Прегледај по Аутор "Radić, Nebojša"

Сада се приказује 1 - 20 од 20
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    ANALIZA NAPONSKOG STANJA KUKE KORIŠĆENJEM MKE
    (Mašinski fakultet, Univerzitet Istočno Sarajevo, 2011) Trifković, Spasoje; Radić, Nebojša; Šehovac, Savo; Košarac, Aleksandar; Milutinović, Miroslav
    Kuka je dio koji se najviše koristi za vješanje tereta kod dizalica. Težina kuke je teret koji dizalica mora uvijek dizati, čime se smanjuje nosivost i povećava potrebna snaga dizanja. Zbog toga, dimenzije kuke treba da imaju najmanje potrebne vrijednosti, pri propisanom stepenu sigurnosti. U ovom radu je izvršena analiza naponskog stanja kuke na uobičajeni način i uz pomoć računara, koristeći metodu konačnih elemenata (MKE). Uobičajeni način proračuna kuke se sastoji u provjeri napona u vlaknima materijala u pojedinim presjecima. Krivi dio kuke je proračunat na dva načina, približnom i tačnom metodom. U prvom slučaju je kuka posmatrana kao pravi stap ekscentrično opterećen, a u drugom kao krivi štap.
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    ANALIZA POUZDANOSTI PODSISTEMA ZA KOPANJE ROTORNOG BAGERA ER - 1250 RELIABILITY ANALYSIS OF BUCKET WHEEL DRIVE ON BUCKET-WHEEL EXCAVAVTOR ER - 1250
    (Elektrotehnički fakultet, Univerzitet u Istočnom Sarajevu, 2010) Trifković, Spasoje; Kraišnik, Milija; Radić, Nebojša
    Rad prikazuje izračunavanje pouzdanosti podsistema za kopanje bagera ER – 1250, za vremenski period od 2006. do 2009. godine. Za analizu otkaza korišćene su dvije metode iz teorije pouzdanosti, analiza stabla otkaza (FTA) i EFTES metoda alokacije pouzdanosti iz razloga njihove velike primjenjivosti i upotrebljivosti u analizama svih perioda životnog vijeka. Za realizaciju proračuna razvijen je programski paket za izračunavanje alociranog inteziteta otkaza i pouzdanosti.
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    ANALYTICAL SOLUTION FOR THERMAL VIBRATIONS OF SINGLE-LAYERED GRAPHENE SHEETS WITH VARIOUS BOUNDARY CONDITIONS
    (University POLITEHNICA Timisoara, 2018) Radić, Nebojša; Jeremić, Dejan
    This paper deals with analysis of thermal vibration behaviour of orthotropic single-layered nanoplate with various boundary conditions. The new first-order shear deformation theory is reformulated using nonlocal differential constitutive relation of Eringen. The governing equations of motion are derived from Hamilton's principle. Using Galerkin method, analytical solution for rectangular nanoplates under various boundary conditions are obtained. Numerical results are presented to show variations of the dimensionless frequency of single-layered nanoplates corresponding to various values of the nonlocal parameter and temperature change.
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    BUCKLING ANALYSIS OF ORTHOTROPIC DOUBLE- NANOPLATE- SYSTEMS BASED ON NONLOCAL TWO- VARIABLE REFINED PLATE THEORY
    (University Politehnica Timisoara, Faculty of Engineering Hunedoara, 2015) Radić, Nebojša; Jeremić, Dejan; Sekulić, Lana
    This paper presents an analytical study on the buckling of orthotropic double- nanoplate-system (DNPS) subjected to biaxial compression using the two-variable refined plate theory and nonlocal elasticity theory. The two - variable refined plate theory takes into account the effects of small scale and transverse shear strains through the thickness of the nanoplate. The theory assumes parabolic distribution of the transverse shear strains through thickness of the nanoplate and does not require shear correction factors. Derived nonlocal governing equations are based on the nonlocal theory and the principle of virtual displacements. The expression for buckling load of a simply supported orthotropic DNPS was derived using the Navier's method.
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    BUCKLING ANALYSIS OF SIMPLY SUPPORTED SQUARE SYMMETRIC LAMINATED COMPOSITE PLATE
    (University POLITEHNICA Timisoara, 2023) Jeremić, Dejan; Radić, Nebojša; Vučetić, Nikola; Kiss, Imre
    To usethe laminated composite plates efficiently, it is necessary to develop appropriate analysis theories to predict accurately their structural and dynamical behavior. The analysis of the behavior of the laminated plates is an active research area because of their complex behavior. The structural instability becomes an important concern in a reliable design of composite plates. The majority of the investigations on laminated plates utilize either the classical lamination plate theory (CLPT), or the first-ordershear deformation theory (FSDT). Various geometries of the plates subjected to compressive load are studied. The present work deals about a buckling analysis of simply supported symmetric composite plate with four layers. It is assumed that composite plate is surrounded by external elastic fundation. Composite plate is modeled by the finite element method and subjected to biaxial compression load. Governing equations are derivedbased on Classical Laminated Plate Theory (CLPT) and computed critical buckling loads were compared with numerical results.
