JP2009145056A - Electromagnetic ultrasonic probe and electromagnetic ultrasonic flaw detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic ultrasonic probe which makes constant a flaw detection sensitivity using an ultrasonic wave, regardless of a distance between an electromagnetic ultrasonic probe and an inspection target, and provides good inspection precision, and also to provide an electromagnetic ultrasonic flaw detector. <P>SOLUTION: The electromagnetic ultrasonic probe 1 is equipped with: a means 3 for producing a magnetic field; and a coil 2 for producing an eddy current in the inspection target 6, and is used for detecting the flaw part in the inspection target 6 in a non-contact state by transmitting and receiving an ultrasonic wave with respect to the inspection target 6 by electromagnetic force. At least two conductors 4 which are electrically connected to each other and arranged at an arbitrary interval so as to provide a predetermined area to the surface opposed to the inspection target, are further provided to the probe 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electromagnetic ultrasonic probe used for detecting a defective portion in an inspection object in a non-contact manner, and an electromagnetic ultrasonic flaw detector using the electromagnetic ultrasonic probe.

  As one of the conventional methods for generating and detecting ultrasonic waves in a non-contact manner on an inspection target such as a metal plate or tube, a method using an electromagnetic acoustic transducer (EMAT) is known. ing. In general, the EMAT is composed of a coil for supplying a high-frequency current and a magnet for applying a magnetic field.

  The EMAT generates a Lorentz force by the interaction between an eddy current generated in the vicinity of the surface of the inspection target due to high-frequency vibration of the current flowing through the coil and a magnetic field created on the inspection target by the magnet. And EMAT generates an ultrasonic wave in a test object by vibrating a test object with this Lorentz force. Furthermore, EMAT can detect the ultrasonic wave in the test object by the reverse physical phenomenon.

  When the inspection object is a ferromagnetic material, the EMAT applies a bias magnetic field by an external magnetic field, and changes the bias magnetic field by a magnetic field generated from a coil close to the inspection object. Thereby, an ultrasonic wave can be generated in the inspection object by changing the magnetostriction. For this reason, a contact medium is not required and ultrasonic waves can be transmitted and received without contact. Also, ultrasonic waves of various modes can be generated and detected by the configuration of the magnets and coils.

  As a conventional technique for examining flaw detection, sound velocity measurement, thickness measurement, material measurement and the like using this EMAT, an electromagnetic ultrasonic measurement method and apparatus have been proposed (for example, see Patent Document 1).

JP 2000-266730 A

However, the prior art has the following problems.
Conventional electromagnetic ultrasonic measurement devices can generate and detect ultrasonic waves in a non-contact manner. However, when there is unevenness on the surface of the inspection object, the distance between the electromagnetic ultrasonic probe and the inspection object cannot be kept constant. As a result, the transmission sensitivity and reception sensitivity of the ultrasonic waves vary depending on the distance between the inspection target and the electromagnetic ultrasonic probe.

  That is, when flaw detection is performed using an electromagnetic ultrasonic probe, the distance between the object to be inspected and the electromagnetic ultrasonic probe may differ depending on the position, so the ultrasonic transmission sensitivity and reception sensitivity vary. Inaccurate inspection is not possible.

  The present invention has been made to solve the above-described problems, and the flaw detection sensitivity using ultrasonic waves is constant regardless of the distance between the electromagnetic ultrasonic probe and the inspection object, and good inspection accuracy is achieved. It is an object of the present invention to obtain an electromagnetic ultrasonic probe and an electromagnetic ultrasonic flaw detector that can be realized.

  An electromagnetic ultrasonic probe according to the present invention includes a means for generating a magnetic field and a coil for generating an eddy current in an inspection object, and transmits and receives ultrasonic waves to and from the inspection object by electromagnetic force. In an electromagnetic ultrasonic probe used for detecting a defective portion in an inspection object, they are electrically connected to each other and arranged at an arbitrary interval so as to have a predetermined area on a surface facing the inspection object. And further comprising at least two or more conductors.

