Effect of heterogeneity of materials and heat cycles on diffusion of hydrogen as a factor of the risk of development of hydrogen degradation of metals

Conclusions The analysis results show that in the presence of hydrogen the nonstationary nature of the thermal effects (heat changes, thermal cycles) in the presence of heterogeneities may on its own be a factor causing a high risk of hydrogen degradation and may be of the implicit type (hidden). The degree of risk depends, in particular, on the kinetics of thermal processes. These defects must be taken into account by estimating the properties of materials after the effect of hydrogen and solving the problems of ensuring safety of structures both in the design stage and controlling efficiency and in determining the optimum (permissible) operating conditions, and also in determining the residual service life. In certain cases the conditions of transition of thermal processes may be of controlling importance for the efficiency of materials in structures.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 6, pp. 7–20, November–December, 1992.     

粗氩冷凝器堵塞故障的处理

因为进分子筛吸附器的空气温度偏高,分子筛吸附器出口空气中二氧化碳含量超标,二氧化碳在粗氩冷凝器换热通道内积聚,造成粗氩冷凝器堵塞,制氩系统停运。介绍粗氩冷凝器堵塞时的参数变化情况和采取的加温措施。     

Evaluation of vibration-induced stresses in teeth of rotor disks of compressors of gas-turbine engines

We show that loads induced in turbine blades by vibration make a significant contribution to the dynamic stressed state of the teeth of compressor disks. The dynamic stresses formed in the teeth of the investigated blade wheels can be as high as 42% of the stresses induced in the blades. Together with fretting corrosion, static stresses, and other factors, this may lead to initiation and propagation of cracks in teeth and, as a final result, their fracture.     

Results of inter-laboratory comparisons of two methods of determining the heat of combustion of natural gas

The D. I. Mendeleev All-Union Scientific Research Institute of Metrology has performed an inter-laboratory comparison of two methods of determining the heat of combustion of natural gas: the direct calorimetric method; and an indirect computational method involving the use of gas chromatography to determine the composition of the gas. The comparison was done with the same level of accuracy maintained in the determination of standards. Good agreement was obtained between the results of the two methods for two samples of natural gas from pipelines. The gas was dried before measurement in each case. The difference seen in the two sets of results might be related to the concentration of water vapor in the gas, which was not checked in the investigation. Translated from Izmeritel’naya Tekhnika, No. 1, pp. 36–40, January, 1998.     

Linearization of families of germs of hyperbolic vector fields

In this article, we develop some techniques to linearize families of smooth vector fields in a neighbourhood of a hyperbolic equilibrium point. In particular, we present the linearizing conjugacy in an explicit way and describe the smoothness of the conjugacy in terms of the eigenvalues of the vector fields.     

基于管道声模态的消声器传递损失计算

传递损失是评价消声器声学性能的一个重要指标。提出了一种方法—管道声模态法代替传统方法估算传递损失。对进出口截面积较小的消声器进行计算和检验,与传统方法比较,结果基本吻合,且过程简单,提高传递损失的计算效率。对进出口截面积较大的消声器,中高频段由于大量高次波的出现,传统方法失效;但低频段管中声波以平面波为主,其结果与传统法一致。因此可以采用管道声模态法快速估算传递损失。     

Simulation of turbulent mode of combustion of gas jets

The diffusion mode of combustion of fuel jets in an oxygen-containing atmosphere occurs very widely both in nature and in engineering. In so doing, a glowing flame is formed, whose geometric dimensions define the energy efficiency of combustion of fuel.The hydrodynamic structure of the flame exhibits a number of differences from the classical jet flows, in particular, from well-studied subsonic turbulent jets [1]. The flames are characterized by a high degree of hydrodynamic instability; however, at the same time, the flame height clearly follows the phenomenon such as the change of laminar mode for turbulent one; by the way, this phenomenon presents a difficult problem for investigation in flows of other types.The diffusion mode of jet combustion is of further interest because of the presence of “scaling” effect, i.e., the dependence of the relative flame height both on the Reynolds number (which is typical of all flows with laminarto-turbulent transition) and on the dimensionless nozzle diameter (d ₀/d*); in so doing, the threshold value of d* divides the entire diversity of dimensions into regions with the presence and absence of this effect.These and other features of burning fuel jets present a serious problem for mathematical simulation of burners and combustors.The paper contains analysis of a number of relations used in different models of turbulent combustion.     

