Mechatronic education at the Faculty of Technical Sciences Novi Sad

Nastajanje inženjerskog polja mehatronike privlači pozornost mnogih tehničkih stručnjaka, akademika i vladinih dužnosnika u posljednjih nekoliko godina, na nacionalnoj i globalnoj razini. Glavni razlog za to je da mnogi suvremeni proizvodi više nisu čisto električni i elektronski ili mehanički. Štoviše, oni su integrirani multidisciplinarni proizvodi koji su izrađeni od podsustava koji zahtijevaju inženjersko znanje iz različitih disciplina. Tako sve veći broj sveučilišta nude tečajeve, certifikate i programe na preddiplomskoj i diplomskoj razini u području mehatronike. Ovaj članak predstavlja obrazovni program mehatronike na Fakultetu tehničkih znanosti Sveučilišta u Novom Sadu u Srbiji. Osim toga, u članku je prikazana procjena studenata programa mehatronike. Provedeno istraživanje omogućilo je bolji uvid u mišljenje studenata o ovom programu, a samim tim i vrijedne povratne informacije koje će omogućiti daljnja poboljšanja programa.The emerging engineering field of mechatronics has caught the attention of many engineering professionals, academics and government officials in recent years, nationally and globally. The main reason for this is that many modern products are no longer purely electrical and electronic or mechanical. Moreover, they are integrated multidisciplinary products which are made from subsystems which require engineering knowledge of different disciplines. Hence, increasing number of universities is offering courses, certificates and programs at undergraduate and graduate levels in the area of mechatronics. This paper presents an educational program in mechatronics at the Faculty of Technical Sciences, University of Novi Sad, Serbia. In addition, student evaluation of the mechatronics program is presented. The conducted survey enabled faculty to gain more insight into student opinions about this program which provided valuable feedback for further program improvements

DESIGN OF A PROPULSION DRIVE SYSTEM FOR LATERAL MOVEMENT OF VESSEL (THRUSTER)

This papers covers propulsion parameter optimization and motion study of bow thrusters. Thrusters parameters for production are decided in relation with vessel length. Lateral thruster parameters are decided in correlation with vessel length. Reason for it is that thrust force is given by value of ship hull resistance and desired speed of lateral movement. Analyzed vessel in this research was “Šibenik 800- working variant”. Model of ship is made in 3D software Solid Works 2017 by use of conceptual drawings provided by company Dunkić Ltd. Hull resistance represents complex physical phenomenon of fluid-structure interaction and very often for its analysis engineers are forced to use software for computational fluid dynamics. Ansys 17.2 with its CFX module was applied for structural analysis. Investigation was divided into two sections to decrease computation time: immersed and dry part. Required propulsion force was given by assumption that acceleration is equal to zero when vessel is moving with designed ultimate speed, whereas amount of propulsion force is equal to resistance force. Considering complex variation of hydrodynamic pressure as function of vessel speed, it is to be expected that acceleration will take infinite amount of time to achieve desired ultimate speed (asymptotic value)

Analytical fluid film force calculation in the case of short bearing with a fully developed turbulent flow

The main purpose of this paper is to define a methodology to determine the analytical approximate closed-form expression of non-steady fluid film force and of the oil film coefficients for the liquid-lubricated journal bearings in the case of a fully developed turbulent flow regime. The considered model is a symmetrical rigid rotor supported on two lubricated journal bearings; this paper considers the cases of the short bearing approximation, introducing the turbulence correction flow factors in the classical Reynolds equation. The proposed methodology gives the opportunity to solve in approximate way the equation governing the distribution of pressure in the bearing oil gap and then to obtain the closed- form expressions for the non-steady fluid forces. This approach shows the benefit of minimising the calculation time required for the non-linear dynamic analysis of rotors on turbulent journal bearings without any significant loss of accuracy giving a better readability of the parameter involved on the system behaviour

Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings

Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces when the threshold speed is overcome by the rotational speed, can generate rotor lateral self-excited vibrations known as “oil whirl” or “oil whip”. These instabilities derive from the interaction between the rotor and the sliding bearing and they are typically sub-synchronous and they contribute to eventual rubbing between rotor and stator with consequent damage to the rotating machines. For these reasons, the aim of this paper is to numerically investigate the differences in the dynamic behaviour of a flexible rotor supported by cylindrical lubricated journal bearings. The study considers two different cases, uncavitated and cavitated lubricated films, in order to develop an original Matlab-Simulink algorithm for the numerical solution of the differential non-linear equations of motion of the unbalanced flexible rotor supported on hydrodynamic journal bearings. The bearings were modelled as uncavitated and cavitated (π-Film) short bearings derived from classical Reynolds’ theory. Dynamic simulation allowed prediction of the shape and size of the orbit performed by the system and evaluation of the vibrating phenomena exerted by the rotor during the motion. The results show that cavitation completely modifies the behaviour of the system in every aspect. The analysis of the diagrams obtained showed that the proposed algorithm provides consistent results and represents a valuable instrument for dynamic analysis of rotating systems

Numerical analysis of constraint effect on ductile tearing in strength mismatched welded cct specimens using micromechanical approach

In this paper, constraint effect on ductile fracture initiation and propagation has been studied. Three-dimensional finite element analyses of mismatched welded joints made of high strength steel, have been performed for centre-cracked tensile (CCT) specimens. Different weld widths and material mismatching ratios have been considered. Ductile fracture parameter crack tip opening displacement at crack growth initiation (CTODi), has been obtained for centre-cracked tensile (CCT) specimens using local approach to fracture and compared with experimental results of single edge bend specimens. Micromechanical complete Gurson model has been applied to investigate fracture behaviour of cracked welded joints. Crack tip constraint has been analysed through stress triaxiality in order to study transferability of fracture parameters from one geometry to anothe

Ductile fracture resistance of the weld metal and heat affected zone in a HSLA steel welded joint

Ductile damage development in welded joints of high strength low alloyed (HSLA) steel NIOMOL 490K was examined experimentally and analyzed using the micromechanical approach. Single-edge notched bend (SENB) specimens, cut from the welded plates and subsequently pre-cracked in HAZ and WM, were tested. True stress - true strain curves of the heat-affected zone (HAZ) and weld metal (WM) were determined on the smooth tensile plate specimen, by application of a combined experimental-numerical procedure which included stereometric strain measurement and finite element analysis. The complete Gurson model (CGM) was applied to estimate the fracture behavior of the analyzed zones of the joint. An important property of this model is that critical damage parameter value (used as failure criterion) is not a material constant-it is calculated in every load step, based on the stress and strain state in the structure. This feature is especially important in the examined joints, since the material heterogeneity causes pronounced stress and strain gradients. Finite element software Abaqus was used for numerical analysis. The crack growth initiation was predicted at the moment when damage parameter reaches its critical value in the element nearest to the crack tip. The advance of damage (i.e. the crack growth) was modeled by tracking the loss of load carrying capacity in the ligament (local stiffness reduction in the elements). It is concluded that the micromechanical approach can be used to assess the effects of constraint and heterogeneity on the fracture of the examined HSLA steel welded joints. HAZ fracture properties concerning both crack growth initiation and stable growth are slightly better in comparison with WM, as obtained by testing the SENB specimens with pre-cracks in these two weld zones. The influence of the finite element (FE) size on the results was also analyzed. It is found that the finite element size near the crack tip strongly influences the prediction of crack initiation and growth, and that there is a very significant difference in appropriate FE size between the WM and HAZ. For the analyzed materials, this size corresponds to the mean free path between the non-metallic inclusions in the examined welded joint zones

Fabrication of polypyrrole gas sensor for detection of NH3 using an oxidizing agent and pyrrole combinations: Studies and characterizations

The organic polymer known as Polypyrrole (Ppy) is synthesized when pyrrole monomers are polymerized. Excellent thermal stability, superior electrical conductivity, and environmental stability are all characteristics of Polypyrrole. Chemical oxidative polymerization was used to synthesize Ppy using Ferric chloride (FeCl3) as an oxidizing agent and surfactant CTAB in aqueous solution. Oxidant (FeCl3) to pyrrole varied in different molar ratios (2, 3, 4 and 5). It was found that increasing this ratio up to 4 increases PPy's conductivity. XRD, FTIR, and SEM were used to characterize Ppy. The conductive nature of Ppy was studied by I–V characteristics. The best conductive polymer is studied for the NH3 gas response