Browsing by Author "Tadić, Branko"

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Analyzing the Influence of the Construction Element Position on Torque Transmission by Friction
(2014) Jeremić, Marija; Matejic, Milos; Bojan, Bogdanović; Tadic, Branko; Miloradović, Danijela; Dragomir, Miljanić
This paper is analyzing the impact of the construction element position of ship winch drum on the effects of torque transmission by friction in the mechanization welding process. The driving and driven wheels (construction elements) were examined for the general case of the load distribution. Based on this examination, the construction of the device that should provide the reliable torque transmission and the movement of the drum in the process of its welding are proposed. This construction is characterized by a high level of flexibility and ability to change the friction torque based on changing drum position in regard to the driving and driven wheels (construction elements). With this new construction, problems related to the movement synchronization are avoided, unlike the all previously known constructions of this type, which lead to the positive impact on the wear intensity of friction gears.
Applications of Friction Stir Processing during Engraving of Soft Materials
(2015) Kočović, Vladimir; Mitrovic, Slobodan; Mihajlovic, Goran; Mijatović, M.; Bogdanović B.; Vukelic, Djordje; Tadic, Branko
Friction stir processing has extensive application in many technological operations. Application area of friction stir processing can be extended to the processing of non-metallic materials, such as wood. The paper examines the friction stir processing contact between a specially designed hard and temperature-resistant rotating tool and workpiece which is made of wood. Interval of speed slip and temperature level under which the combustion occurs and carbonization layer of soft material was determined. The results of the research can be applied in technological process of wood engraving operations which may have significant technological and aesthetic effects.
Conversion of data into information in tribology research
(2014) Erić, Milan; Babic, Miroslav; Mitrovic, Slobodan; Tadić, Branko; Dzunic, Dragan
Relevant and timely information is of crucial importance in scientific investigations and understanding of the phenomena should be precise and explicit. Among others, phases of scientific investigations comprise data acquisition and their structuring into database and data warehouse, followed by their analysis in order to find laws and patterns and comparison with similar data. These activities are aimed at data to become information and for information to grow into knowledge and to further use of that knowledge to formulate decisions and to anticipate future events and possibilities. However; simple analysis of information obtained from conducted research is no longer sufficient, therefore, proactive approach is needed, that is technologies, skills and tools are needed that will assist in rapid decision-making and forecasting. The paper presents architectures for data acquisition, developed databases and reporting, as well as contemporary information technologies used for tribological investigations in area of Metal-Matrix Composites - MMCs, in the light of the above observations.
Data Model for Creating Applications for Maintenance and Management of the Documentation
(2012-06) Aleksić, Nataša; Erić, Milan; Ivanović, Lozica; Tadic, Branko
21 st century is characterized by a very strong interest and importance of quality products and services, as well as the need of effective protection that managers can use the system for making information security program information security performance measurement, which, in addition to improving the process used protection stakeholders for decision making and implementation safety requirements of clients. The idea is that the Technical College of Professional Studies functionally integrated in order to achieve quality education and research. This paper presents a data model for an integrated system of quality high school vocational technical studies as the basis for the development of application software maintenance and management of quality system documentation introduced. The objective of this project task is to try the integration of standards JUS ISO 9001 and ISO 27001 for the Technical High School of Professional Studies.
Design of Modern Concept Tribometer with Circular and Reciprocating Movement
(2007) Marjanovic, Nenad; Tadic, Branko; Ivkovic, Branko; Mitrovic, Slobodan
This paper considers construction and advantage of modern tribometer conception. Tribometer TPD-04 enables simulation of different contact and test types. Special device enables pin on disk, circular and linear reciprocating test types. The main purpose of tribometer was investigation of friction and wear of polymer materials with or without lubricant according to appropriate standards. Tribometer concept and design solution of same subassemblies that provide defined requests fulfill were described in details. Measure system and software for data acquisition and processing results are specially described.
