SU896550A1 - Ultrasonic flaw detector - Google Patents

Description

(54) ULTRASOUND DEFECT TESTS

one

The invention relates to non-destructive ultrasonic testing and can be used to control railroad rails.

The ultrasonic de-4) ultrascope is known, comprising a pulse generator, an emitting transducer, a receiving transducer, an amplifier and an indicator 1.

 The disadvantage of the known flaw detector is low control accuracy.

The closest to the invention in technical essence and the achieved result is an ultrasonic flaw detector containing a series-connected continuous oscillator, a transducer, an amplifier, a filter designed to isolate the per-shift frequency shift, a detector and an indicator 21.

A disadvantage of the known flaw detector is low noise immunity, since with significant changes in the speed of movement the filter must have a wide passband.

The purpose of the invention is to improve the noise immunity.

The goal is achieved by the fact that the ultrasonic flaw detector is equipped with a transducer speed sensor, the input of which is connected to the transducer, and the unit

10, the control for varying the center frequency is proportional to the speed of the converter included between the sensor moving speed sensor and the filter designed to extract the Doppler frequency shift, and the filter is adjustable in frequency band.

The drawing shows the block diagram of the instrument.

20

The ultrasonic flaw detector contains a series-connected continuous-oscillator 1, a transducer 2, an amplifier 3,

filter k, designed to highlight the Doppler frequency shift, detector 5, indicator 6, transducer movement speed sensor 7) 2, whose input is connected to converter 2 output, and control unit 8 connected between transducer speed sensor 7 and the selection of the Doppler frequency shift and performed adjustable bandwidth.

Ultrasonic flaw detector works as follows.

The electroacoustic converter 2 moves along the surface of the Monitored Product E at a speed V.

Converter 2 continuous electrical oscillations, the incoming t of generator 1, converts into ultra-sound and sends it to the test item 9 at an angle i-. . The part of ultrasonic oscillations reflected by the 6t defect and possible signals from interferences are transmitted to the transducer 2 where It performs the generator signal suppression, amplification and extraction of signals with the difference frequency t of the output of the amplifier 3 signals fed to a filter 4 designed to separate the Doppler frequency shift.

Filter A selects signals reflected from the defect, having a difference frequency qj, and filter out Interference signals whose frequency is different from the frequency of useful signals (for example, Signals reflected from the opposite face of the product under test, or impulse noise from an electric} converter. When changing the speed of the 1strading according to the signal received by the speed sensor 7 of the filter 7, the control unit 8 of the filter changes the parameters of the filter C so that the filter bandwidth and average frequency remain optimal for extracting signals reflected from the defect. In this case, the filter band depends on the parameters of converter 2 and changes as the displacement rate of the converter ho changes to the following law:

,

 f (j cosoL-s in

Afa

with f. the frequency of the emitted oscillations;

V

movement speed;

cL beam entry angle.

The average frequency of the filter 4 menet1

with a change in the speed of movement (1 converter in accordance with the shape of

fo 2- fflsinot The signals selected by the filter are detected and fed to the indicator.

Thus, the described flaw detector allows to increase the noise immunity due to the decrease in the total bandwidth of the receiving path.

Claims (1)

1. Kerpin B. Ultrasound. Foreign Literature, 1950, p. 133 -. US patent number 3321959, cl. 73 - 67-7, 197 (prototype). GYuYa g-: