PSI - Issue 33

Tatyana Tretyakova et al. / Procedia Structural Integrity 33 (2021) 1082–1088 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 3. The diagram of quasi-static tension of a sample at a loading rate of 2.4 mm per minute (left) and the enlarged view of ‘stress-elongation’ curve at stage of the jerky flow initiation (right)

Fig. 4. The diagram of quasi-static tension of a sample at a loading rate of 0.24 mm per minute (left) and the enlarged view of ‘stress-elongation’ curve at stage of the jerky flow initiation (right).

In tests with different loading rates, it was shown that a decrease in the rate by one order of magnitude leads to a change in the value of critical deformations, which corresponds to the moment of occurrence of inhomogeneous deformation due to the PLC effect. At a rate of 2.4 mm / min, intermittent deformation is observed at the achieved strain of the order of 5%, and at a rate of 0.24 mm / min at strain of 16%. It is well known that drops on the stress-strain curves are the result of deformation bands initiation and propagation along the specimen length. Fig. 5 and Fig. 6 show sets of plots of longitudinal strain, plotted at equal time intervals 1.5 s along the loading axis, the centers of coordinates are located in the center of the gauge length. By analyzing the configuration of the longitudinal deformation profile (Tretyakova, 2018), it is possible to estimate the moment of initiation of the macroscopic localization of plastic flow due to the PLC bands.