Solution of problems on the stress state of an elastic medium with an inhomogeneous orthotropic cylindrical inclusion

A numerical-and-analytical approach to the investigation of the stress state of an elastic medium with an inhomogeneous cylindrical inclusion is proposed. The stress state is presented as a superposition of two state—the main state written in the analytical form and the disturbed one determined using analytical procedures and a numerical method. The stress state in the vicinity of the hollow cylindrical inclusion is analyzed. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 4, pp. 48–58, July–August, 1999.     

Virial equation of state and ideal-gas heat capacities of pentafluoro-dimethyl ether

A virial equation of state is presented for vapor-phase pentafluoro-dimethyl ether (CF₃−O−CF₂H), a candidate alternative refrigerant known as E125. The equation of state was determined from density measurements performed with a Burnett apparatus and from speed-of-sound measurements performed with an acoustical resonator. The speed-of-sound measurements spanned the ranges 260≤T≤400 K and 0.05≤P≤1.0 MPa. The Burnett measurements covered the ranges 283≤T≤373 K and 0.25≤P≤5.0 MPa. The speed-of-sound and Burnett measurements were first analyzed separately to produce two independent virial equations of state. The equation of state from the acoustical measurements reproduced the experimental sound speeds with a fractional RMS deviation of 0.0013%. The equation of state from the Burnett measurements reproduced the experimental pressures with a fractional RMS deviation of 0.012%. Finally, an equation of state was fit to both the speed-of-sound and the Burnett measurements simultaneously. The resulting equation of state reproduced the measured sound speeds with a fractional RMS deviation of 0.0018% and the measured Burnett densities with a fractional RMS deviation of 0.019%.     

Possible Fulde–Ferrel–Larkin–Ovchinnikov Inhomogeneous Superconducting State in CeCoIn5: Cd- and Hg-doping Studies

CeCoIn₅ undergoes a phase transition within the superconducting (SC) state. A new superconducting state occupies a high field–low temperature (HFLT) corner of the SC state in the H–T plane, and is a strong candidate for realization of the spatially inhomogeneous Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) superconducting state predicted theoretically in 1960s. We present specific heat data on Cd- and Hg-doped CeCoIn₅ that shows that the HFLT phase is suppressed by minute amount of impurities, few hundred parts per million. At this concentration, the average distance between impurities is close to twice the superconducting coherence length ξ, suggesting that ξ is the characteristic length of the HFLT state. We conclude that our investigations support the superconducting, posibly FFLO, origin of the HFLT state.      

The standard base of Russia for measuring small direct-current in the 10<Superscript>−16</Superscript>–10<Superscript>−9</Superscript> a range

The present state of the standard base of Russia for measuring small direct-current in the 10⁻¹⁶–10⁻⁹ A range is considered, and the metrological characteristics of the state primary and transferable standards are given. __________ Translated from Izmeritel’naya Tekhnika, No. 11, pp. 40–42, November, 2007.     

Kinetic Theory of Creep and Creep-Rupture Strength Analysis of Structural Components. Part 2. Limiting State of Non-Uniformly Heated Structural Components

For an arbitrary body (a structural member) subjected to external steady temperature and force actions, a limiting state condition which ensures the uniform strength of the body until its load-carrying capacity is exhausted has been derived using Rabotnov's kinetic theory of creep. A procedure of strength analysis of structural members by the limiting state is put forward. For the case where the limiting state condition is fulfilled only on some individual portions of the body's surface, a procedure of calculating its stress-strain state with the nearest approach to the uniform-strength state is outlined. __________ Translated from Problemy Prochnosti, No. 6, pp. 5 – 14, November – December, 2005.     

Some aspects of workability studies on P/M sintered high strength 4% Titanium carbide composite steel preforms during cold upsetting

Workability is concerned with the extent to which a material can be deformed in a specific metal working process without the initiation of cracks. Ductile fracture is the most common failure in bulk forming process. The formability is a complicated phenomenon which depends on the friction between the preform and the die surface in cold upsetting. A complete experimental investigation on the workability behavior of the steel composite of 4%TiC was performed under different stress states, namely, plane and triaxial stress state conditions. Cold upsetting of the Fe–1.0%C–4%Ti steel composite preforms was carried out applying different lubricants, namely, graphite, zinc stearate and molybdenum disulphide, and without lubricant, and the formability behaviour of the same under plane and triaxial stress state conditions was determined. The curves plotted for different preforms were analysed and relationship was established between the axial strain and the formability stress index under plane and triaxial state conditions. A relationship between the relative density and the axial strain was also established. Various stress ratio parameters, namely, (σ_θ/σ_eff), (σ_m/σ_eff) and (σ_z/σ_eff), under plane and triaxial stress state conditions were determined empirically as a function of the relative density. An attempt is also made to study the variation of slope of the relative density versus stress ratio parameters under plane and triaxial stress conditions with respect to the relative density to identify the pore closure mechanism.     

Reliability of the alpha coordinate-measurement engine

A method of evaluating the technical state of systems when in use that makes it possible to determine the onset of rapid ageing of a system as well as other operating characteristics, such as cost of failure and repair time, is considered. The technical state of the Alpha coordinate-measurement engine is analyzed and recommendations for modernization of the engine are given. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 16–19, December, 2008.     

Universal equipment for technical provision of communication facilities

A technical implementation version of an automatic system is suggested for monitoring the technical state of communication facilities. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 61–63, December, 2006.     

