A promising method for the analysis of notch effect on fatigue strength: Strain energy density approach

Sih proposed the strain energy density (SED) factor S, which was defined as the product of the SED and a critical distance from the point of singularity. Thus, the failure is controlled by the critical value. The SED approach is based on the idea that under tensile stresses, failure occurs when the strain energy density equals to the critical value which needs a precise definition of the related control volume. If the material is ideally brittle, the value of critical value can be evaluated. For the case of blunt notch, the cross section area is treated as a crescent shape with radius being its maximum width as measured along the notch bisector line. Under mixed-mode loading, the control area is no longer centered with respect to the notch bisector. It is centered on the point where the maximum principal stress reaches its maximum value. Unlike the calculation of notch stress intensity factor, the mean value of SED on the control volume has the advantage that it can be determined with high accuracy by using coarse meshes in finite element calculations.