Машински факултет [Научни радови] / Faculty of Mechanical Engineering [Scientific papers]

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A Comparison Study of Fatigue Behavior of S355J2+N, S690QL and X37CrMoV5-1 Steel
(MDPI, 2022) Milovanović, Vladimir; Arsić, Dušan; Milutinović, Miroslav; Živković, Miroslav; Topalović, Marko
Steel of the mild-strength S355J2+N steel grade is the most often used steel for manufacturing carrying sections of constructions exposed to fatigue loads. The use of high-strength steels, such as S690QL, allows for the creation of structures that are light and simple to construct. However, increasing the yield strength of high-strength steels does not result in a corresponding increase in fatigue resistance. As a result, using high-strength steels for constructions subjected to fatigue loading can be a major design concern, raising the question of whether high-strength steels should be used at all. Most of the experimental investigations regarding the hot work tool steel X37CrMoV5-1 found in the literature are focused on its machining and wear resistance, with insufficient attention paid to the cyclic loads. This article evaluates the fatigue properties of mild-strength S355J2+N, high-strength S690QL, and X37CrMoV5-1 steel grades. A SHIMADZU servo-hydraulic testing machine is used to perform uniaxial tensile tests under uniaxial fatigue stress-controlled, fully reversed conditions (tensile–compression testing with R = 􀀀1 stress ratio) in accordance with EN ISO and ASTM standards. The aim of this paper is to highlight the fatigue characteristics of these three steels that are among the most used in their respective groups. Steel S355J2+N belongs to the group of hot-rolled normalized steels, S690QL belongs to the group of improved (quenched + tempered) steels with increased strength, and X37CrMoV5-1 belongs to the group of high-alloyed tool steels for hot work. This choice was made as the tested steels can be considered typical representatives of their groups. Based on the test results of these three steels, which are organized in S–N curves, the fatigue behavior of the entire mentioned groups of steels can be foreseen.
A MODEL OF MANAGEMENT INFORMATION SYSTEM FOR TECHNICAL SYSTEM MAINTENANCE
(University POLITEHNICA Timisoara, Faculty of Engineering Hunedoara, 2018) Medaković, Vlado; Marić, Bogdan
Technical systems for production are increasingly automate, which means that they have to work reliably. Therefore, the rapidly expanding concept of maintenance, where people would say that maintaining a process that allows the management of the technical condition and reliability during the entire life cycle of the system. Traditionally, maintenance has been considered as a support function, non-productive and not a core function adding little value to business. However it has been noticed that many manufacturing industries have used various approaches to improve maintenance effectiveness. An analysis of the problem of machines and industrial systems maintenance as well as maintenance strategies and maintenance management process is presented in this paper. Furthermore, a development process of traditional and modern maintenance management information system is given. The possibility of development maintenance management, applying decision support systems and expert systems, are presented, at the end.
ABC Classification of Risk Factors in Production Supply Chains with Uncertain Data
(Hindawi, 2017) Vujović, Aleksandar; Đorđrvić, Aleksandar; Gojković, Ranka; Borota, Milan
The problem of classification of risk factors in an uncertain environment is part of the risk management problem, which has a critical effect on the competitive advantage of production supply chain. The severities of consequences, their relative importance, and the frequency of occurrence of risk factors are defined by risk management team, depending on their experience and the results of good practice. Fuzzy rating of the severities of consequences and the frequency of occurrence of risk factors are described by linguistic expressions, which are modeled by triangular fuzzy numbers. The risk values, obtained by the materialization of the identified risk factors, are given precisely with the usage of fuzzy algebra rules. The classification criterion is defined as the distance between current risk value and extreme risk values. The proposed model enables determination of the priorities of risk factors. It is illustrated by an example with real-life data from a production supply chain in auto industry.
