Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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STATIC CALCULATION OF SMOKE EXHAUST DUCT CONSTRUCTION IN FIRE CONDITIONS USING FEM
No full textThis paper describes a numerical methodology for analysing the stress and strain state of
structural elements of smoke exhaust ducts under the fire conditions. The research is based on sheet
metal ducts, and the stress and strain state under temperature changes is determined. The numerical
analysis was performed using the finite element method in the software "Abaqus". A review of existing
research in the field of load-bearing capacity of structural elements at elevated temperatures is also
provided in this paper
APPLICATION OF ULTRASOUND FOR DIFFERENT PURPOSES WITH EXAMPLES
No full textIn the last decade application of ultrasound has been increasing. The reason for this is that a wide range of frequencies can be utilized for various purposes. Different scientific fields describe ultrasound in their own way, and from an engineering point of view, the use of ultrasound is quite interesting. The purpose of this paper is to provide an overview of how ultrasound can be applied in diagnostics and welding, including practical examples. Also, during this research dependency between the measured echo of ultrasound wave and depth of founded irregularity is given
Assessment of students’ productivity in context of indoor environmental quality and personal factors
No full textThis study investigates the impact of personal factors on students’ productivity and relation with Indoor Environmental Quality (IEQ) parameters through thermal comfort in a university classroom. The research is based on experimental research involving measurements, 240 productivity tests created for the purpose of the research and participation of 99 respondents. Paper proposes a novel approach, correlating personal occupants’ parameters with thermal comfort and Indoor Air Quality (IAQ) parameters that affect productivity. The novel approach implies the inclusion of all experimentally measured parameters that affect productivity in the Predicted Mean Vote (PMV) calculation, with the aim of distinguishing the impact caused by personal factors alone. This approach has not been used before and presents a significant gap between the existing prediction calculation models in literature and results obtained in real environments. The differences between calculated and measured productivity in real environments can be substantial, reaching over 80%. Approximately 80% of measured productivity values within the PMV range of −0.25–1 are impacted by personal factors. The importance of personal factors might be greater concerning how often they affect productivity, as opposed to the extent of their influence.Project of Technological Development under Grant number 451-03-65/2024-03/200105 from 05.02.2024
The phosphorus negotiation game (P‑Game): frst evaluation of a serious game to support science‑policy decision making played in more than 20 countries worldwide
No full textEnvironmental negotiations are complex, and conveying the interaction between science and policy in traditional teaching methods is challenging. To address this issue, innovative educational approaches like serious gaming and role-playing
games have emerged. These methods allow students to actively explore the roles of diferent stakeholders in environmental decision-making and weigh for instance between sometimes conficting UN Sustainable Development Goals or
other dilemmas. In this work the phosphorus negotiation game (P-Game) is for the frst time introduced. We present the
initial quantitative and qualitative fndings derived from engaging 788 students at various academic levels (Bachelor,
Master, PhD, and Postdoc) across three continents and spanning 22 diferent countries. Quantitative results indicate that
female participants and MSc students beneftted the most signifcantly from the P-Game, with their self-reported knowledge about phosphorus science and negotiation science/practice increasing by 71–93% (overall), 86–100% (females),
and 73–106% (MSc students in general). Qualitative fndings reveal that the P-Game can be smoothly conducted with
students from diverse educational and cultural backgrounds. Moreover, students highly value their participation in the
P-Game, which can be completed in just 2–3 h. This game not only encourages active engagement among participants
but also provides valuable insights into the complex environmental issues associated with global phosphorus production. We strongly believe that the underlying methodology described here could also be used for other topics
Cavitation Erosion of Protective Coating Based on Cordierite Filler and Epoxy Matrix
No full textThe goal of this study is to investigate the surface morphology changes induced
by the cavitation erosion of a coating based on cordierite with an epoxy matrix for an
aluminum substrate. The literature review shows a certain lack of knowledge regarding
the coating’s resistance to wearing induced by water flow, which is a highly important
property of the material immersed in or in contact with water streams. The main idea
behind the investigation is that such a protective coating will also improve the cavitation
erosion resistance of metal substrates. The protective coatings were based on cordierite filler
(88 wt.%) and epoxy resin (7 wt.%). The filler, made of a mixture of kaolin, alumina, and talc,
is obtained by a sintering procedure that took place at 1350 ◦C. X-ray diffraction analysis
and scanning electron microscopy were employed in the characterization of the produced
filler. The adherence of the obtained epoxy-based protective coating and resistance to
water flow were tested by the ultrasonic vibration method (i.e., cavitation erosion testing).
