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Horizontal Boring Mill Machine Feedrate Revitalization with DC Converter and PLC
No full textThis paper presents the revitalization of the feedrate system of the Stankoimport 2620B horizontal boring mill machine using a PLC controller and a DC converter with special reference to the way of adjusting the speed and current loop parameters of the converter using Matlab and OPC server. Using Matlab, a model of auxiliary movement was created and simulated. The simulation model was taken as a reference and connected to the PLC and the DC converter using the OPC server, and based on the comparison of the response difference between the simulation model and the real system, the parameters of the PI controller of the DC converter were tuned. Revitalization and reconstruction was carried out using modern components for the regulation of auxiliary movement. During the reconstruction, the components were integrated into the old system, which represents a special challenge, because the control system dating from 1970 was combined with the new control system. New electrical documentation was designed, software for the PLC controller was developed and written. After revitalization, testing was carried out in real conditions in metal machining and functionality was proven
Impact of Adversarial Examples on Classification: A Comparative Study
No full textVision systems are nowadays based on smart cameras that are integrated into Industrial Control System (ICS) using Industrial Internet of Things (IIoT) principles. The information between smart cameras and/or vision systems and the reminder of ICS is exchanged using different communication protocols. This opens the possibilities for cyber-attacks by malicious adversaries and introduces cybersecurity related challenges. Cyber-attacks on communication between smart cameras and ICS can cause wrong decisions, such as misclassification of images, and system performance issues. Given the significant role of vision systems in industrial processes, timely detection of attacks on communication links between smart cameras and ICS is crucial to mitigate or avoid negative effects. However, adversaries often employ advanced and covert methods to generate stealthy attacks evading conventional detection techniques. One of the emerging threats facing vision systems is Adversarial Examples (AEs) specially crafted to deceive Deep Learning (DL) algorithms for classification of images. In this paper, we explore various types of AEs and their impact on classification models based on DL. Four different techniques are employed for designing AEs. The performance evaluation of the AEs is carried out using a real-world dataset
METHOD OF DETERMINING NON-LINEAR TEMPERATURE DISTRIBUTION ACROSS THE THICK PLATE THICKNESS THAT SIMPLIFIES NUMERICAL CALCULATIONS
No full textIn this paper thermal loading of plate elements under several different heat sources (sinks), while sources are defined by the power and time of action, is considered. The heat sources are placed on the plate element sides parallel to the middle plane, while lateral sides are thermally insulated. Firstly, the dynamic problem was solved in closed analytic form using the technique of integral transformations. While discussing numerical examples that represent establishment of a non-linear distribution of temperature across the thickness of the element, laws on the basis of which this distribution can be calculated relatively simply without solving differential equations are established. Based on that idea, for steel elements, two basic diagrams were formed, which represent the procedure for calculating the temperature distribution. The procedure defined in this paper is suitable for simplifying the procedure of deformation and stress calculations of some real thermal loaded structures, using the finite element method
TWO-STEP-SCALING APPROACH TO SIZE EFFECT MODELING OF FRACTURE TOUGHNESS IN DBT REGION
No full textThis abstract outlines a strategy designed to offer estimates of fracture toughness using the Weibull cumulative distribution function (CDF) within the ductile to brittle transition (DBT) region. The size-effect modeling encompasses the dynamic interplay between brittle and ductile damage/fracture micromechanisms, which coexist in varying proportions within the DBT region depending on temperature. The inherent variability is tackled by employing a 3P-Weibull CDF. Application of the two-step-scaling (2SS) rest upon two scaling conditions along the CDF abscissa and ordinate (governed by the scaling parameters κ and ξ, respectively). The two scaling premises define in the scaled space the size-independent Weibull scale parameter (η⁎) and the common CDF slope S⁎ (i.e., the common PDF (probability density function) maxima), respectively. These two constancy conditions stem from the power law, intricately connected to Weibull statistics. This physically plausible power-law scaling is influenced by the traditional concept that the stress at the crack tip increases proportionally to the crack length raised to a power, establishing a connection between weakest link theory (WLT) and the Weibull statistics. When employing the 2SS scheme, the Weibull CDF adopts a modified WLT form. Finally, temperature-influenced DBT displays resemblances to behavior controlled by strain rates, particularly in scenarios of extreme loading causing shock waves that trigger nearly simultaneous activation of dominant nucleation kernels—an occurrence also witnessed at cryogenic temperatures
Novel insights into the problem of enthalpy and entropy convergence in thermal decomposition of coal slag using the data from non-isothermal kinetic measurements
No full textThis study provides insight into benefits of thermo-chemical conversion of coal slag as recovery process into value-added products. This research involves kinetic analysis of process conducted through non-isothermal thermal analysis measurements, with additional raw material characterization. Kinetic results showed that decomposition proceeds through two consecutive reactions steps (first one, including anorthite P1̅ → I1̅ phase transition, and then production of incongruent melting product (ternary system: CaO·Al2O3·2SiO2 (CAS2), where viscosity of slag changes), and second one including dehydration and formation of meta-muscovite, and subsequently, thermal disruption of muscovite de-hydroxylated phase, which proceeds with breaking of octahedral Al–O bonds), and one single-step reaction (attributed to CO-reduction of hematite to magnetite). Thermodynamic results showed an existence of physically meaningful isokinetic temperature (Tiso), which corresponds to active vibrational frequency of surroundings of SiO2 reaction site, manifested through Si‒O bond weakening by catalytic reaction of freed hydroxide ion (OH−). It was concluded that at temperature T = Tiso, the course of process loses its dependence on temperature and pressure, regulating changes between thermodynamic parameters, through enthalpy-entropy compensation (EEC) effect
CALCULATION OF THE UNCERTAINTY DUE TO SYSTEMATIC ERRORS OF TOTAL PRESSURE MEASUREMENT DURING FAST RESPONSE PROBES CALIBRATION
No full textSimultaneous measurement of 3D velocity and pressure fields, with high sampling rate, is a perpetual challenge. These complex flows exist in many technical systems, as well in nature. Turbulent swirling flow at the axial fan pressure side is one of the most demanding tasks. According to numerous authors, the occurrence of the turbulent swirling flow in ventilation systems is a source of energy loss, displacement of the designed fan duty point, and, as a result possible instability of the fan operation and reduction of the energy efficiency of the entire system.
