JP2008309754A - Ultrasonic probe and ultrasonic flaw detecting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe, by which ultrasonic flaw detection on an object to be tested can be performed even in a highly radioactive site, a contact medium can be used repeatedly and the operation before and after tests is simple. <P>SOLUTION: The ultrasonic probe 1A includes an ultrasonic transducer 2 that transmits and receives ultrasonic signals, a damper 4 disposed on the opposite face of an ultrasonic transmitting and receiving face 3 of the ultrasonic transducer 2, an insulating holder 6 that holds these ultrasonic transducers 2 and damper 4, a metallic case 5 that stores the holder 6, a connector 9 disposed on the upper end of the case 5, lead wires 7, 8 that connect an upper electrode and lower electrode, which are not shown in the figure, disposed on the ultrasonic transducer 2, a cylindrical coupling 11 disposed on the lower end of the case 5, and bentonite 10 that fills up the coupling 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe for detecting an internal defect of an inspection object such as a steel structure or a concrete structure having a high radiation field in a nuclear facility using an ultrasonic reflected wave, and an object using the ultrasonic probe. The present invention relates to an ultrasonic flaw detection method for an inspection object.

  An ultrasonic probe is used as a main device of an ultrasonic flaw detection apparatus that nondestructively inspects internal defects of a steel structure or a concrete structure. This ultrasonic probe propagates ultrasonic waves into the object to be inspected, and detects defect part reflected waves that collide with and reflect the defect part, thereby detecting defects such as cracks and voids inside the object to be inspected. It is to detect.

  When performing such ultrasonic flaw detection, in order to efficiently transmit the ultrasonic wave transmitted from the ultrasonic probe into the inside of the inspection object, the ultrasonic probe is brought into close contact with the surface of the inspection object. There is a need. For this reason, it is indispensable to interpose a viscous contact medium such as liquid glycerin or oil that propagates ultrasonic waves between the surface of the object to be inspected and the ultrasonic probe.

  Conventionally, as an ultrasonic probe for general industry, an ultrasonic probe having an integral structure in which a contact medium such as a soft gel-like substance is provided integrally with an ultrasonic probe has been proposed (for example, Patent Documents 1, 2, and 3)) and all of the conventionally proposed contact media do not have radiation resistance, and in a high radiation field, they cause radiolysis in a short time and their functions are easily lost.

  As a medical ultrasonic diagnostic method, a method of using bentonite as a colloidal clay for testing has been conventionally proposed (see, for example, Patent Document 4). However, in this method, bentonite is directly used during testing. Since it is inserted manually into a human body organ to increase the contrast during examination, it cannot be applied to use in a high radiation field.

  In addition, the conventional ultrasonic probe uses an epoxy resin adhesive for joining the ultrasonic transducer and the case, for example, and the radiation resistance of the epoxy resin is as low as about 100 Gy. In a vitrification facility or the like under a high radiation environment such as h, the adhesive layer cracks in a few hours, making it impossible to use.

  Further, as a damper, there is conventionally known one formed by using a metal powder having a high acoustic impedance and an epoxy resin or a polyurethane resin having a low acoustic impedance (for example, see Patent Document 4). When the used ultrasonic probe is used in a high radiation field, the damper is destroyed in a short time, and the use becomes impossible.

  In the present invention, bentonite used as a contact medium for ultrasonic flaw detection is a material having thixotropy, and thixotropy is a phenomenon in which viscosity is reversibly reduced when force is applied (for example, non-patent literature). 1). In other words, when this bentonite is used as a contact medium, the viscosity is high at rest, but the viscosity is low when pressure is applied, so the adhesion between the ultrasonic probe and the object to be inspected increases, and the propagation characteristics of the ultrasonic wave. Will increase. In particular, when applied to ultrasonic flaw detection of a material having a large surface roughness such as concrete or rock, bentonite as a contact medium is filled in the concave portion of the surface, and it can be expected that the ultrasonic flaw detection performance is efficiently increased.

