SU1682900A1 - Method of testing physico-mechanical parameters of crystalline structure of ferromagnetic bodies - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to control the physicomechanical parameters of the crystal structure of ferromagnetic objects. An increase in the information content of the controp is achieved by registering a number of informative parameters that correlate with the state of the crystal structure of the object being monitored. The controlled object leads to electromagnetic interaction with the eddy current transducer connected to the oscillator. Change its frequency f. fix local extremes and balance frequencies at which the input parameters are equal to zero. As the input parameters, the change in D f of the frequency of the oscillator and the change in DI of its current are recorded. The controlled object is moved to a fixed distance магнит the magnetic field of the eddy current transducer, which is created to converge. By the magnitude of the changes obtained in this case, the degree of quenching is judged, and by the values of the extremes D f, D I and the frequencies of the balance, the other parameters of the monitored object. 3 pe. sl C

Description

The invention relates to non-destructive testing and can be used to control the physicomechanical parameters of ferromagnetic objects.

The purpose of the invention is to increase the information content of monitoring the state of the crystal structure and determining the degree of quenching of ferromagnetic objects.

FIG. 1 shows a block diagram of a device that implements the proposed method; in fig. 2 — graphs of the development of positive and negative contour current increments along the frequency axis f, constructed for samples of normal, annealed, and hard iron; in fig. 3 corresponding dependences for raw and hardened steels, as well as for pure iron at different values of direct bias current.

The device that implements the proposed control method contains an eddy current transducer 1, an auto-oscillator 2 connected via a resistor 3 to the eddy transducer 1, a positive voltage voltmeter 4, an alternating voltage voltmeter 5, a frequency meter 6 and an oscilloscope 7 connected inputs parallel to the resistor 3, the drive for movement, consisting of a worm gear 8 with a control knob 9,

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10 with a scale and a vernier 11.

The controlled ferromagnetic object is fixed at the end of the dielectric rod 10, mounted coaxially with the eddy current transducer 1, which is made in the form of an inductance coil wound on a conical frame with an angle a at the top of 10 °. Resistor 3 is recommended to choose with a resistance of 0.2 ... 0.3 Ohms. The choice of a resistance value above 0.3 ohms worsens the conditions of self-excitation of the oscillator 2, and with a resistance less than 0.2 ohms, the recorded signals decrease without any sensitivity advantages.

The method of monitoring the physicomechanical parameters of the crystal structure of ferromagnetic objects is implemented as follows.

Pre-select control samples with different physico-mechanical parameters to be monitored. For the oscillator 2, the mode of soft excitation is set, its frequency f is monotonously changed and, at each value, the change Af of the frequency of the oscillator 2 and A I is measured by the amplitude of its current under the influence of control samples. To do this, they are brought into electromagnetic interaction with the eddy-current transducer 1 and record the change in frequency A f with the help of frequency meter 6 and the change in amplitude A I according to the magnitude of the voltage detected by a voltmeter 5.

Fig. 2 shows a typical diagram obtained for samples with different crystal structures associated with physico-mechanical parameters. The curves have local extremes and zero crossing points (balance frequencies fe). According to the obtained diagram, the frequency range f of the autogenerator 2 is selected with the greatest correlation connection of local extremes and balance frequencies on the one hand and controlled physical and mechanical parameters on the other. Then a set of informative parameters for the controlled object is determined and judged by its parameters.

To determine the degree of quenching of the test object 12, it is moved along the axis of the eddy current transducer 1 with a monotonically varying density of stepping lines. The latter is achieved by making its winding conical. As the monitored object 12 moves, the input parameters A f and AI change. At the same time, at a certain frequency f of the autogenerator 1, these changes correlate well with the quenching of the object. The corresponding areas for the hardened samples in FIG. 3 are shown as shaded areas, where AI depends on the position of the object 12. The corresponding position is fixed by the nonius 11. In the aggregate

changes in AI and Af at given displacements of an object 12 are judged on the degree of its hardening.

An additional increase in correlation links may be achieved when the sample is magnetized by a constant current. The magnitude of the bias current is determined by the voltage measured by a voltmeter 4. The shape of the current must remain harmonic, which is controlled by an oscilloscope 7.

Claims (2)

1. A method of controlling the physicomechanical parameters of the crystal structure of ferromagnetic objects, which means that eddy currents are excited by a eddy current transducer in a controlled object, the input parameters of the eddy current transducer are measured, the excitation frequency is determined monotonically, and the input parameters equal to zero, and use the received frequency fe to determine the physicomechanical parameters, characterized in that, in order to increase the informativeness of the control no crystal structure of ferromagnetic objects include eddy current converter as part of the oscillating circuit of the oscillator is measured as a parameter insertion signs and absolute values of the increments of ± Af oscillator frequency and the signs and absolute values ± AI increments its current amplitude, further fixed totality frequencies corresponding to the extremums ± Af and ± A), and use the recorded values to determine the physicomechanical parameters of the controlled crystal structure. 2. The method according to claim 1, characterized in that, in order to determine the degree of quenching of objects, choose the exciting inductor of the eddy current transducer with a monotonically varying the density of the power lines, a series of measurements is performed at different density of the power lines and the degree of quenching is judged by the range of measurements in the series. 0062891 -four/ 7Я7 / Fig.Z