Nowadays lifetime calculation in the high cycle fatigue region is
commonly based on S/N curves which are modified by different influences
to ensure accurate results. Especially the application of these models is
important when small components with complex stress distributions are used.
The influence of the stress distribution was considered by the stress gradient
approach which is implemented in the lifetime tool FEMFAT. Specimens
with diameters of D4mm and D7.5mm were used to examine the effect of the
calculation modified by the stress gradient. On the one hand regarding
different types of this approach it can be shown that the results fit very well
compared to the testing results but on the other hand a big difference was
observed when the gradient increases by smaller specimen sizes.