Non-linear transient heat conduction analysis of insulation wall of tank for transportation of liquid aluminum

This paper deals with transient non-linear heat conduction through the insulation wall of the tank for transportation of liquid aluminum. Tanks designed for this purpose must satisfy certain requirements regarding temperature of loading and unloading, duringtransport. Basic theoretical equations are presented, which describe the problem of heat conduction finite element analysis, starting from the differential equation of energy balance, taking into account the initial and boundary conditions of the problem. General 3-D problem for heat conduction is considered, from which solutions for two- and one-dimensional heat conduction can be obtained, as special cases. Forming of the finite element matrices using Galerkin method is briefly described. The procedure for solving equations of energy balance is discussed, by methods of resolving iterative processes of non-linear transient heat conduction. Solution of this problem illustrates possibilities of PAK-T software package, such as materials properties, given as tabular data, or analytical functions. Software alsooffers the possibility to solve non-linear and transient problems with incremental methods. Obtained results for different thicknesses of the tank wall insulation materials enable its comparison in regards to given conditions

MICROSTRUCTURE INFLUENCE ON FRICTION BEHAVIOR OF THE TI6AL4V BIOMEDICAL ALLOY AT LOW LOADS

Dynamic friction coefficient (COF) between Ti6Al4V and Al2O3 was analyzed under low loads (100 mN, 250 mN, 500 mN, 750 mN, 1000 mN), sliding speed (4 mm/s, 8 mm/s, 12 mm/s) at dry contact and in the Ringer's solution. Different Ti6Al4V microstructures were studied: Sample 1 - fully lamellar; Sample 2 - martensitic; sample 3 - equiaxed; and sample 4 - globular microstructure. The maximum COF values varied as: 0.4 - 1.23 (Sample 1), 0.5 – 2.8 (Sample 2), 0.4 – 1.1 (Sample 3), and 0.4 – 2.3 (Sample 4). Lamellar and martensitic microstructures were not beneficial for the tribological response since they exhibited severe wear and very high COF values. The globular Ti alloy microstructure showed extremely high COF and wear under dry conditions. In general, water quenching was not a favorable treatment for tribological behavior. The lowest COF values and wear volumes were exhibited in the case of equiaxed microstructure

Raspberry as a potential commodity exchange material in the Republic of Serbia

Commodity exchange has a very long tradition and in a modern business conditions. Serbia ranks among the world's largest producers of raspberries, exporting more than 90% of total production of this fruit. Considering that Serbia is among global leaders in the export of frozen raspberries and that the process of standardization of the quality and quantity of this type of fruit is relatively simple, the starting hypothesis is that Serbian raspberry can be traded at commodity exchange. The main objective of our research is to analyze the necessary conditions for formation and sustainable functioning of the raspberry commodity exchange, with the emphasis on testing the proposed model of the commodity exchange method of communication between primary raspberry producers (vendors), intermediaries (purchasers, raspberry dealers or exporters of raspberries) and end customers who buy raspberries. We surveyed 100 persons representing the key actors of the Serbian raspberry producers and proposed the model of raspberry trading through commodity exchange.Publishe

The Review of Materials for Energy Harvesting

This paper presents a short review of the piezoelectric materials in energy harvesting. Energy harvesting principle, as the method for obtaining energy from environment has been described. Materials and material combinations for creating an energy harvesting composites are discussed, such as ceramic- and polymer-based composites and their mechanical properties. The list of the mostly used piezoelectric materials is presented and elaborated. Possible applications of the energy harvesting materials are discussed, including nanogenerators, biosensors and biomedical applications.10.13039/100010686-EIT's HEIAccepted for publishin

Electrospinning As The Fabrication Technology For The Energy Harvesting Composites

This paper presents the electrospinning technology as used for the fabrication of the energy harvesting composites, including the review of ceramic-based and polymer-based piezoelectric composites and their electrical outputs for the energy harvesting applications. Energy harvesting is a method for obtaining electrical energy from the environment to be used for powering autonomous electronic devices. Current trend of reducing the size of the devices has led to the increasing number of new energy harvesting materials. Basic principles of fiber fabrication via electrospinning were presented, as well as material characterization methods. The special focus was given to the electrical properties of energy harvesting composites with a review of methods for detecting and measuring electrical outputs of these materials. Electrical performance of the electrospun piezoelectric nanogenerators was discussed.SMART-2M, Innovation Capacity Building for Higher Education in Industry 4.0 and Smart Manufacturing, European Institute of Innovation and Technology (EIT), the European Union’s Horizon 2020 research and innovation program under grant agreement 777204 and projects No. 451-03-9/2021-14/200107 and No. 451-03-9/2021-14/200378, Ministry of Education, Science and Technological Development, SerbiaPublishe

