360-degree three-dimensional DIC measuring device based on rotary double-camera synchronous triggering

Abstract

The invention discloses a 360-degree three-dimensional DIC measuring device based on rotary double-camera synchronous triggering, which comprises an RMT testing machine and an upper computer, and is characterized in that a fixed base, a rotary base, two cameras and a triggering mechanism are arranged in a loading cavity of the RMT testing machine; the rotary base is mounted above the fixed base; moreover, a hole is formed in the center of the rotating base, and a loading shaft and a sample of the RMT testing machine can penetrate through the hole; the triggering mechanism comprises a photoelectric sensor and a plurality of triggering pieces; the photoelectric sensor is fixedly arranged on the fixed base, and the two cameras and the plurality of trigger pieces are fixedly arranged at the edge of the rotary base; the rotating base is provided with a wireless module, and the motor, the photoelectric sensor, the two cameras and the plurality of trigger pieces which are arranged on the rotating base are all connected with the wireless module, so that wireless communication with an upper computer is achieved. The device effectively solves the problems of synchronism, precision and stability of three-dimensional deformation measurement of the rock sample in a narrow space, and is suitable for high-precision dynamic monitoring of a rock mechanical test.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics testing, and in particular to a 360-degree three-dimensional DIC measuring device based on synchronous triggering of rotating dual cameras. Background Art

[0002] In uniaxial compression testing of rock mechanics, precise measurement of the three-dimensional deformation of the specimen surface and the crack propagation process along its circumferential axis is crucial for studying the mechanical behavior of materials. Three-dimensional digital image correlation (3D-DIC), a non-contact measurement method, efficiently acquires full-field displacement and strain data. Currently, two main approaches are used to perform 3D-DIC measurements on specimens. The first is a multi-camera surround monitoring approach. To achieve 360° monitoring of the specimen, six to eight high-resolution cameras are typically arranged evenly around the specimen's circumference, equipped with a dedicated synchronization controller to ensure synchronized triggering of each camera with microsecond-level timing accuracy. This significantly increases the complexity and cost of the system. However, in practical applications, the size of the loading chamber limits the space available for camera installation. Conventional multi-camera arrangements are prone to interference with the loading frame, making them impractical for proper installation and use. Furthermore, differences in trigger signal transmission delays between the multiple cameras can lead to misalignment when stitching the circumferential displacement field, making it difficult to meet the requirements for high-precision monitoring of rock crack propagation.

[0003] The second method is the reflector-assisted imaging method. A reflector group is used to divide the field of view of a single camera into multiple angles, thereby realizing observation of different angles of the sample. This reduces the number of cameras used to a certain extent, and usually 3-4 cameras are required. However, this method has many problems. The mirror curvature error and installation angle deviation of the reflector will significantly increase the image distortion rate and affect the measurement accuracy. The overlap rate between adjacent mirror images is difficult to control, and monitoring blind spots may occur. In addition, due to the uneven reflectivity of the mirror, the grayscale gradient of the collected image is distorted, which increases the image matching error and makes it impossible to accurately distinguish the sub-pixel displacement of the rock crack, which seriously restricts the fine monitoring of the evolution of rock cracks.

[0004] In view of the limitations of existing technologies, there is an urgent need for a three-dimensional deformation measurement device with a compact structure, low cost and high synchronization accuracy to solve the problems of space limitations, poor synchronization and dynamic calibration failure in existing technologies, and provide strong technical support for the development of the field of rock mechanics. Summary of the Invention

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A 360° three-dimensional DIC measurement device based on synchronous triggering of a rotating dual camera includes an RMT test machine and a host computer, wherein a fixed base, a rotating base, two cameras and a trigger mechanism are installed in the loading chamber of the RMT test machine;

[0007] The rotating base is installed above the fixed base, and the rotating base is equipped with a motor so that the rotating base can rotate under the control of the motor;

[0008] Furthermore, the central opening of the rotating base is used for the loading shaft and the specimen of the RMT testing machine to pass through;

[0009] The trigger mechanism includes a photoelectric sensor and a plurality of trigger pieces;

[0010] The photoelectric sensor is arranged on the fixed base, and the two cameras and a plurality of trigger plates are fixedly arranged on the edge of the rotating base;

[0011] The rotating base is equipped with a wireless module, and the motor, photoelectric sensor, two cameras and several trigger pieces configured on the rotating base are all connected to the wireless module, thereby realizing wireless communication with the host computer;

[0012] When each trigger piece rotates with the rotating base to the position of the photoelectric sensor, it can block and reflect the light beam emitted by the photoelectric sensor, thereby generating a pulse signal through the photoelectric sensor;

[0013] After the pulse signal is transmitted to the host computer, the host computer generates a control signal to trigger the exposure of the two cameras, and the image data collected by the two cameras is wirelessly transmitted to the host computer.

