JP4500895B2 - Non-linear electromagnetic ultrasonic sensor, micro-scratch detection apparatus using the same, and micro-scratch detection method - Google Patents

Description

  The present invention relates to a non-linear electromagnetic ultrasonic sensor that detects a micro flaw of 100 μm or less in a solid using non-linear ultrasonic waves, a micro flaw detection apparatus using the same, and a micro flaw detection method.

  Structural material surfaces are most susceptible to damage and degradation due to stress, corrosive environment, high temperature, and the like. If this deterioration damage can be detected at an early stage, a large-scale accident due to main crack propagation can be avoided, and the life of the structure can be extended by adjusting the service conditions. As a conventional nondestructive inspection method, an ultrasonic flaw detection method using linear ultrasonic waves is generally known.

  However, ultrasonic flaw detection using linear ultrasonic waves can detect and evaluate open cracks, but it is extremely difficult to detect almost closed cracks (pseudo-closed cracks) such as initial fatigue cracks. is there. That is, in the quasi-closed crack, a part of the incident ultrasonic wave partially passes through the crack surface, so that a clear reflected wave cannot be obtained. In addition, in the case of a portion that is apparently coupled, such as a welded portion inclusion, but has almost no coupling strength, that is, a so-called kissing bond portion, a reflected wave cannot be obtained for the same reason. It is said that the limit of flaw detection by linear ultrasonic waves is about 1/10 of the wavelength.

  By the way, in recent years, the advantage of nonlinear ultrasonic waves, which enables sensing of microcracks that could not be detected at all by conventional linear ultrasonic waves, has attracted attention and has been studied. Nonlinear ultrasound refers to a phenomenon in which the waveform of the generated ultrasound is distorted before and after propagation. In the nonlinear ultrasonic wave, the frequency and sound speed characterizing the generated ultrasonic wave change as a result of this distortion phenomenon (see FIG. 13).

  As shown in FIGS. 14 and 15, the structure that causes such nonlinear ultrasonic waves is considered as a continuum of particles 50 constituting the structure and a spring 51 that connects them. That is, as shown in FIG. 14, when the ultrasonic wave propagates linearly, the amplitude of the ultrasonic wave is relatively small and is within the elastic limit of the spring 51, so that the state of vibration of the incident ultrasonic wave is transmitted as it is. . On the other hand, as shown in FIG. 15, when a large-amplitude ultrasonic wave is incident, the spring 51 extends and contracts beyond the elastic limit, so that the vibration state of the incident ultrasonic wave cannot be transmitted as it is. become.

  Note that such a nonlinear ultrasonic phenomenon is less likely to occur in a substance having a high binding force, and is less likely to occur in the order of gas, liquid, and solid. Therefore, at present, the use of nonlinear ultrasonic waves is limited to the medical field and is only widespread as a diagnostic apparatus for the human body (substantially considered to be water). On the other hand, in the industrial field, since the object to be handled is mainly solid (metal), non-linear phenomenon is unlikely to occur and it has not been used.

In recent years, the reason why nonlinear ultrasonic waves are generated in a solid material has been proposed and studied differently from the above-mentioned causes. This nonlinear ultrasonic phenomenon is called contact-type nonlinear ultrasonic waves. That is, when an ultrasonic wave reaches a scratched part (a state where there is a void inside), the reflectance of the ultrasonic wave is given by (Z _substance- Z _air ) / (Z _substance + Z _air ). Z is said to be acoustic impedance and is defined as sound speed × density. In the case of _air , Z _air = 0.000428 (Pa · s / m), and in the case of steel, Z _substance = 46.4 (Pa · s / m), and when substituted, almost 100% is reflected. General non-destructive inspection using ultrasonic waves uses this principle to determine the size of reflected ultrasonic waves and detect the presence or absence of scratches.

