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WORKING METHODS IN THE SUBJECT OF DRAFT GEOMETRY AND MODELING AT THE AVIATION ACADEMY
No full textThis paper introduces the methods of teaching subjects of drawing geometry and 3D modeling used in the High Aviation Academy in Belgrade. These courses are attended in the first year of basic vocational studies of the Department of Aeronautical Mechanical Engineering. The paper will present the objectives of studying subjects, learning outcomes, auditory exercises, as well as learning through the work of students
OPTIMIZATION OF STANLEY PLUM DRYING PROCESS USING SOLID FUEL BATCH DRYER WITH TRAYS
No full textDrying fruit is a traditional preservation method that has been used for thousands of years. This technique allows for long-term storage of fruit, keeping it fresh and usable under ordinary storage conditions. In this research, the drying process of the selected variety of Stanley plums was analyzed in a batch dryer with trays using solid fuel. The research aimed to calculate the optimal air temperatures at the inlet and outlet of the heater, as well as the temperature at the outlet of the dryer itself. The constructed dryer has double trays, allowing drying capacities from 1550 kg to 3100 kg of Stanley plums. The main focus was on achieving efficient drying with minimal heat loss. The selection of basic equipment, such as a hot water boiler, circulation pump, heat exchanger, and fan, was tailored to the specificities of the dryer to maximize energy efficiency. The heat
exchanger utilizes compact lamellar Cu-Al technology, while the fan is equipped with a filter section for a cleaner drying process. The use of solid fuels such as biomass brings significant economic benefits, reducing the costs of dried products. However, manual labor and detailed equipment inspection are necessary for each drying cycle, which is the main drawback of this method
Experimental Investigation of the Aerodynamic Performance of a Ducted Propeller
No full textIn flight conditions up to transonic speeds (M < 0.8), there is no more effective element for creating thrust than a propeller. However, duct-free propellers have significant flaws that can affect flight performance: higher thrust demands necessitate a larger propeller diameter, leading to increased mass; noticeable losses at the blade tips occur when local velocities reach transonic speeds (0.8 < M < 1.2); and there are large aero-acoustic emissions due to flow instability and separation on the blades.
Installing a duct around the propeller reduces the propeller load by changing the stream tube flow field. Another benefit of the duct is the creation of additional thrust force, further increasing the efficiency of the propeller of a given diameter. Tip losses can be significantly reduced, and many studies have shown that ducted propellers offer significant potential in reducing sound emissions.
In this study, several test ducts with different exit diameters and inlet lip radii were designed to determine their effect on ducted propeller performance. The ducts were 3D printed using an FDM printer, then sanded and painted to prepare them for testing. All ducts were integrated onto a commercially available 12-inch diameter propeller driven by an electric BLDC motor.
Static and dynamic tests of the propulsion system were performed on a test stand at the wind tunnel facility of the Faculty of Mechanical Engineering in Belgrade. During testing, measurements of thrust force, rpm, and electrical power were performed. Additionally, to investigate the propulsion system's noise emission, sound volume measurements were performed and compared to those obtained for the duct-free propeller. Preliminary analysis of the results shows an improvement in efficiency and noise emission in some test cases, demonstrating the potential for enhancing aerodynamic performance through relatively simple modifications to the propulsion system
Environmental and Social Assessment of SHPP Brza voda 3 - Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)
The electromagnetic vibratory actuator load during the transport of a rigid body on a vibratory conveyor
No full textDuring a vibrational transport of a rigid body on a vibratory conveyor having electromagnetic vibratory actuator, a rigid body exerts by equal, but opposite force to a surface's reaction force. This paper covers research on a reactive force that the body exerts on the EVA during its relative motion. The reactive force is a vector sum of the surface's normal contact force and tangential force of friction, modeled with the Coulomb friction model. For a general case of vibratory transport, the friction force is defined and given as a piecewise function. Additionally, differential equations for the rigid body's relative motion are defined and solved to find potential moments in time when the body starts and stops with relative motion. During the period of the relative motion, a dynamic friction force is used. Conditions for a special case of a no-hopping motion are defined and presented graphically. For a given vibratory conveyor and vibratory regime a graph for reactive force that acts as a load on the EVA is shown. Computer simulation using Solidworks® is performed and its results are compared to the previously obtained mechanical model
A systematic approach of surface texture prediction during high-speed CNC turning of ARNE® (AISI O1) alloyed steel using response surface analysis and artificial neural networks
No full textThe present research reports on the application of the artificial neural networks (ANNs) for the modelling of processed surface texture parameters in turning of a high-strength, high alloyed steel. The variable input parameters of the ANN consisted of cutting speed Vc (m/min), feed rate f (mm/rev), and depth of cut, a (mm) whereas the output parameters that utilised were the average surface roughness Ra and maximum height of the measured profile, Rt. A full factorial experimental design (FF-DOE) was selected for generating the experimental data. The achieved outcomes indicated that, despite the complexity of the process and parameter interactions, the suggested ANN could be efficiently used to forecast the surface texture parameters during the hard turning process, thus confirming the production process planning
Research of the draw hook failures on rail vehicles in Serbia
