Research and simulation of the machining process of difficult-to-cut materials

Heat-resistant and high-alloy steels and alloys are difficult materials to machine. Optimizing the cutting parameters for such materials is a complex and multi-factorial technological process planning task. The paper describes the method of analysis of loading, thermodynamic and stress-strain state of a workpiece while cutting of typical representative of hard-to-cut materials (chromium-nickel alloy IN718) using finite element simulation. Influence of feed rate on cutting force and temperature in the zone of chip formation is given. The paper also analyzes the effect of cutting edge geometry on the thermal and stress state of the workpiece during cutting. Based on the conclusions about the simulation results, an analogy can be made with the processing of such materials. This will significantly reduce the time of technological preparation and decrease the cost of experimental studies.

Mechanisms of structural-phase transformations during crystallization of a solder melt

Problem statement. An important requirement is quality assurance of joining materials with minimal overheating of materials, lowering the soldering temperature and suppressing the interaction of the solder with the materials to be soldered. The heating of the solder and the holder should be as uniform as possible and with a minimum temperature difference along the depth. One solution may be to develop more efficient solders and fluxes, adapted to the high heating rates that are typical when using high frequency currents Purpose. Thus, the problems of uniform heating of parts during brazing are relevant. This is necessary for optimal distribution of the electromagnetic field in the contact area Methodology. The effect of the heating rate was investigated. The composition of the flux and solders on the microstructure of the solders and the brazed seam was performed on the joints of HV510 (DIN), HS345 (DIN), HG30 (DIN) hardmetal plates with steel holders made of 5135 (USA) steel with a section of 25×20. Results. The research of the processes showed that during the contact interaction of low-melting and refractory components of the solders, when the tool was soldered, the solder is formed in the seam and proceeds through several stages. Practical value. Contact interaction of copper-zinc melts with iron particles does not lead to complete dissolution of iron particles. This is explained to the low values of the solubility of iron in copper-zinc melts despite the fact that resistive heat release occurs in the particles. Such iron particles (iron-based alloy) act as a dispersed phase in the structure of the composite material.

Study of the influence of the addition of an exothermic mixture and the ratio of the components of the exothermic mixture on the melting indices at FCAW

An important issue in the processes of strengthening and restoration of surfaces exposed to abrasive, abrasive-corrosive and hydroabrasive wear, using the process of self-protective flux-cored arc welding (FCAW), is to increase the productivity of hardfacing and the quality of the hardfacing metal. The literature review showed that one of the ways to increase the productivity of hardfacing and improve the quality of the hardfaced metal is to add an exothermic mixture to the core filler of flux-cored wire electrode. The effect of composition of filler core during FCAW on the fusion parameters, namely the addition of exothermic mixture (TM), the ratio of exothermic mixture components (CuO/Al), and the ratio of exothermic mixture oxidant to carbon content in the core composition (CuO/C) has been studied. It has been found that the optimum areas for the deposition rate (Gd), deposition factor (ad) and spattering factor (ψs) are observed for the following values of the core components: TM = 25…39, CuO/C = 5…6, CuO/Al = 3…4.

Simulation modelling of dynamic processes due discontinuous frictional treatment of the flat surfaces

Friction treatment refers to surface strengthening (hardening) methods using highly concentrated energy sources. In the course of this processing in the surface layers of the processed surfaces of parts the strengthened layer with nanocrystalline structure is formed. The formed layer has specific physical, mechanical, chemical properties, as well as improved performance properties, which are significantly different from the base metal. A highly concentrated energy source is formed in the contact area of the tool-part due to the high-speed friction (60–90 m/s) of the tool on the treatment surface. Frictional treatment of flat parts according to the kinematics of the process is similar to grinding. The strengthening process was carried out on an upgraded surface grinder. The tool is a metal disk made of stainless-steel. Transverse grooves are formed on the working surface of the tool to intensify the process of forming a strengthened (reinforced) layer with a nanocrystalline structure. The grooves form additional shock loads in the contact area of the tool-treatment surface of the part. These shock loads increase the shear deformation of the metal of the parts’ surface during treatment, which affects into formation the quality parameters of the parts’ surface and surface layer. To study the friction treatment process, the calculation scheme of the elastic system of the machine was developed. A simulation model for the study of dynamic processes that take place during the friction treatment of flat surfaces was built. This model gives possibility to determine the displacements and velocities of the machine table on which the part is fixed and the tool, and to determine their mutual displacement and also calculate the reaction of the machine table.

