Issue 27

T.V. Tretiakova et alii, Frattura ed Integrità Strutturale, 27 (2014) 83-97; DOI: 10.3221/IGF-ESIS.27.10 96 C ONCLUSIONS he present investigation has shown that the non-contact 3-D digital image correlation measurement system Vic- 3D is a highly effective computer-vision-based technique, which provides estimation of the temporal instabilities and spatial localization due to the Lüders behavior, the Portevin–Le Chatelier effect and the shoulder or necking effect during uniaxial tension tests of aluminum-magnesium alloy. The evolution of inhomogeneous axial strain and axial strain rate fields has been illustrated for each stage of material’s deformation. To estimate the kinematics of serrated or jerky flow due to the strain bands propagation, the strain versus time curves and strain diagrams are given here. The experimental results show the recurrence in the strain distribution leveling along the specimen gauge. The changing between the macroscopic localization of the plastic flow, namely the running of the Lüders and PLC bands and the recovery of strain field homogeneity, has been observed. The results provide an important data base for the development of the theoretical and numerical description of the material behavior in conditions of the serrated flow appearance, especially of the mechanisms and regularities of the Lüders and PLC bands nucleation and propagation. A CKNOWLEDGMENTS he work was carried out in the Center of Experimental Mechanics of the Perm National Research Polytechnic University with support of the Russian Foundation for Basic Research (grant № 13-08-00304, № 13-08-96016). N OMENCLATURE L Total length of the specimen (mm) l Gauge length of the specimen (mm) B Total width of the specimen (mm) b Width of the specimen (mm) a Thickness of the specimen (mm) r Transition radius from the grip part to the gauge length of the specimen (mm) P Load (kN) u Displacement (mm) yy  Axial strain (%) max yy  Maximum value of local axial strain (%) av yy  Average value of axial strain (%) max yy   Maximum value of local axial strain rate (%/s) yy   Macroscopic axial strain rate (%/s) В Т  Upper yield point (MPa) Н Т  Lower yield point (MPa) R EFERENCES [1] Krishtal, M.M., Instability and mesoscopic inhomogeneity of plastic deformation (analytical review). Part I. Phenomenology of yield drop and serrated flow, Phys. Mesomech., 7 (5–6) (2004) 5–26. [2] Krishtal, M.M., Instability and mesoscopic inhomogeneity of plastic deformation (analytical review). Part II. Theoretical views on mechanisms of plastic deformation instability, Phys. Mesomech., 7 (5–6) (2004) 27–39 . [3] McCormick, P.G., Venkadesan, S., Ling, C.P., Propagative instabilities: an experimental view. Scripta Metall. Mater., 29 (9) (1993) 1159–1164. T T