Analysis of the Elastoplastic Deformation of the Material in the Process Zone

By the method of digital correlation of speckle images, we record the displacements in the vicinity of the crack tip in plane specimens of D16AT alloy. The field of elastoplastic displacements is determined in the vicinity of the crack tip under static loading. By using the distribution of displacements, we compute the levels of strains ε _y on the continuation of the crack. The theoretical results are in good agreement with the experimental data in estimating the length of the plastic zone for the limiting equilibrium state.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 5, pp. 67–72, September–October, 2004.     

Influence of the state of the lattice on the pair breaking of manganese in superconducting cadmium

The superconducting transition temperature of crystalline and amorphous cadmium doped with dilute Mn atoms was measured. In the first case the initial depression ofT _c as function of concentration isdT _c /dc=5.4 K/at % and in the second casedT _c /dc=2.65 K/at %. Both systems show non linear behavior at higher concentrations, the one in the crystalline state much more than the one in the amorphous state. While the curve in the amorphous state fits the Abrikosov-Gor'kov theory to the experimental limit of 70 mK, i.e., to within 3% of the critical concentration, the curve in the crystalline state does not, but is interpretable with the Müller-Hartmann-Zittartz theory with a Kondo temperature of10 ^–6 K.Supported by the Deutsche Forschungsgemeinschaft in the Sonderforschungsbereich 125, Fehlordnung in Metallen Aachen, Jülich, Köln.     

Estimation of the accuracy of measurements of the corrosion rate by the method of polarization resistance

The method of polarization resistance is extensively used for the determination of the rate of corrosion. At the same time, the accuracy of measurements of the corrosion rate performed with industrial corrosion meters is often not estimated. By using an indicator, we find the accuracy of the measurements of the corrosion rate for 20 steel placed in 1N H₂SO₄ and 0.01N Na₂SO₄ solutions and for 12Kh18N10T steel placed in 1N and 10N H₂SO₄ solutions.Kiev Polytechnic Institute, Kiev. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 31, No. 3. pp. 22–27, May–June, 1995.     

Variety of the representation of the nonstationary temperature of fuel elements depending on the form of the distribution of the heat sources

The author proposes a representation of the solution of the heat-conduction equation in the form of expansions in basis functions that are selected depending on the form of the distribution of the internal heat sources. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 761–772, July–August, 2000.     

On the regularity of the principal value of the double-layer potential

Summary In the present paper we discuss the regularity of the principal value of the potential due to a doublet distribution along the boundary S of a two-dimensional (2-D) open connected set. Assuming S to be a Lyapunov boundary and to be essentially bounded, we prove that the principal value in 2-D is more regular than the one in 3-D. This result is applied to the aerodynamics problem of calculation of potential flows around 2-D bodies.     

On the concept of the yield surface

Summary In this paper we introduce in the theory of plasticity the concept of a family of loading surfaces that are distinct from and enclose the yield surface.The yield surface is the boundary of a region in stress space in which both unloading and reloading produce elastic strains only. In the region of stress space occupied by the family of loading surfaces, reloading produces plastic strains, while unloading produces only elastic strains. Some implications of this concept for the theory of plasticity are considered. In particular, it is shown that the existing proof of convexity of a yield surface is not applicable to the loading surfaces.

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Zusammenfassung Der Begriff der Belastungsflächen, welche verschieden von der Fließfläche sind und diese einschließen, wird in die Plastizitätstheorie eingeführt.Die Fließfläche begrenzt den Bereich im Spannungsraum, in dem Entlastung und Wiederbelastung nur elastische Verzerrungen hervorrufen. Die Belastungsflächen dagegen bedecken den Bereich des Spannungsraumes, in dem Wiederbelastung plastische, Entlastung dagegen nur elastische Verzerrungen erzeugt. Einige Folgerungen für die Plastizitätstheorie werden gezogen. Im besonderen wird gezeigt, daß der bekannte Beweis für die Konvexität einer Fließfläche nicht auf die Belastungsflächen anwendbar ist.

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With 8 Figures

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This work was sponsored by the National Science Foundation of the United States Government.     

