scholarly journals Performance assurance of mechanical engineering construction in the existence of cracks

2019 ◽  
Vol 287 ◽  
pp. 02004
Author(s):  
Nikolay Velikanov ◽  
Sergey Koryagin ◽  
Oleg Sharkov

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.

2014 ◽  
Vol 14 (07) ◽  
pp. 1450019 ◽  
Author(s):  
Pedro Gonzaga ◽  
Faustino N. Gimena ◽  
Lazaro Gimena

This article presents the differential equation in the global coordinates governing the structural behavior of 3D curved beams existing in building structures and civil works. This differential equation presented is of the lower-triangular form, which allows us to obtain the transfer matrix, also of lower-triangular form and with unit diagonal, through simple integrals. The stiffness matrix is determined from the transfer matrix expression, only by reordering operations, without employing additional structural methods, energy theorems or other. This rearrangement can be more easily done under the global system, compared with the natural reference system, since the order of the matrices involved has been reduced. The examples presented show the process to apply this general procedure to derivation of the stiffness matrix of a member from its transfer expression, through reordering operations.


Author(s):  
Maryna Bondarenko ◽  
Mykola Tkachuk ◽  
Andriy Grabovskiy ◽  
Iryna Hrechka

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.


Author(s):  
Sergej Aleksandrovich Nazarenko ◽  
Svitlana Ivanivna Marusenko ◽  
Olena Ivanivna Zinchenko

2020 ◽  
Vol 2 (1) ◽  
pp. 97
Author(s):  
Nelia Yo. Romaniuk

The purpose of the article is to investigate the peculiarities of the modernization of the South-East region of Ukraine in the latter half of the 19th and at the beginning of the 20th century as well as to specify the contribution of entrepreneurs in the formation of the production industry. Methods of research: analysis and synthesis of available information, logical-analytical, problematic-chronological, system-structural methods. The principles of historism, objectivity and consistency, which were the basis of the indicated research methods, made it possible to consider the essence of processes and phenomena, to keep track both of the manifestations of general patterns in the socioeconomic processes in the development of the South-East region of Ukraine and their specific character under the influence of entrepreneurial activity, and also to draw certain conclusions. Key findings: the contribution of entrepreneurs of the South-East Ukraine, which became an important factor in the acceleration of socioeconomic modernization during 1861–1914, is highlighted in the article. Heavy industry became the basis for the modernization in the context of reforms in the latter half of the 19th century, namely production industries related to the extraction of minerals and their processing. During this period, three powerful industrial centers formed: Donetsk coal and metal, Kryvyi Rih ironstone and Nikopol manganese. An important feature of the entrepreneurship development in the South-East region of Ukraine in 1861–1914 was the representation of all population strata: peasants, Cossacks, townsmen, intellectuals, merchants, nobles and foreign capital. They acted as private businessmen and co-owners of collective enterprises. The most common organizational form of entrepreneurship in this period were joint-stock companies, the role and number of which was constantly growing. Conclusions. At the beginning of the 20th century, the Donetsk and Krivyi Rih region became a powerful center of heavy industry (coal, metallurgy, metalworking, machine-building, and chemical). The result of entrepreneurial activity was an increase in production volumes, profitability, the creation of a large number of jobs, the improvement of organization and production technology. Practical value: is determined by the emphasis of the researchers on the need to comprehend the phenomenon of entrepreneurship, its historical lessons, taking into account the powerful factors of this phenomenon and its influence on the contemporary and future civilization development of Ukraine; it is recommended to be used by authors for writing articles, manuals and for development of special courses. Scientific novelty: consists in formulating and studying a relevant topic, which has not received a comprehensive study in historical science. The independent role of entrepreneurship in the capitalist economy at the regional level is shown for the first time; it was proved that the South-East region of Ukraine was the one where the preconditions for the development of private initiative were formed, and also the spread of market relations and entrepreneurship took place; the participation of entrepreneurs in economic modernization as well as the most profitable branches in the region are characterized. Originality: the generalization of experience, practices of profit-making economy of the entrepreneurial strata of the region is used. Type of article: descriptive.


