JPH08105864A - Test apparatus and method using elastic wave pulse - Google Patents

Abstract

PURPOSE: To stably evaluate a subject by transmitting elastic wave pulses to the subject, receiving pulses multiple-reflected in the subject, Fourier- transforming first and the following pulses among the received pulses respectively and obtaining a ratio signal of conversion signals respectively obtained from the above signals. CONSTITUTION: Elastic wave pulses x (ω) are transmitted via a probe 2 to a subject S. A first pulse b1 (t) initially received among those multiple-reflected and propagating and a second pulse b2 (t) reflected according to characteristics Rf (ω) on a border face of the subject S and again propagating in the subject S are selected. Respective functions (ω), b1 (t), b2 (t) are Fourier-transformed to obtain X (ω), B1 (ω), B2 (ω) respectively corresponding to the above functions. A ratio signal B3(ω)=B2(ω)/B1(ω) comprises only transfer functions exhibiting reflection characteristics opposite to those of a material, so that by obtaining this signal, deterioration test and flaw detection can be performed independently of transmission/reception characteristics of the probe and the border face and input signal characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing a deterioration test, a flaw detection test and the like on metallic materials and other general materials by using elastic wave pulses such as ultrasonic pulses and a test method therefor.

[0002]

2. Description of the Related Art The above-mentioned prior art will be described by taking a deterioration test of a steel material by ultrasonic waves shown in FIG. 9 as an example. The characteristics of the linear time-invariant system can be described by its impulse response h (t), and if the response of the receiver when the signal x (t) is input from the pulsar to this system is the signal b (t),
The signal b (t) is equal to the convolution integral of the time functions h (t) and x (t). Time functions b (t), h (t), x
The functions obtained by Fourier transforming (t) are B (ω) and H, respectively.
If (ω) and X (ω), the functions H (ω) and X
The function B (ω) can be expressed in the frequency domain form by the product of (ω). It should be noted that, in the present specification, a function including uppercase letters of the alphabet means a Fourier transformed function. B (ω) = H (ω) X (ω)

Further, the transfer function H (ω) can be expressed as a product of each factor constituting the transfer system as follows. H (ω) = Po (ω) To (ω) D (ω) Rb (ω) D (ω) Tr (ω) Pr (ω) where each transfer function is the Fourier transform of the following characteristic transfer function. Show. Po (ω): Transmission characteristic of probe To (ω): Transmission characteristic of boundary surface D (ω): Transfer characteristic of material Rb (ω): Reflection characteristic of back surface Tr (ω): Reception characteristic of boundary surface Pr (Ω): Transceiver reception characteristics

Therefore, the relationship between B (ω) and X (ω) is as follows. B (ω) = Po (ω) To (ω) D (ω) Rb (ω) D (ω) Tr (ω) Pr (ω)
X (ω) Therefore, the transfer function D as an index showing the deterioration of the steel material
(Ω) is calculated by the following equation. D (ω) = (B (ω) / (Po (ω) Pr (ω) To (ω) Tr (ω) X (ω) Rb (ω))) ^1/2 (a)

Here, in the conventional ultrasonic deterioration test of metallic materials, an ultrasonic test was performed in advance using a reference piece to create a database. The above equation (a) includes the transmission / reception characteristics of the probe, the transmission / reception characteristics of the boundary surface, and the input signal. Therefore, in performing an ultrasonic test in an actual site, it is necessary to accurately reproduce each characteristic in order to accurately evaluate the test based on the database. However, it is very difficult to accurately reproduce each of these characteristics from the standpoint of the contact state between the material surface and the probe, the individual difference of the probe, the individual difference of the pulsar, etc., and the evaluation error due to the test is large. There was a problem.

[0006]

In view of such a problem,
The present invention provides a test apparatus and a test method using elastic wave pulses that can be stably evaluated regardless of the contact state between a test body and a probe or the like, variations in the characteristics of the probe or the like, or the characteristics of the pulsar. The purpose is to provide.

