No 10 (160) (2024)
Additive technologies and laser processing
THE EFFECT OF DIRECT LASER GROWTH PATTERNS ON THE STRUCTURE AND PROPERTIES OF TITANIUM ALLOY VT6
Abstract
The problem of using and developing repair technologies in gas turbine engineering is relevant due to the constantly growing volume of production and the development of gas turbine engines. The manufacturing process of the fan wheel includes stamping followed by machining. The restoration of the fan wheel blades is a promising technology, owing to the high cost of blades in production, as well as the high risk of damage and failure. The most promising repair technology in the aviation engine industry is direct laser growth. The use of low-cost technology for repairing parts by laser clad with the suitable property package compatible with traditional methods of parts production is a priority task. The article presents a comprehensive study of scanning strategies obtained by direct laser growth with coaxial powder feeding on a support plate made of titanium alloy VT6. It is shown that the scanning strategy significantly affects the structure of the pad. The structure affects the mechanical properties. Heat accumulates with an increase in the number of layers. The material warms up and stays at this level for a long time, which can be compared to heat treatment. There is a gradual change in the microstructure from a nonequilibrium one with a different ratio α/α’ to an equilibrium one with a phase composition α + β. All samples are characterized by the formation of elongated columnar grains of the primary β-phase.Multiple thermal cycles lead to the enlargement of the initial β-grain.The data for study in this work is the titanium alloy VT6, which is widely used in the aviation industry.
Science intensive technologies in mechanical engineering. 2024;(10 (160)):3-11
3-11
Technologies of mechanical processing of workpieces
REVISITING TECHNOLOGICAL PARAMETERS DETERMINATION OF COMPLEX SCULPTURED SURFACING FOR GTE BLADES UNDER SMOOTH FINISH
Abstract
Smooth finish is the final stage of finish-machining of a gas turbine engine blades. The blades are characterized by a complex spatial outline of a feather, which has strict requirements for surface roughness. Deviation of geometric shapes, sizes and quality parameters of the blade feather airfoil from the calculated ones worsens the engine's performance characteristics, leads to the loss of power, reduces efficiency and engine reliability, especially under the influence of variable loads caused by changes in operating mode, such as takeoff, landing and etc. As a result, it assumes importance of determining exact technological parameters, such as the clamping force when finishing, in order to achieve minimal deviations in the finish-machining. The results of an experimental study of the change in the contact spot under smooth finish of a simplified model of a GTE blade, depending on the magnitude of the clamping force and the material of the polishing instrument, are presented. The routine of the experiment, the equipment and instrumentation used within the study, as well as the technological modes are described in detail. Theoretical information is provided on the machining pattern and the theoretical value of the contact spot for the forces under consideration using circular discs made of various materials. The results of an experimental study are presented, the relationship between the change in the clamping force and the width of the contact spot is found, and a nomogram of the relationship between the theoretical and experimental values of the half-width of the contact spot under smooth finish is constructed, confirming the possibility of using the Hertz contact problem in determining the contact spot of the polishing wheel. The reference is provided for the application of the obtained data in the design of the technological process of finishing complex sculptured surfaces of the blades of the GTE due to the application of theoretical and experimental methods for calculating the contact spot. The proposed approaches can be used in production to improve the quality and durability of the parts of gas turbine engine blades.
Science intensive technologies in mechanical engineering. 2024;(10 (160)):12-18
12-18
MODELING OF HEAT TRANSFER OPERATION WITHIN THERMAL FRICTION CUTTING FOR CONSTRUCTIONAL STEEL WORKPIECES
Abstract
The influence of anisotropic properties of structural steels on the change in thermal conductivity in various areas of the contact zone under thermal friction cutting is viewed. Obtained mathematical models afford to construct vector equations of thermal conductivity for a medium with different properties in various directions. The developed mathematical dependences made it possible to obtain a model of a scalar temperature field, the results of calculating the temperature field along the workpiece plate are given, taking into account the anisotropy of the thermal properties of the work material. The solution of the equations made it possible to construct temperature fields in a system of relative and physical coordinate systems. The measurement results of the isotherms coincide with the experimental data, so it can be concluded on their interrelationship. As a result of the performed studies, it was proved that in an anisotropic medium, the directions and orientation order of heat flows change towards colder zones of the workpiece and tool due to the difference in the heat transfer coefficients for cold and heated materials. The above process helps to equalize the temperature in the contact area of the tool and the workpiece.
Science intensive technologies in mechanical engineering. 2024;(10 (160)):19-26
19-26
Technologies of electromachining and combined processing
OBTAINING FIXED JOINTS USING ULTRASONIC VIBRATIONS
Abstract
Obtaining fixed joints is one of the most demanding and time-consuming stages of assembling machine-building products. The quality of all-in-one connections determines the reliability of the machine as a whole. This determines the relevance of research aimed at improving the quality of non-removable compounds and at the intensification of their production processes. An effective way to solve this issue is the use of ultrasonic vibrations. The imposition of vibrations on the welded elements leads to a change in the crystallization parameters, grinds the microstructure of the weld, reduces welding deformations and increases the strength of the joint. Deformation of the rivet with an ultrasonic tool takes place when the required force is reduced by more than 10 times and ensures uniform distribution of radial stresses, making shear strength better this way. Ultrasonic treatment of the binding material within the process of its production and oscillation superposition on the adherend parts reduce the viscosity of the adhesive, increase wettability and filling capacity, resulting in shear strength hardening in the adhesive joint. The transmittal of ultrasonic vibrations of the pressed part decreases friction due to its transformation into a quasi-viscous one, which takes down the required pressing force and reduces damage probability for mating surfaces. Ultrasonic cavity-abrasive treatment of complex metal products obtained by additive manufacturing methods makes it possible to reduce roughness in hard-to-reach areas and surface elements, which is not possible by other methods. For each fixed joint type under examination, technical plans are proposed, including both standard operations and additional ones using ultrasonic vibrations, which makes properties improvement for the obtained fixed joints possible.
Science intensive technologies in mechanical engineering. 2024;(10 (160)):27-37
27-37
Technological support of operational properties of machine parts and their connections
TECHNOLOGICAL QUALITY ASSURANCE OF THE SURFACE LAYER AND OPERATIONAL PROPERTIES OF MACHINE PARTS THROUGH EDM PROCESS
Abstract
The problem of technological quality assurance and operational properties of the surface layer of machine parts through EDM process is viewed. Based on physics of EDM process, theoretical and experimental dependences for determining the parameters of the surface layer quality and the operational properties of machine parts on the modes (voltage, current and pulse duration) for various conditions (properties of dielectric fluid, physical and mechanical properties of the tool material and physical and mechanical properties of the workpiece material) of EDM process, are found. Studying these dependencies, it was also found that the formation of surface layer quality parameters and the service characteristics of machine parts are mainly influenced by modes under various conditions of EDM process. It was deemed that the formation of undulation and macro-deviations of the surface, in addition to the modes for various conditions of EDMing, is also influenced by the initial undulation and macro-deviations of both the workpiece and the tool, depending on the machining pattern. As a result, the relationship between quality parameters of the surface layer and the operational properties of machine parts depending on the modes of EDM process was found, the possibilities of EDMing of the quality parameters assurance for the surface layer and the operational properties of machine parts were determined. Obtained results allow us to determine the modes for various conditions of EDM process from scientific point of view. Either the required quality parameters of the surface layer or the required operational properties of machine parts determine different modes for various conditins of EDMing.. This will make the implementation of a single-stage approach in ensuring the required operational properties of machine parts by EDM process possible.
Science intensive technologies in mechanical engineering. 2024;(10 (160)):38-48
38-48