Luders deformation in an aluminum-magnesium alloy was studied in a wide range of loading rates. It was found that the deformation is always accompanied by the propagation of deformation fronts, which move either continuously or intermittently depending on the strain rate. The kinetics of fronts is determined by the reaction of active deformable media to an external mechanical action and is determined by the autowave nature of plastic deformation.

The paper analyzes the elastoplastic transition in Fe–0.025 wt. % C at a temperature of 296–503 K and strain rate of 6.67·10−6–3.33·10−3 s−1. The analysis shows that the lower yield stress increases by a power law with increasing the strain rate, and that its rate sensitivity decreases linearly with increasing the test temperature. At temperatures lower than 393 K, the rate sensitivity of the lower yield stress is normal, and at 393–503 K, it is zero. In the range 393–503 K, the kinetics of the Lüders bands is changed from steady to discrete, and the higher the strain rate, the higher the temperature of this transition. Using the available data on the dynamics of dislocations and diffusion of interstitial impurities in the test alloy, it is demonstrated that the kinetics of Lüders bands are controlled by the effect of dynamic strain aging. If the arrest time of mobile dislocations tw at barriers which are overcome via thermal activation is comparable with the precipitation time of interstitial atoms ta at these dislocations, the motion of a Lüders band is discrete, and the band represents an excitation wave of localized plasticity; its refractory period is determined by the time of dynamic strain aging. If ta >> tw, the band moves monotonically and represents a switching autowave. The results of the analysis suggest that the effect of serrated yielding at the lower temperature boundary of blue brittleness can be suppressed by increasing the strain rate. When the arrest time of dislocations tw decreases, the comparability of tw and ta is broken, and no excitation autowave is formed. The data reported in the paper can be used to develop warm rolling technologies for materials with a sharp elastoplastic transition.

Zirconia-based ceramics is a material with a wide variety of applications. Problems of strength of such ceramics, being prepared by different methods, under different loading conditions, and with different porosity, are of practical importance. Inhomogeneous strain distributions in different-porosity zirconia ceramics during a Brazilian test are studied using the digital image correlation and numerical simulation techniques. Spatiotemporal patterns of strain localization across the compression axis are obtained. It is found that strain components are nonuniformly distributed over the specimen surface, and zirconia experiences macroscopically localized deformation. The fracture patterns reveal the triple-cleft mode. Numerical simulations performed both for a homogeneous material and with consideration for the material inhomogeneity show that different models yield different patterns of inhomogeneous strain distribution under diametral compression. Account for internal friction and dilatancy provides eight-shaped cracks. Random distributions of strength and elastic properties over the computational domain built with the use of pseudo-random number generators and/or Gaussian random fields allow one to control the size of strain inhomogeneities.

Investigations of the kinetics of localized plastic deformation fronts in aluminum alloy 1550 have been made. It has been established that in this alloy fronts of Chernov–Lüders bands (CLB) and Portevin–Le Chatelier bands (PLC) are observed. A distinctive feature of CLB fronts in this material is their discrete movement only in the phase of specimen unloading. Continuous movement of the fronts is possible here if the rate of effective stress restoration through the testing machine is greater than or equal to the rate of stress relaxation controlled by internal processes at a lower structural scale level. After the yield plateau, discontinuous yielding is realized. Nucleation sites of localized deformation fronts at this stage are predefined by CLB fronts. These fronts pass 2–3 times through the entire gauge length of the specimen. Then, at low strain rates, the load curve has a monotonic hardening section, where PLC fronts are not formed. At deformation rates ≥3.33 × 10−4 s−1 such section does not exist. In both cases, fracture occurs in the discontinuous yielding mode. The movement of localized deformation fronts is discussed within the concept of autowaves.

The formation and propagation of strain-induced phase transformation bands were studied in TRIP steels obtained under various thermomechanical processing conditions. The phase transformation during the pseudo-plateau stage is shown to occur as switching autowaves that propagate in the form of the Luders bands. After the annihilation of switching authowaves in the austenite state, the strain hardening is manifested by excitation autowaves being the Portevin-Le Chatelier fronts (PLC). Hot rolling to 63% reduction allows one to avoid the jerky flow stage and the PLC hands. The generation and propagation of martensite transformation bands are evident from the appropriate phase distribution collected via the magnetic measurements.

The kinetics of the martensitic transformation fronts in transformation-induced plasticity (TRIP) steel was studied in relation to preliminary thermomechanical treatment using the digital image correlation method. It was found that warm rolling of steel to 40–63% reduction significantly increases the stress of the onset of strain-induced phase transformation and changes the loading curve stages. The strain-induced phase transformation in TRIP steel occurring through the formation of Lüders and Portevin–Le Chatelier bands is shown to be an autowave process of localized plasticity. The austenite → martensite transformation at the elastic-plastic transition occurs in the form of several switching localized plasticity autowaves. At the jerky flow stage, excitation autowaves of localized plasticity are generated and propagate repeatedly until the strain-induced austenite → martensite transformation is completed. It is shown for the first time that the sources of excitation autowaves in the material are the sites of nucleation or annihilation of switching autowaves.

