A unified prediction model for physically small crack and long crack growth based on modified CTOD

A unified model based on CTOD is proposed to calculate the growth rate of physically small crack (PSC) and long crack (LC). Firstly, an in-situ SEM testing under the single overload condition is performed to reveal that CTOD could be the unique driving parameter for fatigue crack growth (FCG). Then, a unified FCG model is established based on the modified CTOD formula which considers the main physical mechanisms of small crack effect. Additionally, a theoretical equation of the transition crack length from PSC to LC is given. Finally, several datasets of different materials are used to validate the model.