Plastic distortion as a fundamental mechanism in nonlinear mesomechanics of plastic deformation and fracture

Any deformed solid represents two self-consistent functional subsystems: a 3D crystal subsystem and a 2D planar subsystem (surface layers and all internal interfaces). In the planar subsystem, which lacks thermodynamic equilibrium and translation invariance, a primary plastic flow develops as nonlinear waves of structural transformations. At the nanoscale, such planar nonlinear transformations create lattice curvature in the 3D subsystem, resulting in bifurcational interstitial states there. The bifurcational states give rise to a fundamentally new mechanism of plastic deformation and fracture—plastic distortion—which is allowed for neither in continuum mechanics nor in fracture mechanics. The paper substantiates that plastic distortion plays a leading role in dislocation generation and glide, plasticity and superplasticity, plastic strain localization and fracture.     

Mechanism of low-temperature plastic deformation in structural steel

It has been discovered that grade 30KhGSA steel after a high-temperature thermomechanical treatment is more plastic at –196°C than at room temperature, unlike in the case of quenched steel and uncharacteristically for metals or alloys with a bcc crystal lattice. A study has, therefore, been made to establish the temperature characteristic of the resistance to deformation and, especially, to its reversible component, both after an anneal and after a heat treatment of steel. The activation energy and volume of the thermally induced deformation were measured, whereupon the results were analyzed on the basis of the Payerls mechanism with dislocations frozen by interstitial impurities. No differentiation was made between the behavior of steel after a quench and after a high-temperature thermomechanical treatment, respectively, so that differences in the low-temperature diagrams could be related to the peculiarities of nonthermal deformation and to the resistance to brittle fracture.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 26–33, September, 1974.     

Mesomechanics of plastic deformation and fracture of partially crystalline polyethylene

From the standpoint of physical mesomechanics, we have investigated plastic deformation mechanisms and the mechanical properties of partially crystalline polyethylene. We show that from the very beginning, plastic deformation occurs at the mesoscopic level. Fracture is preceded by fragmentation of the material. The observed stages of the process of plastic deformation of polyethylene are qualitatively similar to the stages of this process for metallic materials. The effect of electron bombardment on the mechanical properties of polyethylene is explained by the size reduction in the mesoscopic substructure formed on plastic deformation. Tomsk Polytechnical University. Zhilin University, People’s Republic of China. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 48–53, January, 1997.     

Observation of plastic deformation wave in a tensile-loaded aluminum-alloy

A displacement wave has been observed in a plastically deforming aluminum-alloy sample under a tensile load. The observed wave indicates a recently proposed mechanism concerning how deformation evolves to fracture. The estimated phase velocity of 110 mm/min is three orders of magnitude higher than the tensile speed.     

Scaling of the acoustic emission characteristics during plastic deformation and fracture

The scaling of the amplitude and time distributions of acoustic emission pulses, which reflects the self-similarity of defect structures, is revealed. The possibility of separation of independent contributions to the flow of acoustic emission events, which have substantially different scaling exponents, is shown for porous materials. The differences in the scaling exponents are related to the development of plastic deformation and fracture of the materials. The developed approach to an analysis of acoustic emission can be used to describe its predominant mechanisms during deformation.     

Roughening of fracture surfaces: the role of plastic deformation

Post mortem analysis of fracture surfaces of ductile and brittle materials on the microm-mm and the nm scales, respectively, reveal self-affine cracks with anomalous scaling exponent zeta approximately 0.8 in three dimensions and zeta approximately 0.65 in two dimensions. Attempts to use elasticity theory to explain this result failed, yielding exponent zeta approximately 0.5 up to logarithms. We show that when the cracks propagate via plastic void formations in front of the tip, followed by void coalescence, the void positions are positively correlated to yield exponents higher than 0.5.     

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.     

Critical crack size for fracture during hot metal plastic deformation

During hot plastic deformation cracks originate at grain boundaries after critical deformation. Their propagation is, however, decelerated by the occuring dynamic recrystallization leading to the necessity of new cracks originating along boundaries of recrystallized grains. A model has been elaborated for determining the critical size of these cracks and its validity verified by hot torsion tests accomplished on low-carbon steel.     

广义色散Camassa-Holm模型的奇异孤子

引进一类广义色散Camassa-Holm模型，对其做奇异性分析.通过改进的WTC-Kruskal算法，证明该模型在Painlevé意义下可积，得到了它的一组Painlevé-Bcklund系统和Bcklund变换.应用Maple进行代数运算，得到了丰富的规则(regular)孤子和一类奇异(singular)孤子，扭结(kink)孤子,紧孤子(compacton)和反紧孤子(anti-compacton).特别地，推导出一类在扭结孤子的中间区域包含有一列周期尖点(cuspon)波的奇异结构.在这些规则的孤子系统的基础上，对可积广义系统应用Bcklund变换，得到三类奇异孤子，分别是具有驼峰结构的周期爆破波，具有爆破波结构的扭结孤子和紧孤子. 关键词： 广义Camassa-Holm 模型 周期尖点波 紧孤子 周期爆破波     

Symmetry-breaking instabilities of generalized elliptical solitons

Elliptical solitons in 2D nonlinear Sch?dinger equations are studied numerically with a more-generalized formulation. New families of solitons, vortices, and soliton rings with elliptical symmetry are found and investigated. With a suitable symmetry-breaking parameter, we show that perturbed elliptical solitons tend to move transversely owing to the existences of dipole excitation modes, which are totally suppressed in circularly symmetric solitons. Furthermore, by numerical evolutions we demonstrate that elliptical vortices and soliton rings collapse into a pair of stripes and clusters, respectively, revealing the experimental observations in the literature.     

Collision of water wave solitons

A classification of the time evolution of the two-soliton solutions of the Boussinesq equation is given, based on the number of extrema of the wave. For solitons moving in the same directions, three different scenarios are found, while it is shown that only one of these scenarios exists in case of oppositely moving solitons.     

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.     

Breathers and solitons on two different backgrounds in a generalized coupled Hirota system with four wave mixing

We study breathers and solitons on different backgrounds in optical fiber system, which is governed by generalized coupled Hirota equations with four wave mixing effect. On plane wave background, a transformation between different types of solitons is discovered. Then, on periodic wave background, we find breather-like nonlinear localized waves of which formation mechanism are related to the energy conversion between two components. The energy conversion results from four wave mixing. Furthermore, we prove that this energy conversion is controlled by amplitude and period of backgrounds. Finally, solitons on periodic wave background are also exhibited. These results would enrich our knowledge of nonlinear localized waves' excitation in coupled system with four wave mixing effect.