JPS613055A - Method and apparatus for detecting defect in surface layer - Google Patents

Abstract

PURPOSE:To detect a defect existing near the surface of an object to be inspected satisfactorily, by making an ultrasonic beam incident into the surface thereof with the frequency being varied by several stages to measure and compute surface echoes and combined echoes at respective frequencies. CONSTITUTION:A vertical probe 1 is kept in contact with the surface A without defects of an object 3 to be inspected and an ultrasonic beam is made incident thereinto, for example, at 3MHz. Consequently, a surface echo 7 is reflected with the height thereof being Ps. Then, when an ultrasonic beam is made incident into the surface B with defects, a cominbed echo of the surface echo 7 and a defect echo 6 is reflected with the height being Ph. The frequency of the ultrasonic beam is shifted to 30MHz and the same operation is done to determine the height P's of the surface echo at a point without any defect and the height P'h of te combined echo at a point with defects. As the echo heights Ps, Ph, P's and P'h are in a correlation with the distance and size of the defect, an arithmetic control section 13 performs a computation to detect the location and size of the defect. Therefore, the defect can be detected, at a high accuracy as the echo height is determined by varying the ultrasonic frequency.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention utilizes ultrasonic waves, which are used for flaw detection of members whose strength is disadvantageous if there are defects near the surface, and for internal flaw detection of very thin materials. The present invention relates to a method for detecting surface layer defects and an apparatus therefor.

[Background of the invention]

Conventionally, the following three methods have been commonly used to detect defects near the surface of an object using ultrasonic waves.

(1) In the first method, as shown in Fig. 1, a vertical probe 1 is placed on the subject 3-H through a delay material 2, and the vertical probe 1 is vertically probed toward the defect 4 existing in the subject 3VC. An ultrasonic beam 5 is projected from a sample 1 to a defect 4 and a defect echo 6 generated thereon is captured.

In addition, in FIG. 1, 7 indicates a surface echo.

According to this method, as shown in Fig. 2, the echo height Ps
The defect echo 6 shown by the echo height Pf is separated only outside the path of the delay material 2 from the surface echo 71C shown by , but when the position of the defect 4 is extremely close to the surface of the object 30 +cI'
! The surface echo 7 shown in FIG. 2 and the defect echo 6 overlap, and therefore the distance of the defect 4 shown in FIG. Unable to detect dimensions etc.

In addition, in order to increase the echo resolution, the ultrasonic beam 50
It is conceivable to set the frequency to a high frequency button of 20 MHz, for example, but even in this case, the detectable defect depth is l,
If it is smaller than 5 mm, it is impossible to separate the surface echo 7 and the defect echo 6 shown in FIG. 3 as an example.

becomes undetectable.

(2) The second method is to place the surface wave probe 8 at 5Vc on the object 3 as shown in Fig.
An ultrasonic beam is projected onto the 1C surface, and the presence or absence of the defect 4 is detected based on the defect echo of the surface wave 9.

However, although this method can detect the presence or absence of the defect 4, it cannot detect the size of the defect 4 or the depth of the defect described above.

(3) The third method is a method using an ultrasonic beam,
As is clear from the detection principle of this method, the defects that can be detected are limited to those with a partial sum of several μm from the surface.

[Purpose of the invention]

The present invention has been made in view of the actual situation in the prior art, and its purpose is to eliminate surface defects including defects present at a distance of several μm or more and 1.5 mm or less from the surface of the specimen. An object of the present invention is to provide a method and apparatus for detecting surface layer defects that can detect surface defects.

[Summary of the invention]

In order to achieve this objective, the present invention aims to project an ultrasonic beam onto a defect existing near the surface of the object. The defect depth and defect size are detected based on the echo height of the synthesized echo, and the detection method is based on the height of the surface echo. A surface VC ultrasonic beam is projected to obtain a surface echo, and an ultrasonic beam is projected to a defective button existing near the surface of the object to obtain a composite echo of the surface echo and the defect echo. The above-mentioned surface echoes are obtained using different frequencies of the ultrasonic beam, and the echo heights of these combined echoes and surface echoes and the distance Mf from the surface of the defective object are determined.
In other words, the defect depth and the defect size are detected from the correlation between the defect depth and the defect size.

