JPH0778491B2 - Ultrasonic inspection method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for inspecting a structure or the like by ultrasonic waves, and particularly to detect a defect in a complicated shape such as a turbine disc dovetail groove. The present invention relates to a suitable ultrasonic inspection method and apparatus.

[Conventional technology]

A conventional device for inspecting a complicated shape as shown in FIG. 2 is a probe, a sweeping horizontal amplifier, a detection circuit, a gate generator, a level discriminator as described in JP-A-61-155856. , A gate circuit for detecting a shape echo, a gate circuit for detecting a defect echo, a logical product gate, and a logical sum gate. The contents of the conventional device will be described with reference to the waveform chart of FIG. In FIG. 2, an ultrasonic wave is incident on the DUT 1 from the probe 2 and a reflected wave from the inside of the DUT is received. In that case, if there are defects f and g, reflected waves (hereinafter referred to as shape echo) P _a , from the processed uneven portions a, b, and c of the inspection object
Reflected waves from P _b and P _c and defects f and g (hereinafter called defect echo)
Can receive P _f and P _g . When the shape echoes P _a , P _b , and P _c are obtained in the gates G _a , G _b , and G _c formed to detect the shape echoes, the probe 2 is appropriately placed on the DUT 1. It is judged that the defect echoes P _f and P _g can be installed at the position, and when the defect echoes P _f and P _g are obtained in at least one of the gates G _f and G _g formed to detect the defect echoes P _f and P _g in that state. Is determined to exist.

In FIG. 3, the shape echo P _d that can be received when the defect g does not exist is displayed separately from the defect echo P _g . However, P _d and P _g may overlap depending on the position of the defect g,
Further, the shape echoes P _d and P _e do not disappear due to the sizes of the defects f and g. In the conventional device, no consideration was given to that case.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, consideration is not given to the point where the defect echo and the shape echo overlap depending on the position of the defect, and the shape echo is expected to receive the defect echo even if there is no defect. ), There was a problem of determining that a defect exists even when there is no defect.

An object of the present invention is to inspect an object having a complicated shape such as a turbine disk dovetail groove, depending on the position of a defect,
An object of the present invention is to provide an ultrasonic inspection method and apparatus capable of determining the presence or absence of a defect even when a defect echo and a shape echo overlap each other.

[Means for solving problems]

Among the many shape echoes and defect echoes received, the above-mentioned object focuses on the shape echo of the inspected object in which the defect blocks the incident wave when the defect exists, and the shape echo intensity and the defect Focusing on the fact that the intensity of the shape echo is different when there is no such defect, the presence or absence of a defect is determined from the change in the intensity of the shape echo.

[Action]

Of many received shape echoes and defect echoes, attention is paid to the shape echo of the inspected object in which the defect blocks the incident wave, and it is determined that the defect exists when the intensity of this shape echo changes. Thereby, even if the defect echo overlaps with one of many shape echoes and it is difficult to discriminate the defect echo from the shape echo, the defect can be detected.