Development of Tribometer and Measurement Results of Static Coefficient of Friction Sliding and Coefficient of Rolling Friction by Principle Steep Plane
(2011) Tadic, Branko; Jeremic, Branislav; Vukelic, Djordje; Mitrovic, Slobodan; Erić, Milan
The paper presents a solution of new developed tribometer intended measuring that static coefficient of friction sliding and static coefficient of rolling friction materials of various types. Principles of measurement are theoretically analyzed, presented the basic of structural solutions and some results of measurements. Tribometer is based on the principle of the steep plane and provides a rotation angle of the steep plane with an accuracy of one minute, which provides high precision of measurements. From the point of the possible values of the load contact pairs developed tribometer belongs to a class of micro and nano tribometers.
Eco-design of fixtures based on life cycle and cost assessment
(2019) Vukelic, Djordje; Agarski, Boris; Budak I.; Šimunovic̈ G.; Buchmeister, Borut; Jakovljevic, Zivana; Tadic, Branko
© 2019 DAAAM International Vienna. All rights reserved. The paper presents the new model for eco-design of fixtures based on life cycle and cost assessment. Four fixture types with different mechanical and physical properties as well as different manufacturing costs have been evaluated. The life cycle results show that the environmental impact is closely related to the mass of steel needed for fixture manufacture. On the other hand, the fixture with the largest environmental impact had the smallest total fixture cost and vice versa. The results show that it is possible to implement environmental and cost analysis in fixture design process and to enable comparative analysis of fixture constructions by three standpoints, technical, environmental and economic.
EVALUATION OF THE KINETIC FRICTION COEFFICIENT BY USING „DISC-BLOCK“ FRICTION PAIR OF DIFFERENT WOODEN SAMPLES
(2019) Vukelic, Djordje; Santoši, Željko; Šokac, Mario; Budak I.; Sarić A.; Šimunovic̈ G.; Tadic, Branko
The paper presents the measurement results of the kinetic friction coefficient on wooden specimens. The measurements were carried out according to the „disc-block” friction pair method. Blocks and discs are made of five different types of wood-beech, ash, oak, pine, and fir. Experimental investigations were performed for different values of disc speed (rpm) and with different normal loads on the block. The obtained results indicate that the contact pairs of wood with higher surface hardness have higher values of the kinetic friction coefficient and vice versa. The values of the kinetic friction coefficient had approximately constant values for different experimental conditions with the tendency of a slight decrease while increasing normal load and the speed (number of rpm).
Implementation of automatic identification technology in a process of fixture assembly/disassembly
(2011) Ostojic, Gordana; Stankovski, Stevan; Vukelic, Djordje; Lazarevic M.; Hodolić J.; Tadic, Branko; Odri S.
Radio Frequency Identification (RFID) technology presents automatic identification technology that can be used in product life cycle various phases, especially in the manufacturing phase. The analysis of possible application of RFID technology in machining and inspection operations for fixture manufacturing assembly/disassembly process is presented in this paper. Furthermore, assemble/disassemble fixture manufacturing system structure and conception is presented. An analysis involves hardware and software components that the designed system for assembly/disassembly needs to have. Suggested system verification was done in laboratory conditions. Verification uses ninety-six parts and adequate fixtures. The paper concludes with final remarks, discussing advantages and disadvantages of the developed system. © 2011 Journal of Mechanical Engineering. All rights reserved.
Increasing stiffness of constructions through application of enhancing elements
(2018) Tadic, Branko; Matejic, Marija; Šimunovic̈ G.; Kljajin M.; Kočović, Vladimir; Bogdanović, Bojan; Vukelic, Djordje
© 2018, Strojarski Facultet. All rights reserved. Presented in this work is a study on construction stiffness, based on examination of their neutral lines for various cross-section geometries and different force magnitudes. Investigations were conducted both through numerical simulations and experimentally. The results of numerical simulations indicate that stiffness enhancement reduces deflection in the range of 41-52 %, while the experimental tests showed the reduction of 42-54 %. Also reviewed is comparative analysis between the stiffness results obtained by numerical analyses and experiments, which showed high degree of their compliance. The deviations between the results offered by the two methods are 1-3 %, on average, while in the worst case, which occurs in just a couple of points, the deviation equals 10 %. This study revealed significant increase of element stiffness, which was obtained by employment of additional stiffness enhancing elements.
