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Facta Universitatis, Series : Mechanical Engineering
Journal Prestige (SJR): 0.227
Citation Impact (citeScore): 1
Number of Followers: 6  

  This is an Open Access Journal Open Access journal
ISSN (Print) 0354-2025 - ISSN (Online) 2335-0164
Published by U of Niš Homepage  [12 journals]
  • PARAMETRIC STUDY OF A CNC TURNING PROCESS USING DISCRIMINANT ANALYSIS

    • Authors: Baneswar Sarker, Shankar Chakraborty
      Abstract: In the present day manufacturing scenario, computer numerical control (CNC) technology has evolved out as a cost effective process to perform repetitive, difficult and unsafe machining tasks while fulfilling the dynamic requirements of high dimensional accuracy and low surface finish. Adoption of CNC technology would help an organization in achieving enhanced productivity, better product quality and higher flexibility. In this paper, an endeavor is put forward to apply discriminant analysis as a multivariate statistical tool to investigate the effects of speed, feed, depth of cut, nose radius and type of the machining environment of a CNC turning center on surface roughness, tool life, cutting force and power consumption. Simultaneous discrimination analysis develops the corresponding discriminant function for each of the responses taking into account all the input parameters together. On the contrary, step-wise discriminant analysis develops the same functions while considering only those significant input parameters influencing the responses. Higher values of hit ratio and cross-validation percentage prove the application of both the discriminant functions as effective prediction tools for achieving enhanced performance of the considered CNC turning operation.
      PubDate: 2021-08-29
      Issue No: Vol. 19, No. 3 (2021)
       
  • FFT-BASED IMPLEMENTATION OF THE MDR TRANSFORMATIONS FOR HOMOGENEOUS AND
           POWER-LAW GRADED MATERIALS

    • Authors: Emanuel Willert
      Abstract: It is shown how the Abel transform solution to the general axisymmetric normal contact problem for homogeneous and power-law graded elastic materials, which is paramount for the solution of different classes of tribological problems with the help of the method of dimensionality reduction (MDR), can be written in terms of explicit convolutions. These can be very efficiently evaluated with the 1D Fast Fourier Transform (FFT), which reduces the numerical complexity of the transformations from the order of N2 for the standard matrix-vector-multiplication (MVM) algorithm to the order of N. Convergence and performance of the proposed method are studied in detail. As an illustrative example a fretting wear simulation based on the new implementation is shown, the results of which are compared to the standard MVM implementation.
      PubDate: 2021-08-15
      Issue No: Vol. 19, No. 3 (2021)
       
  • TOWARDS RELIABLE DECISION-MAKING IN THE GREEN URBAN TRANSPORT DOMAIN

    • Authors: Andrii Shekhovtsov, Jakub Więckowski, Bartłomiej Kizielewicz, Wojciech Sałabun
      Abstract: Operational research is a scientific discipline related to the decision theory that allows determining solutions for specific problems related to, for example, widely understood transport. Increasingly popular in this field are issues related to the domain of the green urban transport. In order to support the decision-making process in this area, methods of multi-criteria decision analysis (MCDA) are used more and more often. However, if we solve a specific problem using different MCDA methods, we get different rankings, as each method has a different methodological basis. Therefore, the challenge is how to make a reliable decision. This paper presents a numerical example from the green urban transport domain, which is solved by six different MCDA methods that return a complete ranking. We measure the similarity of these rankings using coefficients rw and WS, and then we propose a simple way of determining a compromise solution. The obtained compromise ranking is guaranteed to be the best match to the selected MCDA methods' rankings, which is proved in the paper. Finally, possible directions for further development work are identified.
      PubDate: 2021-08-14
      Issue No: Vol. 19, No. 3 (2021)
       
  • SPRING BASED ON FLAT PERMANENT MAGNETS: DESIGN, ANALYSIS AND USE IN
           VARIABLE STIFFNESS ACTUATOR

    • Authors: Bartłomiej Kozakiewicz, Tomasz Winiarski
      Abstract: Modern robot applications benefit from including variable stiffness actuators (VSA) in the kinematic chain. In this paper, we focus on VSA utilizing a magnetic spring made of two coaxial rings divided into alternately magnetized sections. The torque generated between the rings is opposite to the angular deflection from equilibrium and its value increases as the deflection grows – within a specific range of angles that we call a stable range. Beyond the stable range, the spring exhibits negative stiffness what causes problems with prediction and control. In order to avoid it, it is convenient to operate within a narrower range of angles that we call a safe range. The magnetic springs proposed so far utilize few pairs of arc magnets, and their safe ranges are significantly smaller than the stable ones. In order to broaden the safe range, we propose a different design of the magnetic spring, which is composed of flat magnets, as well as a new arrangement of VSA (called ATTRACTOR) utilizing the proposed spring. Correctness and usability of the concept are verified in FEM analyses and experiments performed on constructed VSA, which led to formulating models of the magnetic spring. The results show that choosing flat magnets over arc ones enables shaping spring characteristics in a way that broadens the safe range. An additional benefit is lowered cost, and the main disadvantage is a reduced maximal torque that the spring is capable of transmitting. The whole VSA can be perceived as promising construction for further development, miniaturization and possible application in modern robotic mechanisms.
      PubDate: 2021-07-30
      Issue No: Vol. 19, No. 3 (2021)
       
  • THERMAL OSCILLATION ARISING IN A HEAT SHOCK OF A POROUS HIERARCHY AND ITS
           APPLICATION

    • Authors: Fujuan Liu, Ting Zhang, Chun-Hui He, Dan Tian
      Abstract: A building or a bridge might collapse after a heat shock. This paper shows that a porous hierarchy of a coating can effectively prevent a building or a bridge from such damage. A cocoon’s geometrical structure is studied and its resistance to the heat shock is revealed by a thermal oscillator. The theoretical model reveals an extremely low frequency of the thermal oscillator, which is very important for cocoons’ biomechanism, especially in the heat insulation function. At the same time, it shows that the cocoons have the best thickness to protect the pupa from the environment. In addition, surface temperature measurement of hierarchical mulberry leaves is performed. This work provides new insights into biomimetic design of the protective building and coatings.
      PubDate: 2021-07-30
      Issue No: Vol. 19, No. 3 (2021)
       
  • NUMERICAL INVESTIGATION OF THE INFLUENCE OF THE LINK POSITIONING IN THE
           CORONARY STENT INSIDE THE NORMAL ARTERY: A COMPARATIVE STUDY OF TWO
           COMMERCIAL STENT DESIGNS

    • Authors: Chandrakantha Bekal, Satish Shenoy, Ranjan Shetty
      Abstract: This paper investigates the performance of two commercial stent designs inside the normal artery for induced Von Mises Stress and radial displacement pattern. Investigation focuses on identifying the key design feature of the stent structure responsible for varied stress and displacement pattern. Two commercial stent designs, Supraflex (Stent S) and Yukon Choice (Stent T),are modeled using micro CT images and MIMICS® while idealized models are used for investigation. ANSYS Workbench is used to numerically expand the stent inside an idealized normal artery with inflation pressure. The stent and the artery are modeled using elastic-plastic and hyperelastic material models, respectively. The results suggest crucial influence of the link positioning in inducing an area of higher Von Mises Stress and stress gradient. The locations of a higher stress gradient are those in line with unbound stent crowns. Also, higher and uniform arterial displacement can be observed in the locations in line with the bound crown. Results also suggested a considerable difference in arterial distortion induced by two designs, causes for which can also be attributed to the differences in the link placement. The study suggests that the link connections play a crucial role in setting up stress field/radial displacement. Suitable modification of the link positioning can reduce the higher stress gradient and arterial distortion, which probably can reduce arterial injury.
      PubDate: 2021-06-25
      Issue No: Vol. 19, No. 3 (2021)
       
  • IRREVERSIBILITY ANALYSIS IN Al2O3-WATER NANOFLUID FLOW WITH VARIABLE
           PROPERTY

    • Authors: Krishan Kumar, Prathvi Raj Chauhan, Rajan Kumar, Rabinder Singh Bharj
      Abstract: The present numerical work deals with the optimization of the micro-channel heat sink using irreversibility analysis. The nanofluid of Al2O3-water with the different nanoparticles concentration and the temperature-dependent property is chosen as a coolant. The flow is considered as fully developed, steady, and laminar in the constant cross-section of circular channels. Navier-Stokes and energy equations are solved for a single-phase flow with total mass flow rate and heat flow rate as constant. The objective functions related to the frictional and heat transfer irreversibilities are framed to assess the performance of the micro-channel heat sink. The optimum channel diameter corresponding to the optimum number of channels is determined at the lowest total irreversibility for both constant property solution and variable property solution. Designed optimum diameter is observed maximum for 2.5% Al2O3-water nanofluid with μ(T) variation followed by 1% Al2O3-water nanofluid with μ(T) variation, 2.5% Al2O3-water nanofluid with constant property solution, and 1% Al2O3-water nanofluid with constant property solution.
      PubDate: 2021-06-25
      Issue No: Vol. 19, No. 3 (2021)
       
  • ASSESSMENT OF THE QUADRUPLE INJECTION STRATEGY OVER TRIPLE INJECTIONS TO
           IMPROVE EMISSIONS, PERFORMANCE AND NOISE OF THE AUTOMOTIVE DIESEL ENGINE

