Interpretation of creep curves of double-notch copper single crystal specimens

Double-notch specimens were made from copper single crystals in order to re alize a strain by shear on crystal planes {111}, {110}, {100} and {131}. Co mpressive creep tests at 773 K and 873 K yielded complicated creep curves, reflecting the complex stress and strain fields in the specimens. Analysis based on comparison of the curves with respect to Schmid factors of potenti ally active slip systems allowed identification of the bend and the shear c omponent of strain in the zone of shear and the local compressive strain co ntribution to the curve. Under some creep conditions the shear creep curves were separated. It was concluded that the process of shear in the zone of shear is realized mostly by the usual [110]{111} slip systems activated by the shear stress acting in the chosen non-compact sheer plane, while the di rect glide of dislocations on the non-compact shear planes is probably of m inor importance.