The article is a review that addresses the problem of insufficient scientific basis for predicting the durability of polymer composite materials (PCM) during long-term use. Special attention is given to the influence of ultraviolet (UV) radiation and mechanical loads on PCM degradation. The text presents research findings related to polymer degradation under UV radiation, the impact of UV exposure on the mechanical properties of carbon-fiber-reinforced polymer composites, and the mechanisms of yellowing in thin films of epoxy and vinyl ester resins.

Статья представляет собой обзор, в котором рассматривается проблема нехватки научной основы для прогнозирования долговечности полимерных композиционных материалов (ПКМ) при длительной эксплуатации. Особое внимание уделяется влиянию ультрафиолетового (УФ) излучения и механических нагрузок на деструкцию ПКМ. Текст содержит результаты исследований, связанных с деградацией полимеров под воздействием УФ-излучения, влиянием УФ-облучения на механические свойства полимерных композитов с углеродным волокном, а также механизмами пожелтения тонких пленок эпоксидных и винилэфирных смол. The article is a review that addresses the problem of insufficient scientific basis for predicting the durability of polymer composite materials (PCM) during long-term use. Special attention is given to the influence of ultraviolet (UV) radiation and mechanical loads on PCM degradation. The text presents research findings related to polymer degradation under UV radiation, the impact of UV exposure on the mechanical properties of carbon fiber-reinforced polymer composites, as well as the mechanisms of yellowing in thin films of epoxy and vinyl ester resins.

In this paper, the influence of organo-modified montmorillonite (oMMT) on the properties and structure of ultra-high molecular weight polyethylene (UHMWPE) are studied. The technology of preliminary mechanical activation of oMMT in a planetary mill was proposed. The structure and morphology of oMMT before and after mechanical activation in a planetary mill were investigated using scanning electron microscopy and IR spectroscopy. It was found that preliminary mechanical activation leads to dispersion and increase in the porosity of oMMT. Heat treatment at the temperature of the composite material processing does not lead to the destruction of organic modifiers. Studies of the mechanical properties of polymer-silicate composites have revealed that the introduction of preliminary mechanically activated oMMT contributes to the increase of tensile and compressive strength of the composite material based on ultra-high molecular weight polyethylene.

The possibility and technical efficiency of the use of the FA-513 nanomodifier in the formulations of lubricants (Nos. 76 and 4S) are confirmed. The optimal concentrations of FA-513 are found with an impregnation method for lubricants in the production of microplastics. The resulting microplastics exhibit increases in physical and mechanical properties of 12–25%.

The aim of the study is to examine the possibilities of sputtering of multilayer coatings at a high rate of deposition on products of complex shape using inverted magnetrons. The formation of texture and residual stresses in magnetron four-layer Ta/W/Ta/W coatings deposited at voltages from 0 to –200 V on cylindrical and flat copper substrates imitating elements of the surface of complex shape products was evaluated using the X-ray method of inverse pole figures and the sin2Ψ method. The patterns of texture formation in coatings depend mainly on the bias voltage on the substrate (Us), while at Us = –200 V they differ for W and Ta layers. At Us = –100 V, the epitaxial mechanism of texture formation is realized. In the case of a cylindrical substrate, this leads to intense texture (111) of all four layers. In the case of a flat substrate, this can lead to the formation of a single-crystal texture (111) in all layers with a texture maximum width of 12°–14°. The presence of a single-crystal (111) tantalum texture corresponds to the maximum Young moduli and, accordingly, the interatomic bonding forces normal to the coating plane. This suggests that multilayer coatings with an external Ta layer have high tribological characteristics. Increasing the voltage on a flat substrate from 0 to –200 V leads to an increase in residual compressive stresses from 0.5 to 2.7 GPa for the four-layer coating under study.

In this paper we have successfully formed fixed joints by butt friction stir welding of rolled sheets made of Ti-6Al-4V titanium alloy, using tool made of a heat-resistant alloy based on nickel ZhS6U with liquid cooling in the welding process. There was found a formation of a part of the welding tool material in the stirring zone of the fixed connection by methods of metallographic analysis. It was shown by fractography methods that the fracture in the joint zone was ductile, however, when the tool material was caught, the fracture was brittle. In spite of this, by modifying the welding parameters, it became possible to obtain a connection equal to the strength of the base metal.

Permanent joints are successfully formed by butt friction stir welding of rolled sheets made of Ti-6Al-4V titanium alloy, using a tool made of a heat-resistant alloy based on nickel ZhS6U with liquid cooling in the welding process. It is revealed by the methods of metallographic analysis that the fragments of the welding tool material in the stirring zone get dissolved. A fractographic analysis of the fracture surfaces demonstrates that the fracture in the joint zone is ductile, while in the areas with the tool material fragments it is brittle. By varying the friction stir welding parameters a permanent joint is formed, whose strength competes with that of the base metal.

