Plasticity and strength of solids

This article reviews research conducted over the past 15 years at the intersection of the physics and mechanics of a deformable solid on the basis of the concept that plastic deformation and failure represent the evolution of shear-stability loss of a loaded material at various scale levels. This research has led to the founding of a new scientific discipline: the physical mesomechanics of materials, in which a deformable solid is regarded as a multilevel self-organizing system. The development of mechanisms and stages of plastic deformation at different scale levels conforms to the principle of scale invariance. This qualitatively changes the methods of describing the plastic deformation and failure of solids. The most pressing areas of research in the physical mesomechanics of materials are noted; these will determine the basic trends in research on the strength of solids in the next decade. Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 7–34, January, 1998.     

Structural changes during annealing of submicro- and nanocrystalline aluminum alloys

The annealing-induced evolution of the structure and microhardness of submicro-and nanocrystalline Al—3% Mg and Al 1570 alloys produced by torsional severe plastic deformation are studied. Annealing of the Al-3% Mg alloy at 373–423 K and annealing of the Al 1570 alloy at 373–473 K are shown to result in the relaxation of internal stresses and subsequent normal grain growth. As the annealing temperature increases, the microhardness decreases. At higher temperatures (473 K for the Al—3% Mg alloy and 573 K for the Al 1570 alloy), anomalous grain growth takes place. This growth is accompanied by the appearance of numerous grains with a high dislocation density, a high concentration of impurity atoms in grain boundaries, and an increase in the microhardness. These effects are explained.     

Formation of a bistructure of a solid in a computer experiment

Molecular-dynamics was used to investigate the structural changes occurring in a three-dimensional solid when the solid is transferred from an amorphous into a crystalline state. Crystal cells of a new type — pentadecahedrons with five square lateral faces and ten regular triangular faces at the vertices of a cell — were found for the first time in a computer experiment. It is shown that a bistructure consisting of crystal cells of different types, including cells with five-fold symmetry axes, are stable in the solid. Fiz. Tverd. Tela (St. Petersburg) 40, 1919–1924 (October 1998)     

New problems in general relativity

The problem of strong gravitational fields in classical (h = 0) general relativity is discussed. Strong fields require complex space—time topology; they require investigation by the methods of Riemann geometry as a whole over the complete atlas of mappings. Static solutions may not exist; dynamic oscillatory configurations of matter arise. A crucial spherically symmetric self-similar solution is described. The physical consequences are enumerated: there is no gravitational grave for matter and energy — there are no black holes; energy can emerge during and after gravitational collapse. The theoretical conclusions are confirmed by observations. A physical singularity of the infinite-density type arises in solutions with high symmetry. The crucial solution in flat space is continuable at spatial infinity through the singularity with conservation of the arrow of time; continuation through the singularity — the Big Bang — also occurs for cosmological models. Scientific Research Institute of Nuclear Physics, M. V. Lomonsov State University, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–12, March, 1998.     

Holevo-Ordering and the Continuous-Time Limit for Open Floquet Dynamics

We consider an atomic beam reservoir as a source of quantum noise. The atoms are modelled as two-state systems and interact one-at-a-time with the system. The Floquet operators are described in terms of the Fermionic creation, annihilation and number operators associated with the two-state atom. In the limit where the time between interactions goes to zero and the interaction is suitably scaled, we show that we may obtain a causal (that is, adapted) quantum stochastic differential equation of Hudson—Parthasarathy type, driven by creation, annihilation and conservation processes. The effect of the Floquet operators in the continuous limit is exactly captured by the Holevo ordered form for the stochastic evolution     

On the Goldstonic gravitation theory

The physical specificity of gravity as a Goldstone-type field responsible for spontaneous breaking of space-time symmetries is investigated and extended up to supergravity. Problems of the Higgs gravitation vacuum and its matter sources are discussed. A particular “dislocation” structure of a space-time due to Poincaré translation gauge fields and the corresponding modification of Newton’s gravitational potential are predicted.     

