JPS63200058A - Ultrasonic flaw detector - Google Patents

Abstract

PURPOSE:To obtain a flaw detection image having high resolving power, by providing BPF capable of extracting the arbitrary frequency component of the frequency outputted from a receiver to the circuit between a pulser and a peak detector. CONSTITUTION:In an apparatus consisting of a pulser 5 transmitting an ultrasonic pulse to a probe 4, a receiver 6 receiving the reflected wave from an object to be inspected to amplify the same, a peak detector 7 outputting the DC voltage proportional to the peak value of the reflected wave amplified by the receiver 6 and an operational processing part 9, a band-pass filter (BPF)14 extracting the arbitrary frequency component of the frequency band outputted from the receiver 6 is provided to the circuit between the pulser 5 and the peak detector 7. By this constitution, since the setting of the frequency component allowed to pass through BPF14 is arbitrarily changed and the amplitude of the frequency component after passing through BPF14 becomes max. in the region thereof, the flaw detection in the region of the high frequency component or that in the region of a low frequency component can be freely selected and a flaw detection image having high resolving power is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic flaw detection device, and is particularly suitable for an automatic ultrasonic flaw detection device that uses a high frequency probe.

[Conventional technology]

Ultrasonic flaw detection measures the attenuation of ultrasonic waves in the object.

The flaw detection frequency is selected and used depending on the resolution, which is the ability to detect the position and size of the flaw, and is generally used for testing objects made of materials with coarse crystal grains and high attenuation, or at long distances away from the flaw detection surface. A low frequency is used when detecting a certain defect, and a high frequency is used when detecting a defect close to the surface or a minute defect. In this case, the probes used have multiple different flaw detection frequencies, but especially when using a high-frequency probe, the frequency band output from the receiver that receives the reflected waves from the object is limited. Broadly speaking, the amplitude may not reach its maximum at the flaw detection frequency of the probe, but may reach its maximum at a much lower frequency.

An example of a conventional automatic ultrasonic flaw detection device will be explained with reference to FIGS. 4 and 5. FIG. 4 is an overall explanatory diagram of the apparatus, and FIG. 5 is a diagram showing frequency analysis of the output signal of the receiver. In the figure, 1 is a water tank, 2 is water filled in the water tank 1, 3 is a subject placed at the bottom of the water tank 1, 4 is immersed in water 2 and is located at a position opposite to the subject 3. , Y, and Z directions, and is held by a scanner (not shown). 5 is a pulser, which is connected to the probe 4 by a high-frequency cable and is connected to the object 3 by the probe 4. Send ultrasonic pulses towards the target. A receiver 6 is connected to the probe 4 and the pulser 5, and receives and amplifies the reflected wave reflected from the object 3 via the probe 4. A peak detector 7 is connected to the pulser 5 and the receiver 6. A DC voltage proportional to the peak value of the reflected wave from the subject 3 amplified by the receiver 6 is output. 8 is a waveform monitor device that monitors the output waveform value of the peak detector. Reference numeral 9 denotes an arithmetic processing section, and an AD converter 10 connected to the peak detector and inputting its output value. CPU II, which issues an operation command to the scanner and analyzes the frequency of the output signal of the receiver 6, and an image processing device 12. It has a monitor TV 13 for monitoring flaw detection images of the object 3.

In the ultrasonic flaw detection device having the above configuration, relatively high frequency (
When performing flaw detection using the probe 4 (for example, 30 MH2 or higher), the frequency JF range output from the receiver 6 is wide and the frequency analysis as shown in FIG. 5 is performed. The horizontal axis is the frequency (M
H2), the vertical axis shows the amplitude.

In the figure, for example, a probe 4 with a frequency f+ of 50 MH2
When using one frequency f1, the amplitude at one frequency f1 is considerably smaller than the amplitude of a low frequency fo (for example, 25 MHz), and therefore, the frequency f is influenced by the low frequency side component whose amplitude is larger than the frequency f1.

Therefore, the characteristics of the high-frequency probe 4 used for the purpose of obtaining high-resolution images cannot be fully demonstrated, resulting in flaw detection results with low accuracy.

Furthermore, if it is necessary to perform flaw detection at the frequency fO shown in Fig. 5, it is necessary to prepare a probe with a frequency f, but in this case as well, a probe with a frequency f and an amplitude higher than that shown in Fig. 5 must be prepared. This will be affected by large low frequency side components, and will have the same problem as above.

[Problem that the invention seeks to solve]

As mentioned above, in conventional ultrasonic flaw detection equipment, even if a probe with as high a frequency as possible is used to improve resolution, the frequency band of the receiver output is wide.

The amplitude of the ultrasonic wave does not reach its maximum at the flaw detection frequency of the probe, but reaches its maximum at a considerably lower frequency. Due to this influence, the resolution commensurate with the frequency of the probe cannot be obtained, resulting in accurate defect evaluation. The problem was that it was not possible to do so.

The present invention solves the problems of the prior art, and is capable of extracting any frequency component from the frequency band of the probe used. Especially when using a high frequency probe, high frequency components can be extracted. An object of the present invention is to provide an ultrasonic flaw detection device that can obtain a high-resolution flaw detection image of a test object by extracting the low-frequency components and removing the low-frequency components so as not to be affected by the low-frequency components.

