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Сто година радног века котрљајних лежаја
No full textОвај рад је посвећен стогодишњици публиковања пионирског рада Арвида Палмгрена о математичком моделу радног века котрљајног лежаја. Приказан је развој теорије радног века лежаја од Палмгренових полазних истраживања до последње актуелне верзије међународног стандарда за прорачун номиналног радног века. Разматрани су сви релевантни утицајни фактори радног века котрљајних лежаја, као и њихова међусобна повезаност. Наглашена је важност развоја математичких модела за прецизнију процену радног века котрљајних лежаја, што подразумева интеграцију различитих геометријских, кинематских и триболошких параметара самог лежаја, као и параметара радних услова. Уз напредак у истраживању радног века разматрани су утицаји индустрије, као и стандардизација формуле радног века, кроз актуелни међународни стандард за прорачун динамичке носивости и радног века котрљајних лежаја – ИСО 281. Показано је како овај стандард континуирано еволуира у складу са новим сазнањима и технолошким иновацијама. Коначно, рад закључује да је даљи развој ових модела кључан за унапређење поузданости и перформанси котрљајних лежаја у складу са савременим захтевима технологије и тржишта.
Кроз свеобухватан преглед и анализу, овај рад нуди увид у тренутно стање теорије радног века лежаја, наглашавајући заједничке напоре истраживача и представника индустрије, који доносе напредак у овој области
ENHANCING INDUSTRIAL WATER MANAGEMENT: INNOVATIONS IN WASTEWATER RECYCLING
No full textWater treatment is the process of raising water quality so that it can be used for drinking, industrial activities, irrigation, and other uses. There are several physical, chemical, and biological procedures used to remove contaminants from water. This paper examines cutting-edge techniques for recycling wastewater in commercial buildings to reduce water usage. Industrial facilities face challenges in managing water resources sustainably and minimizing their negative environmental impact due to the growing global demand for water and the implementation of more stringent environmental standards. Various wastewater recycling methods are analyzed, such as biological treatments, membrane processes, advanced oxidation techniques, and the incorporation of renewable energy sources. The effectiveness, long-term viability, and environmental impacts of diverse recycling techniques are investigated by examining case studies from various industrial sectors. The research findings highlight the benefits and drawbacks of each approach, providing best practices and ways to implement them in industrial facilities. This paper aims to show improvements in industrial water treatment procedures to accomplish the objectives of sustainable development and water resource protection
Transport and mining machinery cabins’ ergonomic evaluation as a path to its redesign
No full textTransport and mining machinery cabins are still not well adapted to their users, while checklists for their evaluation are not common in the literature. This article proposes a new checklist for ergonomic evaluation and tests its universality empirically with a sample of 96 transport and mining machine operators. The objective of the article is two-fold. First, the article checks whether there are anthropometric dimension differences between different machines’ operators. Second, statistical significance testing regarding items in the proposed checklist is performed to check its universality. Significant differences have not been found between anthropometric dimensions of transport and mining machine operators. Group comparisons prove that mining machines have better ergonomics characteristics of the chair, manual controls and vision field. The recommendation for crane designers is to examine mining machines solutions and analyze the possibility of adapting these solutions, due to anthropometric fit. Wide usage of the checklist is recommended
Kinematic Modeling of a Compliant and Extensible Robotic Manipulator
No full textCompliance properties in robotic manipulators are becoming increasingly important for industry applications. Compliance is now considered one of the desirable properties of the emerging flexible assembly systems. Contrary to the traditional designs, compliance properties increase safety in today's human-robot collaborative systems. This paper methodologically studies the existing compliance robotic system solutions and presents one approach and solution for designing future compliant manipulators. It presents the usefulness of compliance and ways it can be inherently integrated into modern robotic systems. A novel approach to building a robotic manipulator that incorporates compliant joints, capable of easy extension and retraction is proposed. Further, it is shown how compliant kinematics and springs interaction with moving platforms solve spatial mobility
Experimental validation of the FE model of a composite beam
No full textIn order to design a composite beam of a contemporary unmanned air vehicle with vertical
take-off and landing capability, a finite element (FE) model was developed. Structure is
assumed as layered carbon-fiber shell, and is supposed to endure aerodynamic and gravitational
loads. The composite beam was manufactured and experimentally tested in accordance with
the expected operational load regimes (corresponding to 30%, 50%, 70% and 100% throttle).
