Variation of the creep limit and structure of a welded joint in PT-3V titanium alloy under the effect of cyclic loading. Report 2

Comparative analysis of the characteristics of amplitude-dependent internal friction (IF) was carried out to explain reasons leading to an increase of the creep limit of the butt welded joint in PT-3V titanium alloy (PT-2V filler material) after cyclic loading. IF was measured by the method of the direct torsional pendulum on cylindrical specimens representing the gage part of the specimens subjected to preliminary cyclic loading. The data were processed using the Granato-Lucke theory. The results show that the reduction of IF after cyclic loading took place as a result of an increase of the number and redistribution of pinning points of the dislocations. Consequently, the density of mobile dislocations decreases by 8% and the length of dislocation segments by 18%. These processes of stabilization of the structure were completed within 5·10 ⁴ cycles of preliminary loading. Stabilization of the dislocation structure of the material of the welded joint increases its creep limit.Translated from Problemy Prochnosti, No. 4, pp. 35–40, April, 1996.     

Extinction of dispersed heterogeneous systems

We consider extinction of various dispersed systems. Isolated boron particles and boron particles in gases are studied. Stability analysis of steady-state thermal regimes of reacting heterogeneous systems for the case of two parallel reactions on the reaction surface using the Frank-Kamenetskii method gives extinction conditions in oxygen-containing media. Curves of the extinction particle size versus the ambient temperature, oxidizer concentration, and, for particles in gases, also versus the oxidizer-to-fuel ratio are plotted. Approximate analytical calculations showed that the extinction process can be most actively controlled by varying the combustion temperature: a decrease in the latter increases the extinction particle size and decreases the completeness of fuel combustion. It is shown that at low ambient temperatures the extinction particle size for suspensions is larger than that for isolated particles. This effect is caused by a decrease in the oxidizer concentration during combustion of suspensions. At high temperatures, the role of this factor weakens.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 6, pp. 12–19, November–December, 1996.     

Effect of prolonged high-temperature loading on the structure of the KhN65VMTYu alloy

A complex analysis of changes in the structure and in the phase composition arising as a result of both a prolonged operation of articles made of the alloy KhN65VMTYu (EI893) and after conducting imitation tests of model samples. The tests for long-term strength using samples cut out from the body of a large-dimension turbine blade which was exploited for 63 622 h showed that the blade preserved a significant residual reserve of service life (at 750°C and 250 MPa, the time to failure is 4243.5 h).     

The effect of thermodynamic parameters of the adsorption surfactants by lead on the lead’s corrosion rate

For several surfactants, free energies of adsorption (G_a⁰) are calculated relative to a symmetrically chosen standard state. It is shown that they characterize the strength of organic molecule-metal bond. The effect of these surfactants on active corrosion of lead in acetic acid solution, as well as correlation between the inhibition coefficient and the free energy of adsorption (G_a⁰), is studied by measuring the polarization resistance. The corrosion rate of lead in acetic acid solution with and without adding surfactants was studied gravimetrically. In this case, the corrosion rate was virtually independent of surfactant additives and their chemical nature; this is associated with the oxidation of lead surface.Translated from Zashchita Metallov, Vol. 41, No. 1, 2005, pp. 56–60.Original Russian Text Copyright © 2005 by Afanasev, Akulova, Yakovleva.     

Some features of the formation of A1N during the reduction-nitriding of ultrafinely divided alumina

Conclusions A study was made of the process of carbothermic reduction-nitriding of ultrafinely divided alumina in the temperature range 1200–1450C. It was established that the carbothermic reduction-nitriding of ultrafinely divided alumina is accompanied by the formation of intermediate oxycarbide and oxynitride phases. This is a result of the alumina reduction process having a stepwise character and of the formation of solid solutions in the AI-O-N system. It is shown that the resultant aluminum nitride is in the form of polycrystalline particles. The sizes of the particles and of the grains in them are 1–3 and 0.01–0.2 m, respectively. With rise in nitriding temperature, the particles decrease and the grains increase in size.Translated from Poroshkovaya Metallurgiya, No. 11(263), pp. 14–19, November, 1984.     

Prediction of Fatigue Characteristics of Metals at Different Loading Frequences

The procedure for predicting fatigue characteristics by high-frequency test results over lifetime ranges up to 10¹⁰ cycles is proposed. The procedure is based on the fatigue fracture model accounting for the loading frequency and stress ratio. The potentials of the method are exemplified by the tests of smooth specimens and specimens with a stress concentrator from different materials (nickel-, aluminum-, and titanium-base alloys). The prediction results for different loading frequencies (35–10,000 Hz) and stress ratios (from -1 to 0.5) are shown to vary by about 10% from experimentally obtained data.     

Integrated Optimization Models and Problems of Gas Production,Distribution, and Storage

The authors consider the mathematical modeling of flow distribution in gas transmission networks, which take into account the possibility of establishing reserves in underground storage resources and different operation strategies of gas companies. Taking into account the basic technical and economic prerequisites, the problem of determining the optimal production rates for gas fields is analyzed. The proposed mathematical tools are aimed at solving problems of long-term planning, but it can also be applied to the cases of operational control of gas transmission systems.     

Isotropic Kernels for Two-Dimensional Image Interpolation

The paper proposes a technique of the composition of two-dimensional interpolation kernels possessing the approximately isotropic spectral characteristics. The application of these kernels makes it possible to weaken many artifacts that appear at interpolation procedures implemented by the traditional techniques. The paper presents the results of the mathematical simulation that confirm the advantages of the proposed technique.