SU1422797A1 - Method and apparatus for determining thickness of articles - Google Patents

Abstract

The invention relates to non-destructive ultrasonic quality control and can be used to measure the thickness of products, from: any materials with one-way access to their surfaces. The purpose of the invention is to improve the accuracy of measuring the thickness of products. By varying the thickness of the contact layer, the resonance frequencies in the three-component system of the piezoelectric transducer — the liquid co-active layer — the controlled product and the piezo-transducer — the interfacial contact layer are achieved. The thickness of the monitored product is determined at an equal resonant frequency. To implement the method, use is made of a device containing a main and additional piezoplastics, a housing, a holder on which the main additional piezoplates are fixed and which is mounted in a housing for movement, a micrometer screw hinged to the holder and using a screw connection the case, and also the passive piezoplate, identical to the main and additional piezo-plates. The main and additional piezoplates are acoustically loaded through contact liquids, respectively, on the controlled product and the passive piezoplate. Moreover, the speed of propagation of ultrasonic vibrations in 7 kdkotsy, which is filled with a cavity formed by the body, the main piezo plate and controlled by the product, is two times higher than the speed of propagation of ultrasonic vibrations in the liquid, which filling ™ on the cavity formed by the body, passive and passive piezoplastics . The acoustic system, formed by an additional piezoplate, a liquid contact layer and a passive piezoplate, is a model of a two-component piezo-plate system — a liquid contact layer. 2 sec. f-ly, 2 ill. (L CZ with

Description

The invention relates to non-destructive ultrasonic testing and can be used to measure the thickness of articles made of material with unilateral access to their surfaces.

The purpose of the invention is to improve the accuracy of measuring the thickness of products.

FIG. 1 shows the proposed device for carrying out the method in FIG. 2 shows the graphs of the dependence of the resonant frequency of a three-component piezoconverter system; a liquid contact layer transducer — a controlled product (solid lines) and a two-component one. piezoelectric transducer systems - liquid contact layer (dotted line) versus thickness of the contact liquid layer.

The device contains the same external bolster and an additional 2 piezo-plates that serve to excite ultrasonic vibrations (UST), the Pyper plates 1 and 2 are electrically connected to each other and mounted on a common holder 3, which can be moved inside the casing 4 with a micrometer screw 5 connected The chart is nirno with the holder 3 and with the help of a threaded connection with the housing 4, Underneath the additional piezoplate 2, the cozyogastine b is coaxially passive with it, identical to the piezo-plates .1 and 2. It does not cause ultrasonic vibrations and resonant effects and x is involved as a passive layer. This piezo plate is attached to the adjusting disk 7J which is connected to the housing 4 by means of a threaded connection and makes it possible to adjust the distance between the piezo plastics 2 and 6. In addition, the adjusting disk 7 seals the local cavity 8 under an additional piezoplate, which filled with fluid with the speed of ultrasonic vibrations propagating therein by two times lower than the velocity of ultrasonic vibrations in the fluid filling the local cavity 9. under the main piezo plate 1 j, Acoustic cones The motivations of both fluids are the same.

The method of the invention is that the resonant frequency is the same for a three-component system. piezo transducer - liquid contact layer - controlled product and two-component piezo transducer liquid

the contact layer, is equal to the resonant frequency of the unloaded (freely-liberating) controlled product. Knowing this frequency, you can determine the thickness of the product by the Formula that is valid for a product with no loaded surfaces.

ten

nth

(one)

0

five

0

five

0

five

0

five

Where c - the speed of propagation of ultrasonic testing

in the material of the product, f is the resonant frequency; n is the resonance number. .

To implement the method of measuring the thickness of the product, an additional system of layers is used, the dependence of whose resonant frequency on the thickness of the contact layer completely coincides with a similar dependence for a two-component piezoelectric transducer-liquid contact layer. Thus, the additional system is a model of a two component system.

The method is carried out as follows.

Before the measurements, gaps between the main pie plate 1 and product 10 and between the additional 2 and passive 6 pie plates are set. To do this, place the device on the surface of the product 10 and put the main piezoplate 1 in contact with the product 10 using a micrometer screw 5. Next, remove the device from the product 10 and, by rotating the adjustment disk 7, contact the additional 2 and passive 6 piezoplastics. Then, the device is installed on the product 10 and electrically oscillations of variable frequency excite the main 1 and additional 2 piezoplates, and determine the resonant frequencies of the acoustic oscillations in the three-component and two-component systems of the device. Changing the thickness of the liquid contact with the law, rotating the micrometer screw 5 determines the resonance frequency for both systems. This corresponds to the intersection of the dependences of the resonant frequencies of the three-component and two-component systems on the thickness of the liquid contact layer (see Fig. 2). Using the expression (O, determine the thickness of the product under test.

Thus, this method of measuring the thickness of products allows you to try out the measurement accuracy by determining the resonant frequency of the three-component system piezo transducer - liquid contact layer - a controlled product, which completely eliminates the influence of the piezo-plate and the contact layer on the controlled surface. product.

Claims (2)

Invention Formula one . The method of determining the thickness of products, which involves exciting a variable frequency ultrasonic oscillations in a controlled product using a piezoelectric transducer through a liquid contact layer, changes the crowd of the contact layer, and determines the resonant frequency of the system piezoelectric transducer — liquid contact layer — controlled product at various values, the thickness of the contact layer, on the basis of which the thickness of the product under test is determined, characterized in that, in order to increase the measurement accuracy, to The resonant frequencies of the piezoelectric transducer system — a liquid contact layer at different values of the thickness of the liquid contact layer — are determined, and the thickness of the product is determined from the resonance frequency piezotransducer systems, - gp- cosmic contact layer - controlled product and piezotransducer - liquid contact layer. 2. A device for determining the thickness of products, comprising a housing, a holder mounted for movement within the housing, identical main and additional piezoplates, electrically interconnected and mounted on the holder, a micrometric screw connected pivotally to the holder and nocjfbACTBoM of a threaded connection with the body, characterized in that, in order to improve the measurement accuracy, it is equipped with an adjustable hard disk connected to the housing by means of a threaded connection and located coaxially with itel-. a piezoplate, a passive piezo plate (} i, identical to the other two and fixed on the adjusting disk; the cavity formed by the body, additional piezoplasty and the regulating disk is filled with contact liquid; the cavity under the main piezoplastic is designed to fill the working contact liquid with equal acoustic with contraction, and the rate of propagation of ultrasonic oscillations of the neck, than in the first liquid n twice. 1Kh% bb 9 xx obbhhh x boblg - t, 1. : f. 0 : 0.1 c Tlsch1 / but and / d / guest ftoft / noK / mioto C} W itsS nn