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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under given operating conditions. The effects of discontinuous flow lead to a significant decrease in strength and ductility, reduce the quality of the material surface and affect the technological process of processing [1-3]. Macroscopic localization of the plastic flow as a result of the formation of deformation bands leads to the difference in thickness of the material and, as a result, to the formation of defects and premature failure.

Nomenclature σ stress ε strain ε yy

longitudinal strain specimen length

l

elongation

u

time

t

2. Experimental procedure 2.1. Material and specimen geometry The investigations were carried out on the cylindrical samples. A sketch of the specimen is shown in Fig.1. The chemical composition of the alloy in mass fractions according to GOST 4784-97 is presented in Table 1.

Table 1. The chemical composition of the studied aluminum-magnesium alloy. Element Al Mg Mn Fe Si Zn Ti Be Composition, % wt. 92.55 6.12 0.84 0.27 0.17 0.005 0.039 0.001 0.005 Cu

Fig. 1. Sketch of a cylindrical sample for tension tests.

2.2. Test procedure and equipment In order to experimental study the effect of short-term stops and non-monotonic loading in the process of uniaxial tension on the effect of the Portevin-Le Chatelier effect the test program was implemented, see Table 2. The samples were stretched using an ‘Instron 8850’ servo-hydraulic biaxial (tension-torsion) testing machine. The inhomogeneous strain fields were analysed by using a 3D digital image correlation measurement-system ‘Vic-3D’ (Fig. 2).