[0007]

In order to achieve the above object, the test apparatus using the elastic wave pulse according to the present invention is characterized by a pulsar for transmitting an elastic wave pulse x (t) to a test object and a multiplex. Of the pulse and a receiver capable of receiving the pulse propagated in the test body by reflection,
The first pulse b1 (t), which is propagated through the test body and received first by the receiver, and the first pulse b
Pulse selection means for selecting the second pulse b2 (t), which is reflected by the receiving-side boundary surface of the test object and propagates through the test object again, and is received next by the receiver. The first and second pulses b1 (t), b2
Fourier transform means for respectively Fourier transforming (t) to obtain first and second transform signals B1 (ω) and B2 (ω), the second transform signal B2 (ω) and the first transform signal B1.
Ratio signal B3 (ω) = B for evaluating the test body, which is the ratio of (ω)
And a calculation means for obtaining 2 (ω) / B1 (ω).

The characteristic structure of the test method using the elastic wave pulse according to the present invention is that the elastic wave pulse x
(T) is transmitted, the pulse propagated in the test body by multiple reflection is received by the receiver, and the first pulse of the pulses propagated in the test body and received first by the receiver. b1 (t) is Fourier-transformed to obtain a first converted signal B1 (ω), and the first pulse b1 (t) is reflected on the receiving-side boundary surface of the test body and propagates in the test body again. Then, the second pulse b2 (t) received next by the receiver is Fourier transformed to obtain a second converted signal B2 (ω), and the second converted signal B2 (ω) and the first converted signal B1 ( The ratio signal B3 (ω) = B2 (ω) / B1 (ω), which is the ratio to ω), is obtained, and the test sample is evaluated by the ratio signal B3 (ω).

[0009]

The operation of the characteristic configuration of the above-described test apparatus and test method will be described with reference to FIG. 1 as an example. Among the elastic wave pulses x (t) transmitted from the pulser, the pulse selection means is the first pulse b1 (t) that is propagated through the test body and received first by the receiver, and the first pulse b1.
(T) is the characteristic Rf at the receiving-side boundary surface of the test body.
The second pulse b2 which is reflected according to (ω) and propagates through the test body again and is then received by the receiver.
Select (t). Each of these functions x (t), b1
If the Fourier-transformed functions of (t) and b2 (t) are X (ω), B1 (ω), and B2 (ω), the function B
1 (ω) and B2 (ω) can be expressed by the following equations. B1 (ω) = Po (ω) To (ω) D (ω) Rb (ω) D (ω) Tr (ω) Pr
(ω) X (ω) B2 (ω) = Po (ω) To (ω) D (ω) Rb (ω) D (ω) Rf (ω) D
(ω) Rb (ω) D (ω) Tr (ω) Pr (ω) X (ω) Here, each transfer function represents the Fourier transform of the following characteristic transfer function. Po (ω): Transmission characteristic of probe To (ω): Transmission transfer characteristic D (ω): Transfer characteristic of material Rb (ω): Reflection characteristic on back surface Tr (ω): Reception transfer characteristic Pr (ω) : Transducer reception characteristics Rf (ω): Surface reflection characteristics

The ratio signal B3 (ω) is obtained by the calculating means as follows. B3 (ω) = B2 (ω) / B1 (ω) = D (ω) Rb (ω) D (ω) Rf (ω) (a) This equation represents the transfer characteristics of the material and the reflection characteristics of the front and back sides. It is configured only by the transfer function shown, and is not affected by the transmission / reception characteristics of the probe, the transmission / reception characteristics of the boundary surface, and the input signal characteristics.

Then, the test sample is evaluated by the ratio signal B3 (ω). For example, a material deterioration test or the like can be carried out by focusing on D (ω) of the B3 (ω). Therefore, it is possible to carry out a flaw detection test or the like by focusing on Rb (ω).

[0012]

As described above, according to the characteristic configurations of the testing apparatus and the testing method using the elastic wave pulse according to the present invention, the evaluation specific signal is not affected by the transmission / reception characteristics of the boundary surface. Even if the contact state between the probe and the test body and the contact medium were different each time the test was performed, stable evaluation results could be obtained, and the test could be performed quickly. In addition, since the ratio signal is not affected by the transmission / reception characteristics of the probe and the input signal characteristics, it is possible to obtain stable evaluation results even if there is a large individual difference in the probe and pulsar characteristics. , The selection range of the probe etc. became wider and the test became easier. Furthermore, for quality control, it has become possible to use inexpensive probes and pulsars with large differences in characteristics between individuals.

