RU54198U1 - DEVICE FOR ELECTROMAGNETIC ACOUSTIC (EMA) QUALITY CONTROL OF METALS AND ALLOYS - Google Patents

Abstract

The device contains a serially connected synchronizer, a probe pulse generator (GZI), an electromagnetic-acoustic transducer (EMAP), a preamplifier, a pulsed magnetizing electromagnet and a power supply unit, characterized in that it includes an EMA consisting of a multi-element inductor, an arithmetic logic device connected in series with a second DAC unit and pre-amplifier inputs and a replacement board for matching the output of the pre-amplifier with wet inputs testers and flaw detectors, and between the synchronizer and the GZI block, respectively, n blocks of continuously adjustable delays are included, while the EMAT elements are made in the form of a thin metal plate on which the receiving windings are wound, over which the generator winding is wound, and between the outputs of the receiving windings of each element the inductor and the input of the pre-amplifier are sequentially connected to a differential amplifier, a block of controlled delays and a coherent adder. In this case, between each block of formation of a pack of high-frequency signals and a preamplifier of GZI power, a series-connected amplifier-limiter and a coherent adder are connected.

Description

The invention relates to the field of non-destructive testing and can be used in metallurgy, mechanical engineering and in the control of various products (pipes, sheets, welded joints, etc.) during the installation and operation of nuclear and thermal power plants.

For many decades, in the practice of ultrasonic testing of various products from metals and alloys, ultrasonic flaw detection and thickness measurement, and structural measurement using piezoelectric elements as a meter and receiver have been and are widely used. In this case, the necessary condition is the use of fluid between the working surface of the piezoelectric sensor and the surface of the controlled product, the so-called "wet" method.

In practice, the above industries around the world are saturated with "wet" flaw detectors and thickness gauges for general and specialized purposes (see Non-Destructive Testing and Diagnostics: Reference / Edited by V.V. Klyuyev. - M .: Mechanical Engineering, 1995. - P. 142-235.). The issues of the theory of ultrasonic flaw detection, thickness measurement and structuremetry by the wet method are sufficiently deeply and thoroughly covered. Due to the fact that “wet” contact between the surface of the piezoelectric sensors (PEP) and the surface of the controlled product leads to very big troubles (first of all, the instability of the contact depending on the state of the surface of the product, which reduces the accuracy of flaw detection and thickness measurement) for the first time in 1933. The contactless electromagnetic-acoustic (EMA) method of defectoscopy and structurescopy was used. An analytical review of this method (in terms of the development of theory and practice) was carried out by G.A. Budenkov, S.Yu. Gurevich in the article "The Current State of Contactless Methods and Means of Ultrasound Monitoring" ("Defectoscopy", 1981, No. 5, pg. 6-22). This review covers the period up to 1978.

A large surge in the works devoted to theory and practice in the development of EMA methods has occurred around the last 4-6 years. A review of the works (mainly of modern EMA thickness gauges) was reflected, in part, in the article by G. M. Suchkov “Possibilities of modern EMA thickness gauges” (Defectoscopy, 2004, No. 12, pp. 16-35).

It follows from this work that by now various organizations (Scientific Research Institute of Electronic Introscopy Moscow, NIIIN, IES named after Paton Kiev, CJSC NIINN INGO SPECTRUM Moscow, CJSC NIKO-Tube Nikopol, Kharkov Polytechnic Institute and others) a number of EMA thickness gauges for manual and automatic installations, such as UVT-03, UT-40B, UT-80B, EMAT-100, EMAT-1, KRM-Ts- "Delta"; A1270, the distinguishing feature of which is:

- increase in pulse power from 600 W to 12 kW with a current in the inductor up to 100 A (mainly for installations);

- the formation of the optimal shape, duration and frequency of the sinusoidal high-frequency signal;

- a correlation method of processing information or coherent signal accumulation in order to reduce the measurement error and the thickness of the controlled products (A270 and EMAT-100).

The main disadvantages include:

- not enough optimal construction of the EMAT inductor in order to obtain the maximum value of AW w / h pulse (not only by increasing the pulse power of the probe pulse generator (GZI) and increasing the inductor current to 100 A);

- significant values of induction B in the gap - up to 1.2 Tc, which leads to a deterioration in the operational characteristics of the EMAT (its strong attraction to the controlled surface);

- lack of recommendations for managing the EMAT radiation pattern in order to achieve maximum sensitivity.

These disadvantages are largely eliminated in the proposed electromagnetic acoustic transducer (Patent for invention No. 2246101 C 2 G 01 N 29/04) with priority dated March 17, 2003.

This invention proposes a multi-element (multi-inductor) EMAT that can significantly increase AW w / h of the signal, without significantly increasing its power and creating the prerequisites for creating phased arrays that allow you to control the directivity pattern of EMAT, both straight lines (for example, focusing of the ultrasound beam), and creating inclined EMAT.

In view of the foregoing, incl. and these shortcomings, to date, work has progressed significantly on the development of EMA thickness gauges (portable and automated installations). This was reflected in the quantity and quality of EMA thickness gauges and flaw detectors displayed at the 4th International Exhibition and Conference "Non-Destructive Testing and Technical Diagnostics in Industry", Moscow. May 17-20, 2005

At this exhibition were presented:

The company PANAMETRIR-NDT, USA presents a direct EMAT type E110-SB, working in conjunction with the LSB-74-4 flaw detector and filter adapter type 1/2 XA / E110, as well as with thickness gauges 37 DL PLUS and ЕРОСН4 PLUS. (The control range is 2.0-125 mm, at a temperature of the part - from 0 to 80 C, through a thick layer of corrosion).

