In-situ cement-based material tensile test system and method based on image recognition

Abstract

The invention belongs to the technical field of civil engineering material detection, and particularly discloses an in-situ cement-based material tensile test system and method based on image recognition, and the system comprises a substrate, a replaceable strain sensing clamp, a duplex coupling balance forcing device and a non-contact image strain measurement system. The duplex coupling balance forcing device is arranged on the base plate, is connected with a cement-based material tensile test piece to be tested, and is used for applying tensile force to the replaceable strain sensing clamp; the non-contact image strain measurement system is arranged on the base plate, is positioned on one side of the replaceable strain sensing clamp, and is used for acquiring an image of the cement-based material tensile test piece, correcting the image based on a visual positioning module positioned on the surface of the base plate, and resolving by utilizing the corrected image to obtain a strain test result of the cement-based material tensile test piece. According to the invention, the requirement on the field flatness is lower, the test efficiency is higher, and the requirements on the timeliness of emergency response and the effectiveness of disaster prevention and control can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering material testing, and in particular, to an in-situ cement-based material tensile test system and method based on image recognition. Background Art

[0002] Axial tensile specimens of cement-based materials are one of the most common specimens in civil engineering material experiments. The axial tensile strength of cement-based materials and the performance indexes of the interfaces between different materials obtained based on them are indispensable scientific bases for concrete structure design and structural safety assessment. However, in the current tensile test technology system of cement-based materials, when using axial tensile specimens of cement-based materials to complete the test, although this test system can complete the test task with high precision, its huge size has become a limitation that cannot be ignored. Especially in emergency response scenarios such as disaster relief, due to space limitations and the need for rapid assessment, traditional large-scale test systems are difficult to deploy quickly and conduct in-situ detection, which undoubtedly poses severe challenges to the timeliness of emergency response and the effectiveness of disaster prevention and control.

[0003] Meanwhile, in common test systems in the prior art, when installing cement-based tensile materials, it is necessary to keep the specimen horizontal with the test system. Therefore, the requirement for the flatness of the site is relatively high, and a large number of specimens are required to calibrate the specimen, resulting in low test efficiency. Summary of the Invention

[0004] To solve the deficiencies in the prior art, the in-situ cement-based material tensile test system and method based on image recognition provided by the present invention have lower requirements for the flatness of the site and higher test efficiency, and can meet the requirements of the timeliness of emergency response and the effectiveness of disaster prevention and control.

[0005] The present invention adopts the following technical solutions.

[0006] In a first aspect, the present invention provides an in-situ cement-based material tensile test system based on image recognition, including: a substrate and a replaceable strain sensing fixture. The replaceable strain sensing fixture is arranged on the substrate and is used for clamping a cement-based material tensile specimen to be tested; the in-situ cement-based material tensile test system further includes: a dual-coupled balance loading device, which is arranged on the substrate and is connected to the cement-based material tensile specimen to be tested, and is used for applying a tensile force to the replaceable strain sensing fixture; a non-contact image strain measurement system, which is arranged on the substrate and is located on one side of the replaceable strain sensing fixture, and is used for collecting images of the cement-based material tensile specimen, correcting the images based on a visual positioning module located on the surface of the substrate, and calculating strain test results of the cement-based material tensile specimen by using the corrected images.

[0007] Preferably, the substrate includes: a lower reaction force plate, on one side of the upper surface of which a spring is provided, and a vision positioning module is provided on the other side; an upper reaction force plate, provided at the top of the spring and parallel to the lower reaction force plate; wherein, the replaceable strain sensing fixture and the dual-coupling balanced force application device are both provided between the upper reaction force plate and the lower reaction force plate; the non-contact image strain measurement system is provided at the top of the lower reaction force plate and above the vision positioning module.

[0008] Preferably, the dual-coupling balanced force application device includes: two jacks respectively provided on the left and right sides of the replaceable strain sensing fixture; each jack is fixedly connected to the lower reaction force plate at the bottom and contacts the upper reaction force plate at the top, and is used to jack up the upper reaction force plate to apply a tensile force to the replaceable strain sensing fixture; wherein, the two jacks have exactly the same structure and size, and are linked through a connecting rod assembly.

[0009] Preferably, the replaceable strain sensing fixture includes: a fixture-lower, detachably connected to the upper surface of the lower reaction force plate; a first clamping groove penetrating through the opposite side surfaces is provided at the top of the fixture-lower; a fixture-upper, detachably connected to the lower surface of the upper reaction force plate; a second clamping groove penetrating through the opposite side surfaces is provided at the bottom of the fixture-upper: wherein, the fixture-upper and the fixture-lower are symmetrically arranged, and the first clamping groove and the second clamping groove respectively match the shapes of the two ends of the cement-based material tensile specimen, and are used to insert and clamp the two ends of the cement-based material tensile specimen.