Optimization of vibratory conveying upward by inclined track with polyharmonic normal vibrations

The paper is devoted to the research of vibratory conveying of piece goods along an inclined track, performing harmonic longitudinal and polyharmonic normal vibrations. It is considered the conditions of reaching maximum conveying velocity at specified values of frequency and amplitude of longitudinal vibrations – the conditions of maximum dimensionless conveying velocity, depending on several dimensionless parameters in the moving modes without hopping. These dimensionless parameters are the inclination angle parameter – a ratio of an inclination angle tangent to a frictional coefficient, the intensive vibration coefficient – a ratio of the longitudinal amplitude of vibration to the amplitude of the first harmonic of normal vibration and frictional coefficient. Maximal conveying velocity is achieved at the certain values of normal vibration amplitudes and values of phase difference angles between longitudinal and normal vibrations, which are called optimal, and their values are dependent on these two dimensionless parameters, while maximum normal vibration acceleration should be equal to the gravitational acceleration. The research was made by approximate harmonic balance method and by numerical step-by-step integration method, which allows performing calculations with any given accuracy. The results obtained by the two methods are compared. To determine the maximal and optimal values of elevation angles, there are calculated the maximal value of the inclination angle parameter at which the value of dimensionless velocity is equal to zero, and the value of the inclination angle parameter at which a particle moves to a specified height in the minimum time. The optimal values of amplitudes of harmonics of polyharmonic normal vibration are determined in dependence on the inclination angle parameter with the number of harmonics from four to seven. The graphs of these dependencies are presented and the most important values of dimensionless parameters are presented in the table.

Features of repair welding of power hydrocylinder elements

At present, the use of power hydraulic cylinders is an integral part of most industrial equipment. They provide translational and horizontal movements, replacement of goods, fixation, etc. These devices are necessary elements of the equipment where application of the corresponding level of effort is applied. Often hydraulic cylinders are created specialized to perform certain types of work. It should be noted that part of the elements of the power cylinder in the manufacture is combined with welding. Such integral connections provide rigidity of installation, tightness of a design, fatigue strength at multicycle loadings. Difficult operating conditions, significant workloads, the presence of various external factors often leads to the destruction of individual elements of the cylinder. At the same time, the cost of repairing equipment that involves replacement with new power devices is quite high. This causes the implementation of repair and restoration work carried out at specialized enterprises. However, in the case of repairs, there are often a number of problems that require prompt resolution in the production environment. These should include the provision of basic materials with similar physical and chemical properties, the establishment of welding modes, the selection of the necessary welding materials, the use of appropriate techniques for conducting the arc process, etc. Therefore the repaired welded design of the case of the power hydraulic cylinder needs additional studying for weldability of separate elements among themselves, formation of a zone of thermodeformation influence. In general, the repaired hydraulic cylinder should meet the installation operating requirements depending on the purpose. The design of the considered hydraulic cylinder of the press installation is rather technological from the point of view of maintenance of automation of welding process. It contains long welds of a simple ring configuration. At the same time, the significant linear dimensions and the presence of a cylindrical surface cause some complexity in the implementation of processes. The construction material of the power hydraulic cylinder is low-carbon low-alloy steels. The analysis of technological weldability indicates a tendency to crack due to the thermal cycle of welding. The simulation of welds of the power hydraulic cylinder is performed in the work. The number of rollers was taken into account when obtaining butt welds. A comparative analysis of different electrode materials with different doping systems is done. The most applicable welding materials by chemical composition and properties of the weld metal are determined. According to the literature data and the results of comparative analysis, the optimal range of cooling rate of the main material of the hydraulic cylinder was established. The properties and structure of the zone of thermal influence of the butt welds of the power hydraulic cylinder have been studied. The magnitude of deformations and stresses caused by the thermal cycle of welding of the shell structure of the hydraulic cylinder liner is investigated. The admissible parameters of the zone of plastic deformations during butt welding are determined.

Modelling and simulation of pneumatic system operation of mobile robot

Problem statement. Mobile robots are currently of significant interest among researchers and designers all over the world. One of the prospective drives of such robots is equipped by a pneumatically operated orthogonal system. The processes of development and improvement of orthogonal walking robots are significantly constrained because of the lack of an open-access comprehensive scientific and theoretical framework for calculating and designing of the energy-efficient and environmental-friendly pneumatic walking drives. Purpose. The main purpose of this research consists in the kinematic analysis, motion modelling and pneumatic system simulation of the mobile robot with an orthogonal walking drive. Methodology. The research is carried out using the basic laws and principles of mechanics, pneumatics and automation. The numerical modelling of the robot motion is conducted in MathCad software. The computer simulation of the robot kinematics is performed using SolidWorks software. The operational characteristics of the robot’s pneumatic system are investigated in Festo FluidSim software. Findings (results) and originality (novelty). The improved design of the mobile robot equipped by the orthogonal walking drive and turning mechanism is thoroughly investigated. The motion equations of the orthogonal walking drive are deduced, and the graphical dependencies describing the trajectories (paths) of the robot’s feet and body are constructed. The pneumatically operated system ensuring the robot rectilinear and curvilinear locomotion is substantiated. Practical value. The proposed design of the walking robot can be used while developing industrial (production) prototypes of mobile robotic systems intended for performing various activities in the environments that are not suitable for using electric power. Scopes of further investigations. While carrying out further investigations, it is expedient to design the devices for changing the robot locomotion speed and controlling the lifting height of its feet.

