Analysis of uniaxial ratcheting behavior and cyclic mean stress relaxation of a duplex stainless steel

• A constitutive model for uniaxial ratcheting and cyclic mean stress relaxation was proposed.
• Cyclic strain hardening was incorporated by the evolution of isotropic hardening.
• Cyclic plastic deformation under asymmetric stress cycling was investigated.
• Cyclic mean stress relaxation under asymmetric strain cycling was examined.

The growing presence of a non-conventional stainless steel like a super duplex grade S32750 requires clarification of the structural responses to cyclic loading. This study attempted to characterize the uniaxial ratcheting behavior and the cyclic mean stress relaxation of S32750 super duplex stainless steel which had cyclic hardening characteristics under strain-controlled cyclic loading. A constitutive model capable of simulating the uniaxial ratcheting response and the mean stress relaxation was developed in the framework of rate-independent plasticity theory. Verification of the proposed constitutive model was achieved by simulating uniaxial strain- and stress-controlled cyclic loading tests including cyclic mean stress relaxation and comparing the predicted results with the experimental measurements. The influences of mean stress level, stress amplitude and loading history on the uniaxial ratcheting behavior as well as the effects of mean strain and strain amplitude on the mean stress relaxation was further examined through the verified constitutive model.