[0010] Preferably, a lower wedge bar is provided at the top of the lower reaction force plate; a first slot adapted to the outer shape of the lower wedge bar is provided on the fixture-lower in the replaceable strain sensing fixture, and the first slot is used for detachably connecting with the lower wedge bar; an upper wedge bar is provided at the bottom of the upper reaction force plate; a second slot adapted to the outer shape of the upper wedge bar is provided on the fixture-upper in the replaceable strain sensing fixture, and the second slot is used for detachably connecting with the upper wedge bar.

[0011] Preferably, two alignment prompt bars are symmetrically arranged on both sides of the top edge of the lower wedge bar, and are used to prompt whether the lower wedge bar is centered with the fixture-lower; two alignment prompt bars are also symmetrically arranged on both sides of the bottom edge of the upper wedge bar, and are used to prompt whether the upper wedge bar is centered with the fixture-upper.

[0012] Preferably, two built-in strain sensing modules - lower are symmetrically arranged on the opposite side walls of the first clamping groove for sensing the strain of the cement-based material tensile specimen; two data transmission upper contacts - lower are symmetrically arranged on the opposite side walls of the first slot, and each data transmission upper contact - lower is connected to the corresponding built-in strain sensing module - lower through a data transmission cable - lower; a data transmission lower contact - lower is arranged at a position corresponding to the data transmission upper contact - lower on the top surface of the lower wedge bar, for when the lower wedge bar is inserted into the first slot, contacting the data transmission upper contact - lower and importing the data of the built-in strain sensing module - lower into the data display module of the non-contact image strain measurement system.

[0013] Preferably, two built-in strain sensing modules - upper are symmetrically arranged on the opposite side walls of the second clamping groove, two data transmission upper contacts - upper are symmetrically arranged on the opposite side walls of the second slot, and each data transmission upper contact - upper is connected to the corresponding built-in strain sensing module - upper through a data transmission cable - upper; a data transmission lower contact - upper is arranged at a position corresponding to the data transmission upper contact - upper on the bottom surface of the upper wedge bar, for when the upper wedge bar is inserted into the second slot, contacting the data transmission upper contact - upper and importing the data of the built-in strain sensing module - upper into the data display module of the non-contact image strain measurement system.

[0014] Preferably, the non-contact image strain measurement system includes: a hollow clamping plate detachably arranged on the top of the lower reaction plate and above the visual positioning module; four downward-looking cameras arranged in a rectangle and on the lower surface of the hollow clamping plate; the four downward-looking cameras are connected to the strain image test module for collecting the pattern information of the visual positioning module and correcting the image information collected by the strain image test module based on the visual positioning module; the strain image test module is movably arranged on the top of the hollow clamping plate for collecting the image of the cement-based material tensile specimen and calculating the strain test result of the cement-based material tensile specimen based on the corrected image information of the downward-looking cameras; the data display module is arranged on the hollow clamping plate and connected to the strain image test module for displaying the strain test result.

[0015] Preferably, the visual positioning module includes: a plurality of positioning points with different color shades and different pattern sizes; the plurality of positioning points are arranged in a rectangular array.

[0016] Preferably, the non-contact image strain measurement system further includes: a strain measurement system position adjustment module arranged on the top of the hollow clamping plate, and the strain image test module is installed on its top for adjusting the position and test height of the strain image test module on the hollow clamping plate.

[0017] Preferably, the non-contact image strain measurement system further includes: a magnetic adsorption fixing module disposed on the lower surface of the hollow splint for detachably connecting the hollow splint to the lower reaction plate.

[0018] In a second aspect, the present invention provides a method for in-situ tensile test of cement-based materials based on image recognition, which is applied to the aforementioned in-situ tensile test system of cement-based materials based on image recognition, and includes the following steps: clamping a cement-based material tensile test specimen to be tested in a replaceable strain sensing fixture; adjusting the position of the non-contact image strain measurement system so that its test camera faces the cement-based material tensile test specimen; applying a tensile force to the replaceable strain sensing fixture through a two-link coupling balance force application device to tensile the cement-based material tensile test specimen; collecting an image of the cement-based material tensile test specimen through the non-contact image strain measurement system, correcting the image based on the visual positioning module, and calculating the strain test result of the cement-based material tensile test specimen by using the corrected image.

