Bolt pretightening force measuring method and device and testing equipment

Abstract

The invention relates to the technical field of threaded fastener pretightening force relaxation detection, in particular to a bolt pretightening force measuring method and device and testing equipment. The method comprises the following steps: acquiring image information of a to-be-detected service bolt; performing target identification and extraction on feature points at set positions in the image information, and determining actual strain information of the to-be-detected service bolt; and determining the current pre-tightening force of the to-be-measured service bolt according to the actual strain information. According to the technical scheme, the feature point information in the image information of the to-be-tested service bolt is extracted, the actual strain information of the to-be-tested service bolt is determined, and the pre-tightening force value of the to-be-tested service bolt can be determined by comparing the actual strain information with the preset parameter information. The device can obtain a measurement result in real time for the measurement of a service bolt, is high in precision, does not need to damage the bolt, is in a non-contact manner, does not need to spray speckles, and is especially suitable for the looseness detection of a large batch of bolts at different positions in engineering.

Description

Technical Field

[0001] The invention relates to the technical field of preload relaxation detection of threaded fasteners, and in particular to a bolt preload measurement method and device, and testing equipment. Background Art

[0002] Bolt connection has the characteristics of easy assembly and disassembly and high interchangeability. It is one of the common connection methods for many structural parts and is widely used in aerospace, petrochemical, transportation and other fields. In actual working process, bolts may be subjected to axial load and lateral load for a long time, either alone or in combination. With the increase of service life and the influence of external environment, the bolt preload will gradually decrease. When the bolt preload decreases, the bolt will loosen, thereby weakening the strength and stiffness between the bolt and the connected parts, reducing the reliability of the entire system structure, and even causing serious risks of life safety and property loss. Therefore, bolt preload detection is one of the important means to avoid potential risks.

[0003] Current detection methods include torque method, strain gauge method, ultrasonic method or image digital correlation method, etc. The above methods can be used to detect the preload of bolts. However, the above detection methods also have common defects. For example, the torque method uses a torque wrench to measure, and its error rate can reach 40%; the strain gauge method has a complicated pasting process and difficult wiring, and may require drilling measurement, which causes great damage; the ultrasonic method requires the sensor to contact the bolt, which is inconvenient to use in limited space; the image digital correlation method (DIC) is a non-contact measurement method that can non-destructively monitor the deformation size of the nut in real time with high precision, thereby inferring the change of the bolt preload. However, this method requires the construction of a fixed detection platform, and the bolt preload detection is realized under fixed laboratory conditions for the spraying speckle of a single bolt, and there are limitations in the long-term service process detection of engineering service bolts. Summary of the invention

[0004] In order to solve at least the above technical problems existing in the prior art, the present invention provides a bolt preload force measurement method and device, and a testing device.

[0005] On the one hand, the present invention provides a method for measuring bolt preload, the method comprising: acquiring image information of a service bolt to be tested; performing target recognition and extraction on feature points at set positions in the image information, and determining actual strain information of the service bolt to be tested; and determining the current preload of the service bolt to be tested according to the actual strain information.

[0006] In some embodiments, the method for determining the current preload force of the service bolt to be tested based on the actual strain information includes: obtaining preset parameter information, the preset parameter information including preload force values ​​corresponding to different reference strain information; comparing the actual strain information with the reference strain information, and determining that the preload force value corresponding to the reference strain information that is the same as the actual strain information is the current preload force.

[0007] In some embodiments, the method for obtaining the preset parameter information includes: obtaining initial image information of a standard bolt; while applying a preload to the standard bolt, obtaining continuously changing image information and a continuously changing preload value of the standard bolt; comparing the continuously changing image information at different time nodes with the initial image information, determining the reference strain information at different time nodes, and fitting the reference strain information and the continuously changing preload value at the same time node to obtain the preset parameter information.

[0008] In some embodiments, the method of comparing the continuously changing image information at different time nodes with the initial image information to determine the reference strain information at different time nodes includes: performing target recognition and extraction on feature points at set positions of the initial image information and the continuously changing image information; comparing the feature point information to determine the microscopic deformation data of the feature points of the continuously changing image information compared with the initial image information at different time nodes; and determining the reference strain information at different time nodes based on the microscopic deformation data.

