Method for using an observation platform with multi-dimensional dynamic and static combined loading and method for measuring dynamic mechanical parameters of a specimen by using the observation platform

Abstract

The present invention provides a method for using an observation platform with multi-dimensional dynamic and static combined loading and a method for measuring the dynamic mechanical parameters of a specimen by using the observation platform. The present invention is specifically designed for the erection of a high-speed camera, stability problems and the flexibility of experimental personnel to place specimens in a dynamic true triaxial electromagnetic Hopkinson bar test system, can effectively overcome spatial limitations and vibration effects, ensure that the camera maintains a stable position and angle during the test, thereby ensuring the accuracy and reliability of DIC observation, and at the same time ensuring the convenience of experimental personnel to install specimens, enabling quick replacement of specimens and improving the test efficiency. Based on the data obtained by the observation method provided by the present invention, the present invention constructs a dynamic Poisson's ratio formula applicable to two-dimensional dynamic loading scenarios, provides a key method for in-depth analysis of the mechanical behavior of materials, and fills the blank of accurate calculation of the dynamic Poisson's ratio of rock-like materials under two-dimensional dynamic loading.

Description

Technical Field

[0001] The present invention relates to the field of high-end equipment, and particularly to a method for using an observation platform in multi-dimensional dynamic and static combined loading and a method for measuring dynamic mechanical parameters of a specimen by using the observation platform. Background Art

[0002] The research on the dynamic mechanical response of rocks under medium and high strain rates (10 1 s -1 ~10 3 s -1 ) is generally carried out by using a split Hopkinson bar. The invention of patent number US20210318216A1 designs a dynamic true triaxial electromagnetic Hopkinson bar test system. Its innovation lies in that synchronous stress waves can be applied to six incident bars synchronously in three axes and six directions, ensuring that the arrival time error of the six stress waves is within 5 μs, and there is a high degree of consistency among the six stress waves, with the error guaranteed to be within 1%. At the same time, the system can apply true triaxial static loads in three axial directions while applying stress waves, and can achieve triaxial six-direction synchronous dynamic impact under true triaxial static load at most.

[0003] However, the system has a complex structure, diverse loading methods, a narrow operation space, and the loading frame will vibrate during operation, which makes it a major difficulty to use an ultra-high-speed camera for digital image correlation (DIC) observation in the equipment. Note: The high-speed camera in this article is a device that can capture images at a frame rate much higher than that of a conventional camera. Through special imaging technology and a high-speed shutter, it can quickly capture the instantaneous state of an object and decompose the high-speed movement process into a series of clear image frames. By cooperating with the DIC technology, a high-speed camera can analyze the deformation evolution processes such as full-field deformation, local deformation, and shear bands of brittle materials such as rocks under dynamic impact. According to the observation dimension, it is divided into two-dimensional (2D) and three-dimensional (3D) DIC. 2D-DIC is suitable for plane deformation measurement, using a single camera to capture images and analyze the displacement within the plane. 3D-DIC uses two or more cameras to take pictures from different angles to calculate the three-dimensional surface deformation. For 3D-DIC, calibration is a key step, including taking pictures of a calibration board image, calculating camera parameters and double-camera matching, and establishing a mapping relationship between the camera and the object coordinates. After calibration, the position and angle of the camera cannot change, otherwise it needs to be recalibrated to ensure the measurement accuracy. After precise calibration, 3D-DIC can realize the three-dimensional displacement and strain measurement of the complex surface of the specimen and is widely used in material testing and structural analysis.

[0004] However, in the dynamic true triaxial electromagnetic Hopkinson bar test system, since it can achieve multi-dimensional static and dynamic combined loading, its device structure is more complex, resulting in limited observation means. The specimen is wrapped by the loading central frame, and the operation space is narrow. It is difficult to place a camera with a large volume. If the camera contacts the frame of the test system during erection, due to the vibration generated during the system loading process, the position of the camera after calibration will change, and the calibration result will be invalidated, and 3D-DIC observation cannot be continuously carried out. During the test process, calibration needs to be repeated many times, and the test efficiency is extremely low; in addition to the vibration of the system frame caused during a single test process, when replacing the specimen, the general ground erection method of the camera will interfere with the installation of the specimen. If the operator disturbs the camera observation device during the installation of the specimen, it will cause the calibration to be invalidated at best, greatly reducing the experimental efficiency, and at worst, the camera will fall from the erection device, causing equipment damage. The above problems limit the use of traditional high-speed photography and DIC technology in multi-dimensional static and dynamic combinations, resulting in difficulty in effectively observing the dynamic deformation behavior and fracture characteristics of the loaded specimen in multi-dimensional dynamic loading.

