SU1044972A1 - Acoustic method of stress determination in solid media - Google Patents

Abstract

ACOUSTIC METHOD FOR DETERMINING STRESSES IN SOLID ENVIRONMENTS, which means that by means of a receiving-transmitting acoustic transducer, longitudinal and polarized in two directions shear acoustic oscillations are input into the object under study, determine the corresponding acoustic wave propagation speeds , according to the values of the shear and longitudinal vibration velocities determined in the stress object, the initial velocity value is determined dvigovyh oscillation and relative velocity increments of their initial value, which is judged regarding the nature. stress characteristics, characterized in that, in order to make it possible to determine the direction of action of principal stresses in environments with a large attenuation of acoustic oscillations and anisotropic environments, and to increase the accuracy of stresses determination, shear is introduced perpendicular to the plane of action of stresses acoustic oscillations polarized in the third direction, the first polarization direction is chosen arbitrarily in the case of a transition of isotropic and weakly expressed I anisotropy, and in the case of a low-tropic environment. in the direction (On anisotropy, the two other directions of polarization are chosen inclined to the first at acute angles equal in magnitude and opposite in sign, and the angle of inclination of one of the mutually perpendicular directions measured in the tense object values of the three shear vibrations actions of the main voltages relative to the selected first direction of polarization.

Description

The invention relates to non-destructive control methods and can be used as a non-destructive method of measuring stresses, including residual stresses, in I-welding production, in mechanical engineering and other industries. A acoustic method for determining stresses in solid media is known, which means by means of a receiving-transmitting acoustic transducer, longitudinal and two-way shear acoustic oscillations are introduced into the object under study; they receive reflected When the object acoustic signals., define respective velocity of propagation of acoustic vibrations at oppedehennym in a strained object values m sdvigov1h velocities and longitudinal oscillations determined .nachalnoe speed value and shear waves. relative increments - velocities of their initial value, which are judged on the characteristics of stresses 1. The known method does not allow to determine the direction of action of the main stresses in materials with a large attenuation of acoustic oscillations, where only one or two reflected signals are observed. With a sufficient number of signals reflected inside the object, the method allows to determine the main directions only in materials isotropic, such as organic glass,

and-in materials with poorly expressed initial anisotropy of properties, such as low-carbon steels with large thicknesses of steel after special heat treatment, in which the elastic anisotropy caused by stresses significantly prevails over the initial one.

In real materials, the appearance of initial anisotropy, for example, caused by metal, is comparable to the effect of elastic anisotropy caused by applied stresses, and in some materials (titanium alloys, special, high strength steels, aluminum sylaves, fiberglass) - dominates significantly . above the latter. Therefore, when measuring stresses in such materials by the indicated method, the main directions are assumed to be known. In addition, the conditions for ensuring the independence of the velocity measurement results from the amplitude of the received acoustic signal in the measuring devices, in order to provide the method, an automatic adjustment j is introduced.

force, as a result, all the reflected signals are amplified to one level. Therefore, in order to observe a natural series of signals reflected inside the object, it is necessary to have a single channel of force, which complicates the device.

The purpose of the invention is to make it possible to determine the direction of action of principal stresses in environments with a large attenuation of acoustic oscillations and anisotropic environments and to increase the accuracy of the measured dimension.

The goal is achieved by the fact that, according to the acoustic method of determining stresses in solid media, it is concluded that by means of a receiving and transmitting acoustic transducer, longitudinal and polarized shear acoustic oscillations are received into the object under study - signals, determine the corresponding speeds of propagation of acoustic oscillations, according to the values of the velocities of shear and longitudinal vibrations determined in the stressed object The initial value of the shear rate and the relative increments of the velocities from their initial value, which are judged on the characteristics of stresses, are determined, perpendicular to the plane of action of the stresses, polarized and in the third direction, the first direction of polarization is chosen in the case of an isotropic and weakly pronounced anisotropy medium arbitrarily, and in the case of an anisotropic medium in the direction of anisotropy, two different, extreme polarization directions are chosen inclined to the first at acute angles, different by the value and opposite: According to the sign, and according to the values of the propagation velocities of the three shear vibrations measured in the stress of the object, determine the angle of inclination of one of the mutually perpendicular directions of action of the main stresses relative to the selected first direction polarization.

The essence of the method is as follows.

