PSI - Issue 40

6

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

438

The value of the critical shear deformation, which corresponds to the moment of the onset of discontinuous yield and the initiation of deformation bands of the PLC is denoted by γ cr . Inhomogeneous fields of local strain rates are shown in Figure 5.

а

b

c

d

Fig. 5. Inhomogeneous fields of local strain rates (a - 40 frame, b - 41 frame, c - 50 frame, d - 51 frame) of specimen no. 2 during torsion.

For this type of loading, the determination of the critical shear deformation (γ cr ) was hampered by the small amplitude of the jumps in the diagram. In addition, in their form, the jumps significantly differ in amplitudes and frequencies in comparison with those observed because of deformation by uniaxial tension of specimen no. 1. The results obtained under proportional loading show a similar relationship with uniaxial deformation. In this case, the moment of the beginning of the appearance of the first jump on the deformation curve under proportional loading occurs earlier than in uniaxial tension 4. Summary and conclusions Deformation diagrams of thin-walled cylindrical specimens made of Al-Mg alloy were obtained (Figure 2, 4). The images recorded with the Vic 3D Correlated Solutions video system showed deformation bands confirming the occurrence of the PLC effect (Figure 3, 5). The values of the critical deformation corresponding to the moment of the onset of plastic deformation under uniaxial tension, torsion and proportional loading by tension with torsion are determined. According to the data obtained, the moment of the beginning of the appearance of the first jump on the deformation curve under proportional loading occurs earlier than in uniaxial tension, that is explained by more intense interactions of dislocations with the formation of barriers and the formation of Cottrell atmospheres. In the next series of tests, it is planned to investigate the effect of changing the loading trajectory on the magnitude of the jumps in the loading diagrams.