The paper demonstrates that as the energy industry develops, there is a continuous process of improving the designs of contact electrical connections. Bimetallic contacts are becoming more common. Their performance depends on the morphology and strength of the connection layers. Clad workpieces with various heat treatment modes were researched. The strength of the joint of the laminated compound was also determined. With increasing temperature and heat treatment time, the concentration as well as the amount of intermetallic compounds in the weld zone increases. When the layer of intermetallic compounds reaches a certain value, the effects of increasing temperature and increasing time are weakened. Observations show that a low annealing temperature with a short heat treatment time can significantly improve the strength of the clad compound joint.

The Research of the Morphology and Mechanical Characteristics of Electric Bimetallic Contacts

The paper deals with the analysis of the possibility of intensifying the process of drawing sheet workpieces by changing the design of equipment It is shown that this method of sheet stamping is characterized by the introduction of non-waste technologies and the production of parts that do not require final processing However, the task of developing rational technological processes of drawing, requiring the minimum labor input and the cost of manufacturing specified parts with the best quality, is still particularly urgent Modern enterprises operating in conditions of frequent changes in the range of manufactured parts seek to minimize the cost of tools and equipment to reduce the cost of the process Therefore, the unification of the tool, simplification of the design of die tooling in the conditions of flexible serial production will make it possible, with minimal loss of time, to switch to the release of new products A method of pressure-free stamping using a telescopic punch is proposed Also, the fundamental possibility of drawing by the proposed method is confirmed based on the performed research A method for calculating the punch lock springs is developed The demonstrated technological calculations make it possible to proceed to the design and calculation of die tooling and punch power springs, which contributes to the manufacture of high-quality parts, reducing labor intensity and eliminating the use of a double-acting press As a result, the proposed technical measures will reduce the technological cost of the product

The Manufacture of Cylindrical Parts by Drawing Using a Telescopic Punch

The stress-strain state has been studied for a flange of a semiproduct made of an aluminum–copper bimetal under drawing boxes rectangular in plan. These studies are carried out using a grid method, assuming that the material is isotropic and incompressible; the deformation within each cell is uniform; the deformation occurs monotonically; and the stressed state is plane and the deformed state is bulk, but the elastic deformations are negligible. In order to minimize the measurement errors of coordinate grids and reduce the time required for processing information, a CAD software package is used for simulation The billets are rectangles with explosion-welded A4 aluminum and a M4 copper layers subjected to preliminary heat treatment before the operation of drawing. The rectangular billets have been successively drawn to a height of 10 mm; after drawing, the grid and the thickness of the sample under study are measured. The samples of billets have been photographed at an identical focal length and loaded into the application program. In the program, coordinate points are applied to the grid nodes to measure the distances and coordinates of these points before and after deformation. The measurement results show that the greatest deformation is experienced by the corner zones of the billet, where the compressive stresses exhibit an increase from the angle bisector to the walls. These stresses lead to bimetallic billet delamination, as well as to occurring corrugations throughout the copper layer. The drawing is performed for 20 billets and, in each case, the corrugation on the flange surface is observed. Varying the clamping pressure in the range from 0.25 to 0.5 MPa does not lead to any positive results. The end part of the box flange experiences the greatest strain rate, whereas, when approaching the matrix hole, the strain rate exhibits a 20% decrease. The action of angular shear stresses leads to transition-zone discontinuity, which is characterized by the presence of an intermetallic layer having reduced plastic properties.

Experimental Studies on the Stress-Strain State under Drawing Aluminum–Copper Bimetal Parts Rectangular in Plan

The article shows data on determining billet shape while obtaining a box-shaped part from aluminum-copper bimetallic composition. Special attention in the course of finite-element modeling of strain process is paid to the choice of mechanical characteristics of each layer and the nature of the relationship between layers. It is shown that the optimal billet shape for drawing is a “rectangle with cut angles” and copper layer outer position. This billet shape ensures the absence of corrugations with a single junction drawing of aluminum-copper bimetal box-shaped parts, and also provides the least deformation force with minimum intensity of stresses and strains. The absence of folds allows to judge on sufficiently proportionate layer-by-layer strain and preservation of the indissoluble layer-by-layer engagement. This makes possible to design a technological process for the production of bimetallic contacts with the required set of electromechanical characteristics and to recommend it for manufacturing. It is also noted that a more solid and consistent material for obtaining the optimum product handling properties should be located on the outer layer of the part. At the same time, it is advisable to use drawing in the manufacture of bimetallic parts to select, whenever it is possible, materials with approximately the same strength and plastic characteristics, avoiding the occurrence of different stresses in the product layers and, accordingly, distortion or other negative consequences for the finished item. The presence of lamination in a bimetallic composition increases the electrical resistance hundredfold and leads to the product rejection.

