SU1227962A1 - Method and apparatus for vibration testing of articles - Google Patents

Abstract

The invention relates to a method of vibration tests of products and a device for its implementation and provides an increase in the reliability of test results by eliminating the systematic error in measuring vibration at test points of a product caused by parasitic corner oscillations of the product. The method consists in extracting the in-phase component signals of vibration measuring transducers, The set of even-numbered test points of the product. The invention relates to a test technique, namely bu vibration test articles and apparatus therefor, and can be used in testing various products, preferably electronic and radio equipment. The aim of the invention is to increase the reliability of the test results. The goal is achieved by eliminating the systematic error from the pair at an equal distance on equal sides from the line of action of the vibratory force, and the formation of the selected components of the feedback signal to control the excitation level of the product. Isolation of the in-phase components is carried out by summing and dividing the two instantaneous current values of the signals of a pair of transducers. To implement the method, adders and dividers into two are inserted into the feedback loop, a device whose direct circuit contains a series-connected master oscillator, an automatic level controller, a power amplifier, and an electrodynamic vibration exciter. The outputs of the vibration measuring transducers of each pair are connected through an adder and a divider into two with the input of the selector, the output of which is connected to the control input of the automatic level regulator. 2 sec. F-ly, 2 il. Measurement of vibration caused by parasitic angular oscillations of the product, and more accurate maintenance of this predetermined mode of vibration of the product. Fig. 1 shows a diagram of an apparatus for carrying out the proposed method for vibration testing of products; Fig. 2 is a diagram illustrating the components of the vibration acting on a test article at its fastening points. yu sod

Description

The way in-product testing is as follows.

At the same time, the vibrations of the tested product are measured using vibration measuring transducers installed in an even number of test points of the tested product (for example, at its attachment points) in equal distances over different CTOs from the line of action of the vibration-induced Djeft force, from the instantaneous values of the signals the vibration transducers inject common-mode components and form a feedback signal from them. This signal controls the excitation level of the product, maintaining the specified vibration of the product. The isolation of the in-phase components of the signals of the vibration transducers is carried out by averaging the instantaneous, current values of the signals.

The possibility of isolating in-phase components in this way follows from the following.

The system of the movable part of the vibration exciter - a device - the test product in the general case makes angular oscillations around the center of rigidity (point O in FIG. 2) of the elastic suspension of the movable part of the vibration exciter. The control points A and B move in the direction parallel to the Y axis by the action of the vibration-induced force F with accelerations a. and ap,

hell ar- a. add31pg6d, (1)

de

L-hr

"R

+ a - COSi / ,, a „sin si ,,, (2) с and D ng о

- acceleration of translational motion along the axis Y, which should be created by force F;

-tangential accelerations at points A and B, caused by angular vibrations of this theme;

-normal accelerations at points A and B,

Under the condition of equality of the distances m of points A and B to the line of action of the force 50

3 "3, -j. Ld ix i

F (b, b,) we get / a.,,, -A / a

cos

cosoi /. Then, from expressions (1) and nebrega by the quantities a, and how small they are compared to a J.

get

I

AiSe. + 2.2 u ... A, 2 & u

0

five

0

five

0

five

0

five

Thus, with averaging. instantaneously the first current values of the vibration transducer signals, set at 1x at points A and B, acceleration Y of translational movement is highlighted, which is the only thing that should ideally be created by force V,

The identical result is obtained by averaging the instantaneous current values of the signals of vibration transducers installed in another pair of control points

Since in practice, product vibrations at different points can differ significantly, for example, due to insufficient and unequal stiffness of fixtures for fixing the tested product, for generating a feedback signal, the signals of vibro-measuring transducer pairs selected in the described manner are selected (for example, method of maximum or average levels),

The proposed method of vibration tests is carried out by a device containing a series generator, a automatic generator 2 level, a power amplifier 3 and an electrodynamic exciter A, on the movable part 5 of which the tested product 7 is fixed to an even device (in the example of the device, there are 2 pairs of vibration measuring transducers 8, 9 and 10, 11 installed in pairs at an equal distance on either side of the line of action of the vibration-stimulating force, sum Ators 12 and tSg whose inputs are connected to the outputs of vibration measuring transducers, respectively 8, 9 and 10, 1 dividers 14 and 15 into two, and a selector 16, with inputs through which the corresponding adder 12 (13) and divider 14 (15) connect two outputs vibro-measuring transducers 8, 9 (10, 11) The output of the selector 16 is connected to the control input of the automatic LEVEL 2 controller;

The device works as follows

The signals of each pair of vibration measuring transducers 8, 9 (Yu, 1) are fed to adder 12 (13) and further to divider 14 (13) by two, which are used to extract the common-mode components of the instantaneous current values of these signals. Using the selector 16, either the maximum of the signals at the outputs of dividers 14 and 15 is selected by two, or the average value of these signals is determined. The output of the selector 16 (feedback signal) changes the gain of the automatic Torah 2 level controller. Since the summation and division into two instantaneous current values of the signals of vibration measuring transducers excludes components due to parasitic vibration of products, the excitation level is controlled by the true value of the working component of vibration, which contributes to increasing the accuracy of maintaining a predetermined vibration exciter, vibration measurement

test bench and reliability of test results

Claims (2)

1. A method of vibration testing of products, according to which the vibration at the test points of the test product is simultaneously measured and a feedback signal is generated from the signals of the vibration measuring transducers using which regulate the excitation of the product, characterized in that, in order to increase the reliability of the test results, the vibration is measured at an even number of control points 5 that are in pairs at an equal distance on opposite sides of the line of action of the vibration-stimulating force Vibration transducers isolate the in-phase components and form a feedback signal from them. 2. Device for vibration testing of products, containing a series-connected master oscillator, automatic level control, power amplifier and electrodynamic converters and selector, the output of which is connected to the control input of an automatic level regulator, characterized in that it is equipped with adders and dividers into two - according to the number of pairs of vibration measuring converters, and the outputs of the vibration measuring converters of each pair are connected to the input of the selector through an adder and divider two. FROM /five L / "Epi flf, f