UA147333U - ELECTROMAGNETIC METHOD OF METAL IDENTIFICATION - Google Patents

Abstract

The electromagnetic method of metal identification consists in excitation of Foucault currents generated by the alternating electromagnetic field of the transmitting antenna on the surface of the investigated metal sample and analysis of the electromagnetic response signal reflected from the test sample. The identification is performed by analyzing the shape of the response signals and determining their time and spectral characteristics obtained by rotating the test sample around the receiving antenna at least two constant speeds.

Description

The useful model belongs to the physical methods of analyzing the composition of metals and alloys, in particular the non-contact method of metal identification using Foucault currents generated by electromagnetic waves.

Today, chemical, optical emission, and X-ray fluorescence methods of analysis are used to identify metals.

The chemical method of analysis is based on the alternating interaction of a metal sample with various chemical reagents. A change in the color of the reagent or a change in the mass of the precipitate due to chemical interaction is an informative parameter about the compounds present in the metal sample. But this method does not allow to determine the composition of the metal without laboratory tests.

The optical emission method of analysis is used for the study of structures, parts, blanks, etc. It is built on the heating of metal by an electric field that occurs when a spark or arc is created, by a powerful laser or a gas flame. The metal under investigation is partially vaporized, passes through an air or argon medium and is recorded by a spectrometer. The composition of the metal is determined by the radiation spectrum of each component of the material under investigation. Optical emission devices determine even minor impurities in metals, such as the amount of phosphorus, carbon or sulfur in ferrous metals. The high accuracy of the determination of impurities allows you to use them for certification analysis. The device comes already with analytical programs sewn into it, which greatly complicates the analysis of an alloy with an unknown composition, at least approximately.

The X-ray fluorescence method allows to control the composition without damaging the research object, but requires preliminary surface treatment. This type of device can analyze up to several dozen elements in alloys. The size of the sample can be small enough, for example, a chip. The disadvantages of X-ray fluorescent devices include the fact that they do not register elements with an ordinal number in Mendeleev's table less than 11, which does not allow the analysis of materials containing carbon, and this applies to cast iron and steel. In addition, they are less accurate, and the surface of the object being analyzed must be cleaned of paint and rust. That is, such a method also requires the presence of a metal sample and does not allow determining its composition remotely, without laboratory tests.

Therefore, the task of identifying and analyzing the composition of metal objects without damaging them is that

Of the number and hidden in another dielectric medium, is relevant.

One of the ways to solve this problem is the proposed electromagnetic method of detecting and identifying the composition of the metal. It is based on the phenomenon of excitation of eddy currents (Foucault currents) on the surface of the metal under study, which are induced by the electromagnetic field of the radiating coil of the transmitting antenna of the eddy current converter, which is, for example, a component of the radar. These currents create a secondary electromagnetic field, which is registered by the receiving antenna, processed by the electronic unit and transmitted to the indicator device. Useful information about the investigated object is contained in the amplitude, phase and frequency of the echo signal received by the antenna.

There is a well-known method of dichotomous separation of metal into black and colored by means of spectral analysis, which occurs in the antenna of a metal detector (see Abramovych A.O.,

Mrachkkovsky O.D., Furmanchuk V.Yu. Dichotomous differentiation of metal into black and colored by means of spectral analysis. Bulletin of ZHTU. Series "Technical Sciences", Me1 (79), 2017. POI: porz//doi.ogo/10.26642Лп-2017-1(79)-48-51). The problem of dichotomous discrimination is solved by measuring the width and area under the contour of the amplitude spectrum of the received signal. According to the known method, signal processing is carried out by a specially developed program that compares the spectra of ferrous and non-ferrous metal samples with the base ones.

The closest analogue is the method of spectral analysis for distinguishing metals by signals from the eddy current converter of the radar (Arriisayop oi zresiga! apapiuvov TOg divitipdiivpipud teia!5 Bu zidpa!5 iot edau sitepi sopmepegz5 / A. O. Abgatomusii, MU. O. Rodairpu //

That Eavzy Eporeap baby! oi Admapsey Tesppoiodu, KnaiKim. - 2017. MoI. 89 (Mo. 5). R. 51-57 (Zsorivkh). FIGHTS: pyrz//doi.oga/10.15587/1729-4061.2017.110177Y. The proposed method of signal processing allows to determine the type of metal in subgroups of ferrous and non-ferrous metals.

