Papers by Aleksandar Miltenović
The modeling of the friction heat generation has become increasingly important in product design ... more The modeling of the friction heat generation has become increasingly important in product design process including areas such as electronics, automotive, aerospace, railway (e. g. wheel and rail rolling contact, braking systems, and so on), medical industries, etc. Determination of generated friction heat in the contact of wheel and rail is important for understanding the damage mechanisms on these two bodies such as wear. This paper presents a method to determine the friction generated heat in contact of wheel and rail during normal operation using transient structural-thermal analysis in ANSYS software.
In comparison to other types of transmission devices, worm gearsoffer a number of advantages whic... more In comparison to other types of transmission devices, worm gearsoffer a number of advantages which allow fora wide scope of applications in the fields of power and movement transmission. A deficiency of worm gears is a relatively low level of efficiency, especially in extreme operating conditions primarily related to the high transmission ratio and high rotation frequency. Namely, between the coupled flanks of a worm screw and worm wheel there is a significant amount of sliding which results in wear. Consequently, a substantial amount of mechanical energy is converted into heat, i.e. the thermal stability of a worm gear is disrupted as a result of warming. Thereby, the lubricating features of oil are changed, which subsequently results in the destruction of teeth and damage of seals. By means of an experiment and analysis the authors of the paper have determined the operating temperature of worm gears and performed an analysis of their thermal stability.
Market globalization and increased customer demands are leading providers of low product series t... more Market globalization and increased customer demands are leading providers of low product series to the high cost of development and construction. To overcome noted challenges it is necessary to use process of virtual product development. In that way it is possible, even in early phases of product development, to assess the operational product behaviour. Even the specific customer demands are determined before the actual product design phase. The paper presents an up to date concept of virtual product development with application on assessment of operational behaviour of Venturi pumps.
This paper is dedicated to lightweight design of high sided open freight wagon series Eamno, type... more This paper is dedicated to lightweight design of high sided open freight wagon series Eamno, type 159. Design strength was calculated in Department of Railway Engineering at Technical University Sofia and tested at the Bulgarian National Transport Research Institute (NTRI) in 2015. In the same year German railway administration commissioned the wagon. The results of carried out strength calculations show, that the wagon’s construction has very high strength and stiffness. The conclusion from calculations is that wagon construction could be optimized in order to reduce wagon’s own weight and in that way to increase maximal payload capacity of the wagon by keeping the wagon body strength in prescribed limits. The result of the pre-calculations is that the construction of Eamno 159 is oversized due to massive mid solebar, bolsters and transoms. Those elements of wagon underframe have immense impact on own weight of entire wagon body. This motivated the authors to conduct the preliminar...
Facta Universitatis, Series: Automatic Control and Robotics, 2020
The main goal of this paper is to present novel technologies that can contribute to safety, compe... more The main goal of this paper is to present novel technologies that can contribute to safety, competitiveness, efficiency and operational reliability of Railway infrastructure through the development of innovative solutions for measuring and monitoring of railway assets based on machine vision. Measuring the transversal position of the wheels on the rail, as well as identification of the defects of the wheel and the rail (such as deformation of rail head edge, lateral wear, worn wheels, cracks in wheel and rail, rolling contact fatigue, corrugation and other irregularities) can increase reliability and lower maintenance costs. Currently, there is a need on the market for the innovative solution, namely the on-board high-speed stereo camera system augmented with a system that projects custom pattern (fringe scanner system) for measuring the transversal position of the wheels on the rail, robust to environmental conditions and waste along the track that can provide reliable measurements...
The paper presents the new concept of power transmission in wind turbines, by application of a me... more The paper presents the new concept of power transmission in wind turbines, by application of a mechanical Continuously Variable Transmission (CVT). The analysis of the wind energy into electrical energy transformation process is given in regard to optimal transmission ratio of the proposed concept. Comparative analysis of the efficiencies of present and proposed concept of wind turbine power transmission is also performed. The possibilities for linking of concept components are given, as well as the analysis of linking possibilities from the standpoint of optimal operating condition, regulation interval and transmission efficiency ratio. Paper gives the design parameters of the new transmission concept prototype as well as the design of a test bed for experimental validation of the proposed drive train.
The modeling of the friction heat generation has become increasingly important in product design ... more The modeling of the friction heat generation has become increasingly important in product design process including areas such as electronics, automotive, aerospace, railway (e. g. wheel and rail rolling contact, braking systems, and so on), medical industries, etc. Determination of generated friction heat in the contact of wheel and rail is important for understanding the damage mechanisms on these two bodies such as wear. This paper presents a method to determine the friction generated heat in contact of wheel and rail during normal operation using transient structural-thermal analysis in ANSYS software.
