High-strength bolt inspection system and high-strength bolt inspection method

Abstract

To provide a high-strength bolt inspection system and a high-strength bolt inspection method that can objectively determine quality of tightening even for a high-strength bolt in an environment where it is difficult to obtain a clear image, which is a problem with conventional technology to be solved.SOLUTION: A high-strength bolt inspection system, which inspects a high-strength bolt that is tightened with a line mark attached in advance, includes side line generation means, included angle calculation means, and quality determination means. The side line generation means extracts a center of the bolt by performing image recognition processing on an inspection image, and also generates a nut side line, a washer side line, and a base material side line. Furthermore, the quality determination means determines, on the basis of the included angle calculated by the included angle calculation means, whether or not the high-strength bolt is tightened.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The invention of the present application relates to a technique for tightening bolts, and more specifically, to a high-tensile bolt inspection system and a high-tensile bolt inspection method capable of quantitatively determining the degree of tightening of high-tensile bolts (high-tension bolts) by performing image recognition processing.

Background Art

[0002] When joining steel members, bolts may be used. For example, when constructing a bridge with steel main girders, a plurality of steel main girders are arranged in the bridge axis direction, and adjacent steel main girders before and after are connected by sewing abutting plates that abut on both sides with bolts. And in such a case, since a considerable tightening force is required, high-tensile bolts are adopted.

[0003] Normally, when tightening high-tensile bolts, confirmation work is carried out to check whether they are properly tightened. The confirmation work has a direct method of actually measuring the tightening force with a torque wrench or the like, but it is not realistic in the case where a large number of high-tensile bolts are targeted. Therefore, the Japan Institute of Architects has defined the confirmation work for visually checking the tightening of high-tensile bolts in the "Japanese Architectural Standard Specification (JASS)". For example, in the case of a Torx-shaped high-tensile bolt, the tightening work is carried out in three steps: primary tightening, marking, and final tightening during the tightening work, and visual confirmation is carried out after the tightening work. Also, the tightening order of high-tensile bolts is carried out in a complex order from the center to the end of the abutting plate, so as to stretch the wrinkles of the so-called abutting plate. Since it is not an operation of tightening in order from top to bottom, there is a risk of omission of tightening.

[0004] Figure 8 is a schematic plan view showing the nut status of a torque-shear type high-strength bolt, and Figure 9 is a schematic perspective view showing the nut status of a torque-shear type high-strength bolt. In each figure, (a) shows the marked state before final tightening, (b) shows the state after normal final tightening, (c) shows the state where tightening was not performed correctly, and (d) shows the state where the bolt rotated together during final tightening. When performing final tightening, as shown in Figures 8(a) and 9(a), linear (line-shaped) marks (hereinafter referred to as "line marks MK") are made in advance on the bolt BT, nut NT, washer WS, and base material BM (e.g., splice plate). When a torque-shear type high-strength bolt is properly tightened, as shown in Figures 8(b) and 9(b), the line marks on the bolt BT (hereinafter referred to as "bolt line MK1"), the washer WS (hereinafter referred to as "washer line MK3"), and the base material BM (hereinafter referred to as "base material line MK4") remain in their original positions as lines, but the line mark on the nut NT (hereinafter referred to as "nut line MK2") is rotated and moved to some extent.

[0005] In contrast, a torque-shear type high-strength bolt that was deemed to have been left untightened despite being fully tightened will have the bolt line MK1, nut line MK2, washer line MK3, and base material line MK4 remaining in their original positions and forming a line, as shown in Figures 8(c) and 9(c). Similarly, a torque-shear type high-strength bolt that was deemed to have been undertightened will generally be in a state similar to that shown in Figures 8(c) and 9(c). A torque-shear type high-strength bolt that was allowed to rotate together during the final tightening will have the bolt line MK1 and base material line MK4 remaining in their original positions, while the nut line MK2 and washer line MK3 have rotated and moved, as shown in Figures 8(d) and 9(d).

