OPTIMAL DESIGN OF CYLINDRICAL GEARS WITH CONVEX-CONCAVE CONTACT: OBJECTIVE FUNCTION AND VARIABLES PLANNING

Reducing the mass and dimensions of gears is an actual task of modern mechanical engineering. One of the perspective ways to solve it is the use of gearing with a convex-concave contact of the teeth. Therefore, the study is devoted to the development of methods for the optimal design of cylindrical gears with convex-concave contact of the working surfaces. Optimality criteria: minimum contact stresses and (or) minimum relative sliding velocities, taking into account design, geometrical and technological constraints. C-C gearing was chosen as the object of research. It was proposed by the Slovak scientists M. Boshanski and M. Veresh. An objective function is constructed for the case of minimizing contact stresses. The optimality criterion is formulated as follows: contact stresses σH in the mesh must take the minimum possible value when all constraints are met. An objective function is also constructed for the case of minimizing the relative sliding velocities of profiles. The optimality criterion is formulated as follows: the relative sliding s velocities of profiles λ at the extreme points of mesh must take the minimum possible value when all the constraints are met. Variables planning are defined. These are pressure angle at the pole αС, the curvature radius at the upper part of contact path rkh, and the curvature radius at the lower part of contact path rkd. A method for solving the problem of optimal design is chosen. The method of probing the space of design parameters was chosen from all the variety. The points of the LPτ-sequence are used as test points. The method allows you to operate with a significant number of parameters – up to 51, provides a sufficiently large number of evenly distributed test points – up to 220. In further studies, it is planned to form a system of constraints on variables planning, to develop methods and algorithms for solving the problem. Also carry out test and verification calculations to confirm and evaluate the theoretical results. Keywords: gear, convex-concave contact, optimal design, objective function, variables planning

MODERN TRENDS OF DESIGN, RESEARCH AND USE OF HYDRAULIC MACHINES IN DRIVES OF MECHANISMS AND TRANSMISSIONS (REVIEW ARTICLE)

The work is devoted to an overview of modern trends in the design, research and use of hydraulic machines in the drives of mechanisms and transmissions. The analysis of the use of hydromechanical transmissions has been carried out. The advantages and disadvantages of hydromechanical transmissions in comparison with mechanical ones are described. A brief overview of modern approaches to the design of new products, taking into account the existing information technologies, is carried out. We have analyzed modern software products designed to support the project at different stages of the product life cycle. It has been found that at the present time the appearance of individual variants of highly specialized software with a modern interface for synthesizing the structure of a designed product does not make it possible to solve the problems of synthesis and structural analysis of hydro-mechanical transmissions. A review of the analysis of operational factors affecting the fault tolerance and operating parameters of hydrostatic transmissions in general and hydromechanical transmission in particular is carried out. We have also considered the examples of technical solutions that allow to reduce the number of failures associated with the influence of one factor or another, as well as allow to reduce its influence on the parameters of the mechanism. The analysis of sources with information on the study of the parameters of hydrostatic transmissions using field tests or the mathematical apparatus developed by the authors is carried out. The ways of solving problems arising at the stages of design research are outlined. Keywords: design, hydrostatic transmission, hydromechanical transmission, influence of operational factors, synthesis

THEORETICAL BASIСS OF PROVIDING THE TECHNICAL CHARACTERISTICS OF MILITARY AND CIVIL VEHICLES BY JUSTIFICATION OF THE FORM AND PROPERTIES OF THE MATERIALS OF CONTACTING ELEMENTS

Elements of constructions of modern military and civil vehicles usually work in conditions of high contact loads. Аt the stage of their creation, strength studies are carried out using traditional models of contact of bodies of nominal shape. Нowever, the real structural elements have deviations from such models, which are due to design and technological factors: macrodeviation of the shape, surface roughness, strengthening etc. Such perturbations of nominal parameters have a significant effect on the distribution of contact pressure between the elements of military and civil vehicles, however, traditional methods for studying the stress-strain state of contacting bodies do not make it possible to take such factors into account fully, collectively and exhaustively. To eliminate the existing contradiction, a semi-analytical method is proposed, which is based on the development of variational principles and boundary-element sampling. The created models make it possible to take into account the regularities of the influence of shape perturbations and properties of the surface layers of contacting bodies on the stress-strain state. As a result, it becomes possible to justify favorable perturbations by strength criteria. Such models and methods are offered to the work, and on their basis it’s proposed the implementation of research elements of military and civil vehicles for appointment to ensure world class the technical and tactically technical characteristics. Ключові слова: military and civilian vehicles; design and technological factor; stress-strain state; contact interaction; strength

