JPH09113473A - Non-destructive inspection method for material defects - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a non-destructive inspection method for a material defect portion capable of easily and accurately detecting a defect portion of the material by accurately measuring a change in temperature distribution on the surface of the material to be measured. provide. SOLUTION: A reticulate body 3 having a high emissivity is pressed against a surface of a material 2 to be measured, and a flash lamp 4 irradiates a heat ray from above to instantaneously heat the irradiation, and then the irradiation is stopped, and then an infrared camera device 6 is used. A material defect portion of the measured material is detected by measuring the surface temperature distribution of the measured material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to cracks inside various materials such as metals, alloys, plastics and composite materials.
The present invention relates to a nondestructive inspection method for a material defect portion capable of accurately detecting a defect portion such as peeling, pores, composition abnormality, or inclusion of foreign matter in a nondestructive state.

Techniques have been developed for measuring the surface temperature and surface temperature distribution of various substances using an infrared thermograph device,
Widely used. One of the applied technologies is a method of detecting a difference in properties inside a substance by utilizing a change in surface temperature distribution that appears based on a difference in thermal properties inside the substance. Metals, alloys, plastics, composite materials It is being used as a means for nondestructively detecting abnormal parts in various materials.

However, the temperature measurement by the infrared thermography device has a drawback that a measurement error occurs due to the difference in the emissivity of the surface of the material to be measured, and it is impossible to measure the temperature of the material to be measured having a low emissivity such as a polished metallic glossy surface. In some cases In such cases, it is necessary to apply high emissivity paint to the surface of the material to be measured or roughen the surface of the material to be measured, but the material to be non-destructively inspected, such as a beverage can. Food-related products such as and materials requiring high purity often dislike such treatment. In addition, it may be difficult to perform such a process in an inspection of a building or the like that may impair the appearance or an online inspection during the manufacturing process.
Therefore, it is difficult to accurately measure the temperature distribution, that is, to accurately detect the material defect portion of the measured material.

[0004]

2. Description of the Related Art In order to solve such a drawback, for example, in Japanese Unexamined Patent Publication No. 7-35620, a surface temperature distribution of an object to be measured is measured by using an infrared thermograph device, and the surface temperature distribution is measured from the surface temperature distribution. In the nondestructive inspection method for detecting defects inside the measurement object, between the infrared sensor and the measurement object,
A high emissivity layer made of a material having an emissivity of 0.2 or more;
A transparent layer, which is a layer made of an infrared transparent material, is arranged such that the high-emissivity layer is located on the side of the object to be measured and the transparent layer is located on the side of the infrared sensor. A band cut filter for removing a wavelength band including a specific absorption wavelength of infrared rays of the infrared transmission layer within the wavelength band is disposed between the transmission layer and the infrared sensor of the infrared thermograph device, and through these layers, the object to be measured is provided. A non-destructive inspection method has been proposed, which is characterized by measuring the surface temperature distribution of the and detecting defects.

The invention described in the above-mentioned Japanese Patent Application Laid-Open No. 7-35620 discloses an object to be measured by transferring the surface temperature of the object to be measured to the high emissivity layer and measuring the transferred temperature through the transmission layer. The accurate temperature distribution on the surface of the object to be measured can be measured without being affected by the difference in the material and the emissivity of the surface or the degree of unevenness. This temperature distribution measurement enables the detection of defects inside the object to be measured. Becomes

When the surface temperature is measured by an infrared thermograph device, the measurement accuracy is largely affected by the emissivity, and the emissivity of the high emissivity layer is required to be 0.2 or more. Inorganic materials, polymer materials, metals, alloys, composite materials and the like are used. In order to quickly transfer the surface temperature of the DUT to the high emissivity layer, the thickness of the high emissivity layer is preferably 1 mm or less. Furthermore, the surface temperature of the DUT is accurately transferred to the high emissivity layer. To transfer, measure the high emissivity layer close to or in contact with the object to be measured, especially if the surface of the object to be measured has a large curved surface or unevenness, plastic, rubber, grease, water, etc. to improve adhesion. It is said that it is preferable to contact them via the adhesion promoting layer.