Author(s):  
Nikolay Nikitovich Panasenko ◽  
Alexey Vladimirovich Sinelshchikov

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.


2019 ◽  
Vol 18 (3) ◽  
pp. 240-347 ◽  
Author(s):  
N. A. Tkachuk ◽  
S. A. Kravchenko ◽  
V. A. Pylev ◽  
I. V. Parsadanov ◽  
A. V. Grabovsky ◽  
...  

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.


2012 ◽  
Vol 446-449 ◽  
pp. 1366-1369
Author(s):  
Guo Cai Wang ◽  
Fei Li Jin ◽  
Ling Sha ◽  
Le Ping Huang

In view of the large amounts of discarded sludge produced in the process of engineering construction, this paper proposes and makes use of the discarded sludge and compounds a kind of lightweight soil of adjustable intensity. In order to get the physical properties of the lightweight soil, a series of laboratory tests is made to investigate the lightweight EPS beads compounded soil using the sludge as raw material soil, cement as the solidification material, and the effect of cement content, EPS beads volume fraction and curing age, etc. on the density and strength is analyzed. The change regularity is obtained of the density and strength parameters of lightweight soil using recycled sludge with each factor. The research results can provide fundamental basis for the application and quality control of engineering waste soil, and can establish a theoretical foundation for further development and utilization.


Author(s):  
Юлія Борисівна Кракос ◽  
Аліна Олександрівна Приходько

In the light of globalization processes at the present stage of development of the Ukrainian economy, domestic enterprises of the machine-building industry faced the problem of increasing their competitiveness in the world market, which in turn contributed to the Activation of their innovative activities. The need of implement measures to increase the level of investment attractiveness of Ukrainian enterprises, determines the feasibility of the analysis of the current state of the machine-building industry. The aim of study is to investigate the role of machine-building industry production in total industrial complex, the research status, the challenges and to identify priorities for further development of engineering in Ukraine that are taking into account the requirements of the Modern market.  Research object. The object of the research is the machine-building industry of Ukraine and its condition in the conditions of world globalization. Methods. Research methods that were used in the process of writing the article - providing for the application of General scientific and empirical approaches to economic science – were based on a systematic approach. The appliance of the dialectical method allows us to highlight the features of modern innovation processes, furthermore, to explore the problems of creating an investment-attractive environment in the machine-building industry of Ukraine.  The traditional method is applied in the study of previous experience chronology of events and facts in the development of the economy of Ukraine.  General scientific systematical and logical methods were also used to obtain research conclusions.  The basis of the information in this paper is on the researches consisted of monographs, scientific articles of domestic, foreign articles, legal activities of the enterprises and data of the State Statistics Service of Ukraine. The hypothesis of the study. Continuous monitoring of the current state of machine building in Ukraine and implementation of the results of its practical analysis will improve the investment attractiveness of the industry.  Presentation of the main material. In this scientific article the role of mechanical Engineering as the leading industry of economy of Ukraine is investigated.  Based on statistical data, the dynamics of the main indicators of development of the machine-building industry of Ukraine for 2010-2018 was analyzed. Significant problems of the studied area are Identified, priorities for further development are determined.  The originality and practical significance of this study is to investigate deeply the main problems of investment attractiveness of the engineering industry.  also this study’s main provisions can serve as a scientific basis for the development of machine-building enterprises, in the context of the study of the problems of increasing the investment attractiveness of the industry.  Conclusions of the study. Since Mechanical Engineering is one of the leading industries, it is an indicator of the technical level of the country.  Lack of financial resources at the enterprises through problems such as low speed potential restoration of production in industry were solved. This leaded to braking of the General development of mechanical engineering of Ukraine.  In challenging situations of financial and economic activity, the enterprises of the machine-building industry need support from the State, in particular that needs a part of tax incentives for large-scale projects to modernize production facilities and Provide domestic producers with state orders.  According to the results of the conducted research it can be argued that the main stimulus for the realization of the industry’s potential is the lack of material resources.  Therefore, the solution for problems of increasing the investment attractiveness of industry will insure the further development of machine-building complex of Ukraine.


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