Viscoplastic Constitutive Modeling For316L Stainless Steel

In this study, a series of strain cyclic tests including uniaxial loading path,torsional loading path, proportional loading path and non-proportional loading path,etc., were conducted at room temperature and873K on316L austenitic stainless steel.Four-step uniaxial ratcheting experiments were conducted to investigate the effects ofstress amplitude, mean stress, loading history and stress rate on the rate of ratcheting.The experimental results show that:(1) Either at873K or at room temperature underuniaxial strain cycling,316L steel displayed cyclic hardening characteristics, and thehardening level increased with the increase of strain amplitude;(2) Multi-axial straincontrolled tests under non-proportional loading conditions showed significantnon-proportional additional hardening characteristics of the steel;(3) At roomtemperature, ratcheting strain increased with increase of the stress amplitude andmean stress. Under high stress amplitude and mean stress,316L stainless steel tendedto exhibit a gradual ratcheting effect, while at lower levels the shakedown ofratcheting effect was observed. Meanwhile, the ratcheting strain rate increased withdecreasing loading rate.(4) At873K, regardless of changes in stress amplitude andmean stress,316L stainless steel showed the effect of ratcheting shakedown. Theratcheting strain and its rate under different loading rates were almost the same;(5)Under the same stress loading conditions, the ratcheting strain rate of316L stainlesssteel at873K was almost consistent with that at room temperature, but the ratchetingstrain at873K was larger than that at room temperature;(6) At room temperature and873K, the ratcheting behavior of316L stainless steels was affected by loading history.After high loading level history, ratcheting strain rate under the subsequent cyclicloading was reduced. In the meantime, the material with loading history exhibitedsmaller ratcheting strain rate than that without loading history. In summary, at bothroom temperature and873K,316L stainless steel exhibited the features of cyclicstrain hardening, additional non-proportional hardening and loading history effect.Based on the McDowell’s visco-plastic constitutive model and Chaboche’stemperature-dependent constitutive theory, the non-proportionality was embedded inshort back stress modulus and isotropic hardening rule in the model. Simulationresults demonstrated that the modified constitutive model reasonably described the stress-strain relationship of the316L stainless steel whether at room temperature or873K under different loading paths, such as uniaxial loading path, torsional loadingpath, proportional loading path and non-proportional loading path, etc.