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In this paper, we have considered tip interference and radial interference of internal involute spur gears. Equations of tooth profiles are provided and operating constraints for internal gears are defined. The undercutting and interference of the teeth profiles are the main problems for the practical application of internal gears in planetary gear trains, which requires particular attention in the design of planetary gear trains. The problem of avoiding interference of internal involute spur gears is especially challenging. Therefore, it is necessary to create the corresponding geometric models and express the above requirements by the corresponding functional constraints to verify the engagement condition. The developed geometrical model of the tooth surfaces is most helpful in the analysis of meshing interference, contact, and stress analyzing, manufacturing, measuring, and optimizing internal gear sets. The numerical results are tested by computerized simulation of the meshing of internal involute spur gears.

The present paper studies the impingement of compressible air jet on a flat plate primarily from the aspect of its application in the domain of pneumatic metrology, i.e. in cases of small distance between the jet nozzle exit and the flat plate. Besides this direct application in the area of pneumatic metrology, the distance between the nozzle exit and the flat plate has been considerably increased and the case of a free jet was analysed with a view to compare the results applicable in various domains. This experimental study demonstrates that the structures of a free jet and this special case of an impingement jet are totally different. In the pressure distribution of the impingement jet, pressure discontinuity above the flat plate may occur, which is shown to be the result of low intensity shock waves and transonic flow. The experimental results show that the pneumatic sensitivity of a pneumatic comparator is a function of the supply pressure and the internal orifice diameter, as well as that the impingement air jet is a typical case of non-isentropic flow.

The influence of the running-in process operating parameters on tribological properties of the block-on-disc samples in lubricated sliding conditions is analyzed and discussed in detail. Different running-in regimes are achieved by varying the normal load and sliding speed. After the running-in period, during which the operating parameters are varied, all samples are placed in a working regime under the same set of operating conditions. At the end of the running-in period, as well as at the end of the working period, an analysis of the changes in the surface roughness, microhardness, wear rate, and coefficient of friction is performed. Less desirable properties in terms of wear rate and steady-state coefficient of friction are noticed for the samples that were run-in with the operating conditions which were the same as the working regime operating conditions. In the defined test conditions, it is shown that the intensity of normal load applied during the running-in process has a dominant influence on the amount of wear and coefficient of friction value. It was also shown that the running-in process can significantly improve the roughness of the initially rough contact surfaces. The results of experimental testing indicate that the variation of the operating parameters during the running-in process can be used to improve the working ability of the sliding contact surfaces under the mixed lubrication regime.

Планетарни преносници спадају у групу механичких зупчастих преносника, који су широко заступљени за трансформацију и пренос снаге првенствено због компактности конструкције, високе поузданости и степена искоришћења. Полазећи од функције, коју треба да испуни у оквиру неке конструкције, као и све строжих захтева у погледу перформанси преносника, предмет истраживања ове докторске дисертације је развој вишекритеријумског оптимизационог модела планетарног преносника. Развијени модели који задовољавају низ строгих захтева у погледу: компактности конструкције, минимизације губитака у преносу снаге, равномерности расподеле оптерећења, као и поузданости у различитим експлоатационим условима. За постављени проблем вишекритеријумске оптимизације планетарног преносника формиране су одговарајуће критеријумске функције и дефинисан је низ функционалних ограничења, као и одговарајући домени примене свих релевантних величина зупчастих парова са спољашњим и унутрашњим озубљењем и планетарног преносника као сложеног система, у циљу несметане монтаже, поузданог рада и спрезања зупчастих парова. У оквиру докторске дисертације, развијен је одговарајући механички модел за одређивање степена искоришћења истовремено спрегнутих зупчастих парова, у зависности од њихових геометријских параметара, као и од услова подмазивања. Критеријумске функције формираног вишекритеријумског оптимизационог проблема су нелинеарне и неконвексне па се глобално оптимално решење не може нумерички одредити конвенционалним методама оптимизације. Према томе, у циљу решавања овог комплексног оптимизационог проблема потребно је применити метахеуристичке оптимизационе алгоритме. Дакле, постоји стална потреба за побољшањем постојећих и развојем нових метахеуристичких алгоритама и то развојем адаптивних техника за подешавање управљачких параметара и хибридизацијом алгоритама. У складу са тим, у оквиру докторске дисертације детаљно су разматрани метахеуристички алгоритми, који припадају групи еволутивних алгоритама, као, Planetary gearboxes have a wide application in the field of transformation and transmission of power from the drive to the working machine, due to the compact structure, high reliability and efficiency. Due to the increasingly stringent performance requirements, which planetary gearboxes must satisfy, the research in this dissertation is focused on the problem of multi-objective non-linear optimization of planetary gearbox based on hybrid metaheuristic algorithm, which satisfies a number of strict requirements, such as: compact construction, minimization of power loss, load distribution and reliability in different operating conditions. In this work the formulations of the objective functions for the considered multiobjective optimization problem of planetary gearbox have been outlined along with the appropriate constraints. The formulated constraints have been analyzed and appropriate domains of practical applications of internal and external gear pairs have been formulated, with the aim to ensure proper working, mounting and meshing of considered gears. Furthermore, the theoretical formulation and numerical procedure for the calculation of the planetary gearbox power efficiency has been developed in this work. However, the objective functions and developed constraints of the considered Multiobjective planetary gearbox optimization problem are nonlinear and multimodal functions, and therefore the global optimal solution cannot be obtained using the conventional optimization methods. Therefore, in order to solve this multiobjective and complex optimization problem, the research in this dissertation is focused on metaheuristic optimization algorithms, which belong to the group of evolutionary algorithms, including: differential evolution algorithm and genetic algorithm, as well as the algorithms inspired by the biological systems, such as particle swarm optimization algorithm. To overcome difficulties in solving complex optimization problems, in this thesis the consi