[0014] In some embodiments, each camera is equipped with a high-speed shutter, and a piezoelectric ceramic micro-displacer is installed on the lens of each camera. The piezoelectric ceramic micro-displacer is used to adjust the focal length of the camera lens in real time according to the rotation speed.

[0015] In some embodiments, when adjusting the focal length of the camera lens, the displacement to be compensated is calculated using the following formula:

[0016] Δx=m·ω 2 ·r / k;

[0017] Where m is the mass of the lens, ω is the angular velocity of rotation, r is the radius of rotation, and k is the stiffness of the piezoelectric ceramic;

[0018] In the host computer, after the displacement that needs to be compensated is calculated using the above formula, the control signal is wirelessly transmitted to the piezoelectric ceramic micro-displacer. The piezoelectric ceramic micro-displacer drives the lens to move slightly along the axial direction, thereby offsetting the image offset caused by centrifugal motion and ensuring that the optical axis is aligned with the sample surface.

[0019] In some embodiments, an LED light source is further included. The LED light source is fixedly mounted on the inner wall of the loading chamber of the RMT testing machine, and the LED light source is annular and arranged around the sample.

[0020] In some embodiments, a dynamic calibration module is further included, wherein the dynamic calibration module includes a fixed calibration target and a follow-up calibration target;

[0021] The fixed calibration targets are evenly arranged along the circumferential direction on the loading axis of the RMT testing machine and are used to calibrate the intrinsic and extrinsic parameters of the two cameras;

[0022] The follow-up calibration target is evenly arranged on the surface of the sample along the circumferential direction, and deforms or moves synchronously with the sample, so as to capture the actual displacement and deformation of the sample in real time.

[0023] In some embodiments, the patterns of the fixed calibration target and the moving calibration target are checkerboard patterns and / or circular marking dots;

[0024] The fixed calibration target is evenly attached to the loading shaft of the RMT tester using reflective stickers, and / or a pattern is evenly formed on the surface of the loading shaft of the RMT tester by spraying;

[0025] The follow-up calibration target is evenly pasted on the surface of the sample using reflective stickers, and / or a pattern is evenly formed on the surface of the sample by spraying.

[0026] In some embodiments, the fixed calibration target is specifically used to collect images of the fixed calibration target at six angles of 0°, 60°, 120°, 180°, 240°, and 300° by two cameras before the test of the sample begins, collecting 10 frames at each angle, and analyzing and processing the collected images to calibrate the intrinsic and extrinsic parameters of the two cameras;

[0027] The following calibration target is specifically used to change synchronously with the compression of the sample during the test process of the sample. The two cameras automatically capture an image of the following calibration target every 10 seconds to update the calibration parameters and correct the coordinate system offset caused by the deformation of the sample.

[0028] In some embodiments, the number of the trigger pieces is three, and the three trigger pieces are evenly distributed on the edge of the rotating base;

[0029] The trigger piece is made of a magnetic material with a black oxide coating on the surface to improve the absorption rate of infrared light, so that the photoelectric sensor can detect significant light intensity changes from the reflected light, thereby generating a pulse signal.

[0030] In some embodiments, a plurality of screw holes are provided at the edge of the rotating base, and the two cameras and a plurality of trigger plates are fixedly mounted at the screw holes by screws, so that the optical axis angle between the two cameras can be adjusted by changing the mounting position.

[0031] In some embodiments, during operation, the host computer is also used to monitor the time difference between the photoelectric sensor generating a pulse signal and the exposure of the two cameras to collect image data. If the time difference is greater than 0.3ms for two consecutive times, the host computer automatically triggers an audible and visual alarm and suspends operation, prompting the operator to check and adjust.

