An eco-friendly, simple, rapid and cheap method for determining anionic surfactants in natural and waste waters by microextraction-colorimetric method has been developed. The essence of the proposed approach consisted in extraction and concentration of analytes in an acidic medium in the form of associates with organic reagents (methylene blue and acridine yellow) by dispersion liquid-liquid microextraction using a mixture of chloroform-acetonitrile as an extracting and dispersing solvent, followed by aggregation of extractant microparticles by centrifugation and subsequent measurements of color characteristics using a smartphone. The values of the basic components of the RGB colorimetric system were used as an analytical signal to calculate the final color: The selection of optimal conditions for microextraction concentration of anionic surfactants from natural waters (the nature of the extracting and dispergating solvents, the volume of the dispergating solvent) was performed for the sodium dodecyl sulfate — methylene blue system. To study the colorimetric characteristics of the prepared extracts, a smartphone «iPhone X» was used as a color-registering device equipped with a specialized software product «RGBer». To minimize the measurement error by fixing the distance to the object under study and lighting conditions, we propose an installation that increases the accuracy and sensitivity of the determination and makes the method more mobile. The total content of the most common components of detergents was determined: sodium dodecyl sulfate, sulfonol, laureth sulfate and disodium laureth-3-sulfosuccinate. The detection limits ranged within 0.01 – 0.02 and 0.05 mg/liter. The range of detectable contents for all analytes was 0.05 – 1.0 mg/liter. For the determined surfactants, the equations of the relationship between the analytical signal and the concentration were obtained. The calibration graphs are linear with coefficients of the approximation reliability ≤0.98. The correctness of the method was tested on samples of natural water using the spike test procedure. The relative standard deviation of the analysis results does not exceed 0.13. The analysis duration is 20 – 30 min.

The content of uranium and plutonium is the main characteristic of mixed uranium-plutonium oxide fuel, which is strictly controlled and has a very narrow range of the permissible values. We focused on developing a technique for measuring mass fractions of uranium and plutonium by controlled potential coulometry using a coulometric unit UPK-19 in set with a R-40Kh potentiostat-galvanostat. Under conditions of sealed enclosures, a special design of the support stand which minimized the effect of fluctuations in ambient conditions on the signal stability was developed. Optimal conditions for coulometric determination of plutonium and uranium mass fractions were specified. The sulfuric acid solution with a molar concentration of 0.5 mol/dm³ was used as a medium. Lead ions were introduced into the background electrolyte to decrease the minimum voltage of hydrogen reduction to –190 mV. The addition of aluminum nitride reduced the effect of fluoride ions participating as a catalyst in dissolving MOX fuel samples, and the interfering effect of nitrite ions was eliminated by introducing a sulfamic acid solution into the cell. The total content of uranium and plutonium was determined by evaluation of the amount of electricity consumed at the stage of uranium and plutonium co-oxidation. Plutonium content was measured at the potentials, at which uranium remains in the stable state, which makes it possible to subtract the contribution of plutonium oxidation current from the total oxidation current. The error characteristics of the developed measurement technique were evaluated using the standard sample method and the real MOX fuel pellets. The error limits match the requirements set out in the specifications for MOX fuel. The technique for measuring mass fractions of uranium and plutonium in uranium-plutonium oxide nuclear fuel was certified. The relative measurement error of the mass fraction of plutonium and uranium was ±0.0070 and ±0.0095, respectively. The relative error of the ratio of the plutonium mass fraction to the sum of mass fractions of uranium and plutonium was ±0.0085.

Artificial hydroxyapatite exhibits an excellent biocompatibility with tissues of human body. However, poor mechanical properties of hydroxyapatites and low reliability in wet environments restrict their use. These limitations can be overcome by applying the hydroxyapatite as a coating onto metallic implants. X-ray diffraction analysis (restoration of orientation distribution function from pole figures and the Rietveld method) and scanning electron microscopy have been used to study thick (~330 μm) plasma-sprayed hydroxyapatite coatings. The coatings were deposited onto Ti – 2Al – 1Mn alloy substrates, one of which was held at room temperature (20°C) whereas the other substrate was preheated to 550°C. The texture of the coating deposited on substrate held at room temperature is characterized by the (001)[510] orientation, the volume fraction of which is 0.08, while the coating deposited on preheated substrate has the (001)[410] orientation, the volume fraction of which is 0.10. Results of texture analysis are qualitatively supported by the Rietveld refinement data. The problem of the formation of basal texture in plasma-sprayed hydroxyapatite coatings is discussed in terms of quantitative texture analysis in relation to the differences in the substrate temperature and spraying parameters. It was concluded that the quantitative texture analysis is of importance for deeper understanding the effect of spraying parameters on the formation of hydroxyapatite coatings.

The article deals with the algorithm for texture analysis of polycrystalline materials using one direct pole figure (DPF). It is shown that the incomplete direct polar figure {111} for fcc materials contains the necessary information about the material texture. The algorithm provides identification of the preferred texture components in a multicomponent texture material and determination of their properties. The proposed algorithm is as follows. The upper hemisphere of the digital representation of the DPF is scanned by a polar complex of vectors that are normal to the reflection planes. Then the reliability parameters for each orientation are calculated and a set of the most reliable orientations is formed. The chosen orientations are recalculated to the Rodrigues space wherein the preferred texture components are formed by clustering. At the same time, an iterative algorithm with symmetry operators is used to avoid the umklapp effect. Each texture component is represented by the following parameters: Rodrigues mean vector, Miller indices, and Euler angles. The share and scattering of the texture component are also calculated. A method for selecting the optimal number of clusters providing presentation of the texture with the desired degree of detail is proposed. This is achieved by comparing two incomplete direct pole figures taken for {111} and {200} to select the maximum cluster scattering value on which the number of formed predominant texture components depend. The developed algorithm seems promising for rapid texture analysis, in analysis of sharp and weak textures and when there are less than three DPFs.

