SU1516962A1 - Acoustic method of nondestructive checking of quality of articles made of multilayer materials - Google Patents

Abstract

This invention relates to acoustic methods of non-destructive testing. The aim of the invention is to increase the sensitivity of the monitoring due to the detection of defects with less disclosure due to the assessment of the presence of defects by the amplitude maximum of the mutually correlation function of the phase characteristics of the frequency spectrum of the received signals. In a controlled multi-layered product, elastic damped oscillations periodically synchronously excite at two points with vibrators. A receiver located between the vibrators receives oscillations and measures the phase characteristics of the frequency spectrum. The quality of the product is determined by the amplitude of the mutual correlation function of the measured phase-frequency characteristics. 3 il.

Description

The invention relates to acoustic methods of non-destructive testing and can be used in the inspection of products made from multi-layer materials, in particular products made from materials with a large attenuation coefficient of acoustic oscillations.

The aim of the invention is to increase the sensitivity of the control by using as a measured parameter a characteristic that permits the detection of defects with a small opening.

Figure 1 shows the cross-correlation function for a defect-free product; 2 shows the same dp function of a defective product with a defect opening of 0.05 mm; in FIG. 3, the same function for a defective product with a defect opening of 0.1 mm.

An acoustic method for non-destructive quality control of products made from multi-layer materials is as follows.

Synchronous shock excites at two points of the surface elastic damped oscillations. With the help of a receiver located between the excitation points, elastic damped oscillations are received. The phase characteristics of the frequency spectrum of the received signals are measured and their mutual correlation function is determined. The quality of the product is determined by the amplitude of the mutually correlation function of the measured phase characteristics.

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The acoustic method of nondestructive quality control of products from multilayer materials is implemented in the following way.

In a controlled product, for example, a metal plate 30 mm thick with rubber 15 mm thick glued on it, from the rubber side, using two jg vibrators, periodical two-point synchronous elastic excitation of elastic oscillations is produced. The signal f5 is received via a receiver located between the vibrators

g (t) g, (t) + gj (t),

where g, (t) is the signal from the first vibrator; g (t) signal from the second vibra- 20

Torah.

The spectral characteristic 6 (tt) of the received signal is associated with the recorded signal, the direct Fourier transform and is determined from the expression

00

6 (uj) e (t) exp (j (Jt) (u;) + JI, 6 (t)

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 6 (U)) exp j (/ (u;),

thirty

where 6 (i) is the amplitude-frequency characteristic (DFC);

H (a) | arctpl 1 F zo-frequency characteristic (phase response).

Estimation of the information content of the frequency response, phase response and impulse response g (t) by the matrix rank shows that Q is most informative because its rank, which is the number of significant eigenvalues, is higher than the other characteristics with the same number of measurements. The autocorrection function of the Q (f) Lava function t / (to) is determined from the

rage

,

Q (V;) i with (s) 1 / (s +) d, () i /, (u)) ifj (w) D "G - | H () 1 (

l /

jg 5

0

five

g

0

five

Q .c

about

) dVr + | h /) g (1) c1T. where tf, (u) is the frequency response of the signal from the first vibrator;

(u)) - phase response of the signal from the second vibrator.

The second and third terms of the last expression are the functions of mutual correlation of the base characteristics C, (t) and j (w) .no; When a defect is detected, the control conditions are always Cp, (ui) corresponds to the defective area, and 4 () is defect-free or vice versa. An experimental test on a 56 mm diameter necro simulator showed that the presence of a defect with a disclosure of 0.05 mm reduces the maximum of the autocorrelation function by an order of magnitude compared with the maximum of the analogous function corresponding to the defect-free area (from 200 to 20 conventional units). defects with a minimum disclosure (o, 05 mm), and with a large disclosure up to 0.5 mm.

Claims (1)

Invention Formula An acoustic method of nondestructive quality control of products made of multilayer materials, consisting in shock excitation at one point of the product of elastic oscillations, receiving oscillations excited in the product, measuring the parameters of the received oscillations and determining the quality of the product according to measured parameters, sensitivity control, additionally simultaneously excite elastic vibrations at another point of the product, at the same time receive basic and additional vibrations excited in the product, measure the phase characteristics of the frequency spectrum of the received signals, and quality; products are determined by the amplitude of the mutual correlation function of the phase characteristics of the frequency spectrum of the received signals. -0,5 -0,25О 0uf.1 0.25  f (f.} 60 ItO so -20 -0.5 -0.25O Fi9.2 60 kO about -20 0.5 0.25 about 01 / 9.5 O.S5