INFLUENCE OF FRICTION ON INCREASE STIFFNESS OF MODULAR FIXTURE SYSTEMS
(2017-05-17) Matejic, Marija; Matejic, Milos; Novkinic B.; Živković, Milutin; Tadic, Branko
The idea of development of modular fixture systems increased level of stiffness and flexibility based on modular fixture systems that are in the basic form of framed structures. It is assumed that the concept of forming assemblies of modular fixture systems provide greater rigidity and flexibility, greater reliability, which is especially important if you take into account the possible use of these accessories when processing on modern multi-axis numerical machines in which at once basing and tightening treatment performed with a number of different tools. The friction between structural elements of the modular fixture systems are analyzed.
Intelligent design and optimization of machining fixtures
(2016) Vukelic, Djordje; Šimunovic̈ G.; Tadic, Branko; Buchmeister, Borut; Saric T.; Simeunovic N.
© 2016, Strojarski Facultet. All rights reserved. This work presents an integral system for machining fixture layout design and optimization. The optimization module of this system allows determination of optimal positions of locating and clamping elements, which provides required accuracy and surface quality, while at the same time guarantees design of collision-free fixtures. The design module performs selection of required fixture elements based on a set of predefined production rules. Adequate criteria for the selection of fixture elements are defined for locating, clamping, tool guiding, and tool adjustment elements, as well as for fixture body elements, connecting elements and add-on elements. The system uses geometry and feature workpiece characteristics, as well as the additional machining, and process planning information. It has been developed to accommodate machining processes of turning, drilling, milling, and grinding of rotational and prismatic workpieces. A segment of output results is also shown. Finally, conclusions are presented with directions for future investigation.
A method for determination of kinetic friction coefficient under dynamic loading conditions
(2022) Brzakovic, Ljiljana; Kočović, Vladimir; Mitrovic, Slobodan; Busarac, Nina; Tadic, Branko
In general, the kinetic friction coefficient can, under any contact loading condition, be determined using methods completely different from the existing methods based on the measurements of contact load and friction force. The proposed method refers to the determination of kinetic friction coefficient using the dynamic equation of motion for a rotating body, where the active force acts on the rotating body only at the initial moment of motion, while body masses, which are concentrically and eccentrically distributed in relation to the axis of rotation, provide a static and dynamic component of a desired 'sleevebearing' contact load. If the body angle of rotation change is experimentally determined as a function of time, then, based on the dynamic equation of motion, it is possible to determine the current friction coefficient values for the entire time period from the start of the motion to the rotation stop. It can be said that acceleration is a physical and energy indicator for friction and energy dissipation in tribomechanical systems, and that it defines the complete dynamics of the friction process itself.
Micro-cutting of holes by centrifugal force
(2023) Kočović, Vladimir; Vukelic, Djordje; Kostić A.; Bijelić I.; Prica, Miljana; Tadic, Branko
The paper presents a novel process of micro-cutting wherein the material removal is achieved by applying a constant penetration force of the cutting tool into the workpiece. Penetration force is achieved by a specially designed moving assembly comprising a tool and toolholder. Micro-cutting with constant cutting force is performed on conventional machine tools, using conventional cutting tools. The design of the tool and toolholder assembly enables the regulation of the penetration force intensity, i.e. the regulation of cutting depth. The regulation is achieved by changing the mass, eccentricity, and angular velocity of the moving assembly. The obtained results indicate that the applied method provides small cutting depths, a reduction of circularity deviation and roughness, and a more favourable distribution of the material in the surface layer.
