A novel constitutive model for S30408 stainless steel considering strain memory effect: Formulation and implementation

Abstract

To predict seismic behavior of steel structures and conduct performance-based seismic design, a precise constitutive model to accurately reflect the elastic-plastic response of structural steel under various loading protocols is always needed, so that the strength, deformation capacity, and energy dissipation capacity of a steel component or system in case of a severe earthquake can be reasonably evaluated. On the other hand, the constitutive model should be convenient for practical engineering implementation and application. Previous studies show that certain type steel like stainless steel S30408 shows complex features under various strain ranges such as pronounced strain memory effect, unsaturated cyclic softening/hardening under small/large strain amplitudes, which differ from mild steel and low yield point steel. Therefore, the stainless steel S30408 is taken as the research object in this study to develop a new constitutive model to describe structural steels with such complex mechanical properties. First, a new nonlinear isotropic and kinematic hardening rule is extended based on the classical Chaboche model and a functional relationship between the hardening rate (defined as the variation value of peak stress in every adjacent cycle during cyclic loading) and the applied strain amplitude is established through a logistics function to describe the coupling effects. Second, the numerical implementation technique for three-dimensional is elaborated in detail. Third, the numerical implementation technique is extended to plane stress cases by the improved P projection method. Using the numerical integration algorithm, the proposed constitutive model can be successfully incorporated into ABAQUS/Standard through the UMAT subroutine interface which is suitable for both solid and shell elements.