[0019] The beneficial effects of the present invention are as follows. Compared with the prior art, by setting the visual positioning module and the non-contact image strain test module, when clamping the cement-based material tensile test specimen to be tested, it is not necessary to spend a lot of time calibrating it, and the pattern information of the cement-based material tensile test specimen can be directly collected by the strain image test module. During the test, based on the pattern information of the visual positioning module, the pattern information of the cement-based material tensile test specimen collected by the strain image test module is corrected to obtain the corrected pattern information, and then the strain image test module calculates the strain test result of the cement-based material tensile test specimen by using the corrected pattern information. The present invention not only improves the test efficiency of the cement-based material tensile test specimen, but also has higher accuracy, simpler operation, lower requirement for the flatness of the site, and can be applied to emergency scenarios compared with manual calibration by using the correction algorithm.

[0020] In addition, by adopting a two-link coupling balance force application device composed of a jack as the power source and cooperating with a spring, compared with the traditional electro-hydraulic servo universal testing machine, it is not necessary to additionally increase an oil source or supply power, greatly reducing the system volume, making the system structure compact, convenient, more convenient for transportation, applicable to emergency rescue occasions, and capable of improving the effectiveness of disaster prevention and control.

[0021] Furthermore, in order to make the strain test result more accurate, the present invention sets an in-built strain sensing module - upper and an in-built strain sensing module - lower in the replaceable strain sensing fixture. By directly contacting the cement-based material tensile test specimen through the in-built strain sensing module - upper and the in-built strain sensing module - lower, the strain information of the specimen is obtained, and the position of the specimen is adjusted through this strain information, which is beneficial to improving the accuracy of the test result. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the overall structure of the portable in-situ cement-based material tensile test system based on image recognition in the present invention;

[0023] Figure 2 It is a schematic diagram of the separated structure of the replaceable strain sensing fixture in the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the non-contact image strain measurement system in the present invention;

[0025] Figure 4 It is a schematic diagram of the structure of the visual positioning module in the present invention;

[0026] Figure 5 It is the measurement principle diagram of the non-contact image strain measurement system in the present invention.

[0027] Among them, reference numerals: 1. Lower reaction force plate, 11. Lower wedge bar, 111. Lower fixture alignment prompt bar, 112. Data transmission lower contact - lower, 12. Visual positioning module, 2. Upper reaction force plate, 21. Upper wedge bar, 211. Upper fixture alignment prompt bar, 212. Data transmission lower contact - upper, 3. Replaceable strain sensing fixture, 31. Fixture - upper, 311. Built-in strain sensing module - upper, 312. Data transmission upper contact - upper, 313. Data transmission cable - upper, 32. Fixture - lower, 321. Built-in strain sensing module - lower, 322. Data transmission upper contact - lower, 323. Data transmission cable - lower, 4. Spring, 5. Two-link coupling balance force application device, 6. Non-contact image strain measurement system, 61. Strain image test module, 62. Data display module, 63. Lower vision camera, 64. Strain measurement system position adjustment module, 641. Vertical adjustment knob, 642. Horizontal adjustment knob, 65. Hollow splint, 66. Magnetic attraction fixing module; 7. Cement-based material tensile test piece. Specific embodiments

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0029] As Figure 1As shown in the figure, Embodiment 1 of the present invention provides a portable in-situ tensile test system for cement-based materials based on image recognition, including: a substrate, a replaceable strain sensing fixture 3, a spring 4, a dual-coupled balanced force application device 5, and a non-contact image strain measurement system 6.

[0030] The substrate includes: a lower reaction force plate 1 and an upper reaction force plate 2. Among them, a plurality of springs 4 are arranged on one side of the top surface of the lower reaction force plate 1, and a visual positioning module 12 is arranged on the other side. A rectangle is formed by enclosing among the plurality of springs 4. The spring 4 is preferably a high-strength spring, which is made of materials such as high-quality alloy steel or stainless steel, and has a stiffness greater than 50 N / mm. The upper reaction force plate 2 is fixedly installed on the top of the spring 4, and the upper reaction force plate 2 and the lower reaction force plate 1 are connected through the spring 4, and the upper reaction force plate 2 and the lower reaction force plate 1 are arranged in parallel.

[0031] As Figure 4 shown, the visual positioning module 12 includes a plurality of positioning points with different color shades and pattern sizes, and the pattern features of each positioning point are unique. Therefore, by collecting the pattern features of different positioning points, their positions can be quickly locked.

[0032] In a preferred but non-limiting embodiment of the present invention, a plurality of positioning points are arranged in a rectangular array, and each positioning point has a corresponding coordinate. From Figure 4 the view direction, the size of the positioning points gradually increases from left to right, and the color gradually becomes lighter, and the size of the positioning points gradually increases from top to bottom, and the color gradually becomes darker.