IN MEMORY OF PAVLO MYKOLAYOVYCH ANDRENKO

The bright memory of Pavelo Nikolaevich Andrenko will forever remain in the hearts of all who knew him

GENERAL ANALYSIS OF STRESS AND DEFORMATION OF PARTS MOVING WITH HIGH VELOCITY IN A LIQUID OR GAS (REVIEW ARTICLE)

The article provides an analytical review and analysis of stresses and deformations of parts moving at high speeds in a liquid or gas. The working conditions of materials and parts of turbines (blades, rotor and casing) operating at high temperatures and loads are analyzed. The main ways of solving the problem of ensuring the strength of such parts are presented. The main ways to solve the problem of reliability of parts or the product as a whole are given: mathematical modeling (calculated determination of strength, durability and reliability); physical modeling (model testing); testing of full-scale products in reproducible real or operational conditions.It is impossible to speak about the strength of a part only from the calculation of deformations and stresses, even taking into account their change over time, so it is necessary to have strength criteria that establish the relationship between the strength parameters. It is emphasized that in the general case, the criterion of strength should answer the question: will the part collapse or not with the known laws of change in time of stresses, strains and temperatures It is shown that the considered standard characteristics of creep and long-term strength can be directly used in calculations only for those parts in which the uniaxial stress state at constant stresses and temperature is realized, when the working conditions of the material fully meet the test conditions of materials.An analytical view of deformation diagrams is considered as the main means of carrying out practical calculations of material strength. It is shown that in order to determine the stresses and strains in parts that move at high speeds in a liquid or gas, it is necessary to take into account the model of parts exploitation, the processes of creep and thermal fatigue of the material, and the unsteadiness of load processes. Keywords: stresses and deformations of turbine parts; deformation diagram; operating model of turbine parts; creep and thermal fatigue; nonstationarity of loading processes

ALGORITHM FOR EVALUATING MILITARY TECHNICAL EFFICIENCY OF USING MILITARY VEHICLE EQUIPMENT BY PARTS AND DIVISIONS OF THE NATIONAL GUARD OF UKRAINE IN THE COURSE OF BATTLE ACTIONS (OPERATIONS)

The article argues the relevance of determining the indicator of military-technical efficiency of the use of military automobile equipment by units and subunits of the National Guard of Ukraine when performing battle actions (operations). Currently, special indicators are used to assess the state of military automotive equipment, which are a numerical expression of the gauges or their relationship. Existing methods of planning technical support, methods for predicting the quantitative assessment of the military-technical efficiency indicator of the use of military automotive equipment during hostilities need further improvement. The article proposes to use a comprehensive indicator, a generalized coefficient of military-technical efficiency of using military automobile equipment during combat actions (operations), as an indicator of military-technical efficiency of using military automobile equipment in combat conditions, and to determine directions for increasing the efficiency of using military equipment. Keywords: automotive technical support; military automotive equipment; military-technical efficiency of using military automobile equipment; performance indicators; technical readiness coefficient; machine use efficiency during battle actions (operations)

COMPUTATIONAL-EXPERIMENTAL STUDY OF CONTACT INTERACTION OF BODIES WITH NEARLY FORM SURFACES

In many constructions, their elements are in contact with nominally matching (congruent) surfaces. In reality, this contact is disturbed due to deviations in the shape of these surfaces from the nominal. To study the effect of this perturbation on the distribution of contact pressure, the analysis of the stress-strain state of the body system of punched sheet-die is carried out. The middle element of this system deviates from the nominally flat shape. This causes a change in the contact pressure distribution. The proportionality between the clamping force and the level of contact pressure is also lost. The reliability and accuracy of the results obtained by numerical calculation have been experimentally confirmed. Keywords: stress-strain state; contact pressure; contact interaction; method of variational inequalities; Kalker variational principle; finite element method

