№ 6 (144) (2023)

Achievements of cutting materials science in Russia and abroad have been emphasized. Tooling operation specifics using a spherical milling cutter is characterized by slice thick-ness of work material burst layers located in close proximity of the axis and the cutting speed, which tends to zero. A scheme that al-lows calculating the value of the axial cutting force as an integral of the cutter bit angularity relative to the axis of the cutter from the point of origin of the burst layer to its end, is pro-posed. The calculation of the variable part of a certain integral, without taking into account the constant cutting force, was performed using the Mathcad mathematical package. To determine the ratio of the cutting force normal component to the main characteristic, the results of the work, where a special control experiment was carried out to determine the specified components of the cutting force when the burst layer thickness was changed from zero to the beginning of the stable chip separation process, were analyzed. It is found that at the beginning of the chip separation process, the main component of the cutting force rises exponentially (by 2,5 times), and the normal one does not spike.

The efficiency of the application of a new technology for fir-tree slots treatment in turbine discs based on a combination of pre-slotting operations of the «house» by hydro-abrasive treatment (HAT) and final broaching of the herringbone on a CNC machine in comparison with milling, deep grinding and EDM-ing methods is viewed. Problems arising within manufacturing and operating of broaches often cause down-time of both types: main and tool production. At the same time, the set high growth rates of production of gas turbine engines are inevitably restrained, the costs of manufacturing sets of multi-section fir-tree broaches are significantly increasing. To solve the problem, various combined processing techniques are proposed for the application, i.e., the pre-slotting of the «house» of broaches is carried out by various productive cutting methods such as deep grinding, milling, EDM-ing and HAT, while finishing is carried out using finishing profile broaching tech-nique. The pre-liminary calculations of labor intensity and production costs carried out during comparative tests of various combined variants of pre-slotting have proved the advantages of HAT cutting. As a result of the experimental studies, conducted on slotting, using HAT technique with subsequent broaching under final form broach, it was found that channel profile of the preliminary slot with allowances, made for measured profile devi-ation, is in the tolerable limit before final shape of the final broaching, which bears evidence of the slot appropriateness made by HAT method and its readiness for final broaching. After herringbone final broaching an electronic control was conducted and it was found that all the main dimensions in the herringbones are within tolerance limits and are suitable according to technic specifications. It is proposed to carry out further experimental work on particular stock-produced tur-bine disks for making a decision on the introduction of a new technology into mass production.

According to the level of the measurement scale, the friction force changes its nature and is determined by different depend-encies. The paper views a procedure for determining a friction force molecular component based on the evaluation of specif-ic shearing resistance of molecular links un-der the elastic interaction of a silicon nitride cantilever needle having a steel sample, used for scanning a section of a sample surface in the nanometer range with an atomic force microscope (AFM) «FemtoScan» under low loads. A sensitive element (measuring device) of an atomic force microscope acts as a force sensor for measuring both: a normal load very roughly, and a change in the force, applied to the cantilever under known stiffness, including the value of the cantilever rod form alteration. It also changes the load on the sensitive element (to assess the mo-lecular component of the friction force, the route of the «smoothest» surface itself was chosen). The paper also provides an analytical assessment of the contact interaction parameters of a cantilever needle in a nano-scale, rep-resented as a spheri-cal indenter, with an elastic half-space as a surface under study, based on the Hertz theory. Analysis of the calculation and experiment data on measuring the resistance force of the indenter during scanning of the surface under study, showed good convergence of the results with a deviation of even values from the experimental data of no more than 7,5 %. Calculations using the established formulas showed that with an increase in the load on the contact at the nanoscale, the coefficient of friction decreases due to a faster growth of contact spots in the elastic state (provided that angularity of inequalities related to sub-roughness remains constant), which was also confirmed in the course of the experiment.

The research results presented in this article are devoted to the study of the vibration treatment effect on the surface layer of flat samples made of titanium alloy VT-6 obtained using selective laser melting (SLM) technology. Titanium alloys are the materials, used in various fields of industry due to their unique properties, namely high strength and lightness. However, when treating such materials, there is a number of problems connected with the high hardness and complexity of post-processing products after their growing. Post-processing operations require automation for driving down various types of costs. Vibration treatment is one of the possible solutions to this problem. Within studies a sample roughness was measured and the material removal rate was calculated based on the vibration treatment criteria. The results showed that rough grind-ing of flat surfaces into vibrofinishing equipment is an effective method for achieving the required surface parameters when treating products made of titanium alloys obtained by the SLM method. This can result in improved finish, increased produc-tivity and costs saving. The analysis of the results makes it possible to give recommendations for rough grinding of surfaces made of titanium alloys. The process must be carried out in two stages: 1) to have maximum material removal from the sur-face 2) to improve the roughness. Thus, the results of the study can be helpful for various industrial sectors where titanium alloys are used, also contributing to the further development of technologies for products treatment made from difficult-to-machine materials and obtained by using SLM technology.