  In addition, the electromagnetic ultrasonic flaw detector according to the present invention uses the electromagnetic ultrasonic probe according to the present invention to generate ultrasonic waves by electromagnetic force on the inspection target, and the ultrasonic waves scattered by the defective portion in the inspection target. Is an electromagnetic ultrasonic flaw detection apparatus that performs flaw detection on an inspection object, and is based on the capacitance generated between two or more conductors arranged on the electromagnetic ultrasonic probe and the inspection object. Measuring means for obtaining the distance between the ultrasonic probe and the inspection object, and flaw detection sensitivity control means for maintaining the flaw detection sensitivity of the inspection object at a predetermined value based on the distance obtained by the measuring means. is there.

  According to the present invention, at least two or more conductors that are electrically connected to each other and that are arranged at an arbitrary interval so as to have a predetermined area on the surface facing the inspection object are provided in the electromagnetic ultrasonic probe. It is possible to specify the distance between the electromagnetic ultrasonic probe and the inspection object based on the measured capacitance value. It is possible to obtain an electromagnetic ultrasonic probe and an electromagnetic ultrasonic flaw detector that can achieve a high inspection accuracy with a constant flaw detection sensitivity using sound waves.

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

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of an electromagnetic ultrasonic probe (hereinafter referred to as EMAT) in Embodiment 1 of the present invention. In each figure shown below, the same numerals indicate the same or corresponding parts.

  The EMAT 1 according to the first embodiment includes a coil 2, a magnet 3, two conductor plates 4, and a measuring unit 5. The coil 2 is made by winding a conductive wire such as copper into a circular, elliptical, or rectangular spiral shape from several to several tens of turns from the center, a meander shape, or a similar spiral shape on a printed circuit board. A meander pattern is created. The magnet 3 is a means for generating a magnetic field such as a permanent magnet or an electromagnet. Further, the magnet 3 is arranged so that the generated magnetic field acts on the eddy current generated by the coil 2.

  Here, the principle of transmitting and receiving ultrasonic waves by EMAT1 will be described with reference to the drawings. FIG. 2 is a diagram for explaining the principle of generation of ultrasonic waves by EMAT 1 in the first embodiment of the present invention. Here, a case where a Lorentz force is used as an ultrasonic driving force by EMAT1 will be described.

  As shown in FIG. 2, when an alternating current is passed through the coil 2, an eddy current 7 is generated in the vicinity of the surface of the inspection object 6 made of a conductive material. Further, a magnetic field 8 is applied by the magnet 3, and a Lorentz force 9 is generated by the interaction between the eddy current 7 and the magnetic field 8. According to the high-frequency vibration of the eddy current 7, the Lorentz force 9 periodically varies and vibrates the vicinity of the surface of the inspection object 6. Due to this vibration, an ultrasonic wave 10 is generated and propagates through the inspection object 6.

  When an acoustic discontinuity portion 11 (hereinafter referred to as a defect portion 11) such as a defect or a material change region exists in the inspection target 6, the ultrasonic wave 10 propagating through the inspection target 6 is reflected by the defect portion 11. Propagating again in the direction of EMAT1. When the ultrasonic wave 10 reaches the vicinity of EMAT 1, the magnetic field 8 changes with time due to the displacement of the ultrasonic wave 10.

  An eddy current 7 is generated in a direction in which this magnetic field change is prevented. By detecting the eddy current 7 by the coil 2, it is possible to receive a reflected wave from the defect portion 11 existing in the inspection object 6.

  As described above, in EMAT1, since the ultrasonic wave 10 is transmitted and received by electromagnetic force, no contact medium is required between EMAT1 and the inspection object 6, and the ultrasonic wave 10 can be transmitted and received without contact.

