Machine-building Structures Research Articles

Investigation of vibrations of complex mechanical systems

In this work, a unified methodological approach and software for the calculation of structural elements under the action of vibration loads are proposed. Algorithms for determining the dynamic characteristics of machine-building structures are based on methods of forming Rayleigh-type functionals and minimizing them by coordinate descent. This approach avoids the problems associated with the formation, saving and handling of global stiffness and mass matrices. This makes it possible to significantly save the RAM of a personal computer when solving large-scale problems. The developed software is formed according to the modular principle, which makes it possible to improve and develop this package of application programs taking into account modern needs. The proposed software approach was debugged on a large number of applied problems and implemented in engineering practice. The urgent task of determining the stability of the Pico21 centrifuge movement has been solved.

The Stress State of a Thick-Walled Hydraulic Press Cylinder with Concentrators

The article deals with modeling and calculations of volumetric machine-building structures with complex geometry. The relevance of the work lies in the fact that its methodology and results can help design massive structural elements complex in shape, including cylinders of powerful hydraulic presses. Attention is paid to the problems of reducing the metal content of machine-building products and the safe conditions of their operation. Theoretical and applied work is based on numerical methods using analytical solutions to assess the reliability of computer calculation results. The choice of research method is because analytical solutions for massive parts of such a configuration are too complex for numerical implementation. Experimental methods are too expensive and not so universal as to sort out possible variants of shapes and sizes. For the actual model of the press, the capabilities of the finite element method implemented in the ANSYS multipurpose complex were selected and rationally used. The results of the calculations are summarized in the table and shown on the graphs of the stress distribution. Based on the performed calculations (with a reliability check based on the formulas of the theory of elasticity for simplified calculation schemes), conclusions were made to ensure a more even distribution of stresses and a reduction in the metal content of the product.

Computational model of soldered details heating with considering the magnetic field distribution

The main purpose of the software application is to simulate the temperature field in the process of induction pack of elements of machine-building structures of the fuel profile, which will further improve the quality of connections. The program simulates the flange heating process during the induction brazing process. The purpose of the developed module is to provide experimental studies of the induction soldering process. The program provides graphic information during the technological process, provides the ability to adjust the technological parameters, and allows the development of the technological process.

An Integrated Approach to the Optimization of Plates in Plane Stress State Operated at High Temperatures

Many critical elements of building and machine-building structures during their operation are in difficult operating conditions (high temperature, aggressive environment, etc.). In this case, they can be subject to a double effect: corrosion and material damage. Corrosion leads to a decrease in the cross-section of a structure, resulting in stress increase therein. In turn, damage to the material is accompanied by the appearance of microcracks and voids therein, due to inelastic deformation (creep), leading to a deterioration in its physical properties (for example, the elastic modulus) and a sharp decrease in the stress values at which the structure is destroyed. This article continues the study in the field of the optimal design of structures subject to the aforementioned double effect by the example of the optimization of plates with holes in the plane stress state, exposed to high temperatures (in previous works, the use of this approach was demonstrated in the optimization of the bending elements of rectangular and I-sections). Used as a corrosion equation is the modified Dolinsky mode, which takes into account the (additional) effect of the protective properties of an anticorrosive coating on the corrosion kinetics. Taken as a kinetic equation describing the change in material damage, is Yu. N. Rabotnov’s model, which enables to determine the duration of the incubation period of the beginning of the tangible process of material damage. To study the stress state of a plate, the finite element method is used. With a given contour of the plate, found is the optimal distribution of the thickness of the finite elements into which the given plate is divided. Acting as a constraint of the optimization problem is the parameter of damage to the plate material. The approach proposed in this work can be used to solve similar problems of the optimal design of structures operating under conditions of corrosion and material damage, using both analytical solutions and numerical methods.

Calculation of elements of machine-building structures on vibration strength

A method and an automated system for calculating structural elements for vibration strength have been developed. The calculation algorithms are based on a new method of forming Rayleigh-type functionals and minimizing them by the coordinate descent method. The use of the coordinate descent method avoids the problems associated with the formation, storage and operation of global matrices of stiffness and mass. This makes it possible to solve large-scale problems using only the operational memory of the PC. The developed approach allows to solve problems on own and forced fluctuations. The software is formed on a modular basis, which allows you to improve and expand this package of applications. The software has been tested on a large number of test and application tasks. The proposed calculation method and the developed automated system were implemented in engineering practice.

