SU1456874A2 - Ultrasonic flaw detector - Google Patents

Abstract

The invention relates to the field of non-destructive testing and testing of materials by an ultrasonic method and can be used to control products in the metallurgical and machine-building industry. The aim of the invention is to increase the reliability of testing thick products and solids by improving sound by compensating for diffraction losses. This compensation occurs in the adder 5 when a sawtooth voltage generator signal is transmitted to its third input, which passes through the ac amplifier 13 and the additional logarithmic amplifier 14. The magnitude of this signal is proportional to the diffraction loss m. The signal from the output of the adder 5 is proportional to the magnitude of the amplitude of the reflected echo pulses from the bottom and the defect of the investigated product and does not depend on its size or sound absorption coefficient. 2 Il. with $ (L

Description

The invention relates to the field of non-destructive testing by ultrasonic method, can be used to control products in the metallurgical, engineering and other industries and is an improvement of the invention according to the main author. St. No. 1024828.

The aim of the invention is to increase the reliability of control of products of large thickness and with high sound absorption due to compensation of diffraction losses.

Figure 1 presents the structural diagram of the flaw detector; in FIG. 2 - timing charts.

An ultrasonic flaw detector contains a serially connected synchronizer 1, a high-frequency pulse generator 2, an ultrasonic transducer 3, a logarithmic amplifier 4 with a detector, an adder 5, a peak detector 6, a switch 7, two memory units 8 and 9 connected in parallel, a comparator 10, and an analysis unit 11. The second inputs of the peak detector 6, switch 7 and analysis unit 11 are connected to the second and third outputs of synchronizer 1. The flaw detector • also contains serially connected sawtooth voltage generator 12, a large-scale AC amplifier 13 and an additional logarithmic amplifier 14, and the input of the sawtooth voltage generator 12 is connected with the first output of the synchronizer 1, and the outputs of the sawtooth voltage generator 12 and the logarithmic amplifier 14 are connected to the second and third inputs of the adder 5,

Ultrasonic flaw detector operates as follows.

The synchronizer 1 generates clock pulses with a certain repetition rate (figa), which start the high-frequency generator 2. High-frequency pulses generated by the generator 2 (Fig), excite the ultrasonic transducer 3, which is connected to a controlled product (not shown) and excites an ultrasonic pulse in it. Reflected from. the defect and the bottom of the product, ultrasonic vibrations are perceived by the same transducer 3 in the combined mode (or in another separate mode), converted into electrical vibrations and fed to the input of the logarithmic amplifier 4 (Fig.2c). The voltage amplitude at the output of the logarithmic amplifier 4 JJ depends on the amplitude of the voltage at its input according to the law U _Aor = _kln U _BX , where k is the proportionality coefficient; U _6x - voltage on the converter 3.

From the output of the logarithmic amplifier 4, the signals are fed to the first input of the adder 5.

The amplitude of the voltage at the transducer 3 depends on the amplitude of the received ultrasonic pulse A as follows: U _{B) I} = JC; 2A, where X, coefficient of electromechanical conversion during reception; £ - acoustic coupling coefficient taking into account the quality of acoustic contact.

The depth of the defect h and the thickness of the product H are related to the propagation time and Cd of the ultrasonic pulse by the dependences where C _o is the ultrasound speed in the material of the product, and the amplitude of the ultrasonic pulse excited in the product A _o is A ₀ ^=, K, (2Ur » ^g D ^{e and} g the amplitude of the electrical voltage generated by the generator 2 high-frequency pulses (Fig, 26); # ₂ - coefficient of electromechanical conversion during radiation.

Simultaneously with the generator 2 starts the synchronizer 1 sawtooth generator 12 which generates a linearly decreasing in time compensation voltage sound absorption in the material products (fig.2g) and _n = _about ~ (± b where U _o - constant component; a /, - coefficient of proportionality.

The constant component U _{e of} this voltage is determined by a large-scale AC amplifier 13, and the variable component is changed to the required value and supplied to the logarithmic amplifier 14. As a result, a diffraction loss compensation voltage is generated (Fig. 2e) U = = ˜p> 1 nt. Both compensation voltages, the sum of which is shown in FIG. 2e, are supplied to the second and third inputs of the adder 5.

As a result, the voltage at the output of the adder 5 is equal to U = kln ^ ² / u _r -klnt-k & C _e t + ott + + Plnt-U _o .

By adjusting | 3 = k and ei ^! = kS'C _o , it is possible to ensure independence of the control results from the depth of defects.

In this case, “r- ^to 1 * 'hCh

The voltage from the output of the adder 5 15 is supplied to the input of the peak detector 6, which generates a constant voltage proportional only to the positive voltage values. By changing the magnitude of the voltage U _o , you can 20 thereby change the sensitivity of the control.

The peak detector 6 and the switch 7 are controlled by gating pulses (Fig.2zh, and, h), which are generated 25 synchronizer I.

In the absence of strobe pulses, the memory blocks 8 and 9 are disconnected from the output of the peak detector 6 and store the information contained in them; peak 30 detector 6 is in Reset state. When the strobe of the defect (Fig. 2g) is supplied from the synchronizer 1, the peak detector 6 is turned on and its output through the switch 7 _{35 is} connected to the memory unit 8, in which the maximum value of the pulse reflected from the defect is stored (Fig. 2i). In the pause between the defect strobe (FIG. 2g) and the bottom strobe (FIG. 2h), the peak detector 6 returns to the Reset state, and the bottom pulse strobe (FIG. 2z) is connected to the memory unit 8, in which the maximum value is stored echo pulse from the bottom of the product (fig.2k).

The voltage of the outputs of the blocks 8 and 9 of the memory is supplied to the inputs of the comparator 10, which finds the difference of these voltages (Fig.2l) and feeds it to the input of the analysis unit 11. A threshold voltage is applied to the second input of this unit.

If the defect is small or absent, then the voltage difference at the output of the comparator 10 is large, and at the output of the analysis unit 1 1, the signal takes a value of 0, which is a sign of the absence of a defect. If the defect is significant, then the voltage difference at the output of the comparator is small, and at the output of the analysis unit 11, the signal takes the value 1, which is a sign of a defect.

The proposed ultrasonic flaw detector ensures the independence of the inspection results both from the depth of the defects and from the quality of the acoustic contact.

Claims (1)

Claim Ultrasonic flaw detector according to ed. St. No. 1024828, characterized in that, in order to increase the reliability of control, it is equipped with a serially connected large-scale AC amplifier, an input connected to the output of a sawtooth voltage generator, and an additional logarithmic amplifier connected to the third input of the adder. a ji. ___________________________ K -----