The characteristics of the received electromagnetic response are determined by the electrical conductivity and magnetic permeability of the metal sample. According to the known method, the spectral density of the signal is an informative feature. To compare metals with each other, the band and the area under the contours of the signal spectrum are analyzed.

The disadvantage of the closest analogue is the limited range of recognized metals and their alloys due to the insufficient number of informative parameters that can be obtained exclusively in dynamics.

The useful model is based on the task of creating a method of non-contact identification of the type of metals with an increased range of recognition in subgroups of ferrous and non-ferrous metals using Foucault currents generated by electromagnetic waves.

The problem is solved by the fact that in the electromagnetic method of identification of metals, which consists in the excitation on the surface of the investigated metal sample of Foucault currents, created by the variable electromagnetic field of the transmitting antenna, and the analysis of the electromagnetic response signal reflected from the investigated sample, according to a useful model, identification is carried out by analyzing the shape of the feedback signals and determining their time and spectral characteristics, obtained when the test sample rotates around the receiving antenna, at least with two constant speeds.

The identification of the type of metal or alloy is based on the results of the analysis of the form of the dynamic echo signal, which occurs as a result of the formation of Foucault currents by electromagnetic waves in the examined sample during its rotation around the receiving antenna and the determined temporal and spectral parameters.

The technical result is the ability to identify any metals or alloys promptly and with sufficiently high accuracy.

The claimed method can be implemented using a device consisting of mechanical and electronic parts.

The mechanical part (Fig. 1) is needed for the dynamic recording of signals from the studied metal samples by the electronic part. The mechanical part consists of a rod (1) with a mount for metal samples to be tested, a mount (2) for the antenna unit of the electronic part, an electric motor (3), a speed measurement sensor (4) and an electric motor rotation control unit (5).

The electronic part of the device (Fig. 2) consists of a signal generator (6), a transmitting antenna (7), a receiving antenna (8), a low-noise amplifier (9), a phase detector (10), a bandpass filter (11), an analog-differential device (12) and a computer-based digitized signal processing unit (13) (can be replaced by a microcontroller, an EREA-programmed logic integrated circuit or a signal processor).

The proposed method works as follows. The signal generator generates a pulse signal with a 50 96 filling (meander) kHz range, which after the amplifier is fed to the transmitting antenna (parallel oscillating C circuit). The receiving antenna is also a parallel oscillating circuit with a resonant frequency, as in a signal generator. The antenna block is configured so that in the absence of metals near the antenna surfaces, the signal guidance from the transmitting antenna is minimal in the receiving antenna.

The test sample is fixed on the rod (1). Turn on the electric motor (3). The rotation speed of the rod (1) is set using the motor speed control unit (5). The sample begins to rotate over the receiving antenna. The speed of rotation of the sample above the receiving antenna is controlled by the speed sensor (4). For more accurate identification of metals, the test samples are rotated over the receiving antenna at a constant speed without acceleration. To remove a set of signals from each of the metal samples, it is necessary to do this while gradating different speeds of rotation of the sample above the antenna (8), which is carried out using the motor rotation control unit (5) of the mechanical part. The speed of the sample passing over the antenna unit is measured using a non-contact sensor (4), the signal from which is sent to the processing unit (8) of the electronic part.

The transfer of metal over the surfaces of the antennas changes their relationship, the phase and amplitude of the signal changes in the receiving antenna. The rate of change of this amplitude at different gradations of sample transfer speed over the antenna (at different number of revolutions of the shaft of the electric motor of the mechanical part) is different and this gives a larger set of peculiar information features in the form of a feedback signal. From the output of the receiving antenna, the signal is fed to a low-noise amplifier, and then to a phase detector. The phase detector emits a voltage proportional to the phase change between the generator signal and the receiving antenna. Through a band-pass filter, the central frequency of the passband of which is equal to the speed of passage of the sample over the plane of the antenna unit, the signal enters the input of the analog-to-digital converter. The digitized signal is fed to the processing unit, its shape is analyzed, time and spectral characteristics are determined, and the metal type of the sample is identified based on the results obtained. The waveforms at the ADC input from copper and steel samples are shown in Fig.3.