  In the EMAT 1 according to the first embodiment, as shown in FIG. 1, at least two or more conductor plates 4 are arranged at an arbitrary interval, and the surface of each conductor plate 4 facing the inspection target 6 is It has a predetermined area S. FIG. 3 is a diagram schematically showing the relationship between EMAT 1 and inspection object 6 in the first embodiment of the present invention. As shown in FIG. 3, an electrostatic capacity represented by the following formula (1) is generated between each conductor plate 4 and the inspection object 6.

Here, ε ₀ is the dielectric constant of air, and d is the distance between EMAT 1 and the inspection object 6.

  Next, FIG. 4 is an equivalent circuit diagram when the conductor plate 4 is electrically connected in the EMAT 1 according to the first embodiment of the present invention. In the first embodiment, the EMAT 1 has two conductor plates 4. When these two conductor plates 4 are electrically connected, the equivalent circuit is connected in parallel as shown in FIG. When this is combined, the equivalent circuit of FIG. 4B is obtained.

  In FIG. 4B, when the voltage between the terminal 12a and the terminal 12b is v and the current flowing through the circuit is i, the capacitance C is given by the following equation (2).

  Therefore, from the relationship of the above equation (2), the measuring means 5 measures the current i when the voltage v is known, and measures the voltage v when the current i is known. The electrostatic capacitance between EMAT1 and the test object 6 can be obtained. Furthermore, the measuring means 5 can obtain the distance between the EMAT 1 and the inspection object 6 from the measured capacitance using the above equation (1).

  As described above, according to the first embodiment, at least two or more conductors (which are electrically connected to each other and arranged at an arbitrary interval so as to have a predetermined area on the surface facing the inspection object ( A conductor plate is provided in the electromagnetic ultrasonic probe. By using the electromagnetic ultrasonic probe having such a configuration, the distance between the electromagnetic ultrasonic probe and the inspection object can be specified based on the measured capacitance value. As a result, the sensitivity of flaw detection using ultrasonic waves is constant regardless of the distance between the electromagnetic ultrasonic probe and the inspection object, and an electromagnetic ultrasonic probe capable of realizing good inspection accuracy is obtained. Can do.

  In addition, in Embodiment 1 mentioned above, although the structure using three magnets 3 was shown, this invention is not limited to such a structure. What is necessary is just to determine the number of magnets 3, arrangement | positioning, and the positional relationship of the magnet 3 and the coil 2 so that a desired mode may be acquired as the ultrasonic wave 10 to generate | occur | produce.

  Further, as a method for measuring the capacitance, an RC series circuit may be configured, and the capacitance may be measured from charging characteristics using a transient phenomenon of the RC series circuit.

Embodiment 2. FIG.
FIG. 5 is a schematic configuration diagram of the EMAT according to the second embodiment of the present invention. The EMAT 1 according to the second embodiment includes a coil 2, a magnet 3 a, a magnet 3 b having two surfaces coated with a conductive material, and a measuring unit 5. Compared with the configuration of FIG. 1 in the first embodiment, the configuration of FIG. 5 in the second embodiment has a conductive material applied to two surfaces instead of two conductor plates 4 as a conductor. The difference is that the magnet 3b is used.

  The coil 2 is made by winding a conductive wire such as copper into a circular, elliptical, or rectangular spiral shape from several to several tens of turns from the center, a meander shape, or a similar spiral shape on a printed circuit board. A meander pattern is created.

  The magnet 3a is a means for generating a magnetic field such as a permanent magnet or an electromagnet, and is equivalent to the magnet 3 in FIG. Further, at least two magnets 3b are provided and are means for generating a magnetic field such as a permanent magnet or an electromagnet, and a conductive material is applied to the surface. Further, the magnet 3 a and the magnet 3 b are arranged so that the magnetic field acts on the eddy current generated by the coil 2.

  The EMAT 1 having the configuration shown in FIG. 5 according to the second embodiment has at least two magnets 3b arranged at an arbitrary interval. The surface of the magnet 3b is coated with a conductive material, and the surface of the magnet 3b coated with each conductive material facing the inspection object 6 has a predetermined area S. Therefore, the electrostatic capacitance shown by the above equation (1) is generated between the magnet 3b to which each conductive material is applied and the inspection object 6, as in the first embodiment.