Finite-Element Model of Bimetal Billet Strain Obtaining Box-Shaped Parts by Means of Drawing

The paper deals with the results of the finite-element simulation of the process of the tubular workpiece expansion The operability of the criteria of the stability and ultimate strain during the expansion by conical punches is verified The expansion coefficient is limited by the destruction of the workpiece in the form of a longitudinal crack along the weld joint in the heat-affected zone or in the solid metal, which mainly starts at the workpiece end, and also by the loss of the stability of the rigid part of the workpiece, causing the occurrence of a transversal circumferential fold It is demonstrated that the criteria used in production, which are obtained based on various hypotheses and assumptions of experimental information, correlate with numerical models, and their results practically coincide The expansion of the isotropic workpiece is compared with the workpiece with cylindrical anisotropy at the equal conditions of strain It enabled the determination of the initial anisotropy influence on the distribution of stresses and strains during the expansion It is shown that an increase in the anisotropy parameter in the axial direction, as compared with the cylindrical plane, makes it possible to increase the coefficient of the expansion in comparison with the isotropic model of the workpiece The performed development does not exclude the possibility of using the proposed simulation method to solve engineering problems concerning production optimization

Finite-Element Simulation of the Process of the Tubular Workpiece Expansion in the Manufacture of Automotive Parts

The desire to anticipate and predict quality of the manufactured products, its compliance with the technical requirements of the customer at the stage of technology design leads to the development of various methods for theoretical analysis of the processes of plastic deformation. The purpose of these methods is to establish explicit patterns in the processes implemented using the intuitively clear mathematical functions. We have formulated a method for determining relative deformations at a local change in the shape of a closed shell of rotation through radial-rotational profiling. It is shown that it is possible, based on the derived analytical dependences, to predict dimensions of a semi-finished product at the design stage of the technological process. Up to now, there have not been any analytical expressions that would estimate an unambiguous dependence of deformation on the rollers radii ratio, on a billet, and on the magnitude of feed. It is established that the magnitude of relative deformations in three mutually perpendicular directions depends on the ratio of diametrical dimensions of deforming rollers and initial diameter of a billet. Comparison of calculation results, obtained in this work, with experimental data and existing expressions allows us to argue that a given method of calculation demonstrates the accuracy acceptable for the industrial production. This contributes to the possibility to control a field of stresses and deformations in order to manufacture an equally strong wheel rim at the stage of production preparation and a technological process design. The practical application of a given method of calculation would enable technologists and designers to take into consideration the deformation strengthening after each run of profiling. As well as to determine the operational dimensions of semi-finished products and to predict thickness of a finished product in radius transitions of the profile, that is, to intensify the considered process.

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Development of a method to determine deformations in the manufacture of a vehicle wheel rim

The paper presents the research of plastic expansion of a pipe workpiece by punches of various configurations. It is shown that interest in this process is caused by the development of oil production, where there is a need to increase the diameter of well pipes, the automobile industry, where the protection of the driver and passengers in case of accidents comes first. Here, stable plastic deformation plays an important role as a good absorber of kinetic energy, etc. Data on the problems of expanding pipe ends are given, where special attention is paid to the destruction of the end in the form of localization of deformations and appearance of a longitudinal crack. To eliminate this phenomen onvarious technological methods are used. Here the influence of the design and shape of the punch on the localization of deformations along the thickness of the workpiece is researched. Several spatial outlines of the tool are proposed to create an effective reloading of the pipe workpiece in the deformation zone. Based on numerical modeling, the distribution of stresses according to Mises, the displacement of the end of the semi-finished product and logarithmic deformations in the radial direction is shown for each standard size of the punch. Comparative results reveal an increase in the thickness of the workpiece in the dangerous section for all presented punches. The comparison was carried out with a reference tool that has a straight generatrix of a tapered surface. The best results are shown by a punch with an enlarged generatrix at the end of the working stroke. Attention is focused on conducting further research in order to study the possibility of overcritical deformation by the proposed tool.

Numerical modeling of pipe parts of agricultural machinery expansion by stepped punches

The Stress State of the Workpiece at the Radius of Matrix Rounding During Drawing, Considering the Bending Moment

It is shown that high requirements of mechanical strength, corrosion resistance and minimal losses at magnetization reversal during the passage of alternating current are imposed on the connecting elements of electric overhead lines. Sometimes the diameters of the wire ends are increased for the convenience of inserting them into connectors. In pressure treatment this process is known as dispensing. During dispensing the wall thickness of the edge sections decreases and, under certain conditions, destruction of the workpiece may occur in the form of a crack at the end. Besides, overestimated dispensing coefficients result in a loss of stability of the non-deformable part. To avoid these undesirable phenomena and reduce the production cost of tubular connecting elements, the authors of the paper analyze the factors that cause rejects during plastic deformation. It is shown that the yield point of the material and the shell thickness are the workflow main parameters that have a prevailing effect on the loss of stability of the non-deformable part of the workpiece. By changing them, it is possible to achieve the manufacture of high-quality connectors for electrical wires.

Viktor Shchetynin

Papers

Development of a method to determine deformations in the manufacture of a vehicle wheel rim

The Manufacture of Cylindrical Parts by Drawing Using a Telescopic Punch

Numerical modeling of pipe parts of agricultural machinery expansion by stepped punches

The Stress State of the Workpiece at the Radius of Matrix Rounding During Drawing, Considering the Bending Moment

Research of the Stress State While Obtaining Tapered Flares on the Connecting Elements of Electrical Wires