Milan Bizic - Academia.edu (original) (raw)

Papers by Milan Bizic

IMK-14 - Istrazivanje i razvoj, 2021

The task of this paper is determining the zone of influence of a circular hole on the stress stat... more The task of this paper is determining the zone of influence of a circular hole on the stress state of a homogeneous isotropic plate in pure bending condition. For solving the problem, the complex variable method was used which allows the complete analytical determination of the stresses at every point of the plate, and particularly on the contour of the circular hole. The analytical expressions for stresses in the plate of infinite dimensions were the basis for deriving a mathematical formulation which defines the zone as a function of diameter of the hole, inside which there is influence of the hole on the stress state of the plate. Obtained results are verified with FEM using the ANSYS software package whereby the input data for spatial discretization and mesh generation are not previously adjusted but was used a mesh that is generated automatically by the program.

Mechanics Transport Communications - Academic journal,, 2019

Engineering Failure Analysis, Oct 1, 2012

ABSTRACT This paper presents the failure analysis and improvement of suspension system of Fbd wag... more ABSTRACT This paper presents the failure analysis and improvement of suspension system of Fbd wagons for coal transportation. Respecting the existing design of the wagon, the special solution of the rubber elastic element which was subsequently installed in suspension system is designed. The element is very easy to install in existing wagons, between the laminated spring buckle and underframe. The methodology of identifying the causes of unwanted fractures is focused on theoretical and experimental analysis of behavior of suspension system with and without rubber elastic elements. Subsequent installation of rubber elastic elements at about 400 wagons in thermal power plant “Nikola Tesla”, Obrenovac, Serbia, has prevented the very frequent fractures of laminated springs and cracks on the underframes. This has enormously reduced costs of maintenance of wagons and increased the efficiency of railway transportation of coal from mining basin to the thermal power plant.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, Mar 14, 2023

The topic of this paper is the usage of the algorithm of marine predator (MPA) in the optimizatio... more The topic of this paper is the usage of the algorithm of marine predator (MPA) in the optimization of the suspension of rail vehicles with coil springs. The aim is to reduce the mass of set of coil springs as the main parts of rail vehicles suspension. The optimized set of coil springs must satisfy the appropriate conditions related to the suspension characteristics, with the aim of achieving the required operation quality and running security of the observed rail vehicle. Starting from the bi-linear characteristic of rail vehicles suspension and the analytical description of its parameters, an optimization problem is formulated. It is composed of six optimization parameters, an objective function and 16 constraints (eight for each coil spring in the set). The developed approach is applied in two specific examples of suspension optimization of four-axled freight wagons, the first with axle load of 200 kN and the second with axle load of 225 kN. The optimization problem is resolved using MPA. The acquired results showed that the given optimization approach with MPA provide a significant mass decrease compared to conventional design method of rail vehicles suspension with coil springs. The mass decrease of one set of coil springs in both examples is about 15.5%. Given that each considered four-axled freight wagon has 16 sets of coil springs, the decrease of the total coil springs mass per wagon in both examples is more than 60 kg. Since certified rail vehicles are commonly produced in large series, the proposed approach can be very significant for increasing profitability in the rail vehicles industry.

IMK-14, 2019

Ovaj rad prikazuje metodologiju proračuna čvrstoće točkova železničkih vozila prema aktuelnim međ... more Ovaj rad prikazuje metodologiju proračuna čvrstoće točkova železničkih vozila prema aktuelnim međunarodnim standardima. Metodologija je demonstrirana na primeru monoblok točka standardnog osovinskog sklopa teretnog vagona za osovinsko opterećenje od 200 kN. Analiza naponsko-deformacionih stanja i statičkog i dinamičkog stepena sigurnosti točka izvršena je primenom metode konačnih elemenata u softverskom paketu ANSYS. Za određivanje veličine površina kontakta na mestima gde su zadavana opterećenja primenjena je Hercova teorija kontakta između dva elastična tela. Dobijeni rezultati su pokazali da analizirani točak ima potrebne stepene sigurnosti i zadovoljava sve kriterijume čvrstoće definisane standardima.

