JPH07234205A - Nondestructive inspection device - Google Patents

Abstract

PURPOSE:To carry out precise nondestructive inspection by detecting a foreign matter existing in an object to be inspected and minute change in a magnetic field caused by a defect by means of a high sensitive magnetic flux sensor. CONSTITUTION:A magnetic field generating means 6 is installed on a bottom face of a heat insulating container 3, and both of them are covered by a magnetism shielding container 7A. In an inspection area formed in a flange part, 7C in the lower end of the magnetism shielding container 7A, a clearance between the device and an object 1 to be inspected is kept constant by means of a protecting member 8. A magnetic sensor 2 inside the container 3 is provided with a magnetic transformer 200 and a SQUID 201, and the transformer 200 consists of an input coil 202 and pick up coils 203, 204, which are arranged in the vicinity of the inspection area and are wound in reverse direction to each other. Therefore, a uniform fluctuation in a magnetic field such as a change in an environmental magnetic field is compensated by the reversely wound coils 203, 204 so as not to be detected (201). For a local change due to a defect and a foreign matter contained in the object 1 to be inspected, a differential in different magnetic fields is detected (201) by a difference of a relative position between the coils 203, 204 and the object 1 to be inspected, so that influence due to fluctuation in the environmental magnetic field is eliminated, and as a result, precise inspection can be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nondestructive inspection device. More specifically, the present invention has the ability to detect foreign matter and defects contained inside the object to be inspected with extremely high sensitivity,
In addition, the present invention relates to a structure of a novel nondestructive inspection device that is small and portable.

[0002]

2. Description of the Related Art The presence of slight defects in an airframe such as an aircraft or a spacecraft may lead to a serious accident. Therefore, regular inspection and maintenance are strictly performed on this type of aircraft. However, since it is not possible to perform so-called destructive testing on the object to be inspected, the inspections performed are limited to visual and acoustic inspections by operators, and sufficient inspection accuracy is required especially for internal defects. I can't get it. There is also a problem that the efficiency of the inspection work is low.

In the case of a power cable, a signal cable or a cable or a strip as a structural material after being laid, it is possible to inspect the surface and the conductor part to some extent by visual inspection of the surface and the quality of the transmitted signal. There is no known method that can inspect the inside of insulators and tensile strength bodies. Similarly, it is difficult to inspect even the long material as a structural material even after the installation.

[0004]

As described above, in many fields, it is required to accurately detect the presence of fine defects or foreign matter in a long or large member. No inspection device has been developed to meet such requirements. Therefore, it is an object of the present invention to provide a novel inspection device capable of efficiently and nondestructively inspecting a large member or a structure. It is also one of the objects of the present invention to provide an inspection device that can perform an effective nondestructive inspection even when an object to be inspected cannot be moved, such as a construction structural material or a signal cable after being laid. is there.

[0005]

That is, according to the present invention,
A magnetic shielding container that defines a region including a magnetically stable inspection region, a magnetic field generating unit that forms a predetermined magnetic field in the inspection region, and a magnetic field that detects a variation of the magnetic field in the inspection region by using SQUID. It is an inspection device integrally provided with a sensor and a cooling means for cooling the magnetic sensor, and a predetermined interval is set with respect to the non-inspection object so that the inspection object is always located in an inspection area of the inspection device. There is provided a nondestructive inspection device characterized in that it can be conveyed along the inspection object while maintaining it.

[0006]

The inspection apparatus according to the present invention performs a nondestructive and precise inspection by detecting a minute magnetic field change caused by a foreign substance or a defect existing in an object to be inspected by the SQUID which is a highly sensitive magnetic flux sensor. be able to. Further, the main feature is that it is configured so that it can be inspected even for an object to be inspected that is fixed outdoors such as a large structure or a laid cable.

That is, a predetermined magnetic field is generated by the magnetic field generating means in the area defined by the magnetic shielding container for blocking the influence of the external magnetic field to form an inspection area, and the object to be inspected enters the magnetic field. Then, a constant change occurs in the magnetic field according to the magnetic susceptibility or the magnetization of the inspection object. Furthermore, when the inspection object includes a singular point such as a foreign substance or a defect, the presence of the singular point causes a peculiar variation in the change of the magnetic field.
Therefore, the highly sensitive magnetic sensor using the SQUID can detect the specific fluctuation of the magnetic field to perform a quick and precise inspection without destroying the inspection object.

