Features of Unloading and Re-loading Processes of Medium Carbon Steel after Uniaxial Plastic Strain

Abstract

Response of medium carbon steel was investigated experimentally and information on features of unloading and re-loading curves in initial state and unloading and re-loading curves after uniaxial plastic strain was collected. The experiment was a simple tension test using a round specimen and the strain was measured with strain gauges. The experiment results showed that unloading and re-loading curves in initial state are both linear and should be regarded as elastic. However, the unloading and re-loading curves after uniaxial plastic strain are non-linear and form a convex oval. It suggests that there is energy dissipation throughout the unloading and re-loading processes after uniaxial plastic strain. The non-linearity of the two curves is investigated and a trial was made to validate and evaluate the energy dissipation. The results showed that both unloading and re-loading processes after uniaxial plastic strain are plastic, and elastic behaviour disappears as long as uniaxial plastic strain was given. And the dependency of energy dissipation on pre-strain was also investigated.