Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Conceptual Design And Optimization Of Wing Bomb using OpenVSP - Open-Source Program For Computer Modeling
No full textThis paper will present the process of creating a wing bomb model. This UAV is completely designed in OpenVSP and analyzed in the VSPAERO tool. These analyses are very important to get preliminary results that will be used for the next steps of the design and the optimization of the wing bomb. During the development of the conceptual design of this UAV, it was necessary to create several different versions of the model. The OpenVSP program was chosen because it allows engineers to quickly and easily create and modify a model of aircraft
The effect of infill density on fracture toughness results of PLA material
No full textThe main objective of this research is to obtain a comprehensive insight into the influence of infill density on the fracture toughness results of PLA material, used in FDM technology. This paper presents four infill cases (100%; 70%; 40%; 10%) with 0.1 mm layer height. The whole research includes cases from 10 to 100% infill with a 10% increment on three different layer heights (0.3; 0.2; 0.1 mm). The FDM-grade PLA material is brittle hence, the fracture toughness of this material was estimated using the ASTM D5045-14 standard on SENB specimen geometry. This standard requires the plane-strain state near the crack tip to be met to obtain valid results. Three specimens were tested per infill group, all of which met the plane-strain condition. However, when looking at the KIC results from the highest to the lowest infill in all three considered layer configurations, the SENBs start to fail at 50%- onward due to the apparent presence of plasticity. This is evident from the maximum load value in the lower infill cases, where it exceeds the conditional value by more than the limit value of 10%. Therefore, for a better assessment of current results, the J integral approach was also used.contract No. 451-03-66/2024-03/200213 (from February 5th, 2024.
CONTROL OF A LIQUID LEVEL SYSTEM BASED ON A PROPORTIONAL-SUM CONTROLLER USING WHALE OPTIMIZER
No full textThis study is about controlling the liquid level in water tanks, which is one of the challenges in the industry. A nonlinear analytical model is derived and validated against linearized continuous-time and discrete-time models, demonstrating their equivalence under nominal conditions. The classical method for tuning a discrete-time proportional-sum controller was applied, with gains tuned via the Ziegler-Nichols method. Additionally, the controller’s parameters were fine-tuned by using the whale optimization algorithm. Simulation results for the tank system are presented. While Ziegler-Nichols gives a decent base, it can be said that optimization of the controller parameters should be recommended when dealing with similar problems in real-life situations. Results reveal that the optimized controller reduces the sum of squared errors compared to the classical controller, achieving superior accuracy
Dynamic data fusion analysis method for crack tracking in reinforced concrete based on DIC and AE
No full textMonitoring cracks within concrete structures allows for the assessment of performance and load-bearing capacity changes, enabling early preventative measures to enhance safety and durability. This paper addresses the challenges of using Acoustic Emission (AE) technology alone to monitor full-field strain changes at crack locations by implementing a dynamic data fusion method combining Digital Image Correlation (DIC) and AE technology. This method leverages the non-contact monitoring capabilities of DIC with the energy parameter analysis and circular trajectory localization of AE to achieve data fusion on the same specimen. The method is applied during four-point bending tests on reinforced concrete beams to track crack development at various stages. The results demonstrate significant improvements in the accuracy of concrete crack detection, precise tracking of crack evolution, and detailed data analysis of crack position and size at different stages of development. This provides effective experimental support and a theoretical basis for the health monitoring and safety assurance of reinforced concrete structures.Research, No. [451-03-65/2024-03/200105], dated February 5, 202
Drying Kinetics and Stability of Fatty Acids in Grape Pomace Seeds Under Mild Thermal Conditions
No full textGrape pomace, a significant by-product of the wine industry, is rich in
health-promoting compounds, including polyunsaturated fatty acids,
dietary fiber, and polyphenols, and holds strong potential for use in
functional foods and nutraceuticals. This study investigates the effects of
low-temperature convective drying at 40°C on the drying behavior and
fatty acid composition of grape seeds from ten Vitis vinifera L. cultivars.
To model the drying process, six thin-layer drying models were applied.
