Volume 88, №1
SOME LAWS GOVERNING TWISTED TWO-PHASE FLOWS IN THE OVER-BED SPACE OF A FLUIDIZED BED OF FINELY DIVIDED PARTICLES
As a result of experimental investigation of the hydrodynamics of a twisted air fl ow above a fl uidized bed, the character of the effect of particle entrainment from the latter on the distribution of air velocities and pressure in the vortex zone has been established.
Author: E. A. Pitsukha, Yu. S. Teplitskii, and V. A. Borodulya
Keywords: bubbling (fluidized) bed, over-bed space, vortex zone, particle entrainment, gas velocity, particle velocity
DYNAMICS OF A COAGULATING POLYDISPERSE GAS SUSPENSION IN THE NONLINEAR WAVE FIELD OF AN ACOUSTIC RESONATOR
A model of a multivelocity multitemperature polydisperse gas suspension has been constructed with account taken of coagulation. Calculations of the dynamics of an aerosol of a polydisperse composition in an acoustic resonator have been done and the derived regularities have been described. A system of Navier–Stokes equations for a compressible heat-conducting gas was used to describe the motion of a carrier medium. The dynamics of dispersed fractions is described by a system of equations including continuity, momentum, and internal-energy equations. The equations of motion of the carrier medium and dispersed fractions have been written with account of the interphase exchange of momentum and energy. The Lagrangian model has been used to describe the process of coagulation. The change in the dispersity of the gas suspension in the nonlinear fi eld of an acoustic resonator has been analyzed.
Author: A. L. Tukmakov
Keywords: acoustic resonator, Navier–Stokes equations, equations of motion of a polydisperse gas suspension, McCormack explicit scheme, nonlinear and discontinuous vibrations, coagulation of particles
METHOD FOR CALCULATING THE PROCESSES OF MELTING AND SOLIDIFICATION OF HEAT-ACCUMULATING MATERIALS IN FINE CAPSULES
We propose a new method for calculating the processes of melting and solidifi cation of heat-accumulating materials placed inside small-sized elastic capsules of symmetric form. The specifi c feature of the method is the simultaneous solution of the heat conduction equation joined for both phases and the equation for the rate of change in the mass fraction of the new phase in the layer between two neighboring nodes of a stationary computational mesh. The method permits using explicit fi nite-difference schemes for continuous calculations of the nonlinear heat conduction equation without loss of stability at weak and alternating external heat fl ows, as well as in the presence of several phase transition zones in the capsule. The paper presents the results of a test solution of the two-phase Stefan problem for an unbounded plate and the results of calculations for spherical capsules with n-paraffi n in one regenerative convective heat cycle.
Author: V. N. Didenko, R. Z. Kasimov, and D. N. Popov
Keywords: method for heat transfer calculation, zone and degree of phase transition, Stefan problem, stability of a solution, computational modeling
PROCESS OF DISSOLUTION OF POLYDISPERSE MATERIALS IN A UNIT WITH A ROTARY PULSATION APPARATUS
In this article, the authors have presented a mathematical model of the process of dissolution of polydisperse materials in a unit with a rotary pulsation apparatus; the model takes account of the mechanical grinding of dissolved particles. Experimental work on substantiation of the effi ciency of the mathematical dissolution model has been performed. Data on dissolution in the unit with a pulsation apparatus and with a bulk-capacity tank have been compared. Methods for raising the effi ciency of units with rotary-type pulsation apparatuses when the dissolution of dispersed materials is carried out in them have been proposed.
Author: A. A. Kukhlenko, S. E. Orlov, D. B. Ivanova, and M. S. Vasilishin
Keywords: rotary pulsation apparatus, dissolution, kinetics
MODELING OF HEAT AND MOISTURE TRANSFER IN WOOD IN FINISH DRYING BY THE ENERGY OF A MICROWAVE FIELD
A physicomathematical model of heat and moisture transfer in drying materials in the region below the hygroscopicity limit, including also the heating by the energy of a microwave fi eld, has been developed. The developed system of equations has been solved numerically for three cases of drying of a wooden plate: convective drying, drying by the microfi eld-fi eld energy, and drying combining the above two methods, i.e., combined drying. Results of numerical calculations of the temperature, vapor-pressure, and moisture-content distributions in the cross section of the plate at different instants of time, and also of the change in the average moisture content and temperature in the process of drying, have been presented. The calculation results have been analyzed; conclusions on the differences and distinctive features of convective, microwave, and combined heating and drying have been drawn
Author: N. N. Grinchik, A. L. Adamovich, O. A. Kizina, and U. M. Kharma
Keywords: wood, moisture content, convective heating, microwave drying, combined heating and drying
INFLUENCE OF THE VISCOSITY OF A LIQUID ON THE DYNAMICS OF SPREADING OF ITS DROP
A method of experimental investigation of the dynamics of spreading of a spherical drop of a viscous liquid over a horizontal solid surface at a small velocity of collision of the drop with the surface is proposed, and results of such an investigation are presented. A typical pattern of spreading of a liquid drop over a solid surface has been obtained and the quantitative characteristics of this process depending on the viscosity of the liquid were determined. The experimental data on spreading of drops of different liquids over a horizontal solid surface were analyzed by the dynamic wetting angle of these drops, and the results obtained were compared with the analogous data obtained in other works.
