JP2012202867A - Inspection apparatus and inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection apparatus which is capable of easily improving detection accuracy, and an inspection method.SOLUTION: An inspection apparatus 1 comprises: a powder 12 as a coupling member (waveguide member); an elastic wave input/output unit (oscillator 13, transmitting section 14 and receiving section 15) which supplies an incident elastic wave Win to an inspection object 2 side via the powder 12 and acquires a reflection elastic wave Wref from the inspection object 2 side via the powder 12; and an impedance control unit (pressure container 11, pressure piston 17, drive section 18 and control section 19) which changes an acoustic impedance Z of the powder 12 so as to be relatively close to the acoustic impedance Z of the inspection object 2. According to a simple approach, a reflection component in the reflection elastic wave Wref on a surface S1 of the inspection object 2 is reduced and a reflection component in a cavity (defect) 21 inside the inspection object 2 can easily be detected.

Description

  The present invention relates to an inspection apparatus and an inspection method for inspecting voids and defects inside an object to be inspected using elastic waves such as ultrasonic waves.

  As a non-destructive inspection method for inspecting the presence or absence of voids, defects, and the like inside the object to be inspected, a flaw detection method (ultrasonic flaw detection method) using ultrasonic waves, which is a type of elastic wave, can be cited (for example, Patent Documents 1 to 3). This ultrasonic flaw detection method is the most common method for flaw detection of mechanical materials and structures because of the simplicity of the inspection method. The ultrasonic flaw detection method is roughly classified into a contact type and a non-contact type depending on the positional relationship between the vibrator (the probe) and the test object.

JP 2007-192649 A JP 1997-133664 A Japanese Patent Laid-Open No. 1996-105870

  In the contact method, basically, an ultrasonic wave is incident on the inspection object while the vibrator is in direct contact with the inspection object, and the ultrasonic wave reflected by the inspection object is detected, so that the inside of the inspection object is detected. Inspected. In this contact method, an ultrasonic signal can be sent into the inspection object relatively efficiently, but it is difficult to inspect voids and defects in the vicinity of the surface inside the inspection object. This is because the vicinity of the surface is a region (dead zone) where the incident signal (incident pulse) and the reflected signal (reflected echo) cannot be separated for the vibrator.

  On the other hand, in the non-contact type, the inside of the inspection object is inspected by detecting the ultrasonic wave reflected on the inspection object side as described above in a state where the vibrator is not in contact with the inspection object. It is like that. A typical example of this non-contact ultrasonic flaw detection method is a water immersion method using water as an ultrasonic coupling material (waveguide material). In this water immersion method, it is possible to perform flaw detection that is difficult through air having a very small acoustic impedance (characteristic acoustic impedance), and the problem of the dead zone of the vibrator itself as in the contact type described above does not occur. However, the acoustic impedance still generally differs greatly between water (liquid) as the coupling material and the test object that is solid. For this reason, a large reflection component (reflection echo) is generated on the surface of the object to be inspected, and the reflection component due to voids or defects inside the object to be inspected (near the surface) It becomes difficult to separate.

  A non-contact ultrasonic flaw detection method using a gel-like substance as a coupling material instead of water in the water immersion method has also been proposed. However, the difference in acoustic impedance between the object to be inspected and the coupling material is also proposed. Therefore, the same problem as in the case of the above-described water immersion method occurs.

  As described above, conventional inspection methods using ultrasonic waves such as ultrasonic waves (ultrasonic flaw detection methods, etc.) inspect for voids and defects in the vicinity of the surface inside the object to be inspected, regardless of contact type or non-contact type. It was difficult to do so, and the detection accuracy was low.

  In Patent Document 2, a method is proposed in which a predetermined material (powder or the like) is added to the coupling material to adjust the acoustic impedance of the coupling material according to the object to be inspected. However, in such a method, the adjustment range of the acoustic impedance is limited, and it is very complicated to individually adjust the material component of the coupling material for each object to be inspected, so a simple method is proposed. Is desired.

  The present invention has been made in view of such problems, and an object thereof is to provide an inspection apparatus and an inspection method capable of easily improving detection accuracy.

  The inspection apparatus according to the present invention supplies a waveguide material and an incident elastic wave to the inspection object side through the waveguide material, and acquires a reflected elastic wave from the inspection object side through the waveguide material. An input / output unit and an impedance control unit that changes the acoustic impedance of the waveguide material so as to be relatively close to the acoustic impedance of the object to be inspected are provided.

  According to the inspection method of the present invention, the incident elastic wave is supplied to the inspection object side through the waveguide material, and the reflected elastic wave from the inspection object side is acquired through the waveguide material, thereby inspecting the inspection object. When performing, the acoustic impedance of the waveguide material is changed so as to be relatively close to the acoustic impedance of the object to be inspected.