[0006] In this way, after the final tightening is performed, the quality of the tightening can be determined by visually inspecting the line mark MK. However, with this type of visual inspection, discrepancies may occur depending on the inspector. For example, a high-strength bolt that is on the borderline between normal and rotational might be judged as "normal" by one inspector and "rotating" by another. Also, when bridge girders are connected with splice plates, a large number of high-strength bolts are usually used, which may lead to oversights or misjudgments by the inspector.

[0007] Therefore, efforts have been made to objectively determine the quality of high-strength bolt tightening, rather than relying on the subjective judgment of the inspector's visual inspection. For example, Patent Document 1 proposes a technique for photographing high-strength bolts after tightening, determining the angle of the line mark MK contained in the image, and determining the quality of the high-strength bolt tightening based on that angle. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-009932 [Overview of the project] [Problems that the invention aims to solve]

[0009] The technology disclosed in Patent Document 1 is a technique for determining the tightening state of a high-strength bolt according to the angle difference between the nut line MK2 and the base material line MK4, and the angle difference between the washer line MK3 and the base material line MK4. Therefore, in the technology of Patent Document 1, the nut line MK2, the washer line MK3, and the base material line MK4 must be extracted as "lines" from the image.

[0010] However, images of high-strength bolts are prone to shadows and can appear dark overall. In particular, high-strength bolts used in splice plates of bridge girders are difficult to obtain clear images of due to shadows cast by the bridge girders and the bridge girders blocking sunlight. In this case, conventional image recognition technology finds it extremely difficult to properly recognize and extract the entire line. Specifically, the technology in Patent Document 1 cannot extract the nut line MK2, washer line MK3, and base material line MK4 as lines from the image when a clear image is difficult to obtain. In addition, the washer line MK3 is very short, resulting in a low recognition rate as a line, and as a result, it is not possible to determine the tightening state of the high-strength bolt.

[0011] The object of the present invention is to solve the problems of the prior art, namely, to provide a high-strength bolt inspection system and a high-strength bolt inspection method that can objectively determine the quality of tightening even for high-strength bolts in environments where it is difficult to obtain clear images. [Means for solving the problem]

[0012] The present invention focuses on generating a nut line connecting the endpoint of the nut line to the center of the bolt, a washer line connecting the endpoint of the washer line to the center of the bolt, and a base material line connecting the endpoint of the base material line to the center of the bolt by performing image recognition processing, and determining the quality of high-strength bolt tightening based on the angle formed by the nut line, washer line, and base material line. This invention is based on an unprecedented idea.

[0013] The high-strength bolt inspection system of the present invention is a system for inspecting high-strength bolts that have been tightened after line marks have been made on the nut, washer, and base material in advance, and comprises a side line generation means, an angle calculation means, and a quality determination means. Of these, the side line generation means is a means for extracting the center of the bolt and generating a nut side line, a washer side line, and a base material side line by performing image recognition processing on the inspection image (an image in which a tightened high-strength bolt has been acquired). The angle calculation means is a means for calculating the angle formed by two side lines selected from the nut side line, the washer side line, and the base material side line, and the quality determination means is a means for determining the quality of the tightening of the high-strength bolt based on the angle calculated by the angle calculation means.

[0014] The high-strength bolt inspection system of the present invention can also use a machine learning-trained model to recognize bolts, nuts, washers, and base materials from inspection images, and to extract the center of the bolt, the endpoints of the nut line, the endpoints of the washer line, and the endpoints of the base material line.

[0015] The high-strength bolt inspection system of the present invention can also be configured to determine a bolt as untightened when the angle between the base material side line and the nut side line falls below a predetermined unworked threshold, and the angle between the base material side line and the washer side line also falls below the unworked threshold.

[0016] The high-strength bolt inspection system of the present invention can also be configured to determine a bolt as a high-strength bolt that rotates together when the angle between the base material side line and the washer side line exceeds a predetermined defect threshold.

[0017] The high-strength bolt inspection system of the present invention may further include an illumination means for illuminating the shooting position of the image acquisition means using multispectral light.