The work addresses the use of electron beam produced by the linear induction accelerator to generate terahertz radiation pulses of 100 MW power level based on a free electron laser scheme. The beam parameters required for efficient generation are given. The features of transverse beam dynamics when transporting the beam through the linac are investigated. Emphasis is put on the electron injector which geometry and operation parameters mainly determine the beam characteristics at the linac exit. Most of the possible factors contributing to the beam emittance gain in the accelerator are considered. The obtained analytical estimates are compared to the numerical simulation results. The experimental results on compressing and transporting the beam having the electron energy of 5 MeV and the current of 1 kA in the transport system of free electron laser are presented.

The present study is aimed to examine the structure of a welded joint of low-carbon structural steel A 516–55 formed by melting under laser irradiation and by subsequent melt solidification. The main disadvantage of the weld structure in this steel is the formation of plate- and needle-like Widmanstätten ferrite in the conditions of ultra-fast heating and cooling which adversely affects the strength properties of the welded joints. It is shown that the application of ultrasonic vibrations during welding changes the melt solidification conditions and positively affects the dispersion of dendrites and growing Widmanstätten ferrite crystals.

This work is devoted to studying the accumulation of hydrogen in titanium coatings to use a completely new concept of hydrogen accumulators based on a system of easily replaceable cartridges. Modern hydrogen accumulators based on magnesium powder have several problems associated with uneven heating during hydrogen desorption. Increasing the efficiency of hydrogen accumulators and the possibility of their reuse and/or repair remains a topical problem. For the analysis of the microstructure of the received titanium coatings, scanning electron microscopy (SEM) was used, the structural-phase state was studied using x-ray diffraction (XRD) analysis. The coatings were hydrogenation by gas-phase saturation at 450–550 °C. Increased film thickness reduced the storage capacity of coatings. Besides hydrogenation at 450 °C, 20 µm of titanium coatings accumulated 3.96 wt.%, while 80 µm of coatings accumulated 3.98 wt.%. The chemical composition of the coatings before and after the hydrogenation was controlled using glow-discharge optical emission spectroscopy.

In this paper, regularities of the friction stir welding process parameters influence on mechanical properties of welded joints of different thicknesses are investigated. Joints were produced using the same type of tools with a screw-shaped pin. The tests show different dependencies of the joint mechanical behavior on the welding parameters. 2-mm-thick samples are characterized by high values of the ultimate tensile strength and a small variation of those when changing parameters. 10-mm-thick samples are characterized by a lower ultimate tensile strength and a greater variation at changing process parameters.

Deformation and fracture regularities of samples from stainless steel 321 during fatigue testing are investigated. It is revealed that during the cyclic tensile tests according to the scheme "loading-unloading" the samples demonstrate high cycle life in the range of maximum stresses in the cycle from 0.65 UTS to 0.70 UTS. At the stresses of 0.75-0.80 UTS the samples are characterized by lower level of cycle life. It is revealed, that the specimen fracture is localized in the weld seam area. At different values of maximum stress, it is possible both to fracture with a neck formation, and purely fatigue rupture.

This work is devoted to the study of the features of surface wear of tool steel at adhesive contact with an aluminum alloy. It is revealed that with increasing speed and friction distance the depth of the wear path increases as well. With further increase in the speed, the wear depth is reduced due to the fact that adhesive processes are activated at high friction rates and a transfer layer is formed on the steel disc surface. It was observed that the difference in friction coefficient values is not large, which means that the dependence of friction coefficient on the speed is insignificant.

In this paper the regularities of tribological behavior of aluminum alloys under adhesive friction with different counterbody configuration at frictional contact are investigated. The carried out research show essential heterogeneity of the processes passing in material under the influence of the applied loading together with frictional contact. The shape of the counterbody has a direct influence on the processes of fragmentation and plastic deformation in the sample material, while the structure of the wear paths has significant similarities with the friction surface.

The mechanical properties of coatings obtained on the AMg5 alloy surface by friction stir processing of yellow metal L63 have been studied. The samples obtained in this study show high values of coating adhesion to the substrate. The performed works show that in a number of samples it is possible to form defects in the boundary zone leading to a decrease in coating adhesion and leading to material detachment during tensile tests. The structure of fracture surfaces obtained during tensile tests shows a high degree of system component stirring, but also the presence of structural irregularities.