By means of a transmitting acoustic transducer, longitudinal and two-way shear acoustic oscillations are introduced into the object under study, receive acoustic signals reflected inside the object, determine the corresponding acoustic wave propagation velocities, according to the shear and speed velocities determined in the object longitudinal oscillations determine the initial value, the velocity of the shear oscillations and the relative increments of the velocities from their initial value over which It is judged on the characteristics of the stresses, and in order to determine the direction of action of the main stresses in a medium with a large attenuation of acoustic oscillations and in anisotropic environments and to increase the accuracy of stresses in the object under study, shear acoustic oscillations are introduced perpendicular to the plane of action, polarized and in the third direction, the first direction of polarization is chosen, in the case of isotropic and weakly pronounced anisotropy, arbitrarily, and in the case of anisotropic medium s in the direction of anisotropy, the other two polarization directions inclined to the first vybirgiot at acute angles equal in magnitude and opposite in sign, and the measured object in a strained. the values of the propagation velocities of the three shear oscillations of a certain angle of inclination of one of the mutually perpendicular directions of action of the main stresses with respect to the selected first direction of polarization.

We introduce the notation:

()

the velocity of the shear acoustic oscillations that are polarized in the first direction, located at an unknown angle V k. main direction;

5, (C | -) shear velocity, polarized in the direction at an angle (tf-oi) to the main direction, where the known angle

g (.) is the velocity of shear oscillations polarized in the direction under the angle W – Ki) to the main one, where oL is the same known angle;

.)))

 C, W-ot) Cs (tfM) i q (f-ci)

s

K, 0 C + s w × cos V, eivi24 iiiiaf

Y. comp CSOL -sVn Vsiff i SinlMi sin-H /

. 0 1 - “a

C (H

-st ,.

)

(H)

Si

-in.,)

where C and ,, are the propagation velocities of shear acoustic oscillations polarized in the main directions in a stressed object.

The initial value of the velocity of propagation of shear oscillations in the object is determined from the relationship:

. ,, (6)

and the magnitudes and signs of the main stresses are determined by the formulas

where C is the speed of propagation. " neither longitudinal acoustic oscillations in a stressed object; - initial velocity of shear acoustic oscillations;

11, b, the required principal stresses;

A, B, A, N are the proportionality coefficients that are determined by the elastic moduli of the second and third orders of material. In the case of an isotropic and weakly pronounced anisotropy medium, the propagation velocity of shear acoustic oscillations depends little on the 5 position of its polarization plane. It changes mainly under the influence of the stresses acting in the object. Therefore, the measured values of the velocity C5x (H). C5y (0 and) are directly substituted into calculation formulas (1) - (8) for determining the position of the main ones: stresses and stress components. In the case of an anisotropic medium, on-chip anisotropy affects the value of the initial velocity of shear acoustic oscillations. For example, the oscillation speeds, which are polarized in the longitudinal direction of rolling l across, can vary significantly. You can talk about the initial velocity difference.

d co with; -with,

where c and c are the shear rates

acoustic vibrations

polarized respectively parallel and perpendicular to the direction of rolling. In such media, the first direction of polarization of shear acoustic oscillations, which is inclined at an unknown angle f. To the main direction, one should choose the direction of rolling. Then, for the calculation by the formulas () ... (8), the following velocity values are taken

С5л () - С-дСо,

Q (-cC) 1. (-), Cg.xX-) Cg (oL)

f, o

where Cg is the measured speed

shear acoustic oscillations polarized in the first direction located at an unknown angle

to the main direction; in an anisotropic body

CU (-ot} - measured speed

shear acoustic oscillations polarized in the direction at an angle of minus about to the first direction in an anisotropic body

“) The measured speed of shear acoustic oscillations, polarized by the direction at an angle od to the first board in an anisotropic body. Using the proposed spacing method will determine the direction of action of the main stresses in media with a large attenuation of acoustic oscillations in anisotropic media.

Claims (1)

ACOUSTIC METHOD FOR DETERMINING VOLTAGES IN SOLID MEDIA, which consists in the fact that longitudinal and polarized in two directions shear acoustic vibrations are introduced into the object under study by means of a receiving-transmitting acoustic transducer, receive acoustic signals reflected inside the object, determine the corresponding propagation velocities of acoustic vibrations, determined in stressed object, the values of shear and longitudinal vibrations are determined by the initial value of the shear rate x oscillations and relative increments of velocities from their initial value, which are used to judge the characteristics of stresses, characterized in that, in order to provide the possibility of determining the direction of action of the main Stresses in media with high attenuation of acoustic vibrations and anisotropic media and to increase the accuracy of determining stresses, the object, perpendicular to the plane of stress, introduce shear acoustic vibrations polarized in the third direction, the first direction of polarization in in the case of an isotropic medium and weakly pronounced anisotropy, they choose arbitrary in the case of an anisotropic medium - in the direction of anisotropy, the other two directions of polarization are chosen inclined to the first at sharp angles, equal in magnitude and opposite in sign, and according to the values of the propagation velocities of three Shear vibrations determine the angle of inclination of one of the mutually perpendicular directions of action of the main stresses relative to the selected first direction of polarization. > ϊ