[0033] The replaceable strain sensing fixture 3 is arranged between the upper reaction force plate 2 and the lower reaction force plate 1, and the upper part of the replaceable strain sensing fixture 3 is detachably connected to the upper reaction force plate 2, and the lower part of the replaceable strain sensing fixture 3 is detachably connected to the lower reaction force plate 1. The replaceable strain sensing fixture 3 is provided with a clamping mouth for clamping the tensile test piece 7 of the cement-based material to be tested, and the size of the clamping mouth increases or decreases following the up and down movement of the upper reaction force plate 2. The dual-coupled balanced force application device 5 is arranged between the lower reaction force plate 1 and the upper reaction force plate 2, and is used to drive the upper reaction force plate 2 to move up or down, so as to adjust the size of the clamping mouth of the replaceable strain sensing fixture 3.

[0034] The dual-coupled balanced force application device 5 is arranged on the substrate and is connected to the tensile test piece 7 of the cement-based material to be tested, and is used to apply a tensile force to the replaceable strain sensing fixture 3.

[0035] In a preferred but non-limiting embodiment of the present invention, the dual-coupled balanced booster device 5 includes two jacks arranged in linkage. The two jacks are respectively arranged on the left and right sides of the replaceable strain sensing fixture 3, and are both fixedly installed on the top of the lower reaction plate 1 and are in contact with the upper reaction plate 2. The two jacks have exactly the same structure and size and are linked through a connecting rod assembly. Conventional electro-hydraulic servo universal testing machines need to be equipped with an additional oil source. Generally, the external dimensions of the additional oil source tank are 1.2m * 0.6m * 1m. The oil source is one of the reasons for inconvenience. The present invention uses a jack as the power source, does not require an additional oil source, nor does it require power supply, and can further reduce the volume of the system, thereby improving the convenience of the system.

[0036] The non-contact image strain measurement system 6 is magnetically fixed to the visual positioning module 12 of the lower reaction plate 1 through the magnetic attraction fixing module 66. The strain image test module 61 in the contact image strain measurement system 6 faces the cement-based material tensile specimen 7, is used to collect the image of the cement-based material tensile specimen 7, and corrects the image based on the visual positioning module 12 located on the substrate surface, and calculates the strain test result of the cement-based material tensile specimen 7 by using the corrected image.

[0037] As Figure 2 shown, the lower reaction plate 1 is composed of a lower plate body, a lower wedge strip 11 and a visual positioning module 12. The lower wedge strip 11 is fixedly arranged on the top of the lower plate body. The fixture-lower 32 in the replaceable strain sensing fixture 3 is provided with a first slot adapted to the outer shape of the lower wedge strip 11, and is detachably connected to the lower wedge strip 11 through the first slot and the lower wedge strip 11 in a plug-in fit manner.

[0038] Furthermore, two alignment prompt strips 111 are symmetrically arranged on both sides of the top edge of the lower wedge strip 11. The fixture-lower 32 has the same width as the lower wedge strip 11. When the two are not aligned, the alignment prompt strips 111 can be seen, and quick alignment can be achieved through the above method.

[0039] Even further, a data transmission lower contact-lower 112 is also arranged on the top of the lower wedge strip 11, which is used to contact and conduct with the data transmission upper contact-lower 322 located on the bottom surface of the slot of the fixture-lower 32.

[0040] The upper reaction plate 2 is composed of an upper plate body and an upper wedge strip 21. The upper wedge strip 21 is fixedly arranged on the bottom of the upper plate body. The fixture-upper 31 in the replaceable strain sensing fixture 3 is provided with a second slot adapted to the outer shape of the upper wedge strip 21, and is detachably connected to the upper wedge strip 21 through the second slot and the upper wedge strip 21 in a plug-in fit manner.

[0041] The structure and dimensions of the upper wedge bar 21 are the same as those of the lower wedge bar 11. The bottom of the upper wedge bar 21 is also provided with an alignment prompt bar 111 and a data transmission lower contact - upper 212, and their layout positions and connection methods are the same as those of the lower wedge bar 11, so they will not be repeated here.

[0042] The replaceable strain - sensing fixture 3 includes an upper fixture 31 and a lower fixture 32. The upper fixture 31 and the lower fixture 32 are symmetrically arranged and have exactly the same structure. The top of the lower fixture 32 is provided with a first clamping groove running through its front and back. The bottom of the upper fixture 31 is provided with a second clamping groove running through its front and back. The first clamping groove and the second clamping groove are symmetrically arranged and are respectively adapted to the shapes of the upper and lower ends of the cement - based material tensile specimen 7. One end of the cement - based material tensile specimen 7 is inserted into the first clamping groove, and the other end is inserted into the second clamping groove. By driving the upper fixture 31 to move upward through the dual - coupling balanced force - applying device 5, a tensile force can be applied to the cement - based material tensile specimen 7.