[0032] Compared with the existing technology, the 360° 3D DIC measurement device based on synchronous triggering of rotating dual cameras provided by the present invention drives the dual cameras to take periodic images by rotating the base. Combined with a non-contact trigger mechanism and calibration target, it effectively solves the synchronization, accuracy and stability problems of 3D deformation measurement of rock specimens in confined spaces. It has the advantages of compact structure, low cost, easy deployment, high synchronization accuracy and strong anti-interference ability. It is suitable for high-precision dynamic monitoring of rock mechanics tests, especially for high-precision monitoring of dynamic 3D deformation and crack evolution of cylindrical rock specimens in uniaxial compression tests in confined spaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras provided by the present invention;

[0034] Figure 2 Schematic diagram of the rotating base and related structures.

[0035] Description of Figure Numbers:

[0036] 1. RMT testing machine; 2. Camera; 3. Rock sample; 4. Trigger plate; 5. Follow-up calibration target; 6. Fixed calibration target; 7. Photoelectric sensor; 8. Rotating base; 9. LED light source; 10. Fixed base; 11. Host computer; 12. Piezoelectric ceramic micro-displacer. DETAILED DESCRIPTION

[0037] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the following further describes how the present invention is implemented in conjunction with specific implementation methods.

[0038] Reference Figure 1 and Figure 2As shown in a specific embodiment, the present invention provides a 360° three-dimensional DIC measurement device based on synchronous triggering of a rotating dual-camera, comprising an RMT testing machine 1 and a host computer 11, wherein a fixed base 10, a rotating base 8, two cameras 2 and a trigger mechanism are installed in the loading chamber of the RMT testing machine 1; the rotating base 8 is installed above the fixed base 10, and the rotating base 8 is equipped with a motor so that the rotating base 8 can rotate under the control of the motor; and the central opening of the rotating base 8 is used for the loading shaft of the RMT testing machine 1 and the rock sample 3 to pass through; the trigger mechanism includes a photoelectric sensor 7 and a plurality of trigger plates 4; the photoelectric sensor 7 is fixedly arranged on the fixed base 10, and the position On the outside of the rotating base 8, two cameras 2 and several trigger pieces 4 are fixedly arranged at the edge of the rotating base 8; the rotating base 8 is equipped with a wireless module, and the motor, photoelectric sensor 7, two cameras 2 and several trigger pieces 4 configured on the rotating base 8 are all connected to the wireless module, thereby realizing wireless communication with the host computer 11; when each trigger piece 4 rotates to the position of the photoelectric sensor 7 with the rotating base 8, it can block and reflect the light beam emitted by the photoelectric sensor 7, and then generate a pulse signal through the photoelectric sensor 7; after the pulse signal is transmitted to the host computer 11, the host computer 11 generates a control signal to trigger the exposure of the two cameras 2, and the image data collected by the two cameras 2 are wirelessly transmitted to the host computer 11.

[0039] RMT testing machine 1, which can be the existing RMT-150C rock mechanics testing system, is a digitally controlled electro-hydraulic servo testing machine primarily used for mechanical property testing of materials such as rock and concrete. It can perform a variety of rock mechanics tests, including uniaxial compression, uniaxial indirect tension, triaxial compression, and shear. RMT testing machine 1 is connected to host computer 11 via a wired or wireless connection. When host computer 11 generates a control signal to trigger exposure of the two cameras 2, it simultaneously sends a signal to RMT testing machine 1 to record the current operating parameters, achieving hard synchronization and ensuring simultaneous and accurate data acquisition.

[0040] Specifically, the rotating base 8 can be made of high-strength aluminum alloy; its rotation is driven by a harmonic reduction motor, ensuring smooth and precise rotation. It is understood that the rotation principle of the rotating base 8 is similar to that of existing hollow shaft rotating platforms. The motor can be located on the lower side of the rotating base 8 so as not to affect the central opening. Driven by the motor, the rotation of the rotating base 8 is controlled via a gear transmission. Furthermore, the spatial position of the trigger plates 4, the photoelectric sensor 7, and the two cameras 2 do not overlap, ensuring no mechanical interference and ensuring stable operation of the device.

