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Feedrate profile generation with axis constraints using NURBS toolpaths for a Delta-KEOPS parallel kinematics machine
No full textIn numerical control feedrate profile defines the end effector or tool velocity tangent to the desired toolpath. By generat ing an appropriate feedrate profile smooth motion trajectories can be generated. Numerous papers propose a solution to this problem but most consider 3 and 5 axis cartesian machines. In this paper a computationally efficient feedrate profile generation algorithm is proposed for a Delta-KEOPS parallel kinematics machine with linear motor axes. The algorithm
generates a feedrate profile for complex shaped toolpaths defined by Non-Uniform Rational B-Splines (NURBS) while respecting the limitations of velocity, acceleration and jerk in the machines axes. This is a difficult task due to highly nonlinear kinematics of the Delta-KEOPS machine and complex shaped toolpaths. The algorithm was implemented in a PC-based real-time controller. Experimental results are presented which verify the capabilities and computational efficiency of the presented method on an actual machine
INFLUENCE OF PRINTING ORIENTATION ON THE ELASTIC MODULUS OF PA12 SPECIMENS OBTAINED BY SLS TECHNOLOGY
No full textThis paper describes a study that examined the effect of printing orientation on the mechanical characteristics, especially the modulus elasticity, of additive manufacturing (AM)—grade polyamide material. Selective laser sintering (SLS) technology was used to create tensile specimens composed of polyamide 12 (PA12). A specific type of specimen according to the ISO 527-2 standard for tensile specimens was studied to examine mechanical properties. The study looks at two batches of specimens exposed to tensile stress in various orientations inside the powder bed. Mechanical property evaluation utilizes a universal testing equipment, the Simadzu AGS-X. The comparison of horizontally and vertically printed samples attempts to determine if print orientation has a substantial impact on the mechanical qualities of the components
INTEGRATION OF ADDITIVE TECHNOLOGY AND MECHANICAL TESTING FOR THE ANALYSIS OF AUXETIC STRUCTURE CHARACTERISTICS
No full textThe Materials with a negative Poisson’s ratio are recognized as Auxetics materials. Compared to conventional materials it has the counter-intuitive property that during the compression the structure tends to contract and stretch when it expands. These particular attributes identified in the literature have encouraged further research on this topic. The flexible photopolymer resin is used for the test specimens, which have a cylindrical-shell based Auxetics structure. The test specimens are printed on an LCD printer with resin which gives structure ductile properties during the compression test. Using an industry camera the dimensional changes are captured for further research. With Digital Image Correlation method experimental results show different scenarios in varying the dimensions of the structure. Analyzed results give a foundation for future research, giving it a special focus on improving the quality of future tests and giving a perspective of potential applications and manufacturing variations of Auxetics structures
Static Calculation of Container Structure Loaded by Wind and Snow Using the Finite Element Method
No full textThe paper describes analytical and numerical methodology analysing the stress state of structural elements of the
special-purpose container. Research is based on the container supporting structure and the stress state under the
effect of additional loads from wind and snow is determined. Numerical analysis is carried out using the finite
element method in the ABAQUS® software package. After
the numerical calculation, it is concluded that the designed
container will not reach a critical condition due to additional loads. Some of the safety issues should be considered
early in the container life cycle, already during design and
manufacture. It is usually required to apply measures for
safe and healthy work which are determined by regulations
in the field of safety and health at work, and in connection
with the work to be performed
Analysis of the effect of undercuts in misaligned welded joints
No full textThe goal of this paper was to investigate the effect of undercuts, combined with other weldingdefects, onthe integrity of welded joints, and was inspired by previous work on the subject of welded joints withdiffernetdefect combinations. Research presented here relied on the fracture mechanics principles, namelytheFailureAssessment Diagrams (FADs), which was used to determine critical crack lengths, assuming a crackwhichhad initiated in the weld face undercut, for two different cases, both of which had vertical plate misalignmentas one of the defects. Based on the obtained results, it was concluded that a crack in the undercuts was safe, showinggoodagreement with actual behaviour of misaligned specimens during tensile tests. Actual failure of speci<menswith such defect combinations, as determined by experimental and numerical means, would occur inthevicinity of other defects, such as incomplete root penetration
Modal Analysis of Vibratory Conveyors Using Finite Element Simulation in Solidworks
No full textThe dynamic behavior of vibratory conveyors is a
key factor in their efficient operation and structural integrity.
This paper investigates the modal characteristics of a
simplified conveyor model through finite element analysis
performed in Solidworks. The study focuses on identifying
natural frequencies and corresponding mode shapes, which
are essential for tuning actuators and avoiding resonance
related failures. Additionally, the feasibility of approximating
the vibratory trough as a single-degree-of
freedom oscillator is evaluated by comparing analytical
estimates with simulation results. The findings confirm that
the fundamental frequency of the system closely matches the
analytical model, validating this approach for preliminary
design and optimization.451 03-137/2025-03/200105 from 04.02.202
Mašine alatke i roboti nove generacije
No full textMašine alatke i roboti nove generacije je izborni predmet na modulu za proizvodno mašinstvo na 1. godini Master akademskih studija Mašinskog inženjerstva (MAS-MI). Sadržaj knjige je koncipiran prema sadržaju predmeta koji je sistematizovan u 9 tematskih oblasti. Prvo poglavlje prikazuje kratak osvrt na istoriju i budućnost mašina alatki i robota. Obuhvata definicije i klasifikacije mašina alatki i robota, kao i kriterijume na osnovu kojih se izdvajaju mašine alatke i roboti nove generacije.