[0043] Furthermore, two built - in strain - sensing modules - lower 321 are symmetrically arranged on the inner walls of the opposite sides of the first clamping groove for sensing the strain of the cement - based material tensile specimen 7. Two data transmission upper contacts - lower 322 are symmetrically arranged on the wall surface of the first slot. Each data transmission upper contact - lower 322 is connected to the corresponding built - in strain - sensing module - lower 321 through a data transmission cable - lower 323. A data transmission lower contact - lower 112 is arranged at a position corresponding to the data transmission upper contact - lower 322 on the top surface of the lower wedge bar 11. When the lower wedge bar 11 is inserted into the first slot, the data transmission upper contact - lower 322 contacts the data transmission lower contact - lower 112, which is used to export the data of the built - in strain - sensing module - lower 321.

[0044] Similarly, two built - in strain - sensing modules - upper 311 are symmetrically arranged on the inner walls of the opposite sides of the second clamping groove. Two data transmission upper contacts - upper 312 are symmetrically arranged on the wall surface of the second slot. Each data transmission upper contact - upper 312 is connected to the corresponding built - in strain - sensing module - upper 311 through a data transmission cable - upper 313. A data transmission lower contact - upper 212 is arranged at a position corresponding to the data transmission upper contact - upper 312 on the bottom surface of the upper wedge bar 21. When the upper wedge bar 21 is inserted into the second slot, the data transmission upper contact - upper 312 contacts the data transmission lower contact - upper 212, which is used to export the data of the built - in strain - sensing module - upper 311.

[0045] Furthermore, both the data transmission lower contact - lower 112 and the data transmission lower contact - upper 212 are connected to the data display module 62 of the non - contact image strain measurement system 6 through wires, so as to display the data of the built - in strain - sensing module - upper 311 and the data of the built - in strain - sensing module - lower 321 through the data display module 62.

[0046] After applying a tensile force to the cement-based material tensile specimen 7 through the fixture-upper 31, the built-in strain sensing module-upper 311 can sense the compressive strain. When the magnitudes of the compressive strains measured by the two built-in strain sensing modules-upper 311 are equal, it indicates that the cement-based material tensile specimen is under an axial load at this time, and the tensile strength of the material obtained from the experiment is true and effective. When the magnitudes of the compressive strains measured by the two built-in strain sensing modules-upper 311 are not equal, it proves that the cement-based material tensile specimen is under an eccentric tensile load, and fine-tuning of the specimen position and the loading position is required.

[0047] As Figure 3 shown, the non-contact image strain measurement system 6 is composed of a strain image test module 61, a data display module 62, a downward-looking camera 63, a strain measurement system position adjustment module 64, a hollow splint 65, and a height-adjustable magnetic adsorption fixing module 66.

[0048] Among them, the strain image test module 61 is fixed on the upper surface of the hollow splint 65 through the strain measurement system position adjustment module 64. The strain image test module 61 has a test camera, and the test direction of the test camera is parallel to the plane where the upper surface of the hollow splint 65 is located and faces the cement-based material tensile specimen during the test. The strain image test module 61 is used to collect the image information of the cement-based material tensile specimen 7 and, using the DIC (Digital Image Correlation) principle, calculate the strain test result of the cement-based material tensile specimen 7.

[0049] There are four downward-looking cameras 63. The four downward-looking cameras 63 are arranged in a rectangle and fixed on the lower surface of the hollow splint 65. The four downward-looking cameras 63 are all electrically connected to the strain image test module 61. During the test, the downward-looking cameras face the visual positioning module 12. The test camera in the strain image test module 61 sends the collected image information of the cement-based material tensile specimen 7 to the four downward-looking cameras 63.

[0050] As Figure 5 shown, when there is an angle θ between the test surface of the cement-based material tensile specimen 7 and the test direction of the test camera, the four downward-looking cameras 63 refer to the positioning points of the visual positioning module to obtain the position information of the four vertices of the image collected by the test camera. Then, through calculation, the angle θ between the test direction of the strain image test module 61 and the test surface of the cement-based material tensile specimen 7 can be obtained, and the image collected by the test camera is corrected through the trapezoidal correction algorithm. The strain image test module 61 calculates the strain test result (material performance test result) of the cement-based material tensile specimen 7 through the corrected image information.

[0051] Using the non-contact image strain measurement system 6 of the present invention, when installing the cement-based material tensile specimen 7, the calibration process can be omitted. By using the downward-looking camera to correct the collected images, the image information of the cement-based material tensile specimen 7 after alignment can be obtained, making the system operation more convenient, the test more accurate, having lower requirements for the site flatness, and being able to serve higher-precision material property tests based on image recognition.

