Crack growth in Ti-6Al-4V under the conjoint action of high and low cycle fatigue

Abstract The growth of fatigue cracks in Ti-6Al-4V subjected to high-frequency vibratory stresses superimposed on a major stress cycle of large amplitude is studied. When the vibratory stresses, or minor cycles, are inactive, the fatigue cracking processes are with the major-cycle crack growth. Once active, the minor-cycle crack growth may either generate extensive cyclic cleavage or increase the separation of the fatigue striations associated with the periodic major cycles. The contribution of the minor cycles to the total growth rate depends upon their relative size and number, the overall growth rate being predicted by the method of linear summation. In the presence of sustained vibrations, the onset of minor-cycle crack growth limits the useful life of critical rotating components.