Multi-hole probes are great tool for investigation of such complex flows. Recently, pressure transmitters have been integrated into the probe holder, so such probes have a fast response, i.e., a high sampling rate during measurements. The sampling rate depends on the geometry of the probe. The probe presented in this paper can sample several thousand samples per second, up to 10 kHz. This is of great importance, considering the existence of a very high level of turbulence in velocity and pressure.
The unsteadiness, non-homogeneity and three-component nature of such a velocity field, are requirements that lead to a probe geometry with a large number of holes with built-in high-frequency transmitters. This has led to the production of the FRAP (Fast Response Aerodynamic Probe), which has five holes and meets these criteria. Unlike standard probes (Pitot), FRAP probes need to be regularly calibrated.
The calibration process involves complex and time-consuming procedure of placing the probe in each of the working positions or angles of attack and collecting signals and values. The signals need to be processed, and subsequent calculations must be performed to determine the calibration coefficients. Additionally, uncertainties must be calculated, taking into account various factors that may affect the accuracy of the entire process.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. 451-03-137/2025-03/200105 and for research staff no. 451-03- 136/2025-03/20010
Wind Tunnel Testing of a Small UAV Electric Propulsion System
No full textThe purpose of this work was to gather experimental data and validate numerical results of the propulsion system behaviour intended for powering the light UAV “Putnik”, designed by the Beoavia Student Association The Putnik aircraft was designed and manufactured for the ACC2024 (Air Cargo Challenge) competition. According to the competition rules, the use of a T-MOTOR AT2826 KV900 BLDC motor and 3S LiPo battery is mandatory with free choice left for the ESC and propeller. For this purpose, several commercially available propellers were selected and numerically analysed. With the data obtained, Motor-Propeller matching was performed and a few of the most suitable propellers were chosen for testing. In the testing phase, the propulsion system was tested in static conditions after which wind tunnel tests were performed at the wind tunnel facility at the Faculty of Mechanical Engineering in Belgrade.
Wind tunnel tests were done to validate the numerical results and investigate the thrust force as a function of wind speed (flight velocity). Tests were performed at the following velocities: 0, 5, 10, 12, 14, 16, and 20 m/s. Every test lasted approximately 60 seconds, with a linear variation of power between 50 and 100%, defined by a custom PWM (Pulse Width Modulation) script. For data acquisition, custom software was developed by team members. In both static and dynamic testing, the following parameters were measured and obtained: thrust force, current, voltage, RPM, pressure and temperature.
After analysing the experimental results, it was noticed that at lower velocities, the maximal thrust obtained during tests was lower than numerically predicted, however, the thrust change was more linear, resulting in a smaller loss of thrust at greater velocities. Finally, the APC 13x6.5E was chosen, as it had good thrust reserve through the whole velocity range, as well as showing great overall efficiency at the designated cruising speed
Possibilities for utilization of blowdown waste energy in industrial steam boilers
No full textSteam boiler blowdown is a necessary process undertaken in steam boilers to control the level of total dissolved solids (TDS) within the boiler. The number of times a boiler is blown down depends mainly on the quality of boiler feed water. The hot water is usually discharged into a flash or expansion vessel which reduces the pressure of the liquid, and results in flash steam and boiler blowdown water. Heat recovery then may take place, both on the flash steam and boiler blowdown water, by means of heat exchangers. The paper presents the possibilities for reducing heat losses
caused by desalination and blowdown of industrial steam boilers. Techniques for reducing the amount of hot water discharged for the purpose of desalination and blowdown, as well as the possibility of waste energy recovery, were considered. The paper also presents a methodology for determining the flow rate of hot water from boiler desalination and blowdown where it is not possible to measure the flow rate directly, which can be useful when conducting short energy audits. In the paper feasibility of the application of heat recovery systems is presented, based on the results of analysis that was carried out for an industrial scale system in operation