  However, when the ultrasonic wave arrives at the wound and is pushed or pulled, if the ultrasonic amplitude is larger than the width of the gap of the wound, There is a possibility that voids disappear. In such a case, the ultrasonic wave passes through the wound. Therefore, as shown in FIG. 16, an ultrasonic wave having a waveform different from that of the incident ultrasonic wave propagates. However, it is generally said that the ultrasonic amplitude used in the nondestructive inspection is about nm to sub-nm, and the above phenomenon does not occur if the width of the void of the scratch is larger than this value.

  As a crack detection system using nonlinear ultrasonic waves, for example, the one described in Patent Document 1 is known. FIG. 17 is a sensor layout diagram for evaluating a diffusion bonding portion of two kinds of materials as a general detection system for nonlinear ultrasonic waves. An ultrasonic wave having a constant frequency is incident on the materials 54 and 55 via the contact medium 53 from the transmission ultrasonic sensor 52, and the ultrasonic wave that has passed through the diffusion bonding portion 56 is received on the opposite side surface via the contact medium 57. It is received by the ultrasonic sensor 58 for use. In the case where nonlinear ultrasonic waves are generated, the reception-side ultrasonic sensor 58 often has a main ultrasonic component that is significantly different from the main ultrasonic component of the incident ultrasonic wave. In many cases, a broadband type is used for reception. If this is used, it is said that the joint strength can be predicted by measuring the second harmonic amplitude when the material and joining conditions are in a certain range.

  In these conventional nondestructive inspection evaluations using nonlinear ultrasonic waves, a piezoelectric vibrator is used as an ultrasonic sensor. As another ultrasonic sensor, for example, an electromagnetic ultrasonic sensor is also known as described in Patent Document 2, but the electromagnetic ultrasonic sensor has poor transmission efficiency and generates ultrasonic intensity (amplitude). Therefore, there is a common sense that nonlinear ultrasonic detection that requires high-intensity amplitude is impossible. Further, for example, there are Non-Patent Documents 1 and 2 as documents relating to the electromagnetic ultrasonic sensor disclosed by the present inventors.

JP 2001-305109 A JP 2001-13118 A Riichi Murayama, “Basics of Electromagnetic Ultrasonic Sensors”, Nondestructive Inspection, Japan Nondestructive Inspection Association, February 2002, Vol. 51, No. 2, p. 62-67 Riichi Murayama, Hiroyuki Hoshihara, Yuki Fukushige, “Development of Lamb Wave, SH Plate Wave Alternate Excitation Electromagnetic Ultrasonic Probe”, 23rd Symposium on Basics and Applications of Ultrasonic Electronics, Ultrasonic Symposium Steering Committee, November 7, 2002, p. 173-174

  In the piezoelectric vibrator type ultrasonic sensor, as shown in FIG. 18, since an ultrasonic beam is generated from the front surface 60 of the sensor 59, it is necessary to enter the solid material 61 after propagating through the air (the surface of the solid material 61). Since there are irregularities on the order of μm from the microscopic viewpoint, an air layer is always formed if the sensor 59 is placed on the surface. However, as described above, since the ultrasonic wave is reflected 100% at the boundary between air and solid, the ultrasonic beam does not enter the solid material 61 as it is. Therefore, it is essential to apply a contact medium 62 such as water or oil to the front surface 60 of the sensor 59.

  However, when the ultrasonic beam is incident on the solid material 61 through the contact medium 62, it is necessary to consider the nonlinearity of the contact medium 62. Moreover, the nonlinearity of the contact medium 62 is much greater than that of the solid material 61. Therefore, it is extremely difficult to evaluate the nonlinearity of only the solid material 61 by eliminating the nonlinearity of the contact medium 62 from the obtained result. An error also occurs due to uneven coating of the contact medium 62.

  Accordingly, in the present invention, a non-linear electromagnetic ultrasonic sensor capable of detecting a fine flaw of 100 μm or less of a non-inspection material without using a contact medium, a fine flaw detection apparatus using the same, and a flaw detection method The purpose is to provide.

