JPH03199961A - Signal processing method for ultrasonic flaw detecting apparatus - Google Patents

Abstract

PURPOSE:To improve the defect detecting capability by using the value obtained by adding a specified value to the average value of the peak values of flaw detecting signals at every emission as the judging level for acceptance or rejection. CONSTITUTION:A probe 6 emits flaw detecting signals (transmitted wave 13) of, e.g. 5 MHz, at transmitting intervals of 1-5 msec. Then, surface echoes 14 and bottom surface echoes 15 are removed from these signals in a material to be inspecteds, and only the flaw detecting signals 16 are picked up for, e.g. 50 msec. The peak values at every emission are held. The peak values of the flaw detecting signals of about 50-100 times are outputted for 50 msec. However, whether the peak values are noises or defective signals is unknown. Then, the average signal of the peak values for N pieces of the materials to be mea sured 5 is obtained. A specified level value is added to the average value, and the result is made to be the level for judging acceptance or rejection. The level is compared with the detected signal from the ultrasonic flaw detecting apparatus, and the defect is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a signal processing method in an ultrasonic flaw detection device.

(Prior Art) For example, an ultrasonic flaw detection method is generally employed for internal defect inspection of round steel bars. In this ultrasonic flaw detection method, as shown in FIG. 3, the level of the flaw detection signal obtained from the ultrasonic flaw detection device 1 is selected by the pass/fail judgment circuit 2, and if the flaw detection signal is equal to or higher than the disqualification level, the flaw detection signal is signaled. The delay circuit 3 delays the flaw detection signal, and the marking device 4 marks the defective portion of the material 5 to be inspected.

In Fig. 3, 6 is a probe, 7 is water as a medium, and 8 is a probe.
9 is an interface board, 9 is a computer, 10 is a proppy disk, and 11 is a CRT.

12 indicates a printer.

Here, the conventional pass/fail determination circuit 2 will be explained in more detail.

If the flaw detection signal converted into voltage is equal to or higher than a predetermined determination voltage level, a signal is sent to the next stage 1 circuit as a failure, and a defective part of the inspected material is marked. Since there is generally a linear relationship between defect area and defect echo height (defect echo height is proportional to voltage), the pass/fail determination level is determined by the size (area) of the defect to be detected. On the other hand, the flaw detection signal during ultrasonic flaw detection includes, in addition to defect echoes, noise components caused by, for example, the surface roughness of the inspected material, dimensional changes, bends, surface scale, vibrations during transportation, and other electrical disturbances. Therefore, in order to actually determine the pass/fail screening level, it is necessary to consider these noise levels.

For the above reasons, the detection capability limit of an ultrasonic flaw detection device is determined by the level of the flaw detection signal, and the level of this flaw detection signal also depends on the loft (material quality, surface roughness, dimensional change, bending, surface scale) of the inspected material. Therefore, the pass/fail determination level is usually set near the highest level of the flaw detection signal, as shown by the solid line in FIG.

(Problem to be solved by the invention) In setting the pass/fail judgment level as described above, if the overall level of the flaw detection signal is low, the ability to detect the inspected material with a margin in terms of S/N is also important. Since it is determined by

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal processing method for an ultrasonic flaw detection apparatus that can solve these problems and improve defect detection performance.

(Means for Solving the Problems) In order to achieve the above object, a signal processing method of an ultrasonic flaw detection apparatus according to the present invention constantly captures flaw detection signals of a material to be inspected by ultrasonic flaw detection. The peak values of the signals for each emission are averaged, and a certain level value is added to this average value to determine the pass/fail determination level.

(Function) The method of the present invention constantly captures the flaw detection signals of the material to be inspected for ultrasonic flaw detection and uses the averaged signal as the basis for the pass/fail judgment level, so the detection accuracy for minute defects is greatly improved. improve.

(Example) The method of the present invention will be explained below based on an example shown in FIG.

As shown in FIG. 1, while rotating the probe 6, for example,
Emit a MHz flaw detection signal (emission wave 13).

The firing interval at this time is 1 to 2 KHz (1 to 0.5 m
5ec). Since the inspected material 5 is progressing, the scanning is as shown in FIG. 1.

From this signal, only the signal in the inspected material 5, that is, the flaw detection signal 16 excluding the surface echo 14 and bottom surface echo 15, is extracted for, for example, 50 m5ec, and the peak value for each emission is held. Note that since the firing interval is 1 to 0.5 m5 ec, peak values of flaw detection signals are output 50 to 100 times during 5011 sec. Furthermore, it is unclear whether the peak value for each firing is noise or a defective signal.

The averaged signal is further averaged for N pieces of the inspected material 5, and a certain level value is added thereto to determine the pass/fail determination level.

By doing so, it is possible to determine the pass/fail determination level commensurate with the magnitude of the flaw detection signal level.

Then, this pass/fail determination level is compared with the detection signal Sij from the ultrasonic flaw detector 1 to determine a defect.

The above judgment logic is shown below.

Sij>aX liver tenb ... with flaw Sij ≦a
X+b... No flaws However, a: Proportional constant However, if the above judgment logic determines that there is a flaw, a signal is output to the signal delay circuit 3 and a mark is placed on the defective part of the inspected material 5. It is to give.

The initial pass/fail judgment level when carrying out the method of the present invention is determined by passing several test materials and averaging them.

(Effects of the Invention) As explained above, the method of the present invention determines the pass/fail judgment level according to the track record of the level of the flaw detection signal.
As shown by the broken line in Figure 2, for example, when the loft of the inspected material changes and the level of the flaw detection signal decreases overall, detection cannot be achieved when the judgment level is fixed as in the conventional method. This means that even such defects can be detected, improving defect detection performance.

In this embodiment, the case of ultrasonic flaw detection has been described, but it goes without saying that the present invention can be similarly applied to other non-destructive tests such as eddy current flaw detection and leakage magnetic flux flaw detection.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the method of the present invention, FIG. 2 is a drawing showing the effects of the method of the present invention in comparison with a conventional method, and FIG. 3 is a signal processing block diagram of ultrasonic flaw detection. 1 is an ultrasonic flaw detection device, 2 is a pass/fail judgment circuit, 5 is a material to be inspected,
16 is a flaw detection signal. is l#) )N ridge P 1

Claims (1)

[Claims] (1) The flaw detection signals of the material to be inspected are constantly captured, the peak values of these flaw detection signals for each emission are averaged, and a pass/fail judgment is made by adding a certain level value to this average value. A signal processing method for an ultrasonic flaw detection device, characterized in that a signal processing method is used for an ultrasonic flaw detection device.