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    Dynamic Analysis of the Crane with Loading-unloading Trolley on the Slewing Platform
    (Institut IMK "14. oktobar", Kruševac, 2015) Trifković, Spasoje; Gašić, Milomir; Radić, Nebojša; Milutinović, Miroslav; Gašić, Milomir
    Dynamic processes of the cranes with loading-unloading trolley on slewing platform are very complex and require certain simplifications, although efforts should be made to theoretically involve widest range of impacts, with respect to degree of importance of individual impacts. The study of the dynamic behavior of the cranes is very important in terms of precise determination of stress state, as well as the other characteristics of the elements and supporting structures. Dynamic loads of the cranes occur during periods of non-stationary operating regimes of any of its mechanisms. In this paper, we obtain the differential equations of motion of the cranes for some specific cases of movement, based on general multi-mass model of the crane with loading-unloading trolley on slewing platform.
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    INFLUENCE OF ADDITIONAL Pa CONTROLLER TO THE SYSTEM RESPONSE WHEN THE SET POINT IS CHANGING
    (Mašinski fakultet Istočno Sarajevo, Univerzitet u Istočnom Sarajevu, 2020-11) Prodanović, Saša; Dubonjić, Ljubiša; Nedić, Novak; Radić, Nebojša; Prodanović, Saša
    One of the numerous approaches for disturbance rejection is occasionally introducing additional Pa term in parallel to the existing controller. It is strongly important to check effects of its operation to the system's transient processes caused by instant changes of set point, because it is well known that too high values of P term can lead system into unstable state. Therefore, this paper deal with researching of maximum proportional gain that can be used for disturbance rejection if it appear in the transient process (dynamical area of system response). Investigation has been carried out using numeric simulations, on the some characteristic process examples, that were considered in the previous survey of mentioned additional Pa controller.
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    INFORMACIONE TEHNOLOGIJE I SAVREMENI TRENDOVI OBLIKOVANJA ORGANIZACIJE
    (Elektrotehnički fakultet, Univerzitet istočno Sarajevo, 2011) Medaković, Vlado; Radić, Nebojša; Vasković, Srđan
    Cilj ovog rada je da ukaže na nove izazove u modernom korporativnom upravljanju i primjenu informacionih tehnologija kao mogući odgovor u pogledu na visok nivo turbulencija. Pokazalo se da klasična organizacija i upravljanje predstavljaju ograničavajući faktor za primjenu novih tehnologija, naročito informacionih tehnologija i da je neophodno fundamentalno promijeniti korporativni dizajn u cilju postizanja boljih performansi. Kao primjer dat je jedan od novih oblika organizacije, Web Paukova mreža.
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    INVESTIGATION OF VIBRATION RESPONSE OF ORTHOTROPIC DOUBLENANOPLATE SYSTEM SUBJECTED TO INITIAL IN-PLANE PRELOAD
    (University POLITEHNICA Timisoara, 2019) Radić, Nebojša; Jeremić, Dejan
    Analytical methods are employed and explicit solutions for vibrational frequency are obtained for orthotropic doublenanoplate system subjected to an in-plane magnetic field for various boundary conditions. The nonlocal governing equations of motion are derived via Hamilton’s principle with the consideration the Eringen’s differential nonlocal elastic law. Effects of initial preload (compression and tension), magnetic field strength, size of nanoplate, and boundary conditions on vibrational frequency are presented.
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    LEAN WASTE IN THE MANUFACTURING INDUSTRY
    (Mašinski fakultet Istočno Sarajevo, Univerzitet u Istočnom Sarajevu, 2020) Gojković, Ranka; Nestić, Snežana; Radić, Nebojša; Prodanović, Saša
    In principle, the basic idea of achieving Lean production is continuous waste reduction. This implies a reduction of all activities that do not contribute to the successful operation of the company, and thus do not add value to the product or service. Each wastes significantly affects the production time, price as well as the quality of the product, which makes the company less competitive in today's market. By identifying failures that lead to Lean waste and reducing or eliminating them, the wastes are reduced, which leads to a significant improvement in the production process. Continuous improvement in production through waste elimination has been recognized as one of the most important tasks of socially responsible organizations.
