L. B. Zuev

Wave phenomena in low-rate plastic flow of solids

An investigation of plastic flow localization patterns (waves) which are ordered in space and evolve with time has been performed for a wide range of metals and alloys. These waves are found to have the following basic features: the dependence of propagation rate on work hardening coefficient, dispersion law and scale effect. The possibility of addressing plastic flow localization as a self-organization process occurring in a deforming medium is considered. A set of equations appropriate for the description of local flow nuclei is discussed. Consideration is given to a change-over from one local strain pattern to another in accordance with the respective stages of flow. Proposed is a model for interpreting the large-scale periodicities exhibited by the distribution of localized strain nuclei.

Elaboration of speckle photography techniques for plastic flow analyses

A new method for the visualization of plastic flow localization is proposed which is based on first-order statistics of laser speckle patterns. The specific features, applicability and limitations of the proposed method are considered. The setup designed for sample testing is described. The equipment developed has space and time resolution of ~0.03 mm and ~1 s−1, respectively, and makes feasible the real-time investigation of plastic deformation processes. The experimental evidence obtained for plastic flow localization in commercial aluminum alloy is considered.

Pattern formation in the work hardening process of single alloyed γ-Fe crystals

Abstract Experimental evidences on the evolution of macrodeformation fields of extended single Cr-Ni austenitic steel crystals having superequilibrium nitrogen content are interpreted in the framework of the autowave model of plastic flow. A prerequisite to the realization of the different types of deformation structure (autowave), i.e. a solitary moving front, a moving (waves) and a stationary periodical dissipative structure, and the best observing conditions are defined. It is shown that the propagation rate of deformation nuclei is found to be inversely proportional to the work hardening coefficient in the linear work hardening stage of the plastic flow.

Autowave model of localized plastic flow of solids

The features of plastic flow localization at all stages of strain hardening and at the prefracture stage were analyzed. It was shown that macroscopic localization of plastic flow at these stages can be considered as a self-organization process. At the linear hardening stage, an autowave process of flow localization occurs in the sample, which is characterized by the wavelength and propagation velocity. At the prefracture stage, the autowave process collapses with macroneck formation followed by the nucleation of a ductile crack.

The self-excited wave nature of the instability and localisation of plastic deformation

The nature of the localisation of plastic flow observed during deformation of crystalline solids is discussed. The nucleation and evolution of the zones of strain localisation have been shown to reveal certain trends which could be described as autowaves of different kinds initiated by the processes of self-organization. Examples of self-excited wave processes, e.g., phase and excitement waves, that were observed experimentally by the deformation of mono- and polycrystalline metals and alloys are cited. Some of the numerical parameters of self-excited wave processes have been evaluated.

Deformation localization and ultrasonic wave propagation rate in tensile Al as a function of grain size

Abstract The grain-size dependence of the space period (wavelength) of flow localization observed in the stage of parabolic work hardening of polycrystalline Al has been investigated. The dependence behavior has been defined in the range of grain sizes 8×10 −3 ⩽ D ⩽4.5 mm and the significance of the relationship has been elucidated. The effect of grain size on the multi-stage behavior of plastic flow curve and on ultrasonic wave propagation rate has been considered.

On the acoustic properties and plastic flow stages of deforming Al polycrystals

During extension tests of Al polycrystals, in situ measurement of ultrasonic wave velocity (UWV) was carried out for the plastically deforming specimens. UWV has been found to depend on the plastic strain or acting stress of plastic flow. The complicated form of these dependencies is discussed in the context of the concept of evolution of lattice defects. The multistage nature of the plastic flow curve is shown to be associated with UWV. This allows plastic flow stages to be recognized with a higher degree of certainty. Thus, the linear stage of work hardening has been separated for Al polycrystals by the procedure of UWV measurement and certain peculiarities of plastic strains localization as associated with UWV variation have been investigated.

Tensile plastic strain localization in single crystals of austenite steel electrolytically saturated with hydrogen

The effect of interstitial hydrogen atoms on the mechanical properties and plastic strain localization patterns in tensile tested Fe-18Cr-12Ni-2Mo single crystals of austenite steel with low stacking-fault energy has been studied using a double-exposure speckle photography technique. The main parameters of plastic-flow localization at various stages of the deformation hardening of crystals have been determined in single crystals of steel electrolytically saturated with hydrogen in a three-electrode electrochemical cell at a controlled constant cathode potential.

Acoustic emission during the development of a Lüders band in a low-carbon steel

The acoustic emission (AE) during the plastic deformation of a low-carbon steel is experimentally studied. The data obtained on the time localization of AE signals in a sample allow the motion of a Lüders band to be traced. The main informative AE parameters at various stages of plastic flow are analyzed. The results are compared with speckle video filming data and are supported by them. The possibilities of determining plastic deformation stages and Lüders band characteristics using acoustic emission are discussed.

Localized plastic flow and spatiotemporal distribution of acoustic emission in steel

A relationship between the macroscopic localization of plastic flow and the spatiotemporal distribution of acoustic emission has been experimentally established in low-carbon steel deformed via the development of the Chernov-Lüders (CL) band followed by the parabolic strain hardening. It is shown that, as the CL band front propagates at a constant velocity in the sample, the pattern of acoustic emission is different at various stages of motion of this strain localization focus. Immobile foci of the localized flow, which appear at the stage of parabolic strain hardening, are spatially related to the inhomogeneity of strain developed during the CL band propagation.