SU1719981A1 - Method of ultrasonic quality control - Google Patents

Abstract

This invention relates to a technique of non-destructive ultrasonic (UL) control methods. The aim of the invention is to expand the field of application by ensuring control of products of various thickness. A transducer with a damper 9 and a piezoplate 6 is placed in a sound-conducting medium 7 at a given distance above the product 8. The generator 1, using a piezo-plate 6, excites short pulses of ultrasonic vibrations in the damper 9 and product 8. The piezo plate 6 receives the reflected damper 9 and product 8 echo. signals. The time selector 3 selects the bottom echo signal from product 8 and the echo signal reflected by the front face of product 8, passed through the sound-conducting medium 7, piezoplastic 6 and damper 9 and reflected by the free surface of the damper 9. Using the analyzer 5, the spectrum is fixed the total spectrum of the extracted echoes, the values of the frequency minima of the total spectrum are measured and the quality of the product is determined from them. 3 il. $ Ib

Description

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The invention relates to non-destructive testing by ultrasonic methods and can be used to control product quality.

There is a known method for detecting defects in products, which means that short pulses of elastic oscillations are emitted into a controlled product,

echo signals of time selec-JQ of FIG. 2 are selected — the total spectral characteristic obtained on the defect-free portion of a product 150 mm thick from

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by the torus and in the form of the spectrum of these signals, the presence of defects is determined.

This method does not have a sufficiently high sensitivity.

The closest in technical essence to the present invention is a method consisting in arranging a transducer with a damper and piezostatina in a sound-conducting medium above the product, emitting ultrasonic vibrations into the damper and sound-conducting medium by the piezoelectric plate, receiving the reflected damper and product echo from the piezoelectric plate signals, record the total spectrum of the bottom echo from the product and the auxiliary echo, measure the frequency minima of the total spectrum, and determine the quality products. thirty

However, the known method does not allow control of products having a greater thickness, because in order to obtain a minimum in the total spectrum, in this case, it will be necessary to manufacture a converter with a damper, the thickness of which must be commensurate with the thickness of the product, which is practically difficult to implement .

The purpose of the invention is the expansion of the field of application by ensuring control of products of various thicknesses.

The invention allows control of products with a thickness of several millimeters to several meters.

The invention relates to acoustic methods of non-destructive testing.

The essence of the invention is that ultrasonic pulses are emitted through a sound-conducting layer into a controlled product, an echo signal passing through a sound-conducting layer, a piezoplate and a damper and reflected by the free surface of the damper are recorded from the front face of the product. The thickness of the conductive layer, piezoplates and damper is chosen so that the delay time between the echo signal from the free surface

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steel obtained by diffusion welded -KoftJ in FIG. 3 - the same, on the defect in the form of a line non-pair with a maximum size of the line of 60 microns and on the disclosure of 5 microns.

The method is carried out as follows.

A piezoplate 6, operating, for example, in the frequency range from 4 to 6 MHz, is excited by the generator 1 of short pulses. A piezoplast 6 with a thickness hn emits through a sound-conducting fluid 7 with a thickness hja into the product 8 with a thickness b and ultrasonic vibrations with a certain maximum frequency of the spectrum component, for example 5 MHz. Ultrasonic vibrations, after passing through the liquid medium 7, are divided into a reflected echo signal from the front. the edges of the product 8, and the rest of the oscillation energy passes into the product 8 and returns as a bottom echo back to the piezoelectric plate 6. The echo signal reflected from the front face goes back through the sound-conducting medium 7 and the piezoelectric plate reflected the free surface of the damper 9 is returned back to the piezo plate 6, which converts ultrasonic echoes delayed relative to each other into electrical impulses. These echo pulses are amplified by amplifier 2 and through time selector 3, which selects them from other interfering signals, are fed to the oscillator of graph 4 for indication and to the input of spectrum analyzer 5 for spectrum analysis. The height of the sound-conducting layer hjB and its material are chosen such that the delay condition is met. Between the echo pulses

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the damper and the bottom echo satisfied a definite formula. The frequencies of the minima of the total spectrum of the received echo signals are measured and the product quality is determined from them.