Cells with a micrometer screw are still used for testing solid dielectrics at frequencies from units to hundreds of megahertz despite the development of dielectric measurement technology. We present the results regarding elimination of the negative impact of successive stray inductances (L_n) and active resistance (r_n) of such a cell on the accuracy of the dielectric loss tangent (tanδ) determination with allowance for the final value of the Q-factor (Q_k) of the circuit inductor in resonant measurements. Tests with and without a dielectric sample were carried out under the condition of maintaining the cell capacity value. No information is available in the regulatory documents and technical literature about taking the aforementioned parameters into consideration. It is shown that the impact of Ln consists in the overestimation of measured tanδ values. To eliminate this effect, we proposed to introduce an additional factor which depends on L_n, frequency and capacity of the sample into existing formulas used for tanδ calculation. It is also shown that the tanδ error increases significantly with a decrease in the ratio of the dielectric loss characteristics of the measuring circuit with and without a sample which can be attributed to r_n and Q_k. The requirements for r_n and circuit damping without a sample are formulated to ensure the desired accuracy. Conditions providing the possibility of assessing the suitability of a particular equipment for tanδ measurements are specified on basis of the developed requirements. The results experimentally proved in resonance measurements with a Q-meter can be used in high-frequency tanδ measurements to provide the required accuracy.

The goal of the study is determination of the regularities of changes in cyclic strains and related deformation diagrams attributed to the existence of time dwells in the loading modes and imposition of additional variable stresses on them. Analysis of the obtained experimental data on the kinetics of cyclic elastoplastic deformation diagrams and their parameters revealed that in contrast to regular cyclic loading (equal in stresses), additional deformations of static and dynamic creep are developed. The results of the studys are especially relevant for assessing the cyclic strength of unique extremely loaded objects of technology, including nuclear power equipment, units of aviation and space systems, etc. The experiments were carried out on the samples of austenitic stainless steel under low-cycle loading and high temperatures of testing. Static and dynamic creep deformations arising under those loading conditions promote an increase in the range of cyclic plastic strain in each loading cycle and also stimulate an increase in the range of elastoplastic strain due to active cyclic deformation. At the same time the existence of dwells on extrema of stresses in cycles without imposition of additional variable stresses on them most strongly affects the growth of plastic strain ranges in cycles. Imposition of additional variable stresses on dwells also results in the development of creep strains, but their growth turns out to be somewhat less than in the presence of dwells without stresses imposed. The diagrams of cyclic deformation obtained in the experiments are approximated by power dependences, their kinetics being described in terms of the number of loading cycles using corresponding temperature-time functions. At the same time, it is shown that increase in the cyclic plastic deformation for cycles with dwells and imposition of additional variable stresses on them decreases low cycle fatigue life compared to regular loading without dwells at the same stress amplitudes, moreover, the higher the values of static and dynamic creep, the greater decrease in low-cycle fatigue life. This conclusion results from experimental data and analysis of conditions of damage accumulation for the considered forms of the loading cycle using the deformation criterion of reaching the limit state leading to fracture.

The entire cycle of strength tests of the aircraft structure requires large expenditures of time and effort attributed to the manufacture of two full-size aircraft structures and two test rigs. The pace of development of moder_n aviation technology dictates strict requirements for timing and quality of testing, which allows us to ensure competitiveness in the world aircraft market. Therefore, when conducting a full cycle tests, shortening of the testing period becomes of particular importance. We consider a novel approach to strength testing of a full-scale transport aircraft structure which consists in static and fatigue tests carried out on the same object. The developed approach was tried out when testing the full-scale wing structure of a transport aircraft. The tests were carried out on a set-up that allowed reproducing both cases of static loading and variable loads of flight cycles. At the first stage, the static strength was proved by the results of finite-element calculation of the stress state of the structure at ultimate loads using a model verified by the strain measurements of one of the wing consoles under limit loads, as well as by testing typical and critical airframe elements. Samples of full-scale panels were additionally tested for buckling to confirm the load capacity of the upper wing panels. Fatigue tests were carried out in the time span of two design service life. The obtained results showed the possibility of conducting both static and fatigue tests using one and the same full-scale aircraft structure.

When using different formulas for determination of axial and circumferential stresses in the experiments on loading thin-walled tubular specimens with internal pressure the radial stresses are neglected due to their smallness. We propose a novel procedure for determining stresses in the internal pressure loaded thin-walled tubular specimens. The distribution of stresses in the radial direction of a tubular specimen is studied both for the elastic state and for perfectly plastic state according to the Huber – von Mises criterion of an incompressible material. It is shown that the degree of heterogeneity of the stress state depends on the ratio of the wall thickness to the specimen diameter and on the elastic or plastic state of the material. The circumferential stresses are maximal on the inner surface of the specimen and the axial stresses are constant along the radius of the specimen in the elastic state, whereas in the plastic state circumferential and axial stresses are maximal on the outer- and inner surface of the specimen, respectively. The distributions of radial stresses in the elastic and plastic state of the material are almost identical, i.e., both are maximal on the inner surface and equal to zero on the outer surface of the specimen. The values of circumferential and axial stresses on the middle surface of a thin-walled tubular specimen normalized to the internal pressure almost do not depend on the elastic or plastic state of the specimen material thus providing a basis for determination of the mechanical properties of the material from the stress-strain state of the middle surface of the specimen using the Lame formulas for stress calculations. When determining the stress intensity, it is desirable to take into account the radial stresses, since it increases the accuracy of determining the mechanical properties of the material and reduces the sampling range of the yield point for different types of the stress state.