JPS61265563A - Method for signal processing in eddy current flaw detection - Google Patents

Abstract

PURPOSE:To make it possible to detect a shallow flaw with high accuracy, by dividing the surface of a material to be inspected into minute sections and comparing the change quantities or continuities of the signals respectively taken from the sections between said sections. CONSTITUTION:For example, an object 1 to be inspected having a circular cross-section is divided into 10 sections in the circumferential direction and divided in the longitudinal direction at 2.5mm-pitches to form minute sections which are, in turn, subjected to eddy current flaw detection. Generally, because the flaw of along material having a circular cross-section is present in a relatively long length and a high peak signal due to other factor is generated singly and varied largely, judgement is performed as a unit sector at every unit to make it possible to detect a shallow flow with high accuracy.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention 8AFi = *If4ts probing is applied to a material with a circular cross section such as a wire or rod M, and the m of the material surface is determined from the signal.
- Enables high precision determination of even shallow flaws@
! Regarding the method of issue processing.

(Prior art) In general, for detecting surface flaws on gold jl# material, *2 mm,
Penetrant testing*, acoustic explosion testing, or eddy current testing methods are used, but #lii flow testing is suitable for long materials with circular cross sections such as wire rods and steel bars.

fI4 style search l1 is a carp until the alternating current flows through a rod such as metal.
1 when l/'ig is brought close! , if there is a defect, carp/
This is a method of detecting defects by utilizing changes in voltage and current caused by I/KIW.

In this case, the eddy current [voltage or current change signal sent from one flaw detection head only detects defects in the material being tested]
L does not change, but is caused by other electrical or mechanical change devices, 4) or the material itself OIl! i
◎ It is necessary to distinguish only the defects from these signals. ◎ Figure 5 shows the results obtained with the Wi-Fi detector. An example of an analog signal is shown, in which the horizontal axis is the deep sea position of the specimen and the vertical axis is the height of the signal.

Conventional discrimination methods based on such signal techniques generally treat cases where the size of the received signal exceeds a certain height as a defect, and in this case, even if it is not a defect, To improve the accuracy of discrimination by eliminating late bloomers that are mistaken for major defects.

The determination level must be set several times higher than the base noise signal height obtained in the defect-free portion. Generally, it is often 3 times or more, and in this case it is 8/N north 5 or more.

Due to this relationship, when testing steel products with good surface condition using a normal #i flow detector fIi machine, defects are detected from the surface to zero.
It is said that unless the depth is 0.7- or more, it is not possible to determine J with high accuracy.

(Problem to be solved by the invention) Conventionally, products such as steel bars and wire rods have a depth of 5 surface defects #: tO, 10all! even under the strictest standards! However, conditions that are stricter than these 1. For example, the detection of defects with a depth of 0.05 or less has improved due to advancements in processing technology 6 or waste products. If you are 41 years old due to the harsh operating conditions, it is possible to distinguish between defects and non-defects even at a lower signal height, and to detect defects with a shallower depth. The requested L sea urchin and rice nine.

An object of the present invention is to provide an improved signal processing method that makes this possible.

(Means for Solving Problems 1 Effects, Examples) #J The purpose is to divide the surface of the test material into minute sections and conduct a test in each section in gate flow flaw detection of the test material with a circular cross section. ft.
Next, by comparing the signal for changes or continuity between sections.

This is achieved by the sector-based signal processing method of the present invention, which is characterized by determining whether a signal is defective or not. explain.

The 1st mG () is the sector-one-type eddy current testing method of the present invention.For example, the test material (1) with a circular cross section of t1 is divided into 10 equal parts in the circumferential direction and divided into t-8 minute sections in the longitudinal direction at a pitch of 2.5al. Indicates what to do about In the figure, it is assumed that (5) shows a peak value of 6 and is a friend defect.

Assuming that both I
! It is assumed that the surface roughness fL and the outside noise are noise. Other oi* minute sections of the test material show a wave height of 1t7t, but Q
Assume that

Lecture 1 (b) is that belief! This is a development diagram of wave height values.

The signal wave height value of each fLo minute section is entered as the standard value of 1.2.5, of which the wave height value 6 is continuous in the longitudinal direction with a pitch of 5- or more, that is, υ, 2 pitch sections- or more. part(
2) is now considered a defect! Set up a project.

