JPH0213737B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for inspecting internal defects of an object to be inspected using infrared rays.

In general, it has been reported that defects such as cracks and contamination of impurities occur below the metal surface level during the manufacturing and welding processes of metal plates, shapes, etc., but these microscopic defects can be inspected non-destructively. There was no good way.

Conventionally, methods used to find defects inside materials include ultrasonic methods, X-ray methods, and sonic flaw detection methods. However, with these conventional methods, there is a limit to the size of defects that can be detected, and defects in the micron scale are not possible.Due to the nature of the inspection method, there are restrictions on the surface shape of the inspected object, and it is not possible to detect cracks. However, there are problems such as the inability to detect foreign substances.

The present invention was made to solve the above problems, and it is possible to detect the presence or absence of defects, the location of the defects, the shape of the defects, etc. without applying any processing or means to the test object. The purpose is to provide equipment.

More specifically, it is an object of the present invention to detect the presence, location, shape, etc. of defects such as cracks and impurity inclusions below the surface temperature of a conductor based on differences in surface temperature.

It is generally known that when an eddy current is generated on the surface of a conductor, the temperature of the surface of the conductor increases due to Joule heat. The present invention utilizes this principle, focusing on the fact that the surface temperature of a conductor differs depending on the electrical resistance value of the conductor and the defective part, and by measuring the difference or distribution of this surface temperature. ,
This is intended to inspect defective parts directly below the conductor surface.

An internal defect inspection device according to the present invention includes a coil wound in a cylindrical shape for generating an eddy current in an object to be inspected, and a coil fixed in the coil with a focus on one end surface of the coil to generate an eddy current in the object to be inspected. an infrared lens that condenses infrared rays emitted from the coil; and an infrared lens that is fixed in a covered cylinder integrally provided at the other end of the coil in accordance with the focal position of the other infrared lens, and converts the condensed infrared rays into an electrical signal. It is characterized by comprising an infrared detector for converting, a power source for passing current through the coil, and a processor for converting an electrical signal from the infrared detector into temperature or an amount of infrared rays and displaying the result.

Hereinafter, details of the present invention will be explained using the drawings.

FIG. 1 and FIG. 2 are diagrams showing defects existing at a relatively shallow location of an object to be inspected. Figure 1 shows
It shows a cross section of a welded part 3 when two metal plates 1a and 1b are overlapped and their ends 2 are welded, and 4 is a defect generated in this welded part 3. These defects usually caused by welding4
are often bubbles or special oxides. FIG. 2 is a cross-sectional view of one sheet of metal material 5, and 6 represents defects such as cracks that have occurred in the metal material 5. As shown in FIG. This type of defect 6 is caused by the metal material 5
This often occurs during the rolling process during the manufacturing process. As described above, the present invention provides an apparatus for non-destructively inspecting various minute defects occurring in relatively shallow areas of an object to be inspected.

The principle of the present invention will be explained using FIGS. 3 and 4. FIG. 3 is a conceptual diagram of an internal defect inspection device for an inspected object according to the present invention, in which 11 is a coil for generating an eddy current in an inspected object 12 such as a metal plate by electromagnetic conduction; This is a power source for passing current through the coil 11. Current 1 is now in coil 11
4 is caused to flow in the direction of the arrow, a magnetic field 15 is generated in the direction of the arrow, and an eddy current 16 is generated in the object to be inspected 12 placed across the magnetic field 15 according to what electromagnetism teaches. Eddy current 16 is magnetic field 1
5, the current supplied from the power supply 13 to the coil 11 must be alternating current or pulsed. In the case of alternating current, the current is 1
4 alternately, the direction of the magnetic field 15 alternates, causing an eddy current 1 generated in the object 12 to be inspected.
Although the orientation of 6 also changes alternately, this change does not affect the present invention in any way. When a pulsed current is applied instead of alternating current, an eddy current 16 flows at the moment the current flows. Note that the magnitude of the eddy current changes depending on the magnitude of the current flowing through the coil 11, so the current can be adjusted appropriately to obtain a desired magnitude of eddy current.

FIG. 4 shows the temperature state of each part of the test object 12 when an eddy current is generated in the test object 12 shown in FIG. That is, when an eddy current is generated in the object to be inspected 12, Joule heat is generated, but as shown in an enlarged view in FIG. 4, the defect 17 as shown in FIGS. If so, the drag coefficient of this part is either larger or smaller than that of other parts. Therefore, when eddy currents are sequentially generated on the surface of the object to be inspected 12, surface temperature changes occur as shown in FIGS. 4a and 4b. Figure a shows the temperature change on the surface of the object to be inspected 12 when the defect 17 is a defect with a large resistance coefficient, such as a pinhole.
The temperature T2 near 7 is higher than the temperature T1 in other parts.