Figure 1 shows the functional diagram of the device that implements the method of ultrasonic quality control of products; on

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five

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,

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steel obtained by diffusion welded -KoftJ in FIG. 3 - the same, on the defect in the form of a line non-pair with a maximum size of the line of 60 microns and on the disclosure of 5 microns.

The method is carried out as follows.

A piezoplate 6, operating, for example, in the frequency range from 4 to 6 MHz, is excited by the generator 1 of short pulses. A piezoplast 6 with a thickness hn emits through a sound-conducting fluid 7 with a thickness hja into the product 8 with a thickness b and ultrasonic vibrations with a certain maximum frequency of the spectrum component, for example 5 MHz. Ultrasonic vibrations, after passing through the liquid medium 7, are divided into a reflected echo signal from the front. the edges of the product 8, and the rest of the oscillation energy passes into the product 8 and returns as a bottom echo back to the piezoelectric plate 6. The echo signal reflected from the front face goes back through the sound-conducting medium 7 and the piezoelectric plate reflected the free surface of the damper 9 is returned back to the piezo plate 6, which converts ultrasonic echoes delayed relative to each other into electrical impulses. These echo pulses are amplified by amplifier 2 and through time selector 3, which selects them from other interfering signals, are fed to the oscillator of graph 4 for indication and to the input of spectrum analyzer 5 for spectrum analysis. The height of the sound-conducting layer hjB and its material are chosen such that the delay condition is met. Between the echo pulses

where fl, f are respectively top

and the frequency spectrum frequency reflected by the echo damper at the level

o, 5 Hz;

, hn, h ,,, hM is the thickness of the conductive layer, piezoplate, damper and product, respectively, Mj c, Cn, Cd, s is the propagation speed of ultrasonic vibrations in the material of the conductive medium, piezo plate, damper and product, respectively, m / s ,

p 1,2,3

The established delay between these echo pulses, which are analyzed by the spectrum analyzer 5, makes it possible to observe one or several frequency minima in the total spectrum (this depends on the chosen frequency in the spectrum of the bottom echo signal and the number n 1,2,3, ..., i.e., from the magnitude of the delay) in the frequency range from f to f (the boundary frequencies f, and f 2 are selected from the condition of observing a clear contrast interference minimum). The quality of the product is determined for the position of the frequency minimum in the total spectrum given for the defect-free area of the product in Fig. 2, and for the defective area of the product in Fig. 3.

Claims (1)

Invention Formula The method of ultrasonic quality control of products, which consists in placing a transducer with a damper and a piezoplate in a sound-conducting medium above the product, radiating pulses of ultrasonic vibrations into a damper and sound-conducting medium into the piezoplate, receiving echoes from the piezoelectric plate and recording echo signals from the divider, fixing The measured spectrum of the bottom echo signal from the product and the auxiliary echo signal, measure the values of the frequency minima of the total spectrum and determine the quality of the product that distinguishes In order to expand the scope of application by providing control of products of various thickness, the echo signal reflected by the front edge of the product, passing through the sound-conducting medium, piezoplate and damper and reflected by the free surface of the damper, is used as an auxiliary echo signal, and the thickness a sound-conducting layer between the piezoplate and from-1-. the value and thickness h of the damper are chosen from the condition de f one Gl ™ respectively, the upper and lower frequencies of the spectrum reflected by the echo damper at a level of 0.5 Hz; B, b, b, b are the thicknesses of the sound-conducting layer, piezoplates, damper and product, respectively; , the propagation velocity of ultrasonic vibrations in the material of the sound-conducting medium, piezoplates, damper and product  one- si n accordingly, m / s; /, / y / z fig z 44zg / ff) Jmt / 7 Fig.Z Compiled by A.Zakharov Editor A.Lezhnina Tehred M.Didyk Order 768 Circulation VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 6.0 MHz Proofreader M.Samborsk Subscription