Механика Транспорт Комуникации - Научно списание,, 2015

International Journal of Heavy Vehicle Systems, 2018

Experimental testing of the impact of railway wagons has shown that same test conditions with dif... more Experimental testing of the impact of railway wagons has shown that same test conditions with different types of cargo obtained different results. A theoretical model established in this paper enables determination of energy that is lost during the impact and coefficient of restitution. If inappropriate cargo is used, then it is possible to register forces that are more than 50% less than the actual values. It is necessary to determine limit values of coefficient of restitution for every type of wagon and cargo. The results of this paper may be important for improving the international regulations relating to the experimental testing of wagons.

Engineering Failure Analysis, 2012

International Journal of Vehicle Design, 2019

The paper deals with the usage of grey wolf optimiser (GWO) in the optimal design of leaf springs... more The paper deals with the usage of grey wolf optimiser (GWO) in the optimal design of leaf springs with railway vehicles. The main goal is minimisation of mass of leaf spring, with retention required characteristics of suspension system. Based on the exposed analytical model of leaf springs and requirements for suspension system, an optimisation model is developed. The developed model and GWO are applied in the optimal design of leaf spring of 4-axled freight wagon for axle load of 200 kN. The obtained results have shown that the proposed model and GWO provide significant reduction of mass of leaf springs of about 46.7%, in relation to the conventional design method. In addition, the numerical model of leaf spring is developed and the design obtained by GWO is verified by finite element method (FEM) calculation. Proposed approach enables significant material savings and reduction of production costs, as well as the reduction of design time of leaf springs of railway vehicles.

The aim of this paper is to give information about the problems and technical achievements in the... more The aim of this paper is to give information about the problems and technical achievements in the field of braking of railway vehicles. A brief description of the difficulties related to the braking of railway vehicles from the occurrence of rail traffic till today is given. From this it can be seen how engineering challenge is braking for the further development of railway transport. The main problem of further development of passenger and freight railway transport is solved by increasing the degree of automation of braking on a completely new and original way. This problem was solved by the Serbian engineer Dobrivoje Bozic from Kraljevo. Since the adoption of his solutions in 1928 to date, this principle of braking has remained unchanged. The paper gives the description of his solution, and some details from his interesting life. Bozic was the first in the world who was designed and applied completely new solution of three-pressure distributor in the braking system of railway vehicles. Its main characteristic is related to the possibility of gradual release of brakes. This solution was increased a level of automation of braking and provided a faster, safer and better quality of development of railway vehicles and the entire rail transport.

The paper presents the measuring systems for testing the safety and security of railway vehicles ... more The paper presents the measuring systems for testing the safety and security of railway vehicles that are in recent few years developed and built in the Center for Railway Vehicles at the Faculty of Mechanical Engineering Kraljevo. The measuring systems are based on wireless signal transmission and allow testing of quasi-static and dynamic characteristics of railway vehicles in accordance with UIC 518 regulations-quiet running and running safety of railway vehicles and UIC 530-2-Wagons-Running safety (Testing the railway vehicles behavior in repression through the S curve). The following topics are presented in this paper: the measuring system for measurement of lateral force Y and the vertical force Q that occur in contact between wheel and rail, as well as their ratio Y/Q; the test stand for calibration and testing of instrumented wheelsets; the measuring system for measurement of lateral force H and acceleration in the height of axle-box; the measuring system for measurement of the height of wheel lifting; the measuring system for measurement of acceleration of the wagon body; the measuring system for measurement of compressive force at the autocoupler; the measuring system for measurement of lateral movement between wagons; and the measuring system for measurement of temperature in the axle-box. For all measuring systems special software is developed, that allow easy control and adjustment, as well as visualization and storage of obtained measurement results.

During the exploitation of railway vehicles, failures of elements of the suspension are very ofte... more During the exploitation of railway vehicles, failures of elements of the suspension are very often. The fractures on the components of suspension are especially characteristics for freight wagons operating in extreme loading conditions. This causes a decreasing of the efficiency of rail transport and very often can cause a derailments with huge material damage and human victims. The task of this paper is to explore the possibilities for improvement of suspension behaviour through subsequent installation of rubber-metal elements of simple design. The methodology is based on the identification of causes of failures through numerical and experimental analysis of suspension behaviour. These research is basis for design of simple solutions of rubber-metal elements which can be subsequently installed in suspension of wagons. In this paper the proposed methodology is applied on the freight wagons for coal transportation whose suspension is based on laminated springs. Subsequent installatio...

