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Excavator Operators’ Working Conditions and Its’ Failure Rates Prediction by Artificial Neural Network Modelling
No full textPrior studies have demonstrated the importance of maintenance in rais- AQ1
ing mining equipment performance levels together with pollution prevention and
cleaner production. However, operators’ working conditions have not been studied enough in the previous research. In that aim, in this paper, firstly, operators’ AQ2
working conditions in 10 excavators working in Serbia have been analyzed. Later
on, the study uses artificial neural networks (ANN) for developing a quantitative
model for estimating the failure rate of excavators. In order to avoid potential indirect financial losses, which sometimes exceed 15,000 euros per hour, the duration
times of 590 excavator downtimes, measured over 198 days at the Serbian mining
sites, were used as an input to the ANN. This enables the classification of failures
lasting more than an hour based on the preceding 14 days. The most common
type of downtime was found to be technological, according to a Pareto analysis
of the observed data. The findings demonstrate that the non-linear link between
excavation operations and excavator failure rates could be mapped using ANN
modeling. The results also showed that operators’ working conditions very often
have exceeded the boundaries prescribed by regulation, and the suggested ANN
model offers a precise estimate tool for predicting excavator failure rates during
the planning stage. The future research avenue is to continue monitoring working
conditions and failures and to predict in real time precisely the length of time that
an excavator would be down and to find deeper interrelations between operators’
working conditions and an excavator’s downtime
Device for increasing pressure in water supply systems with measurement of accumulated drinking water quality
No full textLow pressure in water supply systems, affecting both residential and industrial facilities, is a common issue in water distribution networks. Water sourced from municipal systems or shallow wells can experience pressure fluctuations or even complete drops, particularly during summer months. Supply from rooftop or overflow reservoirs often fails to maintain sufficient pressure to adequately supply all taps and appliances. Low pressure can also disrupt household devices such as washing machines, dishwashers, and water heaters. To address these problems, pressure-boosting systems are installed, which include additional pumps connected inline with pipelines or accumulation tanks for cases when water supply is interrupted. +The simplest solutions involve hydrophore units (a booster pump combined with a pressure vessel controlled by a pressure switch). However, noise generated by water pipes or booster pumps can cause discomfort for residents, often due to improper pump selection or inadequate regulation. Older centrifugal pumps with fan-cooled motors can create system-wide vibrations, increasing overall noise levels. This paper presents a technical solution for a pressure-boosting device in water supply systems, featuring reservoirs, recirculation pumps, water quality measurement systems, pressure-increasing pumps with PID control, compact electronic pressure transmitters, and expansion tanks. The design ensures silent operation while maintaining constant pressure in the water supply network. The device has been installed and tested in the Tonanti Hotel, Vrnjačka Banja, Serbia.https://doi.ub.kg.ac.rs/10-46793-sbt30
SMOOTHING OF DRAFT FORCE SIGNAL DURING PLOWING BY SAVITZKY - GOLAV FILTER
No full textThe measurement of draft force and soil resistance during plowing can be
performed using a strain transducer. They are placed on the lower tractor links, two sensors
on each side. After calibrating the sensors, acquiring and processing the data, the draft force
Fout and Fin are obtained, which correspond to the measurements on the two sensors on the
outside of the arms and the measurements on the sensors on the inside of the lower links.