Modern society is characterized by a fast rise of world population. This entails excessive consum... more Modern society is characterized by a fast rise of world population. This entails excessive consumption of all resources of the country. Land resources are limited and can be reached relatively quickly to their exhaustion. In this sense, the most important resources are related to the materials and energy. The question arises as to slow down the excessive consumption of these resources. One possible approach is to reduce spending of material and energy resources by using lightweight design. This paper provides an overview and presentation strategy lightweight design as well as a systematic approach to lightweight design.
Transactions of FAMENA, 2020
Overheating of gearboxes with crossed axes, such as crossed helical gearboxes, is one of the grea... more Overheating of gearboxes with crossed axes, such as crossed helical gearboxes, is one of the greatest disadvantages of these gearboxes in comparison with other drives, such as gearboxes with bevel or cylindrical gears. High friction results in the overheating of the transmission and the occurrence of scuffing. The main cause of the overheating is the generation of heat inside the gearbox due to bearing friction, sealing friction and above all, friction between tooth flanks during engagement. By applying the finite element method, thermal stability of a gearbox was predicted, and this procedure was verified on the case of a crossed helical gearbox with an axial distance of 30 mm. Based on the performed numerical investigation, a new procedure for the prediction of heat generation in the crossed helical gear transmission was proposed.
Proceedings on Engineering Sciences, 2019
Slip resistance of footwear sole and floor coverings is the characteristic which seriously depend... more Slip resistance of footwear sole and floor coverings is the characteristic which seriously depend on safety of human movement. There are some adopted standards which prescribe methods of slip resistance testing, but they are often criticized and revised. Tribological parameters are very important in human walking, running, jumping, etc. Friction mechanism of viscoelastic materials on hard bases is described in this paper. Also, influence of some parameters, like rubber hardness, rubber hysteresis, contact condition (dry and wet) and sliding speed are analysed according the testing results obtained in performed experimental research.
Facta Universitatis, Series: Mechanical Engineering, 2017
Residual stresses of the rail wheels are influenced by heat treatment during the manufacturing pr... more Residual stresses of the rail wheels are influenced by heat treatment during the manufacturing process. The quenching process during the manufacturing results in the residual stresses within the rail wheel that may be dangerous for the rail wheel during its operation. Determination of the residual stress in the rail wheel is important for understanding the damage mechanisms and their influence on the proper work of rail wheels. This paper presents a method for determining the residual stresses in the rail wheel during the quenching process by using the directly coupled thermal-structural analysis in ANSYS software.
Machine Design, 2017
A worm drive is widely used in power and movement transmission, and the proper functioning of the... more A worm drive is widely used in power and movement transmission, and the proper functioning of the entire machine system depends on it. The advantages of a worm drive, compared to other types of drives, are primarily reflected in its compact design, large transmission ratio, reliability, the possibility of vibration damping, as well as in structural advantages regarding branching and summarising energy, etc. Its capacity is limited by the emergence of a larger number of boundary conditions when in exploitation. This paper considers load capacity calculations of worm gears according to DIN 3996-2012.
Tehnicki Vjesnik, Aug 15, 2014
Original scientific paper Special kind of basic involute profile of non-standard gearing is calle... more Original scientific paper Special kind of basic involute profile of non-standard gearing is called high contact ratio (HCR) gearing, when the contact ratio is higher and there are always at least two pairs of teeth in contact (εα ≥ 2) and where unit addendum height is not equal one like for standard gearing, so the tooth height is increased and it is bigger than one ha * > 1. When HCR gearing is used, it is not necessary to achieve a greater gear load capacity, but nevertheless there is a greater risk of interference due to a greater height of tooth. Advantage of the HCR gearing is also a higher resistance (load distribution is shared on the more pairs of teeth at the same time) and lower relative noise level of gearing, which can be significantly reduced by using integer HCR factor εα. HCR profiles are more complicated than standard involute profiles, they have greater predisposition for occurring interference, pointed tip thickness, but also undercut of teeth during the production (primary production interference). Due to increased addendum height, there is larger possibility of occurring some interference or pointed tooth tip. Therefore it should prevent these errors and check if all equation and constraints are satisfied. The given method of finding optimal solutions for h * a1, h * a2 and x1 uses Generalized Particle Swarm Optimization Algorithm and MATLAB as a program for optimization. This GPS optimization is a very fast and reliable method.
ACTA Universitatis Cibiniensis, 2015
Product development is a creative task where is systematically created a new product, which makes... more Product development is a creative task where is systematically created a new product, which makes possible to firms to offer attractive, innovative and market oriented products. In conditions of fierce competition and saturated markets, companies that do not innovate are stagnating and disappear from the market. Innovation is therefore every intervention which can reduce production costs, enables optimum utilization of available human, energy and material resources, improve product quality, improve the placement, which leads to an increase in competitiveness. A prerequisite for fulfillment of the above-mentioned tasks is that the companies have engineers with the appropriate competencies, which are able to, through creativity, innovation and fascinating technique of creating new or improving existing products and lunch it on the market. The paper discusses the role and importance of the competences that are necessary for a successful professional career of product development engine...
