Research on local cyclic plastic behavior and fatigue life prediction of notched components based on digital image correlation

Abstract

In this study, the digital image correlation (DIC) method was utilized to monitor the evolution of the strain at the notch root as the number of cycles progresses. The influences of notch type, notch size, and external load (load amplitude F_a, load ratio R) on the evolution of the strain at the notch root and the ratcheting strain rate were investigated. Considering the evolution of the ratcheting strain rate at the notch root, a fatigue life prediction model applicable to notched components with different notch sizes and under different load conditions was developed in terms of the stress concentration factor, the notch nominal stress amplitude, and the load ratio. Compared with the results of the Coffin − Manson model for predicting low − cycle fatigue life using the half − life strain amplitude, most of the predicted values of the proposed model in this paper are within the 1.5 times error band, with the maximum not exceeding the 1.75 times error band, while most of the predicted values of the Coffin − Manson model exceed the 2 times error band. The results indicate that the method in this paper has better prediction accuracy. Additionally, the mean square deviation values of the prediction results of the prediction model considering notch size, load amplitude, and load ratio are reduced by 0.02826, 0.04776, and 0.0424 respectively. The proposed method has certain reference significance for the fatigue analysis of notched components.