Issue 78

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

1   (

0.66   ) - Frequency Ratios

0.05 k  and

1 k  .

Figure 12: Wide-Band Random Background

Results and Discussions. Figs. 13 and 14 display the results obtained from the WB random background analysis with spectral separation ( 0.05 k  ).

0.05 k  ). The dashed grey

Figure 13: Comparison of pseudo-damage estimates under SoR loading with a wide-band background (

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

line represents the reference rainflow counting pseudo-damage (

each predictive method.

The analysis of the results brings the following observations:  Rice's method accurately tracks the Time History load spectrum in the high-amplitude, low-cycle regime; however, it severely overestimates the medium-amplitude range, where cycle counts are significantly higher. Consequently, the resulting damage estimation is extremely conservative (more than 10 times higher than the RFC pseudo damage value), confirming the trend already observed in the Narrowband scenarios.  In this scenario, Equivalent PSD approaches exhibit low damage estimation errors. However, as observed previously, this apparent accuracy is merely the result of an area compensation artifact within the damage integrand. Specifically, the Irvine and RMS Equivalence methods yield reasonable estimates, limiting the underestimation to within 10%. Lalanne's method proves more conservative (+29%), whereas the White Noise Approximation apparently fails to capture the underlying physics, overestimating the damage by nearly 88%. This severe discrepancy is a direct consequence of the white noise assumption inherent to its mathematical formulation. The last presented scenario, described in Figs. 15 and 16, is characterized by an amplitude ratio , / 4 s r a   and spectral coincidence between the components ( 1 k  ).

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