The design of banding shells of rotary units is analyzed. It is shown that combined welding and cast manufacturing of bandings is used in the case of large structural sizes. The basic materials (30, 35, 25 HSL and 30 HML), being used in this process, are characterized by the tendency of forming of hardening structures due to the thermal cycle of welding. As a result of this, the cracks in the heat-effected zone, which lead to the destruction of the connection under the influence of welding residual stresses. The analysis of literature sources has shown that the usage of electroslag welding is perspective during the manufacturing and welding of operational cracks. Thus it is important to define the correct parameters of the welding conditions. In the case of electroslag method they are different from the arc methods and are characterized by the larger amount. In the paper the technological process of welding of banding (tread) ring with the external diameter of 4600 mm, wall thickness of 300 mm and wideness of 500 mm, which is made of steel 35. The defining of regime parameters is made using the following recommended techniques: taking into account the chemical composition of the basic metal; according to the nomogram depending on the ratio of the thickness of the metal to the number of electrode wires; using the calculation (design) method according to the conditions of electroslag welding of the banding. Taking into account the tendency of the steel 35 to cracks forming (cracking), the evaluation of the structure and phase composition and mechanical properties of metal of heat-effected zone of the weld. In order to define the microstructure, the cooling rate of the metal in the range of structural transformations was determined and the diagram of anisothermal decomposition of austenite was used. The technique of determination of the metal cooling rate as a result of the influence of thermal cycle of electroslag welding is proposed in the paper. It is based on the usage of special nomograms which characterize the specific features of the process being studied. The cooling rate equals degrees per second when using the developed process parameters. Also the investigation of temperature distribution in the cross-section of the weld has been carried out. It is shown that there are no significant deviations of temperature when using the proposed regime parameters. This influences the reduction of the level of residual stresses along the thickness of the weld. The analysis of the diagram of austenite transformation has shown that the structure of the steel 35 in the initial state is ferrite one with the mixture of pearlite and bainite. As a result of welding carrying out the structure will have a similar composition with slightly larger content of perlite and bainite. It was defined that their content in the heat-effected zone is as follows: 39 % for ferrite, 61 % for the mixture of perlite and bainite. At the same time, the investigated technology of electroslag process ensures the slow heating and cooling of the areas around the weld and obtaining of satisfactory mechanical properties of the metal. Therefore, the combined usage of existent techniques of regime parameters determination is expedient. Also it is necessary to carry out the verification of physical and chemical properties of the metal of heat-effected zone in order to prevent the formation of hardening structures.

Індекс рубрикатора НБУВ: К233.109.1 + К587,331

Рубрики:

Вплив опромінювання на структуру і властивості алюмінію та його сплавів

Лазерна обробка металів

Шифр НБУВ: Ж44086 Пошук видання у каталогах НБУВ 

In the article, the algorithm for determination of stresses in anisotropic plates with elastic inclusions of another anisotropic material was developed on the basis of complex singular integral equations. The solving of integral equations has been carried out numerically using the method of mechanical quadratures. The strength analysis (calculation of strength) of composite plates with inclusions has been performed using the Hoffman criterion.

The microstructure and hardness of the weld joints of DOMEX 700 steel were investigated. As a result, the optimization of the parameters of robotic arc welding in the environment of protective gases was carried out taking into account the size of the energy per unit length. The optimum modes of welding were determined. The size of the deterioration area, where there is a decrease in hardness in comparison with the main metal, for a thickness of 6 mm is 2,36 mm, and for a thickness of 3 mm is 1,51 mm. The parameters of the robotic welding process in the arc mode in the environment of protective gases for the investigated thicknesses of the DOMEX 700 steel were recommended. As a result, the energy-saving conditions for welding performing were achieved ensuring the required technological strength.