    • Authors: Sanjoy Biswas, Achintya Mukhopadhyay
      Abstract: The present study aims at investigating effectiveness of the quadruple (early-pilot-main-after [epMa]) injection strategy over three different triple [early-main-after (eMa), early-pilot-main (epM) and pilot-main-after (pMa)] injection scheduling in terms of emissions, performance [brake specific fuel consumption (BSFC), torque, brake thermal efficiency (BTE) and fuel economy] and noise. The experimentation was carried out on a heavy-duty BS-IV diesel engine with 45% EGR fraction and fixed main injection (Crank-angle) scheduling at eight different RPMs and three loads of engine (20%, 60% and 100%) using design of experiments(DOE).     This comprehensive study showed that the quadruple injection strategy provides optimum results in both performance and emissions compared to the promising three triple injection strategy. The quadruple injection strategy exhibits the best BTE at all operating conditions and best BSFC at medium to high-speed zone around 0.5–1% inline to reduce combustion noise (CN) level, especially at low speeds and low to medium load of 0.2–2.2 dBA. Among triple injections, the pMa shows the best performance in BSFC, BTE, smoke and THC emissions. The epM is the best in the CO emissions and torque performance in the low-speed zone. Smoke value is marginally higher for the epMa at low to medium speed than the pMa, although average smoke emissions were the best. Taken together, the overall PM emission level was marginally better than Triple Injections, due to the impact of double pilots in combination with post-injection. In addition, NOx emissions were improved (around 3–6%) significantly with quadruple than with triple injections. The epMa injection scheduling also showed improvement in constant speed fuel economy and in pass-by-noise at the vehicle.
      PubDate: 2021-06-25
      Issue No: Vol. 19, No. 3 (2021)
       
  • NUMERICAL SIMULATION OF SINGLE POINT INCREMENTAL FORMING FOR ASYMMETRIC
           PARTS

    • Authors: George-Christopher Vosniakos, Gabriel Pipinis, Protesilaos Kostazos
      Abstract: Single point incremental forming (SPIF) that will produce non-symmetric sheet metal parts has been rarely dealt with so far. SPIF of a Francis hydro-turbine vane made of aluminum alloy is studied as a typical example in this work. At first, a concave geometry, encompassing the desired vane shape is designed, from which the formed part will be ultimately cut out. The necessary SPIF toolpaths are created by using the CAM software normally used for milling processes. Based on these toolpaths, a finite element simulation is setup using shell elements with a particular emphasis on substantial time scaling and due care on tool-sheet contact parameters. For validation purposes the part was manufactured and digitized by a white light scanner. It exhibited tolerable deviation from the targeted nominal geometry. Simulation predicted a significant part of this deviation, proving its indispensability in checking out toolpaths and process parameters for non-symmetric parts, yet at non-negligible computational time.
      PubDate: 2021-06-01
      Issue No: Vol. 19, No. 3 (2021)
       
  • STUDY ON VIBRATION RESPONSE OF A NON-UNIFORM BEAM WITH NONLINEAR BOUNDARY
           CONDITION

    • Authors: Peng Wang, Nan Wu, Haitao Luo, Zhili Sun
      Abstract: Forced vibration of non-uniform beam with nonlinear boundary condition is studied in this paper by proposing an iterative model combining Adomian Decomposition Method and modal analysis. An exponentially tapered beam with a hardening nonlinearity spring boundary is simulated as a case study. The model accuracy is proved by comparing iteration results and analysis solutions with linear and weakly nonlinear boundary conditions. Sin-weep nonlinear frequency spectrum is then obtained by the proposed model. The influence of boundary nonlinearity on the vibration response of non-uniform beam is analyzed. And the effect of different excitation amplitudes on nonlinearity in the vibration response is studied. The mathematical model and numerical solutions proposed in this paper can be used to solve and analysis broad vibration problems on general non-uniform beams with different nonlinear boundary conditionsunder various excitations.
      PubDate: 2021-06-01
      Issue No: Vol. 19, No. 3 (2021)
       
  • IMPROVEMENT OF SURFACE QUALITY OF Ti-6Al-4V ALLOY BY POWDER MIXED
           ELECTRICAL DISCHARGE MACHINING USING COPPER POWDER

    • Authors: Rafiqul Haque, Mukandar Sekh, Golam Kibria, Shamim Haidar
      Abstract: Electrical Discharge Machining (EDM) is one of the most popular non-conventional machining processes that are being used in many high precision manufacturing industries. To increase the EDM performance, a hybrid technique, namely, powder mixed electrical discharge machining (EDM) (PMEDM) is generally used for getting more precise requirements. In this study, an experimental investigation is carried out in order to explore the machining performance of the PMEDM process on Ti-6Al-4V alloy using copper (Cu) powder in the EDM oil dielectric. Taguchi’s L18 orthogonal array design has been utilized for design of experiments and the analysis of variance (ANOVA) has been performed with the help of Minitab-19 software. The optimal parametric setting of Cu powder mixed EDM has been found utilizing the Taguchi - Grey Relational Analysis (GRA) integrated approach and also validation of optimal parametric setting is done through experimentation. It is a novel approach for machining Ti-6Al-4V alloy by this PMEDM technique in which the surface quality has been improved significantly with the addition of suitable amount of Cu powder into the dielectric medium.
      PubDate: 2021-05-26
      Issue No: Vol. 19, No. 3 (2021)
       
  • EFFECTS OF ROTATION ON UNSTEADY FLUID FLOW AND FORCED CONVECTION IN THE
           ROTATING CURVED SQUARE DUCT WITH A SMALL CURVATURE

    • Authors: Mohammad Sanjeed Hasan, Ratan Kumar Chanda, Rabindra Nath Mondal, Giulio Lorenzini
      Abstract: In recent years, the analysis of flow disposition in a curved duct (CD) has greatly attracted researchers because it is broadly used in engineering devices. In the present paper, unsteady flow characteristics of energy transfer (HT) in a rotating curved square duct (CSD) have been presented with the aid of spectral method. The key purpose of this study is to explore rotational effects and heat transfer (HT) of the duct. For this purpose, time-evolution calculation is performed over the Taylor number (-1500 ≤ Tr ≤ 1500) and other parameters are fixed; e.g., Dean number (Dn = 1000), Curvature (δ = 0.015) and Prandtl number (Pr = 7.0, for water). Firstly, time-dependent behavior is accomplished for both clockwise and anticlockwise rotations. It is found that the flow instabilities are certainly governed by the change of Tr that has been justified by sketching phase spaces (PS). To observe the flow features, velocities including axial flow (AF), secondary flow (SF) and temperature profiles are disclosed for both rotations; and it is elucidated that 2- to 6-vortex solutions are generated for physically realizable solutions. Axial flow (AF) shows that two maximum-velocity regimes are produced which induces secondary flow (SF), and, consequently, a strong bonding between the AF and SF has been built up. It is observed that as the rotation is increased, the fluid is mixed considerably which boosts HT in the fluid. Finally, an assessment between the numerical and experimental data has been given, and a good agreement is observed.
      PubDate: 2021-05-21
      Issue No: Vol. 19, No. 3 (2021)
       
  • INVESTIGATION OF THE GLUED INSULATED RAIL JOINTS APPLIED TO CWR TRACKS

    • Authors: Attila Németh, Szabolcs Fischer
      Abstract: This article summarizes the research results related to our own conducted extensive laboratory tests of polymer composite and steel fishplated glued insulated rail joints (GIRJs), namely axial tensile tests as well as vertical static and dynamic tests. The investigation dealt with the examination of GIRJs assembled with steel and special glass-fiber reinforced plastic (polymer composite) fishplates, both of them for CWR railway tracks (i.e. so-called gapless tracks or, in other words, railway tracks with continuously welded rails). The exact rail joint types were MTH-P and MTH-AP, consistently. The MTH P types have been commonly applied for many years in the CWR tracks in Europe, mainly in Hungary. The MTH-AP rail joints consist of fishplates that are produced by the APATECH factory (Russia). They are made of a fiberglass-amplified polymer composite material at high pressure and controlled temperature. This solution can eliminate electrical fishplate lock and early fatigue failures just as it can ensure adequate electrical insulation. The advantage of such rail joints can be that they are probably able to ensure the substitution of the glued insulated rail joints with relatively expensive steel fishplates currently applied by railway companies, e.g. Hungarian State Railways (MÁV). The aim of the mentioned research summarized in this paper is to formulate recommendations on technical applicability and on the technological instructions that are useful in everyday railway operation practice on the basis of the measurements and tests carried out on rail joints in laboratory.
      PubDate: 2021-05-14
      Issue No: Vol. 19, No. 3 (2021)
       
  • LIGHTENING STRUCTURES BY METAL REPLACEMENT: FROM TRADITIONAL GYM EQUIPMENT
           TO AN ADVANCED FIBER-REINFORCED COMPOSITE EXOSKELETON

    • Authors: Cristiano Fragassa
      Pages: 155 - 174
      Abstract: A redesign procedure used for introducing new functional properties in innovative gym equipment is here reported. It is based on a metal replacement action where a tempered steel was firstly replaced by an aluminum alloy and then by high strength-to-weight fiber-reinforced polymers. The effect of fiber properties (as strength and volume ratio) and plies stacking sequences (as thicknesses and orientation) were investigated. Numerical analyses, done by Ansys ACP, allowed evaluating the stress-strain behavior in realistic boundaries and quasi-static loads, comparing materials and layouts in terms of stiffness. The single-layered shell method with additional integration points was preferred as a technique for discretizing composite laminates. Maximum Principal Stress and Maximum Distortion Energy (Tsai-Hill) were applied as anisotropic failure criteria. Changes in geometry were also considered given their relevant effects on parts and processes. Specifically, this paper is focused on a representative component of the main kinematic chain (the ‘forearm’) and details the different redesign phases for that part. The chosen solution consisted of 14 layers of unidirectional and bidirectional carbon fiber-reinforced pre-pregs, offering a 68 % weight reduction with respect to a solid aluminum component with equal stiffness. The part was manufactured by hand lay-up and cured in autoclave. This redesign practice was extended to the rest of the equipment allowing its transformation into an exoskeleton.
      PubDate: 2021-07-11
      DOI: 10.22190/FUME201215043F
      Issue No: Vol. 19, No. 3 (2021)
       
