JP5410651B2 - Surface degradation detection apparatus and method - Google Patents

Description

  The present invention relates to an apparatus and a method for detecting surface deterioration of a structure.

  In the non-destructive inspection of structures in nuclear power plants and other various plants, it is important to detect deterioration and corrosion occurring in structural materials at an early stage. It is known that most of the deterioration and corrosion of general structures are more likely to occur in the welded part and its vicinity than the base material part.

  For example, it is well known that many in-furnace structures in a nuclear power plant are likely to be deteriorated from a welded portion or the vicinity thereof, and the development of a technique for inspecting the portion is underway. In the unlikely event that deterioration or corrosion occurs in the structural material, repair welding is performed to maintain soundness by welding the structural material.

  In general, after welding, in order to confirm the soundness of welding, visual inspection (VT), radiographic inspection (RT), penetration inspection (PT), magnetic particle inspection (MT), ultrasonic inspection A test (UT) or the like is to be performed (see Non-Patent Document 1). Here, it is common to use PT or MT in order to detect a welding failure occurring in the weld surface layer.

  As a technique for inspecting the deterioration state of the surface layer portion of the structure, there is a method of detecting the deterioration state of the material using a leaky surface wave. FIG. 10 shows the device system diagram.

  According to this technique, the incident ultrasonic wave IS emitted from the acoustic lens 100 by the acoustic lens 100 or a method of installing a piezoelectric polymer PVDF (polyvinylidene fluoride) sensor 101 on the curvature surface of the object 1 to be inspected. The object 1 to be inspected is detected by exciting the surface wave S propagating through the surface layer and detecting the leaked surface wave LS in which the surface wave having information on the influence received from the material of the surface layer leaks into the water during propagation. It is possible to detect the deterioration state of the surface layer portion (see Non-Patent Document 2). Further, longitudinal acoustic wave LL is emitted from the acoustic lens 100, and the distance between the acoustic lens 100 and the object 1 to be inspected is measured and reflected in the detection of the deterioration state.

  The above-described inspection methods generally have a problem that is difficult to use on site. For example, the method shown in Non-Patent Document 3 detects a critical angle for generating a leaky surface wave for the purpose of detecting fine grain boundary erosion before macro cracking is detected by a change in sound velocity due to grain boundary erosion. is there.

  In the case of such a method, the angle formed between the probe for transmitting and receiving ultrasonic waves and the inspection object is very important. Such a measurement technique is relatively easy when the surface of the object to be inspected is completely flat.

  However, for example, when unevenness exists on the surface of the object to be inspected in a weld metal part or the like, there is a problem that the critical angle changes according to the unevenness of the inspection location, and accurate measurement becomes difficult.

  Patent Document 1 describes a technique for applying the method shown in Non-Patent Document 2 on site. And in patent document 1, it aims at improving the inspection performance in case deterioration has fixed spread by not only measuring from one specific direction but measuring from several directions. Patent Document 2 proposes a technique for detecting surface layer defects with high accuracy.

  The above-described inspection method can be applied when the actual inspection target is a plane, but many of the actual inspection target surfaces are applied to the inspection target object 1 as shown in FIG. Since there are many cases where the surface is not a flat surface due to the presence of the welding surface 102, the application is often difficult.

This is because the above-described inspection method uses a surface wave propagating on the surface to be inspected. In order to excite the surface wave on the surface to be inspected, ultrasonic waves are emitted to the surface to be inspected at a critical angle. If the surface shape has a complicated shape at this time, the excitation efficiency of the surface wave is increased. Problems such as reduction or inability to excite surface waves occur.
Basics of welding technology, edited by the Japan Welding Society, p. 186 (Industry Bulletin Publishing) Ultrasonic Handbook, Ultrasonic Handbook Editing Committee, p. 380 (Maruzen) "Detection of fine grain boundary erosion on material surface by leaky surface acoustic wave (LSAW) (1st report) Application of water immersion critical angle method", Yasukazu Yokono et al., Nondestructive inspection, Vol. 51, No. 5 (2002) JP 2005-55200 A JP 2001-208729 A

  As described above, the conventional surface deterioration inspection apparatus has a problem that if the surface shape is non-planar, the surface wave cannot be excited or a trace may be left on the surface to be inspected.

  The present invention has been made in consideration of the above-described points, and an object thereof is to provide a surface degradation detection apparatus and method that can be applied even when a surface to be inspected is not a plane.