An Intuitionistic Fuzzy Multi-Criteria Approach for Prioritizing Failures That Cause Overproduction: A Case Study in Process Manufacturing
(MDPI, 2024) Sudžum, Ranka; Nestić, Snežana; Komatina, Nikola; Kraišnik, Milija
Overproduction is one of the most significant wastes of Lean that can occur in any manufacturing company. Identifying and prioritizing failures that lead to overproduction are crucial tasks for operational managers and engineers. Therefore, this paper presents a new approach for determining the priority of failures that cause overproduction, based on an intuitionistic fuzzy Multi-Criteria Optimization model and the Failure Mode and Effects Analysis framework. The existing vagueness in the relative importance of risk factors and their values is described using natural language words, which are modeled with trapezoidal intuitionistic fuzzy numbers. Determining the relative importance of risk factors is defined as a fuzzy group decision-making problem, and the weight vector is obtained by applying the proposed Analytical Hierarchy Process with trapezoidal intuitionistic fuzzy numbers. The compromise solution, as well as the stability check of the obtained compromise solution, is achieved using the proposed Multi-Criteria Optimization and Compromise Solution with trapezoidal intuitionistic fuzzy numbers. The proposed model was applied to data collected from a process manufacturing company.
Analiza temperatura na mjernim mjestima komponenti vjetroagregata 1 u VE „Rudine“
(Savez inženjera i tehničara Srbije, 2022) Krunić, Gojko; Vasković, Srđan; Krile, Srećko; Reščec, Boris; Bojović, Nebojša
U radu je prikazana analiza temperatura na mjernim mjestima pojedinih komponenti vjetroagregata 1 u Vjetroelektrani (VE) „Rudine“. Opisane su karakteristike čvorišta, multiplikatora, generatora i gondole vjetroagregata 1. Prikazana su kretanja temperatura na mjernim mjestima pomenutih komponenti u toku jednog dana tokom različitih ekvidistantnih desetominutnih intervala. Analizirane su minimalne, prosječne i maksimalne temperature na mjernim mjestima komponenti vjetroagregata 1, evidentirana vremena njihovog pojavljivanja i navedeni su desetominutni intervali u kojima su one izmjerene. Upoređivanjem mjernih podataka izmjerenih na mjernim mjestima komponenti vjetroagregata 1 moguće je uočiti njihovu međusobnu zavisnost.
ANALYSIS AND EVALUATION OF KEY INFLUENCING FACTORS ON THE OPTIMIZATION OF THERMAL ENERGY CONSUMPTION IN INDUSTRIAL THERMAL POWER PLANTS
(Vinča Institute of Nuclear, 2024) Simić, Stojan; Orašanin, Goran; Milić, Davor; Vasković, Srđan; Bakić, Vukman; Oka, Simeon; Jovanović, Marina
In the past, the design and operation of industrial thermal power plants did not give importance to energy consumption. Due to the depletion of fossil fuel reserves and the rising of their prices, restrictions in emission of waste gases into atmosphere, and the need to reduce production costs over the last thirty years, greater attention has been paid to optimizing thermal energy consumption. Various technical, technological, and organizational measures are undertaken to reduce thermal energy consumption. This study examines the proposals for improving the efficiency of thermal energy production in four thermal power plants in Bosnia and Herzegovina. The activities aimed at improving energy efficiency are consolidated and presented through five measures. To determine the optimal measure, the criteria for evaluating each measure are defined. These criteria are analyzed and filtered by using the ISM method, and while the fuzzy AHP method was used for their weights. Finally, the fuzzy TOPSIS method for multi-criteria optimization is applied to select the optimal energy efficiency measure for the analyzed thermal power plants. Additionally, the research defines the order of implementing the selected measures to improve the energy efficiency of the studied thermal power plants.
ANALYSIS OF MICROSTRUCTURAL DAMAGE ON C45E STEEL IN THE PROCESS OF COLD UPSETTING OF A CYLINDER
(Faculty of Technical Sciences, Institute for Production Engineering, 2016) Kraišnik, Milija; Vilotić, Dragiša; Šiđanin, Leposava; Šljivić, Milan; Stefanović, Milentije; Ilić, Jovan
From the production point of view, the appearance of cracks of metal components is very negative, except in some metal forming processes when fracture is deemed necessary in order to obtain a product with the required characteristics. However, in general a plastic crack stops further forming processes and is thus a major factor limiting the increase of productivity, especially in cold metal forming. Previous studies have confirmed that the mechanism of nucleation, growth and coalescence of microcavities, which control the level of microstructure damage and lead to initiation and expansion of fracture, are influenced by various factors, with the generated stress state in the forming zone having the strongest influence. In this paper, these problems were investigated in the process of upsetting of cylindrical sample with flat plates. Based on the SEM examination of the microstructure of C45E steel with the aim to quantify microstructural damage and the FEM analysis of the stress state in the critical zone of forming, it can be concluded that there is a different impact of individual components of stress on the accumulation of critical level of damage.