Planetarni prenosnici spadaju u grupu mehaničkih zupčastih prenosnika, koji su široko zastupljeni za transformaciju i prenos snage prvenstveno zbog kompaktnosti konstrukcije, visoke pouzdanosti i stepena iskorišćenja. Polazeći od funkcije, koju treba da ispuni u okviru neke konstrukcije, kao i sve strožih zahteva u pogledu performansi prenosnika, predmet istraživanja ove doktorske disertacije je razvoj višekriterijumskog optimizacionog modela planetarnog prenosnika. Razvijeni modeli koji zadovoljavaju niz strogih zahteva u pogledu: kompaktnosti konstrukcije, minimizacije gubitaka u prenosu snage, ravnomernosti raspodele opterećenja, kao i pouzdanosti u različitim eksploatacionim uslovima. Za postavljeni problem višekriterijumske optimizacije planetarnog prenosnika formirane su odgovarajuće kriterijumske funkcije i definisan je niz funkcionalnih ograničenja, kao i odgovarajući domeni primene svih relevantnih veličina zupčastih parova sa spoljašnjim i unutrašnjim ozubljenjem i planetarnog prenosnika kao složenog sistema, u cilju nesmetane montaže, pouzdanog rada i sprezanja zupčastih parova. U okviru doktorske disertacije, razvijen je odgovarajući mehanički model za određivanje stepena iskorišćenja istovremeno spregnutih zupčastih parova, u zavisnosti od njihovih geometrijskih parametara, kao i od uslova podmazivanja. Kriterijumske funkcije formiranog višekriterijumskog optimizacionog problema su nelinearne i nekonveksne pa se globalno optimalno rešenje ne može numerički odrediti konvencionalnim metodama optimizacije. Prema tome, u cilju rešavanja ovog kompleksnog optimizacionog problema potrebno je primeniti metaheurističke optimizacione algoritme. Dakle, postoji stalna potreba za poboljšanjem postojećih i razvojem novih metaheurističkih algoritama i to razvojem adaptivnih tehnika za podešavanje upravljačkih parametara i hibridizacijom algoritama. U skladu sa tim, u okviru doktorske disertacije detaljno su razmatrani metaheuristički algoritmi, koji pripadaju grupi ev, Planetary gearboxes have a wide application in the field of transformation and transmission of power from the drive to the working machine, due to the compact structure, high reliability and efficiency. Due to the increasingly stringent performance requirements, which planetary gearboxes must satisfy, the research in this dissertation is focused on the problem of multi-objective non-linear optimization of planetary gearbox based on hybrid metaheuristic algorithm, which satisfies a number of strict requirements, such as: compact construction, minimization of power loss, load distribution and reliability in different operating conditions. In this work the formulations of the objective functions for the considered multiobjective optimization problem of planetary gearbox have been outlined along with the appropriate constraints. The formulated constraints have been analyzed and appropriate domains of practical applications of internal and external gear pairs have been formulated, with the aim to ensure proper working, mounting and meshing of considered gears. Furthermore, the theoretical formulation and numerical procedure for the calculation of the planetary gearbox power efficiency has been developed in this work. However, the objective functions and developed constraints of the considered Multiobjective planetary gearbox optimization problem are nonlinear and multimodal functions, and therefore the global optimal solution cannot be obtained using the conventional optimization methods. Therefore, in order to solve this multiobjective and complex optimization problem, the research in this dissertation is focused on metaheuristic optimization algorithms, which belong to the group of evolutionary algorithms, including: differential evolution algorithm and genetic algorithm, as well as the algorithms inspired by the biological systems, such as particle swarm optimization algorithm. To overcome difficulties in solving complex optimization problems, in this thesis the consi

U domenu prenosa i transformacije snage od pogonske do radne mašine zupčasti parovi zbog kompaktnosti konstrukcije, velike pouzdanosti i nosivosti imaju najveću primenu u poređenju sa drugim prenosnicima snage koji obavljaju istu elementarnu funkciju. Saglasno tome, istraživanja u oblasti zupčastih parova imaju značajan doprinos u razvoju savremenih mašinskih konstrukcija. Predmet istraživanja ove doktorske disertacije je razvoj preciznijih matematičkih modela raspodele opterećenja na istovremeno spregnute parove zubaca, kada se u toku dodirnog perioda zubaca smenjuju dvostruka i trostruka sprega, kao i razvoj preciznijih matematičkih modela za analizu uticaja raspodele opterećenja na nosivost korena zubaca i energetsku efikasnost cilindričnih zupčastih parova. Sprovedena istraživanja u ovoj doktorskoj disertaciji su dovela do sledećih rezultata: Razjašnjenje fenomena raspodele opterećenja na istovremeno spregnute parove zubaca u uslovima dvostruke i trostruke sprege, kao i formiranje tačnijih modela za sagledavanje istovremenog uticaja tačnosti izrade, krutosti zubaca i intenziteta opterećenja na karakter raspodele opterećenja. Definisanje tačnijeg kriterijuma za određivanje napona u korenu zupca merodavnog za proveru radne sposobnosti zubaca sa aspekta zapreminske čvrstoće. Njegovom implementacijom u konvencionalne postupke proračuna ISO/DIN standarda, značajno bi se povećao nivo pouzdanosti podataka o radnim i kritičnim vrednostima napona u korenu zupca. Razvijanje tačnijih modela za analizu energetske efikasnosti zupčastih parova na osnovu stepena iskorišćenja., In the field of transmission and transformation of power from the drive to the working machine, due to the compact construction, high reliability and load capacity, the gear pairs have the greatest application compared to other power transmissions that perform the same elementary function. Accordingly, research in the field of gear pairs has a significant contribution to the development of modern machine constructions. The research topic of this doctoral dissertation is the development of more precise mathematical models of load distribution in simultaneously meshed teeth pairs, when during the contact period of the teeth the double and triple mesh take turns, as well as the development of more precise mathematical models for analyzing the influence of the load distribution on the teeth root load capacity and the energy efficiency of the cylindrical gear pairs. The research carried out in this doctoral dissertation led to the following results: Clarification of the load distribution phenomenon in simultaneously meshed teeth pairs in double and triple mesh conditions, as well as the formation of more accurate models for examining the simultaneous effect of the accuracy of production, stiffness of the teeth and load intensity on the load distribution character. Defining a more precise criterion for determining the tooth root stress relevant for checking the working ability of the teeth rating from the aspect of bending strength. It implementing in the conventional procedures of the ISO/DIN standard calculation, the level of reliability of data on the working and critical values of the tooth root stress would be significantly increased. Developing more accurate models for the analysis of the energy efficiency of gear pairs based on the degree of efficiency.

