PSI - Issue 40

Peter V. Trusov et al. / Procedia Structural Integrity 40 (2022) 433–439 Peter V. Trusov et al. / Structural Integrity Procedia 00 (2022) 000 – 000

435

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In real technical processes, the material undergoes complex loading; at the same time, there are practically no works on the experimental study of the PLC effect under complex loading conditions. To determine the parameters of various models, the experimental results obtained under uniaxial loading are insufficient for identifying the models. The existing need to create mathematical models with a sufficient degree of adequacy describing the processes of complex loading, suitable for determining the areas of critical values of the impact parameters leading to spatial inhomogeneity and instability of plastic deformation, leads to the need to develop experimental research methods under complex loading conditions. To identify and verify the parameters of the model presented in Gribov et al. (2020), a program of experimental studies of the deformation of aluminum alloy specimens under complex loading was developed as part of the study of the Portevin - Le Chatelier effect. The article presents the methodology and results of studying the effect of complex loading on the behavior of the Al-Mg alloy. The choice of this alloy is due to the urgency of the problem of stability of its deformation behavior in connection with its wide application in the aviation, chemical industry and transport engineering. Aluminum-magnesium alloys show a tendency to dynamic strain aging at relatively low homologous temperatures, which leads to the appearance of numerous stress surges in the loading diagrams. 2. Experimental data The structural aluminum-magnesium alloy in the form of a thin- walled tube when shipped from the factory (Ø28 mm, wall thickness 5 mm) was selected as the material for the study. 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 used alloy. Al Mg Mn Fe Si

Zn

Ti

Cu

Be

92.55

6.12

0.84

0.27

0.17

0.005

0.039

0.001

0.005

In mechanical tests, thin-walled tubular specimens were used, a sketch of which is shown in Figure 1. The specimens were manufactured on a numerically controlled chuck-center lathe in accordance with GOST 25.505-85. To achieve homogeneity of the microstructure and relieve residual stresses, Al-Mg alloy specimens were annealed in a muffle furnace at 400° C for 3 hours and cooled inside to room temperature.

Fig. 1. Sketch of a thin-walled tubular test specimen for tensile torsion tests.

Mechanical tests on tension, torsion and sharing tension-torsion (proportional loading) were carried out using the biaxial servo-hydraulic test system Instron 8850. Registration of inhomogeneous displacement and strain fields was carried out by using the Vic-3D digital image correlation measurement system.