Problems of Tribology

Analysis of the directions of improving regular micro reliefs

2024-09-14T20:50:53+00:00

The article analyzes the features of planar regular microreliefs with the shape of grooves, the axis of which lies in a plane that is parallel or coincident with the surface on which the microrelief is formed and can be described by a periodic function. It was established that the main parameter that determines the operational properties of a surface with regular microreliefs is the relative area of the microrelief. The hypothesis is put forward that the geometric shape of the grooves of the microrelief practically does not affect the operational properties of the surface. Microreliefs of groove axes that a periodic function can describe are technologically imperfect because when forming the tops of microrelief grooves, the tool must make stops to change the trajectory of movement. The complex geometry of microrelief grooves reduces the productivity of their formation, and the complexity of ensuring regularity ensures the surface's heterogeneous physical and mechanical properties. Directions for improving the forms of microreliefs are proposed, which will ensure an increase in the productivity of their formation and provide an opportunity to control the operational properties of the surface

Self-organization of the tribosystem under non-stationary conditions of friction from the standpoint of deformation-wave representations

2024-09-14T21:19:02+00:00

Mechanisms of structural adaptation of contact surfaces and lubricating materials during friction with the dominance of deformation processes in tribocontact have been analyzed. The purpose of the work was to model the elastic-plastic properties of dissipative structures taking into account the anisotropic properties of the surface layers of the friction pairs and the boundary layers of the lubricating material. The modeling took into account the structural state of the latter formed due to heating and saturation with wear products, along with the physical and mechanical interaction of this layer with the outer surface of the part. An algorithm for determining the distributed tangent force along the length of the boundary layer of the lubricating material adjacent to the part has been developed based on the hypothesis of the wave-like state of the surface layer of the lubricating material on an absolutely flat (non-deformed) rough surface. Herein, under the action of tangent forces, the strip of lubricant is subject to horizontal compression and transverse movement. The distributed tangent stress along the length of the adjacency of the layer of densified lubricant to the part causes micro-slipping of the layer. Amplitude horizontal displacements of the boundary of the lubricant layer are determined when the beam-film is loaded with longitudinal stresses, which leads to partial disorientation of the film and loss of its originally rectilinear structured form, the transition of the lubricant layer to the state of the wave surface of a sinusoid shape. Also, a procedure for calculation of tangent forces causing the loss of elastic stability of the lubricant boundary layers resulting in the direct mechanical destruction of the lubricant boundary layer in the slipping zone of the contact surface is proposed based on the elastic-frictional interaction of this layer with the near-surface layer of the metal

Dependence of wear of friction pairs of the mechanism for loading solid household waste into a garbage truck on the characteristics of antifriction materials

2024-09-15T16:58:37+00:00

The article is dedicated to the establishment a regression dependence of wear of friction units of the mechanism of loading a garbage truck on the properties of antifriction materials. By using a first-order planning of experiment with first-order interaction effects using the Box-Wilson method, an appropriate regularity of wear of friction units of the garbage truck loading mechanism on the properties of antifriction materials has been determined. It is established that, according to the Student's criterion, among the studied factors of influence, the wear of friction units of the garbage truck loading mechanism is most influenced by the pressure in the friction zone, and the least – by the Brinell hardness of the antifriction material. The response surfaces of the objective function – wear of friction units of the garbage truck loading mechanism and their two-dimensional cross-sections in the planes of the influence parameters are shown, which allow to clearly illustrate the specified dependence of this objective function on individual influence parameters. It has been established that an increase in the pressure in the friction zone and sliding speed by 60% leads to an increase in the wear of friction units of the garbage truck loading mechanism during reverse motion by 6.3...34%, depending on the properties of antifriction materials. The expediency of conducting further research to determine ways to further improve the wear resistance of friction units of the mechanism for loading solid household waste into a garbage truck has been shown.

Improving the technology for restoring worn parts based on cold plastic deformation

2024-09-16T17:09:15+00:00

Technological control scheme for forming worn parts during their restoration by deforming broaching is proposed. Particular attention is paid to the study of the stress-strain state, which provided the conditions for creating the necessary plastic flow of the product material towards the worn areas and made it possible to compensate the wear amount in these areas of the product and provide an allowance for subsequent machining. Taking into account the peculiarities of parts restoration technological process, the relationship between the required circumferential strain of the outer surface and the total tension on the hole is established. The influence of the number of deforming elements that perform the required deformation on the accumulated strain on the inner surface of the part was investigated. This made it possible to establish that the maximum accumulated strain of the inner surface is provided by the maximum number of elements with a minimum tension on the element. On the outer surface, the value of the accumulated strain does not depend on the number of deforming elements, but is determined only by the total tension and the workpiece thickness. Based on the simulation of deforming broaching in a wide range of changes in operating parameters, tool geometry and workpiece thickness, an analytical dependence was obtained to determine the angle that ensures the absence of axial strains when the workpiece is deformed. The necessary broaching modes and tool geometry were determined, which will ensure the required dimensions of the machined or restored part.