Preface

The annual International Conference “Actual Problems of Engineering Mechanics” is held for the eighth time. The conference is organized by the Odessa State Academy of Civil Engineering and Architecture (Ukraine, Odessa). As partners involved colleagues from Ukraine (G.S. Pisarenko Institute for Problems of Strength of the National Academy of Sciences of Ukraine), Greece (University of West Attica) and Croatia (University «North»).Unfortunately, because of COVID-19, the conference participants were unable to get together, as in previous years, and were forced to limit themselves to online communication. Nevertheless, the conference in this format of the meeting aroused great interest.The scientific program of the conference included plenary and sectional reports in the following areas:1. Fundamental research in mechanics.2. Computer mechanics.3. Building structures.4. Machine building structures.5. Construction materials.More than 500 participants were registered, 140 reports were submitted. The conference was attended by scientists from 14 countries of the world - Ukraine, Greece, Spain, USA, France, Vietnam, Thailand, China, Japan, Croatia, Poland, Belarus, Russia, Uzbekistan.Conference materials are available in pdf format.List of committees are available in the pdf

OSCILLATIONS OF LAYED STRUCTURES WITH CONSOLIDATED MECHANICAL CHARACTERISTICS

Modern industry requires the creation and use of materials and structures with improved performance. Such structures include layered structures made of com-posite materials. Layered systems made of high-strength composite materials with different layers have found wide application in aviation technology as elements of the bearing surfaces of aircraft, as well as in many other industries. The use of composite plates in loaded structures is one way to improve the weight characteristics of rocket and space technology. Also layered structural elements are widely used in transport engineering, used in construction practice. Multilayer systems in the conditions of bending deformation are the most rational in terms of strength and rigidity. Thus, the improvement of methods for calculating inhomogeneous layered structures is an urgent task. Along with the methods of non-destructive testing, defectoscopy of structures using hardware methods, analytical research methods remain relevant, which allow to predict the possible destruction of the structure. When designing equipment, it is necessary to take into account the real operating conditions of structures. In the process, the mechanisms work under the action of vibration loads, so determining the dynamic characteristics of structures is an urgent task. This determines the need to study the oscillating processes taking into account the real conditions of vibration load, which will determine the optimal design parameters and modes of operation of the machine with the maximum distance from critical modes that are dangerous. One of the reasons for the destruction of elements of machine-building structures is that they resonate. Therefore, the problem of forced oscillations needs to be solved. To solve this problem, it is necessary to determine the natural frequencies and their corresponding natural forms of oscillations. The paper presents a method of calculating a layered structure to determine the physical characteristics for the whole package, taking into account the physical and mechanical characteristics of each of the layers. This approach allows to determine the dynamic characteristics and stress-strain state of multilayer composite structures, using classical equations for homogeneous struc-tures. This approach greatly simplifies the equation and allows you to find a solution that can be used in the design of structures made of composite materials under vibration loads.

USAGE OF CONSTRUCTION-ORIENTED SOFTWARE SCAD FOR ANALYSIS OF WORK OF MACHINE-BUILDING STRUCTURES

Purpose. In the case of analysis of work of the machine-building structures, the direct usage of construction-oriented software developments is impossible, since ideology and methodology for solving various tasks in construction and machine-building are different. Therefore, in the conducting of practical calculations, there is a need for a certain adjustment of the approaches put in the program complexes and their adaptation to the engineering industry. The presentation of the author's experience of the construction-oriented software SCAD usage for Windows for analyzing the work of various machine-building structures, their components and assemblies is the immediate purpose of the publication. Methodology. During a long period of time the author was engaged in analyzing the work of building, mainly thin-walled, steel structures using the Finite Element Method based on the SCAD for Windows software package. At the same time, a considerable number of machine-building structures were considered, including railroad rolling stock units. Most of these tasks grew into a scientific and research problem that needed to be thoroughly researched and analyzed before giving design recommendations. Findings. The publication presents more than a dozen different tasks, typical for the machine-building industry, which the author had to deal with. Static and quasi-static problems, the problem of motion in time, the contact problem, the problem of the cracks deve-lopment, the physical and geometric non-linearity are among them. Accordingly, for each of these problems the main challenges, features and practical techniques developed during the work are presented, as well as the constructed finite element models are presented as an illustration. Originality. The experience of construction-oriented software product usage on the basis of the Finite Element Method for analyzing of the work of machine-building structures is generalized. A number of practical methods and approaches to the solution of various problems in the machine-building sphere are set forth. Practical value. The application of the given information, methods and approaches allows not only to solve concrete practical problems of the machine-building sphere, but also to obtain correct and practically acceptable solutions.