  The present inventor is correct when discussing non-linear ultrasonic waves for plastic strain with respect to the common sense that non-linear ultrasonic waves cannot be detected by an electromagnetic ultrasonic sensor. It was found that whether or not ultrasonic waves are emitted is determined by the relative relationship between the scratch gap and the ultrasonic amplitude. Therefore, it is limited to a finer crack of 100 μm or less, but nonlinear ultrasonic waves can be detected if the ultrasonic amplitude is larger than the gap between the scratches.

  The nonlinear electromagnetic ultrasonic sensor according to the present invention includes an ultrasonic transmitter that is disposed immediately above a material to be inspected and excites surface waves and SH (Share Horizontal) waves using electromagnetic force, and driving of the ultrasonic transmitter. It is composed of a plurality of ultrasonic receivers arranged immediately above a material to be inspected having reception characteristics that are 1 time and real number times the frequency.

  Here, the SH wave refers to a wave having a component that vibrates in a vertical direction (SH direction) in a plane with respect to a traveling direction among surface waves. The SH wave is formally an SH surface wave, but is generally abbreviated as an SH wave. Further, in general, a surface wave refers to a wave that excludes the SH wave. That is, as shown in FIGS. 1A and 1B, the vibration direction of the surface wave and the SH wave is 90 ° different from the traveling direction of the ultrasonic wave. When the plate thickness of the material to be inspected is a thin plate-like solid having the same thickness as the ultrasonic length or several times the wavelength, the surface wave is called a plate wave (Lamb wave), and the SH wave is called an SH plate wave.

  In the nonlinear electromagnetic ultrasonic sensor according to the present invention, when the surface wave and the SH wave are respectively excited from the ultrasonic transmitter, the ultrasonic wave is vertically incident on the slit-shaped flaw of the material to be inspected. Has the effect of closely contacting the wound opening, but the SH wave has no such effect. At this time, the surface wave does not pass because the width of the scratch is widened when the surface wave is pulled, but the surface wave passes because the width of the scratch is narrowed when the vibration is compressed. Thereby, a harmonic component is generated and nonlinear ultrasonic waves can be detected. In addition, since the vibration direction of the SH wave is perpendicular to the width direction of the flaw, the width of the flaw is unchanged, and no harmonic component is generated. On the other hand, when the light is incident in parallel to the slit-shaped scratch, there is an opposite effect. Moreover, when it injects diagonally, there exists an intermediate effect | action. That is, according to the nonlinear electromagnetic ultrasonic sensor of the present invention, information corresponding to the direction of the slit-shaped flaw can be obtained.

  The nonlinear electromagnetic ultrasonic sensor using electromagnetic force according to the present invention is limited to a minute scratch having a length of 100 μm or less in which the ultrasonic amplitude is larger than the length of the slit-like scratch. Since ultrasonic waves can be excited, no contact medium is required between the non-inspection material, the ultrasonic transmitter and the ultrasonic receiver, so it is possible to accurately determine the presence or absence of microcracks. . Further, since this non-linear electromagnetic ultrasonic sensor does not require a contact medium, automatic scanning is extremely simple as long as the posture with respect to the material to be inspected is made to be constant horizontally.

  In the case of an electromagnetic ultrasonic sensor, an ultrasonic beam is generally generated symmetrically from an ultrasonic transmitter due to its driving principle. Therefore, it is desirable to reversely use this characteristic and arrange a plurality of ultrasonic receivers (hereinafter referred to as “ultrasonic receiver group”) symmetrically with respect to the ultrasonic transmitter. As a result, when there is a flaw on either the left or right side, the received signal characteristics of the left and right ultrasonic wave receiver groups greatly change, and it becomes easy to determine whether or not there is a flaw. Such a method for determining the presence or absence of scratches is not feasible with a piezoelectric vibrator type ultrasonic sensor.

  The ultrasonic transmitter may be configured to separately excite the surface wave and the SH wave, but it is desirable that the ultrasonic wave transmitter can alternately excite the surface wave and the SH wave. By being able to excite surface waves and SH waves alternately, it is possible to determine the presence / absence of a flaw and the direction of the flaw only by switching the ultrasonic wave to be excited.

