JP2826013B2 - Ultrasonic flaw detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flaw detection method for measuring a depth position of a defect existing in a subject based on a flaw detection signal from the subject, and more particularly, to an ultrasonic flaw detection method for inputting to an A / D converter. Even if the applied voltage value exceeds the maximum conversion voltage value, the depth position of the defect can be accurately measured.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing the overall structure of an example of a conventional ultrasonic flaw detector. In the figure, reference numeral 1 denotes a subject on which a flaw detection operation is performed by an ultrasonic flaw detection apparatus,
The defect 1 a exists in the subject 1. 2 is the subject 1
The probe 2 transmits an ultrasonic wave toward the subject 1 and receives a reflected wave from the subject 1 and converts the reflected wave into an electric signal (echo signal). I do. Reference numeral 3 denotes a transmitting unit that excites the probe 2 to generate an ultrasonic wave, and 4 denotes a receiving unit that receives the electric signal converted by the probe 2, and the receiving unit 4 is an attenuation having a variable attenuation rate. The circuit includes a circuit 4a, an amplification circuit 4b having a constant amplification factor, and a detection circuit 4c. Reference numeral 5 denotes an A / D converter that converts an output from the receiving unit 4 into a digital value, 6 denotes a waveform memory that stores a digital output from the A / D converter 5, and 7 denotes an address counter that specifies an address of the waveform memory 6. . Reference numeral 8 denotes a timing circuit which controls output timing of the transmission unit 3, conversion timing of the A / D converter 5, and address designation timing of the address counter 7.

[0003] Reference numeral 10 denotes a CPU (central processing unit) for controlling and calculating the entire ultrasonic flaw detector, and 11 denotes a random access memory (RAM) for temporarily storing parameters and data.
An access memory), 12 is a ROM (Read Only Memory) in which processing procedures of the CPU 10 and the like described later are stored, and 13 is a keyboard input unit to which required data is inputted by an operator. Reference numeral 14 denotes a liquid crystal display unit having a predetermined number of liquid crystal dots arranged in a matrix. Reference numeral 15 denotes a display controller for controlling the display of the liquid crystal display 14. The controller 15 is a display memory 15m in which data to be displayed on the liquid crystal display 14 is stored.
It has.

In this example, the maximum number of data that can be displayed on the liquid crystal display unit 14 is equal to the number of horizontally arranged dots constituting the liquid crystal display unit 14, which is the number of addresses in the display memory 15m. Is also equal to The vertical full scale of the liquid crystal display unit is equal to the full scale of the A / D converter 5.

[0005] Reference numeral 16 denotes a first gate circuit. The gate circuit 16 sets an arbitrary measurement range (hereinafter, referred to as a "first gate") for detecting the surface position of the subject 1. The maximum value of the surface echo signal existing in the first gate, that is, the echo signal reflected on the surface of the subject 1, and the address value of the address counter 7 corresponding to the maximum value are detected. Further, the first gate circuit 16 detects whether or not the signal level of the surface echo has exceeded a threshold value input in advance, and determines the address of the address counter 7 corresponding to a location where the signal level of the surface echo has exceeded the threshold value. Find the value.

Reference numeral 17 denotes a second gate circuit provided in parallel with the first gate circuit 16 and has a gate circuit 16 therein.
There is an address counter 17a that is activated in conjunction with. The gate circuit 17 sets an arbitrary measurement range (hereinafter, referred to as a “second gate”) for detecting the depth position of the defect 1a existing in the subject 1, and sets the measurement range within the second gate. The maximum value of the existing defect echo signal and the address value of the address counter 17a corresponding to the maximum value are detected. At this time, the depth position of the defect 1a is
Since the measurement is preferably performed from the surface of the object 1 above, the defect detection operation by the second gate circuit 17 is performed in conjunction with the surface echo detection operation by the first gate circuit 16 in this example (details). Will be described later). The detection of the maximum value of the defective echo by the second gate circuit 17 is started when the signal level of the defective echo exceeds a threshold value input in advance. In FIG. 11, a block 18 indicated by a dashed line indicates the ultrasonic flaw detector main body.

In this example, a flaw detection operation is performed on the subject 1 by a so-called water immersion method. That is, the subject 1 is disposed in a water tank W filled with water Wa, and the probe 2 transmits and receives ultrasonic waves to and from the subject 1 via the water Wa in a state where the probe 2 is not in contact with the subject 1. Do. In the following description,
The subject 1 does not have two opposing flat surfaces such as a plate-like body,
It is assumed that the surface is not a flat surface. Therefore, it is necessary to detect the surface position of the subject 1 and specify the depth position of the defect 1a.