  In the inspection apparatus and inspection method of the present invention, an incident elastic wave is supplied to the object to be inspected through the waveguide material, and a reflected elastic wave from the object to be inspected is acquired through the waveguide material, so that the object to be inspected is obtained. A physical examination is performed. At this time, the acoustic impedance of the waveguide material changes so as to be relatively close to the acoustic impedance of the object to be inspected. Thereby, since the difference in acoustic impedance between the object to be inspected and the waveguide material is reduced, the reflection component on the surface of the object to be inspected in the reflected elastic wave is reduced. Further, since the individual adjustment of the waveguide material according to the object to be inspected is unnecessary, the acoustic impedance control of the waveguide material can be easily performed.

  In the inspection apparatus of the present invention, it is preferable that the impedance control unit controls the acoustic impedance of the waveguide material so as to be substantially the same as the acoustic impedance of the device under test. When configured in this way, the acoustic impedance difference between the object to be inspected and the waveguide material is almost eliminated (desirably 0 (zero)), so that the reflection component on the surface of the object to be inspected is further reduced (is almost eliminated). , 0). Therefore, the detection accuracy is further improved.

  In the inspection apparatus of the present invention, the impedance control unit can change the acoustic impedance of the waveguide material by changing the pressure applied to the waveguide material. In that case, the impedance control unit includes a container for housing the object to be inspected and the waveguide material, a piston for applying pressure to the waveguide material, a drive unit for displacing the piston, and a piston by the drive unit. By controlling the amount of displacement, it is possible to have a control unit that controls the pressure applied to the waveguide material.

  In the inspection apparatus of the present invention, the waveguide material is preferably made of powder. When configured in this way, adverse effects on the object to be inspected by the waveguide material (for example, wetting or contaminating the object to be inspected) are avoided, and the waveguide material can be reused (inspection). This eliminates the need to replace the waveguide material each time), thus improving the convenience of inspection. In this case, the powder may be a mixture of particles having a plurality of types of particle sizes, a mixture of particles of a plurality of types of materials, or a combination thereof (a plurality of types of particles). The particles having a particle diameter and particles of a plurality of types of materials may be mixed). In the case of such a configuration, for example, it is possible to widen the change width of the acoustic impedance in the waveguide material, or to easily fine-tune the value of the acoustic impedance.

  In the inspection apparatus of the present invention, the elastic wave input / output unit outputs one or more vibrators that output incident elastic waves and inputs reflected elastic waves, and an input for generating incident elastic waves to the vibrators. It is possible to have a transmitter for supplying a signal and a receiver for generating an output signal used for inspecting the object to be inspected based on the reflected elastic wave input to the vibrator. In this case, it is preferable to provide a display unit for displaying the time change of the output signal. When comprised in this way, it will become easy to adjust the variation | change_quantity of the acoustic impedance of a waveguide material. That is, for example, while observing the time change of the output signal as needed (in real time), the amount of change in the acoustic impedance is adjusted so that it is easy to observe the reflection component in the voids and defects inside the object to be inspected. Will be able to.

  In the inspection apparatus of the present invention, for example, ultrasonic waves can be used as the incident elastic wave and the reflected elastic wave, respectively. However, in addition to the ultrasonic wave, an elastic wave having a lower frequency may be used according to the condition of the object to be inspected.

  According to the inspection apparatus and the inspection method of the present invention, the acoustic impedance of the waveguide material is changed so as to be relatively close to the acoustic impedance of the object to be inspected. The reflection component on the surface of the inspection object can be reduced. As a result, the power of the elastic wave incident on the inside of the object to be inspected is increased, so that it is possible to easily detect the reflection component in the internal void or defect. In addition, since the reflection component on the surface of the object to be inspected can be reduced, it is possible to detect the reflection component in the vicinity of the surface, such as voids and defects, which was hidden behind the reflection component on the surface of the object under inspection. It becomes easy to do. Therefore, it becomes possible to easily improve the detection accuracy when inspecting voids, defects and the like inside such an object to be inspected (particularly near the surface of the object to be inspected).