  An ultrasonic transmitter that is disposed directly above the material to be inspected to excite surface waves and SH waves using electromagnetic force, and has a reception characteristic that is 1 time and real number times the drive frequency of the ultrasonic transmitter. According to the nonlinear electromagnetic ultrasonic sensor composed of a plurality of ultrasonic receivers arranged immediately above the material to be inspected, it is possible to excite ultrasonic waves on the material to be inspected even without contact, so that no contact medium is required. In addition, it is possible to detect the presence or absence and direction of micro-scratches in the μm to sub-μm region, which was impossible at all in the past. In addition, this makes it possible to predict in advance the remaining life evaluation that could only be performed immediately before substantial destruction with conventional linear ultrasonic waves, and to ensure the security of the structure in a true sense. .

(Embodiment 1)
FIG. 2 is a schematic configuration diagram of the minute flaw detection apparatus according to the first embodiment of the present invention.
In FIG. 2, the minute flaw detection apparatus according to the first embodiment of the present invention includes a nonlinear electromagnetic ultrasonic sensor arranged immediately above a thin plate P as a material to be inspected. The nonlinear electromagnetic ultrasonic sensor includes an ultrasonic transmitter 1 and a plurality of ultrasonic receivers 2a and 2b. The ultrasonic transmitter 1 and the plural ultrasonic receivers 2a and 2b are coils in which conductive wires are wound in a comb shape. The ultrasonic receivers 2a and 2b have reception characteristics for receiving the frequency components of f ₀ and 2f ₀ based on the drive frequency f ₀ of the ultrasonic transmitter 1 respectively. The ultrasonic receiver only needs to have a reception characteristic that is 1 time and real number times the drive frequency f ₀ of the ultrasonic transmitter 1, and in addition to the ultrasonic receivers 2a and 2b, 3f It is also possible to add an ultrasonic receiver (not shown) that receives frequency components of ₀ , 4f ₀ . The ultrasonic receivers 2a, 2b and the like are arranged symmetrically with respect to the ultrasonic transmitter 1 as a center.

(A), (b) of FIG. 3 is explanatory drawing which shows the generation | occurrence | production mechanism of SH plate wave (SH wave) and Lamb wave (surface wave), respectively.
In the case of an SH plate wave, as shown in FIG. 3A, a static magnetic field is applied in a direction perpendicular to the propagation direction of the ultrasonic wave, and the direction of the composite magnetic field with the induction magnetic field generated by the coil current of the ultrasonic transmitter 1 is set obliquely to the left and right. Switch alternately. When the thin plate P is a magnetic material, magnetostriction (stretching / shrinking of the material) occurs in the direction of the composite magnetic field. As a result, an in-plane force is generated perpendicular to the propagation direction of the ultrasonic wave, and the SH plate wave It becomes a driving source. On the other hand, in the case of a Lamb wave, as shown in FIG. 3B, a composite magnetic field change is generated by an induced magnetic field generated at regular intervals in the same direction as the static magnetic field applied in the ultrasonic wave propagation direction. This causes magnetostrictive vibration in the propagation direction of, and is converted to Lamb waves.

  In the microflaw detection apparatus according to the present embodiment shown in FIG. 2, the arrangement of the ultrasonic transmitter 1 and the ultrasonic receivers 2a and 2b so that the excitation of the waves in both modes can be realized by one nonlinear electromagnetic ultrasonic sensor. It has a structure in which a static magnetic field can be loaded in each of a parallel direction and a vertical direction with respect to the direction. That is, a pair of electromagnets 3 a, 3 b, 4 a, 4 b are respectively arranged on the top, bottom, left and right of the ultrasonic transmitter 1 and the plurality of ultrasonic receivers 2 a, 2 b, The driving of the electromagnets 3a, 3b, 4a, 4b is switched.

