Applied Engineering Letters

98-103

Authors: N. Petrović, N. Kostić, N. Marjanović

The complex problem of truss structural optimization, based on the discrete design variables assumption, can be approached through optimizing aspects of sizing, shape, and topology or their combinations. This paper aims to show the differences in results depending on which aspect, or combination of aspects of a standard 10 bar truss problem is optimized. In addition to standard constraints for stress, cross section area, and displacement, this paper includes the dynamic constraint for buckling of compressed truss elements. The addition of buckling testing ensures that the optimal solutions are practically applicable. An original optimization approach using genetic algorithm is verified through comparison with literature, and used for all the optimization combinations in this research. The resulting optimized model masses for sizing, shape, and topology or their combinations are compared. A discussion is given to explain the results and to suggest which combination would be best in a generalized example.

109-114

Authors: V. Mitrevski, C. Mitrevska, T. Geramitcioski, V. Mijakovski

In this paper the drying kinetics of far-infrared vacuum drying of some vegetables and fruits are presented. The experimental data of drying kinetics were obtained on experimental drying setup designed to imitate industrial dryer. Two well-known thin layer drying models from scientific literature were used to approximate the experimental data of drying kinetics in terms of moisture ratio. The performed statistical analysis shows that the model of Aghbashlo gives the best results for approximation of experimental drying data.

65-68

Authors: A. Pastukhov, E. Timashov, T. Parnikova

In the article the application of system approach to the study of thermal stress of units of transmissions of transport and technological machines on the example of cardan joints is considered. The authors carried out the analysis of parameters of diagnosing of cardan joints for the purpose of assessment of their technical condition, in particular, assessment methods on bearing clearance in bearing mount assemblies and in vibration parameters. On the other hand, in the transport equipment diagnosing methods on temperature condition of the work of a unit are widely known. For justification of the practical application of system approach to the solution of problems of preliminary treatment of cardan joints and increase in their reliability the consideration of a unit at three hierarchical levels is necessary: the first is defined by workflows in a bearing mount assembly, the second – directly in the cardan joint, and the third – by workflows of the cardan joint as a part of the drive line. Adaptation of system approach in studying of temperature condition of cardan joints allows to prove the modes of increase in reliability of cardan joints by optimization of their thermal conditions.

76-83

Authors: Dj. Dihovični, M. Medenica

Transient in long pneumatic lines is analyzed from time delay and construction view of point. After presented mathematical model of pneumatic system, there are shown stability issues, and it is calculated length of the pneumatic pipeline for which the system is stable. The paper's main contribution is the application of decision and fuzzy logic in determination the stability of long pipeline from construction perspective by using DB2 database approach, and proposal of possible applications of knowledge database and fuzzy logic in making diagnostics conclusions about the states of the safe operation and reliability of the system.

6-10

Authors: K. Brózda, J. Selejdak, P. Koteš

The application of the FRP (Fiber Reinforced Polymer) rebar is presented in this paper. The various kinds of fibers, depending on the types of the FRP rebar and types of matrix of FRP are listed. The main tasks of matrix and fibers are specified. The two methods of FRP bars production are explained. The selected physical and mechanical properties of the various types of the FRP rebar are shown and compared. The long-term properties of the FRP rebar, as relaxation and creeping processes, are also introduced. The FRP properties were compared to conventional steel reinforcement properties. Moreover, the typical disadvantages of traditional reinforced concrete, as the susceptibility to corrosion were presented. It is shown that the FRP reinforcement is quite opposite, since it has almost total resistance to corrosion. The corrosion factors, to which the FRP is resistant, are presented and explained.

16-21

Authors: J. Luštinec, V. Očenášek, J. Kec

The analysis of hydrodynamic steel sliding bearing with leaded bronze lining, which had a reduced shortened lifetime due to its unequal wear, was carried out. The lining structure of this bearing was compared to those of the bearing with a high lifetime and of the unused bearing. It was shown that the short lifetime is caused by wrong lubricating oil. The use of unsuitable oil led to the formation of hard and brittle layer containing phosphide (Cu3P) at the lining surface. The scaling off particles of the layer influenced the friction conditions and accelerated the wear.

27-31

Authors: W. Matysiak, T. Tański, E. Rusek, P. Snopiński

The article describes the investigation of the effect of electrospinning process parameters wherein the distance between the electrodes was variable, the voltage and the flow rate of the polymer solution was constant for the obtained polymer nanofibers from the solution of PVP/EtOH with concentration of 10% by weight. The morphology of produced nanofibers was examined using a scanning electron microscope (SEM). Based on the SEM images a series of measurements of the nanofibers diameters for each sample were executed and then the results were averaged. The research shows that reducing the distance between the electrodes has a significant impact on the diameter of the PVP nanofibers.

38-42

Authors: M. Morawiec, A. Grajcar

This paper presents some of technical aspects of the twin-spot laser welding of multiphase steels for automotive industry. The dual beam was obtained using a special optical system that divides a laser beam. The investigation was carried out in two main areas of welds, which are fusion and heat affected zones. The results show that in case of analyzed steels the use of twin-spot laser welding leads to changes in martensite morphology compared to single spot laser welding in both zones. The defragmented morphology suggests that tempering-like processes occur during the welding. This phenomenon causes the decrease in weld hardness compared to single spot laser welding.

48-53

Authors: P. Snopiński, T. Tański, W. Matysiak

The present study was initiated to investigate the influence of an ECAP die on the microstructure evolution and properties of commercial Al-Mg aluminum alloy in as-cast state. To characterize microstructural features an optical microscope was used. The properties of the as processed and initial state material were evaluated based on the hardness measurements. It was found that the applied ECAP die has the meaningful influence on the microstructure as well as the properties of the material

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.