[0018] The high-strength bolt inspection method of the present invention is a method for inspecting high-strength bolts using the high-strength bolt inspection system of the present invention, and comprises a bolt tightening step, an image acquisition step, a side line generation step, a narrow angle calculation step, and a quality determination step. Of these, the bolt tightening step involves marking the nut, washer, and base material with line marks and tightening the nut, the image acquisition step involves acquiring an inspection image of the tightened high-strength bolt with line marks by an image acquisition means, the side line generation step involves generating nut side lines, washer side lines, and base material side lines by a side line generation means, the narrow angle calculation step involves calculating the narrow angle formed by two side lines selected from the nut side line, washer side line, and base material side line by a narrow angle calculation means, and the quality determination step involves determining whether the tightening of the high-strength bolt is good or bad by a quality determination means. [Effects of the Invention]

[0019] The high-strength bolt inspection system and high-strength bolt inspection method of the present invention have the following advantages. (1) Since the quality of tightening of high-strength bolts is determined based on the angle between the nut side line, washer side line, and base material side line, it is possible to make a quantitative judgment rather than a qualitative judgment based on the inspector's visual inspection. (2) Since it is not necessary to recognize the entire line from the image, and it is sufficient to recognize the endpoints that make up the nut line, the washer line, and the base material line, the quality of the tightening can be objectively determined even for high-strength bolts in environments where it is difficult to obtain clear images. (3) Even when inspecting numerous high-strength bolts installed on the splice plates of bridge girders, it is possible to suppress the occurrence of inspection omissions and misjudgments. (4) Even when inspecting a large number of high-strength bolts, pass / fail judgments can be made simply by taking pictures with a camera, and inspection result reports can be printed, thus reducing manpower and labor. (5) Even inspectors without extensive experience or knowledge can perform inspections of the same or higher quality as veteran inspectors, which will also help alleviate the shortage of personnel. [Brief explanation of the drawing]

[0020] [Figure 1] Side view schematically showing a front bridge girder and a rear bridge girder connected by an attachment plate. [Figure 2] (a) Plan view schematically showing line marks marked on high-strength bolts before final tightening; (b) plan view schematically showing bolt lines, nut lines, washer lines, and base material lines after final tightening. [Figure 3] Block diagram showing the main configuration of the high-strength bolt inspection system of the present invention. [Figure 4] (a) Model diagram schematically showing nut side lines, washer side lines, and base material side lines generated by side line generation means; (b) model diagram schematically showing a washer side line generated based on a washer line with a part missing. [Figure 5] Model diagram schematically showing the nut condition, nut clamping angle, and washer clamping angle of HTB. (a) Model diagram schematically showing the nut condition of a high-strength bolt in a state where tightening is forgotten, its nut clamping angle, and washer clamping angle; (b) model diagram schematically showing the nut condition of a high-strength bolt in a state of co-rotation and its washer clamping angle. [Figure 6] Flow chart showing a series of processes until determining the adequacy of tightening of high-strength bolts using the high-strength bolt inspection system of the present invention. [Figure 7] Flow chart showing the flow of the main steps of the high-strength bolt inspection method of the present invention. [Figure 8] (a) Plan view schematically showing the nut condition of a bolt in a marked state before final tightening; (b) plan view schematically showing the nut condition of a bolt in a state of being normally tightened; (c) plan view schematically showing the nut condition of a bolt in a state where tightening is forgotten during final tightening; (d) plan view schematically showing the nut condition of a bolt in a state of co-rotation during final tightening. [Figure 9](a) is a schematic perspective view showing the condition of the nut on a marked bolt before final tightening, (b) is a schematic perspective view showing the condition of the nut on a bolt that has been properly final tightened, (c) is a schematic perspective view showing the condition of the nut on a bolt that was left loose during final tightening, and (d) is a schematic perspective view showing the condition of the nut on a bolt that rotated together during final tightening. [Modes for carrying out the invention]

[0021] Examples of the high-strength bolt inspection system and high-strength bolt inspection method of the present invention will be explained with reference to the figures. The present invention can be used in various places where steel materials are connected by high-strength bolts, such as the connection points between steel frames that make up high-rise buildings, but for convenience, the example of high-strength bolts connecting bridge girders with splice plates will be explained here.