Among them, the Logarithmic model provided the best fit for most
cultivars, showing excellent agreement between predicted and
experimental drying curves. Effective moisture diffusivity values varied
considerably among cultivars, reflecting differences in pomace structure
and seed composition. Fatty acid analysis via gas chromatography
revealed that polyunsaturated fatty acids—particularly linoleic acid—were
the predominant lipid class in fresh grape seeds. After drying, a moderate
reduction in polyunsaturated fatty acids was observed, accompanied by a
corresponding increase in saturated fatty acids. Despite these changes,
certain cultivars, such as Prokupac and Merlot, retained favorable
nutritional profiles. The results support the application of mild drying
protocols to preserve the functional quality of grape seeds while improving
energy efficiency. This research contributes to the sustainable valorization
of grape pomace and highlights its potential applications, such as
functional oil ingredients, antioxidants in skincare, and encapsulated
nutraceutical formulations.Contract No. 451-03-137/2025- 03/200116 and Contract No. 451-03-137/2025-03/ 20010
EDGE-AI-ENABLED 2D DIGITAL IMAGE CORRELATION FOR AUTONOMOUS STRUCTURAL HEALTH MONITORING OF STEEL STRUCTURES AND PRESSURE EQUIPMENT
No full textContinuous assessment of in-service steel structures and pressure equipment has been constrained by the high-bandwidth, workstation-level computation traditionally required for digital image correlation (DIC). The large data volumes produced by conventional optical systems have therefore restricted full-field strain monitoring to controlled laboratory environments. To overcome this limitation, an embedded 2D DIC strategy is recommended in this paper. Displacement and strain fields are evaluated directly on a low-power graphics module positioned at the camera head, eliminating the need to stream raw imagery. A streamlined on-device AI model matches the image pixels in real time, while a second AI model instantly converts the resulting strain maps into early damage warnings and clear estimates of the structure’s remaining strength. Only condensed structural health indicators and alarm flags are transmitted, reducing data traffic by more than an order of magnitude. Validation under representative static and cyclic loading scenarios typical of welded joints, pressure vessels and pipework are advised, with particular attention to the rapid detection of critical strain localisations and the early prediction of crack-growth trends. Adoption of such an edge-AI DIC module is expected to deliver a deployable, low-latency pathway toward condition-based maintenance for steel infrastructure and pressure equipment operating under variable service conditions
Application of 2D Digital Image Correlation in Fracture Mechanics: Detecting Strain Localization Prior to Crack Initiation
No full textThe study of fracture mechanics is crucial to understanding the behavior of materials under stress and preventing catastrophic failures. Traditional methods often fail to capture a detailed strain distribution. This mini-review explores the principles, applications, and advantages of two-dimensional digital image correlation (2D DIC) in fracture mechanics, focusing on its role in detecting strain localization before crack initiation. 2D DIC offers a noncontact, full-field measurement technique capable of capturing localized strain behavior with high resolution. This method is compared to traditional approaches to highlight its efficacy. Various studies demonstrate the effectiveness of 2D DIC in capturing fracture behavior. Post-processing of DIC strain maps enables the determination of localized fracture zones, providing valuable information on material failure mechanisms. 2D DIC significantly enhances the predictive capabilities of material failure analysis in fracture mechanics, making it a powerful tool for improving material design and preventing failures
The effect of blade turning angle on rotation improvement of a small horizontal axis wind turbine
No full textOptimization of wind turbine aerodynamic performances implies solving the problem in the domains such as airfoil selection, blade rotation angle, chord optimization, number of blades, appropriate tip speed ratio, etc. The current paper studies the effect of blade rotation angle (β = 5, 7, 10°) on power coefficient (CP), torque (T) and mechanical power (PM) in a small horizontal axis wind turbine (HAWT). The analysis involves two models of blades (V and) of the airfoil
class SD 7003. The first part of the paper employs numerical analysis, that is, Ansys CFX and Ansys Fluent software packages, to define wind turbine characteristics. The obtained results indicate that as the rotation angle (β) increases the CP increases within an appropriate range of tip speed ratio (λ) change. The second part describes experimental investigation conducted on considered HAWT to define the values of T and PM for studied blade rotation angles and comparison with the values obtained from Ansys. Existing differences in values are a consequence of the design of the HAWT, that is, the influence of the mass moment of inertia of the rotor and generator as well as the placement of the generator. Experimental setup and methodology allow for investigating the effect of different blade models, rotor and generator structure on wind turbine torque and mechanical power output characteristic
Evaluation of hull girder ultimate strength for dry cargo inland vessels
No full textUltimate strength of sea-going ships is investigated in literature and addressed in the rules and regulations of classification societies, where detailed contemporary methods are defined. However, no systematic assessments or developed regulations for evaluating the ultimate strength of inland vessels have been introduced. This is concerning, considering that around 15,000 inland vessels navigate in Europe alone. These vessels are generally prone to longitudinal strength issues as they face specific design, operational and regulatory challenges, such as a large length-to-height ratio, shallow draught navigation, frequent grounding and overloading accidents, an older fleet and fewer regulatory requirements compared to sea-going ships. Therefore, this study presents a pioneering evaluation: it assesses ultimate strength of ten inland vessels, addressing this significant gap in literature. Five methods are employed for the calculation of ultimate strength: IACS defined progressive collapse analysis (PCA), three modified PCA methods according to different formulations for buckling of stiffeners, and a nonlinear finite element method. Moreover, maximum total bending moments are calculated in order to examine the margin between ultimate and service loads. Selected inland vessels are found to be particularly vulnerable to hull girder collapse, with some of them having extremely low or no margin with respect to hull girder collapse, largely due to the buckling of structural elements acting as a consequence of the selection of unique, dispersed and specific structural features. The research specifically emphasizes that vessels with longitudinal framing achieve higher ultimate strengths, offering greater structural safety against hull girder collapse
Analysis of Turbulent Swirling Flow in a Pipe downstream of an Axial Fan Impeller: Experimental and Numerical Approaches
No full textExtended abstractMinistry of Science, Technological Development and Innovation of the Republic of Serbia under the Agreement on financing the scientific research work of teaching staff at accredited higher education institutions in 2025, no. 451-03-137/2025-03/200105 and for research staff no. 451-03- 136/2025-03/20010