Time-Dependent Ratcheting Behavior of TA2 Pure Titanium at Room Temperature

Uniaxial asymmetric stress controlled cyclic deformation tests under different stress loading conditions (tension-tension and tension-compression cycle under different stress levels and different stress rates, tension-compression load-holding cycle and variate stress four-level loading) and creep-cyclic deformation alternating tests were conducted on TA2 pure titanium at room temperature. The effects of stress level, stress rate, peak/valley stress holding time and holding form and loading history on ratcheting behavior of TA2 pure titanium were studied. The results show that the ratcheting behavior of TA2 pure titanium exhibited obvious time dependence. Both the ratcheting strain and the area of stress-strain hysteresis loop increased with the decrease of stress rate. The ratcheting strain under the condition of peak stress holding was higher than that under the condition of both peak and valley stress holding, and the longer the holding time was, the greater the ratcheting strain. The final peak strains after creep followed by cyclic deformation and after cyclic deformation followed by creep were similar and lower than those under conditions of peak stress holding, indicating that the alternating creep and ratcheting promoted the plastic deformation.