JP5847010B2 - Nondestructive inspection apparatus and nondestructive inspection method - Google Patents

Description

  The present invention relates to a nondestructive inspection apparatus and a nondestructive inspection method, and more particularly to a nondestructive inspection apparatus and a nondestructive inspection method for inspecting using a guide wave.

Steel cylindrical tanks that store liquids, etc., are affected by the environment in which they are used, and over time, deterioration progresses with corrosion and erosion from the inner surface or outer surface of the barrel, reducing the barrel. May be meat.
In areas where corrosion and erosion are likely to occur, deterioration will cause accidents leading to leakage or rupture of tank contents, so operators should regularly conduct visual inspections and non-destructive inspections using ultrasound. By doing so, accidents are prevented and maintenance of the integrity of the tank is ensured.

As a non-destructive inspection using ultrasonic waves that has been widely used, an ultrasonic thickness gauge is generally used, but has several problems.
The ultrasonic thickness gauge is a single point inspection in which a person measures the thickness of the contact surface between the sensor and the subject point by point, so the inspection range is narrow, tank inspection with a large surface area, and large diameter pipe inspection. Takes a long time, resulting in increased inspection costs. Also, in the measurement of places where it is difficult for humans to enter, for example, in the measurement of the low part and narrow part of the subject installed in the high part or pit, some countermeasures will be taken, It takes time to prepare for the inspection, and as a result, the inspection cost increases.

Therefore, Patent Document 1 discloses a nondestructive inspection apparatus and a nondestructive inspection method using a guide wave which is a kind of ultrasonic wave.
Guide waves are ultrasonic waves that propagate through an object having a boundary surface between a pipe and a plate, and use a characteristic that reflects at a portion where the thickness or shape of the plate changes, that is, a portion where the cross-sectional area in the thickness direction changes. In addition, it is used in a method for inspecting pipes and plate-like inner and outer surfaces together in a long distance section.

In the non-destructive inspection technique by propagating the guide wave, the single mode guide wave used in the guide wave inspection propagates through the object surface over a long distance section and is partially reflected at the part where the shape has changed, Further, most of the signal propagates in the transmission direction with a single mode. This is a technique that can estimate the reflected position and the reflected size by receiving and analyzing various reflected signals reflected in the process of propagation.
The nondestructive inspection apparatus and the nondestructive inspection method using the guide wave of Patent Document 1 are arranged in part along the circumferential direction without depending on the diameter of the cylindrical member, and are parallel to the axial direction of the cylindrical member. Alternatively, an apparatus and an inspection method for inspecting defects by transmitting at an angle have been proposed.

  In the non-destructive inspection method of Patent Document 2, a plurality of probes are arranged in an array to form a phased array probe, and each probe group is sequentially switched to change the incident angle of an ultrasonic transmission wave. A phased array probe method has been proposed in which the height of a defect is evaluated by specifying a probe group that transmits an ultrasonic wave corresponding to the received reflected wave.

JP 2009-109390 A JP 2003-028845 A

  A guide wave, which is a type of ultrasonic wave, propagates through the subject surface over a long distance and changes its shape (for example, a portion whose thickness changes due to the thickness of the tank body being reduced by corrosion). By using the characteristic that guide waves are reflected at, the reflected wave of the guide wave that is transmitted and propagated through the subject surface is received and the received signal is analyzed to determine the position of the reflection spot and the size of the reflection spot. Estimated.

  By the way, in general, a large tank is manufactured in a cylindrical shape by bending several plate materials and connecting them by welding. The joint weld, which is a welded portion of the tank, is linear and has been built up at almost the same height, so that the shape change occurs thicker than the plate thickness. Therefore, when the guide wave transmitted and propagated from the guide wave sensor passes through the weld (hereinafter referred to as the weld line), a part of the guide wave is reflected, and the remaining guide wave passes through the weld line. To propagate in the transmission direction.

In such a large tank having a weld line, when the corrosion progresses during use of the tank and thinning (hereinafter referred to as a defect) is generated in the vicinity of the weld line, the guide wave is Reflected by the part and the defective part and received as a reflected signal.
For this reason, in the nondestructive inspection methods of Patent Document 1 and Patent Document 2, when a defect is formed in the vicinity of the weld line, the reflected signal of the weld line part and the reflected signal of the defective part are received and detected in an overlapping manner, It is difficult to determine the defect signal by classifying both signals.
Also, since the shape change area of the weld line is larger than the defect shape change area, the reflected signal of the weld line is larger than the reflected signal of the defective part, and detection of the reflected signal from the defect near the weld line is detected. Making it more difficult.

