MECHANICS, MACHINE SCIENCE,  MACHINE-BUILDING

Proceedings

MECHANICS, MACHINE SCIENCE, MACHINE-BUILDING

N:1

2019

124 views

EDITORIAL

 

         Dear colleagues and readers,

         We introduce the first issue of  2019 of the journal  “Proceedings of National Polytechnic University of Armenia: Mechanics, Machine  Science, Machine Building ”. The four thematic sections of the journal include 7 articles, which present the latest results of theoretical and applied research in the fields of mechanics, machine science, machine building, and transportation  systems obtained at National Polytechnic University of Armenia, the Institute of Mechanics of NAS,  RA and the Belarussian National Technical University.   We especially  want to mention  the review article on the current state and development prospects of rehabilitation and assisting robotics, the materials of which can be very useful for undergraduate and  graduate students and scientists working in this field.

As before, the publication of this issue was preceded by  hard work of the editors associated with ensuring the  compliance of the proposed articles with the established rules of design of the journal and  the evaluation of the papers` originality.  

Dear authors!

The editorial office  sometimes receives manuscripts of very low quality, which   does not naturally  allow  to accept  such articles  for consideration  and creates additional problems for the Editorial Board. Our second problem is that the bulk of the manuscripts comes to us  in  the last two months of   preprintion  of articles for publication, which threatens to disrupt the timing of the issue.    

In this regard, here is  a huge request to You. When preparing  Your  papers, please follow the rules of their design  given at the end of each issue of our journal,  and please plan to submit the article to the editor in the  first months of the work of the Editorial Board on the  current  issue of the journal.

We hope for further fruitful and mutually beneficial cooperation. We are waiting for your papers on your newest researches and  applied development works.

                                                              

 

Editor-in-chief of the journal      B.S. BALASANYAN

Headings

  • actuator

  • exoskeleton

  • overactuated systems

  • rehabilitation and assistive robotics

  • static balancing.

  • wearable robots

A review of classification methods, evolution and recent developments of rehabilitation and assistive robotics is presented which gives answers to the following questions: how to find information about the type of rehabilitation or assistive device that we are interested in, which problems are already solved in this area, which are still existing, the main design guidelines and perspectives for the future developments. The following classification principles are discussed: general classification with respect to the end users, hardware systems, training paradigm and robot design; comprehensive classification with respect to the actuation systems, the actuator type, DOFs, the  type of sensor, the control system, the human-robot interface, the acting mode and the data of clinical investigation. The main research directions and problems in rehabilitative and assistive robotics are revealed: design problems of static balancing systems, soft material devices, non-traditional actuation means and systems (i.e. electroactive polymers and overactuation) and control methods (i.e. electroencephalography (EEG)/electromyography (EMG) signals). Studies showed that the essential development of this field depends on  three main factors: actuators, mechanical design, human-robot interface. Finally, the future development challenges, perspectives and solution methods of key design problems are presented, where the main innovative components are new soft materials, jointless structures, redundant actuation systems, human-robot interaction sensors and adaptive control systems.

  • вибрация

  • вибродиагностика

  • воздушный зазор

  • вынужденные колебания

  • короткозамкнутый ротор.

  • надежность

  • электромагнитные силы

 The experience of dozens of years in vibrodiagnosing the rotating machines and mechanisms shows that from the standpoint of practical application, it is rather a complicated process because of the presence of non-linear fluctuations in the machines, and non-linear deformation changes of rolling bearing rods.The modern ways of increasing  the reliability and longevity of electrical machines often encounter certain difficulties, depending on the accurate calculation of magnetic and mechanical forces. This is explained by the fact that the reliability of machines is characterized by a wide range of frequency fluctuations, whose  increase  leads to a  loss of fatigue resistance, occurrence  of plastic deformations in  the constructive elements, and thus to  the irregular  operation of the machine. This paper is devoted to the mathematical description of the vibration processes of induction  motors. The issues of vibrodiagnostic signs of defectiveness of the electromagnetic system by modulating the current consumed and the mechanical system by the level of the spectral components of vibration are analyzed. The work is designed for specialists engaged in vibro-adjustment and vibrodiagnostics of various units with drives from induction motors. Particular attention is paid to the detection of static and dynamic eccentricities of the air gap between the rotor and the stator of the induction motors. at the level of 10%, however, in practice, any kind of eccentricity can reach values ​​of about 50%. It has been shown that  by comparing the  results of theoretical analysis of the vibration spectrum  of the motor with those  of discrete measurement  on the machine body,  the defects of the perturbation can be determined and an  adequate decision  can  be made.  

  • глубина проникания

  • индентор

  • магнитное поле

  • проникание

  • электронопластичность.