According to the international regulations, the experimental testing of wagons impact is one of t... more According to the international regulations, the experimental testing of wagons impact is one of the mandatory testing in the phase of certification. During the wagons impact, there is an intensive change of dynamic parameters such as forces, deformations, speeds, accelerations, etc. These parameters are also very important when it comes to the design and verification of wagon structure quality. The purpose of this paper is to point to a very complex problems of the theoretical and experimental determination of dynamic parameters which appear at the wagons impact. In theoretical sense, there are two approaches for solution of this problem. One is related to the formation of differential equations of motion, and the second one is related to the application of the law of conservation of energy and the quantity of motion. In defining the mathematical models, there are usually the certain restrictions: wagon structure, bogie and cargo are considered to be absolutely rigid; railway track is horizontal; the centre of mass of cargo and wagons are moving in parallel and the gaps in subassemblies of wagons are ignored. Such conducted theoretical research are basis for preparation and realization of experimental research which should lead to the proper and satisfying results. In that sense, the moving of cargo during the impact is particularly significant. It is concluded that only mutual theoretical and experimental research can lead to the reliable results of dynamic parameters which occur at the wagons impact.

The intensity of the dynamic load of railway vehicles, in addition to the quality of the track, d... more The intensity of the dynamic load of railway vehicles, in addition to the quality of the track, depends on the elastic and damping characteristics of the suspension system. For existing track conditions can be stated that quality of dynamic behavior and safety of railway vehicles are primarily dependent on the characteristics of the suspension system. Suspension reduces the dynamic load, and thus reduces stresses in wheelsets, axlebearings, bogies, car body, track, etc. Dynamic load of railway vehicles are reduced because suspension elements take over part of the kinetic energy, which leads to the safer and smoother running of the vehicle. In order to reduce the amplitude of oscillation of the vehicle in running and to avoid the risk of resonance, special devices for damping of oscillations are applied. Damping is usually solved through the appropriate friction surfaces, installation of the hydraulic, pneumatic or rubber absorbers, etc. This paper provides the necessary guidance for the application of reinforced rubber elastic elements in suspension of railway vehicles. The concrete solutions of rubber elastic elements, developed and realized in Railway Vehicles Center and Laboratory for testing of constructions at the Faculty of Mechanical and Civil Engineering in Kraljevo, are shown.

The task of this paper is mathematical modelling of a plate weakened by a circular hole in pure b... more The task of this paper is mathematical modelling of a plate weakened by a circular hole in pure bending condition. The mathematical model is formed using the complex variable method, and allows complete analytical solution of stresses at every point of the plate, and especially around the hole where the well-known problem of stress concentration is present. The presented methodology can be applied for the solution of any plate weakened by a circular hole in pure bending condition. In the paper, methodology is applied for the solution of the one concrete example. The comparative analysis has shown a high accuracy of analytically obtained results with FEM results obtained by the calculation in ANSYS 12 software package. The application of the results of this paper is of great importance for quality of design and optimization of thin-walled structures of type plate weakened by a circular hole, which are very common in engineering practice.

The task of this paper is identification of stresses in a homogeneous isotropic disc weakened wit... more The task of this paper is identification of stresses in a homogeneous isotropic disc weakened with an eccentric circular hole which is loaded by pressure in the internal contour of the hole. By application of a complex variable method, the mathematical model that allows complete analytical solution of stresses of the disc is formed. The methodology can be applied for the solution of any disc weakened with an eccentric circular hole. The comparative analysis has shown a high accuracy of analytically obtained results with FEM results obtained by calculations in ANSYS 12 software package. The application of the results of this paper is of great importance for quality design and optimization of thin-walled structures of disc type weakened by a circular hole.

IMK-14 - Istrazivanje i razvoj, 2015

The running of railway vehicles is based on the interaction of wheelset-track or wheel-rail with ... more The running of railway vehicles is based on the interaction of wheelset-track or wheel-rail with precisely defined nominal geometries. In this way, the geometric relationships which allowing smooth running in tangent and curved track are achieved. However, geometries in practice deviate from nominal to a greater or lesser extent. This cause the constant change of geometric relationships between wheels and rails and all dynamic parameters of railway vehicles during the running. For this reason, the modelling of wheel-rail contact geometry is very important task in rail vehicle dynamics. This paper gives a systematic approach to the analysis of wheelset-track and wheel-rail contact geometry. After introducing the parameters of wheelset and track geometry, the non-linear geometric relationships between wheel and rail profiles are analysed, and parameters of wheel-rail contact geometry are defined. In final stage, the functions which combines all analysed parameters are derived. A special discussion about the equivalent conicity as the most important function of wheel-rail contact geometry is given. The methods of its determination and influence on the dynamic behaviour of wheelset and vehicles are discussed. Considerations in the paper confirm the fact that wheel-rail contact geometry and equivalent conicty as function which representing it, play one of the most important role in dynamic behaviour of railway vehicles.

