JP2006162377A - Ultrasonic flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ultrasonic flaw detector constituted so as to measure the corrosion amount of the boundary part of a test object and a solid, even in a state with the periphery of the test object being solidified by the solid, such as concrete or the like. <P>SOLUTION: The ultrasonic flaw detector has a transmission and receiving probe 1, which receives the reflected wave of the ultrasonic wave formed, on the basis of an exciting signal to be transmitted through the test object and propagated through the test object to output a reflected wave electrical signal; and a memory part 35 for preliminarily storing the depth of the gap of the test object, which corresponds to the feature frequency showing the singular points of the frequency characteristics of the echo height of the reflected wave electrical signal, as gap data and equipped with a transmission/reception control unit 3, wherein the frequency characteristics of the echo height of the reflected wave electrical signal are calculated and the feature frequency is specified from frequency characteristics; while the depth of the gap corresponding to the feature frequency is calculated, on the basis of the gap data and the corrosion depth in the boundary surface of the test object and the solid that is in contact with the test object is estimated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic flaw detector that inspects a joint between a solid and a solid in a nondestructive manner, and more particularly to an ultrasonic flaw detector that measures the amount of corrosion in a portion where a sensor cannot be directly accessed. In the present application, the terms “corrosion” and “void” are used, but both refer to the same thing.

  As a conventional method for realizing this type of ultrasonic flaw detector, there is a method for obtaining a corrosion amount of external surface corrosion in a pedestal portion of a pipe (see, for example, Patent Document 1). If there is corrosion in the part of the test body covered with the gantry, the sensor is in a state where it cannot be directly accessed, and of course, visual inspection is also impossible.

  In such a case, a surface wave is generated from one end of the surface of the test body by a surface acoustic wave probe for transmission, and the surface wave propagated through the gantry part is received at the other end of the surface of the test body. Received by the wave probe and records the echo. Then, the depth of corrosion is estimated from the correlation between the echo height and the depth of the notch prepared in advance.

Japanese Unexamined Patent Publication No. 2000-55890 (first page, FIG. 1)

  However, the prior art has the following problems. This inspection method has a drawback that the echo height changes depending on the contact state between the surface acoustic wave probe for transmission and the surface acoustic wave probe for reception and the test body. Patent Document 1 also describes correcting the propagation loss of the contact portion. However, in order to obtain the propagation loss in the surface wave probe, it is necessary to strictly manage the contact state. In other words, unless the contact state is strictly controlled, the method disclosed in Patent Document 1 cannot be applied to the estimation of the corrosion amount.

  Furthermore, this inspection method assumes external corrosion of the pedestal portion of the pipe, and does not assume a state where the periphery of the pipe is solidified with a solid such as concrete. In a state where the periphery of the pipe is hardened with a solid such as concrete, the surface wave leaks into the solid, so that the attenuation due to propagation is large. For this reason, the echo received by the surface acoustic wave probe for reception becomes a signal with a very bad signal-to-noise ratio, making it difficult to measure the amount of corrosion at the boundary between the specimen and a solid such as concrete. There's a problem.

  The present invention has been made to solve the above-described problems. Even in a state where the periphery of the specimen is solidified with a solid such as concrete, the amount of corrosion at the boundary between the specimen and the solid such as concrete is reduced. The object is to obtain an ultrasonic flaw detector capable of measuring.

  The ultrasonic flaw detection apparatus according to the present invention transmits / receives an ultrasonic wave generated based on an excitation signal into a test body, receives a reflected wave of the ultrasonic wave propagated through the test body, and outputs a reflected wave electric signal. And a storage unit for storing in advance the gap depth of the specimen corresponding to the characteristic frequency indicating the singular point of the frequency characteristic of the echo height of the reflected wave electric signal as gap data, Generate and output to the transmitter / receiver probe, obtain the frequency characteristic of the echo height of the reflected wave electric signal based on the reflected wave electric signal from the transmitter / receiver probe, and the characteristic frequency indicating the singular point from the frequency characteristic The depth of corrosion at the interface between the specimen and the solid in contact with the specimen by determining the depth of the gap corresponding to the identified characteristic frequency based on the gap data stored in the storage unit A transmission / reception control device for estimating It includes those were.

  According to the present invention, even in a state where the periphery of the specimen is solidified with a solid such as concrete, the boundary portion between the specimen and the solid such as concrete is obtained by obtaining the frequency characteristics of the echo height of the reflected wave electric signal. It is possible to obtain an ultrasonic flaw detector capable of estimating the amount of corrosion.

  Hereinafter, preferred embodiments of an ultrasonic flaw detector according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of the ultrasonic flaw detector according to Embodiment 1 of the present invention. In FIG. 1, the ultrasonic flaw detection apparatus includes a transmission / reception probe 1, a reception probe 2, and a transmission / reception control device 3. Moreover, the test body 11 to be inspected is in a state in which a part of its surface is hardened with a solid 12 such as concrete. Here, the test body 11 corresponds to, for example, a pipe or a steel plate. Further, the gap 13 indicates the corrosion of the test body 11 generated between the test body 11 and the solid 12.

