Corrosion depth estimation device and corrosion depth estimation method

Abstract

To enable easy and accurate estimation of corrosion depth.SOLUTION: A corrosion depth estimation device is provided, comprising an extraction unit for extracting a corroded area from an image of a surface of a metal structure, a diameter computation unit for computing a diameter of the maximum inscribed circle of the corroded area, and a depth computation unit for computing depth of the corroded area based on the diameter of the maximum inscribed circle.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a corrosion depth estimation device and a corrosion depth estimation method for estimating the depth of corrosion on a metal surface.

Background Art

[0002] Conventionally, in the evaluation of the depth of corrosion (corrosion depth) occurring in an aircraft structure, the corroded part was actually removed and its depth was measured. Therefore, a lot of man-hours were required for this actual measurement work.

[0003] In fields other than aircraft structures, there are technologies for detecting abnormal parts of metal materials using ultrasonic waves, ultraviolet rays, X-rays, photothermal energy, etc. However, these technologies are applied exclusively to those with standardized shapes, such as the measurement of the remaining wall thickness of iron pipes and the detection of damage to aluminum conductor steel-reinforced (ACSR) wires. Therefore, it is difficult to apply these technologies to the evaluation of corrosion occurring in aluminum alloys frequently used in aircraft, or to the evaluation of corrosion in various component shapes and complex locations.

[0004] In this regard, for example, in the technologies described in Patent Documents 1 and 2, based on the perimeter or area of the corroded part calculated from the image data, the corrosion depth or the degree of damage is estimated without actually measuring the corroded part.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] It would be useful to be able to estimate the corrosion depth with higher accuracy. The present invention has been made in view of the above circumstances, and an object thereof is to estimate the corrosion depth simply and with high accuracy.

Means for Solving the Problems

[0007] To achieve the above object, an embodiment of the present invention includes an extraction unit that extracts a corrosion region from an image of the surface of a metal structure, a diameter calculation unit that obtains the diameter of the largest inscribed circle of the corrosion region, a depth calculation unit that calculates the depth of the corrosion region based on the diameter of the largest inscribed circle, and is provided with.

Advantages of the Invention

[0008] According to the present invention, a corrosion region is extracted from an image of the surface of a metal structure, and the diameter of the largest inscribed circle thereof is obtained. Then, the depth of the corrosion region is calculated based on the diameter of the largest inscribed circle. Thereby, the corrosion depth can be estimated simply and with high accuracy.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6A

Figure 6B

Best Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] [Configuration of Corrosion Depth Estimation Device] FIG. 1 is a block diagram showing a schematic configuration of a corrosion depth estimation device 1 according to the present embodiment. As shown in this figure, the corrosion depth estimation device 1 is a computer that evaluates the damage level due to corrosion of an aircraft structure. Specifically, the corrosion depth estimation device 1 includes an operation unit 12, a display unit 13, a storage unit 16, and a control unit 17.

[0012] The operation unit 12 is an operation means for the user to perform various operations for operating the corrosion depth estimation device 1, and includes, for example, a pointing device such as a mouse and a keyboard. The display unit 13 is composed of, for example, a liquid crystal display, an organic EL display, or other displays, and displays various information based on a display signal from the control unit 17. Note that the display unit 13 may be a touch panel that also serves as a part of the operation unit 12, or may perform voice output.

[0013] The storage unit 16 is a memory composed of a RAM (Random Access Memory), a ROM (Read Only Memory), etc. The storage unit 16 stores various programs and data, and also functions as a work area for the control unit 17. In the storage unit 16, a program for executing the corrosion depth estimation process described later is stored in advance, and image data 21 obtained by photographing the corroded part is stored. In addition, depth conversion data 22 for obtaining the corrosion depth P from the image data 21 is stored in advance in the storage unit 16 (see FIG. 5). Details of the depth conversion data 22 will be described later.

[0014] The control unit 17 is composed of, for example, a CPU (Central Processing Unit) or the like, and controls the operations of each part of the corrosion depth estimation device 1. Specifically, the control unit 17 operates each part of the corrosion depth estimation device 1 based on the operation content of the operation unit 12 or the like, develops a program stored in advance in the storage unit 16, and executes various processes in cooperation with the developed program.

