Abstract：The complex stress states at the notch roots on engineering components are usually caused by combinations of geometric discontinuities and multiaxial loading. As to the Theory of Critical Distance, the stress eigenvalue of a point, line or area near the notch root is used as the control parameter of fatigue failure, and a reasonable explanation for the notch effect is put forward. Therefore, the Theory of Critical Distance is considered to be a method of engineering application prospects for predicting the fatigue life of notched specimens. In this paper, the multiaxial fatigue life of notched specimens is predicted according to the Theory of critical distance. Firstly, fatigue tests carried out on 2297 Al-Li alloy under uniaxial and 90° non-proportional loading paths are introduced. Subsequently, the Nominal Stress Approach and the Theory of Critical Distance for multiaxial fatigue life prediction are elaborated. In particular, the value of the critical distance is determined by defining the function relationship between critical distance and fatigue life. The stress state in the vicinity of notch is then analyzed by the finite element method. With the obtained stress state, it is easy to determine the position of the critical plane by the shear stress-Maximum Variance Method. According to the stress parameters on the critical plane, the critical plane stress ratio is defined. Afterwards, the W?hler curve under multiaxial loading is modified by the critical plane stress ratio. Finally, the Theory of Critical Distance and Nominal Stress Approach are used to estimate the multiaxial fatigue life of 2297 Al-Li alloy, and the predicted results are compared. It is found that the Theory of Critical Distance combined with the Modified W?hler Curve Method has high calculation accuracy, for 92% of the predicted data points are in the triple error dispersion band. Compared with the Nominal Stress Approach, the calculation process of the Theory of Critical Distance is not complicated and the results are more reliable.
2023, Vol. 44 
