Bulletin PNRPU. Mechanical engineering, materials science

This study examined the modeling process in the Ansys LS-DYNA software package of the stress-strain state of the working zone of deformation in sheet metal stamping separation operations using a tool with a wear-resistant ion-plasma coating. The object of the study is a working tool (punches and dies) of die tooling for sheet metal stamping processes with a wear-resistant coating based on titanium nitride deposited by ion-plasma spraying and cathodic-ion cleaning methods. The aim of the study was to determine the effect of a wear-resistant coating applied to the working edge of the stamping tool on the stress-strain state in the deformation zone. As part of the study, physical and mathematical models of cutting processes using software packages were proposed, and the stress state of the tool materials in the deformation working zone was evaluated and analyzed. In the modeling process, the finite element simulation of dynamic interactions of solids was used in the Ansys LS-DYNA software package. The following results were obtained: mathematical models of the processes of cutting down the sheet material were constructed (models of the punch, matrix and blanks), a transition was made from 3D-models to simplified coaxial symmetric models that allow one to evaluate the stress-strain state in the working area by separate sections, models of the processes of cutting with different types of tools (with wear-resistant coating and without coating), visual interpretations of the distribution of stress fields in the tool material are obtained, stress graphs are constructed eny and potential energy in the cell surface layer at the critical points of contact on the characteristic process steps of sheet material cutting.

The article analyzes the mechanisms of intensification of heat removal from crystallized granules of metallic materials in the production of granules on an industrial scale. It is known that technologies using high crystallization rates provide a significant strengthening effect of granular material from alloying aluminum alloys with refractory components insoluble in aluminum or having very low solubility (zirconium, chromium, iron, manganese). This makes it possible to create new granular aluminum alloys of increased strength based on the traditional systems Al-Cu-Mg, Al-Zn-Mg-Cu, Al-Mg with alloying with refractory elements in much larger quantities than is used for existing alloys. One of the main factors influencing the formation of supersaturated solid solutions and the formation of the submicroscopic structure of the material is the crystallization rate, which in turn is determined by the rate of heat removal from the formed granule. It has been established that a «steam jacket» is formed around the granule entering the cooling medium, namely a thin layer of steam arising from the transition of the cooling liquid (as a rule, industrial water) in contact with the hot or molten metal into a vaporous state. The formed «steam jacket» is a barrier against the intense heat removal from the cooled pellet. A technology is proposed for intensification of heat removal from crystallized granules of aluminum alloys of the Al-Cu-Mg system in order to increase the crystallization rate. The method is based on the technology of removing the «steam jacket» that inevitably arises around the crystallized melt droplet when the latter enters the water cooling medium. Knocking down the steam shell is possible when the speed of movement of the crystallized object in the water cooling medium increases. Accordingly, in the absence of a vapor shell around the crystallized drop, the thermal conductivity coefficient of the cooling medium increases significantly and the intensity of heat removal increases. It is known that the coefficient of thermal conductivity of water, depending on conditions (temperature and pressure), is 10-30 times greater than the coefficient of thermal conductivity of water vapor. Accordingly, the cooling rate of the melt increases in proportion to the growth of the thermal conductivity coefficient. It was also found that the rate of crystallization depends on other factors affecting the intensity of heat removal and, accordingly, depends on the temperature gradient between the temperature of the crystallized melt and the temperature of the cooling liquid. On the basis of a specially developed industrial installation for the production of granules from aluminum alloys by centrifugation at ultrahigh speeds of rotation of the crucible-sprinkler, it was possible to create the required initial velocity of the melt droplet in the cooling medium, which ensures the removal of the vapor shell. Experimental studies were carried out on granular materials from 2017 and 2024 aluminum alloys. The results of the experiments carried out confirmed the theoretical assumptions. The obtained pressed semifinished products from granules of aluminum alloys of the Al-Cu-Mg system, crystallized at ultra-high cooling rates, are characterized by a significant increase in the strength characteristics of granular materials.