  Then, this invention makes it a subject to provide the nondestructive inspection apparatus and the nondestructive inspection method which can detect suitably the defect produced | generated in the welding part vicinity.

  In order to solve such problems, the present invention provides a guide wave sensor having two rows of ultrasonic probe arrays in which a plurality of ultrasonic probes are arranged at equal intervals on the wall surface of a subject. A non-destructive inspection apparatus for transmitting and propagating a guide wave, receiving a reflected signal of the guide wave, and detecting a defect of the object, wherein the guide wave is transmitted from a welding line formed on the object. An attenuation calibration curve acquisition means for acquiring an attenuation calibration curve from first inspection data obtained by transmitting and propagating perpendicularly to the direction and receiving a reflected signal of the guide wave, and at a significant signal level from the attenuation calibration curve; A signal threshold value setting means for setting a signal threshold value of a reflected signal that can be detected, and a guide wave transmitted obliquely from the guide wave sensor to the direction of the weld line by phased array transmission to propagate the reflected signal of the guide wave Receive the second A reflection signal obtaining means for obtaining 査 data, non-destructive inspection apparatus characterized by comprising a defect evaluation means for evaluating the defect from the second test data and the signal threshold.

  In the present invention, a guide wave sensor having two rows of ultrasonic probe arrays in which a plurality of ultrasonic probes are arranged at equal intervals is installed on the wall surface of a subject, and a guide wave is transmitted. A nondestructive inspection method of a nondestructive inspection apparatus for propagating and receiving a reflected signal of the guide wave to detect a defect of the object, wherein the guide wave is perpendicular to a direction of a weld line formed on the object. A first step of acquiring an attenuation calibration curve from the first inspection data obtained by transmitting and propagating the reflected signal and receiving the reflected signal of the guide wave, and a reflected signal that can be detected at a significant signal level from the attenuation calibration curve. A second step of setting a signal threshold; a guide wave is transmitted obliquely from the guide wave sensor in the direction of the weld line by phased array transmission, and a reflected signal of the guide wave is received; Obtain inspection data Step a is a non-destructive inspection method characterized by and a fourth step of evaluating the defect from the second test data and the signal threshold.

  ADVANTAGE OF THE INVENTION According to this invention, the nondestructive inspection apparatus and the nondestructive inspection method which can detect suitably the defect produced | generated in the welding part vicinity can be provided.

It is a structure schematic diagram explaining the structure of the nondestructive inspection apparatus which concerns on this embodiment, the structure of the tank which is a subject, and the propagation path of a guide wave. It is a flowchart explaining the process of the nondestructive inspection method using the nondestructive inspection apparatus which concerns on this embodiment. It is a schematic diagram which shows the propagation path of the guide wave transmitted to the perpendicular direction from the guide wave sensor. (A) is a graph explaining the relationship between the reception waveform of the reflected wave from a welding line, and an attenuation calibration curve. (B) is a graph explaining the relationship between the reception waveform of the reflected wave from the weld line, the attenuation calibration curve, and the threshold curve. It is a schematic diagram which shows the propagation path of the guide wave transmitted in the diagonal direction from the guide wave sensor. It is a graph explaining the received waveform of the reflected wave in step S106. It is a schematic diagram which shows the propagation path of the guide wave transmitted in the diagonal direction from the guide wave sensor which concerns on a 1st modification. It is a schematic diagram which shows the propagation path of the guide wave transmitted in the diagonal direction from the guide wave sensor which concerns on a 2nd modification. It is a schematic diagram which shows the propagation path of the guide wave transmitted to the perpendicular direction from the guide wave sensor which concerns on a comparative example. It is a graph explaining the received waveform of the reflected wave in a comparative example.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

≪Non-destructive inspection equipment≫
First, the nondestructive inspection apparatus according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram illustrating a configuration of a nondestructive inspection apparatus according to the present embodiment, a configuration of a tank that is a subject, and a propagation path of a guide wave.

As shown in FIG. 1, the nondestructive inspection apparatus includes a guide wave sensor 1 having an ultrasonic probe array 2 and an ultrasonic probe array 3 for transmitting and receiving a guide wave (ultrasound), and ultrasonic transmission / reception. A device 4 and a computer 5 are provided.
The nondestructive inspection apparatus transmits a guide wave from the guide wave sensor 1 to the tank 6 in a state where the guide wave sensor 1 is installed in the tank 6 as the subject, and the defect 7 of the tank 6 (FIG. 3 to be described later). , See FIG. 5), the guide wave sensor 1 receives the reflected wave from the tank 6 so that the defect 7 of the tank 6 can be inspected.