Modelling and prediction of surface roughness in cnc turning process using neural networks
(2020) Saric T.; Vukelic, Djordje; Šimunovic̈ K.; Svalina I.; Tadic, Branko; Prica, Miljana; Šimunovic̈ G.
© 2020, Strojarski Facultet. All rights reserved. The paper presents an approach to solving the problem of modelling and prediction of surface roughness in CNC turning process. In order to solve this problem an experiment was designed. Samples for experimental part of investigation were of dimensions Φ30 × 350 mm, and the sample material was GJS 500-7. Six cutting inserts were used for the designed experiment as well as variations of cutting speed, feed and depth of cut on CNC lathe DMG Moriseiki-CTX 310 Ecoline. After the conducted experiment, surface roughness of each sample was measured and a data set of 750 instances was formed. For data analysis, the Back-Propagation Neural Network (BPNN) algorithm was used. In modelling different BPNN architectures with characteristic features the results of RMS (Root Mean Square) error were controlled. Specially analysed were the RMS errors realised by different number of neurons in hidden layers. For the BPNN architecture with one hidden layer the architecture (4 – 8-1) was adopted with RMS error of 3,37%. In modelling the BPNN architecture with two hidden layers, a considerable amount of architectures was investigated. The adopted architecture with two hidden layers (4-2-10-1) generated the RMS error of 2,26%. The investigation was also directed at the size of the data set and controlling the level of RMS error.
Modelling and simulation of a novel modular fixture for a flexible manufacturing system
(2018) Matejic, Marija; Tadic, Branko; Lazarevic M.; Misic M.; Vukelic, Djordje
© 2018, Vienna University of Technology. All rights reserved. Wrong or inadequate design and manufacture of modular fixtures can lead to deformations and displacements of workpiece and fixture-workpiece assembly, as well. Deformations and displacements can significantly impact final workpiece accuracy, rendering the fixture less efficient. With that in mind, this paper reviews development of a novel multi-purpose solution for a modular fixture design with higher efficiency, higher accessibility and flexibility. The results of simulations and modelling indicate that the proposed modular fixture design has advantages over the existing, conventional modular fixtures. The proposed framed structure of modular fixtures exhibits versatility in that it allows reliable locating and clamping of workpieces featuring complex geometry and shape. The novel design solution for modular fixtures opens new directions for future investigation, regarding selection and optimization of materials, shape and geometry of fixture elements which can be used to extend and upgrade modular fixtures. All this contributes to higher workpiece quality and accuracy, as well as the higher productivity and lower production costs.
Modelling of micro-turning process based on constant cutting force
(2021) Vukelic, Djordje; Kanovic Z.; Šokac, Mario; Santoši, Željko; Budak I.; Tadic, Branko
In this research, an evaluation of the external transverse micro-turning with conventional cutting inserts was performed with a constant cutting force in a dry environment. During machining, the number of revolutions, machining time and cutting forces was varied. Before and after machining, the diameter of the workpiece, circularity and the roughness of the machined surface was measured. The obtained results indicate that with increasing number of revolutions, time and cutting force, the cutting depth increases. The results show that this type of machining can achieve very small cutting depths and reduce circularity deviation and roughness of the machined surface. Based on the experimental results, the modelling of the artificial neural network (ANN) was performed which reliably predicted the change in diameter, cylindricity, and roughness after micro-turning operation, with a mean percentage error smaller than 3 %. It can be concluded that the application of ANN is adequate during the machining process with the constant cutting force, since the output parameters can be predicted with small error, while also reducing effort and costs.