Topography of the strengthened cylindrical surface after frictional continuous treatment

Friction treatment refers to methods of surface strengthening (hardening) of the parts’ working surfaces using highly concentrated energy sources. Concentrated energy flow is formed during high-speed friction of the tool on the treated surface in the area of their contact. A strengthened (reinforced) white layer with a nanocrystalline structure is formed in the surface layer of the treated surface. Friction treatment of cylindrical surfaces of samples made of steel 41Cr4 (hardening and low-temperature tempering) was made on a lathe, and the device for the autonomous drive of the strengthening tool was installed instead of a toolpost. The tool was used with a smooth working part and with transverse grooves on the working part. Experimental researches of the strengthened surfaces’ topography were carried out on a profilometer “TALYScan 150” (Taylor Hobson Ltd, UK). The obtained data were processed in the software “Digital Surf MountainsLab Premium 8.2”. After friction treatment by using the tool with transverse grooves on its working part on the treated surface more evenly distributed peaks than after friction treatment by using the tool with the smooth surface. Analysing the spectral density of the peak’s distribution on the treated surfaces, it can be noted that after friction treatment by using the tool with transverse grooves, the area of the spectra is the lowest in comparison with friction treatment by using the tool with a smooth working part. When using the tool with cross grooves on its working part during frictional treatment allows to receive the best parameters of quality of the treatment surface in comparison with frictional treatment by the tool with a smooth working part. The parameters of the load-bearing capacity curve of the surface treated by the tool with transverse grooves on its working surface are better than after frictional treatment by the tool with a smooth working part. The treated surface by the tool with transverse grooves has a more favourable surface for wear, which was confirmed by research on wear resistance.

Study of the processing of small diagnostic creations on a fluid sourcing by spiral survivals

The article considers the features of the drilling process where there is a change in temperature, hole diameter, and displacement relative to the axis and the impact on the tool, when machining holes with high-speed steel drills there is wear of the transverse edge which is completely rounded to create a conical surface. There is a decrease in the negative value of the front corners on the transverse edge of the decrease in axial force, which led to a decrease in the intensity of wear of the transverse edge. In order of increasing axial force, respectively, and the intensity of wear of the transverse edge, were sharpened and recommended sharpening methods that provide high performance of the drill, the greatest stability, increased drilling accuracy, as well as the lowest cutting force. The analysis of influence of technological methods and ways and equipment on accuracy and quality of deep openings of small diameter is carried out. The effects of the method of lubricating coolant supply on the tool stability and processing productivity are investigated. The analysis of processing on the metal-cutting equipment with constructive development of the device is executed. Also, the stress-strain state of the drilling process by the finite element method with the analysis of external influences on the twist drill is carried out. The results of the research substantiate and recommend technological methods that reduce the deformation of the tool and, as a consequence, increase the quality and accuracy of the dimensions of deep holes of small diameter.

Design and operational peculiarities of four-degree-of-freedom double-legged robot with pneumatic drive and turning mechanism

Problem statement. Mobile robots are of significant interest among scientists and designers during the last several decades. One of the prospective drives of such robots is based on pneumatically operated walking (stepping) system with no use of electric, heat, magnetic or other types of energy. This allows the use of pneumatically-driven robots in the cases when the use of other energy sources is prohibited (e.g., in some gaseous or fluid mediums). At the same time, the walking (stepping) type of moving increases the manoeuvrability and cross-country capability of the mobile robot, and decreases the harmful effect of its interaction with the supporting surface (e.g., the fertile soil surface) in comparison with wheeled or caterpillar drives. Purpose. The main purpose of this research consists in substantiation of structure and parameters of pneumatic system of four-degree-of-freedom mobile robot with orthogonal walking drive and turning mechanism. Methodology. The research is carried out using the basic laws and principles of mechanics, pneumatics and automation. The numerical experiment is conducted in MathCAD software; the computer simulation of the robot’s motion is performed using SolidWorks software; the modelling of the pneumatic system operation is carried out in Festo FluidSim Pneumatic software. Findings (results) and originality (novelty). The improved structure of the mobile robot with orthogonal walking drive and turning mechanism is proposed. The pneumatically operated system ensuring the robot’s curvilinear motion is substantiated. Practical value. The proposed design of walking robot can be used while designing industrial (production) prototypes of mobile robotic systems for performing various activities in the environments that are not suitable for using electric power or other types of energy sources. Scopes of further investigations. While carrying out further investigations, it is necessary to design the devices for changing motion speed of the robot and the height of lifting of its feet.