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FAMENA issue 2, volume 41, Zagreb 2017
Danko Ćorić, Lidija Ćurković, Marijana Majić Renjo
Statistical Analysis of Vickers Indentation Fracture Toughness of Y-TZP Ceramics
The purpose of this study was to investigate and analyse the fracture toughness of yttria stabilized tetragonal zirconia polycrystal (Y-TZP) dental ceramics by means of the Vickers indentation technique. Fracture toughness was analysed under the following loads: 29.42 N, 49.03 N, 196.13 N, and 294.20 N. Cracks that had developed from the vertices of a Vickers indentation were measured and used for the determination of fracture toughness by using nine different models. It was found that fracture toughness depends on the indentation load, the morphology of indentation cracking, and the applied model of fracture resistance. The set of fracture toughness data was analysed using the two-parameter Weibull statistics. The Weibull modulus and the scale parameter were determined by the linear regression method. It was concluded that the Weibull distribution can describe the fracture toughness of Y-TZP ceramics properly.
Key words: Y-TZP ceramics, Indentation test, Fracture toughness, Weibull statistics
Hossein Rafizadeh, Farhad Azimifar, Puya Foode, Mohammad Reza Foudeh, Mohammad Keymanesh
Wrinkling Prediction in Deep Drawing by Using Response Surface Methodology and Artificial Neural Network
The objective of this study is to predict influences of tooling parameters such as die and punch radius, blank holder force and friction coefficient between the die and the blank surfaces in a deep drawing process on the wrinkling height in aluminium AA5754 by using the response surface methodology (RSM) and an artificial neural network (ANN). The 3D finite element method (FEM), i.e. the Abaqus software, is employed to model the deep drawing process. In order to investigate the accuracy of this model, the results are compared with experimental results. The data derived from the FEM are used for modelling the RSM and training an ANN. Finally, the RSM and ANN outputs are compared so as to select the best model. The results of the two methods are promising and it is found that the ANN results are more accurate than the RSM results.
Key words: ANN, deep drawing, FEM, RSM, wrinkling
Meisam Ghafouri, Saeed Daneshmand
Design and Evaluation of an Optimal Fuzzy PID Controller for an Active Vehicle Suspension System
The goal of studying the vehicle suspension systems is to reduce the vehicle vibrations which are due to the irregularities of road levels and the fluctuations in the vehicle velocity. These vibrations are transferred to the body and occupants of vehicles through the suspension system. In general, the main function of an active suspension system is to support the vehicle body by reducing the input vibrations and to provide a safe and smooth ride on a bumpy road surface. In this research, a quarter vehicle model has been employed for designing a suspension system. The road level irregularities have been considered as disturbances to this system. The optimal fuzzy PID (OFPD+I) controller has been used to optimize the performance of the suspension system in reducing the adverse effects resulting from road level irregularities, vehicle braking, and moving around the road curves. To verify the efficacy of the optimal fuzzy PID controller, its performance has been evaluated and compared with the performances of three separate controllers (PID, fuzzy, and fuzzy PID) and a system without any controller. The findings indicate the advantage of the optimal fuzzy PID controller over the other systems. Thus, in the integral of the absolute error criterion for the vehicle body velocity and displacement changes, the OFPD+I controller has a superior performance relative to the other systems.
Key words: Genetic Algorithm, Active Suspension System, Quarter Vehicle Model, Optimal Fuzzy Proportional-Integral-Derivative (PID) Controller
Zorica Djordjević, Mirko Blagojević, Snežana Vulović, Danijela Nikolić, Saša Jovanović
An Investigation Into Hybrid Aluminium/Composite Cardan Shaft
It is a well-known fact that natural resources are becoming increasingly scarce. Consequently, whenever possible in the machine element manufacture, metallic materials should be replaced with new artificial materials. This paper studies the possibility of replacing two cardan shafts of a truck TURBO ZETA 85.14B with one shaft made of aluminium and a composite material, while the basic requirements concerning the given load transfer and fundamental natural frequencies remain satisfied.