[0009] On the other hand, the present invention also provides a bolt preload force measuring device, comprising an acquisition module, a processing module and a comparison module; the acquisition module is configured to acquire image information of a service bolt to be tested; the processing module is configured to perform target recognition and extraction on feature points at set positions in the image information, and determine actual strain information of the service bolt to be tested; the comparison module is configured to determine the current preload force of the service bolt to be tested based on the actual strain information.

[0010] In some embodiments, the acquisition module is also configured to acquire preset parameter information, and the preset parameter information includes preload force values ​​corresponding to different reference strain information; the comparison module is also configured to compare the actual strain information with the reference strain information, and determine that the preload force value corresponding to the reference strain information that is the same as the actual strain information is the current preload force.

[0011] In some embodiments, the acquisition module is also configured to acquire initial image information of the standard bolt, and at the same time, when applying a preload to the standard bolt, acquire continuously changing image information and continuously changing preload value of the standard bolt; the comparison module is also configured to compare the continuously changing image information at different time nodes with the initial image information, determine the reference strain information at different time nodes, and fit the reference strain information and the continuously changing preload value at the same time node to obtain the preset parameter information.

[0012] In some embodiments, the processing module is further configured to perform target recognition and extraction on feature points at set positions of the initial image information and the continuously changing image information; the comparison module is further configured to compare the feature point information, determine the microscopic deformation data of the feature points of the continuously changing image information compared with the initial image information at different time nodes; and determine the reference strain information at different time nodes based on the microscopic deformation data.

[0013] Another aspect of the present invention provides a testing device, including a handheld housing and a circuit board arranged in the handheld housing, the circuit board includes a main processor, and the main processor performs preload force measurement based on the above-mentioned bolt preload force measurement method.

[0014] In some embodiments, an image acquisition module is also included, and the image acquisition module is arranged on a panel on one side of the handheld shell; the image acquisition module is used to obtain image information of the service bolt to be tested and send it to the main processor.

[0015] In some embodiments, a display module is also included, which is arranged on a panel on the other side of the handheld shell; the image acquisition module includes a distance sensor module and an angle sensor module, which are respectively used to measure the distance information and angle information between the service bolt to be tested and the image acquisition module; the display module is used to display the image information of the service bolt to be tested, as well as the distance information and the angle information.

[0016] The present invention provides a bolt preload measurement method and device, and a testing device, which extracts feature point information from the image information of the service bolt to be tested, determines the actual strain information of the service bolt to be tested, and determines the preload value of the service bolt to be tested based on the actual strain information and by comparing it with preset parameter information. The technical solution of the present invention can obtain measurement results in real time for the measurement of service bolts, has the advantages of high precision, no need for damaged bolts, non-contact, no need for spraying speckles, etc., and is particularly suitable for loosening detection of bolts in large quantities and at different positions in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, in which:

[0018] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0019] Figure 1 A flowchart of a bolt preload force measurement method provided by an embodiment of the present invention;

[0020] Figure 2 A structural block diagram of a bolt preload force measuring device provided in an embodiment of the present invention;

[0021] Figure 3 A schematic diagram of the structure of one side of a test device provided by an embodiment of the present invention;

[0022] Figure 4 A schematic diagram of the structure of the other side of the test device provided by an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of a circuit board in a test device provided by an embodiment of the present invention;

[0024] Figure 6 A front view of a service bolt to be tested in the testing equipment provided in an embodiment of the present invention.

[0025] In the figure:

[0026] 1: Handheld housing; 2: Display module; 3: Heat dissipation hole; 4: Power interface; 51: Switch button; 52: Function switch button; 53: Confirm button; 54: Parameter adjustment button; 6: Speaker; 7: Optical cable interface; 8: Data interface module; 9: Enhanced light source; 10: Image acquisition module; 11: Distance sensor; 12: Lithium battery; 13: Circuit board; 14: Positioning hole; 15: Wireless communication module; 16: Image processor; 17: Angle sensor module; 181: Image acquisition independent power module; 182: Main power module; 191: Main processor; 192: Thermal conductive gel; 20: Voice module; 21: Focus system; 22: Image control chip; 23: Distance sensor module; 24: Image module interface; 25: Compilation module; 26: Storage module; 27: Bolts to be tested; 28: Feature points;

[0027] 100: bolt preload force measuring device; 110: acquisition module; 120: processing module; 130: comparison module. DETAILED DESCRIPTION

[0028] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, an embodiment of the present invention provides a method for measuring bolt preload force, the method comprising the following steps:

[0030] Step S10: Establishing a preset parameter information database.

