SU761899A1 - Apparatus for monitoring ferromagnetic material structure using barkhausen's effect - Google Patents

Description

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. - Invention. It relates to the field of nondestructive testing of materials, products and welded joints and can be used to control ferromagnetic materials and products from them in the form of 5 rods, 'bands, sheets ........,

A device is known for monitoring the parameters of ferromagnetic materials by the method of magnetic noise, which contains a generator connected in series, a converter ¹⁰ , from a measuring instrument and a registering unit [H]. . at

This device’s lack of information is another. due to its insufficient sensitivity. '

A device for control. structures of ferromagnetic materials, on. the basis of the Barkhausen effect, containing a series-connected magnetization reversal unit, 1-magnetoiducuclear pre-20 'generator, amplifier, filter and end-. ny block (2]. "

A disadvantage of this device is its low sensitivity. control of the structure of ferromagnetic materials. '25' The closest to the invention is a device for controlling the "Structure of ferromagnetic materials based on the Barkhausen effect, containing series-connected magnetizable 30

magnetic induction converter and amplifier, filter, amplitude selector and terminal block [$].

However, this device is not sufficiently sensitive and its disadvantage is the low intensity of the suppression of the signal from interference, caused by the fact that the magnetization reversal unit. Performed as a generator of infralow frequencies, and the amplitude selector is connected between the amplifier and the filter.

The aim of the invention is to increase the sensitivity of the device.

This goal is achieved by the fact that a filter, an amplitude selector and a terminal unit are connected to the amplifier output, and the magnetization reversal unit is made as a series connection of an operational amplifier whose non-inverting input is connected to (amplifier output and between the inverting input and its output A circuit amplifier is turned on a comparator, and a power amplifier, the output of which is connected to the magnetization reversal winding of a magneto-FD converter.

This embodiment of the block · magnetization reversal allows you to build up from the macroscopic magnetic properties of the controlled product at the output of the converter,

'H ...... - ..,, |.'

,. ' • 761899

3

- group Barkgausen jumps along the lines of magnetization, reduce with the help of the amplitude selector of the spectrum the ..... density of the output signal, due to

signal interference, and convert

filtered and amnlite-select.processor, bath signal in the number of pulses, character of the material

"'' 'of the con- cerned product in' comparison 'with the structure of the reference sample.

FIG. 1 is a block diagram of the device; .on FIG. 2 shows the nature of the change in the magnetic field created by the magnetizing winding and the output emf 1 of the induction transducer; in fig. 3 - the nature of the signal at the output of the filter fil tra; in fig. 4 - experimental 'curve of spectral density

magnetic noise at a frequency of 15 kHz from co. carbon holdings in steel; in fig. 5—20

..... experimental curve.

 tasla 'impulsyuv at the output of the comparator from

carbon content and steel. '

The device contains a block 1 of magnetism ²⁵ ........, a mass-induction transducer 2 with a measuring winding 3 and a winding. 4 magnetization reversal, amplification 5 with feedback circuit b, filter 7ГТплтудный selector 8 and terminal block 9 in 30 as a counter of impulses. Block 1 remag-. The rewiring is made in the form of a serial connection of the operational amplifier 10, the non-inverting input of which is connected to .......... it with the output of the amplifier 5, and between

......... tiruyuschim. entrance and exit operating

the amplifier 10 includes a comparator 11, d 'of the power amplifier 12, the output of which is connected to the winding 4 of the magnetization reversal

converter 1. ^,, ... ⁴⁰

. 'Chain 6 feedback is included between

'output and input of the amplifier 5.,

A measuring channel, including a filter 7, an amplitude selector 8 and a counter of 9 pulses, connected sequentially, is also connected by an input to the output of the self-induction EMF 5 emf.