  In the second embodiment, the EMAT 1 has two magnets 3b coated with a conductive material, and when these two magnets 3b are electrically connected, the equivalent circuit thereof is the same as in the first embodiment. Similarly to FIG. 4, FIGS. 4A and 4B are obtained. Further, the capacitance C is also given by the above equation (2) as in the first embodiment.

  Therefore, the measuring means 5 measures the current i when the voltage v is known from the relationship of the above equation (2), as in the first embodiment, and the current i is known. By measuring the voltage v, the capacitance between EMAT1 and the inspection object 6 can be obtained. Furthermore, the measuring means 5 can obtain the distance between the EMAT 1 and the inspection object 6 from the measured capacitance using the above equation (1).

  As described above, according to the second embodiment, the same effect as in the first embodiment can be obtained even when a magnet having a surface coated with a conductive material is used instead of the conductor plate. be able to.

  In the second embodiment described above, the configuration using one magnet 3a and two magnets 3b is shown, but the present invention is not limited to such a configuration. The number and arrangement of the magnets 3a and 3b and the positional relationship between the magnets 3a and 3b and the coil 2 may be determined so that a desired mode can be obtained as the generated ultrasonic wave 10.

  Further, as a method for measuring the capacitance, an RC series circuit may be configured, and the capacitance may be measured from charging characteristics using a transient phenomenon of the RC series circuit.

Embodiment 3 FIG.
FIG. 6 is a schematic configuration diagram of the EMAT according to the third embodiment of the present invention. The EMAT 1 according to the third embodiment includes two coils 2, a magnet 3, and measurement means 5. Compared with the configuration of FIG. 1 in the first embodiment, the configuration of FIG. 6 in the third embodiment is that two coils 2 are used instead of the two conductor plates 4 as conductors. Is different.

  The coil 2 is formed by winding a conductive wire such as copper in a circular, elliptical, or rectangular spiral shape from several to several tens of turns from the center, or by creating a similar spiral pattern on a printed circuit board. is there. The magnet 3 is a means for generating a magnetic field such as a permanent magnet or an electromagnet. Further, the magnet 3 is arranged so that the generated magnetic field acts on the eddy current generated by the coil 2.

  The EMAT 1 having the configuration shown in FIG. 6 according to the third embodiment has at least two coils 2 arranged at an arbitrary interval. These two coils 2 are wound closely in a spiral shape, and the surface of the coil facing the object to be inspected is regarded as equivalent to the conductor plate 4 in FIG. Let S be the area. In this case, between the coil 2 and the inspection object 6, as in the first embodiment, a capacitance represented by the above equation (1) is generated.

  In the third embodiment, the EMAT 1 has two coils 2, and when these two coils 2 are electrically connected, the equivalent circuit thereof is the same as that of the first embodiment shown in FIG. (A) and (b). Further, the capacitance C is also given by the above equation (2) as in the first embodiment.

  Therefore, the measuring means 5 measures the current i when the voltage v is known from the relationship of the above equation (2), as in the first embodiment, and the current i is known. By measuring the voltage v, the capacitance between EMAT1 and the inspection object 6 can be obtained. Furthermore, the measuring means 5 can obtain the distance between the EMAT 1 and the inspection object 6 from the measured capacitance using the above equation (1).

  As described above, according to the third embodiment, even when a coil is used as the conductor instead of the conductor plate, the same effect as in the first and second embodiments can be obtained.

  In addition, in Embodiment 3 mentioned above, although the structure using three magnets 3 was shown, this invention is not limited to such a structure. What is necessary is just to determine the number of magnets 3, arrangement | positioning, and the positional relationship of the magnet 3 and the coil 2 so that a desired mode may be acquired as the ultrasonic wave 10 to generate | occur | produce.

