CS248651B1 - A method for measuring the wavelength and a device for carrying out this method - Google Patents

Abstract

The invention solves the problem of determining the wavelength during the propagation of harmonic stress waves in an environment with wave dispersion using a fixed position of two sensors. It relates to the field of dynamic diagnostics, dynamic non-destructive testing methods and quality control, based on the graphical representation of the phase velocities of stress waves. It solves the problem of determining the wavelength and phase velocity of propagation by a method that allows for automation of measurement. The essence of the invention is to measure the wavelength during a gradual change in frequency and a fixed position of two sensors with the same phase-frequency characteristics. The invention can be used in non-destructive testing of elements and structures by the phase velocity method, in determining the characteristics of material elasticity, thickness, stiffness and deflection of road structures, in testing the properties of the subgrade, embankments, slabs and walls. Its use is also possible in other areas of technology when studying the properties of environments with wave dispersion.

Description

248 851

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the wave length and the apparatus of performing this method in a wave dispersion environment of a two position sensor. In the dynamic diagnostics of elements and constructions, the method of measuring the phase velocity of the wine propagation is used. Serves to determine the characteristics of material elasticity, element rigidity and quality control. Two methods are applicable in general phasometry. Variable base method at constant frequency! and a variable frequency method at a stable base. In both cases, the principle of measuring the length of a wave in the propagation of harmonics is stressed by the examined environment. Since the variable-frequency method of a fixed base is bound in the prior art to a frequency-independent constant phase velocity, it uses the exclusive variable base method at constant frequency, which is also applicable to a wave-dispersion environment. It consists in measuring the phase difference between the excitation vibration and the oscillation at the sensor at steady frequency, but at different sensor distances from the exciter. The disadvantage of such a solution is the great demands on the operation, the measuring accuracy and the difficult, practically impossible realization of the measurements.

The above disadvantages are substantially eliminated by the method for measuring the length of the wave and the apparatus for carrying out this method of the invention, the principle of which is that the phase difference of the vibration in the wavelength is measured when the wavelength is greater than the distance between the sensors. locations of both sensors. Both sensors with the same phase-frequency characteristics are connected to the object of a distance less than the length of the wave belonging to the lowest frequency, whereby the generator of the harmonic variable force is placed on a common line with the sensors outside the measured section. 2,248 BS1

This process eliminates the tedious and laborious measurements in the multi-position sensor for each selected frequency, saving the single work force required to transmit the sensor to individual positions, improving measurement accuracy and reproducibility, and especially providing a favorable basis for measurement automation.

FIG. 1 shows the arrangement of the sensors with respect to the generator, and FIG. 2 shows the dependence of the phase difference ýi from the frequency f f, which allows for any frequency f in the interval (/ y, -fn) to the basis of the measured value of Aij) * to 27 £ to determine the wave length Λ

The apparatus for carrying out said wave length determination process comprises two sensors 1 and 2 having the same frequency characteristics, the outputs of which are connected to the inputs of the evaluation device 2, e.g., a phase transducer and a variable frequency harmonic generator 4 with selectable frequency , which introduces napatiado object.

In the propagation of harmonic wines of stress in a wave-dispersion environment, the wave length Λ is determined at the fixed position of both sensors 1 and 2 having the same phase-frequency characteristics and which are connected to the environment at a distance of one another. transducer oscillations at a frequency change of the wines of the strain f, propagating through the environment at a frequency range of J to. The distance L of the sensors 2 and 2 is determined by the condition; L -, wherein / 17 is the length of the wave corresponding to the lowest frequency! .

Changing the frequency ® / changes the phase difference tpp. The phase difference A ^ 2JT corresponds to the frequency I at which the wave length A is just equal to the distance Z. Phase difference A (f> = k 2JI3 across k is an arbitrary real number, arises at a frequency where the wavelength Λ is determined by the relation Λ = k - 3 - 248 6S1

Gradual change of frequency in the range up to / ¾ allows to determine the value / any frequency / *. The phase velocity of the spreading of the voltage atia enia * θ of a given frequency is determined from the relation e = / λ.

The use of the invention is possible in the case of non-structural testing of the elements and structures by the phase velocity method, for example in determining the elasticity characteristics of the subsoil material, the embankments, in determining the elasticity and rigidity characteristics of road constructions and other surface systems such as thatch, walls. It is also possible to use it in other areas of the study to study the properties of the environment with a wave dispersion, for example in determining the critical frequency and coincidence frequencies as the sound insulation of wall or thatch elements, in the experimental investigation of the coherent properties of materials.

Claims (2)

P RBD-BT INVENTION 248 831 1 · A method for measuring the wavelength in a wave dispersion environment at a fixed position of two sensors, characterized in that it gradually changes the frequency of the wattages from the lowest frequency at which the wavelength is greater than the distance between the sensors (1, 2). 1 2. Apparatus according to claim 1, characterized in that the transducers / 1 (2 / b by the same phase-frequency characteristics associated with the object of the s at a distance of 1/2) smaller than the wavelength are associated with the lowest frequency. wherein the harmonic variable force generator (4) is located on a common line with the sensors (1 (2) outside the merand distance fL). 1 drawing