Author: V. A. Arkhipov, S. S. Bondarchuk, A. S. Usanina,
Keywords: drop, viscous liquid, spreading, dynamic wetting angle, three-phase contact
DETERMINATION OF THE MOISTURE-SORPTION ISOTHERMS AND ISOSTERIC HEAT OF HENNA LEAVES
Equilibrium moisture desorption and adsorption isotherms of Lawsonia inermis L. (commonly known as henna)
leaves at temperatures of 30, 40 and 50<sup>o</sup> C with a water activity ranging from 0.057 to 0.898 were obtained by the
gravimetric-static method. It was established that when the temperature of these leaves increases, their moisture content increases too with a hysteresis effect. The experimental data on the sorption of the indicated leaves were compared with the corresponding calculation data obtained with the use of the GAB, modifi ed BET, Henderson–Thompson, modifi ed Halsey, modifi ed Oswin, and Peleg models. Evaluation of these models on the basis of statistical processing of the data obtained with them, including the calculus of the standard error and the correlation
coeffi cient, has shown that the GAB and Peleg models represent sorption curves more adequately. The net isosteric
heats of desorption and adsorption of henna leaves were determined by the sorption isotherms constructed using the
Clausius–Clapeyron equation. An expression for predicting these thermodynamic properties of plants is proposed.
Author: S. Bennaceur, B. Draoui, B. Touati, A. Benseddik, A. Saad, and L. Bennamoun
Keywords: henna leaves, equilibrium moisture sorption, isosteric heat of sorption, sorption isotherms
INFLUENCE OF HEAT-EXCHANGE SIMILARITY CRITERIA ON THE DRYING OF INDUSTRIAL FABRICS BY THERMAL RADIATION
The drying of industrial fabrics was investigated within the framework of the heat-and-mass exchange theory by the method of regular regime of heating of a moist body at a constant temperature of the heat-transfer agent. Empirical equations for calculating the main kinetic parameters of drying of the indicated fabrics on the basis of the Boltzmann radiation criterion have been derived. A method of graphical-analytical calculation of the drying kinetics of fabrics is proposed.
Author: A. I. Ol′shanskii, V. I. Ol′shanskii, and S. V. Zhernosek
Keywords: moist material, convection-radiation drying, similarity criteria, regular regime of heating
DESIGN OF A GAS–LIQUID UNBAFFLED STIRRED TANK WITH A CONCAVE BLADE IMPELLER
Experimental investigation of unbaffl ed multiphase (gas–liquid) stirred tanks is conducted with the use of a concave blade impeller to analyze mass transfer, gassed power, and gas holdup. The experiments are carried out with various impeller diameter to tank diameter ratios and impeller clearances. The design criterion for the mass transfer rate is proposed, and its prediction capability is found to be satisfactory. The results show that the gassed power is dependent on the impeller diameter to tank diameter ratio and impeller clearance. The design criteria for gassed power to ungassed power ratio and gas holdup are also introduced. Multiphase modeling is done by employing the computational fl uid dynamics (CFD) techniques to observe the characteristic fl ow pattern transition and to carry out a qualitative analysis of the mass transfer rate.
Author: T. T. Devi and Bimlesh Kumar
Keywords: concave blade impeller, gas holdup, impeller clearance, mass transfer, power number, stirred tank
PYROGRAPHITE FILMS DEPOSITED ONTO A METAL SURFACE IN THE REGIME OF DISPLACEMENT OF THE HEATING ZONE
We have investigated the properties of pyrocarbon films formed as a foil on nickel and copper substrates by means of deposition from a mixture of helium with methane, CH4, or with vapors of ethanol, C2H5OH, at atmospheric pressure. It has been established that when a nickel substrate is heated to a temperature of 1300–1400oC, graphitized films with a high degree of crystallinity are formed on the substrate surface.
Author: S. V. Shushkov, O. V. Korolik, A. V. Mazanik, A. S. Egorov, and M. I. Govorov
Keywords: pyrographite fi lm, gas discharge, plasma-induced heating, graphene structures
SIMULATING THE COMBUSTION OF N POWDER WITH ADDED FINELY DIVIDED ALUMINUM
A mathematical model for combustion of N powder with added aluminum particles is presented. It takes account of the exothermal chemical reaction in the gas phase, convection and diffusion, heating, and combustion of aluminum particles in the gas fl ow, the motion of combustion products, and the lag of the particle velocity behind that of the gas. The results of calculation of the burning velocity of powder correspond to the experimental data on the dependence of this velocity on pressure and aluminum particle size. It has been established computationally that for aluminum particles of diameter less than 20 μm the burning velocity of N powder depends substantially on the size of these particles.
Author: V. A. Poryazov, A. Yu. Krainov, and D. A. Krainov
Keywords: N powder, gas-dispersive medium, aluminum particles, ignition, combustion
SIMULATION OF THE FLAME PROPAGATION IN A METHANE–AIR MIXTURE IN THE PRESENCE OF WATER AEROSOL
We have formulated a physicomathematical model of the fl ame propagation in a combustible gas containing water aerosol based on the thermal-diffusion model of the laminar fl ame propagation in a gas and taking into account the processes of heat and mass transfer between the phase and liquid drops. Computational-theoretical studies of the infl uence of water aerosol characteristics on the fl ame velocity in a lean methane–air mixture have been made. Comparison of the results of calculations with experimental data has shown that there is good agreement between them. Comparison of the effi ciency of using water aerosol and inert gas to stop the spread of fi re has shown that there exists a limiting size of the dispersed phase above which the effi ciency of using water aerosol and inert powders to stop the spread of fi re becomes equal
Author: A. Yu. Krainov
Keywords: combustible gas, water aerosol, fl ame front, computational modeling
MODELING OF THERMOPHYSICAL PROCESSES IN THE IGNITION OF A SMALL WOODEN PLANK
A formulation and a numerical solution based on a mathematical model of a porous reactive medium are given to the problem of ignition of a wooden plank by the action of a fi re source. It is found that the ignition of the original reactant is determined by the processes of heat and mass exchange with the fi re source, drying, and pyrolysis (decomposition and synthesis reactions) of a dry plank, by the reaction of oxidation of carbon dioxide, and also by the thermophysical properties of wood.
Author: E. L. Loboda, D. P. Kasymov, and A. S. Yakimov
Keywords: wood, heat conduction, pyrolysis, ignition, water
MATHEMATICAL MODELING OF ULTRAPOROUS NONMETALLIC RETICULATED MATERIALS
We have developed an imitation statistical mathematical model refl ecting the structure and the thermal, electrophysical, and optical properties of nonmetallic ultraporous reticulated materials. This model, in combination with a nonstationary thermal experiment and methods of the theory of inverse heat transfer problems, permits determining the little-studied characteristics of the above materials such as the radiative and conductive heat conductivities, the spectral scattering and absorption coeffi cients, the scattering indicatrix, and the dielectric constants, which are of great practical interest but are diffi cult to investigate.
Author: O. M. Alifanov, V. V. Cherepanov, and A. V. Morzhukhina
Keywords: reticulated nonmetallic ultraporous materials, reticulated porous ceramics and vitreous carbon, imitation mathematical model.
COMPLEX STUDY OF THE PHYSICAL PROPERTIES OF RETICULATED VITREOUS CARBON
We give an example of using a two-level identifi cation system incorporating an augmented mathematical model covering the structure, the thermal, electrophysical, and optical properties of nonmetallic ultraporous reticulated materials. The model, when combined with a nonstationary thermal experiment and methods of the theory of inverse heat transfer problems, permits determining the little studied characteristics of the above materials. We present some of the results of investigations of reticulated vitreous carbon confi rming the possibility of using it in a number of engineering applications.