A non-destructive inspection apparatus according to the present invention comprises a magnetic shielding container which defines an inspection region in which the influence of an environmental magnetic field is cut off.
A magnetic field generating means for generating a predetermined magnetic field is provided in the inspection area. Here, the magnetic shielding container can be formed of, for example, permalloy or the like.

The nondestructive inspection apparatus according to the present invention is S
A cooling means for the magnetic sensor using the QUID is also provided. That is, the SQUID used in the magnetic sensor is formed to include a superconducting loop including weak coupling, and it is necessary to cool the SQUID to a temperature below the superconducting critical temperature before use. Therefore, according to one embodiment of the present invention, the magnetic sensor includes, for example, a heat insulating container filled with a cooling medium, and is used while being immersed in the cooling medium. Further, as will be specifically described later, the shape of the heat insulating container and the supporting method thereof are devised so that the SQUID can always be kept immersed in the cooling medium during use. The inspection device according to the present invention can be configured by using a small-sized cooler having a cooling capacity up to around the liquid nitrogen temperature.

When actually operating this nondestructive inspection apparatus, it is desirable to provide a temperature sensor that monitors at least the temperature near the SQUID and issues some alarm when the temperature rises. The reason is,
This is because the superconducting circuit including the SQUID normally operates only under the temperature condition below the critical temperature. Further, when the superconducting state is broken, not only the superconducting circuit does not operate normally, but also the boiling of the cooling medium may cause destruction in the extreme case.

According to one embodiment of the present invention, S
It is advantageous to use the QUID formed of an oxide superconducting thin film. Since this type of superconducting material exhibits effective superconducting properties even in the vicinity of the temperature of liquid nitrogen, a nondestructive inspection device capable of accommodating and transporting liquid nitrogen and SQUID in a heat insulating container can be relatively easily constructed.

Further, in the nondestructive inspection device according to the present invention, it is preferable that the magnetic field generating means also be portable. That is, it is preferable to use a permanent magnet that does not require a power source or the like, or to be configured to be easily connectable to an external power source.

Hereinafter, the present invention will be described in more detail with reference to examples, but the following disclosure is merely an example of the present invention and does not limit the technical scope of the present invention.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram schematically showing the basic structure of an inspection apparatus according to the present invention.

As shown in FIG. 1, this inspection apparatus is configured as a nondestructive inspection apparatus for inspecting a rod-shaped inspection object 1 shown in cross section in the drawing. The magnetic sensor 2 is housed inside the heat insulating container 3 together with the cooling medium 4. The upper opening of the heat insulating container 3 has a lid 5 having heat insulating property.
It is sealed by.

A pair of permanent magnets 6 is provided on the bottom surface of the heat insulating container 3.
A magnetic field generating means 6 composed of A and 6B is mounted. The side surfaces of the heat insulating container 3 and the magnetic field generating means 6 are
It is covered with a magnetic shielding container 7A made of Permalloy,
The upper portion of the magnetic shield container 7A is sealed by the magnetic shield cap 7B. Further, the lower end of the magnetic shielding container 7A extends to the side surface and the lower surface of the magnetic field generating means 6 to form a flange portion 7C.

Further, a part of the bottom surface of the heat insulating container 3 defined by the inner end of the flange portion 7C and the inner surface of the magnetic field generating means 6 have a constant space between the inspection device and the object to be inspected. A protective member 8 also serving as a spacer is attached. In view of its function, the protection member 8 is preferably a non-magnetic material, has high wear resistance, and is formed of a material having a low surface friction coefficient. Specifically, various ceramics and fluororesins can be exemplified.

Furthermore, the entire nondestructive inspection apparatus is constructed so that it can be hung and carried by a handle 9 mounted on the top surface of the magnetic shielding container 7,
As long as this non-destructive inspection device is handled by the handle 9,
The heat insulating container 3 is configured so as not to tilt. The reason is that if the heat insulating container 3 is largely inclined and the SQUID is exposed from the cooling medium, the superconducting state of the SQUID or the like is broken and the magnetic sensor does not function.