Next, the operation of the ultrasonic flaw detector 18 shown in FIG. 11 will be described with reference to FIGS. FIG. 12 is a diagram showing a flaw detection area of the subject 1 by the ultrasonic flaw detector 18 of FIG. 11, and FIG. 13 is a diagram showing a waveform of an echo signal obtained from the subject 1 of FIG. In FIG. 13, T is a transmission wave, S is a surface echo, F is a defect echo,
B is a bottom echo. Further, t _g1 and t _g2 indicate the gate start point and the gate end point of the first gate output from the gate circuit 16, respectively.
Correspond to the distances l _g1 and l _g2 starting from the probe ₂ , respectively. Accordingly, the scope A _g between these l _g1 and l _g2 is in the range for detecting the surface of the subject 1. FIG.
Returning to 3, y ₀ is the threshold for detecting the surface echo described above, y _p
Is the maximum value of the surface echo S detected by the gate circuit 16. On the other hand, t _g1 ′ and t _g2 ′ indicate the gate start point and the gate end point of the second gate output from the gate circuit 17, respectively.
_g1 'and _lg2 ', respectively. Therefore, these l
'becomes a range which detects the subject 1 defect 1a, the range A _{g' g1} 'and l _g2' range A _g between defects that are not in is not a detection object in this example. At this time, the gate circuit 17
Is performed in conjunction with the surface echo detection operation by the gate circuit 16 as described above, so that the start point of the distances l _g1 ′ and l _g2 ′ is the threshold value y ₀
Is set to a time point P exceeding. Returning to FIG. 13, y ₀ ′ is a threshold value for detecting the above-described defect echo, and y _p ′ is a maximum value of the defect echo S detected by the gate circuit 17.

Next, a procedure for detecting the depth position of the defect 1a by the CPU 10 will be described. The address value of the maximum value of the surface echo detected by the gate circuit 16 is A _p , the address value when the surface echo exceeds the threshold value y ₀ is A _i , the address of the maximum value of the defect echo detected by the gate circuit 17. 'When the gate circuit 17, since the start of the operation from the point P to the surface echo S as described above exceeds the threshold value y _0, the address value a _p of defect echo maximum' values a _p Figure 13 shows a value shifted by Δt. Accordingly, the distance l _g from the surface to the defect 1a is a value in consideration of the correction value as follows.

1 _g = τ _s ＶV _s ｛A _p ′ − (A _p −A _i )} / 2 where V _s is the sound velocity of the subject 1 and τ _s is the sampling interval of the A / D converter 5 It is. As described above, in order to measure the depth position of the defect 1a existing inside the subject 1,
Address value of the maximum value of the maximum value of the address value A _p and defect echo F of surface echo S in addition to A _p ', surface echo S
There is also required address value A _i when exceeding the threshold value y ₀ of the first gate.

[0010]

However, in the above-described conventional ultrasonic flaw detector, there is a problem that the depth position of the defect echo may not be accurately measured depending on the amplification factor of the receiving section 4. there were. That is, when the attenuation rate of the subject 1 is large, or when the defect 1a is located far away from the surface, the level of the defect echo F displayed on the liquid crystal display unit 14 becomes small, and the gate circuit 1
7 may not be reliably detected. For this reason, the level of the defective echo F displayed on the liquid crystal display unit 14 is increased by increasing the amplification factor of the receiving unit 4 (specifically, decreasing the attenuation factor of the attenuation circuit 4a). On this occasion,
Since the attenuation rate of the water Wa is very small, the level of the surface echo S is relatively large, and a part of the surface echo S may protrude from the liquid crystal display unit 14, as shown in FIG. Specifically, the vertical full scale of the liquid crystal display unit 14 is A
Since the gain is equal to the full scale of the A / D converter 5, the level of the surface echo S becomes larger than the reference voltage value (maximum conversion voltage value) of the A / D converter 5 when the amplification factor of the receiving unit 4 is large, and the output is saturated. Thus, part of the surface echo S apparently protrudes from the liquid crystal display unit 14. Then, the first gate circuit 16, the address of the maximum value of the surface echo S address value (y _p) it is determined that A _p shown in FIG. 3, the actual surface echo maximum (y _sp) on the screen The value is Ak, and the difference between these address values ΔA _k = A _k -A _p
Is a measurement error of the depth position of the defect echo F.