The detection device used in this detection method includes a probe that distributes power to the surface of the subject, a transmitter connected to the probe, and a transmitter that transmits a signal to the probe to project an ultrasonic beam. A receiving section that receives a signal corresponding to the reflected echo from the probe; a frequency converting section that is connected to the transmitting sVc and can be set to each of a plurality of different frequencies; a storage unit that stores synthetic echoes in association with frequency types; and a calculation unit that calculates defect depth and defect size based on the surface echoes and echo heights of the synthetic echoes stored in the storage unit. It has a configuration with

[Embodiments of the invention]

The present invention will be explained below based on the drawings. FIG. 4 is an explanatory diagram showing one embodiment of a detection device used in the surface layer defect detection method of the present invention. First, an embodiment of the detection device will be described with reference to FIG. 4, and then an embodiment of the detection method will be described.

w, In Figure 4, l is the vertical probe, 2 is the delay material, 3 is the object to be inspected, 4 is the defect inside the object 3VC, 5 is the ultrasonic beam, 6 is the defect echo, 7 is the surface echo, These are equivalent to those shown in FIG. 1 above. 10.11j1 The receiving section and the transmitting section connected to the vertical probe IK. Probe it'c send. Reference numeral 12 denotes a frequency conversion section connected to the transmitting section 11, which is capable of setting a plurality of different types of frequencies. Reference numeral 13 denotes an arithmetic control unit connected to the frequency conversion unit 12, which calculates the echo height Ps of the surface echo 7 and the echo height Ph of the composite echo of the surface echo 7 and the defect echo 6 [based on the defect of the defect 4] as described below. It has an arithmetic function for calculating the depth Hl and the size of the defect 4, such as the defect width d, and various control functions. Such arithmetic control section 13 can be configured with a microcomputer.

Reference numeral 14 denotes an amplifying section connected to the receiving section 10Vc, which amplifies the signal received by the receiving section IO. 15 is a storage unit connected to the amplification unit 14 and the arithmetic control unit 13, and stores the echo height Ps of the surface echo 7 received by the reception unit 10 and the echo height of the composite echo of the surface echo 7 and the defect echo 6. It stores data such as pH, control programs, etc. Reference numeral 16 denotes an input section connected to the arithmetic control section 13 and the storage section 15, and includes, for example, a keyboard for inputting a frequency. Reference numeral 17 denotes an output section connected to the arithmetic control section 13 and the storage section 15Fc, and is composed of, for example, a cathode ray tube display fb display device.

Next, an embodiment of a detection method performed using the detection apparatus shown in FIG. 4 will be described.

First, as shown at position A in FIG. 4, the vertical probe 1 is placed on the surface of the object 30 with the delay material 2 interposed therebetween. This position A
It is assumed that no defect 4 exists on the surface layer of the portion of the object 30 to be inspected. Then, by operating the input section 16, the frequency is set to 3, for example.
MHz Ic indication. This signal corresponding to 3 MHz K is sent to the frequency converter 12&c via the arithmetic controller 13.
At the same time, it is also sent to the storage section 15. Storage section 15
corresponds to the type of frequency f6 one area IC3M I-
Memorize the value of 1z -f.

Note that the output unit 17 stores information in the storage unit 15 as necessary that the frequency currently specified by the input unit 16 is 3 MHz.
Displayed by a signal from . On the other hand, the frequency converter 12
is 3 MH by the signal not sent from the arithmetic control section 13.
Set it to be the frequency of z. As a result, the transmitter 11 sends the probe IK signal, and the probe l is 3M I-
An ultrasonic beam 5 having a frequency of 1z is projected onto the subject 3.

Then, the surface echo 7 generated on the surface of the subject 3 by this J1 d is received by the receiving section 10 via the probe 1, and is further amplified by the amplifying section 14 as the echo height Ps of the surface echo 7. Is the frequency of the storage unit 15 3MHz? +X Be memorized in the memorized area. Note that the output unit 17 outputs the surface echo 7 currently stored in the storage unit 15 as needed.
Displays the echo height Ps of .

Next, with the frequency set to 3 MHz as described above, the probe 1 and delay material 2 are placed at 11jA as shown in Fig. 4.
18 in the direction of arrow 18. And now, temporarily, position B
It is assumed that a defect 4 exists in the surface layer portion of the object 30 corresponding to . At this time, a defect echo 6 is generated in the defect 4 by the ultrasonic beam 5 with a frequency of 3 MHz projected from the vertical probe 1, a surface echo 7 is generated on the surface of the object 30, and the defect 4 inherent in the object 3 is generated. For example, if the defect depth H is within 2 mm, f, b, these defect echoes 6 and surface echoes 7 are combined to form a composite echo, and this composite echo is sent to the receiver via the probe 1. 10
It is further amplified by the amplification unit 14, and the frequency 3 is stored in the storage unit 15 as the echo height ph of the synthesized echo.
In the area where MHz is stored, it is stored in correspondence with the previously stored echo height Ps of the surface echo 7.