[0007]

However, after the material to be measured is subjected to a thermal load such as instantaneous heating, the change in the temperature distribution of the surface caused by the thermal diffusion to the surface of the material to be measured is measured to measure the material of the material to be measured. When detecting a defective portion, it is necessary that thermal diffusion from the surface of the material to be measured to the high emissivity layer, that is, transfer be performed quickly and accurately. In the invention of Japanese Patent Laid-Open No. 7-35620 mentioned above, the high emissivity layer is transferred by being brought close to or in contact with the material to be measured. In that case, at the interface between the high emissivity layer and the surface of the material to be measured. There is a problem that voids are likely to occur, and smooth voids at the interface, that is, an air layer, hinder smooth thermal diffusion and make accurate temperature distribution measurement difficult. Further, in the case of contacting through the adhesion promoting layer, there is a problem that heat diffusion does not proceed smoothly due to the heat transfer resistance of the adhesion promoting layer such as plastic or rubber, and an error is likely to occur in temperature distribution measurement.

The present inventor has conducted research to solve the above problems, and as a result, presses a reticulated body having a high emissivity against the surface of the material to be measured to quickly and accurately form the reticulated body from the surface of the material to be measured. It was found that heat was diffused. The present invention has been completed based on this finding, and an object thereof is to provide a nondestructive inspection method for a defect portion of a material that can easily and accurately detect a defect portion of various materials.

[0009]

In order to achieve the above object, a nondestructive inspection method for a material defect portion according to the present invention is such that a net having a high emissivity is brought into pressure contact with a surface of a material to be measured and flashes from above. After irradiating heat rays with a lamp and heating instantaneously, the irradiation is stopped, and then the surface temperature distribution of the measured material is measured using an infrared thermograph device to detect the material defect portion of the measured material. Characterize.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION When a surface of a material to be measured is subjected to a thermal load and then its surface temperature distribution is measured, the temperature distribution on the surface of the material changes due to a material defect portion existing inside the material. For example, if the material to be measured is irradiated with heat rays intermittently by a high-power flash lamp and heated instantaneously, irradiation of the heat rays is stopped, and then the temperature distribution on the surface of the material to be measured is measured, there should be no material defects. For example, the temperature distribution is uniform, but if a material defect exists, the temperature distribution changes corresponding to the thermal characteristics. That is, when the thermal conductivity of the material defect portion is low, the surface temperature corresponding to the material defect portion is higher than the ambient temperature, and a mountain-shaped temperature distribution is exhibited corresponding to the shape of the defect portion. . Conversely, when the thermal conductivity is high, the temperature distribution has a valley shape.

In this case, in order to accurately measure the temperature distribution on the material surface, it is necessary that the material to be measured is heated rapidly and evenly, and the subsequent heat diffusion to the material surface proceeds accurately and quickly. is there. Further, in order to accurately measure the temperature by the infrared thermograph device, it is necessary that the heat radiation from the surface of the material to be measured is large, that is, the emissivity is high.

Therefore, in the present invention, a high emissivity reticulate body is pressed against the surface of the material to be measured so as to improve and uniformize the thermal diffusion rate at the interface between the reticulate body and the surface of the material to be measured. It is possible to instantly and evenly heat at the time of heat ray irradiation. In addition, when measuring the temperature distribution, the thermal diffusion from the surface of the material to be measured to the mesh body proceeds smoothly and the temperature distribution can be accurately transferred, and by using the mesh body having a high emissivity, the temperature measurement accuracy can be improved. It is possible to improve. In order to heat efficiently with a flash lamp, an antireflection agent that prevents reflection of heat rays is applied.However, in the case of a sheet or foil, the application of the antireflection agent and the tendency to cause deformation such as warpage due to drying are In the invention, a net-like body is used that is unlikely to be deformed such as warped.

The reticulate body is not only a material having a high emissivity, for example, a metal or resin such as copper, iron, stainless steel, or steel which has been subjected to an appropriate surface treatment such as oxidation, but also a high emissivity material such as a black paint. It is also possible to use a paint having a high emissivity by applying the paint to a wire mesh having a low emissivity. In addition, the reticulated body is preferably formed by a thin wire so that it can be easily deformed along the shape of the surface of the material to be measured such as a curved surface or the degree of unevenness, and a wire diameter of 0.025 to
Those having a thickness of about 0.050 mm are preferably used. It is preferable that the mesh has a mesh size of 80 to 500 mesh in order to uniformly heat the mesh and to radiate radiation accurately reflecting the temperature distribution.

In order to improve the measurement accuracy, it is necessary to bring the reticulate body into close contact with the surface of the material to be measured so that voids such as an air layer do not occur at the interface. Adhesion can be improved by pressing the surface of the material to be measured with an appropriate pressure. The appropriate pressure is generally 0.005 to 0.020 kg / cm ^{2, although} it varies depending on the properties of the mesh body and the material to be measured.

