A new prediction model of fatigue crack expansion rate based on HRR stress–strain field

Abstract

In this paper, a new model (Cumulative Fatigue Damage-CFD) is constructed to accurately predict the expansion rate of type I fatigue cracks based on the damage accumulation theory. Utilizing the HRR (Hutchinson-Rice-Rosengren) stress–strain field at the crack tip, the model adopts a new size parameter r_c to characterize the size of the cyclic plastic zone at the crack tip, defines a new damage variable D, and derives the theoretical formula of the fatigue crack extension rate model by combining with Miner’s linear cumulative damage theory. The prediction effect of the model was verified using 14 metallic materials and compared with the Pandey (Strain Energy Theory-SET), Chen-Cai (CFD) and LiuX (SET) models. To quantitatively and accurately evaluate the predictive efficacy of the model, a quantitative evaluation method called “point-line distance” is proposed, and a comprehensive comparison is made in terms of three key dimensions: safety, accuracy and economy. The results show that the new model (CFD) can accurately predict the expansion rate of type I fatigue cracks, and the model applies to a wide range of metallic materials and has excellent prediction results, which can better meet the engineering needs for safety and economy.