JP7213511B1 - ULTRASOUND INSPECTION METHOD, ULTRASOUND INSPECTION DEVICE AND PROGRAM - Google Patents

Abstract

Kind Code: A1 A waveform of unnecessary frequency components such as lateral waves propagating on the surface of an object to be inspected from a received waveform received from the object to be inspected when performing ultrasonic inspection by transmitting an ultrasonic signal to the object to be inspected. erase. An ultrasonic wave transmitting unit 32 transmits, as an input waveform, an ultrasonic wave signal that becomes a Gabor wavelet waveform when autocorrelation is calculated from a transmitting probe 33 to an inspection object. Then, the ultrasonic wave receiving unit 34 receives the ultrasonic wave signal reflected or diffracted by the object to be inspected by the receiving probe 35 . Then, the control unit 31 performs cross-correlation calculation between the received waveform received by the receiving probe 35 and the input waveform to pulse-compress the received waveform in the direction of the time axis, and displays it on the display unit 36 . . [Selection drawing] Fig. 1

Description

The present invention relates to an ultrasonic inspection method, an ultrasonic inspection apparatus, and a program.

A TOFD (Time of Flight Diffraction) method is used as one of ultrasonic flaw detection techniques used in non-destructive inspection of structures (for example, Non-Patent Document 1). In this TOFD method, an ultrasonic pulse signal is transmitted from a transmitting probe to an inspection object such as a welded portion, and an ultrasonic signal reflected or diffracted by the inspection object is received by a receiving probe. The received waveform is inspected for defects and the like. According to such a TOFD method, when a defect exists inside the object to be inspected, the presence of the defect can be detected by generating a reflected wave or a diffracted wave at the defect.

Yu Kurokawa, Yoshihiro Mizutani, Hirotsugu Inoue, "Advancement of Defect Height Measurement by TOFD Method Using Time-Frequency Analysis", Nondestructive Inspection, 2006, vol.55, no.12, pp.635-642

In such a flaw detection inspection method by the TOFD method, there may be a problem in the presence of a lateral wave in which the ultrasonic wave transmitted from the transmitting probe propagates on the surface of the inspection object and is received by the receiving probe. . Specifically, when a defect exists in the vicinity of the surface of the inspection object, the lateral wave overlaps with the diffracted wave from the defect, causing a problem of difficulty in identifying the diffracted wave. Thus, if it becomes difficult to identify the diffracted wave from the defect, the defect cannot be detected correctly, and the vicinity of the surface becomes a dead zone in which the defect cannot be detected.

If a correct inspection is to be performed in the presence of such a dead zone, it is necessary to inspect both sides of the object to be inspected, resulting in an increase in inspection time and inspection costs.

The present invention extracts unnecessary frequency components such as lateral waves propagating on the surface of an object to be inspected from a received waveform received from the object to be inspected when performing ultrasonic inspection by transmitting an ultrasonic signal to the object to be inspected. An object of the present invention is to provide an ultrasonic inspection method, an ultrasonic inspection apparatus, and a program capable of erasing waveforms.

In the ultrasonic inspection method according to the first aspect of the present invention, an ultrasonic signal that becomes a Gabor wavelet waveform when autocorrelation is calculated is transmitted as an input waveform from a transmission probe to an inspection object. ,
receiving an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
By performing a cross-correlation operation between the received received waveform and the input waveform, the received waveform is compressed in the direction of the time axis and displayed.

A second aspect of the ultrasonic inspection method of the present invention is the ultrasonic inspection method of the first aspect, wherein the waveform of the Gabor wavelet has characteristics such that a specific frequency component is localized within a short time interval. , which is a waveform that does not contain the frequency component of the lateral wave propagating on the surface of the inspection object.

An ultrasonic inspection method according to a third aspect of the present invention transmits an ultrasonic signal having a Gabor wavelet waveform as an input waveform from a transmission probe to an inspection object,
receiving an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
Display the received received waveform.

An ultrasonic inspection apparatus according to a fourth aspect of the present invention includes a transmission unit that transmits an ultrasonic signal, which becomes a Gabor wavelet waveform when autocorrelation is calculated, as an input waveform from a transmission probe to an inspection object;
a receiving unit that receives an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
and a display unit for compressing the received waveform in the direction of the time axis and displaying the received waveform by performing cross-correlation calculation between the received waveform and the input waveform.

