Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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ULTIMATE STRENGTH OF INLAND VESSELS: RHINEMAX CLASS
No full textWhile the ultimate strength of sea-going ships is extensively explored in scientific literature, its practical application in industry remains limited. On the other hand, rules and regulations for ship construction have already incorporated detailed procedures for ultimate strength assessments in publications such as the Common Structural Rules for Bulk Carriers and Oil Tankers (CSR BC & OT). In contrast, inland waterway vessels (IWV) ultimate strength calculations are not applied in practice at all. Scarcity of literature data on this subject is evident, except for a handful of case studies focused on single vessels. Moreover, due to unharmonized and underdeveloped rules and regulations for IWV, their much older age compared to sea-going ships, and a lower inland waterway transport industry awareness regarding structural safety, IWV can be more prone to sudden collapse of hull girder. In fact, shallow water operations and the presence of bridges along the waterway govern the shallow draught of IWV, their higher length to breadth and length to height ratio than those of sea-going ships, making them vulnerable to the longitudinal strength issues. Recordings show that hull girder collapses on river occurs due to chain events of the various phenomena: grounding, improper overhauling of grounded ship, overloading, hull modulus diminished by severe corrosion and wear, improper maintenance. Therefore, the main aims of this work are to identify gaps in rules and regulations regarding ultimate strength assessments of IWV and to perform benchmarking analysis of ultimate strength for a class of similar IWV (i.e, Rhineclass, the largest on the river Rhine). For that purpose, a progressive-collapse analysis defined in IACS CSR BC & OT is used, which we automated in Python. Moreover, we checked the sensitivity of ultimate strength results by selecting two contemporary approaches for the calculation of ultimate strength of stiffener with attached plating: a) Jonson- Ostenfeld (J-O) and b) Paik-Thayamballi (P-T). Furthermore, our investigation seeks to determine whether there are differences in collapse sequences between IWV and the majority of sea-going ships. Results show that the abovementioned approaches lead to the difference on ultimate strengths of selected ships up to 5% meaning that each one of them will estimate similar ultimate bending moments. Moreover, findings show that Rhineclass inland vessels will firstly collapse as a hull girder before reaching the first-yield bending moment, which is contrary to sea-going ships case. Analyzed IWV will never yield, as their ultimate collapse is completely governed by buckling
Biomimicry potential in structural engineering
No full textComposite materials are widely used in modern structural engineering because of their excellent strength-to-weight ratio, but composites are not only related to man-made structures. Biomimicry is a term related to the imitation of natural phenomena in human engineering science. By combining knowledge about composite materials and natural structures, we can gain insight into how to make more resistant structures. The main goal of this paper is to compare lamina models by applying finite element analysis to obtain information about mechanical characteristics. It was shown that nature-inspired structures have the potential for engineering applications. The mechanical characteristics of those structures can be predicted by applying the finite element method. The concept of biomimicry is intriguing because, in nature, many structures can be used as inspiration for new applications in engineering science
On estimating convergence for Pickard sequences in quasi b-metric and rectangular quasi b-metric spaces
No full textIn this paper, using the same contractive condition as in [ 3], we give an estimate of the d(xn, x∗) for a sequence {xn} in a quasi b-metric space. In addition, we give another proof for the convergence of a sequence {xn}. Examples of estimation for Banach’s, Kannan’s, and Reich’s fixed point theorems are given. Following the same idea, in the second part of talk (paper) we shall introduce notion of the rectangular quasi b-metric spaces and present estimation in this class of spaces. At the end, we give some open problems
where research can be continued
OPTIMIZATION OF STANLEY PLUM DRYING PROCESS USING SOLID FUEL BATCH DRYER WITH TRAYS
No full textDrying fruit is a traditional preservation method that has been used for thousands of years. This technique allows for long-term storage of fruit, keeping it fresh and usable under ordinary storage conditions. In this research, the drying process of the selected variety of Stanley plums was analyzed in a batch dryer with trays using solid fuel. The research aimed to calculate the optimal air temperatures at the inlet and outlet of the heater, as well as the temperature at the outlet of the dryer itself. The constructed dryer has double trays, allowing drying capacities from 1550 kg to 3100 kg of Stanley plums. The main focus was on achieving efficient drying with minimal heat loss. The selection of basic equipment, such as a hot water boiler, circulation pump, heat exchanger, and fan, was tailored to the specificities of the dryer to maximize energy efficiency. The heat exchanger utilizes compact lamellar Cu-Al technology, while the fan is equipped with a filter section for a cleaner drying process. The use of solid fuels such as biomass brings significant economic benefits, reducing the costs of dried products. However, manual labor and detailed equipment inspection are necessary for each drying cycle, which is the main drawback of this method
Mining Management Strategy Towards Circular Economy and Sustainable Development
No full textMining is an important economic branch in Serbia, because it is highly
dependent on coal in the production of electricity. About 70% of electricity in Serbia is
produced in coal-fired thermal power plants. Viewed in the long term from the
perspective of the declared Green Transition until 2035, it is clear that coal exploitation
will decrease in the coming years. However, it cannot happen quickly. It is estimated
that coal will still remain the main source of energy until 2050, in permanent or reserve
operation. In order for this transition to be realized, it is necessary to first provide
appropriate renewable energy sources that enable safety and stability in the production
of electricity, which is not a simple goal. Complex technological processes in mining as
an economic branch facing the big tasks of transition to a green future and a sustainable
economy require a responsible attitude and the application of the modern and innovative
methods of environmental protection. That is why the rehabilitation of the environment
during and after the exploitation of ore deposits is an important and promising research
area. Modern methods of artificial intelligence help to find better solutions for
recultivation, revitalization and arrangement of degraded areas and mining pits faster.