2. Universal thickness gauge "4D4-T" of the company "Votum" Moscow, equipped with EMAT - separate and EMAT - separately combined, using the correlation-phase processing method. The control range is 0.3-60 mm, the error is 10 microns.

3. Association "SPEKIR-GROUP", Moscow.

3.1. EMA thickness gauge A 1270 (mainly for aluminum alloys), using correlation information processing.

- thickness control range - 0.5-100 mm

- measurement resolution - 0.01 mm

- weight - 650 g.

- operating frequencies - 2.5-5.0 MHz.

3.2. EMA - flaw detector A1272, using direct EMAT.

- operating frequencies 0.4; 1.0; 1.8 MHz

- power - batteries

- dimensions - 250 × 160 × 110 mm

- the mass of the electronic unit is 2.7 kg.

4. CJSC NIIIN MNPO "SPECTR", Moscow.

EMAT thickness gauge - 100. Controlled materials including ferromagnetic steels and alloys. Coherent signal accumulation is applied.

- thickness controller range - 3-50.0 mm

absolute error of thickness measurement, d, mm - (0.1 + 0.001 T), where T is the nominal thickness value;

- overall dimensions, electronic unit, mm - 195 × 100 × 45

- weight with batteries "Krona VTs" - not more than 0.6 kg.

5. LLC "Company Nordinkraft", Cherepovets.

EMA installations for automated ultrasonic testing of the type "Mayak-7-02", "North 6-08-3000-2", "Wave 6 - Oskol"

- thickness of the controlled walls - 2-60 mm

- pipe surface temperature - +20 to +400 C

- mass of electronic equipment - ≤250 kg.

6. NPP Vigor, Moscow.

6.1. Multichannel analog-to-digital hardware-software complex UD-EMA-RSP, for single-wire rail monitoring (4D-EMA-RO-2)

- ultrasound frequency, MHz - 1.8 - direct channel

- 1,0 - inclined channel;

- input angle of ultrasonic testing, city. - 0; 45; 90;

- pulse power of the probe pulses, kW - 30.0;

- power consumption, VA - not more than 200.0.

The equipment listed above is mass-produced. The EMA equipment presented at the 2005 international exhibition (and in previous years) indicates a significant gap in the theoretical and experimental studies of the acoustic field of the EMAT depending on its design and circuit solutions, which complicates the development of inclined EMAT for flaw detection of various metals and alloys. To a lesser extent, for well-known reasons, this concerns flaw detection using direct EMAT. In addition to theoretical and experimental studies of the EMAT fields carried out in the above reviews and reference books, in recent years, theoretical studies of the EMAT field have appeared in the case of direct and inclined excitation of ultrasonic scanning of body waves.

Here, intentionally, the works related to the excitation and reception of normal waves by the EMA method are not mentioned, since they are quite well described in the first review and reference book and do not cause special difficulties in the development of EMAT and equipment for defectoscopy and structuroscopy of thin-walled sheets, pipes, including . with correlated surfaces (see the article by G.M.Suchkov, Yu.A. Katasonov "On the practical application of EMAT for flaw detection of the surface of products of complex shape using the echo method", J. Defectoscopy, 1999, No. 10, pp. 15-19 )

In the work of V.E. Chebanov, V.I. Gordeliy "Theoretical and experimental study of EMA converters" (4th National Scientific and Technical Conference and Exhibition "Non-Destructive Testing and Technical Diagnostics - 2003", Kiev, May 19-23, 2003 d) theoretically and experimentally investigated direct EMAT with a butterfly-type inductor, as well as a converter with a variable pitch between the coil conductors.

The calculated and experimental data on the dependence of the amplitude of ultrasonic testing on the reflector and on the angle of its inclination with respect to the vertical are presented. It is noted that, based on these studies, it was possible to design EMAT reliably working at large angles.

However, there are no more or less simple and clear relations for inclined EMATs at a given input angle with the necessary sensitivity.

There is no sufficiently transparent relationship between the dimensions of the EMAT working part and the number of turns, wire diameter with reference to the wavelength λt or λ1, both for linear coils and for spiral coils, gap sizes, design features of sensors providing homogeneous I / O and magnetizing fields that affect the ratio shear and longitudinal components and, as a result, to the EMAT radiation pattern in the radiation - reception mode.

The work of G.M.Suchkov, Yu.A. Katasonov "Experimental studies of a new method of non-contact ultrasonic flaw detection of pipes by the echo method" (J. "Defectoscopy", 1999, No. 11, p. 77-80) presents the results of experimental studies according to the EMA control by the method of мм28 mm pipes with wall thickness d = 1 mm, ⌀51.3 mm, d = 3.5 mm (steel 45), apparently, using normal waves, pipes ⌀168 mm, d = 10.4 mm; ⌀12.3 mm, d = 7 mm using body waves.

Ultrasound pulses excited and received EMAT from one surface. The EMAT working area was 6 × 12 mm. The magnitude of the polarizing magnetic field was 0.6 Tc. The gap between the EMAT and the metal surface was 0.5 mm, the frequency range was 2-2.7 MHz, the pulse duration varied in the range from 1 to 18 periods. In this case, longitudinal and transverse defects were confidently detected on the outer and inner surfaces of the pipes, as well as internal defects in the wall of the sheet pipe when accessed from one side. It is noted that defects with cracks with an opening of less than 0.1 mm and a depth of more than 0.2 mm, as well as lack of penetration in welds, are determined with high reliability.