Extreme values of the force signal as a function of time are extremely pronounced due to
changing conditions during the measurement. This paper investigates the influence of one
of the possible Savitzky-Golav smoothing signal filters. First, the appearance of the force
maps is shown in the experimental field of dimensions 120x60 on which the force effect is
most uniform. The corresponding diagram is also given with a display of the signal based on
the sensor measurements. Then, the data is filtered and the appearance of the new signal
diagram is given. Descriptive statistics finally provides a measure of the influence of the
applied filter. Statistical parameters have shown that the influence of the investigated filter
is minimal.contract registration number: 451-03-137/2025-03/20010
Application of a mobile digital image correlation system for on-site structural integrity assessment
No full textStructural integrity monitoring plays a crucial role in maintaining the safety and reliability
of industrial and civil infrastructure. Conventional inspection techniques often rely on contact
sensors and require operational shutdowns, limiting their efficiency and coverage. Digital Image
Correlation (DIC) provides a non-contact optical alternative that delivers full-field deformation and
strain data. Recent technological developments have enabled the adaptation of DIC into portable
configurations suitable for field deployment. This paper presents the practical potential of a mobile
DIC system for on-site assessment of pressure equipment and civil structures. The approach allows
inspection of pipelines, pressure vessels, bridges, and other load-bearing elements without disrupting
operation, offering early detection of localised deformation and enhanced decision-making for
maintenance planning. Although field implementation requires proper surface preparation and
control of environmental conditions, the system achieves laboratory-grade accuracy when correctly
applied. The mobile DIC concept therefore represents an efficient and reliable tool for real-time
structural evaluation, contributing to safer and more sustainable asset management
COMPUTATIONAL MODEL FOR THE FATIGUE LIFE ESTIMATION OF CYLINDRICAL ROLLER BEARINGS
No full textThis study aims to obtain a computational model for the fatigue life estimation of cylindrical roller
bearings. For this objective, the maximum contact pressure, equivalent static Von Mises stress, and equivalent dynamic Von Mises stress were calculated. The effect of design parameters such as geometrical parameters, material parameters and loading parameters on the fatigue failure of rolling bearings was simulated. Equivalent dynamic Von Mises stresses were determined by considering both the alternating stress and mean stress. The fatigue life of cylindrical roller bearings was estimated by using Basquin’s equation. The results indicate that increasing the roller element radius and length reduces contact pressure and Von Mises stress, leading to an extended fatigue life. Conversely, higher elastic modulus and applied load increase stress levels and shorten bearing life. The findings provide insights for optimizing bearing design, highlighting the importance of selecting appropriate dimensions and materials to enhance durability and reliability.Contract No. 51-03-137/2025-03/ 20010
On two inequalities of G. V. Milovanović and I. Ž. Milovanović and their applications
No full textIn this paper will be presented certain infinite dimensional generalizations of
two inequalities introduced by G. V. Milovanović and I. Ž. Milovanović [A
generalization of a problem given by D. S. Mitrinović, Publ. Elektroteh. Fak.,
Univ. Beogr., Ser. Mat. Fiz. 602–633, 129–132.], and some its applications.451-03-137/2025-03/ 200105 - 4.2.2025
From Lucy Ashton to Future CFD Case Studies: Benchmarking Ship Resistance at Full and Model Scales
No full textAccurate prediction of ship resistance using Computational Fluid Dynamics (CFD) requires thorough validation against both model-scale and full-scale data. This study presents a comprehensive summary of benchmarking efforts for CFD simulations of ship resistance, starting with the Lucy Ashton vessel, a historical case supported by full-scale resistance and boundary layer measurements. The benchmarking scope includes additional reference hulls such as the JBC, DTC and KCS, with resistance prediction errors consistently maintained within ±5%, highlighting the robustness of current CFD practices across different hull forms and scales. To broaden the evaluation, an additional vessel with an extensive experimental dataset-comprising model-scale and full-scale resistance measurements, full-scale self-propulsion data, wake field measurements-was analyzed. This expanded dataset enabled a more detailed assessment of simulation accuracy and scale effects. The outcomes from this study will support the organization of a dedicated CFD workshop, using the additional vessel as a reference case to promote standardized practices and improve simulation accuracy in maritime hydrodynamics.Project no. 451-03-137/2025-03/200105 from 4 February 202
A NOVEL FINITE TIME STABILITY ANALYSIS OF A CLASS NONLINEAR FRACTIONAL ORDER MULTI-STATE TIME DELAY SYSTEMS: A NEW GRONWALL – BELLMAN INEQUALITY APPROACH
No full textIn this contribution, the finite-time stability analysis (FTS) for a class of nonlinear two=term fractional-order multi-state time delay systems (FOTDS) is studied. Based on a new Gronwall-Bellman inequality, a new FTS stability criterion for such systems are established in term of the Mittag-Leffler function. Finally, we provide numerical example to illustrate the applicability of the proposed stability conditions.No. 451-03-137/2025-03/200105 from 04. 02. 2025
KINEMATICS MODELING OF COMPLIANT AND EXTENSIBLE STEWART-LIKE PLATFORM
No full textLabor shortages, sustainability challenges, and the limitations of conventional robotic systems
for delicate tasks like crop harvesting drive the need for innovative solutions. This paper
introduces a low-cost, modular robotic platform that combines passive compliance with
extensibility, enabling safe human–robot collaboration and scalable operation in dynamic
agricultural, medical or industrial environments. The proposed hybrid Stewart-like platform
(SLP) integrates a parallel kinematic structure with scissor mechanisms, using lightweight, 3Dprinted components for rapid prototyping. This study provides detailed design and kinematic
analysis.No. 451-03-137/2025-03/ 200105 from 04.02.2025
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