JP2000088815A - Ultrasonic flaw detection method for non-conductive materials - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide an ultrasonic flaw detection method capable of non-contact inspection of defects inside and on a surface of a test object which is a non-conductive material. SOLUTION: The non-conductive material 7 as an inspection object
A conductive film 14 is formed on the surface of the device, and ultrasonic waves are transmitted and received (20, 21) to the non-conductive material 7 through the conductive film 14 in a non-contact manner using an electromagnetic ultrasonic probe. Perform flaw detection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting flaws inside and on a surface of a non-conductive material by ultrasonic waves.

[0002]

2. Description of the Related Art As a method for non-destructively detecting defects or the like during the production of materials or products, regardless of whether they are metal or non-metal,
Conventionally, an ultrasonic flaw detection method has been used. FIGS. 2A and 2B are views showing an example of the structure of a conventional ultrasonic probe. FIG. 2A shows the structure of a vertical probe, and FIG. 2B shows the structure of an oblique angle probe. 3A and 3B are explanatory diagrams of an ultrasonic flaw detection method using the probe of FIG. 2. FIG. 3A shows an ultrasonic beam path W _F of the oblique flaw detection method, and FIG. shows the beam path length W _F and the defect echo F.

In FIGS. 2 and 3, reference numerals 1 and 2 denote vertical and oblique probes using a piezoelectric element, 3 denotes a piezoelectric element (including other magnetostrictive elements, etc.), and 4 denotes absorption and attenuation of unnecessary ultrasonic vibration. Damper 5 for the protective film on the surface of the piezoelectric element or 5
An acoustic matching layer provided for efficiently transmitting ultrasonic waves, 6 is a wedge (shoe) used in a probe for oblique flaw detection, 7 is an object to be inspected, 8 is water, oil, glycerin, etc. Acoustic coupling, 9 is a defect such as a flaw, or an ultrasonic reflection cause on the back surface of a plate to be measured in sheet thickness measurement or the like, 20 is a transmitted ultrasonic signal (vibration), and 21 is the defect or reflection cause 9 This is an ultrasonic signal (vibration) reflected from the object.

Conventional ultrasonic flaw detection methods generally employ a vertical probe 1 or a bevel probe 2 having a piezoelectric element (vibrator) 3 as a component as shown in FIGS. Is brought into close contact with the inspection object 7, and vibration (ultrasonic waves) 20 generated by applying an electric signal to the piezoelectric element 3 is propagated into the inspection object 7, and the vibration (ultrasonic waves) 20 is inspected. A method is used in which a signal 21 reflected by a defect 9 of the object 7 is reflected as an electric signal by the transmission ultrasonic wave 20 and a reversible propagation mode. At the time of this ultrasonic flaw detection, in order to propagate vibrations (ultrasonic waves) 20 and 21 between the corresponding probes 1 and 2 and the inspection object 7, an acoustic coupler such as water, oil, glycerin, or the like is used. 8 is required.

[0005] As another prior art, as a method capable of transmitting and receiving ultrasonic waves in a non-contact manner, electromagnetic ultrasonic resonance (Electrom)
There is an electromagnetic ultrasonic flaw detection method using a technique called magnetic Acoustic Resonance (EMAR). FIG. 4 is a diagram showing the principle of a conventional electromagnetic ultrasonic flaw detection method, in which (a) shows a transmission mechanism and (b) shows a reception mechanism. Further, reference numeral 12 in the figure denotes a transmission coil, and reference numeral 13 denotes a reception coil. In FIG. 4, an eddy current Ie induced in the inspection object 7 by the external magnetic field B and the current It flowing through the transmission coil 12
Due to a force (Fleming's left-hand rule) F generated by a vector product with t, ultrasonic vibration 20
Is generated, and the reflected ultrasonic signal 21 from the defect 9 can be received via the receiving coil 13 and converted into an electric signal by the reversible path. Electromagnetic ultrasonic testing is like this
In order to electromagnetically couple the sensor and the inspection object,
Ultrasonic testing is possible without contact, without the need for acoustic coupling.

FIG. 5 shows a conventional electromagnetic ultrasonic probe (Electrom).
FIG. 3A is a diagram showing an example of the structure of a magnetic acoustic transducer (referred to as EMAT), in which (a) shows a probe for longitudinal waves and (b) shows a probe for shear waves. FIG. 5 is an excerpt from the "Electro-Magnetic Ultrasound Transducer" electromechanical permanent technical committee material by Kawashima, where 10 is an electromagnet core made of iron, etc., 11 is an exciting coil, and 12 is a transmission Coil, 1
3 is a receiving coil. In FIG. 5, an iron core 10 and an exciting coil 11 are used as means for generating an external magnetic field B, and a transmitting coil 12 (current flowing through this coil is It) is used as means for generating an eddy current Iet in the inspection object 7. Eddy current I due to current Ier generated in inspection object 7 by ultrasonic wave 21 reflected from defect 9 and magnetic field B
r is detected by the receiving coil 13 as a defect signal.

