SU794455A1 - Method and device for magnetic noise structuroscopy - Google Patents

Description

one

The invention relates to non-destructive testing of materials and products from them and can be used to control the structure of ferromagnetic materials after their thermal, cold-plastic processing, as well as to determine the content of individual elements in alloys.

A known method for controlling the quality of ferromagnetic materials is that the product under test is re-magnetized, converts Barkhausen jumps to EMF, amplifies, filters, measures power or other energy parameters of the magnetic noise spectrum at different values of the remagnetizing field, and compares the measured values with the corresponding values reference curve 1. The dependence of the parameters of the noise spectrum on the monitored defects in the structure of the material, as well as its noise immunity, is complex and ambiguous. ychivost associated with the effect on the spectral characteristics of a large number of structural components material and low noise ratio - the useful signal / noise ratio.

The closest in technical essence to the invention is the method of magnetic-noise structuroscopy of ferromagnetic materials, which consists in

that the monitored product is remagnetized, transforms self-induction emf jumps into a periodic signal, limits the signal in amplitude, and is judged on the structure of the material 2.

The method is carried out by a device comprising a generator, to the output of which an induction converter is connected and a broadband amplifier, the input of which is connected to an induction converter.

The main disadvantage of this method and the device based on it is the low control accuracy due to the uncertainty in the choice of the signal limit.

The aim of the invention is to improve the accuracy of the control.

This goal is achieved by the fact that the rate of magnetization reversal of the controlled

products, the magnetizing limit value and the level of restriction are chosen from

dn

 Max,

d-a

Where. N is the measured number of pulses;

and - the value of the monitored parameter

and the structure of the material is judged by the number of pulses over the measurement period, the amplitude of which exceeds the limit level, and the difference of the device that allows this method to be implemented is that it is equipped with a filter connected in series, the input of which is connected to the output of the amplifier, an amplitude limiter and a counter pulses.

The drawing shows the block diagram of the device that implements this method.

The device comprises a generator 1 connected in series, the output of which is connected to an induction converter 2 and a broadband amplifier 3, the input of which is connected to an induction converter, are connected in series to a filter 4 whose input is connected to the output of amplifier 3, an amplitude limiter 5 and a pulse counter 6.

The method with the device is carried out as follows.

Induction transducer 2 is placed on the surface of the test product (not shown).

From the generator 1 to the exciting winding of the induction converter 2 a signal of magnetization reversal is received. The jumps of magnetization arising due to irreversible processes in the local volumes of the product being monitored in the measuring coil of the induction transducer are jumps of the EMF of Barkhausen, which enter the input of the broadband amplifier 3. The amplified ground signal falls on the narrowband tunable filter 4, where it is converted from aperiodic to periodic. According to the Fourier transform, the shape of this signal will be determined both by the amplitudes and by the duration of the Barkhausen jumps, and the frequency / f by the band and average frequency of the filter. In other words, it does not depend on the Barkhausen pulses, but is determined by the characteristics of the filter itself. The resulting periodic signal passes through the limiter 5. The limit level is selected from the conditions for obtaining the maximum sensitivity of the method, d-N

i.e. maximum, where N - measure ed-a

my number of pulses, and - the value of the monitored parameter.

The main variable parameters of the described control method are: the magnetization reversal rate of the monitored material, specified by the alternator; limiting value of magnetizing floor; the level of the signal limit at the output of the limiter. Allocated by the limiter 5 pulses arrive at the counter 6 pulses. Thus, the number of pulses characterizes the material properties of the controlled product.

Claims (2)

1. The method of magnetic-noise restructuroscopy of ferromagnetic materials, which consists in that the product under test is re-magnetized, transforms self-induction EMF jumps into a periodic signal, limits the signal in amplitude and judges the structure of the material, which is different in that reversal of the controlled product, the limiting value of the magnetizing field and the level of restriction are chosen from conditions - max. d-a where L is the measured number of pulses; and - the value of the monitored parameter and the structure of the material is judged by the number of pulses over the measurement period, the amplitude of which exceeds the limit level. 2. A device for carrying out the method according to claim 1, comprising a generator, to the output of which an induction converter and a broadband amplifier are connected, the input of which is connected to an induction converter, characterized in that it is provided with a filter connected in series, the input of which is connected to the output of the amplifier, an amplitude limiter and a pulse counter. Sources of information taken into account in the examination 1. Patent of the GDR No. 71635, cl. G 01 N 27/00, 1970. 2. USSR author's certificate No. 655965, cl. G 01 iN 27/86, 1977 (prototype).