RU2557323C2 - Method of determining dynamic characteristics of elastomers - Google Patents

Abstract

FIELD: testing technology.

SUBSTANCE: test samples of elastomers in the form of cylindrical sleeves put on the lever shafts, are mounted in devices symmetrically located relative to the axis of the vibrator table of the hole. The device provides the ability of synchronous change and fixing the equal angles of the levers inclination to the surface of the table of the vibrator in the range of 0° to 90°. The test samples of elastomers are rigidly attached by vulcanisation or gluing to the shafts of levers and the inner surface of the holes of the device. Over the test samples of elastic material the load is mounted. The table of vibrator with the loaded samples of elastomers is set in a vertical oscillatory motion, the oscillation frequency is gradually changed, and the resonance frequency f is determined, when the amplitude of acceleration of the load is maximised. According to the resonance frequency f the dynamic modulus of elasticity is calculated. By changing the weight of the load, the values of the dynamic modulus of elasticity are determined in the listed sequence. The tests in the same sequence are performed for the other selected samples of the considered batch of elastic materials, the angle of the levers inclination to the surface of the table of the vibrator is sequentially changed and fixed by means of the device, with each determined value of the angle of the levers inclination the value of dynamic modulus of elasticity is determined in the listed sequence, and for each batch of the material - the arithmetic mean values of the modulus of elasticity.

EFFECT: possibility of obtaining dependence of the dynamic modulus of elasticity of unit of elastomer from the angle of the levers inclination to the surface of the table of vibrator and weight of load.

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Description

The invention relates to testing materials, and in particular to methods for determining the dynamic characteristics of elastic materials.

A known method for determining the dynamic characteristics of elastic materials is that they strike a falling spherical load on the test material, record the time the load falls before contact with the material, the time of their contact and the time of the load bounce, calculate the natural frequency of vibrations and determine the dynamic elastic modulus , which is one of the parameters of dynamic characteristics [1].

However, the method does not allow to determine the dynamic characteristics of elastic elements operating in compression-tension and coaxial torsion. Elastic elements operating in compression-tension and coaxial torsion are used in devices for mounting the cab on the vehicle frame to increase vibration protection [2], [3].

Closest to the proposed is a method of testing materials for determining the dynamic modulus of elasticity, consisting in the fact that the test samples of the material are installed on the table of the electrodynamic vibrator, the load is placed over the tested samples of the material, the vibrator table with the loaded samples of material is brought into vertical oscillatory motion, the frequency is gradually changed oscillations, determine the resonance frequency at which the amplitude of the acceleration of the load becomes maximum, according to the resonance frequency the dynamic elastic modulus is calculated using the formula, changing the mass of the load, the dynamic modulus of elasticity is determined in the above sequence, the tests are carried out in the same sequence for other selected samples of the batch of elastic materials under consideration, for each batch of material and the specific mass of the load, the arithmetic mean value of the dynamic modulus is calculated elasticity [4].

The disadvantage of this method is that it does not allow to determine the dynamic characteristics of elastic elements operating in compression-tension and coaxial torsion. These characteristics are necessary when designing vibration isolators containing elastic elements, which, when the machine performs technological operations with a change in the operating mode, rotate with respect to the protected object, smoothly changing the stiffness of the vibration isolators and reducing the vibration of the protected objects.

The objective of the present invention is to expand the capabilities of the method.

The problem is achieved in that in a method for determining the dynamic characteristics of elastic materials, including the fact that the test material samples are mounted on a table of an electrodynamic vibrator, a load is placed on the test material samples, a vibrator table with loaded material samples is brought into vertical oscillatory motion, the vibration frequency is smoothly changed , determine the resonance frequency at which the amplitude of the acceleration of the load becomes maximum, according to the resonance frequency in the form the dynamic elastic modulus is calculated by changing the mass of the load, the dynamic elastic modulus value is determined in the above sequence, tests in the same sequence are carried out for other selected samples of the batch of elastic materials under consideration, for each batch of material and specific mass of the load, the arithmetic average of the values of the dynamic elastic modulus is calculated , a distinctive feature of the prototype is that the tested samples of elastic material in the form of a cylindrical w locks, dressed on the shaft of the levers, are installed in the holes of the device symmetrically located relative to the axis of the vibrator table, which allows simultaneous changes and fixation of equal tilt angles of the levers to the surface of the vibrator table in the range from 0 ° to 90 °, the tested samples of elastic material are vulcanized or glued tightly to the shafts of the levers and the inner surface of the holes of the device, sequentially change and fix using the device the angle of inclination of the levers to the surface the vibrator table, for each set value of the angle of inclination of the levers, the value of the dynamic elastic modulus is determined in the listed sequence, and for each batch of material the arithmetic mean value of the elastic modulus values.

It is known that the elastic properties of elastomers are characterized by a large difference in the moduli of volume compression and shear, which occurs during coaxial torsion. For example, for rubbers, their ratio lies in the range from 500 to 5000 [5, p.21]. At an angle of inclination of the levers of 0 °, elastomers work only on coaxial torsion, and at an angle of inclination of 90 ° they work only on compression-tension. When the angle of inclination of the levers, which is more than 0 °, but less than 90 °, elastomers work simultaneously on compression-tension and coaxial torsion.

With a change in the angle of inclination of the levers, the value of the dynamic elastic modulus of these materials will also change.

Figure 1 presents a diagram of the implementation of the method for determining the dynamic characteristics of elastomers; figure 2 - dependence of the arithmetic mean value of the elastic modulus of the elastomers from the angle of inclination of the levers to the surface of the vibrator table.

The method is implemented as follows.

