JPH0566209A - Method for detecting defect on surface or inside of structure - Google Patents

Abstract

PURPOSE:To judge the width and the depth of a defect and to enhance the detecting accuracy by estimating the actual width and the depth of the object surface of the defect in the same direction based on the temperature distribution in the direction of the object surface which is obtained with the temperature signal from an infrared- ray radiometer. CONSTITUTION:A running truck 3 is provided on the roof of a building 1 in order to heat an outer wall 1A. A gondola 7 is suspended through a winch 5 and a piece of wire 6 which are provided at the tip of an arm 4 extending from the truck 3. A hot-gas blowing means 8 is provided at the gondola 7. In this constitution, the suspending position of the gondola 7 and the position of the running truck 3 are adjusted. The height and the position of the horizontal direction of the gondola 7 are set. The surface of the outer wall 1A is heated with the hot-gas blowing means 8. The observing direction of an infrared-ray radiometer 2 is made to agree with the part of the outer wall 1A. The infrared-ray radiant energy from the part is detected. The detected signal is analyzed with an image analyzing device 20. The presence or absence of the defective part or its place in the region of the outer wall 1A is judged. The width and the depth of the defect can be also estimated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantitatively detecting the width or depth of a surface or internal defect of a structure such as a building, such as a crack.

[0002]

2. Description of the Related Art When a crack is generated on an outer wall or a tile is raised due to long-term use of a structure,
Risk of water leakage and flaking of exterior walls or tiles. Therefore, conventionally, in order to detect these, there has been known a method in which a worker hits the surface with a wooden hammer or the like and the operator judges based on the sound.

However, this not only results in poor workability, but also lacks reliability.

Therefore, a method of detecting a defect which has excellent workability and high reliability has been sought. One of them is a method of detecting radiant energy from the surface of a structure with an infrared radiometer to detect the presence or absence of a defect or the location of the structure.

[0005]

It is known that this method is basically an excellent method, and various improvements have been proposed.

However, even if the radiant energy from the surface of the structure is detected and displayed on, for example, a CRT display device, the inspector only visually determines whether or not the defect is present, and the actual defect is detected. The relationship with the property could not be determined. Further, even if it is judged whether or not there is a defect, the inspector often relies on the feeling of the inspector, so that an inspection error is likely to occur and the normal portion may be erroneously peeled for repair.

Therefore, the main object of the present invention is to not only judge the presence or absence of a defect but also to make a step forward to judge the width and depth of the defect and further improve the detection accuracy.

[0008]

The above-mentioned object is obtained from a radiation temperature signal from the infrared radiometer in a method of detecting a defect of the structure by detecting the radiant energy from the surface of the structure with an infrared radiometer. This can be solved by estimating the actual width and depth of the defect in the target surface in the same direction based on the temperature distribution in the target surface direction.

Further, it is appropriate to multiply the width between the inflection points in the curve showing the temperature distribution by a coefficient (= 1/2 to 1/4) to obtain the actual width of the defective portion.

Further, the surface temperature Tc of the defective portion and the surface temperature Ts of the non-defect portion during the natural heating by sunlight or the heating process when the target surface is artificially heated or the cooling process in the cold state by stopping the heating. The depth of the defect can be estimated based on the degree of change in the temperature difference ΔTc. In this case, in the temperature difference change curve from the start of heating of the temperature difference ΔTc, it is preferable to estimate the depth of the defect based on the time difference from the start of heating to the time when the rate of increase in temperature difference stabilizes.

[0011]

From the results of various experiments to be described later, the present inventor has found that the width between the inflection points in the curve showing the temperature distribution in the direction of the target surface obtained from the radiation temperature signal from the infrared radiometer is the target surface of the internal defect. It was found that there is a correlation with the actual width (actual width dimension) in the same direction. In addition, the width of the inflection point has a coefficient (= 1 /
It was also found that it is appropriate to multiply by 2 to 1/4) to obtain the actual width of the defective portion.

