Spent autocatalysts hold a specific place among secondary raw materials containing precious metals. Precise determination of platinum metals in spent autocatalysts (SA) plays a very important role affecting the economic efficiency of the utilization process. We generalize the existing methods of analysis of spent autocatalysts presented in the literature and methodological developments of the Institute «Giredmet» in collaboration with the Center «ANSERTECO» and NUST «MISiS» regarding the same problem. The main emphasis is made on the use of modern tools for chemical preparation of hard-to-break object like spent autocatalysts: autoclave and microwave opening of the samples. The advantages of using the assay concentration method based on the developments of the Ekaterinburg Non-Ferrous Metals Processing Plant for analysis of spent autocatalysts are concidered. The atomic emission, atomic absorption and chemical spectroscopic methods of SA analysis have been developed and certified along with the guidelines of their further improvement.

 

 

A comparative analysis of three methods of PCB determination in insulating fluids is carried out using capillary gas chromatography with a detection by electron capture (GC-ECD — IEC 61619:1997 »Insulating liquids – Contamination by polychlorinated biphenyls (PCB) – Method of determination by capillary column gas chromatography; EN 12766-2:2001 «Petroleum products and used oils – Determination of PCBs and related products»; FR 1.31.2012.13568 «Method for determination of sum of polychlorinated biphenyls and sum of polychlorinated terphenyls in mineral and synthetic oils, petroleum products and wastes by capillary column gas chromatography»). The first method requires determination of all the congeners in the analyzed sample and encounters the impossibility of their identification at the relatively low content of congeners and interfering impact of the impurities present in the used oils. The second method based on determination of six selected congeners (28, 52, 101, 153, 138, and 180) and subsequent multiplying of the sum of their contents by a factor of 5 is much better, but does not provide evaluation of the accuracy of the results thus obtained. The third method based on the use of technical products for calibration, and an arbitrary number of congeners distributed throughout the elution interval for determination of the content and type of the technical product occupies an intermediate position in comparison with the two previously considered methods and provides estimation of the uncertainty of the result. This method gives an intermediate result in comparison with the two previous ones and allows us to estimate the uncertainty of the result.

 

 

A method for AES-ISP determination of Ti, V, Cr, Fe, Co, Ni, Cu, Zn, and Ta in recycled cemented tungsten carbide is developed including preliminary microwave sample decomposition in a steam pressure vessel (autoclave). We have specified composition of the reaction mixture for sample dissolution and optimized the parameters of microwave heating in the autoclave. Correctness of the results is proved by the method of sample weight variation and spike tests. The results of analysis are compared with the data obtained by standardless method of x-ray fluorescence spectrometry. The technique is characterized by good reproducibility and allows significant reduction of the analysis time due to combination of the multi-element method of AES-ISP and microwave sample preparation.

A possibility of using certain salts of hydrohalic acids as a source of hydrogen halide in an anhydrous medium for determination of epoxide groups is studied. The reagents based on NaBr, LiJ, KJ, KCl in acetate solution of perchloric acid are proposed for potentiometric determination of epoxy groups in organic compounds and epoxy resins.

 

The results of fatigue tests of steel 30 – 35 CHG carried out on a laboratory unit of original design are presented. The unit consists of a fatigue machine, eddy current sensor and electronic measurement module. The structural scheme of the force mechanism of specimen bending upon testing is presented. To avoid runout of the sample we use cycling in conditions of steady stress. The developed eddy current transducer (sensor) consists of cylindrical coil made of a nonmagnetic material with two windings (design and equivalent circuit of the sensor windings are also presented). It is shown that electronic block of the measuring complex consists of a low-frequency generator of sinusoidal current, electronic engine revolution counter capable of automatically stopping of the sample cycling at a given number of cycles, and harmonic analyzer. The operation procedure is considered. The experimental data thus obtained proved that the method provides up to 30 – 40-fold shortening of the test time which is rather convenient for determination of the actual strengthening effect attributed to different types of steel processing, since the endurance limit can be determined both before and after strengthening. The eddy current method provides studying of rather thin surface layers, where fatigue cracks used to originate, thus being convenient for studying chemical heat treatment of steel surface and thin coatings without their destruction upon testing.

