Abstract
The present paper aims to discuss a frequency-domain multiaxial fatigue criterion based on the critical plane approach, suitable for fatigue life estimations in the presence of proportional and non-proportional random loading. The criterion consists of the following three steps: definition of the critical plane, Power Spectral Density (PSD) evaluation of an equivalent normal stress, and estimation of fatigue damage. Such a frequency-domain criterion has recently been validated by using experimental data available in the literature, related to combined proportional and non-proportional bending and torsion random loading. The comparison with such experimental data has been quite satisfactory. In order to further validate the above criterion, numerical simulations are herein performed by employing a wide group of combined bending and torsion signals. Each of such signals is described by an ergodic, stationary and Gaussian stochastic process, with zero mean value. The spectrum of each signal is assumed to be represented by a PSD function with rectangular shape. Different values of correlation degree, variance and spectral content are examined.
Highlights
E ngineering structures suffer from failure associated with fatigue, both at the stage of manufacturing and under service conditions [1]
A much more efficient method of analysis, named frequency-domain or spectral analysis, is that to consider the Power Spectral Density (PSD) function of the loading on the structure, which represents the frequency content of the loading time history
Numerical simulations are here developed, by considering random biaxial loading characterized by different values of the correlation coefficient, zero order moments ratio and central frequencies ratio
Summary
E ngineering structures suffer from failure associated with fatigue, both at the stage of manufacturing and under service conditions [1]. A much more efficient method of analysis, named frequency-domain or spectral analysis, is that to consider the Power Spectral Density (PSD) function of the loading on the structure, which represents the frequency content of the loading time history. Such methods employ an equivalent uniaxial loading to represent the actual multiaxial stress state, opening the possibility to use time- and frequency-domain methods originally proposed for fatigue analysis under uniaxial variable or random amplitude loading. The input data for the fatigue damage calculation is the PSD matrix of the stress tensor (Step 1 in Fig.). 11 Determination of the PSD matrix S x y z ( ) 21 Determination of the PSD matrix S x ' y 'z ' ( )
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