In order to solve the above problems, the present invention provides:
An ultrasonic excitation point is formed in a linear shape, and an ultrasonic excitation mechanism that generates at least one of an isotropically propagated ultrasonic wave and a shock wave from the linear ultrasonic excitation point, and the ultrasonic excitation mechanism A surface deterioration detection device comprising: a receiving mechanism for detecting leakage surface waves and shock waves due to leakage of surface waves excited on the surface of an object to be inspected by the ultrasonic waves or shock waves generated from an ultrasonic excitation point. ,
And forming an ultrasonic excitation point in a linear shape, generating at least one of an isotropically propagated ultrasonic wave and a shock wave from the linear ultrasonic excitation point, and generating the ultrasonic wave generated from the ultrasonic excitation point Or a surface degradation detection method characterized by detecting a leaky surface wave or shock wave due to leakage of a surface wave excited on the surface of the object to be inspected by the shock wave,
I will provide a.

As described above, the present invention provides at least one of isotropically propagating ultrasonic waves and shock waves,
Irradiating to a place other than the inspection target surface of the inspection target object, so that it can be excited regardless of the shape of the inspection target object, and can be excited even when the inspection target surface is not flat. Possible surface degradation detection means can be provided.

  Hereinafter, the overall configuration of a defect detection apparatus to which the present invention is applied will be described first with reference to FIG. 1, and then an embodiment according to the present invention will be described with reference to FIGS.

(Defect detection device)
FIG. 1 shows the overall configuration of a defect detection apparatus to which the present invention is applied. In this apparatus, when the surface excitation wave is irradiated from the ultrasonic excitation mechanism 2 to the surface of the inspection object 1, the shock wave SW is transmitted from the surface of the inspection object 1 to the reflector 4 of the ultrasonic reception mechanism 3. Further, the leaky wave LS is transmitted to the reflector 4 from the surface wave S transmitted through the surface of the inspection object 1.

  The ultrasonic reception mechanism 3 is connected to the reception laser light source 106, the measurement mechanism 107, and the signal recording mechanism 108 via the laser light transmission mechanism 105, and laser light can be transmitted and received between these devices and the reflector 4. Done.

  The reflector 4 is vibrated by the shock wave SW and the leakage wave LS, and changes the reflection of the laser light. As a result, the measurement mechanism 107 and the signal recording mechanism 108 receive and record a signal corresponding to the defect status of the inspection object 1.

  Examples of the periphery of the ultrasonic excitation mechanism 2 and the ultrasonic reception mechanism 3 in the defect detection apparatus configured as described above will be described.

Example 1
(Constitution)
FIG. 2 shows the configuration of the first embodiment of the present invention. In the first embodiment, an ultrasonic excitation mechanism 2 that excites ultrasonic waves on the surface of the object 1 to be inspected, and an ultrasonic excitation source emitted by the ultrasonic excitation mechanism 2, for example, laser light LW, is ultrasonic. The shock wave SW generated by focusing on the excitation point 5, the reflected shock wave SW ′ generated when the shock wave SW is incident on the object 1 to be inspected and reflected, and the shock wave SW is incident on the object 1 to be inspected. And a receiving mechanism 3 that detects a leakage wave LS due to leakage of the surface wave S.

Here, the ultrasonic excitation mechanism 2 in FIG.
(1) As shown in FIG. 3, an ultrasonic excitation point 5 is formed by discharging between two electrodes 6, and a reflected wave (leakage wave LS) when the generated ultrasonic wave US is applied to the inspection object 1. , Shock wave SW, reflected shock wave SW ′) received by the receiving mechanism 3,
(2) As shown in FIG. 4, a configuration in which a plurality of ultrasonic excitation mechanisms 2 are installed, the excitation source LW is focused to form a plurality of ultrasonic excitation points 5 and shock waves SW are generated,
(3) As shown in FIG. 5, the shock wave SW generated by converging the ultrasonic excitation point 5 on the line is given to the deteriorated portion 7, and the shock wave SWR and the reflected shock wave SW ′ affected by the deteriorated portion 7 are received. A configuration for receiving by the mechanism 3 or a means for exciting other ultrasonic waves US or shock waves SW can be considered.

In particular, when the ultrasonic excitation source 4 generated from the ultrasonic excitation mechanism 2 is laser light, examples of laser light sources to be used include Nd: YAG laser, Nd: YLF laser, CO ₂ laser, Er: YAG laser, and titanium. Examples include sapphire lasers, alexandrite lasers, ruby lasers, dye (die) lasers, excimer lasers, and other pulse laser light sources.

