The analytical capabilities of the arc atomic emission analysis for determination the impurities in kaolin clays, the feedstock for producing metallurgical alumina, were studied. The analytical lines of the elements that are most free of interferences are selected. The conditions of the analysis and parameters of the spectrometer are determined: current strength, exposure, interelectrode distance, types and parameters of electrodes, weight of the sample. The detection limits and limits of determination of the following elements are specified: Ca, Cr, Cu, Ga, Mg, Mn, Mo, Nb, Ni, Pb, Sc, Ti, V, Y, Zn, Zr, La. The limits of determination are n x 10^–5 – n x 10^–6 wt.%. A comparative analysis of the samples of kaolin clays previously analyzed by another method in the framework of inter-method comparative tests is carried out. It is shown that there are no significant discrepancies between the results obtained by both two methods.

Operation with positive ions formed from the impact of high energy electrons (usually 70 eV, which exceeds the ionization energy of the molecules) is a standard mode for mass spectrometric detectors of most gas chromatography-mass spectrometric complexes (GC/MS) in the basic configuration. At the same time, we have shown that the option of setting the energy of ionizing electrons (maintained in the design of some serial devices) within the pre-ionization region also allows one to obtain mass spectra of negative ions (NI) which, in turn, significantly expands the analytical potential of standard equipment. The formation of NI occurs in the low-energy range of 0 – 15 eV due to resonant capture of electrons by molecules (REC). In contrast to positive ions, the intensity of NI formation sharply (resonantly) depends on the electron energy and this dependence is characteristic of each chemical compound. Both the relative intensity of the mass-peaks and, in general, the ionic composition of the formed mass spectrum of NI significantly depend on the electron energy. The problem of choosing the optimal energy of ionizing electrons providing the same efficiency of mass-spectrometric determination of all components of complex mixtures of dissimilar compounds is also associated with the features of negative ion formation during chromatography-mass spectrometric analysis. To address the problem, we propose a technique providing generation of complete (in NI composition and intensities) mass spectra of NI through repeated variation of the energy of ionizing electrons in a given range of 0 – 10 eV. Technical implementation of the technique [1] was carried out at the Design Bureau «Chromatec «(Yoshkar Ola, Russia) in the form of a special electronic device, which was tested in pilot operation as part of the gas chromatograph complex with a quadrupole mass spectrometer «Chromatec». We describe the principle of operation of the device and present the results of tests.

A photochemical method for determination of 1,1-dimethylhydrazine H₂NN(CH₃)₂ (unsymmetrical dimethylhydrazine (UDMH)) based on titration of the analyte with photogenerated iodine obtained by irradiation of an auxiliary solution containing potassium iodide and a mixture of sensitizers (EOSIN Y:auramine:fluorescein taken in a molar ratio 1:1:1) in an acetate medium (pH 6) has been developed. With increasing acidity, a decrease in the rate of photogeneration is observed which is most likely attributed to disproportionation of the resultant titrant. Since the titrant (iodine) content is controlled by the voltammetric method, the photochemical titration of UDMH is accompanied by a decrease in the current strength in the circuit of the amperometric setup and stabilization indicates the completeness of the reaction. Measurements of the photogeneration time necessary to compensate for the loss of titrant in the cell upon further irradiation of the solution in the presence of atmospheric oxygen provide quantitative assessing of the UDMH content in environmental objects. Since the analyte interacts with the titrant in a molar ratio 1:2, we suggest the possibility of UDMH oxidation to NDMA (N-nitrosodimethylamine). A photochemical method of UDMH determination in solution is thus developed with the detection and determination limits (0.49 and 1.62) μg/ml, respectively. Unfortunately, the sensitivity of the proposed methodology does not allow determination of a toxic chemical contaminant at the MPC level which necessitates preconcentration of the mobile forms of UDMH by steam distillation in a 40 % sodium hydroxide solution. The developed methodology matches the validation parameters by the indices of linearity, ranking, correctness and thus can be recommended for determination of the UDMH content in any analytical laboratory. The photochemical method was tested in the analysis of soil samples taken from background and contaminated territories as well as natural water. A slight excess of the UDMH content has been found in the soil taken from the former location of the military unit.

