Effect of the free surface on the fatigue crack front curvature at high stress asymmetry

The purpose of this paper is to investigate the effect of the vertex singularity on the fatigue crack front behaviour. Single edge notch bend specimens of steel EA4T and aluminium alloy 7075 of various thicknesses are subjected to the cyclic loading and the angles of the fatigue crack front curvature was measured. The experimental procedure is simulated using finite element analysis. Two methodologies used for the fatigue crack front shape estimation are compared. One is using stress singularity exponent as a controlling parameter and the second one is using stress intensity factor. Both methodologies provide comparable results of crack front formation process and they are in very good agreement with experimental results.