It is a figure showing the schematic structural example of the inspection apparatus which concerns on one embodiment of this invention. It is a characteristic view showing an example of the relationship between the pressure applied to the powder as a coupling material and the acoustic impedance of the powder. It is a figure showing the schematic structural example of the inspection apparatus which concerns on the comparative example 1. FIG. It is a figure showing the schematic structural example of the inspection apparatus which concerns on the comparative example 2. FIG. It is a figure showing the schematic structural example of the inspection apparatus which concerns on Example 1 of embodiment. 6 is a characteristic diagram illustrating an example of a relationship between an elapsed time at the time of inspection according to Example 1 and a voltage value of a reflected wave. FIG. It is a figure showing the example of schematic structure of the inspection apparatus which concerns on Example 2 of embodiment. 6 is a characteristic diagram illustrating an example of a relationship between an elapsed time at the time of inspection according to Example 2 and a voltage value of a reflected wave. FIG. It is a figure showing the example of another test | inspection aspect in the test | inspection apparatus shown in FIG. It is a schematic diagram showing the structural example of the powder as a coupling material which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Embodiment>
[Configuration of Inspection Apparatus 1]
FIG. 1 schematically shows a schematic configuration of an inspection apparatus (inspection apparatus 1) according to an embodiment of the present invention. The inspection apparatus 1 performs inspection (non-destructive inspection) on voids, defects, and the like (here, referred to as voids (defects) 21) inside the inspected object 2 using elastic waves such as ultrasonic waves described later. This is an apparatus (inspection apparatus using a non-contact ultrasonic flaw detection method).

  This inspection apparatus 1 includes a pressure vessel 11 (container), a powder 12 as a coupling material (waveguide material) to be described later, a vibrator (a probe) 13, a transmission unit 14, a reception unit 15, a display unit 16, A pressure piston 17 (piston), a drive unit 18 and a control unit 19 are provided. Here, the vibrator 13, the transmitter 14, and the receiver 15 correspond to a specific example of “elastic wave input / output unit” in the present invention, and the pressure vessel 11, the pressure piston 17, the drive unit 18, and the control unit 19. This corresponds to a specific example of the “impedance control unit” in the present invention. Note that an inspection method according to an embodiment of the present invention is embodied in the inspection apparatus 1 of the present embodiment, and will be described below.

  The pressure vessel 11 is a vessel that accommodates the device under test 2 and the powder 12 and is configured to exhibit high pressure resistance. Such a pressure vessel 11 is made of a material such as stainless steel.

The powder 12 is a medium (coupling material, waveguide material) for efficiently propagating an elastic wave (an incident elastic wave Win and a reflected elastic wave Wref, which will be described later) at the time of inspection. Is filled so as to cover the periphery of the inspection object 2. Examples of such powder 12 include materials such as ceramic powder and metal powder. Of these, alumina (Al ₂ O ₃ ) powder is preferably used especially for flaw detection inspection in engineering plastics, and tungsten (W) powder is used for flaw detection inspection in magnesium (Mg) alloys. Is preferred. This is because the acoustic impedance Z of the material constituting each object to be inspected 2 is included in the range in which the acoustic impedance Z of the powder 12 described later changes. In addition, the particle size of each particle in this powder 12 is about 3-80 micrometers.

  The vibrator 13 outputs (supplies) an incident elastic wave Win (incident signal, incident pulse) to the inspection object 2 side via the powder 12 and also reflects a reflected elastic wave Wref (reflection signal) from the inspection object 2 side. , Reflection echo) is input (acquired), and is composed of, for example, a piezoelectric element using piezoelectric ceramics. Specifically, for example, when a voltage is applied between both surfaces of the piezoelectric element, the piezoelectric element expands and contracts according to the magnitude of the voltage, and converts an electrical signal into a mechanical signal (transmits an incident elastic wave Win). ). On the other hand, when a mechanical signal based on the reflected elastic wave Wref is input, for example, a voltage corresponding to the amount of vibration is generated between both ends of the piezoelectric element, thereby converting the mechanical signal into an electric signal (reflected elastic wave Wref). Receive). The vibrator 13 can transmit the incident elastic wave Win and receive the reflected elastic wave Wref by using the conversion (piezoelectric effect) between the electric signal and the mechanical signal. . Here, a plurality of vibrators 13 are embedded in the pressure vessel 11 and arranged in an array. With such an array arrangement, electronic scanning described later (sequential operation of a plurality of vibrators 13 and directivity control by driving with a phase difference) is realized.

  The transmitter 14 supplies an electric signal for generating an incident elastic wave Win to each vibrator 13.

  The receiving unit 15 generates an output signal used for inspecting the device under test 2 based on an electrical signal corresponding to the reflected elastic wave Wref input to each transducer 13. Such an output signal is output to the display unit 16.

  The display unit 16 displays the time change of the output signal supplied from the receiving unit 15. Specifically, as will be described later, the correspondence between the peak value (voltage value, etc.) of the reflected elastic wave Wref and the elapsed time (reflection time) can be displayed at any time (in real time). In addition, as such a display unit 16, various types of displays such as a CRT (Cathode Ray Tube), a liquid crystal display (LCD), a PDP (Plasma Display Panel), and an organic EL (Electro Luminescence) display are used. It is possible.