[0052] The data display module 62 is used to display the strain data of the unobservable plane in the replaceable strain sensing fixture 3 collected by the built-in strain sensing module - upper 311 and the built-in strain sensing module - lower 321, and display the corrected image recognition material property test results thereon.

[0053] There are four magnetic fixing modules 66, which are fixed at the four corners of the lower side of the hollow splint 65, and their heights are adjustable, and they are detachably connected to the lower reaction plate 1 through magnetic force.

[0054] The strain measurement system position adjustment module 64 includes a vertical adjustment knob 641 and a horizontal adjustment knob 642, and its function is to adjust the vertical position and horizontal position of the strain image test module 61 to facilitate better observation of the test surface of the cement-based material tensile specimen.

[0055] In a preferred but non-limiting embodiment of the present invention, both the vertical adjustment knob 641 and the horizontal adjustment knob 642 control the vertical position and horizontal position of the strain image test module 61 by controlling the gear-rack drive.

[0056] Embodiment 2 of the present invention provides a test method for the portable in-situ cement-based material tensile test system based on image recognition in Embodiment 1, including the following steps:

[0057] Step 1: Clamp the cement-based material tensile specimen 7 to be tested in the replaceable strain sensing fixture 3;

[0058] Specifically, place the cement-based material tensile specimen between the 31 fixture - upper and the 32 fixture - lower. The fixture - upper 31 is fixed to the upper reaction plate 2, and the fixture - lower 32 is fixed to the lower reaction plate 1. When the edge colors of the lower fixture alignment prompt bar 111 and the upper fixture alignment prompt bar 211 are not visible, the alignment step is completed. Apply a small clamping force by operating the dual-coupled balanced loading device 5 to apply a small pre-stress to the tensile specimen. When the built-in strain sensing module - upper 311 and the built-in strain sensing module - lower 321 generate small strain degrees and are displayed on the data display module 62 (for example, 50 με), the specimen installation and fixation step is completed.

[0059] Step 2: Adjust the position of the non-contact image strain measurement system 6 so that its test camera faces the cement-based material tensile specimen 7.

[0060] Specifically, first install the non-contact image strain measurement system 6 on the top of the lower reaction plate 1: Place the non-contact image strain measurement system 6 on the visual positioning module 12.

[0061] Secondly, vertically adjust the vertical adjustment knob 641 and the horizontal adjustment knob 642 to align the center of the camera of the strain image test module 61 with the tensile specimen.

[0062] Step 3: Apply a tensile force to the replaceable strain sensing fixture 3 through the dual-coupled balanced force application device 5 to stretch the cement-based material tensile specimen 7.

[0063] Specifically, by operating the dual-coupled balanced force application device 5, apply a force between the lower reaction plate 1 and the upper reaction plate 2, and this force acts on the cement-based material tensile specimen for loading.

[0064] In view of the possible brittle failure of the cement-based material tensile specimen after reaching the peak stress, utilize the high strength and high stiffness characteristics of the spring 4 to provide additional support to achieve slow continuous loading. Through the data collected by the built-in strain sensing module - upper 311 and the built-in strain sensing module - lower 321, the descending section of the stress-strain full curve reflecting the actual mechanical properties of the specimen can be measured. And the strain time-varying curves collected by the built-in strain sensing module - upper 311 and the built-in strain sensing module - lower 321 are displayed on the data display module 62.

[0065] Step 4: Collect images of the cement-based material tensile specimen 7 through the non-contact image strain measurement system 6, correct the images based on the visual positioning module 12, and use the corrected images to calculate the strain test results of the cement-based material tensile specimen 7.

[0066] Specifically, collect images of the mud-based material tensile specimen 7 through the strain image test module 61, and send the images to the lower-view camera 63. Adjust the visual positioning module 12 through the recognition and positioning of the lower-view camera 63 to automatically correct the images collected by the strain image test module 61. The strain image test module 61 uses the automatically corrected images for non-contact strain measurement and synchronously displays the measurement results on the data display module 62.

[0067] The beneficial effects of the present invention are as follows. Compared with the prior art, by setting up a visual positioning module and a non-contact image strain test module, when clamping a cement-based material tensile specimen to be tested, it is not necessary to spend a lot of time calibrating it, and the pattern information of the cement-based material tensile specimen can be directly collected by the strain image test module. During the test, based on the pattern information of the visual positioning module, the pattern information of the cement-based material tensile specimen collected by the strain image test module is corrected to obtain the corrected pattern information, and then the strain image test module uses the corrected pattern information to calculate the strain test result of the cement-based material tensile specimen. The present invention not only improves the test efficiency of the cement-based material tensile specimen, but also has higher accuracy, simpler operation, lower requirement for the flatness of the site, and can be applied to emergency scenarios when using the correction algorithm compared with manual calibration.

