Bulletin PNRPU. Mechanical engineering, materials science

Considered the issues of system approach to ensure the process's reliability and proposed technical solutions for subsystems and components of precision automated machine tools aimed at minimizing the impact of processes of different speeds on the accuracy metrics precision machining. With accumulated experience of research, proposed the concept of a systematic approach to monitoring, diagnosis and testing of automated precision cutting machines to enhance their accuracy and reliability in the form of multilevel structure. Stages vitally cycle machines are represented by the levels of the organization, and in them there are sublevels, each of which has its end result. In line with global trends of technology development IU-callobrate and organization of production the basis of the needs of those from-the spheres will be high-precision automated types of equipment to create flexible, rapid tool change tube industries. On the basis of complex theoretical and experimental researches of the necessity of increasing the accuracy of movements precision of the working bodies of technological equipment through the use of multi-stage friction gear due to the fact that the known mechanical transmission actuators do not satisfy a number of requirements for their use in the feed drives, providing ultra-precise shaping of the parts. The analysis of contact and power interactions in multi-stage friction gear determines necessary for the construction of ratios is the geometric dimensions of the rollers that provides, in conjunction with the selection of the optimal angle between the vectors of the force of the biasing rollers, the minimum interaction of friction pairs in the transmission of torque, creating a traction force of multi-stage friction gear drive supply module. The mathematical model of the interaction forces that arise when the two-stage friction gear that allows you to optimize the pressing force of the rollers, to improve the efficiency of multi-stage friction PE-of the heating main.

Step gating system with direct sprue is widely used in the foundry industry. In order for this system to fulfill its function, it is necessary to ensure the consistent inclusion of feeders in work. Designing gating system is complicated due to the fact that we have to resort to the method of successive approximations, and in the absence of data on the coefficients of hydraulic resistance. The article describes the method of calculating the unfilled step gating system. First, calculate the optimal time filling of the form. Next, determine the dimensions of the narrow section. First, a tabular value of the coefficient of flow and pre-determined dimensions of those elements of gating system, which cannot be defined constructively. Then, using the Bernoulli equation to determine the exact value of the discharge coefficient, and the size of the gating system are translated. This continues until the received value matches the sufficient precision obtained. The article summarizes the data values of the coefficients of hydraulic resistance gating systems of the various elements required for the calculation. This technique is used for casting “Mould” simulated filling in the software package “ProCAST”. The simulation results confirmed the correctness of methodology. It was possible to provide a series connection of feeders in operation - first form is filled through the lower feeder so long until it is flooded, and the metal in the form reaches a certain level. Then, the metal begins to flow through the upper and feeder, provided with an upper portion of the hot metal castings, thereby providing directional solidification.

The considerable volume of application of laser welding at production of production of responsible and especially responsible appointment is caused both depreciation of the laser equipment, and increase of stability of technologies of laser welding. The great value in technology of welding besides control and management of parameters of process is got by control and management of process of pro-melting of metal of the welded product. The majority of products in which use of laser welding is perspective have small thickness. Due to the danger of emergence of such defects as either burn through and sites of incomplete pro-melting there is a need of an operating control of process of through pro-melting at laser welding. Processes at laser welding it is substantially similar to the processes observed at electron beam welding. In particular material evaporation processes, education and development of the steam-gas channel, interaction of radiation with vapors and plasma allow to use results of researches of electron beam welding in application to processes of control of pro-melting at laser welding. Thus the theoretical and practical researches describing the mechanism of formation of a plasma torch are of great importance. A large number of researches is devoted to studying of process of interaction of laser radiation with the ionized material vapors. The conducted researches are generally directed on studying of the physical nature of the phenomenon and establishment of a number of regularities of origin and development of plasma at laser radiation of surfaces. However applied questions of nature of influence of a plasma torch in various gas atmospheres used at laser processing on depth of pro-melting and power efficiency of this or that laser technology are almost not investigated. Plasma torch, being a source of charged particles at all types of laser processing, provides passing of current, considerable in size. Studying of characteristics of laser plasma, allowed to create registration system. For selection of current from plasma, formed in an area of coverage of a laser beam, the collector of charged particles is used. Record of a signal of current in plasma is made by means of the personal computer equipped with the analog-digital converter. This signal is informative and allows to make an operating control process of through pro-melting of the welded thickness at the expense of an assessment of emission of plasma from a root of a welded seam.

