No 11 (2024)
Materials science in mechanical engineering
METHODOLOGICAL FOUNDATIONS OF THE MATERIALS SCIENCE ASSESSMENT OF THE QUALITY OF LUBRICANTS FOR LOADED INTEGRATIONS OF MACHINES AND MECHANISMS. MESSAGE 1. THE INFLUENCE OF THE MEDIUM ON THE STRESS-STRAIN STATE AND STRUCTURAL CHANGES IN THE ZONE OF CONTACT DEFORMATION OF METALS DURING FRICTION
Abstract
The experimental and theoretical foundations of the material science approach to the assessment of lubricants are described. This approach is based on the analysis of the complex of structurally sensitive properties of antifriction material in the tribodeformation zone and aimed at identifying the significant role in the process of interaction of lubricants with the friction surface. The rheological properties of the surface layer formed in the tribo material under conditions of contact deformation and by the action of a lubricating medium determine the conditions for the formation of a wear-resistant structure. The concepts of the physical-chemical bases of the action of the medium in relation to the problems of elasticity and sliding contact are formulated, describing the behavior of surface-modified materials in the simplest stress-strain states. It is shown that when a surface-hardened material, the residual stresses within external layer are in agreement with the loading stresses, while in the inner volume zone they are opposite to them. The distribution of residual stresses in a surface-hardened sample turns out to be the reverse of the case of a plasticized material. The distribution of residual stresses in a surface-hardened sample turns out to be the reverse of the case of a plasticized material. Schematic diagrams of residual stresses arising in the near-surface formation of the material as a result of its elastic-plastic deformation during tribocontact action in a surface-plasticizing and surface-hardening lubricating medium, are presented. It is shown that in the surface-plasticized near-surface formation, residual stresses are compressive in nature, and in the surface-hardened layer they are tensile. There is a sharp change in the direction of residual stresses between layers at their boundary. The stress distribution over the depth of the material is qualitatively similar to the corresponding schematic diagrams obtained for cases of torsion and bending. Based on the calculation of the diagrams of the components of the residual stress tensor arising in the surface layer of the antifriction material during sliding friction, the conditions for the implementation of the plasticizing and strengthening triboeffect, are shown. It is also shown that among industrial aluminum bronzes, BrA5, BrA7 have the highest wear resistance in surfactants.
Science intensive technologies in mechanical engineering. 2024;(11):3-17
3-17
THE EFFECT OF NANO-CUO AND 2-MERCAPTOBENZTHIAZOLE ON THE MECHANICAL PROPERTIES AND STRUCTURE OF ULTRAHIGH WEIGHT MOLECULAR POLYETHYLENE
Abstract
Currently, the development of polymer composite materials based on ultrahigh molecular weight polyethylene (UHMWPE) is one of the urgent tasks of polymer materials science. This is primarily due to its special mechanical and tribological properties, owing to which UHMWPE is actively being implemented in various industries such as machine building, coating and medicine. However, in order to expand the scope of application, it is necessary to eliminate the disadvantages in the form of low surface hardness and strength. The most effective and economically feasible way to reduce disadvantages is to modify the polymer by introducing various types of fillers. In this paper, the effect of complex fillers including nano-CuO and 2-mercaptobenzthiazole on the physico-mechanical properties and structure of ultrahigh molecular weight polyethylene is analyzed. It is shown that the introduction of complex fillers into UHMWPE increases the deformation and strength properties, the compressive stress increased by 23…35% and the Shore D hardness by 5…6 % compared to the initial polymer. The developed composite materials were characterized using X-ray diffraction analysis, differential scanning calorimetry and scanning electron microscopy. A connection between the decrease in the degree of crystallinity of UHMWPE-based composites with an increase in the content of complex fillers was found. The formation of spherulites in the supramolecular structure of composites has been shown by electron microscopy. Based on the conducted research, it is concluded that the improvement of the physical and mechanical properties of composites is triggered by complex effect of fillers due to the improvement of their co. The developed polymer composite materials can be used as protective coatings and linings in engineering and technological equipment.
