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Deviations Measurements of SLS PA Material at Compressive Specimens
Get PDFSLS technology is a popular choice in various industries worldwide because of its ability to produce complex geometry components with less effort when compared to conventional methods. The technology involves using materials in powder forms, such as polyamides (PA), polystyrenes, thermoplastic elastomers, and polyaryletherketones. In this study, the research focuses on compressive PA12 specimens with CAD model dimensions selected according to the ISO 604 standard, with bulk dimensions of Ø10x20 [mm]. The study utilizes a Fuse 1 (FormLabs, Summerville, MA) 3D printer that employs the SLS technology. This printer is capable of producing objects with different shapes and dimensions simultaneously, provided that they are printed at a minimum distance of 5 [mm] apart. The research involves producing four batches of specimens, each differing in printing orientation (i.e., horizontal and vertical) and printing location (i.e., printed on the edge and in the middle of the powder bed). The printed specimens are scanned, and the obtained scans are compared with the original CAD model in the GOM Inspect program. The highest deviations in all four specimen series are in height, ranging from 0.1 up to 0.15 mm. In the case of vertical specimens printed in the middle of the powder bed, there are also deviations in the width of the specimen
Revitalization of horizontal boring mill machine using plc controller and dc converter
Get PDFIn this paper is presented revitalization of the horizontal boring mill machine Stankoimport 2620B using a PLC controller manufactured by Schneider Electric and a DC converter manufactured by SSD Parker. As the machine is of an earlier production date, this method of feederate regulation in today's time is a problem because it is difficult to get the components in order to perform the maintenance or repair of the machine. The old control system was based on the use of electron tubes and an electromechanical amplifier. For this reason, a reconstruction was made using modern components for the control and regulation of the speed of the DC motor for feedrate moving. During the reconstruction, all AC motors and a DC motor with a tachogenerator were retained. All motors are tested and the brush holders was replaced on the DC motor and new brushes were installed. For the new part of the control system, which was built into the old control system, PLC software was developed and written, and new DC motor control hardware was installed. After revitalization, the machine was successfully tested in metal machining and the functionality of the installed components was proven. This revitalization was useful because the control panel on the machine remained the same as original state and it was not needed additional training of machine operator and also the electricity consumption and noise was reduced
Analysis of static strength of special tool for assembling wagon body
Get PDFThis paper presents the results of a finite element analysis (FEA) conducted on the static strength of an assembly comprising a special tool used for assembling the wagon body including the underframe, body sides, ends, and roof. The assembly was designed by “AMM MANUFACTURING“ from Kragujevac, Serbia. The elements of the assembly were specially designed endure the operational load experienced during the wagon body assembly process without undergoing any permanent deformation. A numerical analysis was performed on the aforementioned special tool, which serves as a support tool for assembling the wagon body. The special tool was constructed using structural and stainless steel. The finite element model (FEM) was created based on a a 3D CAD model obtained from “AMM MANUFACTURING“ and the analysis oof the static strength was carried out using suitable software. The numerical analyses were conducted in compliance with relevant standards. The results obtained demonstrates that the assembly of a special tool is capable of withstand the operational load during the wagon body assembly process without experiencing any permanent deformation
Biomimetics Design of Tooth Root Zone at Cylindrical Gears Profile
Get PDFDuring the last few decades, the requirements for modern machine elements in terms of size reduction, increasing the energy efficiency, and a higher load capacity of standard and non-standard gears have been very prevalent issues. Within these demands, the main goals are the optimization of the gears’ tooth profiles, as well as the investigation of new tooth profile designs. The presented design idea is based on the optimal solutions inspired by nature. Special attention is paid to the new design of the tooth root zones of spur gears in order to decrease the stress concentration values and increase the tooth root fatigue resistance. The finite element method is used for stress and strain state calculations, and the particular gear pair is modeled and optimized for these purposes. For tooth root strength analysis, the estimations are based on the theory of critical distances and the stress gradients obtained through finite element analysis. The obtained stress gradients have shown important improvements in the stress distribution in the transition zone optimized by biomimetics. An analysis of the material variation influence is also performed. Based on the investigations of a particular gear pair, a significant stress reduction of about 7% for steel gears and about 10.3% for cast iron gears is obtained for tooth roots optimized by bio-inspired design