Bentonite is a candidate material for artificial barriers used for geological disposal of radioactive waste, and has a proven track record even in a radiation field with a surface dose rate of about 4 × 10 ⁴ Gy / y emitted from a waste package (for example, (See Patent Document 2).

  As for radiation-resistant resin materials, polyamide resins such as aramid resins represented by Nomex (trade name of DuPont) and Conex (trade name of Teijin) are superior to epoxy resins. (For example, refer nonpatent literature 3).

In addition, as radiation-resistant materials that have recently been in the spotlight, some materials that use silica-based thin films with improved radiation resistance have been put into practical use by suppressing oxygen permeation into polymer materials. (For example, see Non-Patent Document 4).
JP 2005-241337 A JP-A-5-277104 JP-A-3-296658 JP 2005-524711 A JP-A-8-105870 Yuya Kato: Study on properties of grout with thixotropic properties, Abstracts of 57th Annual Conference, Japan Society of Civil Engineers, pp. 773-774-1408 (2002) Minutes of the Nuclear Energy Commission Long Half-life Low-heat Radioactive Waste Disposal Technology Review Meeting (4th) Monday, February 20, 2006 10: 00-11: 57 4P Tadao Higuchi: Radiation-resistant organic materials, radiation and industry, (66), 5 (1995) Yoshinori Kobayashi: Improvement of radiation resistance of polymers by silica membrane, AIST TODAY 2006-01 pp. 24-25 (2006)

  As described above, the conventional ultrasonic probe uses glycerin or oil as a contact medium for bringing the ultrasonic probe into close contact with the surface of the object to be inspected. It becomes impossible to use it in time. In addition, an epoxy resin adhesive is used for joining the ultrasonic transducer and the case, and an epoxy resin is used as a constituent material of the damper. It will become impossible to use in the future. Furthermore, since conventional ultrasonic probes apply a contact medium such as glycerin or oil to the surface of the object to be inspected for each inspection, a large amount of labor is required for the inspection preparation work, and after the test, the inspection object is inspected. Since glycerin or oil applied to the surface of the body must be removed, there is also a problem that a great deal of labor is required for the work of cleaning the inspection object after the inspection.

  The present invention has been made in order to solve the above-described problems of the prior art, and the object thereof is to enable ultrasonic inspection of an object to be inspected even in a high radiation field, to repeatedly use a contact medium, and It is an object to provide an ultrasonic probe that is easy to perform before and after inspection.

  In order to achieve the above object, the present invention relates to an ultrasonic probe. First, an ultrasonic transducer that transmits and receives an ultrasonic signal, and an opposite side of the ultrasonic transducer surface of the ultrasonic transducer A damper provided on the surface, an insulating holding body for holding the ultrasonic vibrator and the damper, a metal case for storing the holding body, and a cylindrical coupling provided in the case. And the coupling is filled with bentonite as a contact medium for ultrasonic flaw detection interposed between the ultrasonic wave transmitting / receiving surface of the ultrasonic transducer and the object to be inspected.

  Since bentonite has thixotropic properties, the viscosity of the bentonite is reduced by receiving ultrasonic waves transmitted from the ultrasonic vibrator, and the bentonite functions as a contact medium that fills the space between the ultrasonic vibrator and the object to be inspected. In addition, bentonite is a material having high radiation resistance and acoustic impedance. Therefore, by using this as a contact medium, the radiation resistance of the ultrasonic probe and the SN ratio of the detection signal can be increased. Furthermore, since bentonite can be easily washed with water, it is possible to facilitate the cleaning work of the inspection object after the inspection. In addition, when bentonite is filled in the coupling, it is not necessary to apply a contact medium to the surface of the object to be inspected for each inspection, so that preparation work before the inspection can be facilitated.

  The present invention also relates to the ultrasonic probe according to the second aspect. In the ultrasonic probe having the first configuration, the ultrasonic transducer and the damper, the ultrasonic transducer and the holding body, and the holding The body and the case were bonded to each other using a radiation-resistant adhesive.

  According to such a configuration, since the radiation resistance of the bonded portion can be increased, an ultrasonic probe that can be used in a high radiation field can be obtained.