<Guide wave sensor 1>
The guide wave sensor 1 transmits a guide wave (for example, guide waves 21 and 41 shown in FIG. 1) when a transmission waveform (transmission signal) is applied from the ultrasonic transmitter / receiver 4, and a reflected wave (for example, FIG. 1). 5 and the reflected wave 51 shown in FIG. 5 to be described later, and the received waveform (received signal) is output to the ultrasonic transceiver 4.

  The guide wave sensor 1 has two rows of ultrasonic probe rows 2 and 3, and each of the ultrasonic probe rows 2 and 3 has a plurality of ultrasonic probes arranged equally in a row. It is configured. The interval between the ultrasonic probe array 2 and the ultrasonic probe array 3 is basically set to be separated by a distance corresponding to ¼ of the wavelength λ of the guide wave. For example, when the transmission frequency is 40 kHz and the material of the subject is a steel material, it is about 20 mm.

  Further, in order to set the guide wave in one transmission direction, transmission is performed between the ultrasonic probe of the ultrasonic probe array 2 and the ultrasonic probe of the ultrasonic probe array 3 opposed thereto. The application time of the waveform (transmission signal) is delayed by about 6.2 μs.

  Further, the nondestructive inspection apparatus according to the present embodiment applies a transmission signal to the ultrasonic probes in the same row at the same time (see FIG. 3 to be described later) and transmission applied to each ultrasonic probe. There is a case where transmission is performed by a phased array method of an electronic scan type that controls the delay time of a signal (see FIG. 5 to be described later), and the ultrasonic probe row 2 and the ultrasonic probe row 3 arranged in two rows. Can be controlled electronically by finely dividing. For this reason, the ultrasonic probe array 2 and the ultrasonic probe array 3 have the same configuration in which the same number of ultrasonic probes are connected in parallel and arranged in parallel so as to correspond one-to-one.

  The ultrasonic probe is constituted by a piezoelectric element, for example. The ultrasonic probe may be configured by a single piezoelectric element, or may be configured as a single ultrasonic probe by connecting a plurality of piezoelectric elements in parallel. The receiving piezoelectric elements may be connected in parallel to constitute a single ultrasonic probe.

  In the nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment, the guide wave sensor 1 (ultrasound probe rows 2 and 3) is an inspection target portion of the tank 6 as shown in FIG. It attaches so that it may become parallel to the direction of welding line W1 (or welding line W2) (refer step S101 shown in FIG. 2 mentioned later).

<Ultrasonic transceiver 4>
In order to transmit a guide wave from the guide wave sensor 1 on the basis of a guide wave transmission command from the computer 5, the ultrasonic transmitter / receiver 4 transmits a transmission waveform to each ultrasonic probe in the ultrasonic probe rows 2 and 3 ( Transmission signal) can be applied. Further, the reception waveform (reception signal) of the reflected wave received by each of the ultrasonic probes in the ultrasonic probe rows 2 and 3 can be output to the computer 5.

  For this reason, the ultrasonic transmitter / receiver 4 includes a transmitter / receiver controller 10, a signal generator 11, a power amplifier 12, a received signal switching unit 13, a receiver amplifier 14, and a high-speed A / D converter 15. I have. Here, the transceiver control unit 10, the signal generation unit 11, and the power amplifier 12 transmit a transmission waveform (transmission signal) to each corresponding ultrasonic probe of the guide wave sensor 1 (ultrasonic probe rows 2 and 3). It functions as an ultrasonic transmitter for applying. Further, the transceiver control unit 10, the reception signal switching unit 13, the receiver amplifier 14, and the high-speed A / D conversion unit 15 are transmitted from each ultrasonic probe of the guide wave sensor 1 (ultrasound probe rows 2 and 3). The received reception waveform (reception signal) is amplified, converted into a digital signal, and functions as an ultrasonic reception unit that outputs to the computer 5.

  The transceiver control unit 10 causes the signal generation unit 11 to generate an excitation signal based on a guide wave transmission command from the computer 5. The excitation signal generated by the signal generator 11 is amplified by the power amplifier 12, and each ultrasonic probe corresponding to the guide wave sensor 1 (ultrasound probe rows 2 and 3) is transmitted as a transmission waveform (transmission signal). Is output. The transceiver control unit 10 can control the timing at which each ultrasonic probe is excited by controlling the timing at which the signal generator 11 generates the excitation signal.

