http://casopisi.junis.ni.ac.rs/index.php/FUMechEng/issue/feedFacta Universitatis, Series: Mechanical Engineering2018-07-15T03:04:11+02:00Dr. Dragan Marinkovic, Associate Professorfumeed@junis.ni.ac.rsOpen Journal Systems<div id="yui_3_13_0_1_1384327394083_3606"><em>Facta Universitatis, series: Mechanical Engineering (FU Mech Eng)</em> is an open access peer-reviewed international journal published by the University of Niš (Republic of Serbia). High quality, refereed papers are published three times a year. Papers reporting original theoretical and/or practice oriented research or extended versions of the already published conference papers are all welcome. The scope of the journal covers the<span> whole spectrum of Mechanical Engineering.</span> Papers for publication are selected through peer reviewing to ensure originality, relevance, and readability. In doing that, the objective is not only to keep the high quality of published papers, but also to provide a timely, thorough and balanced review process.</div><div><span>Editor-in-Chief: Dragan Marinković</span></div>http://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/4112PARAMETERS FORECASTING OF LASER WELDING BY THE ARTIFICIAL INTELLIGENCE TECHNIQUES2018-07-15T03:04:11+02:00Vlastimir Nikolićvnikolic@masfak.ni.ac.rsMiloš Milovančevićmilovancevic@masfak.ni.ac.rsDalibor Petkovićdalibortc@gmail.comLaser welding process is used in many industrial sectors. One of the most important aspects of the laser welding quality refers to the geometrical and mechanical properties of welding joints. In order to develop optimal conditions for the laser welding process it is desirable to know in advance which machining parameters to select. Though there are manuals which recommend specific parameters combinations for the desired laser welding quality it is difficult to cover all possible combinations because of the process nonlinearity. Therefore, in this study the main aim is to establish an algorithm for optimal parameters forecasting of the laser welding process. The algorithm is based on an artificial intelligence approach. The main goal is to forecast the geometrical parameters of the welding joints like front width, front heights, back width and back heights of the welding joints. Experimental process was performed in order to acquire training and testing data of the laser welding process. The obtained results could be of practical importance for engineers in industry.2018-07-15T03:04:10+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3574HEAT TRANSFER ENHANCEMENT AND PRESSURE DROP FOR FIN-AND-TUBE COMPACT HEAT EXCHANGERS WITH DELTA WINGLET-TYPE VORTEX GENERATORS2018-07-13T01:04:06+02:00Seyed Alireza Ghazanfarialireza.ghazanfari@gmail.comMalan Abdul Wahidmazlan@fkm.utm.my<p>Heat transfer rate, pressure loss and efficiency are considered as the most important parameters in designing compact heat exchangers. Despite different types of heat exchangers, fin-and-tube compact heat exchangers are still common device in different industries due to the diversity of usage and the low space installation need. The efficiency of the compact heat exchanger can be increased by introducing the fins and increasing the heat transfer rate between the surface and the surroundings. Numerous modifications can be applied to the fin surface to increase heat transfer. Delta-winglet vortex generators (VGs) are known to enhance the heat transfer between the energy carrying fluid and the heat transfer surfaces in plate-fin-and-tube banks, but they have drawbacks as well. They increase the pressure loss and this should be considered. In this paper, the thermal efficiency of compact heat exchanger with VGs is investigated in different variations. The angle of attack, the length and horizontal and vertical position of winglet are the main parameters to consider. Numerical analyses are carried out to examine finned tube heat exchanger with winglets at the fin surface in a relatively low Reynolds number flow for the inline tube arrangements. The results showed that the length of the winglet significantly affects the improvement of heat transfer performance of the fin-and-tube compact heat exchangers with a moderate pressure loss penalty. In addition, the results show that the optimization cannot be performed for one criterion only. More parameters should be considered at the same time to run the process properly and improve the heat exchanger efficiency.</p>2018-07-13T01:04:06+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/4103FAST NUMERICAL IMPLEMENTATION OF THE MDR TRANSFORMATIONS2018-07-09T12:11:31+02:00Justus Benadmail@jbenad.comIn the present paper a numerical implementation technique for the transformations of the Method of Dimensionality Reduction (MDR) is described. The MDR has become, in the past few years, a standard tool in contact mechanics for solving axially-symmetric contacts. The numerical implementation of the integral transformations of the MDR can be performed in several different ways. In this study, the focus is on a simple and robust algorithm on the uniform grid using integration by parts, a central difference scheme to obtain the derivatives, and a trapezoidal rule to perform the summation. The results are compared to the analytical solutions for the contact of a cone and the Hertzian contact. For the tested examples, the proposed method gives more accurate results with the same number of discretization points than other tested numerical techniques. The implementation method is further tested in a wear simulation of a heterogeneous cylinder composed of rings of different material having the same elastic properties but different wear coefficients. These discontinuous transitions in the material properties are handled well with the proposed method.2018-06-30T19:25:24+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2550A THERMAL ANALYSIS OF THE THREADED SPINDLE BEARING ASSEMBLY IN NUMERICALLY CONTROLLED MACHINE TOOLS2018-06-30T19:26:44+02:00Vladislav Krstićvladanis73@yahoo.comDragan Milčićdragan.milcic@gmail.comMiodrag Milčićmilcic.miodrag@gmail.comA threaded gear in machine tools is a mechanical actuator that converts rotary motion into linear one of the machine axis using a recirculating ball-nut. It provides positioning accuracy, uniform motion, silent operation, reduced wear and an increased service life. The bearing assembly of the threaded spindles should provide load transfer (cutting forces and friction forces) while maintaining high guiding accuracy. Due to a high number of the threaded spindle revolutions and the presence of tension in the bearing and a high axial force originating from the cutting and friction forces, the increased heat load due to friction in the bearings is normally expected. For this reason, this paper presents a thermal analysis of the bearing assembly of the threaded spindle which is realized via an axial ball bearing with angular contact of the ZKLN type, produced by the German manufacturer Schaeffler (INA); in other words, a numerical thermal analysis has been performed.2018-06-30T18:21:12+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3683DETERMINATION OF THE WALL VARIABLES WITHIN THE ZONAL MODEL OF RADIATION INSIDE A PULVERIZED COAL-FIRED FURNACE2018-06-27T01:34:57+02:00Nenad Crnomarkovićncrni@vin.bg.ac.rsSrđan Beloševićv1belose@vin.bg.ac.rsStevan Nemodasnemoda@vin.bg.ac.rsIvan Tomanovićivan.tomanovic@vin.bg.ac.rsAleksandar Milićevićamilicevic@vin.bg.ac.rsDetermination of the wall variables (wall emissivities, wall temperatures, and heat fluxes) when the zonal model of radiation is used in numerical simulations of processes inside a pulverized coal-fired furnaces is described. Two methods for determination of the wall variables, i.e., a repeated run of numerical simulation (RRNS) and a temporary correction of the total exchange areas (TCTEA) are compared. Investigation was carried out for three values of the flame total extinction coefficient and four values of the initial wall emissivities. Differences of the wall variables were determined using the arithmetic means (AMs) of the relative differences. The AMs of the relative differences of the wall variables increased with an increase in the flame total extinction coefficient and changed a little with an increase in the initial values of the wall emissivities. For the selected furnace, the smallest differences of the wall variables were obtained for K<sub>t</sub>=0.3 m<sup>-1</sup> and <strong>e</strong><sub>w,in</sub>=0.7. Although both methods can be used for determination of the wall variables, the RRNS method was recommended because the manipulation with files was easier for it. mmended because the manipulation with files was easier for it.2018-06-27T01:34:56+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2983SMART EQUIPMENT DESIGN CHALLENGES FOR REAL TIME FEEDBACK SUPPORT IN SPORT2018-06-12T00:02:10+02:00Anton Umekanton.umek@fe.uni-lj.siAnton Kosanton.kos@fe.uni-lj.siSmart equipment can support feedback in motor learning process. Smart equipment with integrated sensors can be used as a standalone system or complemented with body-attached wearable sensors. Our work focuses on real-time biofeedback system design, particularly on the application of a specific sensor selection. The main goal of our research is to prepare the technical conditions to prove efficiency and benefits of the real-time biofeedback when used in selected motion-learning processes. The most used wireless technologies that are used or are expected to be used in real-time biofeedback systems are listed. The tests performed on two prototypes, smart golf club and smart ski, show an appropriate sensor selection and feasibility of implementation of the real-time biofeedback concept in golf and skiing practice. We are confident that the concept can be expanded for use in other sports and rehabilitation. It has been learned that at this time none of the existing wireless technologies can satisfy all possible demands of different real-time biofeedback applications in sport.2018-06-12T00:00:41+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3919DYNAMICAL BEHAVIOR OF A HEAT PUMP COAXIAL EVAPORATOR CONSIDERING THE PHASE BORDER’S IMPACT ON CONVERGENCE2018-06-12T00:02:10+02:00Arpad Nyersjnyers1@gmail.comZoltan Pekjnyers1@gmail.comJozsef Nyersjnyers1@gmail.comUsing a dynamical mathematical model, we investigated transient behavior of a water-water heat pump’s evaporator. The model consists of time and space dependent partial differential equations of water, pipe wall and refrigerant. Mathematically the thermal expansion valve (TEV) and compressor are described with lumped parameters and represent the boundary conditions. During the numerical solution of this system of equations the problem emerged of divergence of solutions. It was determined that the cause of the divergence solution was in the location of phase change of the refrigerant. The aim of this paper is, firstly, to display and propose a new approach to the elimination of divergence. In addition, it examines dynamic behavior of the heat pumps’ coaxial evaporator.2018-06-10T19:56:36+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/4014NORMALIZED WEIGHTED GEOMETRIC BONFERRONI MEAN OPERATOR OF INTERVAL ROUGH NUMBERS – APPLICATION IN INTERVAL ROUGH DEMATEL-COPRAS2018-06-12T00:02:10+02:00Dragan Pamučardragan.pamucar@va.mod.gov.rsDarko Božanićdbozanic@yahoo.comVesko Lukovaclukovacvesko@yahoo.comNenad Komazecnkomazec@gmail.comThis paper presents a new approach to the treatment of uncertainty and imprecision in multi-criteria decision-making based on interval rough numbers (IRN). The IRN-based approach provides decision-making using only internal knowledge for the data and operational information of a decision-maker. A new normalized weighted geometric Bonferroni mean operator is developed on the basis of the IRN for the aggregation of the IRN (IRNWGBM). Testing of the IRNWGBM operator is performed through the application in a hybrid IR-DEMATEL-COPRAS multi-criteria model which is tested on real case of selection of optimal direction for the creation of a temporary military route. The first part of hybrid model is the IRN DEMATEL model, which provides objective expert evaluation of criteria under the conditions of uncertainty and imprecision. In the second part of the model, the evaluation is carried out using the new interval rough COPRAS technique.2018-06-07T02:01:12+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3813INVESTIGATION OF THE ENERGY RECOVERY POTENTIALS IN VENTILATION SYSTEMS IN DIFFERENT CLIMATES2018-06-12T00:02:10+02:00Miklos Kassaikas.miklos@gmail.comLaszlo Poleczkykass.miklos@gmail.comLaith Al-Hyarikas.miklos@gmail.comLaszlo Kajtarkajtar@epgep.bme.huJozsef Nyersjnyers1@gmail.comThe aim of this research study was to investigate the energy recovery potentials in ventilation systems under different climatic conditions. The well-known heating degree day from the literature was updated using the weather data of cities with different climates from the past 40 years. As the novelty of this research with the developed procedure drawn up in this study, the energetic possibilities of heat recovery under various climate and operating conditions may be examined in more detail and more realistically than with the methods and available information of current engineering practices. To achieve this long-term and high definition the weather data of several cities are processed in order to evaluate the possibilities of heat recovery on a daily and annual basis.2018-06-07T01:17:58+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3910CLOUD-BASED EXPERT SYSTEM FOR SYNTHESIS AND EVOLUTIONARY OPTIMIZATION OF PLANAR LINKAGES2018-06-12T00:02:10+02:00Rosen Mitrevrosenm@tu-sofia.bgBoris Tudjarovbntv@tu-sofia.bgTodor Todorovtst@tu-sofia.bg<p>The present paper introduces a cloud-based expert system for synthesis and evolutionary optimization of planar linkages. The kinematic structure of the linkage is composed by the modular approach based on Assur’s groups. The dyads are represented as functional blocks with input and output variables. The applied approach for obtaining the geometrical relationships between the input and the output variables of the dyads is based on the use of homogeneous transformation matrices. The developed software system allows a dimensional synthesis of planar linkages by using genetic optimization algorithms. One feature is remote creation of the models of genetic algorithms as well as the receiving of the results by means of a user-friendly interface. By exploiting the application, the user can produce and edit the initial information about the synthesized or optimized linkage; thus he can receive the calculation results as a web page and/or as MS Excel file. An additional mutation of the best chromosome genes by scanning of every gene within its searching space improves the optimal solution. The analyzed numerical case studies show the applicability of the developed software system for mechanism analysis, synthesis and optimization. Because the number of genes is not limited, the linkages with a very big number of design variables can be synthesized by exploiting the developed approach.</p>2018-05-29T00:04:02+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3828A NUMERICAL AND EXPERIMENTAL ANALYSIS OF THE DYNAMIC STABILITY OF HYDRAULIC EXCAVATORS2018-06-12T00:02:10+02:00Dragoslav Janoševićdragoslav.janosevic@masfak.ni.ac.rsJovan Pavlovićjovan.mfn@gmail.comVesna Jovanovićvesna.jovanovic@masfak.ni.ac.rsGoran Petrovićgoran.petrovic@masfak.ni.ac.rsThe paper presents the results of a numerical and experimental analysis of the dynamic stability of hydraulic excavators. The analysis has employed the software developed on the basis of a defined general dynamic mathematical model of an excavator grounded in Newton-Euler equations as well as the measured quantities of the excavator operating state in exploitation conditions. The defined model is used to model the members of the excavator kinematic chain using rigid bodies while the actuators (hydraulic cylinders and hydraulic motors) of the excavator drive mechanisms are modeled with elastically dampened elements. The elastically dampened characteristics of the actuators are defined with regard to the size of the actuator as well as to the compressibility and temperature of the hydraulic oil used in the excavator hydrostatic drive system. To illustrate the analysis, the paper provides the results of the analysis of the dynamic stability of a 16000 kg tracked excavator equipped with a manipulator digging bucket of 0.6 m<sup>3 </sup>in capacity.2018-05-16T01:16:34+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3768A CRITICAL ASSESSMENT OF KASSAPOGLOU'S STATISTICAL MODEL FOR COMPOSITES FATIGUE2018-06-12T00:02:10+02:00Michele Ciavarellaengineeringchallenges@gmail.comGiuseppe Carbonegiuseppe.carbone@poliba.itVladimir Vinogradovvladimir.vinogradov@ncl.ac.uk<p>Kassapoglou has recently proposed a model for fatigue of composite materials which seems to suggest that the fatigue SN curve can be fully predicted on the basis of the statistical distribution of static strengths. The original abstract writes expressions for the cycles to failure as a function of R ratio are derived. These expressions do not require any curve fitting and do not involve any experimentally determined parameters. The fatigue predictions do not require any fatigue tests for calibration". These surprisingly ambitious claims and attractive results deserve careful scrutiny. We contend that the result, which originates from the reliability theory where exponential distributions is sometimes used to model distribution of failures when age (or wearout) has no influence on the probability of failure, does not conform to a fatigue testing with the resulting SN curve distribution. Despite Kassapoglou's attempt to use a wearout law which seems to confirm this result even with wearout, we contend that a proper statistical treatment of the fatigue process should not make wear-out constants disappear, and hence the SN curves would depend on them, and not just on scatter of static data. These concerns explain the large discrepancies found by 3 independent studies which have tried to apply Kassapoglou's model to composite fatigue data.