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The fatigue life of an engineering component is often an important design consideration, but the understanding of this property is somewhat limited. Engineering components often experience stresses due to cyclic multiaxial loads, which eventually cause fatigue failure. The majority of research into fatigue failure, however, has been devoted to modeling and predicting the fatigue life of components subjected to uniaxial loading. Uniaxial loading is easier to test and understand than multiaxial loading, but it is not as likely to occur in applications as multiaxial loading. Several approaches to modeling multiaxial fatigue life have been developed, including the Sines Model and the Findley Model. In order to test the validity of each model, reliable multiaxial fatigue test equipment is required to generate accurate data. Past efforts have attempted to validate multiaxial fatigue life models, but were performed without the benefit of reliable test data. Recently, the Air Force Research Laboratory obtained a MTS 809 Axial/Torsional Test System that is capable of generating accurate multiaxial fatigue data. Throughout this project, the MTS tension-torsion machine was used to generate reliable torsional and multiaxial fatigue data for Ti-6Al-4V test specimens. The data generated by the torsional fatigue tests was used in conjunction with previously generated axial fatigue data to model and predict the fatigue life of Ti-6Al-4V test specimens subjected to multiaxial loading. The MTS tension-torsion machine was the used to test Ti-6Al-4V test specimens under multiaxial loading. The fatigue life of the test specimens subjected to multiaxial loading was then compared to the fatigue life predicted by the models to evaluate how effectively each model predicted the fatigue life of Ti-6Al-4V.

Publication Date


Project Designation

Honors Thesis

Primary Advisor

Robert A. Brockman

Primary Advisor's Department

Structures and Mechanical Systems Group (Research Institute - Aerospace Mechanics)


Stander Symposium poster

Evaluation of Multiaxial Fatigue Models for Ti-6Al-4V