Spectroscopic investigation of the thermal stability of bound hydrogen in a-C: H

Equilibrium between free and bound hydrogen in amorphous hydrogenated carbon has been investigated by infrared spectroscopy. A quasireversible departure of hydrogen from the bound state is observed. The activation energy of the bound-quasifree hydrogen chemical reaction and the rate of return of hydrogen to the bound state are estimated. An energy diagram is proposed for the bound-quasifree hydrogen reaction. Pis’ma Zh. Tekh. Fiz. 23, 1–7 (April 12, 1997)     

Simple method for checking the steady state of fluctuations in linear electronic systems

A simple criterion is considered for checking the steady state of inherent fluctuations in a linear electronic measurement system. __________ Translated from Izmeritel’naya Tekhnika, No. 6. pp. 13–15, June, 2007.     

Formation of intermediate ordered states on spinodal decomposition of alloys

A model of diffusion phase transformations in alloys with a tendency toward ordering is suggested. It accounts for the vacancy mechanism of diffusion and the possible competition of the processes of ordering and decomposition. It is shown that the spinodal decomposition into components A and B from a homogeneous initial state may pass through the stage of formation of isolations of the ordered phase, with their stability being qualitatively increased in the region of low temperatures. The growth of colonies on decomposition of a metastable ordered state has been investigated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 789–795, July–August, 2008.     

Optico-digital correlators

A brief survey of the contemporary state and development of correlation measurements is given. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 18–22, January, 2009.     

Thermodynamic properties of the FC218-HFC 134a refrigerant mixture

Phase equilibria and thermal properties of the FC218-HFC134a mixture have been experimentally studied. A cubic equation of state describing the experimental data obtained is given. Tables of thermodynamic parameters of the mixture in the state of liquid-vapor phase equilibrium are calculated. Odessa State Academy of Cold, Odessa, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 5, pp. 756–760, September–October, 1996.     

Models of thermomechanical behavior of polymeric materials undergoing glass transition

The phenomenological models of the thermomechanical behavior of polymeric materials in a temperature range including the relaxation transition from the highly elastic to the glassy state (vitrification) and the reverse transition (softening) are considered. A model based on the interpretation of the glass transition as a process of gradual increase in intermolecular bonds in the polymer network, “freezing” the current strain with decreasing temperature is developed. A scalar parameter is introduced—the “degree of vitrification,” to establish the quantitative dependence of the relaxation transition completion by temperature. Constitutive relations of thermomechanical behavior of vitrifying polymers in uniaxial and complicated stress states in the “elastic approximation” simplification are obtained. A system of experiments for the identification of the proposed model material functions and constants is formulated and implemented. Analytical model problems are solved, clearly illustrating the mechanism for generation of technological and residual stresses in glass polymers in non-uniform cooling.     

The Convective Instabilities in a Liquid–Vapor System with a Non-equilibrium Evaporation Interface

Rayleigh–Marangoni–Bénard instability in a system consisting of a horizontal liquid layer and its own vapor has been investigated. The two layers are separated by a deformable evaporation interface. A linear stability analysis is carried out to study the convective instability during evaporation. In previous works, the interface is assumed to be under equilibrium state. In contrast with previous works, we give up the equilibrium assumption and use Hertz–Knudsen’s relation to describe the phase change under non-equilibrium state. The influence of Marangoni effect, gravitational effect, degree of non-equilibrium and the dynamics of the vapor on the instability are discussed.     

State equation of mineral sands

The pressure-volume analogy between compressible fluids and macroscopic sand bodies (Ivsic et al. in Phys A, 277:47–61, 2000) is further extended using quantitative determination of corresponding empirical constants based on adapted van der Waals state equation. The isothermal constants obtained by interpretation of triaxial sand tests at so called “critical state of sand” are clearly related to the universal ideal gas properties and molar properties of mineral sands. The corresponding constants for sand and gases or other volatile liquids have the same order of magnitude. The apparent bulk repulsion/attraction effects in sand bodies are also discussed.     

Comparison of the efficiencies of rectification trays in countercurrent motion of phases with allowance for liquid mixing

Consideration is given to a tray liquid in the intermediate state between ideal displacement and total mixing, for which purpose the degree of attaining the latter state by the liquid is introduced. The composition of the vapor after leaving an ideal tray is assumed to be in equilibrium with that of the liquid in its intermediate state. Four variants of interrelation of the real and ideal trays are considered; the efficiencies for the vapor and the liquid are proved to be equal for each of them. Ratios for the efficiencies of all the variants are obtained. A comparison is made of the efficiency ratios as functions of liquid mixing. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 514–519, May–June, 2000.     

Method of the shortcut estimation of rails' reliability by the fatigue strength criterion

The diagram of damage of structural steels under bending and contact loading has been constructed. The criterion of the critical state of steels is proposed, which corresponds to the formation of incipient surface cracks in the rolling friction zone. The methods of shortcut estimation of the damaged state of railway rails, which provide prediction of their reliability and life under service conditions, are proposed. A set of experimental studies is made with objectives to justify the proposed diagram, criterion and methods. __________ Translated from Problemy Prochnosti, No. 1, pp. 88–94, January–February, 2009.     

Method for increasing <Emphasis Type="Italic">β</Emphasis>-SiC yield on solid state reaction of coal fly ash and activated carbon powder

A novel process for increasing β-SiC yield on solid state reaction of coal fly ash and micro powder activated carbon powder has been proposed. β-SiC powder was synthesized at temperature 1300°C for 2 h under vacuum condition with 1 l/min argon flow. Cycling synthesis process has been developed for increasing β-SiC yield on solid state reaction of coal fly ash and activated carbon powder. Synthesized products were analyzed by XRD with Cu-Kα radiation, FTIR spectrometer and SEM fitted with EDAX. The results show that the amount of relative β-SiC is increased with the number of cycling synthesis.