</p>2018-05-15T01:27:51+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3791METHOD OF DIMENSIONALITY REDUCTION IN CONTACT MECHANICS AND FRICTION: A USER’S HANDBOOK. III. VISCOELASTIC CONTACTS2018-06-12T00:02:10+02:00Valentin L. Popovv.popov@tu-berlin.deEmanuel Willerte.willert@tu-berlin.deMarkus Heßmarkus.hess@tu-berlin.de<p class="Abstract">Until recently the analysis of contacts in tribological systems usually required the solution of complicated boundary value problems of three-dimensional elasticity and was thus mathematically and numerically costly. With the development of the so-called Method of Dimensionality Reduction (MDR) large groups of contact problems have been, by sets of specific rules, exactly led back to the elementary systems whose study requires only simple algebraic operations and elementary calculus. The mapping rules for axisymmetric contact problems of elastic bodies have been presented and illustrated in the previously published parts of The User's Manual, I and II, in Facta Universitatis series Mechanical Engineering [5, 9]. The present paper is dedicated to axisymmetric contacts of viscoelastic materials. All the mapping rules of the method are given and illustrated by examples.</p>2018-05-14T14:59:09+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3267A STUDY OF THE ENVIRONMENTAL KUZNETS CURVE FOR TRANSPORT GREENHOUSE GAS EMISSIONS IN THE EUROPEAN UNION2018-07-07T02:36:44+02:00Nikola Petrovićpetrovic.nikola@masfak.ni.ac.rsNebojša Bojovićnb.bojovic@sf.bg.ac.rsMarijana Petrovićmarijanap@sf.bg.ac.rsVesna Jovanovićvesna.jovanovic@masfak.ni.ac.rsIn view of the European Union as one of the main polluters in the word and the fact that GDP per capita in the European Union is equivalent to the 282 percent of the world`s average, it is interesting to study the relationship between transport GHG emissions and the economic activity within the European Union. In the paper, the authors check the environment Kuznets curve hypothesis for members of the EU over the period 2000-2014. The analysis results show that an inverse-U relationship exists between transport GHG emissions and GDP per capita. At the same time, the results indicate that the change of economic structure has influenced the transport GHG emissions in the developed countries, that is, in the countries that record a higher level of GDP per capita.2018-04-15T19:23:02+02:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3600SOLUTION OF ADHESIVE CONTACT PROBLEM ON THE BASIS OF THE KNOWN SOLUTION FOR NON-ADHESIVE ONE2018-02-14T14:53:17+01:00Valentin L. Popovv.popov@tu-berlin.de<p class="Abstract">The well-known procedure of reducing an adhesive contact problem to the corresponding non-adhesive one is generalized in this short communication to contacts with an arbitrary contact shape and arbitrary material properties (e.g. non homogeneous or gradient media). The only additional assumption is that the sequence of contact configurations in an adhesive contact should be exactly the same as that of contact configurations in a non-adhesive one. This assumption restricts the applicability of the present method. Nonetheless, the method can be applied to many classes of contact problems exactly and also be used for approximate analyses.</p>2018-02-14T14:53:17+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3593FRACTURE MECHANICS SIMPLE CALCULATIONS TO EXPLAIN SMALL REDUCTION OF THE REAL CONTACT AREA UNDER SHEAR2018-02-14T14:53:17+01:00Michele Ciavarellaengineeringchallenges@gmail.comIn a very recent paper, Sahli and coauthors [12] (<em>R. Sahli et al., 2018, “Evolution of real contact area under shear”</em>, PNAS, 115(3), pp. 471-476) studied the contact area evolution for macroscopic smooth spheres under shear load in presence of adhesion. It was found that contact area <em>A<sub>A</sub></em> reduces quadratically with respect to shear load T, i.e. <em>A</em>=<em>A</em><sub>0</sub>-<em>alpha<sub>A</sub>T<sup>2</sup></em>, where <em>A</em><sub>0</sub> is the contact area with no shearing, and <em>alpha<sub>A</sub> </em>is the "area reduction parameter" found to be approximately proportional to <em>A</em><sub>0</sub><sup>-3/2 </sup><em></em>across 4 orders of magnitude of<em> A</em><sub>0</sub>. In this note we focus on the smooth sphere/plane contact because we believe that the case of a rough contact requires separate investigations, and we use a known model of fracture mechanics, which contains a fitting parameter b which governs the interplay between fractures modes, in order to find very good agreement between the data and the analytical predictions, developing relatively simple equations. The interaction with modes is limited.2018-02-14T14:53:17+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3555THE “SPORT” OF ROUGH CONTACTS AND THE FRACTAL PARADOX IN WEAR LAWS2018-02-14T14:53:16+01:00Michele Ciavarellaengineeringchallenges@gmail.comAntonio Papangeloantonio.papangelo@poliba.itIn a recent paper in <em>Science</em>, namely, “The Contact Sport of Rough Surfaces”, Carpick summarizes recent efforts in a “contact challenge” to predict in detail an elastic contact between the mathematically defined fractal rough surfaces under (very little) adhesion. He also suggests the next steps that are needed to “fulfill da Vinci’s dream of understanding what causes friction”. However, this is disappointing as friction has been studied since the times of Leonardo and in 500 years, no predictive model has emerged, nor any significant improvement from rough contact models. Similarly, a very large effort we have spent on the “sport” of studying rough surfaces has not made us any closer to being able to predict the coefficient of proportionality between wear loss and friction dissipation which was already observed by Reye in 1860. Recent nice simulations by Aghababaei, Warner and Molinari have confirmed the criterion for the formation of debris of a single particle, proposed in 1958 by Rabinowicz, as well as Reye’s assumption for the proportionality with frictional loss, which is very close to Archard anyway. More recent investigations under variable loads suggest that Reye’s assumption is probably much more general than Archard’s law. The attempts to obtain exact coefficients with rough surfaces models are very far from predictive, essentially because for fractals most authors fail to recognize that resolution-dependence of the contact area makes the models very ill-defined. We also suggest that in the models of wear, rough contacts should be considered “plastic” and “adhesive” and introduce a new length scale in the problem.2018-02-14T14:53:16+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3578A NUMERICAL STUDY OF THE MICROSCALE PLASTIC STRAIN LOCALIZATION IN FRICTION STIR WELD ZONES2018-02-14T14:53:16+01:00Ruslan Balokhonovrusy@ispms.tsc.ruVarvara Romanovavarvara@ispms.tsc.ruEkaterina Batukhtinabatuhtina10902@mail.ruMaxim Sergeevsergeevmaximv@gmail.comEvgeniya Emelianovaemelyanova_es13@mail.ruA crystal plasticity approach was used to study the effects of grain shape and texture on the deformation behavior of friction stir weld (FSW) microregions. The explicit stress-strain analysis was performed for two representative grain structures with equiaxed and extended grains. Grain orientations were assigned to simulate no texture or a weak or strong cubic texture. Calculations have shown that the texture gave rise to earlier plastic strain localization on a larger scale. The highest stresses were found to develop in a non-textured specimen with equiaxed grains where the grain boundaries served as a barrier to dislocation motion. In both equiaxed and extended grain structures with a strong cubic texture no pronounced strain localization was seen on the grain scale but mesoscale shear bands appeared early in the deformation process. The calculations have shown that the microstructure-based simulation is a reasonable tool to study the deformation behavior of FSW materials, which is difficult to be predicted within macroscopic models alone.2018-02-14T14:53:16+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3502SIMULATION OF FRACTURE USING A MESH-DEPENDENT FRACTURE CRITERION IN THE DISCRETE ELEMENT METHOD2018-02-14T14:53:15+01:00Andrey Dimakidav18@yandex.ruEvgeny Shilkoshilko@ispms.ruSergey Psakhiesp@ms.tsc.ruValentin Popovv.popov@tu-berlin.deRecently, Pohrt and Popov have shown that for simulation of adhesive contacts a mesh dependent detachment criterion must be used to obtain the mesh-independent macroscopic behavior of the system. The same principle should be also applicable for the simulation of fracture processes in any method using finite discretization. In particular, in the Discrete Element Methods (DEM) the detachment criterion of particles should depend on the particle size. In the present paper, we analyze how the mesh dependent detachment criterion has to be introduced to guarantee the macroscopic invariance of mechanical behavior of a material. We find that it is possible to formulate the criterion which describes fracture both in tensile and shear experiments correctly.2018-02-14T14:53:15+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3540SIMULATION OF WEAR IN A SPHERICAL JOINT WITH A POLYMERIC COMPONENT OF THE TOTAL HIP REPLACEMENT CONSIDERING ACTIVITIES OF DAILY LIVING2018-02-14T17:39:29+01:00Vladimir Pakhaliukvpakhaliuk@gmail.comAleksandr Poliakovalex_polyakov@inbox.ruThe present study assesses the impact of the main typical activities of patients' daily living (ADL) after total hip arthroplasty (THA) on the wear parameters of sliding couple's materials by simulating linear and volumetric wear according to the Archard's law in a spherical joint with a polymeric element of the total hip replacement (THR). The mathematical wear model, built on the basis of algorithms and custom codes of the finite element analysis in ANSYS and MATLAB software systems, has been studied numerically. The activities used in the model are: level walking, stair ascending-stair descending, chair sitting-chair rising, and deep squatting. They were described by typical waveforms of the angular displacements of the THR's femoral component and the waveforms of the applied force. The results of the simulation show that for the same duration the overall wear value with ADL is significantly higher than in the case of level walking according to the requirements of ISO 14242-1. Therefore, the evaluation of the wear value for ADL is more informative for predicting the functional life time of the THR. Analysis of the simulation results shows that the amount of wear calculated for all activities separately is practically the same as the overall wear value obtained at summary action of ADL. This effect of the independence of contributions to the total amount of wear of each activity makes it possible to significantly simplify the solution of the problem of wear estimation for typical activities, including stochastic ones.2018-02-14T14:53:15+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3547ADHESIVE WEAR: GENERALIZED RABINOWICZ’ CRITERIA2018-02-14T14:53:14+01:00Valentin L. Popovv.popov@tu-berlin.deIn a recent paper in Nature Communications, Aghababaei, Warner and Molinari [5] used quasi-molecular simulations to confirm the criterion for formation of debris, proposed in 1958 by Rabinowicz [4]. The work of Aghababaei, Warner and Molinari improves our understanding of adhesive wear but at the same time puts many new questions. The present paper is devoted to the discussion of possible generalizations of the Rabinowicz-Molinari criterion and its application to a variety of systems differing by the interactions in the interface and by the material properties (elastic and elastoplastic) and structure (homogeneous and layered systems). A generalization of the Rabinowicz-Molinari criterion for systems with arbitrary complex contact configuration is suggested which does not use the notion of "asperity".2018-02-14T14:53:14+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3588ADHESION BETWEEN A POWER-LAW INDENTER AND A THIN LAYER COATED ON A RIGID SUBSTRATE2018-02-23T20:41:25+01:00Antonio Papangeloantonio.papangelo@poliba.itIn the present paper we investigate indentation of a power-law axisymmetric rigid probe in adhesive contact with a "thin layer" laying on a rigid foundation for both frictionless unbounded and bounded compressible cases. The investigation relies on the "thin layer" assumption proposed by Johnson, i.e. the layer thickness being much smaller than the radius of the contact area, and it makes use of the previous solutions proposed by Jaffar and Barber for the adhesiveless case. We give analytical predictions of the loading curves and provide indentation, load and contact radius at the pull-off. It is shown that the adhesive behavior is strongly affected by the indenter shape; nevertheless below a critical thickness of the layer (typically below 1 µm) the theoretical strength of the material is reached. This is in contrast with the Hertzian case, which has been shown to be insensitive to the layer thickness. Two cases are investigated, namely, the case of a free layer and the case of a compressible confined layer, the latter being more "efficient", as, due to Poisson effects, the same detachment force is reached with a smaller contact area. It is suggested that high sensitive micro-/nanoindentation tests may be performed using probes with different power law profiles for characterization of adhesive and elastic properties of micro-/nanolayers.2018-02-14T14:53:14+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3416DUGDALE-MAUGIS ADHESIVE NORMAL CONTACT OF AXISYMMETRIC POWER-LAW GRADED ELASTIC BODIES2018-02-14T14:53:11+01:00Emanuel Willerte.willert@tu-berlin.deA closed-form general analytic solution is presented for the adhesive normal contact of convex axisymmetric power-law graded elastic bodies using a Dugdale-Maugis model for the adhesive stress. The case of spherical contacting bodies is studied in detail. The known JKR- and DMT-limits can be derived from the general solution, whereas the transition between both can be captured introducing a generalized Tabor parameter depending on the material grading. 