Problems of Tribology

Influence of the shape of abrasive soil particles on the regularities of destruction of structural steels during wear

V.I. Dvoruk — Sun, 22 Dec 2024 00:00:00 +0000

The article presents the results of studying the patterns of destruction and their influence on the wear resistance of structural steels: steel 45, steel 65G and steel 28MnB5 when moving in soils with different abrasive particle shape factors. The phenomenon of the presence of a critical abrasive particle shape factor (CPSF) was established, up to which the wear resistance of steels decreases. In the supercritical region, wear resistance is stabilized, and the differences between its values of the studied steels are significantly reduced. When forming wear resistance, the role of the particle shape factor is to regulate active deformation and fatigue phenomena by means of the level of external force action on the working surface and is realized through the rheological-fatigue parameter, which is controlled by the cyclic viscosity of steel deformation. In this regard, the choice of structural steel grade for the manufacture of machine parts intended for use in soils with different abrasive particle shape factors must be made based on its ranking by the rheological-fatigue parameter. It is shown that in the strength basis of the steel wear mechanism under sliding friction in soils with different particle shape factors, in addition to the resistance to the propagation of axial and radial fatigue cracks in the destructive deformation layer, an important role is played by the resistance to the initiation and propagation of lateral fatigue cracks at its boundary with the plastic-destructive deformation layer, and the mechanical component of the contact interaction is decisive. It is established that under wear in soils with different particle shape factors, the action of the softening process is more effective than the hardening process. In the supercritical region, the intensity of steel softening is significantly reduced due to the increase in the effectiveness of the hardening action due to the dispersion hardening of steel. However, no qualitative changes in the metal wear process are observed

Leakage and rotordynamic coefficients of labyrinth-scallop seals

V. Izemenko, A. Zahorulko, Yu. Zahorulko — Sun, 22 Dec 2024 00:00:00 +0000

Reducing leakages and improving the rotor-dynamic damping characteristics of annular seals is an essential problem of sealing technology. A whole range of damping seals are used to seal the shafts of turbomachines, such as honeycomb, hole pattern, pocket, and scallop seals. To reduce the cost and production time, the scallop seals are increasingly used. They showed quite good dynamic and leakage characteristics in the modernization of compressors in the chemical industry. Some designs of scallop seals are able not only to increase dynamic performance (additional use of swirl brakes in the form of semi-open scallops at the inlet) but also thanks to the hybrid design of the scallop and labyrinth seal made of PEEK material, which ensures a minimum clearance between the seal and the shaft, reduce leakages of pumped fluid.

This paper presents the results of calculating the rotordynamic and flow rate characteristics of scallop and labyrinth-scallop seals depending on the operating parameters using computational fluid dynamics (CFD) methods. The CFD was used to calculate the hydrodynamic and rotordynamic characteristics of the seal with shaft whirl. The rotordynamic coefficients were obtained using the frequency excitation method. The obtained characteristics were compared with experimental data available from the literature for annular and labyrinth seals. The study confirmed the relatively low leakages, the high dynamic characteristics of the labyrinth-scallop seals, and the frequency dependence of the stiffness and damping coefficients. It has been confirmed that sickle-shaped scallops create obstacles to the circumferential flow of the working medium. Reducing the circumferential gas flow increases the hydraulic resistance in the grooves and simultaneously minimizes the circulation forces that create shaft whirl, increasing vibration

Increasing the wear resistance of plunger pairs of high-pressure fuel pumps using extreme pressure additives

D.D. Marchenko, K.S. Matvyeyeva, V.M. Kurepin — Sun, 22 Dec 2024 00:00:00 +0000

The paper presents studies and substantiates extreme pressure additives that are in demand in almost all areas where heavy equipment and machines operate: in heavy industry, metallurgy and metalworking, machine tool manufacturing, aircraft and shipbuilding, automotive production, construction, and power engineering. At the same time, the development and use of this type of additives in energy facilities of the agro-industrial complex is very difficult due to their relative high cost, and the lack of a complete scientific study of the problem does not contribute to the widespread use of extreme pressure additives in agricultural tractor engines. Therefore, there was a need to conduct scientific research to assess the effect of extreme pressure additives on the performance of high-pressure fuel pumps and, based on the information obtained, to develop production recommendations. In the course of the research, a functional model of the plunger pair performance indicator was obtained, taking into account the performance properties of summer diesel fuel with extreme pressure additives. The results of experimental studies are presented, taking into account the performance properties of summer diesel fuel with extreme pressure additives. The results of production tests of plunger pairs of high-pressure fuel pumps using summer diesel fuel with an extreme pressure additive have been obtained. The use of summer diesel fuel with an extreme pressure additive allows increasing the service life of plunger pairs of high-pressure fuel pumps from 1230 to 2214 hours; recommendations for using fuel for 14 kN traction class engines have been developed. The friction coefficient decreases from 0.005 to 0.001 when plunger pairs operate on summer diesel fuel with an extreme pressure additive. The results have been obtained for selecting the component composition of the additive in diesel fuel and recommendations for using the extreme pressure additive in diesel fuel have been developed.

