Stress intensity concept

In contrast to the notch stress concept, the stress intensity concept (SIK) does not model a fictitious notch radius, but a sharp V-notch, i.e. ρ_f = 0.0. This means that there is a singularity in the stress field, which is described with the help of stress intensity factors (SIF). They quantify the magnitude of the asymptotic stress distribution. 

On the basis of the polar coordinate system, the local stress distribution is determined near the singularity (stress spike) with the modes I and II of the SIF. Generally local network refinements are necessary for in order to detect the non-linear stress characteristic can. Alternatively, a network with constant element sizes is used in the "Peak Stress Method". This has the advantage that the amount of computation and modeling depth can be kept within limits. After calibration, it is possible using an analytical equation, the stress intensity factor in response to the peak stress be determined.  

Another option is to establish a relationship between the "strain energy density" and the SIF. More details on this can be found in the literature.