Fatigue strength assessment according to the FKM-guideline in case of non-proportional stresses

For a fatigue assessment of mechanical parts which are subject to cyclic loading, and in particular non-proportional stresses, standards like the FKM-guideline only provide conservative as-sessment procedures. Complexity of determining principal stress amplitudes is caused by continuously varying principal stress directions. Therefore Ingenieurbüro Fiedler GmbH developed an innovative tensor transformation approach to evaluate the principal stress amplitudes in case of non-proportional stresses. Compared to the approximate assessment as recommended by the FKM-guideline, the accuracy of life-time assessment can be improved significantly.