  The transmission / reception probe 1 is disposed so as to be in contact with the test body 11 and is excited by an excitation signal received from the transmission / reception control device 3 as an electrical signal, thereby converting the excitation signal into an ultrasonic wave. The transmitter / receiver probe 1 transmits the converted ultrasonic wave into the test body 11 in order to check whether the gap 13 is generated in the test body 11. Further, the transmission / reception probe 1 receives a reflected wave in which the ultrasonic wave propagating in the test body 11 is scattered by the gap 13, converts the reflected wave into a reflected wave electric signal, and transmits the reflected wave electric signal to the transmission / reception control device. 3 is output.

  On the other hand, the receiving probe 2 is arranged in contact with the test body 11 at a position facing the transmitting / receiving probe 1 across the solid 12. The receiving probe 2 receives the transmitted ultrasonic wave propagating in the test body 11, converts it into a transmitted wave electric signal, and outputs the transmitted wave electric signal to the transmission / reception control device 3. .

The transmission / reception control device 3 includes an arbitrary waveform generation unit 31, a transmission unit 32, a reception unit 33, a signal processing unit 34, and a storage unit 35. Driving signal generator 31 is a waveform generator capable of generating a burst signal by any carrier frequency f _0. FIG. 2 is an explanatory diagram of signal waveforms generated by the arbitrary waveform generation unit 31 according to Embodiment 1 of the present invention. The waveform of FIG. 2 shows a signal obtained by applying amplitude modulation to the rising and falling portions of the signal, and this signal will be referred to as a “modulated burst signal” in the following description.

The modulated burst signal having a certain carrier frequency f ₀ generated by the arbitrary waveform generator 31 is amplified by the transmitter 32 and becomes an excitation signal for exciting the transmission / reception probe 1. The transmission unit 32 outputs this excitation signal to the transmission / reception probe 1.

Further, the reception unit 33 receives the reflected wave electric signal from the transmission / reception probe 1 and the reception probe 2 as a reception signal corresponding to the modulated burst signal having a certain carrier frequency f ₀ transmitted from the transmission unit 32. The transmitted electric signals are received and the amplified signals are output to the signal processing unit 34.

The signal processing unit A / D converts the amplified reflected wave electric signal and transmitted wave electric signal into a digital signal, and generates a digital signal of reflected wave echo and transmitted wave echo. Further, the signal processing unit 34 stores the reflected wave echo and the transmitted wave echo, which are digital signals, in the storage unit 35 in association with the carrier frequency f ₀ as frequency characteristic data.

In this manner, the transmission / reception control device 3 can store frequency characteristic data related to a certain carrier frequency f ₀ in the storage unit 35 by performing the above-described series of operations. The transmission / reception control device 3 repeats this series of operations by changing the carrier frequency f ₀ of the modulated burst signal, thereby obtaining reflected echoes and transmitted echo digital signals for the plurality of carrier frequencies f ₀ . Can be acquired and stored in the storage unit 35 as frequency characteristic data.

Here, the range in which the carrier frequency f ₀ is changed, the number of repetitions, and the like can be determined in advance based on the frequency characteristics of the transmission / reception probe 1 and the reception probe 2. Next, a method for estimating the depth of the air gap 13 based on the frequency characteristic data collected in this way will be described.

  When the thickness of the test body 11 is about the same as the wavelength of the ultrasonic wave propagating in the test body 11 to several times, the ultrasonic wave propagating in the test body 11 is a plate wave (that is, a thin plate). Wave that propagates while the entire object is vibrating. When the transmission / reception probe 1 is the same type as a normally used oblique angle probe, the vibration direction of the plate wave is parallel to the paper surface of FIG. 1 (that is, the plate wave is a paper surface). With respect to the vertical or horizontal vibration). This plate wave is called a Lamb wave, but in the following description, it will be referred to as a “plate wave” for simplicity.

  The plate wave propagating in the test body 11 shows a complicated propagation form. Further, the propagation form varies depending on the frequency. The result of confirming this state by sound field simulation is shown below. FIG. 3 is a diagram showing simulation conditions relating to flaw detection according to Embodiment 1 of the present invention, in which the incident angles of the transmission / reception probe 1 and the reception probe 2 are both 57 °.

  As the wedge material of the transmitting / receiving probe 1 and the receiving probe 2, polystyrene was assumed, and the material of the test body 11 was assumed to be a steel plate having a thickness of 9 mm. Furthermore, mortar having a length of 300 mm was assumed as the solid 12 such as concrete. In addition, an air gap 13 having a depth d is provided between the mortar and the steel plate, simulating the depth of corrosion.

FIG. 4 shows a sound field simulation result when assuming a modulation burst signal with a carrier frequency f ₀ = 0.6 MHz in the first embodiment of the present invention and setting the gap depth d to 2 mm. FIG. 4 shows a sound field of 180 μs to 240 μs after excitation of the transmission / reception probe 1 with seven snapshots every 10 μs, and the top diagram shows the transmission / reception probe 1. The sound field is 180 μs after excitation, and the bottom diagram is the sound field after 240 μs.

  In order to make the sound field easy to see, the portion where the mortar is present is enlarged and displayed, and the transmitting / receiving probe 1 and the receiving probe 2 are not shown. Further, the plate wave propagating in the steel plate is shown by shading. In addition, the ultrasonic wave leaking into the mortar is also shown by shading. As time passes, the portion that looks whitish moves to the right, which indicates the propagation of ultrasonic waves.

  In FIG. 4, at the stage of 180 μs, the plate wave propagating from the left side of the drawing reaches a region where the mortar is present and energy is already leaked into the mortar. Next, at the stage of 190 μs, the plate wave reaches the left side of the gap 13, but since the depth d of this gap is a small depth of 2 mm, the plate wave is not scattered much on the left side of the gap. .

