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Risk assessment for hydrogen installations
No full textHydrogen is increasingly being adopted as a clean energy carrier across various industries, including transportation, power generation, and chemical processing. However, due to its unique physical and chemical properties—such as high flammability, low ignition energy, and wide flammability range—hydrogen poses specific safety challenges that must be carefully assessed and managed. This study presents a comprehensive risk assessment for hydrogen installations, focusing on identifying potential hazards, evaluating the likelihood and consequences of hazardous events, and assessing the effectiveness of existing safety barriers
Procedure for Integration of an Articulated Robot Model in а Game Engine Environment
No full textThe versatility and power of modern game engine platforms provide the potential for their use in creating real-time simulation environments within the robotics domain, particularly suitable for immersive and interactive experiences. Equipped with the comprehensive toolsets, extensive toolkits, and built-in features, these integrated development environments support the creation of real-time robot simulation models. Recently, Extended-Reality technology has been used in the development of human-machine interfaces in industrial robotics, in applications such as robot programming, system engineering, and personnel training. In this paper, the procedure for the integration of a vertically articulated robot’s model in the Unity game engine is presented. The main goal of the procedure is to generate a 3D GameObject robot in Unity, starting from a 3D model of the robot obtained using 3D design software. Positioning of robot joints’ local frames in a CAD environment for integration of a robot with Unity is described. The Articulation Body class from Unity’s built-in physics engine, Nvidia PhysX, is used to integrate robot dynamics. Specific XML formats following open-source standards, equipped with elements and attributes specific to robot kinematic and dynamic structure and suitable add-ons, have been used. The procedure is verified using the 6DoF vertically articulated robots RL15 and AD100
WEB SPEED CONTROL BETWEEN INPUT AND OUTPUT CATEPILLAR DEVICE ON CCV LINE USING PID AND SMC CONTROLLER
No full textThis paper presents speed and cable position control between caterpillar (pulling) device on CCV (Catenary Continual Vulcanization Line) production by Royle for production middle voltage cables using PLC controller CompactLogix L35E by Allen Bradley series and DC converters DCS 6RA80 series by Siemens with PID and sliding mode control (SMC). Input caterpillar device is master device on line its speed is regulated using PID from PLC. Output caterpillar as follower device is regulated using SMC with PID sliding surface which is defined equivalent control plus switching control. SMC controller also realized in PLC in discrete form. In this work was used a direct control method because it was measured current cable position all the time. State space model of system is given using Zero order hold (ZOH) discretization and sampling time was realized using the Timed Interrupt routine. Feedback of cable position is given from a non-contact sensor (SAG measure device) by Scholz placed on the vulcanization tube and it is used in the part of the routine for the output caterpillar. As the original machine is earlier production date, a reconstruction was made using modern components for the control and regulation. During the reconstruction, DC motor with a tachogenerator were change with DC motors with encoders, PLC software was developed and written, new electrical panel were made, and mechanical component was changed and installed. It was conducted redesign of some mechanical component to allow usage of implemented speed control method. After revitalization, the machine was successfully tested in cable production and the functionality of the installed components was experimentally proven. This revitalization was useful and the presented method has shown practical value in industrial applications for producing medium voltage cables
TENSILE STRENGTH ANALYSIS OF POLYMERS FABRICATED USING FUSED FILAMENT FABRICATION
