## 4 Conclusions  
Based on the results of the experimental and numerical work conducted in the present paper, the following scientific conclusions can be drawn:  
* Based on the linear-elastic strain energy density concept, a design limit curve was evaluated for the high-strength cast steel alloy G12 MnMo7-4+QT, summarizing the experimental results of three different specimen geometries tested at stress ratios of \(R=-1\), 0 and 0.5 into a unique scatter band, characterized by a scatter index  
Figure 15: Fatigue assessment results of the defect-afflicted cast steel specimens. of \(1:T_{\sigma}=2.08\). The fatigue assessment results of notched specimens tested at \(R=0.5\) were overestimated by the linear-elastic framework. This overestimation was attributed to the occurring mean stress relaxation at high maximum stresses, leading to an effective stress ratio of \(R<0.5\). * A numerical, energy-based methodology was presented to derive the parameter \(\Delta\overline{W}_{97.5\%}^{(e)}\), characterizing the fatigue behaviour of cast steel components affected by inherent shrinkage porosities. Utilizing finite element simulations based on planar projections of corresponding spatial imperfections, \(\Delta\overline{W}_{97.5\%}^{(e)}\) was statistically evaluated as the linear-elastic SED value, exceeding 97.5% of all SED values along the investigated defect contour. Utilization of \(\Delta\overline{W}_{97.5\%}^{(e)}\) to assess the long-life fatigue strength of defect-afflicted cast steel specimens tested at stress ratios of \(R=-1\) and 0 led to a sound agreement of the numerically and experimentally derived results. * The application of a TCD-based long-life fatigue assessment methodology presented in a preceding study yielded fatigue strength values, which showed an overall match to the results obtained by the SED-framework. The energy-based assessment results revealed an improved prediction accuracy, contributing to the simultaneous consideration of stresses and strains in a finite region of highly-stressed material. * Due to the linear-elastic framework, the derived fatigue parameter \(\Delta\overline{W}_{97.5\%}^{(e)}\) can be utilized to assess components in the finite-life regime as well. The assessment of 33 defect-afflicted large-scale specimens led to reasonable fatigue-life predictions, merging into the scatter band of the derived fatigue curve. As the established linear-elastic simulation using sub-modelling provided a methodology based solely on planar projections of complex-shaped spatial defect structures, computational efforts were reduced, depicting the presented framework as an engineering-feasible tool to assess the fatigue behaviour of cast steel components affected by manufacturing process-based imperfections. Further work might focus on the implementation of the non-linear material behaviour in terms of an elastic-plastic strain energy density approach. Ongoing work indicates that the application of the total strain energy density further narrows the scatter of the assessed data points, especially for high stress ratios. As the present study focusses on the assessment of defect-afflicted components subjected to uniaxial loading conditions, the investigation of multiaxial loading provides an interesting topic which should be addressed in future research work. Conceptualization, M.H., M.O. and M.S. ; methodology, M.H. ; software, M.H. and M.O. ; validation, M.H., M.O. and M.S. ; formal analysis, M.H. and M.O. ; investigation, M.H. and M.O. ; resources, M.S. ; data curation, M.H. ; writing--original draft preparation, M.H. ; writing--review and editing, M.H., M.O. and M.S. ; visualization, M.H. ; supervision, M.S. ; project administration, M.S. ; funding acquisition, M.S. All authors have read and agreed to the published version of the manuscript. This research was funded by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology, and Development. Not applicable.