Applied Engineering Letters

98-104

Authors: S.Miladinović, S.Veličković, M.Novaković

An experimental research is performed in this study in order to optimize the parameters of planetary driving gear. An orthogonal array and analysis of variance (ANOVA) are employed to investigate the factors: material, module and gear width on the safety coefficient for surface durability. Statistical methods of signal to noise ratio and ANOVA with 95% confidence were applied to quantify the effects of considered factors as well as to obtain the minimum value of the safety coefficient for surface durability. The results of this analysis have shown that the gear module with 80.953% has the greatest influence on the safety coefficient for surface durability of the gear. The second influential factor is a gear width with 18.392%. And the material with 0.615% has the least influence on the safety coefficient for surface durability of the gear. The regression analysis is also shown in the study.

111-114

Authors: L.Trško, O.Bokůvka, M.Jambor, F.Nový, A.Bača, Z.Florková

Article provides experimental results in the field of ultra-high cycle fatigue behaviour of C55 high grade carbon steel obtained at high-frequency loading (f ≈ 20 kHz, T = 20 ± 10 °C, R = -1). The results confirm a continuous decrease of fatigue lifetime beyond the conventional fatigue limit. Fatigue fracture surfaces were characterized by surface fatigue crack initiation in both high and ultra-high cycle region, what means that that influence of microstructure defects was not significant enough to cause the sub-surface crack initiation.

67-71

Authors: Dj. Dihovicni

The question of pole placement for glass capillary tube drawing process is considered. It is used a frequency domain approach to an arbitrary finite spectrum assignment for multivariable time delay systems in order to control glass capillary tube drawing process. The Padé approximation is used for the system of third order and time delay is eliminated from the transfer function of the process. The responses are shown as well the transfer function of the closed loop after applying finite spectrum method. By choosing state variables it is obtained non degenerative transfer function of process model. The time delays in open loop remained the same as in the closed loop. The all poles are located in the left half plane and system is stable. Appropriate program support for this type of problems is developed in Maple language.

80-84

Authors: H.Monga, S.Baghla

The future developments of the wireless sensor networks and its applications demands for the efficient and secure communication. For the solution of efficient and reliable security needs cryptography algorithms provides good solutions. For providing reliable security schemes mainly data confidentiality now-a-days key management is used. This paper provides a review over cryptography schemes being used to deal with security issues of wireless sensor networks.

40-45

Authors: S.Franjić

The ultimate and main goal of countries in transition is the integration into the European Union and the integration of energy systems is a natural process. The first step is the restructuring of energy systems at the national level, by separating generation, transmission, distribution and supply, followed by the gradual introduction of market rules. After that, the goal is the integration of national energy in continental, first at the regional level. The Republic of Croatia has accepted all the energy requirements of the European Union and implemented them in practice, and the same is expected from the other candidate countries for membership. The energy sector is one of the most important parts of the national economy.

51-56

Authors: M.Neda, J.Waters

Numerical continuous finite element computations of a fluid flow modelling based on ensemble technique are presented herein. This ensemble algorithm is based on time relaxation. At each time step, it requires the storage of a single coefficient matrix with multiple right‐hands sides which corresponds to each ensemble member. Finite element convergence results for the time relaxation ensemble algorithm are presented and tested in a numerical experiment. This numerical experiment supports the theoretical finite element results. The time relaxation efficiency was shown in the second cavity benchmark problem.

8-15

Authors: A.Asonja; E. Desnica; E. Palinkas;

By using the method of finite elements and starting with the possibilities given by the program system ANSYS in the field of application, research has been performed regarding the analysis of static behavior of a centrifugal pump shaft. The computational analysis of static behavior of shaft using the method of finite elements on the examined model during the phase of projecting, was aiming for a timely sighting of critical spots, in order to avoid possible further malfunction. In this way it is possible to examine validity of the basic solution with no need for making the prototypes. By static behavior analysis, in other words, using the method of finite elements it was shown to which extent can certain conditions of exploitation, created tensions, that is shifted knots, cause difficulties in the whole model performance. Analysis of the static behavior of shaft was performed for two cases with different load: the effect of radial force and the torsion moment. A special attention was given to modelling of rolling-element bearings and following of their condition in relation to outside influences.

24-28

Authors: I. Miletić; M. Miletić;

The paper analyses the stability of a rectangular plate which is elastically buckled along longitudinal edges and pressed by equally distributed forces. A general case is analyzed – different stiffness elastic clamping and then special simpler cases are considered. Energy method is used in order to determine critical stress. Deflection function is introduced in a convenient way so that it reflects the actual state of the plate deformation in the best manner. In this way, critical stress is determined in analytic form suitable for analysis. With help of the equation it is easy to conclude how certain parameters influence the value of critical stress. The paper indicates how the obtained solution could be utilized for determining local buckling critical stress in considerably more complex systems – pressed thin-walled beams of an arbitrary length.