On the other hand, the magnetic sensor 2 is a magnetic flux transformer 200.
And SQUID201 are provided, and SQUID201 is
It is connected to an external measuring device 100 via a cable 110 penetrating the lid 5 and the cap 7B. The SQUID 201 used here can be made of, for example, an oxide superconducting material. On the other hand, the magnetic flux transformer 200
The input coil 202 having a large number of turns arranged near the UID 201 and the pickup coils 203, 204 having a small number of turns arranged near the inspection area are connected to each other. Here, a pair of pickup coils 203, 204
Are wound in mutually opposite directions, one pickup coil 203 is directly above the object to be inspected, and the other pickup coil 203 is
204 is arranged to be located on the side of the pickup coil 203. Therefore, the magnetic sensor 2 constitutes a gradiometer as a whole.

That is, in such a configuration, uniform magnetic field fluctuations, such as environmental magnetic field fluctuations, are canceled by the pickup coils 203 and 204, which are wound in opposite directions to each other.
Not detected in ID201. On the other hand, for a local change caused by a defect or a foreign substance included in the non-inspection object, a different magnetic field is detected due to a difference in relative position between the pickup coils 203 and 204 and the inspection object 1. , The difference is detected in SQUID201. Therefore, it is possible to eliminate the influence of the fluctuation of the environmental magnetic field and perform a more precise inspection.

FIG. 2 is a diagram for explaining the operating principle of the inspection apparatus shown in FIG.

As shown in FIG. 2 (a), when the object to be inspected 1 is present in a substantially uniform magnetic field B generated by a magnet, the magnetic field B is dependent on the magnetic susceptibility or magnetization of the object 1 to be inspected. Is stable in a constant state. Further, when a defect X is generated in the inspection object as shown in FIG. 2B or a foreign substance Y is contained in the inspection object as shown in FIG. 2C, the stable magnetic field is It varies depending on the magnetic susceptibility or magnetization of the defect X or the foreign substance Y. The SQUID detects the variation of this magnetic field and outputs it as the variation of the voltage signal.

FIG. 3 is a diagram showing an example of the configuration of a nondestructive inspection apparatus that can be used for inspecting a flat object to be inspected in a large structure such as an aircraft body. It should be noted that common reference numerals are given to constituent elements common to the nondestructive inspection apparatus shown in FIG.

As shown in the figure, this inspection apparatus is constructed as a nondestructive inspection apparatus for inspecting an object 1 to be inspected of a plate material shown in cross section. A heat insulating container 3 in which a cooling medium 4 and a pair of magnetic sensors 2A, 2B are housed and sealed with a lid 5, a magnet 6 mounted on the lower side of the heat insulating container 3 as a magnetic field generating means, and heat insulating It is mainly composed of a container 3 and a magnetic shield container 7 made of Permalloy for covering a magnet. Further, the entire nondestructive inspection device including these members is configured to be carried by the handle 9 attached to the cap 7B of the magnetic shielding container 7D.

Further, a non-magnetic wheel is provided on the side of the magnet 6.
10 is mounted to facilitate the movement of the inspection device while keeping the distance between the bottom surface of the nondestructive inspection device and the inspection object 1 constant. Although only one set of wheels 10 is shown in the figure, it is preferable to mount three or more wheels in order to accurately maintain the distance between the magnetic sensor and the inspection object. Further, in the destructive inspection device as described above, the destructive inspection device may be configured to be self-propelled by adding driving means to the wheel 10. With such a configuration, it is possible to inspect the inside of the pipeline and even in an environment where humans are difficult to approach, such as nuclear power equipment.

Further, the magnetic sensors 2A and 2B used in this inspection apparatus are SQUID 201A and SQUID 201A, respectively.
It has 201B and magnetic flux transformers 200A and 200B. Here, the magnetic flux transformers 200 A and 200 B are input coils 202 A and 202 B arranged near the SQUID 201 and having a large number of turns, respectively, and pickup coils 203 A / 204 arranged near the inspection region and having a small number of turns. A,
It is configured by combining 203 B and 204 B, respectively.
Also, each pair of pickup coils 203A / 204A, 203
B / 204 B are mutually wound in opposite directions, and one pickup 203 A, 203 B is the other pickup coil.
It is arranged at a position farther from the object to be inspected 1 than 204A and 204B. Therefore, each magnetic sensor 2A, 2B constitutes a gradiometer as a whole.

