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Modelling of a Coefficient of Nonlinearity in Dynamics of Deep Groove Ball Bearing with Damage
No full textThe presented research is a part of widely research of the nonlinear dynamic behaviour of rolling bearings, which are the parts of all rotating assemblies and machinery. In accordance with the state-of-the-art requirements for the advanced mechanical design and industrial digitalization, the large experiments and research are performed and the new mathematical model of the dynamic behaviour of rolling bearings with damages is developed. The results obtained for a particular type of deep groove ball bearings are presented, and the possible further research and implementation of the obtained model in digitalized self-monitoring systems is discussed
Modeling of Shaped Charge Jet Penetration Depth: Analytical and Numerical Approach
No full textShaped charge is the most effective armor-piercing mechanism, harnessing explosive charge detonation energy to form and accelerate a hypervelocity metal penetrator known as a jet. The process entails intricate dynamics including detonation wave propagation, its interaction with the metal liner, and subsequent liner collapse leading to jet formation. While both analytical and numerical models offer insight into this complex process, each approach presents distinct challenges. Analytical models, while conceptually straightforward, often rely on simplifications that compromise accuracy. Conversely, uncertainty or even unavailability of relevant material properties and high computational cost are the most important drawbacks of numerical
models. Notably, the jet penetration phase imposes significantly greater computational demands compared to preceding processes of jet formation. This research aims at providing a deeper understanding of the jet interaction with target, as well as on determining its influence on penetration depth. We revisit an analytical model based on the virtual origin concept and
complement it with numerical simulations using Abaqus/Explicit in a pure Eulerian domain. Through comprehensive analysis, we explore various jet parameters – such as kinetic energy, diameter, length, velocity gradient, and effective standoff distance – and their impact on penetration depth. The insights derived from this study hold practical significance for the
preliminary evaluation of the shaped charge’s effectiveness and consequent refinement of the design of shaped charge projectiles or warheads.NITRA, ugovor 451-03-65/2024- 03/200105 od 05.02.202
Development of Energy and Resource Efficient Products According to the Industry 4.0 Principles
No full textSince its debut at the Hanover fair in 2012, the fourth industrial revolution, also known as Industry 4.0, has significantly impacted almost all areas of science and technology. Industry 4.0 aims to digitally oversee and manage entire enterprises along with their interconnected networks. It embodies the seamless and real-time coordination of all value-adding processes, tasks, and services. Presently, Industry 4.0 principles are implemented in the entire lifecycle of a product—from its conceptualization, development, and manufacturing stages to its usage, maintenance, and eventual disposal and recycling. Traditional methodologies in product development, characterized by sequential, integral, and global approaches, have long served as guiding principles for engineers, aiming to create highly functional, cost-effective, technologically advanced, and reliable products capable of competing in the global market. In this area, experts from the Western Europe have played a significant role, enabling Europe's economy to maintain competitiveness against economic giants in Asia and North America, even during the global energy crises, economic challenges, and social upheavals. Modern approaches to product development build upon traditional methodologies, refining and specifying their phases. Furthermore, regulations and standards serve as important guidelines to promote energy and resource efficiency in product development processes.Keynote lectur
Analiza uzroka havarije na visokopritisnom industrijskom parnom kotlu
No full textPrilikom redovnog rada visokopritisnog industrijskog parnog kotla u hemijsko-industrijskom kompleksu na
teritoriji Republike Srbije došlo je do havarije nakon čega je njegov rad interventno zaustavljen. Neposredno pre
havarije uočen je crni dim na izlazu iz dimnjaka. U toku havarije došlo je do izbijanja zadnjeg zida ložišta kao i
do pucanja dve cevi ozračenog isparivača u njegovoj neposrednoj blizini. Nakon havarije izvršen vizuelni pregled
zatečenog stanja gasnog trakta kao i pratećih elemenata vazdušnog trakta kotla. Za potrebe sprovođenja
analize porekla havarije preuzeti su podaci radnih parametara kotla sa lokalnog DCS sistema za ceo radni dan
u kom se predmetna havarija desila. Analizom svih prikupljenih podataka dato je mišljenje o poreklu havarije
kao i postupci koje je potrebno sprovesti u cilju otklanjanja mogućnosti da se havarija detektovanog porekla
ponovi. Nakon sprovedenih preporuka navedenih u ovom radu očekuje se povećanje pouzdanosti i raspoloživosti
predmetnog kotla kao i povećanje bezbednosti osoblja koje opslužuje kotlovsko postrojenje tokom njegovog rada
Renewable Energy Equipment in Biogas Plants
No full textEquipment used in biogas plants includes a broad array of devices and
technical solutions, with significant flexibility in component combinations. Each system demands a comprehensive technical analysis to ensure optimal functionality.