[0041] Traditional multi-camera measurement methods require 6-8 cameras, while reflector methods require 3-4 cameras, resulting in high equipment costs. The present invention only requires two cameras, and by rotating the base 8 to cover a 360° field of view, it significantly reduces the number of cameras and equipment costs. It also eliminates the need for a complex reflector assembly, simplifying the system structure.

[0042] Furthermore, the traditional multi-camera surround layout easily interferes with the loading frame, and the reflector method requires additional installation space. The present invention integrates the dual cameras 2 and the trigger mechanism via a rotating base 8, allowing them to be directly embedded into the loading chamber of the RMT tester 1, effectively avoiding spatial interference and making it particularly suitable for testing environments in confined spaces.

[0043] Preferably, each camera 2 is equipped with a high-speed shutter, and a piezoelectric ceramic micro-displacer 12 is installed on the lens of each camera 2. The piezoelectric ceramic micro-displacer 12 is used to adjust the focal length of the lens of the camera 2 in real time according to the rotation speed.

[0044] The high-speed shutter of camera 2 needs to match the rotation speed of the rotating base to ensure that the images taken at high-speed rotation are free of ghosting and accurately capture the instantaneous state of the sample.

[0045] The piezoelectric ceramic microdisplacer 12 generates deformation by applying voltage, achieving high-precision displacement control from nanometers to micrometers. The piezoelectric ceramic microdisplacer 12 can utilize the existing P-625.1CD closed-loop piezoelectric ceramic driver, which has a displacement range of 0-100 microns, a resolution of 0.03nm, and a response frequency >1kHz, making it suitable for high-speed dynamic compensation.

[0046] Specifically, when adjusting the focal length of the camera 2, the displacement to be compensated is calculated using the following formula:

[0047] Δx=m·ω 2 ·r / k;

[0048] Where m is the lens mass, ω is the angular velocity of rotation, r is the rotation radius, and k is the piezoelectric ceramic stiffness. In the host computer 11, after calculating the displacement to be compensated using the above formula, the control signal is wirelessly transmitted to the piezoelectric ceramic micro-displacer 12. The piezoelectric ceramic micro-displacer 12 drives the lens to slightly shift axially, thereby offsetting the image offset caused by centrifugal motion and ensuring that the optical axis is aligned with the surface of the rock sample 3. This, in turn, ensures image stability and clarity, meeting the requirements of sub-pixel crack monitoring.

[0049] In this embodiment, the rotation radius r is approximately 20 cm, and the rotation speed of the rotating base 8 can be adjusted between 0.1 and 5 rpm as needed. The angular velocity ω is calculated based on this. The lens mass can be measured before the test, and the piezoelectric ceramic stiffness is determined based on the model of the piezoelectric ceramic micro-displacer 12 used. Furthermore, the piezoelectric ceramic micro-displacer 12 has a compensation frequency of 200 Hz and a dynamic adjustment range of ±0.05 mm, effectively compensating for image offset caused by centrifugal motion.

[0050] Preferably, an LED light source 9 is further included. The LED light source 9 is fixedly mounted on the inner wall of the loading chamber of the RMT testing machine 1. The LED light source 9 is annular and arranged around the rock sample 3, without contacting the rotating base 8. The LED light source 9 can be tilted at an angle of 60°, effectively reducing interference from reflections on the surface of the rock sample 3 and improving image quality.

[0051] In traditional solutions, high-speed rotation or vibration can cause image smearing, making it difficult to capture sub-pixel cracks. The present invention uses a high-speed shutter, an LED light source 9, and dynamic compensation with a piezoelectric ceramic micro-displacer 12 to effectively eliminate centrifugal motion blur and accurately resolve sub-pixel displacement of rock cracks, providing a powerful guarantee for precise monitoring of crack evolution.

[0052] Preferably, a dynamic calibration module is also included, which includes a fixed calibration target 6 and a follow-up calibration target 5; the fixed calibration target 6 is evenly arranged along the circumferential direction on the loading axis of the RMT testing machine 1, and is used to calibrate the internal parameters (such as focal length, distortion coefficient) and external parameters (such as the spatial position relationship between the camera 2 and the rock sample 3) of the two cameras 2, providing basic parameters for subsequent image processing and data analysis; the follow-up calibration target 5 is evenly arranged along the circumferential direction on the surface of the rock sample 3, and deforms or moves synchronously with the rock sample 3, and is used to capture the actual displacement and deformation of the rock sample 3 in real time, so as to realize dynamic monitoring of the sample deformation process.

