JPH02167465A - Ultrasonic flaw inspecting method - Google Patents

Abstract

PURPOSE:To decide the property of a defect in a body to be inspected and to deciding whether or not the inspected body is normal according to the use purpose of the inspected body by comparing and analyzing the frequency components of an ultrasonic wave which is sent and entered into the body to be inspected and its reflection echo. CONSTITUTION:A block 1 made of silicon nitride is set in a water tank 3 and a probe 6 is set right above it. The echo reflected by the surface of the block 1 is observed by a spectral analyzer 7 connected to an ultrasonic flaw detector 2 by a high-frequency cable. Then the probe 6 is scanned for automatic flaw detection, whose result is outputted on a plotter 5 to detect indications. The probe 6 is guided to one of them and an observation is made by the analyzer 7. Similarly, the probe is guided to another indication and the analyzer 7 observes an echo which is considered to be a defect part. Then when the high frequency component is smaller than the incident ultrasonic wave, a crack defect is decided and when there is the peak on the center and high and low frequency sides, a hole defect is decided.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic flaw detection inspection method, and more particularly to an ultrasonic flaw detection inspection method that includes determining whether a detected defect is normal or abnormal. .

[Prior art]

Ultrasonic flaw detection has traditionally been widely used to inspect internal defects in steel materials, steel plates, welded parts, machine parts, etc., and in recent years it has also been used as a defect detection method for new materials such as ceramics. However, in these conventional methods, the characteristics of the detected defect are measured by measuring the size of the echo reflected from the defect using an oscilloscope, etc., and the size of the defect is estimated from that value. By automatically scanning the body, the indication of the defect is displayed in a two-dimensional diagram, and the size of the defect can only be estimated based on the size of the indication. However, even if the size of internal defects is the same, the effect on strength is completely different depending on the nature of the defect, and these differences are particularly significant in brittle materials such as ceramics, so it is difficult to judge the defect quality by just the size of the indication. There were problems with estimation. For example, if defects are judged only by size, it is possible to judge a product as defective if it contains scratches that do not actually affect its strength, or to judge a product as good if it contains cracks that are small in size but pose a problem in terms of strength. There was sex.

[Problem to be solved by the invention]

The inventors improved the drawbacks of the above-mentioned conventional technology, analyzed the defect characteristics of defects detected by ultrasonic flaw detection, and conducted intensive studies on an inspection method that can determine whether the detected defects are suitable for use or not. As a result, they discovered that the nature of a defect can be determined by analyzing the frequency components of echoes from the defective part, leading to the present invention.

[Means to solve the problem]

According to the present invention, there is provided an ultrasonic flaw detection and inspection method characterized in that frequency components of ultrasonic waves transmitted and incident on an object to be inspected and reflected echoes are comparatively analyzed.

[For production]

In conventional ultrasonic flaw detection, the results of flaw detection are only shown as indications on a plotter, but the method of the present invention uses a spectrum analyzer to analyze the frequency components of the reflected echoes at the part corresponding to the indication corresponding to the defect. It analyzes and determines whether the defect is a spherical hole or a crack. For example, if the ultrasonic waves transmitted from the probe have a flaw detection frequency of 50 Hz, as shown in Fig. 1, the incident ultrasonic waves When reflected from a crack-like defect, the frequency components of the reflected echo have almost the same frequency component shape as the transmitted incident ultrasound.On the other hand, when reflected from a crack-like defect, the high-frequency components of the reflected echo are scattered. The shape has a small high frequency component,
For spherical defects such as holes, ultrasonic waves are reflected on the surface, mode converted on the defect surface, and echoes that return after propagating on the surface are included, and images at low and high frequencies other than the center frequency are generated. The shape also has a peak on the frequency side.

As described above, in the present invention, the nature of the defect can be determined by analyzing the echo frequency component reflected from the defect in the object to be inspected using a frequency analyzer such as a spectrum analyzer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

The test was carried out using an apparatus as shown in FIG.

50x50x20mm block 1 made of silicon nitride
prepared. An automatic scanning ultrasonic flaw detector equipped with an ultrasonic flaw detector 2, a water tank 3, a scanning device 4 for scanning the probe, and a plotter 5 for outputting flaw detection results was immersed in water with a flaw detection frequency of 50 MHz and a focal length of 25 mm. A focused probe 6 was attached. A spectrum analyzer 7 was also prepared and connected to the ultrasonic flaw detector 2 with a high frequency cable so that the frequency components of echoes could be measured.

First, a silicon nitride block 1 was set in a water tank 2, and the probe 6 was adjusted so as to be directly above the block. At this time,
When the echo reflected from the surface of the block was observed using a spectrum analyzer, it was found that the center frequency was 50 MHz and had a frequency component of ±30 MI (z) as shown in FIG.

Next, when the probe was scanned and automatic flaw detection was performed, several indications that appeared to be defects were detected by the plotter as shown in Figure 3. Therefore, the position of the probe was adjusted on the silicon nitride block so that the probe was placed at the position of indication A among the indications.

When I observed the echo from the indication section at this time using a spectrum analyzer, I found that it was 50M as shown in Figure 4.
A waveform with peaks near Hz, 30MHz, and 70MHz was obtained.

Furthermore, I adjusted the position of the probe on the silicon nitride block so that it was at the position of the indication B, and observed the echo, which was presumed to be the defective part, with a spectrum analyzer. Center frequency 3 as shown in Figure 5
A waveform with a frequency of 5 MHz and a high frequency component smaller than a low frequency component was obtained.

When these two indication parts were marked on a silicon nitride block and each part was cut with a diamond cutter, the former was a spherical hole as shown in Figure 6(a), but the latter was a spherical hole. The crack was as shown in FIG. 6(b).

As is clear from this example, when the high frequency component is small compared to the incident ultrasonic wave, it indicates a crack-like defect, and when there are peaks on the low and high frequency sides in addition to the center frequency, it is a hole-like defect. This makes it possible to determine the nature of defects within the inspected object by analyzing the frequency components of reflected echoes.

〔Effect of the invention〕

While conventional ultrasonic flaw detection simply detects the presence or absence of defects within the inspected object, the method of the present invention
This is an ultrasonic inspection method that can also determine the nature of defects. By the method of the present invention, the nature of defects in the inspected object is determined,
It becomes possible to judge whether the object to be inspected is good or bad depending on the purpose of use.

[Brief explanation of the drawing]

1, 4, and 5 are diagrams showing frequency component waveforms, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIG. 3 is a plotter diagram showing the results of ultrasonic flaw detection. FIGS. 6(a) and 6(b) are cross-sectional views of defect shapes inside the object to be inspected. ■...Silicon nitride block, 2...Ultrasonic flaw detector,
3...Aquarium, 4...Scanning device, 5...Plotter 6...Probe, 7...Spectrum analyzer.

Claims (2)

[Claims] (1) An ultrasonic flaw detection and inspection method characterized in that the frequency components of the ultrasonic waves transmitted and incident on the object to be inspected and the reflected echoes are comparatively analyzed to determine the defect properties of the object to be inspected. (2) If the frequency component of the reflected echo is almost the same as the frequency component of the incident ultrasonic wave, it is a plate-like defect, and if the high frequency component of the reflected echo is smaller than the frequency component of the incident ultrasonic wave, it is a crack-like defect. 2. The ultrasonic flaw detection method according to claim 1, wherein the defect is determined to be a hole-like defect if it has a peak at a low frequency and a high frequency side other than the center frequency.