Studying the process of modification of lithium aluminum alloys

The effect of modification with dispersed compositions on the grain structure and mechanical properties of industrial aluminum alloys has been studied. Aluminum alloys of the Al-Si, Al-Mg-Sc, Al-Cu-Mn systems were modified with dispersed Mg2Si powder with a particle size of up to 200 nm. The amount of modifier to be added to the melt is calculated. The physicochemical properties of dispersed Mg2Si have been studied. Melting of the AMg6, 1570, 2219, AK9ch alloys in the initial state and with the treatment of Mg2Si melts have been carried out. The action of insoluble applications, isomorphic to aluminum, the similarity of the influence of soluble elements holds only when the amount of insoluble addition exceeds the number of crystals formed arbitrarily under the same conditions. Thus, with an increase in the amount of insoluble addition, in particular silicon carbide particles, the grain size first decreases and then remains constant. The mechanism of the influence of dispersed particles of magnesium silicide on the formation of the structure of hypoeutectic aluminum alloys during crystallization is that their bulk is pushed out by the crystallization front into the liquid phase and participates in the refinement of the structural components of the alloy. To determine the optimal amount of silicon carbide modifier, industrial melting and testing were performed on specimens that underwent heat treatment according to the T6 mode (quenching and artificial aging). The quality of cast aluminum alloys during modification depends on many factors: the nature of the dispersed phase, the temperature of the melt, and the modes of its mixing with the introduction of particles. Dependences of the particle size and the amount of the modifier on the mechanical properties of the alloys have been established. The mechanism of interaction of the modifier with aluminum melt during crystallization has been established. In industrial experiments, the most effective size of SiC particles for increasing the σm of the AK9ch alloy from 115 to 260 MPa in the as-cast state has been established. The optimal content of Mg2Si (0.10 %) for increasing the σm of aluminum alloys has been determined.

Studying the effect of heat treatment modes on corrosion resistance of welded joints

Welded joints with corrosion-resistant steels and heat-resistant alloys, which require different modes of heat treatment to achieve the level of mechanical properties specified in the design documentation, are used for the manufacture of parts and components of the turbo-pumping unit (TPU) and liquid rocket engine. Heat-resistant alloys are a large group of alloys on iron, nickel and cobalt bases with the addition of chromium and other alloying elements (C, V, Mo, Nb, W, Ti, Al, B, etc.), whose main feature is to maintain high strength at high and cryogenic temperatures. Heat-resistant alloys are used in the manufacture of many parts of gas turbines in rocketry and jet aircraft, stationary gas turbines, the pumping of oil and gas, hydrogenation of fuel in metallurgical furnaces and many other installations. For the doping of nickel chromium γ-solid solution, several elements are used, which differently influence the increase of heat resistance and processability. Along with the main reinforcing elements (Ti, Al), refractory elements (W, Mo, Nb) are introduced into the alloy, which increase the thermal stability of the solid solution. Heat resistant alloys are based on cobalt. Cobalt has a positive effect on the heat-resistant properties of alloys. The introduction of chromium in cobalt increases its heat resistance and hardness. In addition to chromium, alloys containing cobalt include additives of other alloying elements that improve their various properties at high temperatures. A characteristic feature of these alloys is that they have relatively low heat resistance characteristics at moderate temperatures, which, however, change a little with the temperature up to 900 ° C and therefore become quite high compared to the characteristics of other heat-resistant alloys. A significant drawback of these alloys is their high cost due to the costly cobalt. Nickel-based heat-resistant alloys typically have a complex chemical composition. It includes 12–13 components, carefully balanced to obtain the required properties. The content of impurities such as silicon (Si), phosphorus (P), sulfur (S), oxygen (O) and nitrogen (N) is also controlled. The content of elements such as selenium (Se), tellurium (Te), lead (Pb) and bismuth (Bi) should be negligible, which is provided by the selection of charge materials with low content of these elements, because it is not possible to get rid of them during melting. These alloys typically contain 10–12 % chromium (Cr), up to 8% aluminum (Al) and titanium (Ti), 5–10 % cobalt (Co), as well as small amounts of boron (B), zirconium (Zr) and carbon (C). Molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta) and hafnium (Hf) are sometimes added. Heat-resistant alloys are used for the production of many parts of gas turbines in rocketry and jet aircrafts, stationary gas turbines, for pumping oil and gas products, for hydrogenation of fuel in metallurgical furnaces and in many other installations. Nickel-based heat-resistant alloys are also cryogenic, i.e., they are capable of operating and retaining mechanical properties at very low temperatures (–100 °C to –269 °C). Such alloys are chromium-nickel alloys having an austenitic structure. Not only do they have good mechanical properties that do not change over a large temperature range (–200 °C to 900 °C), they can also work in corrosive environments. Nickel-based heat-resistant alloys typically have a complex chemical composition. It includes 12–13 components, carefully balanced to obtain the required properties. Welded and combined workpieces are made of separate components that are interconnected by various welding methods. Welded and combined blanks greatly simplify the creation of complex configuration designs. Improper workpiece design or incorrect welding technology can cause defects (grooves, porosity, internal stresses) that are difficult to correct by machining. Given that finding replacements with multiple materials, working them out in production, and investigating interconnectivity during thermal forces in a product can take considerable time and money, it would be best to replace one alloy. Unifying the material used would allow the structure to work as a whole, which would increase the manufacturability of the products. After examining the different replacement options, inconel 718 was selected for the study. Studies of welded specimens of inconel 718 alloy-stainless steel for resistance to the ICC have shown that it is not appropriate to use welded inconel 718 for the impeller, it is advisable to use material that would ensure uninterrupted operation in a corrosive environment at cryogenic temperatures. Based on the working conditions of the parts, it is most expedient to make it from heat-resistant chromium-nickel alloys, namely, from float inconel 718 which meets the necessary strength characteristics. The recommended soldering mode is heating up to 950 ± 10 oC, holding for 30 minutes from the moment of loading into the oven, cooling to 3000C with the oven, further in the air, since it has less influence on the corrosion resistance of steels in stainless steel joints. Quality control of inconel 718 alloy by GOST methods similar to that used for the control of X67MBHT type alloys showed the results similar to those obtained by the ASTM and AMS control methods.