At the same time, with the same sensor described above, the method allows to measure the thickness of the product.

At the same time, no information is given on the design of the EMAT, the type of winding, the features of its winding and the features of electronic equipment.

In the work of G.M.Suchkov, Yu.A. Katasonov, V.V. Garkavogo "Experimental studies of sensitive EMAT during defectoscopy of an echo by the method of shear volume waves" (J. Defectoscopy, 200, No. 2, pp. 12-16) are given The results of experimental studies of the sensitivity of direct EMAT in the mode of echo control of metal rails. It is concluded that metal flaw detection is possible using the EMAT using an echo method with a sensitivity close to that of piezoelectric transducers. It is only said about EMAT that it uses a permanent magnet that creates induction in the gap B = 0.6 Tc, the inductor contains 20 turns of copper wire PEV 0.2 mm, the size of the working zone of the inductor is 6 × 12 mm. The probe pulse generator makes it possible to form packets of current pulses with an amplitude of 12-18A and voltage of 200-3000 V in the EMAT inductor. The packet contains from 1 to 18 periods of high frequency current. The filling frequency is adjustable from 1 to 10 periods within 1.8-5 MHz. The generator consumes about 35 watts. The pre-amplifier is made with a gain adjustable within 10-5000 times. The noise brought to the input of the amplifier does not exceed 0.2-0.3 MKV.

There is no information on the type of inductor winding and its features. It is emphasized that the dead zone with the echo control method does not exceed 7-8 mm.

Also known is the work of V.A. Komarov, “Acoustic field of the near radiation zone in EMAT in metals” (J. Defectoscopy, 200, No. 3, pp. 56-68).

In this work, the behavior of body waves generated by a round bus (EMAT winding is close to spiral) is analyzed. The purpose of this article was to obtain information about the behavior of the acoustic field in a solid, well-conducting medium (metal) when it is emitted due to the electromagnetic-acoustic conversion based on inductive emitters. The fundamental difference between contact ("wet") emitters and EMAT emitters is that the former are, as a rule, single-phase (the entire plane emits a field in one phase and is mainly single-phase), while the latter are often two-phase with an inhomogeneous distribution of forces.

For EMAT it is characteristic that the distribution of the projections of the primary field in the material depends on its macroscopic characteristics; electrical conductivity and magnetic susceptibility ratio. The degree of attenuation of the projections of the fields along the interface is significant, changing both the shape of the emitter and the gradients of the projections of the fields along the boundary depending on the magnitude of the mentioned medium parameters. Even the eddy current loop in a conductive medium roughly repeats the current loop in the emitter only at high frequencies.

Based on the calculations and analysis, the following conclusions are made:

- the near zone of EMAT is noticeably smaller than that of "wet" probes;

- the zero radiation maximum, as a rule, attenuates faster than the second, third, etc. As a result, at large distances from the boundary, the directivity pattern is formed by maxima with large serial numbers, and in the near - with smaller ones .;

- in the near zone, the waves are not purely shear or purely longitudinal;

- the zero maximum is formed due to the undamped part of the spectrum and, apparently, propagates with the speed of pure modes. The third extremum also moves at a speed close to the volumetric.

- with a certain accuracy, we can talk about the conditional point (region) of the transition of the near zone to the far radiation zone.

Based on the results of this work, it can be concluded with a certain degree of probability that a multi-element spiral inductor with the ability to phase shift between its sections will allow (by analogy with a piezo transducer); control the transition zone of the near zone to the far one, focus the ultrasound beam and shift it vertically relative to the plane of the controlled product.

Therefore, to control the EMAT radiation pattern and improve the structure of its field, it is advisable to develop the optimal design of a multi-element EMAT and the electronic circuit of its excitation, control and

processing the results of control obtained using EMAT with phasing of gratings.

The most urgent task at present is the theoretical and experimental studies of EMA converters in ferromagnetic materials, the most common in industry. The EMAT theory for non-ferromagnetic materials, in which the effect of the excitation of elastic waves is due to the forces of Ampere, has been sufficiently developed in the works of G.A. Budenkov mentioned in the first review above (see page 1). In the work of G.A. Budenkov, V.N. Kvyatkovsky, and others, the radiation pattern of a sectional EMAT of shear waves was rather carefully constructed, which is a set of parallel tape conductors with an electromagnet. It is shown that the antiphase power supply of the sensor sections provides an inclined input of ultrasonic testing.

In practice, ultrasonic flaw detection is most often necessary to use EMAT with an asymmetric radiation pattern. Such a result can be obtained (see page 1 of the first review) using several flat rectangular frames arranged periodically in space (a lattice-type sensor) and excited with a time shift Δt as an EMAT inducer (J. Defectoscopy, 1974, No. 1, pp. 38-41).

The spatial structure of the fields of body waves excited by EMAT in non-ferromagnetic materials in the near and far diffraction zones was studied by G. G. Lutsenko "On the issue of oblique radiation of bulk shear waves using EMAT," (J. Defectoscopy, 2001, No. 10, pg. 36-47). It is noted that the introduction of waves into the sample at one angle or another is most effective when the inductor is a periodic structure of great length.

It is shown that the introduction of a phase shift during excitation of the inductor elements leads to the expected effects: a rotation of the main maximum and, at the same time, a decrease in the maximum displacement amplitude and an increase in side lobes in the region of small angles.

