Study of the response of a single-dof dynamic system under stationary non-Gaussian random loads aimed at fatigue life assessment

Fatigue assessment of components subjected to random loads is a challenging task both due to the variability in amplitude and frequency of the loads and for the computational times required to perform classical time domain fatigue analysis. The frequency domain approach to fatigue life assessment offers a solution by utilizing the power spectral density of the random load, requiring minimal computational effort. However, frequency domain methods are limited to stationary Gaussian signals, while real-world loads often exhibit non-Gaussian characteristics. Previous research proposed formulas to extend frequency domain methods to non-Gaussian cases, but they require knowledge of the parameters related to non-Gaussianity of the component's stress (skewness and kurtosis), which would require a time domain analysis of the stress history on the component and a strong reduction of the computational advantages. This paper aims to address this gap by conducting an extensive campaign of numerical simulations to evaluate the influence of various parameters on the degree of non-Gaussianity of the response of a system. A single-dof mass-spring-damper system was subjected to non-Gaussian random loads of different natures, and the response is analyzed to determine the values of skewness and kurtosis. The study investigated the influence on non-normality indexes of the system's output of several input parameters, which include both the characteristics of the input load and the properties of the dynamic system. The findings contribute to a better understanding of non-Gaussianity in dynamic systems and pave the way for conducting efficient fatigue analyses in the frequency domain. Future work will extend the study to non-stationary random loads, further advancing the understanding of non-Gaussianity and non-stationarity in dynamic systems.