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The experimental study and theoretical description of the plastic deformation laws and the process of damage accumulation, softening, and formation of material fracture conditions is one of the topical field of study in mechanics of deformable solids. The spatial inhomogeneity of the material plastic flow is observed at various scale and structure levels. One most impressive example of plastic flow macro-localization is the Chernov–Luder’s behavior that is manifested as a nucleation of localized plastic strain bands along the extended specimen at the stage of sharp yield point and yield plateau formation. The Portevin–Le Chatelier effect manifests itself as an unstable plastic flow during tensile tests of some dilute alloys under certain loading conditions of strain rate and temperature. The plastic strain becomes localized in the form of bands that move along a specimen gauge in various ways as the PLC effect occurs. The enhanced interest of researchers in this field is related to the necessity of systematizing available data and obtaining new knowledge on the time–spatial inhomogeneity of the plastic deformation of materials and to the active development of experimental methods of a complex study of the effects of macro localization of plastic flow. The present work deals with the laws of structural carbon steel and Al-Mg alloy behavior under inelastic deformation by using the contemporary optical methods of experimental mechanics: the digital image correlation technique and infrared analysis. The subject of investigation is the inhomogeneity of the local strain rate fields and temperature bursts due to formation and propagation of localized plastic flow bands in uniaxial extension depending on the loading conditions. The main aim of the study is to estimate the influence of the stress concentrators and the additional cyclic impact during uniaxial tension on the effects of serrated flow, on the mechanisms of the deformation bands initiation; to interrelate between local strain jumps and temperature bursts. The research program included mechanical uniaxial tension tests with specimens in the case of constant rate of kinematic loading in the range of average strain rate from 0.33 × 10 −4 s −1 to 0.33 × 10 −2 s −1 and of tests with variable strain rate. Moreover, the uniaxial extension tests with additional cyclic loading, unloads and repeated loads were performed as well. The kinematic loading was provided on the Instron 8850 servo-hydraulic biaxial testing system and the Instron 5989 electromechanical testing system at room temperature. The inhomogeneous deformation and temperature fields were estimated by the digital image correlation measurement system Vic-3D and the infrared system FLIR SC7700M. Specifically in the course of the study of inhomogeneous deformation of an aluminum–magnesium alloy characterized by the manifestation of the Luder’s behavior and the Portevin–Le Chatelier effect, the phenomenon of a quasiperiodic homogenization of the fields of plastic deformations upon the uniaxial tension of samples was revealed. This work was performed at PNRPU and supported by the grant of the Government of the RF (Governmental regulation No. 220, April 9, 2010), Agreement No. 14.B25.310006, June 24, 2013.

We investigate the mechanically induced local deformation effects in single crystalline Ni-Mn-Ga stripes by in situ Digital Image Correlation (DIC). Ni-Mn-Ga stripes of 100 and 200 mm thickness and lateral dimensions of 15 mm × 3 mm are fabricated by cutting and electropolishing a Ni-Mn-Ga bulk single crystal having a 10 M martensite structure. Application of tensile stress causes reorientation of martensite variants being associated with the formation and growth of local strain bands. The true strain in the bands is determined to be about 6% indicating complete local variant reorientation. The stress-strain characteristics are strongly affected by the mechanical boundary conditions. (1) Fixation or clamping the foil specimens during training in a magnetic field results in the formation of a stationary twin boundary (TB) being oriented by 45° with respect to the specimen edge. Subsequent tensile loading causes formation of a strain band with 45° orientation extending in both lateral directions through TB motion. The corresponding twinning stress is about 2 MPa. (2) Bending in out-of-plane direction causes formation of a stationary TB being oriented by about 84° with respect to the specimen edge. In this case, tensile loading causes formation of a strain band with 84° orientation. The corresponding twinning stress is reduced to about 0.7 MPa.