Also, the received waveform (received signal) of the reflected wave received by each ultrasonic probe of the guide wave sensor 1 (ultrasound probe rows 2 and 3) is received by the receiver amplifier 14 via the received signal switching unit 13. Amplified and converted into a digital signal by the high-speed A / D converter 15.
The reception waveform (reception signal) of the reflected wave is output from the transceiver controller 10 to the computer 5 as a digital signal.

<Computer 5>
The computer 5 includes a display unit 16, a transmission time difference setting unit 17 that sets a delay in application time of each ultrasonic probe, a received waveform processing calculation unit 18 a, a data storage unit 18 b, and a control unit 19. The entire nondestructive inspection apparatus can be controlled by being communicably connected to the transmitter / receiver controller 10 of the ultrasonic transmitter / receiver 4.

  The computer 5 includes, for example, a ROM (Read Only Memory) (not shown) in which an initial boot program is stored when the power is turned on, a RAM (Random Access Memory) (not shown) used as a working memory. An HDD (Hard Disc Drive) (not shown) that stores an OS (Operations System), various application programs, and the like and functions as the data storage unit 18b, and a CPU (Central Processing Unit) (not shown) as a central processing unit Etc.), and a CPU (not shown) functions as the transmission time difference setting unit 17, the reception waveform processing calculation unit 18a, and the control unit 19 by executing various application programs.

<< Configuration of subject (tank 6) >>
Next, the configuration of the tank 6 that is the subject in the nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment will be described.
The tank 6 is a container composed of a cylindrical body part and a mirror part arranged above and below. The body of the tank 6 is formed by welding a plurality of metal plates. For this reason, the trunk | drum of the tank 6 has the welding lines W1 and W2 of an axial direction (up-down direction in the paper surface of FIG. 1). In addition, in FIG. 1, although the welding line of the axial direction is illustrated as what is two (welding line W1, W2), it is not restricted to this, There may be three or more.
In addition, the subject in the nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment is described as being the tank 6, but is not limited thereto, and is a cylindrical structure such as a large-diameter pipe. Can be widely applied to.

≪Non-destructive inspection method using non-destructive inspection equipment≫
Next, a nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart for explaining processing of a nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment.

In step S <b> 101, the control unit 19 of the computer 5 causes the display unit 16 to display an instruction screen that prompts the user to attach the guide wave sensor 1 to the body of the tank 6.
The operator attaches the guide wave sensor 1 to the body of the tank 6 according to the instructions on the screen. Here, the guide wave sensor 1 is attached so as to be parallel to the direction in which the weld line W1 (or the weld line W2) of the inspection target portion of the tank 6 extends. In the example of FIG. 1, since the weld lines W1 and W2 extend in the axial direction of the tank 6, the ultrasonic probe row 2 of the guide wave sensor 1 so that the ultrasonic probes are arranged in the axial direction of the tank 6. , 3 are arranged.
When the attachment of the guide wave sensor 1 is completed, the process of the control unit 19 proceeds to step S102.

In step S <b> 102, the control unit 19 of the computer 5 sends a guide wave transmission command including delay information of the application time of each ultrasonic probe set by the transmission time difference setting unit 17 to the transmitter / receiver control unit of the ultrasonic transmitter / receiver 4. 10 and the guide wave 21 is transmitted from the guide wave sensor 1 in the vertical direction.
Then, the control unit 19 of the computer 5 converts the reflected wave received by the guide wave sensor 1 into a digital signal by the ultrasonic transceiver 4 and receives it.

  Here, the propagation path of the guide wave in step S102 will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating a propagation path of a guide wave transmitted in the vertical direction from the guide wave sensor 1 in step S102.

  The transceiver control unit 10 controls the signal generation unit 11 based on the delay information of the application time of each ultrasonic probe set by the transmission time difference setting unit 17 included in the guide wave transmission command, and each ultrasonic wave The application time of the transmission waveform (transmission signal) 20 in the probe is controlled.

Here, in order to transmit the guide wave in the direction of the welding line W1 and to increase the propagation of the guide wave, the transmission waveform (transmission signal) 20 is composed of the ultrasonic probe array 2 and the ultrasonic probe. The transmission direction is controlled by giving a delay to the application time of the child row 3. Further, in order to acquire reference reflection signals (W22 and W23 in FIG. 4 to be described later) from the weld lines W1 and W2 as reference reflection sources, the transmission waveform (transmission signal) 20 is an ultrasonic wave of the ultrasonic probe array 2. The ultrasonic probes are applied at the same time, and the ultrasonic probes in the ultrasonic probe array 3 are applied at the same time.
In this way, in the direction perpendicular to the longitudinal direction of the ultrasonic probe rows 2 and 3 from the guide wave sensor 1 (ultrasound probe rows 2 and 3) and in the direction of the welding lines W1 and W2. A guide wave 21 is transmitted.

