Time-dependent ratcheting of 35CrMo structural steel at elevated temperature considering stress rates

Abstract

Cyclic uniaxial stress-controlled ratcheting behaviors of 35CrMo structural steel were investigated at 500 °C. The effects of stressing rates and stress amplitudes were discussed in detail. Results present that the accumulated ratcheting strain increases with the increment of stress amplitude, while decreases with the reduction of stress rate at elevated temperature. Moreover, the ratcheting evolution curves with increasing number of cycles are similar to traditional static creep curves, and can be mainly divided into three stages. Especially, the ratcheting strain rate during the steady stage can be easily obtained to estimate the ratcheting or shakedown behavior. Furthermore, the steady ratcheting strain rate significantly decreases with increasing the stressing rate when the stressing rate is relatively slow. However, when the applied stressing rate is greater than a critical value, such as  ≥ 2·5 MPa s⁻¹ for  = 200 MPa and  ≥ 25 MPa s⁻¹ for σ_max = 500 MPa, the effect of stressing rate has little effect on the cyclic ratcheting strain rate.

Keywords:

• Ratcheting
• time-dependent
• stressing rate
• shakedown
• 35CrMo steel