Experimental and numerical analysis about the cyclic behavior of the 304L and 316L stainless steels at 350 °C

• Under small strain conditions, uniaxial ratcheting is not significant for both steels.
• Ratcheting is also small but seems more significant for non-proportional loading.
• Large cyclic hardening is observed in both steels under tension–compression loading.
• Significant isotropic cyclic hardening is observed for non-proportional loading.
• The multi-mechanism model predicts well the quasi absence of uniaxial ratcheting.

In a previous study, we have demonstrated that cyclic accumulation of the inelastic strain exhibited by 304L SS at room temperature under tension–compression stress control is mostly due to creep (Taleb and Cailletaud, 2011). The same result in the same conditions is pointed out for 316L SS (Taleb, 2013a). In the present paper, the cyclic behavior of both 304L and 316L stainless steels at 350 °C is investigated. Creep is not significant at this temperature. In addition to tension–compression tests, the effect of non-proportional loading paths (axial-torsion) is considered for both stress and strain controlled conditions. The study suggests that ratcheting is very small with the different mean stress and amplitude used remaining into the assumption of small strains; this observation may be linked to the large cyclic hardening exhibited by both materials. However ratcheting seems more important under non-proportional loading path compared to the equivalent tension–compression conditions. A multi-mechanism model has been used to simulate the whole experimental data base. After the identification process of the material parameters conducted by considering only strain controlled experiments, its predictive capabilities have been evaluated on the stress controlled tests. The model presents a very good quantitative agreement with the quasi absence of ratcheting. However, the model fails in describing the over-hardening (mostly isotropic) observed under monotonic loading when the maximum strain is large (about 4%).