No full textDraw hook failures present significant problems for railway safety and operational efficiency. Although failures on the draw gear are not frequent, they can induce serious problems on the vehicles and infrastructure when some elements break. This paper presents comprehensive research on the potential causes of these failures, aiming to provide insights for prevention measures related to materials, production process, geometry and manipulation practices during train operation. The draw hook, as one of the vital components in connections of wagons and locomotives, ensures the safety and reliability of trains during operation. By analyzing the historical failure data and relevant literature, this study identifies several key factors contributing to coupler failures. Material degradation emerges as a prominent concern, with factors such as fatigue, wear, and corrosion compromising the structural integrity of the coupler hook and other components over time. Overloading during starting, impacts, or improper coupling procedures further increase the risk of failures. Mechanical and physical characteristics of used material, as well as geometric inconsistencies, may also induce failure under operational conditions. Environmental factors, such as extreme temperatures, moisture ingress, and chemical exposure, pose additional challenges by accelerating material degradation and corrosion processes. Understanding the complex interaction of these factors is crucial for developing effective preventive maintenance strategies and for addressing and improving observed imperfections in draw gear elements. Implementing the results from this research can help railway operators and manufacturers of subjected elements mitigate the risk of failures, thereby ensuring the continued reliability and safety of rail transportation systems
Efficiency Analysis of Fragmentation Warheads Through Advanced Modeling Techniques: Experimental and Numerical Study
No full textThis research investigates the efficiency of fragmentation warheads through a comprehensive comparison of numerical and analytical modeling techniques, supplemented by arena tests. Advanced numerical models developed within Ansys Autodyn, alongside the mean area of effectiveness software, demonstrate robust capabilities in predicting warhead-soft target interactions. Our numerical model is supplemented with a complex analytical model, and the integration of these two approaches addresses a significant research gap by providing a thorough evaluation of warhead efficiency. This integrated model serves as a valuable tool for warhead design and optimization. Validated with experimental results, the simulation outcomes show excellent agreement with the arena test data, confirming the accuracy and reliability of the developed models. This study explicitly addresses key research gaps, including the integration between experimental and numerical analyses, the gap between explosive propulsion and the determination of efficiency, and the need for a comprehensive tool for warhead design and optimization. By exploring various warhead design configurations and initiation methods, the research offers critical insights for optimizing warhead performance. Notably, nonuniform barrel-shaped warheads exhibit a wider fragment distribution, significantly improving weapon-target interactions, particularly at lower impact angles. The study delves into the key parameters influencing warhead performance, providing detailed justifications for their selection and evaluating the sensitivities of these parameters on the results. This analysis underscores the importance of choosing appropriate parameters for accurate predictions and effective warhead design. In addition, the research highlights the original achievements in overcoming major difficulties and challenges in the field, such as integrating complex numerical and analytical models for comprehensive evaluation. The findings contribute to the advancement of fragmentation warhead design, offering designers reliable tools and guidelines to enhance lethality and efficiency in weapon-target engagements. Future work aims to expand the software’s capabilities to include diverse targets, fragment types, and interaction geometries, further advancing the field of fragmentation warhead design. By addressing the gaps and challenges identified, this research paves the way for more effective and optimized warhead configurations, enhancing their overall performance and impact
Prototype of SCARA-type industrial robot
No full textOblast primene industrijskih robota se brzo širi uz stalnu potražnju za poboljšanjem njihovih
funkcija, tehničkih karakteristika kao i sistema upravljanja i programiranja. Jedan od ciljeva
aktuelnih istraživanja u okviru Laboratorije za robotiku i veštačku inteligenciju je razvoj
domaćeg industrijskog robota sa mogućnošću automatizovanog programiranja na osnovu
informacija dobijenih od kamere. U okviru ovog rada je predstavljen prvi deo istraživanja koji
podrazumeva razvoj i realizaciju 4-osnog industrijskog robota SCARA konfiguracije. Profesor
Hiroši Makino sa Univerziteta Jamanaši projektovao je SCARA (Selective Compliance Assembly
Robot Arm) robota, koji predstavlja najpoznatiju konfiguraciju robota nastalu na
univerzitetima. Ovaj deo istraživanja obuhvata kinematičko modeliranje projektovanog robota,
njegovu fizičku realizaciju i razvoj sistema upravljanja i programiranja sa integracijom virtuelnog
robota. Sistem upravljanja je realizovan uz pomoć sistema upravljanja otvorene arhitekture
LinuxCNC, koji omogućava dalji razvoj i integraciju informacija sa kamere kao spoljašnjeg senzora.
Razvijeni sistem upravljanja obuhvata i model virtuelnog robota koji predstavlja digitalnu senku
realizovanog SCARA robota. Verifikacija kompletno razvijenog prototipa robota je sprovedena
kroz nekoliko primera realizovanja tehnološkog zadatka laserskog senjenja i graviranja.The field of application of industrial robots is expanding rapidly with a constant demand for improving their functions, technical characteristics as well as control and programming systems. One of the goals of current research within the Laboratory for Robotics & AI is the development of a domestic industrial robot with the possibility of automated programming based on information obtained from the camera. This paper presents the first part of the research, which includes the development and realization of a 4-axis SCARA-type industrial robot. Professor Hiroshi Makino from Yamanashi University designed the SCARA (Selective Compliance Assembly Robot Arm) robot, which representing the most famous robot configuration created at universities. This part of the research includes the kinematic modeling of the designed robot, its physical realization, and the development of the control and programming system with the virtual robot integration. The developed control system is based on the open architecture control system LinuxCNC, which
enables further development and integration of information from the camera as an external sensor. The developed control system also includes a virtual robot model that represents a digital shadow of the realized SCARA robot. The complete robotic system verification was performed through several examples of the technological task of laser cutting and engraving.Za izdavača: Dekan, dr Vladimir Popović, red. prof.
Tehnički urednici:
Prof. dr Saša Živanović, Doc. dr Miloš Pjević, Doc. dr Dušan Nedeljković, Lazar Matijašević, mast. inž. maš.
Štampa: Planeta print