In this way, the material to be measured, which is pressed against the high-emissivity mesh-like body, is irradiated with the heat rays of the flash lamp from above and is heated evenly instantly, and then the irradiation of the heat rays is stopped. The heat transferred from the surface to the inside becomes uneven flow corresponding to the material defect portion, and the temperature distribution on the surface of the measured material changes. This change is measured with high accuracy by the infrared thermograph device through the net having a high emissivity, and it becomes possible to detect the material defect portion. In this case, it is preferable that the measurement data of the temperature distribution is processed by the image processing device to visually detect the material defect portion.

[0016]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Embodiment FIG. 1 is an overall configuration diagram illustrating an apparatus used in the nondestructive inspection method of the present invention. In the apparatus of FIG. 1, the material 2 to be measured is placed on the sample table 1, and the mesh 3 is placed on the surface of the material to be measured.
Is pressed. Two high-power flash lamps 4 are arranged diagonally above the sample table 1, and a lamp power source 5 radiates heat rays with high power. An infrared camera device 6 is arranged directly above the sample table 1, and information regarding the surface temperature distribution of the material 2 to be measured is captured via the mesh body 3.
These pieces of information are sent from the infrared camera device 6 to the thermograph control device 7 and visualized on the display device 8.

Using the above apparatus, a typical experiment was conducted by the following method. Stainless steel wire mesh (wire diameter 0.0
A reticulate body 3 (manufactured by Sonocom Co., Ltd.) in which the emulsion was uniformly applied to 50 mm and a mesh size of 80 mesh was used. Further, as the material 2 to be measured, a material prepared by imitating a flat aluminum plate (B) having a thickness of 0.1 mm on an aluminum plate (A) having a complicated shape was used. Place the reticulate body 3 on the material 2 to be measured, and then about 0.010 kg / cm ²
The sample was placed on the sample table 1 under pressure contact with the sample, and was heated to a temperature of 60 to 70 ° C. by irradiating it with heat rays from the flash lamp 4. After that, the emitted light from the mesh 3 is measured with the infrared camera device 6 over time, the data is processed by the thermograph control device 7, and then the measured material 2 is displayed on the display device 8.
The surface temperature distribution of the was displayed as an image.

As a result, a clear image showing the shape of the complex aluminum plate (A) under the flat aluminum plate (B) could be obtained. That is, if the aluminum plate (A) having a complicated shape under the flat aluminum plate (B) having a thickness of 0.1 mm is regarded as a material defect portion in the aluminum plate, the defect portion can be clearly observed. I understand.

Comparative Example Using the material to be measured 2 prepared by the same method as that of the embodiment, the surface temperature distribution of the material to be measured 2 was measured by the same method as that of the embodiment as it was without using the mesh 3. It was measured. As a result, the images of the camera and the flash lamp due to the reflected light of the flat aluminum plate (B) were only observed on the screen of the display device 8, and the image showing the shape of the complicated aluminum plate (A) was obtained. I could not observe it at all.

[0021]

As described above, according to the nondestructive inspection method for the defect portion of the material according to the present invention, the mesh body having a high emissivity is brought into pressure contact with the surface of the material to be measured so that the surface of the material and the surface of the material to be measured are separated. The thermal adhesion can be improved. Therefore, the thermal diffusion resistance at the interface can be reduced and made uniform, and the thermal diffusion from the material to be measured to the mesh body can proceed accurately and quickly. Furthermore,
By using a net with a high emissivity, it is possible to measure changes in the surface temperature distribution with high accuracy even if the emissivity of the measured material is low, and to easily and accurately detect the material defect inside the measured material. It is possible to

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram illustrating an apparatus used for a nondestructive inspection method for a material defect portion according to the present invention.

[Explanation of symbols]

 1 sample stage 2 material to be measured 3 reticulated body 4 flash lamp 5 power supply for lamp 6 infrared camera device 7 thermograph control device 8 display device

Claims (2)

[Claims] 1. A high-emissivity mesh-like body is pressed against the surface of the material to be measured, and a flash lamp is irradiated from above to heat the wire for instantaneous heating and then the irradiation is stopped, and then the infrared thermograph device is used to measure. A non-destructive inspection method for a defect portion of a material, which comprises detecting a defect portion of the measured material by measuring a surface temperature distribution of the material. 2. The nondestructive inspection method for a defect portion of a material according to claim 1, wherein the net having a high emissivity is a metal net coated with a paint having a high emissivity.