A High Load Clipping Criterion Based on the Probabilistic Extreme Load of Fatigue Spectrum

Abstract

The high load with very low occurrence probability in the fatigue load spectrum may introduce the favorable residual stress at the metal structure notch, so it is necessary to clip the high load of spectrum to avoid a dangerous test result. Based on the time-domain extrapolation principle and the extreme value theory, the probability distribution of high load in the whole-life load spectrum was predicted. Considering the dispersion of high load and the influence of high load on the structural fatigue life, a selection criterion of high load clipping level was proposed, which makes the test result under the corresponding clipped spectrum both conservative and authentic. To demonstrate the rationality and practicality of criterion, the transport aircraft load spectrum was extrapolated and the spectral fatigue tests of 2024-T3 aluminum alloy sheet were conducted, providing reference for the design of fatigue test load spectrum of aircraft structure in practical engineering.