Scanning electron microscopy was used for analysis of the coating’s morphology upon
cavitation erosion. Based on the value of the cavitation erosion rate and the analyzed
final surface damage, it was assessed that the investigated protective coating is resistant to
cavitation erosion
MECHANICAL CHARACTERIZATION OF 3D-PRINTED EXPERIMENTAL PRTS USING DIC METHOD
No full textThe main objective of this paper is to investigate the mechanical behaviour of 3D-printed Pipe Ring Specimen (PRTS) made of polymer materials, with a focus on the influence of infill density and specimen geometry on tensile performance. Two types of PRTS specimens were analysed—PRTS-T1 and PRTS-T2—manufactured using Fused Deposition Modelling (FDM) technology, with varying infill levels (60%, 90%, and 100%). An additional aim of the study is to assess the applicability and limitations of the Digital Image Correlation (DIC) method in characterizing surface deformations during tensile testing of non-standard geometries. Based on the observed fracture locations and the quality of strain field data, recommendations are made regarding specimen selection for further research. Another goal is to compare the experimental results of PRTS specimens with data from the literature concerning flat tensile specimens produced with similar 3D printing parameters. The comparative analysis includes tensile strength values, strain distribution, and deformation patterns, taking into account differences in cross-sectional areas and infill structures. The paper also aims to identify the optimal combination of specimen type and infill percentage that ensures valid and reproducible results while minimizing material usage and production time. This research contributes to establishing testing procedures for non-standard specimens in additive manufacturing and provides a foundation for the further development of experimental methodologies in the field of mechanical characterization of 3D-printed polymer components
DESIGN AND APPLICATION OF A TWO-PART QUADRANGULAR DEVICE FOR FABRICATION OF UNIFORM TEST SAMPLES FOR BOND STRENGTH TESTING BETWEEN ARTIFICIAL TOOTH AND DENTURE BASE
No full textTo improve the precision and standardization of biomechanical testing of bond strength between artificial teeth and denture bases, an innovative two-part quadrangular device was developed using 3D printing technology (Bambu Lab X-1 Carbon) with polymeric materials. The development was based on a digital model of a scanned artificial tooth (Atos Core 200), which served as a reference for producing uniform and reproducible samples. The lower part of the device is designed for forming the denture base and is filled with wax, while the upper part contains an opening with a specially designed guiding surface matching the dimensions of the scanned tooth, enabling precise positioning at a 90° angle relative to the base. This ensures that each sample is identical in orientation and dimensions, which is crucial for reducing variability in testing. The fabricated samples then undergo a standard dental laboratory waxing procedure identical to the waxing phase of removable denture models. This process ensures full compatibility with real clinical conditions of removable denture fabrication, contributing to the validity and relevance of the obtained results. The unique design of the device allows easy and safe removal of samples without damage, further increasing the reliability of mechanical testing. The produced test samples are then tested on a universal testing machine using a device for bond strength testing under variable loading angles, simulating the complex biomechanical conditions present during functional mandibular movements. This innovative approach enables more precise evaluation of adhesive properties between the tooth and denture base and represents a significant step forward in the development and optimization of removable dental prostheses, with the potential to improve their longevity and clinical reliability
Overview and Analysis of Electric Energy Consumption Indicators in Wastewater Treatment Plants
No full textWastewater must be treated before discharge into the recipient to such an extent that it meets standards and regulations on wastewater quality, so as not to damage the environment. Depending on the quality of the influent, different technological procedures are applied, which are more or less energy intensive. Also, with the tightening of the conditions related to the quality of the effluent, the application of more energy-intensive purification technologies occurs, and thus the energy consumption at the plants increases. Wastewater treatment plants are among the biggest consumers of energy. In this paper, electric energy consumption at wastewater treatment plants was analyzed depending on different indicators of specific energy consumption, the applied technological process, and the level of purification
Design And Development Of Lightweight Stabilization Platform For Multicopters Armament
No full textFor the usage of armament that requests precision targeting on mul-ticopters (rotary-wing drones), it is necessary to provide the best possible sta-bilization with some mechanism that, at the same time, must be lightweight. This paper presents a lightweight stabilization platform based on the Stewart platform mechanism. This parallel mechanism (a mechanism that contains a closed kinematic chain) has six degrees of freedom inside the workspace. The platform must be able to stabilize all disturbances due to the flight of the mul-ticopter and must withstand the recoil of armament if it exists
NUMERICAL SOLUTIONS OF COMPRESSIBLE GAS FLOW IN MICROTUBE IN THE CONTINUUM REGIME
No full textUgovor br. 451-03-136/2025-03/ 200105 оd 04.02.2025. god