JPH02132368A - Coupling check method for ultrasonic wave probe - Google Patents

Abstract

PURPOSE:To remove the influence of the state of the bottom surface of a body to be inspected by monitoring the surface reflected wave of the body to be inspected by the ultrasonic wave probe which performs inspection through a liquid contact medium and evaluating its acoustic coupling state. CONSTITUTION:When an ultrasonic wave is sent by a vibrator 3 to the body 2 to be inspected, an echo which returns to the vibrator 3 as its reflected wave is converted into an electric signal, which is monitored on a CRT 8 as sent pulses T, a surface echo S, a bottom surface echo B, and an internal defect echo F. At this time, a coupling check circuit 9 is provided on the side of a receiving circuit 7 and only the surface echo S in the received signal is gated and led out to a circuit 8. Here, a voltage value corresponding to the sound pressure of the echo S is measured and compared with a reference value to decide whether or not the acoustic coupling state is normal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coupling check method for an ultrasonic probe used in ultrasonic flaw detection.

[Conventional technology]

The ultrasonic deep flaw inspection method is well known as a method for inspecting internal defects in metal products, and an ultrasonic probe is used in this ultrasonic deep flaw inspection method. There are various types of ultrasonic probes, and in particular, as a probe that is not affected by the surface roughness of the object to be inspected, the gap between the transducer and the object to be inspected is filled with a liquid couplant. FIG. 6 shows a state of ultrasonic deep flaw inspection using the above-mentioned water immersion probe. In the figure, 1 is a probe, 2 is an object to be inspected, and the probe 1 is composed of a combination of a vibrator 3 and a tank 5 filled with water 4 as a liquid couplant.

Note that 5a is a water supply port of the tank 5, and 5b is a seal for preventing water leakage. The probe 1 is set with a tank 5 in close contact with the surface of the object 2 to be inspected, and is automatically or manually scanned along the surface of the object 2 in the direction of the arrow.

Here, the transducer 3 receives pulse voltage application from the excitation circuit 6, emits ultrasonic waves toward the inspected object 2, converts the echoes that return to the transducer 3 as reflected waves into electrical signals, and sends the receiving circuit to the transducer 3. Transmit pulse T. on CRT display 8 via T. surface echo s. Monitor bottom echo B and internal defect echo F. In addition, a flaw detection waveform diagram displayed on the CRT display 8 is shown in the seventh session.

On the other hand, when performing a flaw detection inspection of the object 2 to be inspected using the probe 1 described above, it is necessary to keep the acoustic coupling between the probe 1 and the object 2 stable at all times. It is.

In other words, if the attitude of the probe 1 is tilted in the process of scanning the probe 1 along the surface of the object 2 to be inspected, the transmitted pulse of the ultrasonic wave emitted from the transducer 1 will be directed toward the object 2 to be inspected from the correct direction. No echoes are detected under normal conditions. Furthermore, if air bubbles are mixed in water as a couplant, the traveling wave of the ultrasonic wave will be attenuated because the acoustic impedance of the air bubbles is larger than that of water.

Therefore, a coupling check has conventionally been performed in order to evaluate the acoustic coupling state between the probe 1 and the object to be inspected 2 during ultrasonic deep flaw inspection. Conventionally, this coupling check method involves monitoring the bottom echo B shown in FIG. 7 to evaluate the acoustic coupling state.

That is, if the contact posture of the probe 1 with respect to the object 2 to be inspected is tilted, or if air bubbles are mixed in the water in the tank 5,
Since the sound pressure of the bottom echo B is significantly reduced, the quality of the acoustic coupling state can be checked by monitoring the bottom echo B.

In addition, in order to automatically perform the above-mentioned coupling check, the bottom echo B is gated and taken out to the coupling check circuit 9 shown in FIG. The quality of the acoustic coupling state is determined by comparing it with a set value. Note that if the acoustic coupling state is determined to be poor based on the determination result, an alarm signal is output to a buzzer lamp or the like, and at the same time, scanning is stopped in the case of automatic scanning.

[Problem to be solved by the invention]

However, the following problems remain in the conventional coupling check method described above.

(1) If the metallographic structure of the object to be inspected is not uniform throughout, if there are some uneven parts, or if there are internal defects, even if the acoustic coupling state of the probe is normal, the cup Because the sound pressure of the bottom echo detected by the ring check decreases, it becomes difficult to distinguish it from a case where the acoustic coupling state is poor.

(2) If the bottom surface of the object to be inspected is sloped or has an uneven surface with waves, the waves reflected from the bottom surface will not return to the probe normally, and as in the previous section, the output of the bottom echo will become unstable and acoustic coupling will occur. The condition cannot be evaluated correctly.

(3) For this reason, when the object to be inspected is in the state described in items (1) and (2) above, the conventional coupling check method does not function properly.

The present invention has been made in consideration of the above points, and provides a coupling check method that allows the state of acoustic coupling between a probe and a test object to be always correctly evaluated, regardless of the state of the test object. The purpose is to provide

[Means to solve the problem]

In order to solve the above problems, the coupling check method of the present invention monitors the surface echo that is reflected from the surface of the object to be inspected and returns to the transducer, and then connects the probe and the object based on the sound pressure of the surface echo. This is designed to evaluate the acoustic coupling state between the test object and the test object.