Uticaj termoelektrana na KiM na životnu sredinu i klimatske promene i njihova budućnost
No full textZa većinu zemalja Zapadnog Balkana energetika zasnovana na fosilnim gorivima koja su korišćena u već značajno starim postrojenjima i sa nekompletnim sistemima za prečišćavanje otpadnih gasova predstavlja ključni izvor i GHG i standardnih zagađujućih komponenti emitovanih iz ovih izvora. Međutim, nastupajući Zeleni dogovor EU i obaveze koje su zemlje regiona preuzele potpisujući Sofijsku deklaraciju vode postojeća termoenergetska postrojenja kraju svog radnog veka. Specifične karakteristike sastava ugljeva Kosovskog basena, posebno u smislu karakteristika pepela, dovode do značajno različitih emisija zagađujućih komponenti u vazduh, u odnosu na druge lignitne ugljeve Srbije. Takođe, korišćenje rashladnih sistema koji nisu zasnovani na protočnim vodotokovima ima svoj uticaj na lokalnom nivou. U radu je analiziran uticaj rada TE na zagađenje vazduha i klimatske promene, ali i uticaj na druge medijume životne sredine.For most of the Western Balkan countries, energy sectors are generally based
on fossil fuel combustion in old generation plants and with not-so-effective
flue gas treatment systems, and as such, they represent a key source of both
GHG and standard pollutants emitted from these sources. However, the
forthcoming European Green Deal together with the commitments made by
the countries of the region by signing the Sofia Declaration on the Green
Agenda for the Western Balkans lead the existing thermal power plants
(TPP) to the end of their operating life. The specific characteristics of the coal
composition of the Kosovo basin, especially in terms of ash characteristics,
lead to significantly different emissions of pollutants into the air compared
to other lignite coals in Serbia. Also, the use of cooling systems that are not
based on watercourses has an impact at the local level. The paper analyzes the
impact of TPP operation on air pollution and climate change, but also the
impact on other environmental media
Air pollution modeling to support strategic environmental assessment: case study - National Emission Reduction Plan for coal-fired thermal power plants in Serbia
No full textThe paper presents a specific method of environmental impact assessment applied in Strategic Environmental Assessment (SEA) for the National Emission Reduction Plan (NERP) in the Republic of Serbia, based on air quality. The specificity of the approach is in the application of a semiquantitative method of multicriteria evaluation based on air dispersion modeling and the integration of SEA goals, indicators and criteria for assessing the impact of the NERP on the quality of air and other environmental elements in this method. When predicting changes in air quality for the planning horizon to 2028, the physical, geographical and climatic characteristics of the area were taken into account, as well as technical measures to reduce SO2 emissions, since this was the dominant pollutant from the Serbian coal-fired power plants studied by the NERP. Air pollution modeling was carried out using the AERMOD software package based on the data collected, and the quantitative results obtained were used in a multicriteria evaluation as part of the SEA. The results of the research indicated the importance of applying this approach in order to significantly increase objectivity in the SEA process, since it is an important element of decision making at the strategic level. In addition, a comparative presentation of the modeling results before and after application of the NERP was an important part of the SEA process, and it provided a clear insight into expected changes in the air quality. This is a key argument for making appropriate policy decisions on spatial, energy, environmental and socio-economic development in the Republic of Serbia, which, like other developing countries, is sluggishly following global trends in energy transition.Contract number 451-03-9/2021-14/20000
Humidity and Temperature Sensing of Mixed Nickel–Magnesium Spinel Ferrites
