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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b

Fig. 1. (a) experimental set-up; (b) specimens with complicated geometry.

2.2. Results As a result, the loading diagrams for specimens of two groups were obtained, analysis of the deformation temperature field in the process of initiation and propagation of deformation bands of a localized plastic flow (Portevin-Le Chatelier bands) was carried out. As an example in fig. 2 shows the typical loading diagrams for samples with a circular rim (a) and a rim of reverse curvature (b).

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b

Fig. 2. (a) Loading diagrams for samples with a circular rim (a) and a rim of reverse curvature (b) during tension test.

The loading diagrams show the manifestation of the effect of jerky flow. When the critical level of plastic deformations is reached, numerous teeth and load failures begin to appear on the ‘ load-elongation ’ curves, which are accompanied by spatial heterogeneity of plastic flow in the material. The vertical dashed line marks the beginning of the process of initiation and propagation of the Portevin-Le Chatelier deformation bands. It should be noted that in the process of uniaxial tension of specimens with a rigid circular rim, the working part lost stability as a result of compressive forces (at a significant level of deformation). In this area, the central part of the plate buckles and bulges. The moment of loss of the sample stability is fixed by estimation of the displacements fields based on the digital image correlation technique. As a result, data was obtained on the configuration and evolution of inhomogeneous fields of longitudinal, transverse and shear deformations, which illustrate the manifestation of the Portevin-Le Chatelier effect in a plane stress state. Numerous deformation bands of a localized plastic flow are recorded on the sample surface. Figure 3