Індекс рубрикатора НБУВ: К641.51-1

Рубрики:

Електродугове зварювання металів

Шифр НБУВ: Ж44086 Пошук видання у каталогах НБУВ 

Purpose. To construct singular integral equations based on solutions of the Green problem and to develop a method for calculating stresses in the vicinity of cracks in anisotropic plates of complex form. Methodology. The investigation was carried out using the theory of elasticity of anisotropic bodies and the method of integral equations. The numerical algorithm for solving the constructed equations was based on Lobatto quadrature formulas. Findings. The method of determination of stresses near cracks in plates of complex form was developed with the help of the apparatus of integral equations. The kernel of the equations were constructed on Green's solutions, which makes it possible to satisfy automatically the boundary conditions on the given contours. Green's solutions were presented and the integral equations were constructed on their basis for the half-plane with a free or rigidly fixed boundary and plates with an elliptical hole, which are weakened by cracks. Also the investigation of stress intensity factors was performed for a system of cracks placed near a straight-line boundary in a half-plane or near an elliptical hole in a plate. Originality. In the article a method for calculating the stress-strain state in anisotropic plates of complex form based on a device of singular integral equations was proposed, the kernels of which are constructed on Green's solutions. Its efficiency is illustrated while considering the plates of various forms with cracks. Practical value. The results of the research presented in this work can be used in calculations of the strength of composite plates of complex form with cracks. The results of the performed calculations give an opportunity to predict the limit equilibrium of composite plates with cracks located close to its straight-line and elliptic boundaries.

The article outlines advantages of applying a comprehensive approach to training specialists in the area of engineering education. Modern approaches to project management in production are analyzed, using the known experience of the European countries and the world. The basic tools of project management that are applied at all stages of implementation of engineering projects are described. Based on the analysis of known project management techniques, it has been established that effective engineering project management is possible by way of involving future professionals in the stages from developing the project idea, goals and objectives to obtaining the desired results and achieving the set goals. It is important to motivate students to think critically and encourage teamwork on a project. In the present article, the authors suggest to consider the process of training specialists in civil and industrial engineering through the prism of the next four phases of the project. The first phase is to prepare the project with elements of structuring. It addresses the issues of the project goals, tasks and results, risk management, project documentation, budgeting, formation and management of the project team. The second phase is project management, which includes drafting a project structural plan (PSP) and work packages, scheduling task completion, resources and costs planning, cost estimation, and time management tools. The third phase is the implementation of the project with control and monitoring. Here, future specialists are working on issues of the project control, financial monitoring, monitoring of resources, communication and interaction between teams, conflict management, change management and keeping necessary documentation. Completion of the project is the fourth stage, which is an integral element of project management. It provides for financial and analytical reporting, documentation for retention of experience, knowledge management, certification and feedback to the project team. Based on teaching practice and considerable practical experience in industry, the authors found out that the process of pedagogical training of future competitive specialists in various areas of civil and industrial engineering should be accompanied by practical and theoretical materials on modern tools for a holistic and integrated approach to project management. At the same time, taking account of the dynamics of political and economic changes in Ukraine and integration with international standards, it is necessary to take a skilled approach to the issue of production change management in the project activity. The global experience reveals that only truly successful organizations anticipate and initiate changes. Thus, the organizations themselves, their goals, objectives and tools are undergoing changes. And the issue of change management itself is the subject for further research by the authors.

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.