  • EXCEL VBA-BASED USER DEFINED FUNCTIONS FOR HIGHLY PRECISE COLEBROOK’S
           PIPE FLOW FRICTION APPROXIMATIONS: A COMPARATIVE OVERVIEW

    • Authors: Dejan Brkić, Zoran Stajić
      Pages: 253 - 269
      Abstract: This review paper gives Excel functions for highly precise Colebrook’s pipe flow friction approximations developed by users. All shown codes are implemented as User Defined Functions – UDFs written in Visual Basic for Applications – VBA, a common programming language for MS Excel spreadsheet solver. Accuracy of the friction factor computed using nine to date the most accurate explicit approximations is compared with the sufficiently accurate solution obtained through an iterative scheme which gives satisfying results after sufficient number of iterations. The codes are given for the presented approximations, for the used iterative scheme and for the Colebrook equation expressed through the Lambert W-function (including its cognate Wright ω-function). The developed code for the principal branch of the Lambert W-function has additional and more general application for solving different problems from variety branches of engineering and physics. The approach from this review paper automates computational processes and speeds up manual tasks.
      PubDate: 2021-07-11
      DOI: 10.22190/FUME210111044B
      Issue No: Vol. 19, No. 3 (2021)
       
  • STUDY TOWARDS THE TIME-BASED MCDA RANKING ANALYSIS – A SUPPLIER
           SELECTION CASE STUDY

    • Authors: Bartłomiej Kizielewicz, Jakub Więckowski, Andrii Shekhovtsov, Jarosław Wątróbski, Radosław Depczyński, Wojciech Sałabun
      Pages: 381 - 399
      Abstract: Decision-making processes increasingly use models based on various methods to ensure professional analysis and evaluation of the considered alternatives. However, the abundance of these methods makes it difficult to choose the proper method to solve a given problem. Also, it is worth noting whether different results can be obtained using different methods within a single decision problem. In this paper, we used three selected Multi-Criteria Decision Analysis (MCDA) methods called COMET, TOPSIS, and SPOTIS in order to examine how the obtained rankings vary. The selection of material suppliers was taken into consideration. The equal weights, entropy and standard deviation methods were used to determine the weights for criteria. Final preferences values were then compared with the WS similarity coefficient and weighted Spearman correlation coefficient to check the similarity of the received rankings. It was noticed that in the given problem, all of the methods provide highly correlated results, and the obtained positional rankings are not significantly different. However, practical conclusions indicate the need to look for improved solutions in the correct and accurate assessment of suppliers in a given period.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210130048K
      Issue No: Vol. 19, No. 3 (2021)
       
  • REGIONAL AIRCRAFT SELECTION WITH FUZZY PIPRECIA AND FUZZY MARCOS: A CASE
           STUDY OF THE TURKISH AIRLINE INDUSTRY

    • Authors: Mahmut Bakır, Şahap Akan, Emircan Özdemir
      Pages: 423 - 445
      Abstract: Aircraft selection is an important issue in achieving long-term goals in the airline industry. For this issue in which multiple conflicting criteria are involved, the extant literature points to the use of multi-criteria decision-making (MCDM) methods. In this respect, this study aims to propose a systematic and comprehensive framework with a focus on the regional aircraft selection perspective. To achieve this, an integrated fuzzy Pivot Pairwise Relative Criteria Importance Assessment (F-PIPRECIA) and fuzzy Measurement Alternatives and Ranking according to the Compromise Solution (F-MARCOS) approach was employed. In this study, in which six regional aircraft alternatives were evaluated according to 14 criteria, data were collected from five decision experts. As a result, it was found that the most pivotal criterion is C33 (Operational Cost), and the least important criterion is C12 (NOx). In addition, CRJ1000 was identified as the most promising regional aircraft alternative. The results of the application were further validated by applying a three-stage sensitivity analysis. The proposed structure is anticipated to assist airline managers in aircraft selection decisions under uncertainty by offering a robust and systematic tool.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210505053B
      Issue No: Vol. 19, No. 3 (2021)
       
  • D NUMBERS – FUCOM – FUZZY RAFSI MODEL FOR SELECTING THE GROUP OF
           CONSTRUCTION MACHINES FOR ENABLING MOBILITY

    • Authors: Darko Božanić, Aleksandar Milić, Duško Tešić, Wojciech Salabun, Dragan Pamučar
      Pages: 447 - 471
      Abstract: The paper presents a hybrid model for decision-making support based on D numbers, the FUCOM method and fuzzified RAFSI method, used for solving the selection of the group of construction machines for enabling mobility. By applying D numbers, the input parameters for the calculation of the weight coefficients of the criteria were provided. The calculation of the weight coefficients of the criteria was performed using the FUCOM method. The best alternative was selected using the fuzzified method, which was conditioned by the specificity of the issue so that in this case, the selection of the best alternative was made using the fuzzified RAFSI method.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210318047B
      Issue No: Vol. 19, No. 3 (2021)
       
  • EVALUATION OF LOGISTIC FLOWS IN GREEN SUPPLY CHAINS BASED ON THE COMBINED
           DEMATEL-ANP METHOD

    • Authors: Nikita Osintsev, Aleksandr Rakhmangulov, Vera Baginova
      Pages: 473 - 498
      Abstract: Supply chains and transport corridors have a significant impact on the socio-economic and environmental situation in the regions where the elements of the logistics infrastructure are located. The achievement of the goals of the concept of sustainable development in these regions is ensured, among other things, as a result of the formation of green supply chain management (GSCM), that is, as a result of changes in existing approaches to supply chain management. Analysis of the practice of supply chain management showed a wide variety of parameters and indicators of logistics flows used in decision-making at different stages of managing these flows. The authors propose a universal system of the logistic flows parameters and indicators for the GSCM, corresponding to the principles of the concept of sustainable development. A methodology for ranking indicators of logistics flows based on a combined DEMATEL-ANP method has been developed. The results of a case study on the evaluation of logistics flows for the GSCM are presented. The ranks of logistics flow indicators obtained in the study are proposed to be used in GSCM to adjust of the logistics flows actual parameters to achieve the goals of the concept of sustainable development.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210505061O
      Issue No: Vol. 19, No. 3 (2021)
       
  • A NEW INTEGRATED GREY MCDM MODEL: CASE OF WAREHOUSE LOCATION SELECTION

    • Authors: Alptekin Ulutaş, Figen Balo, Lutfu Sua, Ezgi Demir, Ayşe Topal, Vladimir Jakovljević
      Pages: 515 - 535
      Abstract: Warehouses link suppliers and customers throughout the entire supply chain. The location of the warehouse has a significant impact on the logistics process. Even though all other warehouse activities are successful, if the product dispatched from the warehouse fails to meet the customer needs in time, the company may face with the risk of losing customers. This affects the performance of the whole supply chain therefore the choice of warehouse location is an important decision problem. This problem is a multi-criteria decision-making (MCDM) problem since it involves many criteria and alternatives in the selection process. This study proposes an integrated grey MCDM model including grey preference selection index (GPSI) and grey proximity indexed value (GPIV) to determine the most appropriate warehouse location for a supermarket. This study aims to make three contributions to the literature. PSI and PIV methods combined with grey theory will be introduced for the first time in the literature. In addition, GPSI and GPIV methods will be combined and used to select the best warehouse location. In this study, the performances of five warehouse location alternatives were assessed with twelve criteria. Location 4 is found as the best alternative in GPIV. The GPIV results were compared with other grey MCDM methods, and it was found that GPIV method is reliable. It has been determined from the sensitivity analysis that the change in criteria weights causes a change in the ranking of the locations therefore GPIV method was found to be sensitive to the change in criteria weights.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210424060U
      Issue No: Vol. 19, No. 3 (2021)
       
  • AN INTEGRATED DECISION-MAKING MODEL FOR EFFICIENCY ANALYSIS OF THE
           FORKLIFTS IN WAREHOUSING SYSTEMS

    • Authors: Eldina Mahmutagić, Željko Stević, Zdravko Nunić, Prasenjit Chatterjee, Ilija Tanackov
      Pages: 537 - 553
      Abstract: In the logistics world, special attention should be given to warehousing systems, cost rationalization, and improvement of all the factors that affect efficiency and contribute to smooth functioning of logistics subsystems. In real time industrial practice, the issue of evaluating and selecting the most appropriate forklift involves a complex decision-making problem that should be formulated through an efficient analytical model. The forklifts efficiency plays a very important role in the company. The forklifts are being used on a daily basis and no logistical processes could be done without them. Therefore, it has been decided to determine their efficiency, which will contribute to the optimization of the process in this logistics subsystem. This study puts forward an integrated forklift selection model using Data Envelopment Analysis (DEA), Full Consistency Method (FUCOM) and Measurement Alternatives and Ranking According to the Compromise Solution (MARCOS) methods. Five input parameters (regular servicing costs, fuel costs, exceptional servicing costs, total number of all minor accidents and damage caused by forklifts) and one output parameter (number of operating hours) were first identified to assess efficiency of eight forklifts in a warehousing system of the Natron-Hayat company using the DEA model. This step allows sorting of efficient forklifts which are subsequently evaluated and ranked using FUCOM and MARCOS methods. A sensitivity analysis is also performed in order to check reliability and accuracy of the results. The findings of this research clearly show that the proposed decision-making model can significantly contribute to all spheres of business applications.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210416052M
      Issue No: Vol. 19, No. 3 (2021)
       
  • AN EXTENDED SINGLE-VALUED NEUTROSOPHIC AHP AND MULTIMOORA METHOD TO
           EVALUATE THE OPTIMAL TRAINING AIRCRAFT FOR FLIGHT TRAINING ORGANIZATIONS