A frequency determination method for automotive nanosensors

The growing popularity of nanosensors in various automotive applications requires new methods for counting the frequency of electrical signals, into which the measured non-electrical parameters are converted. This need is because automobile nanosensors are to register very small changes in the measured parameters that, besides, can change very fast. The paper proposes for use in automotive nanosensors a frequency calculation method based on the principle of rational approximation, which meets the above requirements.

Studying the regularities in public transport vehicle dwell time required for passenger boarding and deboarding

The review of the literature devoted to the research of public transport vehicle (PTV) dwell time required for passenger boarding-deboarding at a stop confirms the importance of taking this time into account when modelling passenger transportation. The data about the dwell time were collected in different time periods for different PTVs in various cities and countries. Thus, there is no general model allowing to define the distribution parameters of dwell time variable and answer the question on the regularities in time values. So, the research of the PTV dwell time at the public transport stops in Kharkiv remains actual. Goal. The search of the regularities in transport system performance indicators including PTV dwell time at a stop will allow to apply relevant mathematical methods for the development of the forecast models which are valuable in the field of organization of passenger transportation and servicing. Methodology. The developed methodology to collect data about PTV dwell time at the stops will allow receiving high-quality survey data. The designed survey sheets enable a surveyor to record all needed information and prepare it for processing. The collected data will allow to define the distribution of the PTV dwell time at a stop. Results. The conducted PTV dwell time survey allowed to collect the sufficient amount of data to estimate the distribution of this variable. During the research, it was determined that the empirical dwell time distribution can be well described with the theoretical gamma distribution. The latter distribution appeared to be applicable for all surveyed PTVs. Originality. The defined distribution of the PTV dwell time at a stop for passenger boarding-deboarding allows receiving the results of passenger flows modelling which are more precise compared to the modelling with no dwell time consideration. The use of the dwell time regularities in the procedure of passenger flows assignment results in the increased precision of flow volumes estimation by up to 14.9 % – from 2.28 % to 1.94 %. Practical value. The received results support the fact that the research of PTV dwell time at a stop is actual, and the solution of the task of dwell time distribution estimation will make it possible to improve passenger flows modelling in public transport route systems.

A system for analyzing large data sets using machine learning algorithms

A system for analyzing large data sets using machine learning algorithms

Studying coefficient of increase of the support surface after deployment of a mobile hoist

Currently, there are about 150 manufacturers of mobile elevating work platforms (MEWP), which are constantly designing and implementing new machines with advanced capabilities. Along with the improvement of hoisting equipment, the support devices of the MEWP are also improved. Therefore, there is a need to investigate the coefficient of increase of the support surface area after the deployment of a mobile hoist for different types of support devices. Goal. The aim of this work is to study how the coefficient of increase of the support surface area after the deployment of the support device depends on the length of the support projecting for different designs of support devices used in MEWP. Methodology. Analytical methods of studying the designs with variable geometrical parameters were used in the work. To obtain the dependences of the coefficient of increase of the support surface area after the deployment of the support device on the length of the support projecting, the methods of mathematical modeling employing computer technology were used. Results. The analysis of the dependences of the coefficient of the support surface area increase after the deployment of the support device on the length of the support projecting showed that the use of the considered support devices enlarges the coefficient of increase of the support surface area from 1.9 with angular supports to 3.4 for Spider type support devices. Originality. It is proposed to consider the coefficient of increase of the support surface area, which enables to take into account the lengths and angles of the supports when determining the support surface area. Practical value. With the results of the study it is possible to choose the type of support device and its geometric parameters at the design stage which will

Effectiveness of the iDOP-PH adhesion promoter in relation to adhesion of the pavement bitumen