Multi-criteria decision-making and life cycle assessment model for optimal product selection: case study of knee support
(2017) Vukelic, Djordje; Budak I.; Tadic, Branko; Šimunovic̈ G.; Kljajić, Vladimir; Agarski, Boris
© 2016, Islamic Azad University (IAU). Selection of the optimal product, where several products’ aspects are expressed through criteria, is a multi-criteria decision-making problem. Besides technical, exploitational, functional, structural, market and aesthetic criteria, nowadays, environmental criteria are inevitable aspects of a modern product. Environmental product properties can be successfully evaluated with a life cycle assessment. This paper proposes a multi-criteria decision-making model for optimal product assessment that uses environmental criteria obtained from a life cycle assessment. The proposed model presents a comprehensive approach that aims to overcome complex decision-making problems for optimal product selection, where special attention is given to the product’s environmental impact. Verification of the proposed multi-criteria decision-making and life cycle assessment model was performed on the case study of optimal knee support selection. By changing the criteria weights in multi-criteria decision-making, a sensitivity analysis was performed. The model output results show the product alternatives ranking that supports decision-making in optimal product selection.
Multi-objective optimization of steel AISI 1040 dry turning using genetic algorithm
(2021) Vukelic, Djordje; Šimunovic̈ K.; Kanovic Z.; Saric, Tomislav; Tadic, Branko; Simunovic, Goran
This study investigated the AISI 1040 steel turning in dry environment with four cutting inserts of different corner radii coated by CVD method. Experimental investigations were performed for different levels of cutting speeds, feeds and depths of cut using a randomized full factorial design. Quality characteristics of the workpiece machined surface were measured (arithmetical mean roughness) as well as the cutting inserts tool life characteristics (average width of flank wear). Machining times and chip volume were calculated, and based on this, chip quantity in time (material removal rate). The response surface approach and analysis of variance were used to determine the effects of input process parameters on the response variables. Based on the derived regression models, multi-objective optimization of output process parameters was performed using genetic algorithm. The objective function was simultaneous minimization of flank wear, minimization of surface roughness and maximization of material removal rate. The parameters of the genetic algorithm (crossover ratio, crossover fraction, mutation rate, Pareto front population fraction) were varied to obtain the optimal values of the objective function. Additionally, a sensitivity analysis was performed, which showed that the selected values of genetic algorithm parameters gave the best (minimum) value of objective function. Instead of the usual approach of obtaining only one combination of optimal parameters as a final solution, the basic idea was to obtain multiple combinations of optimal input process parameters depending on the importance of each output process parameter, i.e. requirements of production. Accordingly, the results of multi-objective optimization showed that there are a large number of Pareto optimal solutions. To validate the optimal input and output process values, confirmation experiments were conducted for selected trials of Pareto optimal results obtained from multi-objective optimization. A mean error percentage of 1.478% and 1.146% for flank wear and arithmetical mean roughness, respectively, proves that the predicted optimum values are confirmed by experimental results.
New integrated approach to the problem of ranking and supplier selection under uncertainties
(2011) Tadic, Danijela; Milanović D.; Misita, Mirjana; Tadic, Branko
The problem of ranking and supplier selection in the uncertain environment is part of a purchasing plan and its relationship has a critical effect on the competitive advantage (high-quality products at lower cost with higher customer satisfaction) of each industrial organization. The considered problem can be stated as a multicriteria decision problem which includes both quantitative and qualitative criteria. The criteria present supplier performances which are defined by the purchasing Management Team depending on the size of industrial organizations and on production type. In this paper, the Management Team, using European Union (EU) recommendations, made a choice of criteria for supplier evaluation. The fuzzy rating weights of each pair of the considered criteria and uncertain criteria values are described by linguistic expressions which are modelled by triangular fuzzy numbers. The fuzzy extent approach for the synthetic extent values of the pairwise comparison for handling fuzzy analytic hierarchical process (AHP) is used to calculate the weight vector. The extension of the fuzzy technique for order preference by similarity to ideal solution (TOPSIS) is applied to rank the suppliers. The proposed model is illustrated by an example. It is shown that the developed model is highly suitable as a decision-making tool for reaching decisions about supplier selection. © 2011 Authors.