2025 Volume 66 Issue 6 Pages 690-697
The effects of the normalized stress intensity factor gradient, C, on the relationship between crack propagation rate, da/dN, and stress intensity factor range, ΔK, in the near-threshold regime were investigated. When the force shedding rate at each crack extension step was less than 2%, and the force shedding interval for crack extension was 50 µm, the value of C exceeded −0.4 mm−1 and a unique da/dN–ΔK relationship independent of the value of C was observed at the same force ratio.
Additionally, a method for the automatic evaluation of crack closure was proposed. In the evaluation of crack closure by the compliance method, compliance measurement were utilized to average strains during loading and unloading. In the relationship between the averaged nonlinear strain and applied force, where the averaged nonlinear strain was normalized by being divided by the linear strain at the same applied force, the crack opening/closing point was clearly identified. This approach allowed for the effective stress intensity factor range (ΔKeff) to be evaluated automatically.
This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 73 (2024) 889–895. Abstract and Captions are slightly modified.