[0013]

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3, 4A and 5. Note that each function in this embodiment is the same as that described in the section of the above action.

FIG. 3 shows a block diagram of a test system 1 for carrying out the test method of the present invention. The test body S in this embodiment is a steel material, and the test system 1 includes an ultrasonic probe 2 that functions as a transducer, a test device 3 configured by a personal computer, and a display device 4. The probe 2 is adhered to the test body S after applying a contact medium such as grease or machine oil.

The test apparatus 3 can receive a pulser 11 that transmits an ultrasonic pulse x (t), which is an example of an elastic wave pulse, through the probe 2, and a pulse that propagates in the test body S by multiple reflection. The receiver 12 has The pulser 11 has a built-in trigger for oscillating a plurality of pulses at regular intervals, and the number of oscillated pulses can be appropriately changed by setting the built-in counter. In this embodiment, 3
It is set to oscillate two pulses.

Pulse b received by receiver 12
(T) is digitized by the A / D converter 13 and stored in the memory 14. The received pulse b (t) is a multiple reflection signal, and the memory 14 averages the received pulse b (t) corresponding to each transmitted pulse. The pulse selection unit 15 uses the averaged received pulse b as described later.
It is a means for selecting the first and second pulses b1 (t) and b2 (t) from (t).

The output from the pulse selecting section 15 is branched into a time domain display system 31 and a frequency domain display system 32 so as to be selectively selectable, and is input to the video circuit 19 again. Is displayed. The time domain display system 31 includes a synchronization circuit 21, and at the time of selection, the horizontal axis is the time axis t and the vertical axis is the signal reception intensity, and the received signal b (t ) Can be displayed.

On the other hand, the frequency domain display system 32 Fourier-transforms the first and second pulses b1 (t), b2 (t), etc. by the fast Fourier transform algorithm, and then the first and second transformed signals B1 (ω). , B2 (ω), and the like, and an FFT analyzer 16 as a Fourier transform means, and first and second calculation units 17 and 18 for performing the calculation to be described later, and in the frequency domain where the horizontal axis is the angular velocity ω. Display signals by representation. The hard disk (HD) 22 stores a database (DB) of transfer characteristics of materials and transfer characteristics of defects, as will be described later. Note that the display form can be displayed by dividing the signal waveform into the real part and the imaginary part, and can also be displayed by dividing the amplitude and phase of each frequency component.

Here, a method of conducting a material deterioration degree test using the test system 1 will be described. First, FIG.
As shown in, the counter in the pulsar 11 is reset and 1 is added to the counter (steps N1 and N2). Then, the pulser emits a pulse having a function x (t), the pulse having a multiple reflection function b (t) is received by the receiver 12, and the waveform as a time function is stored in the memory 13 (N3 to N5). N value of counter is 32
When it is less than N, steps N2 to N5 are repeated again (N
6). When the N value of the counter reaches 32, the pulse transmission is stopped and the signal in the memory is averaged (N
7).

Then, through the time domain display system 31, FIG.
The received pulse b (t) is displayed on the display device 4 in the format shown in (a) (N8). In the present embodiment, by referring to the display of the display device 4 and designating a specific section of the time axis, the first and second bottom surface echoes f1 and f2 are respectively described above as the first and second pulses b1 (t). ), B2 (t) (N9). Based on this selection information, the pulse selection unit 15 selects the first and second pulses b1 (t) and b2 (t) from the received pulse b (t) to select the FFT analyzer 1
6, and the FFT analyzer 16 Fourier-transforms the first and second pulses b1 (t) and b2 (t) into first and second converted signals B1 (ω) and B2 (ω), respectively (N10). ). Then, in the first calculation unit 17, the second converted signal B2 (ω) is converted into the first converted signal B1 (ω) as follows.
The ratio signal B3 (ω), which is the ratio of the two, is divided by
Is obtained (N11). B3 (ω) = B2 (ω) / B1 (ω) = (D (ω)) ² Rb (ω) Rf (ω) (b)

The following is equivalent to the procedure for evaluating the degree of deterioration of the material in the second arithmetic unit 18 using this ratio signal B3 (ω) (N12 to N16).

