Vol 21, No 3 (2019)

Introduction. Integrated automation of production processes is the main achievement of scientific and technological progress. The creation and use of flexible production modules and production complexes for material processing by cutting leads to the acquisition and mass use of numerical control machines (CNC). Also at the same time, there is a trend of obsolescence of the machine stock of enterprises and a decrease in the initial quality of this equipment, therefore, the actual task is to ensure and improve the quality of the products produced while simultaneously reducing their cost. The aim of the work is to increase the effectiveness of technological processes in turning machining on machines with numerical program control due to mathematical and finite element modeling. In this work, the stress-deformed state of a part in the software product SolidWorks Simulation from the effects of cutting forces and on the basis of mathematical modeling were carried out taking into account the strain deviations, a transformable CAD model of the workpiece was obtained and a control program for this machine was developed for this model. When performing the work, the following research methods were used: methods of computational mathematics, mathematical modeling, matrix analysis, statistical processing of experimental results. Experimental studies were carried out using CAD / CAM system SolidWorks Simulation, turning center SMTCL CAK50135, coordinate measuring machine. The article presents a method of controlling the geometric accuracy of parts machined on CNC machines based on mathematical and finite element modeling. The control of the geometry of the parts is made according to the CAD model that characterizes the reference part. Results and Discussion. When processing two batches of blanks, the first of which was processed according to the traditional method, the second according to the offer, and determining the reliability of the technological operation, it was noted that the dispersion field of real values and the standard deviation decreased according to the proposed method, which confirms its effectiveness, since the percentage of probabilistic marriage is significantly reduced. Moreover, the developed model of geometric accuracy control of details, based on mathematical and finite element modeling, also contributes to the reduction of the main technological processing time by eliminating additional refining passes of the cutting tool.

Introduction. The rocket and space industry is one of the most complex industries, it continuously poses more and more complex tasks, the solution of which is possible only with the advent of new and unique technologies. Today, as before, the space rocket industry faces super-ambitious tasks both to improve the spacecraft themselves and to reduce the cost of their production. The cost of a single spacecraft launch is estimated at billions of rubles; this dramatically slows down the development of the industry and therefore requires maximum attention. The high cost of machining parts of the rocket and space industry is due to the many complexities involved in complicating the design of parts, in the use of superalloys capable of operating under extreme conditions of high temperatures and loads, and therefore difficult to process, as well as in increased requirements for quality. In this connection, today, as well as the most urgently needed, new approaches to processing, which in turn are reflected in the high complexity of technological design and the long production time. The purpose of the work: the development of a method for the maximum reduction of labor-intensiveness and terms of designing effective processing of complex parts of the rocket and space industry. Research methods: Large reserves to improve the technology of processing parts, as well as reducing production time lie in the field of digital technology. Therefore, the main research method is finding bottlenecks in CAM-systems, as well as successful cases on automating the design tasks for efficient processing of especially parts from materials that are difficult to process. Results and discussion: Analysis of the issue showed that when designing the processing in the CAM system there are no close links between the control program and technology, machine, tool and detail, these links are still implemented by a person and directly depend on his experience, which makes the design not quality, not effective and increasingly not profitable. Automating such connections will improve the quality of the design and the processing itself, free up human resources from routine work, and also reduce the time and complexity of the design, which will positively affect the results and cost of production of rocket and space technology. The result of this automation is an intelligent processing module for the CAM system. Some of the tasks solved by the module, and implemented as independent libraries, have already successfully established themselves and are being used in various enterprises.