[0068] In addition, by adopting a two-link coupling balance force application device composed of a jack as the power source and cooperating with a spring, compared with the traditional electro-hydraulic servo universal testing machine, there is no need to additionally increase the oil source or supply power, greatly reducing the system volume, making the system structure compact and convenient, and more convenient for transportation. It can be applied to emergency rescue occasions and improve the effectiveness of disaster prevention and control.

[0069] Furthermore, in order to make the strain test result more accurate, the present invention sets an in-built strain sensing module - upper and an in-built strain sensing module - lower in the replaceable strain sensing fixture. By directly contacting the cement-based material tensile specimen with the in-built strain sensing module - upper and the in-built strain sensing module - lower, the strain information of the specimen is obtained, and the position of the specimen is adjusted through this strain information, which is beneficial to improving the accuracy of the test result.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the specific implementation manners of the present invention can still be modified or equivalently replaced, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. In-situ cement-based material tensile test system based on image recognition, comprising: A substrate and a replaceable strain-sensing fixture (3), characterized in that: The replaceable strain-sensing fixture (3) is arranged on the substrate and is used for clamping a cement-based material tensile specimen (7) to be tested; The in-situ cement-based material tensile test system further includes: A dual-coupled balanced force-applying device (5), arranged on the substrate and connected to the cement-based material tensile specimen (7) to be tested, for applying a tensile force to the replaceable strain-sensing fixture (3); A non-contact image strain measurement system (6), arranged on the substrate and located on one side of the replaceable strain-sensing fixture (3), for collecting images of the cement-based material tensile specimen (7), correcting the images based on a visual positioning module (12) located on the surface of the substrate, and calculating the strain test results of the cement-based material tensile specimen (7) by using the corrected images.

2. The in-situ cement-based material tensile test system based on image recognition according to claim 1, characterized in that: The substrate includes: A lower reaction force plate (1), with a spring (4) arranged on one side of its upper surface and a visual positioning module (12) arranged on the other side; An upper reaction force plate (2), arranged on the top of the spring (4) and parallel to the lower reaction force plate (1); Wherein, the replaceable strain-sensing fixture (3) and the dual-coupled balanced force-applying device (5) are both arranged between the upper reaction force plate (2) and the lower reaction force plate (1); the non-contact image strain measurement system (6) is arranged on the top of the lower reaction force plate (1) and above the visual positioning module (12).

3. The in-situ cement-based material tensile test system based on image recognition according to claim 2, characterized in that: The dual-coupled balanced force-applying device (5) includes: Two jacks respectively arranged on the left and right sides of the replaceable strain-sensing fixture (3); Each jack has its bottom fixedly connected to the lower reaction force plate (1) and its top in contact with the upper reaction force plate (2), for jacking up the upper reaction force plate (2) to apply a tensile force to the replaceable strain-sensing fixture (3); wherein, the two jacks have the same structure and size and are linked through a connecting rod assembly.

4. The in-situ cement-based material tensile test system based on image recognition according to claim 2, characterized in that: The replaceable strain-sensing fixture (3) includes: A fixture-lower (32), detachably connected to the upper surface of the lower reaction force plate (1); a first clamping groove penetrating through its opposite side surfaces is arranged on the top of the fixture-lower (32), A fixture-upper (31), detachably connected to the lower surface of the upper reaction force plate (2); a second clamping groove penetrating through its opposite side surfaces is arranged on the bottom of the fixture-upper (31): Wherein, the fixture-upper (31) and the fixture-lower (32) are symmetrically arranged, and the first clamping groove and the second clamping groove respectively match the shapes of the two ends of the cement-based material tensile specimen (7), for inserting and clamping the two ends of the cement-based material tensile specimen (7).

5. The in-situ cement-based material tensile test system based on image recognition according to claim 4, characterized in that: The top of the lower reaction force plate (1) is provided with a lower wedge strip (11); a first slot adapted to the outer shape of the lower wedge strip (11) is provided in the lower fixture (32) of the replaceable strain sensing fixture (3), and the first slot is used for detachably connecting with the lower wedge strip (11); The bottom of the upper reaction force plate (2) is provided with an upper wedge strip (21); a second slot adapted to the outer shape of the upper wedge strip (21) is provided in the upper fixture (31) of the replaceable strain sensing fixture (3), and the second slot is used for detachably connecting with the upper wedge strip (21).