No full textThis paper presents results of the experimental testing of 3D-printed specimens made from various materials. The applied technology for producing these specimens was Fused Filament Fabrication (FFF). The study was conducted in order to reach a conclusion about certain mechanical properties of examined materials, which find the vastest use in commercial 3D printing using FFF method. These materials include Polylactic acid (PLA), Acrylonitrile Butadiene Styrene (ABS), Acrylonitrile styrene acrylate (ASA) and Polyethylene Terephthalate Glycol (PETG). The specimens were produced according to the ISO 20753 standard in a direction perpendicular to the stretching direction to obtain maximum strength. The printer used for producing these specimens was Sindoh 3DWOX 1X. All the printing parameters remained the same for all specimens, excluding the nozzle and bed temperature, which were adjusted according to recommendations for specific materials. The testing was carried out on Shimadzu AGS-X 100kN universal testing machine with a crosshead speed of 1mm/min. The results were focused on elastic properties of materials and tensile strength. ABS showed the lowest values of ultimate tensile strength. PETG proved to be the least elastic, while PLA exhibited both the highest elastic properties and the highest ultimate tensile strength. However, PLA is not suitable for long-term use in places with elevated temperatures since it is prone to deformation. Based on the desired application and mechanical properties, the most suitable material should be chosen
LBFNN algorithm for studying response of shape memory alloy oscillator under Gaussian colored noise and periodic excitation
No full textSolving the Fokker-Planck-Kolmogorov (FPK) equation is a key problem for obtaining the transient response of stochastic dynamical systems. For shape memory alloy (SMA) oscillator systems, factors such as temperature and damping coefficients can affect the safety and normal operation of the system. Therefore, this paper studies the nonlinear dynamic response of SMA oscillator under periodic and Gaussian colored noise excitation. First, the stochastic Itô differential equations and the FPK equation for stochastic SMA system under non-resonant and resonant conditions are derived using the stochastic averaging method. Subsequently, Logistic Basis Function Neural Network (LBFNN) is proposed to solve the FPK equation. In the LBFNN algorithm, a three-layer neural network is used to approximate the solution of the FPK equation. The characteristic of this method lies in transforming the process of solving the FPK equation into solving a system of algebraic equations. The stationary and transient probability density functions of the SMA oscillator under periodic and Gaussian colored noise excitation are obtained. The influence of different parameter values on the SMA oscillator is analyzed, and the correctness of the approximate analytical solutions calculated by the LBFNN is verified using the Radial Basis Function Neural Network(RBFNN). The consistency of the comparison results demonstrates the effectiveness and superiority of the LBFNN algorithm in studying SMA oscillator. The study finds that temperature, damping coefficient and noise intensity can affect the performance of SMA oscillator. This paper shows that using neural networks to study the practical application of SMA materials has good potential.(No. 451-03-137/2025-03/200105
Risk analysis of inlet pipeline in hydro power plant Perućica based on failure analysis diagram
No full textInlet pipeline in the Hydro power plant “Perućica” in Montenegro has been checked in 2024byNDTmethods with a focus on its branch and inlet elbows. In the lower and upper elbow of unit 7 indicationshavebeen detected during the first magnetic particle testing. At the lower elbow “A-side” a crack withlengthof500 mm and depth up to 20 mm was detected, classified as unaccetable. Unacceptable defects were alsofoundinside the upper welded joint in the pipeline branch, with length 150 mm and depth 7 mm, locatedat themidthickness from 14 mm to 21 mm. Having in mind potential catastrophic consequences in the case of afailure, the branch with defects was additionally analysed by means fracture mechanics parameters andstructuralintegrity assessment to estimate risk of its further use. Although material in both cases was not veryfavourable from the fracture mechanics point of view, both defects turned out to be safe for further operation. This conclusion is also based on the fact that there is no mechanism of crack growth (practically nocorrosionand fatigue). Anyhow, since the risk in the case of the inlet elbow was of relatively high level, repair weldingwas recommended and performed
Cavitation erosion damage of pyrophyllite samples reinforced with cordierite, mullite and zirconium-silicate
