Adsorption on solid surface taking into account finite deformations

An earlier-suggested thermodynamic theory of equilibrium single-component adsorption from a liquid on a solid surface bearing an electric charge taking into account its low deformation is extended to the finite deformation region. An accurate solution of compatibility equations and the corresponding equation of the adsorption isotherm and expression for electric surface charge density is derived within the model of two parallel capacitors of the surface-layer structure for the specific form of the functional dependence of the adsorbate surface concentration on independent derivatives of the thermodynamic state.     

Diffusion in solid plate taking into account internal adsorption of diffusing component

The diffusion process of loss in time inside the solid phase (an infinite strip) of substance accumulated up to the initial moment on its two outer boundaries is studied taking into account its internal equilibrium adsorption according to a nonlinear isotherm. The exact upper and lower boundary solutions are obtained for the corresponding nonlinear integral equation. Plots of estimates of the error for the approximate solutions (half sum of the upper and lower boundaries) are presented.     

Evaluation of interconnected production sites taking into account multidimensional uncertainties

The production sites of international companies are becoming increasingly interconnected. Due to the uncertainty of multiple factors, determining a location is a strategic choice entailing high financial risk. For this reason, a method for site evaluation was developed allowing multidimensional, i.e., both quantitative and qualitative, uncertainties to be taken into account. The uncertainties are modeled with both probability and fuzzy-set theory and integrated into a modular-structured monetary calculation model. For the analysis and interpretation of evaluation results, methods have been developed which allow risk assessment. The developed method provides a way to handle existing location risks and can thus ensure the success of manufacturing companies in the long term.     

考虑金属逐步填充的多道焊温度场数值模拟

采用“单元死活”有限元技术自行编制了控制焊接过程金属填充的子程序,利用Marc有限元软件以低碳钢为例进行了三维多道焊温度场的数值模拟。实现了模拟过程中焊接材料的逐步填充,温度场计算结果与试验测量值十分吻合。将计算结果与未考虑材料逐步填充的多道焊计算结果进行了比较。结果表明,是否考虑金属逐步填充对多道焊计算结果影响很大,在多道焊次数较多时不可忽略。为更准确的多道焊应力分析打下了基础。     

Essential shortcomings of Tafel equations in describing electrochemical dissolution kinetics of a solid electrode

A simplified topokinetic dissolution model of a solid taking into account the correlation between the dissolution rate and the atomic surface topography enables one to interpret a linear (in semilogarithmic coordinates) segment of the steady-state curves of the active anodic dissolution of metals. Its slope corresponds to the product of a concentration of kinks and the elementary reaction rate, both of which exponentially depend on the potential, rather than a simple (Tafel) elementary rate of the atom dissolution at a semi-crystal kink. Original Russian Text ? Yu.V. Alekseev, G.Yu. Alekseev, V.A. Bityurin, A.V. Plaskeev, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 6, pp. 568–573.     

The effect of grain boundary on the dissolution of base metal into insert metal during TLP bonding of Ni-base superalloys

The dissolution of base metal into insert metal during TLP bonding of Ni base CMSX-2 superalloys, was studied. The effect of grain size on the dissolution phenomenon was also investigated. TLP bonding of single crystal, coarse grained and fine grained CMSX-2 specimens was carried out at 1373–1548 K for 019.6 ks under 2.3 MPa. During TLP bonding, the dissolution of the base metal into insert metal occurred very rapidly, leading to constant dissolution width at a given holding time. The dissolution width of the base metal broadened with increasing bonding temperature and holding time in all samples used. The dissolution of the base metal into the insert melt pool was governed by Nernst-Brunner’s theory in any grain size of base metal. The saturation time for dissolving base metal shortened, but its width broadened with increasing bonding temperature. The dissolution rate of the base metal increased with decreasing grain size of the base metals.     

Calculation of the thermal cycles of points in automatic welding and surfacing taking special features of melting of parent metal into account

It is shown that the well-known equations proposed by N.N. Rykalin for calculating temperatures and also the main parameters of the thermal cycles of points in automatic welding and surfacing with the allowance made for the factors associated with the melting of parent metal should be corrected.     

基于相变诱导塑性Satoh试验的有限元模拟

通过将相变诱导塑性应变增量引入到总应变增量的分解式中,建立了温度-组织-应力耦合计算的有限元模型.在此基础上,以9Cr1Mo钢作为研究对象,对其Satoh试验进行了有限元模拟,对温度-组织-应力耦合计算以及传统的热弹塑性计算结果进行了对比分析.结果表明,无论在应力的演变上,还是在残余应力水平上,两种计算得到的结果均存在较大差异.由于忽略相变的影响,热弹塑性计算得到的结果无法反映在相变过程中所发生的应力"松弛"现象,与实际结果偏差较大.准确地对焊接应力应变进行预测,需要通过温度-组织-应力耦合考虑相变的影响.     