 

 

Critical analysis of the form of representing correlation between the tensile (ultimate) strength σB and hardness of steels is presented. Simple analytical expressions are derived using statistical analysis, which provide more accurate description of the relationships between Brinell and Rockwell scale hardness values and tensile strength σB. The results of σB calculations by steel hardness using known and developed formulas are compared. The developed formulas are used to analyze changes in σB of carbon steels under the impact of heat treatment. Quantitative evaluations of the effect of quenching and tempering temperatures on the changes in σB values in carbon steels 35, U8, and U10 are based on the results of HRC hardness measurements. The developed formulas can be also used for other steels proceeding from the data on their measured hardness value or reference data presented in literature.

 

 

Current methods of assessing crack resistance of strengthened surfaces using pyramidal indenter are intended only for the case of radial crack formation around the indenter. However, for certain types of hardening coatings, e.g., titanium nitride based coatings, indentation leads to formation of ring rather than radial cracks around the indenter. For this case of crack formation, we propose to use kinetic diagram of indentation to determine the specific energy of elastoplastic deformation which provides formation of the first visible crack. This energy can be used to compare the ability of coatings to withstand any kind of crack formation.

 

 

Analysis of various procedures currently used for determination of the hardness of the abrasive tools in the Russian Federation and abroad showed that the processes of measuring the surface hardness of tools differ from the processes occurred upon interaction of the working surface of the tool with the workpiece surface of the item. All known methods of hardness determination are thus formalized, conditional and and irresponsive to the essence of physical and mechanical processes of grinding. Another disadvantage is their low sensitivity to the change in the structural and mechanical properties of the tool under the impact of environmental factors, coolant-cutting fluid, etc. A pendulum dispersometer is developed to study the surface hardness of tools and simulate the real contact between their working surface and the workpiece surface upon grinding. The design of the pendulum dispersometer, mechanics, and detailed technique for determination of the relative hardness using the dispersion time constant are presented. A close correlation is observed between the hardness values determined with the pendulum dispersometer and specific volumetric fracture energy when the surface of the abrasive tool is dispersed. Data on the hardness values obtained using a pendulum dispersometer and sand-blasting method are compared. Electrocorundum tools on a ceramic bond of different grain sizes (16, 25, 40) with a constant hardness of SM2 determined by the sand-blasting method according to GOST 18118-97 are used as samples. An analysis of the results proved that the hardness values obtained on a pendulum dispersometer reliably reflect the real operating conditions of abrasive tools.

 

 

Nonparametric statistic is one of the points of growth of modern mathematical and statistical methods of research. In nonparametric statistics, rank criteria based on the use of the ranks of the sample elements (observation results), rather than numerical values of the sample elements themselves, take an important place. Ranks are the numbers of sample elements in the corresponding variation series, constructed by rearranging the results of observations in the order of nondecreasing. Distributions of rank criteria are obtained on the assumption of continuity of the distribution functions of the observation results, hence, the probability of coincidence of the values of the random variables forming the analyzed samples should be equal to zero. However, in actual data, there are coincidences. Consequently, the assumption of the continuity of the distribution functions of the observation results is incorrect and known theorems on the distribution of rank statistics, strictly speaking, are not applicable. However, with a small number of coincidences, ranks statistics can be recommended for use, albeit with some corrections. Thus, an additional superstructure is mounted on the classical mathematical-statistical theory to take into account the coincidence of the data. Naturally, the validity of different methods used for accounting the coincidence of calculation data should be considered. We propose a probabilistic-statistical model that explains the occurrence of the coincidences and provides algorithms for their analysis. This model is based on the assumption that data coincidences appears as a result of «sticking together» of the slightly different observation results. We propose to introduce small corrections into each elements of the coincident group of observation results and thus to obtain a sample without coincidences and calculate the value of rank statistics. Having considered various variants of amendments, we obtain a «cloud» of values of rank statistics. Analysis of this «cloud» allows us to obtain statistical conclusions. Two-sample Wilcoxon test is considered as an example.

 

 

A method is proposed for constructing basic sets (confidence intervals for percentiles) using bootstrap simulation as an alternative to currently used approaches. Bootstrap simulation is a method for numerical modeling of distributions based on multiple data reproduction the without using any information regarding the distribution laws. Since the strength characteristics are random variables, statistical estimation with construction of the interval characteristics is required. This is the goal of the study. An illustrative example of constructing the confidence intervals for mean strength value using bootstrap-modeling is considered. To construct the confidence intervals for percentiles of the distributions of the strength characteristics we recommend to assign the distribution to one of the currently known (normal, lognormal distribution or Weibull) laws, unlike the existing non-parametric approach that generally gives a conservative (too low) and thus undesirable results, which is the reason for developing a new approach. A comparison of B-bases, determined by the newly proposed and traditional method is carried out on real samplings of the strength characteristics of composite materials. The specific examples of strength parameters for shear and tensile strength of the specimens made of prepreg HexPly (composite materials, semiproducts) using an autoclave molding method are presented.