Determination of the size of the fatigue prefracture zone by the method of phase-shifting interferometry

We consider a new method for determining the size of the fatigue prefracture zone (a new structural-mechanical parameter d* of constructional materials) by the method of phase-shifting interferometry, based on the results of a comparative analysis of the surface profile of metallic specimens in the neighborhood of a constructional stress concentrator prior to and after a certain quantity of loading cycles. To obtain interferograms in laser light, we applied a Twyman–Green interferometer. Using these results, we determined the 3-D distribution of plastic strains near the concentrator vertex, which enabled us to establish that d* = 256–268 μm for low-carbon 08kp steel at a load ratio R = 0.1. The obtained value of this parameter is in good agreement with data obtained by other methods.     

The Roles of the Mise en Pratique for the Definition of the Kelvin

The mise en pratique (“practical realization”) for the definition of the kelvin (MeP-K) was created by the Consultative Committee for Thermometry (CCT) in 2006 to give practitioners of thermometry a guide to the realization of the kelvin, i.e., measurement of temperature in kelvins, in accord with the International System of Units. In this article, the present and the future content of the MeP-K, the relationship of the MeP-K to other documents relevant to thermometry, the categorization of thermometry techniques in the MeP-K, and the benefits of proposed additions to the 2006 version of the MeP-K are discussed. The three categories of measurements within the MeP-K are: (1) primary methods for measuring thermodynamic temperature T; (2) formal approximations to T, in particular, the International Temperature Scale of 1990 (ITS-90) and the Provisional Low Temperature Scale from 0.9 mK to 1 K (PLTS-2000); and (3) indirect approximation methods that are neither primary nor defined on a temperature scale, yet capable of exceptionally low uncertainties or increased reliability. By providing a framework for primary methods and indirect methods, the MeP-K will foster development and application of new methods, such as the use of absolute radiometry or high-temperature fixed points. The MeP-K provides the CCT with a mechanism to update and to expand the thermometric methods in common use, without imposing on industry the high costs of changing the International Temperature Scale.     

Effects of the morphology of the electrode nanostructures on the performance of dye-sensitized solar cells

This article reports the performances of dye-sensitized solar cells based on different working electrode structures, namely (1) highly ordered arrays of TiO₂ nanorods, (2) highly ordered arrays of TiO₂ nanotubules of different wall thicknesses, and (3) sintered TiO₂ nanoparticles. Even though highest short-circuit current density was achieved with systems based on TiO₂ nanotubules, the most efficient cells were those based on ordered arrays of TiO₂ nanorods. This is probably due to the higher open-circuit photovoltage values attained with TiO₂ nanorods compared with TiO₂ nanotubules. The nanorods are thicker than the nanotubules and therefore the injected electrons, stored in the trap states of the inner TiO₂ particles, are shielded from recombination with holes in the redox electrolyte at open-circuit. The high short-circuit photocurrent densities seen in the ordered TiO₂ systems can be explained by the fact that, in contrast to the sintered nanoparticles, the parallel and vertical orientation of the ordered nanostructures provide well defined electron percolation paths and thus significantly reduce the diffusion distance and time constant.      

The influence of the polarization of the radiation on the accuracy of the transmission of the dimensions of the unit of temperature in radiation thermometry

The results of an investigation of different types of tungsten lamps in order to estimate the components of the error budget of spectrum-pyrometer apparatus are presented. Quantitative relations are considered and the results of experimental research, which enable systematic methods to be developed for eliminating the influence of polarization of the radiation of the lamps in standard radiation thermometry, are analyzed.Translated from Izmeritelnaya Tekhnika, No. 9, pp. 42–45, September, 2004.     

A comparison of the scientific performance of the U.S. and the European union at the turn of the 21st century

In this paper, scientific performance is identified with the impact that journal articles have through the citations they receive. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. However, as soon as the citations received by these publications are taken into account the picture is completely reversed. Firstly, the EU share of total citations is still greater than the U.S. in only seven fields. Secondly, the mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields studied. Thirdly, since standard indicators—such as normalized mean citation ratios—are silent about what takes place in different parts of the citation distribution, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. It is found that in seven fields the initial gap between the U.S. and the EU widens as we advance towards the more cited articles, while in the remaining 15 fields—except for Agricultural Sciences—the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. Finally, for all sciences as a whole the U.S. publication share becomes greater than that of the EU for the top 50% of the most highly cited articles. The data used refers to 3.6 million articles published in 1998–2002, and the more than 47 million citations they received in 1998–2007.     

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.     