That is, in such a configuration, uniform magnetic field fluctuations such as fluctuations in the environmental magnetic field are canceled by the pickup coils 203A, B and 204A, B which are wound in opposite directions, so that SQUIDs 201A, B are generated. Is not detected. On the other hand, with respect to a local change caused by a defect or a foreign substance included in the non-inspection object, a magnetic field different depending on a difference in distance between each pickup coil 203 A, B and 204 A, B and the inspection object 1 is generated. Is detected, the difference is SQUID201
Detected by A and B. Therefore, it is possible to perform the precise inspection by eliminating the influence of the fluctuation of the environmental magnetic field.

FIG. 4 is a diagram conceptually showing one preferred structural example of the magnetic field generating means usable in the nondestructive inspection device shown in FIG.

As shown in the figure, this magnetic field generating means 6
Is composed of a pair of permanent magnet assemblies 6A and 6B. Here, each permanent magnet assembly 6A, 6B is configured by combining a pair of permanent magnets 61, 62, respectively, and one permanent magnet 62 can be rotated as shown by the dotted line in the figure.

The magnetism generating means constructed as described above is operated as follows. First, when operating the nondestructive inspection device, the permanent magnets 61 and 62 are set in the arrangement as shown in FIG. 4 (a). At this time, since the permanent magnets 61, 62 have the same polarity as each other, they generate a strong magnetic field to the outside and generate a strong attractive force to other magnetic substances.

On the other hand, when the inspection is completed, the magnet 62 is rotated to reverse the polarity with respect to the magnet 61, and the arrangement shown in FIG. In this state, the permanent magnets 61, 62 attract each other, and the external magnetic field is very small. Therefore, the external magnetic field substantially disappears, and the attraction force for other magnetic bodies also disappears substantially.

FIG. 5 is a diagram showing another configuration example of the nondestructive inspection device according to the present invention.

As shown in FIG. 5 (a), this nondestructive inspection device is different from the other structural examples in that a small cooling device 40 is incorporated. That is, this nondestructive inspection device is constructed inside a box-shaped magnetic shielding container 70 having a handle 90 mounted on the top and an opening at the bottom. The magnetic field generating means 60 composed of a pair of permanent magnets is arranged at the side of the opening at the bottom of the magnetic shielding container 70. The temperature shielding container 30 made of a non-magnetic material is arranged directly above the magnetic field generating means 60 and is completely covered by the magnetic shielding container 70. Inside the temperature shield container 30, a SQUID 20 as a magnetic sensor is housed. Furthermore, temperature shielded container
A cooling device 40 is attached to the side of 30.

The cooling device 40 used here is constructed by combining a so-called Joule-Thomson type cooling machine 42 with a cooling table 43, and the cooling table 43 is SQ in the heat insulating container 3.
It is located near UID2. This type of chiller
With its own cooling capacity, the SQUID can be cooled to around the liquid nitrogen temperature and can be maintained at that temperature. Therefore, it is possible to carry it for a long time and operate it outdoors for inspection of cables and the like after installation. In reality, the cooler 42 is connected to an external tank of a cooling medium, specifically, a high-pressure cylinder of nitrogen or the like via the ducts 41A and 41B. The function of the apparatus configured as described above as an inspection apparatus is the same as that of the apparatus shown in FIG. 1, and therefore detailed description regarding the operation is omitted.

FIG. 5 (b) is an example in which the portability of the apparatus shown in FIG. 5 (a) is further improved.
44 is housed inside the inspection device, and this cylinder 44 is connected to the cooler 42 via the duct 41A. With this configuration, as long as it can interface the detection signal, it can be used alone as a non-destructive device, so that its application is further widened. Further, since the cooling medium distribution system, which is troublesome to handle, is built in the apparatus, the handling becomes easier. still,
The duct 41B extending to the outside of the inspection device is for discharging the used gas.

