Abstract: The analysis of properties of the antifriction materials suitable for use as materials of a surface of sliding of contact nodes was made and the elastoplastic model for the description of their behavior has been chosen in the work. The general mathematical statement of the problem of friction contact interaction of two elastic bodies through an elastoplastic antifriction layer taking into account all types of a contact state has been made. Check of mathematical statement within numerical realization of an experiment on uniaxial compression of a sample by press plates taking into account friction on the interfaced surfaces has been executed. Assessment of convergence of the numerical solution of the task of contact parameters depending on a number of nodal unknowns has been made, optimum finite element decomposition of the model has been chosen. It has been established that the numerical solution gives a good quantitative capability to results of a natural experiment. It has been established that all paths of deformation have small curvature in all considered points of the polymeric cylindrical sample.
Abstract: The work presents the result of the 3D finite element simulating of four-layer titanium-steel titanium + niobium + copper + steel 12Cr18Ni10Ti composite adapter behavior under axial compression using a SIMULIA/Abaqus software package. The "stress-strain" curves for adapters with various thicknesses of the copper sublayer was obtained. The differences in the deformation of niobium and copper sublayers on the outer and inner surfaces of the adapter was shown.
Abstract: The authors of the paper suggested a recently developed technology of creating oil-filled composites based on aromatic polyamide Phenylone C-2. The depicted approach originates in the functional modification of the matrix base with nanomodified fillers and nanodimensional additives. The paper formulated the principles of absorption modification of mineral nanofiller for creating universal inhibitors of tribosystem or oleaginous polymer, more known as «maslyanit». It was demonstrated that the efficiency of polymer filling is enhanced by the joint application of the methods of preliminary solvent cleaning and dispersion of mineral particles to the nanodispersed state. The increase of the sorption capacity of natural and synthetic minerals was carried out by acid modification of minerals. A set of comparative tribological tests on a friction machine of Amsler II 5018 type according by a «finger-roller» scheme without external lubrication was carried out to evaluate the resistance of composite materials to abrasion at a constant specific pressure. It was found that the introduction of PFPE oil led to a significant decrease of the coefficient of friction practically in the entire loading range only in composites containing Aerosil. While the introduction of PMPS oil, in contrast, strengthened the antifriction effect of the samples, containing spinel and serpentine, in the load range of 209-720 N. The study of physical and mechanical properties of composites was carried out by NanoTest 600 complex. It was established that the samples with the addition of Arimid are characterized with the highest physical and mechanical properties. Besides, it as noted that the addition of PFPE and PMPS oils when creating oil-filled composites results in 20-25% decrease the microhardness and modulus of elasticity values. The carried out researches allowed concluding that the composite with that composition is most suitable for use in non-lubricated friction units.
Abstract: Currently, composite materials composed of a matrix and reinforcing components are widely used as a structural material for various engineering devices designed to operate under extreme loads of different types. By modifying a composite with structure-sensitive inclusions, such as a single-wall carbon nanotube, the mechanical properties, especially elastic characteristics, of the resulting material can be significantly improved. The results of investigation of a single-walled carbon nanotubes chirality influence on its elastic properties are presented. Various configurations of nanotubes, such as zigzag and armchair are considered. The dependences of the nanotube bulk modulus and shear modulus of its diameter are shown.
Abstract: The technological progress constantly raises standards for items operated in rough conditions in order to improve their reliability in a wide range of operating temperatures, fire resistance and sustainability. Researches aimed at discovering flame retardant agents that would help to develop siloxane rubbers with increased fire-resistance are of great scientific interest and have a practical significance. We have studied the effect of aluminium hydroxide on the physical and mechanical properties and fire-resistance of siloxane rubbers. The study has shown that the aluminium hydroxide acts as an effective fire retardant at its content in the rubber over 40 % (wt.), however, it significantly decreases the physical and mechanical properties of the siloxane rubbers and causes difficulties in processing of the rubber mix. The research has shown that the additional introduction of organoclays (5 pts. wt.) improves the fire-resistance of such rubbers, the most effective being montmorillonites modified with alkylbenzyldimethylammonium chloride.
Abstract: According to the standard process, normal electrocorundum is heat treated at 700°C in a rotating drum followed by air cooling. Such heat treatment increases the strength characteristics of abrasive grain. When abrasive paper made from grains with reduced brittleness is working, the effect of reducing the cutting ability due to damage and failure of the cutting surfaces is observed.
An increase in the performance characteristics of the abrasive paper was studied by improving the self-sharpening of the grain. Improvement of this performance is achieved by thermochemical treatment in a regulated gas atmosphere and cooling according to a special schedule. Normal electrocorundum during heat treatment in an oxidizing atmosphere changes the structural characteristics due to the decomposition of a solid solution of Ti2O3 in α-Al2O3 by oxidation to TiO2. The formation of a block grain structure with microcracks increases the probability of chipping during the grinding tool operation and the appearance of new cutting surfaces.
Abstract: Composites and dynamic materials that include conductive components are becoming a suitable choice in different applications. The eddy currents are generated when the conductive components are placed in alternating magnetic field. The eddy currents decrease the primary field and this effect has been well studied and it is used for electromagnetic shielding. Besides, the magnetic field increases in small space near edges of the conductive components. While this effect of magnetic field strengthening is known, it is rarely examined. We will introduce a simple model that can be appropriate for the conductive components in form of long thin sheets. We analytically analyze the model and obtain expressions that give upper bounds for increasing of the net magnetic field. The electromagnetic effect of strengthening should be taken into account when considering an application of the composites. The results are useful for electromagnetic compatibility analysis, non-destructive testing and monitoring of composite and dynamic materials with conductive components.
Abstract: The carbon fiber reinforced polymer composite are widely used in industry as major structural materials. They represent the greatest interest for the production of gas turbine engines parts because of their high specific strength. But before adaptation these materials into the structure, it is necessary to conduct a number of tests, both on test coupon and on structurally equivalent samples for determining physical, in particular, fatigue properties of these materials. However, the high cost of manufacturing coupons for such tests has a negative impact on the adaptation of carbon fiber reinforced polymer composite into the composition of final products. In this paper it is presented a method for fatigue tests of test coupon and structurally equivalent samples of carbon fiber reinforced polymer, aimed at reducing the consumption of coupons which are necessary for obtaining fatigue properties. Based on the developed method, a series of carbon fiber coupons was tested and the fatigue limit was obtained. At the same time, the use of coupons was minimized.
Abstract: A huge increase in performance of devices within the sizes and weight decrease result in high performance thermal interface materials (TIM) are indispensable to application. Thermal grease is one of the most commonly used TIM types. Zinc-oxide based thermal grease (KPT-8) has a low thermal conductivity that leads to overheating. New silicone oil – aluminum nitride high performance thermal grease has been studied. Also the installation for thermal conductivity investigation has been designed and produced. Thermal conductivity value of aluminum nitride-silicone oil thermal grease with 50 % volume fraction was 1,130±0,056 W/(m K), that is 40 % higher than KPT-8 thermal conductivity. Thermal conductivity value was calculated by a number of theoretical models, and the results were compared to the experimental data. The best results have been obtained by modeling within Brugemman and Cheng-Vachon theories.