  The pressurizing piston 17 is a piston for applying pressure to the powder 12 and is located above the inspection object 2 in the pressure vessel 11 (opposite to the embedded surface of the vibrator 13 with the inspection object 2 as a reference). Side). In this case, the pressure piston 17 is displaced (displaced in the vertical direction) as indicated by an arrow P1 in FIG. As will be described in detail later, when the pressure P applied to the powder 12 changes, for example, as shown in FIG. 2, the acoustic impedance Z of the powder 12 changes accordingly (in this example, approximately Change linearly).

  The drive unit 18 drives the pressurizing piston 17 and is configured using, for example, various types of actuators. Specifically, the drive unit 18 is configured to displace the pressurizing piston 17 in the vertical direction (the direction of the arrow P1).

  The control unit 19 controls each operation in the transmission unit 14, the reception unit 15, the display unit 16, and the drive unit 18, and includes, for example, a microcomputer. Particularly in the present embodiment, the control unit 19 controls the pressure P applied to the powder 12 by controlling the amount of displacement of the pressurizing piston 17 by the driving unit 18. Thus, by changing the pressure P applied to the powder 12, the acoustic impedance Z of the powder 12 can be changed accordingly as described above. At this time, although the details will be described later, the control unit 19 is arranged through the drive unit 18 and the pressure piston 17 so as to be relatively close to (preferably substantially the same) the acoustic impedance Z of the object 2 to be inspected. The acoustic impedance Z of the body 12 is changed.

[Operation / Effect of Inspection Apparatus 1]
(basic action)
In this inspection apparatus 1, when an input signal (electrical signal) is supplied from the transmitter 14 to the vibrator 13, each vibrator 13 vibrates in accordance with the input signal and is inspected via the powder 12. The input elastic wave Win is supplied (transmitted) to the body 2 side. Specifically, for example, the plurality of vibrators 13 output the input elastic wave Win in a time division manner.

  Then, the incident elastic wave Win is reflected on the inspection object 2 side (for example, the gap (defect) 21 inside the inspection object 2 or the pressing surface of the pressing piston 17), and the reflected elastic wave Wref is reflected on the vibrator 13 side. Propagate to. Here, since the acoustic impedance Z in the gap (defect) 21 inside the inspection object 2 is generally very low as compared with the acoustic impedance Z of the inspection object 2 itself, the incident elastic wave Win of the inspection object 2 itself is reduced. Reflection occurs. The reflected elastic wave Wref from the inspected object 2 side thus obtained is input to the vibrator 13 via the powder 12. Each vibrator 13 outputs an output signal (electric signal) corresponding to the vibration amount of the reflected elastic wave Wref. Specifically, for example, the plurality of vibrators 13 receive such a reflected elastic wave Wref in a time division manner.

  The display unit 16 displays such a time change of the output signal. Specifically, for example, the correspondence between the peak value of the reflected elastic wave Wref and the elapsed time (reflection time) is displayed in real time, and thereby the presence / absence of voids (defects) 21 in the inspection object 2 is inspected. Is called.

(Effects of characteristic parts)
Next, the operation of the characteristic part in the inspection apparatus 1 of the present embodiment will be described in detail in comparison with comparative examples (Comparative Examples 1 and 2).

(Comparative Example 1)
FIG. 3 schematically shows a schematic configuration of an inspection apparatus (inspection apparatus 101) according to Comparative Example 1. The inspection apparatus 101 of Comparative Example 1 includes a vibrator 13, a transmission unit 14, a reception unit 15, a display unit 16, and a control unit 19. That is, the inspection apparatus 101 is configured such that the pressure vessel 11, the powder 12, the pressure piston 17, and the drive unit 18 are not provided (omitted) in the inspection apparatus 1.

  In this inspection apparatus 101, unlike the above-described inspection apparatus 1 of the present embodiment, a coupling material (waveguide material) is not provided. Therefore, in the inspection apparatus 101, the input elastic wave Win is supplied from the vibrator 13 to the inspection object 2 side via air, and the reflected elastic wave Wref from the inspection object 2 side is supplied via the air to the vibration element 13. Supplied to.

  Here, since the acoustic impedance Z of air is very small, the power radiated from the vibrator 13 into the air is very small. In addition, since there is a large difference in acoustic impedance Z between the air and the device under test 2, most of the slight power radiated into the air is reflected by the surface S1 of the device under test 2 in the inspection apparatus 101. End up. For this reason, in Comparative Example 1, it is almost impossible to detect a reflection component from the gap (defect) 21 inside the inspection object 2.

