Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Enhanced osmotic vacuum dryer for fruits and vegetables
No full textThis paper presents an innovative osmotic vacuum drying system designed to improve the efficiency and quality of fruit and vegetable dehydration. Traditional atmospheric pressure dryers using heated air streams are often inefficient due to high energy consumption and limited operational periods during harvest seasons. Additionally, inadequate temperature and humidity control in conventional dryers can lead to product defects such as surface hardening, incomplete dehydration, or microbial spoilage. The proposed osmotic vacuum dryer addresses these challenges by integrating controlled osmotic dehydration with vacuum drying, ensuring better moisture removal while preserving organoleptic properties. This approach enhances energy efficiency, reduces drying time, and minimizes product deterioration. The study highlights key design features, operational advantages, and potential applications of this technology in the food industry.No. 451-03-137/2025-03/200105, dated February 4, 202
2D Truss optimization using FEM-PSO and Generative AI
No full textThis paper presents the theoretical foundations and
implementation of a web-based application for the Particle
swarm optimization of 2D truss structures. The framework
achieves its objective through the integration of three powerful
computational tools: the Finite Element Method (FEM) for
deterministic structural analysis, Particle Swarm
Optimization (PSO) for heuristic, population-based design
exploration, and Large Language Model (LLM), Google's
Gemini, for automated interpretation of results.
Mathematical foundation of the FEM, the bio-inspired
algorithmic behavior of PSO [1], and the transformer-based
architecture that enables the reasoning capabilities of LLMs
[2] are shown. The result is a tool that not only solves
engineering problem but also serves as a case study in the
powerful emerging synthesis of classical numerical methods
and advanced artificial intelligence.No. 451-03-137/2025-03/200105, dated February 4, 202
Numerical Analysis of a Small-Scale Wind Turbine Blade Airfoil for Low Wind Velocity at Different Angles of Attack
No full textUnfortunately, wind turbines only collect a small portion of the of green energy that the wind produces. Furthermore, due to the noise and discomfort they produce, multi-megawatt wind turbines cannot be installed in urban areas. To reduce the noise as much as possible, tiny horizontal-axis wind turbines with low tip speed ratio can be installed instead. Unfortunately, because this wind turbine operates at low Reynolds numbers, the flow around it is rather complicated. When determining the aerodynamic performance of wind turbine airfoils, the computational grid and turbulence model are crucial. Blade optimization is required to determine an appropriate turbulence model and computational grid, to more precisely compute the aerodynamic performance data of wind turbine airfoils, and to gain a deeper understanding of the nature of flow over an airfoil. The airfoil’s shape, length, angle, and other characteristics are crucial. The present study examines the analysis of a unique airfoil- S814 designed for small-scale horizontal axis wind turbines (HAWT) at varying angles of attack and fixed Reynolds numbers. A thorough analysis of the airfoil S814 has been conducted to illustrate the flow behavior over the airfoil. ANSYS/Fluent software is used to perform a computational fluid dynamics analysis of an airfoils at various angles of attack and a wind speed of 6 m/s. Plots have been created to display the distributions of pressure, turbulence, velocity on airfoil and lift-to-drag coefficient at various angles of attack.contract No. 451-03-65/2024-03/200105 from 5 February 2024
Error bounds of positive interpolatory quadrature rules for functions analytic on ellipses
No full textaccording to Contract 451-03-137/2025-03/200105 dated on February 4, 202
COMPARISON OF LASER INTERFEROMETER SYSTEMS FOR MEASURING POSITIONAL ACCURACY OF MACHINE TOOLS
No full textLaser interferometers have become indispensable tools in the high-precision calibration of machine tools, offering sub-micron resolution and enhanced measurement reliability. Since the introduction of stabilized helium–neon (He–Ne) lasers in the 1960s, manufacturers like Hewlett-Packard (HP), Renishaw, and Lasertex have developed systems with increasingly advanced capabilities. This paper presents a technical and historical comparison of three key interferometric systems: HP’s 5525A, Renishaw’s XL-80, and Lasertex’s HPI 3D. The analysis includes specifications such as laser stability, resolution, environmental compensation, and dynamic measurement capabilities. The HP 5525A, although historically significant, lacks modern portability
and software integration. In contrast, Renishaw’s XL-80 offers compactness, advanced environmental compensation, and compatibility with international metrology standards. Lasertex’s HPI-3D introduces next generation capabilities, such as real-time vibration analysis, nanometric resolution, and full 3D geometric evaluation. The comparative findings suggest a clear technological evolution toward higher precision, modularity, and software-driven diagnostics in laser interferometry.Conference proceedings [Elektronski izvor] : 60th Anniversary of the Association of Production Engineering of Serbia
/ 40th International Conference of Production Engineering ICPES 2025 - Serbia 2025, Nis, Serbia, 18th - 19th
CIP - Каталогизација у публикацији
Народна библиотека Србије, Београд
621.7/.9(082)(0.034.2)
621.7/.9:669(082)(0.034.2)
681.5(082)(0.034.2)
005.6(082)(0.034.2)
004.896(082)(0.034.2
Combined approach for integrity assessment of welded joints with multiple defects
