On the characterization of the critical plane with a simple and fast alternative measure of the shear stress amplitude in multiaxial fatigue

The goal of this work is not only to characterize the critical plane determination as a well-posed problem, but also to propose an alternative measure for the shear stress amplitude. Usually such an amplitude is characterized by the radius of the Minimum Circumscribed Circle (MCC) to the shear stress vector history in a material plane. In the present paper, a measure which considers a Maximum Rectangular Hull (MRH) is discussed. Available experimental data involving proportional and nonproportional stress paths and a critical plane criterion are invoked to compare the fatigue strength estimates based on both methods (MCC and MRH). It is shown that the multiaxial fatigue estimates are improved for most data evaluated when the equivalent shear stress amplitude is computed in terms of the MRH.