New Multiaxial HCF Criteria Based on Instantaneous Fatigue Damage Tracing in Components with Complicated Geometries and Random Non-Proportional Loading Conditions

Majority of the available high-cycle fatigue (HCF) criteria have been proposed based on definition of an equivalent stress. Although these criteria have shown good agreements with results of the fatigue tests performed in particular conditions, majority of them do not consider all effects that have to be taken into account: mean normal and shear stresses, phase shift and different or random frequencies of the stress components, relative time locations of the extrema of the time histories of the stress components, etc. In the present article, based on the microscopic fatigue failure observations reported by some prominent references, new HCF criteria are proposed in three categories to overcome the mentioned shortcomings: (1) critical plane approach; (2) energy approach; and (3) integral approach. A relevant fatigue life assessment algorithm is also proposed and results of the prominent criteria are compared with results of the proposed criteria as well as the experimental results prepared by the author. To introduce a comprehensive study, the criteria are evaluated for components with complicated geometries under proportional, non-proportional, and random loadings. Results reveal that predictions of the proposed energy and integral approaches are more accurate.