  In the third aspect of the present invention, the ultrasonic probe having the first configuration is configured such that the outer surface of the damper is covered with a radiation-resistant coating film.

  According to such a configuration, since the radiation resistance of the damper can be improved, an ultrasonic probe that can be used in a high radiation field can be obtained.

  According to the present invention, fourthly, with respect to the ultrasonic probe, in the ultrasonic probe having the first configuration, the coupling is detachably attached to the case.

  According to such a configuration, since it is easy to fill the coupling with bentonite, it is possible to easily fill the coupling with bentonite having a different moisture content depending on the material of the object to be inspected, and to detect the ultrasonic wave for various purposes. Tactile application becomes easy.

  On the other hand, the present invention relates to an ultrasonic flaw detection method. First, an ultrasonic transducer that transmits and receives an ultrasonic signal, and a damper provided on a surface opposite to the ultrasonic transmission / reception surface of the ultrasonic transducer; An insulating holding body for holding the ultrasonic vibrator and the damper, a metal case for storing the holding body, and a cylindrical coupling provided in the case, and the inside of the coupling Using an ultrasonic probe filled with bentonite as a contact medium for ultrasonic flaw detection interposed between the ultrasonic wave transmitting / receiving surface of the ultrasonic transducer and the object to be inspected, the tip of the coupling is attached to the tip of the coupling. The ultrasonic wave is transmitted from the ultrasonic wave transmitting / receiving surface of the ultrasonic vibrator to the bentonite while being in contact with the surface of the inspection object, and the bentonite is reduced in viscosity to perform the flaw detection inside the inspection object. .

  According to such a configuration, since the ultrasonic probe filled with bentonite as a contact medium for ultrasonic flaw detection in the coupling is used, the radiation resistance and the SN ratio of the ultrasonic probe are improved, and before inspection. Preparation work and cleaning work of the inspection object after the inspection can be facilitated.

  The present invention also relates to the ultrasonic flaw detection method. Second, in the ultrasonic flaw detection method of the first configuration, when the surface roughness of the inspection object is large, the moisture content of the bentonite is increased, and When the surface roughness of the specimen is small, the water content ratio of the bentonite is lowered.

  According to this configuration, when the surface roughness of the object to be inspected is large, the viscosity of bentonite can be reduced to improve the adhesion of bentonite to the surface of the object to be inspected. Moreover, when the surface roughness of a to-be-inspected object is small, the viscosity of bentonite can be enlarged and the consumption by the flow-out of bentonite can be suppressed.

  Since the ultrasonic probe of the present invention is formed by filling bentonite as a contact medium for ultrasonic flaw detection in the coupling, the radiation resistance and SN ratio of the ultrasonic probe are improved, and before inspection. The preparatory work and the cleaning work of the inspection object after the inspection can be facilitated.

  Moreover, since the ultrasonic flaw detection method of the present invention uses an ultrasonic probe filled with bentonite as a contact medium for ultrasonic flaw detection in the coupling, the radiation resistance and the SN ratio of the ultrasonic probe are low. In addition, the preparatory work before the inspection and the cleaning work of the inspection object after the inspection can be facilitated.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of the ultrasonic probe according to the first embodiment in use, and FIG. 2 is a graph showing the acoustic impedance of bentonite compared with the acoustic impedance of other main contact media.

  As shown in FIG. 1, an ultrasonic probe 1A according to the first embodiment is opposite to an ultrasonic transducer 2 that transmits and receives an ultrasonic signal and an ultrasonic transmission / reception surface 3 of the ultrasonic transducer 2. A damper 4 provided on the side surface, an insulating holder 6 that holds the ultrasonic transducer 2 and the damper 4, a metal case 5 that houses the holder 6, and an upper end portion of the case 5 Leads 7 and 8 for connecting the connector 9 to the connector 9 provided on the (end portion on which the damper 4 is disposed) and upper and lower electrodes (not shown) provided in the ultrasonic transducer 2 and the connector 9. And a cylindrical coupling 11 provided at the lower end of the case 5 (the end on the side where the ultrasonic wave transmitting / receiving surface 3 is disposed) and a bentonite 10 filled in the coupling 11.

