Fatigue crack growth behavior tests are performed on 2024-T351 alumimum alloy to investigate the influence of pseudo random loadings. Wide and narrow band wave are generated by computer simulation. Crack opening points are measured and crack growth rate based on the measured crack opening point is predicted. Crack length and crack closure are measured by unloading elastic compliance technique.
It is observed that the crack opening point varies from cycle to cycle within one block under pseudo random loadings. When maximum range pair stress ratio is zero, the change of the crack opening point is significant. In the case of narrow band wave, the crack opening points become low at large amplitude region. In the case of wide band wave, however, it is difficult to find any tendency. When maximum range pair stress ratio is -1, the crack opening point does not change significantly. The predicted crack growth rate based on the measured crack opening points is less than the measured crack growth rate.