The nondestructive inspection device configured as described above is different from the other configuration examples shown in FIGS. 1 and 3 in that the posture of the inspection device can be freely changed. It can also be advantageously used in the inspection of large structures.

In the inspection apparatus shown in FIG. 5, the SQUID is used alone as the magnetic sensor. However, as already described with reference to FIGS. 1 and 3, a magnetic flux transformer is added, and A pickup coil of a magnetic flux transformer may be formed by a pair of reversely wound coils, and the magnetic sensor may be a gradiometer.

[0038]

As described in detail above, the nondestructive inspection device according to the present invention is a portable inspection device capable of promptly detecting extremely fine defects or foreign matters. This device can be configured not only to detect the presence or absence of defects and impurities, but also to detect the position and distribution of defects and impurities.

Further, since it can be used for so-called fieldwork by devising a cooling device, it can be used for inspection of cables fixed outdoors and after installation, and for airframes such as ships and aircraft, steel frames, rebar structures, etc. It can also be used favorably for inspection of large structures.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a nondestructive inspection device according to the present invention.

FIG. 2 is a diagram for explaining the operation of the nondestructive inspection device according to the present invention.

FIG. 3 is a diagram showing another configuration example of the nondestructive inspection device according to the present invention.

FIG. 4 is a diagram showing a specific configuration example of a magnetic field generation unit that can be used in the nondestructive inspection device shown in FIG.

FIG. 5 is a diagram showing still another configuration example of the nondestructive inspection device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inspected object, 2 ... Magnetic sensor, 3 ... Heat insulation container, 4 ... Cooling medium (liquid nitrogen), 40 ... Cooling device, 41 ... Duct, 42 ... Joule Thomson cooler, 43 ... Cooling stand, 44 ... Cylinder, 5 ... Lid, 6 ... Magnetic field generating means, 61, 62 ... Permanent magnet, 7 ... Magnetic shielding container, 8 ... Spacers, 9 ... Handles, 10 ... Wheels

Claims (9)

[Claims] 1. A magnetically shielded container defining an area including a magnetically stable inspection area, a magnetic field generating means for forming a predetermined magnetic field in the inspection area, and a magnetic field in the inspection area using SQUID. An inspection device integrally provided with a magnetic sensor for detecting a variation and a cooling means for cooling the magnetic sensor, wherein the object to be inspected is always located in an inspection area of the inspection device, with respect to the non-inspected object. The non-destructive inspection device is configured so as to be conveyed along the inspection object while maintaining a predetermined interval. 2. The nondestructive inspection apparatus according to claim 1, wherein the cooling means is an adiabatic container containing a cooling medium cooled to a superconducting critical temperature or lower together with the magnetic sensor. Destruction inspection device. 3. The non-destructive inspection apparatus according to claim 2, wherein the heat insulating container is supported so as not to be significantly inclined, and the magnetic sensor is always immersed in the cooling medium. A nondestructive inspection device characterized in that 4. The nondestructive inspection device according to claim 1, wherein the magnetic field generating means strengthens the mutual magnetic field and the first relative position for canceling the mutual magnetic field. A non-destructive inspection device comprising a plurality of permanent magnets configured to be movable between a matching second relative position. 5. The nondestructive inspection device according to claim 1, wherein one end is in contact with the tip of the nondestructive inspection device and the other end is in contact with the surface of the object to be inspected. A non-destructive inspection device having a non-magnetic spacer formed thereon. 6. The non-destructive inspection apparatus according to claim 5, wherein the spacer is a non-magnetic wheel mounted on the non-destructive inspection apparatus so as to roll on the surface of the inspection object. A nondestructive inspection device characterized in that 7. The nondestructive inspection device according to claim 1, wherein a temperature sensor is arranged around the magnetic sensor. . 8. The nondestructive inspection apparatus according to claim 1, wherein the magnetic sensor includes a magnetic flux transformer. 9. The non-destructive inspection device according to claim 8, wherein the magnetic flux transformer includes a pickup coil having the same number of windings that are reversely wound with each other, and the magnetic sensor constitutes a gradiometer. Characteristic non-destructive inspection device.