First and second pulses b1 (t), b2 (t)
The plate thickness L of the test body S can be obtained by the following equation, where Δt is the reception time interval of τ and C is the sound velocity of the longitudinal wave of the test body S. L = Δt × C / 2 Further, Lo is the plate thickness of the reference test body S, and Rbo (ω) and Rfo are the reflection characteristics of the front and back sides obtained in advance, respectively.
Assuming (ω), the transfer characteristic Do (ω) of the material obtained by converting the plate thickness into the reference length is as follows (N12). Do (ω) = (D (ω)) ^{1 / L} = [{B3 (ω) / (Rbo (ω) Rfo (ω))} ^1/2 ] ^{1 / L} ... (c)

On the other hand, the transfer characteristic Do (ω, j) of the material converted to the reference length is obtained by using a plurality of reference pieces with the deterioration degree j as a parameter, and this is registered in the HD22 as a database. The transfer characteristic Do for comparison from the HD 22 is set by instructing an appropriate deterioration degree j.
Select (ω, j) (N13). Then, as shown in the following equation, the transfer characteristic Do (ω) of the material obtained from the received signal and the transfer characteristic Do (ω, j) of the material selected from the database are obtained.
Then, the difference ΔDo (ω) with is obtained (N14). ΔDo (ω) = Do (ω) −Do (ω, j) (d)

The transfer characteristic difference ΔDo (ω) is displayed on the display device 4 (N15), and whether or not ΔDo (ω) is flat is judged by visual inspection or an automatic discrimination program (N16). If ΔDo (ω) is flat, it is possible to estimate and evaluate the degree of deterioration of the test body using the degree of deterioration j at that time, and the process ends. If ΔDo (ω) is not flat, steps N13 to N15 are repeated again.

Each value in the above-mentioned database is measured by the following procedure using a reference piece having, for example, a portion having a thickness Lo and a portion having a thickness Lo / 2 which is a half thereof as shown in FIG. First, in the portion of thickness Lo, the following equation is established. B3 (ω) = B2 (ω) / B1 (ω) = (D (ω)) ² Rbo (ω) Rfo (ω) (e)

On the other hand, assuming that the ratio signal and the material transfer characteristics in the thickness Lo / 2 portion are B3'D ', the following equations hold. B3 ′ (ω) = B2 ′ (ω) / B1 ′ (ω) = (D ′ (ω)) ² Rbo (ω) Rfo (ω) = (D (ω) ^1/2 ) ² Rbo (ω) Rfo (Ω) = D (ω) Rbo (ω) Rfo (ω) (f) B3 ′ (ω) ² = (D (ω)) ² (Rbo (ω) Rfo (ω)) ² (g)

Therefore, the transfer characteristics Do of the reference material obtained by converting the plate thickness into the reference length by using the equations (e) to (g) Do
(Ω) and the reflection characteristic Rbo (ω) Rfo (ω) can be obtained as in the following equation. B3 (ω) / B3 ′ (ω) = D (ω) Do (ω) = (D (ω)) ^{1 / Lo} B3 ′ (ω) ² / B3 (ω) = Rbo (ω) Rfo (ω)

According to experiments conducted by the inventors, when a probe having a characteristic frequency of 10 MHz is used, the reflection characteristic Rb (ω) Rf (irrespective of whether the surface of the steel sheet is sandblasted or not. It has been confirmed that ω) is almost constant.

Next, a second embodiment will be described with reference to FIGS. 4 (b) (c) and 6. The present embodiment relates to a case where the test system 1 is used to evaluate a defect generated in a test body by a vertical flaw detection test. That is, the “evaluation of a test body” in the present invention includes not only the evaluation of the material properties of the test body but also the case of evaluating the occurrence and progress of defects in the test body.

