Comparative evaluation of fatigue life estimation under variable
amplitude loading through damage models based on entropy.
Abstract
Three fatigue damage models based on entropy, originally developed for
constant amplitude loading, were assessed and compared each other in
order to state whether its applicability can be extended towards
variable amplitude loading conditions. A variable amplitude loading
history, applied on a 2024-T3 aluminum alloy reported in the literature,
was processed using both rainflow cycle counting and spectral techniques
to transform it into a distribution of simple processes with constant
amplitudes, then the damage models were assessed under the new loading
conditions. The results showed that the model by Khonsari, combined with
the rainflow technique, exhibited the highest accuracy with respect to
the referenced experimental results with -0.67 standard deviation from
the average data and 16% error from the median. Therefore, it is
possible to assess the fatigue damage accumulation in metallic materials
under variable amplitude loading through a thermodynamic approach with
models developed for constant amplitude loading.