Comparison of Notch-Stress with Strain-Controlled Low Cycle Fatigue of Alpha-Beta Titanium Alloys

摘要

Prior studies of the present authors provided two different tests of low cycle fatigue endurance of the same set of titanium alloys. Strain controlled push-pull deformation of axial specimens covered crack initiation life of up to 1000 cycles. Notch stress controlled tensile load cycling extended the range to 1 million cycles. All of Ti-6Al-4V, the test materials varied in oxygen content and in effective grain size. The results could not be compared directly because of the disparity in the controlling variables; strain and stress excursions respectively. It is found that both kinds of data form a consistent set if the total stress excursion is used as a basis of comparison, except for cases of overly high notch loading. The earlier strain-controlled results were modeled by a cumulative cyclic creep strain criterion for crack initiation. This criterion appears to embrace also the notch stress results, thus providing a promising means for extrapolating fatigue data. (Author)