The alloy system Ti-Nb widely used in the manufacture of implants. First of all this is due to a low elastic modulus and bioinert properties of the alloy. The most widespread of these alloys are obtained in dentistry and orthopedics. To date, the alloy system Ti-Nb is mainly produced by traditional metallurgy techniques. With further subtractive obtaining final product generates large quantities waste. In this regard, the increased cost of the final product. These technology is the opposite of additive manufacturing. Selective laser melting has a technology that allows to print parts made of metal powders and their mixtures. Its essence lies in that the layer of material in powder form is fused by the laser. Then, in the fused layer of powder is applied to the next layer and the process repeated. The technology is used to create complex products and working prototypes. In this paper, we consider the possibility of using selective laser melting to produce a binary alloy from a composite powder of Ti-Nb. The samples panel is obtained 10 ´ 10 mm at different technological parameters. The samples were prepared by a layer by layer laser synthesis machine “VARISKAF-100 MV”. It allows control the following process parameters: the laser power; speed and scanning step; the heating temperature of the powder; layer thickness; the diameter of the focus spot of the laser. All samples were prepared in a protective atmosphere of argon, after preliminary vacuumization. It were constructed dependences to the changes of porosity and thickness of the fused layer of the laser power at different scanning speeds. It was established that all of the controlled process parameters, the greatest influence on the formation of the fused layer has a scanning speed and laser power.

Ultra high temperature ceramic materials (UHTC) based on zirconium and hafnium borides are of a great interest for the construction of materials exploited at extreme environment at temperatures more than 2000 оС in oxidative gas flow. UHTC materials have high melting points, high oxidation stability and thermal shock resistance. Perspective sintering method is spark plasma sintering (SPS). During SPS process at high local temperatures up to several thousand degrees spark plasma occurs between powder particles and it leads to the chemical reactions between components in the powder composition with the formation of new phases influencing on the ceramics properties. In present work thermodynamic calculations of Gibbs energy change of possible reactions at spark plasma sintering of compositions based on zirconium and hafnium borides within 0-5000 оС were carried out. The probability of secondary phase formation during sintering was estimated. Mechanical activation of powder compositions was carried out with the use of high energy planetary-type mill. The powders were dried and sintered with the use of spark plasma sintering method. Shrinkage temperature of every composition was determined. Apparent density and open porosity were measured with the use of hydrostatic weighing method. The ceramics density was more than 95%. X-ray analysis showed that sintered ceramic materials included phases ZrB2, HfB2, ZrO2, α- and β-SiC, La2O3. In some samples there are additional peaks indicating on the possible presence of complex oxides LaBO3 and LaYO3. Sintered ceramic materials were investigated with the use of scanning electron microscopy. Boundary phases were observed between ceramic grains. Element composition of these phases was detected. Element analysis showed that the elements from oxide additives were concentrated in grain boundary phases.

The object of research is the process of formation of the roughness of the machined surface during wire electrical discharge machining (WEDM). The roughness of the machined surface by WEDM depends on many factors: the properties of the working fluid, the properties of the material being processed, the properties of the electrode-wire, pulse parameters (the time of turning on and off a pulse voltage in the gap, current, etc.)., The wire speed, the height of the workpiece and others. Taking into account the many factors influencing the formation of WEDM roughness of the machined surface for the analysis of the relationship is the use of appropriate techniques of experimental design. The aim is to study the influence of experimental stress and wire speed formation surface finish at wire-wire electric discharge machining. Experimental research is conducted by the method of full factorial experiment. The main factors selected for the experiment, select the wire speed (m/min) and the gap voltage (B). It is shown that an increase in voltage U , in the processing of titanium VT3 and Steel 09G2S, machined surface roughness Ra, microns increases. It is found that increasing the voltage U, in the processing of aluminum and steel 40HN2M2, machined surface roughness Ra, microns decreases. By increasing the speed of wire winding v (m/min), treated aluminum, and titanium VT3, machined surface roughness Ra, microns decreases in low ranges. It was determined that the monitoring parameter wire speed v (m/min) when processing steel grade 09G2S and 40HN2MA has no significant effect on the formation of the roughness of the machined surface.

For quality castings necessary to prevent non-metallic inclusions in the mold cavity. To ensure the specified requirements necessary to ensure the proper operation of the cell gating system - slag trap. It is necessary to ensure that during flow along the entire length slag trap slag particles, even those who initially were on bottom surfaced over the full height of the channel. slag trap in flow rate should be such that the metal flow could not entrain the particles already in its pop-top. This becomes possible when the flow rate does not exceed a certain limit value. In today's foundries are a lot of methods for calculating gating systems on which the findings are different. This article summarizes data on critical flow rate, the flow of metal to the slag particles of iron-carbon alloys, as well as the average ramp rate of the metal in the mold. Calculations gating systems by standard techniques and methodology proposed by the authors, slag trap calculations made taking into account that the gating system in this case should be closed. It is shown that not all the methods give adequate results, as standard methods of calculation adopted by the weight of the gating system oscillating in the range of 10-20%. Drawing the method of calculating the gating system, based on the critical velocity of flow of the metal in slag trap gives the results of calculations in the form of cross-sectional dimensions of elements and the length of the gating systems slag trap, based on specified parameters foundry and model guidance, unlike conventional techniques.