Further, regarding the depth of the defect, the surface temperature Tc of the defect portion in the heating or cooling process of artificially heating the target surface, even if it is a natural temperature rise by sunlight,
The defect depth can be estimated based on the degree of change of the temperature difference ΔTc between the surface temperature Ts of the defect-free portion and the surface temperature Ts.
In this case, in the temperature difference change curve from the start of heating of the temperature difference ΔTc, it is desirable to estimate the depth of the defect based on the time difference from the start of heating to the time when the rate of increase in temperature difference stabilizes. In the present invention, the width of the defect does not matter in its direction.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. First, the outline of the defect detection apparatus of the present invention will be described. In FIG. 1, reference numeral 1 is a building as a structure, and an infrared radiometer 2 that gazes at an outer wall 1A thereof is installed on the ground.

The infrared radiometer 2 is installed so as to be vertically and horizontally adjustable. Further, in order to heat the outer wall 1A, a roof traveling carriage 3 is provided on the roof of the building 1, and a gondola 7 is suspended through a suspension winch 5 and a wire 6 provided at the tip of an arm 4 protruding from the roof. The gondola 7 is provided with hot gas spraying means 8.

As shown in FIG. 2, the hot gas spraying means 8 is preferably traversable along a running rail 9 laid in the gondola 7 in a direction parallel to the surface of the outer wall 1A. In this traverse, a roller 12 that comes into contact with the rail 9 by a traverse drive motor 11 provided in the hot gas blowing carriage 10 is provided.
By rotating. Reference numerals 13A and 13B are traverse stoppers. On the other hand, in order to bring the hot gas blowing means 8 into and out of contact with the outer wall 1A, as shown in FIG. Forward / reverse drive motor 15
It is supposed to be able to move forward and backward. This forward / backward movement is performed, for example, by rotating the auxiliary wheel 16 as illustrated. Reference numeral 17 shown by an imaginary line is a traverse wheel. Furthermore, in order to heat the entire height range, the hot gas blowing means 8 can be swung vertically. The swinging is performed by rotating the support shaft 8a of the hot gas blowing means 8 by the swinging motor 18.

On the other hand, an infrared radiometer 2 placed on the ground
Also, it is desirable to translate the traveling rail 19 parallel to the outer wall 1A. Further, the detection signal from the infrared radiometer 2 is input to an image analysis device 20 equipped with a signal processing device, and the signal is further displayed on a display device such as a CRT display device 21 or recorded on a flexible disk or the like. Is becoming

In the apparatus thus constructed, the gondola 7 is set at a predetermined height and horizontal position by adjusting the hanging position and the roof traveling vehicle position. Then, by the hot gas spraying means 8, the outer wall 1
Hot gas is blown onto the surface A to heat it. The visual direction of the infrared radiometer 2 is adjusted so as to coincide with the outer wall 1A portion, and the infrared radiant energy from the outer wall 1A is transferred from the outer wall 1A after the start of heating by the hot gas blowing means 8 or after a lapse of a predetermined time. To detect. This detection signal is subjected to image analysis by the image analysis device 20, and the presence or absence of a defective portion in the outer wall 1A region or its location mainly determined from the current viewing direction signal of the infrared radiometer 2 is determined.

In the present invention, the signal obtained by the infrared radiometer 2 is processed as follows to detect the width and depth of the defect. <Experiment 1> That is, the thickness is 80 mm, the width is 200 mm, and the length is 20 in advance.
A cavity with a width of b50 mm and a depth of h13 mm (from the back to 67 mm) was artificially formed in the central portion of a 0 mm mortar sample plate, and the surface was actually flush with the outer wall 1A of the building. And heat gas (heat flux q = 0.4 W /
cm ² ), forcibly heating for 6 minutes, and during the cooling process at 2 minute intervals from the stop of heating to 14 minutes later, the radiation temperature distribution of the radiant energy from the target sample was investigated on the ground,
The results shown in FIG. 4 were obtained. The result is that, firstly, the temperature difference (distribution) between the defective portion and the normal portion does not appear clearly after 2 minutes from the start of heating, but clearly after 4 minutes, especially after 6 minutes, Second, for example, it was found that the width b '= 105.3 mm between the inflection points in the curve showing the temperature distribution after 6 minutes is about twice the actual width b = 50 mm of the defective portion.