HISTORY OF DEVELOPMENT AND MANUFACTURE OF TRACTORS AND PRIME-MOVERS BY THE STATE ENTERPRISE «KHARKIV DESIGN BUREAU OF ENGINEERING NAMED AFTER A. A. MOROZOV» AND STATE ENTERPRISE «MALYSHEV PLANT» (REVIEW ARTICLE)

The review article systematizes information and studies the history of designing tractors and prime-movers at the State Enterprise «Kharkiv Design Bureau for Mechanical Engineering named after A. A. Morozov» and their manufacture by the State Enterprise «Malyshev Plant » from the origin of such production in Kharkiv to the present time. The role of Kharkiv in providing the country with special equipment is revealed. Detailed biographical information about chief designers of this technique (B. N. Voronkov, N. G. Zubarev, M. N. Shchukin, A. I. Avtomonov, M. D. Borisyuk, A. D. Motrich, M. P. Kalugin, P. I. Sagir, B. I. Kalchenko) provided, their role in the development and improvement of designs of special-purpose machines is indicated. The main technical characteristics of basic models of tractors and prime-movers are presented. The main problems in the production of these types of equipment are mentioned. The article contains information about various modifications of AT-T, their main differences and purposes are indicated. Keywords: tractor, prime-mover, SE «Kharkiv Design Bureau of Engineering Named after A. A. Morozov», SE «Malyshev Plant», National Technical University «Kharkiv Polytechnic Institute»

SENSITIVITY OF STRENGTH, RIGID AND DYNAMIC CHARACTERISTICS OF THE CONSOLE ROTOR TO VARIATION OF DESIGN PARAMETERS

The analysis sensitivity of strength, rigid and dynamic characteristics of the console rotor to variation of design parameters in paper describes The speed of rotation of the shaft, the material of the impeller vary. The dependences of radial and axial displacements on the angular velocities of rotation and the modulus of elasticity of the impeller material are established. For objects of the type of rotary systems with a cantilever arrangement of the impeller, not one, but a set of criteria has been introduced into consideration, which should be taken into account in the research of this type of objects. The tendencies of change of the first and second critical rotational speeds from the modulus of elasticity, rotor rotational frequencies and density of the impeller material are also determined. On this basis, recommendations have been developed for determining the design parameters of the rotor part of the air blower with a cantilevered impeller. Keywords: air blower; critical rotation speed; natural vibration frequency; rotary system; stress-strain state

DEVELOPMENT OF STATISTICALLY AVERAGED MODELS OF DEFORMATION OF MATERIALS WITH RANDOM NETWORK STRUCTURE OF DIFFERENTLY ORIENTED FIBERS

The paper describes the developed statistically averaged models of deformation of materials with a random network structure of differently oriented fibers. New methods of stress-strain analysis and micromacromechanical models of material deformation in the volume of bodies made of material with a network structure taking into account structural and physical nonlinearities have been created. These models are based on the micromechanics of network structures at the level of statistical sets of their chains. The novelty of approaches, models, methods and results is the creation of theoretical foundations for the analysis of the deformation of non-traditional network materials. Nonlinear mathematical models of material deformation in the form of a chaotic network structure of one-dimensional fragments are proposed, which are constructed involving fundamentally new approaches to the description of physical and mechanical properties at the micro level of statistical sets of fiber chains and spatial homogenization of their macroproperties. Compared to traditional models, they more adequately model the features of material deformation in the form of spatial chaotic and ordered network structures, as they do not involve a number of additional non-physical hypotheses. This creates fundamentally new opportunities not only for analyzing the properties of such materials, but also when creating new ones with specified properties. Using the created methods, models and research tools, the basis for solving a number of model and applied problems has been created. The nature of deformation of non-traditional materials with a network structure of one-dimensional elements is determined. The macro-properties of these materials are established on the basis of the developed micromechanical models, variational formulations and averaging methods. Keywords: stress-strain state, network structures, contact interaction, finite element method, contact pressure, machine parts, variational formulation