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.     

A new type of plastic deformation waves in solids

The plastic flow of metals and alloys in a single-crystal and a polycrystalline state involves processes in which different types of wave are generated. In the easy-glide and linear work-hardening stages of flow, waves of new type are found to propagate. The motion velocity of these waves is found to be inversely proportional to the work-hardening coefficient. An attempt is made to relate the new wave type to the self-organisation phenomena observable in deforming crystals. The propagation rate of these waves is shown to depend on the energy flow through the specimen tested. The space period of the local strains region is proportional to the logarithm of the specimen length.     

Role of local nanostructural states in plastic deformation and fracture of solids

The paper substantiates the concept of physical mesomechanics that the basis for nonlinear behavior of solids under plastic deformation and fracture is the formation of nanostructural states in local highly nonequilibrium zones. Their structural transformations and two-phase decay govern the generation of strain-induced defects and cracks. Nonlinear wave mechanisms of nanostructural states influence on plastic deformation and fracture are discussed.     

Resonant photoemission in highly localized versus weakly localized solids

We report on comparative study of angle-resolved photoelectron spectra of Ni metal and CeGd at theM _III andN _IV,V soft-x-ray absorption threshold, respectively. OnM _III resonance, the valence-band photoemission (PE) intensity of Ni follows a cos²-behavior, while the intensity of the 6-eV satellite is independent of the angle of emission relative to the E-vector of the incoming beam. On the other hand, the 4f Ce PE signal behaves cos² onN _IV,V resonance. This clearly shows that the resonant enhancement of the 6-eV PE satellite of Ni is mainly caused by an incoherent Auger decay and cannot be described as a resonant PE process.     

Kinetics of localized plastic flow during deformation and fracture of a D1 alloy

The stress-strain curve of a polycrystalline duralumine (D1) is studied to find three basic deformation stages: linear hardening, parabolic hardening (n = 1/2), and prefracture (n < 1/2). The results obtained show special features of macrolocalization of the plastic flow of the alloy under review. The distribution patterns of localized plastic flow domains develop according to deformation stages. The prefracture stage is characterized by self-correlated motion of the domains to the point of subsequent fracture. It follows from an analysis of the plastic flow localization kinetics that both hardening and softening domains coexist in the specimen in the prefracture stage. The domains move with a constant velocity inherent to each of them and linearly dependent on the position of their nucleation point. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 68–73, November, 2007.     

Autowave mechanics of plastic flow in solids

The regularities of the development of localized plastic deformation of solids have been analyzed. A correlation of the products of linear and velocity parameters of elastic and plastic deformations is found for some metals and nonmetals. A hypothesis about relationship between the characteristics of elastic and plastic deformation is formulated on this basis. An empirical relationship between the regularities of plastic flow and quantum-mechanical characteristics is found.     

Scale invariance of plastic deformation of the planar and crystal subsystems of solids under superplastic conditions

The theory of structural transformations in the planar sybsystem (surface layers and internal interfaces) of solids under plastic deformation is developed. The theory is based on a consideration for local curvature of the crystal lattice, with new structural states arising in its interstices, responsible for plastic distortion. To satisfy the superplastic condition, such high-rate mechanisms should develop in both planar and 3D crystal subsystems. In a translation-invariant crystal, this condition is met by concentration fluctuations. The multiscale criterion of superplasticity is formulated based on the scale invariance of plastic deformation of the planar and crystal subsystems in a deformable solid. Beyond the criterion, superplasticity passes to the creep mode with restricted plasticity of the material.     

Special features of the localized plastic deformation and fracture of high-chromium steel of the martensitic class

The deformation behavior of high-chromium steel (0.4%C–0.6%Si–0.55%Mn–12.5%Cr) of martensitic structure upon quenching and of sorbitic structure upon high-temperature tempering has been investigated. Each of the states is shown to be represented by a particular stress-strain curve. The stress-strain curve for the steel in the martensitic state consists of a single linear-hardening stage, whereas in the sorbitic state, it exhibits a three-stage deformation pattern. The plastic flow of the examined material in the two states has been found to be of a localized character. The evolution of localized-strain center distributions follows the law of plastic flow, i.e., it depends on the deformation stages in the stress-strain curve. The fracture process is determined by the kinetics of the localized-strain centers in the final (prefracture) deformation stage in the stress-strain curve.     

Anomalous plastic deformation in nichrome

The temperature dependences of the properties of Kh20N80 Nichrome under tension have been found. Decarbonization of the alloy showed that there are two regions of anomalous strengthening, at 400–450 and 600–700 °C. The first region is attributed to order in the binary system, while the second is attributed to carbide aging. Correlation analysis of the oscillograms of the tension diagrams showed no local relationship between the load discontinuities and the intervals between them. The inadequacies of existing models for discontinuous flow are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 12–17, November, 1970.     

Relaxation waves in plastic deformation

Conclusion Experimental study of distortion fields of plastically deformed solids performed on a wide range of materials including fine- and coarse-grain body- and face-centered polycrystals, as well as amorphous alloys reveals that in these materials plastic deformation develops in the form of waves having translational and rotational components. This fact is in accordance with the currently developed theory of a turbulent mechanical field, which also has translational and rotational components.The plastic deformation waves are observable at a macroscopic structural level, and their spatial period (wavelength) is determined by the dimensions of the deformed object and dimensions of the basic structural elements (for a polycrystal, the grain size). The propagation rate of these waves is significantly less than the characteristic propagation rate of an elastic excitation and the velocity of previously described plastic waves which are produced by shock deformation, which latter speed is determined by the hardening coefficient.The character of plasticity waves depends on the form of the material's deformation curve, and on the stage of the hardening curve. The distribution of plastic distortion components changes especially significantly in prefailure regions, which allows detection of the latter long before formation of a macroscopic crack. The role of rotations in forming the failure process has been established.A synergetic interpretation of plasticity wave formation has been proposed, based on synchronization of relaxation acts occurring at stress concentrators during the deformation process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 19–35, February, 1990.