 The influence of discharge currents and magnetic fields on the physical properties of metals is studied. In order to increase the protective properties of metal barriers, it is important to study the phenomenon of collision of a deformable indenter and a half-space accompanied by a discharge current and a magnetic field. On the basis of the one-dimensional model, as well as under the assumption of the non-deformability of the penetrating indenter, simple theoretical models describing the nature of the penetration of the indenter into the metal barrier and its interaction with the magnetic field are proposed. However, as the experimental results show, the assumption of non-deformability of the penetrating indenter is not justified.

       The current flowing through the indenter leads to a decrease in the yield strength of the indenter material  , i.e. to the softening of the indenter, which in turn leads to its strong blunting and an increase in the strength of the resistance to penetration. The dependence of the yield point on the magnetic field induced in the indenter due to the discharge current, which is known as the effect of electron plasticity, is considered in numerous works.

        Based on the proposed models and the results of previous experiments, an important result was obtained – the presence of a discharge current and, as a consequence, the magnetic field leads to a significant reduction in the depth of penetration of the indenter into the metal barrier.

Due to the high pressure on the contact surface of the indenter and the barrier, as well as taking into account the effect of electron plasticity, it is important to take into account the deformation of the indenter. In high-velocity collision problems, the penetration process is described by a hydrodynamic model, where the shape of the indenter does not play a large role.

  • аналитический метод

  • компьютерное моделирование.

  • напряжения Мизеса

  • окружные напряжения

  • упрочнение материала

  • чистый изгиб

  • широкая стальная полоса

Considering that  the results of theoretical studies of various technological processes are often compared with the data of modeling in the automated software environment (ASE), the process of pure bending of a wide steel strip is studied in the ASE ABAQUS environment. It is based on the finite element method, i.e. the separation of machine parts according to a certain shape, size,  number of elements, etc.

A band sewn from two sides (a pinched beam), loaded from two ends of equal states of equal resultant forces F = q b (where q is the intensity of a uniformly distributed load across the width b of the band). The magnitude of the external bending moment  is determined from the plot of the bending moments of the strip.

As a  material for  the strip, steel with digital data of the  deformation diagram is used  for which its yield strength and stress limit state are known. The band simulation results in  the determination of the values ​​of all components of the stress-strain state, including the  circumferential, radial stresses and the Mises stresses.

The  wide band was bent in the case of . Out of  all the components of the stress-strain state, the data of the Mises stress  and the circumferential stress  are analyzed. It is shown that the circumferential stress  on the inner surface is , and on the outer surface it is   .

The circumferential stresses in the zones of the external surfaces of tension and compression are determined using simple analytical formulas. To do this, first, from the table of the Mises stress pattern, the corresponding value of the deformation diagram is selected: . In the stretching zone we obtain: , and in the compression zone -   .

A comparative analysis of the simulation results in the ASE ABAQUS of the main circumferential stresses with the calculated data performed by an analytical method is carried out. It is found that the difference of the resulting voltages is on average

  • внешняя среда.

  • инновация

  • машиностроительная организация

  • оценка

  • системный подход

  • устойчивость

  • эффективность

The concept of efficiency of an industrial machine building organization and modern approaches to its assessment are considered. The market economy has made significant adjustments in the system of methodology for assessing the  economic efficiency. The main problem is to establish the  criteria for the effectiveness of the organization and guidelines for their definition. The theoretical and practical aspects of the efficiency of an industrial machine building organization and the prerequisites for its provision are analyzed. In modern conditions, an important prerequisite for improving the efficiency of an organization is the stability of its activities as the ability to restore equilibrium under the influence of internal and external vibrations. The concept of organization stability is based on an effective change management system, which includes all the  planned and controlled changes in production processes, structures and strategies.

As a result of the research, a systematic approach to assessing the effectiveness of an organization is considered appropriate  given that the survival of an organization on the market ultimately depends on its ability to adapt to the external environment. The main factors and directions for increasing the efficiency of industrial machine building organizations in Armenia are substantiated, of which scientific and technical measures, innovative activities, organizational reorganizations, and improvement of the management system are especially important. The concept and content of the efficiency of an industrial machine building organization are discussed and summarized. The essence of efficiency is reduced to the realization of the objectives of the organization while maintaining the established cost / income ratio. It is emphasized that the choice of the best option for solving production and economic problems can be carried out only with the help of a group of criteria characterizing various aspects of efficiency.

  • промышленные испытания.

