Tension—compression behaviour of annealed oxygen-free high-conductivity copper after strain cycling in the plastic range

Abstract

When copper is cycled between fixed limits of strain it ends towards a settled cyclic state. The two curves which form the tension-compression stress-strain loop will have the same shape but, no matter what point is chosen on the loop for the return to zero stress, the material will not be left with symmetrical tension-compression properties. This is because of the Bauschinger effect. It is demonstrated that the Bauschinger effect can be eliminated by cycling down to zero stress and zero strain using progressively decreasing strain amplitudes. Relatively few cycles suffice and, when the strain range is small, the structural strain-hardening effect is not noticeably reduced. Even with the largest range investigated (± 1 per cent plastic strain) the structural resoftening is slight. The significance of the subsequent tension and compression stress-strain curves is discussed.