<Experiments 2 and 3> Similarly, only the width b is 20
When the radiation temperature distribution was examined under the same conditions except that mm and 10 mm were used, the results shown in FIGS. 5 and 6 were obtained. The width b'between the inflection points in each case is 72.2
mm, 35 mm, and actual widths b = 20 mm, 3.61 times and 3.5 times 10 mm. In any case, from the correlation of these results,
The change in the width b ′ between the inflection points corresponds to the change in the actual width. Therefore, conversely, by knowing the width b'between the inflection points, the actual width of the defect can be estimated by multiplying the coefficient by 1/2 to 1/4.
Although not described in detail, since the actual width b of the structure is rarely 50 mm and is usually 30 mm or less, the width b ′ between the inflection points has a coefficient (= 1/3). It is practical to multiply by 1/4) to obtain the actual width b.

<Experiment 4> On the other hand, under the same conditions as in Experiment 1, the surface temperature Tc of the defect portion and the surface temperature T of the non-defect portion.
When the temperature difference ΔTc (= Tc−Ts) from s was examined,
The results shown in FIG. 7 were obtained. It was found that this temperature difference reached its maximum 2 minutes after the heating was stopped and then gradually decreased.

<Experiment 5> Knowing such a temperature difference is useful for various judgments. That is, in FIG. 8 and FIG.
6 is a graph of an experimental result showing the correlation between c and the depth h or width b of the defect portion with one of the latter as a parameter. The result is the temperature difference when heating for 6 minutes and then cooling for 1 minute. From this result, it is found that the temperature difference ΔTc becomes smaller as the actual width b becomes smaller and the depth h becomes larger. Therefore, under the condition that the heat flow rate is constant, the depth h of the defect can be estimated by the temperature difference ΔTc in addition to the width. <Experiment 6> Further, under a certain same heating condition, the radiation temperature rises when a defect portion having a certain defect width and various depths is heated, as shown in FIG. In the temperature difference change curve from the start of heating of the temperature difference ΔTc,
It is better to judge the depth of the defect based on the time difference from the start of heating to the time when the rate of rise in temperature difference stabilizes, for example, the time from the intersection of the tangent line passing through the point where the rate of change is constant and the time axis. It was found to be suitable.

On the other hand, it is desirable to forcibly heat the surface of the structure when judging defects. When detecting internal defects on a surface heated by sunlight, as described above, the temperature difference between the defective part and the normal part is prominent due to the small heat flux. It takes time. In addition, it is easily affected by changes in the flow of outside air, changes in the temperature inside the room, and thermal conduction interference inside the outside wall due to convection, and the effects of reflected light from the outside wall of the building on the opposite side. It is difficult to detect underground structures such as tunnels that do not receive sunlight.

Therefore, it is desirable to forcibly heat the surface to be measured. Furthermore, by forcibly heating, it is possible to detect the temperature change in the heating process and / or the cooling process after the heating is stopped, and to detect the presence or absence of a defect at an optimum time. Also, a halogen lamp or the like can be used as the heating means, but this halogen lamp is not always sufficient in heat flux as well as receiving interference of reflected light. It is suitable to use a hot gas blowing machine because it does not suffer interference.

The forced heating temperature is preferably 40 to 100 ° C. In addition, since the heating rate also becomes a problem, the amount of heat ejected from the hot gas blowing means is adjusted in relation to the material of the structure and the structure, the surface texture such as unevenness, the presence or absence of a heat insulating material in the back or the material thereof. The amount of heat input to the surface per unit time can be adjusted by adjusting the distance to the target surface by, for example, the forward / backward movement mechanism described above. Forced heating can be performed continuously or intermittently.

<Experiment 7> On the other hand, if the conditions are met, it is possible to sufficiently perform measurement by natural heating by sunlight. 11
Is the surface temperature Tc of the defect portion from 8:00 am to 8:00 pm for the artificial defect with depth h = 13 mm and width b = 53 mm,
Surface temperature Ts of defect-free portion and temperature difference ΔT between them
It is the result of examining the change with time of c (= Tc-Ts). According to this result, it is understood that there is a sufficient temperature difference not only during the daytime but also in the evening as the cooling process, and the temperature difference is stable in the evening.

