Issue 42

T.V. Tetyakova et alii, Frattura ed Integrità Strutturale, 42 (2017) 303-314; DOI: 10.3221/IGF-ESIS.42.32 303 Influence the loading conditions and the stress concentrators on the spatial-time inhomogeneity due to the yield delay and the jerky flow: study by using the digital image correlation and the infrared analysis Tatyana V. Tretyakova * , Valery E. Wildemann Center of Experimental Mechanics, Perm National Research Polytechnic University, 29 Komsomolsky prospekt, Perm 614990, Russia cem.tretyakova@gmail.com, wildemann@pstu.ru A BSTRACT . The paper deals with the investigation of the temporal instabilities and spatial localization due to the Lüders behavior and the Portevin–Le Chatelier effect in the carbon steel C1010 and the aluminum- magnesium alloy AA5052, which manifest the unstable plastic flow. The digital image correlation technique and the infrared thermography were used to capture and study the processes of the initiation and propagation of the deformation bands. The main part of the research focuses on the estimation of the influence of the loading system’s stiffness on the irregular plastic flow, which was carried out on flat specimens with complicated geometry and on specimens with additional deformable parts. K EYWORDS . Plasticity; Experimental strain analysis; Stress concentrator; Digital image correlation; Infrared analysis. Citation: Tretyakova, T. V., Wildemann, V. E., Influence the loading conditions and the stress concentrators on the spatial-time inhomogeneity due to the yield delay and the jerky flow: study by using the digital image correlation and the infrared analysis, Frattura ed Integrità Strutturale, 42 (2017) 303-314. Received: 09.03.2017 Accepted: 18.08.2017 Published: 01.10.2017 Copyright: © 2017 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION he experimental study of the mechanical behavior of the structural materials and the spatial-time inhomogeneity of plastic deformation is an important subject in mechanics of deformable solids. In uniaxial tension tests, some metals and alloys exhibit irregular plastic flow. At the stage of the yield delay the unstable flow results in inhomogeneous deformation due to the Chernov-Lüders behavior. On the surface of a specimen during the yield point and the yield plateau forming the deformation bands of localized plastic flow initiate and propagate along the gauge length. A.H. Cottrell put forward the theoretical description of the upper/lower stress, in which case the yield point on the stress-strain curve explained by dislocation theory at the microscopic level. It is well known, that aluminum-magnesium alloy manifests the Savart-Masson effect in conditions of the strength loading ( 0 ε const   ) or the Portevin-Le Chatelier effect in conditions of the kinematic loading ( 0 σ const   ) in a given range of temperature and strain/stress rate [1-3]. The jerky flow results in the numerous drops on the load diagrams and T