Probabilistic Modeling of Fatigue Life Prediction of Notched Specimens Combining Highly Stressed Volume and Theory of Critical Distance Approach

Notch and size effects significantly influence the fatigue performance of engineering components, which is crucial for ensuring structural integrity. A novel probabilistic fatigue life prediction Kt-V-L model considering both the size and the notch effect, based on the theory of critical distance L (TCD) and the improved highly stressed volume V (HSV) method, is proposed in this study. The new definition more accurately characterizes fatigue damage and accumulation, overcoming the underestimation issues of traditional HSV methods under high-stress or low cycle fatigue (LCF) conditions. Specifically, the Weibull distribution is also proposed to characterize the material fatigue failure probability. The experimental data of 26Cr2Ni4MoV, En3B, and TC4 materials with varying notched sizes are utilized for the model validation and comparison. In addition, the predictive ability of the point method (Kt-V-L-PM) and line method (Kt-V-L-LM) under the novel proposed model was explored and evaluated. The predicted lives of 26Cr2Ni4MoV specimens fall within the ±2 scatter band of the Kt-V-L-LM, while the Kt-V-L-PM shows increasing deviation with larger notches due to its limited ability to capture stress gradients. For En3B and TC4, the predicted lives are within ± 2 life factors, verifying the model’s reliability and accuracy. Furthermore, fracture morphology analysis reveals the influence of notches on fatigue performance and elucidates the fracture failure mechanisms.