  Next, at a stage of 200 μs, a state is shown in which the plate wave has entered under the gap 13 and has reached the right side of the gap 13. Next, at the stage of 210 μs, a state is shown in which the plate wave is scattered on the right side of the gap 13, and the intensity of the scattered wave is considerably stronger than the scattering on the left side of the gap 13.

  In normal ultrasonic flaw detection, if there is no obstacle that prevents the propagation of ultrasonic waves, the ultrasonic waves are not scattered, but in the case of plate waves, scattering occurs only as the thickness of the propagating steel plate changes. . This is a characteristic unique to plate waves. Further, it is considered that the intensity of scattering caused by the change in the plate thickness changes depending on the plate thickness, frequency, and gap depth d of the propagating steel plate.

  The scattered plate wave propagates leftward in FIG. 4 (that is, in the direction of the transmission / reception probe 1), and is received by the transmission / reception probe 1 as an echo of a reflected wave. On the other hand, the transmitted plate wave propagates rightward in FIG. 4 (that is, in the direction of the receiving probe 2), and is received by the receiving probe 2 as an echo of the transmitted wave.

  FIG. 5 is a diagram showing echoes of reflected waves and echoes of transmitted waves obtained by simulation in the first embodiment of the present invention. As shown in FIG. 5, under the simulation conditions, the reflected wave and the transmitted wave are received as echoes, and the peak value of the amplitude of the waveform of such a reflected wave or transmitted wave corresponds to the echo height. FIG. 6 is a diagram showing propagation paths of the reflected wave and the transmitted wave of the plate wave in the first embodiment of the present invention. As shown in the figure, the places where the plate waves are scattered are two places on the left side and the right side of the gap.

Thus, when there is a gap 13, the reflected wave and the transmitted wave are received as echoes, and the echo height is considered to vary depending on the plate thickness, frequency, and gap depth d. Therefore, the plate thickness was fixed at 9 mm, the same simulation was performed by changing the carrier frequency f ₀ and the gap depth d, and the frequency characteristic of the echo height was obtained.

FIG. 7 is a diagram showing frequency characteristics of the echo height of the reflected wave in the first embodiment of the present invention. This frequency characteristic shows the frequency characteristic of the echo height of the reflected wave when the carrier frequency f ₀ is changed in steps of 0.1 MHz from 0.2 MHz to 1.0 MHz, and the depth d of the air gap 13 is a parameter. It is said. There are five depths d of the gap 13: 0, 2, 3, 4, 6 mm.

  Next, the frequency characteristics of the echo height of the reflected wave in FIG. 7 will be described. In the low frequency region of 0.5 MHz or less, the echo height increases as the gap depth d increases. The echo received in this low frequency region is equivalent to the reflected wave in which the plate wave is scattered on the left side of the air gap, and the echo of the size corresponding to the size of the obstacle is received as in normal ultrasonic flaw detection. Has been. It should be noted that even though d = 0 mm, echoes appear to be received, but this is a plate wave scattered at the left end of the mortar and can be ignored.

On the other hand, in a high frequency region of 0.5 MHz or higher, a plate wave propagates in a special mode in which energy is concentrated near the bottom surface of the steel plate. This will be described with reference to FIG. FIG. 8 shows a sound field simulation result when assuming a modulation burst signal with a carrier frequency f ₀ = 0.8 MHz in the first embodiment of the present invention and setting the gap depth d to 4 mm. That is, compared with FIG. 4 on the left, the carrier frequency f ₀ is changed from 0.6 MHz to 0.8 MHz, and the gap depth d is changed from 2 mm to 4 mm.

  In FIG. 8, since the carrier frequency is high, it can be seen that the energy of the plate wave is concentrated on the bottom surface of the steel plate. Since energy concentrates in the vicinity of the bottom surface of the steel plate, the energy leaking into the mortar can be suppressed. As a result, the attenuation associated with propagation becomes small, so that a plate wave that can propagate over a long distance is obtained. That is, a phenomenon opposite to the general idea that the attenuation is large when the frequency is high occurs.

  In the plate wave in such a phenomenon, the energy in the vicinity of the boundary surface between the mortar and the steel plate is small, so if the depth d of the gap 13 is small, the energy is hardly scattered on the left side of the gap 13. FIG. 8 is a diagram in the case of d = 4 mm. For example, when d = 1 mm, the plate wave is hardly scattered on the left side of the gap 13 and is under the gap 13. Become.

  The plate wave that has submerged under the gap 13 is converted from a special mode in which energy is concentrated near the bottom surface of the steel plate to a normal plate wave mode. The plate wave is scattered when it reaches the right side of the gap 13, and a large reflected wave is generated. The echo received in the high frequency region of 0.5 MHz or higher is a reflected wave thus scattered on the right side of the gap 13.

  Since the intensity scattered on the right side of the gap 13 is considered to change depending on the thickness and frequency of the propagating steel plate and the depth d of the gap 13, the frequency characteristics are complicated as shown in FIG. For example, when d = 2 mm, the maximum value is shown at 0.6 MHz, and when d = 4 mm, the maximum value is shown at 0.8 MHz.

