Residual stress-strain state of the collector assembly of a steam generator in the process of press-fitting of heat-exchange pipes

The influence technological heredity connected with the manufacturing process on the strength and service life of the assembly of joints of the collector and heat exchange pipes of a steam generator proves to be one of the main causes of premature failures of steam generators of water-cooled reactors of nuclear power plants. We present the results of a numerical simulation of the process of press-fitting of heat-exchange pipes in the collector. We determine the residual stress-strain state of the collector assembly depending on the basic technological parameters of press-fitting (the initial gap between the pipe and the collector, the pressure of hydraulic press-fitting, and the boundaries of the region of application of pressure) and strength characteristics of the materials of the collector and pipes. We also estimate the influence of the additional mechanical flaring of pipes and redistribution of local stresses in the course of consecutive hydraulic press-fitting on the level of residual stresses in the collector assembly. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 2, pp. 66 – 86, March – April, 1998.     

Influence of heat-resistant coatings on the state of thermal stress of model of gas turbine engine blades in nonsteady heat exchange

The finite-element method was applied to calculate the thermal state and the state of stress and strain of a wedge-shaped model with a heat-resistant coating (heat shield) subjected to heat cycling by a gas stream. We analyzed the influence of the method of discretization of the section of the model and of the method of specifying the characteristics of the materials of the base and of the coating on the accuracy of the solution of the problem of thermoelasticity. We obtained data on the influence of the technological factors and of the thickness of the heat shield on the kinetics of the state of thermal stress of the material of the models. It was established that a ceramic layer changes the asymmetry of the cycle to the side of tensile stresses and shifts the maximum of the stresses into the range of lower temperatures.Translated from Problemy Prochnosti, No. 6, pp. 24–30, June, 1994.     

The absorption of carbon and nitrogen monoxides by ultradisperse aqueous system: Computer experiment

The method of molecular dynamics is used to investigate the effect of absorption of carbon and nitrogen monoxides on the spectral characteristics of a disperse aqueous system. The absorption of CO molecules causes the reduction of the real and imaginary parts of permittivity, and the absorption of NO molecules results in smoothing out of the frequency dependence of these characteristics, which corresponds to that of a system of clusters of pure water. The integral absorptance and reflectance of IR radiation decrease after the attachment of CO molecules to water clusters and undergo insignificant changes as a result of absorption of NO molecules. An increase is observed in the integral power of emission of infrared radiation by disperse aqueous systems which absorbed CO or NO molecules. The clustering of water vapor causes an abrupt reduction of the number of scattering centers and the anti-greenhouse effect.     

大跨度缆索承重桥梁非线性静风扭转失稳机理的研究

建立了静风荷载作用下大跨度缆索承重桥梁的非线性扭转失稳模型,导出了求解平衡路径的非线性方程。对于静风扭转平衡路径的稳定性进行了全过程的理论分析。分析了升力矩系数和扭转刚度的非线性特性对于稳定条件、失稳点以及失稳机理的影响。静风扭转失稳的性质为跳跃式极值失稳。发生失稳的条件取决于升力矩系数和扭转刚度的曲线形状。只有当升力矩系数曲线有上凹段或扭转刚度曲线有下凹段存在时,扭转失稳才有可能发生。对于升力矩系数曲线不存在上凹段和扭转刚度曲线不存在下凹段时,平衡路径是稳定的,不会发生静风扭转失稳。扭转刚度的弱化是引起静风扭转失稳的因素之一。升力矩系数的非线性特性将引起等效刚度弱化,也是引起静风扭转失稳的因素之一。当初始攻角较大时,这种等效刚度弱化效应尤其应该给予重视。提出了新的失稳临界风速公式。公式统一,包含了非线性失稳及线性理论的结果;公式简洁,形式上与线性理论的公式相同。对于线性扭转刚度或线性升力矩系数的情形,临界点的物理意义明确、便于图解。新的临界风速公式还反映了初始攻角的影响。初始攻角增大,临界风速减小。     

