Normal load effects in fretting fatigue of titanium and aluminum alloys

Normal pressure in the fretting fatigue process is one external variable that affects structural component life and its effect is relatively easy to study under controlled laboratory conditions. Consequently, specimens of Ti-6Al-4V (MA) and aluminum 7075-T6 were tested under varying normal pressure conditions to evaluate its effect on these two important materials. The results show that Ti-6Al-4V (MA) (mixed h.c.p. and b.c.c. structure) and aluminum (f.c.c. structure) behave differently under similar normal pressure conditions. The aluminum undergoes significant life reduction from fretting damage but appears to be insensitive to normal load changes. On the other hand, the life dependency of the titanium to fretting damage is very sensitive to normal pressure. This phenomenon is explained in terms of local crystallographic effects and microscopic variations in toughness of the two materials.