  And the guide wave 21 reflects in the location where shapes, such as board thickness, change like the welding lines W1 and W2 which have been built up linearly at the same height. In FIG. 3, a weld line W <b> 1 that is built up at a position away from the guide wave sensor 1 by a distance L <b> 1 is thicker than the plate thickness of the body of the surrounding tank 6, so The part is reflected and propagates as a reflected wave 22 in the direction opposite to the transmission direction of the guide wave 21. The reflectivity varies depending on the shape of the overlay, but reflects about 10% or more.

The remaining guide waves 21 propagate through the welding line W1 in the transmission direction. The guide wave 21a that has passed through the weld line W1 is one of the guide waves 21a at the place where the next shape has changed, here, the weld line W2 that is built up and provided at a position away from the guide wave sensor 1 by a distance L2. The part is reflected and propagates as a reflected wave 23 in the direction opposite to the transmission direction of the guide wave 21.
Then, the remaining guide wave 21a passes through the welding line W2 and propagates in the transmission direction.

  The reflected waves 22 and 23 reflected by the welding lines W1 and W2 are received by the guide wave sensor 1, amplified by the receiver amplifier 14 of the ultrasonic transceiver 4, and converted into a digital signal by the high-speed A / D converter 15. The data is output from the transceiver control unit 10 to the computer 5.

  The digital signal of the reception waveform input to the computer 5 is processed by the reception waveform processing calculation unit 18a and displayed on the display unit 16 as the reception waveform S1 (see FIG. 4A). 4A, the vertical axis represents the amplitude (signal intensity) of the reflected wave, and the horizontal axis represents the propagation time from the transmission of the guide wave from the guide wave sensor 1 to the reception of the reflected wave and the propagation of the guide wave. It is the distance from the guide wave sensor 1 calculated from the velocity to the reflection source. The received waveform S1 is stored in the data storage unit 18b.

Returning to FIG. 2, in step S <b> 103, the reception waveform processing calculation unit 18 a of the computer 5 generates the attenuation calibration curve 31. Here, the attenuation calibration curve 31 is a curve for calibrating that the amplitude (signal intensity) is attenuated by the propagation of the guide wave and the reflected wave.
Regarding the generation of the attenuation calibration curve 31, first, the received waveform processing calculation unit 18 a determines the weld line thickness relative to the plate thickness of the barrel from the height of the weld line W 1 and the weld line W 2 and the plate thickness of the barrel of the tank 6. The ratio of the height is obtained by calculation. These data are stored in advance in the data storage unit 18b.
Then, the received waveform processing calculation unit 18a includes a ratio of the weld line overlay height to the plate thickness of the body part, a reflected signal W22 based on the reflected wave 22 from the weld line W1 shown in FIG. An attenuation calibration curve 31 (see FIG. 4A) is generated based on the reflected signal W23 based on the reflected wave 23 from W2.

  Returning to FIG. 2, in step S104, the received waveform processing calculation unit 18a generates a threshold curve 32 (see FIG. 4B) based on the attenuation calibration curve 31 generated in step S103. Here, the threshold curve 32 is a threshold for determining whether or not the signal has a significant signal level as a reflected signal. The threshold value is set as a ratio with respect to the plate thickness of the body part from the required specification of the nondestructive inspection, the detection lower limit level of the guide wave sensor 1 and the noise level. Further, it may be set from the ratio of the detection signal and the noise signal.

  For example, in FIG. 4B, a case where 10% of the reflected signal from the known welding lines W1 and W2 is set as the threshold curve 32 is shown. The significant signal level set here (threshold curve 32) is a signal set by comparing the two because the signal levels of the known welding lines W1 and W2 are known from the relationship between the plate thickness and the weld overlay. A threshold level can be calculated. Therefore, the size of the defect (the sectional area of the defect when viewed in the guide wave traveling direction) can be estimated by comparing the main signal threshold level with the defect signal level of the main measurement.

  Returning to FIG. 2, in step S105, the transmission time difference setting unit 17 of the computer 5 sets the delay time (transmission delay time) of the application time of each ultrasonic probe. The transmission delay time will be described with reference to FIG. 5 together with step S106 described later.