  Next, a method for measuring the depth d of the gap 13 using the frequency characteristic of the echo height of the reflected wave will be described. As described above, the echo of the reflected wave received by the transmission / reception probe 1 exhibits a complicated frequency characteristic as shown in FIG. 7 in a high frequency region of 0.5 MHz or higher. This characteristic depends on the plate thickness, the frequency, and the depth d of the gap 13, but among these parameters, only the depth d of the gap 13 is unknown at the time of inspection.

That is, if the frequency characteristics of FIG. 7 are obtained in advance before the inspection, the depth d of the air gap 13 can be obtained. For example, the reflected wave is received by the transmission / reception probe 1 by changing the carrier frequency f ₀ , the frequency characteristic of the echo height of the reflected wave is obtained, and when the frequency showing the maximum value is 0.6 MHz, d = 2 mm and the measurement result is output, and when the frequency indicating the maximum value is 0.8 MHz, d = 4 mm and the measurement result is output.

  In addition, there is a measurement method in which d is obtained according to the echo height of the reflected wave in the low frequency region of 0.5 MHz or less, as in the case of normal ultrasonic flaw detection. However, since the echo height largely depends on the contact state between the transmission / reception probe 1 and the test body 11, there is a problem that the contact state must be strictly managed.

  On the other hand, the method of measuring d from the frequency characteristics of the reflected wave in a high frequency region of 0.5 MHz or higher does not depend much on the contact state between the transmission / reception probe 1 and the test body 11. That is, although the magnitude of the amplitude of the observed reflected wave electrical signal differs depending on the contact state between the transmitter / receiver probe 1 and the test body 11, the characteristics shown by the frequency characteristics can be measured without significant differences. For example, the frequency indicating the maximum value tends to extract the same value without depending on the contact state. Therefore, in the ultrasonic flaw detector of the present invention, it is not necessary to strictly manage the contact state between the transmission / reception probe 1 and the test body 11.

  The frequency characteristic of the echo height of the reflected wave has been described above. Next, the frequency characteristic of the echo height of the transmitted wave will be described. FIG. 9 is a diagram showing the frequency characteristics of the echo height of the transmitted wave in Embodiment 1 of the present invention, and is the frequency characteristic of the echo height of the transmitted wave obtained by the same simulation as in FIG.

  As shown in the figure, although the amplitude changes somewhat depending on the value of d, there is no difference due to the value of d as in the frequency characteristics of the reflected wave shown in FIG. That is, it is difficult to measure the depth d of the gap 13 using the frequency characteristic of the echo height of the transmitted wave.

  However, it is also difficult to measure the value of d only by ignoring the transmitted wave and using only the frequency characteristic of the echo height of the reflected wave. The reason will be described below.

  When the value of d is measured only with the frequency characteristic of the echo height of the reflected wave, if no echo of the reflected wave is received, it is determined that there is no gap 13 and “d = 0 mm”. However, even when the contact state between the transmission / reception probe 1 and the test body 11 is extremely poor, or even when the transmission / reception probe 1 fails, the echo of the reflected wave is not received. That is, not only when there is no gap 13 but also when the apparatus is not operating normally, the echo of the reflected wave is not received. Therefore, a function for checking whether the apparatus is operating normally is necessary. An echo of transmitted waves can be used for this check.

  The transmitted wave echo is naturally not received when the contact state between the transmission / reception probe 1 and the test body 11 is extremely poor, or when the transmission / reception probe 1 fails. However, when the apparatus is operating normally, it is received regardless of the presence or absence of the gap 13 and the depth. Therefore, the transmitted wave echo is used as a judgment material for the check function of “normal” when the transmitted wave echo is received and “abnormal” when it is not received.

  If it is determined from the transmitted wave received by the receiving probe 2 that the transmitting / receiving probe 1 is “abnormal”, the operator confirms the operation of the transmitting / receiving probe 1 alone. Alternatively, the contact state between the transmission / reception probe 1 and the test body 11 is checked, and the setup of the apparatus is performed again.

  The method for measuring the depth d of the air gap 13 has been described above. This is a method for measuring the depth of corrosion as it is, and a series of processes will be described using a flowchart. FIG. 10 is a flowchart for explaining how to determine the corrosion amount of the ultrasonic flaw detector according to Embodiment 1 of the present invention. Before the start of measurement, the transmission / reception control device 3 obtains in advance the frequency characteristic of the reflected wave of the test body 11 whose depth of the air gap 13 is known, and the depth of the air gap 13 of the test body 11 corresponding to the characteristic frequency. Is previously stored in the storage unit 35 as gap data. The characteristic frequency is a frequency indicating a singular point of the frequency characteristic of the echo height of the reflected wave electric signal, and can be, for example, a frequency indicating a maximum value.

  In step S1001, the arbitrary waveform generator 31 in the transmission / reception control device 3 sets a carrier frequency at which flaw detection is started. The frequency at this time may be within the required frequency range, and need not be the lower limit or the upper limit of the required frequency.

  Next, in step S <b> 1002, the arbitrary waveform generator 31 creates a modulated burst signal based on the set carrier frequency and transmits it to the transmitter 32.

  Next, in step S1003, the transmission unit 32 amplifies and outputs the modulated burst signal received from the arbitrary waveform generation unit 31, and excites the transmission / reception probe 1. The incident angle of the transmitting / receiving probe 1 is set to an angle at which the plate wave is efficiently excited. As a result, the plate wave propagates into the test body 11.