(Comparative Example 2)
On the other hand, the inspection apparatus (inspection apparatus 201) according to Comparative Example 2 illustrated in FIG. 4 includes a container 200, a coupling material (waveguide material) 202, a vibrator 13, a transmission unit 14, a reception unit 15, a display unit 16, and A control unit 19 is provided. That is, this inspection apparatus 201 is provided with the container 200 and the coupling material 202 in place of the pressure container 11 and the powder 12 in the inspection apparatus 101 of Comparative Example 1, and omits the pressurizing piston 17 and the drive unit 18. It has become a thing.

  In this inspection apparatus 201, for example, a liquid such as water or a gel-like substance is used as the coupling material 202. The input elastic wave Win is supplied from the vibrator 13 to the inspection object 2 side via the coupling material 202, and the reflected elastic wave Wref from the inspection object 2 side vibrates via the coupling material 202. It is supplied to the child 13. In the configuration shown in FIG. 4, water used as the coupling material 202 corresponds to an inspection method called a “water immersion method”.

  In the inspection apparatus 201, the inspection is performed using a coupling material 202 having a value of the acoustic impedance Z larger than that of air. For this reason, the difference in the acoustic impedance Z from the object 2 to be inspected is smaller than that in the first comparative example, and the gap (defect) 21 inside the object 2 to be inspected can be detected.

  However, the acoustic impedance Z is usually still greatly different between the liquid or gel substance as the coupling material 202 and the inspected object 2 that is solid. For this reason, a large reflection component on the surface S1 of the inspection object 2 remains, and it is difficult to detect the reflection component in the gap (defect) 21 near the surface S1 of the inspection object 2. That is, also in this comparative example 2, the detection accuracy of the voids (defects) 21 near the surface S1 of the inspection object 2 is particularly low.

  In Comparative Example 2, a method of adjusting the acoustic impedance Z of the coupling material 202 according to the object 2 to be inspected by adding a predetermined material (powder or the like) to the coupling material 202 is also conceivable. However, the range of the acoustic impedance Z that can be adjusted by adding powder or the like is limited to a narrow range, and adjusting the material components of the coupling material 202 individually for each object to be inspected 2 is as follows. It becomes very complicated.

(Embodiment)
On the other hand, in the inspection apparatus 1 of the present embodiment, as shown in FIG. 1, the control unit 19 is configured so that the drive unit 18 and the pressure piston are relatively close to the acoustic impedance Z of the device under test 2. 17, the acoustic impedance Z of the powder 12 is changed. Specifically, the control unit 19 controls the pressure P applied to the powder 12 by controlling the amount of displacement of the pressurizing piston 17 by the driving unit 18. Then, for example, as shown in FIG. 2, the acoustic impedance Z of the powder 12 is changed by utilizing the fact that the acoustic impedance Z of the powder 12 changes as the pressure P applied to the powder 12 changes. Z is controlled. That is, the control unit 19 changes the acoustic impedance Z of the powder 12 by changing the pressure P applied to the powder 12.

  Thus, when the acoustic impedance Z of the powder 12 changes so as to be relatively close to the acoustic impedance Z of the object 2 to be inspected, the difference in the acoustic impedance Z between the object 2 and the powder 12 is as described above. Compared with Comparative Examples 1 and 2, it becomes smaller. As a result, in this embodiment, compared with Comparative Examples 1 and 2, the reflection component on the surface S1 of the inspection object 2 in the reflected elastic wave Wref is reduced, and a void (defect) inside the inspection object 2 (near the surface). It becomes easy to detect the reflection component at 21.

  At this time, it is preferable that the control unit 19 controls the acoustic impedance Z of the powder 12 so as to be substantially the same (preferably the same) as the acoustic impedance Z of the device under test 2. In such a control, the difference in acoustic impedance Z between the object to be inspected 2 and the powder 12 is almost eliminated (desirably 0 (zero)), so that the reflection component on the surface S1 of the object to be inspected 2 further increases. Reduce (almost disappears or becomes 0). Therefore, it becomes even easier to detect the reflection component in the gap (defect) 21 inside the inspection object 2 (near the surface) and the reflection component on the surface S1 of the inspection object 2.

  Further, in the present embodiment, the individual adjustment of the material of the coupling material 202 (here, the material of the powder 12) according to the object to be inspected 2 as described above in the comparative example 2 is unnecessary. The acoustic impedance Z in the body 12 can be easily controlled.

