EXPERMENTAL STUDIES ON AXIAL TIME-DEPENDENT CYCLIC DEFORMATIONS OF CYCLIC SOFTENING MATERIAL AT ROOM TEMPERATURE

The time-dependent cyclic strain characteristics and ratcheting behaviors of a cyclic softening material, tempered 42CrMo steel, were studied by axial cyclic tests at room temperature. The effects of straining and stressing rates, peak/valley strain and stress holding with certain hold-times and different loading charts (i.e., triangle and sine charts) on the cyclic softening and ratcheting behaviors of the material are discussed. It is shown that the cyclic softening and ratcheting behaviors of the tempered 42CrMo steel present obvious time-dependent characteristics at room temperature, i.e., the cyclic deformation behaviors of the material depend not only on loading rates to a great extent, but also on hold-time and loading charts. Some significant results useful to construct a time-dependent constitutive model for such cyclic softening materials are obtained.