| Abstract: | The mechanical behaviour of fatigued pure nickel monocrystals oriented for single slip was studied in push-pull tests at room temperature. Especially the cyclic hardening curves, the cyclic stress-strain curve and the shape changes of the hysteresis loops were investigated in the range of the plastic resolved shear strain amplitude, γap, between 10-10 and 10-2. In this range the cyclic stress-strain curve exhibits a plateau which is related to plastic strain localization in persistent slip bands (PSBs) developing within the residual “matrix” volume. Using a two-phase model the cyclic saturation mechanical behaviour of the PSB and the matrix volumes has been determined. An explanation has been given of the constant plateau stress τB of the cyclic stress-strain curve by taking into account the nucleation stress for PSBs depending on the plastic resolved shear strain amplitude of the matrix volume. Further, the propagation rate of PSBs after strain amplitude increase in the plateau range has been calculated by applying the two-phase model. |