In step S106, the control unit 19 of the computer 5 outputs a guide wave transmission command including delay information (transmission delay time) of the application time of each ultrasonic probe set by the transmission time difference setting unit 17 in step S105. It transmits to the transmitter / receiver control part 10 of the transmitter / receiver 4, and the guide wave 41 is transmitted from the guide wave sensor 1 in the diagonal direction.
Then, the control unit 19 of the computer 5 converts the reflected wave received by the guide wave sensor 1 into a digital signal by the ultrasonic transceiver 4 and receives it.

  Here, the propagation path of the guide wave in step S106 will be described with reference to FIG. FIG. 5 is a schematic diagram illustrating a propagation path of a guide wave transmitted in an oblique direction from the guide wave sensor 1 in step S106.

  The transceiver control unit 10 performs signal generation unit 11 based on the delay information (transmission delay time) of the application time of each ultrasonic probe set by the transmission time difference setting unit 17 in step S105 included in the guide wave transmission command. And the application time of the transmission waveform (transmission signal) 40 in each ultrasonic probe is controlled.

Here, the transmission waveform (transmission signal) 40 is an ultrasonic probe farthest from the measurement site with respect to the ultrasonic probes of the ultrasonic probe array 2 so that the guide wave 41 is transmitted at an angle θ toward the measurement site. The delay is made at regular intervals in order from the acoustic probe. Similarly, the ultrasonic probes in the ultrasonic probe array 3 are delayed at regular intervals in order from the ultrasonic probe farthest from the measurement site. The transmission waveform (transmission signal) 40 controls the transmission direction by giving a delay to the application time of the ultrasonic probe array 2 and the ultrasonic probe array 3.
In this way, in step S106, the angle θ with respect to the vertical direction of the ultrasonic probe rows 2 and 3 from the guide wave sensor 1 (ultrasound probe rows 2 and 3), and the weld lines W1, A guide wave 41 is transmitted in the direction of W2.

  As described above, the guide wave 41 transmitted in the oblique direction at the angle θ is partially reflected by the welding line W1 that is built up at the same height in a straight line to become the reflected wave 42, and the remaining wave The guide wave 41 becomes a guide wave 41a that propagates in the transmission direction through the welding line W1. Here, as shown in FIG. 5, by causing the guide wave 41 to enter obliquely with respect to the linear welding line W <b> 1, the reflected wave 42 can be set in a direction different from the direction in which the guide wave 41 has entered. .

  Therefore, the delay time (transmission delay time) of the application time of each ultrasonic probe set in step S105 is such that the reflected wave 42 from the weld line W1 is outside the guide wave sensor 1 as shown in FIG. It is set to generate a transmission waveform (transmission signal) 40 that propagates through the region and has the transmission direction (angle θ) of the guide wave 41 in which the guide wave sensor 1 does not receive the reflected wave 42 from the welding line W1.

  Further, when there is a defect 7 in the vicinity of the weld line W1 of the inspection target portion, a part of the guide wave 41 is reflected by the defect 7 in which the thickness of the body portion is changed, and the reflected wave 51 is reflected by the guide wave sensor 1. Is detected. This is because the weld line W1 has a straight and fixed shape, and the reflected wave propagates in a fixed direction (the direction of the reflected wave 42 shown in FIG. 5), whereas the defect 7 has an indefinite shape. A part of the reflected wave becomes a reflected wave 51 propagating in the direction of the guide wave sensor 1 and is detected by the guide wave sensor 1.

  The reflected wave 51 reflected by the defect 7 is received by the guide wave sensor 1, amplified by the receiver amplifier 14 of the ultrasonic transceiver 4, converted into a digital signal by the high-speed A / D converter 15, and the transceiver controller 10. To the computer 5.

  The received waveform digital signal input to the computer 5 is processed by the received waveform processing calculation unit 18a and displayed on the display unit 16 as the received waveform S2 (see FIG. 6). In FIG. 6, the vertical axis represents the amplitude (signal intensity) of the reflected wave, and the horizontal axis represents the distance from the guide wave sensor 1 to the reflection source.

Returning to FIG. 2, in step S <b> 107, the received waveform processing calculation unit 18 a evaluates the received waveform S <b> 2 (see FIG. 6) that is a measurement signal.
The received waveform processing calculation unit 18a compares the received waveform S2 (see FIG. 6) received in step S106 with the threshold curve 32 generated in step S104, and outputs a signal having a signal strength greater than the value of the threshold curve 32. The signal from the defect 7 is evaluated. In the example of FIG. 6, since the reflected signal P1 at the position of the distance L1 has a signal intensity higher than the value of the threshold curve 32, it is evaluated that there is a defect 7 at the position of the distance L1. Further, from the ratio (H2 / H1) between the peak height H1 of the reflected signal P1 and the value H2 of the threshold curve 32 at the peak position of the reflected signal P1, the size of the defect 7 (when viewed in the guide wave traveling direction). The cross-sectional area of the defect) can be estimated.
In addition, since the area | region where distance L is 0 vicinity is a dead zone of a nondestructive inspection apparatus, the signal in this area | region is disregarded.