The efficiency of thermal power plants significantly depends on the efficiency of belt conveyor systems. Conveyor idlers, as key parts of belt conveyors, are often the main cause of bulk material transportation systems failures. Testing the operational characteristics of conveyor idlers in laboratory and exploitation conditions is a prerequisite for any progress in the field of increasing energy efficiency of conveyor systems. This paper describes an analysis and discussion of testing results for different types of conveyor idlers, in terms of their performances under the act of predefined radial load. Tests were conducted on a new conveyor idler's testing machine developed at the University of Belgrade-Faculty of Mechanical Engineering. The presented tests are performed in order to determine the quality of carrying and return conveyor idlers. The obtained results will help in solving the key problems in the critical areas of conveyor systems and will increase their energy efficiency. Finally, the expected results can potentially reduce the financial and energy losses which conveyor idlers cause in belt conveyor systems, as well as in the whole system of thermal power plants.

The impact of geometric parameters of teeth and lubricating oils to the efficiency of involute internal spur gears, when the transverse contact ratio is 2 lt epsilon(alpha) lt = 3, has been analyzed in this paper. The mathematical model and computer program for determining the current and the effective value of the efficiency have been developed. The influence of the character of load distribution and energy losses due to heating effects during the meshing period is included in the factor of load distribution. The results of computer simulation are given in the form of a diagram of the current values of the efficiency during the meshing period. Also, the values of effective efficiency for the considered cylindrical gear pairs have been calculated.

Planetary gears, obtained by the kinematic combinations of toothed pairs with external and internal contacts, are able to provide considerably improved performance compared to the gear pairs with fixed axes, however if not properly designed they can exhibit poor performance regarding gear efficiency. In this regard, and given the fact that majority of research paper concerning this topic emphasize that planetary gears have generally better weight-to-power ratio and improved efficiency compared to the gear pairs with fixed axes, this paper examines the above statements. The main aim is to determine the domain of feasible gear ratios for which the planetary gear sets exhibit better performance, in terms of efficiency and weight-to-power density, than the classical fixed axes gears. In this work, the model of instantaneous gear efficiency is presented and applied to study the efficiency of both standard and high contact ratio involute spur gears. Approximate expressions for the friction power losses and for the efficiency are presented assuming the friction coefficient is changeable along the path of contact.

In the strides of the most advanced technological achievements, the use of polymers is becoming increasingly evident both in everyday life and in engineering practice. Complex structures made of polymers attract more attention from scientists and researchers, as their application increases in the most diverse fields of science. This phenomenon requires constant improvement of knowledge and technologies for the production of polymeric structures and parts, but it is equally important to establish reliable databases on the behavior of newly-introduced materials under different load conditions. This work is based on the establishment of statistical correlation between parameters of 3D printed models and their mechanical characteristics in conditions of static axial loading.

The advanced development of additive technologies over the past years led to the fact that parts made by these technologies have been increasingly used in the most diverse engineering applications. One of the most famous and the most applied additive technology is 3D printing. In this paper the influence of the material type on the operational characteristics of spur gears manufactured by the 3D printing technology is analyzed, after the experimental testing performed on a back to back gear test rig, in the predefined laboratory conditions.

By kinematic combinations of toothed pairs with external and internal contacts, we can obtain planetary gears with a considerably improved performance than the corresponding ones with fixed axes, as well as planetary gears with notably poor performance regarding the efficiency. In regard to that, the reference literature and papers almost regularly emphasize that planetary gears, under the same technical conditions, have a smaller mass and a higher degree of efficiency than the ones with fixed axes. The main aim of this paper is to examine the above statement and to determine the scope of the gear ratios in which the planetary gears are more suitable than the fixed axes gears.

Application of typization in the process of designing mechanical sub-assemblies and assemblies is one of the ways to reduce the cost of production. Therefore, nowadays, not only roller bearings, bolts, wedges, etc. are produced as standard machine elements but, by the usage of typization, a production of a large series of typified subassemblies and assemblies, such as electric motors, pumps, power transmissions, etc., is increasing. Increased application of typified parts, sub-assemblies and assemblies in mechanical systems requires an increase in their safety and reliability during operation. Accordingly, in this paper, the load capacity of the typified machine parts series from the aspect of their structural strength is analyzed. It has been shown that there is a scattering of calculated results of the safety factor of members of the typified series from the aspect of the structural strength. The paper presents a proposal for a calculation methodology by which the mentioned scattering of the results of load capacity of typified machine parts series can be significantly reduced.

