ] = √ (2+ ) (1 − ) 3 2 (0.88 + 4.64 13.32 2 +14.72 3 − 5.6 4 ) 1 √ 1000 (7) a [mm]