[0031] The initial image information of the standard bolt is obtained, and the model of the current standard bolt is recorded, wherein the standard bolt can be interpreted as a bolt of the same bolt model that has not been screwed (unused). For example, the position where the initial image information is collected is the end face image information of the standard bolt nut.

[0032] The main processor performs denoising, edge detection, and random Hough transform operations on the initial image information, and then extracts feature points and identifies targets. For example, the locations of feature points are set at the center area and edge area of ​​the nut end face.

[0033] During the extraction and target recognition operations, the main processor performs standardized cropping on the initial image, retains the complete nut end face image, grayscales the initial image, and binarizes it using the adaptive threshold method. If the binary image happens to contain only white areas with feature point pixel values ​​of 255, the next step can be performed; if it also contains other noise point interference, morphological processing such as corrosion or expansion is performed to ultimately remove the interfering part.

[0034] After image processing is completed, a coordinate system is constructed, and a unified distance representation is selected, such as Euclidean distance or Manhattan distance, to determine the coordinates of the feature points in the image. The coordinate positions are used as reference coordinates for calculating strain.

[0035] Subsequently, when a preload is applied to the standard bolt, as the standard bolt is rotated, a preload is generated between the standard bolt and the connecting piece, and the preload changes continuously. In this process, continuously changing image information and continuously changing preload values ​​of the standard bolt are obtained.

[0036] After the main processor performs denoising, edge detection, and random Hough transform operations on one of the continuously changing image information, it performs target recognition and extraction on the feature points at the set positions of the continuously changing image information; the same processing method as the initial image is used to determine the coordinate information of the feature points.

[0037] Repeat the above operation to complete the target recognition and extraction of feature points for all continuously changing image information. After determining the coordinate information of the feature points, the displacement of the feature points in the current continuously changing image information can be determined. Through the change of geometric relationship, the feature point strain is calculated by the deformation (displacement), that is, the reference strain information corresponding to the current continuously changing image information.

[0038] By comparing the feature point information, the microscopic deformation data of the feature points compared with the continuously changing image information and the initial image information at different time nodes are determined. The microscopic deformation data contains the coordinate change information of the feature points, that is, the displacement. The coordinate information of the current feature point is compared with the reference coordinate. As the preload changes, the displacement of the coordinate information changes differently. The reference strain information at different time nodes is determined based on the microscopic deformation data (displacement change information of different displacement coordinate information).

[0039] Then, when obtaining the continuously changing preload value information obtained when screwing the standard bolt, the reference strain information and the continuously changing preload value at the same time node are fitted to obtain the preset parameter information, thereby obtaining the preset parameter information database of the current model standard bolt.

[0040] For example, the reference strain information at the same time node and the continuously changing preload value are fitted to obtain the preload-strain correlation curve and the fitting constitutive model.

[0041] According to the above method, image acquisition and preload force acquisition are performed on standard bolts of different models, and a preset parameter information database of standard bolts of different models is established.

[0042] After the collection of preset parameter information is completed, the service bolt to be tested can be tested. Before the test, the corresponding preset parameter information is selected according to the model of the service bolt to be tested.

[0043] Step S20: Acquire image information of the service bolt to be tested; collect image information by image acquisition equipment. When testing the service bolt to be tested, collect image information of the end face of the nut of the service bolt to be tested by image acquisition equipment.

[0044] The image captured by the image acquisition device is preprocessed, and then the main processor performs denoising, edge detection, and random Hough transform operations on the image.

[0045] Step S30: target recognition and extraction of feature points at set positions in the image information, the method includes: the main processor performs standardized cropping on the image, retains the nut end face image, grayscales the image, and then binarizes it through an adaptive threshold method. If the binary image happens to contain only white areas with feature point pixel values ​​of 255, the next step can be performed; if it also contains other noise point interference, morphological processing such as corrosion or expansion is performed to finally remove the interference part.

[0046] After completing the image processing, a coordinate system is constructed and a unified distance representation is selected, such as Euclidean distance or Manhattan distance, to determine the coordinates of the feature points in the image, determine the displacement of the feature points in the currently acquired image information, and obtain the feature point strain through the change of geometric relationships and the deformation calculation, that is, the actual strain information corresponding to the current image information.

