PSI - Issue 18

Tretyakov M.P. et al. / Procedia Structural Integrity 18 (2019) 816–822 Author name / Structural Integrity Procedia 00 (2019) 000–000

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The determining value for the course of relaxation processes at the postcritical stage of deformation is played by the test temperature. In Fig. 6 (b) shows, the relaxation curves obtained at different test temperatures: 400 °С (black line), 500 °С (blue line) and 600 ° С (red line). These curves correspond to the shutter speed at the postcritical stage of deformation at a level of achieved elongations of 3 mm.

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Fig. 6. Curves of relative load reduction with exposures at different elongations achieved at 600 °С (a) and initial sections of relaxation curves at fixed elongation of 3 mm (b) at different test temperatures: 400 °С (black line), 500° С (blue line), 600 °C (red line).

To summarize the experimental data in Fig. 7 shows the dependences of the relative reduction of the load on the degree of deformation attained at the postcritical stage at different test temperatures. The experimental values (points) and their linear approximations correspond to a temperature of 400 °C (black points), 500 °C (blue points) and 600 °C (red points).

Fig. 7. The dependence of the relative reduction of the load at exposures at the postcritical stage from the level of deformations at different test temperatures: 400 °С (black points), 500 °С (blue points), 600 °С (red points).

The relaxation processes in the samples of the examined steel under tension at the postcritical stage of deformation substantially depend on the test temperature and the degree of elongation attained at the time of the beginning of exposure. An increase in temperature leads to a more intensive decrease in the relative load during exposures (Fig. 6a). An increase in the degree of postcritical deformation leads to an increase in the intensity of relaxation processes, and this effect is most pronounced with increasing temperature (Fig. 7).