Analysis of synthesized non-Gaussian excitations for vibration-based fatigue life testing

Abstract

Certain applications require that some critical components must undergo qualification tests to check their suitability with respect to vibration excitations. Measured field data are commonly considered as reference for the synthesis of random stationary signals used as excitations for shakers. The current procedures usually generate test profiles in terms of PSD, corresponding to random processes with Gaussian probability distribution of values. Such signals may be unrealistic in representing the characteristics of the reference data if the latter are not Gaussian. The Kurtosis parameter is often used to synthetically represent the amount and the amplitude of signal peaks. Its value is 3.0 for Gaussian signals, whereas higher values hold for signals featuring high peaks, e.g. due to micro-shocks. In case of accelerated fatigue life tests, the synthesized signal must induce, in a limited duration, the same fatigue damage which the reference signal cause on the component throughout its expected lifetime. The Fatigue Damage Spectrum (FDS) is generally used to quantify the fatigue damage potential associated with the excitation. The test signal is synthesized targeting the same FDS of the reference profile. This paper presents two kurtosis-control algorithms of signal synthesis in combination with a technique able to match the prescribed FDS.