Additional Cyclic Hardening of metals under Tension-Torsion and Triaxial Tension-Compression Loadings

Abstract

The additional cyclic hardening due to the nonproportionality of the loading has been shown for the first time by H. Lamba and O. Sidebottom, [1]. These first experimental results have clearly shown that the constitutive models developed from uniaxial experiments were not able to predict the behavior of metals under complex loadings. Since, a great number of experiments have been made in order to understand the hardening and the softening of metals under multiaxial loadings, [2], [3], [4], [5]. Now, a lot of phenomenological models of elasto-plasticity have been proposed for the description of the additional cyclic hardening under complex paths. In all cases, the authors consider that out of phase tension-torsion test leads to the maximum hardening, [6], [7], [8]. This hypothesis is now controversial. On one hand, some experimental data obtained, on a Nickel-Base alloy (waspaloy), with “butterfly” loading path, [9], exhibit a higher hardening than the one corresponding to a 90 deg. out-of-phase path. On the other hand, some simulations made with a micromechanical model due to G. Cailletaud lead for some very complex loading paths to a very high cyclic hardening, again higher than the one corresponding to an out-of-phase path.