machinery
Not a member yet
8395 research outputs found
Sort by
Мобилни уређаји за гашење пожара у моторним возилима
Get PDFУ првом делу разматрања је изложена класификација мобилних уређаја за
гашење пожара, као и преглед законске регулативе која прописује обавезу држања мобилних
уређаја за гашење пожара у моторним возилима. У другом делу се разматра
учестаност различитих узрока пожара на моторним возилима, на основу које су дати
предлози за избор мобилних уређаја за гашење пожара намењених за употребу у моторним
возилима
Calibration of a Hybrid Machine Tool from the Point of View of Positioning Accuracy
No full textThe development of machine tools in the last twenty years includes, among other things,
the application of mechanisms with a non-linear kinematic structure as the mechanical basis of
machines. This results in significant improvements in kinematic characteristics and problems related to non-linear dependencies of the accuracy of the drive elements and the realization of movement in the machine’s external coordinates. The paper presents an approach to machine tool calibration based on the original O-X glide mechanism based on the ISO 230-4 standard with the mono- and bi-directional compensation of systematic errors and adaptation to the specifics of the mechanism’s kinematics. A machine tool prototype was designed and built for the research presented in the paper. The obtained results indicate the possibility of applying the existing recommendations and standards for testing the accuracy of machine tools with the need to correct the methodology by using linear and non-linear kinematic structures in machine tools
Fractional order time delayed acceleration feedback control of inverted pendulum system
No full textThe issue of human balancing in the sagittal plane using fractional order time delayed acceleration feedback is studied in this contribution. The problem of asymptotic stability of closed-loop fractional order neutral time delay system is solved by applying the D-decomposition approach. Stability regions in the control parameters space are determined using this method. Special attention was focused on the consideration of the influence of the time delay on the asymptotic stability of the system. Finally, simulation results are presented to illustrate the superiority and effectiveness of the proposed method
Residual life estimation of damaged structures exposed to high pressures and temperatures
Get PDFThis paper deals with the damage growth in High-Pressure Turbine (HPT) cooling holes of the case assembly made of Inconel 718. Several marks (cuts) were made on cooling holes into parent material during the service due to the non-skilled use of Electrical Discharge Machining (EDM) in the workshop. After a certain time, the case assembly returned to the workshop with all EDM marks cracked. Since HPT case assembly is not repairable and the only method for fixing this issue is its replacement with the new or used one (which might be pretty expensive), it was decided to use numerical analysis to estimate Paris coefficients for used Inconel 718, since the number of cycles and crack growth from the initial position were known, based on data obtained from the workshop. Firstly, finite element method (FEM) based numerical analysis was conducted in order to simulate crack propagation to match the one observed in the workshop, and then a multi-objective genetic algorithm – The standard response surface type - full second order polynomials – was used to obtain required Paris coefficients. The objectives of this optimization were the crack length and the corresponding number of cycles of crack growth. Obtained Paris coefficients were then used to estimate the residual life of HPT case assembly
Environmental status in correlation with water quality parameters of the South Morava river
Get PDFThe South Morava River is very important resource for the City of Vranje. Its water serves for irrigation of agricultural land and for drinking, so the water quality and its environmental status is of great importance. Water quality control in the South Morava is done on a monthly basis by chemical and physical methods. Controlling is done at two measuring points from which the samples are taken, namely the village of Mezgraje, near the Railway Bridge, and the site of Mramora Novo Selo. Tests of water samples from the South Morava River included determination of: general parameters, nutrients, salinity, organic substances and microbiological parameters. Measured values of the investigated physicochemical parameters at the sampling location at Mezgraja village level, with the Railway Bridge, dominantly correspond to class I, except for BOD5 corresponding to class V, HPC corresponding to class IV, TOC, phenolic compounds and total nitrogen corresponding to class II, nitrites, orthophosphates, ammonium ion, copper and iron content corresponding to Class III,. At the same location, the measured values of microbiological parameters correspond to Class IV. The water of South Morava River, from the physico-chemical aspect, has a mixed excellent to poor environmental status, while from a microbiological point of view it has a moderate environmental status at Mramor (Novo Selo) or poor ecological status at the level of the village of Mezgraja, at the Railway Bridge. The results of the water quality control tests show that the water is nutrient-poor and has microbiological parameters present in MPN/100 ml
Numerical simulations of fly ash pneumatic conveying from a thermalpower plant using OpenFOAM
