SU547689A1 - Device for measuring the attenuation coefficient of acoustic waves in a moving sheet material - Google Patents

Description

 Since the measurement of the attenuation coefficient of acoustic oscillations is performed by a contactless method, the accuracy and reliability of the measurement does not depend on the speed of movement of the material. In addition, there is dry friction between the fixed support and the moving sheet material, as a result of which broadband ultrasonic vibrations are generated in the web, which propagate along the sheet plane and are partially emitted into the environment. The sheet material being produced is almost unlimited sreshchak (along the length of hundreds of meters) .I Compared with the length of the ultrasonic waves generated by dry friction, it has a significant absorption of ultrasonic, therefore the reflected signals can be neglected. In this connection, it is possible to establish the frequency dependence of the attenuation coefficient of ultrasonic vibrations in a moving sheet material.

Figure 1 shows the functional diagram of the device; in fig. Figure 2 shows the frequency response of the S / c0 spectral density of the noise signal generated by dry friction between a moving paper web (speed V 5 m / s) and a fixed support (young spherical body 22 mm in diameter).

The device contains a fixed support 1, which is in direct acoustic contact with the sheet material 2. On the upper side of the material, at a certain distance from it, the first 3 and second 4 receivers of acoustic oscillations are installed in a direction in which the sheet moves. The measurement circuit contains two siachronically tunable filters 5 and 6, an amplitude ratio meter 7 and a recording recorder 8, the recorder 8 clock output is connected in parallel with the control inputs of both filters 5 and 6, the first amplitude ratio meter input 7 through the first filter 5 is connected to the output of the first receiver 3, and the second input using a filter 6 is sucked to the output of the second receiver 4, and the output of the amplitude ratio meter 7 is connected in series with the input of the recorder 8.

The device works as follows.

 the dry friction between the fixed support i and the moving sheet material 2 in the latter generates intense broad-band ultrasonic oscillations (see Fig. 2) which spread along the plane of the sheet. These ultrasonic vibrations in the environment create an acoustic wave that is applied by the first 3 and second 4 receivers. Since the receivers are installed in series from the radiator at a distance from one another, therefore the second pr1.: Minik receives acoustic signals that have passed an additional path along the sheet plane relative to the acoustic signals received by the first receiver. Therefore 60

the second receiver receives acoustic signals of lower amplitude. The difference in amshopod depends on the physical properties of the material under study to absorb acoustic vibrations. The received signals are fed to the outputs of synchronously tunable filters 5 and 6, which are simultaneously controlled by a clock recorder 8. Therefore, the first and second inputs of the amplitude ratio meter 7 are supplied with signals of a certain frequency, respectively, from the first 3 and second 4 receivers. Electrical (mtp proportional to the ratio AJ / AJ from the output of the meter ratio 7 in the form of a constant voltage is applied to the recorder 8, where AI and Aj are the amplitudes of the acoustic signals received by the first 3 and second 4 receivers respectively. The attenuation coefficient is determined by formula

2gb fucked

B / m,

in Ag and Le

2

Where

Ag2ogge

l is the distance between the receivers And is kept constant; Therefore, the continuously recorded value Аj / А- on a tape with a logarithmic scale of the recorder uniquely determines a. The scale of the samopioc is graduated in units of attenuation (d B / m). ;

The filters controlled by the recorder sequentially overlap the wide frequency range. Therefore, this device automatically determines the frequency dependence of the attenuation coefficient of the ultrasonic vibration in the moving material. When measured at other distances, this is learned by calibrating the recorder 8.

The value of a is related to the molecular structure (X) and the state of the material and in most cases cannot be calculated theoretically. Therefore, much attention is paid to the experimental determination of a. ;

It should be noted that the frequency dependence of a gives significant information about the structure of polymeric materials, in particular paper, cardboard, artificial leather, etc.

Tests have shown the reliability and greater accuracy of the device in determining the dependence of the attenuation coefficient of ultrasonic vibrations in sheet materials moving at speeds of up to 20 m / s. Therefore, the introduction of the proposed device will allow to control the mechanical properties of polymeric sheet materials during their manufacture, which will minimize the time required for testing and adjusting the process equipment, creates the possibility of automatic control of the technological process.

Claims (3)

Claims 1. Device for measuring the attenuation coefficient of acoustic waves in dvlzh ttssms a sheet of material containing an emitter, a first and a second receivers of ultrasonic vibrations, and a measurement unit, characterized in that, in order to improve the accuracy, the measurement unit has two flutters electrically connected, respectively, to the first and second ultrasonic oscillations, the amplitude ratio measurement element , the inputs of which are connected to the output of the filters, and a recorder connected by its input with the output of the amplitude ratio measurement element, and the input with filters. 2. Device according to claim 1, characterized in that the emitter of ultrasonic vibrations | it is made in the form of a fixed support, which is able to interact with the moving material with sheet material. Sources of information taken into account state expertise: 1. USSR author's certificate N 169903, M.C. b01N29 / 00,1963g. 2. Patent Franschi If 2195351, M. Kp. G 01Y 29/04, 1974 3. USSR author's certificate W 323738, M-Cl G 01 N 33/34, 1972. ///////// .f 85 de 4i5epy relatively ,, s g nof oeoSazo / jpoBHa 17,2-Yu fj Ki 65 five 200SOD YuOO 2m5000 20000 50000 WOOD f Hz FIG. 2