Science intensive technologies in mechanical engineering. 2024;(11):14-23
14-23
Surface layer quality, contact interaction, friction and wear of machine parts
METHODS FOR IMPROVING STRESS-STRAIN PROPERTIES AND TRIBOLOGICAL CHARACTERISTICS OF HEAVILY LOADED METAL AND POLYMER TRIBOSYSTEMS
Abstract
An approach for transformation of destructive friction force to creative one in metal polymer friction units including a wide class of friction and antifriction tribomaterials, as well as lubricants, is presented in the article. For metal tribosystems, the research of nitride, diamond-like (DLC), high-energy coatings (HEC) is presented as creative possibilities. The main modern coating methods are viewed: vacuum arc deposition method of coatings, magnetron spraying method, ion vapor deposition of carbon coatings of the DLC class. The features of high-entropy coatings (HPC) and coatings with form memory effect (FME) are discussed. The main advantages and disadvantages of these methods are described, as well as modern types of coatings obtained by the PVD method are presented. Materials and research methods are given, including deposition of coating by BRV600 installation, investigation of physical and mechanical properties, tribological tests. To obtain high indicators of physical and mechanical properties and tribological characteristics, the following parameters were determined: for nitride coatings CrAlSiN - the optimal thickness, for carbon coatings of the DLC class and combined coatings CrAlSiN + DLC – the optimal coating thickness and technological modes of coating deposition - the amount of nitrogen supply %N and the current of induction coils λ, for high-energy coatings TiCrZrHfNb is the coating thickness, and for CuCrMnFeCoNi the effect of copper on the friction ratio and wear resistance. To obtain high indicators of physical and mechanical properties and tribological characteristics, the following parameters were determined: for nitride coatings CrAlSiN – the optimal thickness, for carbon coatings of the DLC class and combined coatings CrAlSiN + DLC – the optimal coating thickness and technological modes of coating deposition – the amount of nitrogen supply %N and the current of induction coils λ, for high-energy coatings TiCrZrHfNb is the coating thickness, and for CuCrMnFeCoNi the effect of copper on the friction ratio and wear resistance. The obtained coatings have found their application in heavily loaded tribosystems: the blades of the turbocharger of the 2TE25A diesel locomotive and the spline connection of the transmission of the steering rotor of the MI-26 helicopter. High-entropy coatings are proposed for dampers that are installed in the attachment points of the engine to the pylon or the pylon to the wing of the long-haul aircraft.
Science intensive technologies in mechanical engineering. 2024;(11):24-31
24-31
Technologies of electromachining and combined processing
RESEARCH INTO THE POSSIBILITIES FOR THE IMPROVEMENT OF A NUMBER OF OPERATIONAL PROPERTIES USING WAVE STRAIN HARDENING
Abstract
The paper states the need to identify a processing method through which increased operational properties in the work material can be obtained within a single process step. To solve the raised problem, the use of wave strain hardening (WSH) technology is proposed. The peculiarity of the technology lies in the possibility of simultaneous control of a number of technological parameters and the effect on the processed material of prolonged shock pulses characterized by the transfer of impact energy to the deformation site of more than 65%. Due to the presence of a large number of controlled process variables, the WSH allows fine adjusting of the uniformity of hardening and forming hardened areas at a depth of up to 15 mm. Due to the fine adjustment of the uniformity of hardening it becomes possible to avoid the formation of excessive cold work hardening of the surface layer and it makes great difference between WSH and other dynamic methods of surface plastic deformation, for example, stamping. With uneven hardening of WSH, solid and viscous regions take regular turns in the surface layer, forming a heterogeneous structure. The analysis of literature sources has shown that the presence of such areas in the surface layer makes it promising for purposes of operational properties improvement. The paper presents the results of experimental studies of the effect of the heterogeneous structure created by WSH on the operational properties: resistance to contact staining; cyclic strength under alternating loads, corrosion resistance. Laboratory studies of operational properties were carried out both using production equipment and specially designed facilities. The results obtained indicate the prospects of using WSH for operational properties increase and the existence of a "universal" operation mode.
Science intensive technologies in mechanical engineering. 2024;(11):32-40
32-40
Technologies of mechanical processing of workpieces
EFFECTIVE WAYS OF SHARPENING METAL-CUTTING TOOLS MADE OF RAPID STEEL AND HARD ALLOYS
Abstract
The problems of increasing the efficiency of the sharpening operation of metal-cutting tools made of rapid steel and sintered-hard alloys are viewed. Cutters with sintered-hard alloy plates, as well as high-speed steel drills, have been on the tapis as metal-cutting tools. The paper examines various methods of sharpening metal-cutting tools for increasing their durability, as well as stable durability maintaining after regrinding. The influence of various sharpening methods on various merit rates, such as surface roughness, microhardness and the amount of transcrystalline stresses in the material, has been studied as well. Research for the durability period determination in turning carbide plates were carried out under turning process of stepless rollers made of chromium-nickel alloy, and drills made of rapid steel, when drilling holes in boiler steel. According to the research results, it can be seen that these methods can significantly increase the durability period of the sharpened tools. Research for the durability period determination in turning carbide plates were carried out under turning process of stepless rollers made of chromium-nickel alloy, and drills made of rapid steel, when drilling holes in boiler steel. According to the research results, it can be seen that these methods can significantly increase the durability period of the sharpened tools. The results showed that these combined methods can increase the durability of tools by another 15…20 %. Thus, taking into account the results of the performed studies using high-tech methods for sharpening metal-cutting tools made of rapid steel and sintered-hard alloys, it can be concluded that the sharpening method is highly effective, being based on the use of grinding abrasive wheel, which is chromium-impregnated and while supplying of an iodine-containing liquid coolant to the work zone. It was found that when using this sharpening method, a higher resistance index is achieved in two-component carbide plates of turning cutters, if comparing to single-component carbide plates.
Science intensive technologies in mechanical engineering. 2024;(11):44-48
44-48