SU1436057A1 - Method of providing acoustic contact in ultrasonic measurements - Google Patents

Abstract

This invention relates to the field of ultrasound measurements. The purpose of the invention is to increase the reliability of contact. In the course of control, two magnetic fluids (MF) with different saturation magnetizations are introduced into the gap between the ultrasonic transducer and the product, and they are influenced by a magnetic field. The parameters of the magnetic field are chosen from the ratio M (4H) - - p, c, where M, J5 is the difference between the magnetizations and densities at the free MF boundaries; C is the surface tension; (vH); - gradient of tension in the neighborhood of free boundaries of the MF; experimental constant. 1 il.

Description

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The invention relates to ultrasound measurements, is intended to control products having a complex relief, and is an improvement of the invention according to the authors, No. 697916.

The aim of the invention is to increase the contact reliability by eliminating the magnetostatic instability of the contact magnetic fluid.

The drawing is a diagram explaining how to create an acoustic contact.

The diagram shows the controlled product 1 and the piezoelectric element 2 of the ultrasonic transducer between which the contact magnetic fluid 3 and the surrounding second magnetic fluid 4 are placed with a magnetization smaller than the magnetization of the first contact fluid 3. The magnetic fluids 3 and 4 are held in the gap gap between the ultrasound transducer and product 1 using a magnet 5 converter.

The introduction of additional magnetic fluid 4 in the working gap reduces

action of parasitic pressure P

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applied to the free boundary of the magnetic liquid zvzgeoprovod and, leading to delamination of the magnetic liquid acoustic duct, and, consequently, to a change in the sound transparency and stability of the acoustic contact.

In this case, the tension of the second magnetic fluid 4 must be less than the intensity of the first contact magnetic fluid 3 so that the second magnetic fluid 4 does not force out the first contact magnetic fluid 3. The second magnetic fluid must be introduced so that it surrounds the first contact fluid. magnetic fluid 3, since if a fluid with a higher magnetization is surrounded by a fluid with a lower magnetization, the liquid-liquid interface stabilizes, and the liquid-liquid interface st - air is less susceptible to instability than at the moment when the liquid with higher magnetization is on the periphery. The parameters of the magnetic field are chosen so that they satisfy the condition

M (l7H) - f g

0.5G ° -M: 27; c /,

| g

J5

20 25

thirty

35

40

45

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where M, j is the difference between the magnetization and density of the adjacent liquids in the vicinity of their free boundaries; G - surface tension

free borders; e is a constant defined by

experimentally; (GZN) - gradient of intensity in

neighborhood free boundaries.

The method of creating acoustic contact is carried out as follows. In the process of conducting ultrasonic measurements, two magnetic fluids, 3 and 4, with greater and smaller magnetization, are introduced into the gap between the product 1 and piezoelectric transducer 2. Magnetic fluid 3 is introduced into the region of the piezoelectric element 2, and fluid 4 is introduced along its periphery. The magnetic fluid is held in the slit gap by the magnet 5. Fluid 4m6t is supplied both once, for example with a syringe, and with the help of automatic donation systems.

Then the parameters of the magnetic field are changed until they satisfy the specified ratio. After this, it can be considered that there is a good acoustic contact between the transducer and the product and ultrasonic measurements can be made.

The constant, rf, is needed to determine the parameters of the magnetic field, is set in advance for different pairs of liquids using the following procedure.

For measurement, a plane-parallel cuvette with a variable thickness of 0-3 mm, into which the test liquids are poured, is used. In the side walls of the cell, piezo transducers are installed at a frequency of 5 MHz, operating in the shadow mode. Selected magnetic fluids are poured in such a way that the interface is at the level of piezoelectric elements. The cuvette is placed in a magnetic field of a given configuration. By changing the magnitude of the field, we fix the change in the transmitted ultrasound signal to the intensity I (average in the working area) 5 at which the instability occurs (deformation of the boundary). The magnetization of a fluid is determined by the magnetization curve using the relay-shift method. Surface Voltage and Density

liquids are determined by known methods. The gradient of the magnetic field dH is determined by the shape of the pole tips and can be easily calculated within the working area. The calculation is carried out according to the specified formula. As samples of magnetic fluids, magnetic fluids can be used on kerosene (sound conducting fluid) and on water (optional). It has been established that in order to eliminate the instability of the separation of the first and second liquids, it is necessary that in / 0.85, for the boundary, the second magnetic

Claims (1)

liquid - air (/ J 0.75. Claims of the invention The method of creating acoustic contact with ultrasonic measurements on the author. St. No. 697916, characterized in that, in order to increase contact reliability, between the second liquid having ferromagnetic properties is additionally introduced by the generator and the product so that it surrounds the first contact liquid and does not mix with it, and with a magnetization less than the magnetization of the first liquid, and the parameters of the magnetic field are selected from the field M (N) - o ( m,  -..with, de -constant determined experimentally; -difference of magnetization and density of the first and second liquids in the circumference of their free boundaries; vH - gradient of intensity in neighborhood free boundaries; G is the surface tension of free boundaries.