〔Example〕

First, a method for surely detecting a defect even when the defect echo and the shape echo have a complicated shape is described. As an inspected object having a complicated shape, consider the disc dovetail groove shown in FIGS. 4 (a) and 4 (b).
Here, FIG. 4 (b) is a detailed view of a portion A of FIG. 4 (a). The tail groove shaped portions a, b, c, d, e are formed in parallel (or concentrically) with the moving direction AR of the ultrasonic probe. The depth d, which is a part of the body to be inspected
An artificial defect of length l is provided. The point at which the ultrasonic intensity becomes maximum perpendicular to this artificial defect (hereinafter referred to as the sound axis)
The probe 2 for transmitting and receiving ultrasonic waves is installed in such a position as to hit. At this time, as shown in FIG. 4, the corner of the object to be inspected is used as a reference, and the distance from this reference to the probe 2 is L (in practice, the reference may be anywhere). With the L fixed, the probe 2 is scanned in the direction of the arrow AR shown in FIG. 4, and the probe 2 is installed in the place where there is no artificial defect. The received waveform at this time is shown in FIG. Processed concavo-convex part b, d, e of the inspection object 1
The shape echoes from the can be received, which are indicated by P _b , P _d , and P _e in FIG. Next, while the L is fixed, the probe 2 is scanned and fixed on the place where the artificial defect exists. The received waveform at this time is
Shown in the figure. Figure 6 shows the defect depth (slit depth) d = 2m
m, FIG. 7 shows a received waveform with a defect depth (slit depth) d = 1 mm. Both FIGS. 6 and 7 show three types of defect lengths l = 2, 4, 8 mm. The propagation time of the defect echo P g from the defect _g is several hundred ns as long as the propagation time of the shape echo P _d (Fig. 4).
They match with different degrees. Therefore, the defect echo P _g and the shape echo P _d cannot be discriminated, and the shape echo P _d may be determined as the defect echo P _g . In addition, FIG.
The defect echo P _g of (a) and (b) is the shape echo of FIG.
_Less than P _d . Therefore, there is a possibility that it can be judged that there is no defect in FIGS. 6 (a), 7 (a), and (b).
This is due to the interference between the shape echo P _d and the defect echo P _g . Focusing on the shape echo P _e in FIGS. 5, 6, and 7,
P _e when there is a defect (a 6,7 view) is summer small compared to P _e in the absence of defects (Figure 5). This is because when the defect g exists, a part of the incident ultrasonic wave is reflected by the defect g and does not reach the shape e. The ratio of the shape echo P _e when there is a defect to the shape echo P _e1 when there is no defect is plotted on the vertical axis, and the defect length 1 is plotted on the horizontal axis, as shown in FIG.
It shows in (b). As is clear from FIG. 8, P _e / P _e1 <1
That is, it can be determined that the defect g exists when P _e <P _e1 . Furthermore, FIG. 8 shows the characteristics of the defect
Since the value of P _e / P _e1 is different, the defect size can be obtained from the value of P _e / P _e1 .

Here, the case where the defect is located above the shape b has been described, but the same applies to the case where the defect exists above the shapes a and c.

The case where the defect g exists above the shape b will be described below as a representative.

An ultrasonic inspection apparatus for embodying this method is shown in FIG. Probe 2, transmission pulser 3, amplification circuit 4, gate generation circuit 5,
It comprises a switching circuit 6, a peak detection circuit 7, a wave height discrimination circuit 8, and an AND gate 9. First, the switching circuit 6 connects the amplification circuit 4 and the peak detection circuit 7. The probe 2 is installed in advance on a portion of the object to be inspected, which is confirmed to be free of defects (or a standard object to be inspected which is confirmed to be free of defects) (the installation position is L away from the reference position). Position). A pulse voltage is applied to the probe 2 by the transmission pulser 3, and the inspection object 1
An ultrasonic wave is injected inside. Shape echo from DUT 1
P _d , P _e, etc. are received by the same probe 2, amplified by the amplifier circuit 4, and then transmitted to the peak detection circuit 7. The transmitted signal is shown in FIG. 9 (a). On the other hand, in the gate generation circuit 5, the output from the transmission pulser 3 is used as a trigger to set the gate at the time when the shape echo P _e can be received (FIG. 9 (d)) and input it to the peak detection circuit 7. The peak detection circuit 7 detects the peak of the shape echo P _e in the gate set by the gate generation circuit 5 (SL in FIG. 9 (a)) and transmits the value to the wave height discrimination circuit 8. Then, the switching circuit 6 disconnects the amplification circuit 4 from the peak detection circuit 7, and connects the peak detection circuit 7 to the wave height discrimination circuit 8. As shown in FIG. 4, the probe 2 is installed at a position on the DUT 1 which is away from the reference position by L. Similarly to the above, a pulse voltage is applied from the transmission pulser 3 to the probe 2,
An ultrasonic wave is incident on the device under test 1 and an echo is received by the probe 2. The received echo is amplified by the amplifier circuit 4 and sent to the wave height discrimination circuit 8 (FIG. 9 (b)). In the wave height discrimination circuit 8, the output from the peak detection circuit 7 or a value smaller by a preset range is set as the threshold level SL (Fig. 9), and when the echo is larger than this SL, it is set as the level "1". If it is smaller than SL, output as level "0". This output C is shown in FIG. 9 (c). The shape echo P _{b, which} has a shorter propagation distance than the shape echo P _e , is always SL.
It becomes larger and becomes level "1", but the shape echo P _e is
If there is no defect, the level is "1", and if there is a defect, the level is "0". The AND gate 9 takes the theoretical product of the output of the gate generation circuit 5 and the output of the wave height discrimination circuit 8,
It becomes as shown in FIG. 9 (e). That is, the level is always "0" when there is a defect, and the gate generation circuit 5 when there is no defect.
The level becomes "1" in the gate set in. Therefore, by looking at the output of the AND gate 9, it is possible to know whether or not there is a defect.