ANALYSIS OF POSSIBILITIES FOR DISTURBANCE REJECTION IN THE DECOUPLED MULTIVARIABLE PROCESS
(Faculty of Engineering Hunedoara, University Politehnica Timisoara, 2016) Prodanović, Saša; Nedić, Novak
Proper behavior of multivariable process isn't guaranteed only through the disabling influence of its mutual coupling (interaction), but also compensation of disturbance has very important role. Investigation of disturbance that can be rejected by previously decoupled 2×2 process has been presented in this paper. Considered flow tank, as a multivariable process, was controlled using PI controllers. The aim was to determine limit of disturbance intensity under whose influence system can operate correctly, and in that way additionally check validity of designed decoupler, i.e. chosen non-conventional control. General expression for periodic rising signal that can be introduced into process in order to present array of disturbances has been derived, too.Investigation was supported by simulations.
Analysis of Power Losses in Constrained Cycloid Drive
(Sveučilište u Slavonskom Brodu, Stojarski fakultet, 2023) Mačkić, Tihomir; Marjanović, Nenad; Tica, Milan; Troha, Sanjin; Milutinović, Miroslav; Rašović, Nebojša; Raos, Pero
The aim of this paper is to present a theoretical model for efficiency evaluation of a simple cycloid drive train with one degree of freedom (DOF) or constrained cycloid drive. In order to evaluate the efficiency, it is necessary to find the losses generated in the simple cycloid drive, where only losses depending on the load were considered. Expressions for determining speed ratios, efficiency, velocities and forces acting inside the cycloid drive are presented. These expressions are implemented in the theoretical model, where the places where the losses occur are defined. A computer program was created to facilitate analysis and obtain loss values based on different input data. Only load-dependent losses were considered in the theoretical model and computer program. In order to verify the theoretical model, experimental measurements were performed. A physical model of the simple cycloid drive train was created and analyzed on the test bench. The results for "S1" operating mode, i.e. when shaft 2 is stopped, show a mean value of the efficiency of 63.49%, for experimental measurements, while the mean value for theoretical analysis is 65.25%. For the operating mode "S2", i.e. with shaft 1 stopped, the mean value of the experimental measurements of the efficiency is 60.9%, while the theoretical mean value is 62.82%.
Analysis of Power Losses in Constrained Cycloid Drive
(Strojarski Facultet, Sveucilist Joseph Jurj Strossmayer in Osijeka, 2023) MAČKIĆ, Tihomir; MARJANOVIĆ, Nenad; TICA, Milan; TROHA, Sanjin; MILUTINOVIĆ, Miroslav; RAŠOVIĆ, Nebojša
The aim of this paper is to present a theoretical model for efficiency evaluation of a simple cycloid drive train with one degree of freedom (DOF) or constrained cycloid drive. In order to evaluate the efficiency, it is necessary to find the losses generated in the simple cycloid drive, where only losses depending on the load were considered. Expressions for determining speed ratios, efficiency, velocities and forces acting inside the cycloid drive are presented. These expressions are implemented in the theoretical model, where the places where the losses occur are defined. A computer program was created to facilitate analysis and obtain loss values based on different input data. Only load-dependent losses were considered in the theoretical model and computer program. In order to verify the theoretical model, experimental measurements were performed. A physical model of the simple cycloid drive train was created and analyzed on the test bench. The results for "S1" operating mode, i.e. when shaft 2 is stopped, show a mean value of the efficiency of 63.49%, for experimental measurements, while the mean value for theoretical analysis is 65.25%. For the operating mode "S2", i.e. with shaft 1 stopped, the mean value of the experimental measurements of the efficiency is 60.9%, while the theoretical mean value is 62.82%.