<Experiment 8> At this time, the entire defect can be known by image-processing the signal from the radiation thermometer and examining the temporal changes in the radiation temperature distribution in the width direction and the length direction. Figures 12 and 13 show panels with artificial defects with depth h = 20 mm, width b = 40 mm, and length = 40 mm, installed on the third floor of a building and radiated in the width and length directions. It shows the results of examining the change over time in the temperature distribution. According to this result, it can be understood that the defects can be clearly judged from 1:00 to 2:00 pm and 8:00 pm. In particular, the temperature difference between the defect portion and the non-defect portion in the radiation temperature distribution clearly appears not only in the temperature rising process of the outer wall but also in the cooling process. It was also found that the length or area of the defect can be determined by examining the radiation temperature distribution not only in the width b of the defect but also in the length direction. <Experiment 9> The relationship between the temperature difference ΔTc, the width b, and the depth h has the relationship shown in FIG. It has been found that can be sufficiently estimated.

If the heating is not forced, it can be corrected by the heat flux of sunlight, the air temperature, the flow velocity of the air flow, the wall temperature directly measured by a thermometer other than the radiation thermometer, and the like. Further, in any case, it is preferable to correct the surface material, unevenness, reflectance and the like.

The present invention can be used not only for the diagnosis of the outer wall of the building described above, but also for the diagnosis of roofs, chimneys, dams, dikes, tunnels, bridges, roads (overpasses), subways, and the like. Further, cracks, peeling, lifting, and the like can be detected as the property of the defect.

[0029]

As described above, according to the present invention, not only the presence / absence of a defect but also the width and depth of the defect can be judged one by one and the reliability can be enhanced. ..

[Brief description of drawings]

FIG. 1 is a schematic diagram of defect detection equipment.

FIG. 2 is a vertical sectional view of the gondola.

FIG. 3 is a schematic diagram of an installation example of a hot gas blowing device.

FIG. 4 is a graph of experimental results of the present invention.

FIG. 5 is a graph of experimental results of the present invention.

FIG. 6 is a graph of experimental results of the present invention.

FIG. 7 is a graph of experimental results of the present invention.

FIG. 8 is a graph of experimental results of the present invention.

FIG. 9 is a graph of experimental results of the present invention.

FIG. 10 is a graph of experimental results of the present invention.

FIG. 11 is a graph of experimental results of the present invention.

FIG. 12 is a graph of experimental results of the present invention.

FIG. 13 is a graph of experimental results of the present invention.

FIG. 14 is a graph of experimental results of the present invention.

Claims (5)

[Claims] 1. A method for detecting defects in a structure by detecting radiant energy from the surface of the structure with an infrared radiometer, based on a temperature distribution on a target surface obtained from a radiation temperature signal from the infrared radiometer. A method for detecting a surface or internal defect of a structure, comprising estimating an actual size of the internal defect. 2. The surface of the structure according to claim 1, wherein the width between the inflection points in the curve showing the temperature distribution is multiplied by a coefficient (= 1/2 to 1/4) to obtain the actual width of the defective portion. Or how to detect internal defects. 3. The depth of the defect is estimated based on the degree of change in the temperature difference ΔTc between the surface temperature Tc of the defect portion and the surface temperature Ts of the defect-free portion shown in the temperature distribution in the previous period.
A method for detecting surface or internal defects of the structure described. 4. A method of detecting a defect of a structure by detecting radiant energy from the surface of the structure by an infrared radiometer, wherein an object surface is artificially heated, and a defect portion in the heating or cooling process is detected. A method of detecting a surface or internal defect of a structure, which comprises estimating a depth of a defect based on a degree of change of a temperature difference ΔTc between a surface temperature Tc and a surface temperature Ts of a defect-free portion. 5. The depth of the defect is estimated on the basis of the time difference from the heating start time to the time when the temperature difference increase rate is stabilized in the temperature difference change curve from the heating start of the temperature difference ΔTc. A method for detecting surface or internal defects in structures.