[0022] 1.Overview Figure 1 is a schematic side view showing the front girder BGa and the rear girder BGb connected by splice plates SPB. As shown in this figure, splice plates SPB are sometimes used to connect steel bridge girders. More specifically, the front girder BGa and the rear girder BGb are butted together in the direction of the bridge axis, and with splice plates SPB placed against both webs BGw, the splice plates SPB and webs BGw are fastened together with multiple (64 in the figure) high-strength bolts HTB to connect them, thereby connecting the front girder BGa and the rear girder BGb. In this figure, only the webs BGw are connected using splice plates SPB, but of course, flanges BGf can also be connected using splice plates SPB.

[0023] As shown in Figure 1, when connecting steel bridge girders with splice plates SPB, high-strength bolts HTB, such as torque-shear type high-strength bolts and high-strength hexagonal bolts, are used. As previously mentioned, when tightening high-strength bolts HTB, a check is performed to ensure that they are properly tightened, and therefore, line marks MK are marked on the nuts of the high-strength bolts HTB as shown in Figure 2. Figure 2 is a schematic plan view showing the nut status of a high-strength bolt HTB (for example, a torque-shear type high-strength bolt), where (a) is a schematic plan view showing the line marks MK marked before final tightening, and (b) is a schematic plan view showing the bolt line MK1 (line mark on bolt BT), nut line MK2 (line mark on nut NT), washer line MK3 (line mark on washer WS), and base material line MK4 (line mark on base material BM) after final tightening. Note that Figure 2(b) shows the state where the bolts rotate together during final tightening.

[0024] As shown in Figure 2, the line mark MK before final tightening is marked from the center of the bolt BT of the high-strength bolt HTB toward the base material BM (splice plate SPB in Figure 1), resulting in bolt line MK1 on bolt BT, nut line MK2 on nut NT, washer line MK3 on washer WS, and base material line MK4 on base material BM. In the present invention, the quality of the tightening is determined based on an image of the nut condition of the high-strength bolt HTB taken after final tightening (hereinafter referred to as the "inspection image"), that is, based on the various lines included in the inspection image.

[0025] 2. High-strength bolt inspection system Next, the high-strength bolt inspection system of the present invention will be described. The high-strength bolt inspection method of the present invention is a method for determining the quality of tightening of high-strength bolts using the high-strength bolt inspection system of the present invention. Therefore, the high-strength bolt inspection system of the present invention will be described first, and then the high-strength bolt inspection method of the present invention will be described.

[0026] Figure 3 is a block diagram showing the main components of the high-strength bolt inspection system 100 of the present invention. As shown in this figure, the high-strength bolt inspection system 100 of the present invention is configured to include a side line generation means 101, a narrow angle calculation means 102, and a pass / fail determination means 103, and may also be configured to include an illumination means 104, an image acquisition means 105, a line extraction means 106, a model generation means 107, an output means 108, an inspection image storage means 109, an inspection result storage means 110, a trained model storage means 111, and the like.

[0027] Of the main elements constituting the high-strength bolt inspection system 100, the side line generation means 101, the narrow angle calculation means 102, the pass / fail determination means 103, the line extraction means 106, and the model generation means 107 can be manufactured as dedicated components, or a general-purpose computer device can be used. This computer device is equipped with a processor such as a CPU, memory such as ROM or RAM, input means such as a mouse or keyboard, and a display, and can consist of personal computers (PCs), servers, tablet PCs such as iPads (registered trademark), and mobile terminals including smartphones. When using a computer device equipped with a display, it is preferable to use that display as the output means 108.

[0028] The inspection image storage means 109, the inspection result storage means 110, and the trained model storage means 111 can utilize the storage device of a general-purpose computer or be built on a database server. When built on a database server, it can be located on a local network (LAN) or on a cloud server that stores data via the internet.

[0029] The following describes in detail each of the main elements constituting the high-strength bolt inspection system 100 of the present invention.

[0030] (Method for acquiring images) The image acquisition means 105 can capture the nut condition of high-strength bolts HTB using still images, videos, or continuous still images, and can utilize digital cameras, digital video cameras, smartphones, tablet PCs, etc. The still images, or each image constituting a video or continuous still image (i.e., inspection images) acquired by the image acquisition means 105 are stored in the inspection image storage means 109 (Figure 3). The shooting range of the inspection image can be set to capture the condition of only one nut, to capture the condition of multiple nuts (for example, eight nuts), or, as shown in Figure 1, to capture the condition of all nuts at the connection point (all 64 nuts in total in the figure). Both videos and continuous still images consist of images (frames) acquired at extremely short intervals, but since videos generally consist of 24 to 60 images per second (i.e., 24 to 60 fps), here, continuous still images are specifically defined as images consisting of less than 24 fps or more than 60 fps.