[0005] In view of this, it is necessary to design an observation platform and its usage method to improve the test efficiency and increase the diversity of observation results. Summary of the Invention

[0006] To solve the problems in the prior art, the present invention provides an observation platform for multi-dimensional static and dynamic combined loading, a usage method of the observation platform, and a method for measuring the dynamic mechanical parameters of a specimen using the observation platform.

[0007] An observation platform for multi-dimensional static and dynamic combined loading, the observation platform includes: an observation platform fixed frame system, an observation platform XYZ spatial position adjustment system, a camera Z-direction fine adjustment system, a camera observation system, a camera pitch angle adjustment system, a camera protection system, and a camera position determination system;

[0008] The entire observation platform is connected to the top wall panel or the side wall panel through the observation platform fixed frame system;

[0009] The XYZ spatial position adjustment system of the observation platform uses all-electric screw control. In the XYZ spatial position adjustment system of the observation platform, the X+-direction servo motor of the spatial position adjustment system drives the X+-direction transmission screw of the spatial position adjustment system to rotate. The X+-direction transmission screw of the spatial position adjustment system drives the X+-direction transmission slide of the spatial position adjustment system to move in the X+-axis direction. Similarly, the X--direction servo motor of the spatial position adjustment system drives the X--direction transmission screw of the spatial position adjustment system to rotate. The X--direction transmission screw of the spatial position adjustment system drives the X--direction transmission slide of the spatial position adjustment system to move in the X--axis direction. In the X-direction linear guide of the spatial position adjustment system, the X+-direction transmission screw of the spatial position adjustment system and the X--direction transmission screw of the spatial position adjustment system are arranged simultaneously. The two transmission screws are parallel but offset.

[0010] The Z-direction fine adjustment system of the camera finely adjusts the position of the camera observation system in the Z-axis direction, and realizes the relative adjustment of the Z-axis position between the two cameras during the calibration of the 3D-DIC camera through this Z-direction fine adjustment system of the camera to assist in quickly completing the calibration.

[0011] The camera pitch angle adjustment system is used to realize the adjustment of the observation angle of the camera observation system relative to the specimen.

[0012] The camera protection system is fixed through the camera connecting plate to protect the camera observation system.

[0013] The position information of the camera is determined according to the camera position determination system.

[0014] As a further improvement of the present invention, the camera protection system uses a transparent material with a certain strength. The impact-breaking protection baffle of the camera protection system is designed to have the shape of a tail boss, and a groove is provided on the camera connecting plate.

[0015] The usage method of the observation platform with multi-dimensional dynamic and static combined loading, where the observation platform with multi-dimensional dynamic and static combined loading is the above-mentioned observation platform, specifically a method for evaluating and resetting the position stability of the camera observation system, including the following steps:

[0016] Step 1: Determination of the initial position of the camera. The initial three-dimensional coordinates of the camera are determined through a laser rangefinder to establish a reference position.

[0017] After completing the three-dimensional calibration, the position information of the camera is determined according to the camera position determination system. The measurement and positioning logic is: first, measure the distance from the rangefinder to the positioning plate.

[0018] Step 2: Calculation of the position offset after perturbation. Quantify the offset of the camera after being perturbed, and judge whether resetting is required.

[0019] Quantify the initial position information of the camera as: The specific measurement method is as follows: For the left ultra-high-speed camera, use the left X-direction laser rangefinder to measure the distance between the left X-direction laser rangefinder and the left X-direction laser ranging positioning plate, and define this distance as the position x of the left ultra-high-speed camera on the X-axis 0l , use the left Y-direction laser rangefinder to measure the distance between the left Y-direction laser rangefinder and the left Y-direction laser ranging positioning plate, and define this distance as the position y of the left ultra-high-speed camera on the Y-axis 0l , use the left Z-direction laser rangefinder to measure the distance between the left Z-direction laser rangefinder and the top wall panel, and define this distance as the position z of the left ultra-high-speed camera on the Z-axis 0l ;

[0020] For the right ultra-high-speed camera, use the right X-direction laser rangefinder to measure the distance between the right X-direction laser rangefinder and the right X-direction laser ranging positioning plate, and define this distance as the position x of the right ultra-high-speed camera on the X-axis 0r , use the right Y-direction laser rangefinder to measure the distance between the right Y-direction laser rangefinder and the right Y-direction laser ranging positioning plate, and define this distance as the position y of the right ultra-high-speed camera on the Y-axis 0r , use the right Z-direction laser rangefinder to measure the distance between the right Z-direction laser rangefinder and the top wall panel, and define the right Z-direction laser rangefinder as the position z of the right ultra-high-speed camera on the Z-axis 0r ; After i tests, record the first test after calibration as the first time. Here, i refers to the number of tests in which the calibration result fails due to multiple cumulative disturbances; due to the action of various additional factors, refer to the initial position measurement method of the reference camera to measure the position information of the camera after being disturbed, and the camera position becomes The formula for the offset of the camera position relative to the initial position at this time is When the 3D-DIC calibration result fails after multiple disturbances, according to the positions of the two cameras when the calibration is initially completed Reset it;