[Effect]

Surface echoes that propagate through the liquid couplant and reflect off the surface of the object to be inspected can be caused by tilted probe posture. If air bubbles are present in the couplant, the sound pressure will decrease, but
Even if the bottom surface of the object to be inspected is uneven or the internal structure is uneven, it will not be affected at all. Therefore, by monitoring the surface echo, it is possible to always correctly evaluate the quality of the acoustic coupling between the probe and the object to be inspected based on the sound pressure, regardless of the condition of the object to be inspected.

〔Example〕

Figures 1 to 5 show the acoustic coupling state between the probe and the test object according to the coupling check method of the present invention, and the C
This figure shows a waveform diagram monitored on an RT display. In order to automatically perform the coupling check, the coupling check circuit 9 is provided on the receiving circuit side as described in FIG. Take out,
Here, the voltage value corresponding to the sound pressure of the surface echo is measured or compared with a reference set value to determine whether the acoustic coupling state is good or bad.

First, Fig. 1(a) shows a normal acoustic coupling state in which the probe 1 is correctly set on the surface of the object to be inspected 2, and the couplant water 4 does not contain any air bubbles. A basic state is shown in which the bottom surface of the object to be inspected 2 is also a flat surface parallel to the top surface, and FIG. 3B shows a monitoring waveform diagram corresponding to FIG. Incidentally, in the figure (c), the symbol G represents a gate for taking out the surface echo S to the coupling check circuit of FIG. 6.

On the other hand, Fig. 2(a). In (b), the acoustic coupling is normal, but the bottom surface of the object to be inspected 2 has an uneven surface 2a.
FIGS. 3(a) and 3(b) show a coupling check state and its monitoring waveform diagram when an internal defect 2b exists in the inspected object 2.

Here, if we compare Figures 2 and 3 with Figure 1, we find that
In the cases shown in Figures 2 and 3, the bottom echo B is clearly attenuated, while the surface echo S propagates through the water without being affected by the bottom surface unevenness or internal defects of the object to be inspected 2, and is transmitted to the oscillator. Return to 3. Therefore, the sound pressure of the surface echo S is the same as in the case of FIG. 1, and by monitoring the surface echo S as described above, the acoustic coupling state can be checked correctly.

Next, FIGS. 4 and 5 show a coupling check state when the acoustic coupling between the probe 1 and the object to be inspected 2 is not normal. That is, FIG. 4(a) shows a state in which the probe 1 is tilted and is not correctly set on the surface of the object 2 to be inspected. In this state, the ultrasonic waves emitted from the transducer 3 will be incident on the inspection object 2 at an oblique angle, so they will be scattered on the surface, and the surface echo S received by the transducer 3 will be as shown in figure (b). The sound pressure is reduced compared to the case shown in FIG. Moreover, FIG. 5 shows a state in which air bubbles 4a are mixed in water 4, which is a couplant. In this state, the ultrasonic waves emitted from the transducer 3 are attenuated by the bubbles 4a while propagating through the water 4, and the sound pressure of the surface echo S is the same as in the case of Fig. 4, as shown in the figure. decreases to Therefore, by monitoring the surface echo S, it is possible to correctly determine through a coupling check that the acoustic coupling state is poor.

In addition, as a method for monitoring the surface echo S, as described above, a gate is applied to the output signal of the probe and only the surface echo is taken out to the coupling check circuit, where it is automatically judged as good or bad. It is also possible to evaluate the acoustic coupling state of the probe 1 by visually inspecting the pulse height of the surface echo S on the screen of the CRT display 8 shown.

〔Effect of the invention〕

As explained above, the ultrasonic probe coupling check method according to the present invention monitors the surface echo that is reflected from the surface of the object to be inspected and returns to the transducer, and performs detection based on the sound pressure of the surface echo. Since the acoustic coupling state between the probe and the test object was evaluated, the state of the test object, that is, the bottom surface of the test object was not parallel to the surface and had an uneven surface. Even if the internal structure is non-uniform, the acoustic coupling state between the probe and the object to be inspected can always be correctly checked without being affected by these conditions.

[Brief explanation of the drawing]

FIGS. 1(a), (c) to 3(a), (b) are shown in FIG. 4(a) when the acoustic coupling state between the probe and the test object is normal. (B) and Figures 5 (a) and ■) are coupling check state diagrams and monitoring waveform diagrams according to the method of the present invention when the acoustic coupling state is poor, and Figure 6 is the structure of the water immersion probe. Also, FIG. 7 is a diagram showing the state of ultrasonic flaw detection of the object to be inspected, and a monitoring waveform diagram in FIG. 6. In the figure,

Claims (1)

[Claims] 1) Coupling of an ultrasonic probe in which the gap between the transducer and the surface of the object to be inspected is filled with a liquid couplant, and the ultrasonic pulses emitted from the transducer are made to enter the object through the couplant. This is a check method in which surface echoes reflected from the surface of the object to be inspected and returned to the transducer are monitored, and the state of acoustic coupling between the probe and the object to be inspected is evaluated based on the sound pressure of the surface echoes. A coupling check method for an ultrasonic probe, characterized in that: