Evolution of the Stored Energy Density in a X2CrNiMo17-12-2 Austenitic Steel Under Cyclic Loading Conditions

In the present work, the impact of cyclic loading conditions on the accumulation of stored energy in an austenitic steel is investigated. For this purpose, in situ X-ray diffraction analyses were carried out to estimate the stored energy density from integral breadths. Specifically, uniaxial cyclic tests were performed for different stress amplitudes, loading ratios and numbers of loading cycles. The Williamson and Hall method was used to evaluate the microstructural changes resulting from a loading history. The comparison with experimental data available in the literature suggests that the number of cycles to failure is not solely related to the stored energy density. Indeed, while the loading ratio impacts the number of cycles to failure, it has no visible influence on the stored energy density. Also, whatever the loading ratio is, energy is mostly stored during the first loading cycle. No significant evolution of the stored energy density is observed during the following loading cycles. Finally, experimental results indicate that the fraction of the work that is stored within the material is small, about a few percent for the investigated loading conditions.