[0021] At the same time, define the formula for the position stability index: S(i) = (Δx(i)) 2 +(Δy(i)) 2 +(Δz(i)) 2 , when S(i) is close to the critical value, perform a reset adjustment referring to the position when the calibration is completed

[0022] As a further improvement of the present invention, the smaller the value of S(i), the more stable the position of the camera observation system. In the test, S(i) is not greater than 10 mm 2 .

[0023] A method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional static and dynamic combined loading. Applying the above-mentioned observation platform with multi-dimensional static and dynamic combined loading to measure the dynamic mechanical parameters of the specimen under dynamic loading, including the following steps:

[0024] Step 1, specimen preparation;

[0025] Step 2, specimen installation and loading system preparation;

[0026] Step 3, observation platform debugging, camera calibration and observation:

[0027] Based on the observation platform with multi-dimensional static and dynamic combined loading, first select two cameras with the same parameters. Relying on the frame and three-dimensional adjustment mechanism of the platform, adjust the spatial positions of the two cameras so that their optical axes are symmetrically distributed on both sides of the central normal of the measured surface, and adjust the observation angle according to the feedback of the camera imaging software to ensure that the measured area is completely covered by the central imaging area of the two camera targets and the images are clear;

[0028] Set the camera parameters;

[0029] In one-dimensional dynamic loading, based on the 3D-DIC observation of this observation platform, the displacement and strain along the loading axis can be observed, and at the same time, the displacement and strain in the axial direction orthogonal to the loading axis can also be observed. Assuming that the X-axis is used as the loading axis, the displacement and strain along the X-axis in one-dimensional dynamic loading are respectively denoted as and The stress along the loading axis is calculated by the stress wave theory The orthogonal axes are the Y-axis and the Z-axis, and the corresponding displacements and strains are denoted as and and Furthermore, in combination with the dynamic true triaxial electromagnetic Hopkinson bar test system, the out-of-plane displacement of the specimen surface in two-dimensional dynamic loading is observed for the first time, so as to calculate the strain in the out-of-plane direction of the specimen. In two-dimensional loading, the X-axis and the Y-axis are used as the loading axes, and the displacements and strains along the X-axis and the Y-axis in two-dimensional dynamic loading are respectively denoted as and and The stress along the loading axis is calculated by the stress wave theory and The orthogonal axis is the Z-axis, and the corresponding displacements and strains are denoted as and

[0030] Step 4, measurement of dynamic mechanical parameters:

[0031] When the dynamic mechanical parameter is the dynamic Poisson's ratio, the calculation method is as follows:

[0032] According to the above-obtained observation results, calculate the dynamic Poisson's ratios of the specimen under one-dimensional loading and two-dimensional loading respectively:

[0033] Referring to the definition of the static Poisson's ratio, the one-dimensional dynamic Poisson's ratio:

[0034] According to the observation results of this observation method, obtain the dynamic Poisson's ratio of two-dimensional dynamic loading:

[0035]

[0036] As a further improvement of the present invention, step 4, measurement of dynamic mechanical parameters: When the dynamic mechanical parameter is the elastic deformation energy of the specimen, the calculation method is as follows: For the evolution calculation of the specimen deformation energy, it is considered that the specimen is an elastic body before the crack appears, and the elastic deformation energy E under different-dimensional loadings e Calculate respectively according to the following formulas:

[0037] Elastic deformation energy of the specimen under one-dimensional dynamic loading:

[0038]

[0039] Decompose the elastic deformation energy into volumetric deformation energy and shape deformation energy:

[0040] The volumetric deformation energy is:

[0041] The shape change energy is:

[0042] Energy ratio R 1 Is defined as the ratio of the volumetric deformation energy to the shape change energy:

[0043] Elastic deformation energy of the specimen under two-dimensional dynamic loading:

[0044] Decompose the elastic deformation energy into volumetric deformation energy and shape deformation energy,

[0045] The volumetric deformation energy is:

[0046] The shape change energy is:

[0047] Energy ratio R 2 Is defined as the ratio of the volumetric deformation energy to the shape change energy:

[0048]

[0049] Through R i Real-time calculate the energy distribution of the specimen during the dynamic deformation process. If the measured R i Mutation: Such as from Ri > 1 decreases to R i < 1 indicates that the material changes from volume deformation dominance to shape distortion dominance. At this time, it corresponds to the critical state of crack nucleation. Denote this time as the deformation turning point, and the elastic deformation energy is the peak value of elastic deformation energy

