Technical components are subjected to cyclic loading conditions that can be arbitrarily complex in the most general case. For analytical fatigue strength verifications in the finite life regime both the uniaxial material characteristics by means of Wöhler curves as well as a representative equivalent fatigue damage parameter (FDP) for multiaxial cyclic loadings have to be determined. For simple loading conditions, the fatigue assessment can be performed using well-known and verified strength hypotheses for quasi-static loading conditions. However, for complex non-proportional cyclic loading conditions with rotating principle stress directions the application of these hypotheses is not sufficiently verified. Hence, advanced stress, strain or energy based strength hypotheses in critical plane formulation are used. These hypotheses require considerable numerical efforts.
The fatigue concept (MPA AIM-Life) enables an assessment of complex fatigue loading conditions with different advanced strength hypotheses. An interface to the finite element code ABAQUS allows the fatigue assessment of complex component geometries. Based on fatigue tests of specimens made from ferritic and austenitic materials under uniaxial and multiaxial loading conditions (tension/torsion) the accuracy of different strength hypotheses is demonstrated. Therefore the fatigue analysis assessment included in codes and standards is compared to different advanced fatigue damage parameters.