Nowadays, rapid prototyping technologies are available at very affordable prices. This is the main reason why they are being used in almost all industry sectors. 3D printers are currently being widely used for rapid prototyping and development of the new products. However, taking into account the permanent progress of rapid prototyping materials mechanical characteristics (usually different kinds of plastics), 3D printers are sometimes used even for production of the failed parts replacements - operating at the low load and rotational speed conditions. This is the main goal of this paper - to establish optimal 3D printing parameters (printing direction, layer height and percent of infill) which will allow printed gears to replace failed steel gears, for at least some time, enough for spare steel gears to be produced and delivered on site. Taking into account previously mentioned facts, the application of the 3D printed gears can potentially provide the reduction of maintenance delays in different industrial facilities (factories, workshops, etc.) which will consequently lead to significant energy and financial savings.

Osnovna ideja na kojoj se zasnivaju bazni ciljevi disertacije je identifikacija ekstremno teških uslova eksploatacije mašinskih struktura i njihovih opterećenja koji predstavljaju kompleksnu interakciju izuzetno visokih toplotnih i nehomogenih uticaja, intenzivnih uticaja strujanja fluida, uticaja visokih brzina rotacije, sopstvenih i prinudnih vibracija i dr. Ovi su uticaji prisutni kod gasogeneratora turbomlaznih i turbovratilnih motora za koji je bilo potrebno razviti inovativno konstrukcijsko rešenje multifunkcionalne pregrade između rotora kompresora i turbine. Za realizaciju postavljenog cilja razvijena je odgovarajuća metodologija inženjerskog dizajna zasnovana na iterativnom razvoju, ispitivanju i analizi stanja i razaranja delova pregrade, pod nazivom Failure-based Design – FBD. Razvijen je skup od pet konstrukcijskih rešenja ove pregrade. Četvrto rešenje je postalo prihvatljivo za eksploataciju u ovim uslovima, a peto rešenje je ostvarilo sve funkcije i zadovoljilo sve zahteve. Za ovu svrhu sprovedena su mnoga eksperimentalna ispitivanja, brojne numeričke analize strujanja fluida (CFD), analiza toplotnog stanja (raspodele temperature), proračuna napona i deformacija delova pregrade, razvoj konstrukcijskih rešenja i dr. Radi realizacije osnovnog cilja, rad je obuhvatio širok spektar eksperimentalnih sadržaja, značajan broj numeričkih analiza i proračuna, analiza brojnih specifičnih havarijskih oštećenja i predloženih konstrukcijskih rešenja da bi se ova razaranja izbegla., The general idea on which the basic goals of the dissertation are founded on is the identification of extremely hard conditions of mechanical structures and their loads which represent a complex interaction of several influences, i.e. extremely high heat, nonhomogeneous influences, intensive influences of fluid flow, high rotation speeds, its natural and forced vibrations etc. These influences are present at the gas generator of turbojet and turboshaft engines for which there was a need to develop an innovative construction solution for the multifunctional bulkhead between the compressor rotor and the turbine. In order to accomplish the set goal, an appropriate methodology of engineering design was developed which is based on iterative development, testing and analysis of the state and damage of the parts of the bulkhead, which is called Failure-based Design – FBD. A set of five construction solutions for the bulkhead was developed. The fourth solution became acceptable for exploitation in these conditions, while the fifth solution accomplished all functions and met all the requirements. In order to achieve this, numerous experimental testings were performed, along with many numerical analyses of the fluid flow (CFD), heat state (temperature distribution), stress and deformations calculations of the bulkhead parts, the development of construction solutions etc. In order to achieve basic goal, the paper encompassed a wide range of experiments, a significant number of numerical analyses and calculations, analyses of many specific damages and suggested construction solutions so as to avoid these damages.

Информације из стручне литературе, као и искуствени подаци, показују да велики проценат енергетских губитака термоелектрана потиче од система тракастих транспортера и њихових кључних компоненти – транспортних (носећих) ваљака. Зато су управо ови склопови, чија је функција да пренесу оптерећење услед масе транспортне траке и транспортованог терета на носећи рам, изабрани за објекат истраживања дисертације. Са циљем повећања поузданости, и смањења финансијских и енергетских губитака узрокованих непланираним отказима, развијене су нове и унапређене постојеће експерименталне процедуре за испитивање кључних карактеристика транспортних ваљака – обједињене у комплексну експерименталну методологију испитивања. Међу развијеним процедурама, по значају се посебно истиче процедура за испитивање радних карактеристика котрљајних лежаја (критичних компоненти транспортних ваљака) – под дејством контаминирајућих честица са површинских копова угља. Научне хипотезе представљене дисертације се односе управо на ову процедуру, односно, напредним статистичким методама (применом софтверских пакета најновије генерације) је позитивно одговорено на питање да ли постоје статистички значајне зависности између посматраних радних карактеристика вештачки контаминираних котрљајних лежаја – вибрација, температура и времена рада. Утврђене статистичке корелације су потом имплементиране у постојећу једначину за прорачун радијалног зазора котрљајних лежаја. Према развијеној експерименталној методологији је испитан велики број узорака транспортних ваљака, различитог типа, произведених од различитих произвођача. Након анализе и дискусије добијених резултата, поређењем са искуственим подацима из праксе и резултатима до сада реализованих истраживања у предметној области, развијена методологија је успешно верификована, па се може даље примењивати за процену квалитета транспортних ваљака и њихових котрљајних лежаја., Relevant literature, as well as practical experience, has shown that large percentage of thermal power plant energy losses is caused by overland conveyor systems and their key components – conveyor idlers (rollers). That’s the main reason why this assemblies, with function to transfer the load from the conveyor belt and transported material to the supporting frame, are chosen as an object of research presented in this dissertation. In order to improve reliability and decrease financial and energy losses due to unplanned maintenance, a new conveyor idlers testing procedures were developed (some of existing were improved) – and joined in complex experimental testing methodology. Among developed testing procedures, experimental procedure for conveyor idler’s rolling bearings testing is the most important – because it provides the information about the influence of exploitation contamination particles (from the open pit coal mines) on rolling bearing’s operational characteristics. Scientific hypothesis presented in this dissertation are related primarily to this experimental procedure. It was confirmed that statistically significant correlations between artificially contaminated rolling bearing’s vibrations, temperatures and time in operation could be established. One of generated correlation was afterward implemented in existing equation for rolling.

