Mechanics
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ISSN 1734-8927
e-ISSN: 2300-7060
Issue Date
2007
Volume
Vol. 26
Number
No. 3
Description
Journal Volume
Mechanics
Vol. 26 (2007)
Projects
Pages
Articles
The use of piezoelectric elements to control vibrations of ax SMA material shaft
(Wydawnictwa AGH, 2007) Gałkowski, Zdzisław
In the paper an analysis of the influence of structural friction and piezoelectric elements on damping of torsional vibration in a shaft is presented. The structural friction between the piezoelectric actuators and the shaft is taken into account. It is assumed that the shaft is made of SMA material. A dependency describing the equivalent Kirchhoff modulus and the equivalent viscotic damping coefficient is introduced for the assumed material. For the purpose of the analysis a mathematical model of a permanent shaft-sleeve joint is formulated. The obtained differential equations of motion are solved using the asymptotic Bogoliubov-Krylov-Mitropolsky method via developing relations for derivatives of amplitude and phase. The obtained equations are solved for the case of harmonic excitation with uniformly increasing frequency of the driving torque and the effect of the gain factor magnitude on the damping level is examined. On the grounds of numerical simulations the growth of damping efficiency in the joint as a function of the gain factor is confirmed.
A new vibroacoustic method for shaft crack detection
(Wydawnictwa AGH, 2007) Gosiewski, Zdzisław; Sawicki, Jerzy Teodor
Various excitation techniques have been developed to extract information on dynamic state of rotating machinery. This paper will address the effectiveness of selected excitations and analysed signals towards health monitoring of rotating machines from the shaft crack point of view. The computer simulation study is based on the uncracked and cracked Jeffcott rotor models and the efficiency of the selected approaches is examined. As the excitation we have considered the rotor unbalance, additional harmonic forces, and input conditions. The combined resonances as diagnostic indicators of the cracked shaft are good seen in the total frequency spectrum in the case when we consider the difference between the spectra of cracked and uncracked shaft. We have also introduced a new model of the rotor which allows us to use different method of signal processing for the crack detection and the evaluation of its deep. So more, in such model we can take into account the number of excitation planes and directions of the applied forces, the choice of the analysed signals (e.g. transient, steady-state).
Computer simulation of a planar aerostatic two-coordinate relative base with electromagnetic drive
(Wydawnictwa AGH, 2007) Huścio, Tomasz
The paper describes the construction and the principle of operation of a planar aerostatic two-coordinate relative base with electromagnetic drive. Stages and results of the computer simulation of the planar aerostatic two-coordinate base are presented.
Experimental study of vibration control in a 3 DOF pitch-plane model of an MR vehicle suspension
(Wydawnictwa AGH, 2007) Sapiński, Bogdan; Martynowicz, Paweł
The paper is concerned with the experimental study of vibration control in a vehicle suspension model equipped with independently controlled magnetorheological (MR) dampers in front and rear sections of the vehicle body, and in the driver's seat suspension. Pitch-plane suspension model with one pitch degree of freedom (DOF) and two bounce DOFs was considered. The system was tested under harmonic excitations with an open loop and feedback. Performance of standard skyhook controller was compared with cascade controllers, in which the reference resistance forces determined by linear-quadratic or skyhook principles were fed to the inverse model of an MR damper. The tests were conducted in the experimental setup with measurement and control system configured in MATLAB/Simulink environment.
Analysis of thermodynamic losses in regeneration systems of the extraction back-pressure power unit in a combined heat and power plant
(Wydawnictwa AGH, 2007) Tokarz, Tadeusz; Karpiel, Tomasz
An algorithm is developed for computing thermodynamic losses in the regeneration systems of the back-pressure power unit in a combined heat and power plant. Thermal measurements taken under the typical working loads were utilised to compute and analyse variability of the thermodynamic losses in heat exchangers of the high-pressure and low-pressure regeneration systems in the heating and pseudo-condensing modes of operation.