To compare metals with each other, the area of the spectrum under contour 5, the lower and upper limits of the transmission band (Fig. 4) are analyzed (Informative features (5, p, and) in the spectrum of the signal from steel and copper samples placed next to each other) (see A.O. Abramovych, O.D. Mrachkovskii, and V.Yu. Furmanchuk, Dichotomous differentiation of metal into black and colored by means of spectral analysis. Bulletin of ZHTU. Series "Technical Sciences", Me1i (79), 2017. BO: perz //дой.ого/10.26642/Лп-2017-1(79)-48-511. But often these spectral characteristics are not enough for accurate identification of metals in subgroups of ferrous and non-ferrous metals.

An important informative parameter for determining the type of metal is the curvature coefficient

Kg of the contour of the spectrum, which can be obtained in dynamics and which characterizes the ratio of the spread of the spertra in the Yailirynspenva area, at the level of -25 95 from the top, is defined as:

Kui 5 A OY 255 and si vi de - the width of the spectrum at the base, - the width of the spectrum at the level -25 95 from the top.

To increase the range of metal detection, the test samples are rotated over the antenna unit, at least with two different speeds. The spectra of a copper sample (electrotechnical copper) and copper alloy coins (19th century Kreuzer and 18th century Siberian denga) at two different sample transfer speeds over the antenna block are shown in Fig. 6 (Spectra from a copper sample (electrotechnical copper) and copper alloy coins (19th century Kreutzer and 18th century Siberian denga) at two different speeds of moving the sample over the antenna block).

In the time domain, the signal is replaced by a corresponding graphic-digital image, in which the informative feature is the number of extremes and their mutual relationship, see Abramovich

A. O. The method of graphic images in the radio engineering system of near location / A. O. Abramovych, I. S.

Kashirskyi, V.O. Piddubny // Proceedings of the International Scientific and Technical Conference "Radio Fields, Signals and Systems". - Kyiv. - 2018. - P. 173-175). The method of graphic images makes it possible to remotely analyze the composition of a metal object and determine the specific metal in subgroups of ferrous and non-ferrous metals, which the object under study consists of. But for a more accurate identification, especially in the case of complex metal alloys, one more informative dynamic parameter of the signal-echo is determined, namely the coefficient E5 of the symmetrization of the signal, which is defined as: negative) according to the amplitude of the signal, manifested for different metals and alloys at different speeds of rotation of the sample at different speeds (Fig. 5 - digitized amplitude-normalized signals from copper, steel samples and copper alloy coins at two different speeds

From carrying the sample over the antenna unit)

That is, the rotation of the sample at different speeds allows you to expand the functionality of the device that implements this method, thanks to a significant increase in the information gain, which is defined as M; where M. number of different rotation speeds.

Therefore, by using different rotation speeds, we significantly increase the accuracy of information about a specific type of metal. At only one speed, we can get 7 informative coefficients, which gives 7 informative features about the studied sample, and if there are 10 speeds, then we will get 70 informative features.

All the determined time and spectral characteristics obtained during the analysis of the waveform make it possible to represent a specific type of metal or alloy as a generalized image, which is recorded in the memory of the processing unit and is subsequently used for comparison and identification of the studied metal samples.

All metal samples used in the author's research were commensurate with the diameter of the receiving antenna.

The claimed method allows to remotely and quickly determine the type of metal or alloy thanks to the use of modern digital technologies.

The electromagnetic method of metal identification can also be used in the case when two objects are in close proximity to each other, for example, in the case of a product made of several different metals, or in medicine, when it is necessary to identify the type of foreign metal object in the human body.

Claims (1)

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