Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Data interoperability and digital measurement twins in coordinate metrology
No full textU radu je predstavljeno jedno rešenje problema interoperabilnosti između dva različita DMIS (Dimensional Measuring Interface Standard) koda u kontekstu digitalnih mernih blizanaca (DMB) za Industriju 4.0. U svrhu istraživanja, konfigurisan je merni sistem koji uključuje numerički upravljanu mernu mašinu (NUMM), merni predmet i stezni pribor. DMB obuhvata virtuelne i fizičke komponente, pri čemu je virtuelna komponenta kreirana u CAD okruženju korišćenjem PTC Creo softvera. Krajnji izlaz iz virtuelnog i realnog merenja jesu DMIS datoteke. U radu je sprovedena analiza i poređenje DMIS kodova iz različitih softverskih okruženja (PTC Creo i PC-DMIS) kako bi se identifikovale i prevazišle prepreke interoperabilnosti. Istraživanje naglašava značaj usklađivanja kodova za tačno i efikasno funkcionisanje komunikacionog protokola između virtuelne i fizičke komponente DMB, kao i za poboljšanje simulacije i optimizaciju mernih putanja. Razlike u
strukturi i sintaksi kodova mogu uticati na tačnost merenja i zahtevaju dodatne korake kako bi se osigurala ispravna komunikacija između različitih NUMM. Ovaj rad pruža i pregled procesa inspekcije od modeliranja do stvarnih merenja na NUMM, ističući osnovne razlike između dva DMIS koda. Rezultati ukazuju na informacione praznine i izazove interoperabilnosti, te predlažu načine za njihovo prevazilaženje.The paper presents a solution to the interoperability problem between two different DMIS (Dimensional Measuring Interface Standard) codes in the context of digital measuring twins (DMT) for Industry 4.0. For the purpose of the research, a measuring system based on coordinate measuring machine (CMM), a measuring part and a fixture was configured. DMT includes virtual and physical components, with the virtual component created in a CAD environment
using PTC Creo software. The final output from virtual and real measurements are DMIS files. The paper analyzes and compares DMIS codes from different software environments (PTC Creo and PC-DMIS) in order to identify and overcome interoperability barriers. The research emphasizes the importance of code alignment for the accuracy and efficient functioning of the communication protocol between the virtual and physical components of the DMT, as well as for the improvement of simulation and optimization of measurement paths. Differences in code structure and syntax can affect to the measurement accuracy and require additional steps to ensure proper communication between different CMMs. This paper also provides an overview of the inspection process from modeling to real measurements on CMM, highlighting the basic differences between the two DMIS codes. The results indicate information gaps and interoperability challenges, and suggest ways to overcome them.Za izdavača: Dekan, dr Vladimir Popović, red. prof.
Tehnički urednici:
Prof. dr Saša Živanović, Doc. dr Miloš Pjević, Doc. dr Dušan Nedeljković, Lazar Matijašević, mast. inž. maš.
Štampa: Planeta print
Research and Engineering Activities in the Field of the Fire Protection at the UCIPS and the UB FME
No full textAt the University of Criminal Investigation and Police Studies (UCIPS) and the University of Belgrade Faculty of Mechanical Engineering (UBFME) are conducted research and engineering activities of interest for the complex topics with focus on the fire protection. In this paper will be presented in short research and engineering activities at both universities and three departments. Technical means of the police, Forensic engineering, Trasology, Termographic tests, Inspection and technical supervision, Analytical methods in forensic sciences, Expertise in forensic engineering, Forensic processing of the crime scene, Prevention and suppression offires, accidents and explosions, Tactics of special purpose police units, Security system for person and property, Environmental safety, Safety in emergency situations, Risk menagement in the protection and rescue system, Security protection of persons and property are studied at the UCIPS. At the UB FME are studied Risk analysis and Design of fire protection systems, Testing of the fire protection equipment and Expert analysis for court cases of fire accidents. In addition, at the UB FME Hydraulic Machinery and Energy Systems Department are studied, and developed pumps, fans and compressors with adequate systems and fluid flow measurement techniques
Finite Element Analysis of product tanker deckhouses under severe sea state conditions
No full textRegulatory bodies for ships (i.e., classifications societies) generally require finite element analysis when
existing ship structures are modified or non-conventional structures are added onboard. On each of two sister
ships (product tankers), both classed and with an overall length of 183.2 m, deckhouse structures were
mounted on the decks after years of navigation. These deckhouses, made of standard shipbuilding steel
comprising plates and stiffeners, are intended to store ballast treatment systems due to the lack of internal
storage inside of ships. The deckhouses are subjected to various load combinations that simulate extreme
conditions ships can encounter, including roll, heave, and pitch. The loads considered consist of the weight of
the structure and its internal equipment, as well as dynamic loads such as wind velocity, seawater pressure on
the deckhouses’ walls, and accelerations due to the ship rolling in severe sea and weather conditions.
