Volume 22, Issue 2 (March 1994)
Fatigue Crack Propagation in a Specimen with a Complicated Cross-Section; Characterization of the Stress Intensity Factor
In order to predict the fatigue life of machine equipment, the fatigue crack propagation law has up to now been investigated using specimens with a simple cross-section shape. In this study, a specimen with three grooves cut in the loading direction was used to clarify crack propagation and crack closure behavior at points of discontinuous change in thickness. It was found that the crack propagation curve showed a complicated variation in the vicinity of the grooves and that the variation of crack closure behavior correlated well with it. The stress intensity factor was evaluated using the calibration curve between the crack propagation rate and the effective stress intensity factor range obtained from a similar smooth specimen. Results showed that the stress intensity factor of the grooved specimen was higher in front of the first groove and lower behind it, compared to the smooth specimen. As the crack crossed the first groove, the crack propagation rate exhibited a local maximum as a function of the maximum value of stress intensity factor.