[0031] When the image acquisition means 105 photographs the nut condition of the high-strength bolt HTB, it is preferable to illuminate the shooting position with the illumination means 104. As will be described later, various lines such as the bolt line MK1 and the nut line MK2 are automatically extracted from the inspection image acquired by the image acquisition means 105. At this time, if the inspection image is acquired with illumination by the illumination means 104, it becomes easier to extract the various lines. Furthermore, the inventors have found that by using multispectral light, which is multiple invisible light rays invisible to the human eye such as infrared light, it is possible to take images without reflection from the various lines, and by using such inspection images, the various lines can be extracted with higher accuracy. For this reason, when acquiring an inspection image with the image acquisition means 105, it is desirable to illuminate the shooting position with multispectral light using the illumination means 104.

[0032] (Line extraction means) The line extraction means 106 is a means for extracting the center point of the bolt BT and the bolt line MK1, nut line MK2, washer line MK3, and base material line MK4 from the inspection image. More specifically, after recognizing each component (bolt BT, nut NT, washer WS) and the base material BM that constitute the high-strength bolt HTB, the center point of the bolt BT is extracted, and the line mark MK attached to the bolt BT is extracted as the bolt line MK1, the line mark MK attached to the nut NT is extracted as the nut line MK2, the line mark MK attached to the washer WS is extracted as the washer line MK3, and the line mark MK attached to the base material BM is extracted as the base material line MK4.

[0033] Various conventional image recognition technologies can be used to extract various lines. For example, various lines can be automatically extracted using machine learning technology. When various lines are automatically extracted using machine learning, the various lines are automatically extracted by inputting the inspection image into the "trained model" generated by the model generation means 107. This trained model is generated by machine learning a large number of "training data" such as images showing bolts BT, nuts NT, washers WS, base material BM, as well as images showing the center point of bolt BT, line marks MK, bolt line MK1, nut line MK2, washer line MK3, and base material line MK4. The machine learning used to generate the trained model can employ deep learning such as CNN (Convolutional Neural Network), as well as various conventional machine learning technologies. This allows the trained model to be used differently depending on the type and color of the marker; for example, a trained model specifically for oil-based pens if the marker is an oil-based pen, and a trained model specifically for chalk if the marker is chalk. Furthermore, the trained model generated by the model generation means 107 is stored in the trained model storage means 111 (Figure 3).

[0034] (Means for generating side lines) The side line generation means 101 is a means for generating various side lines based on the center point of the bolt BT extracted by the line extraction means 106 and various lines. More specifically, as shown in Figure 4(a), it generates a nut side line (dashed line in the figure) connecting the center point CP of the bolt BT and the endpoint of the nut line MK2, a washer side line (dashed line in the figure) connecting the center point CP and the endpoint of the washer line MK3, and a base material side line (dashed line in the figure) connecting the center point CP and the endpoint of the base material line MK4. In this figure, various side lines are generated by connecting the endpoint (white dot in the figure) located on the center point CP side (so to speak, the starting point side) of various lines with the center point CP. However, it is not limited to this, and various side lines can also be generated by connecting the endpoint located on the opposite side of the center point CP (so to speak, the ending point side) with the center point CP. Furthermore, in the case of torque-shear type high-strength bolts, there is a pin tail (a projection at the tip of the bolt that secures the introduced axial force by fracture), and since the bolt line BK1 cannot be directly marked from the center of the bolt BT, it is difficult to detect the center point CP. However, by using a trained model generated by machine learning, the center of the circle on the bottom surface of the bolt tip can be automatically detected and recognized as the center point CP.