An object of the present invention is to provide an ultrasonic flaw detection method capable of accurately measuring the depth position of a defect echo even when the voltage value input to the A / D conversion means exceeds the maximum conversion voltage value. To provide.

[0012]

The present invention will be described with reference to FIGS. 1, 4, 5 and 9, which show an embodiment of the present invention. When the reflected wave is converted into a digital signal by the A / D conversion means 5 to obtain a flaw detection signal, when the voltage input to the A / D conversion means 5 exceeds the maximum conversion voltage value, The method is applied to a method for measuring the depth position of the defect 1a existing in the inside. The invention according to claim 1 is a step of exciting the ultrasonic probe 2 by transmitting means 3 and transmitting ultrasonic waves toward a test piece 1 ′ formed of the same material as the subject 1. And an echo obtained from the test piece 1 ′
Receiving the test sample 1 'at the same amplification factor as at the time of flaw detection, and calculating the respective positions of the maximum value yp' of the surface echo S and the maximum value yp 'of the bottom surface echo B of the test piece 1'. Obtaining a flaw detection signal from the subject 1 using the transmitting means 3, the ultrasonic probe 2, the receiving means 4, and the A / D converting means 5, and
Using the respective positions of the surface echo maximum value yp and the bottom surface echo maximum value yp 'in the test piece 1', the thickness Lg and the sound velocity Vs of the test piece 1 ', and the flaw detection signal from the subject 1. Calculating the depth position of the defect 1a present in the subject,
The above-mentioned object is achieved. The invention of claim 2 is
A step of exciting the ultrasonic probe 2 by transmitting means 3 and transmitting ultrasonic waves toward a test piece 1 ′ formed of the same material as the subject 1; Receiving the received echo with the same amplification factor as that at the time of flaw detection of the subject 1 by the receiving means 4, and the position of the maximum value yp3 of the surface echo S and the maximum value yp3 of the bottom surface echo B1 of the test piece 1 '. Calculating the position of the maximum value yp3 'of the echo B2 double-reflected in the test piece 1'; and calculating the maximum value yp3 of the bottom surface echo and the double reflection echo calculated in the step. Calculating the sound velocity Vs of the test piece 1 'by using the position of the maximum value yp3' and the thickness Lg of the test piece; and the transmitting means 3, ultrasonic probe 2, receiving means 4, and A Flaw detection signal from the subject 1 using the A / D conversion means 5 And obtaining, sound speed Vs of the 'respective positions of the at the surface echo maximum yp and the bottom echo maximum YP3, the test piece was calculated in the step 1' calculated the test piece 1 by the process, and the The above object is achieved by providing a step of calculating a depth position of the defect 1a present in the subject using a flaw detection signal from the subject 1.

[0013]

[Action]

- The thickness of the claims 1 surface echo maximum y _p of the maximum value y _p and bottom echo B of S 'can detect the position of, and the test piece 1' acoustic velocity V _s is applied Rarere if specimens can be calculated . However,
Position of the surface echo maximum y _p when the input voltage value to the A / D converting means 5 exceeds the convertible voltage value may not be accurately determined. Therefore, the thickness L of the test piece 1 '
_{When g} is known and compared with the thickness of the test piece obtained by the flaw detection operation on the test piece 1 ', a correction value for measuring the depth position of the true defect 1a can be obtained. - Ultrasonic is one reciprocation of the test piece with the claim 2 bottom echo B ₁ and double reflected echo B _2, thus the thickness L _g of the test piece 1 '
If it is known it can be calculated sound velocity V _s of the test pieces with these bottom echo B ₁ and double reflected echo B _2.

In the means and means for solving the above problems which explain the constitution of the present invention, the drawings of the embodiments are used for easy understanding of the present invention. However, the present invention is not limited to this.

[0015]

【Example】

-First Embodiment- A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a first embodiment of an ultrasonic inspection apparatus to which the ultrasonic inspection method according to the present invention is applied, and is a block diagram showing an overall configuration. In the following description,
The same components as those in the above-described conventional example are denoted by the same reference numerals, and description thereof will be simplified.

