Knowing all characteristics of rotational system vibrations is most significant for a maintenance technician or engineer. Vibrations are carriers of a machine condition and by analysis of the vibration characteristics, it is possible to find what is the real cause of the vibrations. As a part of the research of rotational machinery vibrations, mathematical modeling of a rotational system is common tool before research is transferred to a real physical model. As an excellent method for this purpose, the best candidate could be a Finite Element Method. In this paper, an analysis of a Finite element model of rotational system motor – flexible coupling – rotor is presented. As a fault analyzed in this paper, misalignment and rotating looseness are modeled as external loads. For this FEM model of a rotational system is shown that it is suitable for the analysis of rotational machinery vibrations.

Vibrations are common phenomenon in the rotating machinery, which could carry important information about condition of the rotating machinery. All specific failures in rotating machinery have their own characteristics of the vibrations. By measuring and analysis of vibrations cause of increased vibrations could be determined. Since misalignment and rotating looseness have similar frequency spectrum characteristics, it is difficult to determine which one of the failures is present. When cause of increased vibrations is determined, it is possible to plan the future steps for the repairing and neutralising present cause of the possible failure. Process of vibration analysis followed by present cause of increased vibration in rotating machinery repairing is presented in this paper through example on the ventilation system for smoke drain in the thermal power plant. ARTICLE HISTORY Received 15.01.2018 Accepted 03.03.2018 Available 15.03.2018

This paper presents an analysis of beam elon-gation influence on the postbuckling displacements in case of axial compression by a force depending on axial deformation of the beam. It is performed both numerical and experimental analysis of this effect. Numerical analysis is done by using finite elements method. Nonlin-ear equilibrium equation is derived and solved using the method of simultaneous iterations. Verification of numeri-cal results is done by experimental analysis. Both numeri-cal and experimental results show significant influence of the beam elongation on postbuckling displacements.

This paper provides a review of the literature, progress and changes over the years on fault detection of gears using vibration signal processing techniques. Analysis of vibration signals generated by gear in mesh has shown its usefulness in industrial gearbox condition monitoring. Vibration measurement provides a very efficient way of monitoring the dynamic conditions of a machine such as gearbox. Various vibration analysis methods have been proposed and applied to gear fault detection. Most of the traditional signal analysis techniques are based on the stationary assumption. Such techniques can only provide analyses in terms of the statistical average in the time or frequency domain, but can not reveal the local features in both time and frequency domains simultaneously. Frequency/quefrency analysis, time/statistical analysis, time-frequency analysis and cyclostationarity analysis are reviewed in regard for stationary and nonstationary operation. The use of vibration signal processing detection techniques is classified and discussed. The capability of each technique, fundamental principles, advantages and disadvantages and practical application for gear faults detection have been examined by literature review.

Flexible lines for the production of welded girders SP-088 was designed in 1988 by the reputation of the existing constructive solutions that has the possibility of creating girders of different dimensions. The possibility of changing the parameters is done manually, which is set-up time needed eight to ten o'clock. As the market demands require less quantities of the same dimensions, carrier, or more frequent change of the parameters and the production of girders of different dimensions that are present at the time of the great economic crisis in the world and by us, the market demands a lot sharper in terms of time delays. With the economic standpoint, this flexible line has become non-productive for reasons that require frequent changes of parameters and dimensions of girder and therefore must be given to a new constructive solution for flexible lines SP-008 in order to meet market demands.Development of new flexible lines SP-008, as well as the development of computer technology have created new approaches and solutions for the acceleration and automatically adjusts the parameters of a porter, or making an appropriate application-software required for computer control, which is a goal and this work.

This paper presents numerical approach to post-buckling analysis of thin rectangular plates loaded in its plane, where deformation of middle plane is neglected. Numerical analysis is performed by finite elements method, dividing plate into mesh of twelve d.o.f. rectangular Kirchhoff finite elements. Outlines of deriving nonlinear equilibrium equation containing third order nonlinearities, arising from large displacement, are presented. Solution of equilibrium equation is obtained using iterative method. Numerical analysis is simplified using results of eigenvalues of linear stability analysis.