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mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} </style> <![endif]-->2018-02-14T14:53:11+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3619FOREWORD2018-02-14T18:36:32+01:00Sergey G. Psakhiesp@ispms.tsc.ru<p><span>Foreword to the thematic issue entitled: </span></p><p><em>Adhesion and Friction: Simulation, Experiment, Applications</em></p><h1> </h1>2018-02-14T14:53:10+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3539ADHESIVE FORCE OF FLAT INDENTERS WITH BRUSH-STRUCTURE2018-03-16T11:22:25+01:00Qiang Liqiang.li@tu-berlin.deValentin L. Popovv.popov@tu-berlin.deWe have numerically studied adhesive contact between a flat indenter with brush structure and an elastic half space using the boundary element method. Various surface structures with different size, number and shape of the “pillars”, as well as their distributions (regular or random) have been investigated. The results validate the theoretical prediction that the adhesive force in contact of an indenter with discontinuous areas is roughly proportional to the square root of the real contact density (“filling factor”).2018-02-14T14:53:10+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3473NUMERICAL INVESTIGATION OF THE INFLUENCE OF THE DOUBLY CURVED BLADE PROFILES ON THE REVERSIBLE AXIAL FAN CHARACTERISTICS2018-06-12T00:02:09+02:00Živan Spasićzivans@masfak.ni.ac.rsMiloš Jovanovićjmilos@masfak.ni.ac.rsJasmina Bogdanović-Jovanovićbminja@masfak.ni.ac.rsSaša Milanovićbminja@masfak.ni.ac.rs<p class="Abstract"><strong>Abstract</strong>. In reversible axial fans a change in the direction of the impeller rotation is accompanied with a change in the direction of the working fluid flow. To satisfy the flow reversibility, the impeller blades are usually designed with straight symmetrical profiles. The flow reversibility may also be achieved by using asymmetrical blade profiles in which, to satisfy the equality of the leading and trailing angle of the profiles, the mean line of the profile has to have a double curvature in the shape of the stretched letter 'S'. The paper numerically investigates the influence of the doubly curved blade profiles on the reversible axial fan characteristics. Numerical simulations are carried out on an axial fan only with the impeller, with the blades that have double-curved mean line profiles for different values of the angles at the profile ends. For numerical simulation the ANSYS CFX software package is used. Results of the numerical simulation are shown in diagrams Δp(Q), h(Q) and P(Q) at different angles of the profile ends. On the basis of the simulation and analysis of the characteristics, appropriate conclusions are proposed, along with the most advantageous profile of the blades.</p>2018-01-18T00:07:30+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2466IMPACT OF SKINFOLD THICKNESS ON WAVELET-BASED MECHANOMYOGRAPHIC SIGNAL2018-06-12T00:02:09+02:00Eddy Kruegerkruegereddy@gmail.comEduardo M. Scheereneduardo.scheeren@pucpr.brCarla Daniele Pacheco Rinaldinrinaldin99@gmail.comAndré E. Lazzarettiandrelzt@yahoo.com.brEduardo Borba Nevesneveseb@gmail.comGuilherme Nunes Nogueira-Netoguinnn@gmail.comPercy Nohamapercy.nohama@gmail.comSurface mechanography (MMG) is a non-invasive technique that captures signs of low-frequency vibrations of skeletal muscles through the skin. However, subcutaneous structures may interfere with the acquisition of MMG signals. The objective of this study was to verify the influence of skinfold thickness (ST) on the MMG wavelet-based signal in the rectus femoris muscle during maximal voluntary contraction in two groups of individuals: group I (n = 10, ST <10 mm ) and group II (n = 10, ST equal to or> 20 mm). Negative correlation was observed between the 19 Hz, 28 Hz and 39 Hz frequency bands with ST. There was a statistical difference in almost all frequency bands, especially in the X and Y axes. All MMG axes in group II presented higher magnitudes in frequency bands 2 and 6 Hz (like low-pass filter). Thus, these results can be applied to calibrate MMG responses as biofeedback systems.2018-01-16T01:57:08+01:00Copyright (c) 2018 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2398THERMAL BUCKLING ANALYSIS OF FUNCTIONALLY GRADED CIRCULAR PLATE RESTING ON THE PASTERNAK ELASTIC FOUNDATION VIA THE DIFFERENTIAL TRANSFORM METHOD2017-12-09T11:34:20+01:00Fatemeh Farhatniazh_farhat@yahoo.comMahsa Ghanbari-Mobarakehmahsa.ghanbari99@yahoo.comSaeid Rasouli-Jazisaeid.rasouli@iaukhsh.ac.irSoheil Oveissisoheil.oveissi@gmail.com<p>In this paper, we propose a thermal buckling analysis of a functionally graded (FG) circular plate exhibiting polar orthotropic characteristics and resting on the Pasternak elastic foundation. The plate is assumed to be exposed to two kinds of thermal loads, namely, uniform temperature rise and linear temperature rise through thickness. The FG properties are assumed to vary continuously in the direction of thickness according to the simple power law model in terms of the volume fraction of two constituents. The governing equilibrium equations in buckling are based on the Von-Karman nonlinearity. To obtain the critical buckling temperature, we exploit a semi-numerical technique called differential transform method (DTM). This method provides fast accurate results and has a short computational calculation compared with the Taylor expansion method. Furthermore, some numerical examples are provided to consider the influence of various parameters such as volume fraction index, thickness-to-radius ratio, elastic foundation stiffness, modulus ratio of orthotropic materials and influence of boundary conditions. In order to predict the critical buckling temperature, it is observed that the critical temperature can be easily adjusted by appropriate variation of elastic foundation parameters and gradient index of FG material. Finally, the numerical results are compared with those available in the literature to confirm the accuracy and reliability of the DTM to determine the critical buckling temperature.</p>2017-12-09T11:34:20+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2311CRANIOFACIAL STRESS PATTERNS AND DISPLACEMENTS AFTER ACTIVATION OF HYRAX DEVICE: FINITE ELEMENT MODELLING2017-12-09T11:34:19+01:00Sergei Bosiakovbosiakovsm@gmail.comAnastasiya Vinokurovajaneraven@mail.ruAndrei Dostadummmyyy@yahoo.com<p>Rapid maxillary expansion is employed for the treatment of cross-bite and deficiency of transversal dimension of the maxilla in patients with and without cleft of palate and lip. For this procedure, generally, different orthodontic appliances and devices generating significant transversal forces are used. The aim of this study is the finite-element analysis of stresses and displacements of the skull without palate cleft and the skull with unilateral and bilateral cleft after activation of the Hyrax orthodontic device. Two different constructions of the orthodontic device Hyrax with different positions of the screw relative palate are considered. In the first case, the screw is in the occlusal horizontal plane, and in the other, the screw is located near the palate. Activation of the orthodontic device corresponds to the rotation of the screw on one-quarter turn. It is established that the screw position significantly affects the distributions of stresses in skull and displacements of the cranium without palate cleft and with unilateral or bilateral palate cleft. Stresses in the bone structures of the craniums without cleft and with cleft are transferred from the maxilla to the pterygoid plate and pharyngeal tubercle if the screw displaces from the occlusal plane to the palate. Depending on the construction of the orthodontic appliance, the maxilla halves in the transversal plane are unfolded or the whole skull is entirely rotated in the sagittal plane. The stresses patterns and displacements of the skull with bilateral palate cleft are almost unchanged after activation of the orthodontic devices with different positions of the screw, only magnitudes of stresses and displacements are changed. The obtained results can be used for design of orthodontic appliances with the Hyrax screw, as well as for planning of osteotomies during the surgical assistance of the rapid maxillary expansion.</p>2017-12-09T11:34:19+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2830COMPUTERIZED RADIAL ARTERY PULSE SIGNAL CLASSIFICATION FOR LUNG CANCER DETECTION2017-12-09T11:34:19+01:00Zhichao Zhangrainkissthesun@126.comAnton Umekanton.umek@fe.uni-lj.siAnton Kosanton.kos@fe.uni-lj.siPulse diagnosis, the main diagnosis method in traditional Chinese medicine, is a non-invasive and convenient way to check the health status. Doctors usually use three fingers to feel three positions; Cun, Guan, and Chi of the wrist pulse, to diagnose the body’s healthy status. However, it takes many years to master the pulse diagnosis. This paper aims at finding the best position for acquiring wrist-pulse-signal for lung cancer diagnosis. In our paper, the wrist-pulse-signals of Cun, Guan, and Chi are acquired by three optic fiber pressure sensors of the same type. Twelve features are extracted from the signals of these three positions, respectively. Eight classifiers are applied to detect the effectiveness of the signal acquired from each position by classifying the pulse signals of healthy individuals and lung cancer patients. The results achieved by the proposed features show that the signal acquired at Cun is more effective for lung cancer diagnosis than the signals acquired at Guan and Chi.2017-12-09T11:34:19+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3368INFLUENCE OF THE CHANGING LOCAL CLIMATE ON WIND POTENTIALS OF MOUNT KOPAONIK2017-12-19T10:57:06+01:00Predrag Živkovićpzivkovic@masfak.ni.ac.rsMladen Tomićtomicmladen@yahoo.comDragana Dimitrijevićdragana.dimitrijevic@masfak.ni.ac.rsIvana Kecmanivana933@hotmail.comMirko Dobrnjacdobrnjac.mirko@gmail.comObtaining all acceptable locations is one of the main tasks for siting wind turbines. The economic factors are usually very limiting. Very thorough analyses are needed in order to ensure the project finalization. Nevertheless, even after all the steps are made, some problems may occur. One of them is the real status of the winds in the so-called climatology period. This paper focuses on the influences of the changing winds after the preliminary estimations are done. The estimations are obtained using the WAsP simulation software. The results are compared in terms of quality and quantity of the wind data and capacity factor. Finally, an economic analysis is done.2017-12-09T11:34:18+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3349EXPERIMENTAL INVESTIGATION OF THE CONVECTIVE HEAT TRANSFER IN A SPIRALLY COILED CORRUGATED TUBE WITH RADIANT HEATING2017-12-09T11:34:17+01:00Milan Đorđevićmilan.djordjevic@pr.ac.rsVelimir Stefanovićveljas@masfak.ni.ac.rsMića Vukićmicav@masfak.ni.ac.rsMarko Mančićmarkomancic@yahoo.comThe Archimedean spiral coil made of a transversely corrugated tube was exposed to radiant heating in order to represent a heat absorber of the parabolic dish solar concentrator. The main advantage of the considered innovative design solution is a coupling effect of the two passive methods for heat transfer enhancement - coiling of the flow channel and changes in surface roughness. The curvature ratio of the spiral coil varies from 0.029 to 0.234, while water and a mixture of propylene glycol and water are used as heat transfer fluids. The unique focus of this study is on specific boundary conditions since the heat flux upon the tube external surfaces varies not only in the circumferential direction, but in the axial direction as well. Instrumentation of the laboratory model of the heat absorber mounted in the radiation field includes measurement of inlet fluid flow rate, pressure drop, inlet and outlet fluid temperature and 35 type K thermocouples welded to the coil surface. A thermal analysis of the experimentally obtained data implies taking into consideration the externally applied radiation field, convective and radiative heat losses, conduction through the tube wall and convection to the internal fluid. The experimental results have shown significant enhancement of the heat transfer rate compared to spirally coiled smooth tubes, up to 240% in the turbulent flow regime.2017-12-09T11:34:17+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3351DETERMINATION OF AVERAGED AXISYMMETRIC FLOW SURFACES AND MERIDIAN STREAMLINES IN THE CENTRIFUGAL PUMP USING NUMERICAL SIMULATION RESULTS2017-12-09T11:34:16+01:00Jasmina Bogdanović-Jovanovićbminja@masfak.ni.ac.rsDragica Milenkovićdragica.milenkovic@masfak.ni.ac.rsŽivojin Stamenkovićzikas@masfak.ni.ac.rsŽivan Spasićzivans@masfak.ni.ac.rsOne of the most important aims<em> </em>in the turbo pump design is to achieve an optimal design of the pump impeller. The basic assumption in the design procedure of the impeller is that of the axisymmetric fluid flow. It can be confirmed or disputed by using the method presented in the paper, which uses the results of numerical simulation of fluid flow in the pump impeller. The method is actually a procedure for determining averaged axisymmetric flow surfaces and meridian streamlines. Furthermore, according to the obtained streamlines, a correction of the impeller blade geometry can be made (if the streamlines deviate significantly from the assumed axisymmetric ones). It is also possible to calculate the specific works of the elementary stages and compare them with the previous assumptions. The pump impeller torque can be calculated as well.2017-12-09T11:34:16+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2032FORCED CONVECTION DRYING OF INDIAN GROUNDNUT: AN EXPERIMENTAL STUDY2017-12-12T23:19:38+01:00Ravinder Kumar Sahdevravindersahdev.uiet@mdurohtak.ac.inMahesh Kumarmkshandilya1@gmail.comAshwani Kumar Dhingraashwani_dhingra1979@rediffmail.com<p>In this paper, convective and evaporative heat transfer coefficients of the Indian groundnut were computed under indoor forced convection drying (IFCD) mode. The groundnuts were dried as a single thin layer with the help of a laboratory dryer till the optimum safe moisture storage level of 8 – 10%. The experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by a simple linear regression analysis and consequently, the convective heat transfer coefficient (CHTC) was determined. The values of CHTC were used to calculate the evaporative heat transfer coefficient (EHTC). The average values of CHTC and EHTC were found to be 2.48 W/m<sup>2 o</sup>C and 35.08 W/m<sup>2 o</sup>C, respectively. The experimental error in terms of percent uncertainty was also estimated. The experimental error in terms of percent uncertainty was found to be 42.55%. The error bars for convective and evaporative heat transfer coefficients are also shown for the groundnut drying under IFCD condition.</p>2017-12-09T11:34:15+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3350NUMERICAL COMPUTATION AND PREDICTION OF ELECTRICITY CONSUMPTION IN TOBACCO INDUSTRY2017-12-09T11:34:13+01:00Mirjana Lakovićlmirjana@masfak.ni.ac.rsIvan Pavlovićpivan@masfak.ni.ac.rsMiloš Banjacmbanjac@mas.bg.ac.rsMilica Jovićmilica.jovic@masfak.ni.ac.rsMarko Mančićmarkomancic@masfak.ni.ac.rs<p class="Abstract">Electricity is a key energy source in each country and an important condition for economic development. It is necessary to use modern methods and tools to predict energy consumption for different types of systems and weather conditions. In every industrial plant, electricity consumption presents one of the greatest operating costs. Monitoring and forecasting of this parameter provide the opportunity to rationalize the use of electricity and thus significantly reduce the costs. The paper proposes the prediction of energy consumption by a new time-series model. This involves time series models using a set of previously collected data to predict the future load. The most commonly used linear time series models are the AR (Autoregressive Model), MA (Moving Average) and ARMA (Autoregressive Moving Average Model). The AR model is used in this paper. Using the AR (Autoregressive Model) model, the Monte Carlo simulation method is utilized for predicting and analyzing the energy consumption change in the considered tobacco industrial plant. One of the main parts of the AR model is a seasonal pattern that takes into account the climatic conditions for a given geographical area. This part of the model was delineated by the Fourier transform and was used with the aim of avoiding the model complexity. As an example, the numerical results were performed for tobacco production in one industrial plant. A probabilistic range of input values is used to determine the future probabilistic level of energy consumption.