Asphalt pavement is permanently influenced by various environmental conditions and traffic load. Because of this after a certain period numerous defects may appear on the surface of the road pavement. These defects include peeling, chipping, pots, cracks etc. The low water proof resistance of the asphalt concrete (conditioned by low adhesion of the bitumen to aggregate surface) is considered to be one of the reasons for appearance of these defects. Adhesion promoters’ use is the most common method to increase adhesion activity of pavement bitumen. Goal. The objective of the current research work is the evaluation of influence of the domestic adhesion promoter iDOP on the conventional and adhesion properties of bitumen. Methodology. To achieve this goal, the following was done: the effect of the adhesive promoter iDOP on the standard quality indicators of bitumen was determined according the requirements of the current standards DSTY 4044 and SOU 45.2-00018112-067; the effect of the adhesive promoter on the adhesion of bitumen to the glass surface (according to the DSTU B.V.2.7-81 method) and to the surface of aggregates with different mineralogy was evaluated by the rotating bottle method according to DSTU EN 12697-11; the thermal stability of the iDOP-PH promoter was tested by simulating the technological ageing of bitumen according to the method given in GOST 18180 and the RTFOT method. Results. Grounding on the experimental data obtained, it was found that the adhesive promoter iDOP-PH does not affect the standard indicators of the quality of bitumen (penetration, softening and breaking point temperatures, ductility). During hardening with the RTFOT method, a slight inhibitory effect of the promoter is observed, which appears as an increase in the values of residual penetration and ductility compared to bitumen without promoter. The iDOP-PH promoter increases the adhesive capacity of bitumen, which is confirmed by the adhesion data determined by the improved method given in GOST B.V.2.7-81 and the rolling bottle method. Originality. It is shown that the iDOP-PH promoter has a relevantly low thermal stability. With this the main factor affecting the decrease in thermal stability is the long time exposing of the binder at high temperature by GOST B.V.2.7-81 method. Practical value. It is shown that the promoter concentrations recommended by the supplier are insufficient, and to ensure the required values of the adhesion (standardized in СОУ 45.2-00018112-067) it is advisable to increase the concentration of the iDOP-PH promoter in bitumen to 0.3 - 0.6%.

Stress state of the main girders of the overhead ingot-lifting crane

The analysis of stresses in the main beams of the bridge well crane is carried out in the work. Different types of load are considered: lifting with a pickup, and also loading on a bar from the side The stresses that occur in these cases are determined experimentally, theoretically, and with the help of software. Investigations of the stress state of box beams of cranes with rigid suspension by different methods indicate the reliability of the methods.

Development of a technological complex for thermofriction hardening of products with a circular cross section

There are many methods of influencing the structural state of the surface of products of different shapes and different purposes. At the same time, the increase in the relevance of the application of a particular method is closely related to its ability to provide high hardening rates while reducing the cost of such products. The TFН technology has already shown its high efficiency in strengthening surfaces [1]. In addition, studies were conducted on the hardening of surfaces of different profiles [2]. However, the best results are achieved when hardening flat surfaces. In this regard, it is entirely appropriate to conduct research that is related to the development of a technological complex that would include the optimal ratio of processing factors to ensure the necessary level of hardening in the studied objects that have a circular cross-section. Goal. The purpose of this work is to develop a technological complex for processing objects with a circular cross-section. To achieve this goal, metallographic and durometric studies of samples in the initial state and after processing were carried out. At the same time, the changes in the structure and mechanical properties that occur in steel due to processing were studied. Method. The method of thermal friction hardening includes a combined effect of heat and deformation on the treated surface. The peculiarity of this method is the deformation under short-term heating conditions. This makes it possible to further strengthen pre-hardened materials. Results. Under the influence of TFC, significant changes are observed in the structure of cylindrical samples made of 65G steel. This is expressed by the formation of a so-called "white surface layer" in the surface of these samples, which has an ultra-high microhardness [13, 14]. The properties of this layer depend on the initial state of the material, the conditions and modes of conducting TFН.

Increasing the corrosion resistance of turbine

The reliability of the vane apparatus of steam turbines largely determines the operation of the turbine as a whole. The results of scientific research indicate that the surface operation of the blades in the wet - steam flow is caused by a combination of corrosion and drip erosion. The presence of chemical elements and compounds in the working fluid intensifies the process of blade wear. The pH value of the working environment, which can fluctuate significantly during operation, has a significant effect on the wear characteristics. The influence of methods of strengthening the leading edges of steam turbine blades made of steel is analyzed 15Х11МФ on corrosion resistance. Corrosion tests of blade samples were carried out, the inlet edges of which were strengthened in three ways: high current amplification, electrospark alloying with T15K6 alloy, electrospark alloying with steel 15Х11МФ According to the results of the tests, the layer strengthened by hardening by high-frequency currents has the lowest corrosion rate, the layer strengthened by electrospark alloying with T15K6 hard alloy has the highest. The corrosion rate of the layer reinforced by electrospark alloying of steel 15H11MF is 2.1 less than that of the layer reinforced with T15K6 alloy.