Effects of cyclic frequency and contact pressure on fretting fatigue undertwo-level block loading

Fretting fatigue tests involving the contact of flat and cylindrical titani um alloy Ti-6Al-4V surfaces, and constant- and two-level block remote bulk stresses are described. The constant-amplitude tests have been performed at cyclic frequencies of 1 and 200 Hz. The two-level block spectra involve th e superposition of a l-Hz, low-cycle fatigue (LCF) constant-amplitude compo nent and a 200-Hz, high-cycle fatigue (HCF) component. Two values of contac t pressure are considered. The cyclic frequency of 200 Hz is found to curta il the constant-amplitude fretting fatigue life regardless of the contact p ressure applied. Increasing the contact pressure reduces life at 1 Hz but d oes not have any effect at 200 Hz. Under two-level block loading, the frett ing fatigue life is determined primarily by the stress amplitude and high-c yclic frequency of the HCF component of the load spectrum. The LCF componen t is found to play a secondary role in the determination of the two-level b lock fretting fatigue life. Fracture topographies for the different test co nditions are documented.