SU147792A1 - Method of measuring vibration isolation - Google Patents

Description

Methods are known for measuring the obstacle zibroizolyatsii, which are paved by using a semi-infinite rod, excited by a transverse force, in the middle part of which the obstacle is fixed, and the amplitudes of oscillations along the rod are recorded using a vibrating receiver and a level recorder. The use of such methods is ineffective, since it requires a considerable amount of time for laboratory research. Vibroinsulation of obstacles in laboratory conditions.

In order to significantly reduce the time spent on measurement, in the proposed method, the obstacle vibration isolation is determined by comparing the known input impedance of the rod without interfering with the variable input impedance of the rod on which the test obstacle is installed.

The drawing shows the block diagram of the device, see opioavim method.

In the middle part of the semi-infinite rod 1, one end of which is made in the form of a wedge, test obstacle 3 is fixed to eliminate reflection from the end immersed in sand 2. To eliminate energy leakage, the opposite end of the rod / is fastened through a fastening using a mechanical filter not specified in the drawing, consisting of alternating masses and elastic springs. The resonant frequency of the filter should be less than the lowest frequency studied. The rod / is excited by an electrodynamic driver 4, made of an electrodynamic loudspeaker with a power of about 1-2 watts with an annular magnetic system, and a sound generator 5.

On the exciter 4 to the point of excitation of the rod / installed miniature piezoelectric vibration detectors 6, 7, electric

M 147792

a signal from which is fed to measuring sensors 8, 9 with a pointer device. From the output of the amplifiers 8, 9 the signal goes to the f. Meter W.

Vibration Isolation In npstvst determined from the ratio:

In Wig 14

where d is the coefficient of the passage of the energy of the bending waves through the obstacle.

The energy expended on the excitation of the rod, with the input imeda-nsom force F

The input impedance of the rod with respect to the transverse excitation force

2 ,. - -M / + /),

where "TO, C" sg is the mass of a rod per unit length and the speed of the bending waves in a rod: not.

If there is an obstacle on the rod, the input impedance

ZV "-CHA + UCH

where an b b are real coefficients.

Consequently, “iberoizol of an obstacle after transformations is found in the form:

B / O /

Thus, to determine the vibration isolation of an obstacle, it is necessary to measure the input impedance of the rod with the obstacle installed using an electrodynamic driver 4 with a known mass T of the magnetic system.

When the oscillatory velocity |, n is the exciter, the force acting on the rod at a frequency and F / cell |, „.

In this case, the impedance of the rod

where - oscillatory speed of the rod at the point of excitation. ,, The last equality can be written as

ZK com -, - (-sina-f / cosa),

 -TWeating an oscillation amplitude of the exciter and rod at the point of excitation; and - phase shift between inmi.

From a comparison of the obtained value of the impedance of the rod with its value in the presence of an obstacle on the rod, we find that

a-pYSina; 6 p7soza, where (--j

- rod thickness; C ,,,, is the velocity of longitudinal waves in the rod.

db

W -

a2 + b

db

jiotri m

 oi-s „, /