PSI - Issue 33

Tatyana Tretyakova et al. / Procedia Structural Integrity 33 (2021) 1013–1018 Author name / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 4. Distribution of principal stresses in the radial direction in the concentrator: groove with a radius of 5 mm (a); groove with an angle of 157 ° and a radius at the apex of 5 mm (b); groove with an angle of 140 ° and a radius at the apex of 5 mm (c); groove with an angle of 140 ° and a radius at the apex of 5 mm (d). 4. Results and discussions It is of interest to detect the effect of intermittent flow, which manifests itself in the form of load discontinuities in the loading diagram. To be able to compare and analyze the data obtained, the experimental dependences were plotted in the coordinates stress - displacement. In this case, stress is the force applied to the sample with the concentrator, referred to the minimum cross-sectional area of the sample. As a result, loading diagrams of specimens with different types of concentrators were obtained, presented in the coordinates stress - displacement. As an example, Fig. 5 shows typical diagrams plotted in ‘stress-elongation’ coordinates for specimens with an annular groove of various geometries. The diagram shows the manifestation of the Portevin-Le Chatelier effect (see Fig. 5). Additionally, mechanical tests for uniaxial tension with unloading and repeated loading were carried out at the stage of strengthening the material in order to influence the level of critical deformation of the manifestation of the effect of discontinuous yield (Fig. 6).