SYMPOSIA PAPER Published: 01 January 1993

A Proposed Model for Biaxial Fatigue Analysis Using the Triaxiality Factor Concept


A biaxial fatigue model for axial-torsion strain cycling is proposed which includes elastic and plastic strain life regimes at elevated temperatures. The biaxial fatigue model is based on the concept that the transition from the plastic strain region to the elastic strain region on the bilinear fatigue life curve occurs at a cycle at which the elastic and plastic strain components of the total applied strain are equal. This transition corresponds to the intersection of the elastic and plastic strain lifelines of either a uniaxial or a torsional strain cycling condition. The transition point can combine the fatigue strength and fracture ductility coefficients of the material. The von Mises yield criterion was modified by using the Davis and Connelly triaxiality factor (TF) to account for the effects of the stress state and strain rate on the fracture ductility at elevated temperatures, which decreases as TF increases. Experimental data by the authors as well other available data were analyzed on the basis of the proposed model.

Author Information

Zamrik, SY
The Pennsylvania State University, University Park, PA
Mirdamadi, M
NASA-Langley Research Center, Hampton, VA
Davis, DC
The Pennsylvania State University, University Park, PA
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Developed by Committee: E08
Pages: 85–106
DOI: 10.1520/STP24797S
ISBN-EB: 978-0-8031-5243-4
ISBN-13: 978-0-8031-1862-1