A review of non-contact methods for determining the surface tension of liquids along with analysis of the physical effects underlying them is presented. A review of non-contact methods for determining the surface tension of liquids along with analysis of the physical effects underlying them is presented. The advantages, disadvantages, possible ranges of measurements and scope of non-contact methods are discussed. Passive methods do not require any stimulation of the measurement object whereas active methods, when implemented, affect the liquid under study. Electrical, electromagnetic, acoustic, jet, and mechanical methods used for excitation of capillary waves are described in analysis of the methods based on capillary waves intended to study the properties of surface-active substances. We also considered methods based on the processes occurred in an oscillating or rotating levitating drop of liquid (containerless technology) used to study the properties of melts and methods based on local deformation of the liquid surface by the electric field, acoustic pulse, and gas jet. It is shown that aerodynamic methods based on deformation of the liquid surface under control by a gas stream are the most promising for standard laboratory conditions. It is noted that containerless methods should be used in zero gravity tests, whereas the methods based on capillary waves or deformation of the liquid surface with a focused acoustic pulse appeared useful in testing inviscid liquids. Methods based on electrical deformation of the liquid surface under control are limited with the thickness of the liquid layer, relatively high sensitivity to the density and dielectric constant of the liquid, and some other uncontrolled factors. It was also noted that aerodynamic non-contact method of the surface tension determination is characterized by low sensitivity to the density and viscosity of the controlled liquid. The presented review of non-contact methods of the surface tension determination provides optimal choice of the method most suited for solving specific measurement problems.

A statistical analysis of the grain size distribution is important both for developing theories of the grain growth and microstructure formation, and for describing the size dependences of various characteristics of the physical and mechanical properties of polycrystalline materials. The grain size distribution is also an important characteristic of the structure uniformity and, therefore, stability of the properties of the products during operation. Statistical Monte Carlo modeling of single-phase and equiaxed polycrystalline microstructures was carried out to determine the type of statistically valid distribution function and reliable estimates of the average grain size. Statistical parameters (mean values, variances, variation coefficient) and distribution functions of the characteristics of the grain microstructure were obtained. It is shown that the distribution function of the effective grain sizes for the studied polycrystal model is most adequately described by γ-distribution, which is recommended to be used in analysis of the experimental distribution functions of grain sizes of single-phase polycrystalline materials with equiaxed grains. The general average (mathematical expectation) of the effective grain size (projection diameter) with γ-distribution function (parameters of the distribution function are to be previously determined in analysis of the grain structure of polycrystalline materials) should be taken as a statistically valid and reliable estimate of the average grain size. The results of statistical modeling are proved by the experimental data of metallographic study of the microstructures of single-phase model and industrial materials with different degree of the grain structure heterogeneity.

Analysis of the operational data related to rails failure showed that contact-fatigue defects consistently hold a prominent place. The goal of the study is to show the possibilities of using modern numerical methods in calculation assessment of the service life of rails before the onset of contact fatigue crack formation on a running surface depending on the values of axial load. To calculate a stress-strain state in the area of contact interaction between the wheel and rail a detailed finite-element model implemented in the MSC. Marc software package is used. The analysis revealed complex multiaxial and non-proportional nature of the stress-strain state. The Brown – Miller multiaxial fatigue model implemented in the MSC. Fatigue software package was taken to determine accumulation of the contact fatigue damages on a rail running surface. The model is based on the assumption that maximum fatigue damages in the metal occur in the area with the maximum shear stress. The impact of normal stresses in this area is also taken into account. The results of a comparative computational analysis of the rail life time confirm that the service life decreases with increasing axial loads, all other conditions being the same. With a share of 20% of freight trains with axle loads of 25 tonf in a daily pattern one should expect a decrease in the contact fatigue life of rails by 3 – 4 %. It is possible to improve the method for prediction of the contact fatigue life of rails in terms of experimental definition of the fatigue and strength characteristics of the rail steel depending on the degree of hardening of the running surface, their probabilistic properties and the use of a cumulative distribution of vertical forces taking into account the structure of the freight traffic passing through the section.

