## 4 Evaluation of Quality and Efficiency
### Quality and Efficiency Criteria  
In order to evaluate the methods described, the load-notch-strain curves generated with the methods described in Section 3 are compared to a reference load-notch-strain curve. The reference load-notch-strain curve is regarded as the \"true\" load-notch-strain curve and is determined by FEA with a very fine mesh. Alternatively, experimentally determined load-notch-strain curves or experimentally determined fatigue lives could also be used as a reference. However, this has the decisive disadvantage that certain simplifying assumptions made by the FKM guideline nonlinear cannot be exactly reproduced by real components or specimens. These include, for example, the description of the material behaviour by the approach according to Ramberg and Osgood or the assumption of a cyclically stabilized material behaviour. Furthermore, the comparison of calculated and experimental results is expected to show a bias in most cases. This bias, however, is due to the calculation concept itself and the accuracy of the FKM guideline nonlinear, and not the procedure for estimating the load-notch-stain-curve that shall be examined in this contribution. The approximated load-notch-strain curves generated using the methods described in Section 3 aim to reproduce the true curve as accurately as possible. Since the simplified generated load-notch-strain curve and the reference curve each consist of pairs of values from elastic stress and notch strain, and the associated local stress is also used as an input value for service life calculation in addition to the notch strain, a quality evaluation based on the load-notch-strain curve alone does not lead to meaningful results as a basis for a recommendation. The more interesting result for a user is the effect on the calculated service life. Therefore, the latter is used for the quality evaluation. For the service life calculation, the previously mentioned algorithms of the FKM guideline nonlinear [25] are used. For the load-notch-strain curve, the curves determined with FEA are used. The calculation procedure--reduced to the most necessary steps--is shown schematically in Figure 11 and explained briefly below. On the one hand, information about the component, such as the geometry and tensile strength of the material, are required as input variables. On the other hand, the load-time history and load configuration, meaning the vector of all forces and/or moments, must be known. The starting point for describing the material behaviour is the tensile strength. From this, the corresponding cyclic material properties K\({}^{\prime}\) and n\({}^{\prime}\) are estimated with the method according to [PERSON] et al. [45; 46]; see Equations (4) and (5). The quality ratings in this contribution are limited to estimated cyclic properties for the material group steel. However, a significant deviation in the findings determined in this manner to other material groups is not expected. With the cyclic material properties estimated in this way, the material law can be inputted into the FEA to determine the load-notch-strain curve. The geometry is then transferred to the FEA, loads are applied according to the specified load configuration, and the load-notch-strain curve is determined as described above, considering the maximum load occurring in the load-time history. In addition, the load parameter Wohler curve is estimated from the tensile strength, which also takes into account the influences of geometry and load type by considering support factors due to stress gradients and size effects. Thus, the service life is determined for a failure probability of 50%. Since the service lives are only used for a qualitative comparison, the application of the safety concept contained in the FKM guideline nonlinear is not necessary. The safety factors are set to 1. Another input variable is the load on the component.