Introduction. Vibrations always accompany the cutting process and affect the quality parameters of the parts and the state of the cutting process is estimated by the intensity of tool wear. Vibrations, generated by the machine itself (spindle group beats, kinematic perturbations, variations of the allowance, etc.), as well as specially controlled vibrations, introduced into the cutting zone to improve the quality of parts manufacturing, are considered in the paper. The trajectories of shape-generating movements depend on the trajectories of the executive elements of the machine, additional vibrations and elastic deformation displacements of the tool relative to the workpiece are changed by the vibrations. The trajectories of shape-generating movements are the main factor in the formation of the geometric topology of the part surface in the unity of geometric accuracy, waviness and surface roughness. However, to date, there is no consensus about the influence of vibrations on the quality parameters of the part. Method of research. The influence of vibrations on the trajectory of shape-generating movements of the tool tip relative to the workpiece is considered on the basis of mathematical modeling of the dynamic cutting system in the paper as the main factor determining the geometric topology of the part. In contrast to the well-known works, first, the dynamic link parameters are provided in the state coordinates. Secondly, the machines influence of the vibration perturbances on dynamic properties (for instance stabiliti) and machining result (primly geometric topology) is considered. Results and discussion. The simulation results, revealing the effects of nonlinear dynamics, which can cause both improvement and deterioration of the parameters of geometric topology, are presented. These effects appear in the formation of a dynamic constant component of deformation displacements, in the formation of the various attracting sets of deformation displacements along the trajectory and its bifurcations. The ways of improving the quality of the surface formed by the cutting process taking into account agreement of the input and (or) existing naturally external perturbations with the properties of the dynamic system and CNC-controlled trajectories of the executive elements of the machine are outlined. The aim of the research is to improve the efficiency of the process in terms of the quality of parts manufacturing. It can also be used to dynamically monitor state of the process during machining, such as tool wear.

Introduction. The main parameter that determines the efficiency and quality of the flow forming is the value and nature of the distribution of the material’;s deformation resistance over the wall thickness of the workpiece. In the technical literature, devoted to the study of this process, there is not enough information to correctly assign technological regimes and processing conditions. The work is devoted to an experimental study of changes in the resistance of deformation of low carbon steel in the process of flow forming, depending on the degree of deformation and the angle of taper of the deforming roller. The aim of the work is to determine the non-uniform distribution of the resistance of the deformation of low-carbon steel through the thickness of the wall of the workpiece after the flow forming depending on the degree of deformation and the angle of taper of the deforming roller. Research methods. The process of flow forming of blanks having an initial wall thickness of 6.5 mm and an outer diameter of 203 mm is carried out on a three-roller horizontal-rolling machine SRG-0.6-1500 using a direct method. Plastic shaping of the material of the blanks is carried out at different degrees of deformation on the mandrel with a diameter of 190 mm deforming rollers with a diameter of 260 mm with an angle of taper equal to 20 ° and 30 °. The deformation resistance of the material through the wall thickness is determined on longitudinal specimens cut from machined blanks using the indenter insertion method and measuring the hardness with a Vickers tip. The uneven distribution of the strain resistance is estimated by a coefficient defined as the ratio of the resistance of the deformation of the outer surface to the resistance of the deformation of the internal volumes of the wall of the workpiece. Results and discussion. The highest values of strain resistance are obtained on the outer surface of the workpieces treated with a roller, and the smallest values are recorded in the internal volume of the wall of the workpieces. The estimation of the non-uniformity of the distribution of the deformation resistance over the wall thickness of the workpiece is made using an irregularity coefficient equal to the ratio of the deformation resistances of the outer layer and the internal volumes of the wall of the workpiece. It is revealed that the most dangerous zones subjected to destruction in the process of rotational drawing are the internal volumes of the material adjacent to the outer surface layer of the workpiece. It is established that the non-uniformity coefficient of stress distribution when processing with a roller with a taper angle α = 30 ° is about 10% more than with a taper angle α = 20 °. With an increase in the degree of deformation, the coefficient of uneven distribution of stresses increases, but very slightly. The resulting patterns are explained, in particular, by the influx that forms in front of the roller. According to the results obtained, general recommendations are given on the purpose of the degree of deformation and the angle of taper of the roller when performing the flow forming. In addition, the empirical dependences of the strain hardening of the material for different volumes of the workpiece are obtained. The proposed method for determining the uneven distribution of stresses can be used in the development of pressure treatment processes and in the design calculations of structural elements.