Finite-element analysis of contact characteristics and friction modes of the "valve-guide" of the internal combustion engine

2024-09-17T05:48:05+00:00

Modeling the performance of the "valve-guide" engine pair using modern software is an effective tool both for identifying weak points in the design and for predicting the behavior of the friction unit in operation. In this study, the method of finite element analysis was chosen as a tool to study the contact and antifriction parameters of the friction pair of the internal combustion engine "directional valve". Using the FEM application program, the raw data on the material, surface dimensions, loads, and motion kinematics are described. Based on the constructed finite-element model of the "valve-guide" conjugation, an analysis of the influence of determining tribological factors: sliding speed in contact, temperature, skew angle, friction coefficient on contact stresses both for each part of the friction pair and in the process of contact interaction was carried out. A consolidated matrix of the results of the numerical experiment was built, and the conclusions regarding the influence of each factor on the tribological characteristics were substantiated. Algorithms of influence on the design, technological and operational factors for prolonging the resource of the friction pair of the internal combustion engine "valve-guide" are outlined

Adhesive built-up edge on tool steels due to friction and wear

2024-09-19T20:39:55+00:00

When processing metals by cutting, there are a number of materials prone to growth. This phenomenon leads to a change in the geometry of the cutter, cutting forces and surface quality, final dimensions of the part. In friction nodes: shaft-sleeve, piston-sleeve, etc. this phenomenon causes jamming. In this work, experimental studies of the processes of dry friction of tool steels with coatings were carried out to evaluate the effectiveness of reducing the growth process. As a result, it was established that the nature of formation, destruction and size of growth of materials prone to growth depends on the chemical composition of the material and modes of friction. High-strength chromium-manganese steels are most prone to growth and microseizures. It is shown that the well-known recommendation of increasing speed cannot always be used to prevent build-up, but it can be achieved by using single-layer and multi-layer coatings with a defect-free structure and moderate friction modes. It was found that electrolytic single-layer nickel and chromium coatings contribute to the formation of growth on the studied materials and this phenomenon does not depend on the modes of friction, while the same chemical coatings, which have an almost defect-free structure, are almost not prone to growth formation.

The effect of manganese and carbon on the mechanical properties of the welded layer of the bucket teeth of the Hadfield steel excavator

2024-09-20T16:03:09+00:00

The paper investigates the effect of the surfacing composition’s chemical structure (the manganese and carbon concentrations’ ratio) on the mechanical properties of the surfacing layer on Hadfield steel for increasing the durability of the products made from it, namely the excavator bucket’s teeth. Two criteria, namely the impact toughness and wear resistance of the coating, were chosen as optimization parameters. The assessment of the impact strength of the deposited coating was carried out on the Sharpie samples on the pendulum copra, and the wear test was carried out according to the Brinly-Haworth scheme in the conditions of samples’ abrasion with quartz sand. Wear resistance of Hadfield steel, containing 1.1% C and 13% Mn, was taken as a unit of wear resistance in these experiments. To determine the optimal coating modes, the active experiment with the application of mathematical planning methods was conducted. The obtained response surfaces and graphs of equal output lines make it possible to establish the level of studied factors’ influence on the optimization parameter. In order to analyze the influence of given factors on the optimization criteria, scatter plots with histograms were constructed, which make it possible to determine the rational values of the selected optimization criteria graphically - impact toughness and wear resistance of the coating

The patterns of changes in the degree of lubrication of the crankshaft bearings of car engines depending on the parameters of the load-speed modes of operation

2024-09-24T03:59:57+00:00

The practice of operating machines and mechanisms indicates that bearing wear is one of the main reasons for limiting their durability. This especially applies to the sliding bearings of crankshafts of car engines, where the intensity of wear of their working surfaces significantly depends on the properties of the lubricant. An experimental study of the wear resistance of the sliding bearings of the crankshafts of car engines was carried out on the KI-5543 model break-in and braking stand. In experimental studies, BELZONA Super E-Metal insulating material was used to provide electrical isolation of the main and connecting rod bearings of the crankshaft from the cylinder block of the car engine. The experimental dependencies of the values of the criteria characterizing the degree of lubrication of the friction surfaces on the parameters of the load-speed modes (the moment of the applied force and the frequency of rotation of the crankshaft) were obtained. The ranges of values of the investigated parameters, in which the effective operation of the sliding bearings of the crankshaft of car engines is implemented, have been revealed.

Tribotechnical processes of the soil environment interaction with the working bodies of soil tillage and earthmoving machines reinforced with composite materials

2024-09-24T20:49:57+00:00

The work presents the study results of the stress-strain state of the soil, as a continuous medium filled with abrasive particles under the action of the working bodies of soil tillage and earthmoving machines. One of the main properties of the soil, which determines the specifics of the force interaction of the working surfaces of the working bodies of soil tillage and earthmoving machines with the technological environment, is taken into account, namely the tendency of the contact layer of the treated layer to compaction.

The relationship between stress in the soil and the wear of the working bodies of soil tillage and earthmoving machines has been established experimentally. A theoretical analysis is presented for the stress-strain state of the local region of the strengthened surface layer that is used in the working bodies of soil tillage and earthmoving machines, in which the filler, inclusion or strengthening phase is placed.

An analysis of the contact characteristics of the stress-strain state and their changes during friction and wear was carried out based on the formulation and solution of the contact interaction problems of abrasive soil particles with the inhomogeneities of the composite coatings components based on ultra-high molecular weight polyethylene with fillers during strengthening of the working bodies of soil tillage and earthmoving machines.

Computer modeling was performed to study the nature of stress distribution in the reinforced surface layer of the working bodies of soil tillage and earthmoving machines in the area of the contact zone in stationary and dynamic conditions. The contact problem is formulated, the boundary conditions and the solution in the form of components of the stress field are given. The characteristics of the filler, their content in the composite material and coating are taken into account, the relationship between the stress-strain state and wear is established.