Acoustic disturbances in a mixture of liquid with vapor-gas bubbles

Results are given of theoretical study into the propagation of acoustic disturbances in mixtures of liquid with vapor-gas bubbles in view of interphase diffusion mass transfer. A unified general dispersion relation is obtained, which defines the propagation of harmonic disturbances in two-phase mixtures of liquid with bubbles of vapor and gas in the plane, spherical, and cylindrical cases. Numerical calculations are performed of the evolution of weak pulse disturbances of pressure of different geometries in liquids with vapor-gas bubbles at different values of parameters of the medium. It is demonstrated that the velocity of propagation of waves significantly decreases with increasing initial concentration of vapor in vapor-gas bubbles, and the wave damping significantly increases. In so doing, the effect of vapor content on the dynamics of acoustic disturbances significantly increases with the initial volume content of bubbles. The nonmonotonic dependence of damping of pulse disturbance of pressure on the initial radius of bubbles in liquid with vapor-gas bubbles in the presence of phase transformations is demonstrated.     

Experimental investigation of the regularities of inelastic deformation of metals in complex processes of loading under conditions of elevated temperatures

The article describes the study of the regularities of inelastic deformation of metal in isothermal complex processes of loading on paths in the form of two-link broken lines. The results of the experiments under complex loading of tubular specimens of heat-resistant alloy ÉI437 showed that the slope of the strain vector to the path of loading depends on the length of the arc of this path up to the point of its break; however, with the development of plastic deformations this dependence becomes weaker, and it may be neglected. The change of the slope of the strain vector to the path of loading depends on the temperature, and it does not depend on the speed of the loading process within the limits of its change by one order of magnitude; with angles of break of the path of loading exceeding /2 the dependence of the above-mentioned slope of the strain vectors on the length of the arc of the path of loading past the point of its break is not universal.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 12, pp. 3–8, December, 1989.     

元代肖形印的图文融合策略与设计启示

目的 通过对元代肖形印图文融合特征的分析归纳,总结其图文组织关系与印面经营策略,在完成元代肖形印图形传统文化价值挖掘与保护的基础上,尝试为传统视觉经典的当代设计转化继承带来有益思考。方法 从元代肖形印图文融合的历史文化背景入手,分析其出现的缘由与特征,并在此基础上梳理探讨元代肖形印的图文融合策略,及其对当代设计的关联启示。结论 与先秦及汉代肖形印不同,图文融合是元代肖形印的显著特征,其具有多样化的适形、多层次意指和多元素碰撞的核心构建逻辑。文字的图形化、雅文化的大众普适及符号凝练的求同存异,则分别是元代肖形印对图文融合需求、市民文化需求和形式法则需求的具体回应,这便成为现代设计对元代肖形印图形继承转化的有效切入点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Continual model of propagation of corrosion cracks for the evaluation of the service life of structures

On the basis of the mechanics of dispersed fracture, we develop a continual model of propagation of corrosion cracks for the evaluation of the service life of structural elements. The results of numerical simulation of the process of crack growth in specimens made of austenitic stainless steel of the 18-8 type performed on the basis of the experimental data available from the literature demonstrate the reliability of the proposed model. We obtain the solutions of the problem of service life of the rectilinear segments of heat-exchange pipes of steam generators of nuclear power plants and apply these solutions to establish a noticeable dependence of the service life on the size of the pipes, pressure in the primary coolant circuit, and chemical compositions of corrosive media.     