This research will not only look for solutions in the field of compensation and/or
environmental restoration in the mining industry, but will also make a step forward
towards the use of some mining residues and their recycling. The goal is to use them as
raw materials in another economic branch. The motive is environmental protection with
zero waste reduction. The task is to introduce a circular economy. For a linear economy
in which raw materials are only used and waste is deposited, and the environment is
polluted, it has long been understood that it is an unsustainable and outdated approach.
Sustainable development requires that the principles of circular economy be applied in
mining, and artificial intelligence as a modern tool in the function of finding advanced
solutions for environmental restoration and reuse of discarded raw materials helps in achieving those goals. The research presented here improves the economics of the
mineral-raw material complex and upgrades it to the level of sustainable mining
Information Technology In The Function Of Circular Economy and Sustainable Development
No full textThe integration of information technologies (IT) into the framework of circular economy and sustainable
development has become increasingly crucial in addressing contemporary environmental challenges. This
paper presents a comprehensive review of the role of IT in advancing circular economy principles and
fostering sustainable development practices. Information technologies such as big data analytics, Internet of
Things (IoT), blockchain, and artificial intelligence (AI) are examined for their potential to optimize resource
management, enhance supply chain transparency, and facilitate the transition towards a circular economy
model. Moreover, the paper explores how IT solutions contribute to sustainable production and consumption
patterns, enabling businesses and consumers to make informed decisions that minimize negative
environmental impact. Additionally, the synergies between IT and renewable energy systems are discussed,
highlighting their combined potential to drive sustainable development initiatives. Furthermore, the
challenges and opportunities associated with the application of IT in the context of circular economy and
sustainable development are outlined, emphasizing the need for interdisciplinary collaboration and policy
support. Overall, this review paper underscores the pivotal role of information technologies in promoting
circularity, resource efficiency, and environmental stewardship within the framework of sustainable
development goals
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
DAMAGE ANALYSIS AND RESTORING OF STRUCTURAL INTEGRITY OF PELTON RUNNER AFTER REPAIR WELDING: CASE STUDY,
No full textThis paper presents the repair welding technology of a Pelton runner blade, including an analysis of damage caused by cavitation. Extreme exploitation conditions resulted in crack initiation followed by its propagation to a length 200 mm, detected during regular annual maintenance, compromising Peltron turbine’s structural integrity. The base material of the Pelton turbine is steel X3CrNiMo13-4, and as well as the blade geometry itself, required special attention during the process of defining the repair welding technology. An austenitic electrode was used for this purpose along with a welding technology defined in a way to counter the initiation of new cracks at the same location. Following the NDT, the Pelton runner was put back into exploitation, along with recommendations for further monitoring
INTEGRITY OF THE STEAM COLLECTOR MADE OF STEEL 12X1MF
No full textThe method of proving the integrity of the output collector of the steam super heater manufactured from the material 12X1MF, presented in the paper, is a material for working at elevated temperatures that is most often used in facilities of thermal power plants. Proving the integrity of the assembly was performed primarily using non-destructive testing methods, software processing of metallographic samples, conventional methods of proving the stress state in the material, application of the finite element method for the entire assembly and hydrostatic testing of the assembly with cold water pressure. Each collector segment is individually tested for the overall integrity of the super heater outlet collector. In addition to conventional methods of testing with/without destruction, software processing of the microstructure was also used in order to evaluate the proportion of the beanie phase in the structure, which is the main quality feature of the 12X1MF material. The qualification of the welding technology with additional materials available on the European market was an indispensable part of the proof of the integrity of the welded joints as the most critical segments of the assembly. The final stage of the assessment of the integrity of the assembly was the finite element method and hydrostatic testing of the assembly with cold water pressure
Ревитализација аутоклава намењеног за сушење сировог угља (лигнита)
No full textТехничко решење је применљиво (пре свега) у циљу санације опреме под притиском, конкретно аутоклава. Такође, техничко решење се може користити за репаратуру заваривањем/наваривањем оштећених делова опреме под притиском и сличних делова који су изложени сличним условима у току експлоатације. Репаратура посуде под притиском је поред свих техничких предности које су остварене, утицала и на остваривање велике економске добити, будући да је целокупна ревитализација изведена у погонима фирме наручиоца и са постојећим капацитетима. Такође, ово техничко решење се може применити у циљу елимисања оштећења, односно поправки и делова других грана индустрије који су изложени сличним радним условима у току експлоатације