  Next, in step S1004, the transmitting / receiving probe 1 and the receiving probe 2 receive the reflected plate wave and the transmitted wave as echoes. Here, the incident angle of the receiving probe 2 may be the same as or different from the incident angle of the transmitting / receiving probe 1. However, the incident angle is set so that the plate wave propagating through the specimen 11 can be received efficiently.

  Next, in step S <b> 1005, the reception unit 33 amplifies the echoes received by the transmission / reception probe 1 and the reception probe 2 and sends them to the signal processing unit 34.

  Next, in step S1006, the signal processing unit A / D converts the amplified echoes of the reflected wave and the transmitted wave, and converts the converted data into a digital signal from the modulated burst generated in the previous step S1002. The frequency is stored in the storage unit 35 as frequency characteristic data in association with the carrier frequency corresponding to the signal.

  Next, in step S1007, the signal processing unit 34 performs flaw detection using all of the plurality of predetermined carrier frequencies, and determines whether or not the collection of frequency characteristic data for the plurality of carrier frequencies has been completed. If it is determined that the collection of frequency characteristic data has not been completed, the process proceeds to step S1008. On the other hand, if it is determined that the collection of frequency characteristic data has been completed, the process proceeds to step S1009.

The plurality of carrier frequencies determined in advance are determined based on the frequency characteristics of the transmission / reception probe 1 and the reception probe 2. For example, f ₀ = 0.2 MHz, 0.3 MHz, 0.4 MHz,... 0.8 MHz, 0.9 MHz, and 1.0 MHz are determined. The method of determining the carrier frequency varies depending on the case, but the range to be changed and the frequency interval thereof are selected so that the difference in frequency characteristics clearly appears depending on the depth of the gap 13, as shown in FIG.

  If the collection of the frequency characteristic data has not been completed, in step S1008, the arbitrary waveform generation unit 31 sets a new carrier frequency other than the previously set carrier frequency. Thereafter, by repeating the processes of steps S1002 to S1007, the frequency characteristic data for the new carrier frequency is obtained and stored in the storage unit 35.

  By repeating such processing, when one set of frequency characteristic data for a plurality of carrier frequencies set in advance is obtained, the processing shifts to processing after step S1009 by the signal processing unit 34. First, in step S <b> 1009, the signal processing unit 34 reads out frequency characteristic data in which the carrier frequency and the echo are associated from the storage unit 35.

  Next, in step S1010, the signal processing unit 34 determines whether or not an echo of the transmitted wave is received by the reception probe 2 based on the read frequency characteristic data. Specifically, the signal processing unit 34 determines whether or not the echo height of the transmitted wave exceeds a predetermined threshold value, and if it does not exceed the threshold value, notifies the operator that the state is abnormal. . Thereafter, in step S1013, the operator re-sets up the apparatus.

  On the other hand, if the threshold value is exceeded, the signal processing unit 34 performs the processing after step S1011 assuming that the apparatus is operating normally. In step S1011, the signal processing unit 34 obtains the characteristic frequency from the frequency characteristic of the height of the echo of the reflected wave obtained by the transmission / reception probe 1 with respect to the carrier frequency, based on the read frequency characteristic data.

  In the flowchart of FIG. 10, a frequency indicating a maximum value is obtained as the characteristic frequency. That is, the characteristic frequency is obtained by identifying the carrier frequency at which the echo height has a maximum value from the echo height of the reflected wave for each carrier frequency.

  Finally, in step S1012, the signal processing unit 34 is stored in advance in the storage unit 35 as gap data corresponding to the frequency indicating the maximum value specified from the frequency characteristic data of the echo of the reflected wave. The depth of the air gap is specified from the depth of the air gap corresponding to the frequency (characteristic frequency) indicating the maximum value, and the amount of corrosion is estimated using the depth of the specified air gap as the depth of corrosion.

  The above is a series of processes for estimating the depth of corrosion by the ultrasonic flaw detector according to Embodiment 1 of the present invention. First, the modulation burst signal generated in step S1002 is determined depending on the case, and how much amplitude modulation is required needs to be determined as appropriate. In some cases, a signal that is not subjected to amplitude modulation may be used.

By applying amplitude modulation, the characteristics of the frequency component of the carrier frequency f ₀ can be obtained more accurately. On the other hand, when the amplitude modulation is not applied, the influence of other frequency components other than the carrier frequency f ₀ is likely to appear as a characteristic compared with the case where the amplitude modulation is applied, but the generated signal is simple. There is merit that can be made.

  Next, the method of changing the carrier frequency in step S1008 is not required to be changed uniformly or decreased within the required frequency range. The carrier frequency may be changed randomly. Of course, it may be changed to a uniform increase or a uniform decrease. Further, the frequency intervals may be equal intervals or not equal intervals. As a result, a predetermined carrier frequency is selected so that a difference in frequency characteristics clearly appears depending on the depth of the gap 13.

  Furthermore, the frequency characteristics of the transmitting / receiving probe 1 and the receiving probe 2 are wide enough that the difference in frequency characteristics depending on the depth of the air gap (that is, the amount of corrosion) becomes clear. Is desirable. Further, the frequency characteristics of the echo height may be obtained by correcting the frequency characteristics of these probes, and the corrosion amount may be obtained from the frequency characteristics.

  Further, in FIG. 1 or FIG. 3, the case where the transmission / reception probe 1 is installed on the left side of the figure and the reception probe 2 is installed on the right side of the figure has been described. However, if it is desired to measure the amount of corrosion near the right side of the figure, the installation positions of the two probes may be exchanged. Since measurement is performed using echoes of reflected waves received by the transmission / reception probe 1, a signal having a higher S / N ratio is obtained as the corrosion position is closer to the transmission / reception probe 1.