  Further, as a method for measuring the capacitance, an RC series circuit may be configured, and the capacitance may be measured from charging characteristics using a transient phenomenon of the RC series circuit.

  In the first to third embodiments described above, two conductor plates (Embodiment 1), two magnets (Embodiment 2), two coils (Embodiment) are used as at least two conductors in EMAT. Embodiment 3) has been described. However, the two or more conductors in the present invention are not limited to such a configuration. As at least two or more conductors in EMAT, a conductor plate and a magnet, a conductor plate and a coil, or a combination of a magnet and a coil may be used.

Embodiment 4 FIG.
In the first to third embodiments, the EMAT of the present invention has been described. In contrast, in Embodiments 4 to 6 described below, an electromagnetic ultrasonic flaw detector using the EMAT of the present invention will be described.

  FIG. 7 is a schematic configuration diagram of an electromagnetic ultrasonic flaw detector (hereinafter referred to as a flaw detector) according to Embodiment 4 of the present invention. In each figure shown below, the same numerals indicate the same or corresponding parts.

  The flaw detection apparatus according to the fourth embodiment includes EMAT 1, measurement means 5, position control unit 12, transmission unit 13, and reception unit 14. Here, any one of EMAT1 described in the first to third embodiments is applied to EMAT1. In addition, the position control part 12 in this Embodiment 4 is corresponded to a flaw detection sensitivity control means.

  Next, the operation of the flaw detector according to the fourth embodiment will be described. In FIG. 7, EMAT 1, which is used for both transmission and reception, is arranged in proximity to the inspection object 6 and performs a flaw detection of the defective portion 11 in the inspection object 6. An arbitrary drive signal for driving EMAT1 is input from the transmitter 13 to EMAT1. When the drive signal is input to EMAT1, an eddy current is generated in the inspection object 6 by the coil 2 included in EMAT1. Further, a magnetic field is applied to the inspection object 6 by the magnet 3 included in EMATl.

  As a result, Lorentz force, which is an interaction between eddy current and magnetic field, is generated in the inspection object 6, and the inspection object 6 vibrates by this Lorentz force. This vibration is converted into an ultrasonic wave and propagates into the inspection object 6. The ultrasonic wave propagated in the inspection object 6 is scattered by the defect portion 11 in the inspection object 6, and a part of the scattered wave propagates again in the direction of EMAT1 and is received by EMAT1. The ultrasonic wave received by EMAT 1 is subjected to signal processing in the receiving unit 14, and position information of the defective part 11 is detected.

  The EMAT1 in the fourth embodiment uses the EMAT1 described in any of the first to third embodiments. For this reason, the measuring means 5 can obtain distance information between the EMAT 1 and the inspection object 6. Therefore, the position control unit 12 refers to the distance information as a feedback amount, determines a correction amount so that the distance between the EMAT1 and the inspection object 6 becomes a predetermined target distance regardless of the measurement point, and the EMAT1 is determined based on the correction amount. The position is feedback controlled.

  As described above, according to the fourth embodiment, the distance between the EMAT and the inspection object can be kept at a predetermined target distance regardless of the flaw detection position by the function of the position control unit. Thereby, an electromagnetic ultrasonic flaw detector can be obtained in which fluctuations in flaw detection sensitivity due to ultrasonic waves caused by differences in the distance between the EMAT and the inspection object are suppressed.

  In the flaw detection apparatus according to the fourth embodiment, the EMAT has been described for the configuration for both transmission and reception. However, the EMAT may be different for transmission and reception.

Embodiment 5 FIG.
In the previous embodiment 4, the position control of EMAT1 is performed based on the measurement result of the distance between EMAT1 and inspection object 6, so that the ultrasonic wave generated by the difference in distance between EMAT1 and inspection object 6 is used. The case where the fluctuation of the flaw detection sensitivity is suppressed has been described. On the other hand, in the fifth embodiment, a case will be described in which fluctuations in flaw detection sensitivity due to ultrasonic waves are suppressed by a method different from that of the fourth embodiment.