The ultrasonic flaw detector of this embodiment has the same basic configuration as the above-described conventional ultrasonic flaw detector. That is, the ultrasonic flaw detector 18 includes a probe 2 that transmits and receives ultrasonic waves to and from the subject 1 and a transmitting unit that applies a pulse signal to the probe 2 to excite the probe 2. 3, a receiving unit 4 for receiving an echo signal from the probe 2, an A / D converter 5 for A / D converting an output from the receiving unit, and a waveform memory 6 for storing a digital output from the converter 5.
An address counter 7 for specifying an address of the waveform memory 6; a timing circuit 8 for controlling the timing of the transmitting unit 3, the A / D converter 5 and the address counter 7; a CPU 10 for controlling the entire apparatus; A ROM 11 for temporarily storing processing procedures to be described later, a keyboard input unit 13 ′ for data input, a liquid crystal display unit 14 for waveform display,
A display unit controller 15 for controlling the display of the liquid crystal display unit 14, a first gate circuit 16 for detecting the surface position of the subject 1, and a second gate circuit 17 for detecting the defect position of the subject 1 are provided. Provided roughly. The receiving unit 4 includes an attenuation circuit 4a having a variable attenuation rate, an amplification circuit 4b having a constant amplification rate, and a detection circuit 4c, as in the conventional example. However, the details of the keyboard input unit 13 'and the ROM
The processing procedure stored in the memory 20 differs from that of the above-described conventional example (details will be described later).

The first gate circuit 16 and the second gate circuit 17 are, for example, disclosed in Japanese Patent Application No.
Similar to the one disclosed in the specification of Japanese Patent Application No. 269381 or Japanese Patent Application No. 2-257978, a gate signal generating circuit and a maximum value detecting circuit are provided. In addition, a function of detecting the maximum value in each gate is provided, but details thereof are omitted.

FIG. 2 is a plan view showing details of the keyboard input unit 13 '. In FIG. 2, 13'a is the number "0"
13'b is a decimal point key for inputting a decimal point, 13'c is a sound speed key for inputting a sound speed, 13 '
d is a gate level key for inputting a gate level (that is, a threshold), 13'e is a gate start key for inputting a gate start point, 13'f is a gate end key for inputting a gate end point, 1 '
3'g is a set key for setting the entered numerical value,
13'h is a surface echo correction key for surface echo correction described later.

Next, the ultrasonic flaw detection method of this embodiment will be described with reference to the flowcharts of FIGS. 1 to 5 and FIG. First, prior to the flaw detection operation on the subject 1, the subject 1 is formed of the same material as the subject 1.
A test piece 1 ′ having the same thickness as that of FIG.
As shown in FIG. Test piece 1 'shown in FIG. 4 is a thick plate having a thickness of L _g having mutually parallel two planes, the speed of sound is the same V _s the subject 1.
Further, even if a defect exists in the test piece 1 ', the subsequent operation is not significantly affected. However, as shown in FIG. It is preferable that the type of is not mistaken. Therefore, it is also possible to use a portion where no defect exists in the subject 1 as the test piece 1 '.

Next, a test operation for the test piece 1 'is performed in the same procedure as the test operation for the subject 1. That is, a pulse signal is transmitted from the transmission unit 3 to the probe 2, and the probe 2 is excited by the pulse signal to generate and transmit an ultrasonic wave toward the test piece 1 '. The transmitted ultrasonic wave is water W
The light reaches the test piece 1 ′ via a and is reflected on the surface and the bottom surface thereof. The reflected wave from the test piece 1 'reaches the probe 2 by following a path reverse to that at the time of transmission, and the probe 2 converts the reflected wave into an echo signal proportional to the level of the reflected wave. The echo signal is amplified to an appropriate level in the receiving unit 4, converted into a digital signal in the A / D converter 5, and stored in the waveform memory 6. Further, the echo signal stored in the waveform memory 6 is also stored in the display memory 15m of the display unit controller 15 via the CPU 10, and the signal stored in the display memory 15m is displayed on the screen of the liquid crystal display unit 14. Will be displayed. FIG. 5 is a diagram showing a state in which an echo signal obtained from the test piece 1 ′ shown in FIG. 4 is displayed on the screen of the liquid crystal display unit 14. At this time, the flaw detection operation on the test piece 1 'is performed at the same amplification factor (specifically, the attenuation factor of the attenuation circuit 4a) as the flaw detection operation on the subject 1.

