The present thesis deals with the numerical analysis of specific failure modes of high loaded gear sets. These are pitting and flank breakage. Aim of the work was the development of a tool, which is capable of analysing the local stress condition and assessing the risk of pitting and flank breakage. At the beginning, an overview of the occurring stresses in a tooth of a gear is given. A strength hypothesis must meet some requirements in order to evaluate the stress conditions in a tooth. For this purpose, different strength hypotheses were investigated, and the shear stress intensity hypothesis was selected for further implementation. This very theory is able to provide the assessment of the material exposure in a gear flank comparable to the risk of pitting and flank breakage. A tool has been programmed and can be universally used to process loading conditions for evaluating material exposure of any gear set. With this theory the possibility of assessing the local loading conditions of a tooth of a gear is given, involving the local material properties. The basis of these calculations are the results of finite element simulations. A sensitivity study allowed a fine adjustment of the tool and determined the magnitude of the influence of important parameters of the tool. Furthermore, a concept of considering the number of load cycles was implemented. The last chapter of this thesis will ultimately be separated in two parts. First, the application of the tool will be done on bevel gears of a differential gear set with various loading conditions. The second part deals with bevel gears with an additional axial offset, the so-called hypoid gears. The results then subsequently have been compared to measured results from the testbed. The occurrence of pitting and flank breakage could be determined at a bevel and a hypoid gear set for certain loading conditions. With the results of the tool the detection of pitting and flank breakage at a gear tooth is possible. By incorporating the load cycle number, a conservative estimate of the lifetime of a gear set can be made. This developed method and final workflow should build a basis for early assessments of risks of pitting and flank fracture in bevel gear sets and make a contribution for assessing the load capacity in prospective design processes.