  FIG. 8 is a schematic configuration diagram of a flaw detection apparatus according to Embodiment 5 of the present invention. The flaw detection apparatus according to the fifth embodiment includes EMAT 1, measurement means 5, transmission unit 13, and reception unit 14. Here, any one of EMAT1 described in the first to third embodiments is applied to EMAT1.

  Compared with the configuration of FIG. 7 in the previous embodiment 4, the configuration of FIG. 8 in the present embodiment 5 does not have the position control unit 12, but transmits the distance measurement result by the measuring means 5 to the transmission unit 13. The point of feedback is different. In addition, the transmission part 13 in this Embodiment 5 is corresponded to a flaw detection sensitivity control means.

  Next, the operation of the flaw detection apparatus in the fifth embodiment will be described. In FIG. 8, EMAT 1, which is used for both transmission and reception, is arranged in proximity to the inspection object 6 and performs a flaw detection of the defective portion 11 in the inspection object 6. An arbitrary drive signal for driving EMAT1 is input from the transmitter 13 to EMAT1. When the drive signal is input to EMAT1, an eddy current is generated in the inspection object 6 by the coil 2 included in EMAT1. Further, a magnetic field is applied to the inspection object 6 by the magnet 3 included in EMATl.

  As a result, Lorentz force, which is an interaction between eddy current and magnetic field, is generated in the inspection object 6, and the inspection object 6 vibrates by this Lorentz force. This vibration is converted into an ultrasonic wave and propagates into the inspection object 6. The ultrasonic wave propagated in the inspection object 6 is scattered by the defect portion 11 in the inspection object 6, and a part of the scattered wave propagates again in the direction of EMAT1 and is received by EMAT1. The ultrasonic wave received by EMAT 1 is subjected to signal processing in the receiving unit 14, and position information of the defective part 11 is detected.

  The EMAT1 in the fifth embodiment uses the EMAT1 described in any of the first to third embodiments. For this reason, the measuring means 5 can obtain distance information between the EMAT 1 and the inspection object 6. Therefore, the transmission unit 13 refers to the distance information measured by the measuring unit 5, determines a correction amount according to the distance between the EMAT1 and the inspection object 6, and according to this correction amount, the drive signal (voltage or voltage) of the EMAT1. Change the current.

  More specifically, when the distance between the EMAT 1 and the inspection target 6 is large, the transmission unit 13 increases the drive signal (voltage or current) according to the distance. On the other hand, when the distance between the EMAT 1 and the inspection object 6 is small, the transmission unit 13 reduces the drive signal (voltage or current) according to the distance. According to the distance between EMAT 1 and inspection object 6, by obtaining in advance a driving signal that makes the flaw detection sensitivity constant, the flaw detection sensitivity using ultrasonic waves by EMAT 1 becomes constant regardless of the flaw detection position. In addition, the transmission intensity of the ultrasonic wave can be corrected.

  As described above, according to the fifth embodiment, the size of the drive signal can be varied according to the distance between the EMAT and the inspection target by the function of the transmission unit. Thereby, the transmission intensity of the ultrasonic wave can be corrected so that the flaw detection sensitivity using the ultrasonic wave by the EMAT is constant regardless of the flaw detection position. Thereby, an electromagnetic ultrasonic flaw detector can be obtained in which fluctuations in flaw detection sensitivity due to ultrasonic waves caused by differences in the distance between the EMAT and the inspection object are suppressed.

  In the flaw detection apparatus according to the fifth embodiment, the EMAT has been described for the configuration for both transmission and reception. However, the EMAT may be different for transmission and reception.