Science of Sintering, 2015
Crossed helical gears have an important position in power transmission. Important advantages of t... more Crossed helical gears have an important position in power transmission. Important advantages of the crossed helical gears are the small design, the realization of high ratios in one stage, and the low noise characteristics. The paper presents a theoretical and experimental research of mesh efficiency, tooth friction coefficient and wear for a wheel of crossed helical gears made of Fe1.5Cr0.2Mo sintered steel with sinter-hardening treatment and without additional treatment. The calculation method is also given for the determination of wear load capacity of the worm with a helical gear made of Fe1.5Cr0.2Mo sintered steel with sinter-hardening treatment. These results provide product developers with the first important clues for indicators for calculation of the worm with a helical gear.
CVT преносника је тренутно у великом замаху. Предвиђа се да ће у скоријој будућности ови преносни... more CVT преносника је тренутно у великом замаху. Предвиђа се да ће у скоријој будућности ови преносници углавном заменити класичне преноснике снаге, нарочито у области преноса снаге код друмских возила. Поред концептуалних иновација у овој области, истраживања обухватају и испитивање погодности нових high-tech материјала при изради елемената преносника, као и утицаја квалитета израде на експлоатационо понашање CVT преносника. У овом раду приказана су најзначајнија савремена концептуална решења савремених CVT преносника и дат пример могуће примене оваквих преносника при преносу снаге код ветрогенератора. Research and development of CVT is currently in a momentum. It is foreseen that in not so distant future these power transmitters will replace the classical transmitters, especially in power transmission in road vehicles .Along the conceptual innovations in the research area, their research encompass the applicability of high tech materials in manufacturing of transmission elements, as w...
Tribology in Industry
Rubber is a very flexible material with many desirable properties which enable its broad use in e... more Rubber is a very flexible material with many desirable properties which enable its broad use in engineering practice. Rubber or rubber-metal springs are widely used as anti-vibration or anti-shock components in technical systems. Rubber-metal springs are usually realized as a bonded assembly, however especially in shock absorbers, it is possible to realize free contacts between rubber and metal parts. In previous authors research it was observed that friction between rubber and metal in such case have a significant influence on the damping characteristics of shock absorber. This paper analyzes the development process of rubber or rubber-metal shock absorbers realized with free contacts between the constitutive parts, starting from the design, construction, testing and operation, with special emphasis on the development of rubber-metal springs for the buffing and draw gear of railway vehicles.
Wind turbine is perspective source of electric energy considering advantages of wind energy. Nece... more Wind turbine is perspective source of electric energy considering advantages of wind energy. Necessity of multiplicator application as a component of wind turbine is implication of incompatible number of rpm of rotor and number of rpm of generator. Currently approach (method) connecting turbine with permanent convertible number of rpm and generator with constant number of rpm by multiplicators with constant transmission ratio came out non-effectively. In order to exceed this multiplicators disadvantages, new concept of wind turbine power transmissions is anticipated differential power transmission and power transmitters with variable transmission ratio (CVT) instead of multiplicators with constant transmission ratio uses for adjusting turbine impeller work with generator work. In this paper possibility of this kind of power transmitters application is given.
Tribology in Industry
In most of the cases, the friction is considered as a negative side-effect concerning energy loss... more In most of the cases, the friction is considered as a negative side-effect concerning energy loss following every process of the power transmission. However, the friction has significant positive side effects, because it is an indispensable prerequisite for the movement of people, machines, transportation means and others. Efficiency of these movements mostly depends on the friction between rubber and different materials such as metals, concrete, earth, wood, plastic, etc. Certain standards relating to measurement and determination of the friction characteristics of rubber were established. However considering that tribology of the rubber is very complex problem, numerous studies around the world are conducted. This paper gives an overview of some of the existing standards and conducted researches in this area. The paper also provides an overview of theoretical and experimental studies of friction the rubber and the other materials, which are done at Faculty of Mechanical Engineering in Niš.
Transactions of FAMENA
Crossed helical gears with steel worms and sintered steel wheels are widely used in motor vehicle... more Crossed helical gears with steel worms and sintered steel wheels are widely used in motor vehicles and household appliances. Besides the experimental study of a prototype transmission, the simulation using the finite element method (FEM) is another possibility to test gears under load in the design phase and to optimize them. As part of this paper, a piece of software was developed that enables calculation of wear-related variables, such as the Hertzian stress H , the minimum lubrication film thickness h min and the glide path s g , for every single point of the contact between worm and worm gear.
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Papers by Aleksandar Miltenović