Example 1
Here, FIG. 5 schematically shows an inspection mode according to Example 1 of the present embodiment. In Example 1, a magnesium (Mg) alloy (acoustic impedance Z = 8.6 MPa · s / m) was used as the object to be inspected 2A, and tungsten (W) powder was used as the powder 12. FIG. 2 described above shows a change characteristic of the acoustic impedance Z of the tungsten powder with respect to the pressure P applied to the tungsten powder. According to FIG. 2, the acoustic impedance Z of the tungsten powder changes substantially linearly from 6.0 MPa · s / m to 9.0 MPa · s / m as the pressure P increases from 12 MPa to 32 MPa. I understand. Here, the acoustic impedance Z of tungsten powder is set to 8.6 MPa · s / m (pressure P = 31.8 MPa) so that the acoustic impedance Z of the magnesium alloy is equal to 8.6 MPa · s / m. I made it. In Example 1 and Example 2 described later, the number of transducers 13 in the inspection apparatus 1 is one. Since the first embodiment corresponds to the embodiment in the case where there is no gap (defect) 21 in the inspection object 2A, the ultrasonic waves as the input elastic wave Win and the reflected elastic wave Wref are applied to the inspection object 2A. It was confirmed whether it permeates to some extent. The frequency of this ultrasonic wave was 5 MHz, and the average particle size of the tungsten powder was 4.2 μm.

  FIG. 6 shows a characteristic example (an example of the relationship between the reflection time and the voltage value of the reflected elastic wave Wref) at the time of the inspection according to the first embodiment. The display content (flaw detection figure) on the display unit 16 is shown in FIG. It corresponds. As shown in FIG. 6, the reflection component on the surface S1 of the object 2A to be inspected is extremely different from the reflection component (piston surface reflection component, back surface reflection component; the same applies hereinafter) on the surface (pressure surface) S0 of the pressure piston 17. Since it is small, it turns out that most components (energy) of incident elastic wave Win pass 2 A of to-be-inspected objects, and are reflected in surface S0 of the pressurization piston 17. FIG. On the other hand, in the water immersion method which is a conventional inspection method, the magnitude of the reflection component on the surface S1 is approximately the same as the reflection component on the surface S0 in FIG. Therefore, it was confirmed that the reflection component on the surface S1 of the object to be inspected 2 is greatly reduced as compared with the conventional inspection method.

(Example 2)
FIG. 7 schematically illustrates an inspection mode according to Example 2 of the present embodiment. In Example 2, a test object 2B made of a magnesium alloy having a thickness of 0.6 mm is disposed adjacent to the test object 2A, and the test objects 2B and 2A are stacked in this order from the vibrator 13 side. It became a structure. The interface S <b> 2 between these inspection objects 2 </ b> B and 2 </ b> A corresponds to a void (defect) 21 existing inside the entire inspection object 2. That is, Example 2 corresponds to the example in the case where the void (defect) 21 exists in the inside of the inspection object 2 (near the surface on the vibrator 13 side), and therefore corresponds to the void (defect) 21. The magnitude of the reflection component at the interface S2 was confirmed. In Example 2, as in Example 1, the acoustic impedance Z of tungsten powder is set to 8.6 MPa · s / m (pressure P = 31.8 MPa).

  FIG. 8 shows a characteristic example (an example of the relationship between the reflection time and the voltage value of the reflected elastic wave Wref) in the inspection according to the second embodiment. For example, the display content (flaw detection figure) on the display unit 16 It corresponds to. Here, in FIG. 6 corresponding to the embodiment in the case where the inspection object 2 has no defect, the reflection component from the interface S1 has a small value. On the other hand, in FIG. 8 in which the inspected objects 2A and 2B simulating internal defects near the surface S1 are present, a large reflection component is observed because there is a reflection component from the interface S2. In FIG. 6, since most of the incident elastic wave Win sent from the vibrator 13 is transmitted without being reflected at the interface between the object 2 and the powder 12, a very large reflection from the surface S0. Components are observed. On the other hand, in FIG. 8, since most of the incident elastic wave Win is reflected at the interface S2, the component transmitted through the interface S2 is small. Therefore, the reflection component from the interface S0 is very small. It is getting smaller. For these reasons, by making the acoustic impedance Z between the object to be inspected 2 and the powder 12 relatively close, the inside of the object to be inspected 2 (particularly in the vicinity of the surface S1 of the object to be inspected 2) is inspected. It was confirmed (provided) that the accuracy of detection was improved.

