Modeling of Surface Crack Advance in Round Wires Subjected to Cyclic Loading

This paper shows the evolution of the surface crack front in round bars constituted of different materials (determined by the exponent m of the Paris law), subjected to fatigue tension loading (with free ends) or fatigue bending loading. To this end, a numerical modeling was developed on the basis of a discretization of the crack front (characterized with elliptical shape) and the crack advance at each point perpendicular to such a front, according to a Paris-Erdogan law, using a three-parameter stress intensity factor (SIF). Each analyzed case was characterized by the evolution of the semielliptical crack front, studying the progress with the relative crack depth a/D of the following three key variables: (i) crack aspect ratio a/b (relation between the semiaxes of the ellipse which defines the crack front); (ii) maximum dimensionless SIF; and (iii) minimum dimensionless SIF.