As shown in FIG. 4, by moving the probe 2 in the direction of the arrow AR while fixing the distance L from the reference position, the entire object 1 to be inspected can be inspected.

Another embodiment is shown in FIG. In the embodiment shown in FIG. 1, it is necessary to first inspect the standard inspection object or the portion of the inspection object confirmed to be free from defects. This example is omitted in the embodiment shown in FIG. First, the switching circuit 6 controls the peak detection circuit 7 and the peak memory at the initial position.
Connect with 10. The probe 2 is installed at an arbitrary position on the DUT 1 that is L away from the reference position. By applying a pulse voltage to the probe 2 by the transmission pulser 3, an ultrasonic wave is incident on the subject 1 and an echo is received by the same probe 2. The received echo is amplified by the amplification circuit 4 and sent to the peak detection circuit 7. The peak detection circuit 7 detects the peak of the echo within the gate set to receive the shape echo P _e by the gate generation circuit 5, that is, the peak of the shape echo P _e , and stores it in the peak memory 10 at the initial position. Next, the switching circuit 6 connects the peak detection circuit 7 and the division circuit 11. The probe 2 is scanned in the direction of arrow AR in FIG. The operation up to the peak detection circuit 7 is the same as described above. The peak of the shape echo P _e at the new installation position of the probe 2 is sent to the division circuit 11. In the division circuit 11, the ratio P between the peak P _ei-1 stored in the peak memory 10 at the initial position and the current peak P _{ei
Ask for ei-1} / P _ei . If the inspection of the initial position is defective (or not) and the current inspection is also defective (or not), the result of the division circuit 11 is 1. On the other hand, if the inspection of the initial position is not defective (or is present) and the current inspection is defective (or not), the result of the division circuit 12 is other than 1. The defect presence / absence determining circuit 13 determines that there is a defect when the result (P _ei-1 / P _ei ) of the dividing circuit 13 is other than 1 or outside a preset range.

Another embodiment is shown in FIG. Move the probe 2 from the reference position to L
It is installed at a remote position, and a pulse voltage is applied to the probe 2 by the transmission pulser 3 so that an ultrasonic wave is incident on the DUT 1. The echo from the device under test 1 is amplified by the amplification circuit 4 and sent to the peak detection circuit 7. The peak detector circuit 7 determines the peak of the echo in the gate shape echo P _e in the gate generating circuit 5 is set at can be received. This peak
It is stored in the peak memory 10 at the previous position. The control circuit 14 and the probe scanning device 13 scan the probe 2 in the direction of the arrow AR in FIG. 4 while keeping the distance L from the reference position fixed. The probe position detecting device 15 sends the position of the probe 2 to the display device 17, and outputs a signal indicating that the position of the probe 2 has changed.
Send to D-gate 9. The peak of the shape echo P _e at the new position is sent to the peak memory 10 and division circuit 11 at the previous position. However, the memory contents of the peak memory 10 at the previous position have not been updated yet. The divider circuit 11 divides the peak shape echo P _e at the position before being stored in the peak memory 10 of the position before the peak shape echo P _e at the new position. When the division is completed, a signal indicating that the division is completed is sent to the AND gate 9. Defect presence / absence determination circuit 12
Then, the presence / absence of a defect is determined based on the division result of the division circuit 11. That is, similar to the embodiment of FIG. 10, if the division result is other than 1 or is outside the preset range, it is determined that there is a defect. When it is determined that there is a defect, the probe 2 sent from the probe position detection circuit 15 on the display device 17
Display that there is a defect in the position of. On the other hand, the AND gate 9 takes the logical product of the probe position change signal sent from the probe position detection circuit 15 and the division end signal sent from the division circuit 11, and both signals are at level "1". At this time, level "1" is output. The output signal from this AND gate 9 is
It serves as a probe position change signal of the probe position detection circuit 15 and a reset signal of the peak memory 10 at the previous position. That is, this signal updates the memory contents in the peak memory 10 at the previous position to the peak of the shape echo P _e at the new position. The above is repeated each time the probe 2 is scanned to a new position. This has the advantages that the switching circuit 6 is not required and that the defect position can be automatically obtained.

