Issue 42

T.V. Tetyakova et alii, Frattura ed Integrità Strutturale, 42 (2017) 303-314; DOI: 10.3221/IGF-ESIS.42.32 309 Figure 6 : Set of the profiles of the longitudinal strain ( ε yy ) showing the effect of the quasi-periodic character during the uniaxial tension test. The influence of the stress concentrators Fig. 7 presents the load-displacement curve obtained for uniaxial tension test on the flat specimen with stress concentrators (a pair holes with diameters of 3 mm), for a nominal strain-rate of 1.67·10 −3 s −1 . Fig. 8 shows the evolution of the inhomogeneous local strain rate and temperature fields. It is important to notice, that the loading curves include the stage of the yield plateau forming, despite the stress concentrators); also, the plastic flow localizes in the form of the strain bands on the specimen surface. When load increasing, the Chernov-Lüders bands passed lengthwise the specimen surface. Figure 7 : The load-displacement curve for uniaxial tension test on the flat specimen with two holes. The influence of the loading system’s stiffness It is well known, that the interaction between a loading system and deformable solid bodies plays a key role in the transition from the stage of equilibrium damage accumulation to the non-equilibrium, or avalanche, stage of the material’s failure. The original experimental methods, which provide managing of the loading system characteristics, were used for this study of the mechanical behavior and the patterns of the macroscopic localization of the plastic flow with taking into account the real properties of the loading conditions. The flat specimens (Al-Mg alloy) with additional deformable parts (see Fig. 3 (c)) and specimens with the complicated geometry (Fig. 3 (d)) were tested on the uniaxial tension with a constant nominal strain rate of 1.67·10 −3 s −1 .