JPS6196459A - Division type ultrasonic probe transmitting/receiving circuit - Google Patents

Abstract

PURPOSE:To detect a flaw immediately under the surface of a material to be tested highly accurately by outputting pulses from a control circuit for a fixed period synchronously with timing for exciting a transmission side oscillator and turning on a switching means by pulses. CONSTITUTION:An one-shot circuit 32 is provided with an FF35, a capacitor 33 for setting up pulse width by changing a time constant and a resistor 34. The waveform of an output signal from the circuit 32 is set up to the high level during about 2-5muS synchronously with the timing for exciting the transmission side oscillator 5, and during the high level of the output signal, the collector and emitter of a transistor (TR) are shorted. Even if an induced electric pulse is excited on the side of a transmission side oscillation 6 during the short, the electric pulse applied to the oscillator 6 is less than about 0.1V which is the saturation voltage of the TR31. Therefore, a wave reflected from the front surface of a delay material 4 is prevented from being mixed with a wave reflected from a defect or the back of the material 21 to be tested, so that a flaw immediately under the surface of the material 21 and the thickness of an extremely thin plate can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a split-type ultrasonic probe transmitting/receiving circuit used in ultrasonic thickness gauges and flaw detection devices.

Conventional technology> The ultrasonic probe 1 has delay members 3 and 4 pasted on both sides of a partition wall 2 made of a covering acoustic shielding material, and a transmitting side having a semicircular cross section on top of the delay members 3 and 4. It is constructed by pasting a vibrator 5 and a receiving side vibrator 6, respectively.

Conventionally, an ultrasonic probe or flaw detector using such a split-type ultrasonic probe 1 is equipped with a transmitting/receiving circuit as shown in FIG. This transmitter/receiver circuit includes an oscillation circuit 11, a pulse generation circuit 12, and an amplifier circuit 13. The F pulse generation circuit 12 includes a thyristor 15. Equipped with a capacitor 1G and resistors 17, 18, and 19, the thyristor 15 is activated in synchronization with the pulse from the oscillation circuit 11, and a high voltage (50 to I U l) V is generated.
) is input to the transmitting side transducer 5 of the split-type ultrasonic probe 1. The ultrasonic waves emitted from the transmitter side transducer 5 propagate through the delay element 3 and the test material 21, and the ultrasonic echoes reflected by the reflection section are transmitted through the delay element 4 (;' t (It is received by the lt11 transducer 6, and then the amplification circuit. When performing flaw detection, the path I shown in FIG. Back side of inspection material 21 → inspection material 2
1 surface→receiving side delay material 4→receiving side transducer 6 path I
The ultrasonic echoes generated during the passage of the test material 21 are observed to check for defects. In addition, in the case of thickness measurement, the ultrasonic echo from the back side of the material to be inspected 21 is received by the receiving side transducer 6, and the ultrasonic wave propagates through the delay material 3.4 from the time from the time of transmission to the time of reception. The propagation time in the test material 21 obtained by subtracting the time is measured, and the thickness is determined by multiplying 1/2 of this propagation time by the propagation speed (velocity of sound) specific to the test material 21.

<Problems to be Solved by the Invention> By the way, according to experiments, in the above-mentioned split-type ultrasonic probe 1, due to the mutual stray capacitance of the cable 23, 24, the transmitting side transducer 5, and the receiving side transducer 6, etc. Due to the effect,
It was found that an induced nt% pulse of about 34 dB of the electric pulse applied to the transmitting side vibrator 5 was excited to the receiving side vibrator 6 side.

This is 4'l 2 when the transmission pulse voltage is 100v.
A pulse voltage of V is excited in the receiving side vibrator 6, and the receiving side vibrator 6, which originally has electro-vibration reversibility, generates an ultrasonic wave. The generated ultrasonic wave has a delay JfA on the receiving side
n, is reflected by the front surface of this delay material 4, propagates again along the same path, and reaches and is received by the receiving side oscillator 6 (11). According to another experiment, the received voltage obtained when traveling back and forth through the delay material 4 is approximately -35 clB of the transmitted voltage, that is, under the above conditions, the received voltage is approximately 5 mV. On the other hand, with such split-type ultrasonic probes, the received voltage changes depending on the thickness of the material being tested, that is, the material to be measured.In other words, it is best to have a thickness/received voltage characteristic. That is, because of the acoustic shielding material 2 interposed between the transducer 5°6 and the delay material 3.4 on the transmitting and receiving sides, the received reflected signal from the extremely thin material to be measured is small, and It is common for thick materials to be measured to exhibit a slope characteristic in which the received signal decreases as the thickness increases due to sound attenuation and diffusion within the material. For example, a thickness of 1 mm obtained with the I″f wave probe 1
The magnitude of the received signal from the back side of the material to be measured 21 made of steel of +- grade, that is, the received voltage propagated through path 2, is at most 10 mV, and is not significantly different from the received signal obtained through path 11. I understand.

FIG. 5 specifically shows these phenomena. The waveform (,) in FIG. 5 is the waveform of the transmitting side vibrator 3, and T
is the waveform of the electric pulse applied to the transmitting side vibrator 5, and S is the waveform of the reflected wave from the front surface of the transmitting side delay material 3. On the other hand, the waveform (b) in FIG.
, T' is the waveform oscillated from the receiving side vibrator 6 by the electric pulse induced by the above-mentioned induction, and S' is the reflected wave of this waveform T' from the front surface of the receiving side delay material 4. , R are reflected waves from a defect or the back surface of the test material 21 in the above-mentioned path I.