  Further, as a receiving element of the ultrasonic receiving mechanism 3 for detecting the generated shock wave or ultrasonic wave, a piezoelectric element, a laser light receiving element, or the like can be considered. In particular, when the ultrasonic receiving mechanism 3 generates laser light (FIG. 2), interference measurement or the like can be considered. As the interference measuring mechanism 7 to be used, a Michelson interferometer, a homodyne interferometer, or a heterodyne interferometer is used. Fizeau interferometer, Mach-Zehnder interferometer, Fabry-Perot interferometer, photorefractive interferometer, and other laser interferometers are also conceivable. As a method other than the interference measurement, a knife edge method is also conceivable.

(Function)
The operation of the first embodiment of the present invention will be described with reference to FIG. 2 and FIGS. In the above-described method, when the ultrasonic excitation source 4 between the object to be inspected 1 and the ultrasonic excitation mechanism 2 is focused on the ultrasonic excitation point 5 (condensed in the case of laser light), cavitation and breakdown occur. And various waves (SW) such as sound waves, ultrasonic waves, and shock waves are generated. The generated ultrasonic wave or shock wave isotropically propagates from the ultrasonic excitation point 5 and reaches the surface of the inspection object 1.

  Here, many components of the reached ultrasonic waves and shock waves are reflected by the surface to be inspected (SW ′). On the other hand, there is also a component that changes to a mode that propagates inside or on the surface of the inspection object. Among the changes in the ultrasonic wave propagating through the inspection object, for example, the surface wave S propagates on the surface of the inspection object 1, but the criticality according to the acoustic impedance of the environment where the inspection object 1 is installed. A leakage wave LS leaks to the installation environment of the inspection object 1 at the corner.

  Here, as shown in FIG. 6, when the deteriorated part 7 exists in the inspection object 1, the surface wave S that propagates is the surface wave S in which the amplitude, frequency, etc. of the surface wave are changed depending on the state of the deteriorated part 7. 'Become. The surface wave S ′ subjected to this change is a leaky wave LS that leaks into the environmental medium at a critical angle calculated from the sound velocity of the environmental medium on which the inspection object 1 is placed and the inspection object 1. 'Become.

  Here, the environmental medium is generally water, but in addition to this, it is a medium different from the material of the object 1 to be inspected, such as air, oil, or liquid metal, and any medium that can transmit ultrasonic waves and shock waves. Anything is possible.

  By detecting this leaky wave LS ′ by the ultrasonic receiving mechanism 3, it is possible to detect deterioration information of the inspection object 1. Here, the deteriorated portion 7 is, for example, an opening defect, a closing defect, a surface layer intrinsic defect, corrosion, a microcrack, a dislocation, a slip, and the like, and other deterioration states are also conceivable.

  As shown in FIG. 7, the generated surface wave S is propagated into the environmental medium through the opening 7 when the deterioration occurring in the inspection object 1 is an opening defect 7. Is converted into an underwater propagating sound wave SOR. By detecting this underwater propagating sound wave SOR, it is possible to detect deterioration information caused by the surface state of the inspection object 1 such as an opening defect.

  Further, the shock wave SW generated from the ultrasonic excitation point 5 is emitted hemispherically from the irradiation point. At this time, as shown in FIG. 8, when the opening defect 7 is generated on the surface of the inspection object 1, the propagating shock wave SW is changed at the opening 7 of the surface opening defect, and the shock wave in the healthy portion is changed. It is converted into a shock wave SWR having a waveform component different from the reflection. By detecting the shock wave SWR affected by the deterioration portion 7, it is possible to detect deterioration information caused by the surface state of the inspection object 1, particularly the opening defect 7.

(effect)
In the first embodiment shown in FIGS. 2 to 8, ultrasonic waves and shock waves generated from the ultrasonic excitation point 5 are propagated isotropically by the ultrasonic excitation source 4 emitted from the ultrasonic excitation mechanism 2. .

  As a result, even if the inspection object 1 has irregularities such as the welded surface shown in FIG. 11, the isotropically propagated ultrasonic waves and shock waves are always transmitted to the inspection object 1. It has a component having a critical angle capable of exciting S. For this reason, it is possible to excite surface waves without depending on the shape of the inspection object 1.

  Further, it becomes possible to detect the surface opening defect or the like from the reflection component of the shock wave propagating isotropically. As described above, according to the first embodiment, it is possible to provide surface deterioration detection means that can be applied to a shape in which the surface to be inspected is not a flat surface, which is a first problem of the present invention.

  In the first embodiment, for example, in the case of the test method shown in FIG. 1, the laser light emitted from the ultrasonic excitation mechanism 2 is collected on the surface of the inspection object 1, and ultrasonic waves and shock waves are generated. Although excited, the energy density of the focused laser beam is very high, so the surface of the object 1 to be inspected may oxidize and leave traces from irradiation.