As a result, when a Lamb wave is generated, the left and right electromagnets 3 a and 3 b are driven by the changeover switch 6, and a static magnetic field is generated horizontally with respect to the coil of the ultrasonic transmitter 1. At the same time, a high-frequency pulse electric signal having a frequency component of the fundamental frequency f ₀ is supplied from the pulsar 7 to the ultrasonic transmitter 1. A lamb wave is generated in the thin plate P by the interaction between the two. In the case of this principle, since there is no distinction between right and left with respect to the ultrasonic transmitter 1, Lamb waves are generated symmetrically. The generated Lamb waves are converted into electrical signals when passing through the left and right ultrasonic receivers 2a and 2b.

  The electrical signals converted by the ultrasonic receivers 2a and 2b are amplified by the amplifier 9 via the changeover switch 8, and the frequency analysis is performed by the frequency analyzer 10. If there is a flaw in the propagation process of the Lamb wave and the above-mentioned nonlinear ultrasonic wave generation conditions are met, the waveform is distorted, and the information can be acquired by the frequency analyzer 10.

  Next, when the SH plate wave is generated, the upper and lower electromagnets 4 a and 4 b are driven by the changeover switch 6. The ultrasonic transmitter 1 is driven in the same manner as described above, and an SH plate wave is generated by the interaction between the two. The following process is the same.

  FIG. 4 shows a procedure for evaluating microcracks by the microscratch detection apparatus of FIG.

(S101)
The left and right electromagnets 3a and 3b are driven by the changeover switch 6, and an ultrasonic wave (Lamb wave f ₀ ) is transmitted from the ultrasonic transmitter 1 in the Lamb wave mode.
(S102)
The Lamb wave f ₀ is detected by the left and right ultrasonic receivers 2a and 2b.
(S103)
The frequency component of the received signal is analyzed by each combination of the ultrasonic transmitter 1 and the ultrasonic receivers 2a and 2b. The frequency component ratio of 1 times the fundamental frequency f ₀ and real numbers 2f ₀ , 3f ₀ ,... Is calculated on the left side and the right side, respectively.
(S104)
If the calculated values on the left and right sides are the same, there will be no scratch on either side, and if the calculated values on the left and right sides are different, there will be a minute flaw in the direction perpendicular to the propagation direction of the ultrasonic waves.

(S105)
The changeover switch 6 drives the upper and lower electromagnets 4a and 4b, and transmits ultrasonic waves (SH plate wave f ₀ ) from the ultrasonic transmitter 1 in the SH plate wave mode.
(S106)
The SH plate wave f ₀ is detected by the left and right ultrasonic receivers 2a and 2b.
(S107)
The frequency component of the received signal is analyzed by each combination of the ultrasonic transmitter 1 and the ultrasonic receivers 2a and 2b. The frequency component ratio of 1 times the fundamental frequency f ₀ and real numbers 2f ₀ , 3f ₀ ,... Is calculated on the left side and the right side, respectively.
(S108)
If the calculated values on the left and right sides are the same, there will be no scratch on either side, and if the calculated values on the left and right sides are different, there will be a minute flaw parallel to the ultrasonic propagation direction.

  As described above, when there are micro cracks in the thin plate P, the evaluation results greatly differ between the left ultrasonic receivers 2a and 2b and the right ultrasonic receivers 2a and 2b. High degree of data can be obtained.

(Embodiment 2)
FIG. 5 and FIG. 6 are schematic configuration diagrams of a minute flaw detection apparatus according to the second embodiment of the present invention.
In the microflaw detection apparatus according to the second embodiment of the present invention, the SH plate wave and the Lamb wave are separately generated by the nonlinear electromagnetic ultrasonic sensor, so that the electromagnets 3a and 3b and the electromagnets 3b and 6b as shown in FIG. The electromagnets 4a and 4b are separately configured. Other configurations are the same as those in the first embodiment.

