Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Influence of Infill Pattern on Ballistic Resistance Capabilities of 3D-Printed Polymeric Structures
No full textRecent technological advances have expanded the use of 3D-printed polymer components across industries, including a growing interest in military applications. The effective defensive use of such materials depends on a thorough understanding of polymer properties, printing techniques, structural design, and influencing parameters. This paper analyzes the ballistic resistance of 3D-printed polymer structures against 9 × 19 mm projectiles. Cuboid targets with different infill patterns—cubic, grid, honeycomb, and gyroid—were fabricated and tested experimentally using live ammunition. Post-impact, CT scans were used to non-destructively measure projectile penetration depths. The honeycomb infill demonstrated superior bullet-stopping performance. Additionally, mechanical properties were experimentally determined and applied in FEM simulations, confirming the ability of commercial software to predict projectile–target interaction in complex geometries. A simplified analytical model also produced satisfactory agreement with experimental observations. The results contribute to a better understanding of impact behavior in 3D-printed polymer structures, supporting their potential application in defense systems
Managing fuel consumption and emissions for hybrid electric vehicles through optimization of engine operation
No full textThis paper presents a multi-objective optimization framework for improving internal combustion engine performance in hybrid electric vehicles, specifically targeting the minimization of fuel consumption and emissions (CO, NOx, HC, PM). The proposed method integrates normalized objective functions with weighted factors to develop a unified performance index, facilitating the simultaneous optimization of multiple conflicting objectives. Utilizing the NSGA-II algorithm, a diverse set of Pareto optimal points is generated, each representing different trade-offs between the objectives. The study’s results demonstrate significant improvements in engine performance through the application of the unified ICE operation map, showcasing a notable reduction in emissions with only a slight increase in fuel consumption. The methodology was validated via MATLAB simulations on two case studies involving parallel and series hybrid electric vehicles, employing a custom synthesized drive cycle for energy management strategy evaluation. The unified map enabled real-time control and efficiency improvements by balancing different emission parameters, thus optimizing ICE operation across various conditions
TOWARDS SMART ENGINEERING PRODUCTS
No full textThe evolution of traditional engineering products is moving towards the development of smart products, which are characterized by intelligence, networking and adaptability to the user. Using the elements of Industry 4.0, such as artificial intelligence (AI), Internet of Things (IoT), digital twins (DT) and data analytics (BDA), their design, manufacturing and life cycle management are carried out on a new basis. That is why smart engineering products are characterized by self-monitoring, autonomous decision-making and optimization of their work in real time. All this leads to greater satisfaction of their users, due to improved efficiency, reliability and a better user experience. Also, smart products include issues of cyber security, data privacy, interoperability and sustainability, which must be considered in order to fully realize the potential of smart engineering solutions in them. This paper provides an analysis and synthesis of smart engineering products (SEP) from the aspect of their development, characteristics, application examples and future research in this area
Influence of the Involute Gear Teeth Profile Shape and Running-In on Surface Load Capacity of Cylindrical Gear Pairs
No full textIn this article, the simultaneous influence of profile shape variation and running-in of the involute gear teeth on the surface load capacity of cylindrical gear pair was examined. Experimental investigations were carried out on spur gears in laboratory conditions, using a back-to-back gear test rig. Different involute profile shapes are achieved by varying the gear teeth pressure angle. Different running-in regimes were achieved by varying the torque of the gear pair in the initial period of operation. By modifying the profile and adequate running-in in short period of time, the following are reduced: the intensity of wear, the amount of surface damage, and friction on the contact surfaces of gear teeth. Greater benefits of a higher pressure angle and running-in were observed with driven gears. It is shown that the negative sliding on the dedendum of the driving gears teeth has a greater effect on the generation of surface fatigue compared to the driven gears
teeth, due to the direction of the friction force. The obtained results indicate that by varying the shape of the involute profile and running-in parameters, the surface load capacity of spur gears can be significantly improved, such that a longer operational life and greater efficiency of the gear drive in exploitation can be achieved.451-03-137/2025-03/20010
Hybrid GA-ANFIS and PSO-ANFIS techniques for nonlinear DC motor system modeling
No full textThis research focuses on nonlinear modeling techniques for direct current (DC) motor, with permanent magnets in the stator, using optimized adaptive neuro-fuzzy inference systems (ANFIS). The traditional linear model fails to accurately represent the dynamics of a DC motor due to nonlinear friction effects. To address this limitation, a nonlinear model incorporating Tustin’s friction model is proposed and evaluated against experimental data. Despite improvements over the linear model, challenges remain due to the discontinuity introduced by the signum function in friction representation, necessitating smoother approximations like hyperbolic tangent for control applications. The nonlinear modeling approach also does not fully capture the dynamics of the real-world behavior of the object. To achieve a robust and accurate model across all operational conditions without approximations, three ANFIS variants are developed. These models employ diverse approaches to generate fuzzy rules, such as grid partitioning and fuzzy C-Means clustering. The second and third models undergo optimization using two different nature inspired optimization algorithms. Comparative analysis reveals that all ANFIS models yield superior performance, with GA-ANFIS on top, accurately predicting DC motor velocity under varying input conditions such as step, sinusoidal, and chirp signals. Experimental validation demonstrates that the optimized ANFIS model closely tracks the real-world behavior of the DC motor, offering promising prospects in every type of control, especially in direct inverse control in which the