Introduction. Laser welding is one of the most effective methods of welded seams formation. High welding speed, ability to weld without the use of filler wire make laser welding one of the most promising welding methods. Another advantage over traditional arc welding is the ability to weld parts in a single pass without cutting edges. Laser welding continuously expands the range of applications, but still it is difficult to apply this type of welding to some materials. These materials include aluminum-magnesium alloys. Due to the various thermal properties of the aluminum matrix and magnesium, the main alloying element is burned out. Another problem in laser welding of Al-Mg alloys is high porosity. As a result, laser welded seams of Al-Mg alloys cannot be used in manufacture due to its low strength. The purpose of the work is to study the effect of ultrasonic influence on the formation structure of the welded seam of AA5083 alloy, obtained by laser welding. Results and discussions. Specimens of conventional laser welding and ultrasonic assisted laser welding are obtained. It is shown that under ultrasonic influence in the process of laser welding the shape of the weld changes. It is not possible to obtain a welded seam without pores, but it is shown that the number of gas pores decreases under ultrasonic influence. Quantitative estimation of energy investments on a volume fraction of the melted metal and value of penetration of laser radiation under the influence of ultrasound is carried out. It is also shown that the volume fraction of secondary particles in the weld metal decreases with an increase in the power of ultrasonic influence. Studies of microhardness welded seams showed a slight increase in microhardness values with ultrasonic influence in comparison with conventional laser welding. As a result of X-ray analysis it was found out that laser welding samples with ultrasonic influence with power 500 W have the nearest parameter of the lattice to the initial material. Also with the power of ultrasonic influence of 500 W the welded seams have the greater distortion of the crystal lattice among the examined ones.

Introduction. Electrolytic iron plating is widely used to improve the wear resistance and hardness of surfaces, as well as restoring worn machine parts. However, the properties of electroplated coatings can change during operation, and even prolonged aging does not lead to stabilization of these properties. Reduction the stabilization time is achieved by heat treatment, the calculation of which regimes for ultra-dispersed coatings should be carried out based on the diffusion laws of point defects. Goal of the work is to calculate the effective diffusion coefficient, taking into account the grain boundary diffusion in the ultra-dispersed electrolytic iron and, on the basis of this coefficient, to find the conditions of heat treatment necessary to stabilize the properties of coatings. Methods of research. Scanning and transmission electron microscopy are used to study the grain structure and intergrain boundaries; thermodynamic calculations are applied in order to find diffusion coefficients; the Comsol Multiphysics program is selected to determine the temperature and time required to stabilize the properties of iron. Results and discussion. An expression for determining the effective diffusion coefficient for ultra-dispersed electrolytic iron, taking into account the influence of intergrain boundaries is obtained. Thermodynamic calculations have shown that, in comparison with the volume coefficient, the effective diffusion coefficient can be two orders of magnitude higher and is largely determined by the size of the grain. Using the method of microstructural analysis, the conditions for obtaining ultradispersed coatings with a large proportion of intergrain boundaries are determined and it is experimentally confirmed that it makes sense to take into account the contribution of grain boundary diffusion, when grain sizes are less than 100 nm, which corresponds to hard conditions of coating deposition. Computer simulation showed that as compared to previously known data, the annealing temperature of ultradispersed iron coatings can be reduced by 50 °C.

Introduction. Products containing cemented carbides (WC-Co), operating at high temperatures, experience large temperature deformations. The calculation accuracy of these deformations depends on the accuracy of the thermal coefficient of linear expansion (TCLE). In the literature, the data on the TCLE values for tungsten-cobalt cemented carbides vary significantly; TCLE type, experimental conditions are often not specified, and the correlation of TCLE and temperature is often neglected. The purpose of the work. The focus of this research is TCLE of tungsten-cobalt cemented carbide with different cobalt content in the range of 3-20 wt. %. The objective of the research is obtaining correlation between the linear thermal deformation and the temperature for tungsten-cobalt cemented carbide with different cobalt content and updating the TCLE values in view of its change as related to the temperature. The methods of investigation. The study used push-rod dilatometer Netzsch 402 PC to obtain experimental data in air. To eliminate low temperature distortions of the push-rod dilatometer due to the design features of this device a special method of experimental data processing is applied. This method includes calculation of true TCLE based on the deformations of the samples obtained from dilatometer; approximation the estimated TCLE by a linear function with its further integration by temperature for obtaining the correlation between the relative thermal deformation and temperature. Results and Discussion. The study obtained experimental values of linear thermal expansion in the range from 20 to 650°С and calculated true TCLE. It is found that a relationship of the true TCLE on the temperature is linear and calculated the coefficients of the corresponding approximating functions for different cobalt content. Also the study derived dependences of the relative thermal deformations of tungsten-cobalt cemented carbide for different cobalt content from the temperature, and provided the corresponding polynomial approximant coefficients. Moreover it is found, that with increasing the cobalt content, the value of TCLE and the rate of its change with temperature enlarge linearly. As the result study provides generalized formulas enabling to calculate for cemented tungsten carbide the relative thermal deformation, the true and mean TCLE based on the known temperature and cobalt content by weight. The results may help to calculate thermal deformation and stresses in a consisted cemented tungsten carbide products.