Application of tubular elements in the chemical industry is widely used. The special properties of materials and their reaction to the welding thermal cycle is quite complex. This is especially true of titanium alloys, which when heated are sensitive to environmental influences, require special welding techniques and undergo residual welding deformations. The welded joints of tubular elements made of titanium alloy brand PT-7m, which undergo transverse deformations due to welding, are studied. It is necessary to ensure high-quality sealed welds. Analysis of the literature has shown that to obtain a guaranteed penetration it is necessary to increase the power of the arc discharge or perform multi-pass welding. This will provide larger cross sections of welded parts and should provide the specified strength characteristics. However, this technology, in turn, leads to an increase in residual deformation in the vicinity of the welded joint due to the intensive increase in the coefficient of linear expansion when heating the material. Also, the special thermophysical properties of titanium alloy such as increasing the affinity for gases when heated, increasing the grain size lead to a decrease in strength properties. In the presented work it is proposed to use a mechanical angular deformer with an indicator head and a reference base for the study of transverse residual deformations. Peculiarities of measuring sockets and methods of their preparation are revealed. A calculation scheme for determining the amount of deformation has been developed, which has been tested on flat welded specimens and transferred to tubular elements. The sequence of deformation measurement process is described and the peculiarities of their formation on flat samples and tubular sections are studied. The constructive decision of a welded joint of pipes which provides use of a compensation ring is offered. This approach allows to provide reliable protection of the root of the seam and its optimal formation with minimal residual deformation. At the same time it is possible to reach the reproducible form of a dagger of similar penetration in one pass. The result is a welded joint of the lock type, which is sealed and has a free formation of the seam root with high-quality protection by the gas atmosphere. The use of pulsed arc welding with a non-fusible electrode in an argon environment with filler wire allows to minimize the thermal impact on the base metal. Statistical processing of experimental data on the parameters of the welding mode and their influence on the residual transverse welding deformations is carried out. To obtain an unambiguous statistically reliable answer about the valid law of distribution of experimental data of the results of strain measurement, the balancing procedure and the development of an analytical approximation distribution model are involved. It is shown that the measured values of the residual transverse deformation of the welded assembly are correctly described by the Laplace distribution, which predicts (probability not worse than 90 %) a decrease in the average value of the deformation value by 1,3 times.

Currently, there is a tendency to increase the depth of gaseous and liquid fossils extraction. Therefore, prospecting and developing new deposits is promising. There is also a need to create new freshwater sources and implement relevant geological work based on this need. It is essential to have information about the characteristics of the explored slabs and the geology of the fields in general. Implementation of engineering and geological core drilling exploration is the most acceptable and provides the necessary data. Here, the peculiarities of the technological schemes of the process implementation make it possible to obtain separate sections of structures at a depth of the drilling equipment. It is essential to use traditional equipment, recommended for decades and provides the necessary results [1 - 3]. In the drilling process, you can achieve different diameters and depths of wells execution, obtain fossil samples etc. Engineering and geological exploration drilling is now taking on increased use in various industries [3]. Therefore, the problem of providing highquality drilling tools, the stability of their operating characteristics, and the possibility of usage in different conditions is an urgent need today. Modern drilling problems determine the usage of components of the core set with the appropriate physical and mechanical characteristics. Especially it relates to elements close to the drilling tool and the place of fossil; destruction - drill pipe. It is installed immediately after the crown core drill and receives almost the same loads and effects during working [1 - 3]. Conditions for the implementation of the process of core drilling are characterized primarily by the effect on the elements of the significant axial and twisted core set forces. There is the influence of the corrosive and active environment of the fossil in the washing and lubricating liquids well, etc. High temperatures are also observed at the drilling sites [3], which negatively affect the working tool and speed up its operation. As a result, there is an intensive shock, and abrasive core pipe wear and operation indicators change their constructive size. As a result, it is necessary to replace the operated drill string periodically. Considering modern technical and economic factors, it may be decided to repair a pipe to its original size in many cases. There are tasks for providing the appropriate characteristics of the core pipe surface. It is possible to model such properties of the new surface that functionally the best meet the conditions of the drilling process of a given geological formation. The peculiarities of applying the therapeutic layer on the surface of the core pipe are investigated in work. The experience shows that using electric arc surfacing under the flux layer is expedient. This provides the necessary adhesion of the applied layer and promotes obtaining resistance to the operation surface of the core pipe. At the same time, there is high-quality protection and the possibility of additional alloying through the flux-slaggy welding bath. Using electrode powder type wires creates conditions for flexibility to achieve the established characteristics of functional layers [4 - 6]. The filling flux, located in the cross-section of the electrode wire, can be easily changed by chemical composition. At the same time, it is possible to make relatively small parties of a wire with the set characteristics. The technological scheme justification about the core pipe surfacing is performed. It provides the previous displacement of the electrode butt size from the zenith of the core pipe to prevent the welding bath from spreading. The structural pipe size , the requirements for residual deformations, and the conditions of shapping the welded layer show the practicality of welding on a helix.