Note that the output unit 17 is currently configured to output data to the storage unit 151c as needed.
The echo height Ph of the stored synthetic echo is displayed.

Next, the probe 1 and the delay material 2 are moved to the position AV shown in FIG. 4, for example.
C. Go back and operate the input section 16 to set the frequency to 30M, for example.
HzK instruction. Instruction 30 M I (, Z IC equivalent'
The signal f is sent to the frequency conversion section 12 via the calculation control section 13 and is also stored in the storage section 15. Storage part 1
5 to 30 in another area corresponding to the type of frequency (II
Memorize the value of z. 7. The output section 17 can be configured as necessary.
Now, the signal button from section 15 displays that the frequency specified by input section 16 is 30 MHz. On the other hand, the frequency converter 12 converts the frequency from 3 MHz to 30 MI (z) according to the signal sent from the arithmetic controller 13. As a result, the transmitter 11 sends the probe lVc signal. , the probe l projects an ultrasound beam 5 with a frequency of 30 MHz onto the object 31C f/, Io
With this &'CL, the echo height P s' of the surface echo 7 corresponding to the frequency 30 MHz is obtained in the same manner as described above, and this echo height P s' is stored in the storage section 150 at the frequency 30 MHz.
It is stored in the area where Hz is stored. Note that the output unit 17 necessarily displays the echo height P s' of the surface echo 7 that is currently stored in the storage unit 15VC.

Next, with the frequency set at 30 MHz, the probe 1 and delay material 2 are moved from position A to position 8 in FIG. 4. At this time, a defect echo 6 and a surface echo 7 are generated in the same manner as described above, which becomes a composite echo, and the echo height Ph' of this composite echo is 30M
I(z is stored in the area where it is stored in correspondence with the echo height PS' of the surface echo 7 previously stored.

Note that the output section 17 displays the echo height Ph/ of the synthesized echo currently stored in the storage section 15, if necessary.

For example, f corresponding to the frequency of 30 MHz is stored in the storage unit 15.
When the echo height Ph/ of the synthesized echo is stored, the calculation control unit 13j'! The echo of the surface echo 7 is increased correspondingly to the frequency 3 MHzK stored in the storage unit 15.
, the echo of the synthesized echo increases and the Ph of the lower rC (
1) Calculate the equation (2) below, and read out the echo height P s/ of the surface echo 7 and the echo height Ph/ of the composite echo corresponding to the frequency of 30 MHzK f7).

Ph=(Ps"-)K2Ps,"Pb'=(Ps/2-1-K"Ps/Madashi, K
: Echo reflectance of defect 4, i.e. defect F-6
The ratio of the echo height of the surface echo 7 to the echo height of the surface echo 7...Unknown quantity λ: Wavelength λ' of frequency 3 MHz, Wavelength H of frequency 30 MHz: Defect depth... ...It is an unknown quantity. And (1) above. From equation (2), the unknown H
1K is required.

Note that the echo reflectance from defect 4 (σ) is determined by the defect width d, and generally has the relationship shown in equation (3) below.

K = c d (3) where C
is a constant, and this constant C must be determined in advance by experiment.

Therefore, an operation is performed to find the defect @d using K obtained as described above and equation (3). The defect depth Hl and defect width d thus obtained are displayed on the output section 17 as necessary.

In the detection device and detection method configured in this way, ultrasonic beams 5 of different same wave numbers are individually projected, and the echo height of the surface echo 7 and composite echo corresponding to the frequency is determined. Since the defect depth H1 and the defect width d can be determined, and since the echo heights of these surface echoes and composite echoes can be easily obtained, it is possible to obtain the defect depth H1 and the defect width d. 1.
It is possible to reliably detect surface layer defects, including defects 4 located at a position of 5 mm or less, and to display them in real time.

In addition, in the above example, by calculating the equation (11, (2))
The defect depth H is calculated by calculating the rate of change in the echo height of the synthesized echo ΔP (= Ph
/Ph/) and the defect depth H (mm) is the defect width d.
= 1 mm, VC has the relationship as shown in FIG.
30 MI (echo height Ph of the composite echo corresponding to z,
When Ph/ is obtained, Konera's Ph, lP from Ph/
It is also possible to calculate KH immediately from the correlation between lP and [I stored in the storage unit 15.

Further, in the embodiment of the detection device described above, the output unit 17 is provided with a display device, but the present invention is not limited to this, and the output unit 17 may be configured with a recording device such as a printer.

Further, in the embodiment of the detection device described above, the input f'AI6 is configured by a keyboard to instruct the frequency, but the present invention is not limited to this. It is also possible to configure the input section 16 with an on/off switch that simply instructs the start and end of the detection operation.

In addition, in the embodiment of the above detection method, the echo height Ps of the surface echo 7 is determined at position A with the frequency set to 3MH2&CL as shown in FIG. Then, with the frequency set to 30 MHzVc, the echo height Ps' of the surface echo 7 was determined at position AIC, and the echo height Ph/ of the composite echo was determined at position B. However, the present invention is not limited to this. At position Avc, first set the frequency to 3MHz#fc (,
When the echo height Ps of cut surface echo 7 and the frequency are 3
Echo height Ps' of surface echo 7 when set to 0MHz
, then change the frequency to 3MH at position BIC.
Find the echo height Ph of the synthesized echo when zrc and the echo height Ph' of the synthesized echo when the frequency is 30M)lzVc(, IcL.

In addition, in the above embodiment, the type of frequency is 3 MHz, 3
0 MHz, but the present invention is not limited to this (, 3 MHz, 130 MHz, !:H different7). Determine the depth Hl and the defect width d, and in that case, a correlation between lP and H similar to that shown in FIG. 5 will be obtained.

〔Effect of the invention〕

Since the method for detecting surface defects of the present invention and its 9'-Ry constitute vcN' as described above, the defects exist at a position of several μm or more and 1.5 mm or less from the surface of the specimen.
2. Good detection of surface defects including filter defects. ), therefore, it is possible to perform internal flaw detection of surface layer IC surface materials and products, which was previously impossible, and it is highly effective in detecting defective products with high precision.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the first example of the conventional surface defect detection method, Figure 2 +j, :F Figure 3 is an explanatory diagram showing a second example of a conventional surface defect detection device, and Figure 4 is an explanatory diagram showing a second example of a conventional surface defect detection method. FIG. 5, an explanatory diagram showing an embodiment, is a characteristic diagram showing the relationship between the rate of change ΔP of a synthetic echo and the defect depth H, which can be applied in the surface defect detection method of the present invention. l... Vertical probe, 2... Delay material, 3
...Object to be inspected, 4...Defect, 5...
...Ultrasonic beam, 6...Defect echo, 7...
...Surface echo, 8...Bevel probe, 10
. . . Receiving section, 11 . . . Transmitting section, 12.
... Frequency conversion section, 13 ... Arithmetic control section, 14 ... Amplification section, 15 ... Storage section, 1
6...Input section, 17...Output section. Figure 1 Child 2 Figure 3 Demon 4 Figure

Claims (2)

[Claims] (1) In a method for detecting defects existing near the surface of a test object, an ultrasonic beam is projected onto the surface of the test object to obtain a surface echo, and an ultrasonic beam is projected onto the defect to obtain a surface echo. and the defect echo in the above defect, and the synthesized echo and the surface echo are obtained respectively by different frequencies of the ultrasonic beam, and the echo heights of these synthesized echoes and surface echoes and the defect echo in the defect are determined. A method for detecting surface defects, comprising detecting the distance of the defect from the surface of the object to be inspected and the size of the defect from a correlation between the distance from the surface of the object and the size of the defect. (2) In addition to projecting an ultrasonic beam onto the surface of the object to obtain surface echoes, projecting the ultrasonic beam to defects existing near the surface of the object to compare surface echoes with defect echoes from the defects mentioned above. A synthesized echo is obtained, and the synthesized echo and the surface echo are obtained by using different frequencies of the ultrasonic beam, and the echo heights of these synthesized echoes and surface echoes and the distance of the defect from the surface of the object are determined. and the correlation with the size of the defect, in a detection device used in a surface defect detection method for measuring the distance of the defect from the surface of the object to be inspected and the size of the defect, a transmitting section that is connected to the probe and transmits a signal for projecting an ultrasound beam to the probe, and a receiving section that receives a signal corresponding to a reflected echo from the probe; a frequency converting section that is connected to the section and can be set to each of a plurality of different types of frequencies; a storage section that stores the surface echo and composite echo received by the receiving section in association with the frequency type; a calculation section that calculates the distance of the defect from the surface of the object and the size of the defect based on the echo heights of the surface echo and the composite echo stored in the surface layer. Defect detection equipment.