The evolution of kinematic and isotropic hardening in the case of complex uniaxial loading

This paper is concerned with uniaxial behaviour of four different construction steels in the plastic range. A set of monotonic and cyclic loading (tension-compression) experiments was conducted on round bar specimens made 18G2A, St3s, 40H and 45 steel at room temperature. First two materials show cyclic hardening but different behaviour in the case of monotonic loading (large and small plasticity knee) and the last two ones show cyclic softening. Results concerning monotonic loading, strain controlled symmetric cyclic loading and stress-controlled non-symmetric cyclic loading (ratchetting) are presented. All experiments were performed on similar specimens, the same laboratory equipment and using the same experimental technique.

Using the ''two point'' technique of successive unloadings, the standard physical quantities and the stress jumps corresponding to the opposite direction of plastic straining were measured. For the Huber-Mises yield surface such data enable to follow the evolution of kinematic and isotro-pic hardening.