Evaluation of Crack Growth in Overloaded Specimen with Sharp Notch

摘要

A simple method of evaluating the crack propagation rate of a specimen with sharp notch by using an effective stress intensity factor range was proposed. This study also had a special purpose of evaluating the crack propagation after overload. A 6mm long U-shaped notch was cut in the center section of the specimen. The notch root raidus ρ was chosen as 0.1mm and 1mm. These were regarded as center notched specimens. The crack propagation behavior of these specimens was compared with a center cracked specimen. Push-pull fatigue tests were carried out under stress ratios R=0, -1, and -1.5. After overload, retardation of crack growth was observed under R=0 and -1, in the cases of the notched specimen and center cracked specimen. However, where R=-1.5, the acceleration of crack growth was observed after overload in both types of specimens. Even though crack growth was accelerated or decelerated, the rate was able to be evaluated by effective stress intensity factor range. The effective stress intensity factor range of the center cracked specimen could also be applied to that of the notched specimen with, ρ=0.1mm and 1mm.