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    MECHANICAL BUCKLING OF DOUBLE-LAYERED GRAPHENE SHEETS EMBEDDED IN AN ELASTIC MEDIUM USING A NONLOCAL NEW FIRST-ORDER DEFORMATION THEORY
    (University POLITEHNICA Timisoara, 2017) Radić, Nebojša; Jeremić, Dejan
    This paper investigates the buckling behavior of double-layered graphene sheets (GSs) with vaious boundary conditions. It is assumed that two graphene sheets are bonded by an internal elastic medium and surrounded by external elastic fundation. Governing equations are derived based on new first-order sher deformation theory (NFSDT), while the expressions for the buckling load are given in explicit form for a graphene sheets with all edges simply supported (SSSS) and all edges clamped (CCCC). The equations of equilibrium of the nonlocal model have been derived by using the vertical displacement method. Two characteristic types of buckling are considered (in-phase buckling and out-of-phase buckling). The influence of small scale coefficient, aspect ratio, stiffness of internal elastic medium and external elastic fundation on the nonlocal buckling load is explained. Keywords: Analytical modelling, Buckling, Nano-structures
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    NUMERICAL ANALYSIS OF FREE UPSETTING CYLINDER USING FEM WITH EXPERIMENTAL VERIFICATION
    (Elektrotehnički fakultet, 2011) Radić, Nebojša; Kraišnik, Milija; Trifković, Spasoje
    This paper describes numerical simulation of upsetting process of cylindrical specimen by flat die performed by Finite Element Analysis on the bases of results of experimental research. Software CATIA V5 R18 is used for modeling and simulation. Having in mind that during the upsetting process large deformation occurred, nonlinear analysis is performed. It is needed to take into consideration large displacement and contact friction, as well as large pressure cylinder and rigid die. Results gained by Finite Element Analysis and by experiment show high degree of similarity, so this way of modeling could be used for even more complex technology of plasticity.
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    Numerical research of thermal stress in a gas burner with a cylindrical mantle in relation to its construction
    (2020) Prohaska, Biljana; Radić, Nebojša; Gvero, Petar
    Over the last few years there has been a great interest in research into the improvement of gas condensing boilers with pre-mixing. Many researchers are concerned with the improvement of the construction of these boilers, whose individual parts directly affect some parameters such as combustion efficiency, burning intensity, flame stability and NOx emissions. The outer mantle of a cylindrical burner stands out among the parts of the structure as the said parameters depend on it This paper analyses the outer cylinder of the premixed burner in relation to thermal stress. Numerical FEM analysis was performed based on experimental measurements and CFD input data. The tests were carried out in different gas and different materials. The results obtained show different thermal stresses which are dependent on the different gas and materials on the outer cylindrical mantle. This indicates the necessity to optimize materials and patterns applied to the outer cylindrical mantle of the burner, which will be the subject of further research.
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    POREĐENJE REZULTATA SOPSTVENIH FREKVENCIJA KARBONSKIH NANOCIJEVI DOBIJENIH METODOM KONAČNIH ELEMENATA (MKE) I ANALITIČKOM METODOM
    (Mašinski fakultet, Univerzitet Istočno Sarajevo, 2014) Vučetić, Nikola; Radić, Nebojša; Milutinović, Miroslav; Trifković, Spasoje; Košarac, Aleksandar
    Kroz ovaj rad je izvršeno poređenje rezultata sopstvenih frekvencija karbonskih nanocijevi dobijenih korišćenjem MKE analize i analitičke metode. Svako tijelo ima sopstvenu frekvenciju kojom osciluje ukoliko nije izloženo dejstvu spoljašnjih sila. Cilj rada je da se utvrdi jednakopravnost MKE analize i analitičke metode u izračunavanju sopstvenih frekvencija karbonskih nanocijevi. Izračunate su sopstvene frekvencije karbonskih nanocijevi kružnog i kvadratnog poprečnog presjeka putem MKE analize i analitičke metode, te je izvršeno poređenje dobijenih rezultata prikazanih tabelarno i na dijagramima. Na osnovu dobijenih vrijednosti može se zaključiti da se odstupanja u rezultatima pri određivanju sopstvenih frekvencija nanocijevi putem MKE analize i analitičke metode nalaze u dozvoljenim granicama.
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    THE INFLUENCE OF CARBON FIBER ORIENTATION ANGLE ON BUCKLING PROPERTIES OF FOUR–LAYER SYMMETRIC LAMINATE UNDER BIAXIAL COMPRESSION
    (University POLITEHNICA Timisoara, 2022) Jeremić, Dejan; Radić, Nebojša; Vučetić, Nikola; Kiss, Imre
    The present work focused on the buckling of four–layer symmetric laminate subjected to biaxial compression. Governing equations are derived based on Classical Laminated Plate Theory (CLPT). The composite plates are bonded by an internal elastic medium and surrounded by external elastic foundation. The influences of carbon fiber orientation angle and aspect ratio on critical buckling load are demonstrated for symmetric laminate. We analyzed four lamination scheme which fiber angle orientation is equal to 0°, 30°, 45° and 90°.
