TENSION AND TORSION FATIGUE TESTING OF A NEAR-ALPHA TITANIUM-ALLOY

A comprehensive programme of research has been devised to produce a biaxial fatigue database for the titanium alloy IMI685. The present paper describes the experimental techniques employed during the programme and examines analytical methods of describing fatigue under conditions of tension and torsion loading. The results from cyclic tension and torsion tests are included for the alloy in its basketweave and aligned microstructural condition. The tension and torsion data compare favourably over a range of lives from 10(3) to 10(5) if a modified version of the von Mises criterion for effective stress is used. The problem of defining a consistent failure criterion for torsion tests is addressed. To this end, the use of theta creep analysis software is introduced. It was found that this approach provided a satisfactory measure of torsional life for specimens that failed by a variety of mechanisms.