  As described above, in the present embodiment, since the acoustic impedance Z of the powder 12 is changed so as to be relatively close to the acoustic impedance Z of the object 2 to be inspected, the reflected elastic wave Wref is obtained by a simple method. The reflection component on the surface S1 of the object to be inspected 2 can be reduced. As a result, the power of the incident elastic wave Win to the inside of the inspection object 2 is increased, so that it is possible to easily detect the reflection component in the internal void or defect. In addition, since the reflection component on the surface S1 of the inspection object 2 can be reduced, voids and defects in the vicinity of the surface S1 that were hidden behind the reflection component on the surface S1 of the inspection object 2 by the conventional method were not visible. It becomes easy to detect the reflection component in the above. Therefore, it is possible to easily improve the detection accuracy when inspecting voids, defects, and the like inside such an object to be inspected (particularly in the vicinity of the surface S1 of the object to be inspected 2).

  Further, since the reflection component on the surface S1 of the inspection object 2 can be suppressed, for example, as shown in FIG. 9, when inspecting the inspection object 2 having a complicated shape (having the rough surface S1), The incident elastic wave Win can be efficiently incident on the inside of the inspection object 2 and the detection accuracy can be improved.

  Furthermore, in the present embodiment, as described above, the incident elastic wave Win can be efficiently incident on the inside of the inspection object 2, so that it is limited to the voids and defects near the surface inside the inspection object 2. Accordingly, it is possible to detect a gap, a defect, or the like in a deep portion (for example, near the center) inside the inspection object 2 with higher accuracy than the conventional method.

  In addition, in particular, when the control unit 18 controls the acoustic impedance Z of the powder 12 so as to be substantially the same as the acoustic impedance Z of the object 2 to be inspected, The difference in the acoustic impedance Z of the test object 2 is almost eliminated (desirably becomes 0), so that the reflection component on the surface S1 of the inspection object 2 can be further reduced (almost eliminated or 0), and the detection accuracy is further improved. It becomes possible to improve.

  In addition, since the coupling material (waveguide material) is made of the powder 12, adverse effects on the inspection object 2 by the coupling material (for example, wetting or contamination of the inspection object 2) can be avoided. In addition, the coupling material can be reused (it is not necessary to replace the coupling material every time the inspection is performed), so that the convenience during the inspection can be improved. .

  Furthermore, since the display unit 16 for displaying the time change of the output signal supplied from the receiving unit 15 is provided, the amount of change in the acoustic impedance Z of the powder 12 can be easily adjusted. That is, for example, while observing the time change of the output signal as shown in FIG. 8 at any time (in real time), the acoustic impedance is easily observed so that the reflection component in the voids and defects in the inspection object 2 can be easily observed. The amount of change in Z can be adjusted.

<Modification>
Then, the modification of the said embodiment is demonstrated. In addition, the same code | symbol is attached | subjected to the same thing as the component in embodiment, and description is abbreviate | omitted suitably.

  In the above embodiment, for example, as shown in FIG. 10A, the case where the powder 12 is composed of the particles 12 having one kind of the particle size R1 has been described. May be configured as follows.

  That is, for example, as shown in FIG. 10B, the powder 12 is a particle (particle 121 having a particle size R1 and particle 122 having a particle size R2) having a plurality of types (here, two types) of particle sizes R1 and R2. ) May be mixed. In general, since the acoustic impedance Z tends to decrease as the particle size decreases, in this case, for example, the change width of the acoustic impedance Z in the powder 12 is widened, or the value of the acoustic impedance Z is finely adjusted. It becomes possible to make it easy.

  Alternatively, for example, as shown in FIG. 10C, the powder 12 is a mixture of particles 121 and 123 of a plurality of types (here, two types) of materials (a plurality of types of materials having different acoustic impedance Z). You may do it. Even in such a configuration, it is possible to widen the range of change of the acoustic impedance Z in the powder 12 and to facilitate fine adjustment of the value of the acoustic impedance Z.

  10B and FIG. 10C in combination (powder 12 is a mixture of particles having a plurality of types of particle diameters and particles of a plurality of types of materials, respectively). It is good. That is, for example, as shown in FIG. 10C, the powder 12 may be formed by mixing particles 121 having a particle size R1 and particles 123 having a particle size R3.

<Other variations>
While the present invention has been described with reference to the embodiments and modifications, the present invention is not limited to these embodiments and the like, and various modifications can be made.

  For example, in the above-described embodiment and the like, a case has been described in which the coupling material (waveguide material) is made of powder and the acoustic impedance Z is adjusted by pressure. However, the present invention is not limited to this. That is, the acoustic impedance Z may be adjusted by using a material whose volume and physical properties change depending on the electric field or magnetic field as the coupling material and changing the applied electric field or magnetic field. In addition, the acoustic impedance Z may be adjusted by using a material whose physical properties change or phase change depending on the temperature as a coupling material and changing the temperature.