Analysis of the Influence Parameters on the Support Structure Stiffness of Large Radial-Axial Bearings
(University of Ljubljana Faculty of Mechanical Engineering, University of Ljubljana et al., 2019) Тrifković, Spasoje; Zdravković, Nebojša; Gašić, Мilomir; Savković, Мile; Marković, Goran
In certain types of crane and earth-moving machinery, such as portal cranes, loaders and excavators, the transfer of loads to crane tracks or the terrain is accomplished by means of undercarriage frames composed of box-like girders. The hypothesis that all four supports of the undercarriage frame do not lie in the horizontal plane is the basis for the formation of a calculation model. This paper analyses the influence of geometric parameters of box-like girders on the magnitude of additional forces at the supports of those frames when one of the supports is raised or lowered relative to the horizontal plane for the size Δ. Theoretical dependences between moments of inertia and stiffness under bending and torsion of those girders were thus established. Obtained relations leads to more concise forms of expressions for influential coefficients in Maxwell-Mohr integrals and simplifies optimization methods in the design of support structures. With experimental verification of the results, the influences of geometric parameters on the stiffness of the support structure are confirmed, and preconditions are created for further analysis of the connection made by large diameter bearings.
Analysis of the Influence Parameters on the Support Structure Stiffness of Large Radial-Axial Bearings
(Union of Mechanical Engineers and Technicians of Slovenia, etc., 2019) Тrifković, Spasoje; Zdravković, Nebojša; Gašić, Мilomir; Savković, Мile; Marković, Goran
In certain types of crane and earth-moving machinery, such as portal cranes, loaders and excavators, the transfer of loads to crane tracks or the terrain is accomplished by means of undercarriage frames composed of box-like girders. The hypothesis that all four supports of the undercarriage frame do not lie in the horizontal plane is the basis for the formation of a calculation model. This paper analyses the influence of geometric parameters of box-like girders on the magnitude of additional forces at the supports of those frames when one of the supports is raised or lowered relative to the horizontal plane for the size Δ. Theoretical dependences between moments of inertia and stiffness under bending and torsion of those girders were thus established. Obtained relations leads to more concise forms of expressions for influential coefficients in Maxwell-Mohr integrals and simplifies optimization methods in the design of support structures. With experimental verification of the results, the influences of geometric parameters on the stiffness of the support structure are confirmed, and preconditions are created for further analysis of the connection made by large diameter bearings.
Analysis of the Shifting Capabilities of Planetary Gear Trains with Coplanar Planet Gearsets
(Technical University of Sofia, 2023) Vrcan, Željko; Troha, Sanjin; Marković, Kristina; Tica, Milan; Milutinović, Miroslav; Mitrev, Rosen
This paper deals with the comparison of two different simple planetary gearsets. The first type is a 2k-h, variant A geartrain, while the other is a simple planetary gearset with coplanar paired planets. Methods for the kinematic synthesis of both gear trains are explored, together with the analysis of the transmission ratios that can be achieved by the gearsets. Both gear trains are analysed for the possibility of operating as a reversing gear train within their design limitations. The type with paired planets is of particular interest, as it can be built in a configuration that will have a transmission ratio of -1. This also enables compound gear trains having equal transmission ratios in both directions of rotation of the output shaft to be built.
ANALYSIS OF DYNAMIC BEHAVIOR OF ROTATING MACHINES
(Faculty of Engineering Hunedoara, University Politehnica Timisoara, 2014) Antunović, Ranko; Veg, Aleksandar
Operating supervision and the condition monitoring of the rotating machines, deploying exact diagnostic methods, can be considered as a good insight into the current state of a technical system and exact assessment of maintenance necessity. In this way, one can survey a large scale of machines and processes, without loss of reliability, as well reducing the costs of maintenance and increasing system profitability. This is the paramount demand of the modern production philosophy. The paper, consideres importance of data selection and implementation of appropriate diagnostic techniques with particular emphasis on the analysis of the dynamic behavior of rotating machinery. Shown are some of the results of diagnostic analysis that have been conducted on machines in a real operation, applying advanced methods of technical diagnostics.
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.