  Even in such a configuration, similarly to the first embodiment, the Lamb waves are transmitted by driving the electromagnets 3a and 3b shown in FIG. 5, and the signals received by the left and right ultrasonic receivers 2a and 2b are transmitted. By analyzing the frequency component, it is possible to detect the presence or absence of a flaw in the direction perpendicular to the propagation direction of the ultrasonic wave. Further, by driving the electromagnets 4a and 4b shown in FIG. 6, SH plate waves are transmitted, and by analyzing the frequency components of the signals received by the left and right ultrasonic receivers 2a and 2b, the propagation direction of the ultrasonic waves It is possible to detect the presence or absence of scratches in the parallel direction.

(Embodiment 3)
7 and 8 are schematic configuration diagrams of a micro-scratch detection device according to the third embodiment of the present invention.
In the microflaw detection apparatus according to the third embodiment of the present invention, the ultrasonic receivers 2a and 2b are arranged only on the left and right sides of the ultrasonic transmitter 1. Other configurations are the same as those of the second embodiment.

  Even in such a configuration, the electromagnets 3a and 3b shown in FIG. 7 are driven to transmit Lamb waves, and the frequency components of the signals received by the left and right ultrasonic receivers 2a and 2b are analyzed. It is possible to detect the presence or absence of a flaw in the direction perpendicular to the ultrasonic wave propagation direction. Further, by transmitting the SH plate wave by driving the electromagnets 4a and 4b shown in FIG. 8 and analyzing the frequency components of the signals received by the left and right ultrasonic receivers 2a and 2b, the propagation direction of the ultrasonic waves It is possible to detect the presence or absence of scratches in the parallel direction.

  FIG. 9 shows the evaluation results in the Lamb wave mode when the drive frequency of the ultrasonic transmitter 1 is 1 MHz and the reception characteristics of the ultrasonic receivers 2a and 2b are 1 MHz and 2 MHz. In this example, evaluation was made by processing the micro slits S in the thin plate (steel plate) P. The Lamb wave entered perpendicularly to the slit S as shown in FIG. In addition, although the application range of the micro flaw detection apparatus of the present invention is originally aimed at a range where the slit width is narrower, it was processed as small as possible by machining. In addition, the indicated slit width is the width of the opening, and the bottom is expected to be extremely thin.

  FIGS. 9B and 9C show the results of frequency analysis of the received signal when the slit width is 20 μm. The intensity ratio of each main frequency component is plotted for each slit width in FIG. is there. From this figure, the width of the slit bottom when the slit width is 20 to 30 μm is approximately the same as the amplitude of the ultrasonic vibration, and the main frequency component 2 MHz with respect to the intensity ratio of the main frequency component, that is, the main frequency component 1 MHz of the transmitted ultrasonic wave. It can be seen that it occurs strongly.

  FIG. 10 shows a case where an SH plate wave is incident perpendicular to the slit. In this case, as described above, since the SH plate wave has no effect of narrowing the slit width, no significant difference occurs.

  FIG. 11 shows an example in which a Lamb wave and an SH plate wave are incident in parallel to the slit. In this case, as described above, the effect of narrowing the slit width is generated in the SH plate wave, so that a significant difference is generated.

FIG. 12 is a diagram comparing a micro-scratch detection apparatus using the nonlinear electromagnetic ultrasonic sensor of the present invention and a micro-scratch detection apparatus using a conventional linear ultrasonic sensor.
As described above, according to the minute flaw detection apparatus using the nonlinear electromagnetic ultrasonic sensor of the present invention, it is possible to detect a minute flaw in the μm to sub-μm region which has never been possible in the past. As a result, for example, as shown in FIG. 12, when the conventional linear ultrasonic sensor is used, the remaining life evaluation can be performed only immediately before the substantial destruction, and the nonlinear electromagnetic ultrasonic sensor of the present invention is not effective. When is used, it is possible to make a prediction in advance, and it is possible to ensure the security of the structure in a true sense.