6. The in-situ cement-based material tensile test system based on image recognition according to claim 5, characterized in that: Two alignment prompt strips (111) are symmetrically arranged on both side edges of the top of the lower wedge strip (11) for prompting whether the lower wedge strip (11) is centered with the lower fixture (32); Two alignment prompt strips (111) are also symmetrically arranged on both side edges of the bottom of the upper wedge strip (21) for prompting whether the upper wedge strip (21) is centered with the upper fixture (31).

7. The in-situ cement-based material tensile test system based on image recognition according to claim 5, characterized in that: Two built-in strain sensing modules-lower (321) are symmetrically arranged on the opposite side walls of the first clamping groove for sensing the strain of the cement-based material tensile specimen (7); two data transmission upper contacts-lower (322) are symmetrically arranged on the opposite side walls of the first slot, and each data transmission upper contact-lower (322) is connected to the corresponding built-in strain sensing module-lower (321) through a data transmission cable-lower (323); A data transmission lower contact-lower (112) is arranged at a position corresponding to the data transmission upper contact-lower (322) on the top surface of the lower wedge strip (11) for contacting with the data transmission upper contact-lower (322) when the lower wedge strip (11) is inserted into the first slot and importing the data of the built-in strain sensing module-lower (321) into the data display module (62) of the non-contact image strain measurement system (6).

8. The in-situ cement-based material tensile test system based on image recognition according to claim 7, characterized in that: Two built-in strain sensing modules-upper (311) are symmetrically arranged on the opposite side walls of the second clamping groove, two data transmission upper contacts-upper (312) are symmetrically arranged on the opposite side walls of the second slot, and each data transmission upper contact-upper (312) is connected to the corresponding built-in strain sensing module-upper (311) through a data transmission cable-upper 313; A data transmission lower contact-upper (212) is arranged at a position corresponding to the data transmission upper contact-upper (312) on the bottom surface of the upper wedge strip (21) for contacting with the data transmission upper contact-upper (312) when the upper wedge strip (21) is inserted into the second slot and importing the data of the built-in strain sensing module-upper (311) into the data display module (62) of the non-contact image strain measurement system (6).

9. The in-situ cementitious material tensile test system based on image recognition according to claim 2, wherein: The non-contact image strain measurement system (6) includes: A hollow clamping plate (65) detachably disposed on the top of the lower reaction plate (1) and above the visual positioning module (12); Four downward-looking cameras (63) arranged in a rectangle and disposed on the lower surface of the hollow clamping plate (65); the four downward-looking cameras (63) are connected to the strain image test module (61) for collecting the pattern information of the visual positioning module (12) and correcting the image information collected by the strain image test module (61) based on the visual positioning module (12); A strain image test module (61) movably disposed on the top of the hollow clamping plate (65) for collecting images of the cementitious material tensile specimen (7) and calculating the strain test result of the cementitious material tensile specimen (7) based on the corrected image information of the downward-looking camera (63); A data display module (62) disposed on the hollow clamping plate (65) and connected to the strain image test module (61) for displaying the strain test result.

10. The in-situ cementitious material tensile test system based on image recognition according to claim 9, wherein: The visual positioning module (12) includes: a plurality of positioning points with different shades of color and different pattern sizes; the plurality of positioning points are arranged in a rectangular array.

11. The in-situ cementitious material tensile test system based on image recognition according to claim 9, wherein: The non-contact image strain measurement system (6) further includes: A strain measurement system position adjustment module (64) disposed on the top of the hollow clamping plate (65) with the strain image test module (61) mounted on its top for adjusting the position and test height of the strain image test module (61) on the hollow clamping plate (65).

12. The in-situ cementitious material tensile test system based on image recognition according to claim 9, wherein: The non-contact image strain measurement system (6) further includes: A magnetic adsorption fixing module (66) disposed on the lower surface of the hollow clamping plate (65) for detachably connecting the hollow clamping plate (65) to the lower reaction plate (1).

13. A method for in-situ tensile test of cement-based materials based on image recognition, which is applied to the in-situ tensile test system of cement-based materials based on image recognition according to any one of claims 1-12, characterized in that, Including the following steps: Clamp the cementitious material tensile specimen (7) to be tested on the replaceable strain sensing fixture (3); Adjust the position of the non-contact image strain measurement system (6) so that its test camera faces the cementitious material tensile specimen (7); Apply a tensile force to the replaceable strain sensing fixture (3) through the dual-coupled balanced force application device (5) to stretch the cementitious material tensile specimen (7); Collect images of the cementitious material tensile specimen (7) through the non-contact image strain measurement system (6), correct the images based on the visual positioning module (12), and calculate the strain test result of the cementitious material tensile specimen (7) using the corrected images.

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