Figure 2 A) is the same test material (1 piece @ bright method) for comparison.
1) The defect (A) is assumed to show a wave height value of 6, indicating that 11 eddy current flaws are to be carried out on 4 plane sections of an m circle divided at the same pitch of < 2.5 m. , surface roughness), foreign rice noise (Q is assumed to be the same as in Figure 1 (a). And in Figure 2 (b), the highest wave height value in one revolution of the circumference is 1.2.5WK value. It is 4o expressed as 4o.The slow thread part (2) with wave height value 6 is a rough mark other than a defect, n,
This shows that errors caused by foreign noise are also caused by defects and are determined to be constant.The following is a detailed logical explanation of the defects, J-determination, and method of the present invention described above. be. That is, in the conventional discrimination method, based on the base noise that appears as a puck, anything that appears higher than this is recognized as a defect.

The components of general busy base noise are inherent noise of the device itself, noise of the power supply, foreign-American noise from peripheral devices, and operation! This includes noise due to mechanical vibration caused by a, etc., and signals and noise due to the surface and internal properties of the material being tested are added to this. Of course, if you want to accurately adjust the radius,
Although each of these noise conditions is set to Ml so that the influence of fi is small, these noises still change individually, and the height of the base noise rises and falls considerably when the test material is inspected. As a result, the height of No. 8, which is frequently used as a defect, must be set high, that is, the height of the defect must be set in a direction that increases the depth of the defect, in order to accurately discriminate the defect.

In contrast, the present invention is intended to make it possible to identify noise and defective parts that occur due to various causes by means other than the height level. The circumferential cross section of is equally divided into a plurality of sections, and the surface elongation of each divided section is determined as a unit sector. Defects in general circular cross-section long materials exist over a relatively long length, and signals of high wave height due to other factors occur sporadically and have large fluctuations, so Figure 1 and Second
As can be seen from the comparison with the figure, it can be seen that the signal processing method of the present invention is reasonable and can detect shallow defects with high accuracy and without misidentification. Now, the present invention will be explained using a 10-sector one-way system as an example, and the more the song is divided into 2 parts, the better the discrimination accuracy will be. Furthermore, the signal processing method of the present invention is based on the fact that the defect signal is relatively long in the longitudinal direction of the specimen and is shorter due to other factors. This can be carried out using an averaging method that adds and averages the signal heights of the song section-〇 signal.

In Fig. 3 (a), the defective part of the material to be inspected (1) shows a high value of ti of 5, the other parts show a high value of 1t), and t shows a high value of 20. The result shown in Fig. 5 (b) is obtained primarily, but when the averaging of the two sections No. 1111M is carried out, it becomes as shown in Fig. ag3 e →, and as a result, the difference between defects and non-defects becomes even more At the same time, since the maximum value indicated by the base noise becomes small, it becomes possible to set the wave height value to a low force for defect discrimination, that is, llK with a shallow defect depth, and the detection of minute defects becomes '@bird'.

Since the tendency for base noise to occur is that the number of generated original waves increases as the wave height decreases, the effect of increasing the number of waves to be added when performing averaging is significant.

If the addition value & is too large, the deviation of the defect position will become large, so it must be considered in conjunction with the method of use. Figure 4 shows one combinator O act when the method of the present invention is implemented. Fig. 4k) shows the vicinity of the flaw signal, and Fig. 4k) is an analog signal from the computer, and the pack ground noise wave height is 1096 and the dust detection is low, LL/150%.
In this case, the height /I/ is set to 100%. Figure 84 (
b) shows the *m knowledge event signal f from the t computer which performs signal processing according to the method of the present invention. When using a machine to detect defects on one side, the discrimination m
The degree can also be increased by the prior art.
Minimum 0.050 when installed in alpro* removal device
It was possible to detect even the defect R of
:) No. 8 processing can be performed.

[Brief explanation of the drawing]

Fig. 1 (a) is a perspective view showing the sector division method of the t-th test material to which the signal processing of the present invention is applied; Figure 5 (4) is a perspective view showing the inner circumferential surface section of the same material to be tested for comparison;
is a perspective view of the test material when adding averaging in the method of the present invention & Figure 5 (+2) is a diagram of the signal peak value, Figure 5
Figure 4 shows the value table for nine cases in which the additive average increases.
Figure 4) is an analog signal waveform diagram of the vicinity of the flaw in the fubinita actupunto according to the present invention. The event signal diagram, M5#A, is an analog signal 0 diagram of the flow detection using conventional tIL technique.
(A)...Defect part, @...i11 rough surface 1 part. (Q - Noise outside the fist.

Claims (2)

[Claims] (1) Divide the surface of the material to be inspected into micro sections and compare the amount of change or continuity between the sections of the signal captured in each section to determine whether the signal is due to a defect or not. A method of signal processing in eddy current flaw detection. (2) The invention according to claim 1, which makes it possible to emphasize low signals generated from minute defects by adding and averaging the signal heights of several sections on the longitudinal extension of the test material. Signal processing method in eddy current flaw detection.