SU1442869A1 - Torsion pendulum for determining mechanical properties of materials - Google Patents

Abstract

The invention relates to a test technique and can be used to measure the viscoelastic properties of materials. The aim of the invention is to improve the performance and informativeness of the results of the determination of the properties of materials by expanding the frequency range of the test. The torsional tick is equipped with an additional electrodynamic system, the movable coil of which is connected to the inertial part of the tiller. When direct current flows through the moving and stationary coils of the additional system, an additional force arises that accelerates or decelerates the oscillation of the pilot depending on the direction of the currents in these coils. The direction of the currents is set by the switch that connects the DC source to the coils in the corresponding polarity. .4 silt, cl

Description

four

ir

with

The invention relates to a test technique, namely, to a technique for determining viscoelastic xapaKTepKC tick (internal friction j dynamic modulus of elasticity, dynamic viscosity and so on), and can be used in the machine-building, chemical industry for the express control of physical-mechanical properties of liquids and solids,.

The purpose of the invention is to improve the performance and informativeness of the determination results by realizing the determination of the mechanical properties of materials at several hours.

Figure 1 shows the structure of the proposed torsion tandem; Fig, 2 section in Fig, 1 | in FIG. 3 a section BB in FIG. 1; FIG. 4 is a block diagram of the electronic part of the torsion bar.

The case comprises a housing 1, in the lower part of which a movable gripper 2 is fixed, the inertial part 3f of which is a rod of a twisting antenna with a movable gripper 4 in which sample 5 is fixed, Around the latter an electric furnace 6 is installed, Against grippers 2 and 4 In housing 1, grooves 1 are made to fasten sample 5 in grippers 2 and 4. A movable coil 8 is fastened to the rod of the torsion bar, which together with. A stationary coil 9 fixed in the frame of the tambourine forms a rotation angle sensor, which simultaneously serves as an electrodynamic system for twisting the sample 5. The coils 8 and 9 are mounted on a torsion tandem so that their magnetic fluxes are mutually orthogonal. A movable coil 10 is also mounted on the rod of the tambourine, which, together with the fixed coil II, forms the second electrodynamic system. The coils 10 and P of this system are structurally installed so that their magnetic fluxes are coaxial. The balancing system contains two blocks 12, a bracket J3 of a special design, a counterweight 14, suspensions to which pass through tubes 15 in stationary coils 9 and 11. Counter weight 14 balances moving weight

torsion tick system, a cone-shaped rod 16 allows you to lower and substitute a torsion rod using an electromagnetic gripper

with u

)five

0

5 30. . , Q hp

WITH

five

0

nick from vertical technological channels.

The electronic part of the tandem contains sources of alternating current 17 and direct current 18 connected to coil 9, detector 19 connected in series, connected to the first terminal of coil 8, amplifier 20, alternating voltage converter 2 to constant, comparison units 22 and electronic gain control 23. power amplifier 24 and excitation current meter 25, the output of which is connected to the second output of the coil 8, connected in series to the amplifier-limiter 26, whose input is connected to the output of the detector 19, and the second output This is connected to the second input of the electronic gain control unit 23, and the frequency meter 27, the reference voltage unit 28, the output of which is connected to the second input of the comparison unit 22, and a recorder 29, the input of which is connected to the second output of the field current meter 25. The electronic part also contains an adjustable DC source 30 connected to the series-connected coils 10 and 11 via the switch 31.

The twisting tutorial works in the following way.

When the torsion ticker oscillates, the alternating magnetic field of the stationary coil 9 fed from the alternating current source 17 induces in the moving coil 8 EMF with a frequency of 10 kHz.

A 10 kHz signal coming from the coil 8, modulated by low-frequency oscillations, enters the detector 19. The amplitude of this signal is a measure of the angle of the oscillator. The use of a high carrier frequency to transmit information about the angular displacements of the pendulum significantly increases the sensitivity of the angle sensor and allows you to reliably separate the signal taken from the angle sensor from the low frequency alternating current. The signal from the detector 19 simultaneously enters the amplifier 20 and the amplifier-limiter 26. After amplification, in the amplifier 20, it is converted into a constant voltage by the converter 21.

A constant voltage proportional to the amplitude of oscillations is compared to

In block 22, with the reference voltage coming from the output of the reference voltage block 28. The latter is the sensor of the amplitude of oscillations of the ticker. In block 22, the specified amplitude of oscillation is compared with the real one, and the difference signal from the output of block 22 is used as a control signal in the block. 23 electronic gain control. Here comes the signal from the amplifier-limiter 26. In the latter, the detected signal of the steering angle sensor is converted to a square voltage shifted in phase by 90 relative to the input signal. This phase shift is a prerequisite for the excitation of non-damping oscillations of the pendulum. The electronic gain control unit 23 provides a predetermined amplitude of oscillations of the tandem. Phased out by 90 ° relative to the input signal, the excitation signal from the output of the electronic adjustment unit 23 is amplified by the power amplifier 24 and through the excitation current meter 25 enters the moving coil 8. When an alternating current of the coil 8 interacts with a constant magnetic field of the coil 9 fed from DC source 18 (coil 9 is simultaneously energized from the alternating current), an alternating torque occurs. As a result, persistent torsional oscillations occur at the natural frequency of the system (the direction of oscillation is indicated by the arrow in Fig. 1). C, the exciter current meter 25, which is a measure of the energy loss during oscillations of sample 5, goes to the recorder 29. frequency counter 27.

When direct current flows from controlled current source 30 through mobile 10 and stationary 11 coils connected in series through switch 31, an additional electrodynamic system, due to the interaction of the magnetic fields of the coils, an additional force arises that affects the oscillator vibration. The current from the regulated current source 30 through the moving coil 10 always flows in one direction, while the direction of the current through the non-moving coil 11 can be changed using the switch 31.

9 .

When contacts I and II, III and IV are closed in switch 31, the current passes through the katuiki of an additional electrodynamic system, thus creating in the coil I1 a magnetic flux of such a direction that, when interacting with the magnetic flux of the moving coil 10,

It has a strong force that has an effect on the frequency of oscillation of the ticker, and it is less resonant.

Otherwise, when in the switch 31 contacts I and III are closed.

II and IV, the magnetic flux of the coil 1 is directed in the opposite direction. The additional force thus accelerates the oscillations of the symbol and the frequency is higher than the resonant one.

On a prototype with low-frequency oscillations of a torsion tick at a resonant frequency of 2 Hz using an additional electrodynamic system ;. it is possible to reduce the frequency of

Lebapy to 1 Hz and increase the frequency

up to 4 Hz, i.e. change the oscillation frequency twice. The change in the oscillation frequency depends on the magnitude of the current in the coils 10 and 11 of the additional electrodynamic systems.

Claims (1)

Invention Formula Torsion tiller for determining the mechanical properties of materials, containing a mobile and fixed grippers, inertial part connected to a moving gripper, electrodynamic system for twisting an inertial part and a registration system connected to an electrodynamic system, characterized in that, in order to increase the performance and informativeness of the determination results, it is equipped with a second electrodynamic system consisting of a moving coil mounted on the inertial part and a fixed coil, a switch, the first input of which is connected to the first output of the moving coil of the second electrodynamic system, and the second and third inputs are connected to the terminals of the fixed coil by the second electrodynamics system, and a source of direct current, the negative pole of which is connected to the fourth input of the switch, and the positive pole to the second output of the moving coil of the second electrodynamic system. Phases. i