Relation of the title length of a journal article to the length of the article

The great importance of titles being highly informative is almost unanimously accepted in literature, assuming that the more informative titles are, the more effectively they serve their functions. The most common measure of title “informativeness” has been the number of “significant” (i.e., non-trivial) words included in it, and one of the factors which might be associated with it is the length of the paper, measured by its number of pages. The present study attempted to test, in a large group of journals from different areas and over six decades, the hypothesis that a paper with more pages will have more “significant” words in its title. Large samples of original research papers were drawn from each decade year of twenty-four leading journals selected from the sciences, the social sciences and the humanities. For each paper, the number of “significant” words in the title was correlated with the number of pages. Findings indicate a difference between the scientific journals on the one hand, and the social sciences and humanities journals on the other. A moderate positive correlation was found in most scientific journals for many periods. In the social sciences journals, and to a greater extent, in the humanities journals, a significant positive correlation was limited to only a few periods, while the rest showed a very low correlation, or even a negative one. The different findings for the sciences are perhaps attributable to their unique inherent features. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of the fluoride additives on the oxidation of AlN

The oxidation of AlN powder added by the fluorides at temperatures below 700°C in air was discovered in this study. The obvious onset of oxidation of AlN with cryolite and YF₃ additions is below 700°C with the product of α-Al₂O₃ phase, which usually occurs in single AlN powder above 1100°C. The changes on the weight and the FTIR spectra of the AlN powder fired at temperatures lower than 700°C show that cryolite and YF₃ greatly promote the oxidation of AlN powder at these temperatures. Different from the action of cryolite and YF₃ powder, CaF₂ has no obvious effect on the oxidation of AlN. A possible oxidation process, in part corroborated by FTIR and XRF, was proposed to explain the results in the experiments. The oxidation kinetics of AlN in the presence of cryolite were also discussed at the temperatures ranging from 550 to 700°C from the data of the weight gains in this region. The result shows that the oxidation follows a linear law, which implies a reaction rate-controlled process. The considerably low activation energy of 67 kJ mol⁻¹, which is associated with the quick oxidation and the formation of α-Al₂O₃ at temperatures below 700°C, was determined from the slope of the line fit.     

Investigation of the harmonic composition of the periodic solution of the Korteweg-de Vries equation

An investigation is made of the behavior of the nth harmonic of the periodic solution of the Korteweg-de Vries equation as a function of the index n in the intermediate region which is not usually investigated by soliton theory. The asymptotic forms obtained allow the harmonic behavior to be determined more accurately. Pis’ma Zh. Tekh. Fiz. 25, 6–10 (February 26, 1999)     

Study of the influence of the basicity and chromate-chloride anionic composition in the synthesis of the cancrinite–sodalite system

The influence of basicity and anionic composition (CrO₄²⁻ and Cl⁻) was studied in the synthesis of chromate-cancrinite and chlorosodalite zeolites. Zeolite X was used as starting material by using different NaOH concentrations (3, 8 and 16 M) and variable weight ratio (NaCl/(NaCl + K₂CrO₄)) equal to: 0.00, 0.25, 0.50, 0.75, and 1.00 in such a way that the total grams were 1.5 g. The syntheses were carried out at 80 °C and autogenous pressure during 40 h. The crystals obtained were characterized by powder X-ray diffraction (XRD), FT-IR spectroscopy, and scanning electron microscopy (SEM) coupled with an energy-disperse X-ray detector (EDX). Depending on the basicity employed and anionic composition (CrO₄²⁻ and Cl⁻), the chromate-cancrinite or chlorosodalite zeolite was obtained. Owing to a low 3 M NaOH concentration and 100% Cl⁻, chlorosodalite mixed with zeolite X was observed in the XRD pattern. Owing to another Cl⁻–CrO₄²⁻ proportions, inclusive to 100% CrO₄², the starting material were not transformed (3 M NaOH). Pure chromate-cancrinite was produced when 8 and 16 M NaOH and 0% Cl⁻ concentrations were used. Chloride anions showed a strong structure directing effect for sodalite framework structure in comparison with chromate anions which favoring the cancrinite structure. Therefore, we determined pure chlorosodalite, when it was used until 75%Cl⁻ (8 M NaOH) and 25% (16 M NaOH). Results showed that cancrinite or sodalite zeolites are separately formed.