Issue 38

C. Xianmin et alii, Frattura ed Integrità Strutturale, 38 (2016) 319-330; DOI: 10.3221/IGF-ESIS.38.42 319 A statistically self-consistent fatigue damage accumulation model including load sequence effects under spectrum loading Chen Xianmin, Sun Qin, Dui Hongna School of Aeronautics, Northwestern Polytechnical University, Xi’an, 710072 PR China Fan Junling Aircraft Strength Research Institute, Xi’an, 710065, PR China A BSTRACT . A probabilistic methodology is proposed to evaluate fatigue damage accumulation and fatigue lives of specimens under variable amplitude loading. With probabilistic modifications in the present model, the calculative consistency is achieved between fatigue damage and fatigue life. The load sequence effects on fatigue damage accumulation are properly accounted for variable amplitude loading. The developed damage model overcomes the inherent deficiencies in the linear damage accumulation rule, but still preserves its simplicity for engineering application. Based on the Monte Carlo sampling method, numerical verification of this model is conducted under two kinds of spectrum loading. The predicted probabilistic distributions of fatigue lives are validated by fatigue tests on Al-alloy straight lugs. K EYWORDS . Fatigue damage; Fatigue life; Probabilistic statistical model; Load sequence effect; Statistical self-consistency. Citation: Xianmin, C., Qin, S., Hongna, D., Junling, F., A statistically self-consistent fatigue damage accumulation model including load sequence effects under spectrum loading, Frattura ed Integrità Strutturale, 38 (2016) 319-330. Received: 03.05.2016 Accepted: 30.08.2016 Published: 01.10.2016 Copyright: © 2016 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION atigue damage is one of the most common failure modes encountered in engineering structures. Therefore fatigue failure prediction is widely carried out during various processes, such as engineering structural design, safety assessment and optimization. In the past decades, many damage models have been presented to quantitatively analyze fatigue damage and failure of materials and components. However, the mechanisms and process of fatigue failure under variable amplitude loading conditions are random in nature owing to a variety of indeterminable factors in materials as well as external environments. The linear cumulative damage rule, firstly proposed by Palmgren in 1924 and subsequently by Miner in 1945 [1], is widely used for fatigue analyses of structures under variable amplitude loading. It can be expressed as: D=∑(ni/Ni). After that, many developments have been made to get more accurate predictions, including the nonlinear damage rules, such as damage curve based method [2], ductility exhaustion model [3], continuum damage mechanics approach [4] and energy- based damage method [5]. The fatigue damage accumulation within these models and approaches are mostly based on deterministic concepts, whereas in practice, damage accumulation is usually of stochastic nature. F