JP2980272B2 - Visualization method of micro crack - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for visualizing fine cracks generated on a surface to be observed of an object, which are difficult to recognize with the naked eye.

[0002]

2. Description of the Related Art Conventionally, methods for investigating the presence, location, length, etc. of fine cracks generated on the surface of an object include:
(1) magnetic particle testing, (2) penetration testing, (3) ultrasonic testing,
(4) Methods such as visual observation have been mainly used.

[0003]

However, in the above methods (1) to (3), when the same part is inspected and observed several times, the surface to be observed is treated with a special chemical each time, or the special method is used. It is necessary to use a device. Although the method of visual observation in (4) is simple, even when the observation is performed at a distance of about 30 cm to the surface to be observed, the width is about 5 cm due to the limit of visual acuity.
It is impossible to visually recognize cracks of / 100 mm or less.

[0004] Accordingly, an object of the present invention is to provide a method for enhancing and visualizing fine cracks while utilizing the simplicity of visual observation.

[0005]

The method of the present invention will be described with reference to the sectional view of the observation surface 11 of the fine crack 9 shown in the embodiment of FIG. The transparent thin film 2 having a structure that generates the fine voids 1 inside the tensile stress applying portion is closely adhered to the surface 11 to be observed of the object 7, and the transparency due to the fine voids 1 generated in the transparent thin film 2 at the cracks 9 of the surface 11 to be observed. Fine cracks from drop 9
To visualize. The transparent thin film 2 adheres to the observation surface 11 with such a strength that the transparent thin film 2 does not peel off even if the observation surface 11 is cracked. A minute void 1 is generated inside 2.

In the illustrated example, a plurality of fibers 5 are made of a transparent resin 3.
A fibrous film, such as a transparent resin-impregnated paper, obtained by solidifying the above is used as the transparent thin film 2. When a fine crack 9 is generated on the surface 11 to be observed, a tensile stress is applied to a local portion of the transparent thin film 2 which is in close contact with the crack portion 9, and as shown in FIG. As a result, fine voids 1 are generated inside the transparent thin film 2. Due to the fine voids 1, the transparency of the transparent thin film 2 at the cracks decreases. However, the transparent thin film 2 is not limited to the transparent resin-impregnated paper in the illustrated example, but any structure that generates the fine voids 1 inside the tensile stress applying section is sufficient.

[0007] Preferably, the surface 11 to be observed is dark, and a change in lightness caused by a decrease in the transparency of the transparent thin film 2 is emphasized for visualization.

[0008]

In general, the observation surface 11 selectively absorbs a part of the visible light, and exhibits a certain color by the remaining reflected light which is not absorbed. Since the transparent thin film 2 is transparent enough to transmit almost all visible light, the color of the observation surface 11 does not change even if the transparent thin film 2 is brought into close contact with the observation surface 11. When a tensile stress is applied to the transparent thin film 2 at the cracked portion 9 of the surface to be observed 11 and a minute void 1 is generated inside the transparent thin film 2, light is scattered by the minute void 1 and transparency is reduced, and the crack 9 is emphasized. be able to. According to observations made by the present inventor, almost all light is scattered by the fine voids 1, and the portions where the fine voids 1 occur appear to be white.

Preferably, the surface 11 to be observed has a dark color having a wide range of selective absorption of light, and light is scattered at the cracks 9 with the dark surface 11 to be observed as background. And visualize it. Further, it is also possible to emphasize and visualize the cracked portion 9 by irradiating, for example, light of a color selectively absorbed by the observation surface 11 instead of white light including all colors.

In this way, the object of the present invention is to provide "a method for enhancing and visualizing fine cracks while utilizing the simplicity by visual observation".

[0011]

1 and 2 show an embodiment of the present invention in a tensile test in which an object 7 is a concrete prism. As shown in FIG. 2, the object 7 has a height of 26 cm and a length of 300 c.
It is a square prism made of concrete having a thickness of 10 cm and a thickness of 10 cm. Cracks 9 were generated from the notches 13 by applying a tensile load f from both ends in the longitudinal direction of the object 7, and the cracks 9 were observed by the method of the present invention and a conventional method of visual observation.

As the transparent thin film 2, a fibrous sheet impregnated with an acrylic resin into a fibrous sheet and cured so as to be in a nearly transparent state is used. . As the fibrous sheet, for example, paper having a thickness of about 0.03 mm can be used. In addition, the present invention is not limited to a method of forming the transparent thin film 2 in advance and then bonding the transparent thin film 2 to the surface 11 to be observed. The transparent thin film 2 which is in close contact with the surface 11 to be observed can be formed.

In the embodiment shown in FIG. 2, since the object 7 is a white concrete prism and is observed under sunlight, the surface 11 to be observed is colored black in advance. However, the observation surface of the present invention
11 is not limited to black.

FIG. 3 shows a photograph of the observation result according to the embodiment of the present invention, and FIG. 4 shows a photograph of the observation result by conventional visual observation. In each case, cracks were caused by the same tensile load f, and images were taken so that the height of the object 7 was the same. In the photograph of FIG. 4, a blue line traced beside the crack 9 is written on the surface 11 to be observed, and the crack is located right next to the blue line. 3 and FIG. 4, both of the cracks 9 have a maximum width of about 8/100 mm, but the cracks that cannot be recognized by the naked eye in the conventional visual observation of FIG. In the embodiment, it is visualized.

[0015]

As described above, the method for visualizing fine cracks according to the present invention employs a structure in which a transparent thin film having a structure in which fine voids are generated at cracks is brought into close contact with the surface to be observed. Play. (1) Even if it is about 1m to 2m away from the observation surface,
The presence / absence, position, length and the like of a crack having a width of about 5/100 mm can be visually observed. (2) If the surface to be observed is processed once before the observation, it is not necessary to perform the processing every time thereafter. (3) Since the crack is visualized with emphasis, not only the oversight of the crack is reduced, but also the improvement in the measurement accuracy of the length and shape of the crack can be expected. (4) By selecting a transparent thin film that is resistant to damage and durable, long-term crack observation is possible. (5) By selecting the quality of the fiber, the quality of the resin, the thickness of the transparent thin film, the combination of the fiber and the resin, etc., the degree of crack enhancement and visualization can be improved, and the crack detection sensitivity can be increased. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an embodiment of the present invention.

FIG. 3 is a photograph of an observation result by the method of the present invention.

FIG. 4 is a photograph of an observation result by a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fine void 2 Transparent thin film 3
Resin 5 Fiber 7 Object 9
Crack 11 Observed surface 13 Notch to induce crack

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 21/84 G01N 21/88

Claims (4)

(57) [Claims] 1. A transparent thin film having a structure in which fine voids are generated inside a tensile stress applying section is closely adhered to a surface to be observed, and cracks are caused by a decrease in transparency due to fine voids generated in the thin film at cracks in the surface to be observed. Visualization method of micro cracks that are visualized. 2. The method for visualizing fine cracks according to claim 1, wherein said transparent thin film is a fibrous film in which a plurality of fibers are densely solidified with a transparent resin. 3. The method for visualizing fine cracks according to claim 1, wherein the transparent thin film is a fibrous film obtained by impregnating a fibrous sheet with a transparent resin and curing the fibrous sheet. 4. The method for visualizing fine cracks according to claim 1, 2 or 3, wherein the surface to be observed is darkened.