Fatigue crack growth prediction of small corner crack emanating from fastener holes in aircraft structures

Linear-elastic fracture mechanics methods are widely accepted for damage tolerance design and analysis in aircraft structures. To improve the damage tolerant life of aircraft structures, it is mostly efficient way if the initial flaw (crack) size can be reduced without any loss of weight penalties. However this is indispensably required to predict the growth behavior for small cracks ranging in length from 10 /spl mu/m to 1mm. Conventional linear-elastic analyses of small cracks are considered inadequate because of microstructural influences and the nonlinear stress-strain behavior at notches in the crack-front region. The purposes of this investigation were to carry out the fatigue crack growth test of small corner crack emanating from fastener hole in the range of surface crack length between 0.2-1.6mm with center-hole tension specimen for 2024-T3 aluminum alloy. And both of the elastic and elastic-plastic fracture mechanics parameters were evaluated to correlate to crack growth behaviors of small corner crack. The effective stress intensity factors were also considered to take into account the crack closure effects on the basis of the measurements of crack opening loads during crack growth test. The comparison of the fatigue crack growth behaviors between predicted and test results was finally presented.