[0035] Incidentally, depending on the clarity and degree of shading of the inspection image, it is possible that the line extraction means 106 may not extract the entire length of each line. For example, in Figure 4(b), the washer line MK3 is extracted by the line extraction means 106, but the entire washer line MK3 is not extracted; a part of it is missing, meaning it is only partially extracted. However, since the present invention generates various side lines by connecting the center point CP of the bolt BT with the endpoints of each line, it is not necessary to recognize the entire length of each line; in other words, it is sufficient to extract the endpoints of each line, and therefore, even in the example in Figure 4(b), the washer side line is appropriately generated.

[0036] (Included angle calculation means) The angle calculation means 102 is a means for calculating the angle between the nut side line and the base material side line (hereinafter referred to as the "nut angle"), and also for calculating the angle between the washer side line and the base material side line (hereinafter referred to as the "washer angle"). More specifically, as shown in Figure 5, the center point CP of the nut side line (bolt BT center) and the center point CP of the base material side line are superimposed, and the vertex angle formed by these two line segments is calculated as the nut angle. Similarly, the center point CP of the washer side line and the center point CP of the base material side line are superimposed, and the vertex angle formed by these two line segments is calculated as the washer angle.

[0037] (Method for determining quality) The quality determination means 103 is a means for determining whether the tightening of the high-strength bolt HTB is good or bad according to the size of the nut angle and washer angle calculated by the angle calculation means 102. Figure 5 is a schematic model diagram showing the nut condition, nut angle, and washer angle of the high-strength bolt HTB, where (a) shows the nut condition, nut angle, and washer angle of a bolt that has been deemed to have been left ungight, and (b) shows the nut condition, washer angle, and other dimensions of a bolt that has been allowed to rotate freely.

[0038] As shown in Figure 5(a), in the case of high-strength bolts HTB that were deemed to have been left untightened despite being fully tightened, or high-strength bolts HTB that were deemed to have been undertightened, the bolt line MK1, nut line MK2, washer line MK3, and base material line MK4 are arranged in roughly the same straight line. Therefore, when the nut angle falls below a predetermined angle threshold (hereinafter referred to as the "unworked threshold") and the washer angle also falls below the unworked threshold, the quality determination means 103 determines that the high-strength bolt HTB is a "high-strength bolt that was left untightened".

[0039] On the other hand, as shown in Figure 5(b), in the final tightening, the high-strength bolt HTB that is allowed to rotate together is considered to have both the nut line MK2 and the washer line MK3 rotated and moved. Therefore, when the washer angle exceeds a predetermined angle threshold (hereinafter referred to as the "defect threshold"), the quality determination means 103 determines that the high-strength bolt HTB is a "high-strength bolt that rotates together". Note that the state in which the nut line MK2 and the washer line MK3 rotate simultaneously and are at the same line position is sometimes expressed as "around the axis". Since this "around the axis" is a type of "co-rotation", to avoid complexity, it is possible to determine both "around the axis" and "high-strength bolt that rotates together" as "high-strength bolts that rotate together", or of course, it is also possible to determine them as "high-strength bolts around the axis".

[0040] (Example of use) The following describes an example of determining the quality of tightening of high-strength bolts (HTB) using the high-strength bolt inspection system 100 of the present invention, with reference to Figure 6. Figure 6 is a flowchart showing the sequence of steps from determining the quality of tightening of high-strength bolts (HTB) using the high-strength bolt inspection system 100 of the present invention. The center column shows the actions to be performed, the left column shows what is necessary for those actions, and the right column shows what results from those actions.

[0041] The high-strength bolts (HTB) to be inspected are those that have been marked after initial tightening and then fully tightened. For this marking, various colors and types of markers (such as line types) that have been conventionally used, such as oil-based pens or chalk, can be used.

[0042] Once the final tightening of the high-strength bolt HTB to be inspected is complete, the image acquisition means 105 acquires inspection images. The model generation means 107 then performs image recognition on the acquired inspection images to recognize the bolt BT, nut NT, washer WS, and base material BM, and extracts the center point CP of the bolt BT (Step 210 in Figure 6), and extracts the bolt line MK1, nut line MK2, washer line MK3, and base material line MK4 (Step 220 in Figure 6).