The conclusion indicates the possibility of oblique input of a shear wave in a metal with an eddy current excitation mechanism and a sufficiently small distance between the inductor plane and the metal surface. However, an increase in the input angle is associated with a decrease in the amplitude of the shear wave in comparison with the maximum possible value that is observed with in-phase excitation and vertical magnetic polarization. Therefore, to implement large input angles using EMAT, it is advisable to develop EMAT with the highest possible sensitivity.

The analysis of the above theoretical and experimental studies on the EMA method of ultrasonic testing of metals and alloys (non-ferromagnetic and ferromagnetic) largely gives an idea of the physical processes that occur when excitation and reception of ultrasonic testing of pulses of different frequencies depending on the type of inductor coil, the gap, the magnetization field using permanent and pulsed magnets. Based on certain assumptions, ultrasonic fields and their characteristics in the near and far zones of the radiation pattern were studied depending on the shape of the inductor coils, the direction of the current in their sections and the size of the gap. At the same time, theoretical studies in most cases do not provide specific relationships for calculating EMATs of straight lines and especially inclined ones with given parameters in sensitivity, characteristic of the radiation pattern of the ultrasonic scanning field, especially for ferromagnetic steels. At the same time, experimental EMATs have been developed taking into account well-known theoretical studies. But basically, taking into account the depth of penetration of specific developers, they take place in physical processes during the excitation and reception of ultrasonic testing by the EMA method.

Thanks to this, first of all, EMA thickness gauges (including portable mass-produced) and flaw detectors, which are not inferior to modern "wet" thickness gauges and flaw detectors in their operational characteristics (thickness determination errors and the detection of minimum acceptable defects), are developed, and by performance characteristics such as

control over highly corroded surfaces and non-metallic coatings coated with a thick layer, temperature of controlled products and speed of control in an automated mode, surpasses “wet” thickness gauges and flaw detectors. However, there are a number of disadvantages of the EMA control method. First of all, it is the impossibility of controlling a large class of non-metallic products (plastic, concrete, etc.), the influence of the magnetostrictive effect in the control of ferromagnetic metals, the absence of sufficiently sensitive EMATs of an inclined type, especially on input angles of more than 40-50 °, a large value of induction in the gap, which provides the necessary sensitivity, but with a strong attraction of EMAT to the surface of the controlled product (especially for ferromagnetic steels), which prevents scanning of the product. Especially for portable EMA thickness gauges and flaw detectors. All this indicates that the "wet", EMA thickness gauges and flaw detectors, at present and in the foreseeable future, will only complement each other. And since all industries in all industrialized countries are saturated with “wet” thickness gauges and flaw detectors of high class with the possibility of ultrasonic testing of metal and nonmetallic products using numerous control technologies, it is currently advisable to develop universal EMA attachments with the set of necessary EMATs for “wet” thickness gauges and flaw detectors, using their hardware for selection, processing and presentation of the received information about the characteristics of the controlled product in the form of required for a specific control technology. This solution is also advisable from an economic point of view, since not all consumers are able to additionally buy an expensive finished version of an EMA thickness gauge or flaw detector.

The current developments in the development of EMAT and electronic equipment for EMA control of various products are reflected in numerous patents, articles and reference books.

In view of the above, the aim of the present invention is to develop a portable EMA device with higher sensitivity,

noise immunity and the possibility of defectoscopy of metals and alloys using inclined EMAT, including for large input angles of ultrasonic testing.

A known electromagnetic-acoustic flaw detector (A.S. SU 1377716 A1, G 01 N 29/24 of May 3, 1989), in which, with the aim of increasing the sensitivity of the flaw detector, its EMAT is made differential. The signals on both coils are in-phase and their outputs are fed to the inverse and non-inverse inputs of the differential amplifier.

This solution has limited application because it is designed to detect defects whose plane is parallel to the surface of the controlled product (direct EMAT).

Also known is an electromagnetic-acoustic transducer (A.S. SU 1587439 F1 G 01 N 29/04 of 08/23/90), containing a magnetic system of two bi-permanent permanent magnets mounted on a ferromagnetic plate and symmetrically elongated first flat coil elongated symmetrically along the line of connection of the magnets and two similar flat coils located coaxially with the first one below the other and electrically separate, the first and second coils being connected in series and receiving, and the third exciting. Moreover, the total number of turns of the receiving coils is an order of magnitude greater than the number of turns of the exciting coil, and the overall dimensions of the exciting coil do not exceed the dimensions of the receiving coils.

Such a solution, indeed, can significantly increase the sensitivity of the EMA method, but is applicable only for thickness measurement and flaw detection by direct EMAT.

A known electromagnetic-acoustic transducer (A.S. No. 357518, G 01 N 29/24 of 12/11/72), in which antiphase currents flow in each rectilinear section of sections of inductance coils and the EMAT generates an acoustic field in the form of a flat antiphase antenna array in the form of two main petals, the maxima of which are tilted at a given angle to the surface of the product.

The disadvantages of this EMAT should include, first of all, the presence of two lobes and low sensitivity due to the large inductance of the EMAT coil.

Also known EMAT (AS No. 487343, M, 5, G 01 N 29/2) containing a pulsed electromagnet and an exciting (receiving) element. In this case, the electromagnet is made in the form of a flat magnetizing conductor with a matching transformer and a pulse current source connected to it, and the exciting element is in the form of a trapezoidal frame made of a flat tape connected to another transformer and designed to be located symmetrically with respect to the magnetizing between the flat magnetizing conductor and the controlled product conductor.

