Fatigue life evaluation of notched components affected by multiple factors

Abstract

Accurately assessing the fatigue performance of components is the key to ensuring structural integrity and reliability, but there is a lack of fatigue life prediction methods that effectively couple the stress gradient effect, the non-proportional additional strengthening effect, and the size effect. Accordingly, a fatigue life prediction model for notched specimens under multiaxial loading is established by analyzing the influence of tension–torsion proportional load and tension–torsion non-proportional load on the fatigue strength of notched specimens. Firstly, based on the energy critical plane method, the location of the critical plane is determined with the help of the coordinate transformation principle. Secondly, the material constant is used to quantify the level of cyclic strengthening, and a non-proportional additional strengthening function is proposed by considering the influence of phase difference. Thirdly, the influence of the non-uniform stress field at the notch root on the fatigue life is considered, and the distribution of equivalent stress on the specific paths is extracted and normalized to give an equivalent stress gradient factor. Then, a fatigue strength reduction factor is constructed by considering the influence of different notch geometrical parameters. Finally, a fatigue life assessment method for notched specimens is proposed based on the Manson–Coffin equation. With the help of the test data of three materials, En8, Al7050-T7451, and GH4169, the method is validated and compared with the calculation results of the Manson–Coffin equation, SWT model, and FS model. The results show that the prediction accuracy of the method in this study is high, which is located in the two-fold error dispersion band, and the prediction results are better than that of the other three models.