    • Authors: Çağlar Karamaşa, Darjan Karabasevic, Dragisa Stanujkic, Alireza Rezanezhad Kookhdan, Arunodaya Raj Mishra, Mehmet Ertürk
      Pages: 555 - 578
      Abstract: Aircraft’s training is crucial for a flight training organization (FTO). Therefore, an important decision that these organizations should wisely consider the choice of aircraft to be bought among many alternatives. The criteria for evaluating the optimal training aircraft for FTOs are collected based on the survey approach. Single valued neutrosophic sets (SVNS) have the degree of truth, indeterminacy, and falsity membership functions and, as a special case, neutrosophic sets (NS) deal with inconsistent environments. In this regard, this study has extended a single-valued neutrosophic analytic hierarchy process (AHP) based on multi-objective optimization on the basis of ratio analysis plus a full multiplicative form (MULTIMOORA) to rank the training aircraft as the alternatives. Moreover, a sensitivity analysis is performed to demonstrate the stability of the developed method. Finally, a comparison between the results of the developed approach and the existing approaches for validating the developed approach is discussed. This analysis shows that the proposed approach is efficient and with the other methods.
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210521059K
      Issue No: Vol. 19, No. 3 (2021)
       
  • COMBINING THE SUITABILITY-FEASIBILITY-ACCEPTABILITY (SFA) STRATEGY WITH
           THE MCDM APPROACH

    • Authors: Sarfaraz Hashemkhani Zolfani, Ramin Bazrafshan, Parnian Akaberi, Morteza Yazdani, Fatih Ecer
      Pages: 579 - 600
      Abstract: Suitability-Feasibility-Acceptability (SFA) is a fundamental tool for the development and selection of strategy. Any type of decision-making problem can be resolved by Multiple Criteria Decision Making (MCDM) methods. In this research, we explore the complexity of determining the proper goal market for the Chilean fish market. This study proposed a combined approach of SFA with MCDM methods in a real case study. The proposed structure helps to assign the best market for Chilean export fish to West Asia. Three countries (Saudi Arabia, the United Arab Emirates, and Oman) are selected as a target market in this region, and then related criteria are obtained from various sources. In order to develop a new market for the Chilean fishery industry, five major criteria, including the potential of a target market, region's economic attractiveness, consumption of the seafood, location, cost of transportation, and country risks, were selected based on the SFA framework. Calculating the criteria weights is performed by the Best-Worst (BWM) method, and ordering the alternatives is operated by Measurement Alternatives and Ranking according to compromise Solution (MARCOS) methods. The results showed that Oman is the best destination (importer) for the Chilean fish market (Salmon fish as the case).
      PubDate: 2021-10-06
      DOI: 10.22190/FUME210711062Z
      Issue No: Vol. 19, No. 3 (2021)
       
  • SELF-CONSISTENCY CONDITIONS IN STATIC THREE-BODY ELASTIC TANGENTIAL
           CONTACT

    • Authors: Emanuel Willert
      Abstract: The contact problem for an elastic third-body particle between two elastic half-spaces is considered. The contact is assumed to consist of three Hertzian contact spots. The normal and tangential contact problems are analyzed analytically considering partial slip in the contacts and the influence of third-body weight. Self-consistency conditions between global equilibrium and the contact solution are formulated to give criteria, under which circumstances static slip and stationary sliding are possible states for the third-body particle. The sliding case is solved in detail.

      PubDate: 2021-04-30
      Issue No: Vol. 19, No. 1 (2021)
       
  • EXPERIMENTAL RESEARCH INTO MARBLE CUTTING BY ABRASIVE WATER JET

    • Authors: Andrzej Perec, Aleksandra Radomska-Zalas, Anna Fajdek-Bieda
      Abstract: The article presents research on the erosion of the metamorphic rock - marble by the Abrasive Water Jet (AWJ). The fragmentation of abrasive grains during the erosion process is demonstrated. The effect of the cutting process's most important parameters as traverse speed, nozzle ID, and abrasive mass flow rate, on the maximum cutting depth, is shown. To create a mathematical-statistic model of the erosion process, the methodology of the response surface (RSM) was used for modeling. The polynomial equation of the second degree is chosen for developing the regression model. Studies have shown the optimal parameters of the process, to reach the highest depth of the cut. Additionally, the erosion wear of a focusing tube under different process conditions is presented.
      PubDate: 2021-04-29
      Issue No: Vol. 19, No. 1 (2021)
       
  • INVESTIGATION OF INFLUENCES OF FABRICATION TOLERANCES ON OPERATIONAL
           CHARACTERISTICS OF PIEZO-ACTUATED STICK-SLIP MICRO-DRIVES

    • Authors: Xuan-Ha Nguyen, Hung-Anh Nguyen
      Abstract: Piezo-actuated stick-slip micro-drives (PASSMDs) are often used in microrobotic applications due to their advantages of a straightforward design and good operational characteristics. In this work, influences of fabrication tolerances on operational characteristics of PASSMDs are theoretically investigated. A dynamic model describing the whole macroscopic movement of the driver’s runner and the actuators, and the microscopic behavior of the frictional contacts using the method of dimensionality reduction, was used. Three essential parameters of the drives including the angle between working surfaces of the runner, the alignment angle between two actuator blocks on each side of the runner, and the stiffness of an individual actuator, whose values are impacted by the tolerance of the fabrication and assembly process, were considered as the input of the investigation. By performing hybrid-dynamic simulations, influences of these parameters on the drives' operational characteristics, including the repeatability of the step length, the critical amplitude phenomenon, and the maximal-achievable driving frequency/velocity, were evaluated. Simulation results show that these parameters significantly influence on the characteristics of the drives. The contribution of this work is so important that several important phenomena of PASSMDs, which are experimentally detected, are physically explained for the first time. The results of this work could help designers to optimize for better generations of PASSMDs.
      PubDate: 2021-04-12
      Issue No: Vol. 19, No. 1 (2021)
       
  • RELATION OF KINEMATICS AND CONTACT FORCES IN THREE-BODY SYSTEMS WITH A
           LIMITED NUMBER OF PARTICLES

    • Authors: Kristin M. de Payrebrune
      Abstract: In many tribological systems, an intermediate layer of a limited number of abrasive particles exist. Thereby, the resulting wear and friction phenomena are desirable in many manufacturing processes, such as lapping or polishing, whereas in machine elements, they are unwanted due to reducing lifetime or performance.For a better understanding of the contact phenomena and the interaction of tribological systems with an intermediate layer of a limited number of particles, fundamental investigations are carried out on a tribometer test rig. For this purpose, two test scenarios are investigated, a) the kinematics and contact forces of single geometrically defined particles such as dodecahedron, icosahedron and hexahedron, and b) the contact forces and surface roughness of a layer of silicon carbide particles of different sizes.The measured ratio of tangential to normal force can be used as an indicator of the dominating kinematics of the particles and of the generated surface roughness, respectively. The higher the force ratio, the higher the tendency to slide for a given particle type and paring of particle and counter body.For one geometrically defined particle the short-time Fourier transform additionally helps to distinguish the state of motion since the excited frequencies during rolling are reduced.  For a layer of silicon carbide particles, the velocity and particle size have the strongest influence on the overall motion and the surface roughness produced. Larger particles tend to slide and create more scratches, while smaller particles tend to roll and create indentations in the counter body. Furthermore, for the same particle size, an increase in velocity causes a transition from sliding to rolling, resulting in an increased surface roughness.
      PubDate: 2021-04-12
      Issue No: Vol. 19, No. 1 (2021)
       
  • FOREWORD TO THE THEMATIC ISSUE: WEAR PARTICLE TRANSPORT AND EMISSION:
           MECHANISMS AND ENVIRONMENTAL IMPLICATIONS

    • Authors: Georg-Peter Ostermeyer, Valentin L. Popov
      Abstract: The papers of the present Special Issue as well as a number of papers of the subsequent Issues of Facta Universitatis – Series Mechanical Engineering represent extended versions of the research works presented at the International Workshop "Wear particle transport and emission: Mechanisms and environmental implications" which was carried out online from 24. to 25. February 2021.
      PubDate: 2021-04-01
      Issue No: Vol. 19, No. 1 (2021)
       
  • USER DEFINED GEOMETRIC FEATURE FOR THE CREATION OF THE FEMORAL NECK
           ENVELOPING SURFACE

    • Authors: Miloš Stojković, Milan Trifunović, Jelena Milovanović, Stojanka Arsić
      Abstract: There is a growing demand for application of personalized bone implants (endoprostheses or macro-scaffolds, and fixators) which conform the anatomy of patient. Hence the need for a CAD procedure that enables fast and sufficiently accurate digital reconstruction of the traumatized bone geometry. Research presented in this paper addresses digital reconstruction of the femoral neck fracture. The results point out that User-Defined (geometric) Feature (UDF) concept is the most convenient to use in digital reconstruction of numerous variants of the same topology, such as in this kind of bone region. UDF, named FemoNeck, is developed to demonstrate capability of the chosen concept. Its geometry, controlled by a dozen of parameters, can be easily shaped according to anatomy of femoral neck region of the specific patient. That kind of CAD procedure should use minimally required set of geometric (anatomical) parameters, which can be easily captured from X-ray or Computed Tomography (CT) images. For the statistical analysis of geometry and UDF development we used CT scans of proximal femur of 24 Caucasian female and male adults. The validation of the proposed method was done by applying it for remodeling four femoral necks of four different proximal femurs and by comparing the geometrical congruency between the raw polygonal models gained directly from CT scan and reconstructed models.
      PubDate: 2021-03-28
      Issue No: Vol. 19, No. 1 (2021)
       