Substantiation of Thin-Walled Structures Parameters Using Nonlinear Models and Method of Response Surface Analysis

The article deals with the development of approach for providing of structural strength of complicated thin-walled machine-building structures, which operate in the conditions of geometric and physical nonlinearities using design solution validation. The developed approach is based on the use of mathematical model for stress-strain state taking into account geometric and physical nonlinearities and methods of approximation for constructing functions describing the evaluated characteristics of the object under study. The various factors behind the search for design solutions (including characteristics of strength, rigidity, technological and economic factors), are being added into this function. The developed algorithm for rational parameters search, which takes into account the peculiarities of the response surface shape observed in solving applied problems, is applied to them. In this case, the solution is sought over the whole range of parameter changes. Thus, in the search process, global trends of changes in design decisions are taken into account, and not local ones, as in other approaches. This allows obtain a rational solution that is stable to changes in parameters, which are possible in course of design work and production conditions. Investigations are illustrated on the freight rail-car, tractor cabin frame, carrier personnel hull.

Discrete and Continual Strengthening of Contacting Structural Elements: Conception, Mathematical and Numerical Modeling

The paper proposes a variant of discrete and continual strengthening of contacting elements of machine-building structures. One of the parts is strengthened discretely, and its counterpart is strengthened continually. The resulting pair combines positive qualities of two different types of strengthening methods. Investigations on stressed-deformed state of the treated fragments provides a basis for conclusion about high efficiency of the proposed combined strengthening method. While applying the method mechanisms of negative feedback between the stages “loading – contact interaction – friction – wear” are involved unlike with conventional versions of strengthening technologies. In this way, positive integral effect results from an application of the developed strengthening technology. This effect is significantly higher than the sum of effects obtained owing to application of every strengthening technology. In this case a favorable distribution of contact pressures between contacting bodies has been ensured. This, in its turn, leads to a decrease in wear that prevents a sharp increase in loads acting between bodies. Thus stabilization of the investigated processes occur. The papers considers stress-strain state of a representative fragment of the investigated system in order to demonstrate positive effects arising from the contact of strengthened bodies. Results of the calculations indicate validity of forecast assumptions. Indeed, the strengthened zones can bear high loads. However, due to high tribo-mechanical properties of the material in the hardened zones, friction and wear in them are much lower than for a base material. Due to this, all positive components of the total effect are formed. This effect is supported by the fact that a counterpart is processed continually. In particular, metals from aluminum-type materials are coated with a thin layer of oxides by forming them in a strong electric field of a special medium. Formed solid phases of oxides serve as a structural basis for formation of surface layers. In combination with discretely strengthened surfaces of counterparts the formed pair acquires high strength, antifriction and anti-wear properties.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ РАСЧЕТНО-ДИНАМИЧЕСКИХ МОДЕЛЕЙ ПОРТОВЫХ КРАНОВ НА ОСНОВЕ ОДНО- И ДВУМЕРНЫХ КОНЕЧНЫХ ЭЛЕМЕНТОВ

The finite element method is widely used in strength calculations of machine-building structures and has a significant list of basic finite elements used to build the discrete finite element computable dynamic models of load-lifting cranes. The article describes static and dynamic characteristics of a computable dynamic model (CDM). CDM is designed to determine stiff features (developing stiffness matrix) and to define the deflected mode of the structures by using different means in structural mechanics, which have been chosen by a designer. Dynamic parameters are determined according to CDM to describe eigen and forced oscillations of crane structures under external action. The quality analysis of CDM of bearing metal structures of bridge cranes built on the basis of bar-shaped open and closed profiles and plate finite elements is based on comparison of the total flexural rigidity of the girders and eigen frequencies and eigenforms of oscillations of their CDM. The general methodology for building equations of motion for crane systems with many (n) degrees of freedom is based on their bar and plate finite elements, the latter are based on Kirchhoff theory of plates. Comparative analysis of the eigenforms of oscillations of the plate and bar CDM of crane with 130/32 t and 33.5m span has been given, the advantages of two types of CDM important for design analysis of strength and seismic resistance in designing bridge cranes are revealed. There has been substantiated the need to develop new methods of calculating finite element models taking into account the dimensional effect. The structures are recommended to regard as unified dimensional systems allowing for different types of non-linearity.

Performance assurance of mechanical engineering construction in the existence of cracks

The purpose of this paper is to consider the development of engineering ways of preventing the further development of through cracks in the sheet elements of the complex technical structures. The latest individual approach to the assessment and assurance of performance of structures with cracks, which is to take into account the features of their operation, has been applied in this work. Preference is given to methods that reduce the concentration in the danger zone. Studies have shown that the most appropriate and effective ways to prevent the further development of a through crack are the structural methods and combinations of the structural and technological methods. The effectiveness of these methods was determined on the basis of the strength uniformity approach of structural elements with a crack. The criterion of strength uniformity from the position of fatigue and brittle strength with an error on the safe side is the value of theoretical stress concentration factor [K]. The[K] value was made on the basis of generalization and analysis of cases of crack formation, the results of tests of typical components of hull structures and welded joints. The safe concentration of stresses near the holes of various purposes in the members of the machine-building structures is in the range from 2 to 4. Taking into account the relevant requirements for the ratio of the radius of curvature and the width of the cutout, we obtain 3.5. The value of the criterion К1 is determined by the ratio of the calculated crack length to the diameter of the hole drilled at its ends and the location of the crack.