Optical Coherence Tomography (OCT) Imaging Technology

This paper presents short review of the OCT technology concepts, including the recently emerging low-cost OCT devices. Technology concept of Fourier-domain OCT, based on spectral interferometry, is presented: spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). Technical properties of the recently developed low-cost OCT solutions are reviewed. Advanced OCT measurements in clinical ophthalmology are discussed, with relevant case studies. Further research directions that consider AI-based methods in OCT imaging is briefly presented.Accepted for publishin

Izabrana poglavlja iz metrologije: Praktikum za laboratorijske vežbe

Одлуком Наставно – научног већа Факултета инжењерских наука, Универзитета у Крагујевцу, бр. 01-1/1913-19 од 02. 07. 2020. године одобрено је издавање ове публикације као помоћног универзитетског уџбеника – практикумаPublishe

Friction and wear properties of copper-based composites reinforced with micro- and nano-sized Al2O3 particles

Copper-based composites with hard particles are widely applied in electrical sliding contacts such as those in railway overhead current collection system, lead frame in large scale integrated-circuit, welding electrodes, transfer switches and electrical contact material. Powder metallurgy is the most applicable technology way of producing the copper-based composites, especially when the matrix material is reinforced with second phase particles. Two copper-based composites reinforced with micro-sized Al2O3 particles (app. 750 nm in size) and nano-sized Al2O3 particles (less than 100 nm in size), and produced by powder metallurgy technology, were compared with a Cu-Cr-Zr alloy produced by casting technique. The tribological tests were carried-out on ball-on-disc nanotribometer, under the high-load (1 N), low-speed (8 mm/s) dry sliding condition. The addition of micro-sized Al2O3 particles did not showed so beneficiary effect, since this composite had the lowest hardness and wear resistance, and at the same time, the highest coefficient of friction. On the other hand the addition of nano-sized Al2O3 particles increased considerably hardness of composite and improved the wear resistance to a significant extent, and also reduces the coefficient of friction

General Overview and Applications of Ceramic Matrix Composites (CMCs)

This article presents a general overview of ceramic matrix composites (CMCs) and their applications. General properties are presented and most common types of ceramic matrices and different reinforcements. High temperature in processing and service of CMC components require optimal matrix – reinforcement combinations that must consider their temperature resistance, chemical compatibility and thermal expansion mismatch. General insights into mechanisms that govern the crack deflection and arresting in CMCs are presented. Typical oxide and non-oxide CMCs are shortly described, whereas matrices made of alumina (Al2O3), zirconia (ZrO2) and silicon carbide (SiC) accounts for the major part of applied composites today. Aerospace applications have been the most influential drive of CMCs development and research, but applications of CMCs are very important in versatile areas where components operate in hostile high temperature environments, like heat engines and nuclear reactors, also including metal cutting tools, energy conversion and storage devices, military systems, and electronic/electrical applications. Alumina and zirconia have been important in development and application of bioceramics, as well. Carbon and carbon based composites are presented, including carbon nanotubes (CNTs) and graphene and their roles in CMCs. Review of the latest research is shortly given, comprising hybrid composites and development of CMCs for wear resistant and self-lubricating materials, electromagnetic shielding and wave absorption, environmental barrier coatings, energy harvesting systems and piezo-devices, and ultra-high temperature ceramic matrix composites (UHTCMCs).Accepted for publishin

Cost optimization of additive manufacturing in wood industry

© Faculty of Mechanical Engineering, Belgrade. Software packages for 3D design and additive manufacturing (AM) technologies, initially known as rapid prototyping (RP) have emerged during the last years, as a cutting edge solutions for custom prototyping. These new tools and technologies lower the design costs, but also allow rapid creation of fully functional components. This paper describes the FDM and 3DP rapid prototyping technologies that were used to create elements and tools in the wood industry field. Total costs of manufacturing related to the fabrication of sample elements and tools are analysed. One of the main recognised issues of wider application of rapid prototyping technologies is their still very high costs related to all production aspects, starting with a lack of available materials, material cost, up to high cost of available commercial equipment, usually focused only on specific solutions and limited range of materials. Generally, AM costs can be divided into the group of fixed costs and variable ones. This paper deals with the optimization of the production costs of fabricated elements in case of small-scale production, and optimization of variable costs (processing and post-processing, costs of enforcement, and material costs)