SU1460623A1 - Method of determining acoustic resistance of materials with uneven surface - Google Patents

Abstract

The invention relates to acoustic methods of non-destructive testing and can be used to test materials with an uneven surface. The aim of the invention is to expand the field of application of the method by making it possible to carry out the measurement with dry contact of the test and reference materials. The test material NiSH is in contact with the reference, the test material is emitted through the reference ultrasonic pulse, the coefficient R is determined, the reflections: ultrasound from the border of the sample f II is the reference material, then the acoustic resistance of the reference material is changed by one of the following ways: by changing its chemical composition, by means of its mechanical voltage, by applying an external electric or magnetic field when used as a reference electrostriction or magnetostrictive materials, respectively. The material under study is emitted through a reference ultrasonic pulse, the coefficient R is determined, and the acoustic resistance Zx of the material under study is determined by the formula (1 + + Rj) -Z, (1 + H2) (K, -K), where Z, - initial acoustic resistance of the reference material; acoustic resistance of the reference material after the change. 4 hp f-ly, 1 ip. S

Description

The invention relates to a-acoustic-non-destructive testing methods and can be used to study materials with an uneven surface.

The purpose of the invention is to expand the field of application of the method by making it possible to carry out the measurement with dry contact of the test and reference materials.

The drawing shows an acoustic diagram explaining the implementation of the method.

The method for determining the acoustic resistance of materials with an uneven surface is implemented as follows.

Test material I, which has an uneven surface, is brought into contact with the reference material.

2. An ultrasonic transducer (not shown) radiates ultrasonic oscillations 3 and 4 with amplitude in the direction of the contact boundary. Part 5 of oscillation 3, falling into contact with the test, emitted 1 and reference 2 material, passes into the material under study 1, and part 6 then emit another impulse from telesonic oscillations in the direction of the contact boundary under investigation - this is the ionic material. In general, e amplitude A, dd differs from the initial one. As the acoustic resistance of the reference material varies, the ratio of the amplitudes of the parts

Swings reflected in the opposite direction 5 and 6 also change. Wherein

. The oscillations 4, falling into the places where the contact 1 and the reference 2 materials are not in contact, are fully reflected in the opposite direction in the form of oscillations 7. The oscillation part 6 and the oscillations 7 form together an echo signal reflected from the dry contact boundary.

The following relationships are fulfilled:

the amplitude of the oscillation 7 does not change with respect to the APDD, thus the relations

15

20

 -o (, A i, + 0 (1,

where is the amplitude of the new reflected signal;

R is the reflection coefficient of the ultrasound in the places of contact between the studied and reference materials. Measure the amplitude of A. and determine the final ratio V.A. ultrasound reflection from the boundary of the contact to be investigated. reference material.

(.

, + oi,

-ci.A naA + ct R A

noiTJ

OUT

R A - the amplitude of the reflected signal;

true initial ultrasound reflection coefficient at the points of contact between the test and reference materials; shares of the area-. the surface of the reference material, respectively, in the places of its contact and the absence of contact with the surface of the material under study. Amplitude measurement

and ci. echo A

Otp

and determine the value

, /. / l I

the initial coefficient, / Aptd, the reflection of the ultrasound from the dry contact boundary of the studied material is the reference material.

Next, the acoustic impedance of the reference material is varied. This operation is performed by one of the following methods: replacing the source material with another one with excellent acoustic resistance, chemical action on the reference material, mechanical loading of the reference material, applying external electric and magnetic fields to the reference material, and of the material, respectively, use either electrostriction 1L 1 or magnetostriction material.

Then, a pulse of ultrasonic vibrations in the direction of the contact boundary is emitted again - the reference material under investigation. In general, its amplitude A, dd differs from the original. As the acoustic resistance of the reference material varies, the ratio of the amplitudes of the parts

5 and 6 also vary. Wherein

the amplitude of oscillation 7 with respect to the ADF does not change, thus the relations

 -o (, A i, + 0 (1,

where is the amplitude of the new reflected signal;

R is the reflection coefficient of ultrasound at the points of contact between the test and reference materials. Measure the amplitude of A. and determine the final ratio V.A. ultrasound reflection from the dry contact boundary under study -. reference material.

Considering that

R

Z2.-Z,

R

. Z., + Z,

where Z and Z are the initial and modified, respectively, acoustic resistances of the reference material,

The desired value of the acoustic resistance of the material under study is determined by the discharge

Zi (H-R2) -Z, (l + R,)

R, -R formula of the invention

Claims (5)

1. The method for determining the acoustic resistance of materials with an uneven surface, which means that the material under study is brought into contact with the reference material, emits ultrag., A sound impulse, receives echoes reflected from the test area — the reference material — an echo signal, measure it amplitude, determine the coefficient I of the ultrasound reflection from the dry contact boundary of the test - the reference material and the data obtained are used to find the acoustic resistance Z of the material, differing In order to expand the field of application of the method by providing measurements with dry contact between the test and reference materials, they change the acoustic resistance of the reference material, re-emit an examined ultrasound pulse in the direction of the boundary, take the reflected the echosignal, its amplitude is measured, the ultrasonic reflection coefficient Rj from the dry boundary is determined, the test material is the reference material, and the acoustic resistance Z of the test material Yedelev dissolved by the formula 7 - L2.Ll. ± L-li. , / t tch . Z is the initial acoustic impedance of the reference material; acoustic resistance of the reference material after the change. Z. with 0 5 0 five 2. The method according to claim 1, characterized in that the change in acoustic resistance of the reference material is made by using as a reference material with a different chemical composition, 3. The method according to claim 1, characterized in that the change in acoustic resistance of the reference material is produced by mechanical loading of this material. A, a method according to claim 1, characterized in that an electrostriction material is used as a reference material and the acoustic resistance is changed by changing the electric field applied to the electrostriction material. 5. A method according to claim 1, characterized in that the reference material is a magnetostriction material, and the change in its acoustic resistance is carried out by changing the magnetic field applied to the magnetostrictive material.