Drugo poglavlje polazeći od osnovnih pojmova modularnosti i rekonfigurabilnosti prikazuje rekonfigurabilne i prilagodljive mašine alatke i tehnološke sisteme.
U trećem poglavlju se razmatraju obradni sistemi za obradu velikim brzinama. Navode se primene i prednosti ovakvih obradnih sistema. Razmatra se tipičan predstavnik obradnog sistema za obradu glodanjem velikim brzinama. Četvrto poglavlje prikazuje definicije procesa brze izrade prototipova i klasifikaciju procesa sa dodavanjem materijala. Daju se primeri mašina za procese sa dodavanjem materijala, kao i primeri primene tih mašina. Peto poglavlje razmatra mašine alatke i robote sa paralelnom kinematikom kroz definicije, klasifikacije i mogućnosti primene. Dato je
i kinematičko modeliranje paralelnih mehanizama koje obuhvata rešavanje
i
Mašine alatke i roboti nove generacije
inverznog i direktnog kinematičkog problema, određivanje Jakobijan matrice
i analizu radnog prostora. Šesto poglavlja obuhvata mašine alatke za višeosnu obradu. Pokazuju
se primeri mašina alatki za višeosnu obradu glodanjem i analiziraju mogućnosti njihovog programiranja. Sedmo poglavlje prikazuje obradne sisteme za višeosnu obradu na bazi
robota kroz njihovo kinematičko modeliranje i analizu sistema upravljanja i programiranja.
Osmo poglavlja razmatra mikrotehnologije i adekvatne mašine alatke za te tehnologije, kao predstavnike nove generacije mašina alatki za mezo i mikroobradu. Deveto poglavlje kroz prikaz aktivnih nosećih struktura mašina alatki, primere etalona i primere kompenzacija u obradnom sistemu obuhvata mašine alatke visoke tačnosti.Рецензенти: др Бранко Кокотовић, ванредни професор и др Слободан Табаковић, редовни професор
За издавача: Декан, проф. др Владимир Поповић
Главни и одговорни уредник: проф. др Небојша Манић
Одобрено за штампу одлуком Декана Машинског факултета у Београду бр. 1/2025 од 20.02.2025. године
Штампа: Birograf comp doo, Београд
Тираж: 120 примерака
COBISS.SR-ID 16593383
Chatter in Manufacturing System – Prediction and Detection
No full textChatter is a phenomenon that periodically occurs in machining systems. Its occurrence in machining
processes excites the tool and other elements of the machining system, creating „chatter marks“ on the
workpiece surface, which affects the quality of the machined surface and dimensional accuracy. An
increased noise level is another indicator of the presence of chatter. These consequences have driven
researchers and global companies to develop machining systems or software for their programming,
aiming at the prediction, detection, and suppression of chatter in machining systems. A large number of
mathematical models and software solutions have been developed and published in leading international
journals. The topic of this paper is a review of the current state of research on chatter, with an emphasis
on the methods and techniques for chatter prediction and detection in machining systems.contract no. 451-03-137/2025- 03/200105 dated 4 February 202
Energy and exergy analysis of a hybrid ORC power plant
No full textOrganic Rankine cycles (ORCs) are highly recommended technology to generate electricity from low-temperature sources such as geothermal sources. The
performance of the cycle mostly depends on operation conditions, installed equipments and selection of working fluid. This paper presents a comparative energy
and exergy analysis of a geothermal-biomass Organic Rankine cycle (ORC) for
three working fluids: R113, R245fa, and R600a. In addition, analyzed ORC is
compared with the Rankine cycle that runs on Serbian lignite from the aspect of
equivalent CO2 emission and necessary primary energy. The analyzed system is
an ORC power plant with two heat sources – geothermal water from Vranjska
Banja and wood biomass. The results revealed the highest thermal and exergy efficiency with R113, 14.53%, and 41.64%, respectively, as well as the turbine power
output of 4.21 MW with 73.20 kW pump power input. Exergy analysis showed the
highest exergy destruction rate in the heat exchanger with flue gases made by wood
combustion (80-89%) and the highest obtained exergy efficiency of 41.64% in the
case of R113. If the power plant used Serbian lignite as a fuel for the same thermal
power input, it would need between 133-169 kt/year of lignite, which would result
in CO2 emission of around 63-80 kt/yea
Pregled i klasifikacija nacionalnih propisa iz oblasti zaštite od požara
No full textInženjeri, čak i oni koji nisu specijalizovani za zaštitu od požara, se u okviru svoje delatnosti u različitim ulogama sreću sa propisima iz oblasti zaštite od požara, na primer: prilikom projektovanja, tehničke kontrole projektne dokumentacije, izvođenja, nadzora nad izvođenjem, tehničkog prijema objekta, održavanja instalacija i dr. U ovom radu izložen je pregled propisa iz oblasti zaštite od požara i predstavlјena je jedna njihova klasifikacija, koja bi trebalo da olakša čitaocu snalaženje u materiji. Dat je i skraćeni pregled povučenih propisa; obuhvaćeni su zakoni, uredbe, naredbe, pravilnici i odluke dok će specifični tehnički standardi biti obrađeni u narednim brojevima časopisa