No full textPresence of various types of defects is an unavoidable issue when it comes to welded joints. Typicalapproach to dealing with this problem includes the effects of individual defects, without consideringthecombined influence of several different defect types on the integrity of a welded joint. Research whichwill bepresented here includes the initial steps and the development of a method for analysing the effects of multipletypes of welded joint defects, using a number of different approaches - with the main focus on experimentsand numerical simulations based on the finite element method. This research, inspired by real problemsencountered in engineering practice, initially focused on the geometry of welded joints with defects, asanimportant factor in terms of stress concentration, which could decrease the load-bearing capacity of aweldbya significant margin. As the methodology continued to develop, experimental tests were included, inordertoprovide input data for the numerical models, and to verify their accuracy. The experimental part of thisresearch was further improved by combining it with stereometric monitoring methods - mainly Digital ImageCorrelation (DIC). In this way, a more detailed insight into the behaviour of welded joints with defectswasobtained, providing an extensive and reliable base of information, which could be used by and comparedtothe numerical simulations. In the more recent experimental and numerical analyses, the welded joint itself for consideredinmoredetail, by observing each of its regions - the parent material (PM), the weld metal (WM) and the heat affectedzone (HAZ) - in terms of mechanical properties. The goal was to include different values of yieldstress, tensile strength and deformation for each individual zone, which would correspond to the experimentallydetermined values. For the HAZ, it was not possible to experimentally obtain these values, hence aniterativemethod was developed to determine them using the FEM models, by comparing the results with DICimages. Metallurgical aspects were also an important factor which was included in these analyses, as knowledgeabout what kind of microstructures occurred in each region during welding was crucial in determiningtheexpected mechanical properties of the HAZ. Due to specific conditions during welding (in order toobtainrelevant defects), it was assumed that the microstructures would deviate from those obtained under regularconditions. Taking all of the above into consideration resulted in a quick, effective and reliable methodofdetermining the influence of multiple defects on the structural integrity of welded joints. Next step, whicharecurrently underway, include the application of this methodology to a different combination of materials-namely a welded joint between a ferritic steel and an austenitic stainless steel
From Lucy Ashton to Future CFD Case Studies: Benchmarking Ship Resistance at Full and Model Scales
No full textAccurate prediction of ship resistance using Computational Fluid Dynamics (CFD) requires thorough validation against both model-scale and full-scale data. This study presents a comprehensive summary of benchmarking efforts for CFD simulations of ship resistance, starting with the Lucy Ashton vessel, a historical case supported by full-scale resistance and boundary layer measurements. The benchmarking scope includes additional reference hulls such as the JBC, DTC and KCS, with resistance prediction errors consistently maintained within ±5%, highlighting the robustness of current CFD practices across different hull forms and scales. To broaden the evaluation, an additional vessel with an extensive experimental dataset-comprising model-scale and full-scale resistance measurements, full-scale self-propulsion data, wake field measurements-was analyzed. This expanded dataset enabled a more detailed assessment of simulation accuracy and scale effects. The outcomes from this study will support the organization of a dedicated CFD workshop, using the additional vessel as a reference case to promote standardized practices and improve simulation accuracy in maritime hydrodynamics.Project no. 451-03-137/2025-03/200105 from 4 February 202
Evaluation of Firing Reliability and Penetration Depth of 3D Printed PLA Projectiles for 9x19 mm Ammunition
No full textRecent advances in 3D printing technologies and polymer materials have opened new possibilities in various engineering fields, including the defense industry. Among these developments, the concept of 3D printed ammunition has attracted growing attention due to its low cost, rapid prototyping potential, and material flexibility. However, this trend is also raising concerns regarding the reliability, safety, and possible misuse of such ammunition, especially given the limited
research available in this domain. In this study, several series of bullet projectiles were produced using an FDM 3D printer with PLA filament, designed according to NATO standards and integrated into live 9×19 mm ammunition. An experiment was conducted to evaluate firing reliability, weapon function, and target penetration behavior using a wooden board as a simplified terminal medium. All shots were successfully fired and analyzed in terms of operational consistency and penetration depth. Based on the experimental results, a preliminary analytical model was developed to support future research and enhance the predictive understanding of such projectiles. The results indicate promising potential for further development of 3D printed ammunition, with practical implications for both research and controlled applications
Environmental and energy aspects of subcooled condensate and steam trap operation
No full textThis paper analyzes the condensate subcooling effect on the condensate return line and the impact of steam trap condition in advancing sustainability goals by reducing greenhouse gas emissions, improving resource efficiency, and enhancing overall process reliability. This paper aims to demonstrate the calculation of condensate subcooling in the condensate return line and the benefits of subcooled condensate for the proper operation of steam traps. The findings highlight that steam trap optimization represents a cost-effective strategy for industries seeking to align with carbon reduction targets while achieving measurable economic and ecological benefits
Pregled i klasifikacija nacionalnih propisa iz oblasti zaštite od požara
No full textInženjeri, čak i oni koji nisu specijalizovani za zaštitu od požara, se u okviru svoje delatnosti u različitim ulogama sreću sa propisima iz oblasti zaštite od požara, na primer: prilikom projektovanja, tehničke kontrole projektne dokumentacije, izvođenja, nadzora nad izvođenjem, tehničkog prijema objekta, održavanja instalacija i dr. U ovom radu izložen je pregled propisa iz oblasti zaštite od požara i predstavlјena je jedna njihova klasifikacija, koja bi trebalo da olakša čitaocu snalaženje u materiji. Dat je i skraćeni pregled povučenih propisa; obuhvaćeni su zakoni, uredbe, naredbe, pravilnici i odluke dok će specifični tehnički standardi biti obrađeni u narednim brojevima časopisa