Friction in a Model of Hamiltonian Dynamics

We study the motion of a heavy tracer particle weakly coupled to a dense ideal Bose gas exhibiting Bose-Einstein condensation. In the so-called mean-field limit, the dynamics of this system approaches one determined by nonlinear Hamiltonian evolution equations describing a process of emission of Cerenkov radiation of sound waves into the Bose-Einstein condensate along the particle’s trajectory. The emission of Cerenkov radiation results in a friction force with memory acting on the tracer particle and causing it to decelerate until it comes to rest.

“A moving body will come to rest as soon as the force pushing it no longer acts on it in the manner necessary for its propulsion.”—— Aristotle     

Deformational methods of material nanostructuring: Premises,history, state of the art,and prospects

Brief history of origin and development of methods of deformational nanostructuring of materials (DNM) also referred to as methods of severe plastic deformation (SPD) are presented. Principles and efficiencies of the most widespread DNM methods — torsion under quasi-hydrostatic pressure (THP), equal channel angular pressing (ECAP), and hydrostatic isothermal forging (HIF) — are analyzed. Results of pioneer research of the structure and properties of nanomaterials produced by these methods are given. Prospects for the DNM application in industrial technologies of metal treatment and product manufacturing are indicated. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 47–59, May, 2008.     

Effect of the primary particle morphology on the micromechanical properties of nanostructured alumina agglomerates

Depending on the application of nanoparticles, certain characteristics of the product quality such as size, morphology, abrasion resistance, specific surface, dispersibility and tendency to agglomeration are important. These characteristics are a function of the physicochemical properties, i.e. the micromechanical properties of the nanostructured material. The micromechanical properties of these nanostructured agglomerates such as the maximum indentation force, the plastic and elastic deformation energy and the strength give information on the product properties, e.g. the efficiency of a dispersion process of the agglomerates, and can be measured by nanoindentation. In this study a Berkovich indenter tip was used for the characterisation of model aggregates out of sol–gel produced silica and precipitated alumina agglomerates with different primary particle morphologies (dimension of 15–40 nm). In general, the effect of the primary particle morphology and the presence or absence of solid bonds can be characterised by the measurement of the micromechanical properties via nanoindentation. The micromechanical behaviour of aggregates containing solid bonds is strongly affected by the elastic–plastic deformation behaviour of the solid bonds and the breakage of solid bonds. Moreover, varying the primary particle morphology for similar particle material and approximately isotropic agglomerate behaviour the particle–particle interactions within the agglomerates can be described by the elementar breaking stress according to the formula of Rumpf.     

Evaluation and use of the Pd | SrCe0.95Yb0.05O3| Pd electrochemical reactor for equilibrium-limited hydrogenation reactions

The current — overpotential characteristics of the H₂ - Pd - SCY interphase have been studied at atmospheric total pressure and temparatures between 400 – 550 °C in the single chamber reactor — cell: Pd | SCY | Pd. The results of I−η measurements indicate that the apparent anodic and cathodic charge tranfer coefficients are equal to: α_a=α_c=0.5. The present results are compared to those obtained with the single — chamber reactor cell: Ag | SCY | Ag. A solid state proton (H⁺) conducting reactor — cell with Pd electrodes was tested for the ammonia synthesis from its elements at atmospheric pressure. At 570 °C, over 75% of the ectrochemically supplied hydrogen was converted into NH₃. The thermodynamic requirement for a high pressure process was eliminated. Paper presented at the 5th Euroconference on Solid State Ionics, Benalmádena, Spain, Sept. 13–20, 1998.     