The necessity and possibility of using nanoindentation in studying the physical and mechanical properties of plasma-hardened wheel steel are considered. The goal of the study is demonstration and substantiation of significant differences in the mechanical properties and behavior of the materials in nanoscale tests from those determined in traditional macroscopic tests. The method was implemented using a NanoHardnessTecter nanohardness tester. The electric field formed in the nanoscale hardness tester pressed on the indenter and the diamond tip of the indenter is immersed in the surface layer of the material under study. The characteristics of the surface layer are determined using the developed software. Knowledge of the physicomechanical characteristics of the material (hardness, Young’s modulus, elastic recovery, etc.) which affect the wear resistance of the surface layers, allows one to evaluate and select the optimal surface modification technology using plasma hardening. The credibility of determination depends on the parameters of measuring equipment and compliance with the requirements to the depth of the imprint depending on the thickness of the hardened layer. The studies were carried out on the samples cut from the rim and crest of a railway wheel subjected to surface plasma hardening on a UPNN-170 installation (Russia). It is shown that the hardness (according to Vickers HV and H) of the rim is greater, and Young’s modulus, on the contrary, is less than the corresponding characteristics of the crest. Moreover, the wear resistance of hardened structural steel increases after nanostructural friction treatment.

A reciprocating friction machine Tribal-T intended for automated quality control of the rubbing surfaces of tribopairs is described. The distinctive feature of the machine consists in implementation of the forced relative motion due to the frictional interaction of the rubbing surfaces fixed on the drive and conjugate platforms. Continuous processing of the signals from displacement sensors is carried out under conditions of continuous recording of mutual displacements of loaded tribopairs using classical approaches of the theory of automatic control to identify the tribological characteristics. The machine provides consistent visual real time monitoring of the parameters. The MATLAB based computer technologies are actively used in data processing. The calculated tribological characteristics of materials, i.e., the dynamic friction coefficient, damping coefficient and measure of the surface roughness, are presented. The tests revealed that a Tribal-T reciprocating friction machine is effective for real-time study of the aforementioned tribological characteristics of materials and can be used for monitoring of the condition of tribo-nodes of machines and mechanisms.

Validation of the forensic methods (FM) is one of the main procedures for the standardization of forensic activities used to verify the reliability of the obtained results of the studies. This procedure is widely adopted in the organizations of the European Network of Forensic Science Institutes (ENFSI), which also includes the Russian Federal Centre of Forensic Science of the Ministry of Justice of the Russian Federation (RFCFS). Two types of FM can be distinguished in metrological aspects: forensic method of measurements (FMM) and forensic methods of testing (FMT). We have shown earlier that unlike the developed methodological approaches to the FMM validation which gained practical application in the RFCFS laboratories, the FMT validation procedures give rise to many questions which are widely discussed in the scientific literature. The most significant difficulties in FM validation are attributed to selection of the validation parameters, development of the validation experiment and performance of statistical calculations. We propose methodological approaches to the statistical assessment of the FMM and FMT parameters to be used in practice of forensic experts. Moreover, we present a number of recommendations on the validation procedure, list of the validation parameters, and consider specific schemes of the experiments to be used for assessing of the quality indicators of FMM and FMT. The results of multiple determination of the controlled index in the referenced samples and standard additives are presented to assess the suitability of the FMM using common formulas for calculation of the statistical parameters. Case study of the FMT validation procedure «Microscopic Examination of Textile Fibers» is considered. The expediency of using probabilistic estimate of the share of false test results, as well as calculation of the likelihood ratio in assessing the reliability of forensic methods of testing and competence of the experts is demonstrated.