  In step S108, the control unit 19 stores the received waveform S2 received in step S106 and the evaluation result of step S107 (the presence / absence of the defect 7, the distance to the defect 7, the size of the defect 7) in the data storage unit 18b.

In step S109, the control unit 19 determines whether or not the measurement of the measurement site of the weld line W1 to be inspected is completed.
If the measurement has not been completed (No at S109), the process of the control unit 19 proceeds to Step S110.
In step S110, the control unit 19 sets a new measurement site in, for example, the direction Y1 (see FIG. 5). That is, the angle θ in the transmission direction of the guide wave 41 is set. Then, the process of the control unit 19 returns to step S105, the transmission delay time is set so that the guide wave is transmitted to the set measurement site, and the above-described processes (S106 to S108) are executed. The transmission delay time is automatically calculated by inputting the positional relationship between the guide wave sensor 1 and the measurement site to the computer 5. By repeating this process, measurement can be performed while changing the measurement site in the direction Y1.

On the other hand, when the measurement is completed in step S109 (S109 / Yes), the process of the control unit 19 proceeds to step S111.
In step S111, the control unit 19 determines whether or not the inspection is finished. When the inspection has not been completed (No at S111), the process of the control unit 19 proceeds to Step S112.
In step S <b> 112, the control unit 19 causes the display unit 16 to display an instruction screen that prompts the user to move the guide wave sensor 1 attached to the body of the tank 6.
The operator moves the guide wave sensor 1 in accordance with the instructions on the screen. Here, the guide wave sensor 1 is attached so as to be parallel to the extending direction of the weld line W1 (or the weld line W2) of the inspection target portion of the tank 6 as in step S101. And the process of the control part 19 returns to step S105, and performs above-described process (S105-S110).
On the other hand, when the inspection is completed in step S111 (S111: Yes), the processing of the nondestructive inspection method using the nondestructive inspection apparatus according to the present embodiment is ended.

<Action and effect>
Here, the operation and effect of the present embodiment will be described in comparison with the comparative example.
FIG. 9 is a schematic diagram illustrating a propagation path of the guide wave 21 transmitted in the vertical direction from the guide wave sensor 1 according to the comparative example. FIG. 10 is a graph illustrating the received waveform S2 of the reflected wave 22C in the comparative example.
As shown in FIG. 9, when the guide wave 21 is transmitted in the vertical direction, if there is a defect 7 in the vicinity of the weld line W1, the reflected wave from the weld line W1 and the reflected wave from the defect 7 are overlapped to produce a reflected wave 22C. As shown in FIG. 10, the reflected signal W22 based on the reflected wave from the weld line W1 and the reflected signal P1 based on the reflected wave from the defect 7 overlap with each other, and the reflected signal P1 based on the reflected wave from the defect 7 Detection becomes difficult.

  On the other hand, according to the nondestructive inspection method of the nondestructive inspection apparatus according to the present embodiment, as shown in FIG. 5, the reflected wave 42 from the welding line W <b> 1 propagates in the outer region of the guide wave sensor 1. By transmitting the guide wave 41 obliquely at an angle θ, as shown in FIG. 6, the detection of the reflected signal P1 based on the reflected wave from the defect 7 is facilitated, and the defect 7 in the vicinity of the weld line W1 Can also be suitably detected. Thereby, the oversight of defects can be prevented, and the reliability of inspection can be improved.

  Moreover, according to the nondestructive inspection method of the nondestructive inspection apparatus according to the present embodiment, as shown in steps S101 to S104 in FIG. Using the lines W1 and W2) as reference reflection sources, an attenuation calibration curve 31 between the amplitude and distance of the received signal is acquired, and a threshold (threshold curve 32) is determined based on the attenuation calibration curve 31. Yes. The size of the defect 7 can also be evaluated by comparing the threshold value (threshold curve 32) with the reflected signal P1 based on the reflected wave from the defect 7.

≪Modification≫
The nondestructive inspection apparatus according to this embodiment is not limited to the configuration of the above embodiment, and various modifications can be made without departing from the spirit of the invention.

  In step S106, as shown in FIG. 5, it has been described that the guide wave 41 is transmitted with a certain delay in order from the ultrasonic probe farthest from the measurement site, but the present invention is not limited to this.

