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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speeds were determined, and the sequence of loading and holding the samples in accordance with the objectives of the study were chosen.

b

a

Fig. 2. (a) sketch of solid cylindrical specimen; (b) specimen before test.

To register changes in the geometric dimensions of the samples during the test procedure, the technique involves the use of axial and transverse extensometers, which can be used in a high-temperature furnace. The use of a transverse extensometer makes it possible to record the change in the transverse contraction of the sample during the postcritical deformation process. Tests are carried out at an elongation rate of samples of 6 mm/min, either until complete destruction, or to the required level of deformation at the postcritical stage, after which exposure is performed at constant sample deformation or load level with recording of all test parameters. Heating and holding samples at a test temperature up to 500 °C is carried out for at least 2 hours, at a temperature of 600 °C - at least 3 hours, which ensures uniform heating of the sample and equipment. 3. Test results and discussion In accordance with the considered methodology, tensile tests were performed at high temperatures with the construction of complete deformation diagrams containing drop-down sections. The implementation of the postcritical deformation stage and the changing of the mechanical characteristics of the steel X15CrNi12-2, depending on the temperature, are considered by Wildemann and Tretyakov (2019). The loading of the samples was accompanied by stops at various stages of elastoplastic and postcritical deformation. Stops with the retention of the achieved elongation are implemented every 0.75 mm. The study of the effect of temperature on the rheological behavior of steels at the postcritical stage of deformation was carried out at temperatures of 400 °C, 500 °C and 600 °C.

a

b

Fig. 3. Loading curves of a sample of steel X15CrNi12-2 with holdings on position at various elongations at temperature of 400 °С (a) and 500 °С (b). The obtained deformation diagrams of steel X15CrNi12-2 are shown in Fig. 3 for a temperature of 400 °С (a) and