Application of material models and assessment of strains in a surgeline under cyclic thermal loading

Inelastic constitutive models in commercial finite element (FE) programs are examined with respect to their capability of describing cyclic thermal loading. Neither isotropic nor linear kinematic hardening alone gives correct answers. Therefore, a model with combined isotropic and kinematic hardening based on Chaboche is implemented in an FE program and validated by appropriate experiments. This model is applied to assess the safety of a piping loop in a nuclear power plant subjected to cyclic loading. The numerical simulation shows a purely elastic behaviour of the surgeline after two cycles (elastic shakedown) as indicated by previous strain gauge measurements.