An ultrasonic inspection apparatus according to a fifth aspect of the present invention includes a transmission unit that transmits an ultrasonic signal having a Gabor wavelet waveform as an input waveform from a transmission probe to an inspection object;
a receiving unit that receives an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
and a display for displaying the received received waveform.

A program according to a sixth aspect of the present invention comprises a step of transmitting, as an input waveform, an ultrasonic signal that produces a Gabor wavelet waveform when autocorrelation is calculated, from a transmission probe to an object to be inspected;
receiving an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
and a step of compressing the received waveform in the direction of the time axis and displaying the received waveform by performing a cross-correlation operation between the received received waveform and the input waveform.

According to the present invention, when performing ultrasonic inspection by transmitting an ultrasonic signal to the inspection object, from the received waveform received from the inspection object, unnecessary frequencies such as lateral waves propagating on the surface of the inspection object It becomes possible to erase the waveform of the component.

1 is a block diagram showing the configuration of an ultrasonic inspection apparatus 10 according to one embodiment of the present invention; FIG. It is a figure for demonstrating the flaw detection principle by general TOFD method. FIG. 2 is a schematic diagram of received waveform data obtained by the TOFD method; FIG. 10 is a diagram showing a state in which a defect exists in the vicinity of the surface on which the transmitting probe 33 and the receiving probe 35 are installed; FIG. 5 is a schematic diagram of received waveforms in the state as shown in FIG. 4; 1 is a schematic diagram for explaining a TOFD method using pulse compression technology; FIG. FIG. 10 is a diagram showing an example of an input waveform x(t) that becomes a Gabor wavelet when autocorrelation is calculated; Figure 8 shows a received waveform y(t) obtained using an input waveform x(t) as shown in Figure 7; FIG. 9 is a diagram showing a received waveform z(t) after pulse compression of the received waveform y(t) shown in FIG. 8; FIG. 8 is a diagram showing the flow of a series of simulation processes using the input waveform x(t) of FIG. 7; FIG. 8 is a diagram showing a waveform obtained by pulse-compressing the input waveform x(t) shown in FIG. 7; It is a figure which shows the simulation result at the time of performing TOFD method by making the waveform of a Gabor wavelet into an input waveform.

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an ultrasonic inspection apparatus 10 according to one embodiment of the present invention.

As shown in FIG. 1, the ultrasonic inspection apparatus 10 of this embodiment includes a control unit 31, an ultrasonic transmission unit 32, a transmission probe 33, an ultrasonic reception unit 34, and a reception probe 35. , and a display unit 36 .

Under the control of the control unit 31 , the ultrasonic transmission unit 32 transmits an ultrasonic signal as an input waveform from the transmission probe 33 to the inspection object.

The ultrasonic receiver 34 receives ultrasonic signals reflected or diffracted by the object to be inspected by the receiving probe 35 and transfers them to the controller 31 .

The control unit 31 displays the ultrasonic signal transferred from the ultrasonic wave receiving unit 34 on the display unit 36 .

First, before explaining the operation of the ultrasonic inspection apparatus 10 of this embodiment, FIG. 2 shows the principle of flaw detection by a general TOFD method.

When looking for defects such as scratches in an inspection object by the TOFD method, an ultrasonic pulse signal is transmitted from the transmission probe 33 to the inspection object such as a welded part, and reflected or diffracted by the inspection object. The presence or absence of defects is inspected based on the received waveform of the ultrasonic signal received by the receiving probe 35 .

In this TOFD method, when a defect exists inside the object to be inspected, the existence of the defect can be detected by generating a diffracted wave from the defect. FIG. 3 shows a schematic diagram of received waveform data obtained by the TOFD method.

The receiving probe 35 first detects a lateral wave 41 propagating on the surface, and then detects diffracted waves 42 and 43 from the upper and lower ends of the defect, respectively, if a defect exists. Finally, a back surface reflected wave 44, which is a reflected wave from the back surface, is detected.

In such a flaw detection inspection method based on the TOFD method, the existence of the lateral wave 41 may pose a problem. For example, FIG. 4 shows a state in which a defect exists in the vicinity of the surface on which the transmitting probe 33 and the receiving probe 35 are installed. FIG. 5 shows a schematic diagram of received waveforms in the state shown in FIG.

