Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Development of the Turbulent Swirling Flow Velocity Profiles in the Axial Fan Jet
No full textTurbulent swirling flow in the jet generated by
the axial fan impeller with twisted blades is studied
in this paper. Three velocity components are
obtained by using three-component laser Doppler
velocimetry system in ten measured sections.
Downstream flow development and continual
deformation of all velocity profiles with gradients in
radial and axial directions are obvious. It is shown
that circumferential velocity significantly deforms
profile of the axial velocity which gets M-shape
with weak reverse flow region in the central flow
zone in the first two measuring sections. This
phenomenon is still not well explained, especially
from the mathematical point of view.
Derivatives of all three velocity components in
radial direction are calculated for velocity field
analysis. Axial velocity profile in the downstream
sections becomes more uniform, with the strict
hierarchy of the positive gradient of the axial
velocity in axial direction in domain 0 < r/R < 0.5.
Character of distribution of the axial velocity out of
this region shows jet expansion. Maximum of the
axial velocity doesn’t belong to the jet core. In the
jet axis vicinity profile of the axial velocity is
concave even in the last measuring section. It means
that the transformation process is not completed.Ministry 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- 137/2025-03/20010
A Computational Study on the Influence of Explosive Type on Shaped Charge Jet Velocity in 64 mm Warhead
No full textConstant development of protective materials and armored systems requires continuous improvements in the field of anti-tank ammunition development. One of the most commonly used anti-tank explosive ordnance are shaped charge projectiles/warheads. Serbia has been globally recognized for decades in the production of high-quality hand-held rocket launchers equipped with various calibers of shaped charge ammunition. One of the most famous representatives is the 64 mm hand-held rocket launcher, better known as “Zolja“. Although it has been in use for decades and it has insufficient capabilities against more modern protection systems, retaining the traditional design and long-established production technologies, along with the use of more potent and modern explosives, could significantly enhance its penetration power. This paper uses analytical calculation and numerical simulation to analyze how different explosive materials affect the velocity of shaped charge jet of 64 mm M80 warhead, which ultimately directly impacts its penetration capabilities
Quadrature rules with quasi-degree of exactness
No full textMany quadrature rules are designed to be exact for easily integrable functions similar to the integrand. The Gauss formula with nodes is exact on the space of all polynomials of degree and it represents a unique optimal interpolatory quadrature rule. It is suitable for application if the integrand is polynomial-like. Note that a function can be similar to certain polynomials, but not similar to some other polynomials. This motivates us to construct a quadrature rule exact only on a subspace of polynomials that share certain properties with the integrand. After choosing arbitrary points (at which the integrand is defined), we transform the given integral into a sum of an integral that does not cause a quadrature error and an integral with a property that the points are the zeros of its modified integrand. Then, we approximate the integral of the modified integrand by an -point formula exact on the subspace of polynomials of degree with fixed zeros (those fixed zeros are not a disadvantage, since the modified integrand has the same zeros) -- such a formula is said to have a quasi-degree of exactness
Generalized Averaged Gaussian Quadrature Rules: A Survey
No full textaccording to Contract 451-03-137/2025-03/200105 dated on February 4, 202
Aeroelastic Behavior of 3D-Printed Tapered Polylactic Acid Plates Under Subsonic Flow Conditions
No full textThis research investigates the aeroelastic stability of tapered polylactic acid (PLA) plates produced through fused deposition modeling (FDM) under low-Mach-number airflow conditions. While the static properties of 3D-printed structural components for drones, unmanned aerial vehicles (UAVs), and unmanned aircraft systems (UAS) have been thoroughly explored, their dynamic behavior, especially flutter, has been less studied. This study applies a binary flutter model to thin PLA plates, and the analytically predicted flutter speeds are compared with experimental data from wind-tunnel tests. The strong agreement between theoretical predictions and experimental results confirms the validity of the proposed dynamic aeroelastic analysis approach. This methodology provides valuable insights into designing aerodynamic lifting and stabilizing surfaces for UAS applications
APPLICATION OF FINITE ELEMENT ANALYSIS (FEA) SIMULATIONS IN MEASURING ROOT SURFACE TEMPERATURE DURING CRYOTHERAPY
No full textThe aim of this study is to implement Finite Element Analysis (FEA) simulations in order to obtain data that could not be acquired through in vitro experimental setups. Several in vitro experiments conducted at room temperature have shown that cryotherapeutic effects on the root surface of tooth can be achieved using specific root canal irrigation protocols. However, clinical conditions—such as body temperature and tissue moisture—differ significantly from those in a laboratory setting, raising questions about the direct applicability of these protocols in clinical practice.
