Issue 78

F. Veschi et alii, Fracture and Structural Integrity, 78 (2026) 44-73; DOI: 10.3221/IGF-ESIS.78.04

 The approaches based on Equivalent PSD show a fundamental inability to represent the actual physics of the SoR phenomenon, mainly visible in the integrand function panel (top right). While they exhibit a reasonable match in the low-amplitude/high-cycle region, their probability tails seem to fail to account for the presence of a pure tone. This structural flaw leads to an overestimation of high-amplitude events and a severe penalization of medium amplitude cycles, exactly where the influence of the sine wave is dominant. From this behaviour, one can infer that the relatively low errors in damage estimation obtained from the analysis of this loading scenario come from a mathematical compensation of the integrands' areas, combined with a relatively low Basquin exponent ( m ), rather than actual physical accuracy. The Irvine and RMS Equivalence methods seem to yield the best estimates, suggesting being highly useful in practice despite being physically inaccurate. Lalanne and White Noise Approximation methods are too conservative in this scenario.

0.05 k  ). The

Figure 9: Statistical comparison of the predictive models under SoR loading with a narrow-band background ( reference RFC probability density function is depicted as a shaded grey histogram in the first panel.

1 k  ). The dashed grey

Figure 10: Comparison of pseudo-damage estimates under SoR loading with a narrow-band background (

RFC PD ). Percentages above the bars indicate the relative error of

line represents the reference rainflow counting pseudo-damage (

each predictive method.

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