  The ultrasonic transducer 2 has a required piezoelectric element sandwiched between an upper electrode and a lower electrode, and a peripheral surface is bonded to the inner surface of the holding body 6. In the ultrasonic transducer 2 of this example, the lower electrode is an ultrasonic transmission / reception surface 3, and the ultrasonic transducer 2 is excited by a transmission wave output from the main body of an ultrasonic flaw detector (not shown), so that the ultrasonic transmission / reception is performed. An ultrasonic pulse is transmitted from the wavefront 3 into the inspection object 12 through the contact medium 10. In addition, the ultrasonic pulse reflected on the defect in the inspection object 12 and the bottom surface of the inspection object 12 is received by the ultrasonic transducer 2 and converted into an electric signal, and is transmitted through the connector 9 to the ultrasonic flaw detector. Sent to the main unit.

  The damper 4 has a function of quickly reducing the mechanical free vibration of the ultrasonic transducer 2 and improving the resolution of the ultrasonic probe 1A. For example, a metal block or metal powder with high acoustic impedance is used. A material formed by mixing with a resin material having low acoustic impedance is used. The damper 4 is bonded to the back surface of the ultrasonic transducer 2, that is, the surface opposite to the ultrasonic wave transmitting / receiving surface.

  The case 5 is formed into a required shape and size using a metal material such as aluminum.

  The holding body 6 is for ensuring insulation between the ultrasonic vibrator 2 and the case 5, is formed of a resin material, and is bonded to the inner surface of the case 5. Lead wires 7 and 8 for connecting the upper electrode and lower electrode of the ultrasonic vibrator 2 to the connector 9 are wired along the inner surface of the holding body.

  Similar to the case 5, the coupling 11 is formed of a metal material such as aluminum and is detachably attached to the case 5. As a means for attaching the coupling 11 to the case 5, fastening or fitting can be used. Thus, when the coupling 11 is configured to be detachable from the case 5, the coupling 11 can be easily removed by removing the coupling 11 from the case 5. The child 1A can be used conveniently, and bentonite having a different water content depending on the material of the object 12 to be inspected can be refilled into the coupling 11 as appropriate. The application of the probe 1A is facilitated, and the versatility of the ultrasonic probe 1A can be enhanced.

The adhesive for bonding the ultrasonic vibrator 2 and the damper 4, the adhesive for bonding the ultrasonic vibrator 2 and the holding body 6, and the adhesive for bonding the holding body 6 and the case 5 have excellent radiation resistance. A polyamide-based resin such as an aramid resin represented by Nomex or Conex is used. Further, this kind of radiation-resistant resin material is also used as the resin material constituting the damper 4 and the resin material constituting the holding body 6. Thereby, the radiation resistance of the ultrasonic probe 1A can be improved. That is, the radiation resistance of the epoxy resin is about 10 ² Gy, whereas the polyamide resin is about 10 ⁷ Gy. Therefore, the ultrasonic probe 1A of this example is sufficiently used in a high radiation field. be able to.

  Bentonite 10 is a generic name for weakly alkaline claystones that are mainly composed of the clay mineral montmorillonite and siliceous minerals such as quartz, α-cristobalite, and opal, and have high acoustic impedance, thixotropy and radiation resistance. In addition, since the material cost is low and the object to be inspected 12 can be easily cleaned after the inspection is completed, it is particularly suitable as a contact medium for ultrasonic flaw detection performed in a high radiation field.

That is, as shown in FIG. 2, the bentonite 10 is approximately compared to the acoustic impedance (1.5 × 10 ⁵ g / cm ² / s) of water that may be used as a contact medium for ultrasonic flaw detection. It has an acoustic impedance that is 2.7 times higher than that of glycerin, polystyrene, and acrylic, which are other typical materials used as a contact medium for ultrasonic flaw detection. In addition, FIG. 2 has shown the acoustic impedance of each substance normalized on the basis of the acoustic impedance of water. When a contact medium having a high acoustic impedance is used in this way, the acoustic propagation performance of the ultrasonic wave from the ultrasonic probe 1A to the object to be inspected 12 is improved and the SN ratio of the ultrasonic reflected wave is increased. A defect of the inspection object 12 can be detected.

