2017:05 Robust structural verification of pressurized nuclear components subjected to ratcheting, part two – stress-strain curves for cyclic elastoplastic analysis.


Pressurized components in nuclear applications that are subjected to cyclic loading may exhibit progressive deformation, so called structural ratcheting. If the component is made out of a material that are deformation hardening, it may also exhibit material ratcheting. The combined effects of structural- and material ratcheting are not taken into account in the methods and material models currently used for structural verification of pressurized nuclear components.


The project aims to develop guidelines on how to evaluate pressurized nuclear components subjected to ratcheting in a rational and conservative way that are code compliant with ASME III. In part one (SSM 2015:43) experimental studies where performed with two different laboratory test set ups, one called "two-rod test" and the other a tube test. Numerical studies with five different constitutive models where investigated for the ferritic steels P235 and P265 as well as the austenitic steel 316L. The constants in the constitutive models are based on material characterization via tensile testing and fully-reversed strain controlled cycling.This report constitutes the second and final part of the project. It contains the experimental results of uniaxial testing of ferritic pressure vessel steels at elevated temperatures. It also contains stress-strain curves for stainless steels. These results give complementary information on material behaviour so that cyclic elastoplastic analysis, as specified in part one, can be performed to analyse ratcheting.


  • The presence of the yield plateau in the stress-straincurve of ferritic steels presents a problem when analysing ratchetingwhich is resolved with these results.
  • Stress-strain curves for cyclic elastoplastic analysisof the ferritic pressure vessel steels 16M03 and P250GH are determinedexperimentally.
  • The curves of 16M03 and P250GH are scaled to fit code values of strength according to SS-EN 10028.
  • Information is also given for the ferritic pressure vessel steels P235GH, P265GH and P295GH as well as for the stainless steels 316L/1.4404 and 304L/1.4307.
  • The curve data are also given in tabular form to allow for convenient input in finite element analysis software.