Figure b shows the surface temperature change when defect 17 is a defect with a small resistance coefficient;
The temperature T2 near 7 is lower than the temperature T1 in other parts. Therefore, by detecting the location where the surface temperature is changing, it is possible to non-destructively inspect the presence of various defects occurring in a relatively shallow location of the inspection object 12.

Next, an embodiment of the internal defect inspection apparatus for an inspected object according to the present invention will be described with reference to FIG.
Note that portions in the figure that correspond to those in FIG. 3 are given the same reference numerals and their explanations will be omitted. 11 in the diagram
12 is a coil, 12 is an object to be inspected, and 13 is a power source.
Note that both ends of the coil 11 are electrically connected to a power source 13. Reference numeral 18 denotes an infrared lens made of gelatin or silicon fixed at a position where the surface of the object to be inspected 12 is focused in order to focus the infrared rays emitted from the surface of the object to be inspected 12 onto the infrared detector 19. be. An infrared detector 19 made of indium antimony or the like is placed at the other focal point of the lens 18 to convert the infrared rays collected by the lens 18 into electrical signals, and its output is sent to the processor 20. is supplied to The processor 20 amplifies and digitally converts the electrical signal from the infrared detector 19, compares it with a temperature conversion ratio stored in advance by a microcomputer, converts it into a temperature, and displays the result. The display method is
Any method that can determine the temperature distribution may be used. In the above example, a method of converting into temperature was described, but a method of displaying, for example, intensity of color based on the amount of infrared rays may also be used.

The operation of the apparatus for inspecting internal defects of an object to be inspected configured as described above will be explained below. Now power supply 1
When a pulsed current is passed through the coil 11 from the coil 11, an eddy current is generated in the vicinity of the surface of the object to be inspected 12 as described above, and as a result, the temperature in the vicinity increases. When the surface temperature rises, the temperature of the object to be inspected 12 increases in proportion to it.
Infrared rays are emitted from the surface. The emitted infrared rays are sent to an infrared detector 19 by an infrared lens 18.
The light is focused on the detector 19 and converted into an electrical signal. This electrical signal is converted into a desired form of temperature or infrared radiation by the processor 20 and visualized. Therefore, the coil 11 is connected to the object to be inspected 12.
By sequentially moving the object 1 on the surface and supplying a constant electromagnetic force to the coil 11,
As a result, temperature changes as shown in FIGS. 4a and 4b are obtained, and the location and approximate state of the defect inside the object to be inspected 12 can be known. Although a single infrared detector 19 is shown in FIG. 5, the infrared detectors 19 may be arranged in a line or in a mosaic, and these linear or mosaic detectors may be used. This will allow you to determine the size, shape, etc. of the defect.

As explained above, according to the present invention, it is possible to accurately identify small defects under the surface of a conductor, and since the inspection apparatus of the present invention can be constructed in a relatively small size, there is no need to move the object to be inspected for inspection. Without any
Furthermore, it has many advantages such as not requiring any processing on the object to be inspected, making it very effective for use in non-destructive testing.

In addition, since the coil is heated by placing the coil in close contact with the object to be inspected, the air inside the coil is also heated and the heat dissipation of the conductor, which is the object to be inspected, is suppressed. Since there is no incident light, even minute defects can be detected accurately.

Note that the present invention can be used not only for inspecting defects as described above, but also for inspecting the adhesion state of a conductor to a substrate in a printed circuit board, etc., and inspecting the adhesion state of a plating layer in plating, etc., to obtain similar effects. be able to.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of an object to be inspected according to the present invention, FIG. 3 is a conceptual diagram of an internal defect inspection apparatus according to the present invention, and FIG. FIG. 2 is a temperature curve diagram showing a case in which a defect with a large resistance coefficient exists, and b shows a case in which a defect with a small resistance coefficient exists. FIG. 5 is a partially cutaway schematic diagram showing an embodiment of the internal defect inspection apparatus according to the present invention. 11...Coil, 12...Test object, 13...
Power source, 18... Infrared lens, 19... Infrared detector, 20... Processor.

Claims (1)

[Claims] 1 A coil wound into a cylindrical shape for generating an eddy current in the object to be inspected, and a coil fixed in the coil focusing on one end face of the coil to condense infrared rays emitted from the object to be inspected. an infrared lens fixed at the other focal point of the infrared lens in a covered cylinder integrally provided at the other end of the coil, and an infrared detector configured to convert the focused infrared light into an electrical signal; An internal defect inspection device comprising: a power source for passing a current through a coil; and a processor that converts an electrical signal from the infrared detector into a temperature or an amount of infrared rays and displays the converted value.