Referring to FIG. 5, when a defect exists near the surface, the lateral wave 41 overlaps the diffracted waves 42 and 43 from the defect, making it difficult to distinguish between the diffracted waves 42 and 43. I understand. When it becomes difficult to distinguish the diffracted waves 42 and 43 from the defect in this manner, the defect cannot be detected correctly, and the vicinity of the surface becomes a dead zone in which the defect cannot be detected.

If a correct inspection is to be performed in the presence of such a dead zone, it is necessary to inspect both sides of the object to be inspected, resulting in an increase in inspection time and inspection costs.

Here, the lateral wave 41 propagating on the surface of the inspection object and the diffracted waves 42 and 43 from the defect have different frequency bands. For example, when the frequency of the input waveform is 5 MHz, the main frequency components of the lateral waves are concentrated at 1-3 MHz, and the main frequency components of the diffracted waves are concentrated at 3-7 MHz.

Therefore, in order to solve the above problems, the ultrasonic inspection apparatus 10 according to the present embodiment uses a method described below to transmit ultrasonic signals from the transmission probe 33 to the inspection object. By optimizing the input waveform, lateral waves in the received waveform are eliminated.

First, before describing the ultrasonic inspection method according to the present embodiment, the pulse compression technique will be described with reference to FIG. FIG. 6 is a schematic diagram for explaining the TOFD method using the pulse compression technique.

Pulse compression technology increases the transmission energy without increasing the peak voltage by expanding the input waveform in the direction of the time axis, and compresses the received waveform in the direction of the time axis to reduce the SN ratio while maintaining the spatial resolution. It is a technique to improve. Here, the SN ratio means the ratio between the diffracted wave component due to a defect or the like and the noise component in the received waveform.

In the TOFD method using pulse compression technology, the input waveform x(t) is a waveform expanded in the time axis direction, and this input waveform x(t) is transmitted from the transmission probe 33 to the inspection object. Then, the receiving probe 35 receives an ultrasonic signal from the object to be inspected. Then, pulse compression is performed on the received waveform y(t) by performing a cross-correlation operation between the received waveform y(t) and the input waveform x(t). Specifically, pulse compression is performed by convoluting the received waveform y(t) and the time-reversed conjugate of the input waveform x(t). That is, the waveform z(t) after pulse compression is expressed as z(t)=y(t)*x(-t).

Then, in the TOFD method using this pulse compression technique, an input waveform that eliminates the lateral wave was examined. It was found that lateral waves can be eliminated in the TOFD method using the technique.

An example of such an input waveform x(t) is shown in FIG.

FIG. 8 shows the received waveform y(t) obtained by the simulation shown in FIG. 6 using the input waveform x(t) shown in FIG. Then, when the received waveform y(t) shown in FIG. 8 was pulse-compressed to obtain the received waveform z(t) after pulse compression, the result is as shown in FIG. FIG. 10 shows the flow of a series of simulation processes using the input waveform x(t) of FIG. 7 as described above.

Referring to the received waveform z(t) after pulse compression in FIG. 9, it can be seen that the lateral wave has almost disappeared and is significantly smaller than the diffracted wave. In other words, even if a defect exists in the vicinity of the surface of the object to be inspected, it can be sufficiently detected.

It is possible to eliminate the lateral wave component in the received waveform by executing the flaw detection inspection method by the TOFD method using as the input waveform x(t) a waveform that becomes a Gabor wavelet when the autocorrelation is calculated in this way. becomes. Therefore, the ultrasonic inspection apparatus 10 of the present embodiment performs flaw detection inspection on the inspection object using the input waveform x(t) as shown in FIG.

That is, when the TOFD method using the pulse compression technique is performed, the ultrasonic wave transmission unit 32 receives an ultrasonic signal having a Gabor wavelet waveform as an input waveform from the transmission probe 33 when the autocorrelation is calculated. Send to things. Then, the ultrasonic wave receiving unit 34 receives the ultrasonic wave signal reflected or diffracted by the object to be inspected by the receiving probe 35 . Then, the control unit 31 performs cross-correlation calculation between the received waveform received by the receiving probe 35 and the input waveform to pulse-compress the received waveform in the direction of the time axis and displays it on the display unit 36 . .

Waveforms that become Gabor wavelets when autocorrelation is calculated include not only waveforms that completely match Gabor wavelets when autocorrelation is calculated, but also waveforms that approximate Gabor wavelets when autocorrelation is calculated. In other words, it also includes waveforms whose autocorrelation calculations result in approximately (approximately) Gabor wavelets.