Another embodiment is shown in FIG. In the embodiment shown in FIG. 11, since the number of the probe 2 is one, it is necessary to store the peak of the shape echo P _e at the position in front of the probe 2. This memory is eliminated in the embodiment shown in FIG. Prepare another set of the same probe 2, amplifier 4, and peak detection circuit 7 that have been used up to now, and set probe 2A from probe 2 to the arrow AR in FIG.
Install them so that the ultrasonic waves from both probes do not interfere with each other in the direction of. The operation up to the peak detection circuit 7, 7A is the same as described above. The division circuit 11 calculates the peak ratio of the shape echo P _e at the positions of the probes 2 and 2 ′. If both positions are positions without defects or positions with defects, the result of the division circuit 11 is 1, and if either position is a position without defects and the other position is a position with defects. , The result of the division circuit 11 is different from 1. Therefore, the defect presence / absence determination circuit 12 determines that there is a defect when the result of the division circuit 12 is other than 1 or is outside the preset range.

Another embodiment is shown in FIG. In the above examples, only the presence / absence of defects is judged. As described above, from FIG. 8, it is possible to determine the size of the defect from the value of the ratio P _e / P _e1 of the echo P _e having the defect shape and the shape echo P _e1 having no defect. Recognize. That is, large values of P _e / P _e1 when defect is small, a small value of P _e / P _e1 when defect is large. . In the embodiment shown in FIG. 13, the defect size is determined from the value of P _e / P _e1 . Basically, the defect size determination circuit 17 and the display circuit 16 are added to the embodiment of FIG. The switching circuit 6 connects the peak detection circuit 6 and the peak memory 10 at a position where there is no defect, and uses a standard object to be inspected or a part of the object to be inspected which is confirmed to be free of defects, The peak of the shape echo P _e when there is no defect is stored in the peak memory 10 at the position where there is no defect. Next, the switching circuit 16 connects the peak detection circuit 7 and the division circuit 11. The division circuit 11 divides the peak of the shape echo P _e obtained by scanning the probe 2 away from the reference position in the direction of arrow AR and the memory content of the peak memory 10 at the position where there is no defect. The result is 1
Other than the above or outside the preset range, if there is a defect, the defect presence / absence determination circuit 12 determines. The defect size measuring circuit 17 obtains the size of the defect from the value of P _e / P _e1 . The relationship between the values of the defect dimensions P _e / P _e1 must be obtained in advance by experiments or calculations. For example, the characteristic shown in FIG. 6 is used. The presence or absence of a defect and the measurement result of the defect size are displayed on the display device 16.

Figure 14 is an example of an experiment using a computer. This example is the eleventh
It corresponds to the embodiment of the figure. The newly added parts are the A / D converter 20, the interface 18, and the computer 19. The A / D converter 20 selects the outputs of the transmission pulser 3 and the amplification circuit 4 and takes in and performs AD conversion. The interface 18 performs various connection controls. The computer 19 forms the center of the processing, and its detailed flow is shown in FIG.

It goes without saying that the embodiment using a computer can be applied to the other embodiments described above.

〔The invention's effect〕

According to the present invention, when a defect is present, focusing on the reflected wave (shape echo) from the shape in which the defect blocks the incident ultrasonic wave,
Since the presence / absence of a defect can be determined from the change in the intensity of the shape echo, the presence / absence of a defect can be reliably determined even when the object to be inspected is complicated and the defect echo and the shape echo of a part overlap each other, making it difficult to distinguish. is there. In addition, since the intensity ratio of the shape echo to the sound portion is close to the defect size, the defect size can be obtained.

[Brief description of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 and FIG. 3 are explanatory views of a conventional method, FIG. 4 is a view showing inspection conditions and defect shapes, FIG. 5, FIG. 6, FIG. , FIG. 8 is a diagram for explaining the contents of the method of the present invention, FIG. 9 is a diagram of the signal waveform of FIG. 1, and FIG.
FIG. 11, FIG. 12, FIG. 12 and FIG. 13 are other embodiments of the present invention,
FIG. 14 is an embodiment diagram of using a computer, and FIG. 15 is its flow chart. 1 ... Inspected object, 2 ... Probe, 3 ... Transmission pulser, 4
...... Amplification circuit, 5 ...... Gate generation circuit, 6 ...... Switching circuit, 7 ...... Peak detection circuit, 8 ...... Wave height valve circuit, 9 ......
AND gate, 10 ... Peak memory, 11 ... Division circuit, 12
... Defect presence / absence determination circuit, 13 ... Probe scanning device, 14 ...
... Control circuit, 15 ... Probe position detection circuit, 16 ... Display device, 17 ... Defect size determination circuit.

