Measurement of vibrations of a wing

In the paper vibrations of a wing are investigated experimentally by using the method of time averaged projection moiré. Experimental setup is developed and the results obtained by using the experimental procedure are analyzed. Interpretation of projection moiré images on a shallow surface is more complicated than on a plane surface. For this purpose, a special simplified two-dimensional numerical model is developed and used in hybrid experimental – numerical procedures of investigation of vibrations of a wing

Measurement of large amplitude plane vibrations of two dimensional structures

In the paper large amplitude plane vibrations of an elastic structure are investigated experimentally by using the method of time averaged geometric moiré. Investigations of a two-dimensional problem are performed. Experimental setup is developed and the results obtained by using the experimental procedure are analyzed. On the basis of a one-dimensional model graphical relationships for linear variation with respect to longitudinal coordinate of amplitude of vibrations are obtained. They provide the background for interpretation of partially exposed time averaged moiré. Recommendations for the choice of background intensity are provided

Piecewise constant control of a precise measurement platform

Control of a precise measurement platform is investigated in this paper. Piecewise constant control procedure on the basis of finite element in time and the method of least squares is proposed. It is demonstrated that the proposed technique can be used to follow not only a predetermined law of displacement variations, but also velocity variations. Computational experiments with a system comprising one degree of freedom are used to illustrate the efficiency of the proposed technique

Comparison of hysteresis of high accuracy positioning system with piezoelectric actuators

In the paper, high accuracy positioning systems with flexible elements are investigated. In the analyzed systems, piezoelectric actuators are used for the transmission of motion and the hystereric phenomenon in them is investigated. Effect of the hysteretic phenomena to the precision of the high accuracy positioning systems is of special importance. For the investigations, a special experimental setup was designed and produced as well as the method of the experimental procedure was proposed. The experimental setup includes a computer, a piezocontroller, an inductive displacement sensor and a dynamic data collector. The dynamic data collector is used for the collection of data and for the transfer of data to the software for further processing. Numerical modelling of the hysteretic was performed by using the Matlab/Simulink software. In the process of investigations, it was determined that the maximum dispersion error of the hysteretic model is less than 5 % when compared with the experimental results. Thus, it is concluded that the proposed method of hysteretic phenomenon modelling is suitable for modelling of high accuracy positioning systems with flexible elements, which are controlled by piezoelectric actuators

Selection of number of gaps in superimposed moiré measurements

Plane vibrations of a two dimensional elastic structure are investigated in this paper. Vibrations taking place according to the eigenmode are represented by using the method of stroboscopic geometric moiré. Selection of number of gaps when using the superimposed moiré technique is investigated and recommendations for choosing of their number are provided

Reflection moiré for the measurement of wing vibrations

Investigation of time averaged reflection moiré measurements of vibrations of a wing is performed in this paper. Interpretation of reflection moiré images on a shallow surface of a wing is more complicated than on a plane surface. For this purpose, a special simplified two-dimensional numerical model is developed and the possibilities of application of this method of measurement of vibrations are investigated

Measurement of plane vibrations of a two dimensional elastic structure

Plane vibrations of a two dimensional elastic structure are analyzed in this paper. The vibrations taking place according to the eigenmode are represented by using the method of stroboscopic geometric moiré. This requires to perform the investigation for two mutually perpendicular directions of moiré fringes. Here the superimposed moiré technique is proposed to represent both images at the same time

Measurement of stability of a pipe system with flowing fluid

The two dimensional system of coupled vibrating pipes is investigated. The model of a pipe system consisting from two dimensional beams is employed. The problem of stability because of the reduction of stiffness caused by the flow of fluid is solved and the stability eigenmodes are determined. The places where the deflections of the stability eigenmodes are large are recommended for the location of measurement devices

Investigation of effect of acoustic field to coagulation of particles in air flow

In the paper theoretical and experimental investigations of the effect of acoustic field to coagulation of particles in air flow are presented. For the conduction of experimental investigations, a special experimental setup with measurement devices was designed and used. Principle of operation of the proposed experimental setup is presented and the method of conduction of experimental investigations is described. Investigations of effectiveness of coagulation of rigid particles of very small diameter have been performed and dependencies from the sound pressure of the acoustic field and its frequency were investigated. For excitation of the acoustic field two sound generators were used: piezoelectric and aeroacoustic. As a result of the performed investigations it was determined that with the increase of the frequency of acoustic excitation velocity of coagulation of particles increases when the diameter of the particles does not exceed 1 μm. For the most effective coagulation of the particles having the diameter up to 1 μm ultrasonic frequency is required. For the particles with the diameter larger than 1 μm frequency lower than ultrasonic is required. Dependencies of velocity of coagulation of particles from the frequency of acoustic signal and from its amplitude were determined. Initial granulometric constituent parts were compared with the constituent parts obtained after the experimental investigations

Circular-linear model of the force of dry friction

In the numerical methods taking into account the force of dry friction numerical approximation is used when performing calculations. Circular-linear approximation for the local transition region is recommended. Results of numerical calculations are presented. The advantages of using this proposed representation are seen from the obtained results presented in this paper