In this state, the operator operates the keyboard input unit 1
When the 3 ′ surface echo correction key 13′h is pressed, the ultrasonic inspection apparatus 18 enters a surface echo correction mode, and a correction value is calculated according to the procedure shown in the flowchart of FIG. First, in step S1, the operator uses the gate start point key 13'e, the gate end point key 13'f, and the number keys 13'a,
Wait until the first gate is set in the area where the surface echo S exists. Next, in step S2, similarly, the operator waits until the operator sets the second gate in the range where the bottom surface echo B exists using the gate start key 13'e, the gate end key 13'f, and the numeric key 13'a. .

When the first gate is set by the operator,
The first gate circuit 16 detects the address value A _p of the address counter 7 corresponding to the maximum value y _p and the maximum value y _p of the surface echo S present in the first gate in a step S3, in addition , detects an address value a _i of the address counter 7 at the time when the signal level of the surface echo S exceeds the threshold value y _0. Similarly, when the second gate is set by the operator, the second gate circuit 17 sets the maximum value y _p ′ of the bottom echo B existing in the second gate and the address counter 17a corresponding to the maximum value. detecting the address value a _p '. As described above, the address value A _p ′ starts from the time point P when the signal level of the surface echo S exceeds the threshold value y ₀ (see FIG. 3).

In step S4, the operator presses the sound speed key 1
Using 3'c and numeric keys 13'a, waits for inputting a sound velocity V _s and the thickness L _g of the test piece 1 ', then the program proceeds to step S5. In step S5, based on the detected value and the input value of the above, the correction value [Delta] L _k is calculated by the CPU 10.

As described above, the address value of the maximum value of the surface echo detected by the first gate circuit 16 is A _p , the address value when the surface echo S exceeds the threshold value y ₀ is A _i , and the second value is A _i .
Assuming that the address value of the bottom echo maximum value detected by the gate circuit 17 is A _p ′, the measured value l _g ′ of the thickness of the test piece 1 ′ calculated from these address values is obtained by the following equation.

[Number 2] _{l g '= τ s · V} s {A p' - in _{(A p -A i)} /} 2 where, tau _s is the sampling interval of the A / D converter 5, V _s is input by the operator This is the sound speed of the test piece 1 '. However, the measured value l _g 'of the thickness of this test piece 1' is
As is clear from the above discussion, the thickness is larger by ΔL _k than the thickness L _g of the true test piece 1 ′. True thickness L
_{Since g} is known, the correction value ΔL _k is

## EQU3 _## It can be obtained by ΔL _k = l _g ′ −L _g . This correction value ΔL _k is temporarily stored in the RAM 11.

In step S6, the process waits for the operator to press the surface echo correction key 13h. After that, the program exits the surface echo correction mode and returns to the normal flaw detection mode. After that,

Equation 4] _{l g = τ s · V s} - The use of _{{A p '(A p -A} i)} / 2-ΔL k, it is possible to measure the true defect depth l _g without error .

Second Embodiment A second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a diagram showing a second embodiment of an ultrasonic inspection apparatus to which the ultrasonic inspection method according to the present invention is applied, and is a block diagram showing an overall configuration. The ultrasonic flaw detector of this embodiment has the same basic configuration as the ultrasonic flaw detector of the first embodiment. However, in the ultrasonic flaw detector of the present embodiment, in addition to the first and second gate circuits 16 and 17, a third gate circuit 21 is provided in parallel with these gate circuits 16 and 17. The gate circuit 21 has two measurement ranges (hereinafter, “third gate”) for the echo signal.
In addition to setting the "fourth gate", the maximum value of the echo signal existing in the third and fourth gates and the address value of the address counter 21a corresponding to this maximum value are detected. Here, the third gate is a measurement range set to an arbitrary range for detecting the bottom surface position (bottom echo) of the test piece 1 ′, and the fourth gate is multiplexed within the test piece 1 ′. This is a measurement range set to an arbitrary range for detecting a reflected echo (multiple reflection echo).

Next, the ultrasonic flaw detection method of this embodiment will be described with reference to the flowcharts of FIGS. 7 to 9 and FIG. First, as in the first embodiment, prior to the flaw detection operation on the subject 1, a test piece formed of the same material as the subject 1 and preferably having the same thickness as the subject 1 is used. 1 ′ was prepared, and the water Wa in the water tank W was prepared as shown in FIG.
Place within. Test piece 1 shown in FIG. 8 'is a thick plate having a thickness of L _g having mutually parallel two planes, the speed of sound is the same V _s the subject 1.