The kinetics of deformation processes at yield plateau in materials with dislocation and martensitic mechanisms for the implementation of shear processes at the microscopic level is studied. In both cases, the formation and propagation of switching autowaves occur, which are represented by the fronts of localized plastic deformation. Autowave velocities nonlinearly depend on the loading speed. It is established that the nature of nonlinearity is the same for both materials studied.

The paper presents the structure and nature of plastic deformation macrolocalization in metastable austenitic-martensitic steel in relation to preliminary thermomechanical processing. Preliminary processing affects the amount of metastable austenite, staging and type of deformation curves, evolution of localized plastic deformation autowaves. It is shown that, during TRIP steel deformation n, one type of autowaves (switching) is changed to another (excitation). The autowave transformation mechanism has been established, in which nucleation sites of switching autowaves are sources of excitation autowaves.

The paper studies the changes in the velocity of ultrasonic Rayleigh waves depending on strain localization on the yield plateau in carbon steel. Inhomogeneous plastic flow in such materials is manifested in the form of Luders bands. It is shown that in the case of the propagation of several bands, the front velocities are coherent throughout the deformation process. The ultrasonic velocity is shown to decrease monotonically as the volume of plastically deformed material increases.

The deformation of materials with unstable phase structure such as titanium nickelide (nitinol) and steel with transformation induced plasticity (trip-steel) was studied within the framework of the autowave theory. It was established that at the initial stages of deformation a strain induced martensitic phase transformation occurs in both materials, which is realized as switching autowaves of localized plastic deformation. In nitinol it occurs completely, while in TRIP steel the remaining unstable austenite under further deformation expose a transformation similar to the Portevin-Le Chatelier effect with formation of waves of excitation of localized plastic deformation.

The article considers the approach to solving such problems of technical diagnostics and industrial safety expertise, such as carrying out a "stress test", namely loading to the yield point with subsequent leak testing, and estimating the residual life of the technical device. The approach is based on research of localized plastic deformation behavior in mechanical tensile testing of low-carbon specimens in the initial state and after 25 years of use in thermal power equipment. It was established that during the test, long before the global loss of stability, stable localized deformation zones are formed in the material subsequently becoming points of failure. In material after use, occurrence of such zones is seen earlier than in the initial steel. A parameter defining the amount of homogeneous material without localized deformations is proposed that can be used to predict the state of long operated thermal power equipment.

The paper provides research data on macroscopic plastic flow inhomogeneities in metals: Chernov–Luders bands and Portevin—Le Chatelier effect. Their evolution regularities and motion kinetics are analyzed, showing that Chernov–Luders fronts and Portevin–Le Chatelier jump-like straining can be treated respectively as macroscopic auto-wave processes of switching and excitation in deformed media of various origins.

The elastic-plastic transition occurs in materials having a sharp yield point simultaneously with the nucleation and propagation of Chernov-Luders bands (CLBs). It is found that the time it takes for a given CLB to be nucleated differs by about an order of magnitude from its propagation rate. The CLB fronts would travel in a concerted manner, so that their motion rates taken together at any time would make up a constant value. An increase in the deformation rate would bring about a nonlinear increase in the motion rates of CLB fronts.

A study was made of the processes involved in the nucleation and propagation of Chernov–Luders bands in low carbon steels. It is found that the deformation bands are nucleated in the deforming sample at stress levels that are significantly lower relative to the upper yield limit. A sharp yield point is found to occur on the deformation curve, with its ascending and descending branches corresponding to the band nucleus “ingrowth”. Following the sharp yield point, a mobile Chernov–Luders band proper is observed for the yield plateau. The rate of deformation band fronts has been determined for both the band “ingrowth” and the band propagation stage. The occurrence of mobile band front(s) is considered. Thus, the conventional assumption that the deformation front is a boundary separating deformed and non-deformed material regions represents facts only approximately.

The effect of hydrogen embrittlement on the localized plastic deformation of aluminum alloy D1 was investigated. The studies were performed for the test samples of aluminum alloy subjected to electrolytic hydrogenation. It is found that the mechanical properties and localized plastic deformation parameters of aluminum alloy are affected adversely by hydrogen embrittlement. The hydrogenated counterpart of alloy has a lower degree of ductility relative to the original alloy; however, the plastic flow behavior of material remains virtually unaffected. Using scanning electron and atomic force microscopy methods, the changes in the fracture surface were investigated. The deformation diagrams were examined for the deformed samples of aluminum alloy. These are found to show all the plastic flow stages: the linear, parabolic and pre-failure stages would occur for the respective values of the exponent n from the Ludwik-Holomon equation. Using digital speckle image technique, the local strain patterns were being registered for the original alloy D1 and the counterpart subjected to electrolytic hydrogenation for 100 h.