 

 

Some aspects of using protective polymer films in practice of x-ray fluorescence are considered. Data of practice guidelines regulating the measurement procedure in part of the requirements for x-ray films, are summarized. Data of practice guidelines regulating the measurement procedure in part of the requirements regarding x-ray films, are summarized. A review and comparison of the physical and chemical properties of films presented on the Russian market are analyzed. The influence of the polymer type on the absorption of secondary fluorescence intensity is shown for the Ká lines of Al, Si, and Ti. The analysis of the dependence of fluorescence intensity on the atomic number of the radiating element is considered for different polymer types. Chlorine- and sulfur-containing films can be used as filters of secondary fluorescence. Regulatory requirements for different thicknesses of films and actually different thicknesses are specified for a polypropylene film. Decreases and fluctuations of the fluorescence intensity of the analytical lines of light elements are calculated as a function of the unevenness of physical and chemical properties of the films thus used. The influence of impurities present in the polymer material on the intensity of the analytical lines of these elements is estimated. Important from a practical point of view performance characteristics of the films are analyzed. Recommendations regarding the types of polymers are specified depending on the analytical tasks being solved.

Relatively simple formulas are derived for calculating the thermal diffusivity by a numerical-analytical method in the asymmetric temperature field T (x, τ) of an infinite plate of thickness R obtained as a result of a physical experiment. By solving the inverse heat conduction problem, the thermal diffusivity values are calculated for each time interval Δτ_i = τ_i – τ_i – 1 by the temperatures at three points of the plate with the coordinates x = 0, z, R (0 < z < R) for the time moments τ_i. We estimated the complexity and accuracy of the thermal diffusivity determination a_t(T) from the test (initial) temperature field of a steel plate (thickness R = 0.07 m) calculated by the method of finite differences with a given thermal diffusivity a_s(T) under boundary conditions of the second and third kind. The function a_t(T) is set by a broken line and the magnitude of ax varied almost threefold during numerical experiment. The root-mean-square deviation of a_t(T) from the initial dependence a_s(T) for the entire time range is 3%. The largest errors are observed after change in the sign of the derivative das(T)/dT. On the linear part of the function a_s(T), the error of a_t(T) determination did not exceed 2%. The method presented in the article does not require strict compliance with the standard boundary conditions: constant temperature of the ambient media, the same heat flow, adiabatic conditions on one of the plate surfaces, which simplifies the organization of the experiment to be carried out in real conditions of the material operation. The method is relatively simple and illustrative and data processing data processing can be easily programed using Microsoft Excel.

 

 

 The possibility of using magnetometric analysis based on measuring the magnetic permeability of samples for determination of the structural characteristics of ferritic-martensitic steels possessing high stability of undercooled austenite is substantiated. The structure of those steels at room temperature consists of martensite and high-temperature δ-ferrite. A facility has been designed and manufactured that provides measuring the magnetic permeability and, using the data thus obtained, determine the Curie temperature of ferritic-martensitic steel samples upon cooling them from the temperatures of the gamma region to room temperature. The inductance coil connected in parallel with the capacitor is the heart of the installation. The oscillatory circuit is tuned to a resonant frequency in the range 40 – 80 kHz. The test piece is placed in the coil preheated to a temperature of 1100°C and in fact is the inductor core. It is shown that the relative change in the inductance of the coil together with the sample during continuous cooling depends on the structural class of the steel under test. For ferritic-martensitic steel the change is two-staged: the first abrupt change (at a higher temperature) corresponds to the onset of ferromagnetism in the ferrite, the second is smoother occurs upon further cooling due to martensite formation. For ferritic steel samples there is only one sharp change at the Curie temperature of the ferrite. When testing samples of austenitic steel, there is no abrupt change in the magnetic permeability up to room temperature. It is shown that the magnitude of the effect corresponding to the onset of ferromagnetism in ferrite is proportional to the content of δ-ferrite in the structure. This makes it possible to separate the contribution of two ferromagnetic structural components, martensite and δ-ferrite. The developed technique also makes it possible to determine the temperatures of the beginning (Mn) and the end (Mk) of the martensitic transformation. The implementation and experimental errors of the developed installation and measuring technique are estimated.