[0047] Step S40: Determine the current preload force of the service bolt to be tested according to the actual strain information. In the preset parameter information database, different reference strain information corresponds to different preload force values ​​in the service bolts of the current model. The actual strain information is compared with the reference strain information. When the actual strain information is the same as the reference strain information, or when the actual strain information is within the range of the reference strain information, the preload force value corresponding to the reference strain information is the current preload force of the service bolt to be tested.

[0048] Based on the above bolt preload force measurement method, after determining the preset parameter information database, the preload force information of the service bolt to be tested can be tested in real time to achieve fast and accurate testing.

[0049] like Figure 2 As shown, an embodiment of the present invention provides a bolt preload force measuring device 100, comprising an acquisition module 110, a processing module 120 and a comparison module 130; the acquisition module 110 is configured to acquire image information of a service bolt to be tested; the processing module 120 is configured to perform target recognition and extraction on feature points at set positions in the image information, and determine actual strain information of the service bolt to be tested; the comparison module is configured to determine the current preload force of the service bolt to be tested according to the actual strain information.

[0050] In some embodiments, the acquisition module 110 is also configured to acquire preset parameter information, which includes preload force values ​​corresponding to different reference strain information; the comparison module 130 is also configured to compare the actual strain information with the reference strain information, and determine that the preload force value corresponding to the reference strain information that is the same as the actual strain information is the current preload force.

[0051] In some embodiments, the acquisition module 110 is also configured to acquire initial image information of the standard bolt, and at the same time, when applying preload force to the standard bolt, acquire continuously changing image information and continuously changing preload force value of the standard bolt; the comparison module 130 is also configured to compare the continuously changing image information at different time nodes with the initial image information, determine the reference strain information at different time nodes, and fit the reference strain information and the continuously changing preload force value at the same time node to obtain preset parameter information.

[0052] In some embodiments, the processing module is further configured to perform target recognition and extraction on feature points at set positions of the initial image information and the continuously changing image information; the comparison module is further configured to compare the feature point information, determine the microscopic deformation data of the feature points of the continuously changing image information compared with the initial image information at different time nodes; and determine the reference strain information at different time nodes based on the microscopic deformation data.

[0053] It should be noted that the description of the bolt preload force measuring device in the embodiment of the present disclosure is similar to the description of the bolt preload force measuring method embodiment described above, and has similar beneficial effects as the method embodiment, so it will not be repeated. Figure 1 The present invention will be understood from the description of the accompanying drawings.

[0054] An embodiment of the present invention provides a testing device, including a handheld shell and a circuit board arranged in the handheld shell. Various functional components are arranged on the handheld shell, such as heat dissipation holes or power supply interfaces, etc. The circuit board integrates image acquisition, display and processing modules for completing image testing operations.

[0055] The following describes in detail the various structures of the testing device provided by the embodiment of the present invention, and the positional relationship and connection relationship between the various structures in conjunction with the accompanying drawings.

[0056] like Figures 3 to 6 As shown, the circuit board 13 includes a main processor 191, and the main processor 191 performs a preload test based on the above-mentioned bolt preload measurement method.

[0057] For example, the handheld housing 1 is in the shape of a flat rectangular parallelepiped, and its appearance is similar to that of an existing mobile communication terminal. The circuit board 13 is arranged in the handheld housing 1, wherein the shape of the circuit board 13 is similar to the cross-sectional shape of the handheld housing 1, and a positioning hole 14 is arranged at the edge of the circuit board 13. A positioning column is arranged on the inner wall of the handheld housing 1, and the positioning column cooperates with the positioning hole 14 to fix the circuit board 13 in the handheld housing 1.

[0058] The main processor 191 is arranged on the circuit board 13, and a thermal conductive gel 192 is arranged between the main processor 191 and the circuit board 13 to facilitate timely heat dissipation of the main processor 191. An image acquisition module 10 and a display module 2 are also configured on the circuit board 13. The acquisition lens of the image acquisition module 10 is arranged on one side of the handheld shell 1, and the display module 2 includes a touch screen, which is arranged on the other side of the handheld shell 1.

[0059] The image acquisition module 10 includes an image processor 16, an angle sensor module 17, an image acquisition independent power supply module 181, a focus system 21, an image control chip 22, a distance sensor module 23, and an image module interface 24. The image acquisition module 10 is used to receive image information sent by a capture lens or camera, to pre-process the image, and to send the image information to the main processor 191.