</p>2017-12-09T11:34:13+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1905RADIAL FORCE IMPACT ON THE FRICTION COEFFICIENT AND TEMPERATURE OF A SELF-LUBRICATING PLAIN BEARING2017-12-12T23:16:28+01:00Nada Bojićnalemfkg@gmail.comDragan Milčićdragan.milcic@gmail.comMilan Banićmilan.banic@outlook.comMiroslav Mijajlovićmijajlom@masfak.ni.ac.rsRužica Nikolićruzicarnikolic@yahoo.comSelf-lubricating bearings are available in spherical, plain, flanged journal, and rod end bearing configurations. They were originally developed to eliminate the need for re-lubrication, to provide lower torque and to solve application problems where the conventional metal-to-metal bearings would not perform satisfactorily, for instance, in the presence of high frequency vibrations. Among the dominant tribological parameters of the self-lubricating bearing, two could be singled out: the coefficient of friction and temperature. To determine these parameters, an experimental method was applied in this paper. By using this method, the coefficient of friction and temperature were identified and their correlation was established. The aim of this research was to determine the effect of radial force on tribological parameters in order to predict the behavior of sliding bearings with graphite in real operating conditions.2017-12-09T11:34:11+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2839A NOVEL HYBRID METHOD FOR NON-TRADITIONAL MACHINING PROCESS SELECTION USING FACTOR RELATIONSHIP AND MULTI-ATTRIBUTIVE BORDER APPROXIMATION METHOD2017-12-11T18:30:18+01:00Prasenjit Chatterjeeprasenjit2007@gmail.comSupraksh Mondalspmondal@gmail.comSoumava Boralboral.ju@gmail.comArnab Banerjeearnabbanerjee31@yahoo.inShankar Chakrabortys_chakraborty00@yahoo.co.in<p>Selection of the most appropriate non-traditional machining process (NTMP) for a definite machining requirement can be observed as a multi-criteria decision-making (MCDM) problem with conflicting criteria. This paper proposes a novel hybrid method encompassing factor relationship (FARE) and multi-attributive border approximation area comparison (MABAC) methods for selection and evaluation of NTMPs. The application of FARE method is pioneered in NTMP assessment domain to estimate criteria weights. It significantly condenses the problem of pairwise comparisons for estimating criteria weights in MCDM environment. In order to analyze and rank different NTMPs in accordance with their performance and technical properties, MABAC method is applied. Computational procedure of FARE-MABAC hybrid model is demonstrated while solving an NTMP selection problem for drilling cylindrical through holes on non-conductive ceramic materials. The results achieved by FARE-MABAC method exactly corroborate with those obtained by the past researchers which validate the usefulness of this method while solving complex NTMP selection problems.</p>2017-12-09T11:34:11+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2590DETERMINATION OF RESIDUAL STRESS IN THE RAIL WHEEL DURING QUENCHING PROCESS BY FEM SIMULATION2017-12-12T23:14:11+01:00Miloš Miloševićmmilos@masfak.ni.ac.rsAleksandar Miltenovićaleksandar.miltenovic@masfak.ni.ac.rsMilan Banićmilan.banic@outlook.comMiša Tomićmisa.tomic@masfak.ni.ac.rsResidual 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.2017-12-09T11:34:10+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2835CASTING IMPROVEMENT BASED ON METAHEURISTIC OPTIMIZATION AND NUMERICAL SIMULATION2017-12-09T11:34:09+01:00Radomir Radišaradomir.radisa@li.rsNedeljko Dučićnedeljko.ducic@ftn.kg.ac.rsSrećko Manasijevićsrecko.manasijevic@gmail.comNemanja Markovićnemmke@yahoo.comŽarko Ćojbašićzcojba@ni.ac.rsThis paper presents the use of metaheuristic optimization techniques to support the improvement of casting process. Genetic algorithm (GA), Ant Colony Optimization (ACO), Simulated annealing (SA) and Particle Swarm Optimization (PSO) have been considered as optimization tools to define the geometry of the casting part’s feeder. The proposed methodology has been demonstrated in the design of the feeder for casting Pelton turbine bucket. The results of the optimization are dimensional characteristics of the feeder, and the best result from all the implemented optimization processes has been adopted. Numerical simulation has been used to verify the validity of the presented design methodology and the feeding system optimization in the casting system of the Pelton turbine bucket.2017-12-09T11:34:09+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3295A NEW WINCH CONSTRUCTION FOR SMOOTH CABLE WINDING/UNWINDING2017-12-09T11:34:08+01:00Mirjana Filipovićmirjana.filipovic@pupin.rsLjubinko Kevacljubinko.kevac@gmail.comNew constructive solutions of the winches for single-row radial multi-layered cable smooth winding/unwinding are described. Two new structural solutions of winches are defined. The nonlinear phenomenon of a cable smooth winding/unwinding process on the winch by using one of the two proposed constructive solutions is defined and analyzed. To facilitate understanding of this concept, the cable winding/unwinding process on only one winch is analyzed. The obtained variables which characterize the kinematics of the cable smooth winding/unwinding process are nonlinear and smooth. This result is important because the systems for the smooth cable winding/unwinding process on the winch could be parts of any cable driven mechanism. These systems can be used in various fields of human activity. For the verification of the presented theoretical contributions, a novel software package named SMOWIND – OW has been developed using MATLAB.2017-12-09T11:34:08+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3361METHOD OF CONVERSION OF HIGH- AND MIDDLE-SPEED DIESEL ENGINES INTO GAS DIESEL ENGINES2017-12-09T11:34:08+01:00Mikhail G. Shatrovmikl-shatrov@yandex.ruVladimir V. Sinyavskisinvlad@mail.ruAndrey Yu. Dunina.u.dunin@yandex.ruIvan G. Shishlovastra510@yandex.ruAndrey V. Vakulenkoengener_avto@yandex.ruThe paper aims at the development of fuel supply and electronic control systems for boosted high- and middle-speed transport engines. A detailed analysis of different ways of converting diesel engine to operate on natural gas was carried out. The gas diesel process with minimized ignition portion of diesel fuel injected by the Common Rail (CR) system was selected. Electronic engine control and modular gas feed systems which can be used both on high- and middle-speed gas diesel engines were developed. Also diesel CR fuel supply systems were developed in cooperation with the industrial partner, namely, those that can be mounted on middle-speed diesel and gas diesel engines. Electronic control and gas feed systems were perfected using modeling and engine tests. The high-speed diesel engine was converted into a gas diesel one. After perfection of the gas feed and electronic control systems, bench tests of the high-speed gas diesel engine were carried out showing a high share of diesel fuel substitution with gas, high fuel efficiency and significant decrease of NO<sub>х</sub> and СО<sub>2</sub> emissions.2017-12-09T11:34:08+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3243BICYCLE HELMET DESIGN AND THE VIRTUAL VALIDATION OF THE IMPACT, AERODYNAMICS AND PRODUCTION PROCESS2017-12-09T11:34:07+01:00Bojan Boshevskibosevskibojan6694@live.comIle Mircheskiile.mircheski@mf.edu.mkThis paper presents the development process of a bicycle helmet through individual research, creation, presentation and analysis of the results of the most important product development stages. The quality of the development and manufacturing process of the protective equipment for extreme sports is an imperative for a successful product and its flawless function. The design of the bicycle helmet is made following the rules of the design in order to create a well-founded and functional product. After creating design sketches, a virtual prototype was developed in "SolidWorks" using the required ergonomic dimensions. 3D printed model of the human head with adapted ergonomic dimensions and the designed bicycle helmet was developed in order to verify the applied ergonomic measures. The virtual model will be used as an input in the finite element analysis of the helmet impact test based on the EN1078 standard and the aerodynamic simulations executed in "SolidWorks Simulation and Flow Simulation", for verification of the impact and aerodynamic properties. Virtual testing of aerodynamic features and the ability of the bicycle helmet to allow ventilation of the user's head indicate that the helmet performs its function in the desired way. Also, the virtual prototype will be used for the production process simulation in "SolidWorks Plastics" in order to analyze the production of the bicycle helmet. The polycarbonate helmet outer shell is subject to a number of simulations for the sake of analyzing the production process in order to obtain the desired characteristics of the polycarbonate outer shell and to avoid the disadvantages that occur in the manufacturing process. The main goal of this paper is to develop a safety bicycle helmet with improved ergonomic, validation of impact, aerodynamic characteristics and production process in order to produce a high quality product for mass use.2017-12-09T11:34:07+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2973A CAD-BASED CONCEPTUAL METHOD FOR SKULL PROSTHESIS MODELLING2018-06-12T00:02:09+02:00Marcelo Rudekmarcelo.rudek@pucpr.brYohan B. Gumielyohan_bg@hotmail.comOsiris Canciglierir Jrosiris.canciglieri@pucpr.brNaomi Asofunaomi_asofu@hotmail.comGerson L. Bichinhogerson.bichinho@gmail.comThe geometric modeling of a personalized part of the tissue built according to individual morphology is an essential requirement in anatomic prosthesis. A 3D model to fill the missing areas in the skull bone requires a set of information sometimes unavailable. The unknown information can be estimated through a set of rules referenced to a similar yet known set of parameters of the similar CT image. The proposed method is based on the Cubic Bezier Curves descriptors generated by the de Casteljou algorithm in order to generate a control polygon. This control polygon can be compared to a similar CT slice in an image database. The level of similarity is evaluated by a meta-heuristic fitness function. The research shows that it is possible to reduce the amount of points in the analysis from the original edge to an equivalent Bezier curve defined by a minimum set of descriptors. A study case shows the feasibility of method through the interoperability between the prosthesis descriptors and the CAD environment.2017-11-25T23:29:08+01:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2794ALTERNATIVE METHOD FOR ON SITE EVALUATION OF THERMAL TRANSMITTANCE2017-11-15T06:53:32+01:00Aleksandar Jankovićaleksandar.jankovic@aggf.unibl.orgBiljana Antunovićbiljana.antunovic@aggf.unibl.orgLjubiša Preradovićljubisa.preradovic@aggf.unibl.orgThermal transmittance or U-value is an indicator of the building envelope thermal properties and a key parameter for evaluation of heat losses through the building elements due to heat transmission. It can be determined by calculation based on thermal characteristics of the building element layers. However, this value does not take into account the effects of irregularities and degradation of certain elements of the envelope caused by aging, which may lead to errors in calculation of the heat losses. An effective and simple method for determination of thermal transmittance is in situ measurement, which is governed by the ISO 9869-1:2014 that defines heat flow meter method. This relatively expensive method leaves marks and damages surface of the building element. Furthermore, the final result is not always reliable, in particular when the building element is light or when the weather conditions are not suitable. In order to avoid the above mentioned problems and to estimate the real thermal transmittance value an alternative experimental method, here referred as the natural convection and radiation method, is proposed in this paper. For determination of thermal transmittance, this method requires only temperatures of inside and outside air, as well as the inner wall surface temperature. A detailed statistical analysis, performed by the software package SPSS ver. 20, shows several more advantages of this method comparing to the standard heat flow meter one, besides economic and non-destructive benefits.2017-08-02T15:54:15+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3039MICROSTRUCTURE AND MICROMECHANICS OF SHALE ROCKS: CASE STUDY OF MARCELLUS SHALE2017-11-15T06:52:47+01:00Hui Duhdu4@lsu.eduKristen Carpenterkcarp17@lsu.eduDavid HuiDHui@uno.eduMileva Radonjicmileva@lsu.edu<p class="Abstract">Shale rocks play an essential role in petroleum exploration and production because they can occur either as source rocks or caprocks depending on their mineralogical composition and microstructures. More than 60% of effective seals for geologic hydrocarbon bearing formations as natural hydraulic barriers constitute of shale caprocks. The effectiveness of caprock depends on its ability to immobilize fluids, which include a low permeability and resilience to the in-situ formation of fractures as a result of pressurized injection. The alteration in sealing properties of shale rocks is directly related to the differences in their mineralogical composition and microstructure.</p><p class="Abstract">Failure of the shale starts with deterioration at micro/nanoscale, the structural features and properties at the micro/nanoscale can significantly impact the durability performance of these materials at the macroscale, therefore, study at micro/nanoscale becomes necessary to get better understanding of the hydraulic barriers materials to prevent failure and enhance long-term geologic storage of fluids.</p><p class="Abstract">Indentation tests were conducted at both micro and nanometer level on Marcellus shale samples to get the mechanical properties of bulk and individual phase of the multiphase materials. The mechanical properties map were created based on the nano indentation results and the properties of each individual phase can be correlated with bulk response in the multiphase composite; the effect of each component on the microstructure and bulk mechanical properties can be better understood.</p>2017-08-02T15:54:14+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2856DETERMINATION OF IMPORTANT PARAMETERS FOR PATENT APPLICATIONS2017-11-15T06:50:29+01:00Dušan Markovićdusanmarkovictc@gmail.comDalibor Petkovićdalibortc@gmail.comVlastimir Nikolićvnikolic@masfak.ni.ac.rsMiloš Milovančevićmilos.milovancevic@gmail.comNebojša Denićnebojsa.denic@pr.ac.rs<p>This research study is an analysis of patent applications based on different input parameters. Nine patent indicators for describing patent applications are retrieved from the World Bank database. The method of ANFIS (adaptive neuro fuzzy inference system) is applied to selecting the most important parameters for patent applications. The inputs are: charges for the use of intellectual property for payments and receipts, research and development expenditure, trademark applications for residents and nonresidents, researchers in research and development (R&D), technicians in R&D and high-technology exports. As the ANFIS outputs, patent applications for nonresidents and residents are considered. The results show that the combination of research and development expenditure and technicians in R&D is the most influential combination of input parameters for patent applications.