No full textThis study investigates the cavitation erosion resistance of pyrophyllite-based composites reinforced with 20 wt.% of cordierite, mullite and zirconium-silicate, sintered at 1200 °C. The phase composition and microstructural features of the sintered samples were analyzed using XRD and scanning electron microscopy (SEM). Cavitation resistance was evaluated using the ultrasonic vibratory method with a stationary sample according to ASTM G32, by monitoring the mass loss and surface degradation as a function of exposure time. The results show that the addition of refractory phases with higher hardness significantly improves the cavitation resistance of pyrophyllite. Among the investigated compositions, the sample reinforced with cordierite (P+C) exhibited the lowest cavitation rate (0.145 mg/min) and minimal surface damage, attributed to its compact and homogeneous microstructure that suppresses microcrack initiation and propagation. The samples containing zirconium-silicate (P+Z) demonstrated moderate improvement, while mullite-reinforced samples (P+M) showed the least enhancement due to their elongated grain morphology facilitating brittle fracture. These findings indicate that cordierite is the most effective reinforcing phase for improving the cavitation durability of pyrophyllite-based ceramics, enabling their potential application in hydrodynamic systems exposed to cavitation-induced wear
Solar and Wind Power – Sustainability at UB-FME
No full textTo stimulate and facilitate the transition to a more sustainable and cleaner future, several renewable energy possibilities (wind and solar in particular) are considered for the University of Belgrade, Faculty of Mechanical Engineering (UB-FME). The paper presents an initial study of the possible energy contributions that could be achieved in the near future by distributing solar panels or small wind turbines across the rooftop surface, in addition to improved education and raising awareness of the sustainability related issues in general public. The initial estimates indicate that an additional 30-300 MWh could be generated annually, but further socio-techno-economic analyses should be conducted
Research of flexible plum-shaped guided wave transducer circular array for damage detection of plate metal
No full textUltrasonic guided wave transducers have become a key technology in the field of structural health monitoring due to their broad detection range and high sensitivity. However, traditional rigid sensors, which are mounted on the surfaces of complex structures, face challenges relating to mechanical integration and limited electrical and design flexibility. In order to address these issues, an innovative annular flexible omnidirectional plum-shaped interdigital guided wave (IGW) transducer array was developed and integrated into an experimental setup to assess its feasibility. The plum-shaped IGW transducer is fabricated using electric field-assisted jet deposition micro–nano three-dimensional printing technology. By designing the interdigital transducer structure on a piezoelectric substrate, the transducer array exhibits both wideband characteristics and the ability to detect waves from all directions. Experimental results confirm the array’s excitation and reception capabilities, demonstrating its wideband response. The excitation bandwidth and receiving bandwidth of the transducer are 610 and 510 kHz, respectively. Moreover, build an experimental platform to test the damage location ability of the transducer array. The calculated damage coordinate has an error of 2.89 mm from the actual damage coordinate, which does not exceed the radius of the magnet (≤3 mm). The effectiveness of the IGW transducer array for damage detection in plate structures is validated through time-domain delay superposition and multiplication techniques
Mehanizmi oštećenja cevi izlaznog međupregrejača pare nastali nakon 200.000 časova eksploatacije
No full textToplotnopostojani čelik klase 12H1MF već dugo godina se koristi u našim postrojenjima za izradu
elemenata termoenergetskog sistema. Čelik 12H1MF se koristi za izradu posuda pod pritiskom, koje su izložene istovremenom dejstvu povišene temperature, kao i unutrašnjem i spoljašnjem pritisku. U ovom radu je izvršeno eksperimentalno ispitivanje koje se odnosi na vizuelnu i dimenzionu kontrolu, merenje tvrdoće, hemijsku analizu, kao i mikrostrukturnu karakterizaciju cevnog luka izrađenog od čelika 12H1MF. Cevni luk je dobijen hladnim savijanjem cevi izlaznog međupregrejača pare nakon 200.000 časova eksploatacije na temperaturi od 540°C i maksimalnom radnom pritisku od 4,6 MPa. Na osnovu dobijenih eksperimentalnih rezultata može se potvrditi da je cevni luk oštećenjen usled dejstva gasne korozije, kao i da je došlo po pojave razugljeničenja površinskog sloja materijala na spoljašnjoj površini cevi izloženoj dejstvu dimnih gasova, dok do degradacije materijala nije došlo i pored dugotrajne eksploatacije. Ispitivanjem je utvrđeno da nije došlo do pojave puzanja materijala što potvrđuje da nije narušen integritet ove cevi