[0060] The components of the image acquisition module 10 are integrated in an area of ​​the circuit board 13. A voice module 20 is arranged on the circuit board 13 above the area. The voice module 20 can receive voice commands and send control information through voice commands, such as controlling volume, model selection, etc. A wireless communication module 15 is arranged on the side of the area. The wireless communication module 15 can realize wireless communication with components on the circuit board 13 or external terminal devices. The main processor 191 is located below the area.

[0061] A main power module 182 is also provided in the area where the main processor 191 is located, and a data storage module 26 and a program compiling module 25 are provided on one side of the main power module 182 .

[0062] When in use, the side of the handheld shell 1 on which the touch screen is set is the front side. When in use, the user holds the handheld shell 1 with the touch screen facing the user for human-computer interaction. A sound outlet is arranged above the touch screen. The speaker 6 arranged inside can broadcast voice information and broadcast it to the outside through the sound outlet. As shown in the figure, the test result is broadcast through the speaker 6. The side of the handheld shell 1 on which the collection lens is set is the back side. The back side of the handheld shell 1 is located above the collection lens / camera and is also provided with an enhanced light source 9, and a distance sensor 11 (such as the transmitting end and receiving end of the distance sensor 11 and other structural parts) and a lithium battery 12 are arranged below.

[0063] Physical buttons are arranged on the top of the handheld housing 1, including a switch button 51, a function switching button 52, a confirmation button 53 and a parameter adjustment button 54. A heat dissipation hole 3 and a power interface 4 are arranged on one side of the handheld housing 1, and an optical cable interface 7 and a data interface 8 are arranged on the other side. The heat dissipation hole 3 can dissipate the heat in the handheld housing 1 in time to prevent the internal structure of the handheld housing 1 from operating in a high temperature environment for a long time. The power interface 4 can be connected to an external power source or a charging device, and various interfaces, such as the optical cable interface 7 and the data interface 8, are used for information transmission.

[0064] The following is an explanation of the method for using the test device provided by the embodiment of the present invention, wherein the method for using the test device mainly includes a preparation step, a preset parameter information collection step and a test step.

[0065] The preparation steps include: the user holds the handheld housing 1 and presses the top switch button 51 to start the system. After the system self-check is completed and initialized, the touch screen displays the human-computer interactive operation interface.

[0066] The camera (image acquisition function) is turned on by touching the touch screen or by the function switching button 52 , and the main control program of the image control chip 22 inside the image acquisition module 10 starts to run, detects whether the accessories of the image acquisition module 10 are normal, and then initializes the camera parameters.

[0067] Then, the automatic image correction operation is performed: the user presses the top function switch button 52 to start the distance sensor module 23 and the angle sensor module 17, then presses the top confirmation button 53 to confirm the start, and then presses the function switch button 52 twice in a row to return to the image acquisition module 10 display screen.

[0068] The distance information and angle information are obtained by the distance sensor module 23 and the angle sensor module 17, and the angle and distance parameters of the service bolt 27 to be tested are displayed in real time on the touch screen. The user can manually adjust the tilt angle of the handheld housing 1 and the distance between the camera and the service bolt 27 to be tested according to the parameter information, such as displaying the standard bit image on the touch screen, ensuring that the end face image of the service bolt 27 to be tested is in the standard bit image displayed on the touch screen, such as the center of the cross of the standard bit image, and ensuring that the image displayed on the touch screen is uniform and has no jitter.

[0069] Then, the parameters of the camera / collection lens, such as aperture, focal length, etc., are adjusted through the top parameter adjustment button 54 to further fine-tune the camera / collection lens collection image. If the light intensity of the end face image of the service bolt 2727 to be tested is uneven, the enhanced light source 9 is turned on through the top function switching button 52, and the enhanced light source 9 automatically adjusts the light intensity according to the surrounding environment to ensure a clear image.

[0070] After the preparation steps are completed, the test equipment has the ability to acquire images. The test equipment is first used to obtain standard image information and establish a preset parameter information database.

[0071] First, a type of bolt is selected as a standard bolt, and an image is captured by pressing the confirmation button 53. The focus system 21 locks the focus and then captures the image. The captured image is transmitted to the image processor 16 for preprocessing, which includes image denoising, image enhancement, etc. The preprocessing is transmitted to the main processor 191 through the image module interface 24. The main processor 191 performs denoising and edge detection operations on the captured image, and then extracts the feature points 28 and identifies the target. The image information captured in this step is the initial image information. The initial strain information is obtained by extracting the feature points 28 and identifying the target on the initial image.

