Multilayer Kinematic Hardening Model for Carbon Steel and its Application to Inelastic Analyses of an Elbow Subjected to Cyclic In-Plane Bending

Carbon steel STS410 (JIS Standard), which is widely used for high pressure piping components, exhibits cyclic hardening under repeated loading. Extreme seismic loading can cause repetitive large strains, eventually leading to the failure of components. For failure assessment of such components, inelastic analyses using cyclic plasticity constitutive models are needed. In this paper, a multilayer kinematic hardening model for cyclic plasticity, equipped with a set of standard stress-strain characteristics, is developed for STS410 under isothermal condition of various temperatures. This model can express not only the nonlinearity of stress-strain relations, but cyclic hardening of a material by introducing a generic stress-strain relation composed of a combination of monotonic and steady state cyclic stress-strain curves. Finite element large deformation elastic-plastic analyses with this model are conducted for a cyclic in-plane bending test of an elbow. The proposed constitutive model predicted well characteristic features of global deformation and local strain behaviors of the elbow.