Embodiment 6 FIG.
In the previous embodiment 4, the position control of EMAT1 is performed based on the measurement result of the distance between EMAT1 and inspection object 6, so that the ultrasonic wave generated by the difference in distance between EMAT1 and inspection object 6 is used. The case where the fluctuation of the flaw detection sensitivity is suppressed has been described. Further, in the previous embodiment 5, based on the measurement result of the distance between EMAT1 and inspection object 6, the ultrasonic transmission intensity is corrected so that the flaw detection sensitivity using ultrasonic waves by EMAT1 is made constant. A case has been described in which fluctuations in flaw detection sensitivity due to ultrasonic waves caused by differences in the distance between EMAT1 and inspection object 6 are suppressed. On the other hand, in the sixth embodiment, a case will be described in which fluctuations in flaw detection sensitivity due to ultrasonic waves are suppressed by a method different from the fourth and fifth embodiments.

  FIG. 9 is a schematic configuration diagram of a flaw detection apparatus according to Embodiment 6 of the present invention. The flaw detection apparatus according to the sixth embodiment includes EMAT 1, measurement unit 5, transmission unit 13, and reception unit 14. Any of the EMAT1 described in the first to third embodiments is applied to the EMAT1.

  Compared with the configuration of FIG. 8 in the previous embodiment 5, the configuration of FIG. 9 in the present embodiment 6 is the same in the components itself, but the distance measurement result by the measuring means 5 is transmitted to the transmission unit. Instead of feeding back to 13, the receiving unit 14 is fed back. The receiving unit 14 in the sixth embodiment corresponds to flaw detection sensitivity control means.

  Next, the operation of the flaw detection apparatus in the sixth embodiment will be described. In FIG. 9, EMAT 1, which is used for both transmission and reception, is arranged in proximity to the inspection object 6 and performs a flaw detection on the defective portion 11 in the inspection object 6. An arbitrary drive signal for driving EMAT1 is input from the transmitter 13 to EMAT1. When the drive signal is input to EMAT1, an eddy current is generated in the inspection object 6 by the coil 2 included in EMAT1. Further, a magnetic field is applied to the inspection object 6 by the magnet 3 included in EMATl.

  As a result, Lorentz force, which is an interaction between eddy current and magnetic field, is generated in the inspection object 6, and the inspection object 6 vibrates by this Lorentz force. This vibration is converted into an ultrasonic wave and propagates into the inspection object 6. The ultrasonic wave propagated in the inspection object 6 is scattered by the defect portion 11 in the inspection object 6, and a part of the scattered wave propagates again in the direction of EMAT1 and is received by EMAT1. The ultrasonic wave received by EMAT 1 is subjected to signal processing in the receiving unit 14, and position information of the defective part 11 is detected.

  The EMAT1 in the sixth embodiment uses the EMAT1 described in any of the first to third embodiments. For this reason, the measuring means 5 can obtain distance information between the EMAT 1 and the inspection object 6. Therefore, the receiving unit 14 refers to the distance information measured by the measuring unit 5, determines a correction amount according to the distance between the EMAT 1 and the inspection object 6, and corrects the detected signal according to the correction amount. .

  More specifically, when the distance between the EMAT 1 and the inspection object 6 is large, the receiving unit 14 amplifies the detection signal according to the distance. On the other hand, when the distance between the EMAT 1 and the inspection object 6 is small, the receiving unit 14 attenuates the detection signal according to the distance. By detecting the amplification factor / attenuation rate of the detection signal so that the flaw detection sensitivity is constant according to the distance between the EMAT 1 and the inspection object 6, the flaw detection using the ultrasonic waves by the EMAT1 regardless of the flaw detection position. The ultrasonic detection signal can be corrected so that the sensitivity is constant.

  As described above, according to the sixth embodiment, the magnitude of the detection signal can be varied according to the distance between the EMAT and the inspection object by the function of the receiving unit. Thereby, the detection signal of the ultrasonic wave can be corrected so that the flaw detection sensitivity using the ultrasonic wave by EMAT is constant regardless of the flaw detection position. Thereby, an electromagnetic ultrasonic flaw detector can be obtained in which fluctuations in flaw detection sensitivity due to ultrasonic waves caused by differences in the distance between the EMAT and the inspection object are suppressed.