Status and problem of metrological provisioning of agriculture

Conclusions The accumulated experience of metrological provisioning of agriculture testifies to the fact that in the near future it will be necessary to have: further growth and improvement of the activity of all members of the departmental metrological service; the creation and broadening of the technical base of collective farms, state farms, and state purchasing organizations; the introduction of the newest progressive methods and means for measurements; the improvement of the forms of surveillance of measuring equipment and the increasing of its effectiveness; constant growth and strengthening of the base of metrological servicing of agriculture; and the strengthening of the training and the increasing of the qualifications of specialist-metrologists.Successful implementation of this entire complex of measures for improving the metrological provisioning of agriculture is the guarantee of timely solution of the problems set forth by the Party and by the government for further growth of this important branch of the people's economy.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 80–82, May, 1973.     

Numerical analysis of equations of motion and energy balance of high-pressure electrodeless discharge in flowing gas

Mechanisms are analyzed of interaction between a laminar gas flow (velocity of flow of molecular gas of up to 10 m/s) and a high-pressure (of the order of atmospheric pressure) contracted electrodeless plasma formation. The solution of a set of equations of motion and energy balance (with specific energy input of up to 3 J/cm³) for a weakly compressible gas is used to obtain the profiles of components of velocities and temperature of gas flow. It is demonstrated that the plasma formation (exhibiting a transverse dimension of up to 6 mm and longitudinal dimension of up to 30 mm) affects significantly the formation of the field of velocities of flowing gas. The preferred mechanism of heat transfer in the direction of the axis of flow is by forced convection. The rate of radial transfer of energy to periphery is defined by thermal conductivity. Experimental results are given of axial distribution of temperatures for a given plasma formation in the air, which are in adequate agreement with experiment.     

接枝氯丁胶粘剂的合成与表征技术

本文介绍了接枝氯丁胶粘剂的合成,聚合反应转化率、接枝率的测定方法及接枝共聚反应的确证,从复合材料的角度,讨论了相态结构与胶粘剂性能的关系。对接枝机理、胶粘剂的热性能进行了探讨,特别就IR、XPS、TEM、SEM、TGA等现代分析手段在接枝氯丁胶粘剂表征方面的应用作了详细的叙述,并给出了一种简易快速的TEM试样处理技术。     

Prediction of Strain Hardening and Fatigue Life of Cyclically Unstable Materials

The data on cyclic deformation of materials with different cyclic properties are analyzed. The relationship between the level of additional strain hardening and the mechanical characteristics of a material is established. The proposed models take into account the influence of the form of stressed state on strain hardening and durability under conditions of nonproportional cyclic deformation. The models are constructed on the basis of the analysis of the experimental data on cyclic deformation of 304 stainless steel. The prediction of strain hardening and durability is performed with separate analysis of the influence of shape of the cycle and the form of stressed state. To take into account the influence of shape of the cycle, we use the coefficient of disproportionality of the cycle and the parameter of sensitivity to disproportionality. To take into account the form of stressed state, we use the coefficient of the form of stressed state and the corresponding parameter of sensitivity to the form of stressed state. The results of prediction of both strain hardening and durability of materials on the basis of the proposed phenomenological models reveal their fairly high efficiency. __________ Translated from Problemy Prochnosti, No. 5, pp. 118 – 130, September – October, 2005.     

Efficiency of the method of spectral vibrodiagnostics for fatigue damage of structural elements. Part 1. Longitudinal vibrations, analytical solution

On the basis of an analysis of the asymptotics of higher approximations to solutions of a differential equation of longitudinal vibrations of a macroelastic body whose nonlinearity is explained by the hysteresis and “breathing” of the damaged material in the process of its cyclic deformation under conditions of tension-compression, we estimate the applicability of the spectral characteristics of strain cycles of the body under conditions of its natural or resonance vibrations to the diagnostics of fatigue damage of structural elements. It is shown that if nonlinearity is explained solely by the hysteresis of the material, then even the most representative first higher odd harmonics revealed in the vibration spectrum have very small amplitudes and the analysis of their variations is, in fact, similar to the analysis of the variations of the logarithmic decrement of vibrations (regarded as an integral characteristic of the dissipative properties of the material of the investigated element) but has lower resolution. At the same time, the discontinuities of the material appearing in the process of strain cycling are characterized by formation of numerous microcracks or a macrocrack and result in more clear detection of the representative constant component and even harmonics (mainly the second and fourth ones) in the spectrum of strain cycles of a vibration-insulated structural element in the process of its natural or resonance vibrations. These characteristics may serve as sensitive and efficient parameters for detection of fatigue damage to the material.     

