Abstract Mixed mode-I/II/III fatigue crack growth experiments and their simulations are performed using a system permitting all possible combinations of three-dimensional mixed mode loading conditions. The so-called Compact Tension-Shearing and Tearing (CTST) specimens used in the experiments are made of 7075-T651 aluminum alloy. Different mixed mode loading conditions are considered and the applicability of a previously developed new 3-D fracture criterion on 3-D mixed mode fatigue problems is evaluated. Crack growth surfaces obtained from numerical simulations and experiments are compared using existing criteria in the literature and the developed criterion. Especially for highly mixed mode conditions, the developed criterion predicts the crack growth surface better than the MTS criterion by reducing nearly half of the latter’s deviation from the experimental surface. Based on the computed mixed mode stress intensity factors, comparisons of lives show that most mixed mode fracture criteria underpredict fatigue crack propagation lives. Numerical analyses are also performed on a cylindrical steel bar under combined tension–torsion fatigue load to further validate the method presented. The predicted results showed good agreement with experimental data from the literature.

中文翻译：

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三维混合模式-I/II/III疲劳裂纹扩展问题的计算建模与实验

摘要 混合模式-I/II/III 疲劳裂纹扩展实验及其模拟是使用允许所有可能的三维混合模式加载条件组合的系统进行的。实验中使用的所谓紧凑型拉伸剪切和撕裂 (CTST) 试样由 7075-T651 铝合金制成。考虑了不同的混合模式载荷条件，并评估了先前开发的新 3-D 断裂准则对 3-D 混合模式疲劳问题的适用性。使用文献中的现有标准和开发的标准来比较从数值模拟和实验中获得的裂纹扩展表面。特别是对于高度混合模式的条件，通过将 MTS 标准与实验表面的偏差减少近一半，开发的标准比 MTS 标准更好地预测裂纹扩展表面。基于计算出的混合模式应力强度因子，寿命比较表明，大多数混合模式断裂标准都低估了疲劳裂纹扩展寿命。还在拉扭疲劳载荷下对圆柱形钢筋进行了数值分析，以进一步验证所提出的方法。预测结果与文献中的实验数据显示出良好的一致性。还在拉扭疲劳载荷下对圆柱形钢筋进行了数值分析，以进一步验证所提出的方法。预测结果与文献中的实验数据显示出良好的一致性。还在拉扭疲劳载荷下对圆柱形钢筋进行了数值分析，以进一步验证所提出的方法。预测结果与文献中的实验数据显示出良好的一致性。