Volume 35, Issue 5 (September 2007)
Crack Growth Behavior in Overloaded Specimens with Sharp Notch in Low Carbon Steel
The purpose of the present study is to evaluate fatigue crack propagation after tensile overloading. A 6-mm long u-shaped notch was cut in the center section of the specimen. Notch root radii of 0.1, 1, and 2 mm were chosen for ρ. 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. A special investigation was made into the results for ρ=1 mm. After overload, retardation of crack growth was observed under R=0 and −1 for the notched specimens and center-cracked specimens. However, where R=−1.5, crack growth acceleration 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 the effective stress intensity factor range after 0.2 mm of crack growth from the notch root.