  • THE ENHANCED HOMOTOPY PERTURBATION METHOD FOR AXIAL VIBRATION OF STRINGS

    • Authors: Ji-Huan He, Yusry O. El-Dib
      Abstract: A governing equation is established for string axial vibrations with temporal and spatial damping forces by the Hamilton principle. It is an extension of the well-known Klein-Gordon equation. The classical homotopy perturbation method (HPM) fails to analyze this equation, and a modification with an exponential decay parameter is suggested. The analysis shows that the amplitude behaves as an exponential decay by the damping parameter. Furthermore, the frequency equation is established and the stability condition is performed. The modified homotopy perturbation method yields a more effective result for the nonlinear oscillators and helps to overcome the shortcoming of the classical approach. The comparison between the analytical solution and the numerical solution shows an excellent agreement.
      PubDate: 2021-03-25
      Issue No: Vol. 19, No. 1 (2021)
       
  • RECENT IMPROVEMENTS OF THE OPTICAL AND THERMAL PERFORMANCE OF THE
           PARABOLIC TROUGH SOLAR COLLECTOR SYSTEMS

    • Authors: Asaad Yasseen Al-Rabeeah, István Seres, István Farkas
      Abstract: Parabolic trough solar collectors (PTSCs) are commonly used for applications that reach a temperature of up to 500 °C.  Recently, improving the efficiency of PTSCs has been the focus of research because PTSCs have advantages, such as cost and size reduction and improved optical and thermal performance.  This study summarizes relevant published research on the preparation, properties and experimental behavior of the optical and thermal properties of PTSCs. Analyzing of the thermal modeling method presents a steady and transient heat transfer analysis.  Optical efficiency depends on material properties, such as mirror reflectance, glass cover transmittance, receiver absorption–emission, intercept factor, geometry factor and incidence angle. Also analyzed and discussed are the models used in computational fluid dynamics to study the physical properties of PTSCs. Lastly, studies on PTSC performance and enhancement, including novel designs, enhancement of passive heat transfer and laden flows of nanoparticles inside the absorber tube, are presented and examined separately. Nanofluids have illustrated their advantages and ability to increase heat transfer rates. Moreover, other works that aimed to enhance the optical and thermal efficiency of PTSCs are evaluated.
      PubDate: 2021-03-15
      Issue No: Vol. 19, No. 1 (2021)
       
  • TAGUCHI OPTIMIZATION OF MULTIPLE PERFORMANCE CHARACTERISTICS IN THE
           ELECTRICAL DISCHARGE MACHINING OF THE TIGR2

    • Authors: Sıtkı Akıncıoğlu
      Abstract: Electrical discharge machining (EDM) provides many advantages for the shaping of metallic materials. It also provides better surface quality for Ti alloys used in the defense industry.  In this study, experiments were carried out with different EDM parameters using the Titanium (Gr2) alloy. A number of novel industrial processes have been developed as a result of advances in technology. For a product to be developed, these novel approaches must be utilized to determine optimum parameters. The Taguchi method was applied in the experiments with EDM. The impact the test parameters had on the performance characteristics of tool wear rate, material removal rate, depth, and surface roughness were analyzed by the variance analysis (ANOVA). Quadratic regression analyses were carried out to reveal the correlation between the experimental results and the predicted values. According to the ANOVA results for material removal rate (MRR), tool wear rate (TWR), depth, and surface roughness, the most effective factor was amperage, at 99.66%, 99.56%, 87.95%, and 81.12%, respectively.  The best value for average surface roughness was determined to be 3.29 µm obtained at 120 μs time-on, 8 A, and 40 μs time-off.
      PubDate: 2021-03-11
      Issue No: Vol. 19, No. 1 (2021)
       
  • DESIGN AND CALIBRATION OF THE SYSTEM SUPERVISING BELT TENSION AND WEAR IN
           AN INDUSTRIAL FEEDER

    • Authors: Tomasz Ryba, Miroslaw Rucki, Zbigniew Siemiatkowski, Damian Bzinkowski, Michal Solecki
      Abstract: In the paper, the issue of the supervision of belt tension and wear in industrial feeder is addressed. The designed system is based on strain gauges that are built into the roller and are subject to the belt pressure at each revolution. In order to assess the effectiveness of this system, calibration and uncertainty analysis was performed. As a result, it was demonstrated that the main source of uncertainty was the function of approximation, while the others were orders of magnitude smaller. The final function provided results with accuracy of ca. 10% of actually measured value, which was assumed to be a good result for this particular industrial application.
      PubDate: 2021-03-07
      Issue No: Vol. 19, No. 1 (2021)
       
  • LI-HE’S MODIFIED HOMOTOPY PERTURBATION METHOD FOR DOUBLY-CLAMPED
           ELECTRICALLY ACTUATED MICROBEAMS-BASED MICROELECTROMECHANICAL SYSTEM

    • Authors: Naveed Anjum, Ji-Huan He, Qura Tul Ain, Dan Tian
      Abstract: This paper highlights Li-He’s approach in which the enhanced perturbation method is linked with the parameter expansion technology in order to obtain frequency amplitude formulation of electrically actuated microbeams-based microelectromechanical system (MEMS). The governing equation is a second-order nonlinear ordinary differential equation. The obtained results are compared with the solution achieved numerically by the Runge-Kutta (RK) method that shows the effectiveness of this variation in the homotopy perturbation method (HPM).
      PubDate: 2021-03-02
      Issue No: Vol. 19, No. 1 (2021)
       
  • TEMPERATURE-DEPENDENT PHYSICAL CHARACTERISTICS OF THE ROTATING NONLOCAL
           NANOBEAMS SUBJECT TO A VARYING HEAT SOURCE AND A DYNAMIC LOAD

    • Authors: Ahmed E. Abouelregal, Hamid Mohammad-Sedighi, Seyed Ali Faghidian, Ali Heidari Shirazi
      Abstract: In this article, the influence of thermal conductivity on the dynamics of a rotating nanobeam is established in the context of nonlocal thermoelasticity theory. To this end, the governing equations are derived using generalized heat conduction including phase lags on the basis of the Euler–Bernoulli beam theory. The thermal conductivity of the proposed model linearly changes with temperature and the considered nanobeam is excited with a variable harmonic heat source and exposed to a time-dependent load with exponential decay. The analytic solutions for bending moment, deflection and temperature of rotating nonlocal nanobeams are achieved by means of the Laplace transform procedure. A qualitative study is conducted to justify the soundness of the present analysis while the impact of nonlocal parameter and varying heat source are discussed in detail. It also shows the way in which the variations of physical properties due to temperature changes affect the static and dynamic behavior of rotating nanobeams. It is found that the physical fields strongly depend on the nonlocal parameter, the change of the thermal conductivity, rotation speed and the mechanical loads and, therefore, it is not possible to neglect their effects on the manufacturing process of precise/intelligent machines and devices.
      PubDate: 2021-03-02
      Issue No: Vol. 19, No. 1 (2021)
       
  • CALIBRATION OF MATERIAL MODELS FOR THE HUMAN CERVICAL SPINE LIGAMENT
           BEHAVIOUR USING A GENETIC ALGORITHM

    • Authors: Marina Franulović, Kristina Marković, Ana Trajkovski
      Abstract: Research of biomaterials in loading conditions has become a significant field in the material science nowadays. In order to provide better understanding of the loading effects on material structures, complex material models are usually chosen, depending on their applicability to the material under consideration. In order to provide as accurate as possible the material behavior modeling of the human cervical spine ligaments, the procedure for calibration of two material models has been evaluated. The calibration of material models was based on the genetic algorithm procedure in order to make possible optimization of material parameters identification for the chosen models. The influence of genetic algorithm operators upon the results in evaluated procedure has been tested and discussed here and the simulated behavior of the material has been compared to the experimentally recorded stress stretch relationship of the material under consideration. Since various influential factors contribute to the genetic algorithm performance in calibration of complex material models and identification of material parameters, additional possible improvements have been suggested for further research.
      PubDate: 2021-02-28
      Issue No: Vol. 19, No. 1 (2021)
       
  • EXPERIMENTAL ANALYSIS OF THE EFFECT OF THE WOVEN ARAMID FABRIC ON THE
           

    • Authors: Sojan Andrews Zachariah, Satish Shenoy, Dayananda Pai
      Abstract: Remarkable advances in the research and development of micro/mini Unmanned Aerial Vehicles (UAVs) seek thin, lightweight and strong materials for their structural applications. As these structures involve various loading conditions in both the in-plane and through-the-thickness directions during their life cycle, the assurance of the structural stability in each direction is deemed mandatory. The woven Aramid fibers as high strain materials (HSM) are known to improve the through-the-thickness impact strength. However, the addition of the HSM can affect the overall tensile behavior of composite laminates. This study investigates the effect of the woven Aramid fiber on the in-plane tensile behavior of Carbon/ epoxy laminates. Laminates are fabricated using an easy and cost-effective Vacuum Assisted Resin Infusion Molding (VARIM) setup. A uniaxial tensile test was conducted to analyze the tensile behavior of Carbon/Aramid hybrid composites. The effect of adding the woven Aramid layer and the Carbon fabric sequence on the tensile modulus, strain to failure and modulus of toughness are investigated in this study. The results revealed that the presence of Aramid has a positive hybrid effect on the failure strain, exhibiting pseudo-ductile behavior with a compromise in the tensile modulus of the virgin Carbon/epoxy laminate.
      PubDate: 2021-02-20
      Issue No: Vol. 19, No. 1 (2021)
       