Get PDFU radu je prikazan numerički proračun pada pritiska pri pneumatskom transportu letećeg pepela iz termoelektrane. Cilj istraživanja je verifikacija razvijenog modela upoređivanjem numeričkih rezultata sa merenjima pritiska duž cevovoda. Numerički model je razvijen na osnovu obimnih eksperimentalnih istraživanja sprovedenih na sistemu pneumatskog transporta pepela kolubarskog lignita, velikog kapaciteta i velike dužine. Ojler-Ojlerov pristup omogućava sveobuhvatno istraživanje složenih pojava pri pneumatskom transportu, uzimajući u obzir dvofaznu prirodu sistema i pružajući mogućnost sagledavanja ponašanje čestica, pada pritiska i drugih ključnih parametara. Formiranje mreže za Ojler-Ojlerove simulacije u OpenFOAM-u predstavlja složen proces, što uključuje definisanje računskog domena, generisanje odgovarajuće mrežne strukture i postavljanje odgovarajućih graničnih uslova i za gasnu i za čvrstu fazu. Potrebno je pažljivo razmatranje da bi se što vernije predstavila geometrija i definisali svi parametri u pneumatskim transportnim sistemima. Ojler-Ojlerove numeričke simulacije pneumatskog transporta pepela u kosoj cevi su sprovedene u OpenFOAM-u, koristeći paket twoPhaseEulerFoam solver. Numerička mreža je formirana kao O-mreža za deonicu cevovoda dužine 90 m, prečnika 0,2604 m i nagiba od 1,885 °. Sve ćelije mreže su značajno veće od prečnika čestica pepela. Rezultati numeričkih simulacija u pogledu pada pritiska se veoma dobro slažu sa eksperimentalnim rezultatima za ispitivani slučaj. Iako je Ojler-Ojlerov model izutno složen u smislu definisanja graničnih uslova, pokazao se kao pouzdan za za razmatrani slučaj, odnosno za razmatrane uslove.This paper presents a numerical calculation of pressure drop in pneumatic conveying of fly ash from a thermal power plant. The objective of this research is to verify the developed model by com-paring the numerical results with pressure measurements taken along the pipeline. The numerical model is developed based on extensive experimental research conducted on a high-capacity and long-distance pneumatic conveying system for Kolubara lignite ash. The Euler-Euler approach enables a comprehensive investigation of the complex dynamics involved in pneumatic conveying, considering the two-phase nature of the system and providing valuable insights into the particle behavior, pres-sure drop, and other key parameters. Creating a mesh for Euler-Euler simulations in OpenFOAM can be a complex process. It involves defining the computational domain, generating a suitable mesh structure, and ensuring proper boundary conditions for both the gas and solid phases. Careful con-sideration is required to accurately represent the geometry and capture the relevant flow physics in pneumatic conveying systems. In this study, Euler-Euler numerical simulations of pneumatic convey-ing of ash in an inclined pipe are conducted in OpenFOAM, using twoPhaseEulerFoam solver. Nu-merical mesh is generated as an O-grid for a pipeline section with a length of 90 m, a diameter of 0.2604 m, and an inclination of 1.885 °. All mesh cells are significantly larger than the ash diameter
STRUCTURAL INTEGRITY ASSESSMENT OF WELDS ON PRESSURE VESSELS
Get PDFThe paper presents assess the integrity of welded joints on pressure vessels made from HSLA steel. Risk based approach is applied using Failure Analysis Diagram to assess likelihood of failure. Special attention is paid on cracks defects by advanced ultrasonic testing which are unacceptable by standards, but difficult to be repaired. Structural integrity assessment was performed based on evaluation of fracture mechanics parameters, which has been used to improve safety of welded structures, focusing on welded joints on pressure vessel, as the most critical components. Simple engineering method is presented, based on the Failure Analysis Diagram (FAD) to explain evaluation of fracture mechanics parameters and their critical values in order to assess structural integrity of welded joints
The Arithmetic Optimization Algorithm for Multi-Objective Mobile Robot Scheduling
Get PDFIn recent years, metaheuristic algorithms have become increasingly advantageous for solving many real-world optimization-based engineering tasks. Integrated process planning and scheduling of machine tools and mobile robots utilized for transportation tasks in a manufacturing environment represents one such task. Since the number of solutions increases exponentially with the addition of either parts, machines, or robots, this task belongs to a group of NP-hard problems. Therefore, for its successful resolution, it is essential to use efficient algorithms that are able to explore vast solution space and provide optimal solutions. In this paper, we propose an algorithm for solving integrated scheduling of machine tools and mobile robots based on a novel arithmetic metaheuristic optimization. The arithmetic optimization algorithm belongs to a group of stochastic population-based algorithms inspired by arithmetic mathematical operations. The main advantage of the proposed algorithm is in a well-suited balance between exploration and exploitation phases that are appropriate for extremely hard multi-objective optimization. A multi-objective metric is utilized to evaluate obtained Pareto front solutions in terms of the exploration capabilities in the solution space. The proposed algorithm is compared with two other state-of-the-art metaheuristic algorithms. The experimental evaluation is carried out on 20 benchmark problems, and the results show the advantages of the proposed algorithm
Smart materials and contemporary context for the functionalization of renewable energy sources in the gallery space
Get PDFBy considering new studies on the possibility of implementing smart materials in museum-gallery
spaces which give the context for some modern models of functioning renewable energy sources,
this paper examines the universality of descriptions such context. Methodologically, in the use of an
analytical apparatus on the relation principle of Ars Inveniendi – Ars Combinatoria, the work is
inspired by Leibniz's philosophical ideas.Razmatranjem novih studija o mogućnost primene smart materijala u muzejsko-galerijskim
prostorima koji daju kontekst za neke savremene modele funkcionalizacije obnovljivih izvora
energije, u ovom radu ispituje se univerzalnost deskripcije takvog konteksta. Metodološki, u
korišćenju analitičkog aparata na relaciji principa Ars Inveniendi – Ars Combinatoria, rad je
inspirisan Lajbnicovim filozofskim idejama