Most of the structural components undergo multi-axial stress and strain variations during cyclic loading and the prediction methods of fatigue life are still in the limelight of engineering science. One part of these methods are the so-called critical plane models, which assume that fatigue failure will occur on planes facing the highest value of a predefined parameter. In the past decades, a large number of experimental results were published, in which multiaxial fatigue phenomena was introduced from the point of view of the material background. According to these studies, many physical factors, like cyclic hardening, hydrostatic pressure etc. influence fatigue life but most of the fatigue life prediction methods only consider the stress and strain variation. In this work, a new critical plane parameter will be introduced, which includes the effect of accumulated equivalent plastic strain in one cycle, the mean value of stress triaxiality and mean stress, and the effect of shear strain on fatigue life is weighted by taking the ductility of the material into account. To be able to judge the effectiveness of the new parameter, five published experimental results with 145 load cases, including high and low cycle fatigue, were analysed, the elongation at fracture for the tested materials ranged from 14-160%. The results were compared to two commonly used methods and an improvement in the prediction capability of critical plane orientation was observed, and the prediction capability is not restricted to particular load cases as it is experienced in case of other methods.
Döbrentei et al. (Mon,) studied this question.