On characteristic lengths used in notch fracture mechanics

In this paper, four kinds of characteristic length parameters used in a local notch fracture criterion are presented: (1) a characteristic length ρ c generally connecting to the notch radius, (2) a characteristic distance X c considered as intrinsic to material and connected to the microstructure, (3) a critical distance d 0 considered as intrinsic to material and connected to the fracture process zone, (4) an effective distance X ef considered as a characteristic of the stress distribution. Each approach is discussed. The paper ends with the author’s opinion about the different methods.