Cyclic stress-strain curves, fatigue life curves, shape and area of hysteresis loops, and dislocation substructures were investigated on polycrystalline copper and copper-31% zinc specimens cycled with constant plastic strain amplitudes in low amplitude, high cycke region (N > 105 cycles to fracture). In particular, the aim was (1) to determine how far a cyclic mechanical equation of state can be applied for Cu (way slip materil) and for CuZn (planar slip material) in this low amplitude region, (2) to determine to what extent the dislocation substructures depend on the prior deformation history and (3) to check the validity of the semi-empirical relations between the plastic parameters and the number of cycles to fracture, which are often used for high amplitude cycling, in the low amplitude region.
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