As described above, in order to generate an ultrasonic wave by the electromagnetic ultrasonic resonance technique, a magnetic field and a current are indispensable.
If the inspection object 7 is a conductor, an eddy current Iet is generated on the surface of the inspection object 7 in a direction to cancel the high-frequency current It flowing through the transmission coil 12 incorporated in the probe. The ultrasonic wave 20 can be generated by the combination with B, and the ultrasonic vibration 21 can be captured as the electric signal Ir by the receiving coil 13 or the like incorporated in the probe by the reversible path. However, when the inspection object is a non-conductor, the eddy current Iet does not occur on the surface of the inspection object, and the ultrasonic wave 20 cannot be generated on the inspection object. I can not use it.

[0008]

In a conventional method for transmitting and receiving ultrasonic waves by an ultrasonic probe having a piezoelectric element as a component, an acoustic coupling body is provided between the ultrasonic probe and the inspection object. Since the ultrasonic probe needs water, oil, glycerin, and the like, the ultrasonic probe must be brought into contact with the inspection object without fail, and therefore, there is a limit in increasing the speed for improving the efficiency of the inspection. In addition, even when performing automatic flaw detection, in the case of an upward inspection, it is necessary to take measures to prevent air or the like from entering between the ultrasonic probe and the inspection object. Further, in the contact type ultrasonic flaw detection method, the size of the ultrasonic transmission / reception signal is affected by the surface roughness of the inspection object, and the defect may be overlooked.

Further, the conventional electromagnetic ultrasonic flaw detection method as a method capable of transmitting and receiving ultrasonic waves in a non-contact manner can be applied when the object to be inspected is a conductor. In such a case, since no eddy current is generated on the surface of the inspection object, ultrasonic waves cannot be generated on the inspection object, so that the electromagnetic ultrasonic flaw detection method cannot be used. There was a problem that it could not be performed.

[0010]

According to a first aspect of the present invention, there is provided a method for ultrasonically inspecting a non-conductive material for defects inside and on a surface of the non-conductive material. A conductive film is formed on the surface of the non-conductive material as described above, and flaw detection is performed by transmitting and receiving ultrasonic waves to and from the non-conductive material via the conductive film.

According to a second aspect of the present invention, there is provided an ultrasonic flaw detection method for a non-conductive material according to the first aspect of the present invention, wherein the inspection object has a conductive film formed on a surface of the non-conductive material. As means for transmitting and receiving ultrasonic waves, an ultrasonic ultrasonic probe is used to transmit and receive ultrasonic waves in a non-contact manner.

According to a third aspect of the present invention, there is provided a method for ultrasonically inspecting a non-conductive material according to the first aspect of the present invention, wherein the method comprises the steps of: An electromagnetic ultrasonic probe is used as one of the means for transmitting ultrasonic waves to the object and the means for receiving ultrasonic waves from the inspection object.

According to a fourth aspect of the present invention, there is provided an ultrasonic inspection method for a non-conductive material according to any one of the first to third aspects, wherein the surface of the non-conductive material is electrically conductive. As a method of forming a film, application of a conductive paint,
Any of the methods of applying a conductive adhesive, applying a conductive liquid, and bonding a conductive film or sheet is used.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is an explanatory diagram of a method for electromagnetically ultrasonically inspecting a non-conductive material according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 7 denotes an inspection object, 12 denotes a transmission coil, 13 denotes a reception coil, 1
4 is a conductive paint, 20 is a transmitted ultrasonic signal (vibration), and 21 is an ultrasonic signal (vibration) reflected from a defect. In FIG. 1, an electromagnetic ultrasonic probe (EMA)
The components of T) are not the essence of the present invention, so the details are omitted, and the external magnetic field B, transmission coil 12, reception coil 13, current I
Only t and Ier and eddy currents Iet and Ir generated thereby are illustrated. Further, the inspection object 7 is a non-conductive material, and FIG. 1 shows a state in which a conductive paint 14 is applied to the surface of the inspection object 7.