Spur gear load carrying capacity and mass are primarily dependent of the tooth root stress. Geometric and kinematic parameters of gear teeth pairs produce multiple effects on the tooth root stress: through tooth root critical section location and root fillet radius, tooth profile shape and load leading point location on tooth profile, as well as through tooth stiffness. In the conventional calculation procedure, according to ISO standard, the influence of geometric and kinematic parameters of the gear pair on the tooth root stress is considered through the "contact ratio factor" Y-epsilon , whose values are determined using the approximate expressions. To view the real effects of geometric and kinematic parameters of the gear pair on the tooth root stress analytical model is developed, defining non-dimensional relative stress factor. The analysis comprises two groups of cylindrical gear pairs with different gear ratios and different coefficients of addendum modification. The results obtained are compared with the results of standard calculation procedure according to ISO standard. In addition, the developed analytical model is used to explain the assumptions, physicality and boundary conditions of the "contact ratio factor" Y-epsilon.

Informacije iz stručne literature, kao i iskustveni podaci, pokazuju da veliki procenat energetskih gubitaka termoelektrana potiče od sistema trakastih transportera i njihovih ključnih komponenti – transportnih (nosećih) valjaka. Zato su upravo ovi sklopovi, čija je funkcija da prenesu opterećenje usled mase transportne trake i transportovanog tereta na noseći ram, izabrani za objekat istraživanja disertacije. Sa ciljem povećanja pouzdanosti, i smanjenja finansijskih i energetskih gubitaka uzrokovanih neplaniranim otkazima, razvijene su nove i unapređene postojeće eksperimentalne procedure za ispitivanje ključnih karakteristika transportnih valjaka – objedinjene u kompleksnu eksperimentalnu metodologiju ispitivanja. Među razvijenim procedurama, po značaju se posebno ističe procedura za ispitivanje radnih karakteristika kotrljajnih ležaja (kritičnih komponenti transportnih valjaka) – pod dejstvom kontaminirajućih čestica sa površinskih kopova uglja. Naučne hipoteze predstavljene disertacije se odnose upravo na ovu proceduru, odnosno, naprednim statističkim metodama (primenom softverskih paketa najnovije generacije) je pozitivno odgovoreno na pitanje da li postoje statistički značajne zavisnosti između posmatranih radnih karakteristika veštački kontaminiranih kotrljajnih ležaja – vibracija, temperatura i vremena rada. Utvrđene statističke korelacije su potom implementirane u postojeću jednačinu za proračun radijalnog zazora kotrljajnih ležaja. Prema razvijenoj eksperimentalnoj metodologiji je ispitan veliki broj uzoraka transportnih valjaka, različitog tipa, proizvedenih od različitih proizvođača. Nakon analize i diskusije dobijenih rezultata, poređenjem sa iskustvenim podacima iz prakse i rezultatima do sada realizovanih istraživanja u predmetnoj oblasti, razvijena metodologija je uspešno verifikovana, pa se može dalje primenjivati za procenu kvaliteta transportnih valjaka i njihovih kotrljajnih ležaja., Relevant literature, as well as practical experience, has shown that large percentage of thermal power plant energy losses is caused by overland conveyor systems and their key components – conveyor idlers (rollers). That’s the main reason why this assemblies, with function to transfer the load from the conveyor belt and transported material to the supporting frame, are chosen as an object of research presented in this dissertation. In order to improve reliability and decrease financial and energy losses due to unplanned maintenance, a new conveyor idlers testing procedures were developed (some of existing were improved) – and joined in complex experimental testing methodology. Among developed testing procedures, experimental procedure for conveyor idler’s rolling bearings testing is the most important – because it provides the information about the influence of exploitation contamination particles (from the open pit coal mines) on rolling bearing’s operational characteristics. Scientific hypothesis presented in this dissertation are related primarily to this experimental procedure. It was confirmed that statistically significant correlations between artificially contaminated rolling bearing’s vibrations, temperatures and time in operation could be established. One of generated correlation was afterward implemented in existing equation for rolling.

У овом раду приказан је развој метода за процену настанка и ширења заморних прслина у циљу повећања радног века и поузданости машинских елемената и машинских система у условима замора. Детаљно је изложена и анализирана доступна научна литература из теоријских поставки феномена замора. Посебно је анализирана примена постојећих метода и теорија на решавање проблема заморних оштећења и отказа код машинских елемената. Развијање нових метода за процену настанка заморних прслина изложено је са различитих аспеката, с обзиром да се ради о резултатима мултидисциплинарних истраживања овог феномена, уз примену и интеркорпорирање доступних савремених аналитичких , нумеричких и експерименталних метода. Посебна пажња посвећена је верификацији развијених метода, кроз неколико приступа. За верификацију су коришћени сопствени експериментални резултати, као и резултати других аутора. У циљу бољег разумевања развијених метода, а пре свега методологије широких могућности примене, детаљно је описана примена на конкретном и веома сложеном проблему отказа машинског елемента у условима заморног оптерећења., This dissertation presents development of methods for assesment of crack initiation and propagation as part of the goal: increase of working life and reliability of machine elements and systems under fatigue loading. Детаљно je изложена и анализирана доступна научна литература из теоријских поставки феномена замора. Посебно је анализирана примена постојећих метода и теорија на решавање проблема заморних оштећења и отказа код машинских елемената On the basis of available scientific literature, the fenomenon of fatigue is analysed. The emphasize is on this research was application of existing methods and theories on failure prevention. Development of new methods for assessment of crack initiation is presented in detail, due to fact that multidisclipinary research is basis for application, analytical, numerical an experimental methods. The important part of presentation of developed methods, with significant potentials, is application on real and complex problem of failures of mechanical elements due to combination of fatigue and corrosion.