  Also, if the location of corrosion in a part covered with solids such as concrete is unknown, obtain two types of frequency characteristic data by exchanging the installation positions of the two probes on the left and right. Depth can also be estimated. Alternatively, two types of frequency characteristic data can also be obtained by providing the receiving probe 2 with the same transmission / reception function as the transmitting / receiving probe 1 and performing a switching operation from the transmission unit 32.

  Furthermore, although the method of estimating the depth of corrosion using the maximum value of the frequency characteristic as the characteristic frequency is explained here, the characteristic frequency does not need to be particular about the maximum value if the measurement uses the characteristic of the frequency characteristic. . For example, if the amount of corrosion can be estimated using the minimum value as a result of calculating the frequency characteristic of the echo height, the minimum value can also be used as the characteristic frequency. Or it is also possible to estimate the amount of corrosion from the combination of the maximum value and the minimum value.

  Finally, incident angles of the transmitting / receiving probe 1 and the receiving probe 2 will be described. The incident angles of these probes need to be set so that plate waves can be transmitted and received efficiently, but this depends on the thickness and frequency of the test body 11. When the thickness of the test body 11 and the frequency band in which the probe 1 for transmission / reception and the probe 2 for reception change are changed, it is necessary to change appropriately according to these.

  According to the first embodiment, flaw detection can be performed from the frequency characteristics of the echo height of the reflected wave with respect to the carrier frequency by performing flaw detection using the modulated burst signal with the carrier frequency changed. Furthermore, the characteristic frequency specified from the frequency characteristic of the echo height does not depend on the contact state between the probe and the test body. As a result, the amount of corrosion can be estimated without strictly managing the contact state between the probe and the test specimen, and even when the periphery of the test specimen is solidified with a solid such as concrete, It is possible to estimate the amount of corrosion at the boundary with the solid.

Embodiment 2. FIG.
In the first embodiment, a modulation burst signal is generated in the arbitrary waveform generation unit 31, flaw detection is performed by changing the carrier frequency of the modulation burst signal, and the depth of the gap 13 is determined from the gap data indicating the gap depth corresponding to the characteristic frequency. Estimated. In this case, since the frequency characteristic data is acquired by changing the carrier frequency for flaw detection, it takes time to estimate the corrosion amount.

  Therefore, in the second embodiment, a case where the corrosion amount is estimated using a signal having a wide frequency band in one excitation signal will be described. Since the configuration of the apparatus is the same as that in FIG. 1, it will be omitted and the operation will be described below.

  The ultrasonic flaw detector according to the second embodiment excites the transmission / reception probe 1 with a signal having a wide frequency band, and performs signal processing on the frequency spectrum of the echo of the reflected wave received by the transmission / reception probe 1. Calculated by the unit 34. In this way, if the depth of the air gap 13 is estimated from the frequency spectrum based on one excitation signal having a wide frequency band, corrosion can be performed in a shorter time than the method of performing flaw detection by changing the carrier frequency of the modulated burst signal. Quantity results are obtained.

  FIG. 11 is an explanatory diagram of a signal waveform generated by the arbitrary waveform generation unit 31 according to the second embodiment of the present invention. A signal having a wide frequency band is a spike-like signal as shown in FIG. In the second embodiment, instead of flaw detection by changing the carrier frequency of the modulated burst signal, the transmitting / receiving probe 1 is excited with a spike-like signal having a wide frequency band as shown in FIG. The depth of 13 is obtained.

  FIG. 12 is a flowchart for explaining how to determine the corrosion amount of the ultrasonic flaw detector according to Embodiment 2 of the present invention. As in the first embodiment, before starting measurement, the transmission / reception control device 3 obtains in advance the frequency spectrum of the reflected wave of the test body 11 whose depth of the gap 13 is known, and performs a test corresponding to the characteristic frequency. The depth of the gap 13 of the body 11 is stored in advance in the storage unit 35 as gap data. This characteristic frequency is a frequency indicating a singular point of the frequency spectrum of the reflected wave, and can be, for example, a frequency indicating a maximum value.

  In step S <b> 1201, the arbitrary waveform generation unit 31 generates a spike-like signal and transmits it to the transmission unit 32. The spike-like signal is not limited to a signal load having a negative amplitude as shown in FIG. 11, and includes a signal having a positive amplitude. An impulse signal is also included in the spike signal.

  Next, in step S1202, the transmission unit 32 amplifies the spike-like signal generated by the arbitrary waveform generation unit 31, and excites the transmission / reception probe 1. The incident angle of the transmitting / receiving probe 1 is set to an angle at which the plate wave is efficiently excited. As a result, the plate wave propagates into the test body 11.

  Next, in step S1203, the transmitting / receiving probe 1 and the receiving probe 2 receive the propagating plate wave reflected wave and transmitted wave as echoes. Here, the incident angle of the receiving probe 2 may be the same as or different from the incident angle of the transmitting / receiving probe 1. However, the incident angle is set so that the plate wave propagating through the specimen 11 can be received efficiently.

  Next, in step S <b> 1204, the reception unit 33 amplifies the echoes received by the transmission / reception probe 1 and the reception probe 2, and sends them to the signal processing unit 34.

