The effect of treatment with a pulsed magnetic field on the triboacoustic characteristics of polymer friction composites containing up to 20 wt

In this paper, we study the effect of corrosion inhibitors in compositions of friction composites on corrosion processes and noise generation in friction units. Model composites containing complex corrosion inhibitors as target additives were prepared. Tribological tests of the friction composite were performed using the “plane-to-plane” scheme. Transfer films on the surface of a steel counterbody are shown to be formed predominantly by laminar wear particles of the composite with sizes up to 50 μm. X-ray photoelectron spectroscopy data confirmed the presence in the transfer films of all elements related to the main components of the friction material, including corrosion inhibitors. Climatic tests were carried out. In a friction pair with a composite containing no corrosion inhibitor, continuous corrosion of the metal counterbody is shown to be predominant while pitting actively develops over time. The degree of corrosion damage to the surface reaches 90–95

The paper presents the results of experimental studies of the influence of treatment by an amplitude modulated high-frequency electromagnetic field on the dynamic mechanical and triboacoustic characteristics of friction composites with a polymer matrix intended for operation in unsteady friction units of brake devices of machines. It was found that in the dynamic mechanical characteristics, the effect of magnetic field treatment manifests itself most significantly in the change in the tangent of the angle of mechanical losses (a decrease in the maximum values of the tangent of mechanical losses to 52%), as well as in the change in the dynamic instability of friction and the spectral characteristics of frictional noise components in the range above 2 kHz.

The results of experimental studies of the influence of non-equilibrium low-temperature plasma on the dynamic mechanical characteristics that determine the vibroacoustic activity of tribocouplings and the tribotechnical properties of friction polymer composite materials with a polytetrafluoroethylene matrix are presented). The aim of the study was to establish the effect of surface treatment of composites with low-temperature plasma of a high-frequency capacitive discharge in air on their dynamic mechanical characteristics and tribotechnical properties. Using non-resonant dynamic mechanical analysis methods, it has been established that plasma treatment leads to a decrease in the values of the tangent of mechanical losses of composites in the surface layer in the entire investigated temperature range (293–473 K), while there is a shift in the peaks of the tangent corresponding to the α- and β-transitions of the polymer matrix of the composite, to the area of higher temperatures. The values of the dynamic modulus of elasticity of the composite showed a tendency to a slight increase; however, this increase is at the limit of the sensitivity of the method. It was found that plasma treatment of friction composites results in stabilization and an increase in the dynamic friction coefficient, as well as a decrease in the wear rate.

The paper presents results of the tribotechnical and acoustic characteristics of copper-based frictional composite materials depending on the composite structure and content of metallic (tin, iron) and carbon (coke, graphite) additives in the composition. Changes in the studied characteristics are most pronounced under dry friction conditions. The introduction of the additives leads to reduced friction components of noise to 56 dB. In the boundary friction mode, the greatest effect of introduced target additives on the acoustic characteristics does not exceed 11 dB relative to the material without additives. For a composite based on 12% tin bronze, an increase in the graphite content from 10 to 30 vol % results in a 5 dB noise reduction.

This part of the paper devoted to the development of mechanism and machine mechanics in Belarus and cooperation with Bulgarian official and public organizations (see the first part of the paper). Successively the input in mechanism and machine terminology, standardization (elaboration of complex of standards on reliability, tribo-fatigue, gear failure modes etc.), quality management (system, techniques and tools, quality factors of machines and their components, methods of designing gear manufacturing processes etc.) are covered. It is considered informational support above mentioned topic through the edition of scientific journals; participation of Belorussian and Bulgarian scientist and engineers in international conferences, provided by one or other parties, as well as third one; interaction between scientific institutions.

The parameters of the boson peak (BP) and the first sharp diffraction peak (FSDP) in (As2S3)x(GeS2)1x glasses measured using high-resolution Raman spectroscopy and high-energy synchrotron X-ray diffraction measurements are examined as a function of x. It has been found that there is no correlation between the positions of BP and FSDP. The BP position shows a nonlinear composition behavior with a maximum at about x = 0.4, whereas the FSDP position changes virtually linearly with x. The intensities of both BP and FSDP show nonlinear composition dependences with the slope changes at x = 0.4, although there is no direct proportionality. Analysis of the partial structure factors for the glasses with x = 0.2, 0.4 and 0.6 obtained in another study has shown that the cation-cation atomic pairs of Ge–Ge, Ge–As and As–As make the largest contribution to FSDP, where the Ge–Ge and Ge–As pairs are dominant.