Wear resistance and lubricity of the spiral oil distribution profile of the valve guide sleeves of an internal combustion engine

O.V. Dykha, A.A. Vychavka, M.O. Dykha — Sun, 22 Dec 2024 00:00:00 +0000

Valve guides are crucial for maintaining the correct alignment, positioning, and clearance of the valve stem as it moves in the cylinder head. When the guides are heavily worn, the engine begins to consume oil and the valve mechanism becomes noisy. Reliable lubrication of the inner surface of the guide bushing ensures the wear resistance of the valve-guide pair. This work proposes a special tool and technology for obtaining an oil-retaining profile on the inner surface of the valve guide, which increases the oil capacity of the surface, and therefore improves the lubrication conditions in the valve-guide friction pair. A gas labyrinth seal is created in the connection, which prevents oil from entering the combustion chamber. The surface of the bushing bore is strengthened due to the sealing of the surface. The results of wear tests of guide bushings with spiral oil-retaining grooves confirmed their effectiveness in terms of wear resistance. The wear rate of the bushings with grooves for the entire time range of the tests is on average 20% less than the wear rate of the bushings without grooves

Dependence of wear intensity on the coating material of the hydraulic cylinder of the garbage truck’s sealing plate

O.V. Bereziuk, V.I. Savulyak, V.O. Kharzhevskyi, A.Ye. Alekseiev — Sun, 22 Dec 2024 00:00:00 +0000

The article is dedicated to the study of the influence of the coating material on the wear rate of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate. By means of a first-order planning of experiment with first-order interaction effects using the Box-Wilson method, an adequate dependence of the wear rate of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate on the coating material was determined. It is established that according to the Student’s criterion, among the studied factors of influence, the intensity of wear of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate is most affected by the iron content in the coating, the least – by the chromium content, and the nickel content affects only indirectly in interaction with the iron content. The response surfaces of the goal function – the intensity of wear of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate and their two-dimensional sections in the planes of the influence parameters are shown, which allow to clearly illustrate the specified dependence of this goal function on individual influence factors. The expediency of conducting further research to determine ways to further improve the wear resistance of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate is shown

Research on the wear resistance of the material cylinder of an automatic injection molding machine during plastics processing

V.A. Honchar — Sun, 22 Dec 2024 00:00:00 +0000

The article presents experimental studies of the pressure in the material cylinder of the D3328 automatic injection molding machine when processing various plastics, as well as experimental studies of wear along the length of the material cylinder of the DB3328 automatic injection molding machine after processing PS 68-30 fiberglass. Specially designed strain gauge pressure sensors were used. Signals from the sensors were output to an oscilloscope through the amplifying equipment and recorded on an oscillogram. The magnitude and distribution of pressure along the length of the material cylinder will significantly affect the amount of wear of both the screw and the cylinder. It was established that the pressure in the material cylinder of automatic injection molding machines is distributed unevenly along its length. The nature of the pressure distribution along the length of the material cylinder when processing various materials: during the injection period, the maximum pressure occurs in the melt zone with a subsequent sharp decrease in the middle zone and a slight increase in the loading zone. At the same time, the nature of the pressure change for all materials is similar at a diametrical gap between the screw and the cylinder δ=0.17 mm. With an increase in the gap δ to 0.74 mm, the nature of the pressure distribution in the injection zone changes only when processing fiberglass, which is due to the partial ingress of glass fibers into the gap between the screw and the cylinder. Its magnitude and nature of the distribution along the length for different materials are different and depend on the physical, mechanical and rheological characteristics of these materials, the design of the screw and the technological modes of processing. The maximum pressure occurs in the melt zone during the period of material injection into the mold for 0.4-0.5 s.

Modeling of contact stresses and evaluation of wear life of a valve mechanism guide with lubricating grooves

K.E. Holenko, A.A. Vychavka, M.O. Dykha, V.O. Dytyniuk — Sun, 22 Dec 2024 00:00:00 +0000

Valve guides are crucial for maintaining proper alignment, positioning, and valve stem clearance as it moves in the cylinder head. Valve bushings are subjected to load and sliding friction; with excessive wear of the guides, the engine begins to consume oil and the valve mechanism becomes noisy. This paper proposes the use of a special knurling to restore and increase the wear resistance of guide bushings. The profile tool is designed to restore valve guides by rolling a spiral groove on the inner surface of the sleeve. After applying this technology, a spiral oil-retaining profile remains on the surface of the sleeve bore. . Using the Solid model, the effect of changing the geometry of the guide bore by the lubricating grooves on the maximum and average stress indices in the guide-valve contact was analyzed. It was found that the maximum stresses of the model with grooves are lower than those of the model with a smooth guide surface. Based on the finite element model, the durability of the valve-guide pair with oil-retaining grooves was analyzed and it was determined how many cycles the contact surface of the guide can withstand. It was established that by reducing the contact pressure, the actual resource of the guide with grooves increased.

Cavitation-erosion resistance of eutectic coatings in sodium chloride solution

M. Pashechko, V. Holubets, J. Zubrzycki, O. Tisov — Sun, 22 Dec 2024 00:00:00 +0000

The paper presents original research results related to the resistance of proprietary eutectic coatings applied to C45 structural steel to cavitation-erosion wear. This type of wear is encountered in devices operating in the chemical, petrochemical, heat and power industry and other industries. The research was conducted on a unique measuring stand developed by the authors. The research was conducted in a highly corrosive environment, i.e. sodium chloride solution. As a result of the research work, curves of the change in the electrode potential of C45 steel with different surface conditions and its polarization curves were obtained. Thanks to these curves, it was possible to determine the optimal method of protecting the tested steel against cavitation-erosion wear