Nº 10 (148) (2023)

The operation of obtaining cylindrical products with a titling pad made of titanium alloy VT6 is viewed in the article. The operation involves impacting a bar blank made of titanium alloy VT6 with the use of a punch having sloped edge. When obtaining parts having titling pad made of difficult-to-form alloys, it is necessary to formulate the modes of technology. It is required to specify the rates of deformation and the impact of contact friction on the kinematics of the material flow and the force of shape change to assess the capabilities of the process performed by CAE modeling. Therefore, the simulation of obtaining cylindrical products with a titling pad made of titanium alloy VT6 was performed in the DEFORM modeling program. The influence of the speed conditions of the operation on the change in the values of stress intensities in the product was found. The dependences of the influence of the angles and rates of deformation on the landing force are revealed. The results of theoretical studies obtained during the simulation were summarized. A regression analysis of the results obtained during the simulation was performed. Based on the simulation results, expressions for estimating the intensity of stresses are obtained. The results of regression modeling are in good agreement with the results of computer modeling. Using quantitative modeling results, a regression assessment of the force was taken. Regression equations in natural values are obtained for the assessment of the impact of key process parameters during setup, which can be useful directly when assigning technological modes of titanium alloy blanks setup. The results can be used in the implementation of manufacturing technologies for parts with flange seals, characterized by the best strength characteristics and good load resistance.

The problem of obtaining high-quality plate welds made of AL9 alloy and powder by selective laser melting is viewed. Welded butt joints of plates of AK9CH alloy with a thickness of 3.0 mm were made by melting welding (automatic argon arc and electron beam welding) and friction stir welding. After welding the base metal of the AK9 alloy plates and their welded joints were subjected to X-ray transmission, computed tomography, metallographic analysis and mechanical tests for static tension and static three-point bending. X-ray inspection of welded joints made by automatic argon arc and electron beam welding revealed multiple porosity inside welds. The nuclei of pores in the weld metal are spherical micropores, formed in the parent metal during selective laser melting. The diameter of these micropores is 150...200 microns. In the welding bath during fusion welding, micropores develop up to 420...1070 microns in diameter in case of argon arc welding and 215...420 microns in case of electron beam welding. Metallographic analysis of cross-sections of welded joints performed by fusion welding revealed a characteristic pore distribution in the weld metal. So in case of argon arc welding, the largest pores were located near the front surface of the weld. In the fusion zone at the border of the weld and the base metal, pores with a diameter of 80.220 microns were located in the form of chains along the entire thickness of the plates being welded. When testing welded joints for static tension, the destruction of joints occurred precisely in this zone. The strength coefficient of the AK9 alloy joints obtained by fusion welding is as follows: for automatic argon arc welding 0.46, for electron beam welding - 0.66. It is established that the problem of porosity of welded joints is eliminated when using solid -phase welding for jointing (friction stir welding). The strength coefficient of the jointing of the AK9CH alloy plates made by friction stir welding is at the level of 0.81.0.86 of the time resistance of the base metal. The destruction of welded joints occurs along the mixing zone. In the weld zone during friction stir welding, as a result of dynamic recrystallization, a fine-grained equiaxed structure with an average grain size of 4.5...6.2 microns was formed with virtually no pores. The parent metal is represented by a cellular structure in which there are pores up to 168 microns in size.

The possibilities of theoretical analysis based on numerical modeling of complex processes of additive manufacturing by selective laser melting method are viewed. Methods of high-precision modeling of the formation of a single melt bath are discussed, taking into account the geometry of the formed powder layer, the energy distribution in the spot, the effects of ray re-reflection, the vapor recoil force, the Marangoni effect and denudation mechanisms. Experimental studies on the cultivation of samples from BrX copper powder with particles of 20...50 microns in size by selective laser melting using continuous fiber laser radiation with a wavelength of 1.064 microns were carried out. In particular, all the experiments were carried out under conditions when growing conditions and modes are completely coincident with the calculated model. To assess the accuracy of the modeling system, the dimensions of the melting region and the morphology of the surface of the melt were compared. The presented computational model was used in the development of technology for growing products from copper alloy powders using selective laser melting method. Research in the field of modeling the stress-strain state in a composite material formed in the SLP process, consisting of an Ak9ch alloy matrix reinforced with titanium carbide particles, is also presented. Calculations were performed to identify the influence of shape (sphere, icosahedron, prism), size (1,0 microns; 5,0 microns; 10 microns) and mass concentration (1,0 %; 3,0 %; 5,0 %; 7,0 %; 10 %; 15 %), taking into account the presence of pores of various shapes. The results of calculations are compared with the results of experiments. Numerical models with subsequent experimental approbation of the optimal variant make it possible to significantly reduce the time spent for the development of new complex and promising additive technologies.

Currently, the grinding operation of fabrication mill rollers through the use of fine-grained wheels is the most progressive method of finishing, because it saves from labor-intensive finishing processes in the technological cycle allowing to get a desired accuracy of the size, shape, surface roughness, physical and mechanical properties of the work material along with the reduction of manufacturing content. Considering that grinding rate of fine-grained wheels increases with an depth-of-cut increase in a single grain, the method of calculating grinding cycles by radial force for finishing of cold reduction rollers using fine-grained abrasive wheels is viewed. The calculation was carried out, and the optimal modes of a high-performance grinding cycle of parts made of steel 9X2, 55...60 HRC, wheels 1-400x50x203 63C M14 CM 8B with a change in the radial component of the cutting force at the cycle stages were determined. For experimental verification of the calculated cycle, grinding samples d×l = 65×250 mm at a constant radial force corresponding to a given surface roughness and with a change in radial force were tested. Radial grinding force was set by technological system tightness and maintained by a device for registering a radial force within each run. During the experiments, the following measurements: removal of metal to diameter with a lever bracket; surface roughness parameters on a profilometer-profilograph mod. 201 were carried out. The conducted tests proved the effectiveness of design cycles with a change in radial force. When using the proposed cycles, a given surface roughness is provided, while the productivity of the operation increases by 2,0 – 2,5 times.

Assembly is an important stage of production that has a substantial impact on the quality of manufactured products. Due to the complexity of structures, severization ofquality requirements and increased technical and economic characteristics of manufactured products, taking into account constant scientific and technological progress in machine building, the task of quality assuarance and achieving the maximum identity of products is becoming more and more relevant. The success of assembly automation projects implementation is associated with the need for geometric and technological design concurrency. The success of the implementation of assembly automation projects is associated with the need for both geometric and technological design concurrency. The article describes an approach to solving this problem considering the consistent technological improvement of the product through assembly prism. Currently, the problem of assembly quality is a key one in mechanical engineering field. The article discusses the intercoordination of the assembly with all the stages of production, going before. An analysis of the problems associated with assembly production in this area was carried out. The level of assembly automation in Russia in the field of mechanical engineering does not exceed 10%. An increase in the level of assembly automation can be achieved only through the creation and research of new methods of automatic and robotic assembly. The article describes the technological capabilities and applications of new methods of automatic assembly. The possibilities of samples of experimental assembly equipment, created and studied at the universities of Russia, are studied. A particular problem is the lack of a single source manufacturer of automatic assembly equipment in Russia. The article draws attention to the need of the creation and implementation of intelligent assembly equipment and technologies. As a result of this analysis, issues have been identified, the solution of them can be made at the sector-specific and state levels.