</p>2017-08-02T15:54:13+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2880THE MONOSPIRAL MOTORISED CABLE REEL IN CRANE APPLICATIONS2017-11-15T06:51:47+01:00Vojkan Kostićvojkan.kostic@elfak.ni.ac.rsNebojša Mitrovićnebojsa.mitrovic@elfak.ni.ac.rsBojan Bankovićbojan.bankovic@elfak.ni.ac.rsMilutin Petronijevićmilutin.petronijevic@elfak.ni.ac.rsThe main consideration of any reeling system is the effect it has on cable tensions and hence cable life. This paper explains the relationship of reel torque to cable tensions and the reasons why this relationship is so important. Such system is characterized by variable parameters, primarily a variable moment of inertia and a variable diameter of the coiled cable. For these reasons, in order to ensure proper dimensioning of the drive, it is necessary to know the motor torques that need to be developed as a function of the coiled cable. The motor should be able to develop the required torques in a very wide speed range. It is shown that for properly sizing the motor it is necessary take into account the dynamics of the cable reel drive. In this paper monospiral motorized cable reel for winding power cable in crane applications with frequency converter fed induction motor is analyzed. Also, the equipment selection procedure for the real crane with concrete data is shown. Experimental results are recorded during the crane commissioning in real condition.2017-08-02T15:54:13+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2860SIMULATION OF FRICTIONAL DISSIPATION UNDER BIAXIAL TANGENTIAL LOADING WITH THE METHOD OF DIMENSIONALITY REDUCTION2017-10-15T22:20:38+02:00Andrey V. Dimakidav18@yandex.ruRoman Pohrtdummy12345891@yahoo.comValentin L. Popovv.popov@tu-berlin.deThe paper is concerned with the contact between the elastic bodies subjected to a constant normal load and a varying tangential loading in two directions of the contact plane. For uni-axial in-plane loading, the Cattaneo-Mindlin superposition principle can be applied even if the normal load is not constant but varies as well. However, this is generally not the case if the contact is periodically loaded in two perpendicular in-plane directions. The applicability of the Cattaneo-Mindlin superposition principle guarantees the applicability of the method of dimensionality reduction (MDR) which in the case of a uni-axial in-plane loading has the same accuracy as the Cattaneo-Mindlin theory. In the present paper we investigate whether it is possible to generalize the procedure used in the MDR for bi-axial in-plane loading. By comparison of the MDR-results with a complete three-dimensional numeric solution, we arrive at the conclusion that the exact mapping is not possible. However, the inaccuracy of the MDR solution is on the same order of magnitude as the inaccuracy of the Cattaneo-Mindlin theory itself. This means that the MDR can be also used as a good approximation for bi-axial in-plane loading.2017-08-02T15:54:12+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2797THE INFLUENCE OF VISCOELASTICITY ON VELOCITY-DEPENDENT RESTITUTIONS IN THE OBLIQUE IMPACT OF SPHERES2017-10-15T22:20:37+02:00Emanuel Willerte.willert@tu-berlin.deStephan Kusches.kusche@tu-berlin.deValentin L. Popovv.popov@tu-berlin.de<p class="Abstract">We analyse the oblique impact of linear-viscoelastic spheres by numerical models based on the Method of Dimensionality Reduction and the Boundary Element Method. Thereby we assume quasi-stationarity, the validity of the half-space hypothesis, short impact times and Amontons-Coulomb friction with a constant coefficient for both static and kinetic friction. As under these assumptions both methods are equivalent, their results differ only within the margin of a numerical error. The solution of the impact problem written in proper dimensionless variables will only depend on the two parameters necessary to describe the elastic problem and a sufficient set of variables to describe the influence of viscoelastic material behaviour; in the case of a standard solid this corresponds to two additional variables. The full solution of the impact problem is finally determined by comprehensive parameter studies and partly approximated by simple analytic expressions.</p>2017-08-02T15:54:11+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2916FEATURES OF THE Σ5 AND Σ9 GRAIN BOUNDARIES MIGRATION IN BCC AND FCC METALS UNDER SHEAR LOADING – A MOLECULAR DYNAMICS STUDY2017-11-15T06:44:49+01:00Andrey I. Dmitrievdmitr@ispms.ruAnton Yu. Nikonovdummy12345891@yahoo.comMolecular dynamics simulation of metallic bicrystals has been carried out to investigate the behavior of the symmetrical tilt grain boundaries under shear loading. Σ5 and Σ9 grain boundaries in Ni and α-Fe were analyzed. It is found that behavior of the defect depends not only on the structure of boundaries but also on the type of crystal lattice. In particular it is shown that under external stress the grain boundary (GB) behaves differently in the BCC and FCC metal. A comparison of the values of displacement of various types of GB due to their migration caused by shear deformation is carried out. The results can help us to understand the features of the plastic deformation development in nanoscale polycrystals under shear loading.2017-08-02T15:54:11+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2849REMOTE CONTROL OF THE MECHATRONIC REDESIGNED SLIDER-CRANK MECHANISM IN SERVICE2017-11-15T06:49:39+01:00Miša Tomićmisa.tomic@masfak.ni.ac.rsMiloš Miloševićmmilos@masfak.ni.ac.rsNevena Tomićnenatomic@gmail.comNenad D. Pavlovićpavlovic@masfak.ni.ac.rsVukašin Pavlovićvuxa86@gmail.com<p class="Abstract">Slider-crank mechanisms are used in many machines where there is a need to transform rotary motion into translation, and vice versa. Implementation of the control into a mechanical assembly of the slider-crank mechanism offers a wide range of applications of such controlled mechanism in mechatronic systems. This paper shows an example of the remote control of the angular velocity of the crank in a mechatronic redesigned slider-crank mechanism in order to achieve the desired motion of the slider. The remote control is achieved over the Internet connection and the appropriate software which is executed in the user’s internet browser. The aim of this paper is to present the applied control algorithm as well as to explain advantages of the possibility to remotely run a mechatronic redesigned slider-crank mechanism in service. This is done through an example of using a controlled slider-crank mechanism in a remote laboratory experiment.</p>2017-08-02T15:54:10+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2832DECOUPLING CONTROL OF TITO SYSTEM SUPPORTED BY DOMINANT POLE PLACEMENT METHOD2017-11-15T06:48:24+01:00Novak N. Nedićnedic.n@mfkv.kg.ac.rsSaša Lj. Prodanovićsasa.prodanovic77@gmail.comLjubiša M. Dubonjićdubonjic.lj@mfkv.kg.ac.rsAppropriate approach to the nature of systems is a significant precondition for its successful control. An always actual issue of its mutual coupling is considered in this paper. A multivariable system with two-inputs and two-outputs (TITO) is in the focus here. The dominant pole placement method is used in trying to tune the PID controllers that should support the decoupling control. The aim is to determine parameters of the PID controllers which, in combination with decoupler, can obtain a good dynamical behavior of the system. Therefore, this kind of the centralized analytically obtained controller is used for object control. Another goal is to simplify the tuning procedure of PID controllers and enlarge the possibility for introducing the given approach into practice. But the research results indicate that the proposed procedure leads to the usage of P controllers because they enable the best performances for the considered object. Also, it is noticed that some differences from the usual rules in selection of the dominant poles gives better results. The research is supported by simulations and, therefore, the proposed method effectiveness, regarding the system behavior quality, is presented on several examples.2017-08-02T15:54:09+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2827AUTOMOTIVE APPLICATIONS OF EVOLVING TAKAGI-SUGENO-KANG FUZZY MODELS2017-11-15T06:47:26+01:00Radu-Emil Precupradu.precup@aut.upt.roStefan Preitldummy12340@yahoo.comClaudia-Adina Bojan-Dragosdummy12340@yahoo.comMircea-Bogdan Radacdummy12340@yahoo.comAlexandra-Iulia Szedlak-Stineandummy12340@yahoo.comElena-Lorena Hedreadummy12340@yahoo.comRaul-Cristian Romandummy12340@yahoo.comThis paper presents theoretical and application results concerning the development of evolving Takagi-Sugeno-Kang fuzzy models for two dynamic systems, which will be viewed as controlled processes, in the field of automotive applications. The two dynamic systems models are nonlinear dynamics of the longitudinal slip in the Anti-lock Braking Systems (ABS) and the vehicle speed in vehicles with the Continuously Variable Transmission (CVT) systems. The evolving Takagi-Sugeno-Kang fuzzy models are obtained as discrete-time fuzzy models by incremental online identification algorithms. The fuzzy models are validated against experimental results in the case of the ABS and the first principles simulation results in the case of the vehicle with the CVT.2017-08-02T15:54:08+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2877ROBOT LEARNING OF OBJECT MANIPULATION TASK ACTIONS FROM HUMAN DEMONSTRATIONS2017-11-15T06:46:33+01:00Maria Kyrarinimkyrar@iat.uni-bremen.deMuhammad Abdul Haseebhaseeb@iat.uni-bremen.deDanijela Ristić-Durrantristic@iat.uni-bremen.deAxel Gräserag@iat.uni-bremen.de<p class="Abstract">Robot learning from demonstration is a method which enables robots to learn in a similar way as humans. In this paper, a framework that enables robots to learn from multiple human demonstrations via kinesthetic teaching is presented. The subject of learning is a high-level sequence of actions, as well as the low-level trajectories necessary to be followed by the robot to perform the object manipulation task. The multiple human demonstrations are recorded and only the most similar demonstrations are selected for robot learning. The high-level learning module identifies the sequence of actions of the demonstrated task. Using Dynamic Time Warping (DTW) and Gaussian Mixture Model (GMM), the model of demonstrated trajectories is learned. The learned trajectory is generated by Gaussian mixture regression (GMR) from the learned Gaussian mixture model. In online working phase, the sequence of actions is identified and experimental results show that the robot performs the learned task successfully.</p>2017-08-02T15:54:06+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2577MODELLING AND CONTROL OF H-SHAPED RACING QUADCOPTER WITH TILTING PROPELLERS2017-10-15T22:20:37+02:00Ahmed Alkamachiamrk1978@gmail.comErgun Ercelebiercelebi@gantep.edu.trTraditional quadcopter suffers terribly from its underactuation which implies the coupling between the rotational and the translational motion. In this paper, we present a quadcopter with dynamic rotor tilting capability in which the four propellers are allowed to tilt together around their arm axis. The proposed model provides leveled forward/backward horizontal motion and therefore, ensures a correct view of the onboard camera, and increases the vehicle speed by reducing the air drag. The rotor tilt mechanism also provides an instant high speed in the forward or reverse direction and offers a quick and solid air brake to restrain that fast moving speed. The nonlinear dynamical model for the quadcopter under consideration is derived using Newton-Euler formalization. A control strategy is then proposed aimed to control the altitude, attitude, and the forward speed of the obtained model. Finally, a numerical simulation is used to integrate the system model with the controller and to test the system performance. Simulation results are reported to demonstrate the advantages of the proposed novel configuration.2017-08-02T15:54:05+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3026NOISE CONTROL OF VEHICLE DRIVE SYSTEMS2017-11-15T06:46:00+01:00Ulrich Gabbertulrich.gabbert@ovgu.deFabian Duvigneaufabian.duvigneau@ovgu.deStefan Ringwelskistefan.ringwelski@ovgu.deThe paper presents an overall simulation approach to control the noise emission of car engines at a very early stage of the design process where no real prototypes are available. The suggested approach combines different physical models and couples different software tools such as multi-body analysis, fluid dynamics, structural mechanics, magneto-electrodynamics, thermodynamics, acoustics and control as well. The general overall simulation methodology is presented first. Then, this methodology is applied to a combustion engine in order to improve its acoustical behavior by passive means, such as changing the stiffness and the use of damping materials to build acoustic and thermal encapsulations. The active control by applying piezoelectric patch actuators at the oil sump as the noisiest part of the engine is discussed as well. The sound emission is evaluated by hearing tests and a mathematical prediction model of the human perception. Finally, it is shown that the presented approach can be extended to electric engines, which is demonstrated at a newly developed electric wheel hub motor.<em></em><br /><em></em>2017-08-02T15:54:05+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/3069FOREWORD2017-10-15T22:20:38+02:00Vlastimir Nikolićvlastimir.nikolic@junis.ni.ac.rsDragan Marinkovićdragan.marinkovic@junis.ni.ac.rsForeword to the issue dedicated to the SAUM 2016 conference.2017-08-02T15:54:04+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2209FROM ART TO ENGINEERING: A TECHNICAL REVIEW ON THE PROBLEM OF VIBRATING CANVAS PART I: EXCITATION AND EFFORTS OF VIBRATION REDUCTION2017-10-15T22:20:39+02:00Kerstin Krachtkkracht@gmx.netThomas Kletschkowskithomas.kletschkowski@haw-hamburg.de<p>Cultural assets are witnesses of past times with versatile worth. The irreplaceability of those treasures of art makes their protection our major task. This article reflects the commitment and results of 40 years of conservators’ research to protect canvas - objects of cultural heritage - particularly from mechanical loads. It gives a classification of mechanical loads that act upon canvas during transport, exhibition and storing in depot. Furthermore, it gives an overview of different approaches which were used over years to protect canvas from various mechanical loads. This article tends to bridge the gap between restorers’ knowledge and methods and concepts known from engineering dynamics. Restorers’ first steps using engineers’ methods are brought up and the necessity of theoretical modeling which has not started so far are pointed out.</p>2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2453IMPLEMENTATION OF THE LEAN-KAIZEN APPROACH IN FASTENER INDUSTRIES USING THE DATA ENVELOPMENT ANALYSIS2017-10-15T22:20:40+02:00Sunil Kumarsunil.panchal2007@gmail.comAshwani Kumar Dhingraashwani_dhingra1979@rediffmail.comBhim Singhbhimsingh2008@gmail.comThis research paper is an attempt to improve the quality system of ten small scale fastener manufacturing industries through the implementation of the Lean-Kaizen approach using the Data Envelopment Analysis (DEA) Charnes Cooper & Rhodes (CCR) model with constant returns to scale (CRS). Output maximization is taken as the objective function to identify the percentage scope of improvements. The data is collected by paying personal visits to the selected industries for three inputs (manpower, maintenance, and training of employees) and two outputs (quality, on-time delivery) of their quality system. The DEA CCR model is applied to identify efficiency scores of the quality system by taking the most efficient industry as a benchmark for the rest of the organizations. The Lean-Kaizen approach is applied to identify waste / non-value added activities in outputs of the selected industries. Four Kaizen events are proposed to eliminate waste / non-value added activities in their quality system. The data collected after the Kaizen events are further analyzed by the DEA CCR model. The improvements in efficiency scores of the selected industries are presented as findings in this research paper. Two fastener industries became 100% efficient while the rest of the organizations reported 8% to 49% improvements in their efficiency scores of the quality system. The conclusions are made as the Lean-Kaizen using DEA is found to be an effective approach to improve the quality system of fastener industries. This study will be beneficial for researchers, practitioners and academicians for tackling the inefficiencies in the organization.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2733MULTILAYERED PLATE ELEMENTS WITH NODE-DEPENDENT KINEMATICS FOR THE ANALYSIS OF COMPOSITE AND SANDWICH STRUCTURES2017-10-15T22:20:40+02:00Stefano Valvanostefano.valvano@polito.itErasmo Carreraerasmo.carrera@polito.itIn this paper a new plate finite element (FE) for the analysis of composite and sandwich plates is proposed. By making use of the node-variable plate theory assumptions, the new finite element allows for a simultaneous analysis of different subregions of the problem domain with different kinematics and accuracy, in a global/local sense. In particular higher-order theories with an Equivalent-Single-Layer (ESL) approach are simultaneously used with advanced Layer-Wise (LW) models. As a consequence, the computational costs can be reduced drastically by assuming refined theories only in those zones/nodes of the structural domain where the resulting strain and stress states present a complex distribution. On the contrary, computationally cheaper, low-order kinematic assumptions can be used in the remaining parts of the plate where a localized detailed analysis is not necessary. The primary advantage of the present variable-kinematics element and related global/local approach is that no ad-hoc techniques and mathematical artifices are required to mix the fields coming from two different and kinematically incompatible adjacent elements, because the plate structural theory varies within the finite element itself. In other words, the structural theory of the plate element is a property of the FE node in this present approach, and the continuity between two adjacent elements is ensured by adopting the same kinematics at the interface nodes. According to the Unified Formulation by Carrera, the through-the-thickness unknowns are described by Taylor polynomial expansions with ESL approach and by Legendre polynomials with LW approach. Furthermore, the Mixed Interpolated Tensorial Components (MITC) method is employed to contrast the shear locking phenomenon. Several numerical investigations are carried out to validate and demonstrate the accuracy and efficiency of the present plate element, including comparison with various closed-form and FE solutions from the literature<em>.</em>2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/619APPLICATION OF THE PERFORMANCE SELECTION INDEX METHOD FOR SOLVING MACHINING MCDM PROBLEMS2017-10-15T22:20:39+02:00Dušan Petkovićdulep@masfak.ni.ac.rsMiloš Madićmadic@masfak.ni.ac.rsMiroslav Radovanovićmirado@masfak.ni.ac.rsValentina Gečevskavalentina.gecevska@mf.edu.mkComplex nature of machining processes requires the use of different methods and techniques for process optimization. Over the past few years a number of different optimization methods have been proposed for solving continuous machining optimization problems. In manufacturing environment, engineers are also facing a number of discrete machining optimization problems. In order to help decision makers in solving this type of optimization problems a number of multi criteria decision making (MCDM) methods have been proposed. This paper introduces the use of an almost unexplored MCDM method, i.e. performance selection index (PSI) method for solving machining MCDM problems. The main motivation for using the PSI method is that it is not necessary to determine criteria weights as in other MCDM methods. Applicability and effectiveness of the PSI method have been demonstrated while solving two case studies dealing with machinability of materials and selection of the most suitable cutting fluid for the given machining application. The obtained rankings have good correlation with those derived by the past researchers using other MCDM methods which validate the usefulness of this method for solving machining MCDM problems.2017-04-04T00:00:00+02:00Copyright (c) 2017 http://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1667AN APPLICATION OF MULTICRITERIA OPTIMIZATION TO THE TWO-CARRIER TWO-SPEED PLANETARY GEAR TRAINS2017-10-15T22:20:39+02:00Jelena Stefanović-Marinovićjelena_s_m@yahoo.comSanjin Trohasanjin.troha@gmail.comMiloš Milovančevićmilovancevic@masfak.ni.ac.rs<p class="Abstract"><strong></strong>The objective of this study is the application of multi-criteria optimization to the two-carrier two-speed planetary gear trains. In order to determine mathematical model of multi-criteria optimization, variables, objective functions and conditions should be determined. The subject of the paper is two-carrier two-speed planetary gears with brakes on single shafts. Apart from the determination of the set of the Pareto optimal solutions, the weighted coefficient method for choosing an optimal solution from this set is also included in the mathematical model.</p>2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2094DEEP DRAWING TECHNOLOGY WITH WALL IRONING IN MASS PACKAGING INDUSTRY2017-10-15T22:20:39+02:00Saša Ranđelovićsassa@masfak.ni.ac.rsMladomir Milutinovićmladomil@uns.ac.rsVladislav Blagojevićvlada@masfak.ni.ac.rsAluminum is a metal that is being increasingly used in the packaging industry in the modern metal forming technology, but it also provides a good opportunity for effective advertising and product promotion. Processing technologies for aluminum plastic deformation ensure superior packaging that meets the most rigorous demands in the food, pharmaceutical, chemical, and other industries. It is the case of mass production with very little material loss that offers the possibility of multiple recycling. On the other hand, today's products for general purpose consumers cannot be imagined without aggressive advertising that has a major impact on customers. Modern graphics techniques for printing images and different basic surfaces offer great opportunities that manufacturers use widely in the promotion and sale of their products.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2199A THEORETICAL-EXPERIMENTAL APPROACH FOR ELASTO-DAMPING PARAMETERS ESTIMATION OF CONE INERTIAL CRUSHER MOUNTING2017-10-15T22:20:39+02:00Rosen Mitrevrosenm@tu-sofia.bgSimeon Savovss.ss@abv.bg<p class="Abstract">The present paper deals with estimation of the elasto-damping parameters of a cone inertial crusher mounting. The numerical values of these parameters are crucial for accurate reproduction of the machine vibrational behavior and dynamical model adequacy. Due to the significant difficulties arising during the purely theoretical determination of the stiffness and damping parameters of the rubber vibroisolators it is well-suited to use a theoretical-experimental approach. The developed approach is based on the theoretical determination of the mounting stiffness parameters as a function of two experimentally measured natural frequencies of the mechanical system. The crusher is represented as a six degrees of freedom system with two planes of symmetry. By using the system characteristic polynomial, the theoretical derivation of mathematical relationships for the mechanical system natural frequencies as a function of stiffness, inertial and geometrical parameters is performed. A good agreement is shown when comparing the experimental and the theoretical results for the system kinematical characteristics.</p>2017-04-04T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1955FUNCTION K - AS A LINK BETWEEN FUEL FLOW VELOCITY AND FUEL PRESSURE, DEPENDING ON THE TYPE OF FUEL2017-10-15T22:20:39+02:00Boban Nikolićnboban@masfak.ni.ac.rsMiloš Jovanovićmilosjovanovic@open.telekom.rsMiloš Miloševićmmilos@masfak.ni.ac.rsSaša Milanovićmsasa@masfak.ni.ac.rsRegarding the application of vegetable oil based fuels in diesel engines, it is necessary to fully examine and understand the processes which take place in fuel delivery systems, namely, the processes of injection, mixture formation and combustion as well as emission characteristics. The paper provides an analysis of fuel flow in high pressure tubes of the fuel injection system, with the aim of determining function K as a link between fuel flow velocity and fuel pressure, and observing the influence of certain physical characteristics of the fuel upon the given function. The analysis presents the speed of sound and density, as fuel characteristics which affect the K function. The paper determines the speed of sound, density and bulk modulus for four fuels (pure rapeseed oil RO, biodiesel B100, a mixture of biodiesel and diesel B50, and diesel D), and forms appropriate K functions for each fuel in the pressure range from the atmospheric one to 1600 bar.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1972IMPLANT MATERIAL SELECTION USING EXPERT SYSTEM2017-10-15T22:20:39+02:00Miloš Ristićmilos.ristic@vtsnis.edu.rsMiodrag Manićmiodrag.manic@masfak.ni.ac.rsDragan Mišićmisicdr@gmail.comMiloš Kosanovićmilos.kosanovic@vtsnis.edu.rsMilorad Mitkovićmitkovic@gmail.com<p class="Abstract"><span lang="EN-GB">Most certainly, in the field of medicine there is a great contribution of new techniques and technologies, which is reflected in an entire system of health care services. Customized implants are both fully geometrically and topologically adjusted so as to meet the needs of individual patients, thus making each implant unique. Their production requires joint efforts of a multidisciplinary team of different profile experts who combine their knowledge in the Implant knowledge model. Thus, we develop an expert system which should help or replace humans in the process of Implant material selection. This paper gives an overview of the expert system concept for the given problem. Its task is to carry out a selection of biomaterial (or class of material) for a customized implant. The model significantly improves the efficiency of preoperative planning in orthopaedics.</span></p>2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2259THERMAL EFFECT ON FREE VIBRATION AND BUCKLING OF A DOUBLE-MICROBEAM SYSTEM2017-10-15T22:20:39+02:00Marija Stamenković Atanasovs_marija86@yahoo.comDanilo Karličićdanilozmaj@gmail.comPredrag Kozićkozicp@yahoo.comGoran Janevskigocky.jane@gmail.comThe paper investigates the problem of free vibration and buckling of an Euler-Bernoulli double-microbeam system (EBDMBS) under the compressive axial loading with a temperature change effect. The system is composed of two identical, parallel simply-supported microbeams which are continuously joined by the Pasternak’s elastic layer. Analytical expressions for the critical buckling load, critical buckling temperature, natural frequencies and frequencies of transverse vibration of the EBDMBS represented by the ratios are derived and validated by the results found in the literature. Also analytical expressions are obtained for various buckling states and vibration-phase of the EBDMBS. The temperature change effect is assumed to have an influence on both the microbeams. The length scale parameter, temperature change effect, critical buckling load, thickness/material parameter, Pasternak’s parameter and Poisson’s effect are discussed in detail. Also, as a clearer display of the thermo-mechanical response of EBDMBS, the paper introduces a critical scale load ratio of the modified and the local critical buckling loads in low-temperature environs. Numerical results show that the critical buckling temperatures for classical theories are always higher than the critical buckling temperature for MCST systems.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2682NORMAL LINE CONTACT OF FINITE-LENGTH CYLINDERS2017-10-15T22:20:40+02:00Qiang Liqiang.li@tu-berlin.deValentin L. Popovv.popov@tu-berlin.deIn this paper, the normal contact problem between an elastic half-space and a cylindrical body with the axis parallel to the surface of the half-space is solved numerically by using the Boundary Element Method (BEM). The numerical solution is approximated with an analytical equation motivated by an existing asymptotic solution of the corresponding problem. The resulting empirical equation is validated by an extensive parameter study. Based on this solution, we calculate the equivalent MDR-profile, which reproduces the solution exactly in the framework of the Method of Dimensionality Reduction (MDR). This MDR-profile contains in a condensed and easy-to-use form all the necessary information about the found solution and can be exploited for the solution of other related problems (as contact with viscoelastic bodies, tangential contact problem, and adhesive contact problem.) The analytical approximation reproduces numerical results with high precision provided the ratio of length and radius of the cylinder are larger than 5. For thin disks (small length-to-radius ratio), the results are not exact but acceptable for engineering applications.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2694A 3-NODE PIEZOELECTRIC SHELL ELEMENT FOR LINEAR AND GEOMETRICALLY NONLINEAR DYNAMIC ANALYSIS OF SMART STRUCTURES2017-10-15T22:20:40+02:00Gil Ramagil.rama@tu-berlin.deComposite laminates consisting of passive and multi-functional materials represent a powerful material system. Passive layers could be made of isotropic materials or fiber-reinforced composites, while piezoelectric ceramics are considered here as a multi-functional material. The paper is focused on linear and geometrically nonlinear dynamic analysis of smart structures made of such a material system. For this purpose, a linear 3-node shell element is used. It employs the Mindlin-Reissner kinematics and the discrete shear gap (DSG) technique to alleviate the transverse shear locking effects. The electric potential is assumed to vary linearly through the thickness for each piezoelectric layer. A co-rotational formulation is used to handle the geometrically nonlinear effects. A number of examples involving actuator and sensor application of piezoelectric layers are considered. For the validation purposes, the results available in the literature and those computed in Abaqus are used as a reference.2017-04-04T00:00:00+02:00Copyright (c) 2017 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2329ADHESION EFFECTS WITHIN THE HARD MATTER – SOFT MATTER INTERFACE: MOLECULAR DYNAMICS2017-10-15T22:20:41+02:00Alexey Tsukanova.a.tsukanov@yandex.ruSergey Psakhiedummyx@yahoo.comIn the present study three soft matter – hard matter systems consisting of different nanomaterials and organic molecules were studied using the steered molecular dynamics approach in order to reveal regularities in the formation of organic-inorganic hybrids and the stability of multimolecular complexes, as well as to analyze the energy aspects of adhesion between bio-molecules and layered ceramics. The combined process free energy estimation (COPFEE) procedure was used for quantitative and qualitative assessment of the considered heterogeneous systems. Interaction of anionic and cationic amino acids with the surface of a [Mg4Al2(OH)122+ 2Cl–] layered double hydroxide (LDH) nanosheet was considered. In both cases, strong adhesion was observed despite the opposite signs of electric charge. The free energy of the aspartic amino acid anion, which has two deprotonated carboxylic groups, was determined to be –45 kJ/mol for adsorption on the LDH surface. For the cationic arginine, with only one carboxylic group and a positive net charge, the energy of adsorption was –26 kJ/mol, which is twice higher than that of chloride anion adsorption on the same cationic nanosheet. This fact clearly demonstrates the capability of “soft matter” species to adjust themselves and fit into the surface, minimizing energy of the system. The adsorption of protonated histamine, having no carboxylic groups, on a boehmite nanosheet is also energetically favorable, but the depth of free energy well is quite small at 3.6 kJ/mol. In the adsorbed state the protonated amino-group of histamine plays the role of proton donor, while the hydroxyl oxygens of the layered hydroxide have the role of proton acceptor, which is unusual. The obtained results represent a small step towards further understanding of the adhesion effects within the hard matter – soft matter contact zone.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2391FOREWORD2017-10-15T22:20:41+02:00Dragan Marinkovićdragan.marinkovic@junis.ni.ac.rs<p>Foreword to the thematic issue entitled:</p><p><em>TRIBOLOGY AND CONTACT MECHANICS IN BIOLOGICAL AND MEDICAL APPLICATIONS</em></p><em></em>2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2176INDENTATION OF FLAT-ENDED AND TAPERED INDENTERS WITH POLYGONAL CROSS-SECTIONS2017-10-15T22:20:40+02:00Qiang Liqiang.li@tu-berlin.deValentin L. Popovv.popov@tu-berlin.deUsing the Boundary Element Method, we numerically study the indentation of prismatic and tapered indenters with polygonal cross-sections. The contact stiffness of punches with flat bases in the form of a triangle and a square as well as a number of higher-order polygons is determined. In particular, the classical results of King (1987) for indenters with triangle and square base shapes are revised and more precise numerical results are provided. For tapered indenters, the equivalent transformed profile used in the Method of Dimensionality Reduction (MDR) is determined. It is shown that the MDR-transformed profile of polygon-based indenters with power function side is given by the power function with the same power; it differs from the 3D profile only by a constant coefficient. These coefficients are listed in the paper for various types of indenters, in particular for pyramidal and paraboloid ones. The determined MDR-transformed profiles can be used for study of other contact problems such as tangential contact, normal contact with elastomers, and, in an approximate way, to adhesive contacts.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2275THE JKR-ADHESIVE NORMAL CONTACT PROBLEM OF AXISYMMETRIC RIGID PUNCHES WITH A FLAT ANNULAR SHAPE OR CONCAVE PROFILES2017-10-15T22:20:40+02:00Emanuel Willerte.willert@tu-berlin.deQiang Liqiang.li@tu-berlin.deValentin L. Popovv.popov@tu-berlin.deThe JKR-adhesive frictionless normal contact problem is solved for the flat annular and the conical or spherical concave rigid punch indenting an elastic half space. The adhesive solution can be derived analytically from the non-adhesive one, the latter one being calculated by the boundary element method. It is found that the annular flat punch will always start to detach at the outer boundary. The pull-off forces for both concave punch shapes almost do not depend on the pull-off boundary regime and can be significantly larger than the pull-off force for the cylindrical flat punch.