A frequency-domain model assessing random loading damage by the strain energy density parameter

The paper presents a new fatigue damage assessment model defined for the strain energy density parameter. The model is defined for calculations in the frequency domain for the case of narrowband loading. Analytical expressions are derived for the probability density function of peaks, the level crossing spectrum, and for the expected damage that is directly linked to the power spectral density of the strain energy parameter. The paper presents a theoretical proof which shows that the damage obtained for the energy model is equal to the damage obtained for the stress model. A numerical example is used to verify the correctness of the proposed frequency-domain damage estimation formula by comparison with experimental and time-domain fatigue life estimation results for two simulated random time-histories for the case of narrowband and broadband loading. The comparison between experimental and calculation results confirm the very good agreement between frequency and time domain approaches.