Contracting a single provider offers streamlined compatibility and operational
guarantees but limits customization options. In contrast, modular construction
accelerates project timelines and reduces costs, while engaging multiple specialized
contractors increases investor involvement but also raises risks. Both approaches
carry distinct advantages, underscoring the importance of balancing operational
efficiency with investment flexibility when designing and building biogas facilities
Environmental and Social Assessment of SHPP Brza voda 1 - Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)
The Relative Values of a Moisture Percentage in Building Envelopes: Moisture’s Spots with a Moisture Meter
No full textThere is a substantial lack of data relating to the hygrothermal traits of existing buildings and building materials. Moisture analysis in building envelopes is 1D (one-dimensional), 2D and 3D effects and feedback can be neglected. Many European standards treat a moisture percentage in building envelopes as surface and interstitial moisture condensation, such as BS EN ISO 10211, BS EN ISO 13788, BS EN ISO 15148, and BS EN 15026. In this manuscript, there was a tendency to capture a relative quantity of superficial moisture, by metering spots on the inner and outer surface of wall lining systems with a moisture meter. The metering specimens were the buildings with different envelopes: a wooden hut-house, a masonry building and a building partially sheeted in stone. The referent heights on wall linings, for taking the moisture data were specified as 50 cm for a wooden and masonry building and 80 cm for a stone-sheeted building, from the ground. The several conclusions were brought. The buidling’s envelope is much influenced by the weather. The outer material surface in a shadow can possess a slight moisture quantity. One of the recommendable issues, originating from this manuscript is to abolish or reduce the buildings’ vulnerability to climate fluctuations immediately at the beginning of construction
Analysis of failures of elements of draw gear and impacts on the safety of rail vehicles
No full textRail transportation is one of the most efficient ways of transporting goods and passengers. Alongside modern and reliable infrastructure systems, special emphasis is placed on the reliability, availability, and safety of rail vehicles. The draw gear device plays a pivotal role in ensuring operational safety and efficiency. However, failures within this system can lead to catastrophic consequences, compromising the safety of both passengers and goods. This paper analyzes the root causes and impacts of draw gear failures on rail vehicle safety through a comprehensive analysis of historical data, current data, and simulation of failure by numerical analysis.
The analysis reveals that draw gear failures stem from various factors, including material fatigue, design deficiencies, improper maintenance, and operational conditions. These failures can result in the breakage of elements that can cause derailments, collisions, and other accidents. Such incidents pose significant risks to human life, property, and the environment. Furthermore, the economic implications of such failures, including repair costs, service disruptions, and legal liabilities, underscore the importance of proactive mitigation strategies.
By identifying common failure modes and their underlying mechanisms, this research provides valuable information and data for enhancing the reliability and safety of draw gear systems. Results obtained from these analyses can be used to improve design, material selection and characteristics, maintenance, and monitoring technologies. Additionally, the analyzed data emphasize the importance of industry collaboration in mitigating the risks associated with draw gear failures and ensuring the continued safety and efficiency of rail transportation systems
OpenFOAM NUMERICAL SIMULATION AND EXPERIMENTAL VALIDATION OF HIGH CAPACTY LONG DISTANCE FLY ASH PNEUMATIC CONVEYING FROM A 620 MW THERMAL POWER PLANT
No full textThe authors conducted pressure drop numerical simulations of multiphase gas-solid flow characteristics, within a fly ash pneumatic conveying system, in 620 MW thermal power plant. The objective of this study is to verify the OpenFOAM model by comparing the numerical results with pressure measurements taken along the considered pipeline. The numerical model is developed on the base of extensive experimental research of high-capacity long-distance pneumatic conveying system for Kolubara lignite fly ash. The numerical simulations of pneumatic conveying were performed using the Euler-Euler approach in OpenFOAM, that is twoPhaseEulerFoam solver, for the air mass flow rate of 5500 Nm3/h, the fly ash mass flow rate 77 t/h. The calculation input air pressure at the pipeline outlet was assumed to be as measured approximately 234 kPa, the air-ash mixture temperature was 373,15K, the mean ash particle diameter of 0.128 μm, and physical density of ash 2100 kg/m3. Numerical mesh is generated as an O-grid for the first two pipeline sections, first with a length of 90 m, a diameter of 0.2604 m, and an inclination of 1.885 degree, and the second with a length of 102 m, a diameter of 0.3097 m, and an inclination of 2.163 degree, while every mesh cell is substantially larger than the diameter of the ash particle. The applied Euler-Euler approach enables a comprehensive investigation of the complex dynamics involved in pneumatic conveying, considering the two-phase nature of the system and providing valuable insights into the particle behavior, pressure drop, and other key parameters. The comparison of the experimental and numerical model simulations data show good agreement regarding pressure drop. Although Euler-Euler model is complex in terms of necessary closure models, it might prove itself as reliable for simulated conditions in future studies
Concept of a complex redundant machine tool intended for the wire-cutting process
No full textU okviru rada je prikazan koncept jedne mašine alatke koja predstavlja unapređenje prethodno već izgrađene kompleksne mašine MOMA-W. Predložena mašina, namenjena za proces obrade sečenja žicom, sačinjena je od dva mehanizma sa paralelnom kinematikom. Svaki od mehanizama poseduje po tri stepena slobode, što ukupno čini šest stepeni slobode koje poseduje predložena mašina. Kako je za proces obrade sečenja žicom neophodno da mašina poseduje četiri stepena slobode, kojima se obezbeđuje željena pozicija i orijentacija žice, dodatna dva stepena slobode predloženu mašinu čini redudantnom. Kako bi bilo moguće rešiti kinematičke probleme uvode se dodatni uslovi za rešavanje kinematičkih problema kojima se sam proces obrade poboljšava.This paper presents the machine tool concept, which improves the previously built complex machine MOMA W. The proposed machine, intended for wire-cutting, consists of two mechanisms with parallel kinematics. Each of the mechanisms has three degrees of freedom, which makes a total of six degrees of freedom possessed by the proposed machine. Since the wire-cutting process requires the machine to have four degrees of freedom, which ensures the desired position and orientation of the wire, the additional two degrees of freedom make the proposed machine redundant. To solve kinematic problems, additional conditions are presented, that in principle improve the machining process.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