Therefore, finite element analysis is performed following the procedure outlined in Lloyd’s Register’s Rules and
Regulations for the Classification of Ships, using the Von Mises stress criterion to assess the structural response
of the deckhouses. Moreover, three scantling cases are considered, varying based on the addition of corrosion
allowances to the net thicknesses of elements. Since the requirement was to prevent a significant increase in
the total steel weight of the ship after the installation of the deckhouses, the analysis aimed to determine the
minimum scantlings necessary to withstand the loads.
The results indicated that some cases failed to meet the criteria, primarily due to large spans of stiffeners
lacking transversal support. It was particularly the case with the port side deckhouse (larger structure and
spans) in almost all loading and scantling cases, whilst the starboard deckhouse needed structural
modifications in critical areas to satisfy the requirement
Fifty Years of the Ćirić Fixed Point Theorem on Quasi-Contractions
No full textThe notion of quasi-contractions was introduced by Lj. B. Ćirić [ 2]. The paper
[2] has been cited over 700 times up to now. The result on existence and uniqueness of fixed point for quasi-contractions by Ćirić is one of the most general results in the metrical fixed point theory (see [ 1]). In this talk (paper), we present a short survey of development of theory of quasi-contractive mappings, their generalizations and applications. Further, using quasi-contractive inequality with the non-linear comparison function, we obtain a result on existence and uniqueness of the common fixed point for hybrid pair
of single-valued and multi-valued mapping defined on b-metric spaces. Our result generalizes earlier results obtained in [ 3] and [ 4]. Also, we give the application of the obtained results to dynamic systems
Analysis of Dross Formation in Co2 Laser Axygen Cutting Using Machine Learning Model
No full textDross formation is a multifaceted issue in laser cutting. It not only requires post-processing operations but also entails a wider heat-affected zone and poses additional health hazards in the working environment. In this study, a machine learning model using multiple binary logistic regression was developed to predict the conditions for dross formation in CO2 laser cutting of mild steel. Laser power, cutting speed, and oxygen pressure were considered as input variables. The model was developed using experimental data from two crossed experimental designs: Taguchi’s L25 orthogonal array and a full factorial design 33. Statistical analysis showed no significant difference between the model predictions and the observed outcomes.
The study revealed that the most decisive input variable for dross formation is the cutting speed, with the probability of dross formation increasing as cutting speed increases. After developing the logistic regression model, laser cutting process windows were created for different combinations of laser cutting parameters within the experimental hyper-space. It was observed that cutting speeds over 5.5 m/min result in dross formation, and that with an increase in laser power, it is necessary to further decrease cutting speed to prevent dross formation
Specifics of Experimental and Fem Approaches in Structural Integrity Assessment of Penstock Made of HSLA Steel
No full textTaking into account the history of problems concerning high-strength low-alloyed (HSLA)
steel used for manufacturing of penstocks (partly presented by authors in previous studies), this paper is oriented toward specifics on structural integrity assessment of construction in question.