  In the flaw detection apparatus according to the sixth embodiment, the EMAT has been described for the configuration for both transmission and reception. However, the EMAT may be different for transmission and reception.

It is a schematic block diagram of the electromagnetic ultrasonic probe in Embodiment 1 of this invention. It is a figure explaining the generation principle of the ultrasonic wave by the electromagnetic ultrasonic probe in Embodiment 1 of this invention. It is the figure which showed typically the relationship between the electromagnetic ultrasonic probe in Embodiment 1 of this invention, and a test object. In the electromagnetic ultrasonic probe of Embodiment 1 of this invention, it is an equivalent circuit diagram at the time of connecting a conductor board electrically. It is a schematic block diagram of the electromagnetic ultrasonic probe in Embodiment 2 of this invention. It is a schematic block diagram of the electromagnetic ultrasonic probe in Embodiment 3 of this invention. It is a schematic block diagram of the electromagnetic ultrasonic flaw detector in Embodiment 4 of this invention. It is a schematic block diagram of the electromagnetic ultrasonic flaw detector in Embodiment 5 of this invention. It is a schematic block diagram of the electromagnetic ultrasonic flaw detector in Embodiment 6 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electromagnetic ultrasonic probe, 2 coils, 3, 3a, 3b magnet, 4 conductor board, 5 measuring means, 6 inspection object, 11 defect part, 12 position control part, 13 transmission part, 14 reception part.

Claims (6)

Means for generating a magnetic field and a coil for generating an eddy current in the inspection object, for transmitting and receiving ultrasonic waves to and from the inspection object by electromagnetic force, and for detecting a defective portion in the inspection object without contact In the electromagnetic ultrasonic probe used for
An electromagnetic ultrasonic probe further comprising at least two or more conductors that are electrically connected to each other and arranged at an arbitrary interval so as to have a predetermined area on a surface facing the inspection object. Tentacles. The electromagnetic ultrasonic probe according to claim 1,
The two or more conductors are composed of a conductor plate, a magnet, a coil, or a combination thereof. The electromagnetic ultrasonic probe according to claim 1 or 2, wherein an ultrasonic wave is generated by an electromagnetic force on the inspection object, and ultrasonic waves scattered by a defect portion in the inspection object are received and the inspection is performed. An electromagnetic ultrasonic flaw detector for flaw detection of an object,
Based on the capacitance generated between the two or more conductors arranged on the electromagnetic ultrasonic probe and the inspection object, the distance between the electromagnetic ultrasonic probe and the inspection object is determined. Measuring means to be obtained;
An electromagnetic ultrasonic flaw detector comprising: flaw detection sensitivity control means for maintaining the flaw detection sensitivity of the inspection object at a predetermined value based on the distance obtained by the measuring means. The electromagnetic ultrasonic flaw detector according to claim 3,
The flaw detection sensitivity control means uses the distance obtained by the measurement means as a feedback amount, so that the distance between the electromagnetic ultrasonic probe and the inspection object becomes a predetermined target distance. An electromagnetic ultrasonic flaw detector comprising a position control unit for controlling the position of an acoustic probe. The electromagnetic ultrasonic flaw detector according to claim 3,
The flaw detection sensitivity control means is configured to detect the electromagnetic ultrasonic wave in accordance with the distance obtained by the measurement means so that the flaw detection sensitivity based on the ultrasonic waves scattered by the defect portion in the inspection target becomes a predetermined value. An electromagnetic ultrasonic flaw detector comprising: transmission-side intensity correction means for correcting the intensity of ultrasonic waves generated by a touch element. The electromagnetic ultrasonic flaw detector according to claim 3,
The flaw detection sensitivity control means is configured to detect the electromagnetic ultrasonic wave in accordance with the distance obtained by the measurement means so that the flaw detection sensitivity based on the ultrasonic waves scattered by the defect portion in the inspection target becomes a predetermined value. An electromagnetic ultrasonic flaw detector comprising: a receiving-side intensity correcting means for correcting the intensity of an ultrasonic wave received by a toucher.

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