Numerical Investigation into the Impact of Dimensional and Geometric Tolerances on the Long-life Fatigue Strength of Mechanical Components

Complex assemblies need to address ever-increasing cost-efficiency requirements. Therefore it is necessary to max out permissible stresses during the design process. In addition, there is a need to match estimated lifetimes more and more exactly, so it is important to predict accurately the effective stresses on mechanical parts. This paper examines the impact of size and geometric tolerance on stress and long-life fatigue strength. For this purpose an in-house software tool has been developed which makes it possible to generate a CAD model with simultaneous consideration of all geometric tolerances. The resultant model has a stochastically deformed shape but still corresponds to its engineering drawing. In a second step an FE analysis is performed to determine the influence of these tolerances on the long-life fatigue strength of the parts. These results are compared with the results for the model without the geometric tolerances (using only nominal CAD data).