При создании акустических композитов особое внимание уделяют получению легких, высокопрочных, экологически безопасных, биоразлагаемых композитов; технологиям пористых волокнистых композитов и повышению их звукопоглощающей способности.Цель работыанализ исследований и коммерческих достижений в области создания акустических композитов и шумопонижающих конструкций на основе экологически безопасных компонент и нанонаполнителей.На основе проведенного обзора патентной и научно-технической информации показано, что традиционные пути и методы создания акустических материалов в значительной мере исчерпаны

БолгарияЦель работысоздание акустических композитов на основе полимерных связующих и природных наполнителей, сочетающих одновременно высокие характеристики звукопоглощения и звукоизоляции

The choice of objects of research for reducing vibration of parts and increasing the durability of machine designs and, consequently, the noise level in industrial premises is stated and justified. Methods for obtaining vibration-absorbing polymer compositions and samples for their testing under vibration conditions are described, as well as methods for studying viscoelastic properties, chemical structure, adhesive strength, microhardness, impact strength of polymer coatings and thermal conductivity of the obtained samples from compositions based on homopolymers filled with organomineral ingredients. The results of studies of the vibration-absorbing and adhesive-strength properties of polymer composite materials based on epoxy polymers and an organomineral filler - rubber powder are presented.

The choice of objects of research for reducing vibration of parts and increasing the durability of machine designs and, consequently, the noise level in industrial premises is stated and justified. Methods for obtaining vibration-absorbing polymer compositions and samples for their testing under vibration conditions are described, as well as methods for studying viscoelastic properties, chemical structure, adhesive strength, microhardness, impact strength of polymer coatings and thermal conductivity of the obtained samples from compositions based on homopolymers filled with organomineral ingredients. The results of studies of the vibration-absorbing and adhesive-strength properties of polymer composite materials based on epoxy polymers and an organomineral filler - rubber powder are presented.

The influence of surface roughness of a steel counterbody on friction (coefficients of static and dynamic friction) and wear parameters is investigated for friction composite materials that operate in a transmission oil medium. The wear rate of composites and the level of dynamic instability of tribological conjugations (chatter, vibration, and noise) are shown to exhibit a non-monotonic dependence on the roughness of a steel counterbody with a common local minimum, which is typical of various friction materials. A rapid diagnostic method of tribotechnical and NVH-testing of friction materials intended for operation in oil is proposed as well.

The given chapter presents a comparative analysis of the technologies presently employed for the repair, using reinforcing wraps/sleeves made of polymeric composite materials, of the areas with volumetric surface defects (also named local metal loss defects) of the transmission pipelines intended for hydrocarbons (petroleum, liquid petroleum products, natural gas, etc.) or other fluids. The above-mentioned technologies are also compared with other pipeline repair technologies (using metallic components and eventually requiring welding operations to be performed) in order to underline their advantages especially in the conditions in which it is preferable, due to the economic benefits, to perform the repair works on the in-service pipeline (without stopping the fluid supply). In addition, the technologies used to apply coating systems (containing polymeric composite materials) intended for the corrosion protection of the transmission pipelines or for the repair of such protection system are also compared and analysed.

In addition to the friction coefficient and the linear wear intensity of the frictional materials, the vibroacoustic characteristics are of importance, especially for the stationary friction units. Noise and vibration in the friction units lead to the problems connected with the technological operation of materials. This paper presents the results of studies of tribotechnical and vibroacoustic characteristics of highly filled friction composites depending on the content of iron oxide (Fe 2 O 3 ). Based on the results of tribotechnical tests and noise measurement generated by stationary friction, it is established that the optimum tribotechnical and vibroacoustic properties of friction composites are obtained within the range of low concentrations of iron oxide (0.6–1.2 wt %).

The development of new materials and composites with desired mechanical properties requires methods for evaluation of their elastic moduli. The direct measurements of the shear and longitudinal ultrasonic pulse are the simplest approach for solution of these tasks. Among the drawback of the traditional ultrasonic methods are narrow bandwidth and necessity of the relatively large volume of the material for testing. Laser excitation of ultrasound is based on optoacoustic conversion that induces bulk pulses of about tens nanosecond duration and can be applied for time-resolved measurements of velocities. The paper considers several experimental arrangements, which combine laser excitation of probe ultrasonic pulses and their detection for measuring the velocities of longitudinal and shear pulses. The features of detection in single crystal and polycrystalline nickel as well as steel specimens are discussed.

The given chapter presents a review of the materials, presently employed within the composite repair systems (based on reinforcing wraps/sleeves made of polymeric materials), and intended for the areas with volumetric surface defects (also named local metal loss defects) of the transmission pipelines for the transportation of hydrocarbons (petroleum, liquid petroleum products, natural gas, liquefied petroleum or natural gas) or other fluids (water, ammonia, etc.). The categories of materials investigated are polymeric fillers (used to fill the volumetric surface defects and to reconstruct the external configuration of the pipe before repairing it), fibre reinforced composites (the main component of the repair system ensuring its mechanical strength), adhesive materials (used to bind the successive layers of the reinforced composite wrap).