Furthermore, although the TOFD method using the pulse compression technique has been described above, the present invention is also applicable to the TOFD method that does not use the pulse compression technique.

A TOFD method that does not use a pulse compression technique uses, as an input waveform, a pulse signal that is not expanded in the direction of the time axis. Therefore, FIG. 11 shows a waveform obtained by pulse-compressing the input waveform x(t) shown in FIG. When the input waveform x(t) is pulse-compressed, the cross-correlation operation between the same input waveform x(t) is calculated, and as a result, the input waveform x(t) self Correlation calculation is performed.

The waveform thus obtained is a Gabor wavelet waveform and does not contain the frequency component of the lateral wave propagating on the surface of the inspection object. The waveform of the Gabor wavelet is a waveform having characteristics such that specific frequency components are localized within a short time interval.

That is, the input waveform x(t) shown in FIG. 7 is an ultrasonic signal that becomes a Gabor wavelet waveform when the autocorrelation is calculated.

When the TOFD method that does not use the pulse compression technique is performed, the ultrasonic transmission unit 32 transmits an ultrasonic signal having a Gabor wavelet waveform as an input waveform from the transmission probe 33 to the inspection object. Then, the ultrasonic wave receiving unit 34 receives the ultrasonic wave signal reflected or diffracted by the object to be inspected by the receiving probe 35 . Then, the control unit 31 displays the received waveform received by the receiving probe 35 as it is on the display unit 36 .

FIG. 12 shows a simulation result when the TOFD method is performed using the Gabor wavelet waveform as an input waveform.

Even in this case, a waveform similar to the received waveform z(t) after pulse compression is obtained as the received waveform y(t). However, in this case, there is a demerit that the signal-to-noise ratio deteriorates because the pulse compression technique is not used.

According to the ultrasonic inspection method of the present embodiment described above, when performing ultrasonic inspection by transmitting an ultrasonic signal to the inspection object, from the received waveform received from the inspection object, the surface of the inspection object can eliminate lateral waves propagating However, the present invention is not limited to erasing lateral waves from a waveform received from an object to be inspected. The present invention can be used not only when performing ultrasonic inspection by transmitting ultrasonic signals to an object to be inspected, but also when investigating ultrasonic wave propagation characteristics for each frequency for high attenuation materials such as porous materials. It can be applied, and an effect can be obtained that waveforms of unnecessary frequency components contained in received waveforms can be eliminated.

Furthermore, according to the present invention, it is possible to obtain an effect that it becomes possible to transmit and receive elastic waves of a specific frequency with a high SN ratio.

REFERENCE SIGNS LIST 10 Ultrasound inspection device 31 Control unit 32 Ultrasound transmission unit 33 Transmission probe 34 Ultrasound reception unit 35 Reception probe 36 Display unit 41 Lateral waves 42, 43 Diffracted waves 44 Backside reflected waves 70 TOFD method experimental apparatus

Claims (4)

An ultrasonic signal that produces a Gabor wavelet waveform when the autocorrelation is calculated is transmitted as an input waveform from the transmission probe to the inspection object,
receiving an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
compressing the received waveform in the direction of the time axis and displaying the received waveform by performing cross-correlation calculation between the received waveform and the input waveform;
Ultrasound method. The waveform of the Gabor wavelet is a waveform having characteristics such that specific frequency components are localized within a short time interval, and is a waveform that does not include the frequency component of the lateral wave propagating on the surface of the inspection object. Item 1. The ultrasonic inspection method according to item 1. a transmission unit that transmits an ultrasonic signal, which becomes a Gabor wavelet waveform when autocorrelation is calculated, as an input waveform from the transmission probe to the inspection object;
a receiving unit that receives an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
a display unit for compressing and displaying the received waveform in the direction of the time axis by performing cross-correlation calculation between the received waveform and the input waveform;
Ultrasound inspection equipment with. a step of transmitting, as an input waveform, an ultrasonic signal whose autocorrelation results in a Gabor wavelet waveform from the transmission probe to the inspection object;
receiving an ultrasonic signal reflected or diffracted by the inspection object with a receiving probe;
a step of compressing the received waveform in the direction of the time axis and displaying the received waveform by performing a cross-correlation operation between the received waveform and the input waveform;
A program that causes a computer to run

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