Key words: composite materials, hybrid drive shaft, natural frequency, strain gauges
Nenad Panić, Branko Katana, Zvonimir Ivan Mrčela
Determining an Allowable Wear of Worm Wheels
The paper presents an analysis based on the two criteria used to determine an allowable sliding wear of the worm gear side teeth and of the worm wheels. In both cases, two undesirable consequences occurred. The first one is a reduction in the tooth root cross section, which may lead to tooth fracture. The other one is the appearance of tooth tapers. Both consequences are undesirable in all types of gear transmissions because of the risk of tooth fracture.
Key words: worm wheels, tooth fracture, tooth wear, tooth taper, tooth root
Kumar, Chattopadhyaya, Ghosh, Krolczyk, Vilaca, Kumar, Srivastava, Shariq, Triphathi
Characterization of Friction Surfaced Coatings of AISI 316 Tool over High-Speed-Steel Substrate
Nowadays friction surfacing (FS) has become a popular solid state surface coating technology suitable for a range of substrates. The technology has the ability to produce coatings with marginal dilution and good metallurgical bonding. The present study has aimed at producing a single-track and a three-track overlapping coatings on high-speed steel substrates using an AISI 316 consumable rod. Microhardness of coatings was examined by a Vickers micro hardness tester. Coatings of all the friction surfaced samples in as-deposited condition showed significant hardness. The infrared thermography showed that the peak temperature achieved by the AISI 316 coating was about 1020 °C. The coatings, thus attained, were further analysed for their microstructural features and interfacial characteristics by using FE-SEM. The EDX analysis showed the presence of nickel, chromium and oxygen, which indicates the formation of oxide compounds. The formation of AISI 316 deposits on the HSS substrate and the effect of coating overlapping are discussed in this article.
Key words: Friction surfacing, overlapping coatings, micro hardness, infrared thermography, AISI 316, Field Emission Scanning Electron Microscopy (FE-SEM).
Vekteris, Trumpa, Turla, Šešok, Iljin, Mokšin, Kilikevičius, Jakštas, Kleiza
An Investigation Into Fault Diagnosis in a Rotor-Bearing System with Dampers Used in Centrifugal Milk Separators
This paper deals with the problems encountered in the fault diagnosis in damped rotor-bearing systems used in centrifugal milk separators. It is shown that direct bearing vibration measurements are more reliable than indirect (through rotor housing) vibration measurements. However, in most cases it is not possible to measure bearing vibrations directly. The factors causing large diagnostic measurement errors, such as the influence of the vibration damping system, step-up gear and electric motor noise are discussed in the paper. It is established that vibration measurements of the damping system are noninformative and cannot be used to diagnose faults in bearings. It is proposed to use the vibration spectra correlation to predict bearing failures in rotor-bearing systems of this type.
Key words: centrifugal milk separator, bearing fault diagnosis, vibration signal analysis, correlation.
Božena Tokić
Shared Responsibility for a Clear and Accessibly Written Scientific Paper
In this paper, a hypothesis of shared responsibility for a clear and accessibly written scientific paper published in a scientific journal is put forward and discussed. Among the parties sharing the responsibility, i.e. the author, the peer reviewer, the editor-in-chief together with the editorial board, and the language editor, the author has the greatest responsibility. Producing a clear and reader-friendly text to present a scientific content in a proper way is not an easy task for the author. The purpose of this paper is, therefore, to highlight some important issues related to scientific writing, such as the structure of the paper, precision and clarity of the text, terminology, abbreviations, and spelling. The challenges of academic writing are illustrated by characteristic examples taken from the papers published in the Transactions of FAMENA. Some experience-based tips on how to develop academic writing skills and recommendations for improving the quality of the text are given in conclusion.
Key words: a clear and reader-friendly text, shared responsibility, academic writing skills
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