  Further, in the above-described embodiment, the case where the incident elastic wave Win and the reflected elastic wave Wref are each mainly composed of ultrasonic waves has been described. However, the present invention is not limited to this. Alternatively, an elastic wave having a lower frequency may be used. Here, when a relatively high frequency ultrasonic wave is used, for example, the reflection component at the surface S1 and the reflection component at the interface S2 can be easily separated on the time axis. Is desirable.

  This is because of the following reasons in detail. That is, in the conventional method, first, since the reflection component on the surface S1 is relatively large, the power of the elastic wave incident on the inside of the object to be inspected becomes small. Further, since the reflected elastic wave from the defect or the like inside the object to be inspected is re-reflected at the interface (surface S1), the power of the reflected elastic wave when returning to the vibrator 13 is further reduced. Therefore, the reflection component on the surface S1 and the reflection component on the interface S2 can be separated on the time axis (the reflection component on the surface S1 and the reflection component on the internal defect or the like are separated from each other on the time axis). It can be said that it is difficult to detect a reflection component due to an internal defect or the like with the conventional method even in a state in which it exists at a position. On the other hand, in the method described in the above embodiment and the like, since the reflection component and re-reflection component on the surface S1 are suppressed by adjusting the acoustic impedance Z, a reflected wave having sufficient power can be obtained from an internal defect or the like. It is done. In addition, the reflection component due to the internal defect or the like is present at a different position on the time axis from the reflection component on the surface S1, and thus can be easily detected. As a result, it is possible to detect even smaller internal defects or the like by the method of the above-described embodiment or the like.

  In addition, in the above-described embodiment and the like, the configuration of the inspection apparatus has been specifically described, but the configuration of the inspection apparatus is not limited to this, and other configurations may be employed. Specifically, for example, the inspection may be performed using one transducer instead of a plurality of transducers. Further, the vibrator may be arranged on two or more surfaces of the pressure vessel. Further, the coupling material may not be disposed around the entire periphery of the object to be inspected, but may be disposed, for example, only at a part between the vibrator and the object to be inspected.

  DESCRIPTION OF SYMBOLS 1 ... Inspection apparatus, 11 ... Pressure vessel, 12 ... Powder (coupling material), 121, 122, 123 ... Particle, 13 ... Vibrator, 14 ... Transmission part, 15 ... Reception part, 16 ... Display part, 17 ... Pressurized piston, 18 ... drive unit, 19 ... control unit, 2, 2A, 2B ... inspected object, 21 ... gap (defect), Win ... incident elastic wave, Wref ... reflected elastic wave, S0, S1 ... surface, S2 ... interface, R1, R2, R3 ... particle size.

Claims (11)

A waveguide material;
An elastic wave input / output unit for supplying an incident elastic wave to the inspection object side through the waveguide material, and acquiring a reflected elastic wave from the inspection object side through the waveguide material;
An inspection apparatus comprising: an impedance control unit that changes an acoustic impedance of the waveguide material so as to be relatively close to an acoustic impedance of the object to be inspected. The inspection apparatus according to claim 1, wherein the impedance control unit controls the acoustic impedance of the waveguide material so as to be substantially the same as the acoustic impedance of the object to be inspected. The inspection apparatus according to claim 1, wherein the impedance control unit changes an acoustic impedance of the waveguide material by changing a pressure applied to the waveguide material. The impedance controller is
A container for housing the device under test and the waveguide material;
A piston for applying pressure to the waveguide;
A drive unit for displacing the piston;
The inspection apparatus according to claim 3, further comprising: a control unit that controls a pressure applied to the waveguide member by controlling a displacement amount of the piston by the driving unit. The inspection apparatus according to claim 1, wherein the waveguide material is made of powder. The inspection apparatus according to claim 5, wherein the powder is a mixture of particles having a plurality of types of particle sizes. The inspection apparatus according to claim 5, wherein the powder is a mixture of particles of a plurality of types of materials. The elastic wave input / output unit is
One or more vibrators for outputting the incident elastic wave and inputting the reflected elastic wave;
A transmitter for supplying an input signal for generating the incident acoustic wave to the vibrator;
8. The inspection according to claim 1, further comprising: a receiving unit that generates an output signal used for inspection of the object to be inspected based on the reflected elastic wave input to the vibrator. apparatus. The inspection apparatus according to claim 8, further comprising a display unit that displays a time change of the output signal. The inspection apparatus according to claim 1, wherein each of the incident elastic wave and the reflected elastic wave is an ultrasonic wave. When inspecting the object to be inspected by supplying incident elastic waves to the inspected object side through the waveguide material and acquiring the reflected elastic waves from the inspected object side through the waveguide material. ,
An inspection method for changing the acoustic impedance of the waveguide material so as to be relatively close to the acoustic impedance of the object to be inspected.

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