Novel analytical model for fatigue cumulative damage estimation under random loading

摘要

A newly nonlinear cumulative damage model associated with the S-N curve, which preserves the compatibility conditions established for S-N plane, was proposed and assessed by Eskandari and Kim in 2015. The model requires one exponent, in addition to the S-N curve, to calculate the residual strength. A methodology is established to determine analytically the lower bound value of the exponent. However, this value proved to be too low for a quasi-isotropic glass-fibre laminate, based on published residual strength data. Further on, good predictions are obtained for ascending and descending ordered block spectrum. Yet it failed at fully random spectrum. The model was modified by imposing a very small decrease on model exponent towards the lower bound value, each time an increase in peak stress occurs. This modified model has been found to give good agreement with fatigue experimental data at different spectrum loads.