PSI - Issue 17

Tatyana Tretyakova et al. / Procedia Structural Integrity 17 (2019) 906–913 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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In our previous work [Tretyakova et al (2017), Tretyakova et al (2018)], when studying the Chernov-Lüders deformation and effect of serrated flow, we used the method of constructing a series of strain profiles based on data obtained by the digital image correlation technique. The series of longitudinal strain profiles shown the quasi-periodic behavior of plastic deformation. The alternation of macroscopic leveling of longitudinal strain on the sample surface and stages of significant localization of plastic flow due to the initiation and propagation of the Chernov-Lüders and Portevin-Le Chatelier bands is noted. It is interested to estimate the occurrence of the quasi-periodic behavior in materials under the complex stress state. Fig. 11 shows the profiles of longitudinal strain constructed with an equal ti me interval Δt of 16.5 seconds along the loading axis (axis Oy) for the specimen with a rigid circular rim.

Fig. 12. Profiles of longitudinal strain constructed with an equal time interval Δt of 16.5 seconds along the loading axis (axis Oy) for the specimen with a rigid circular rim.

3. Analysis Analyzing the fracture surfaces of the samples, it can be noted that for the sample with the rigid rim of inverse curvature, the macroscopic failure occurred as a result of tensile forces in the longitudinal direction. Stretching of the material in the transverse direction is registered only in the initial elastic deformation stage, which indicates the need for further adjustment of the geometric parameters of this type of specimen. As a result, in this work the testing procedure of experimental study of the spatial-time inhomogeneity under the complex stress state was tried out. There were used the specimens with a special complicated geometry and analysis of strain and temperatures fields by using the digital image correlation technique and the infrared thermography. The high efficiency of the proposed technique for obtaining experimental data on the kinetics of macroscopic localization of plastic flow is shown. During the mechanical testing, it was noted that further optimization of geometric parameters is required in order to create a wider range of complex stress state of the material, which will be the subject of the work at the next stage. Acknowledgements The study was carried out in the Center of Experimental Mechanics of Perm National Research Polytechnic University and funded by the Russian Science Foundation according to the research project № 18 -79-00242 .

References

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