Fatigue damage evolution in structural materials above and below the fatigue limit

摘要

The evolution of fatigue damage in four different structural materials has been studied experimentally and the main stages of the damage and the relevant mechanisms were demonstrated. The cyclic hardening-softening curves, the cyclic stress-strain curves and the fatigue life curves for polycrystalline copper, 3 16L steel, duplex steel and Al-Li alloys were reported. The changes of their internal structure, the evolution of the surface relief and the kinetics of early crack growth were studied at the same time. The most important mechanisms that represent physical realisation of the fatigue damage were exposed and their relative importance for the determination of the fatigue life was discussed.