The operation of FIG. 1 configured as described above will be described. In FIG. 1, a defect (not shown) in the non-conductive material,
In a case where the thickness and the like are inspected by the non-contact electromagnetic ultrasonic inspection method at high speed without being affected by the surface roughness, the conductive paint 14 is applied to the surface of the inspection object 7 in advance. .
An electromagnetic ultrasonic probe (EMA)
Applying T), when an external magnetic field B exists,
When a high-frequency current It is applied to the transmission coil 12, an eddy current Iet can be generated in the conductive paint 14, so that a force Fa is generated, which is the ultrasonic signal 20. This ultrasonic signal 2
Since the conductive paint 14 and the non-conductive test object 7 are in close contact with each other and generate a force Fb, the value 0 propagates into the test object 7.

On the contrary, the ultrasonic signal 21 reflected from a defect (not shown) of the non-conductive test object 7 is transmitted to the conductive paint 14 and interacts with the magnetic field B existing there to cause a high-frequency current. Ier is generated in the conductive paint 14, and an eddy current due to the current is generated in the receiving coil 13 of the electromagnetic ultrasonic probe (EMAT). Therefore, the electromagnetic ultrasonic inspection technique can be applied, and efficient non-contact ultrasonic inspection can be realized. After the inspection is completed, the surface property of the inspection object can be maintained by removing the conductive paint 14 as necessary. Alternatively, the conductive paint 14 may be used as it is or as a part of the coating material without being removed.

In the embodiment of the electromagnetic ultrasonic inspection method for a non-conductive material shown in FIG. 1, a copper-based paint is used as the conductive paint 14, but other conductive paints (for example, silver-based, nickel-based, Other) is also possible. The method of applying the conductive paint was also performed by hand coating with a brush in this example,
Conductive coating on the surface of non-conductive material such as application of conductive paint by automatic coating machine, baking coating of conductive paint, application of conductive adhesive, application of conductive liquid, or bonding of conductive film or sheet The method of forming is not subject to any restrictions. Regarding the thickness of the conductive film or coating, the skin depth is determined by the material of the conductive paint used and the frequency of the current (eddy current generated). The thickness is preferably equal to or greater than the thickness expressed as 1 / e. In the embodiment, the resistivity of the copper paint is 1.72 μΩ · c.
m, the relative permeability is 1, the frequency of the eddy current is 2 MHz, and the penetration depth δ is about 0.01 mm.
It is possible to secure a sufficient thickness for δ by a normal coating method.

As for the structure of the electromagnetic ultrasonic probe (EMAT), as a means for generating a magnetic field, there are a method using an electromagnet, a method using a permanent magnet, and the like. There are also various types of coils such as a transmission / reception integrated type and an independent type, and there are various combinations of a magnetic field generation method, an eddy current generation / detection method, and the like, but the structural form is not a constraint of the present invention. Also, regarding the mode of ultrasonic waves generated and received by the electromagnetic ultrasonic probe (EMAT), the electromagnetic ultrasonic probe (EMAT)
There are longitudinal waves, transverse waves, SH waves, surface waves, etc., depending on the structure described above, but the ultrasonic mode is not a constraint of the present invention.

As described above, according to the first embodiment, by forming a conductive film on the surface of a non-conductive material as an inspection object, the non-conductive material is contacted through the conductive film in a non-contact manner. Inspection can be performed using the electromagnetic ultrasonic inspection method that can transmit and receive ultrasonic waves to improve the inspection speed of non-conductive products, improve the efficiency of inspection, and the effect of the surface roughness of the inspection object High quality inspection can be performed without receiving

Embodiment 2 In Embodiment 1 shown in FIG. 1, means for transmitting ultrasonic waves to an inspection object having a conductive film formed on the surface of a non-conductive material and receiving ultrasonic waves from the inspection object The embodiment in which the ultrasonic flaw detection is performed in a non-contact manner by using an electromagnetic ultrasonic probe (EMAT) provided with both means for performing the above-described steps has been described. In the second embodiment,
It has only one of the means for transmitting ultrasonic waves to the inspection target having the conductive film formed on the surface of the non-conductive material, or the means for receiving ultrasonic waves from the inspection target. An embodiment in which ultrasonic flaw detection is performed using an electromagnetic ultrasonic probe will be described.

When using an electromagnetic ultrasonic probe having only means for transmitting ultrasonic waves to the inspection object In this case, a small displacement based on ultrasonic vibration reflected from a defect or the like of the inspection object is measured in a non-contact manner. Non-contact ultrasonic flaw detection can be performed by receiving reflected ultrasonic waves using a means (for example, a laser displacement meter using a Michelson interferometer, an eddy current sensor, or the like). When a contact type is acceptable, reflected ultrasonic waves may be received by a probe using a conventional piezoelectric element.

