JPS598776B2 - How to check the coupling of an ultrasonic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for checking the contact status, that is, the coupling status, between a probe and a subject in ultrasonic flaw detection.

In the ultrasonic flaw detection method, especially in the direct contact method in which the ultrasonic probe must be brought into contact through a thin film (hereinafter referred to as a force plant) using oil or other couplant, the contact situation between the probe and the specimen is It has been found that the transmission of ultrasonic waves to a subject is significantly influenced by the presence of a staghorn (cabulicida) condition.

For this reason, the coupling status has conventionally been checked as follows.

In the vertical flaw detection method, for steel plates, steel pipes, pressure vessels, etc., which have surfaces parallel to the surface to be inspected, coupling is performed by monitoring the amplitude fluctuation of the ultrasonic waves reflected from the bottom surface, that is, the bottom echo. Checking is in progress.

However, this method has the disadvantage that if a bottom surface parallel to the test surface cannot be obtained or if the bottom surface has a complicated shape, the bottom echo will vary significantly and effective coupling information cannot be obtained. Ta. In addition, in the angle angle flaw detection method, a vertical transducer is built into the angle probe, and this vertical transducer monitors the bottom echo as in the case of the vertical flaw detection method. The coupling status of angle flaw detection was estimated.

However, while vertical flaw detection uses longitudinal waves, general oblique flaw detection uses transverse waves, and the wave mode of the ultrasonic wave is different, as well as the direction of propagation of the sound. Ta.

Also, this method requires two sets of vibrators and cables,
There is a problem that the internal structure of the probe is also complicated, making it larger than in the case of a single vibrator. Moreover, if the bottom surface of the object is not parallel to the surface to be inspected, there is a drawback that an effective coupling check cannot be performed as in the case of vertical flaw detection. The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a method that can perform a reliable coupling check using a normal probe regardless of the shape of the bottom surface. It is something to do.

In other words, the present invention sends ultrasonic waves to a metal object using an ultrasonic probe, extracts a flaw detection signal, and then amplifies this signal to reveal forest-like echoes reflected from the metal structure of the object. let it come out,
Next, the coupling of the probe is checked based on this forest echo.

An example in which the method of the present invention is applied to angle angle flaw detection will be described below.

As shown in the figure, in the angle angle flaw detection method, an angle angle flaw detector 2 is placed on the test surface 1a of a metal object 1 to perform flaw detection, but in the present invention, the coupling state is checked and feedback is performed automatically. It adjusts the gain to keep the coupling situation constant.

That is, the pulses transmitted from the pulse generator 3 are converted into ultrasonic beams by the oblique probe 2 and penetrate into the subject 1 .

If there is a defect in the object 1, this ultrasonic beam will be reflected by the object 1, but even if there is no defect, it will be reflected, albeit weakly, by the constituent crystals of the metal structure into the receiving system 4.
It is reaching as a forest echo. Next, the ultrasonic waves that have reached the receiving system 4 are alternately input, for example, one repetition frequency at a time, to the flaw detection signal system 6 and the forest echo signal system 7 via the electronic switch 5.

The signal input to the flaw detection signal system 6 is amplified by an amplifier 8,
As shown in display 9 or through gate 10, recording system 1
7 will be automatically recorded. In this case, the forest echo is not observed in the display 9 because it is considerably smaller than the flaw detection detection level obtained by adjusting the sensitivity using a standard test piece or the like. On the other hand, the signal input to the forest echo signal system 7 is transmitted to the amplifier 11.
is amplified in the same way as the above amplifier 8, and is further amplified by another amplifier 1.
2, it receives an amplification of about 20 to 30 dB, which is shown in display 13. In this case, since this signal is considerably amplified, a change in the coupling state between the probe 2 and the test surface 1a can be easily observed as an amplitude change a of the forest echo. Further, the forest echo signal passes through a gate 14, a defect discrimination circuit 15 and an integration circuit 16, and is automatically recorded in a recording system 17. Here, the defect discrimination circuit 15 detects when a gate range defect signal or other interference echo appears because the shape and amplitude level of the interference echo or defect signal are significantly different from the forest echo. It is to be removed. Further, the integration circuit 16 obtains an integral value of (echo amplitude) x (signal acquisition time), and outputs a signal from as wide a range as possible to average the countless forest-like echoes that exist.
Further, the output signal of the integrating circuit 16 is input to an alarm system 18 using a blinking buzzer, light emitting diode, or the like. Furthermore, it is possible to feed back to the automatic gain adjustment circuit 19 as an input signal to correct changes in coupling conditions on-line. According to the above embodiment, when the coupling condition becomes poor during manual flaw detection, the time integral value of the forest echo filled with voltage becomes smaller than a certain value, and a warning is issued by means such as a buzzer or a flashing signal. Flaw detection can be performed while always maintaining a good coupling condition.

Furthermore, in the case of automatic flaw detection, the coupling status can be automatically recorded moment by moment along with detection of the flaw detection signal, so it is possible to check for defective coupling locations even after the flaw detection has been completed.

Furthermore, this coupling check signal can be fed back to automatically adjust the gain of the flaw detection signal, significantly improving the reliability of automatic flaw detection. Furthermore, in both manual and automatic flaw detection, unlike conventional coupling checks, it is completely unaffected by the shape of the bottom surface, increasing the range of applications. It goes without saying that the method of the present invention can be applied not only to the angle flaw detection method but also to the vertical flaw detection method. In addition, the ultrasonic waves input to the flaw detection signal system 6 and forest echo signal system 7 are 1
It is not limited to each frequency, but may be more than that. As described above, according to the present invention, a coupling check can be performed regardless of the shape of the bottom surface, and the performance and reliability of the ultrasonic automatic flaw detection system are improved. However, this method can be applied to both the vertical flaw detection method and the oblique flaw detection method.
Furthermore, it has remarkable effects, such as being applicable to various types of systems, from simple portable equipment for manual flaw detection to advanced automatic flaw detection systems during use of nuclear power plants.

[Brief explanation of the drawing]

The drawings are block diagrams showing one embodiment of the present invention. 1...Subject, 1a...Test surface, 2.
...Angle flaw detector, 3...Pulse generator,
4... Receiving system, 5... Electronic switching device, 6
...Flaw detection signal system, 7 ... Forest echo signal system, 8 ... Amplifier, 9 ... Display, 1
0...Gate, 11...Amplifier, 12
...Amplifier, 13...Display, 14...
... Gate, 15 ... Defect discrimination circuit, 16
... Integration circuit, 17 ... Recording system, 18
...Alarm system, 19...Hakudo gain adjustment circuit.

Claims (1)

[Claims] 1. After transmitting ultrasonic waves into a metal object with an ultrasonic probe and extracting a flaw detection signal, this is amplified to reveal forest-like echoes reflected from the metal structure of the object, A method for checking the coupling of an ultrasonic probe, characterized in that the coupling of the probe is then checked based on the forest echo.