  • ON THE INFLUENCE OF MULTIPLE EQUILIBRIUM POSITIONS ON BRAKE NOISE

    • Authors: Sebastian Koch, Emil Köppen, Nils Gräbner, Utz von Wagner
      Abstract: Brake noise, especially brake squeal, has been a subject of intensive research both in industry and academia for several decades. Nevertheless, the state of the art simulations does not provide a predictive tool, and extensive experimental investigations are still necessary to find an appropriate design. Actual investigations focus on the consideration of nonlinearities which are in fact essential for this phenomenon. Unfortunately, by far not all relevant effects caused by nonlinearities are known. One of these nonlinear effects that the actual research focuses on is the limit cycle behavior representing squeal. In contrast to this, the actual paper considers the influence of the equilibrium position established while applying the brake pressure. The elements of the brake, namely, the carrier, caliper and pad, are highly nonlinear and elastically coupled and allow for multiple equilibrium positions depending e.g. on the initial conditions and transient application of the brake pressure while the frictional contact between the pads and the disk may excite small amplitude self-excited vibrations around this equilibrium, i.e. squeal. The current paper establishes a method and corresponding setup, to measure the position engaged by the brake components using an optical 3D-measuring system. Subsequently, it is demonstrated that in fact different equilibrium positions can be engaged for the same operation parameters and that the engaged position can be decisive for the occurrence of squeal. In fact, certain positions result in squeal while others do not for the same operation parameters. Taking this effect into consideration may have significant consequences for the design of brakes as well as simulation and experimental investigation of brake squeal.
      PubDate: 2021-02-15
      Issue No: Vol. 19, No. 1 (2021)
       
  • ON THE AFFERRANTE-CARBONE THEORY OF ULTRATOUGH TAPE PEELING

    • Authors: Michele Ciavarella, Robert M. McMeeking, Gabriele Cricrì
      Abstract: In a simple and interesting theory of ultratough peeling of an elastic tape from a viscoelastic substrate, Afferrante and Carbone find that there are conditions for which the load for steady state peeling could be arbitrarily large in steady state peeling, at low angles of peeling - what they call "ultratough" peeling (Afferrante, L., Carbone, G., 2016, The ultratough peeling of elastic tapes from viscoelastic substrates, Journal of the Mechanics and Physics of Solids, 96, pp.223-234). Surprisingly, this seems to lead to toughness enhancement higher than the limit value observed in a very large crack in an infinite viscoelastic body, possibly even considering a limit on the stress transmitted. The Afferrante-Carbone theory seems to be a quite approximate, qualitative theory and many aspects and features of this "ultratough" peeling (e.g. conformity with the Rivlin result at low peel angles) are obtained also through other mechanisms (Begley, M.R., Collino, R.R., Israelachvili, J.N., McMeeking, R.M., 2013, Peeling of a tape with large deformations and frictional sliding, Journal of the Mechanics and Physics of Solids, 61(5), pp. 1265-1279) although not at “critical velocities”. Experimental and/or numerical verification would be most useful.
      PubDate: 2021-02-15
      Issue No: Vol. 19, No. 1 (2021)
       
  • NOVEL METHODOLOGY FOR REAL-TIME STRUCTURAL ANALYSIS ASSISTANCE IN CUSTOM
           PRODUCT DESIGN

    • Authors: Milan Zdravković, Nikola Korunović
      Abstract: Mass-customization is related to optimizing the balance between flexibility, strongly required by the customer-focused industries and manufacturing efficiency, which is critical for market competitiveness. In the conventional industries, the process of designing, validating and manufacturing a product is long and expensive. Some of the common approaches for addressing those issues are parametric product modeling and Finite Element Analysis (FEA). However, the costs involved are still relatively high because of the very special expertise needed and the cost of the specialized software. Also, the specific design of the product cannot be validated in a real-time, which often leads to making hard compromises between the specific customer requirements and the structural properties of the product in its exploitation. In this paper, we propose the novel methodology for real-time structural analysis assistance for custom product design. We introduce the concept of so-called compiled FEA model, a Machine Learning (ML) model, consisting of dataset of characteristic product parameters and associated physical quantities and properties, selected ML algorithms and the sets of associated hyperparameters. A case study of creating a compiled FEA model for the case of internal orthopedic fixator is provided.
      PubDate: 2021-01-29
      Issue No: Vol. 19, No. 1 (2021)
       
  • AN EXPERIMENTAL STUDY ON THIRD-BODY PARTICLE TRANSPORT IN SLIDING CONTACT

    • Authors: Qiang Li, Iakov A. Lyashenko, Jasminka Starcevic
      Pages: 001 - 005
      Abstract: An experiment is designed to study the third-body particle transport in a rough contact. To study the influence of particles in a pure form, it is assured that the first bodies have no contact and the sliding is very slow, so that the process can be considered as quasistatic. An example of sliding contact of a 3D printed “rough body” on small spheres artificially located on a rubber layer is presented. The trajectory of particles during the sliding is captured for studying their movement and the correlation to the fluctuation of normal and tangential force.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201211016L
      Issue No: Vol. 19, No. 1 (2021)
       
  • A DISCRETE ELEMENT FORMALISM FOR MODELLING WEAR PARTICLE FORMATION IN
           CONTACT BETWEEN SLIDING METALS

    • Authors: Evgeny V. Shilko, Aleksandr S. Grigoriev, Alexey Yu. Smolin
      Pages: 007 - 022
      Abstract: The paper describes an advanced discrete-element based mechanical model, which allows modelling contact interaction of ductile materials with taking into account fracture and surface adhesion by the cold welding mechanism. The model describes these competitive processes from a unified standpoint and uses plastic work of deformation as a criterion of both local fracture and chemical bonding of surfaces in contact spots. Using this model, we carried out a preliminary study of the formation of wear particles and wedges during the friction of rough metal surfaces and the influence of the type of forming third body (interfacial) elements on the dynamics of the friction coefficient. The qualitative difference of friction dynamics in the areas of the contact zone characterized by different degrees of mechanical confinement is shown.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201221012S
      Issue No: Vol. 19, No. 1 (2021)
       
  • A FRACTURE-INDUCED ADHESIVE WEAR CRITERION AND ITS APPLICATION TO THE
           SIMULATION OF WEAR PROCESS OF THE POINT CONTACTS UNDER MIXED LUBRICATION
           CONDITION

    • Authors: Hui Cao, Yu Tian, Yonggang Meng
      Pages: 023 - 038
      Abstract: Adhesive wear is one of the four major wear mechanisms and very common in almost all macro-, micro- or nanotribosystems. In an adhesive wear process, tiny material fragments are pulled off from one sliding surface and adhered onto the counterpart. Later these fragments form loose particles or transfer between the contact surfaces. Because of the topographical and physicochemical property non-uniformity of engineering surfaces, adhesive wear happens heterogeneously on the loaded sliding surfaces, and it is also discontinuous during sliding or rolling motion owing to the damage accumulation and fracture occurred inside the subsurface layers. Taking account of these characteristics, a novel fracture-induced adhesive wear criterion has been proposed in this study in order to predict local wear of material in sliding. Moreover, the proposed wear criterion is applied to predicting wear particle formation and morphology evolution of mixed lubricated rough surfaces during reciprocating sliding, and the simulation results are compared with the ball-on-disk experimental measurements.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME210108021C
      Issue No: Vol. 19, No. 1 (2021)
       
  • A RIGOROUS MODEL FOR FREQUENCY-DEPENDENT FINGERPAD FRICTION UNDER
           ELECTROADHESION

    • Authors: Fabian Forsbach, Markus Heß
      Pages: 039 - 049
      Abstract: In the electroadhesive frictional contact of a sliding fingerpad on a touchscreen, friction is enhanced by an induced electroadhesive force. This force is dominated by the frequency-dependent impedance behavior of the relevant electrical layers. However, many existing models are only valid at frequency extremes and use very simplified contact mechanical approaches. In the present paper, a RC impedance model is adopted to characterize the behavior in the relevant range of frequencies of the AC excitation voltage. It serves as an extension to the macroscopic model for electrovibration recently developed by the authors, which is based on several well-founded approaches from contact mechanics. The predictions of the extended model are compared to recent experimental results and the most influential electrical and mechanical parameters are identified and discussed. Finally, the time responses to different wave forms of the excitation voltage are presented.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME210105015F
      Issue No: Vol. 19, No. 1 (2021)
       
  • FRICTION BEHAVIOR OF ALUMINUM BRONZE REINFORCED BY BORON CARBIDE PARTICLES

    • Authors: Alexey Yu. Smolin, Andrey V. Filippov, Evgeny V. Shilko
      Pages: 051 - 065
      Abstract: A promising composite material for tribotechnical applications based on aluminum bronze with reinforcing boron carbide particles fabricated by a special electron beam additive deposition technique was studied experimentally and numerically. Tribological experiments showed that reinforcing by carbide particles allowed reducing the coefficient of friction from 0.26 to 0.19 and improving the wear resistance by 2.2 times. Computer modeling reveals two main factors playing a significant role in the friction behavior of the studied metal matrix composite: the mechanical effect of reinforcing ceramic inclusions and effective hardening of the metal matrix due to the peculiarities of the 3D electron beam printing. The mechanical effect of hardening inclusions determines a more rounded shape of wear particles, preventing wedging, and thereby increasing the stability of friction. Strengthening the metal matrix leads to reducing the number of wear particles.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201226013S
      Issue No: Vol. 19, No. 1 (2021)
       
  • THE CERAMIC MODULAR HEAD IMPROVEMENT IN THE DESIGN OF A TOTAL HIP
           REPLACEMENT

    • Authors: Vladimir Pakhaliuk, Aleksandr Poliakov, Ivan Fedotov
      Pages: 067 - 078
      Abstract: For the first time, a design of a modular ceramic ball head of a total hip joint replacement (THR) friction pair has been developed, which has the properties of a metal in conjunction with the stem neck and the properties of a ceramics on bearing surface of the pair. This is achieved by creating a low-cost, low-toxic, durable fixed connection of the head made of alumina or zirconia ceramics and the titanium-based alloy sleeve to obtain a brazed joint that is efficient in human synovial fluid. With the help of finite element analysis, a quantitative assessment of the strength and rigidity of the proposed head design was performed and its use in modern hip arthroplasty was indicated. The approbation of the proposed design solutions for creating a THR ceramic head with a titanium-based alloy sleeve brazed was carried out.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201212010P
      Issue No: Vol. 19, No. 1 (2021)
       