[0072] The method for extracting the feature point 28 and identifying the target includes: the main processor 191 performs standardized cropping on the image, retains the nut end face image, grayscales the image, and then binarizes it through an adaptive threshold method. If the binary image happens to contain only the white area with a pixel value of 255 of the feature point 28, the next step can be performed; if it also contains other noise point interference, morphological processing such as corrosion or expansion is performed to finally remove the interfering part.

[0073] After completing the image processing, a coordinate system is constructed, and a unified distance representation is selected, such as Euclidean distance or Manhattan distance, to determine the coordinates of the feature point 28 in the image, to determine the coordinates of the feature point 28 in the currently acquired image information, and to calculate and obtain the initial strain information based on the coordinate position information.

[0074] Subsequently, a torque wrench is used to gradually apply pre-tightening force to the standard bolt, and when tightening the standard bolt, image information of the end face of the standard bolt nut is continuously obtained. With the assistance of the angle sensor module 17 and the distance sensor module 23, the degree of image offset in the touch screen and the degree of correction required can be determined, and the display position of the image on the touch screen can be adjusted so that the shaking of the standard bolt is automatically corrected and the center of the image is kept constant before and after image capture.

[0075] The image processor 16 corrects the continuously collected images and transmits the image information to the main processor 191 through the image module interface 24. The main processor 191 extracts the feature points 28 and identifies the target of each continuous image information to obtain the strain information of each continuous image information. By comparing the microscopic deformation of the feature points 28 of the nut end face of the standard bolt at different time nodes and the initial state, the surface strain of the bolt head at different times is calculated in real time. At different time nodes, the preload force on the standard bolt is also different. Therefore, the deformation of the feature points 28 of the nut end face of the standard bolt is also different. The coordinates of the feature points 28 at different time points can be determined by extracting and identifying the target of the feature points 28, and then the displacement of the feature points 28 can be calculated to determine the surface strain.

[0076] The preload data measured by the torque wrench is imported into the test equipment through the data interface 8, and the calculation module is selected based on the touch screen to fit the preload and strain to obtain the preload-strain correlation curve and the fitting constitutive model. The current data is recorded through the data storage module 26 to complete the calibration and parameter storage of this model of bolt.

[0077] Then, the test equipment is used to repeat the above steps for other types of standard bolts. After all the information data of the standard bolts of the tested model are calibrated and stored, the fitting parameters can be called at any time to detect the preload force of the bolts of the model, and the current preload force can be tested in real time.

[0078] Test steps: First, through the function switching button 52, the bolt model data stored in the storage module 26 is called, the model of the current service bolt 27 to be tested is selected, and then image acquisition is performed, and the acquired position is the end face of the nut of the service bolt 27 to be tested.

[0079] The collected image is preprocessed by the image processor 16, and then transmitted to the main processor 191 through the image module interface 24. The main processor 191 automatically performs denoising, edge detection, and random Hough transform operations according to the currently selected bolt model, and finally performs target recognition and extraction on the feature points 28, such as the surface center area and edge area of ​​the nut end face, so as to obtain the strain information of the service bolt 27 to be tested. The target recognition and extraction method and the strain information calculation method are described above.

[0080] The preload-strain constitutive model of the service bolt 27 to be tested is called through the function switching button 52, and the preload is calculated based on the strain information of the service bolt 27 to be tested obtained by the main processor 191. The current preload size is displayed in real time on the touch screen. At the same time, the touch screen can be used to select to store the data in the storage module 26. At this time, if the preload is lower than the alarm threshold set by the user, the speaker 6 will issue a warning.

[0081] After the preload force test of the current service bolt 27 to be tested is completed, exit the current interface by pressing the function switch button 52, aim the device lens at the next service bolt 27 to be tested, open the camera interface by pressing the function switch button 52, repeat the above test steps, and the preload force of the service bolt 27 to be tested can be monitored in real time one by one.

[0082] The present invention provides a bolt preload measurement method and device, and a testing device, which extracts feature point information from the image information of the service bolt to be tested, determines the actual strain information of the service bolt to be tested, and determines the preload value of the service bolt to be tested based on the actual strain information and by comparing it with preset parameter information. The technical solution of the present invention can obtain measurement results in real time for the measurement of service bolts, has the advantages of high precision, no need for damaged bolts, non-contact, no need for spraying speckles, etc., and is particularly suitable for loosening detection of bolts in large quantities and at different positions in engineering.

