An Alternative Measure for the Shear Stress Amplitude in Critical Plane Based Multiaxial Fatigue Models

ABSTRACT. The goal of this work is to propose and to assess an alternative measure for the shear stress amplitude in critical plane based multiaxial fatigue criteria. Usually such amplitude is characterized by the radius of the minimum circle circumscribing the shear stress history in a material plane. Here, an alternative measure which considers the maximum circumscribed rectangle (MCR) in terms of its Frobenius norm is considered. The computation of the shear stress amplitude by the minimum circle and by the maximum rectangle was conducted for a number of experimental data available in the literature involving proportional and nonproportional stress paths. Then a critical plane criterion was invoked to estimate the fatigue endurance based on such values. It is shown that the multiaxial fatigue estimates were improved for most data evaluated when the shear stress amplitude was computed in terms of the maximum box. Some critical assessment concerning the classical definition of the critical plane was also addressed in this work