Application of Multi Criteria Decision Making for the Selection of Optimal Solid Wood Fuel Supply
(Faculty of Electrical Engineering, University of East Sarajevo, 2018) Vasković, Srđan; Gvero, Petar; Batinić, Krsto; Halilović, Velid; Medaković, Vlado; Musić, Jusuf
Production of solid fuels from wooden biomass is defined with appropriate energy chain of supply. The notion of energy chain concept has been defined as the trajectory of energy transformations from the fuel source or energy sources to useful energy form to end users. Supply chain for production solid fuels from wooden biomass is also energy chain with high importance in biomass energy planning. In this paper, base for testing and research is developed mathematical model in previous published paper with preliminary note titled as “Multi-Criteria Optimization Concept for the Selection of Optimal Solid Fuels Supply Chain from Wooden Biomass“ at Croatian Journal of Forest Engineering. Three supply chains have been included in comparison: production of wood chips at the terminal – variant 1, production of pellet – variant 2 and production of wood chips by means of a mobile chipper in a forest – variant 3. The VIKOR methodology is used for total ranking all mentioned chains. Real input data have been used for mathematical calculation correspond to Bosnia and Herzegovina conditions.
Application of Two-Carrier Planetary Gear Trains to Shifting Gearboxes
(Technical University of Sofia, 2023) Troha, Sanjin; Vrcan, Željko; Marković, Kristina; Tica, Milan; Milutinović, Miroslav; Mitrev, Rosen
This article deals with two-carrier planetary gearsets having two connecting and two external shafts, which may operate as two-speed gearboxes when brakes are placed on two external shafts. Analysis of the S16WN(S/E) gearbox is performed using the torque method, the specific torques are determined on all shafts, and then used to calculate both transmission ratios. The kinematic scheme of the gearbox has been synthesized, and the relative power flows have been identified. Efficiency functions are calculated for both gear ratios. The graphical representation of the transmission ratio functions for both gear ratios was used to obtain the diagram of the shifting capabilities of the S16WN(S/E) gearbox. The importance and utility of such diagrams and the relevant equations for the determination of ideal torque ratios of the component gear trains is explained. The size of the transmission ratio domain suggests that the S16WN(S/E) gearbox has a wide area of possible applications.
APPLICATION POTENTIAL OF SOME CRITERIA OF DUCTILE CRACK IN BULK FORMING PROCESSES
(University POLITEHNICA Timisoara, 2016) Kraišnik, Milija; Vilotić, Dragiša; Šiđanin, Leposava; Stefanović, Milentije; Anić, Jelica
Ductile crack criteria are unavoidable tool for material formability analysis. Their basic task is foreseeing the location of crack occurrence and critical value of deformation level in the course of forming process. However, in order to provide successful application of certain criterion it is necessary to be familiar with material characteristics, specificities of forming processes and forming conditions. For all the above mentioned reasons this paper deals with the analysis of application potential of some widely used criteria of ductile crack in cold bulk forming processes according to representative literature resources. Results can contribute better understanding of phenomenon of material microstructure damage and adequate choice of ductile crack criterion in the analysis of formability in various processes and forming conditions.
APPROACH TO DEVELOPMENT OF THE LEAN CONCEPT PROJECT
(University POLITEHNICA Timisoara, Faculty of Engineering Hunedoara, 2023) Marić, Bogdan; Medaković, Vlado; Kiss, Imre
We are on the threshold of joining the European Union (EU) and our business environment is experiencing a severe economic and financial crisis, which is a part of the global crisis. Based on the fact that mental and technological creativity grows just in times of crisis, the Lean concept is gaining recognition and becoming a challenge to future scientists, researchers and entrepreneurs in our country. Inspired by the Japanese automotive industry, it is synonymous with a good way to get out of the crisis. The time of crisis in giving us the best time to develop the strategies of work process improvement and the application of Lean concept. The crisis facilitates the use of new paradigms with completely new mental models in the business of organizational systems. This concept provides a focus on people, their training in work processes, teamwork and continuous improvement. They are crucial for the efficiency level in the use of key resources: people, techniques, property or capital invested in human labour performance.
BIOMASS AND SUSTAINABLE DEVELOPMENT OF LOCAL COMMUNITIES
(University Politehnica Timisoara, Faculty of Engineering Hunedoara, 2014) Vasković, Srđan; Medaković, Vlado
Energy production from biomass is very specific because they use different technologies to obtain useful products. All the conversion of biomass into useful energy, efficiency factor describes the energy chain, from biomass resources as the energy source. This includes the collection and preparation of remains, and storage of organic residues to the end use and the conversion of biomass into heat or electricity. In Bosnia and Herzegovina there are many possibilities for both growing and using forest for energy producing. Successful examples taken from forestry management practice in EU countries can be useful for enterprises, owners, commerce and environment in BiH.

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