When using an electromagnetic ultrasonic probe having only means for receiving ultrasonic waves reflected from a defect or the like of an inspection object In this case, means for generating ultrasonic vibrations on the inspection object without contact (for example, Laser ultrasonic wave transmission means that generates thermal stress by pulse heating with laser to generate ultrasonic vibration)
By transmitting ultrasonic waves by using the method, ultrasonic flaw detection can be performed in a non-contact manner. In the case where a contact type may be used, an ultrasonic wave may be transmitted by a probe using a conventional piezoelectric element.

As described above, according to the second embodiment, by forming a conductive film on the surface of a non-conductive material to be inspected, the non-conductive material is contacted through the conductive film in a non-contact manner. An electromagnetic ultrasonic probe capable of transmitting or receiving ultrasonic waves to other non-contact means for receiving ultrasonic waves (such as a laser displacement meter or an eddy current sensor) or transmitting ultrasonic waves in a non-contact manner By using the means (laser ultrasonic transmitter or the like) together, the inspection of the non-conductive product can be performed accurately and efficiently in a short time.

In the ultrasonic flaw detection technique, the object to be measured is not only the defect of the material or its joint, but also the thickness of the material, the physical property of the material, and the like. -The subject of inspection is not subject to any restrictions on invention. Examples of the non-conductive material to which the ultrasonic testing method of the present invention can be applied include polyethylene, FRP, resin, polymer material, porcelain, concrete and the like, and the applicable material range is wide.

[0025]

As described above, according to the present invention, there is provided a method for detecting flaws inside and on a surface of a non-conductive material by ultrasonic waves. Is formed, and the flaw detection is performed by transmitting / receiving ultrasonic waves to / from the non-conductive material through the conductive film, so that an electromagnetic ultrasonic flaw detection method which cannot be conventionally applied to a non-conductive material is used. Inspection and inspection can be performed by sending and receiving ultrasonic waves in a non-contact manner, improving inspection speed and improving inspection efficiency, and performing high-quality inspection without being affected by the surface roughness of the inspection object it can.

According to the present invention, there is provided an electromagnetic ultrasonic probe capable of transmitting or receiving ultrasonic waves in a non-contact manner with respect to an inspection object having a conductive film formed on the surface of the non-conductive material. The combined use of the probe and another means for receiving ultrasonic waves in a non-contact manner or a means for transmitting ultrasonic waves in a non-contact manner makes it possible to inspect a non-conductive product accurately and efficiently in a short time.

According to the present invention, the method of forming a conductive film on the surface of the non-conductive material includes applying a conductive paint, applying a conductive adhesive, applying a conductive liquid, or forming a conductive film. Alternatively, since any one of the sheet bonding methods is used, a conductive film can be easily formed by selecting a method suitable for the shape and characteristics of the non-conductive material.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an electromagnetic ultrasonic inspection method for a non-conductive material according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a structural example of a conventional ultrasonic probe.

FIG. 3 is an explanatory diagram of an ultrasonic flaw detection method using the probe of FIG. 2;

FIG. 4 is a diagram showing the principle of a conventional electromagnetic ultrasonic flaw detection method.

FIG. 5 is a diagram showing a structural example of a conventional electromagnetic ultrasonic probe.

[Description of Signs] 1 Vertical probe 2 Angle probe 3 Piezoelectric element 4 Damper 5 Acoustic matching layer 6 Wedge (Shoe) 7 Inspection object 8 Acoustic coupling 9 Defect 10 Electromagnet core 11 Excitation coil 12 Transmission coil 13 Receiving coil 14 Conductive paint 20 Transmitted ultrasonic signal 21 Reflected ultrasonic signal

Claims (4)

[Claims] 1. A method for detecting flaws inside and on a surface of a non-conductive material by ultrasonic waves, comprising: forming a conductive film on a surface of the non-conductive material as an object to be inspected; Ultrasonic flaw detection of the non-conductive material by transmitting and receiving ultrasonic waves to and from the non-conductive material. 2. A method for transmitting and receiving ultrasonic waves to and from an inspection object having a conductive film formed on the surface of the non-conductive material, using an electromagnetic ultrasonic probe to transmit and receive ultrasonic waves in a non-contact manner. 2. The ultrasonic inspection method for a non-conductive material according to claim 1, wherein: 3. A means for transmitting an ultrasonic wave to an inspection object having a conductive film formed on a surface of the non-conductive material,
The ultrasonic flaw detection method for a non-conductive material according to claim 1, wherein an electromagnetic ultrasonic probe is used as one of means for receiving an ultrasonic wave from the inspection object. 4. A method for forming a conductive film on the surface of the non-conductive material includes applying a conductive paint, applying a conductive adhesive, applying a conductive liquid, or bonding a conductive film or sheet. 4. The ultrasonic inspection method for a non-conductive material according to claim 1, wherein any one of the methods is used.