Fatigue life estimation of structures subjected to vibratory loading

Abstract

Fatigue life is commonly estimated by an analysis of the stress time history through a peak-valley counting method and the damage is calculated thanks to a damage summation method. Unfortunately, vibratory loadings are often random and this kind of calculation would be very time consuming. Such spectra require other methods and that's why especially dedicated models have been developed. Known as spectral methods, they enable to calculate the fatigue damage in the frequency domain where the loading is expressed as a power spectral density function (PSD) of stresses [1]. Based on a large variety of PSD and fatigue spectrum, the objective of the study has been to test and compare the accuracy of different models found in the literature such as the one's developed by Dirlick [2] or Tovo-Benasciutti [3]. The robustness and the sensitivity of different parameters such as the mean stress correction methods, the RMS value or the slope of the Wöhler curve, have been studied too. Finally an introduction to the safety factors to apply to these models is proposed in order to take account of their discrepancy.