system model is inverted and used as a controller. This approach enables precise control actions based solely on observed system dynamics, avoiding the pitfalls of approximation-based methods
Performance assessment and techno-economic analysis of the thermal plasma gasification of biomass using air and steam as gasification medium
No full textIn this study, a techno-economic analysis of biomass gasification using a thermal plasma with air and steam as gasification media is presented. The analysis includes a parametric evaluation of various operating parameters, including process temperature, equivalence ratio and steam-to-fuel ratio. The aim is to determine the optimum gas composition characterized by a high proportion of combustible components and minimal harmful by-products. The parametric study covered a temperature range of 500–2000 K, equivalence ratios of 0.1–0.7 and steam-fuel ratios of 0.5–2.5. The results show that the optimum process temperature is around 1200 K. Furthermore, the analysis shows that the best energy properties of the producer gas are achieved at the lowest gasification medium-fuel ratios. The energy analysis favors steam plasma gasification over air plasma gasification. When using air, the produced gas has a heating value of 9.42 MJ/Nm3 and an H2/CO ratio of 1.03, whereas when using steam as the gasification medium, the heating value of the gas is higher, amounting to 10.36 MJ/Nm3, and the H2/CO ratio is 1.74. The economic analysis also favors steam gasification and shows significantly lower costs for energy production, estimated at 47.5 €/MWh compared to 74.5 €/MWh for air plasma gasification. The sensitivity analysis also shows that under certain conditions, when biomass is available at minimal or no cost, the cost of producer gas by steam plasma gasification can fall below the market price of natural gas. These results underline the techno-economic advantages of steam plasma gasification in converting biomass into a competitive and sustainable energy source
Aging Effects on the Bending Performance of DLP and FDM Printed PLA
No full textThis research explores how 3D-printed PLA parts change over time, both mechanically and structurally. Two common 3D printing methods: Fused Deposition Modeling (FDM), which uses PLA filament, and Digital Light Processing (DLP-LCD), which uses a PLA-like resin are compared. Test specimens were examined right after printing, then again after one and two months of aging under everyday indoor conditions that included regular cleaning to simulate real-world use. To observe changes, three-point bending tests were used to assess flexural strength, stiffness, and strain, and microscopy helped reveal structural changes inside the materials.
Specimens made with FDM printing showed minimal changes over time. Their stiffness (flexural modulus) remained mostly unchanged, strength dropped slightly (by up to 9%), and flexibility (strain at failure) increased moderately (up to 17%). This suggests the material stayed strong and elastic, with a slight shift toward being more ductile.
In contrast, the PLA-like resin specimens printed with DLP-LCD technology showed a clear decline in performance. Their stiffness and strength dropped significantly - down to about 45% and 43% of their original values—and their flexibility increased similarly. These results point to a shift in the material’s behavior: it became softer and more flexible, but at the cost of structural integrity.
In summary, FDM-printed PLA held up well over time, making it a reliable choice for parts that need to retain their shape and strength. On the other hand, the resin-based parts showed signs of weakening, highlighting how important it is to match the right material and printing method to the demands of the final application.Contract No. 451-03-136/2025-03/200105; Contract No. 451-03-137/2025-03/20010
Comparison of Serial and Parallel Implementations of ILC in a Closed-Loop Feedback System
No full textIterative Learning Control (ILC) is a data-driven strategy for precise trajectory tracking in systems that operate repetitively under similar reference trajectories, disturbances, and
initial conditions. Despite more than three decades of development, some implementation aspects of the learned ILC signals remain underexplored. This paper compares serial and parallel ILC signal implementations within a closed-loop feedback system. Although both approaches have been equally addressed in the literature, our findings show that the serial implementation provides clear advantages in achieving desired performance.No. 451-03-137/2025-03/200105 from 04.02.2025;
451-03-136/2025-03/20006
Metaheuristic search algorithm hyperparameter tuning for simulation-based engineering optimization tasks
No full textRegardless of how the objective function behaves, metaheuristic search techniques can be used to approach the optimal solution; however, task-specific hyperparameter selection is required. The computational cost of the simulation-based objective function evaluation makes it impossible to solve this process in time. Artificial intelligence tools can be used to increase automation and decrease the amount of time needed for engineering optimization tasks. The developed procedure can reduce uncertainty and increase the design cycle's efficiency, which together accelerate innovation.XXXIII. Nemzetközi Gépészeti Konferencia – OGÉT 202
Ecological aspects and occupational safety in welding processes: Contemporary approaches and challenges
No full textWelding is one of the fundamental technological processes in contemporary industrial production, playing a key role in sectors such as automotive, aerospace, shipbuilding, and civil engineering. Despite its indispensability, welding operations are associated with significant environmental and occupational health concerns. These include the emission of toxic gases and fine particulate matter, high energy consumption, intense noise, and thermal radiation, all of which can adversely affect both the environment and the health and safety of workers. This paper explores the ecological aspects of welding processes, with special attention given to current challenges and innovative solutions aimed at minimizing environmental impact and enhancing occupational safety. The analysis includes a review of modern techniques such as laser welding, friction stir welding, and hybrid welding methods, which offer improved energy efficiency and reduced emissions. Additionally, the paper addresses the importance of proper ventilation systems, protective equipment, and continuous monitoring of air quality in workspaces. A multidisciplinary approach that combines engineering innovations, environmental protection strategies, and occupational safety regulations is necessary to meet the growing demands for sustainable and safe industrial practices. This study highlights the need for further research and cross-sector collaboration in order to develop eco-friendlier and worker-conscious welding technologies.No. 451-03-137/2025-03/200105, dated February 4, 202