Claims (6)

[Claims] 1. A reflected wave from a processed uneven portion in an object to be inspected in which an incident ultrasonic wave is blocked by a defect is extracted within a propagation time range in which a preset reflected wave can be received, and a defect is obtained by the extracted reflected wave intensity. In the ultrasonic inspection method for detecting the defect, the intensity of the reflected wave from the processed uneven portion having no defect is compared with the intensity of the reflected wave from the processed uneven portion at an arbitrary position, and the size-related defect determination is performed. 2. A timing for outputting a gate signal in accordance with a transmission timing at a time when a probe for transmitting / receiving ultrasonic waves and a reflected wave from a processed uneven portion in a body under inspection where a defect blocks incident ultrasonic waves can be received. Means, peak detecting means for obtaining the maximum intensity of the reflected wave obtained by the gate signal by the timing means, reflected wave intensity from the processing uneven portion having no defect obtained by the peak detecting means, and processing received at an arbitrary position An ultrasonic inspection apparatus comprising: a determination unit that compares the peaks of the intensity of reflected waves from the uneven portion and determines the presence of a defect based on the magnitude relationship between the peaks. 3. A timing for outputting a gate signal according to a transmission timing at a time when a probe for transmitting / receiving an ultrasonic wave and a reflected wave from a processed uneven portion in a body under inspection where a defect blocks an incident ultrasonic wave can be received. Means, peak detecting means for obtaining the maximum intensity of the reflected wave obtained by the gate signal by the timing means, and maximum intensity obtained by the peak detecting means is the maximum of the reflected wave from the processing uneven portion having no defect obtained in advance. A means for gradually dividing by the strength, a means for judging a defect from the result of this division, a relationship between the result of the division and the defect size obtained in advance, and the result of the division obtained are compared to determine the defect size. An ultrasonic inspection apparatus comprising a means for obtaining and an ultrasonic inspection apparatus. 4. A gate signal is output in accordance with a transmission timing at a time when a probe for transmitting / receiving ultrasonic waves and a reflected wave from a processed uneven portion in a test object where a defect interrupts incident ultrasonic waves can be received. The timing means, the peak detection means for obtaining the maximum intensity of the reflected wave obtained by the gate signal by the timing means, and the peak value of the reflected wave intensity from the processing uneven portion having no defect previously obtained by the peak detection means As a threshold value, a wave height discriminating means for obtaining a magnitude relationship between the threshold value and the intensity of the reflected wave from the processed uneven portion received at an arbitrary position,
An ultrasonic inspection apparatus comprising: a determination unit that determines the presence of a defect based on the magnitude relationship. 5. A gate signal is output in accordance with a transmission timing at a time when a probe for transmitting / receiving ultrasonic waves and a reflected wave from a processed uneven portion in a body under inspection where a defect blocks incident ultrasonic waves can be received. Timing means, peak detecting means for obtaining the maximum intensity of the reflected wave obtained by the gate signal by the timing means, and the reflected wave intensity at the initial probe position or the previous probe position obtained by the peak detecting means. Peak storage means for storing a peak, division means for obtaining a ratio between the peak value stored in the peak storage means and the peak value of the reflected wave intensity received at an arbitrary probe position, and the presence of a defect from the division result. An ultrasonic inspection apparatus comprising: a determination unit for determining 6. A gate signal according to a transmission timing at a time when two probes for transmitting and receiving ultrasonic waves and a reflected wave from a processed uneven portion in a body under inspection where a defect blocks incident ultrasonic waves can be received. And a maximum intensity of the reflected wave obtained from the gate signal by the timing means 2
Number of peak detection means, division means for obtaining a ratio of two peak values of reflected wave intensities from the processed uneven portion in the inspected body obtained by the two peak detection means, and existence of a defect from the division result. An ultrasonic inspection apparatus comprising: a determination unit for determining