Such an EMAT is cumbersome, consumes a lot of power, since a large current passes through 1 turn. In addition, it is ineffective, because, despite the large current in one turn, the total value of AW for the high-frequency pulse is small. Such an EMAT, most likely, can be used for powerful stationary installations.

A known series of inventions for the development of EMAT for the excitation of normal waves:

- A.S. No. 410306, G 01 N 29/24, is devoted to the development of a continuous EMAT for the excitation of normal waves in cylindrical products;

- A.S. No. 596876, M, class 5, G 01 N 29/10 - it is devoted to the development of an EMA method for controlling ferromagnetic products, in which the vector of the low-frequency magnetic field is oriented with respect to the remote sides of the inductor frame at an angle, the value of which is chosen from the conditions for obtaining equal amplitudes pulses of transverse and longitudinal normal waves at a given control base.

It is known "Device for electromagnetic-acoustic control" (A.S. No. 1784909 A1, G 01 N 29/24), in which, in order to improve the accuracy of determining the location of defects and the reliability of control, in its inductor are the internal sections of the nth coil in series interfaced

sections of the remaining coils. Moreover, all coils are electrically connected and arranged so that the mating sections with open keys are turned on in the opposite direction, and the non-mating sections are electrically according to. In this case, the reliability of the control is achieved due to the excitation of probe ultrasonic pulses along a sufficiently long contour and their registration in the local area with the most uniform distribution of the elastic field.

This construction of the inductor provides in-phase excitation of shear (or longitudinal) ultrasonic waves on the surface of the controlled product (within the ultrasonic ultrasound wavelength) with a phase of high-frequency sinusoidal pulses. Its main disadvantage is the complex design of the inductor and its large inductance, which complicates the obtaining of high sensitivity.

Also known is an electromagnetic-acoustic transducer (A.S. RU No. 37833 U 1; 7 G 01 N 29/24 of 05/10/2005) containing a separately combined inductor, with each w / h coil formed by eight spaced apart each other with on-connected windings, and each subsequent winding located from the periphery to the center (apparently a spiral coil), in relation to the previous one, contains a large number of turns. In addition, this EMAT is made with the possibility of excitation by pulsed signals with different filling frequencies, at which acoustic signals are generated, the maximums of which correspond to angles of 35 ° and 60-65 °, with minimal radiation at other angles.

Obviously, here there is an experimental selection of the winding circuit, providing in-phase excitation and selection of excitation frequencies of the high-frequency pulses, providing the summation of the phases on an inclined line, with the corresponding input angles. Such an EMAT does not follow from the above theoretical studies (including studies of the authors of the application) and a valid sample is not presented, except for an inclined EMAT with an input angle of 40 ° to control the rails.

From the point of view of achieving the goal of ensuring noise immunity and increasing the sensitivity of an EMA device, an analogue can serve

"Ultrasonic thickness gauge" (Patent RU, No. 2185600, C 1; 7 G 01 B 17/02 of 07/20/2002), which contains a follower connected synchronizer, a probe pulse generator, separately combined EMAT (according to RU patent, No. 31305 ; U 1; 7 H 04 R 1/00, G 01 N 29/04 dated 07/27/2003), preamplifier, ADC, coherent signal storage, unit for setting modes and selecting parameters of high-frequency pulses, connected between the second input coherent storage of signals and synchronizer, arithmetic-logical device (made on a microprocessor) connected in series with a second DAC unit and connected between the third input of the coherent signal storage device and the inputs of the pre-amplifier and a crystal oscillator connected to the fourth input of the coherent signal storage device. Based on this patent, the above-mentioned serial EMAT-100 type thickness gauge is developed.

Its disadvantages include the strong attraction of EMAT to the surface of ferromagnetic controlled products and the inability to control the directivity pattern of the sensor.

From the point of view of a constructive solution, the prototype of the claimed invention is an EMA prefix "Rhythm-1", to an ultrasonic "wet" flaw detector (see J. Flaw detection, 1972, No. 6, p. 125) and a message by G. Budenkov etc. "Attachment to the DUK-613 flaw detector (see" Information leaflet "No. 484-74, Chelyabinsk, Central Scientific and Technical Research Institute, 1974, pp. 1-4). The EMA attachment includes an EMAP, a pulsed magnetizing electromagnet, a generator in / h of probe pulses, inductor, pre-amplifier for connection to wet flaw detectors.

However, the prefix has large dimensions (320 × 250 × 170 - electronic unit and 80 × 115 mm - EMAT) and large power consumption - ≥200 VA.

The prefix is made on the old electronic components base and does not correspond to the modern level. In addition, flaw detection was carried out only by direct EMAT.

The closest analogue in technical essence for solving the set goals is the electromagnetic-acoustic transducer for ultrasonic

material control, including a magnetization system and n probing pulse generators, each of which is connected to electrically isolated inductors (inductors) with the same direction of winding coils and passive element (R and C) forming a total of n independent high-frequency pulse generators.

In this case, the active elements (transistors) are made with the possibility of their inclusion synchronously or with a phase shift (see Patent RU 22246106 C 2 G 01 N 29/04, with priority dated 03/17/2003).

However, this technical solution, which in fact is a multi-element inductor with n high-power generators connected to it (according to the number of inductors), can only be the basis for developing an EMA device that realizes its goals.

Therefore, it does not solve the goals declared by the proposed EMA devices:

- development of a multi-element inductor of increased sensitivity, which, in conjunction with n high-frequency pulse generators and the corresponding elements of the electronic circuit, ensures the implementation of a system with phasing arrays, which will provide for the formation of an ultrasonic beam pattern with specified characteristics, including ultrasound input angles into a controlled product, processing of ultrasonic pulses received from the product in order to increase the noise immunity and control sensitivity with EMA t Altimeter and flaw detection.

