SU1303929A1 - Ultrasonic method of checking elasticity constant of isotropic thin-sheet materials - Google Patents

Abstract

The invention relates to non-destructive testing and can be used in ultrasonic testing of the physicomechanical properties of isotropic thin-sheet materials. The object of the invention is to increase the control accuracy by measuring the frequencies of the longitudinal and shear zero symmetric Lamb waves excited in the product. According to the method in the test material, the longitudinal and shear zero symmetric normal Lamb waves sj and SQ are excited, take them and measure their level. The excitation and reception of these waves is carried out by contactless electromagnetic-acoustic transducers with given spatial periods of the structure (S - A ,, 5 - - 1 (they change the frequency of excitation of these waves within 0.1 fd i0, 5, where d is the thickness The frequencies f, and f2 are recorded, at which the maximum received waves S and S | j are observed, and by these frequencies the constant elasticities are determined by the calculated formulas. 1 c.

Description

eleven

The invention relates to non-destructive testing and can be used for ultrasonic testing of the physicomechanical properties of isotropic thin-sheet materials.

The purpose of the invention is to improve the control accuracy by measuring the frequencies of zero symmetric Lamb waves excited in the products and the shear normal wavelength.

The drawing shows a device for implementing the proposed method

The device contains an evil magnet

No-acoustic emitters 1 and 2 of Lamb waves and shear normal waves. Generators 3 and 4 connected to radiators 1 and 2 and frequency meters 5 and 6, electromagnetic-acoustic receivers 7 and 8, amplifiers 9 and 10 connected to receivers 7 and-8 and indicators 11 and 12 of the received signal.

The method is carried out as follows.

At the frequency counter 6, the value of the hour is 5 you f 2 corresponding to this maximum. During the measurements, for both electroacoustic paths, the frequencies f of the excitation signal are varied within the limits satisfying the condition 0 0.1 f – d CO, 5 (f,, MHz; d, mm), where d is the thickness of the sheet material. In this range, the phase velocity

zero symmetric Lamb S waves

„And shear normal wave SQ n

In the studied thin sheet, it depends on the frequency. According to the measured rial 13 by means of an electromagnetic-acoustic radiator 1, at f values, and with known for

The Xj and the waves determine the constant elasticities by the formulas

The signal from generator 3 is applied, and a zero symmetric Lamb wave S is excited. Take this in full

The electrically magnetically-acoustic receiver 7 amplifies it in amplifier 9 and evaluates its magnitude by the signal level using indicator 11. As radiator 1 and receiver 7, contactless electromagnetic-acoustic Lamb wave transducers with a periodic magnetisation field are taken magnetic structure. These transducers most effectively excite and fi fi up an elastic symmetric Lamb wave S | .j, whose wavelength coincides with the period of the structure of the emitter 1 and receiver 7. In the process of measurement, changing the frequency of the generator 3, achieve a coincidence of length 7i, the rippled wave S with the period of emitter 1. This coincidence is judged by the maximum level of the received signal on the indicator 1 1 and the value of frequency f ,, corresponding to this maximum is recorded on frequency counter 5. In addition, in material 13, using an electromagnetic-acoustic emitter 2, to which a signal from generator 4 is applied, excite the shear sim

metric normal wave S °. This wave is received by receiver 8, the signal from which is fed through amplifier 10 to the signal level indicator 12.

The emitter 2 and the receiver 8 have the same periods of the magnetic structure. In the process of measurements, by changing the frequency of the generator 4, the length of the excited wave Sj is achieved, with the period of the structure of the emitter 2 and the receiver 8. This coincidence is judged by the maximum of the received signal on the indicator 12 of the signal level and fixed on the frequency meter 6 f 2 corresponding to this maximum. During measurements for both electroacoustic paths, the frequency f of the excitation signal is varied within the limits satisfying the condition 0 0.1 f – d CO, 5 (f, MHz; d, mm), where d is the thickness of the sheet material. Phase speeds in this range

zero symmetric Lamb S waves

„And shear normal wave SQ not

 dependent on frequency. By measured

dependent on frequency. By measured

the values of f, and for known lengths Xj and waves, constant elasticities are determined by the formulas

thirty

40 K

:) 1 2 (, f,

40 K

 - R .)

 E 4 p (A f

R (

f j-j

3 4 (Ar f-2

) 2, 1

 A, f,

where is the Poisson's ratio;

PJ-shear modulus;

Young's modulus;

K-module bulk elasticity;

p is the density of the material.

40 K

Claims (1)

50 claims The ultrasonic method of controlling the constant elasticity of isotropic thin-sheet materials, 55 that the material under study excites a zero symmetric normal Lamba wave S, takes this wave and measures its parameters. 13 according to which constant irregularities are defined, characterized in that, in order to increase the accuracy of control, they also excite and accept a shear zero symmetric normal wave sj, in the process of excitation of a wave, Lamba Sj, and shear normal wave S change the frequency f their excitation within the limits of the condition 0.1 fd, where f is the frequency in mHz, d is the thickness of the material under test in mm, before obtaining the maximum amplitudes of the received waves SP and SQ, the frequencies f and f, j are measured, corresponding to maximum amplitudes, and are determined by the formulas   12 ( I L, f T 1303929 | U p (A.f,). . pf A.f.) i - (, LA t G, J p to Where fo J5 one  0 E - K P of the length, respectively, of the Lsmba wave Sg and the shear normal wave So at the maximum amplitude; Young's modulus; bulk modulus; material density.