[0015] [Corrosion Depth Estimation Process] Subsequently, a corrosion depth estimation process for estimating the corrosion depth of an aircraft structure will be described. FIG. 2 is a flowchart showing the procedure of the corrosion depth estimation process, FIGS. 3A and 3B are examples of image data of the corroded part. FIG. 4 is a diagram for explaining the corrosion depth estimation process, and FIG. 5 is a graph showing an example of the depth conversion data 22. In the corrosion depth estimation process, the corrosion depth (depth of corrosion) is estimated based on an image of the corroded part. Then, based on the estimated corrosion depth, the damage level (degree of damage) of the structure is determined. The corrosion depth estimation process is executed by the control unit 17 of the corrosion depth estimation device 1 reading and developing a predetermined program from the storage unit 16.

[0016] As shown in FIG. 2, first, preprocessing of the corroded part to be evaluated is performed (step S1). Here, an operator exposes a metal surface of a predetermined range including a black corroded part (corroded area) by, for example, peeling off the surface coating of the corroded part to be evaluated with sandpaper. The structure to be evaluated is not particularly limited, but in this embodiment, it is an aircraft structure made of an aluminum alloy.

[0017] Next, an image of the corroded part is acquired (step S2). Here, the surface of the structure including the corroded part is photographed with a camera at a required resolution, and the image is acquired. As a result, for example, as shown in FIG. 3A, two-dimensional image data 21 including the corroded part 30 is obtained. The acquired image data 21 is stored in the storage unit 16. Note that the image data 21 is not particularly limited in its data format or the like, as long as it contains information that can extract the corrosion area in step S3 described below.

[0018] Next, the control unit 17 of the corrosion depth estimation device 1 extracts the corrosion area 31 from the corrosion part 30 based on the image data 21 of the corrosion part 30 (step S3). The corrosion area 31 refers to the part of the corrosion part 30 where the metal corrosion has progressed to a certain extent or more. Here, for example, based on the color information of the image data 21, the part of the corrosion part 30 with a color density (close to black) equal to or greater than a predetermined threshold is set as the corrosion area 31. As a result, as shown in, for example, FIG. 3B, a plurality of corrosion areas 31 are extracted from the corrosion part 30. Note that the image information used for extracting the corrosion area 31 is not particularly limited, and information such as changes in luminance or contrast may be used, for example. Also, at least one corrosion area 31 may be extracted in this step.

[0019] Next, the control unit 17 obtains the maximum inscribed circle diameter for each of the corrosion areas 31 extracted in step S3 (step S4). Here, as shown in, for example, FIG. 4, the control unit 17 sets the maximum inscribed circle S included in the corrosion area 31 based on the shape of the corrosion area 31 in the image data 21, and obtains the maximum inscribed circle diameter D as its diameter. Note that the calculation of the maximum inscribed circle diameter D does not have to be performed for all the corrosion areas 31, and only the corrosion areas 31 with a size equal to or greater than a predetermined size may be targeted, for example.

[0020] Next, the control unit 17 converts the maximum inscribed circle diameter D into the corrosion depth P using the depth conversion data 22 (step S5). Here, the control unit 17 calculates the corrosion depth P by inputting the maximum inscribed circle diameter D into the depth conversion data 22 read from the storage unit 16. The depth conversion data 22 is, for example, correlation data representing the correlation between the maximum inscribed circle diameter D and the corrosion depth P, and is preset based on actual measurement, for example. In the example of FIG. 5, the plots in the figure are the measured values of the maximum inscribed circle diameter D and the corrosion depth P, and the solid line (thick line) is the linear approximation formula of these and is the depth conversion data 22 of the present embodiment. Note that the data format of the depth conversion data 22 is not particularly limited as long as it can convert the maximum inscribed circle diameter D into the corrosion depth P, and it may be, for example, a conversion table or the like.

[0021] Next, the control unit 17 determines the damage level (degree of damage) of the structure due to the corrosion based on the corrosion depth P obtained in step S5 (step S6). Specifically, if the maximum corrosion depth P obtained in step S5 is less than a predetermined value A, the control unit 17 determines that repair is not required. If it is greater than or equal to the value A and less than a value B (> the value A), it determines that repair is necessary (repairable). If it is greater than or equal to the value B, it determines that replacement is necessary (non-repairable). However, this determination method is not particularly limited. For example, the distribution, size of the corrosion depth P in the corrosion part 30, the part in the structure, etc. may be taken into consideration.

