SU1564519A2 - Installation for determining damping properties of materials in torsional tests - Google Patents

Abstract

The invention relates to a testing technique, in particular, to devices for determining the damping properties of materials under torsional vibrations under various temperature conditions. The aim of the invention is to expand the temperature range and improve the accuracy of the installation. For this, the oscillatory system of the installation, made in the form of a torsion tandem with energizers located on it, is equipped with an optical system that converts torsional vibrations into electrical signals that are insensitive to the parasitic rotation of the torsion attachment as a whole and to the effect of temperature. The optical system consists of a light source, a photodetector, and a luminous flux modulator installed between them in the form of two circular rings with windows, rigidly connected with the corresponding disks of the torsion dial. An oscillation detection unit is associated with an oscillation excitation unit, which makes it possible to perform an automatic oscillation disruption under the same predetermined initial conditions. 1 il.

Description

The invention relates to the study of the properties of materials under variable loads, in particular, to installations for the study of energy dissipation in materials during vibrations, and can be used to determine the damping properties of materials during torsional vibrations.

The purpose of the invention is to expand the temperature range of the plant and increase its accuracy.

The drawing shows the proposed installation.

The installation contains a torsion bar formed by the test sample 1 with two rigidly fixed, at its ends, inertial axially symmetric elements consisting of bottom parts 2 and glasses 3. Two edges of the force-suppressors are rigidly and diametrically fixed at the 4 edges of glasses 3 4 and 5, and the energizers in a pair are mounted on different glasses in such a way that the excitation force arising between them acts perpendicular to the axis of sample 1. The force-exciters can be electromagnetic or other types. The powering device is connected to the excitation unit 6 oscillations

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niy The oscillation receiver is made in the form of an optical projection system including a light source 7, for example, in the form of a collimator, a mirror 8, a light flux modulator consisting of two circular rings 9 and 10 rigidly and coaxially connected to corresponding glasses 3 Rings 9 and 10 made with identical Windows, evenly distributed around the entire circumference of the rings and having the shape of sectors of a circular ring. The width of the jumpers between the windows is equal to the width of the windows, the jumpers of one of the rings are located opposite the windows of the other ring. The receiver also includes a dual convex lens 11 and a photodetector 12. The installation also includes an oscillation detection unit 13, which consists, for example, of an amplifier, an analog-digital converter, a digital storage device, a comparison element and a control element (not shown). The output of the photodetector 12 is connected to the input of the oscillation detection unit 13. The output of the vibration detection unit 13 is connected to the input of the vibration excitation unit 6. The oscillatory system is suspended on a thin steel filament 14, which coincides with the continuation of the axis of sample 1.

The installation works as follows.

The light beam from the light source 7 is guided by a mirror 8 perpendicular to the circular ring 9 of the light flow modulator along its entire circumference. Using the excitation unit 6, signals with the required frequency and amplitude are received alternately for each pair of causative agents 4 and 5, i.e. in opposite phase. Due to the direction of the force interaction, perpendicular to the os of sample 1, a torque is transmitted through the glasses 3 to sample 1. In this case, the glasses 3 perform cyclic rotations around the axis of the sample 1 in opposite directions together with the bottom parts 2 and the circular rings 9 and 10 of the light flux modulator. At the same time, the windows of one of the rings begin to project onto the windows of the other ring and transmit the luminous flux. Due to the lens 11, the total luminous flux from the windows located around the entire circumference of the modulator is fed to the input of the photoreceiver.

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I2 and changes its intensity depending on the degree of overlap of the windows of one ring with jumpers of another, i.e. depending on the angle of twisting of the sample 1. The electrical signal at the output of the photodetector 12 is proportional to the angle of twist of the sample and is recorded in the oscillation detection unit 13. The achievement of the greatest amplitude of oscillations of a torsion tusk at a given level of power supplied to the silo power unit 4 and 5 indicates the onset of a resonant mode of oscillation. This is determined in the vibration detection unit 13 by comparing (For some predetermined length of time, consecutive samples of vibration amplitudes, after which, from the vibration detection unit 13, a signal is sent to the input of the vibration excitation unit 6, which stops the power supply to the exciters 4 and 5. and registering a damped free oscillation process. Since the suspension thread 14 is long enough and has a negligible torsional stiffness, and there are even the smallest, almost unavoidable due to axisymmetry in the mass distribution of the torsion torsion, with oscillations, the parasitic rotation and rocking of the oscillatory system as a whole with respect to the suspension axis occurs slowly. However, due to the fact that the luminous flux is assembled on the photoreceiver 12 from the entire circumference of the ring module the torus, the indicated displacement of the modulator together with the torsion peak does not cause changes in the character and intensity of the signals at the input and, accordingly, at the output of the photodetector 12, .e. will not affect measurement accuracy.

Since the light flux modulator is resistant to high and low temperatures, this makes it possible to equip the oscillatory system with a suitable heater or cooler (not shown), which allows extending the temperature range of the installation without reducing the accuracy of the results.

The elimination of the subjective factor in determining the beginning of the process of damped oscillations (moment of failure

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oscillations) and its automatic determination at the installation due to the connection of the oscillation detection unit with the oscillation excitation unit improves the accuracy of the installation by stabilizing and identifying the initial conditions of the damped oscillations process.

Claims (1)

The invention The installation for determining the damping properties of materials at torsional vibrations according to auth.St. No. 1485064, characterized in that, in order to increase accuracy 0 five 196 measuring and expanding their temperature range, it additionally contains two rigidly and coaxially connected with glasses disc rings with windows evenly distributed around the entire circumference of the rings and having the shape of a sector, the width of the jumper between the windows is equal to the width of the window, the jumpers of one of the rings are opposite the windows of the other rings, as well as a light source and a photodetector, the output of the photodetector being connected to the input of the oscillation detection unit, the output of which is connected to the input of the vibration excitation unit.