PSI - Issue 41

Alexander Inozemtsev et al. / Procedia Structural Integrity 41 (2022) 544–549 Author name / Structural Integrity Procedia 00 (2019) 000–000

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2. Experimental study An experimental study was carried out to gain deeper insight into mechanisms of plastic strain localization in specimens of aluminum alloy AMg6 with a "tendency" to plastic flow instability, which were subject to static deformation and dynamic loading tests on the split Hopkinson pressure bar. To study the processes of plastic strain localization in the predominant shear mode under dynamic loading on the split Hopkinson pressure bar, we developed by Sokovikov M.A. at al. (2014).and patented special-shaped (U shaped) specimens and the corresponding tooling to ensure realization of a plain strain state in the tested specimens. All specimen cross-sections are parallel to the lateral surfaces and the slip plane (Fig.1c) are in similar stress strain states. This observation is confirmed by the results of numerical simulation by Bilalov D.A. at al. (2018). In order to identify the characteristic stages of strain localization, the thermodynamics of the deformation process and the development of localized shear fracture under dynamic loading was studied by "in-situ" recording of temperature fields using the CEDIP Silver 450M high-speed infrared camera. Spatial-temporal resolution of infrared camera are as follows: sensitivity not less than 25 mK at 300°K, spectral range 3-5 μm, maximum frame size 320x240 pxl, coordinate resolution ("pixel size") ~ 0.2 mm, time resolution ~ 0.25 ms. The analysis of temperature field on the lateral surface in real time allowed us to conclude that temperature field and plastic strain distribution patterns are similar in all parallel cross-sections to the lateral surface. The test specimen, the scheme of experiments and the results are shown in Fig. 1.

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Fig.2. Fragments of U-type specimens No. 4 (a), No. 5 (b) and No. 6 (c) made of AMg6 alloy after dynamic tests on the split Hopkinson pressure bar: 1-4 are the areas of plastic strain localization in the regions of geometric stress concentrators; 5 are the areas of plastic strain localization and shear fracture in specimen No. 5; x20.

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Fig.3. Fragments of U-type specimens No. 1 (a), No. 2 (b) and No. 3 (c) made of AMg6 alloy after static tests; areas 1-4 are the regions of localization of plastic strain in geometric stress concentrators; 5 is localization of plastic strain in specimen No. 2; 6 is localization of plastic strain and shear fracture in specimen No. 3; x20.