The device works as follows: "Zom. ... ..." ....) .... ·

Block 7 of magnetization reversal, operates in ⁵⁰ automatic mode of maintaining a constant rate of change of magnetic induction / b / & / 7 / == const1 / at the frequency of magnetization reversal. When the device is turned on at the first moment, the zero generated by the winding 4, 55 is zero, and the signal at the output of the converter 2 in winding 3, proportional to <1Ыс11, will also be equal to zero. The same will be TB voltage on peiat-certified input of the amplifier) 10. On. an inverted ⁶⁰ 'input of amplifier 10 with comparator 11 will

- z _and d tsbsuupat _ann th voltage output S.

amplifier 10 is the voltage amplified in;

force 12, will flow on the winding _; /

. 4 transducer 2, causing fast iz- ⁶⁵

*four

The change in the current in the winding 4 (and, consequently, in the magnetic field) until the rock voltage at the output of the amplifier 5, proportional to ЫЙМ, does not equal, to the voltage coming from the comparator 11. As

only .voltage '...... at the output of the amplifier

10 reaches a certain value, the comparator 1Ϊ switches the polarity of the block 1, and the direction of the magnetization / changes, to the opposite. A new cycle of ⁷ reversal will begin.

The bandwidth of the amplifier 10 is limited by the required frequency of the magnetization reversal of the ferromagnetic product.,. The magnetization reversal time can be adjusted by changing the gain of the amplifier 5 by the circuit 6.

FIG. 2. Characteristic curves 13–15 are given, respectively, of the change in -, the load-carrying voltage, the emf and the current in 'magnetized'. winding 4, which are automatically provided by unit 1. In areas AB,

CT), EM, CT with a length of 1c of the curves shown. The magnetization reversal occurs mainly due to the Barkhausen jumps. Curve 14 Shows the nature of the change in the EMF at the output of the winding 3 of the induction driver in the 7Ζ / 7 / = οοηδί mode, this is the direct proportionality of time intervals between the individual Barkgausen jumps.

Δ / ΐ. changes in induction ΑΒϊ, respectively. Forging these Barkgauzen races. On the other, On the other hand, the change in ΔΒ1 in the first approximation is proportional to the volume of magnetization reversal in the ferromagnetic sample ΔίΑ, which to a large extent depends on the structure of the material under test. Thus, the analysis of the Barkgausen jumps in time allows -. 'judge the structure of the material.

'I

An analysis of the self-induction EMF of the transducer 2, amplified by the amplifier 5, is carried out in the measuring channel, where at the output of the narrow-band high-frequency filter 7 a signal 15 is generated, the character of which is shown in FIG. 3. It is a sequence of 'bipolar \ impulos, · following with intervals Δ /, ίου = -, depending only on the band

^ω πορ

filter pass. The amplitude of these pulses is proportional to the spectral density of the magnetic noise, depending, in particular, on Δ ι, as well as on the frequency and amplitude of other noise sources and induced. Emf which are the '. Signal, interference. The spectral. / Noise density associated with the signal. Interference, on average, does not exceed a certain level And _then , which is specified in the device by the amplitude selector 8. The selector 8 passes only, "those:. Impulses, , Ven, A ,,,,;,. The C-cheg of these pulses is produced by a counter 9.

. five

Tests of the proposed device in comparison with the known device, recording spectral density, were carried out with reference to the control of carbon content in carbon steels. The test results are given ¹ on

. ί FIG. 4 and 5, where the dependence of the spectral density of noise at a frequency of 15 kHz on the carbon content in steel (curve 16) is shown, and direct 17 shows the dependence on carbon content and the number of pulses detected by the instrument (according to the invention). Due to the high 'sensitivity of the proposed device' to a change in the structure 'of steel, due to a change in its carbon content, this relationship becomes unambiguous. Increased economic efficiency of the proposed device is associated with the expansion of the possibilities of monitoring defects in the structure of products.

Claims (1)

Ф о рм ул and. and s about b e 't e n i Device for (control of the structure of fer (romagens> 1x materials based on the Barkhausen effect ^- containing a sequence of connected magnetization block, (cagN | Itoiyadu.ktsianny converter and amplifier, filter, ^ amplitude selector and terminal block, characterized by ⁵ that, with a whole increase in the sensitivity of the device, to the output of the booster amplifier are switched on. Successively connected filter, amplitude self-oscillation and terminal block, and the magnetization reversal unit is made as About the serial connection of the operational amplifier, the non-inverting input of which is connected to the output of the amplifier, and between the inverting input and the output of the operational amplifier is on 5 a comparator, and a power amplifier, the output of which is connected to the magnetization reversal winding of a magnetic-induction converter. four ' ABOUT