Manifestation of Hydrogen and Low-Temperature Brittleness in Near-Threshold Cyclic Crack Resistance of Materials

We experimentally show that the realization of conditions of plane deformation at the tip of a fatigue crack is not sufficient for guaranteeing the unique dependence of the crack growth rate on the range of the stress intensity factor, which is explained by the effect of crack closure. We describe advantages and disadvantages of the effective range of the stress intensity factor as a parameter that determines the mechanical conditions for the propagation of a fatigue crack. We analyze the phenomenon of positive influence of strengthening factors (a decrease in the temperature of testing and hydrogenation) on the cyclic crack resistance of materials in a low-amplitude range of loading determined with regard for the effect of crack closure. The decrease in the crack growth rate and the increase in fatigue thresholds are intensified as the level of loading decreases and the ductility of materials increases. Differences in the influence of strengthening factors in low- and high-amplitude ranges of loading are explained by different mechanisms of fracture controlled by the shearing strength and the tensile strength, respectively. We give several examples of the mechanical behavior of materials that show the inversion of the influence of hydrogen on the resistance to fracture: fatigue fracture of smooth steel specimens in gaseous hydrogen, high-temperature corrosion fatigue of preliminary hydrogenated titanium alloys, and the influence of hydrogenation on the wear resistance of structural steels in the process of friction and cavitation and on the parameters of cutting of a tool steel.     

Special features characteristic of the use of differential scanning calorimetry for the investigation of the kinetics of thermal decomposition of energetic materials

The results of analysis of mathematical models of “ideal” differential scanning calorimeter are used for determining the experimental conditions which provide for the minimal level of errors of determination of the kinetic constants of exothermal reactions of thermal decomposition of energetic materials under conditions of constant-rate heating of samples and in the isothermal mode. The predicted estimates of admissible values of the basic parameters of models (mass of samples, rate of heating, temperature range of investigations, and so on) are based on the experimental data largely obtained in the investigation of cyclotetramethylenetetranitramine (HMX).     

The influence of elastic-dissipative coupling parameters on resonant vibrations of systems with violated cyclic symmetry

This paper deals with the regularities of the influence of the variation of the elastic-dissipative coupling parameters of subsystems on the formation of resonant vibrations of systems with a violated cyclic symmetry, like shrouded blade assemblies, and gives the results of numerical calculations. The formation of the amplitude-frequency characteristics and the distribution of resonant vibration amplitudes of the systems under study is shown to depend on the relationship between elastic and dissipative characteristics of coupling of the subsystems. When the elastic coupling is stiff, which provides localization of vibrations of the elastically-coupled system, the introduction of dissipative coupling does not cause any changes in the behavior of the amplitude-frequency characteristics, and the degree of localization is almost independent of the dissipative properties of the coupling. As the stiffness of the elastic-dissipative coupling grows, the localization of vibrations shows up only at certain values of the dissipative characteristics of the coupling. Institute for Problems of Strength, National Academy of Sciences of Ukraine, Kiev, Ukraine. Translated from Problemy Prochnosti, No. 1, pp. 102–115, January–February, 1999.     

诠释新产品概念的设计方法研究

通过创新产品分析和国内企业现状以及相关领域现有设计方法分析,借鉴现有设计方法的优势,构建了以情景故事法为框架,以故事板为过程分解手段,通过动漫综合式表达的设计方法,实现新产品概念的表达和诠释,为战略上设计前期概念的合理分析和打造企业多部门参与产品开发的创新平台提供了保证。