Развијене процедуре у овом раду заснивају се на коришћењу поузданости машинског система и компонената као гранични услов за одређивање конструкцијских и других параметара, као својство компонената и као показатељ квалитета система..., Procedures developed in this paper are based on the use of reliability of mechanical systems and components as a boundary condition to determine the construction and other parameters, such as feature of components and indicator of system quality...

The impact of load distribution in meshed teeth, teeth geometry and manufacturing accuracy on wear of the spur gear tooth flanks is studied in this paper. The original geometry of teeth is impaired wearing. Due to that, the load distribution is uneven, dynamic forces are increased, and energy efficiency is decreased. The aim of the theoretical and experimental studies, carried out in this paper, is to reach more accurate model for the analysis of tooth flanks load carrying capacity, taking into account a larger number of impacts on the tooth flanks stress state. A mathematical model for the contact stress during contact period is developed, depending on the value and sign of base pitch difference of meshed teeth. The impact of pitch point's position during the meshed teeth contact period was observed. In order to establish a correlation between the tooth flank failures and developed mathematical model, the appropriate experimental studies were carried out. The cemented spur gear pairs were examined on back-to-back gear test rig under conditions of maximum operational load. The results are presented in this paper.

Генерално посматрано, сви машински системи се састоје од погонске и радне групе, односно погонске и радне машине. Спој ових машина се остварује посебним склоповима, машинским елементима – спојницама. Њихова основна функција је преношење оптерећења и кретања са погонске на радну машину. Познато је да су спојеви најчешће најслабија карика у сваком машинском систему. Сагласно великом скупу различитих радних и погонских машина, са различитим радним перформансама, развијен је велики број различитих спојница. Међутим, код транспортних средстава и других машина, услови рада налажу различите међусобне положаје погонске и радне машине. Име и појам посебне врста спојница везано је за пионире у конструкцији ових спојница, славног италијанског научника Ђеролама Кардана (Gerolamo Cardano, 1501-1576) и Роберта Хука (Robert Hooke, 1635-1703). Конструкциона решења ових спојница пролазила су кроз различите фазе развоја. Динамика развоја конструкционих решења ових спојница приказане је у посебном Поглављу 3 овe дисертације. Карданове спојнице (карданска вратила) су посебна врста механизама за преношење обртног момента, односно снаге, који спајају вратила чије се осе налазе просторно под извесним сталним или у току рада променљивим углом, дозвољавајући, при томе, у току времена релативно померање. Ово померање може бити угаоно и транслаторно. Главни показатељи радне способности карданових спојница је њихов радни век и степен поузданости. Највећи утицај на ове показатеље раднe способности има карактер расподеле линијског оптерећења код спрегнутих делова Карданове спојнице. У циљу расветљавања феномена расподеле линијског оптерећења и сагледавања степена компатибилности између геометријских карактеристика спрегнутих делова и расподела линијских оптерећења, у дисертацији су формирани аналинтички и нумерички модели под одговарајућим предпоставкама., general, all mechanical systems consist of drive and driven groups, or driving and driven machines. The connection of these machines is achieved by special joints, machine elements - couplings. It is known that these joints are often the weakest link in any mechanical system. Pursuant to a large set of different drive and driven machines with different operating performance, a large number of different coupling types were developed. However, а working conditions of transport vehicles and other machinery require different mutual positions of the driving and operating machinery. The name and concept of one type of couplings is related to the pioneers in the design of these joints, the famous Italian scientist Gerolamo Cardano (1501-1576) and Robert Hooke (1635-1703). The designs of these couplings are passed through various stages of development. The innovative designs development dynamics of these couplings are shown in a separate chapter 3 of this study. Cardan joints (cardan shafts) have a large range of applications in mechanical engineering because of the capability of transferring the load and motion from one shaft to another with different joint angle allowing, thereby, over time relative movement. This movement can be angular and translational. The main indicators of functional ability of cardan coupling are their service life and reliability. The greatest influence on these indicators of functional ability has the character of the linear load distribution on cardan joints rolling parts. In order to shed some more light to the phenomena of linear load distribution and correlation between the geometric characteristics of rolling elements and the distribution of the linear load, analytical and numerical models under appropriate assumptions are established in this study. The obtained results shows, that with the standard (the existing) geometry of rolling parts, the engagement of points in root of Cardan cross jurnal in the load transfer is negligible due to very

Cardan joints have a wide range of applications in mechanical engineering because of the capability of transferring the load and motion from one shaft to another with different joint angle. The vital parts of these joints have a limited life due to insufficient surface strength in the area of rolling parts contact. Load distribution of Cardan joints composite parts have a major impact on their capacity and service life. Therefore, a detailed analysis of load distribution along the line of contact between Cardan Cross pins and rolling parts – needles, was carried out in this paper. Appropriate analytical and numerical models are developed. Based on the developed models, it is possible to optimize the geometrical parameters in terms of uniformity of load distribution of Cardan joints component in contact

The purpose of this paper is to present the method for solving multiobjective nonlinear optimization of planetary gear trains. Optimization of gear train was successfully accomplished using the genetic algorithm (GA). The weighting method is used to approximate the Pareto set. This method transforms the multiobjective optimization problem into single-objective optimization problem by associating each objective function a weighting coefficient and then minimizing the weighted sum of the objectives. The GA based approach produced quite satisfactory results promptly supplying the designer with the preliminary design parameters of planetary gear train for different gear ratios. The results showed that the genetic algorithm is useful and applicable for optimization of planetary gears desgin.