  • NUMERICAL MODEL OF A LOCAL CONTACT OF A POLYMER NANOCOMPOSITE AND ITS
           EXPERIMENTAL VALIDATION

    • Authors: Andrey I. Dmitriev
      Pages: 079 - 089
      Abstract: In the paper a model of a local contact of a polymer-based nanocomposite was developed within the method of a movable cellular automaton. The features of mechanical behavior of nanocomposite at the mesoscale level under dry sliding were studied with explicit account for the microprofile of the counterbody surface and the characteristic sizes of nanofiller. Factors that contribute to the conditions for the formation of a stable tribofilm of silica nanoparticles are analyzed. Two other parameters like sample geometry and the value of relative sliding velocity are also examined. It is shown that the thickness of tribofilm depends on stress conditions at the contact, and the friction coefficient decreases with increasing sliding velocity similar to one observed experimentally. To ensure the low friction properties of polymer nanocomposite, particles whose sizes are comparable with the characteristic size of the substrate microprofile are preferred. Results of numerical simulation are in good correlation with available experimental data.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201225007D
      Issue No: Vol. 19, No. 1 (2021)
       
  • MODELING OF TITANIUM ALLOYS PLASTIC FLOW IN LINEAR FRICTION WELDING

    • Authors: Vladimir A. Skripnyak, Kristina Iokhim, Evgeniya Skripnyak, Vladimir V. Skripnyak
      Pages: 091 - 104
      Abstract: The article presents the results of the analysis of the plastic flow of titanium alloys in the process of the Linear Friction Welding (LFW). LFW is a high-tech process for joining critical structural elements of aerospace engineering from light and high-temperature alloys. Experimental studies of LFW modes of such alloys are expensive and technically difficult. Numerical simulation was carried out for understanding the physics of the LFW process and the formation laws of a strong welded joint of titanium alloys. Simulation by the SPH method was performed using the LS DYNA software package (ANSYS WB 15.2) and the developed module for the constitutive equation. The new coupled thermomechanical 3D model of LFW process for joining structural elements from alpha and alpha + beta titanium alloys was proposed. It was shown that the formation of a welded joint occurs in a complex and unsteady stress-strain state. In the near-surface layers of the bodies being welded, titanium alloys can be deformed in the mode of severe plastic deformation. A deviation of the symmetry plane of the plastic deformation zone from the initial position of the contact plane of the bodies being welded occurs during a process of LFW. Extrusion of material from the welded joint zone in the transverse direction with respect to the movement of bodies is caused by a pressure gradient and a decrease in the alloy flow stress due to heating. The hcp-bcc phase transition of titanium alloys upon heating in the LFW process necessitates an increase in the cyclic loading time to obtain a welded joint.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201225014S
      Issue No: Vol. 19, No. 1 (2021)
       
  • FRICTION UNDER LARGE-AMPLITUDE NORMAL OSCILLATIONS

    • Authors: Mikhail Popov
      Pages: 105 - 113
      Abstract: Building on a recently proposed contact-mechanical theory of friction control by external vibration, the case of large-amplitude normal oscillation is revisited. It is shown that the coefficient of friction can be expressed in particularly simple form if the waveform of the displacement oscillation is triangular or rectangular, and the contact stiffness is constant. The latter requirement limits the scope of the exact solutions to contacts between a plane and a flat-ended cylinder or a curved shape with a wear flat, but the adopted methodology also enables efficient numerical solution in more general cases.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME201226017P
      Issue No: Vol. 19, No. 1 (2021)
       
  • BUBBLE DYNAMICS-BASED MODELING OF THE CAVITATION DYNAMICS IN LUBRICATED
           CONTACTS

    • Authors: Thomas Geike
      Pages: 115 - 124
      Abstract: Cavitation is a common phenomenon in fluid machinery and lubricated contacts. In lubricated contacts, there is a presumption that the short-term tensile stresses at the onset of bubble formation have an influence on material wear. To investigate the duration and magnitude of tensile stresses in lubricating films using numerical simulation, a suitable simulation model must be developed. The chosen simulation approach with bubble dynamics is based on the coupling of the Reynolds equation and Rayleigh-Plesset equation (introduced about 20 years ago by Someya).Following the basic approach from the author’s earlier papers on the negative squeeze motion with bubble dynamics for the simulation of mixed lubrication of rough surfaces, the paper at hand shows modifications to the Rayleigh-Plesset equation that are required to get the time scale for the dynamic processes right. This additional term is called the dilatational viscosity term, and it significantly influences the behavior of the numerical model. 
      PubDate: 2021-04-01
      DOI: 10.22190/FUME210112027G
      Issue No: Vol. 19, No. 1 (2021)
       
  • AN ANALYTICAL APPROACH TO THE THIRD BODY MODELLING IN FRETTING WEAR
           CONTACT: A MINIREVIEW

    • Authors: Ivan I. Argatov, Young Suck Chai
      Pages: 125 - 131
      Abstract: In fretting wear contact, the third body is defined as the wear debris bed between two contacting bodies. The problem of third-body modelling is considered from a point of view of contact mechanics. This paper is restricted to a discussion of recent developments in analytical modelling of fretting wear contact.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME210103018A
      Issue No: Vol. 19, No. 1 (2021)
       
  • GUIDELINES TO SIMULATE LINEAR VISCOELASTIC MATERIALS WITH AN ARBITRARY
           

    • Authors: Maximilian Forstenhäusler, Enrique A. López-Guerra, Santiago D. Solares
      Pages: 133 - 153
      Abstract: We provide guidelines for modeling linear viscoelastic materials containing an arbitrary number of characteristic times, under atomic force microscopy (AFM) characterization. Instructions are provided to set up the governing equations that rule the deformation of the material by the AFM tip. Procedures are described in detail in the spirit of providing a simple handbook, which is accompanied by open-access code and workbook (Excel) sheets. These guidelines seek to complement the existing literature and reach out to a larger audience in the awareness of the interdisciplinary nature of science. Examples are given in the context of force-distance curves characterization within AFM, but they can be easily extrapolated to other types of contact characterization techniques at different length scales. Despite the simplified approach of this document, the algorithms described herein are built upon rigorous classical linear viscoelastic theory.
      PubDate: 2021-04-01
      DOI: 10.22190/FUME200920009F
      Issue No: Vol. 19, No. 1 (2021)
       
  • SHAPE OF A SLIDING CAPILLARY CONTACT DUE TO THE HYSTERESIS OF CONTACT
           ANGLE: THEORY AND EXPERIMENT

    • Authors: Valentin L. Popov, Iakov A. Lyashenko, Jasminka Starcevic
      First page: 175
      Abstract: We consider a classical problem of a capillary neck between a parabolic body and a plane with a small amount of liquid in between. In the state of thermodynamic equilibrium, the contact area between the bodies and the liquid layer has a circular shape. However, if the bodies are forced to slowly move in the tangential direction, the shape will change due to the hysteresis of the contact angle. We discuss the form of the contact area under two limiting assumptions about the friction law in the boundary line. We also present a detailed experimental study of the shape of sliding capillary contact in dependence on the roughness of the contacting surfaces.
      PubDate: 2021-01-20
      DOI: 10.22190/FUME201221005P
      Issue No: Vol. 19, No. 1 (2021)
       
  • MESOSCALE DEFORMATION-INDUCED SURFACE PHENOMENA IN LOADED POLYCRYSTALS

    • Authors: Varvara Romanova, Ruslan Balokhonov, Olga Zinovieva
      First page: 187
      Abstract: The paper reviews the results of numerical analyses for the micro-and mesoscale deformation-induced surface phenomena in three-dimensional polycrystals with the explicit account for the grain structure. The role of the free surface and grain boundaries in the appearance of the grain-scale stress concentrations and plastic strain nucleation is illustrated on the examples of aluminum polycrystals. Special attention is paid to the discussion of mesoscale deformation-induced surface roughening under uniaxial tension.
      PubDate: 2021-01-27
      DOI: 10.22190/FUME210102006R
      Issue No: Vol. 19, No. 1 (2021)
       
  • HAMILTONIAN-BASED FREQUENCY-AMPLITUDE FORMULATION FOR NONLINEAR
           OSCILLATORS

    • Authors: Ji-Huan He, Wei-Fan Hou, Na Qie, Khaled A. Gepreel, Ali Heidari Shirazi, Hamid Mohammad- Sedighi
      First page: 199
      Abstract: Complex mechanical systems usually include nonlinear interactions between their components which can be modeled by nonlinear equations describing the sophisticated motion of the system. In order to interpret the nonlinear dynamics of these systems, it is necessary to compute more precisely their nonlinear frequencies. The nonlinear vibration process of a conservative oscillator always follows the law of energy conservation. A variational formulation is constructed and its Hamiltonian invariant is obtained. This paper suggests a Hamiltonian-based formulation to quickly determine the frequency property of the nonlinear oscillator. An example is given to explicate the solution process.
      PubDate: 2021-01-09
      DOI: 10.22190/FUME201205002H
      Issue No: Vol. 19, No. 1 (2021)
       
  • COMPUTATIONAL MICROSTRUCTURE-BASED ANALYSIS OF RESIDUAL STRESS EVOLUTION
           IN METAL-MATRIX COMPOSITE MATERIALS DURING THERMOMECHANICAL LOADING