[0053] Furthermore, the patterns of the fixed calibration target 6 and the follow-up calibration target 5 are checkerboard patterns and / or circular marking points; the fixed calibration target 6 is evenly pasted on the loading shaft of the RMT testing machine 1 using reflective stickers, and / or a pattern is evenly formed on the surface of the loading shaft of the RMT testing machine 1 by spraying; the follow-up calibration target 5 is evenly pasted on the surface of the rock sample 3 using reflective stickers, and / or a pattern is evenly formed on the surface of the rock sample 3 by spraying.

[0054] The fixed calibration target 6 is specifically used to collect images of the fixed calibration target 6 at six angles of 0°, 60°, 120°, 180°, 240°, and 300° before the test of the rock sample 3 begins. Ten frames are collected at each angle. The collected images are analyzed and processed to calibrate the internal and external parameters of the two cameras 2.

[0055] The follow-up calibration target 5 is specifically used to change synchronously with the compression of the rock sample 3 during the test process of the rock sample 3. The two cameras 2 automatically capture an image of the follow-up calibration target 5 every 10 seconds to update the calibration parameters and correct the coordinate system offset caused by the deformation of the rock sample 3.

[0056] Traditional calibration targets, once fixed, cannot adjust to specimen deformation, rendering calibration parameters ineffective. During the loading process, the present invention analyzes the displacement changes of the follower calibration target 5 to dynamically compensate for coordinate system offsets caused by overall specimen movement and deformation, improving the accuracy of full-field strain calculations. This eliminates the need for frequent test interruptions and recalibration. Dynamic feedback from the follower calibration target 5 enables real-time calibration during loading, effectively improving test efficiency and data reliability.

[0057] Preferably, the number of trigger pieces 4 is three, and the three trigger pieces 4 are evenly distributed at the edge of the rotating base 8, with a circumferential interval of 120°; the trigger pieces 4 are made of a magnetic material (such as neodymium iron boron or ferrite) with a black oxide coating on the surface to improve the absorption rate of infrared light, so that the photoelectric sensor 7 can detect significant changes in light intensity from the reflected light, thereby generating a pulse signal.

[0058] Preferably, multiple screw holes (not shown) are provided on the edge of the rotating base 8, and the two cameras 2 and the plurality of trigger plates 4 are fixedly mounted at the screw holes by screws. This allows the optical axis angle between the two cameras 2 to be adjusted by changing the mounting position. For example, the optical axis angle between the two cameras 2 can be adjusted within a range of 60° to 90° to optimize the viewing angle of the rock sample 3 as needed.

[0059] Preferably, when working, the host computer 11 is also used to monitor the time difference between the photoelectric sensor 7 generating a pulse signal and the two cameras 2 exposing and collecting image data. If the time difference is greater than 0.3ms for two consecutive times, the host computer 11 automatically triggers an audible and visual alarm and suspends operation, prompting the operator to check and adjust.

[0060] Traditional multi-camera trigger signal transmission delays vary significantly, leading to errors in the splicing of the circumferential displacement field. The present invention uses non-contact hard triggering of the trigger plate 4 and the photoelectric sensor 7 to ensure signal delays of less than 0.3ms, ensuring strict spatiotemporal alignment of multi-angle images and meeting the requirements of high-precision monitoring.

[0061] In a specific embodiment, when using the 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras provided by the present invention to conduct an experiment, the following steps may be included:

[0062] Step 1: Accurately install the rotating base 8 in the loading chamber of the RMT testing machine 1, ensuring that its central opening is coaxial with the loading axis of the RMT testing machine 1 to ensure accurate placement and uniform force on the rock sample 3; and, pre-install the photoelectric sensor 7 on the fixed base 10, install two cameras 2 and three trigger plates 4 on the rotating base 8, complete the circuit connection, and adjust the optical axis angle of the two cameras 2 according to actual needs to obtain the best observation effect.

