Y. Hos et alii, Frattura ed Integrità Strutturale, 34 (2015) 133-141; DOI: 10.3221/IGF-ESIS.34.14 140 describing the process should therefore be based on a crack driving force parameter of the elastic-plastic fracture mechanics. Here, the closure-free cyclic  J eff is applied first to the uniaxial case. Even for this relatively simple case the problem of realistically estimating the effective ranges becomes apparent. The simulation with a finite element based node release scheme requires the application of an advanced plasticity model which is superior to the Chaboche model as it is supplied in commercial software. Especially ratcheting should be described realistically as this process occurs near the crack tips in a very pronounced way. Otherwise the predicted plasticity induced crack closure is unrealistic. Without a satisfactory solution for determining the plasticity induced crack closure the non-proportional mixed mode case is hard to tackle. First measurements have shown that – and this is obvious – friction and roughness induced closure processes come up, especially for non-planar crack surfaces. This modelling challenge will have to be met in the future. 10 -4 10 -3 10 -2 da/dn in mm/cy cle 1 5 10 50 100  J eff in N/mm open symbols: crack closure from simulation closed symbols: crack closure from measurement circles: left crack squares: right crack Figure 10 : Experimentally determined fatigue crack growth rates from specimen R-001, pure tension-compression with max 45kN F  and 1 F R   , steel S235, plotted over  J eff the latter calculated for measured and simulated effective ranges. A CKNOWLEDGEMENT he German Research Foundation (Deutsche Forschungsgemeinschaft) is greatly acknowledged by the authors for financial support under grant Vo729/13-1. R EFERENCES [1] Zerres, P., Vormwald, M., Review of fatigue crack growth under non-proportional mixed-mode loading, International Journal of Fatigue 58 (2014) 75–83. [2] Chaboche, J.L., Dang Van, K., Cordier, G., Modelization of the strain memory effect on the cyclic hardening of 316 stainless steel, 5 th Int. Conf. Struct. Mech. in Reactor Techn., L (1979) L11/3. [3] Boller, Chr., Seeger, T., Materials data for cyclic loading, Elsevier, 1 (1987). [4] Zerres, P., Brüning, J., Vormwald, M., Risswachstumsverhalten der Aluminiumlegierung AlMg4.5Mn unter proportionaler und nichtproportionaler Schwingbelastung, Materials Testing, 53 (2011) 109-117. [5] Zerres, P., Brüning, J., Vormwald, M., Fatigue crack growth behavior of fine-grained steel S460N under proportional and non-proportional loading, Engineering Fracture Mechanics, 77 (2010) 1822-1834. [6] Hos, Y., Vormwald, M., Freire, J.L.F., Using digital image correlation to determine mixed mode stress intensity factors in fatigue cracks, Proceedings of COTEQ 2015, Conference on Technology of Equipment, organized by ABENDI, Brazilian Society for NDT and Inspection, (2015). [7] Hos, Y., Vormwald, M., Freire, J.L.F., Measurement and simulation of strain fields around crack tips under mixed- mode fatigue loading, Frattura ed Integrità Strutturale, 42 (2015) 42-55. DOI: 10.3221/IGF-ESIS.33.06. T