The initial plan for research involved designing an in vitro experiment that would simulate the real conditions of a tooth embedded in bone. The setup included P1000 temperature sensors attached to the root surface, with the tooth placed in a water bath maintained at body temperature (37°C) to replicate a humid physiological environment. However, the results exhibited significant anomalies, including unexpected temperature fluctuations, which were attributed to inadequate insulation of the sensors from the surrounding fluid. Despite multiple attempts, a reliable method of sensor attachment and waterproofing could not be achieved. To overcome these limitations, FEA simulations were implemented to computationally recreate the desired clinical conditions. The simulation model was validated using previously published data obtained at room temperature, which had been successfully established in earlier studies. The outcomes of the simulations aim
to determine whether cryotherapeutic effects can also be achieved under clinical conditions. Additionally, by manipulating key variables such as fluid volume, temperature, flow rate, dentin wall thickness, and irrigation time, FEA allows for the identification of optimal parameters for inducing cryogenic effects in clinical conditions.po Ugovoru 451-03-136/2025-03/ 200105 оd 04.02.2025. go
DEVELOPMENT OF COATINGS FOR THE PROTECTION OF METALS STRUCTURES BASED ON PYROPHYLLITE, ZEOLITE AND TALC
No full textThe goal of this work is the development of two types of protective coatings based on pyrophyllite and
talc and coatings based on pyrophyllite and zeolite. For two types of coatings, a mixture of 80% pyrophyllite,
grain size 20 μm and 20% talc, grain size 15 μm, i.e. 80 % pyrophyllite, grain size 20 μm and 20% zeolite,
grain size 15 μm, was used as a filler, respectively. In the composition of the coating, the total amount of
refractory filler was 85%, binder based on epoxy resin 7-10%, 1-2% organic additives and solvent based on
water. Pyrophyllite contributed to the improvement of thermos stability and mechanical resistance of the
coating, talc improved the ability to adhere and coat filler grains, while zeolite contributed to the improvement
of microporous adsorption of active phases, gases, heat, toxins, heavy metals. The manufacturing technologies
of these coatings are ecologically clean. The characterization of the obtained coatings was carried out using
the XRD, SEM and ultrasonic vibration method with a stationary sample according to the ASTM G32
standard. Research has shown that the obtained coatings increase the anti-corrosive and thermal protection of
metal substrates, and in particular, the resistance to wear and cavitation erosion is increased. This provides
wide possibilities of application of these coatings in industry, construction, energy, military industry
Inertial Amplification Effects on Wave Dispersion in Metastructures with Elastic and Rigid Segments
No full textWe investigate a metastructure made from unit cells with coaxial Timoshenko beams and
rigid bodies, and an inertial amplifier attached at the left end. The inertial amplification mechanism
is consisted of two auxiliary masses which are connected with rigid bars to both the beam and main mass. Using a combination of the transfer matrix method and the spectral element method, we examine how changing one design parameter affects the dispersion properties. Inertial amplification induces low-frequency wave attenuation without increasing system mass, which is one of the key challenges in metastructure design. These findings offer an effective strategy for wave control in periodic structures composed of elastic and rigid segments, with potential applications in lightweight acoustic insulation and seismic isolation for structures such as buildings and bridges.No. 451-03-137/2025-03/200105 from 4.2.202
Modal Analysis of Vibratory Conveyors Using Finite Element Simulation in Solidworks
No full textThe dynamic behavior of vibratory conveyors is a
key factor in their efficient operation and structural integrity.
This paper investigates the modal characteristics of a
simplified conveyor model through finite element analysis
performed in Solidworks. The study focuses on identifying
natural frequencies and corresponding mode shapes, which
are essential for tuning actuators and avoiding resonance
related failures. Additionally, the feasibility of approximating
the vibratory trough as a single-degree-of
freedom oscillator is evaluated by comparing analytical
estimates with simulation results. The findings confirm that
the fundamental frequency of the system closely matches the
analytical model, validating this approach for preliminary
design and optimization.451 03-137/2025-03/200105 from 04.02.202
Primena i dimenzionisanje hidrociklona u papirnoj industriji
No full textKonstantni deo papir mašine je deo pripreme papirne mase između rezervoara u kome se skladišti razvlaknjena papirna masa i natočnog korita. Sastoji se od više tehnoloških celina koje obavljaju različite funkcije kao što su izdvajanje nečistoća, rafinacija, deaeracija (uklanjanje vazduha) i razvodnjavanje mase, tj. kontrola koncentracije čvrste materije, pre nego što papirna masa bude ravnomerno raspodeljena po širini papir mašine u natočnom koritu. Dobro projektovan sistem obezbeđuje kontinuirani protok suspenzije sa stalnom koncentracijom, kvalitetom i protokom, pri konstantnom pritisku, ka natočnom koritu. Poželjno je da varijacije protoka mase budu manje od 1% u odnosu na nominalnu vrednost. Hidrocikloni imaju ključnu ulogu u sistemu pripreme papirne mase jer poboljšavaju njenu čistoću pre nego što ona stigne do natočnog korita. Oni predstavljaju posebnu vrstu centrifugalnih prečistača koji uklanjaju neželjene čestice iz suspenzije, kao što su: pesak, druge čvrste čestice mineralnog porekla, metalne čestice, ostaci boje, plastika. Princip rada hidrociklona zasniva se na tangencijalnom ubrizgavanju papirne mase velikom brzinom, pri čemu se u uređaju stvara vrtložno kretanje. Zahvaljujući centrifugalnim silama, teže čestice (nečistoće) se potiskuju ka spoljnim zidovima i izlaze kroz otvor/priključak u donjem delu uređaja, dok tečna faza manje gustine, tj. prečišćena suspenzija izlazi kroz otvor/priključak u gornjem delu uređaja i nastavlja ka natočnom koritu. U ovom radu je analizirana primena hidrociklona u papirnoj industriji i prikazana je metodologija za dimenzionisanje i izbor ovih uređaja