Next, a test operation for the test piece 1 'is performed in the same procedure as the test operation for the subject 1. FIG. 9 shows FIG.
FIG. 5 is a diagram showing a state in which an echo signal obtained from the test piece 1 ′ shown in FIG. In Figure 9, T is the transmitted wave, S is a surface echo, B ₁ is 'reflected bottom echo once with the bottom surface of, B ₂ test piece 1' test piece 1 echo reflected once on the bottom surface of the Is a double reflection echo reflected on the surface of the test piece 1 'and once again on the bottom surface of the test piece 1'. At this time, the flaw detection operation on the test piece 1 ′ is performed at the same amplification factor as the flaw detection operation on the subject 1.

In this state, the operator operates the keyboard input unit 1
When the 3 ′ surface echo correction key 13′h is pressed, the ultrasonic inspection apparatus 18 enters the surface echo correction mode, and the correction value is calculated according to the procedure shown in the flowchart of FIG. First, in step S11, the operator sets the gate start key 13'e,
Using the gate endpoint keys 13'f and numeric keys 13'a, surface echo S, first each range in the presence of bottom echo B ₁ and double reflected echo B _2, third and fourth
Wait to set the gate.

When the first gate is set by the operator,
The first gate circuit 16 detects the address value A _p of the address counter 7 corresponding to the maximum value y _p and the maximum value y _p of the surface echo S present in the first gate in a step S12, in addition , detects an address value a _i of the address counter 7 at the time when the signal level of the surface echo S exceeds the threshold value y _0. Similarly, when the third and fourth gates are set by the operator, the third gate circuit 21 outputs the bottom echoes B existing in the third and fourth gates, respectively.
₁ and double reflected echo B ₂ of the maximum value y _p3, y _p3 ', and the address value of the maximum value to the corresponding address counter 21a A _p3, A _p3' to detect. As described above, these address values A _p3 and A _p3 ′ start from the point P when the signal level of the surface echo S exceeds the threshold value y ₀ (FIG. 9).
reference).

In step S13, the operator presses the numeric key 1
Wait for input of thickness Lg of test piece 1 'using 3'a. In step S14, the CPU 10 calculates the sound speed of the test piece 1 'based on the detected value and the input value.

As described above, the address value of the maximum surface echo detected by the first gate circuit 16 is A _p , the address value when the surface echo S exceeds the threshold value y ₀ is A _i , and the third value is A _i .
Bottom echo maximum is detected in the gate circuit 17 and double reflected echo maximum address value, respectively A _p3, A
'When a test piece 1 which is calculated from these values' _p3 sound velocity V _s of is obtained by the following equation.

(Equation 5) Here, τ _s is the sampling interval of the A / D converter 5, and L _g is the thickness of the test piece 1 ′ input by the operator. As shown in FIG. 8, the ultrasonic between the bottom echo B ₁ and double reflected echo B ₂ is 'has one round trip inside, thus, τ _s · (A _p3' specimen 1 -A _p3) Represents the propagation time of the ultrasonic wave actually making one round trip in the test piece 1 '. Therefore,
Acoustic velocity V _s was calculated by the above equation is the measured value at that time, its accuracy is very high.

Next, in step S15, step S13
Based on the detected values sound velocity V _s and has already been obtained obtained by obtained correction value [Delta] L _k by CPU 10.
First, similarly to the above-described first embodiment, a measured value l _g 'of the thickness of the test piece 1' is obtained based on the following equation.

L _g ′ = τ _s ＶV _s ｛A _p ′ − (A _p −A _i )} / 2 where V _s is the test piece 1 ′ obtained in step S 13.
Is the actual measured value of the sound speed. However, the measured value l _g ′ of the thickness of the test piece 1 ′ is a value larger by ΔL _k than the thickness L _g of the true test piece 1 ′, as is clear from the above discussion. Thus, similarly to the first embodiment, the correction value ΔL _k is calculated by the CPU 10 based on the following equation.

Equation 7] ΔL _k = l _g '-L _g The correction value [Delta] L _k is temporarily stored in the RAM 11.

In step S16, the process waits for the operator to press the surface echo correction key 13'h, after which the program exits the surface echo correction mode and returns to the normal flaw detection mode. After that,

Equation 8] _{l g = τ s · V s} - The use of _{{A p '(A p -A} i)} / 2-ΔL k, it is possible to measure the true defect depth l _g without error .

