Numerical and experimental analysis of fatigue crack growth under random loading

This article analyses fatigue crack growth under random loading using experimental results taken from literature on the subject and from growth simulations carried out using the Strip Yield Model. The capacity of the Strip Yield Model in representing the retardation effects produced during the growth process is analysed. The effect of different statistical parameters of the random load process and of the representative histories of the same on the crack growth life and on the variability of the results obtained in different representative tests of the same real load process is likewise studied. Some of the parameters considered are the bandwidth of the random loading process, the number of cycles of the load histories employed and the effect of truncating the histories. It can be seen that under certain conditions, the numerical model employed can quite closely predict some of the behaviours of the crack growth. Likewise, it can also be seen that the bandwidth has a significant effect on the fatigue life, and that the length of the histories employed in tests or simulations has a great effect on the variability of the obtained results. It can also be seen that, although the elimination of the overloads tends to give rise to shorter lives, in certain cases, from a statistical point of view, it may be the origin of non-conservative predictions.

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