At least six samples are taken from each batch of elastomers for testing. The number of simultaneously tested samples take two pieces.

The tested samples of elastic material in the form of cylindrical bushings 1, worn on the shafts 2 of the levers 3, are installed in the holes B and C of the device 6 symmetrically located relative to the axis U-U of the table 4 of the vibrator 5.

The device 6 provides the possibility of synchronous changes and fixing equal angles φ of the tilt of the levers 3 to the surface of the table 6 of the vibrator 5 in the range from 0 ° to 90 °.

The test samples 1 of the elastic material by vulcanization or gluing are rigidly attached to the shafts 2 of the levers 3 and the inner surface of the holes B and C of the device 6.

The first load 7 is installed over the tested samples of elastic material 1. The vibrator table 4 with loaded samples of material 1 is brought into a vertical oscillatory motion, setting the measuring amplifier 8 to automatically maintain a constant amplitude of the acceleration of the load 7. Using a low-frequency measuring sound generator 9, set the oscillations with a frequency of 5 Hz

The oscillation frequency is smoothly changed and the resonance frequency f is determined at which the acceleration amplitude of the load 7 becomes maximum. The acceleration amplitude is recorded using accelerometers 10 and a vibration meter 11.

The resonance frequency f calculate the dynamic modulus of elasticity E _D (N / m ² ) of the elastomer according to the formula [4, p.4]

$$E_D=\frac{\mathrm{four}{\pi }^2{f}^{2}Mh}{F},\left(\mathrm{one}\right)$$

where f is the resonance frequency, Hz;

M is the mass of the cargo, kg;

h is the thickness of the sleeve of the elastomer sample under load, m;

F is the total surface area of the simultaneously tested samples, perceiving the load, m ² .

Changing the mass M of the load 7, determine in the listed sequence the value of the dynamic elastic modulus E _D.

Tests in the same sequence are carried out for other selected samples of the batch of elastic materials under consideration.

For each batch of material and a specific mass M of load, the arithmetic mean value of the values of the dynamic elastic modulus is calculated.

Consistently change and fix using the device 6 the angle φ of the tilt of the levers 3 to the surface of the table 6 of the vibrator 5 in the range from 0 ° to 90 ° and change the mass M of the load 7.

For each set value of the angle of inclination of the levers 3 and the mass M of the load 7, the value of the dynamic elastic modulus is determined in the above sequence, and for each batch of material the arithmetic mean value of the elastic modulus is determined.

As a result of testing on a vibrating electrodynamic stand VEDS-10A in accordance with the claimed method for determining the dynamic characteristics of elastomers, experimental data were obtained for rubber grade 1378.

Using the obtained resonance frequencies f using formula (1), we calculated the values of the dynamic elastic modulus of the tested rubber samples and the arithmetic mean values of the elastic modulus of the rubber lot under study.

Figure 2 shows the obtained dependence of the dynamic elastic modulus E _D on the angle φ of the inclination of the levers 3 to the surface of the table 6 of the vibrator 5.

As test samples, rubber bushings having a length of 50 mm, an outer diameter of 50 mm, an opening of 20 mm were used.

The load on the samples was adopted 10 KN / m ² .

According to the research results, it can be concluded that with an increase in the angle of inclination φ of the tested rubber samples, the value of the dynamic elastic modulus decreases.

Information sources

1. USSR author's certificate No. 697873, cl. G01N 3/30, 1978.

2. USSR copyright certificate for invention No. 300368. Device for mounting the cab on the car frame. Publ. 04/07/1971. Bull. No. 13.

3. USSR copyright certificate for the invention No. 1604653. Device for mounting the cab on the vehicle frame. Publ. 11/07/1990. Bull. No. 41.

4. Soundproof and sound absorbing materials. Test methods. GOST 16297-80. The publication is official. State Construction Committee of the USSR. M .: Publishing house of standards, 1988.

5. Lyapunov V.T., Lavendel E.E., Shlyapochnikov S.A. Rubber vibration isolators. Directory. - L .: Shipbuilding, 1988 .-- 216 p.

6. Vibration in technology. Directory. Volume 4 / Ed. E.E. Lavendela. - M.: Mechanical Engineering, 1981.

Claims (1)

A method for determining the dynamic characteristics of elastic materials, namely, that the test samples of the material are installed on the table of the electrodynamic vibrator, the load is placed over the test samples of the material, the vibrator table with the loaded samples of the material is brought into vertical oscillatory motion, the vibration frequency is smoothly changed, the resonance frequency is determined, when which the amplitude of the acceleration of the load becomes maximum, according to the resonance frequency, the dynamic guests, changing the mass of the cargo, determine the value of the dynamic elastic modulus in the sequence listed, tests in the same sequence are carried out for other selected samples of the batch of elastic materials under consideration, for each batch of material and specific mass of the load, the arithmetic average of the values of the dynamic elastic modulus is calculated, characterized in that the tested samples of elastic material in the form of cylindrical bushings, worn on the lever shafts, are installed in a symmetrically located e relative to the axis of the vibrator table, the holes of the device, which provides the possibility of synchronous changes and fixing equal angles of inclination of the levers to the surface of the table of the vibrator in the range from 0 ° to 90 °, the tested samples of elastic material by vulcanization or gluing are rigidly attached to the shaft of the levers and the inner surface of the holes of the device, sequentially change and fix with the help of the device the angle of inclination of the levers to the surface of the vibrator table, at each set value of the angle of inclination of the lever in the listed sequence, the value of the dynamic elastic modulus is determined, and for each batch of material the arithmetic mean value of the elastic modulus values.

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