  Next, in step S1205, the signal processing unit 34 directly A / D-converts the reflected echo and the transmitted wave echo after amplification, and stores the received echo signal data converted into a digital signal in the storage unit 35. Remember.

  Next, in step S <b> 1206, the signal processing unit 34 reads the received echo signal stored in the storage unit 35.

  Next, in step S1207, the signal processing unit 34 determines whether or not an echo of the transmitted wave is received by the reception probe 2 based on the read reception echo signal. Specifically, the signal processing unit 34 determines whether or not the height of the echo exceeds a predetermined threshold value, and if it does not exceed the threshold value, notifies the operator that the state is abnormal. Thereafter, in step S1210, the operator re-sets up the apparatus.

  On the other hand, if the threshold value is exceeded, the signal processing unit 34 performs the processing from step S1208 onwards assuming that the apparatus is operating normally. In step S1208, the signal processing unit 34 obtains a frequency spectrum of the echo obtained by the transmission / reception probe 1 by performing frequency analysis on the read received echo signal of the reflected wave. Further, the signal processing unit 34 obtains a frequency at which the frequency spectrum has a maximum value as a characteristic frequency.

  Here, as a method for obtaining the frequency spectrum, there is a fast Fourier transform, but other methods may be used as long as they can be obtained by other methods without using the fast Fourier transform. In the case of fast Fourier transform, the received echo signal is often multiplied by various window functions (eg, rectangle, humming, Hanning, Kaiser, etc.). It is determined appropriately according to the frequency characteristics of the probe 1 and the like.

  Finally, in step S1209, the signal processing unit 34 corresponds to the frequency indicating the maximum value specified from the frequency spectrum of the echo of the reflected wave, and the maximum stored in the storage unit 35 in advance as gap data. From the depth of the gap corresponding to the frequency indicating the value (characteristic frequency), the depth of the gap is specified, and the amount of corrosion is estimated using the specified depth of the gap as the depth of corrosion.

  The above is a series of processes for estimating the depth of corrosion by the ultrasonic flaw detector according to Embodiment 2 of the present invention. In the second embodiment, a spike-like signal is generated by the arbitrary waveform generator 31, which excites a wide frequency band signal by the transmission / reception probe 1, and transmits a wide frequency band signal to the transmission / reception probe. This is because it is necessary to receive the signal 1 and the receiving probe 2. That is, if the frequency spectrum of the ultrasonic wave propagating to the test body 11 is a wide band, there is no need to stick to spike-like signals. For example, a stepped signal may be used.

  Further, the characteristic frequency of the frequency spectrum in the second embodiment is not so much in the contact state between the transmission / reception probe 1 and the test body 11 in the same manner as the characteristic frequency in the frequency characteristic of the reflected wave described in the first embodiment. It can be determined without dependence.

  Further, the frequency characteristics of the transmission / reception probe 1 and the reception probe 2 are wide enough to make the difference in the frequency spectrum depending on the corrosion amount clear as in the first embodiment. desirable. Further, the frequency characteristics of these probes may be corrected to obtain the echo frequency spectrum, and the corrosion amount may be obtained from this frequency spectrum.

  Similarly to the first embodiment, when the amount of corrosion near the right side of the figure is to be measured, the installation positions of the two probes may be exchanged. Since measurement is performed using echoes of reflected waves received by the transmission / reception probe 1, a signal having a higher S / N ratio is obtained as the corrosion position is closer to the transmission / reception probe 1.

  In addition, if the location of corrosion in a solid-covered part such as concrete is unknown, two types of frequency spectrum data obtained by exchanging the positions of the two probes on the left and right sides are obtained. The depth of can also be estimated. Alternatively, two frequency spectrum data can be acquired by providing the receiving probe 2 with a transmission / reception function similar to that of the transmitting / receiving probe 1 and performing a switching operation from the transmission unit 32. .

  Furthermore, although the method of measuring the depth of corrosion using the maximum value of the frequency spectrum as the characteristic frequency has been described here, the characteristic frequency does not need to be particular about the maximum value if the measurement uses the characteristic of the frequency spectrum. . For example, if the amount of corrosion can be measured using the minimum value as a result of calculating the frequency spectrum of the echo, the minimum value can also be used as the characteristic frequency. Or it is also possible to estimate the amount of corrosion from the combination of the maximum value and the minimum value.

  Finally, incident angles of the transmitting / receiving probe 1 and the receiving probe 2 will be described. The incident angles of these probes need to be set so that a plate wave can be efficiently transmitted and received as in the first embodiment, but this differs depending on the thickness and frequency of the test body 11. When the thickness of the test body 11 and the frequency band in which the probe 1 for transmission / reception and the probe 2 for reception change are changed, it is necessary to change appropriately according to these.

  According to the second embodiment, flaw detection is performed using a signal having a wide frequency band, and the depth of corrosion can be estimated from the characteristics of the frequency spectrum. Furthermore, the characteristic frequency specified from the characteristics of the frequency spectrum does not depend on the contact state between the probe and the test body. As a result, the amount of corrosion can be estimated without strictly managing the contact state between the probe and the test specimen, and even when the periphery of the test specimen is solidified with a solid such as concrete, It is possible to estimate the amount of corrosion at the boundary with the solid.

  In addition, the amount of corrosion can be estimated using one type of excitation signal with a wide frequency band without using multiple modulated burst signals with different carrier frequencies, reducing the time taken to estimate the amount of corrosion. can do.

