Constitutive model with memory-surface shrinking rule for cyclic plasticity of structural steel

A constitutive model is proposed for both the cyclic hardening and softening of structural steel. A shrinking rule is incorporated into the memory surface for cyclic softening. The theoretical formulation of the proposed model is derived under cyclic loading with a gradually decreasing strain amplitude. The material constants are iden-tified by numerically minimising the difference between the theoretical result and a single material test result using a genetic algorithm. The proposed model is validated by comparing numerical and material test results under various cyclic loadings for structural steel, where the model exhibits good ability to qualitatively and quantitatively evaluate the stress amplitude variation. The model is implemented in Abaqus FEA software, and the convergence rate of the consistent tangent operator is evaluated. FEA with the consistent tangent operator yields a quadratic convergence.