Author: O. M. Alifanov, V. V. Cherepanov, and A. V. Morzhukhina
Keywords: reticulated vitreous carbon, two-level identifi cation system, thermal and optical properties
THERMOPHYSICAL CHARACTERISTICS OF THE PROTECTIVE COATING OF THE SOLDERING ROD
An analytical dependence of the change in the soldering temperature on the material, thickness of the soldering rod protective coating, and the time of soldering is obtained. The relation derived allows one to ensure the needed temperature of contact soldering of electronic and electrical-engineering components and, consequently, their high quality
Author: V. N. Shtennikov
Keywords: soldering, heat transfer, soldering rod, protective coating, soldering time, temperature
MEASUREMENT OF THE THERMAL-CONDUCTIVITY COEFFICIENT OF NANOFLUIDS BY THE HOT-WIRE METHOD
In this work, the authors present results of adaptation and testing of the hot-wire method for determination for the thermal-conductivity coeffi cient of nanofl uids. A mathematical model of heat transfer with allowance for free convection has been constructed to elucidate the parameters of an experimental setup and the range of its applicability. The experimental procedure has been tested on measurements of the thermal conductivities of water and ethylene glycol. The thermal-conductivity coeffi cient of a nanofl uid has been measured at room temperature. The nanofl uid under study was prepared on the basis of ethylene glycol and alumina nanoparticles. The concentrations of the nanoparticles ranged from 0.5% to 2% by volume. Good agreement has been obtained between the measured values of the thermal-conductivity coeffi cient and the data of other authors
Author: A.V. Minakov, V. Ya. Rudyak, D. V. Guzei, M. I. Pryazhnikov, and A. S. Lobasova,
Keywords: heat conduction, hot-wire method, free convection, nanoparticles, nanofl uid, CFD (computational fluid dynamics), experiment.
COMPUTATIONAL AND EXPERIMENTAL INVESTIGATIONS INTO THE MASS LOSS OF A CARBON MATERIAL IN THE SUBLIMATION REGIME OF ITS THERMOCHEMICAL DESTRUCTION
The authors give results of an experimental investigation into the ablation characteristics of a modern fine granular carbon material in the high-enthalpy jet of a TT-1 arc-heated facility  ("TsNIImash" Federal State Unitary Enterprise), and also results of computational and experimental investigations into the parameters of the jet of this facility. Data given in the article provide a basis for studying the regularities of the mass loss of the carbon material in a sublimation regime of its thermochemical destruction.
Author: V. V. Gorskii, S. L. Zolotarev, and A. A. Olenicheva
Keywords: carbon material, sublimation, oxidation, combustion loss
COMPUTATIONAL MODELING OF CONJUGATE HEAT TRANSFER IN A CLOSED RECTANGULAR DOMAIN UNDER THE CONDITIONS OF RADIANT HEAT SUPPLY TO THE HORIZONTAL AND VERTICAL SURFACES OF ENCLOSURE STRUCTURES
We have carried out computational modeling of nonstationary conductive-convective heat transfer in a closed rectangular domain in a conjugate formulation with a local heat source (a gas infrared radiator). Four variants of possible description of the radiant energy distribution over the inner surfaces of enclosures have been considered. As a result of the computational modeling, differential (temperature fi elds and stream functions) and integral (Nusselt numbers) heat transfer characteristics have been obtained. It has been shown that the radiant fl ux distribution infl uences the heat transfer intensity.
Author: G. V. Kuznetsov, T. A. Nagornova, and A. É. Ni
Keywords: infrared radiator, radiative heating, conjugate heat transfer, computational modeling, natural convection, heat conduction
METHODS TO ELIMINATE THE OVERHEATING OF HIGH-CURRENT ELECTROOPTICAL SYSTEMS
The use of high-current electrooptical systems (EOSs) becomes increasingly topical at present. However, in typical high-current EOSs, intense thermal regimes in the EOS-platform drives often give rise to overheating which may end in the failure of the EOS. It has been shown that such evident measures as blowing and painting of the EOS casing and displacement of the platform drive inside the EOS volume do not cause the temperature regimes to substantially change. Also, it has been shown that the use of a nontraditional antibacklash transmission in the platform drive may lead to a substantial decrease in the overheating inside the EOS casing.
Author: V. T. Budai and N. V. Kasatkin
Keywords: electrooptical systems, thermal regimes, heat-transfer coefficient
NUMERICAL AND PHYSICAL SIMULATION OF THE LOW-VELOCITY AIR FLOW IN A DIFFUSER WITH A CIRCULAR CAVITY IN THE CASE OF SUCTION OF THE AIR FROM THE CENTRAL CYLINDRICAL BODY POSITIONED IN THE CAVITY
Comparative analysis of the results of solution of the steady-state Reynolds equations closed with the use of the shear-stress transfer model for the air fl ow in a divergent channel with suction of the air from the surface of the cylindrical central body positioned in the circular vortex cavity built in the lower wall of the channel with the corresponding experimental data has been performed
Author: S. A. Isaev, S. V. Guvernyuk, M. A. Zubin, P. A. Baranov,
Keywords: control of separation fl ow, vortex cavity, central body, suction of air, diffuser, turbulence
A METHOD OF DECREASING THE DRAG OF A HEAVY-DUTY TRUCK WITH THE USE OF FRONT AND STERN BOARD GENERATORS OF LARGE-SCALE VORTICES
A method of improvement of the aerodynamic and working characteristics of automobiles with the use of generators of large-scale vortices is proposed. The drag of a model container truck, on which board vortex generators were positioned in front of the cab of the truck and at the rear of its container, was experimentally investigated. By varying the geometric parameters of the model truck, its rational arrangement providing a decrease in the drag of the truck and an economy of the fuel consumed by it was determined.
Author: S. A. Isaev, Yu. F. Gortyshov, V. M. Gureev, Yu. S. Opara, and I. A. Popov
Keywords: heavy-duty truck, board generator of vortices, drag
MODEL OF MASS TRANSFER IN LIQUID–LIQUID EXTRACTION IN A TURBULENT FORWARD FLOW
A mathematical description of the process of mass transfer in a continuous phase in the turbulent motion of two mutually insoluble liquids has been obtained on the basis of an assigned law of damping of turbulent pulsations in the boundary layer. The basic parameters of the model have been found in terms of the hydraulic resistance of a droplet in motion. Consideration has been given to the use of the mathematical mass-transfer model in apparatuses with mixing devices. Agreement has been shown between results of calculation of mass-transfer coeffi cients and experimental data.
Author: A. G. Laptev, T. M. Farakhov, and O. G. Dudarovskaya
Keywords: liquid–liquid extraction, mass transfer, extraction effi ciency, packings, transfer phenomena, turbulence
NUMERICAL AND ANALYTICAL SIMULATION OF THE STRUCTURE OF A SUPERSONIC GAS FLOW IN A VARIABLE-SECTION CHANNEL WITH POWER SUPPLY
The influence of a periodic supply of power pulses to the gas fl ow in a variable-section channel on the formation of shock structures in this fl ow was investigated. Parameters of the power supply providing different regimes of flow in the indicated channel and criteria of these regimes were determined on the basis of the solution of the problem of a powerful explosion with the use of the similarity theory and the homochronicity number. The results of the numerical simulation of the fl ow in the variable-section channel with power supply in the quasi-one-dimensional approximation and of the fl ows in cylindrical and plane channels were compared. The applicability of the analytical dependences obtained was substantiated by the results of the numerical solution of the quasi-one-dimensional and two-dimensional Euler equations for the fl ow of an ideal gas in the indicated channels.
Author: V. P. Zamuraev and A. P. Kalinina
Keywords: supersonic flow, variable-section channel, pulsed power supply, Euler equations
MODEL OF TURBULENT FLOW OF RHEOLOGICAL SOLUTIONS OF FOAMING AGENTS IN CHANNELS OF AUTOMATIC FIRE-EXTINGUISHING SYSTEMS
A model of turbulent flow of a rheological solution of a foaming agent in a cylindrical channel of an automatic fi re-extinguishing system is proposed; this model allows for the viscous stresses produced in the region of hydraulic roughness of the channel. Integral equations are obtained for calculation of the fl ow velocity and rate of fl ow of the foaming agent in the indicated channel, and also of the hydraulic resistance and head loss in it. Recommendations on practical use of the proposed theoretical model have been developed.
Author: I. I. Polevoda, I. V. Karpenchuk, M. Yu. Striganova, and É. É. Shatilo
Keywords: automatic fi re-extinguishing system, turbulent fl ow, non-Newtonian fl uid, foaming agent
FEATURES OF THE NONISOTHERMAL VISCOELASTIC JET FLOW THROUGH A MOLDING EXTENSION
We have investigated the steady creeping nonisothermal fl uid fl ow with free surface for a polymer fl uid at the inlet to the molding channel and at its outlet. The fl uid motion is described by the mass, momentum, and energy equations complemented by the constitutive Giesekus equation of the fl uid state. We have analyzed the distribution pattern of the fl uid velocity in the outfl owing jet and the pressure, stress, and temperature fi elds with increasing degree of heating of the molding channel wall. We present the results of calculating the dependence of the swelling coeffi cient of the polymer fl uid on the extension geometry, the rheological model parameters, and the temperature factors.