[0063] Step 2: Paste high-precision checkerboard and circular marking points on the loading axis of the RMT testing machine 1 as a fixed calibration target 6; evenly spray the speckle pattern on the surface of the rock sample 3 to provide abundant feature points as a follow-up calibration target 5 to facilitate subsequent image matching and displacement calculation; place the processed cylindrical rock sample 3 at the center of the loading axis of the RMT testing machine 1, start the preview mode of the LED light source 9 and the camera 2, and carefully adjust the pitch angle of the camera 2 to ensure that the rock sample 3 completely covers the field of view of the two cameras 2, providing a clear and complete picture for subsequent image acquisition.

[0064] Step 3: Adjust the position of rotating base 8 so that two cameras 2 capture images of fixed calibration target 6 at six angles: 0°, 60°, 120°, 180°, 240°, and 300°. Capture 10 frames at each angle to obtain sufficient image data. By analyzing and processing the captured images, the intrinsic and extrinsic parameters of camera 2 are precisely calibrated, providing accurate parameter support for subsequent 3D deformation measurement.

[0065] Step 4: Start rotating base 8 at a preset speed and monitor the time difference between the pulse signal output by photoelectric sensor 7 and the exposure signal from camera 2, ensuring that the delay is less than 0.3ms to achieve precise synchronization control. If the time difference exceeds 0.3ms twice in a row, host computer 11 will automatically trigger an audible and visual alarm and suspend operation, prompting the operator to check and adjust the test to ensure the accuracy and reliability of the test.

[0066] Step 5: Activate the uniaxial compression test function of RMT testing machine 1. Rotating base 8 rotates at a constant speed, driving two cameras 2 to trigger an exposure every 120° and synchronously record image data. During this process, the high-speed shutter, LED light source 9, and piezoelectric ceramic micro-displacer 12 work together to ensure the captured images are clear and free of smear, meeting the requirements of sub-pixel crack monitoring.

[0067] Step 6: During the uniaxial compression test, tracking calibration target 5 changes synchronously with the compression of rock specimen 3. The camera automatically captures an image of tracking calibration target 5 with each exposure, updating calibration parameters in real time to accurately correct for coordinate system offsets caused by the deformation of rock specimen 3. Dynamic feedback from tracking calibration target 5 enables real-time calibration during the test, eliminating the need for frequent test interruptions and recalibration. This effectively improves the accuracy of full-field strain calculations and ensures the reliability of test data.

[0068] In summary, the 360° 3D DIC measurement device based on synchronous triggering of rotating dual cameras provided by the present invention effectively solves the synchronization, accuracy, and stability issues of 3D deformation measurement of rock specimens in confined spaces by driving the dual cameras for periodic shooting via a rotating base and combining structures such as a non-contact trigger mechanism and a calibration target. The device has the advantages of compact structure, low cost, easy deployment, high synchronization accuracy, and strong anti-interference performance. It is suitable for high-precision dynamic monitoring of rock mechanics tests, and is particularly suitable for high-precision monitoring of dynamic 3D deformation and crack evolution of cylindrical rock specimens in uniaxial compression tests in confined spaces.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should all be covered by the scope of the claims of the present invention.

Claims

1. A 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras, characterized in that: The invention comprises an RMT testing machine (1) and a host computer (11), wherein a fixed base (10), a rotating base (8), two cameras (2) and a trigger mechanism are installed in a loading chamber of the RMT testing machine (1); The rotating base (8) is installed above the fixed base (10), and the rotating base (8) is equipped with a motor so that the rotating base (8) can rotate under the control of the motor; Furthermore, the central opening of the rotating base (8) is used for allowing the loading shaft of the RMT testing machine (1) and the rock sample (3) to pass through; The trigger mechanism includes a photoelectric sensor (7) and a plurality of trigger sheets (4); The photoelectric sensor (7) is fixedly arranged on a fixed base (10) and is located outside a rotating base (8); the two cameras (2) and a plurality of trigger plates (4) are fixedly arranged at the edge of the rotating base (8); The rotating base (8) is equipped with a wireless module, and the motor, photoelectric sensor (7), two cameras (2) and a plurality of trigger plates (4) equipped with the rotating base (8) are all connected to the wireless module, thereby realizing wireless communication with the host computer (11); When each trigger piece (4) rotates with the rotating base (8) to the position of the photoelectric sensor (7), it can block and reflect the light beam emitted by the photoelectric sensor (7), thereby generating a pulse signal through the photoelectric sensor (7); After the pulse signal is transmitted to the host computer (11), the host computer (11) generates a control signal to trigger the two cameras (2) to expose, and the image data collected by the two cameras (2) are wirelessly transmitted to the host computer (11).

2. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1 is characterized in that: Each camera (2) is equipped with a high-speed shutter, and a piezoelectric ceramic micro-displacer (12) is installed on the lens of each camera (2). The piezoelectric ceramic micro-displacer (12) is used to adjust the focal length of the lens of the camera (2) in real time according to the rotation speed.

3. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 2, characterized in that: When adjusting the focal length of the camera (2), the displacement to be compensated is calculated using the following formula: Δx=m·ω2·r / k; Where m is the mass of the lens, ω is the angular velocity of rotation, r is the radius of rotation, and k is the stiffness of the piezoelectric ceramic; In the host computer (11), after the displacement amount to be compensated is calculated by the above formula, the control signal is wirelessly transmitted to the piezoelectric ceramic micro-displacer (12). The piezoelectric ceramic micro-displacer (12) drives the lens to slightly move along the axial direction, thereby offsetting the image offset caused by the centrifugal motion and ensuring that the optical axis is aligned with the surface of the rock sample (3).

4. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1, characterized in that: It also includes an LED light source (9), which is fixedly arranged on the inner wall of the loading chamber of the RMT testing machine (1), and the LED light source (9) is annular and arranged around the rock sample (3).

5. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1, characterized in that: It also includes a dynamic calibration module, which includes a fixed calibration target (6) and a follow-up calibration target (5); The fixed calibration targets (6) are evenly arranged along the circumferential direction on the loading axis of the RMT testing machine (1) and are used to calibrate the internal and external parameters of the two cameras (2); The follow-up calibration target (5) is evenly arranged on the surface of the rock sample (3) along the circumferential direction, deforms or moves synchronously with the rock sample (3), and is used to capture the actual displacement and deformation of the rock sample (3) in real time.

6. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 5, characterized in that: The patterns of the fixed calibration target (6) and the follow-up calibration target (5) are checkerboard patterns and / or circular marking points; The fixed calibration target (6) is evenly attached to the loading shaft of the RMT test machine (1) using a reflective sticker, and / or a pattern is evenly formed on the surface of the loading shaft of the RMT test machine (1) by spraying; The follow-up calibration target (5) is evenly adhered to the surface of the rock sample (3) using a reflective sticker, and / or a pattern is evenly formed on the surface of the rock sample (3) by spraying.

7. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 5, characterized in that: The fixed calibration target (6) is specifically used for, before the test of the rock sample (3) begins, the two cameras (2) respectively collect images of the fixed calibration target (6) at six angles of 0°, 60°, 120°, 180°, 240°, and 300°, collecting 10 frames at each angle, and analyzing and processing the collected images to calibrate the internal and external parameters of the two cameras (2); The follow-up calibration target (5) is specifically used for synchronously changing with the compression of the rock sample (3) during the test process of the rock sample (3), and the two cameras (2) automatically capture an image of the follow-up calibration target (5) every 10 seconds to update the calibration parameters and correct the coordinate system offset caused by the deformation of the rock sample (3).

8. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1, characterized in that: The number of the trigger pieces (4) is three, and the three trigger pieces (4) are evenly distributed on the edge of the rotating base (8); The triggering piece (4) is made of a magnetic material with a black oxide coating on the surface to improve the absorption rate of infrared light, so that the photoelectric sensor (7) can detect significant light intensity changes from the reflected light, thereby generating a pulse signal.

9. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1, characterized in that: A plurality of screw holes are provided at the edge of the rotating base (8), and the two cameras (2) and the plurality of trigger plates (4) are fixedly mounted at the screw holes by screws, so that the optical axis angle between the two cameras (2) can be adjusted by changing the mounting position.

10. The 360° three-dimensional DIC measurement device based on synchronous triggering of rotating dual cameras according to claim 1, characterized in that: During operation, the host computer (11) is also used to monitor the time difference between the photoelectric sensor (7) generating a pulse signal and the two cameras (2) exposing and collecting image data. If the time difference is greater than 0.3ms for two consecutive times, the host computer (11) automatically triggers an audible and visual alarm and suspends operation, prompting the operator to check and adjust.

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