Thin­walled structures: analysis of the stressed­strained state and parameter validation

The approach is developed to substantiate technical solutions for thin-walled machine building structures. It implies that the problem is considered in the space of generalized parameters. These parameters combine design and technological factors, as well as operating conditions. In addition, we introduce criterial and constraint dependences to a given space. In the generated uniform parametric space an approximated response surface is constructed, which stretches over a discrete set of solutions to analysis problems. For example, based on the results of examining the stresses-strained state, maximum stresses or displacements, mass or other controlled magnitudes are determined. They are unambiguously computed (a point in a common parametric space) for a specific set of variable generalized parameters. Having a cloud of such points, it is possible to construct an approximated response surface. Approximation constraints are also built on it. Next, by using the methods of nonlinear programming, we search on the set of permissible values for the minimum (or maximum) of quality function of the examined structure. Specifically, for the thin-walled structures, important parameters are the shape and dimensions in a plan, as well as thickness of individual elements. Using a number of structures as examples, authors of present work performed analysis of influence of these parameters on the strength of designed structures.

Development of Timing of High Efficiency for Diesel Engine

In this article questions on development and calculation of a perspective design of the gas-distributing mechanism created at level of the invention, ICE of locomotives are considered. The technique of design of the main geometrical and thermodynamic features on an example of one of the presented technical solutions is offered. Results of researches are recommended to design, research and machine-building structures for their possible use in practice.

Method of estimation of residual operation life of materials under long-term statistic loading

In the modern machine building production with high level of competitiveness, the great importance plays the performance and reliability of parts and components of various machine building structures, which often operate under a power impact of various factors. In this regard, there is a need to improve the methods of diagnostics of the condition of the material for fabrication of these constructions. The study determined the current value of the accumulated damage of the material, which was performed using the proposed experiment-calculated method of estimation of the residual operation life of the material under the long-term statistic loading, and which was based on the experimental determination of three values of the accumulated damage at the initial stage of damage. The authors proposed to use the value of specific work of deformation as a criterion of damage, which allowed the identification of damage parameter as the ratio of the current and total values of the specific work of deformation. The developed method of kinetic diagrams of damage allows the reliable estimation of the exhausted and residual operation life of the material. Thus, the results of the research are of scientific and practical interest. The authors showed the possibility of constructing a method of rapid diagnostics estimation of damage of the material in relation to the operating structures

Complex Research of Perspective Suspension for Locomotives

<b> </b>In this article questions on creation and calculation of a perspective design of adaptive torsion suspension for the locomotives, including hydromechanical dampers of fluctuations of adaptive type. The design procedure of the main kinematic and geometrical characteristics on a locomotive example 2ТЭ10Л, supplied with the specified technical solutions, and studying of fluctuations and power loading of its running gears is offered. Thus, the dynamic settlement scheme on the basis of Foygt-Kelvin's elastic and viscous model is developed. The bench pilot studies, allowed to specify parameters and characteristics of the above-stated designs are carried out. Expected economic effect of possible introduction of development will make 850 thousand rubles a year on one locomotive. Materials of this article were discussed at various conferences of leading higher education institutions of the Russian Federation. Results of researches are recommended to design, research and machine-building structures for their possible use in practice.

Modeling problems in the strength analysis of machine-building structures

Modeling problems in the strength analysis of machine-building structures

New computational and experimental methods for determining the elastic and strength characteristics of materials and for predicting the behavior of structures

Experimental methods for determining the physicomechanical characteristics of powder, polymer, and composite materials under thermal-force static and dynamic loads are presented. The results of the experimental investigations are used in numerical methods for calculating the stress — strain state and the stability and for describing the supercritical behavior as well as in methods for efficient design of strong machine-building structures made from new constructional materials.

A system for the self-excitation of oscillations in elastic structures during dynamic tests

The working principle is described and the technical characteristics of a developed system for the self-excitation of oscillations in elastic bodies with a resonant frequency of a selected tone are presented. This system, which makes it possible to maintain the required level of oscillations at a given point and to monitor the frequency of the phase resonance automatically with a rapid response, can be used to conduct bench resonance and frequency tests of different machine-building structures.