Prediction of Fatigue Crack Growth for 7075-T7351 Aluminum Alloy under Various Flight Load Spectra

摘要

A plasticity-induced crack-closure model was used to calculate fatigue crack growth lives of middle crack tension specimens made of a 7075-T7351 aluminum alloy subjected to four simulated flight load histories. Experimentally observed crack growth behavior from the literature were compared to crack growth calculations obtained using the FASTRAN life prediction code, employing material property data extracted from the NASGRO material database. To account for a loss of crack front constraint during crack growth, crack growth rate dependent constraint factors were selected to correlate large crack growth rate data as a function of the effective stress intensity factor range under constant amplitude loading. FASTRAN predictions with the transition from flat-to-slant crack growth behavior resulted in ±30% difference from the test lives to failure.