[0043] Once the model generation means 107 extracts the center point CP and various lines, the side line generation means 101 generates the nut side line (Step 230 in Figure 6), the washer side line (Step 240 in Figure 6), and the base material side line (Step 250 in Figure 6). Once the various side lines are generated, the angle calculation means 102 calculates the nut angle (Step 260 in Figure 6) and the washer angle (Step 270 in Figure 6). The quality determination means 103 then compares the nut angle and the washer angle with an unworked threshold, and further compares the washer angle with a defective threshold to determine whether the tightening is good or bad. Specifically, the quality determination means 103 determines that the high-strength bolt HTB is a "high-strength bolt that was not tightened" when both the nut angle and the washer angle are below the unworked threshold. Furthermore, the quality determination means 103 determines that a high-strength bolt HTB is a "high-strength bolt that rotates together" when the washer angle exceeds the defect threshold. In addition, the quality determination means 103 determines that high-strength bolts HTB that are not classified as "high-strength bolts that were not tightened" or "high-strength bolts that rotated together" are "normal high-strength bolts." The results determined by the quality determination means 103 can be displayed in real time on an output means 108 such as a display, and alert information such as a warning sound can be output when a high-strength bolt is classified as "high-strength bolts that were not tightened" or "high-strength bolts that rotated together." Furthermore, by using a display connected to the internet as the output means 108, it is possible to check the inspection results from a remote location without having to go to the site, so-called remote presence is also possible.

[0044] The series of procedures described above are repeated for all high-strength bolts (HTB) to be inspected, and the inspection is completed.

[0045] 3. Inspection method for high-strength bolts Next, the high-strength bolt inspection method of the present invention will be explained with reference to Figure 7. The high-strength bolt inspection method of the present invention is a method for determining the quality of tightening of high-strength bolts using the high-strength bolt inspection system 100 described so far. Therefore, explanations that overlap with the content described for the high-strength bolt inspection system 100 will be avoided, and only the content specific to the high-strength bolt inspection method of the present invention will be explained. In other words, the content not described here is the same as that described in "2. High-strength bolt inspection system".

[0046] Figure 7 is a flowchart showing the main steps of the high-strength bolt inspection method of the present invention. As shown in this figure, first, all high-strength bolts HTB to be inspected are marked using a marker such as an oil-based pen (Step 10 in Figure 7), and then the final tightening is performed (Step 20 in Figure 7). Once the final tightening of all high-strength bolts HTB is complete, inspection images are acquired by the image acquisition means 105 (Step 30 in Figure 7).

[0047] Upon acquiring the inspection image, the model generation means 107 recognizes the bolt BT, nut NT, washer WS, and base material BM, and extracts the center point CP of the bolt BT (Step 40 in Figure 7), and extracts the bolt line MK1, nut line MK2, washer line MK3, and base material line MK4 (Step 50 in Figure 7). After extracting the various lines, the side line generation means 101 generates the nut side line, washer side line, and base material side line (Step 60 in Figure 7), and the angle calculation means 102 calculates the nut angle and washer angle (Step 70 in Figure 7). Then, the pass / fail determination means 103 determines whether the high-strength bolt HTB to be inspected is a "high-strength bolt that was not tightened," a "high-strength bolt that rotates together," or a "normal high-strength bolt" (Step 80 in Figure 7). [Industrial applicability]

[0048] The high-strength bolt inspection system and high-strength bolt inspection method of the present invention can be used at various locations where steel members are connected by high-strength bolts, such as the connection points of bridge girders and the connection points of steel frames that make up high-rise buildings. Considering that the present invention provides high-quality steel structures and, in a sense, high-quality social capital (infrastructure), it can be said that this invention is not only industrially applicable but also has the potential to make a significant contribution to society. Furthermore, bridge girders and the like have more than 100,000 high-strength bolts, and a great deal of effort is required for tightening inspections and report creation. Therefore, the present invention can reduce manpower and labor, and even inexperienced inspectors can perform inspections of the same or higher quality as experienced inspectors, thus contributing to alleviating the shortage of skilled workers. [Explanation of Symbols]

