SU150553A1 - Device for measuring mechanical resonance frequencies - Google Patents

Description

Devices for measuring the mechanical resonant frequencies of various parts containing a mechanical vibration exciter connected to a measuring device are known. Such devices have relatively low sensitivity and do not provide a sufficiently high accuracy of measuring the resonant frequencies of non-magnetic parts associated with massive, hardly-involved elements of construction.

The increase in the sensitivity of the described device is achieved by exciting the investigated part by means of an electromagnet powered by alternating amplitude-modulated voltage, and using an optical Michelson-Uvar interferometer as a mechanical detector.

Diagram of the device shown in the drawing.

The investigated non-magnetic part 1, which is, for example, an element of an electrovacuum device, is partially covered with a ferromagnetic film 2 and an electromagnet 3 is installed near it, on the ferrite core of which windings 4 tons 5 are wound. Windings 5, which serve to bias the core of the electromagnet 3, with a key 6 connect to source 7 constant voltage. The power winding 4 is connected via a switch 8 to a modulator 9, which simultaneously plays the role of an amplifier of amplitude-modulated oscillations used to power the electromagnet 5.

Two sound generators / O and 11 are connected to modulator 9, one of which serves as IB as a source of excitation oscillations, and the second is used as a source of modulating signal.

No. 150553-2. The frequency of exciting oscillations can be adjusted over a wide range. The lower modulating frequency is in the order of several tens of hertz and does not change during the measurement process.

As a mechanical detector of oscillations excited by an electromagnet 8 in a part /, an optical interferometer 12 by Michelson-Uvarsky, whose movable system, made in the form of a rod 13, is connected on the one hand to a mirror not shown in the drawing, and on the other hand to a probe 14, serves .

The probe / -: / is made in the form of a curved elastic metal wire that touches the test part 1.

By smoothly changing the frequency of the exciting oscillations, it is achieved to coincide with the intrinsic resonant frequency of the mechanical oscillations of the part. When a part is excited at its resonant frequency, the amplitude of the mechanical oscillations of this part increases, which is fixed by means of an interferometer 12.

The interferometer is also a detector of amplitude modulated oscillations excited in part 7. The detection process occurs due to the fact that the natural frequency of the probe 14 (in the direction of the axis of the rod 13) is higher than the modulating frequency and lower than the smallest frequency of the exciting oscillations, and its inertia with a large so that the probe can follow the signal change. At the same time, the probe has a sufficiently small inertia that does not prevent it from following the low-frequency envelope.

The device can be used in those cases when visual observation of oscillations is impossible due to small amplitudes of oscillations of the investigated part, and fixing of vibration sensors on the investigated detail is impossible.

Subject invention

A device for measuring mechanical resonant frequencies of various parts, for example, vacuum devices, containing a mechanical vibration exciter and a detector of these oscillations, is different in that, in order to increase the sensitivity of the device and the accuracy of measurements of resonant frequencies of non-magnetic parts associated with massive structural elements It uses an electromagnet powered by a variable amplitude modulated voltage, installed near the test piece, as the exciter of oscillations. The ferromagnetic film is tangibly coated, and the Michelson-Uvarsky optical interferometer is used as a mechanical detector, the mobile system of which is made in the form of a rod connected to a mirror and a probe made of a curved elastic wire that touches the part to be tested.