SU1613945A1 - Method and apparatus for acoustic inspection of properties of ferromagnetic materials - Google Patents

Abstract

The invention relates to non-destructive testing and can be used for acoustic control of the properties of ferromagnetic materials. The purpose of the invention is to improve the accuracy and performance of control by eliminating the operation of manually setting the generator frequency to the sample frequency. In the test sample of the test material, the excitation and reception coils, as well as amplifiers and positive feedback circuits, excite elastic oscillations at the sample's own resonant frequency, which determine the ultrasonic wave propagation velocity and its length. The self-oscillating excitation process is periodically interrupted and the acoustic quality factor of the material, which characterizes the quality of the sample material, is automatically measured by the decay of freely damped oscillations. 2 sp.f-ly, 2 ill.

Description

The invention relates to non-destructive testing and can be used to acoustic control the properties of ferromagnetic materials.

The purpose of the invention is to improve the accuracy and performance of control by eliminating the operation of manually setting the generator frequency to the sample frequency.

Figure 1 shows the block diagram of the device for acoustic control of ferromagnetic materials; figure 2 - timing charts of the device; FIG. 3-4 will take care of the device.

A device for acoustic control of ferromagnetic materials contains an electronic switch 1, amplifier 2 connected to its output and excitation coil 3 connected to it, preliminarily set to be placed on sample 4 from a controlled ferromagnetic material, receiving coil 5, also designed to be placed on the sample 4, the amplifier-driver 6 connected to the receiving coil 5, the output of which is connected to the input of the electronic switch 1.

The device also contains a shaper 7 low-frequency envelope connected to the output of the amplifier-shaper 6, and a two-level scheme)

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8 comparison, connected to the output of the imaging unit 7, and the output to the control input of the electronic key 1, the second output of which is connected to the pulse counter 9. The second output of the amplifier-former 6 is connected to the input of the electronic key 1 and the input of the frequency meter 10. The method of acoustic control of the properties of ferromagnetic materials is carried out as follows.

The drive coil 3 and the take-up coil 5 are placed on the sample 4 of the test material. The sample is placed in a constant magnetic field with intensity H (the source is not shown).

At the moment of switching on the power, as a result of transients in the output circuits of amplifier 2, a nonnormable current pulse arises, which, as it passes through the coil 3, is excited and interacting with a constant magnetic field H, causes an initial magnetostrictive excitation of the sample in a wide frequency spectrum. However, due to resonant properties, in magnetostriction vibrators, oscillations with a wavelength corresponding to twice the length of the sample are dominant as energetically most favorable.

As a result of the magnetoelastic effect in the receiving coil 5, which surrounds the oscillating sample, electrical signals are sent with a half-wave resonance frequency of the sample, which through the amplifier-shaper 6 and further through the open electronic switch 1 arrive at the input of the amplifier 2. Thus, positive feedback is organized supporting the auto-oscillatory process of increasing the excitation current in the coil 3 until the electronic key 1 is opened by the output signal of the comparison circuit 8, to the input of which a signal arrives 6 -formirovatel output amplifier (2a), the detected and filtered by the low-frequency envelope generator 7 (Figure 26).

When this signal reaches a predetermined amplitude, the comparison circuit generates a logic level signal for switching the electronic key 1 (Fig. 2b). The electronic key 1 opens the feedback circuit, thereby interrupting the self-oscillatory process, and connects to the amplifier circuit the pulse counter 9, which registers the amplified and generated signals of the receiving coil 5 caused only by the free oscillating ultrasonic oscillations of sample 4 (Fig. 2a, d, section

Ii) The decay of freely damped oscillations is determined and, according to it, the acoustic quality factor, the value of which characterizes the quality of the sample material. When the amplitude is free

The 2 damped oscillations fall to an intensity of 1 times less than its maximum level, the comparison circuit 8, analyzing the level of the low-frequency envelope, again forms

d logical signal dx1I switch the electronic key (fig.2a, b, c). The counting of damped oscillations stops, the frequency meter 10 fixes the resonant frequency of the sample, according to which

5, the propagation velocity of the ultrasonic waves in the sample and its length are determined.

Invention Formula

1. The method of acoustic control of the properties of ferromagnetic materials, which consists in the fact that in a sample of a controlled material by the interaction of constant and alternating magnetic fields, excite acoustic oscillations, measure the resonant characteristics and use them to determine the controlled properties of the material, characterized in that In order to improve the accuracy and performance of the control, ultrasonic oscillations excite in a self-oscillating mode at its own resonant frequency of the sample, by which l dissolved propagation velocity of ultrasonic waves in the sample, oscillatory drive mode periodically interrupted and during which time the decay of the damped free oscillations measured acoustic quality factor and its value is determined by the quality of the sample material.

2. A device for acoustic control of the properties of ferromagnetic materials, containing a series-connected electronic switch, amplifier and excitation coil, after the connection of the receiving coil and the second amplifier, a two-level comparison circuit and a pulse counter, which is accurate for performance and accuracy. control, it is equipped with a frequency meter and shaper low frequency envelope connected between the output of the second

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the amplifier and the input of the two-level comparison circuit, the second amplifier is designed as an amplifier-amplifier, the output of the two-level comparison 5 is connected to the control input of the electronic switch, the second output of which is connected to the pulse counter, and the second output of the second

Q amplifier is connected to the input of an electronic switch and a frequency meter.

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Claims (1)

Claim 1. The method of acoustic control of the properties of ferromagnetic materials, which consists in the fact that in the sample of the controlled material by the interaction of constant and variable 35 magnetic fields excite acoustic vibrations, measure the resonance characteristics and use them to determine the controlled properties of the material, characterized in that, in order to increase the accuracy and performance of the control, ultrasonic vibrations are excited in a self-oscillating mode at the natural resonance frequency of the sample, which determines the propagation speed ultrasonic waves in the sample, the self-oscillating regime of excitation is periodically interrupted and during this time 5θ, the decay of free damped oscillations measures the acoustic quality factor and determines the quality of the sample material from its value. 55 2. A device for acoustic control of the properties of ferromagnetic materials, containing a series-connected electronic key, an amplifier ^{5 5} 613 945 an exciter and an excitation coil, series-connected a receiving coil and a second amplifier, a two-level comparison circuit and a pulse counter, characterized in that, in order to improve the accuracy and control performance, it is equipped with a frequency meter and a low-frequency envelope driver connected between the output of the second amplifier and the input of the two-level comparison circuit, the second force spruce formed as a shaper-amplifier, the output of two-level circuits 5, the comparison is connected to the control input of the electronic key, the second output of which is connected to the pulse counter, and the second output of the second amplifier Ιθ is connected to the electronic key input and the frequency meter. j