[0049] 100 High-strength bolt inspection system of the present invention 101 (Side line generation means of high-strength bolt inspection system) 102 (Means for calculating narrow angle of high-strength bolt inspection system) 103 (Means for determining whether a high-strength bolt is good or bad) 104 Lighting means (of the high-strength bolt inspection system) 105 Image acquisition means (of the high-strength bolt inspection system) 106 Line extraction means (of the high-strength bolt inspection system) 107 Model generation means (for high-strength bolt inspection system) 108 Output means (of the high-strength bolt inspection system) 109 (Inspection image storage means for high-strength bolt inspection system) 110 (Inspection result storage means for high-strength bolt inspection system) 111 (Trained model storage means for high-strength bolt inspection system) Bridge girder ahead of BGa Bridge girder behind BGb BGf (bridge girder) flange BGw (bridge girder) web plate BM base material BT (high-strength bolt) bolt CP (center point of the bolt) HTB High-Strength Bolts MK Line Mark MK1 (of the line marks) Bolt line MK2 (Nut line among the line marks) MK3 (of the line marks) Washer line MK4 (of the line marks) base material line NT (high-strength bolt) nut SPB attachment plate WS (washer for high-strength bolts)

Claims

1. A system for inspecting high-strength bolts that have been tightened after line marks have been applied to the nuts, washers, and base material in advance, A line extraction means that extracts the center of the high-strength bolt by performing image recognition processing on an inspection image of the tightened high-strength bolt, and also extracts the nut line related to the nut, the washer line related to the washer, and the base material line related to the base material, A side line generating means for generating a nut side line connecting the endpoint of the nut line and the center of the high-strength bolt, a washer side line connecting the endpoint of the washer line and the center of the high-strength bolt, and a base material side line connecting the endpoint of the base material line and the center of the high-strength bolt, An angle calculation means for calculating the nut angle formed by the nut side line and the base material side line, and the washer angle formed by the washer side line and the base material side line, The system includes a quality determination means that determines whether the tightening of the high-strength bolt is good or bad based on the angle calculated by the angle calculation means, A high-strength bolt inspection system characterized by the following features.

2. The side line generating means generates the nut side line using the endpoint of the nut line closest to the center of the high-strength bolt, generates the washer side line using the endpoint of the washer line closest to the center of the high-strength bolt, and generates the base material side line using the endpoint of the base material line closest to the center of the high-strength bolt. The high-strength bolt inspection system according to feature 1.

3. The side line generating means generates the nut side line using the endpoint of the nut line furthest from the center of the high-strength bolt, generates the washer side line using the endpoint of the washer line furthest from the center of the high-strength bolt, and generates the base material side line using the endpoint of the base material line furthest from the center of the high-strength bolt. The high-strength bolt inspection system according to feature 1.

4. The quality determination means determines that the high-strength bolt has been left ungight when the angle between the base material side line and the nut side line is below a predetermined unworked threshold, and the angle between the base material side line and the washer side line is also below the unworked threshold. A high-strength bolt inspection system according to any one of claims 1 to 3.

5. The quality determination means determines that the high-strength bolt is rotating together when the angle between the base material side line and the washer side line exceeds a predetermined defect threshold. A high-strength bolt inspection system according to any one of claims 1 to 3.

6. A method for inspecting a high-strength bolt using the high-strength bolt inspection system described in claim 1, A bolt tightening step in which a person applies the line marks to the nut, the washer, and the base material, and tightens the nut, The image acquisition means includes an image acquisition step of acquiring an inspection image of the high-strength bolt that has been tightened after being marked with the line mark, The line extraction means performs image recognition processing on the inspection image to extract the center of the high-strength bolt, and also extracts the nut line, the washer line, and the base material line in a line extraction step, The side line generation means includes a side line generation step that generates a nut side line connecting the endpoint of the nut line and the center of the high-strength bolt, a washer side line connecting the endpoint of the washer line and the center of the high-strength bolt, and a base material side line connecting the endpoint of the base material line and the center of the high-strength bolt. The angle calculation means includes an angle calculation step which calculates the nut angle formed by the nut side line and the base material side line, and the washer angle formed by the washer side line and the base material side line. The quality determination means includes a quality determination step for determining whether the tightening of the high-strength bolt is good or bad, A method for inspecting high-strength bolts, characterized by the following features.

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