FIG. 7 is a schematic diagram showing a propagation path of a guide wave 41A transmitted in an oblique direction from the guide wave sensor 1 according to the first modification.
As shown in FIG. 7, the transmission waveform (transmission signal) 40 </ b> A may be applied so that the guide wave is focused in the vicinity of the measurement site. By applying the transmission waveform (transmission signal) 40A in this way, the amplitude (signal strength) of the reflected wave 51A from the defect 7 can be increased. The amplitude (signal intensity) of the reflected wave 42A from the weld line W1 also increases, but the reflected wave 42A from the weld line W1 propagates in the outer region of the guide wave sensor 1.

FIG. 8 is a schematic diagram illustrating a propagation path of a guide wave 41B transmitted in an oblique direction from the guide wave sensor 1 according to the second modification.
In FIG. 7, the measurement site is described as being in the direction Y1, but as shown in FIG. 8, the measurement site may be in the direction Y2.

1 Guide wave sensor 2, 3 Ultrasonic probe array 4 Ultrasonic transmitter / receiver 5 Computer 6 Tank (subject)
7 Defect 10 Transmitter / Receiver Control Unit 11 Signal Generation Unit 12 Power Amplifier 13 Reception Signal Switching Unit 14 Receiver Amplifier 15 High-Speed A / D Conversion Unit 16 Display Unit 17 Transmission Time Difference Setting Unit 18a Reception Waveform Processing Calculation Unit 18b Data Storage Unit 19 Control Unit 20, 40, 40A, 40B Transmission waveform 21, 41, 41A, 41B Guide wave 22, 42, 51, 42A, 51A, 42B, 51B Reflected wave (reflected signal)
31 Attenuation calibration curve 32 Threshold curve (signal threshold)
W1, W2 Welding lines W22, W23 Reflected signal S1 Received waveform (first inspection data)
S2 Received waveform (second inspection data)

Claims (5)

A guide wave sensor having two rows of ultrasonic probe arrays in which a plurality of ultrasonic probes are arranged at equal intervals is installed on the wall surface of the subject, and a guide wave is transmitted and propagated. A non-destructive inspection apparatus for detecting a defect of the object by receiving a reflected signal of
Attenuation calibration curve acquisition that obtains an attenuation calibration curve from first inspection data obtained by transmitting a guide wave perpendicularly to the direction of the weld line formed on the object and propagating it, and receiving a reflected signal of the guide wave Means,
A signal threshold value setting means for setting a signal threshold value of a reflected signal that can be detected at a significant signal level from the attenuation calibration curve;
Reflected signal acquisition means for transmitting a guide wave obliquely from the guide wave sensor with respect to the direction of the welding line by phased array transmission and propagating it, receiving a reflected signal of the guide wave and acquiring second inspection data; ,
A nondestructive inspection apparatus comprising: defect evaluation means for evaluating the defect from the second inspection data and the signal threshold value. The attenuation calibration curve acquisition means includes
The nondestructive inspection apparatus according to claim 1, wherein the attenuation calibration curve is acquired using a reflection signal from the weld line. The reflected signal acquisition means includes
A phased array transmission is performed from the guide wave sensor by controlling a delay time of an application time of the ultrasonic probe so that a propagation path of a reflected wave from the weld line is outside the guide wave sensor. The nondestructive inspection device according to claim 1. The reflected signal acquisition means includes
The phased array transmission is performed from the guide wave sensor by controlling a delay time of the application time of the ultrasonic probe so that a guide wave to be transmitted is focused on a portion of the weld line. The nondestructive inspection device described. A guide wave sensor having two rows of ultrasonic probe arrays in which a plurality of ultrasonic probes are arranged at equal intervals is installed on the wall surface of the subject, and a guide wave is transmitted and propagated. A non-destructive inspection method for a non-destructive inspection apparatus for receiving a reflected signal of the object and detecting a defect of the object,
A first step of acquiring an attenuation calibration curve from first inspection data obtained by transmitting a guide wave perpendicularly to the direction of the weld line formed on the object and propagating it, and receiving a reflected signal of the guide wave; ,
A second step of setting a signal threshold of the reflected signal that can be detected at a significant signal level from the attenuation calibration curve;
A third step of transmitting and propagating a guide wave obliquely with respect to the direction of the welding line from the guide wave sensor by phased array transmission, receiving a reflected signal of the guide wave, and acquiring second inspection data;
And a fourth step of evaluating the defect from the second inspection data and the signal threshold value.

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