  However, in the first embodiment, the laser beam is focused on a place away from the inspection target 1 instead of the surface of the inspection target 1, and the focused laser light diffuses again. Even if the laser beam reaches the inspection object 1, the energy density is sufficiently low, and no trace is left on the surface of the inspection object 1.

(Example 2)
(Constitution)
FIG. 9 shows the configuration of the second embodiment of the present invention. In the second embodiment, an ultrasonic generation mechanism 8 is installed at the ultrasonic excitation point 5 of the ultrasonic excitation source 4 emitted from the ultrasonic excitation mechanism 2 in the first embodiment.

  With such a configuration, an ultrasonic wave or a shock wave SW is generated at the ultrasonic excitation point 5, the surface wave S is excited on the inspection object 1, and an opening defect on the surface of the inspection object 1 is generated by the shock wave. While the inspection object 1 is not directly irradiated with laser light, there is no fear of leaving a trace on the surface of the inspection object 1.

Explanatory drawing which shows the structure of the defect detection apparatus which is an application object of this invention. Explanatory drawing of an effect | action of the ultrasonic excitation mechanism in 1st Example of this invention. Explanatory drawing of an effect | action of the ultrasonic excitation mechanism in 1st Example of this invention. Explanatory drawing of an effect | action of the ultrasonic excitation mechanism in 1st Example of this invention. Action | operation explanatory drawing about the degradation location of the to-be-inspected object in 1st Example of this invention. Action | operation explanatory drawing about the degradation location of the to-be-inspected object in 1st Example of this invention. Action | operation explanatory drawing about the degradation location of the to-be-inspected object in 1st Example of this invention. Action | operation explanatory drawing about the degradation location of the to-be-inspected object in 1st Example of this invention. Action explanatory drawing regarding the 2nd Example of this invention. Explanatory drawing which shows the apparatus structure for the conventional surface deterioration test | inspection. Explanatory drawing which shows an example of the surface state of a test target object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Test object 2 ... Ultrasonic excitation mechanism 3 ... Reception mechanism 4 ... Ultrasonic excitation source 5 ... Ultrasonic excitation point 6 ... Electrode 7 ... Degradation 8. ..Ultrasonic generation mechanism 100 ... acoustic lens 101 ... piezoelectric element 102 ... welded metal surface with irregularities 105 ... laser light transmission mechanism 106 ... received laser light source 107 ... measuring mechanism 108 ... Signal recording mechanism S ... Surface wave S '... Surface wave affected by deterioration LS ... Leakage wave LS' ... Leakage wave affected by deterioration LW ... Laser Light SW ... Shock wave SW '... Reflected shock wave SWR ... Shock wave affected by deterioration SOR ... Sound wave diffracted at the opening and propagating in the environmental medium

Claims (8)

  An ultrasonic excitation point is formed in a linear shape, and an ultrasonic excitation mechanism that generates at least one of an isotropically propagated ultrasonic wave and a shock wave from the linear ultrasonic excitation point, and the ultrasonic excitation mechanism A surface deterioration detection device comprising: a receiving mechanism for detecting leakage surface waves and shock waves due to leakage of surface waves excited on the surface of an object to be inspected by the ultrasonic waves or shock waves generated from an ultrasonic excitation point. . In the surface degradation detection apparatus according to claim 1,
The ultrasonic excitation mechanism forms the linear ultrasonic excitation point at a place other than the surface to be inspected. In the surface degradation detection apparatus of Claim 1 or 2,
The apparatus for detecting surface degradation, wherein the ultrasonic excitation mechanism is a pulse laser light source. In the surface degradation detection apparatus according to claim 3,
A surface deterioration detection apparatus that irradiates a generation mechanism for generating at least one of an ultrasonic wave and a shock wave with laser light emitted from the ultrasonic excitation mechanism. In the surface degradation detection apparatus according to claim 1,
The surface deterioration detection apparatus, wherein the ultrasonic excitation mechanism is a piezoelectric element. In the surface degradation detection apparatus in any one of Claims 1 thru | or 5,
A surface deterioration detection apparatus comprising two or more ultrasonic excitation mechanisms.   An ultrasonic excitation point is formed in a linear shape, and at least one of an isotropically propagated ultrasonic wave and a shock wave is generated from the linear ultrasonic excitation point, and the ultrasonic wave generated from the ultrasonic excitation point or A surface deterioration detection method characterized by detecting a leaky surface wave or shock wave due to leakage of a surface wave excited on the surface of an object to be inspected by a shock wave. In the surface degradation detection method of Claim 7,
A method for detecting surface deterioration, wherein the ultrasonic excitation point is focused on a place other than a surface to be inspected in the object to be inspected.

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