Ensuring the basic level of quality of a technical product by developing and implementing an expert system that ensures the absence of failures and defects at the stage of operation of this product. The failure-free calculation is performed in order to ensure compliance with the requirements for the failure-free performance of parts during the operation of the product. If the actual reliability values do not correspond to the design parameters, then the design of parts and Assembly units is adjusted in order to achieve the design (required) reliability of the product. First, they develop a functional model of the product, and then, based on this scheme, they make a scheme for calculating the reliability of the product. The study of the reliability of technical products has shown that the lack of product reliability is associated with a number of problems. The paper provides a list of measures that can be used to improve the technical level and quality of a technical product. The article describes the need to develop an expert system to ensure the quality of technical products at a high level. The described ES should give an assessment of the expected quality of parts or products before transferring the design documentation to production. The introduction of such an expert system will make it possible at the pre-production stages (development of CD, etc.), to take measures to eliminate possible defects in parts, Assembly units and products before the start of product operation. In the course of the work, the following conclusions were made: the reliability index of a technical product calculated by the method of General quality management is higher than using the method of classical reliability theory, an algorithm was developed in which, after all the above measures, it is assumed that the production of technical products corresponding to a high technical level of quality is provided with a 95% probability.

Light metals, especially aluminum and magnesium alloys, are increasingly used in electronics, mechanical engineering, and aerospace, due to the organic ratio of strength, mass, and low density. These reactive metals also have the disadvantage of low corrosion resistance, so it is necessary to use surface protective layers that are resistant to corrosion and wear. The protective layers it is possible to obtain as by anodizing and the application of galvanic-plasma modification. Galvano-plasma modification allows applying an oxide layer to the surface of aluminum and its alloys, which contributes to the creation of more solid, dense, corrosion-resistant coatings. As with all coating technologies, the successful development of electroplating modification requires high accuracy, stability to pre-treatment of the substrate, as well as careful monitoring of the electrolyte state and process parameters. The article discusses the principles and process of coating by electroplating, including the basics of oxide deposition, the technology used and typical characteristics of coatings. Industrial applications are considered simultaneously with coating requirements. The formation of an oxide coating by galvano-plasma modification is a special, and already well-tested process. Appropriate control of the electrolyte composition and process conditions allows the use of the latest types of coatings with technologically attractive physical and chemical properties. The development of electroplating-plasma modification technology over the past decade has made it possible to obtain coatings with a controlled appearance, hardness, corrosion resistance and tribological properties for various industries. Coatings on the surface of the aluminum alloy Ak12mmgn obtained by electroplating modification are partially considered.

The actively developing additive manufacturing makes it possible to use such beam energy sources as an electron beam and a laser beam for surfacing metal parts from powder materials. The quality of the resulting structure depends on many factors. These factors include the thermo physical properties of the powder and substrate, as well as the physical processes of the interaction of energy beams and materials. Methods for estimating the parameters of additive technologies described in the literature often make it difficult to verify and predict the results of calculations. The proposed method for the use of dimensionless parameters in a simple analytical model for heating samples coated with a layer of powder makes it possible to reduce the number of variables. The thermal model of the process provides a connection between the dimensionless coordinates and the values of the dimensionless temperature. A normalized diagram was built for the processing of a powder material with additive technologies using concentrated energy beams. The diagram is constructed on the basis of a simple analytical model of heating powder layers by a moving linear heat source. Recommended for selective melting is the interval of the diagram for points subject to processing below the line of maximum dimensionless temperature or below the line of maximum thermal efficiency. The range of processing parameters, as well as the ability to predict the optimal energy parameters of an electron beam or a laser beam, with selective melting can be determined depending on the dimensionless beam velocity. The diagram represents useful background information and methodology to select the appropriate processing parameters in the early stages of development not only the sintering additive powder materials, but also to assess the depth of heating of a particular material. It can be used in the heat treatment using the energy beam sources.