  • растительное масло

  • реактор

  • смазочно-охлаждающая жидкость

  • ультразвук

  • экология

  • эмульгирование

           One of the most important tasks to increase the efficiency of processing difficult-to-cut materials, as well as improve the ecology of their production is improving the compositions and technology for obtaining environmentally friendly lubricating –coolant fluids with an extended service life, including ultrasonic emulsification methods. Recommendations on the use of environmentally friendly and sustainable emulsion of sunflower oil in water obtained by the  application of ultrasonic vibrations (UST) are given, using a new scheme of simultaneous superposition of high-frequency and low-frequency oscillations in liquid media, which allows to intensify the process of USE up to 2.1 times, and increase the kinetic steadiness  of the resulting emulsion up to 1.6.

          The issues of the coolant application, in the form of a 5% emulsion of sunflower oil in water are considered at the Armenian stone-processing enterprises when cutting and processing natural stones with expensive diamond tools. On the basis of production studies carried out in LLC Almakar and LLC TAROS, when sawing and processing granite and marbles with diamond tools, it was found that the use of 5% emulsion of sunflower oil in water compared to technical water reduced the  wear of diamond tools up to 1.19 ... 1.28 times.

         Based on these studies, it was found that the widely used coolant brand sulfofresol (GOST 122-54) can be replaced by 5% emulsions of sunflower oil in water, as it is almost as good as sulfofresol, does not contain harmful substances, is easily diluted with water, does not pose a danger to the operator and staff, is more than 20 times cheaper than sulfofresol and does not require additional costs for disposal.

  • активированные электролиты

  • анодное микродуговое оксидирование

  • двигатель внутреннего сгорания

  • полирадикалы

  • термостойкое покрытие

  • ультразвук.

A promising trend in increasing the life of a wide range of products operating under thermal loads and intense mechanical wear is the use of the method of anodic microarc oxidation (AMDO), which results in the formation of protective coatings in the  critical zones of thermally loaded objects that reduce the operational risks. The possibility of increasing the performance characteristics of the internal combustion engine due to the formation in the critical zones of parts of the cylinder-piston group of heat-resistant coatings by the AMDO method in activated polyradicals and ultrasound electrolytes are considered, and the results proving the effectiveness of the developed technology are presented. It is shown that in the internal combustion engine containing components of the CPG with protective oxide coatings in the contact zone, greater stability of the main characteristics is provided with an increase in the crankshaft speed: the average temperature of their heating is reduced by 25…30%, by reducing the heat sink to the environment through the treated piston and cylinder head, the temperature in the combustion chamber increases, which leads to an increase in the engine power by an average of 4…6% and a decrease in fuel consumption by 5…7%. At the same time, an increase in the external speed characteristic of the internal combustion engine is  recorded, which improves its adaptability to the load changes. These data are an evidence of the operation of the internal combustion engine in a more economical regime and high efficiency. In constructive  terms to the modernization carried out in the process of AMDO coating reducs the thermal gap between the piston and the cylinder, reduces the oil burning, improves the environmental performance, as well as the  noise of internal combustion engines.

Council

Proceedings has been published since 1998, the journal since 2012

Editorial Council of Proceedings:  Yu.L. Sarkissyan  (Editor-in-chief, doctor of tech. sciences), A.Kh. Grigoryan (vice Editor-in-chief, doctor of tech. sciences),  A.G. Avetisyan (responsible secretary, doctor of tech. sciences),  S.G. Aghbalyan (doctor of tech. sciences),  M.K. Baghdasaryan (doctor of tech. sciences),  B.S. Balasanyan (doctor of tech. sciences),  N.B. Knyazyan (doctor of tech. sciences), V.Z. Marukhyan (cand. of tech. sciences), S.H. Simonyan (doctor of tech. sciences)

Editorial Council of the journal: B.S. Balasanyan (Editor-in-chief of the journal, doctor of tech.sciences), M.G. Harutyunyan (vice Editor-in-chief of the journal, cand. of tech. sciences), A.S. Babayan (responsible secretary of the journal, cand. of tech. sciences), V.H. Arakelyan (doctor of tech. sciences, France), A.K. Amiryan (doctor of tech. sciences), A.G. Kharatyan (cand. of tech. sciences), A.N. Mikhailov (doctor of tech. sciences, the Ukraine), G.V. Musayelyan (cand. of tech. sciences), A.R. Papoyan (doctor of tech. sciences), G.L. Petrosyan (doctor of tech. sciences), M.G. Stakyan (doctor of tech. sciences), H.G. Shekyan (doctor of tech. sciences), L.A. Shekyan (doctor of phys.-math. sciences)

 

Editors: Zh. S. Seyranyan, H.Ts. Petrosyan, H.Z. Ghazaryan

© National  Polytechnic  University  of  Armenia (NPUA)  “Tchartaraget”  Publishing  House

Address: 0009, Yerevan, 105 Teryan str., NPUA,

i.polytechnic.am