[0083] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0084] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0085] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for measuring bolt preload, characterized in that: The method comprises: Acquire image information of the service bolt to be tested; Performing target recognition and extraction on feature points at set positions in the image information, and determining actual strain information of the service bolt to be tested; The current preload force of the service bolt to be tested is determined according to the actual strain information.

2. The bolt preload force measurement method according to claim 1, characterized in that: The method for determining the current preload force of the service bolt to be tested according to the actual strain information comprises: Acquire preset parameter information, wherein the preset parameter information includes preload force values ​​corresponding to different reference strain information; The actual strain information is compared with the reference strain information to determine a preload force value corresponding to the reference strain information that is the same as the actual strain information as the current preload force.

3. The bolt preload force measurement method according to claim 2, characterized in that: The method for obtaining the preset parameter information includes: Obtaining initial image information of standard bolts; At the same time, when the pre-tightening force is applied to the standard bolt, continuously changing image information and continuously changing pre-tightening force value of the standard bolt are obtained; The continuously changing image information at different time nodes is compared with the initial image information to determine the reference strain information at different time nodes, and the reference strain information at the same time node is fitted with the continuously changing preload force value to obtain the preset parameter information.

4. The bolt preload force measurement method according to claim 3, characterized in that: The method of comparing the continuously changing image information at different time nodes with the initial image information to determine the reference strain information at different time nodes includes: Performing target recognition and extraction on feature points at set positions of the initial image information and the continuously changing image information; Comparing the feature point information, determining microscopic deformation data of the feature points of the continuously changing image information compared with the initial image information at different time nodes; The reference strain information at different time nodes is determined according to the microscopic deformation data.

5. A bolt preload force measuring device, characterized in that: It includes an acquisition module (110), a processing module (120) and a comparison module (130); The acquisition module (110) is configured to acquire image information of the service bolt to be tested; The processing module (120) is configured to perform target recognition and extraction on feature points at set positions in the image information, and determine actual strain information of the service bolt to be tested; The comparison module (130) is configured to determine the current preload force of the service bolt to be tested according to the actual strain information.

6. The bolt preload force measuring device according to claim 5, characterized in that: The acquisition module (110) is further configured to acquire preset parameter information, wherein the preset parameter information includes preload force values ​​corresponding to different reference strain information; The comparison module (130) is further configured to compare the actual strain information with the reference strain information, and determine the preload force value corresponding to the reference strain information that is the same as the actual strain information as the current preload force.

7. The bolt preload force measuring device according to claim 5, characterized in that: The acquisition module (110) is further configured to acquire initial image information of the standard bolt, and simultaneously acquire continuously changing image information and continuously changing pre-tightening force values ​​of the standard bolt when a pre-tightening force is applied to the standard bolt; The comparison module (130) is further configured to compare the continuously changing image information at different time nodes with the initial image information, determine the reference strain information at different time nodes, and fit the reference strain information at the same time node with the continuously changing preload force value to obtain the preset parameter information.

8. The bolt preload force measuring device according to claim 5, characterized in that: The processing module (120) is further configured to perform target recognition and extraction on feature points at set positions of the initial image information and the continuously changing image information; The comparison module (130) is further configured to compare the feature point information, determine the microscopic deformation data of the feature points of the continuously changing image information compared with the initial image information at different time nodes; and determine the reference strain information at different time nodes according to the microscopic deformation data.

9. A testing device, characterized in that: The invention comprises a handheld housing (1) and a circuit board (13) arranged in the handheld housing (1), wherein the circuit board (13) comprises a main processor (191), and the main processor (191) performs preload measurement based on the bolt preload measurement method according to any one of claims 1 to 5.

10. The bolt preload force measuring device according to claim 9, characterized in that: It also comprises an image acquisition module (10), wherein the image acquisition module (10) is arranged on a panel on one side of the handheld housing (1); The image acquisition module (10) is used to obtain image information of the service bolt to be tested, and send the image information to the main processor (191).

11. The bolt preload force measuring device according to claim 10, characterized in that: It also comprises a display module (2), wherein the display module (2) is arranged on a panel on the other side of the handheld housing (1); The image acquisition module (10) comprises a distance sensor module (11) and an angle sensor module (17), which are used to measure the distance information and the angle information between the service bolt to be tested and the image acquisition module respectively; The display module (2) is used to display the image information of the service bolt to be tested, as well as the distance information and the angle information.

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