Get PDFTemperature- and humidity-sensing properties were evaluated of NixMg1-x spinel ferrites (0 ≤ x ≤ 1) synthesized by a sol-gel combustion method using citric acid as fuel and nitrate ions as oxidizing agents. After the exothermic reaction, amorphous powders were calcined at 700 °C followed by characterization with XRD, FTIR, XPS, EDS and Raman spectroscopy and FESEM microscopy. Synthesized powders were tested as humidity- and temperature-sensing materials in the form of thick films on interdigitated electrodes on alumina substrate in a climatic chamber. The physicochemical investigation of synthesized materials revealed a cubic spinel Fd3m phase, nanosized but agglomerated particles with a partially to completely inverse spinel structure with increasing Ni content. Ni0.1Mg0.9Fe2O4 showed the highest material constant (B30,90) value of 3747 K and temperature sensitivity (α) of −4.08%/K compared to pure magnesium ferrite (B30,90 value of 3426 K and α of −3.73%/K) and the highest average sensitivity towards humidity of 922 kΩ/%RH in the relative humidity (RH) range of 40–90% at the working temperature of 25 °C
Controlling highway toll stations using deep learning, queuing theory, and differential evolution
No full textTraffic congestion is, nowadays, one of the most important highway problems. Highway tolls with booth operators are one of the causes of traffic congestion on highways, especially in rush hour periods, or during seasonal holiday travels. The value of driver waiting time (needed to stop and pay the toll) and the cost of the toll booth operators can reach up to about one-third of the revenue. In this paper we propose a novel methodology for continuous-time optimal control of highway tolls by predicting the optimal number of active modules (booths) in toll stations. The proposed methodology is based on a combination of recurrent neural networks, queuing theory, and metaheuristics. We utilized several recurrent neural network architectures for predicting the average intensity of vehicle arrivals. Moreover, the prediction error of the first recurrent neural network was modelled by another one in order to provide confidence estimates, additional regularization, and robustness. The predicted intensity of vehicle arrival rates was used as an input of the queuing model, whereas differential evolution was applied to minimize the total cost (waiting and service costs) by determining the optimal number of active modules on a highway toll in continuous time. The developed methodology was experimentally tested on real data from highway E70 in the Republic of Serbia. The obtained results showed significantly better performance compared to the currently used toll station opening pattern. The solutions obtained by solving a system of differential equations of the queuing model were also validated by a simulation procedure
APPLICATION OF MXENE NANOSHEETS FOR IMPROVING MACHINE ELEMENTS PROPERTIES
Get PDFDue to a growing energy problems in the last decades, different ideas and methods for saving
energy and efficiency improvement become more and more requested. Taking into account that almost half of the energy losses in machines and mechanisms occur in frictional processes thus the importance of improving tribology performances in different machine elements is rather clear.
Machine elements such as gears, rolling and sliding bearings in various applications are usually operating with different lubricants in order to reduce friction and wear of their contacting surfaces. Besides surfaces in contact cannot be conventionally lubricated due to legal and environmental restrictions or physical limitations, in applications in food, textile, paper or medical industry as well as limitations due to ultra-clean conditions, extreme temperatures, radiation or vacuum, solid lubricants gain more and more attention due to the possibility to maintain essential lubrication properties. MXenes are a novel class of new two-dimensional materials, derived from well established MAX phases such as Ti3AlC2, which have the ability for a wide use in fields and applications due to their unique structure and properties. The distinct structure, low shear resistance, and easy-to-modify ability endow MXenes with particularly superior lubrication potentials. Authors of the paper present an overview synthesis and variety of MXenes, their mechanical and frictional properties dealing with ideas for possible applications in several machine elements aimed to reduce friction, wear rate and improve their performances making longer working life
Control of Direct Current Motor by Using Artificial Neural Networks in Internal Model Control Scheme
Get PDFIn this research, control of the Direct Current motor is accomplished using
a neuro controller in the Internal Model Control scheme. Two Feed
Forward Neural Networks are trained using historical input-output data.
The first neural network is trained to identify the object's dynamic
behavior, and that model is used as an internal model in the control
scheme. The second neural network is trained to obtain an inverse model
of the object, which is applied as a neuro controller. Experiment is
conducted on the real direct current motor in laboratory conditions.
Obtained results are compared to those achieved by implementing the
Direct Inverse Control method with the same neuro controller. It was
demonstrated that the proposed control method is simple to implement and
the system robustness is achieved, which is a great benefit, aside from the
fact that no mathematical model of the system is necessary to synthesize
the controller of the real object