SU794474A1 - Device for measuring spatial attenuation coefficient of mechanical oscillations - Google Patents

Description

and the subtraction circuit, the inputs of which are connected to the outputs of the peak detectors, and the output to the recorder input, while the crank-and-rocker mechanism is installed between the working nozzle of the distribution chamber and the sample under test with the possibility of matching the small pox of the additional vibration receiver with the axis of the working nozzle in the extreme position of the scenes .

The drawing shows a block diagram of the proposed device.

The device consists of a distribution chamber 1 with a working nozzle 2, connected by a flexible hose 3 to a water mains, the main 4 and an additional 5 vibrating receivers, two spectral analyzers 6 and 7, two peak detectors 8 and 9, two logarithmic amplifiers 10 and 11, subtraction circuits 12, an electric signal level recorder 13 and a crank-cam mechanism 14 with a rocker 15, driven by a motor 16. In this case, the vibration receiver 5 is fixed with a pad nozzle on the slide 15. The vibration receiver 4 is fixed on the sample under test 17. Utility chamber 1 is mounted on a movable carriage 18 connected by a mechanical thrust 19 with a mechanism for pulling chart paper of a recorder 13 .;

The device works as follows.

When water is supplied under pressure to the distribution chamber 1 by means of a nozzle 2, a jet of water 20 is formed, which falls on the sample 17 and excites vibrations in it. By means of the curvature-rocker mechanism 14, the vibration receiver 5 is periodically introduced into the jet, and the motion of the swinging arm 15 is adjusted so that the time the jet acts on the vibration receiver 5 is equal to the jet impact time on the sample under study.

The vibration receiver 4 accepts a pulse signal, which with the help of the spectrum analyzer 7 and the peak detector 9 is converted into a constant signal, the amplitude of which can be written as

; X (, e - ", (1)

where XQ is the initial level proportional to the pressure in the distribution chamber; (A is the proportional coefficient); - the distance between the points of excitation and reception; a - coefficient of spatial

fading out.

The vibration receiver 5 receives a pulse signal, which with the help of the spectrum analyzer 6 and the peak detector 8 is converted into a constant signal, the amplitude of which can be written as

.P, (2)

where B is the proportionality coefficient.

Signals from peak detector outputs

8 and 9 after passing logarithmic

amplifiers 10 and 11 and subtraction circuits 13

form a signal whose amplitude Z is not

depends on pressure P

  {gB-l-lgP-lgA-lgP + “Mge lg4 +. (3)

l

This signal is given on the input of the recorder 13 and is recorded on a chart paper. By switching on the mechanism of drawing paper through mechanical connection 19, the carriage 18 with the distribution chamber 1 moves along the sample under study 17 towards the vibration receiver 5. As a result, the value of g decreases and, consequently, the amplitude of the signal recorded on the oscillogram increases.

The spatial attenuation coefficient a is measured according to the curve obtained by lime methods, for example, by the slope tangent.

The use of the proposed device for measuring the spatial attenuation coefficient of mechanical oscillations increases the accuracy of measurements by eliminating the influence of the inconsistency of water pressure on the results of measurements.

Claims (2)

Invention Formula A device for measuring the coefficient of spatial attenuation of mechanical vibrations, containing a distribution a chamber with a working nozzle connected to the water mains, a vibro-receiver mounted on the sample under study, a spectrum analyzer connected to the vibro-receiver, and a recorder, which differs from the free end of the scenes additional vibration tester, an additional spectrum analyzer connected to an additional vibration receiver, the first and second logarithmic amplifiers connected respectively to the outputs of the spectrometer analyzers, first and second peak detectors, connected respectively to the outputs of logarithmic amplifiers, and a subtraction circuit, the inputs of which are connected to the outputs of peak detectors, and the output to the recorder input, while the crank-and-rocker mechanism is installed between the working nozzle of the distribution chamber and the sample under test with the possibility of matching the axis of the additional vibration receiver with the axis nozzles at the extreme position backstage.  Sources of information taken into account during the examination 1. Klyukin I. I. et al. Acoustic measurements in shipbuilding. L., “Shipbuilding, 1968, p. 235. 2. Demidenko, TF, et al. Wave propagation in a rod with resonant ribs. - Acoustic Journal, ed. AN SSSR, 1975, XXI, 6, p. 873. Yoda