Therefore, there is a problem that flaw detection with high viscosity or thickness measurement cannot be performed because there is a case where flaw detection is performed directly under the surface of the test material 21 with high sensitivity or when the thickness of the extremely thin test material 21 is measured.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to enable flaw detection directly below the surface of a test material and highly accurate detection and measurement of the thickness of an extremely thin test material.

Means for Solving the Problems> In order to achieve the above object, the configuration of the present invention includes a switching means that electrically shorts both ends of the receiving side vibrator, and a switching means that is synchronized with the timing of exciting the transmitting side vibrator. The device is characterized in that it includes a control circuit that outputs a signal that turns on the switching means for a certain period of time.

<Operation> With the above configuration, a signal is output from the control circuit in synchronization with the timing of exciting the transmitting side vibrator. Upon receiving this signal, the switching means is turned on for a certain period of time in synchronization with the timing of exciting the transmitting side vibrator, and both ends of the receiving side vibrator are electrically short-circuited. For this reason, the receiving side transducer is not excited by the transmitting signal.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, 1 is a transmitting side vibrator 5. Receiving side transducer 6
and a split-type ultrasonic probe with delay material 3.4 etc., 1
Reference numeral 1 is an oscillation circuit, 12 is a pulse generation circuit, 13 is an amplifier circuit, and 21 is a test material, which have the same configuration as the conventional example shown in FIG.

Further, 31 is a switching transistor as a switching means for short-circuiting both ends of the receiving side vibrator 6;
receives the tri signal from the oscillation circuit 11 and generates a signal of 2 to 5μ.
This is a one-shot circuit as an example of a control circuit that inputs one of the pulses of s to the base of the transistor 31. The above one-shot circuit 32 has 7 lip 70 lip 3
5 and a capacitor 34 and a resistor 34 for setting the pulse by changing the time constant. As shown in FIG. 2(b), the waveform of the output signal of the one-shot circuit 32 is synchronized with the timing at which the transmitting side vibrator 5 is excited.
The output signal remains at a high level for -5 μs, and while the output signal is at a high level, the left and emitter of the transistor 31 are short-circuited.

Therefore, while this is short-circuited, the receiving side transducer 6
Even if the induced electric pulse is excited on the receiving side transducer 6
The electric pulse applied to the transistor 31 is equal to or less than the saturation voltage o, iv of the transistor 31.

Therefore, the magnitude of the induced pulse l's2 to the side of the receiving side transducer 6 in this embodiment, as shown in the waveform T' in the diagram, is as follows: Electrical induction pulse (1/10 or less compared to the size of the waveform T in FIG. 5). Therefore, as shown in the waveform (c) in FIG. The reflected wave S' from the front surface of the delay material 4 (almost negligible) and the test material 21
There is no confusion with internal defects or reflected waves R from the back surface, and it is possible to perform highly sensitive flaw detection just below the surface of the test material 21 and measure the thickness of an extremely thin plate.

In the above embodiment, a one-shot circuit is used as the control circuit, but the circuit is not limited to this, and any type of circuit can be used as long as it outputs pulses for a certain period of time in synchronization with the timing of excitation of the transmitting side vibrator. It's okay.

<Effects of the Invention> As is clear from the above description, in the split-type ultrasonic probe transmitting/receiving circuit of the present invention, the control circuit emits pulses for a certain period of time in synchronization with the timing of exciting the transmitting side transducer. output and this pulse turns on the switching means,
Since both ends of the receiving transducer are short-circuited to greatly reduce the influence of electrical induction, it is possible to detect flaws just below the surface of the test material with high accuracy. The thickness of thin measuring materials can be measured with high precision.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a split type ultrasonic probe transmitting/receiving circuit according to an embodiment of the present invention, and Fig. 2 is a waveform U-ff5 of the above embodiment.
3 (a), ffs 3 ti (1 (b) is a plan view and front view of a split-type ultrasonic probe, FIG. 4 is a circuit diagram of a conventional split-type ultrasonic probe transmitting/receiving circuit, and The figure is a waveform diagram of the conventional split-type ultrasonic probe transmitting/receiving circuit. 1... split-type ultrasonic probe, 5... transmitting side transducer,
6... Receiving side vibrator, 11... Oscillation circuit, 12...
- Pulse generation circuit, 13... Amplification circuit, 21... Test material, 32... One-shot times H8, 31.) transistor. Patent applicant: 1 person other than Kawasaki Steel Corporation

Claims (1)

[Claims] (1) In an ultrasonic thickness gauge or flaw detection device using a split-type ultrasonic probe having a transmitting-side transducer and a receiving-side transducer, a switching means for electrically shorting both ends of the receiving-side transducer; , a control circuit that outputs a signal to turn on the switching means for a certain period of time in synchronization with the timing of exciting the transmitting side vibrator, and the receiving side vibrator is activated by electrical induction of the transmitted excitation electric energy. A split-type ultrasonic probe transmitting/receiving circuit characterized in that it is configured to prevent vibration excitation.