Statistical aspect of the independence principle of heterogeneous reactions taking into account the surface state

The independence principle of electrode reactions is shown to be no more than a particular example of the theoretical-probabilistic regularities determined by the statistical nature of a large scope of systems studied by the chemical kinetics. It does not exclude but explains the possible mutual effect of different reactions on each other. In the case of a mass exchange between a structured solid and a solution or a gas, the independence principle should be formulated in terms of the superficial atom positions determined by the number of close neighbors. Original Russian Text ? Yu. V. Alekseev, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 339–347.     

The electrochemical deoxidation of metal oxides by calcium using a solid oxide membrane

The reduction of a metal oxide by calcium in a CaCl₂ melt produces metal and calcium oxide (CaO) dissolved in the molten chloride. To minimize waste salts, the reacted salts have to be regenerated. This can be done either by converting CaO to CaCl₂ by chlorination with Cl₂ and adding calcium metal or by electrochemical deoxidation of CaO. In the first method, the addition of calcium metal increases the amount of reacted salts, and consequently the waste salts, while in the second method the quantity of reacted salts remains constant. The electrochemical deoxidation of CaO occurs in one step and the produced oxygen is evacuated. This article describes a study of the electrochemical deoxidation of CaO using a solid oxide membrane. A. Martin is with LEPMI and CEA/Valduc; D. Lambertin, G. Bourges, and L. Pescayre are with CEA/Valduc; J.-C. Poignet and J. Fouletier are with LEPMI; and M. Allibert is with LTPCM.     

Mathematical modeling taking into account of intrinsic kinetic properties of cylinder-type vanadium catalyst

The method to calculate internal surface effective factor of cylinder-type vanadium catalyst Ls-9 was giv-en. Based on hypothesis of subjunctive one dimension diffusion and combined shape adjustment factor with three-step catalytic mechanism model, the macroscopic kinetic model equation about SO2 oxidation on Ls-9 was deduced.With fixed-bed integral reactor and under the conditions of temperature 350 - 410℃, space velocity 1800-5000h^-1 , SO2 inlet content 7%-12%, the macroscopic kinetic data were detected. Through model parameter estimation,the macroscopic kinetic model equation was obtained.     

Numerical simulation of sheet hydroforming taking into account analytical pressure and fluid flow

The paper treats the modeling and simulation of sheet metal hydroforming taking into account fluid pressure and fluid velocity effects. A hydro-mechanical model is proposed to determine the fluid flow and the pressure variation in the die cavity in case of sheet hydroforming. The hydrodynamical model for the fluid flow between the sheet and the blank holder is based on Reynold's equation. A numerical and experimental hydromechanical deep drawing of a cylindrical cup validates the predictions of the proposed approach.     

An upper bound solution for flat tool forging taking into account the bulging of sides

An upper bound solution is constructed for determining the die pressure developed during forging of a rectangular bar with flat tools. The tools do not cover the entire length of the bar. During the compression of the bar the material undergoing deformation bulges out from the sides. The solution arrived at, gives the average die pressure. The assumptions made are: the friction stress at the metal-die interface is constant, the material is rigid, perfectly plastic and the forging is done at slow speeds.     

The surface tension of a solid in the presence of adsorption and electric charge on its surface taking account its finite strain

Studies of the thermodynamic theory of equilibrium single-component adsorption from a liquid on a charged solid surface taking into account its finite strain are continued. The adsorption isotherm equation and surface tension of a solid are derived in the special case of the surface-layer equation within the model of two parallel capacitors. The constraint equations are obtained for parameters of the theory with capacitive curves measured on an unstrained metallic surface.     

The method for calculating the welding conditions taking into account the restrictions for the maximum temperature in heating

The problem of heat conductivity in arc and electron beam welding of rings and bars (parallelepiped) with a rectangular cross section with and without rapid cooling of the surface is investigated. The problem is solved analytically taking into account the dimensions of the component and welding technology (welding conditions and the sequence of making sections of the multilayer welded joint). A method is proposed for the determination of the welding conditions taking into account restrictions for the maximum temperature of heating the reference zone of the component. It is shown possible to replace the large-scale ring by a small-scale parallelepiped when investigating temperature fields in fusion welding.     

A dissolution model of base metal in liquid brazing filler metal during high temperature brazing

Controlling the dissolution of the base metal in the liquid filler metal is very significant for both brazing and soldering processes, in particular for high temperature brazing. A model for quantitatively evaluating the dissolution thickness of base metal in liquid brazing filler metal is established, that produces consistent predictions with experiment.