Modern production run castings are widely used in engineering and automotive construction. Particularly in the case of complex geometries, such as the cylinder housing, post-processing of the surfaces is only possible with a high manufacturing effort, respectively some surfaces cannot be machined due to restrictions of accessability leading to as-cast surfaces on the part. However, as-cast surfaces have a significant impact on the fatigue strength behaviour and therefore on the lifetime of components. To assess the fatigue strength of cast aluminium surfaces, a sub-area-based surface layer assessment model was developed within the CD Laboratory for Manufacturing Process-Based Component Design. The purpose of this master thesis is to evaluate and validate this method taking into account an additional casting orientation and load direction, a more component-like specimen geometry and statistically extending this method for an additional cast Al-Si-alloy. The investigation comprises two materials, EN AC-42100 and EN AC-46200, for each one half-ring-shaped specimens are taken out from cast series components and are subsequently exposed to tumescent bending loading. In addition, the surface of the half rings is scanned with a digital optical microscope and the characteristic values pit depth Sv and multiaxial notch root radius ρ are determined. The tested specimens are analyzed by fracture surface analysis to determine the crack initiating defect. With these findings, the surface layer assessment model can be applied enabling the statistical evaluation of the long-life fatigue strength. The comparison of the surfaces shows that the material EN AC-42100 (K_t50 = 3.36) exhibits 30 % increased stress concentration factors than the material EN AC-46200 (K_t50 = 2.32). Therefore, one would expect that the long-term fatigue strengths are directly proportional, but the fatigue tests are contrary. The unified experimental long-term fatigue strength of the material EN AC-42100 is σ_a50 = 0.46 and of the material EN AC-46200 σ_a50 = 0.38. This is caused by the significant sub-surface porosity of the EN AC-46200 material of approximately 0.5 - 2 % in the highly stressed areas. The comparison of the experimentally determined fatigue strength with the sub-area-based fatigue strength resulting from the surface layer assessment method shows that in 93 % of all cases the experimental fatigue life matches the calculated in a conservative manner. Thus, it is statistically proven that the sub-area-based surface layer fatigue assessment is well applicable to aluminium castings independent of the primary solidifcation direction.