First, the step N1 performed first in FIG.
To N7 correspond to the case where the test is performed on the defective portion, and are substantially the same as steps N1 to N7 in the first embodiment. In the defective portion, the received pulse b (t) is displayed as shown in FIG. 4 (b) (N8). Each pulse includes a first defect echo f3 and a first bottom surface echo f from left to right.
4. It corresponds to the second defect echo f5 which is again received by the probe due to the reflection of the first defect echo on the receiving side boundary surface. In this embodiment, the first and second defect echoes f3 and f5
Are respectively the above-mentioned first and second pulses b1 (t) and b2.
It is selected as (t) (N9).

By the way, the transfer characteristic Do (ω) of the test body S
Changes due to deterioration, so it is necessary to correct it later to remove the effect. Therefore, by changing the position of the probe, the received pulse b (t) in the normal part shown in FIG.
Then, the first and second bottom surface echoes f8 and f9 are selected again as the above-mentioned first and second pulses b1 (t) and b2 (t), respectively (N9, N10).

Based on these selection information, the pulse selector 15 selects the first and second pulses b1 from the received pulse b (t).
(T) and b2 (t) are selected for each of the tests on the defective part and the normal part and output to the FFT analyzer 16.
Fourier-transformed first and second transformed signals B1 (ω), B
A pair of 2 (ω) is obtained (N11). Then, the first calculation unit 1
7, the ratio signal B3 (ω) is obtained for each of the tests on the defective portion and the normal portion (N12, N13).

In step N14, Do (ω) is obtained in the same manner as in step N12 of the first embodiment, and further the transfer characteristic D1 (ω) of the material having the defect depth L1 is obtained. If the reception time interval of the first and second pulses b1 (t) and b2 (t) is Δt1, the defect depth L1 can be calculated by the following equation. L1 = Δt1 × C / 2 In order to convert the plate thickness to the reference length, the following correction is made. D1 (ω) = (Do (ω)) ^{1 / L1} (h) Since D (ω) can be replaced with D1 (ω) in the defective portion, the following equation holds. B3 (ω) = (D1 (ω)) ² Rb (ω) Rf (ω) (i) In order to evaluate the defective portion, the following formula is obtained using formula (h) (i) (N15). . B3 (ω) / (D1 (ω)) ² = Rb (ω) Rf (ω)
= RbRf (ω)

On the other hand, the reflection characteristic RfRb (ω, k) is obtained by using a plurality of reference pieces having different parameters k as indices of the type and degree of defects, and an appropriate reflection is obtained from the database as in the first embodiment. The characteristic RfRb (ω, k) is selected (N16). Then, the difference ΔRfRb (ω) between the reflection characteristic RfRb (ω) obtained from the above equation and the reflection characteristic RfRb (ω, k) selected from the database is obtained as in the following equation (N17). That is, steps N16 to N1 of FIG. 6 corresponding to steps N13 to N16 of FIG. 5 of the first embodiment.
9, it is possible to evaluate defects.

Next, another embodiment of the present invention will be listed. In the third embodiment shown in FIG. 7, unlike the probe 2 of the first embodiment, the probe 2 is configured only for receiving multiple reflection pulses, and the pulse transmission is performed by the probe of the test body S. Child 2
Impact hammer 5 provided on the back surface of Even in this case, the second converted signal B2 (ω) and the first converted signal B1
The ratio signal B3 (ω), which is the ratio to (ω), has the form of the above equation (a) as in the first embodiment, and is a function that does not include unnecessary factors.

In the fourth embodiment shown in FIG. 8, the liquid tank 6
The liquid stored inside corresponds to the test body S. The evaluation test is performed by bringing the probe 2 functioning as a transducer into contact with the outer surface of the liquid tank 6 using a contact medium. In this case, as a new transfer function of the transfer system, the transfer characteristic Q (ω) of the liquid tank 6 itself and the liquid tank 6 and the test body S
The transmission / reception characteristics Uo (ω) and Ur (ω) of the boundary surface between and are added, but these new transfer functions are canceled in the process of obtaining the ratio signal B3 (ω), and the ratio signal is expressed by the same equations as in the above embodiments. The format is (a). According to this embodiment, the test body S
Signals such as changes in the type of liquid and composition of the liquid in B3
It becomes possible to evaluate using (ω). In addition, it is possible to perform an evaluation test on whether or not liquid is present in the liquid tank 6.