[0022] [Technical effects of the present embodiment] As described above, according to the present embodiment, the corrosion region 31 is extracted from the image data 21 of the corrosion part 30, and the maximum inscribed circle diameter D thereof is obtained. Then, the corrosion depth P is calculated based on the maximum inscribed circle diameter D. Thereby, it is possible to simply estimate the corrosion depth P only by image analysis without the need to actually measure the corrosion part 30 (corrosion region 31). As a result, it is sufficient to obtain the image data 21, so it can be suitably applied to the evaluation of parts with complex shapes or parts deep inside the structure where actual measurement work is difficult. Further, as a feature amount of the image data 21 for obtaining the corrosion depth P, the maximum inscribed circle diameter D is used instead of the perimeter or area of the corrosion region 31. Thereby, the corrosion depth P can be obtained with high accuracy.

[0023] That is, the inventors have found by actual measurement that the maximum inscribed circle diameter D of the corrosion region 31 has a higher degree of correlation with the corrosion depth P than the perimeter or area of the corrosion region 31. Here, an actual measurement example of the perimeter of the corrosion region 31 and the corrosion depth is shown in FIG. 6A, and an actual measurement example of the area of the corrosion region 31 and the corrosion depth P is shown in FIG. 6B. As shown in these figures, no good correlation was found between the perimeter and area of the corrosion region 31 and the corrosion depth P. On the other hand, as shown in FIG. 5, a good correlation was found between the maximum inscribed circle diameter D of the corrosion region 31 and the corrosion depth P. This is considered to be because the corrosion on the metal surface and the corrosion in the depth direction progress at the same erosion rate. That is, the corrosion region with the maximum inscribed circle diameter is considered to be the deepest part of the corrosion in the corrosion occurrence range. Therefore, by using the maximum inscribed circle diameter D of the corrosion region 31, the corrosion depth P can be estimated with higher accuracy than using the perimeter or area.

[0024] Further, according to the present embodiment, based on the obtained corrosion depth P, the damage level (degree of damage) of the aircraft structure (metal structure) is determined. Thereby, for example, when it is determined that the corrosion depth P is impossible to repair, the corrosion removal work can be immediately stopped, and the man-hours for unnecessary corrosion removal work, inspection, and measurement can be reduced. As a result, it is possible to shorten the delivery time of the regular maintenance machine, increase the number of maintenance machines, improve the aircraft operation rate, and reduce the repair cost.

[0025] [Others] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in the above embodiment, an aluminum aircraft structure was cited as the structure (metal structure) to be evaluated. However, the material of the metal structure according to the present invention is not limited to aluminum, and its application is not limited to aircraft applications. However, acquisition of the depth conversion data 22 becomes necessary according to the material. Also, the method of image analysis (for example, the method of extracting the corrosion region 31, etc.) may need to be changed according to the corrosion mechanism, etc. for the material.

[0026] Also, in the analysis of the image data 21, machine learning or other methods may be used to improve the accuracy. In addition, the details shown in the above embodiment can be appropriately changed without departing from the gist of the invention.

Explanation of Reference Numerals

[0027] 1 Corrosion depth estimation device 16 Storage unit 17 Control unit (extraction unit, diameter calculation unit, depth calculation unit) 21 Image data 22 Depth conversion data (correlation data) 30 Corroded part 31 Corrosion region S Maximum inscribed circle D Maximum inscribed circle diameter (diameter of the maximum inscribed circle) P Corrosion depth (depth of the corrosion region)

Claims

1. An extraction unit that extracts a corrosion region from an image of the surface of a metal structure, A diameter calculation unit that obtains the diameter of the maximum inscribed circle of the corrosion region, A depth calculation unit that calculates the depth of the corrosion region based on the diameter of the maximum inscribed circle, A corrosion depth estimation device comprising the above.

2. Comprising a storage unit that stores in advance correlation data representing the correlation between the diameter of the maximum inscribed circle and the depth of the corrosion region, The depth calculation unit calculates the depth of the corrosion region from the diameter of the maximum inscribed circle based on the correlation data stored in the storage unit. The corrosion depth estimation device according to Claim 1.

3. Comprising a determination unit that determines the degree of damage of the metal structure based on the depth of the corrosion region. The corrosion depth estimation device according to Claim 1.

4. The metal structure is made of aluminum. The corrosion depth estimation device according to Claim 1.

5. An acquisition step of acquiring an image of the surface of a metal structure, An extraction step of extracting a corrosion region from the image acquired in the acquisition step, A diameter calculation step of obtaining the diameter of the maximum inscribed circle of the corrosion region, A depth calculation step of calculating the depth of the corrosion region based on the diameter of the maximum inscribed circle, A corrosion depth estimation method including the above.

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