Author: B. A. Snigerev
Keywords: viscoelastic incompressible fluid, Giesekus rheological model, nonisothermal flow with free surface
UNSTEADY RADIATIVE-CONVECTIVE BOUNDARY-LAYER FLOW OF A CASSON FLUID WITH VARIABLE THERMAL CONDUCTIVITY
The unsteady two-dimensional flow of a non-Newtonian fl uid over a stretching surface with the effects of thermal radiation and variable thermal conductivity is investigated. The Casson fl uid model is used to characterize the nonNewtonian fl uid behavior. First, using a similarity transformation, the governing time-dependent partial differential equations are transformed into coupled nonlinear ordinary differential equations with variable coeffi cients. Then the transformed equations are solved numerically under appropriate boundary conditions by the shooting method. An exact solution corresponding to the momentum equation for a steady case is found. The obtained numerical results are analyzed as to the effect of the pertinent parameters on the fl ow and heat transfer characteristics.
Author: M. Gnaneswara Reddy
Keywords: unsteady boundary layer, Casson fl uid, variable thermal conductivity, thermal radiation, stretching surface
DUAL-PHASE-LAG MODEL OF WAVE PROPAGATION AT THE INTERFACE BETWEEN ELASTIC AND THERMOELASTIC DIFFUSION MEDIA
A dual-phase-lag diffusion model, augmenting the Fick law by the inclusion of the delay times of the mass flow and the potential gradient at the interface between two media into it, is proposed. The effects of refl ection and refraction of plane waves at the interface between an elastic and a thermoelastic diffusion media were investigated with the use of this model. It was established that the ratios between the amplitudes and energies of the waves refl ected and refracted at the interface between the indicated media are determined by the angle of incidence of radiation on this interface, the frequency of the incident wave, and the thermoelastic and diffusion properties of the media. Expressions for the ratios between the energies of different refl ected and refracted waves and the energy of the incident were derived. The variation in these ratios with change in the angle of incidence of radiation on the indicated interface was calculated numerically and represented graphically
Author: R. Kumar and V. Gupta
Keywords: thermoelastic medium, diffusion, dual-phase lag, reflection, transmission
METHOD OF RELAXATION MOMENTS FOR STUDYING NONLINEAR LOCALLY NONEQUILIBRIUM PROCESSES OF TRANSFER OF POLYMERIC SYSTEMS
A method for simulating the processes of transfer of thermodynamic systems with polymeric microstructure is considered. The method is based on the classical locally equilibrium medium-state entropy concept expanded by the introduction of a structural tensor parameter whose evolution characterizes the nonlinear anisotropic relaxation properties of a thermodynamic system and the associated transfer phenomena. The dynamic, thermal, and mass transfer characteristics of macrotransfer are determined by corresponding integrals of relaxation moments.
Author: V. I. Popov
Keywords: polymeric systems, conservation laws, rheological equations of state, locally nonequilibrium transfer processes, entropy, relaxation
DESTRUCTION AND ACCOMPANYING PHENOMENA IN A FERROMAGNETIC Ni2MnGa SINGLE CRYSTAL WITH A SHAPE-MEMORY EFFECT
Features of the shape of a macroscopic interplanar crack have been studied, and phenomena accompanying destruction in a monocrystalline ferromagnetic Ni2MnGa alloy with shape memory have been analyzed. It has been established that the initiation of destruction in Ni2MnGa is actively infl uenced by the processes of slip and interaction of twin boundaries in twin planes which are at small angles to each other, and also by the formation of Rose channels. On the source side of the surface at which the crack has nucleated, it is tooth-shaped. On this surface, there are signs of rotation of the crystal lattice from twins with boundaries parallel and perpendicular to the crack′s edges. The opening of the crack in its boundary regions leads to partial untwining
Author: O. M. Ostrikov and E. V. Shmatok
Keywords: destruction, mechanical twinning, ferromagnetic alloy with a shape-memory effect.
DEVELOPMENT OF THE REGIMES OF SEMIAUTOMATIC CONTACT SOLDERING
The infl uence of the soldering rod length on the contact soldering temperature has been studied. The results of investigations were taken as a basis for incorporating a high-speed semiautomatic regime of soldering integrated circuits with planar leads to multilayer printed circuit boards. It has been established that to ensure an optimum soldering temperature it is necessary to take account of the temperature of the soldering rod before soldering, its length and diameter, and the soldering time when the rod is short
Author: V. N. Shtennikov
Keywords: contact soldering, multilayer printed circuit board, temperature, heat exchange, solder