Kardanove spojnice se široko primenjuju u mašinstvu zbog mogućnosti prenošenja opterećenja i obrtnog kretanja sa jednog vratila na drugo, čije se ose međusobno seku pod promenljivim uglom. Vitalni delovi ovih spojnica imaju ograničeni radni vek zbog nedovoljne površinske čvrstoće kontaktnih površina spregnutih delova. Raspodela opterećenja spregnutih delova Kardanove spojnice ima veliki uticaj na nosivost i njihov radni vek. U tom cilju, u ovom radu, detaljno je analizirana raspodela opterećenja duž linije dodira rukavca Kardanovog krsta i kotrljajnih tela - iglica. Razvijeni su odgovarajući analitički i numerički modeli. Na osnovu razvijenih modela, moguće je izvršiti optimizaciju geometrijskih veličina sa aspekta ravnomernosti raspodele opterećenja spregnutih delova Kardanove spojnice., Cardan joints have a wide range of applications in mechanical engineering because of the capability of transferring the load and motion from one shaft to another with different joint angle. The vital parts of these joints have a limited life due to insufficient surface strength in the area of rolling parts contact. Load distribution of Cardan joints composite parts have a major impact on their capacity and service life. Therefore, a detailed analysis of load distribution along the line of contact between Cardan Cross pins and rolling parts - needles, was carried out in this paper. Appropriate analytical and numerical models are developed. Based on the developed models, it is possible to optimize the geometrical parameters in terms of uniformity of load distribution of Cardan joints component in contact.

This paper is a part of the case study of a power plant fan failure. The roller bearing of the fixed fan shaft support was completely damaged. As this bearing arrangement is realized by double-pressed joint (inner ring-bush and bush-shaft), influence of inadequate joints fits on the bearing failure under the real temperature conditions is analyzed in this paper.

Energy efficiency of thermal power plants depends on the vital plant elements' reliability levels. In order to preserve high level of energy efficiency, the vital elements' operational capability is continually monitored via observing the working temperature, vibration and noise levels. Yet, however, in spite of this, and usually due to inadequate maintenance, inadequate assembly, errors in the design or manufacturing processes, or due to accidents, abrupt failures of the plant's vital elements can occur. An example for this is the volumetric destruction of the fresh air fan shaft due to melting of the shaft at the shaft's stationary support. In addition to shaft destruction, the fan bearing and wheel blades have undergone destruction as well. This breakdown has occurred in the course of continual monitoring of the bearing service temperature and vibrations levels. Former studies, aimed at determining the breakdown causes, were based on the detailed examination of the damaged elements' materials and detailed analysis of the bearing setting arrangement. Considering the fact that the shaft stationary support was realized by means of a double-pressed joint, a thorough analysis has been made in this paper of the pressed joint operational capability in the boundary service conditions, in order to determine the extent to which the pressed joint participated in the breakdown.

Traction shafts and axles of railway vehicles are designed to be safe and reliable in normal service conditions Accidental and unpredictable conditions including bad exploitation (rail tracks, maintenance and extreme long service life) make the probability of shaft and axle fracture realistic. This article contains the experience and analysis of the traction shafts and axles fractures and fracture processes. Research also shows service conditions with results presented in the form of service stress spectrums. Besides normal service conditions, the results also include unpredictable phenomenon such as natural torsion vibrations of the shaft and wheels caused by stick-slip processes at the moment of the set in motion of a full-loaded train or at the moment of braking. These vibrations create an extremely high level of torque which is the main cause of cracks initialization. The next part of the article contains the results of the traction shafts and axles endurance research. The results of testing are transformed using the results of calculation by the FE method and by statistical estimation of the failure probability distribution. The main part refers to the interaction (impact) of service stress probability and failure (endurance) probability. which leads to the traction shaft (axle) reliability definition. Using the established model, locomotive traction shaft reliability is calculated and analyzed. The final part of the article contains suggestions for the traction shafts (axles) failure prevention

External load of ball bearing is transferred from one ring to other one through balls. In the radially loaded bearing all balls are not simultaneously active. Simultaneously active balls participating in load transfer are in loaded zone. Load distribution between balls in loaded zone is unequal. Width of loaded zone depends on bearing internal radial clearance. The loaded zone decreases with increasing clearance. Consequently, the load distribution between balls becomes more unequal. It leads to decreasing of ball bearing service life. The analysis of influence of internal radial clearance on the radially loaded deep groove ball bearing service life is carried out in this paper. For this purpose a new mathematical model is derived respecting classic ball bearing life theory and by introduction of a new parameter reduced load distribution factor.

Početak novog veka opterećuju tri velika globalna problema: ekonomski energetski i ekološki. Oni su toliko kulminirali da su postali svakodnevna tema, na različitim nivoima, a u cilju iznalaženja potencijalnih rešenja. U spektru mogućih rešenja nalazi se i reparatura mašinskih delova. Domen dejstva tehnologije reparature u rešavanju nastalih globalnih problema prikazan je u ovom radu., A Beginning of the 21st century is characterized by three major and global problems: economic, energetic and ecologic. Those problems are so accumulated, that they become every day theme on all levels in a way to solve them. In a spectrum of possible solutions is a machine parts reparature. The reparature technology scope is shown in this paper.

