Components made of cast materials are of great importance in many branches of the industry. The freedom of design as well as the economical serial production are the motivating forces to facilitate cast components. However, casting as manufacturing process is linked with mostly unavoidable, production technology-based casting defects that severely differ in their final geometry. These imperfections complicate the fatigue assessment of as-cast structures based on quality classes extremely. In this master thesis a new design methodology for notch stress intensity-based fatigue assessment of casting defect afflicted parts is presented. Thereby, an extensive simulation chain was developed that uses a cellular automaton to produce numerically generated virtual pore structures, which allow the numerical fatigue strength assessment of defect afflicted material. These virtual pores are similar to real casting defects in their geometrical appearance and are parametrizable by the user. Beside the adjustable generation of virtual pore structures, the interactive simulation chain enables an automated fatigue assessment. A comparison between the numerically calculated fatigue results of virtual pores and the experimentally derived test data shows a realistic approximation of the actual bearable stresses of real casting defects. The simulation chain delivers slightly conservative results. Parameter studies where carried out to evaluate the influence of the angular position of the pore. These studies resulted in plausible trends of the NSIF and the assessed fatigue strength, where the NSIF increases with increasing rotation angle, which causes the derived fatigue strength to decrease. A comparison between the stress distributions on the surface of real and virtual casting defects delivered similar location parameters of the distributions, which only differ about six percent on average. Therefore, the presented design methodology delivers cyclic fatigue assessment results, which lead to the conclusion of a similar damage behaviour of numerically generated and real pores. This allows a fatigue strength assessment of representative cast steel defects without the need of CT-scans for characterization of casting pores. The presented simulation chain delivers a geometrically comparable defect structure with an included, mapped fatigue strength assessment, which allows the catalogization of manufacturing process-based pores according to cast quality classes in principle. This establishes the basis for a standardized, economically-optimized design of cast steel structures.