The problem is solved due to the fact that the proposed device uses a block of n generators of high-frequency probe pulses and a multi-element inductor, each of which consists of a generator and two receiving windings located one above the other, and the winding of which is made of sections with the same or opposite the direction of the winding, the corresponding phase sign in / h of the probe pulse, differential amplifiers connected between the respective receiving windings of each inductor and the input of the pre-amplifier , ADC, coherent signal storage, first DAC,

unit for setting modes and selecting parameters of the high-frequency pulses, connected between the second input of the coherent signal storage device and a synchronizer, arithmetic - a logic device connected in series with the second block of the DAC and connected between the third input of the coherent signal storage device and the corresponding inputs of the pre-amplifier and a crystal oscillator connected to the fourth input coherent drive signals. In addition, between the synchronizer and the block of n probing pulse generators / n are included, respectively, n blocks of continuously adjustable clock delays, and a plug-in board for matching its output with the input of the receiving path of “wet” thickness gauges or flaw detectors is connected to the output of the first DAC.

In addition, between the outputs of each differential amplifier and the input of the pre-amplifier, a series-connected block of controlled delay of the receiving signal and the corresponding input of the coherent adder are connected, and series-connected in series between each of the blocks for the formation of an I / O pack of sinusoidal signals and the corresponding preliminary pre-amplifier of the power of the probing I / O signal limiter amplifier and a second coherent adder, the second input of which is connected to the output of the corresponding unit ormirovaniya packs in / hr sinusoidal signals.

The EMAT inducers are made in the form of a thin metal plate (frame), on which the receiving windings are wound, on top of which the generator winding is wound with an ordinary winding and which are placed between the tread and the permanent or pulsed magnet, and a thin layer of magnetic glue is placed between the last and upper plane of the inductors low electrical conductivity. In addition, the EMAT inductor can be made in the form of three thin metal plates located one above the other, which can be made of copper wire or a wire of constant-type alloys; nichrome, or fechral.

In addition, a focusing permanent magnet or obliquely polarized can be used as a permanent magnet for EMAT.

The invention is illustrated by the drawings presented in figure 1; 2; 3; four; 5; 6; 7; 8; 9; 10.

Figure 1 presents a device for EMA quality control of metals and alloys in the form of an attachment to the "wet" thickness gauges and flaw detectors, where:

1 - synchronizer;

2 - block n continuously adjustable delays of the clock;

3 - a block of high-frequency sinusoidal pulse generators, each of which consists of a series-connected block forming a pack of sinusoidal signals with an adjustable number of periods from 1 / 4λ to n periods (3-1; 3-2; ... 3-n), blocks of preliminary amplifiers (4-1; 4-2; ... 4-n) and power amplifiers (5-1; 5-2; ... 5-n);

4 - EMAT;

5 - permanent magnet;

6 - generator windings of a multi-element inductor (in this case, 4 elements);

7, 8 - receiving windings of the inductor;

9 - a thin layer of magnetic glue with low electrical conductivity, excluding the induction of eddy currents and, therefore, the appearance of ultrasonic interference pulses in the body of a permanent magnet;

10 - input differential amplifier;

11 - pre-amplifier;

12-ADC;

13 - coherent storage of signals;

14 - the first DAC;

15 - replacement card matching output of the first DAC with the input of the receiving paths of the "wet" thickness gauges and flaw detectors;

16 - the second DAC for generating analog signals providing the operation of the preliminary amplifier 11 in the MARU, AGC and tracking values

the gap between the working surface of the EMAT and the surface of the controlled product;

17 - arithmetic-logical device;

18 - crystal oscillator;

19 - unit for setting modes and selecting parameters of high-frequency pulses;

20 - switching power supply;

21 - battery pack.

Figure 2. the design of a linear 4-element frame of the EMAT inductor is presented (top view), where

L is the length of the inductor;

h is the total thickness of the generator and receiving windings;

b is the thickness of the screen;

B is the length of the plate (22) of the frame for winding the windings of the inductor.

In figure 3. is a side view of this frame, where:

d is the height of the inductor;

b is the thickness of the frame for winding the windings of the inductor;

K is the width of the winding of one of the 4 elements of the inductor;

H is the width of the 4-element inductor.

Figure 4. section AA is shown of one of the n elements of the EMAT inductor (figure 2), where:

δ is the thickness of the tread EMAT;

5 - permanent magnet;

23 - a thin magnetic pad of ferrite;

24 - tread;

25 - controlled product;

λ = Ct / f, where f is the frequency in / h of the generator,

Ct is the propagation velocity of shear ultrasonic vibrations;

λ is the shear wavelength.

5. presents a functional diagram of the connection of the receiving coils of the inductor:

27; 29; 31; 33 - differential amplifiers of the receiving signal;

28; thirty; 32; 34 - blocks adjustable delay received from the product signals;

35 - coherent adder;

26 - diodes for limiting the amplitude of the probe pulse;

11 - pre-amplifier (see also Figure 1);

6. The scheme of reflection of ultrasonic testing from defect D in a controlled sample 25 and the course of the central rays 1, 2, 3, 4 to a 4-element inductor are presented, from which it follows that for each element of the inductor, with inclined excitation and reception of ultrasonic testing with an inclined EMAT, the reflected signal comes with a time shift Δt due to the difference in the distance Δ1 from the defect to the corresponding element of the EMAT inductor.