  The elements contained in bentonite 10 are the main elements that make up the crust, such as Si, Al, Fe, etc., which are similar to the chemical composition of common rocks, have the property of easily taking up water molecules, and can be dried. For example, water molecules are released, and if they are brought into contact with water again, they can easily take up water. Therefore, it can be reused repeatedly. And, since it has a thixotropic property in which the viscosity is high at rest, but the pressure is low (about 0.1 to 0.3 MPa), it is used as a contact medium for ultrasonic flaw detection. Sometimes, the adhesion between the ultrasonic probe 1A and the object to be inspected 12 is increased, and the acoustic propagation performance of ultrasonic waves from the ultrasonic probe 1A to the object to be inspected 12 is improved. As a result, since the S / N ratio of the ultrasonic reflected wave increases, the defect of the inspection object 12 can be detected with high accuracy. In particular, it is possible to secure the adhesion between the ultrasonic probe 1A and the inspection object 12 by using the thixotropy of the bentonite 10 for the inspection object 12 having a large surface roughness such as concrete or rock. Therefore, ultrasonic flaw detection can be performed under favorable conditions.

  Bentonite 10 is a candidate material for an artificial barrier used for geological disposal of radioactive waste, and is excellent in radiation resistance. Therefore, by using bentonite 10 as a contact medium, an ultrasonic probe that can be used in a practical high radiation field can be obtained.

  Furthermore, bentonite 10 is a kind of clay and is abundant on the earth, so it is inexpensive and its price is about 1/10 compared with other commercially available contact media. Since bentonite 10 is a kind of clay, it can be prepared simply by adding water to the solid powder and stirring it, making it easy to perform preparatory work prior to ultrasonic flaw detection and easy cleaning with water. The cleaning operation after the ultrasonic flaw detection can be facilitated. Therefore, the ultrasonic flaw detection cost can be reduced.

  Hereinafter, an ultrasonic flaw detection method using the ultrasonic probe 1A configured as described above will be described.

  First, the coupling 11 is removed from the case 5, and the bentonite 10 whose water content ratio is appropriately adjusted is filled in the coupling 11. That is, the water content of bentonite exhibits thixotropy in the range of 0% to 400%, and the viscosity at the time of driving the ultrasonic vibrator changes depending on the water content, so that it depends on the type and surface roughness of the test object 12. Change the water content. For example, when the surface roughness of the inspection object 12 is large, the moisture content of the bentonite 10 is increased to decrease the viscosity of the bentonite when the ultrasonic vibrator is driven, and the adhesion of bentonite to the surface of the inspection object 12 To increase. On the contrary, when the surface roughness of the inspected object 12 is small, the water content ratio of the bentonite 10 is lowered to increase the viscosity of the bentonite when the ultrasonic vibrator is driven, and the consumption due to the bentonite 10 flowing out is suppressed. After filling with bentonite 10, coupling 11 is attached to case 5.

  Next, after the tip of the coupling 11 is brought into contact with the object to be inspected 12, the main body of the ultrasonic flaw detector (not shown) is operated, and the upper portion of the ultrasonic transducer 2 is connected via the connector 9 and the lead wires 7 and 8. An excitation signal is transmitted to the electrode and the lower electrode, and an ultrasonic wave is transmitted from the ultrasonic transducer 2.

  The ultrasonic wave transmitted from the ultrasonic transducer 2 is propagated into the inspection object 12 via the bentonite 10 filled in the coupling 11. At that time, the bentonite 10 receives an ultrasonic wave and decreases its viscosity, and is in close contact with the surface of the inspection object 12.