Experimental testing of parent material, i.e. HSLA steel, such as microstructure analysis, impact toughness testing and hardness measuring provide insight into characteristics of parent material properties. Considering geometry of penstock and specific requirements, finite element method (FEM), i.e. ABAQUS, was used to assess the structural integrity of penstock as a whole, specific the longitudinal welded joint under the different internal (working) pressure. It should be emphasized that a slight undermatching effect was investigated by FEM approach in this case. Focus is being put on plastic deformation investigation on aforementioned welded joint under maximum internal pressure of 120 bar
ЕГЗОСКЕЛЕТ ЗА РУЧНИ АЛАТ
No full textЕгзоскелет за ручни алат, саСТОЈИ се из спољашње цеви (9) кроз КОЈУ Је клизно уметнута унутрашња цев (13), при чему су и кроз спољашњу цев (9) и кроз унутрашњу цев (13) пробушени отвори (9а, 13а) тако да се положај унутрашње цеви (13) у односу на спољашњуцев (9) подешава завртњем (11) за фиксирање међусобног положаја његовим провлачењем кроз отворе (9а, 13а). На крај унутрашње цеви (13), која се усмерава према рамену или надлактици корисника причвршћен је кундак (12), а са друге стране завртњем (6) причвршћен је носач (5) шипки (4). На шипке (4) клизно је навучена шипка (17) савијена у "U" профил, а на њу клиз но навучена шипка (18). На шипку (18) навученаје цев (1) на коју је причвршћен доњи стезач (2) алата, на који је завртањском везом причвршћен горњи стезач (3) алата. Између носача (5) и спољашње цеви (9) постављен је еластични прстен (8), На спољашњу цев (9) навучена је чаура (10) са чичак траком (14), а друга чичак трака (16) причвршћенаје за носач (5). Механизам је универзално применљив за све кориснике без обзира на телесне димензије и масу, а нарочито за раднике који на послу значајно време проводе у коришћењу ручних електричних алата нпр. бушењу малим електричним бушилицама и одвртачима
CALCULATION OF THE UNCERTAINTY DUE TO SYSTEMATIC ERRORS OF TOTAL PRESSURE MEASUREMENT DURING FAST RESPONSE PROBES CALIBRATION
No full textSimultaneous measurement of 3D velocity and pressure fields, with high sampling rate, is a perpetual challenge. These complex flows exist in many technical systems, as well in nature. Turbulent swirling flow at the axial fan pressure side is one of the most demanding tasks. According to numerous authors, the occurrence of the turbulent swirling flow in ventilation systems is a source of energy loss, displacement of the designed fan duty point, and, as a result possible instability of the fan operation and reduction of the energy efficiency of the entire system.
Multi-hole probes are great tool for investigation of such complex flows. Recently, pressure transmitters have been integrated into the probe holder, so such probes have a fast response, i.e., a high sampling rate during measurements. The sampling rate depends on the geometry of the probe. The probe presented in this paper can sample several thousand samples per second, up to 10 kHz. This is of great importance, considering the existence of a very high level of turbulence in velocity and pressure.
The unsteadiness, non-homogeneity and three-component nature of such a velocity field, are requirements that lead to a probe geometry with a large number of holes with built-in high-frequency transmitters. This has led to the production of the FRAP (Fast Response Aerodynamic Probe), which has five holes and meets these criteria. Unlike standard probes (Pitot), FRAP probes need to be regularly calibrated.
The calibration process involves complex and time-consuming procedure of placing the probe in each of the working positions or angles of attack and collecting signals and values. The signals need to be processed, and subsequent calculations must be performed to determine the calibration coefficients. Additionally, uncertainties must be calculated, taking into account various factors that may affect the accuracy of the entire process.Ministry of Science, Technological Development and Innovation of the Republic of Serbia under the Agreement on financing the scientific research work of teaching staff at accredited higher education institutions in 2025, no. 451-03-137/2025-03/200105 and for research staff no. 451-03- 136/2025-03/20010
Environmental and Social Assessment of SHPP Brza voda 1 - Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)
Environmental and Social Assessment of SHPP Mojanska 3 - Expertise
No full textM103 - The expertise is done for Deloitte Consulting co. The investor was EIB (European Investment Bank)