In the correspondence between the claims and the embodiment, the transmitting unit 3 is a transmitting unit, the receiving unit 4 is a receiving unit,
The / D converter 5 constitutes A / D conversion means. The details of the ultrasonic flaw detection method of the present invention are not limited to the above-described embodiment, and various modifications are possible.

[0036]

As described above in detail, according to the present invention, even when the voltage value input to the A / D conversion means exceeds the maximum conversion voltage value, the surface position of the subject can be accurately calculated. It is possible to do. Therefore, the depth position of the defect can be accurately measured even when the attenuation rate of the object is large or when the defect exists at a position far away from the surface. In particular, according to the second aspect of the present invention, since the sound velocity of the object having the temperature dependency is actually measured, the depth position of the defect can be measured more accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an overall configuration of an ultrasonic inspection apparatus to which an ultrasonic inspection method according to a first embodiment of the present invention is applied.

FIG. 2 is a plan view showing details of a keyboard input unit of the first embodiment.

FIG. 3 is a diagram illustrating an example of an echo signal obtained from a subject.

FIG. 4 is a front view showing a test piece used in the first embodiment.

5 is a diagram showing an example of an echo signal obtained from the test piece of FIG.

FIG. 6 is a flowchart for explaining the operation of the first embodiment.

FIG. 7 is a block diagram showing an overall configuration of an ultrasonic inspection apparatus to which the ultrasonic inspection method according to the second embodiment of the present invention is applied.

FIG. 8 is a front view showing a test piece used in the second embodiment.

FIG. 9 is a diagram illustrating an example of an echo signal obtained from the test piece of FIG. 8;

FIG. 10 is a flowchart for explaining the operation of the second embodiment.

FIG. 11 is a block diagram showing an overall configuration of an example of a conventional ultrasonic flaw detector.

FIG. 12 is a diagram showing a flaw detection area of a subject by the ultrasonic flaw detection apparatus of FIG. 11;

13 is a diagram illustrating an example of an echo signal obtained from the subject in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Subject 1a Defect 1 'Test piece 2 Probe 3 Transmitter 4 Receiver 5 A / D converter 6 Waveform memory 7 Address counter 10 CPU 13' Keyboard input unit 16 First gate circuit 17 Second gate circuit 20 ROM 21 Third Gate Circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 29/00-29/28

Claims (2)

(57) [Claims] When a flaw detection signal is obtained by converting a reflected wave from an object obtained by an ultrasonic probe into a digital signal by an A / D converter, the signal is input to the A / D converter. A method for measuring a depth position of a defect existing in the subject when a voltage value exceeds a maximum conversion voltage value, wherein a transmitting unit excites the ultrasonic probe, and Transmitting ultrasonic waves toward a defect-free test piece formed of the same material as the sample, and receiving echoes obtained from the test piece by a receiving unit at the same amplification factor as at the time of flaw detection of the subject. Calculating the respective positions of the maximum value of the surface echo and the maximum value of the bottom surface echo of the test piece; and using the transmitting unit, the ultrasonic probe, the receiving unit, and the A / D conversion unit. Obtaining a flaw detection signal from the subject; Present in said surface echo maximum and the respective positions of the bottom echo maximum, thickness and speed of sound of the test piece, and using said testing signals from the subject in the subject in the specimen is calculated by Calculating a depth position of the defect to be inspected. 2. When the reflected wave from the subject obtained by the ultrasonic probe is converted into a digital signal by an A / D converter to obtain a flaw detection signal, the signal is input to the A / D converter. A method for measuring a depth position of a defect existing in the subject when a voltage value exceeds a maximum conversion voltage value, wherein a transmitting unit excites the ultrasonic probe, and Transmitting ultrasonic waves toward a defect-free test piece formed of the same material as the sample, and receiving echoes obtained from the test piece by a receiving unit at the same amplification factor as at the time of flaw detection of the subject. Calculating the position of the maximum value of the surface echo and the maximum value of the bottom surface echo of the test piece; and calculating the position of the maximum value of the double-reflected echo in the test piece, The bottom echo maximum value calculated by the process Calculating the sound velocity of the test piece by using the position of the maximum value of the double reflection echo and the thickness of the test piece; and the transmitting unit, the ultrasonic probe, the receiving unit, and the A / D conversion. obtaining a flaw detection signal from the subject using the device, respective positions, the test piece was calculated by the process of the surface echo maximum value and the bottom echo maxima in the test piece was calculated by the step Calculating a depth position of a defect existing in the subject using the sound velocity of the subject and a flaw detection signal from the subject.