Solid neon moderated electrostatic or magnetic positron beam

A high intensity variable energy positron beam has been constructed at Brookhaven National Laboratory (BNL). Positrons from a 97 mCi²²Na source are moderated by a thin layer of solid neon. A magnetic guiding system delivered up to 5×10⁶ e⁺/sec to an experiment. Currently, tests are under way to facilitate the operation with the magnetic guiding system or—for other experimental sites—with an electrostatic beam transport. The electrostatic lenses are fabricated from μ-metal. No compensation of the earth's magnetic field is required. Several experiments can utilize the beam on a time-sharing basis. In the near future, the source will be replaced by⁶⁴Cu, which has a much higher activity. Beam intensities up to 10⁹ e⁺/sec are expected.     

Poly-Essential and General Hyperelastic World (Brane) Models

This article provides a unified treatment of an extensive category of non-linear classical field models whereby the universe is represented (perhaps as a brane in a higher dimensional background) in terms of a structure of a mathematically convenient type describable as hyperelastic, for which a complete set of equations of motion is provided just by the energy-momentum conservation law. Particular cases include those of a perfect fluid in quintessential backgrounds of various kinds, as well as models of the elastic solid kind that has been proposed to account for cosmic acceleration. It is shown how an appropriately generalised Hadamard operator can be used to construct a symplectic structure that controles the evolution of small perturbations, and that provides a characteristic equation governing the propagation of weak discontinuities of diverse (extrinsic and extrinsic) kinds. The special case of a poly-essential model—the k-essential analogue of an ordinary polytropic fluid—is examined and shown to be well behaved (like the fluid) only if the pressure to density ratio w is positive.     

Evolution of large-scale correlations in a strongly nonequilibrium Bose condensation process

The evolution of off-diagonal correlation functions (for the example of a single-particle density matrix) in the process of Bose condensation of an initially nonequilibrium interacting gas is discussed. Special attention is given to the character of the decay of the density matrix at distances much greater than the size of the quasicondensate region. Specifically, it is shown that the exponential decay of the density matrix necessarily presupposes the presence of a chaotic vortex structure — a tangle of vortex lines — in the system. When topological order is established but there is no off-diagonal long-range order, the density matrix decays with distance according to a power law. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 495–501 (10 April 1998)     

Resonance states in 16O+16O, 12C+16O, α+16O and α+12C with modified Morse potentials

The resonance states in ¹⁶O+¹⁶O, ¹²C+¹⁶O, α+¹⁶O and α+¹²C are described using modified Morse potential proposed earlier whose success has already been demonstrated in the case of ¹²C+¹²C system. The general validity of such a potential with long range, shallow depth and repulsive soft core determined from the resonance data itself is being examined through the present study of the resonances in the above four systems. In each system, the experimental data of a large number of states have been successfully described with a modified Morse potential. The success points out a common mechanism of the origin of these states, and reaffirms authentically the diatomic-like rotational and vibrational picture of the nuclear molecular resonances proposed previously. The close resemblance between the physics of diatomic molecules and nuclear molecular resonances extending to the level of potential which is Morse type in both the cases — although belong to two different areas of physics — is further strengthened through the present study.      

Correlation Inequalities for Interacting Particle Systems with Duality

We prove a comparison inequality between a system of independent random walkers and a system of random walkers which either interact by attracting each other—a process which we call here the symmetric inclusion process (SIP)—or repel each other—a generalized version of the well-known symmetric exclusion process. As an application, new correlation inequalities are obtained for the SIP, as well as for some interacting diffusions which are used as models of heat conduction,—the so-called Brownian momentum process, and the Brownian energy process. These inequalities are counterparts of the inequalities (in the opposite direction) for the symmetric exclusion process, showing that the SIP is a natural bosonic analogue of the symmetric exclusion process, which is fermionic. Finally, we consider a boundary driven version of the SIP for which we prove duality and then obtain correlation inequalities.     

Operational resolutions and state transitions in a categorical setting

Abstruct We define a category with as objects operational resolutions and with as morphisms — not necessarily deterministic — state transitions. We study connections with closure spaces and join-complete lattices and sketch physical applications related to evolution and compoundness. An appendix with preliminaries on quantaloids is included.