7. presents (in plan) a schematic representation of a linear EMAT inductor consisting of 64 elements, each of which is made on the frame shown in figure 2 and 3.

On Fig. presents a three-element ring-type inductor with generator windings 6 and receiving windings 7 and 8 located one below the other, where 9 is a layer of magnetic glue with low electrical conductivity (in particular, epoxy is densely mixed with iron or steel filings).

10. a functional diagram is presented for generating a probing sinusoidal signal, where 3-1 is a block for generating a packet of sinusoidal oscillations;

- 36 - amplifier limiter to a stable amplitude value, much less than the original signal;

- 37 - a coherent adder, from the output of which (point C in Fig. 9) the signal is fed to the forming unit (power amplifier) of a powerful probe pulse.

In Fig.9. voltage plots at the nodal points of the circuit of FIG. 10 are presented.

This scheme allows to increase the noise immunity of the device from exposure to pulsed fields.

This form of the probe pulse (with a step on the leading and trailing edges of the half-period) will provide protection against impulse noise, which is unlikely to have such a shape of the leading and trailing edges.

The arithmetic-logical device of the set-top box selects useful signals according to the shape of the fronts (and, by the way, by the duration of half-periods when comparing them with the duration of the half-period of the probe pulse).

The device operates as follows.

Under the action of the synchronization pulse coming from the "wet" thickness gauge or flaw detector, the synchronization unit of the device 1 is launched (see Figure 1).

From its output, the synchronization pulse starts n blocks of continuously adjustable delays 2, each of which, according to the well-known algorithm, sets its own delay value Δt. Blocks 3 of the formation of high-frequency pulses are launched from its outputs, in which the selected parameters are set by the operator - the operating frequency f, the number of periods of its oscillations. Then this pack of radio pulses arrives at blocks 3-1; 3-2; ... 3-n for pre-amplification, and then from its outputs pulses are supplied to the corresponding power amplifiers (5-1; 5-2; ... 5-n), the load of which is the generator inductor of each element inductors 6. Under the influence of these radio pulses, eddy currents arise on the surface of the controlled product, the interaction of which with the permanent magnet field 5 according to the Lorentz law, ultrasonic vibrations arise, which propagate into the product 25 (figure 4) and are reflected from its bottom or from defect D ( see Fig.6) arrive at the surface a component of the product whose displacements (shear or longitudinal) interacting with the field of the permanent magnet 5 cause Foucault currents on the surface of the product, which induce electrical impulses in the receiving windings 7, 8 of the inductor 4 v / h. Receiving windings of each element

inductor (see figure 5.) included counter. Therefore, out of the outputs of two windings of each element of the inductor, antiphase pulses arrive at the corresponding inputs of the corresponding differential amplifiers 27, 29, 31, 33. From their outputs, the doubled pulse is supplied to the corresponding blocks of controlled delays (28, 30, 32, 34). The delay value in each of these blocks is set deliberately - with a thickness gauge, this delay is “0”, for flaw detection with a set angle of input of ultrasonic testing - by a certain value Δt, corresponding to the difference in the path of the rays Δ1 from defect D to the corresponding element of the inductor (see Fig.6 )

Common-mode pulses from the outputs of these delays arrive at the coherent adder 35 (Fig. 5), the resulting pulse from which is supplied to the device pre-amplifier 11, and from it to the ADC (12), in which the signals are converted into a code supplied to the coherent common-mode signal storage device ( 13). Code signals from its output go to the first DAC 14, and from it to the plug-in board 15 matching the output of the first DAC 14 with the input of the receiving paths of the “wet” thickness gauge or flaw detector.

Block 19 serves to set the modes and select the parameters of the high-frequency pulses.

The arithmetic-logical device 17 together with the crystal oscillator 18 serves to generate the device operating modes, process incoming information and generate using the second DAC (block 16) in certain cycles of the device, the signals for controlling the pre-amplifier 11 thereby providing at certain intervals of the cycle, specified by the synchronizer 1, the MARU, AGC or detuning modes from the changing gap in the process of product control.

In order to reduce the influence of pulsed electrical noise, between the shaper of the high-power sinusoidal signal packet, a limiter amplifier 36 and a coherent adder 37 are turned on (see FIG. 10), the output of which is a sinusoidal signal with steps at the leading and trailing edges of the half-periods (see Fig. 9).

The likelihood of interference with such exotic fronts is very small, which allows using the arithmetic logic device 17 (Figure 1) and a coherent signal storage 13 to select useful signals with a stepped form of the trailing and leading edges received from the controlled product.

This processing and selection of useful signals occurs in the first half of the period of probing pulses, when the mode of the preliminary amplifier 11 is transferred to the MARU mode. In this mode, all received signals (useful and interference) have the same amplitude, which allows to increase the accuracy of selection and subsequent processing. Then the pre-amplifier 11 is transferred to the AGC mode, in which the ratio of the amplitudes of the received signals (but without interference) has the original value. This sequence of useful signals from block 15 (Fig. 1) is input to the “wet” thickness gauge and flaw detector, where their further selection, processing, visualization and necessary measurements are made in electronic blocks of “wet” thickness gauges and flaw detectors in accordance with the technology laid down in them Ultrasonic testing of products in various industries.

The above new technology for manufacturing elements of a linear inductor and a simple technology for its manufacture is extremely important for increasing the sensitivity of EMAT and significantly simplifying the manufacturing technology of multi-element EMAT.

