SU845079A1 - Method of non-destructive inspection of magnetostriction materials - Google Patents

Description

(54). THE METHOD OF NON-DESTRUCTIVE CONTROL / IAGNITOSTRICTION MATERIALS

I

The invention relates to methods for non-destructive testing and can be used to control the quality of heat treatment or the magnitude of mechanical stresses in magnetostrictive materials.

There is a method of measuring mechanical loads applied to magnetostrictive materials, which implies that ultrasonic vibrations are excited with the help of an electromagnetic field, change the frequency of the electromagnetic field, achieve a resonance of ultrasonic vibrations, and determine the applied value by the obtained resonant frequency load 1.

The disadvantage of this method is the inability to control the quality of magnetostrictive materials.

The closest to the invention to the technical essence is the method of non-destructive control of magnetostrictive materials, which consists in the fact that a controlled polarizing magnetic field is created in the controlled material, excites ultrasonic vibrations without contact, transforms these vibrations into

an electrical signal, and according to its parameters the controlled material is judged 2.

However, this method does not provide high accuracy of control, which is explained by the low accuracy of fixing the extremum amplitude of ultrasonic vibrations due to the smooth nature of its change with variation of the magnitude of the polarizing magnetic field.

The purpose of the invention is to increase the accuracy of the control.

This goal is achieved by choosing the time interval between two consecutive extremes of the first or second harmonics as the informative parameters of the received electrical signal.

FIG. 1 shows a diagram of an apparatus for implementing the proposed method; in fig. 2 - time dependences of the envelope of the first and second harmonics, converted into an electrical signal of ultrasonic vibrations.

The device that implements the method consists of a generator of high-frequency signals 1, a stimulating coil 2, material 3, a receiving coil 4 connected through a selective amplifier 5 to the input of a phase comparator 6, the output of which is connected to a digital 7-time meter, an excitation-induced magnetizing system coils comprising a magnetizing unit 8 connected in series (for example, an electromagnet) and an adjusting unit 9, a receiving coil magnetizing system, including a magnetizing unit 10 and an adjusting node 11.

The device works as follows.

The high-frequency signal produced by the generator 1 is fed to the driving coil 2 and, due to the magneto-fraction effect, excites material 3 in the presence of alternating low-frequency polarizing field H and elastic oscillations. The amplitude of the low-frequency polarizing magnetic field is optimally set for the elastic oscillations by means of the adjusting unit 8 of the excitation coil magnetization system. Ultrasonic vibrations in the presence of a constant polarizing field Do not excite electromagnetic oscillations above the material in the area of the receiving coil 4, in which they are converted into an electrical signal. The magnitude of the constant polarizing field is optimal for reception. But in the electromagnet 10, the biasing system of the pickup roller is set using the adjusting node P. The selective amplifier 5 extracts from the received signal the oscillations at the generator frequency 1 or at the frequency twice the frequency of the generator and amplifies them.

The envelopes of the high-frequency signal of the first (top) or second harmonics obtained at the output of the selective amplifier 5, depending on the time, are shown in FIG. 2. The period of the signal T is constant and corresponds to the period of the low-frequency polarizing field N. The ratio of the time intervals f, and t varies depending on the degree of heat treatment or the magnitude of the mechanical stresses. The selected harmonic signal, passing further through the phase comparator 6, to the input of which a reference signal from the high-frequency signal generator is fed, is converted and fed to a digital time interval meter 7, which measures the duration of interval 2, or t Compare the result with the corresponding time interval for reference sample, it is possible to judge the degree of thermal processing or the value of mechanical eg. in the test sample.

On the basis of the proposed method, it is easier to create more accurate and reliable devices for monitoring magnetostrictive materials, which work fully automatically due to the possibility of automatically measuring with high accuracy selected informative parameters.

Claims (2)

1. US patent number 3942369, class. G 01 N 29/00, 1976. 2. USSR author's certificate for application No. 2651309 / 25-28, cl. G 01 N 29/00, 1978 (prototype).