[Means for solving problems]

The present invention includes: a pulser that causes a probe to emit ultrasonic pulses; a receiver that is connected to the probe and the pulser and receives and amplifies reflected waves from a subject via the probe;
In an ultrasonic flaw detection apparatus having a peak detector connected to the pulser and the receiver and outputting a DC voltage proportional to the peak value of the reflected wave amplified by the receiver, and an arithmetic processing section that performs arithmetic processing on the output value of the peak detector. , in the circuit between the pulser and the peak detector,
By providing a bandpass filter that extracts any frequency component from the frequency band output by the receiver, it is possible to extract any frequency component from the frequency band of the probe used, resulting in high resolution and precision. This makes it possible to obtain flaw detection images that allow good defect evaluation.

[Operation] When a bandpass filter is inserted in the circuit between the pulser and the peak detector, for example, in the circuit between the receiver and the peak detector, any desired frequency band set in the bandpass filter can be filtered out of the frequency band output by the receiver. Only the frequency components in the region pass through the bandpass filter and are sent to the peak detector, and flaw detection is performed using the sent frequency components. The setting of the frequency components to be passed through the band-pass filter can be changed arbitrarily, and the frequency components after passing through the band-pass filter have the maximum amplitude in that region, so when using a high-frequency probe, You can freely select flaw detection in the component region or low frequency component region, and not only can you obtain a high-resolution flaw detection image, but also enable flaw detection in different frequency bands with the same probe.

〔Example〕

Embodiments of the present invention will be described with reference to FIGS. 1 to 3. Figure 1 is an overall explanatory diagram of the device corresponding to Figure 4;
The figure shows frequency analysis when the output of the receiver passes through a bandpass filter.

FIG. 3 is a comparison diagram of two adjacent defect images between the conventional method and the present invention. In the figure, the same reference numerals as in FIGS. 4 and 5 indicate the same parts. Reference numeral 14 denotes a bandpass filter interposed in the circuit between the receiver 6 and the peak detector 7, which extracts and passes only the frequency components in a desired arbitrary range set out of the frequency band output by the receiver 6, and passes the filter to the peak detector. can be entered. The setting of the frequency components to be passed through the band-pass filter 14 can be changed arbitrarily, and the amplitude of the frequency components to be passed has a maximum in that region.

When performing flaw detection using the device provided with the band-pass filter 14, the output frequency of the receiver 6 is determined by the band-pass filter 14.
By passing through, frequency analysis as shown in FIG. 2 is obtained. FIG. 2 is a diagram corresponding to the above-mentioned FIG. 5, in which the component of the maximum amplitude frequency f in FIG. 5 has been largely removed,
Only the components in the high frequency region of f are extracted, indicating that the amplitude at fl is maximum. The results of flaw detection at the frequency f+ shown in Figure 2 are shown in Figure 3 (b).
The two defects Fl+F2 near V13 are clearly separated and displayed, whereas the conventional frequency f shown in FIG.
The result of flaw detection in Figure 3(a) is that the resolution is poor because it is affected by components in the low frequency region f, which has a large amplitude.
The separated two defects FItF2 are evaluated as one defect F. When using a relatively high-frequency probe like this, it is not only possible to obtain a high-resolution flaw detection image by extracting the high-frequency components, but also to use a bandpass filter 1.
By changing the setting of the frequency that passes through 4, it is possible to detect flaws in low frequency components using the same probe, and the same effects and effects as those obtained by detecting flaws using a low frequency probe can be obtained. . This is the same effect as having a plurality of probes with different frequencies, and not only facilitates the flaw detection operation but also has cost benefits.

In the embodiment described above, the bandpass filter 14 was placed between the receiver 6 and the peak detector 7, but it may be placed between the pulser 5 and the receiver 6. In addition, although the description has been made for the case where the probe 4 is a focused type and the water immersion method is used, the flaw detection is the same even when a general probe is used instead of a focused type and a direct contact method is used for flaw detection, and the frequency is high (e.g. 30 MH2 or more), but similar actions and effects can be obtained even in the case of several MH2.

〔Effect of the invention〕

As explained above, the ultrasonic flaw detection device according to the present invention includes a bandpass filter that can extract any frequency component from the frequency band output from the receiver in the circuit between the pulser and the peak detector. , it is possible to extract any frequency component of the probe used, and especially when using a high frequency probe, it is possible to remove the low frequency component and extract the desired high frequency component, thereby eliminating the influence of the low frequency component. It is possible to obtain high-resolution flaw detection images without being exposed to
This has a significant practical effect in enabling highly accurate defect evaluation.

[Brief explanation of the drawing]

Fig. 1 is an overall explanatory diagram of an embodiment of the ultrasonic flaw detection device according to the present invention, Fig. 2 is a diagram showing frequency analysis of a bandpass filter output signal, and Fig. 3 is a diagram showing a conventional example of two adjacent defect images. This is a comparison diagram. FIG. 4 is an overall explanatory diagram of an example of a conventional device, and FIG. 5 is a diagram showing frequency analysis of the output signal of the receiver of FIG. 4. Figure 2 Figure 3 (a) (b) Figure 5

Claims (1)

[Claims] 1. A pulser that causes the probe to emit ultrasonic pulses; a receiver that is connected to the probe and the pulser and receives and amplifies reflected waves from the object via the probe; In an ultrasonic flaw detection device, the pulser and An ultrasonic flaw detection device characterized in that a bandpass filter for extracting an arbitrary frequency component from a frequency band output from the receiver is provided in a circuit between the peak detector and the receiver.