Although ultrasonic waves are used as elastic wave pulses in each of the above-described embodiments, the present invention can be carried out using pulses other than ultrasonic waves. In addition, although the longitudinal wave propagating in the test body is used as the pulse in each of the above embodiments, the transverse wave propagating in the test body may be used as the pulse. The specimen includes metal and other general materials, as well as any solid or liquid capable of transmitting elastic wave pulses. It is also possible to evaluate the degree of defects such as cracks generated on the surface of the thin plate using surface waves, or to evaluate the surface roughness of the thin plate. In the first embodiment described above, the database was constructed by the transfer characteristic D (ω) of the material, but the reflection characteristic Rb (ω) Rf (ω)
It is also possible to construct the database in the form of B3 (ω) including the above and to configure the second calculation unit 18 so as to compare this with the ratio signal B3 (ω) obtained from the received pulse.
The "ratio signal B3" referred to in the claims of the present invention.
(Ω) ”means that the second converted signal B2 (ω) is the first converted signal B
The first converted signal B1 is not limited to one divided by 1 (ω).
The value obtained by dividing (ω) by the second converted signal B2 (ω) is also included.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a transfer function between a probe and a test body.

FIG. 2 is an explanatory diagram showing a relationship between a probe and a reference piece used when obtaining a reference transfer function Do (ω).

FIG. 3 is a block diagram showing an outline of a test system.

FIG. 4 shows a waveform of a reception pulse b (t), (a) is a reception waveform for evaluating the degree of material deterioration in the first embodiment, and (b) is a flaw detection test at a defect portion in the second embodiment. (C) is the received waveform when the flaw detection test is performed on the normal part in the second embodiment.

FIG. 5 is a flowchart showing a test procedure in the first embodiment.

FIG. 6 is a flowchart showing a test procedure in the second embodiment.

FIG. 7 is a view corresponding to FIG. 1 in the third embodiment.

FIG. 8 is a view corresponding to FIG. 1 in a fourth embodiment.

FIG. 9 is an explanatory diagram of a transfer function between a conventional probe and a test body.

[Explanation of symbols]

 11 pulser 12 receiver 15 pulse selecting means 16 Fourier transforming means 17 computing means S test piece.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Suetsugu 1-18-14 Kitahorie, Nishi-ku, Osaka City Osaka Prefecture Non-destructive inspection Co., Ltd. No. 14 Nondestructive Inspection Co., Ltd.

Claims (2)

[Claims] 1. A pulsar (11) for transmitting an elastic wave pulse x (t) to a test body (S), and a receiver (12) capable of receiving the pulse propagated through the test body (S) by multiple reflection. Of the pulses, the first pulse b1 (t) propagated through the test body (S) and received first by the receiver (12), and the first pulse b1.
The second pulse b2 that (t) is reflected by the receiving-side boundary surface of the test body (S) and propagates again in the test body (S) and is received next by the receiver (12).
The pulse selection means (15) for selecting (t) and the first and second pulses b1 (t) and b2 (t) are respectively Fourier-transformed to obtain first and second converted signals B1 (ω) and B2.
Fourier transform means (16) for obtaining (ω), and a ratio signal B3 (ω) = B2 (for test sample evaluation, which is the ratio of the second transform signal B2 (ω) and the first transform signal B1 (ω). ω) /
A test apparatus using an elastic wave pulse, comprising: an arithmetic means (17) for obtaining B1 (ω). 2. An elastic wave pulse x (t) is transmitted to a test body (S), and the pulse propagated in the test body (S) by multiple reflection is received by a receiver (12). , The first pulse b1 (t) propagated through the test body (S) and received first by the receiver (12) is Fourier-transformed to obtain a first converted signal B1 (ω), and The one pulse b1 (t) is reflected at the boundary surface on the receiving side in the test body (S), propagates again in the test body (S), and is then received by the receiver (12) in the second pulse b2. Fourier transform of (t) is performed to obtain the second converted signal B2 (ω), and the second converted signal B2 (ω) is obtained.
And a ratio signal B3 which is a ratio of the first converted signal B1 (ω)
(Ω) = B2 (ω) / B1 (ω) is obtained, and the ratio signal B
The test method using the elastic wave pulse for evaluating the test body (S) by 3 (ω).