Fatigue analysis of a round bar with a sickle-shaped crack

A step-by-step numerical procedure is employed to analyse the fatigue crack propagation of an initial sickle-shaped crack in a smooth round bar under cyclic tension or bending. The crack front is described by an elliptical arc during the whole fatigue life. The stress-intensity factor along the crack front is determined through a linear elastic finite element analysis for different values of crack aspect ratio and crack depth, and the fatigue crack growth is evaluated by applying the Paris-Erdogan law. The results are plotted in terms of stress-intensity factor range variations, crack paths, crack depth evolutions and crack shape evolutions. By varying the type of loading, a slight effect on the aspect ratio variation can be observed, whereas the influence on the crack depth evolution curves is remarkable.