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2307TANGENTIAL DISPLACEMENT INFLUENCE ON THE CRITICAL NORMAL FORCE OF ADHESIVE CONTACT BREAKAGE IN BIOLOGICAL SYSTEMS2017-10-15T22:20:40+02:00Iakov A. Lyashenkonabla04@ukr.netThe dependencies of the critical components of normal and tangential forces corresponding to the contact breakage between a parabolic indenter and an elastic half-space have been determined taking into account adhesive interaction. In order to describe the adhesive contact, the method of dimensionality reduction (MDR) and the modified rule of Heß taking into account tangential displacements have been used. The influence of the surface energy depending on the indenter separation angle has been studied.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2324MODIFYING AND EXPANDING THE SIMULATION OF WEAR IN THE SPHERICAL JOINT WITH A POLYMERIC COMPONENT OF THE TOTAL HIP PROSTHESIS2017-10-15T22:20:40+02:00Vladimir Pakhaliukvpakhaliuk@gmail.comAleksandr Poliakovalex_polyakov@inbox.ruMikhail Kalininkalininsev@mail.ruYevgenii Pashkovpashkov@sevsu.ruPavel Gadkovde1taman@yandex.uaThe existing model of wear, based on the classical Archard equation, in the spherical joint of a total hip prosthesis comprising an acetabular cup of ultra-high molecular weight polyethylene (UHMWPE) in combination with a metal or ceramic femoral head is modified and expanded. With this model, studies are conducted using the finite element analysis in terms of cumulative linear and volumetric wear for the ISO 14242-1 demands and additionally for the conditions during walking gait. Also they are carried out for the head diameter of 28 mm at the constant and the variable wear factor, where the variable wear factor is adopted from the modified formula for the dependence on the contact pressure.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2327NUMERICAL STUDY OF STRESS-STRAIN LOCALIZATION IN THE TITANIUM SURFACE MODIFIED BY AN ELECTRON BEAM TREATMENT2017-10-15T22:20:40+02:00Ruslan Balokhonovrusy@ispms.tsc.ruVarvara Romanovadummyx@yahoo.comAlexey Panindummyx@yahoo.comSergey Martynovdummyx@yahoo.comMarina Kazachenokdummyx@yahoo.com<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;" lang="EN-US">Numerical simulation is performed to investigate the mesoscale stress-strain localization in a surface-modified commercial titanium alloy. The calculated crystalline microstructure corresponds to that observed in experiments and is accounted for in an explicit way as initial conditions of a dynamic boundary-value problem. The latter is stated in terms of plane strain developing in microstructure subjected to tension and is solved numerically by the finite-difference method. Elastic-plastic constitutive models were built to describe the experimental mechanical response both of the substrate and of the modified layer. Plastic strain localization is found to depend on the grain yield strength.</span>2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2333BIOSIMILAR ARTIFICIAL KNEE FOR TRANSFEMORAL PROSTHESES AND EXOSKELETONS2017-10-15T22:20:41+02:00Aleksandr Poliakova.m.poljakov@sevsu.ruVladimir Pakhaliukvpakhaliuk@gmail.comNikolay Lozinskiynlozinskiy@inbox.ruMarina Kolesovamarishaclass@mail.ruPavel Bugayovpasha_ba@mail.ruPetro Shtankomech@zntu.edu.ua<p><span lang="EN-US"><span style="font-family: Times New Roman; font-size: small;">Artificial knees play an important role in transfemoral prostheses, lower extremity exoskeletons and walking robots. Their designs must provide natural kinematics, high strength and stiffness required in the stance phase of gait. Additionally, modern artificial knee is the principal module by means of which the prosthesis control is performed. This paper presents a prototype of an artificial polycentric knee, designed on the basis of the hinge mechanism with cross links. In order to increase strength and stiffness, the elements of the joint have curved supporting surfaces formed in the shape of centroids in relative motion of links of the hinge mechanism. Such construction is a mechanical system with redundant links but it allows for providing desirable characteristics of the artificial knee. Synthesis of the hinge mechanism is made by a method of systematic study of the parameter space, uniformly distributed in a finite dimensional cube. Stiffness of bearing surfaces elements of knee was determined by solving the contact problem with slippage of surfaces relative to each other.</span></span></p>2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2328THE BOUNDARY ELEMENT METHOD FOR VISCOELASTIC MATERIAL APPLIED TO THE OBLIQUE IMPACT OF SPHERES2017-10-15T22:20:41+02:00Stephan Kusches.kusche@tu-berlin.deThe Boundary Element Method (BEM) for elastic materials is extended to deal with viscoelastic media. This is obtained by making use of a similar form of the fundamental solution for both the materials. Some considerations are attributed to the difference of the normal and the tangential contact problem. Both normal and tangential problems are furthermore assumed to be decoupled. Then the oblique impact of hard spheres with an incompressible viscoelastic half-space (linear standard-model) is studied. By assuming stick conditions during impact, one obtains the dependence of the two coefficients of restitution as functions of two input parameters. This result is expressed in an elegant and compact form of the fitting function.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2369CRITICAL VELOCITY OF CONTROLLABILITY OF SLIDING FRICTION BY NORMAL OSCILLATIONS IN VISCOELASTIC CONTACTS2017-10-15T22:20:41+02:00Mikhail Popovmpopov@fastmail.fm<p style="margin-left: 0.3in; margin-right: 0.3in; font-weight: normal;"><span style="font-size: small;">Sliding friction can be reduced substantially by applying ultrasonic vibration in the sliding plane or in the normal direction. This effect is well known and used in many applications ranging from press forming to ultrasonic actuators. One of the characteristics of the phenomenon is that, at a given frequency and amplitude of oscillation, the observed friction reduction diminishes with increasing sliding velocity. Beyond a certain critical sliding velocity, there is no longer any difference between the coefficients of friction with or without vibration. This critical velocity depends on material and kinematic parameters and is a key characteristic that must be accounted for by any theory of influence of vibration on friction. Recently, the critical sliding velocity has been interpreted as the transition point from periodic stick-slip to pure sliding and was calculated for purely elastic contacts under uniform sliding with periodic normal loading. Here we perform a similar analysis of the critical velocity in viscoelastic contacts using a Kelvin material to describe viscoelasticity. A closed-form solution is presented, which contains previously reported results as special cases. This paves the way for more detailed studies of active control of friction in viscoelastic systems, a previously neglected topic with possible applications in elastomer technology and in medicine.</span></p>2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/2345METHOD OF DIMENSIONALITY REDUCTION IN CONTACT MECHANICS AND FRICTION: A USER'S HANDBOOK. II. POWER-LAW GRADED MATERIALS2017-10-15T22:20:41+02:00Markus Hessmarkus.hess@tu-berlin.deValentin L. Popovv.popov@tu-berlin.deUntil recently, the only way of solving contact problems was to applythree-dimensional contact theories. However, this presupposes higher mathematical and numerical knowledge, which usually only research groups possess. This has changed drastically with the development of the method of dimensionality reduction (MDR), which allows every practically oriented engineer an access to the solution of contact problems. The simple and contact-type dependent rules are summarized in the first part of the user manual; they require contacts between elastically homogeneous materials. The present paper forms the second part of the user handbook and is dedicated to the solution of contact problems between power-law graded materials. All the MDR-rules are listed with which normal, tangential and adhesive contacts between such high-performance materials can be calculated in a simple manner.2016-12-08T00:00:00+01:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/92SPLITTING THE TOTAL EXERGY DESTRUCTION INTO THE ENDOGENOUS AND EXOGENOUS PARTS OF THE THERMAL PROCESSES IN A REAL INDUSTRIAL PLANT2017-10-15T22:20:41+02:00Goran Vučkovićvucko@masfak.ni.ac.rsMića Vukićmicav@masfak.ni.ac.rsMirko Stojiljkovićmirko.stojiljkovic@gmail.comMiloš Simonovićsmilos@masfak.ni.ac.rsThe total exergy destruction occurring in a component is not only due to the component itself (endogenous exergy destruction) but is also caused by the inefficiencies of the remaining system components (exogenous exergy destruction). Hence care must be taken in using the total exergy destruction of a component for making decisions to optimize the overall energy system. In this paper, a complex industrial plant is analyzed by splitting the component’s exergy destruction into its endogenous part (the part resulting totally from the component’s irreversibilities) and its exogenous part (resulting from the irreversibilities of the other components within the system). It is observed that the steam generator has the dominant effect. From the total exergy destruction in the steam generator, 1,097.63 kW or 96.95% come from internal irreversibilities in the component, while the influence of other components on the loss of useful work in the steam generator is only 3.05%.2016-08-02T00:00:00+02:00Copyright (c) 2016 http://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1170CAD/CAM DESIGN AND GENETIC OPTIMIZATION OF FEEDERS FOR SAND CASTING PROCESS2017-10-15T22:20:41+02:00Nedeljko Dučićnedeljko.ducic@ftn.kg.ac.rsŽarko Ćojbašićzcojba@ni.ac.rsRadomir Radišaradomir.radisa@li.rsRadomir Slavkovićradomir.slavkovic@ftn.kg.ac.rsIvan Milićevićivan.milicevic@ftn.kg.ac.rsThe paper proposes methodology of feeder design and optimization for sand casting process. Casting part is a part of excavator buckets, i.e. holder of the cutting tooth. Process of design and optimization is based on the application of the rules, which are the result of many years of work researchers in the field of metal casting. Computer Aided Design (CAD) is used as a methodology in the design of feeders. Genetic Algorithm (GA) as an artificial intelligence technique is used in the optimization process of the feeder geometry. Computer Aided Manufacturing (CAM) is used as methodology that involves numerical simulation of the casting process. Numerical simulation is used to verify the validity of the optimized geometry of the feeding system.2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1292INSTABILITY OF THE RAYLEIGH-BENARD CONVECTION FOR INCLINED LOWER WALL WITH TEMPERATURE VARIATION2017-10-15T22:20:41+02:00Sadoon Ayedsadun_kad@yahoo.comGradimir Ilićgradei@masfak.ni.ac.rsPredrag Živkovićpzivkovic@masfak.ni.ac.rsMića Vukićmicav@masfak.ni.ac.rsMladen Tomićtomicmladen@yahoo.comThis paper deals with an analysis of a two-dimensional viscous fluid flow between the two parallel plates inclined with respect to the horizontal plane, where the lower plate is heated and the upper one is cooled. The temperature difference between the plates is gradually increased during a certain time period after which it is temporarily constant. The temperature distribution on the lower plate is not constant in x-direction, there is a longitudinal sinusoidal temperature variation imposed on the mean temperature. We have investigated the wave number and amplitude influence of this variation on the subcritical stability and the onset of the Rayleigh-Bénard convective cells, by direct numerical simulation of 2D Navier-Stokes and energy equation.2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1577SOFTWARE TOOL FOR LASER CUTTING PROCESS CONTROL – SOLVING REAL INDUSTRIAL CASE STUDIES2017-10-15T22:20:42+02:00Miloš Madićmadic@masfak.ni.ac.rsMarko Kovačevićmarkko.marce@gmail.comMiroslav Radovanovićmirado@masfak.ni.ac.rsVladislav Blagojevićvlada@masfak.ni.ac.rs<span style="font-family: 'Times New Roman','serif'; font-size: 10pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">Laser cutting is one of the leading non-conventional machining technologies with a wide spectrum of application in modern industry. It order to exploit a number of advantages that this technology offers for contour cutting of materials, it is necessary to carefully select laser cutting conditions for each given workpiece material, thickness and desired cut qualities. In other words, there is a need for process control of laser cutting. After a comprehensive analysis of the main laser cutting parameters and process performance characteristics, the application of the developed software tool “BRUTOMIZER” for off-line control of CO<sub>2</sub> laser cutting process of three different workpiece materials (mild steel, stainless steel and aluminum) is illustrated. Advantages and abilities of the developed software tool are also illustrated.<br /></span>2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1319ADAPTIVE NEURO-FUZZY COMPUTING TECHNIQUE FOR PRECIPITATION ESTIMATION2017-10-15T22:20:42+02:00Dalibor Petkovićdalibortc@gmail.comMilan Gocićmgocic@yahoo.comShahaboddin Shamshirbandshamshirband1396@gmail.com<p><em></em>The paper investigates the accuracy of an adaptive neuro-fuzzy computing technique in precipitation estimation. The monthly precipitation data from 29 synoptic stations in Serbia during 1946-2012 are used as case studies. Even though a number of mathematical functions have been proposed for modeling the precipitation estimation, these models still suffer from the disadvantages such as their being very demanding in terms of calculation time. Artificial neural network (ANN) can be used as an alternative to the analytical approach since it offers advantages such as no required knowledge of internal system parameters, compact solution for multi-variable problems and fast calculation. Due to its being a crucial problem, this paper presents a process constructed so as to simulate precipitation with an adaptive neuro-fuzzy inference (ANFIS) method. ANFIS is a specific type of the ANN family and shows very good learning and prediction capabilities, which makes it an efficient tool for dealing with encountered uncertainties in any system such as precipitation. Neural network in ANFIS adjusts parameters of membership function in the fuzzy logic of the fuzzy inference system (FIS). This intelligent algorithm is implemented using Matlab/Simulink and the performances are investigated. The simulation results presented in this paper show the effectiveness of the developed method.</p>2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1617AN EFFICIENT CO-ROTATIONAL FEM FORMULATION USING A PROJECTOR MATRIX2017-10-15T22:20:42+02:00Viet Anh Nguyenvietanh.nguyen@siemens.comManfred Zehnmanfred.zehn@tu-berlin.deDragan Marinkovićdragan.marinkovic@tu-berlin.de<p style="margin: 0cm 21.25pt 0pt;"><span lang="EN-US"><span style="font-family: Times New Roman; font-size: small;">Co-rotational finite element (FE) formulations can be seen as a very efficient approach to resolving geometrically nonlinear problems in the field of structural mechanics. A number of co-rotational FE formulations have been well documented for shell and beam structures in the available literature. The purpose of this paper is to present a co-rotational FEM formulation for fast and highly efficient computation of large three-dimensional elastic deformations. On the one hand, the approach aims at a simple way of separating the element rigid-body rotation and the elastic deformational part by means of the polar decomposition of deformation gradient. On the other hand, a consistent linearization is introduced to derive the internal force vector and the tangent stiffness matrix based on the total Lagrangian formulation. It results in a non-linear projector matrix. In this way, it ensures the force equilibrium of each element and enables a relatively straightforward upgrade of the finite elements for linear analysis to the finite elements for geometrically non-linear analysis. In this work, a simple 4-node tetrahedral element is used. To demonstrate the efficiency and accuracy of the proposed formulation, nonlinear results from ABAQUS are used as a reference.