It is a block diagram of the ultrasonic flaw detector in Embodiment 1 of this invention. It is explanatory drawing of the signal waveform generate | occur | produced in the arbitrary waveform generation part in Embodiment 1 of this invention. It is a figure which shows the simulation conditions regarding the flaw detection in Embodiment 1 of this invention. This is a sound field simulation result when assuming a modulation burst signal having a carrier frequency f ₀ = 0.6 MHz in Embodiment 1 of the present invention and setting the gap depth d to 2 mm. It is a figure which shows the echo of the reflected wave and the echo of the transmitted wave which were obtained by the simulation in Embodiment 1 of this invention. It is a figure which shows the propagation path of the reflected wave and transmitted wave of a plate wave in Embodiment 1 of this invention. It is a figure which shows the frequency characteristic of the echo height of the reflected wave in Embodiment 1 of this invention. It is a sound field simulation result when assuming a modulation burst signal having a carrier frequency f ₀ = 0.8 MHz in Embodiment 1 of the present invention and setting the gap depth d to 4 mm. It is a figure which shows the frequency characteristic of the echo height of the transmitted wave in Embodiment 1 of this invention. It is a flowchart for demonstrating how to obtain | require the corrosion amount of the ultrasonic flaw detector in Embodiment 1 of this invention. It is explanatory drawing of the signal waveform generate | occur | produced in the arbitrary waveform generation part in Embodiment 2 of this invention. It is a flowchart for demonstrating how to obtain | require the corrosion amount of the ultrasonic flaw detector in Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Probe for transmission / reception, probe for 2 reception, 3 transmission / reception control apparatus, 11 test body, 12 solid, 31 arbitrary waveform generation part, 32 transmission part, 33 reception part, 34 signal processing part, 35 memory | storage part.

Claims (8)

A transmitter / receiver probe that transmits ultrasonic waves generated based on the excitation signal into the test body, receives a reflected wave of the ultrasonic wave propagated through the test body, and outputs a reflected wave electric signal;
A storage unit that preliminarily stores the gap depth of the test object corresponding to the characteristic frequency indicating the singular point of the frequency characteristic of the echo height of the reflected wave electrical signal as gap data; A frequency characteristic of the echo height of the reflected wave electrical signal based on the reflected wave electrical signal from the transmission / reception probe, and a characteristic frequency indicating a singular point from the frequency characteristic And determining the depth of the air gap corresponding to the specified characteristic frequency based on the air gap data stored in the storage unit, whereby the boundary surface between the test body and the solid in contact with the test body An ultrasonic flaw detection device comprising: a transmission / reception control device for estimating the depth of corrosion in the steel. The ultrasonic flaw detector according to claim 1,
A receiving probe for receiving a transmitted wave of the ultrasonic wave propagated through the test body and outputting a transmitted wave electric signal;
When the echo height of the transmitted electric signal from the reception probe is equal to or less than a predetermined threshold, the transmission / reception control device abnormally detects an ultrasonic wave transmitted from the transmission / reception probe to a test body. An ultrasonic flaw detector characterized by determining that there is. The ultrasonic flaw detector according to claim 1 or 2,
The transmission / reception control device includes:
An arbitrary waveform generator for generating a plurality of burst signals having different carrier frequencies as the excitation signal;
A transmitter that sequentially outputs the excitation signals having different carrier frequencies to the probe for transmission and reception;
A receiver for amplifying the reflected wave electrical signal from the transmitter / receiver probe;
The echo height of the amplified reflected wave electrical signal is stored in the storage unit as a frequency characteristic in association with the carrier frequency, a characteristic frequency indicating a singular point is identified from the frequency characteristic, and the identified characteristic frequency is An ultrasonic flaw detector comprising: a signal processing unit that obtains a corresponding gap depth based on the gap data stored in the storage unit. The ultrasonic flaw detector according to claim 3,
The ultrasonic inspection apparatus characterized in that the signal processing unit estimates the depth of corrosion by specifying a frequency at which an echo height has a maximum value in the frequency characteristic as a characteristic frequency indicating a singular point. The ultrasonic flaw detector according to claim 3,
The ultrasonic inspection apparatus characterized in that the signal processing unit estimates a corrosion depth by specifying a frequency at which an echo height has a minimum value in the frequency characteristic as a characteristic frequency indicating a singular point. The ultrasonic flaw detector according to claim 1 or 2,
The transmission / reception control device includes:
An arbitrary waveform generator for generating a signal having a wide frequency band as the excitation signal;
A transmission unit that outputs the excitation signal to the probe for transmission and reception;
A receiver for amplifying the reflected wave electrical signal from the transmitter / receiver probe;
A frequency spectrum of the amplified reflected wave electrical signal is calculated, a characteristic frequency indicating a singular point is identified from the frequency spectrum, and a gap depth corresponding to the identified characteristic frequency is stored in the storage unit. An ultrasonic flaw detector comprising: a signal processing unit that is obtained based on air gap data. The ultrasonic flaw detector according to claim 6,
The ultrasonic inspection apparatus characterized in that the signal processing unit estimates the depth of corrosion by specifying a frequency at which the frequency spectrum has a maximum value as a characteristic frequency indicating a singular point. The ultrasonic flaw detector according to claim 6,
The ultrasonic inspection apparatus characterized in that the signal processing unit estimates a corrosion depth by specifying a frequency at which the frequency spectrum shows a minimum value as a characteristic frequency indicating a singular point.

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