Effect of Loading Spectrum Clipping and Truncation on Fatigue Crack Growth Behavior of 7475-T7351 Aluminum Alloy under Variable Amplitude Loading

The paper summarizes conclusions based on fatigue crack growth experiments and numerical calculations focused on full commuter aircraft spectrum optimization. The fatigue crack growth experiments were performed on 7475-T7351 alloy. Sequences with different truncation (omission) and clipping stress levels were investigated. All experimental data are supported by extensive numerical crack growth analyses using FASTRAN and AFGROW software. The sequence with a clipping of 2.78 g values and omission level of 10 MPa was assessed as an optimum from point of view of time saving and test credibility. Omission of any higher stress range affects the fatigue crack propagation significantly.