On the mechanism of action of inhibitors of hydrogenation in the process of electrodeposition of metals

We develop a new approach to the investigation of the effect of inhibitors of hydrogenation of the base in the process of electrodeposition of metals. We established the relationship between the structure of molecules of the inhibitor, their ability to interact with atomic hydrogen, their adsorption properties, the contents of various forms of hydrogen in steel, and physicomechanical parameters of the latter. On the basis of the results of quantum-chemical computations of electron parameters of molecules, we demonstrate the possibility of prediction of the efficiency of inhibitors of hydrogenation and regularities of changes in the strength and plastic properties of steel. Dnepropetrovsk State University, Dnepropetrovsk. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 32, No. 6, pp. 7–17, November–December, 1996.     

Two methods of investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels

We present two methods for the investigation of the influence of hydrogen on the propagation rate of a crack and behavior of fracture of high-strength steels. The method for investigation of the influence of electrolytic hydrogenation on a subcritical growth of a crack in high-strength steels is based on the use of simple beam specimens of a certain geometry and on the application of lateral loading in such a way that the stress intensity factor can be constant at the tip of a preliminary induced crack. The method is of great importance for the performance of comparative experiments in evaluating the influence of active media and structural anisotropy of specimens made of high-strength steels with limited sizes on their corrosion crack resistance. Typical examples of the application of the method to investigation of the role of electrolytic hydrogenation in subcritical propagation of cracks and their branching in highstrength steels are given. The method for investigation of heat release under strain and fracture of hydrogenated specimens involves the use of microcalorimetric devices, which allow one to study the influence of hydrogenation on peculiarities of the kinetics of elastic and plastic strains of high-strength steels. We illustrate the efficiency of the method proposed by plotting the “load-elongation” curves and corresponding (in time) characteristics of heat release power in the process of strain and fracture of specimens made of a high-strength steel. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 34, No. 4, pp. 113–120, July–August, 1998     

Reduction of influence of variation in center frequencies of RF echoes on estimation of artery-wall strain

Atherosclerotic change of the arterial wall leads to a significant change in its elasticity. For assessment of elasticity, measurement of arterial wall deformation is required. For motion estimation, correlation techniques are widely used, and we have developed a phase-sensitive correlation method, namely, the phased-tracking method, to measure the regional strain of the arterial wall due to the heartbeat. Although phase-sensitive methods using demodulated complex signals require less computation in comparison with methods using the correlation between RF signals or iterative methods, the displacement estimated by such phase-sensitive methods are biased when the center frequency of the RF echo apparently varies. One of the reasons for the apparent change in the center frequency would be the interference of echoes from scatterers within the wall. In the present study, a method was introduced to reduce the influence of variation in the center frequencies of RF echoes on the estimation of the artery-wall strain when using the phase-sensitive correlation technique. The improvement in the strain estimation by the proposed method was validated using a phantom. The error from the theoretical strain profile and the standard deviation in strain estimated by the proposed method were 12.0% and 14.1%, respectively, significantly smaller than those (23.7% and 46.2%) obtained by the conventional phase-sensitive correlation method. Furthermore, in the preliminary in vitro experimental results, the strain distribution of the arterial wall well corresponded with pathology, i.e., the region with calcified tissue showed very small strain, and the region almost homogeneously composed of smooth muscle and collagen showed relatively larger strain and clear strain decay with respect to the radial distance from the lumen.     

Evaluation of vibration-induced stresses in teeth of rotor disks of compressors of gas-turbine engines

We show that loads induced in turbine blades by vibration make a significant contribution to the dynamic stressed state of the teeth of compressor disks. The dynamic stresses formed in the teeth of the investigated blade wheels can be as high as 42% of the stresses induced in the blades. Together with fretting corrosion, static stresses, and other factors, this may lead to initiation and propagation of cracks in teeth and, as a final result, their fracture. Translated from Problemy Prochnosti, No. 6, pp. 95–101, November–December, 1997.     

Evaluation of solid dispersions of Clofazimine

Clofazimine (CLF) was formulated with polyethylene glycol (PEG) and polyvinyl pyrrolidone (PVP) as a solid solid dispersion (SSD) to increase the aqueous solubility and dissolution rate of the drug. Different molecular weights of PEG (1500, 4000, 6000, and 9000 Da) and PVP (14,000 and 44,000 Da) were used in different drug:carrier weight ratios (1:1, 1:5, and 1:9) and their effect on the dissolution performance of the drug was evaluated in USP Type 2 apparatus using 0.1 N HCl medium. The dissolution rate was compared with corresponding physical mixtures, a currently marketed soft gelatin capsule product, and free CLF. The effect of different methods of preparation (solvent/melt) on the dissolution rate of CLF was evaluated for PEG solid dispersions. Saturation solubility and phase solubility studies were carried out to indicate drug:carrier interactions in liquid state. Infrared (IR) spectroscopy and X-ray diffraction (XRD) were used to indicate drug:carrier interactions in solid state. Improvement in the drug dissolution rate was observed in solid dispersion formulations as compared to the physical mixtures. The dissolution rate improved with the decreasing weight fraction of the drug in the formulation. Polyvinyl pyrrolidone solid dispersion systems gave a better drug release profile as compared to the corresponding PEG solid dispersions. The effect of molecular weight of the PEG polymers did not follow a definite trend, while PVP 14,000 gave a better dissolution profile as compared to PVP 44,000. Improvement in saturation solubility of the drug in the solid dispersion systems was noted in all cases. Further, IR spectroscopy indicated drug:carrier interactions in solid state in one case and XRD indicated reduction in the crystallinity of CLF in another. It was concluded that solid-dispersion formulations of Clofazimine can be used to design a solid dosage form of the drug, which would have significant advantages over the currently marketed soft gelatin capsule dosage form.     