  Non-linear electromagnetic ultrasonic sensor of the present invention, micro-flaw detection apparatus and micro-flaw detection method using the same, initial fatigue that cannot be detected by an ultrasonic test using conventional linear ultrasonic, detection of creep damage, kissing bond, Detecting microcracks is useful for inspection of structures that require extremely strict inspection levels to ensure the safety of nuclear power plants and thermal power plants, and evaluation of remaining life of fuel tanks and gas pipes.

It is explanatory drawing which shows the difference in the mechanism of the nonlinear ultrasonic wave generation by a surface wave and SH wave. It is a schematic block diagram of the micro flaw detection apparatus in 1st Embodiment of this invention. (A) is explanatory drawing which shows the generation mechanism of SH plate wave (SH wave), (b) is explanatory drawing which shows the generation mechanism of Lamb wave (surface wave). It is a flowchart which shows the evaluation procedure of the micro crack by the micro flaw detection apparatus of FIG. It is a schematic block diagram of the micro flaw detection apparatus in 2nd Embodiment of this invention. It is a schematic block diagram of the micro flaw detection apparatus in 2nd Embodiment of this invention. It is a schematic block diagram of the micro flaw detection apparatus in 3rd Embodiment of this invention. It is a schematic block diagram of the micro flaw detection apparatus in 3rd Embodiment of this invention. It is a figure which shows the evaluation result by Lamb wave mode. It is a figure which shows the evaluation result at the time of entering SH plate wave perpendicularly | vertically with respect to a slit. It is a figure which shows the evaluation result at the time of entering a Lamb wave and SH plate wave in parallel with respect to a slit. It is the figure which compared the micro flaw detection apparatus using the nonlinear electromagnetic ultrasonic sensor of this invention, and the micro flaw detection apparatus using the conventional linear ultrasonic sensor. It is explanatory drawing of a nonlinear ultrasonic wave. It is a figure which shows a mode that an ultrasonic wave propagates within the elastic limit of a spring. It is a figure which shows a mode that an ultrasonic wave propagates exceeding the elastic limit of a spring. It is a figure which shows the mode of ultrasonic propagation in case an ultrasonic amplitude is narrower than the width | variety of the space | gap of a crack. It is a sensor layout in the case of evaluating diffusion junctions of two kinds of materials as a general detection system for nonlinear ultrasonic waves. It is a figure which shows the mode of the ultrasonic wave propagation by a piezoelectric vibrator type ultrasonic sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic transmitter 2a, 2b Ultrasonic receiver 3a, 3b, 4a, 4b Electromagnet 5 Power supply 6, 8 Changeover switch 7 Pulsar 9 Amplifier 10 Frequency analyzer

Claims (5)

  An ultrasonic transmitter that is disposed directly above the material to be inspected to excite surface waves and SH waves using electromagnetic force, and has a reception characteristic that is 1 time and real number times the drive frequency of the ultrasonic transmitter. A non-linear electromagnetic ultrasonic sensor comprising a plurality of ultrasonic receivers arranged immediately above the material to be inspected.   The nonlinear electromagnetic ultrasonic sensor according to claim 1, wherein the plurality of ultrasonic receivers are arranged symmetrically with respect to the ultrasonic transmitter.   The nonlinear electromagnetic ultrasonic sensor according to claim 1, wherein the ultrasonic transmitter is capable of alternately exciting the surface wave and the SH wave.   The nonlinear electromagnetic ultrasonic sensor according to any one of claims 1 to 3, an amplifier for amplifying an electric signal received by the nonlinear electromagnetic ultrasonic sensor, and frequency analysis based on the electric signal amplified by the amplifier A micro-scratch detection device having an analyzer. The surface wave and the SH wave are respectively transmitted from the ultrasonic transmitter by using the electromagnetic force arranged immediately above the material to be inspected.
Ultrasonic signals propagated through the inspection object by a plurality of ultrasonic receivers arranged immediately above the inspection object having reception characteristics of 1 and real number times the driving frequency of the ultrasonic transmitter, respectively. Receive,
Amplifying electrical signals received by the plurality of ultrasonic receivers;
A micro-scratch detection method that performs frequency analysis based on the amplified electrical signal.

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