Abstract

This paper describes and presents an experimental program of low-cycle fatigue tests of austenitic stainless steel 08Ch18N10T at room temperature. The low-cycle tests include uniaxial and torsional tests for various specimen geometries and for a vast range of strain amplitude. The experimental data was used to validate the proposed cyclic plasticity model for predicting the strain-range dependent behavior of austenitic steels. The proposed model uses a virtual back-stress variable corresponding to a cyclically stable material under strain control. This internal variable is defined by means of a memory surface introduced in the stress space. The linear isotropic hardening rule is also superposed. A modification is presented that enables the cyclic hardening response of 08Ch18N10T to be simulated correctly under torsional loading conditions. A comparison is made between the real experimental results and the numerical simulation results, demonstrating the robustness of the proposed cyclic plasticity model.

Highlights

  • Austenitic stainless steels, for example, 316L in PWR and 08Ch18N10T in the Russian VVER concept, are usually used for components in primary circuit reactor internals, in main primary pipes, and so forth

  • The experimental data from the identification series (IDF) series of experiments can be plotted into fatigue diagram ea -N f, where N f is the number of cycles to failure and ea is the amplitude of the total strain

  • The compared variables are the amplitudes of the torque measured during the experiment (Ta exp ) and computed by the finite element (FE) simulations (Ta sim )

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Summary

Introduction

Austenitic stainless steels, for example, 316L in PWR (pressurized water reactor) and 08Ch18N10T in the Russian VVER concept (water–water power reactor), are usually used for components in primary circuit reactor internals (a block consisting of guided tubes, a core barrel, a core barrel bottom and a core shroud), in main primary pipes, and so forth. A description and a short history of the development of constitutive models of cyclic plasticity has been provided by the authors in a previous publication [2] Their goal is to describe as accurately as possible the stress-strain behavior of the material, which is found on the basis of experiments under cyclic loading. Low-cycle fatigue tests of this type were presented for example, by Jin et al in Reference [7] They presented results for 316L stainless steel under proportional and non-proportional loadings. In another study, Xing et al [8] presented the results of experimental testing on 316L stainless steel under proportional and non-proportional loadings with various strain amplitudes. A comparison between the real experimental results and the numerical simulation results demonstrates the robustness of the constitutive plasticity model

Experimental Setup
Experimental Program
Constitutive Model with Strain Range Dependency
Cyclic Plasticity and Memory Surface
Kinematic Hardening
Modification for Torsional Loading
Identification of Material Parameters
FE Simulations
Experimental and Simulation Results
Findings
Discussion
Conclusions

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