Abstract
Cyclic plastic response of a ferritic stainless steel in a wide domain of plastic strain amplitude was measured. Cyclic hardening-softening curves show important cyclic softening during most of the fatigue life. Cyclic stress-strain curve and the Manson-Coffin life curve have different slopes in the domain of low and high strain amplitudes. Derived Wöhler curve can be approximated by a single power law in a wide domain of stress amplitudes. Study of dislocation structures using transmission electron microscopy revealed different internal structures in two domains of plastic strain amplitude. The shape of the cyclic stress-strain curve and cyclic softening were discussed in terms of dislocation structure produced during cyclic straining.

Key words
cyclic plasticity, ferritic steels, dislocation structures, cyclic softening, fatigue life

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