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    The influence of different lamina positions on buckling properties of composites plates under biaxial compression
    (2019) Jeremić, Dejan; Radić, Nebojša
    The present work focused on the buckling of composite plates subjected to biaxial compression using classical laminated plate theory (CLPT). The two composite plates are bonded by an elastic medium. Classical laminated plate theory (CLPT) is utilized for deriving the governing equations. Difference between 4-ply symmetric lamination scheme with different material properties and fiber orientation angle (0° and 30°) is shown. The study show that the mechanical properties of the composite materials depending on the fiber orientation angle and lamina positions.
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    The Mechanical Modeling of Thermomechanical Processes for Thin- Walled Cylinders
    (Faculty of Mechanical Engineering, Belgrade University, 2024) Prochaska, Biljana; Radić, Nebojša; Nebojša, Srđan
    The problem of stress in perforated thin-walled cylinders due to mechanical and thermal load was analyzed for cases where the load of the system varies both along the cylinder circumference and axially. Starting from the solution and considerations for a smooth thin-walled cylinder, the concept was expanded and the distribution of deformations caused by thermal loads on the cylinder and the resulting stresses in the structure of the thin-walled perforated cylinder was observed for a specific form of perforation. The cylindrical perforated burner is one of the main elements of premixed condensing boiler for home heating systems. The quality of combustion, and thus the heat load on the outer sheath of the burner, largely depends on the layout, shape and dimensions of the perforation. This paper presents the mechanical modeling of thermomechanical processes of a cylindrical gas burner with premixing for a triangular layout or the so-called checkerboard shape of perforation.
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    The Mechanical Modeling of Thermomechanical Processes for ThinWalled Cylinders
    (Faculty of Mechanical Engineering, Belgrade, 2024) Prochaska, Biljana; Radić, Nebojša; Bulatović, Srđan; Rašuo, Boško
    The problem of stress in perforated thin-walled cylinders due to mechanical and thermal load was analyzed for cases where the load of the system varies both along the cylinder circumference and axially. Starting from the solution and considerations for a smooth thin-walled cylinder, the concept was expanded and the distribution of deformations caused by thermal loads on the cylinder and the resulting stresses in the structure of the thin-walled perforated cylinder was observed for a specific form of perforation. The cylindrical perforated burner is one of the main elements of premixed condensing boiler for home heating systems. The quality of combustion, and thus the heat load on the outer sheath of the burner, largely depends on the layout, shape and dimensions of the perforation. This paper presents the mechanical modeling of thermomechanical processes of a cylindrical gas burner with premixing for a triangular layout or the so-called checkerboard shape of perforation.
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    Uticaj interakcije lokalnog i distorzionog oblika gubitka stabilnosti tankozidih profila otvorenog poprečnog presjeka na smanjenje nosivosti u postkritičnoj fazi
    (Institut IMK "14. oktobar", 2012) Radić, Nebojša; Trifković, Spasoje; Jeremić, Dejan; Milutinović, Miroslav; Gašić, Milomir
    U radu se razmatra problem određivanja vrijednosti lokalnog i distorzionog kritičnog napona tankozidih profila otvorenog poprečnog presjeka. Kod tankozidih nosača gubitak stabilnosti se dešava u zoni elastičnosti i pri relativno malim vrijednostima kritičnog napona. Sa povećanjem opterećenja u postkritičnoj fazi pri određivanju nosivosti potrebno je uzeti u obzir interakciju lokalnog i distorzionog oblika jer dolazi do značajnog smanjenja nosivosti u odnosu na slučaj kada se ta interakcija zanemaruje.
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    Vibration analysis of orthotropic double-nanoplate system subjected to unidirectional in-plane magnetic field with various boundary conditions
    (International Organization Of Scientific Research (IOSR), 2018) Radić, Nebojša; Jeremić, Dejan; Mijatović, Biljana
    The present study investigates the vibration behaviour of orthotropic double-nanoplate system subjected to an in-plane magnetic field and in-plane preload with various boundary conditions. The nonlocal governing equations of motion are derived via Hamilton’s principle with the consideration the Eringen’s differential nonlocal elastic law, where the influences of the Lorenz magnetic force are obtained via a Maxwell’s relation. Analytical methods are employed and explicit solutions for vibrational frequency are obtained for orthotropic double-nanoplate system for various boundary conditions. The obtained results are compared with the results available in the literature to check their validation. Effects of nonlocal parameter, magnetic field strength, number of half waves, initial preload (compression and tension), size of nanoplate and boundary conditions on vibrational frequency are presented.