The essence of the novelty is that the receiving and generator windings are wound on a flat thin frame, the length of which (Fig. 2) corresponds to the effective length of the linear EMAT.

The windings of the receiving and generator windings (as shown in FIG. 4) wound on each other are inductively coupled and the inductance of each winding depends on the number of turns of the winding and the core material (frame plate).

As a result of this, very wide possibilities arise for changing the magnitude of the inductance of each winding depending on the core material with a constant number of turns.

So, for example, 10 turns of copper wire ⌀0.14 mm, wound on a brass plate with a thickness of 0.2 mm and a length (turn) of 16 mm, showed a value of L = 0.38 μH when measuring the inductance, and the same 10 turns of the same wire wound on the same plate of electrical steel showed a value of L = 3.5 μH. This allows you to change (decrease) the value of the inductance of the generator winding of the elements of the inductor to very small values of L. Moreover, for example, in the element of the inductor with the number of turns of the generator winding, suppose 10 W, you can get L <0.35 μG or less! Then the current in the winding of the generator winding of such an element will be I = U × dt / L = 600 × 0.1 / 0.35≈200 A.

If the entire inductor consists of only 3 elements (total number of turns = 30W), then the total value AW = 30 × 200 = 6000 AW.

Consequently, a sharp increase in the number AW of the generator winding will lead to a significant increase in the sensitivity of such an EMAT. And this is not the limit. Therefore, in the future, it is possible with an increase in the sensitivity of EMAT to reduce the magnetizing constant field strength to a value at which EMAT will be very weakly attracted to the surface of the controlled product made of ferromagnetic steels.

Another very useful feature of such an EMAT is that the receiving windings can be made of wire of the Constantan, Nichrome, or Fehral type (Handbook of Elementary Physics. - M .: Nauka, 1975.-P.140.), Which will allow better coordination output impedance of receiving windings with input impedance of electronic circuits of amplifiers. When developing multi-element EMAT inductors, the number of turns of the generator winding can be significantly less than 10 W.

Therefore, this winding can be made, for example, from fechral wire. In which the iron content reaches 80%.

Therefore, an EMAT made of such wires is equivalent to a decrease in the gap by an amount equal to the double sum of the diameters of the two receiving and

one generator winding, which will also lead to an increase in the sensitivity of this EMAT with the same permanent magnet.

In addition, the possibility of a sharp decrease in the inductance of the generator winding of the inductor element when using a winding wire, for example, from a material of the type Fechral, will make it possible to realize a probe pulse generator with almost a load close to a low active resistance. This will make it possible, with a modern element base, to use an active powerful element (transistor) with a large pulsed current (≥200 A) with a relatively small voltage on current-carrying electrodes (collector-emitter). This will minimize the design and reduce the power consumption of the probe pulse generator.

Claims (8)

1. A device for electromagnetic acoustic (EMA) quality control of metals and alloys, containing a serially connected synchronizer, a generator of probing high-frequency pulses, including an inductor with a magnetizing electromagnet and a preliminary amplifier, the output of which is connected to the receiving path of a wet flaw detector or thickness gauge, characterized the fact that it uses a block of n generators of probing high-frequency (V / h) pulses and a multi-element inductor, each of which consists of a generator and two receiving circuits a coil located one below the other, the winding of which is made of sections with the same or opposite direction of the winding, corresponding to the signs of the phase in / h, the probe pulse, differential amplifiers connected between the corresponding receiving windings of each inductor and the input of the pre-amplifier, analog-to-digital converter (ADC ), a coherent signal storage device, a first digital-to-analog converter (DAC), a unit for setting modes and selecting parameters of a high-frequency pulse, connected between the second input coherently a drive signal and a synchronizer, arithmetic logic unit, connected in series with a second DAC unit and connected between the third input signal and the coherent accumulator corresponding preamplifier inputs and the crystal oscillator connected to the fourth input signal of the coherent accumulator. 2. The device according to claim 1, characterized in that between the synchronizer and the block n of generators of high-frequency sensing pulses are included, respectively, n blocks of continuously adjustable delays of the synchronizing pulse, and a removable card matching its output with the input of the receiving path is connected to the output of the first DAC "wet" thickness gauges and flaw detectors. 3. The device according to claim 1, characterized in that the EMAT inductors are made in the form of a thin metal plate on which the receiving windings are wound, on top of which the generator winding is wound with an ordinary winding, and which are placed between the tread and a permanent or pulsed magnet, and between the last and the upper plane of the inductors placed a thin layer of magnetic glue with low electrical conductivity. 4. The device according to claim 3, characterized in that the EMAT inductors are made in the form of three thin plates located one below the other, on which ordinary windings, respectively, two receiving windings and a generator winding are wound. 5. The device according to claim 1, characterized in that between the outputs of each differential amplifier and the output of the preliminary amplifier are connected in series to the controlled delay unit of the receiving signal and the corresponding input of the coherent adder. 6. The device according to claim 1, characterized in that between each of the blocks of the formation of a pack of high-power sinusoidal signals and the corresponding preliminary power amplifier of the sounding high-frequency pulse, a series-connected limiter amplifier and a second coherent adder are connected, the second input of which is connected to the output the corresponding unit for the formation of a pack of high-power sinusoidal signals. 7. The device according to claim 1, characterized in that a focusing or obliquely polarized permanent magnet is used as a permanent magnet for EMAT. 8. The device according to claim 1, characterized in that as a wire for winding the generator and receiving coils of the inductor elements, copper wire or wires from alloys of the Constantan, Nichrome or Fehral type can be used.