    • Authors: Ruslan Balokhonov, Varvara Romanova, Eugen Schwab, Aleksandr Zemlianov, Eugene Evtushenko
      First page: 241
      Abstract: A technique for computer simulation of three-dimensional structures of materials with reinforcing particles of complex irregular shapes observed in the experiments is proposed, which assumes scale invariance of the natural mechanical fragmentation. Two-phase structures of metal-matrix composites and coatings of different spatial scales are created, with the particles randomly distributed over the matrix and coating computational domains. Using the titanium carbide reinforcing particle embedded into the aluminum as an example, plastic strain localization and residual stress formation along the matrix-particle interface are numerically investigated during cooling followed by compression or tension of the composite. A detailed analysis is performed to evaluate the residual stress concentration in local regions of bulk tension formed under all-round and uniaxial compression of the composite due to the concave and convex interfacial asperities.
      PubDate: 2021-02-08
      DOI: 10.22190/FUME201228011B
      Issue No: Vol. 19, No. 1 (2021)
       
  • FRACTAL APPROACH TO MECHANICAL AND ELECTRICAL PROPERTIES OF GRAPHENE/SIC
           COMPOSITES

    • Authors: Yu-Ting Zuo, Hong-Jun Liu
      First page: 271
      Abstract: Graphene and carbon nanotubes have a Steiner minimum tree structure, which endows them with extremely good mechanical and electronic properties. A modified Hall-Petch effect is proposed to reveal the enhanced mechanical strength of the SiC/graphene composites, and a fractal approach to its mechanical analysis is given.  Fractal laws for the electrical conductivity of graphene, carbon nanotubes and graphene/SiC composites are suggested using the two-scale fractal theory. The Steiner structure is considered as a cascade of a fractal pattern. The theoretical results show that the two-scale fractal dimensions and the graphene concentration play an important role in enhancing the mechanical and electrical properties of graphene/SiC composites. This paper sheds a bright light on a new era of the graphene-based materials.
      PubDate: 2021-01-06
      DOI: 10.22190/FUME201212003Z
      Issue No: Vol. 19, No. 1 (2021)
       
  • A STRUCTURED FRAMEWORK FOR RELIABILITY AND RISK EVALUATION IN THE MILK
           PROCESS INDUSTRY UNDER FUZZY ENVIRONMENT

    • Authors: Nand Gopal, Dilbagh Panchal
      First page: 307
      Abstract: This paper aims at proposing a novel integrated framework for studying reliability and risk issues of the curd unit in a milk process industry under uncertain environment. The considered plant’s complex series-parallel configuration was presented using the Petri Net (PN) modeling. The Fuzzy Lambda-Tau (λ-τ) approach was applied to study and analyze the reliability aspects of the considered plant. Failure dynamics of the curd unit has been analyzed with respect to increasing/ decreasing trends of the tabulated reliability indices. Availability of the considered plant shows a decreasing trend with an increase in spread values. For improving the system’s availability, a risk analysis was done to identify the most critical failure causes. Using the traditional FMEA approach, the FMEA sheet was generated on the basis of expert’s knowledge/experience. The Fuzzy-Complex Proportional Assessment (FCOPRAS) approach was applied within FMEA approach for identification of critical failure causes associated with different subsystem/components of the considered plant. In order to check the consistency of the ranking results, the Fuzzy Technique for Order of Preference by Similarity to Ideal Solution (FTOPSIS) was applied within the FCOPRAS approach. Ranking results are compared for checking consistency and robustness of critical failure causes related decision making which would be useful in designing the finest maintenance schedule for the considered curd unit.  Overheating/moisture lead to winding failure (MSCP5), visible sediment of milk jam in filter (MBFP3), improper quality of oil (H4), blade breakage (CTK4), wearing in gears (PFM11), and cylinder leakage (CFM7) were recognized as the most critical failure causes contributing to system unavailability. The analysis results were supplied to the maintenance manager for framing a suitable time-based maintenance intervals policy for the considered unit.
      PubDate: 2021-01-13
      DOI: 10.22190/FUME201123004G
      Issue No: Vol. 19, No. 1 (2021)
       
  • GREEN SUPPLIER SELECTION BASED ON THE INFORMATION SYSTEM PERFORMANCE
           EVALUATION USING THE INTEGRATED BEST-WORST METHOD

    • Authors: Hamed Fazlollahtabar, Navid Kazemitash
      First page: 345
      Abstract: Information Systems (IS) have become crucial for all the organizations to survive in contemporary technology-oriented environment. Consequently, the number of companies and organizations which have invested widely in their IS infrastructures to present better services and to produce higher value products is increasing. On the other hand, nowadays, because of the increase of governmental rules and serious requirements of more people in the case of environmental protection, it seems necessary for all the enterprises to follow these regulations if they want to survive in the global markets. However, what is at issue here is not just the companies’ agreement with the environmental laws; in addition, they should apply some strategies to decrease the negative environmental impacts of their products in some countries. Thus, the aforementioned arguments are the reasons for the compulsory use of the green supplier selection (GSS) in all firms. Considering the mentioned contents, the purpose of this study is representation of the relation between ISs and GSS as two vital components of firms in a novel way which has not been done before. Actually, it shows the ISs' performance or effectiveness to select the green suppliers taking into account the different levels of importance of GSS measures (including eight criteria and 31 sub-criteria), using a multi-criteria decision-making method called Best Worst Method (BWM) to identify the weights (importance) of GSS measures and compute the GSS performance of 10 ISs in a company using the data gathered in a survey from ISs' experts.
      PubDate: 2021-03-15
      DOI: 10.22190/FUME201125029F
      Issue No: Vol. 19, No. 1 (2021)
       
  • A NEW LOGARITHM METHODOLOGY OF ADDITIVE WEIGHTS (LMAW) FOR MULTI-CRITERIA
           DECISION-MAKING: APPLICATION IN LOGISTICS

    • Authors: Dragan Pamučar, Mališa Žižović, Sanjib Biswas, Darko Božanić
      First page: 361
      Abstract: Logistics management has been playing a significant role in ensuring competitive growth of industries and nations. This study proposes a new Multi-Criteria Decision-making (MCDM) framework for evaluating operational efficiency of logistics service provider (LSP). We present a case study of comparative analysis of six leading LSPs in India using our proposed framework. We consider three operational metrics such as annual overhead expense (OE), annual fuel consumption (FC) and cost of delay (CoD, two qualitative indicators such as innovativeness (IN) which basically indicates process innovation and average customer rating (CR)and one outcome variable such as turnover (TO) as the criteria for comparative analysis. The result shows that the final ranking is a combined effect of all criteria. However, it is evident that IN largely influences the ranking. We carry out a comparative analysis of the results obtained from our proposed method with that derived by using existing established frameworks. We find that our method provides consistent results; it is more stable and does not suffer from rank reversal problem.
      PubDate: 2021-03-18
      DOI: 10.22190/FUME210214031P
      Issue No: Vol. 19, No. 1 (2021)
       
  • A NOVEL INTEGRATED MCDM-SWOT-TOWS MODEL FOR THE STRATEGIC DECISION
           ANALYSIS IN TRANSPORTATION COMPANY

    • Authors: Irena Đalić, Željko Stević, Jovo Ateljević, Zenonas Turskis, Edmundas Kazimieras Zavadskas, Abbas Mardani
      First page: 401
      Abstract: In this paper, based on the Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis, a matrix of Threats, Opportunities, Weaknesses and Strengths (TOWS) was formed. It represents possible business strategies of the transport company. To choose the right plan, a model based on the integration of Fuzzy PIvot Pairwise RElative Criteria Importance Assessment (fuzzy PIPRECIA), Full Consistency Method (FUCOM) and Measurement Alternatives and Ranking according to COmpromise Solution (MARCOS) methods, has been formed. A case study was conducted in the transport company from Bosnia and Herzegovina which provides services on the domestic and the European Union market for 20 years and belongs to a group of small and medium enterprises (SMEs). The SWOT analysis in this transport company was the basis for forming the TOWS matrix, which represents a set of possible business strategies. These strategies are the basis for developing five basic alternatives. The transport company should choose the best one of them for future business. The research focuses on forming a model for choosing the best strategy by which the transport company seeks to improve its business. Decision-making (DM) is not a straightforward sequence of operations, so the harmonization of methods as well as the verification of their results, are essential in the research. This model is applicable in SMEs that make these and similar decisions. Using this model, companies can adjust their business policies to the results of the model and achieve better business results. This research is the first that allows the use of such a model in making strategic decisions.
      PubDate: 2021-03-18
      DOI: 10.22190/FUME201125032D
      Issue No: Vol. 19, No. 1 (2021)
       
  • MEASURING EFFICIENCY CHANGE IN TIME APPLYING MALMQUIST PRODUCTIVITY INDEX:
           A CASE OF DISTRIBUTION CENTRES IN SERBIA

    • Authors: Milan Andrejić, Milorad Kilibarda, Vukašin Pajić
      First page: 499
      Abstract: In the last decade, more and more attention has been paid to the efficiency of logistics systems not only in the literature but also in practice. The reason is the huge savings that can be achieved. In a very dynamic market with environmental changes distribution centers have to realize their activities and processes in an efficient way. Distribution centers connect producers with other participants in the supply chain, including end-users. The main objective of this paper is to develop a DEA model for measuring distribution centers’ efficiency change in time. The paper investigates the impact of input and output variables selection on the resulting efficiency in the context of measuring the change in efficiency over time. The selection of variables on the one hand is a basic step in applying the DEA method. On the other hand, the number of basic and derived indicators that are monitored in real systems is increasing, while the percentage of those used in the decision-making process is decreasing (less than 20%). The developed model was tested on the example of a retail chain operating in Serbia. The main factors changing the efficiency have been identified, as well as the corresponding corrective actions. For measuring efficiency change in time Malmquist productivity index is used. The developed approach could help managers in the decision-making process and also represents a good basis for further research.
      PubDate: 2021-04-30
      DOI: 10.22190/FUME201224039A
      Issue No: Vol. 19, No. 1 (2021)
       
 
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