  The ultrasonic wave propagated inside the inspection object 12 is reflected by a defect inside the inspection object and the bottom surface of the inspection object 12. These ultrasonic reflected waves are received by the ultrasonic transducer 2, converted into an electric signal, and transmitted to a main body such as an ultrasonic flaw detector via the connector 9. Thereby, the presence / absence of a defect, the size of the defect, and the position of the defect can be detected.

  Thereafter, while transmitting ultrasonic waves from the ultrasonic transducer 2, the ultrasonic probe 1A is scanned in the surface direction of the inspection object 12, and ultrasonic inspection in a necessary range is performed. After the inspection, the surface of the inspection object 12 is washed with water as necessary.

  Next, a second embodiment of the ultrasonic probe according to the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of the ultrasonic probe according to the second embodiment in use.

As shown in FIG. 3, the ultrasonic probe 1 </ b> B of this example is characterized in that the outer surface of the damper 4 is covered with a radiation-resistant coating film 13. The coating film 13 prevents radiation deterioration of the damper 4 due to radiation, and a film that forms a gas permeation barrier on the surface of the damper 4 to prevent oxygen from entering. In this example, a silica coating film 13 having a thickness of about 100 nm was formed around the damper 4. According to this coating film 13, as described in Non-Patent Document 4, a radiation resistance of about 5.4 × 10 ⁵ Gy can be expected. Others are the same as those of the ultrasonic probe 1A according to the first embodiment, and therefore, the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  Since the outer surface of the damper 4 is covered with the radiation-resistant coating film 13 in the ultrasonic probe 1B of this example, the radiation resistance of the ultrasonic probe can be further improved.

It is sectional drawing of the use condition of the ultrasonic probe which concerns on 1st Embodiment. It is a graph which shows the acoustic impedance of a bentonite compared with the acoustic impedance of another main contact medium. It is sectional drawing of the use condition of the ultrasonic probe which concerns on 2nd Embodiment.

Explanation of symbols

1A, 1B Ultrasonic probe 2 Ultrasonic transducer 3 Ultrasonic wave transmitting / receiving surface 4 Damper 5 Case
6 Holding body 7, 8 Lead wire 9 Connector 10 Contact medium 11 Coupling 12 Inspected object 13 Coating film

Claims (6)

  Ultrasonic transducer for transmitting / receiving ultrasonic signals, damper provided on the surface opposite to the ultrasonic wave transmitting / receiving surface of the ultrasonic transducer, and insulating holding body for holding the ultrasonic transducer and the damper And a metal case for housing the holding body, and a cylindrical coupling provided in the case, and an ultrasonic wave transmitting / receiving surface of the ultrasonic transducer and an object to be inspected in the coupling An ultrasonic probe characterized by being filled with bentonite as a contact medium for ultrasonic flaws interposed therebetween.   The ultrasonic transducer and the damper, the ultrasonic transducer and the holding body, and the holding body and the case are bonded using a radiation-resistant adhesive. Ultrasonic probe.   An ultrasonic probe characterized in that the outer surface of the damper is covered with a radiation-resistant coating film.   The ultrasonic probe according to claim 1, wherein the coupling is detachably attached to the case.   Ultrasonic transducer for transmitting / receiving ultrasonic signals, damper provided on the surface opposite to the ultrasonic wave transmitting / receiving surface of the ultrasonic transducer, and insulating holding body for holding the ultrasonic transducer and the damper And a metal case for housing the holding body, and a cylindrical coupling provided in the case, and an ultrasonic wave transmitting / receiving surface of the ultrasonic transducer and an object to be inspected in the coupling An ultrasonic probe filled with bentonite is used as a contact medium for ultrasonic flaws interposed between the ultrasonic transducers, and the tip of the coupling is in contact with the surface of the object to be inspected. An ultrasonic flaw detection method comprising: transmitting ultrasonic waves from an ultrasonic wave transmitting / receiving surface to bentonite to reduce the viscosity of the bentonite and performing flaw detection inside the object to be inspected.   The water content ratio of the bentonite is increased when the surface roughness of the test object is large, and the water content ratio of the bentonite is decreased when the surface roughness of the test object is small. 5. The ultrasonic flaw detection method according to 5.

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