Spoljašnje opterećenje kotrljajnog ležaja se sa jednog prstena na drugi prenosi preko kotrljajnih tela. Pri tome je raspodela opterećenja na kotrljajna tela neravnomerna. Stepen neravnomernosti raspodele opterećenja zavisi od unutrašnje geometrije ležaja i intenziteta spoljašnjeg opterećenja. U ovom radu su definisana i razmatrana dva granična slučaja raspodele opterećenja kod kugličnog kotrljajnog ležaja opterećenog spoljašnjim radijalnim opterećenjem. To su idealno ravnomerna i izrazito neravnomerna raspodela opterećenja. Stvarna raspodela opterećenja je između ova dva granična slučaja. Novi matematički model raspodele opterećenja je razvijen na osnovu klasične teorije kotrljajnih ležaja i uvođenjem nove originalne veličine, definisane kao faktor raspodele opterećenja. Razvijeni matematički model obuhvata sve pomenute relevantne uticaje na raspodelu opterećenja u kotrljajnom ležaju (broj kotrljajnih tela u ležaju, unutrašnji radijalni zazor i spoljašnje opterećenje)., External load of rolling bearing is transferred from one ring to the other one through the rolling elements. Load distribution between rolling elements is unequal. Degree of load distribution unequality depends on internal geometry of bearing and magnitude of external load. Two boundary load distributions in radially loaded ball bearing were defined and discussed in this paper. These are ideally equal and extremely unequal load distribution. Real load distribution is between these boundary cases. The new mathematical model of load distribution is developed respecting classic rolling bearing theory and by introduction of new, original value defined as load distribution factor. Developed mathematical model includes all main influences on load distribution in rolling bearing (number of rolling elements, internal radial clearance and external load).

U radu je prikazano varijantno konstrukciono rešenje mašine za pakovanje prehrambenih proizvoda. Na osnovu tehno-ekonomske analize pokazano je da originalno i varijantno konstrukciono rešenje imaju približno istu tehničku vrednost, s tim što varijantna konstrukcija ima veću ekonomsku vrednost opravdanost. Ekonomska opravdanost postignuta je pogodnim konstrukcionim rešenjem i primenom domaćih komponenti i tehnologije izrade., The construction variation of packing machine in food processing is shown in this paper. By the techno-economic analyses it is shown that original and new construction has the same construction value, but the new construction has a better economic value – validity. Better economic value has achieved with new construction and engaging domestic components and production technology.

Polazna pretpostavka istraživanja u ovom radu je da se isplativa poboljšanja mogu postići na postojećim pogonima dozatora i dodavača uglja u termoelektrani "Nikola Tesla" u Obrenovcu. Inovacija je zamena mehaničkog varijatora frekventnim pretvaračem. Ona je eliminisala sve delove na kojima su najčešće bile popravke. Na osnovu odgovarajućih ispitivanja, merenja i analiza upoređeni su pogoni bez i sa frekventnim pretvaračem, sa dva aspekta. Tehničko upoređenje oba pogona sprovedeno je na njihovim performansama održavanju i radnom veku. Za ekonomsko upoređenje korišćene su MAPI metoda metoda sadašnje vrednosti i ekvivalentnih godišnjih troškova i metoda roka povraćaja sredstava. Polazeći od specifičnosti rada oba pogona, definisane su pretpostavke, mere i aktivnosti, koje su direktno uticale na izbor i kombinovanu primenu metoda za ocenu ekonomske efikasnosti investicionih ulaganja i metoda nastalih redukcijom troškova održavanja i popravki. Ova tehnička i ekonomska upoređenja su pokazala višestruke prednosti i koristi pogona dozatora sa frekventnim pretvaračem., A basic assumption of this paper is that economic beneficial upgrading of batcher on coal conveyer in fossil fuel power plant can be achieved. Innovation is mechanic variator replacement with frequency converter wherewith all parts which had frequent repairs were eliminated. The installations with and without frequency converter were compared from two aspects, the economic and technical one. For economic comparison the MAPI method, method of current value and equivalent annual expenses, as well as a method of repay date were used. These technical and economic comparisons approved that upgrading is reasonable.

According to improper bearing mounting on the a fresh air fan shaft in fosilfuel power plant, loss of operational reliability of immobile spherical roller bearing took place. That caused total failure of the fresh air fan installation. The consequence of this failure was a damage of the impeller with blades, and a total fracture of the shaft at the bearing sleeve spot. A comprehensive investigation took place to determine a cause of installation failure. In repair, as a constructional improvement, the bearing seating design was changed with purpose of bearing life extension, due to protection of asset fresh air fan components from destruction.

U radu je opisano originalno i varijantno konstrukciono rešenje regulatora protoka goriva sa kliznim dvostepenim i moduliranim sistemom regulacije koji se ugrađuje u protočne kotlove tipa 'Vaporeks'i 'Termopak' na naftu i mazut. Regulacijom protoka goriva povećava se efikasnost kotla. Regulacija protoka se obavlja na osnovu razlike pritisaka u regulatoru i mlaznici gorionika. Varijantnim konstrukcionim rešenjem originalna livena konstrukcija regulatora protoka goriva zamenjena je zavarenom konstrukcijom domaće proizvodnje., The original and variant construction solutions of the fuel flow regulator with the sliding two-stage and modular control system which is to be build-in continuous flow boilers of "Vaporeks" and "Termopak" types fired with oil and masut have been reviewed in this paper. By regulating the flue flow, the boiler efficiency is increased. The flow regulation is carried out on the basis of pressure difference in the regulator and the burner nozzle. By variant construction solution, the original cast construction of fuel flow regulator is replaced with the welded construction of domestic producer.