IMK-14 - Istrazivanje i razvoj, 2017

Sile u kontaktu točak-šina predstavljaju glavne uticajne parametre i pokazatelje kvaliteta dinami... more Sile u kontaktu točak-šina predstavljaju glavne uticajne parametre i pokazatelje kvaliteta dinamičkog ponašanja železničkih vozila. Njihovo tačno određivanje ima veliki praktični značaj u procesima razvoja i ispitivanja železničkih vozila. Iskustva pokazuju da je najbolji način za određivanje ovih sila eksperimentalno ispitivanje odnosno merenje koje može biti stacionarno (sistemi na koloseku) i kontinualno (sistemi na vozilu). Kada se radi o mernim sistemima na vozilu, čija upotreba je obavezna u mnogim slučajevima sertifikacije i atestiranja železničkih vozila prema međunarodnim standardima, ne postoji univerzalno tehničko rešenje. Kao posledica toga, danas postoji veliki broj rešenja ovakvih mernih sistema koji su uglavnom zasnovani na primeni instrumentalizovanih osovinskih sklopova. Cilj ovog rada je da analizira najznačajnije metode i definiše osnove merenja sila u kontaktu točak-šina i položaja tačke kontakta primenom instrumentalizovanih osovinskih sklopova. Rezultati rada mogu biti veoma značajan izvor informacija za naučnike i inženjere, imajući u vidu nedostatak literature i naučnih publikacija u ovoj oblasti. Ključne reči: Sile u kontaktu točak-šina, Instrumentalizovani osovinski sklop, Eksperiment, Železnička vozila. 0. UVOD Mehanizam nastanka iskliznuća je usko povezan sa silama u kontaktu točak-šina koje izazivaju vibracije, habanje, termičke pojave, buku, zamor, otkaze i druge neželjene efekte u eksploataciji železničkih vozila. Poseban značaj ima vertikalna sila Q i bočna sila Y čiji je odnos Y/Q ključan za ocenu sigurnosti protiv iskliznuća (Sl. 1). Sl. 1: Sile u kontaktu točak-šina IMK-14-Istraživanje i razvoj u teškoj mašinogradnji Osnove eksperimentalnog određivanja sila u kontaktu točak-šina primenom instrumentalizovanih osovinskih sklopova

Tehnika, 2016

Otkaz ležaja osovinskog sklopa spada među najčešće uzroke iskliznuća železničkih vozila koja su u... more Otkaz ležaja osovinskog sklopa spada među najčešće uzroke iskliznuća železničkih vozila koja su uglavnom praćena ogromnom materijalnom štetom i ljudskim žrtvama. Savremene železnice intenzivno rade na razvoju i uvođenju odgovarajućih sistema za ranu detekciju neispravnosti ležajeva, koja se po pravilu manifestuje njegovim pojačanim zagrevanjem. Najčešći pristup zasniva se na primeni stacionarnih mernih stanica lociranih na određenim mestima duž trase pruge. Postoji i inovativni pristup koji podrazumeva primenu sistema za merenje i kontinualno praćenje temperature kućišta ležišta osovinskih sklopova. Osnovni cilj je da se omogući rana detekcija neispravnosti ležaja i da se spreči potencijalno iskliznuće. Ovaj rad bavi se analizom postojećih rešenja za detekciju neispravnosti ležajeva sa posebnim osvrtom na princip rada i glavne prednosti i nedostatke. U radu su prikazane osnove jednog novo-razvijenog bežičnog mernog sistema za kontinualno praćenje temperature kućišta ležišta osovinskih sklopova. Merni sistem je testiran u realnim uslovima i može se veoma uspešno primeniti kod komercijalnih železničkih vozila. Osnovni zaključak je da su sistemi za kontinualno praćenje temperature ležajeva daleko efikasniji od stacionarnih sistema. Dobijeni rezultati mogu biti značajni za sve one koji se bave ovakvim i sličnim problemima, problemima razvoja, eksploatacije i održavanja železničkih vozila, strategijama, propisima, itd.