Static forces, simulating two thrust forces generated by propellers connected to electric engines
and loads from the tail surfaces, were introduced as illustrated in Fig. 1 (left). Strain was
measured at six locations distributed along the beam. A very good comparison between
numerical and experimental results is achieved. Slight discrepancies can be attributed to
manufacturing omissions, insufficient knowledge of mechanical properties of the laminas
making-up the composite structure, and simplifications and idealizations of the numerical
model
APPLICATION OF WASTE RAW MATERIALS AS A REINFORCEMENT FOR PROTECTIVE COATINGS BASED ON PYROPHYLLITE
No full textIn this study, pyrophyllite was used for the first time in the composition of protective refractory coatings together with supplementary waste resources. The proposed refractory coatings are applicable for metallic and non-metallic structures, with the option of using them to protect machinery components in the chemical industry, metallurgy, and mining. Given that pyrophyllite has a low hardness, the goal was to improve the coating's resistance to cavitation erosion by adding 20 wt.% of hard refractory materials, i.e., crushed and micronized waste bricks based on mullite and corundum, respectively. Previous studies have demonstrated that protective coatings using a pyrophyllite filler have refractory qualities but insufficient resistance to cavitation erosion. As a result, the composition of refractory coatings, the preparation techniques, and the coating manufacturing process were altered. This study presents a simple method for combining conventional coatings made of refractory fillers (primary resource: pyrophyllite) with waste materials (mullite brick and corundum brick) used as reinforcement in protective refractory coatings for metal and non-metal structural elements that are highly resistant to cavitation erosion
Deep Learning-based Visual Servoing Algorithm For Wheeled Mobile Robot Control
No full textProduction-oriented companies that aspire to the concept of Industry 4.0 primarily focus on the increasing
flexibility and reconfigurability of the entire manufacturing system. By integrating a robotic material
transport/handling system that features a high level of efficiency, flexibility, and intelligence, the entire manufacturing
system reaps the benefits. With that in mind, the authors propose a deep learning-based visual servoing algorithm for
the intelligent control of a wheeled mobile robot. By utilizing a visual servoing algorithm, mobile robotic systems can
flexibly and efficiently adapt their trajectories to real-world conditions. Moreover, deep learning algorithms allow
mobile robots to learn robust visual features that make visual servoing even more applicable. The authors utilize
state-of-the-art deep learning models to train the mobile robot to perform visual servoing even without distinct
features that are necessary for such a system to function properly. Experimental evaluation with the own developed
mobile robot RAICO – Robot with Artificial Intelligence based COgnition has shown the benefits of the proposed
visual control algorithm
Dielectric and magnetic response of mechanically activated Mn-doped SrTiO3 ceramics
No full textThis research was focused on the influence of manganese (Mn) incorporation at Sr and/or Ti sites on the microstructure, relative dielectric permittivity and specific magnetization of strontium titanate (SrTiO3) ceramics. A solid-state method was used for the preparation of mechanically activated (10, 30 and 120 min) Mn-doped SrTiO3 ceramics with various manganese dioxide (MnO2) weight percentages (1.5, 3 and 6 wt%). Rietveld's analysis showed that the mean crystallite size in doped-activated SrTiO3 ceramics is smaller than in undoped ceramics, which is a consequence of additional crystal structure distortion due to ion substitution. Changes in the Raman spectra indicated dopant incorporation in the SrTiO3 lattice. The microstructural analysis pointed out a decrease in the mean grain size with increasing dopant concentration and time of activation. The highest values of permittivity and magnetization were observed for Mn-doped SrTiO3 ceramic mechanically activated for 120 min. Based on all the above, the optimal electrical and magnetic properties of SrTiO3 ceramics can be achieved by the appropriate choice of mechanical activation time and dopant concentration
Numerical Investigation of Fatigue Behavior in Ti-6Al-4V Orthopedic Hip Implants Subjected to Different Environments
No full textIn this paper, hip implants made of Ti-6Al-4V titanium alloy are analyzed numerically using Extended Finite Element Method XFEM. The combined effect of corrosion and fatigue was considered here since this is a common cause of failure of hip implants. Experimental testing of Ti-6Al-4V alloy was performed to determine its mechanical properties under different working environments, including normal, salty, and humid conditions. The integrity and life of the hip implant were assessed using the Linear Elastic Fracture Mechanics (LEFM) approach. For this purpose, the conditional fracture toughness Kq using CT specimens from all three groups (normal, humid, salty conditions) were determined. This provided insight into how different aggressive environments affect the behavior of Ti-6Al-4V alloy; i.e., how much its resistance to crack growth would degrade depending on conditions corresponding to the real exploitation of hip implants. Next, analytical and XFEM analyses of fatigue behavior in terms of the number of cycles were performed for all three groups, and the obtained results showed good agreement, confirming the validity of the integrity assessment approach shown in this work, which also represented a novel approach since fatigue and corrosion effects were investigated simultaneously
Numerical Investigation and Optimization of a Morphing Airfoil Designed for Lower Reynolds Number
Get PDFA novel concept of morphing airfoils, capable of changing camber and thickness, is proposed. A variable airfoil shape, defined by six input parameters, is achieved by allowing the three spinal points (at fixed axial positions) to slide vertically, while the upper and lower surfaces are determined by the lengths of the three corresponding ribs that are perpendicular to the spine. Thus, it is possible to find the most appropriate geometric configuration for a wide range of possible operating conditions often present with contemporary unmanned aerial vehicles. Shape optimizations for different Reynolds numbers and different cost functions are performed by coupling a genetic algorithm with simple panel method flow calculations. The obtained airfoils are presented and compared, whereas the proposed concept is validated by more advanced flow simulations. It appears that improvements in aerodynamic performance of nearly 20% can be expected at Re ranging from 0.05 × 106 to 0.1 × 106. The proposed methodology shows promise and can be applied to different types of lifting surfaces, including wing, tail or propeller blade segments. To check the viability of this method for producing airfoils that can be used in a practical sense, structural analysis of one of the obtained geometries using a simplified 1D finite element method as well as a more detailed 3D analysis are performed. The model is then 3D-printed on a fused deposition modeling (FDM) printer with a polyethylene terephthalate glycol (PETG) filament, and the capability of the airfoil to adequately morph between the two desired geometries is experimentally shown