SU1104410A1 - Converter for measuring speed of sound in materials - Google Patents

Abstract

CONVERTER FOR MEASURING THE SPEED OF SOUND IN THE MATERIALS, comprising a case, a rectangular piezoplate placed inside it, and a protective bottom, characterized in that, in order to improve the accuracy and performance of measurements, the sizes of the piezoplate sides are chosen from the ratios where mm -frequency, for work on which a piezoplate is intended, Hz.

Description

The invention relates to an ultrasonic measuring technique and can be used to measure the velocity of propagation of longitudinal waves during surface testing, for example, with non-destructive testing of building materials.

A known transducer for measuring the speed of sound in materials, comprising a prism and a piezoelectric transducer, placed on it, the ultrasonic vibrations being introduced into the material at the first critical angle 1.

The disadvantage of the transducer is insufficiently wide area of application, since the input under the first critical angle is carried out only in those materials, the speed of propagation of longitudinal waves in which corresponds to a given angle of the prism.

The closest to the technical essence of the invention is a transducer for measuring the speed of sound in materials, comprising a housing, a rectangular piezoplate accommodated therein and a protective bottom. In this case, the transducers intended for operation at different frequencies contain a square plate of 20x20 mm 2.

The disadvantage of the known transducer is that the accuracy and performance of measurements is not high enough, because acoustic signals from all elementary parts of the radiating plate arrive at a different time at the receiving point and, therefore, the received signal is stretched and has an insufficiently large amplitude.

The aim of the invention is to increase the accuracy and performance of measurements of the speed of sound in materials.

The unrelated goal is achieved by the fact that in a transducer for measuring the speed of sound in materials, comprising a housing, a rectangular piezoplate placed in it and a protective bottom, the dimensions of the piezoplate sides are selected from the ratios:

B io-iVe / t

where d fe is the width and length of the piezoplates, mm;

f is the frequency for which the piezoplate is intended to be used, Hz.

FIG. I shows a transducer for measuring the speed of sound in materials; in fig. 2 - the same. side view; in fig. 3 - projection of the piezoplates of the converter onto the surface of the controlled product.

A transducer for measuring the speed of sound in materials comprises a housing 1, a rectangular piezoplate 2 and a protective bottom 3 located therein. The dimensions of the piezoplate sides are chosen from the ratios

a “f - 106; (one)

B lO-iV f, (2)

where 6 is the width and length of the piezoplates 2, mm;

f is the frequency for which the work is intended

piezoplastin 2, Hz.

A transducer for measuring the speed of sound in materials operates as follows.

The converter is installed with a protective bottom 3 on the controlled product. A rectangular piezoelectric element 2 is supplied with a voltage pulse through an electrical connector (not shown) mounted in converter case 1. Under the action of this pulse, the piezoplastin 2 emits an acoustic signal to the controlled product. The longitudinal oscillations propagating in the product reach the reception point K, located, for example, at a distance of 1 on a straight line coinciding with the transverse axis of the piezoplate. The difference At at the time of arrival in seconds from the near and far points O and N of the piezoplate, lying on its transverse axis, to the point K of reception is equal to

Ati a / c, (3)

Where

with. - velocity of propagation of longitudinal waves in the material of the controlled product, mm / s.

This difference Ati in order for the signals at the point of reception to add up must be no longer than the time C of the rise of the pulse front, i.e.

(four).

The rise time of the pulse front is characterized by the natural frequency of the piezoelectric element, i.e. the frequency f, for which the piezoplate is designed to operate.

(five).

The speed of sound in solid materials varies in a wide range, but can be reliably limited to below 3-10 mm / s. Substituting this particular value into equality

(3) and using (4) and (5), it is easy to get an expression that corresponds to the formula ().

Consequently, the width a of the piezoplates is chosen in such a way that the signals are almost simultaneously received at the receiving point. The difference At g of the time of arrival in seconds from the near point O of the piezoplate, lying on its transverse axis, and from the point M of the piezoplastin.

Claims (1)

A TRANSDUCER FOR MEASURING THE SPEED OF SOUND IN MATERIALS, comprising a housing, a rectangular piezo-plate placed in it and a protective bottom, characterized in that, in order to improve the accuracy and performance of measurements, the dimensions of the sides of the piezo-plate are selected from the ratios 10"; BilO’V — where s, c are the width and length of the piezoelectric plate, mm; f is the frequency for which the piezoelectric plate is intended to operate, Hz. <Oh SU „„ 1104410