</span></span></p>2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1634REDUCTION OF RESIDUAL SHEAR STRESS IN THE LOADED CONTACT USING FRICTION HYSTERESIS2017-10-15T22:20:42+02:00Adrian Kraftadrian.kraft@posteo.deRoman Pohrtroman.pohrt@tu-berlin.de<p class="Abstract">We investigate the tangential contact problem of a spherical indenter at constant normal force. When the indenter is subjected to tangential movement, frictional shear stresses arise at the interface and do not vanish when it is moved backwards. We study the evolution of shear stress when the indenter is moved back and forth at falling amplitude. The method of dimensionality reduction (MDR) is employed for obtaining the distribution of stick and slip zones as well as external forces and the final stress distribution. We find that the shear stress decreases. For the special case of linearly falling amplitude of the movement, we observe uniform peaks in the shear stress. The absolute value of the shear stress peaks is reduced best for a high number of back-and-forth-movements with slowly decreasing amplitude.</p>2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1662THE PATH TOWARDS ACHIEVING A LEAN SIX SIGMA COMPANY USING THE EXAMPLE OF THE SHINWON COMPANY IN SERBIA2017-10-15T22:20:42+02:00Srđan Mladenovićmaki@masfak.ni.ac.rsPeđa Milosavljevićpedja@masfak.ni.ac.rsNevena Milojevićnevenaja@yahoo.comDragan Pavlovićdraganpavlovic10369@gmail.comMilena Todorovićmilenatod1@yahoo.comIn the last twenty years, many companies have realized that the demands of the global market, including more demanding and receptive customers, have set new standards for production flexibility. Gradual reduction of mass production, characteristic of a large number of companies, has opened space for the introduction of a new system which focuses exclusively on the customer. The customer-oriented system was created with the idea that process optimization would lead to the production of a relatively cheap product, delivered on time and with the best possible quality. Such a system is achieved by applying the Lean Six Sigma concept. The aim of this paper is to identify all of the defects that occur as losses and complicate the process of production in order to achieve the Lean Six Sigma level in the Shinwon Company. The original data from the Shinwon company were identified, collected and analyzed, using the methods and tools of the Lean Six Sigma concept (Process Mapping, 5S audit, Pareto diagram, Ishikawa diagram, Seven basic wastes and SPC analysis), in order to present the effectiveness of the quality management system and to evaluate the possibility of its continuous improvement.2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1750BROWNIAN HEAT TRANSFER ENHANCEMENT IN THE TURBULENT REGIME2017-10-15T22:20:42+02:00Suresh Chandrasekharsur.chandrasekhar@gmail.comVaarin Majumdar Sharmadummy1@yahoo.com<p class="Abstract">The paper presents convection heat transfer of a turbulent flow Al2O3/water nanofluid in a circular duct. The duct is a under constant and uniform heat flux. The paper computationally investigates the system’s thermal behavior in a wide range of Reynolds number and also volume concentration up to 6%. To obtain the nanofluid thermophysical properties, the Hamilton-Crosser model along with the Brownian motion effect are utilized. Then the thermal performance of the system with the nanofluid is compared to the conventional systems which use water as the working fluid. The results indicate that the use of nanofluid of 6% improves the heat transfer rate up to 36.8% with respect to pure water. Therefore, using the Al2O3/water nanofluid instead of water can be a great choice when better heat transfer is needed.</p>2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1854RELIABLE ROBUST CONTROLLER FOR HALF-CAR ACTIVE SUSPENSION SYSTEMS BASED ON HUMAN-BODY DYNAMICS2017-10-15T22:20:42+02:00Mohammad Gudarzimohammad.gudarzi@gmail.comThe paper investigates a non-fragile robust control strategy for a half-car active suspension system considering human-body dynamics. A 4-DoF uncertain vibration model of the driver’s body is combined with the car’s model in order to make the controller design procedure more accurate. The desired controller is obtained by solving a linear matrix inequality formulation. Then the performance of the active suspension system with the designed controller is compared to the passive one in both frequency and time domain simulations. Finally, the effect of the controller gain variations on the closed-loop system performance is investigated numerically.2016-08-02T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1637MODELS FOR INTRALAMINAR DAMAGE AND FAILURE OF FIBER COMPOSITES - A REVIEW2017-10-15T22:20:43+02:00Klaus Rohwerklaus.rohwer@dlr.de<p>In order to fully exploit the potential of structures made from fiber composites, designers need to know how damage occurs and develops and under what conditions the structure finally fails. Anisotropy and inhomogeneity cause a rather complex process of damage development which may be one reason for an exceptionally large number of existing models. This paper intends to provide an overview over those models and give some hints about current developments. As such it is an updated version of a recent publication [1]. The survey is limited to laminates from unidirectional layers out of straight continuous fiber polymer composites under quasi-static loading. Furthermore, focus is laid on intralaminar damage.<br />Many failure models smear out the inhomogeneity between fibers and the matrix. Simply limiting each stress component separately can lead to surprisingly good results as documented in the first World-Wide Failure Exercise. Interpolation criteria consider mutual influence of normal and shear stresses, predominantly through a quadratic failure condition. Traditionally one distinguishes between interpolation criteria and physically based ones. As an important physical effect the difference between fiber failure and inter-fiber failure is considered. Furthermore, stress invariants are taken as a basis, increased shear strength under compression is accounted for, and characteristic failure modes are captured. Fibers and the matrix material are characterized by a large disparity in stiffness and strength. Micromechanical models consider this inhomogeneity but suffer from the difficulty to determine relevant material properties. Compressive strength in fiber direction has attracted special attention. However, the role of kink band formation, which is observed in the failure process, seems to be not yet fully understood.<br />In summary it must be concluded that despite the tremendous effort which has been put into the model development the damage and failure simulation of fiber composites are not in a fully satisfying state. That is partly due to lack of accurate and reliable test results.</p><p> </p>2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/711AN ADVANCED COARSE-FINE SEARCH APPROACH FOR DIGITAL IMAGE CORRELATION APPLICATIONS2017-10-15T22:20:42+02:00Samo Simončičsamo.simoncic@fs.uni-lj.siMelita Kompolšekmelita.kompolsek@gmail.comPrimož Podržajprimoz.podrzaj@fs.uni-lj.siThe paper presents a newly developed fine search algorithm used in the application of digital correlation. In order to evaluate its performance a special purpose application was developed using C# programming language. The algorithm was then tested on a pre-prepared set of the computer generated speckled images. It turned out to be much faster than the conventional fine search algorithm. Consequently, it is a major step forward in a never ending quest for a fast digital correlation execution with sub pixel accuracy.<!--?xml:namespace prefix = "o" ns = "urn:schemas-microsoft-com:office:office" /-->2016-04-01T00:00:00+02:00Copyright (c) 2016 http://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1210EXPERIMENTAL FORCED SOLAR THIN LAYER GINGER DRYING2017-10-15T22:20:43+02:00Mahesh Kumarmk_shandilya@yahoo.comIn this research paper, the convective and the evaporative heat transfer coefficients of ginger (zingiber officinale) drying in an indirect solar cabinet dryer under the induced forced convection mode is presented. Experiments were conducted during the month of March 2015 under the climatic conditions of Hisar, India (29°5’5”N latitude and 75°45’55”E longitude). The experimental data obtained for solar drying of a constant ginger mass of 150 g has been used to determine constants ‘C’ and ‘n’ in the Nusselt number expression using linear regression analysis; consequently, the convective and the evaporative heat transfer coefficients have been evaluated. The average value of constants ‘C’ and ‘n’ were evaluated as 0.999 and 0.318, respectively. The average values of the convective and the evaporative heat transfer coefficients were found to be 3.95 W/m2 °C and 160.47 W/m2 °C, respectively, for the given mass samples of ginger. The average collector efficiency was observed to be 14.5%. The experimental error in terms of percentage uncertainty was found to be 20.87%.2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1332BENDING VIBRATION AND STABILITY OF A MULTIPLE-NANOBEAM SYSTEM INFLUENCED BY TEMPERATURE CHANGE2017-10-15T22:20:43+02:00Danilo Karličićdanilozmaj@gmail.comSanja Ožvatsanjao@uns.ac.rsMilan Cajićcaja84@gmail.comPredrag Kozićkozicp@yahoo.comRatko Pavlovićratko@masfak.ni.ac.rsIn this study, we analyzed the bending vibration and stability of a multiple-nanobeam system (MNBS) coupled in elastic medium and influenced by temperature change and compressive axial load. The MNBS is modeled as the system consisting of a set of m identical and simply supported nanobeams mutually connected by Winkler’s type elastic layers. According to the Euler - Bernoulli beam and nonlocal thermo-elasticity theory, the system of m coupled partial differential equations is derived and solved by means of the method of separation of variables as well as the trigonometric one. Analytical solutions for natural frequencies and critical buckling loads of elastic MNBS are obtained. The effects of nonlocal parameter, temperature change and the number of nanobeams on the natural frequencies and the buckling loads are investigated through numerical examples. Thus, this work can represent a starting point to examine dynamical behavior and design of complex nanobeam structures, nanocomposites and nanodevices under the influence of various physical fields.2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1364A STUDY OF THIN FILM LUBRICATION AT NANOSCALE FOR A FERROFLUID BASED INFINITELY LONG ROUGH POROUS SLIDER BEARING2017-10-15T22:20:43+02:00Jimit R. Patelpatel.jimitphdmarch2013@gmail.comGunamani Deherigm.dehri@rediffmail.comThe study aims at analyzing the performance of a ferrofluid-based infinitely long rough porous slider bearing which makes use of thin film lubrication at nanoscale. The stochastic model of Christensen and Tonder has been employed to analyze the effect of surface roughness while the Neuringer-Rosensweig’s model has been adopted to study the magnetization effect. The pressure distribution in the bearing system has been obtained by solving the associated stochastically averaged Reynolds type equation. The results indicate that although the transverse roughness is supposed to affect the bearing system adversely, the situation remains fairly better in the case of thin film lubrication at nanoscale. In fact, the consideration of thin film lubrication at nanoscale results in an all round improved performance, even for lower strength of the magnetic intensity. However, the couple stress adds a little more to this positive effect.2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1379SOLAR VACUUM TUBE INTEGRATED SEAWATER DISTILLATION - AN EXPERIMENTAL STUDY2017-10-15T22:20:43+02:00Selcuk Selimliselcukselimli@karabuk.edu.trZiyaddin Receblizrecebli@karabuk.edu.trSemra Ulkersmrulkr@uludag.edu.trThe subject of this study is the seawater distillation process enhancement through integration of the solar vacuum tube into the system. Positive effects on the rate of distillated freshwater achieved by means of the enhanced system have been investigated experimentally. Experiments were done in the Turkish city of Samsun in the Black Sea region. A distillation pond setup having the volume of 0.015m3 and a water surface area of 0.24m2 was constructed. The distillation pond is covered with a condensation glass and also equipped with a 0.15m solar vacuum tube that is inclined at an angle of 30o to the ground, a feed water tank connected with a ball cock, and distillated fresh water tank. Experimental results have shown that the rate of distilled fresh water was enhanced for about 62.5% by integrating the solar vacuum tube and the natural distillation pond. Isolation of the condensation glass not only prevents the light transmission to the pond but also heat loss from the pond; hence the rate of the distillated fresh water is increased for about 137.5% due to the natural distillation.2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1521LIMITING PROFILE OF AXISYMMETRIC INDENTER DUE TO THE INITIALLY DISPLACED DUAL-MOTION FRETTING WEAR2017-10-15T22:20:43+02:00Qiang Liqiang.li@tu-berlin.deRecently the final worn shape of elastic indenters due to fretting wear was analytically solved using the method of dimensionality reduction. In this paper we extend this model to dual-motion fretting wear and take into account that the indenter is initially pressed with constant indentation depth and moved horizontally with constant displacement. Two key parameters, the maximal indentation depth during oscillation and the stick area radius in the final state as well as the liming shape of indenter are analytically calculated. It is shown that the oscillation amplitudes and the initially indented or moved displacements have an influence on the final shaking-down shape.2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1629MU-SYNTHESIS BASED ACTIVE ROBUST VIBRATION CONTROL OF AN MRI INLET2017-10-15T22:20:43+02:00Atta Oveisiatta.oveisi@gmail.comTamara Nestorovićtamara.nestorovic@rub.de<p class="Abstract">In this paper, a robust control technique based on μ-synthesis is employed in order to investigate the vibration control of a funnel-shaped structure that is used as the inlet of a magnetic resonance imaging (MRI) device. MRI devices are widely subjected to the vibration of the magnetic gradient coil which then propagates to acoustic noise and leads to a series of clinical and mechanical problems. In order to address this issue and as a part of noise cancellation study in MRI devices, distributed piezo-transducers are bounded on the top surface of the funnel as functional sensor/actuator modules. Then, a reduced order linear time-invariant (LTI) model of the piezolaminated structure in the state-space representation is estimated by means of a predictive error minimization (PEM) algorithm as a subspace identification method based on the trust-region-reflective technique. The reduced order model is expanded by the introduction of appropriate frequency-dependent weighting functions that address the unmodeled dynamics and the augmented multiplicative modeling uncertainties of the system. Then, the standard D-K iteration algorithm as an output-feedback control method is used based on the nominal model with the subordinate uncertainty elements from the previous step. Finally, the proposed control system implemented experimentally on the real structure is to evaluate the robust vibration attenuation performance of the closed-loop system.</p>2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1689MODAL TRIGGERED NONLINEARITIES FOR DAMAGE LOCALIZATION IN THIN WALLED FRC STRUCTURES – A NUMERICAL STUDY2017-10-15T22:20:43+02:00Tobias Rademachertobias.kaempf@tu-berlin.deManfred Zehnmanfred.zehn@tu-berlin.de<p>This paper presents a novel method for detecting locations of damages in thin walled structural components made of fiber reinforced composites (FRC). Therefore, the change of harmonic distortion, which is found by current research to be very sensitive to delamination, under resonant excitation will be derived from FEM-simulation. Based on the linear modal description of the undamaged structure and the damage-induced nonlinearities represented by a nonlinear measure, two spatial damage indexes have been formulated.<br />The main advantage of this novel approach is that the information about the defect is represented mainly by changes in the modal harmonic distortion (MHD), which just needs to be measured in one (or few) structural points. The spatial resolution is given by the pairwise coupling of the MHD with the corresponding mode shapes.</p>2016-04-01T00:00:00+02:00Copyright (c) 2016 Facta Universitatis, Series: Mechanical Engineeringhttp://casopisi.junis.ni.ac.rs/index.php/FUMechEng/article/view/1429FOREWORD2017-10-15T22:20:45+02:00Miroslav Trajanovićtraja@masfak.ni.ac.rsOsiris Canciglieri Jrosiris.canciglieri@pucpr.br<p>Foreword to the thematic issue entitled:</p><p><em>BIOMEDICAL ENGINEERING - ONE OF THE GREATEST ENGINEERING CHALLENGES</em></p>2015-12-09T00:00:00+01:00Copyright (c) 2015 Facta Universitatis, Series: Mechanical Engineering