No 3 (2024)
Technologies of electromachining and combined processing
MODELING OF SHARP EDGE SMOOTHING OF TURBINE BLADES ANGULAR FANS BY THE METHOD OF ED MILLING OPERATION ON MULTI-AXIS CNC MACHINES
Abstract
The article views efficiency improving issues, quality and accuracy of sharp edge smoothing for numerous angular fans in the turbine blades of gas turbine engines made of heat-resistant nickel alloys and used in modern growing passenger aviation transport based on the development of ED milling new technology for modern multi-axis CNC machines with a rotating hollow electrode and a high-pressure fluidsupply of a special flush through the electrode body. An automated process for sharp edge machining has been developed for the production of more than 200 differently placed angular fans with a diameter of 0,45…0,6 mm in one blade instead of labor-intensive manual benchwork, where various needles, abrasive and metal rotary files are used. It is found that modeling and the development of special software resulted in a uniform radius of smoothing with high accuracy due to automatic ED milling operation along the entire trailing edge of each angular hole in the turbine blades at a multi-axis machining electro discharge center. The use of a rounded edge of the outlet ports provides more efficient cooling of the turbine blades and higher performance of gas turbine engines. At the same time, it is found that with a significant efficiency improving in blade sharp edge machining, a higher quality of the rounded edge surfaces in the holes is ensured. The results of the conducted research are recommended for the adoption of technologies in the aircraft engine industry.
Science intensive technologies in mechanical engineering. 2024;(3):3-11
3-11
WEAR RESISTANCE INCREASE IN CYLINDRICAL FRICTIONAL INTERFACE USING COMBINED ELECTROMECHANICAL PROCESSING
Abstract
Processing technology and technological equipment for the formation of a wear-resistant surface layer by implanting materials based on tungsten carbide (WC), are viewed. The effect of implanted WC powder on the formation of gradient wear-resistant structures in the friction surface of carbon steel formed during the implementation of combined electromechanical processing (WRCEMP) technology, has been studied. Resulting from heat and pressure impact in the zone of plastic deformation, intensive austenization of steel occurs with dissolution of WC powder and subsequent formation of highly dispersed composite structures caused by the decomposition of undercooled tangstem-supersaturated austenite. Combined comparative friction and wear tests were carried out for structural steel 45 with a graded structure of a hardened surface and rather expensive and technologically- difficult to obtain modern wear-resistant coatings and materials. The issue of WRCEMP technology practical application used for the «axis of satellite – satellite» friction pair is viewed. An assessment of the durability increase of the «axis of satellite – satellite» interface during the implementation of the considered processing methods and innovative technology was taken. Recommendations for the use of combined electromechanical processing technology at machine-building enterprises as a highly effective way to ensure and improve the performance of machine parts at the stage of their manufacture are given.
Science intensive technologies in mechanical engineering. 2024;(3):12-21
12-21
Surface layer quality, contact interaction, friction and wear of machine parts
MICROORGANISMS EFFECT AND FRICTION GEOMODIFIER INFLUENCE ON THE TRIBOLOGICAL PROPERTIES OF GREASE LUBRICANTS
Abstract
Parts wear process always associates with the operation of machines and mechanisms. An important task is to minimize friction energy losses, and it is lubricants that are used for that, which, in turn, can contain various dispersed components. These components are divided into three groups: being formed during the friction process, some entering friction units from the outside and others, being purposefully added. The paper studies in detail the influence of such dispersed components as microorganisms (microscopic mold fungi) and purposefully added fillers, in particular, serpentinite, on the processes of friction and wear. The conditions of occurrence and mechanism of biological damage, as well as toxins released by microorganisms are viewed. The structure and principle of action of serpentinite are given. To perform the tests, four different brands of greases were used (Lita, TSIATIM-201, GOI-54p and MS-70), as well as samples of lubricants with mycotic molds lesion in Petri dishes and fine serpentinite powder. Tribological tests were carried out on a Bosch PBD-40 machine, and the diameters of wear spots of the balls located in the friction unit were measured using a DigiMicro 2.0 digital microscope. As a result of conducted tests, it was found that in case of using greases with mold fungi in the friction unit, deterioration of tribotechnical characteristics such as average friction force and mean diameter of the wear spot was most often observed as compared to basic lubricants. And when using a lubricant composition consisting of contaminated lubricant and serpenitinite, there has always been an improvement in these tribotechnical indicators as compared to contaminated greases without serpentinite, so it proves the effectiveness of filler addition.
Science intensive technologies in mechanical engineering. 2024;(3):22-30
22-30
Technological support of operational properties of machine parts and their connections
PASSENGER CAR BODY STIFFENING
Abstract
Methods for ensuring the required stiffness of passenger car bodies are viewed, making it possible to identify the main de-sign solutions and the technology of their assembly. Alternate designs of stiffening carriage frame with additional elements, using one and two cross ridge partitions, as well as a model with two partitions connected by longitudinal elements were obtained. The lowest bending vibrations frequency, maximum stresses acting in the frame stiffening zone, as well as the mass penalty due to the introduction of additional elements were adopted as the criterion for choosing a rational constructive solution for stiffening supporting structures. The effectiveness analysis of the proposed constructive solutions is carried out within the framework of the accepted criteria using the finite element method. It was found that the most optimal way for body stiffening is a model with two load-bearing partitions interconnected by longitudinal elements. This alternate design renders possible, with a slight increase in body weight, to increase body stiffness up to 8,92 Hz and reduce the maximum stresses acting in the amplification zones to 167,2 MPa. It has been found that stiffening owing to two load-bearing parti-tions interconnected by longitudinal elements, is effective and workable, therefore it is recommended for further new designs of passenger car bodies. In this regard, the technological process of assembling the body with a strengthen design has been developed and its assembly design project is presented. It is found that the change in the process operation of the passenger car body production due to new elements do not require the additional production lines, since assembly can be performed using the equipment available on the existing production line. It is recommended to use a portal contact point machine with a double inlet current supply in the process operation, which will ensure the quality of the assembly process.
Science intensive technologies in mechanical engineering. 2024;(3):31-41
31-41
TECHNOLOGICAL RUNNING-IN TIME REDUCE FOR FRICTION SURFACES
Abstract
The process control analysis for the period of running-in of friction pair parts is carried out. Technological and other ways for running-in time reduce are given. The mode and equipment of low-temperature annealing in silicon dioxide are presented. Roughness measurement instrument, chemical composition measurement, structure and wear measurement of the surface are provided. It is found that under low-temperature annealing in silicon dioxide, the surface roughness is smoothed according to the main roughness parameters. The height roughness parameters Ra, Rmax decreased: Ra (parameter) by 4,5 times; the Rmax (parameter) by 5,1 times. The stepwise parameters S, Sm had differently directed movement: the parameter Sm increased by 2.2 times; the parameter S decreased by 1,6 times. A decrease in the height Ra, Rmax and an increase in the stepwise Sm roughness parameters proves surface smoothing resulted from annealing. A decrease in the parameter S indicates a general decrease in the number of roughness peaks. It should also be noted that the value of the parameter of the tp profile reference curve decreases by 50 %, as a characteristic of reducing the bearing capacity of the material. The results of the chemical analysis showed an increase in the amount of silicon in the surface layer and a decrease in the amount of chromium. Metallographic analysis made it possible to come at the formation of a surface layer enriched with silicon. As a result of wear tests, it was found that the total wear of a sample friction pair after low-temperature annealing decreased as compared to the base sample. Under wear tests, the cylinder-plane scheme was used at the load of 30 N.
Science intensive technologies in mechanical engineering. 2024;(3):42-48
42-48