Today, a big challenge for engineers is the market's demand to meet the lowest possible costs. Through the process of optimal construction, the constructor has the opportunity to meet market requirements at the lowest possible costs. The procedure includes defining sets of dimensional parameters by specifying an objective function with constraints that represent a function called the constraints. This final thesis includes the lifetime calculation procedure on one example of a simplified crankshaft model. In the introductory part, the importance of the optimization process is described and the ways of approaching the process itself are described, as well as the importance of calculating the service life for the purpose of determining the service life of the structural part until failure occurs. The thesis describes in more detail the mathematical formulation of the optimization process itself, and it also contains described methods with the help of which the process itself is performed. The largest part of the thesis includes a description of the optimization procedure and calculation of lifetime on one example of a simplified crankshaft model using the program package: "ANSYS - Workbench". The last chapter presents the analysis and comparison of the results. In the last chapter, the results of the calculation of the lifetime of the original crankshaft model were compared with the calculated lifetime of the optimized model.