Abstract
In this paper, the inelastic material models for Type 316H stainless steel, which is one of the principal candidate materials for elevated temperature design of the advanced high temperature reactors (HTRs) pressure retained components, are investigated and the required material parameters are identified to be used for both elasto-plastic models and unified viscoplastic models. In the constitutive equations of the inelastic material models, the kinematic hardening behavior is expressed with the Chaboche model with three backstresses, and the isotropic hardening behavior is expressed by the Voce model. The required number of material parameters is minimized to be ten in total. For the unified viscoplastic model, which can express both the time-independent plastic behavior and the time-dependent viscous behavior, the constitutive equations have the same kinematic and isotropic hardening parameters of the elasto-plastic material model with two additional viscous parameters. To identify the material parameters required for these constitutive equations, various uniaxial tests were carried out at isothermal conditions at room temperature and an elevated temperature range of 425–650 °C. The identified inelastic material parameters were validated through the comparison between tests and calculations.
Highlights
One of main issues in the development of advanced high temperature reactors (HTRs), such as sodium-cooled fast reactors, molten salt-cooled reactors, lead or lead-bismuth-cooled reactors, and high or very high temperature gas-cooled reactors, is to develop design materials applicable for elevated temperature services with long life times over 60 years.In elevated temperature design, the strain or deformation-based design is important because structural failure modes are deeply related to a large accumulated plastic strain, creep strain, creep rupture, and creep-fatigue damage
To identify the material parameters required for these constitutive equations, various uniaxial tests were carried out at isothermal conditions at room temperature and an elevated temperature range of 425–650 ◦ C
The strain or deformation-based design is important because structural failure modes are deeply related to a large accumulated plastic strain, creep strain, creep rupture, and creep-fatigue damage
Summary
One of main issues in the development of advanced high temperature reactors (HTRs), such as sodium-cooled fast reactors, molten salt-cooled reactors, lead or lead-bismuth-cooled reactors, and high or very high temperature gas-cooled reactors, is to develop design materials applicable for elevated temperature services with long life times over 60 years. For the purpose of the elevated temperature design by the inelastic analysis method, the inelastic material models should be able to express time-independent cyclic material behavior and time-dependent viscous behavior to cover all design temperature ranges of the HTRs. There have been studies with the same purpose for 9Cr-1Mo-V steel [15,16], which is one of the allowed Class A design materials in ASME-Division 5. The inelastic material models for Type 316H, which is one of principal candidate materials for the elevated temperature design of the HTRs components, is investigated and the required number of material parameters is simplified to be ten for the elasto-plastic model and to use additional two for the unified viscoplastic model. The identified inelastic material parameters are validated through the comparison between tests and calculations
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