Analysis of the specific features of loading of the elements of landing gears of aircrafts aimed at the evaluation of the load-bearing capacity of the structure

We propose a computational scheme of the aircraft nose landing gear and perform the analysis of weak sections in the landing-gear lever by the finite-element method. We determine the loading modes in which the landing-gear lever is subjected to disproportional cyclic loads, which should be taken into account in the evaluation of the service life and determination of the properties of applied materials. __________ Translated from Problemy Prochnosti, No. 4, pp. 87–93, July–August, 2008.     

Investigation of the properties of samples of lengthwise-extended shape using the velocity of propagation of an electromagnetic field

It is shown that the velocity of propagation of an electromagnetic field in samples of extended shape with a constant cross section depends on the structure of the sample material, its magnetic properties and, in particular, the viscosity, shape and dimensions of the cross section and the excitation frequency.     

输入估计值的测量不确定度评定

本文所介绍的与1993年由ISO等7个国际组织联合发表的《测量不确定表示指南》（简称《指南》）完全一致，只是指南上的实用于物理测量的绝大多数领域，而本文介绍的仅适用于校准实验的测量。同时本文主要侧重于对输入估计值的A类测量不确定度和B类测量不确定度的评定的介绍，为输出估计值的测量不确定度评定奠定了良好的基础。     

Investigations of the spatial distribution of the energy characteristics of plasma radiators for a system of assurance of uniformity of measurements in nanolithography

A comparator that incorporates an imaging system and a position-sensitive detector is developed. The comparator supports the formation of spectro-zonal images with calibration in units of radiance and radiant intensity through the use of synchrotron radiation. A comparator is needed to obtain information about the distribution of the radiance of plasma radiators used in nanolithography in the area of extremal vacuum ultraviolet radiation. __________ Translated from Izmeritel’naya Tekhnika, No. 5, pp. 41–45, May, 2007.     

Equilibrium composition of products of melting of main minerals involved in the composition of basalt

Using the method of thermodynamic simulation, the equilibrium composition of products of heating of plagioclases, pyroxenes, peridots, and magnetite is determined in a temperature range of 1000–1400°C in inert, oxidizing, and reducing atmospheres. The possibility of controlling the products of melting and crystallization of the above minerals is shown, and the behavior of a series of accessory metals (Ti, Mn, Cr, V) in these processes is evaluated.     

Investigation of probable cause of damage of steam drum of naphtha cracking furnace

This investigation was primarily aimed to examine the probable causes of damage in steam drum of heat recovery boiler in a naphtha cracking plant. Large number of cracks was detected of varying length on the inner surface of the drums. Preliminary visual examination, magnetic particle inspection, in situ metallographic examinations were carried out at the site. Detailed optical microscopic analysis along with scanning electron microscopic (SEM) and transmission electron microscopic (TEM) examinations on the scooped samples from different locations of the steam drum were carried out to understand the metallurgical reasons for damage. Stress analysis was carried out on the steam drum on the basis of strength for the internal pressure. Finally, it was concluded that metallurgical factors as well as operating conditions were responsible for the cause of damage in the steam drum.     

Formulation of the latent heat of fusion of ice in aqueous solution

A calculation method to define the latent heat of fusion of ice in aqueous solution in the situation of the variation in the ice packing factor being infinitesimal is proposed. The calculation of the latent heat considers the effects of dilution and freezing-point depression, and the latent heat was calculated for five actual solutions, ethanol, ethylene glycol, propylene glycol, NaCl and NaNO3 solutions. Additionally, experiments in which ice was added to the five solutions were conducted to compare with the results of the calculations. Differential scanning calorimetry analysis was performed and the measurements and calculated values compared with respect to the specific enthalpy of the ice/solution mixture. Finally, since the values obtained by the measurements and calculations are in good agreement, the calculating method proposed in this study has proven to be adequate.