[0050] As a further improvement of the present invention, the relationship between the peak value of the elastic deformation energy of the specimen, the deformation turning point and the characteristics of dynamic disturbance is further constructed: for dynamic loading, the pulse width T and amplitude A of the loading are two important factors. Discuss the relationship between the deformation turning point, the peak value of the elastic deformation energy and the pulse width and amplitude of the loading for one-dimensional dynamic loading, and establish the following functional relationship: On the basis of discussing the relationship between the deformation turning point, the peak value of the elastic deformation energy and the pulse width and amplitude of the loading for two-dimensional dynamic loading, further consider the amplitude ratio between the two loads the influence on the above two parameters, and establish the following functional relationship:

[0051] As a further improvement of the present invention, in the specimen preparation step:

[0052] (1) According to the loading requirements of the dynamic true triaxial electromagnetic Hopkinson bar test system, the specimen is processed into a standard cube configuration of 51mm×51mm×51mm;

[0053] (2) Speckle field production: Thoroughly clean the observation surface of the specimen with anhydrous ethanol to remove surface oil stains and particulate impurities, forming a flat base; then uniformly spray a white primer on the observation surface, and the thickness of the primer <

[0054] 0.5mm. Wait for it to naturally cure in a constant temperature and dry environment for several hours, and then prepare the speckle field in the next step.

[0055] As a further improvement of the present invention, adjust the spatial positions of the two cameras so that their optical axes are symmetrically distributed on both sides of the central normal of the measured surface. In this step, the adjustment is carried out by using the usage method of the above-mentioned multi-dimensional dynamic and static combined loading observation platform.

[0056] As a further improvement of the present invention, set the camera parameters to meet the following requirements: the synchronous trigger error is less than 1 μs, and the camera shooting speed ≥ 100000 frames / second.

[0057] The beneficial effects of the present invention:

[0058] The present invention is specifically designed for the installation of ultra-high-speed cameras, stability issues, and the flexibility of experimental personnel to place specimens in a dynamic true triaxial electromagnetic Hopkinson bar test system. It can effectively overcome space limitations and vibration effects, ensuring that the camera maintains a stable position and angle during the test, thereby guaranteeing the accuracy and reliability of DIC observations. At the same time, it ensures the convenience of experimental personnel to install specimens, allows for quick specimen replacement, and improves the test efficiency. A camera protection system is designed to prevent camera damage caused by the splashing of broken specimens. By introducing high-speed cameras and DIC technology, the 2D or 3D deformation field observation of brittle materials under one-dimensional or two-dimensional static and dynamic combined loading has been successfully achieved. The present invention not only enriches the diversity of observation results, improves the test efficiency, but also reduces the time cost of multiple repeated calibrations, providing reliable technical support for in-depth research on the deformation and failure characteristics of materials under complex dynamic stress conditions.

[0059] Based on the data obtained by the observation method provided by the present invention, the present invention constructs a dynamic Poisson's ratio formula applicable to two-dimensional dynamic loading scenarios, providing a key method for in-depth analysis of material mechanical behavior and filling the gap in the accurate calculation of the dynamic Poisson's ratio of rock-like materials under two-dimensional dynamic loading.

[0060] The reliable data obtained by the observation method is the basis for constructing a calculation system for the evolution of specimen deformation energy. For one-dimensional and two-dimensional loading, accurate displacement, strain, and stress data are obtained through an observation platform, and the corresponding calculation methods for elastic deformation energy are given. The elastic deformation energy is decomposed, and an energy ratio is defined. The change of this ratio is used to judge the transition of the material deformation state, providing a quantitative analysis method for studying the dynamic deformation of rock-like materials.

[0061] In one-dimensional and two-dimensional dynamic loading, considering the characteristics of the loading pulse width, amplitude, etc. of the dynamic load, and combining with the calculation method for the evolution of specimen deformation energy, relevant functional relationships are established. This provides a new perspective for understanding the mechanical behavior of rock-like materials under dynamic loading and helps in the dynamic mechanics research of rock-like materials.

[0062] Detailed description of specific effects: The present invention designs an observation platform separated from the loading device. The entire observation platform is connected to the top floor slab through the fixed frame system of the observation platform. Transverse stiffeners are arranged inside the fixed frame system of the observation platform to enhance the torsional and flexural resistance of the cross-section of the fixed frame system of the observation platform. Through the fixed frame system of the observation platform, the separation of the observation platform from the plane of the loading device is achieved, so that it is not directly affected by the vibration of the loading device, nor indirectly disturbed because it is erected on the same ground as the loading device. Below the fixed frame system of the observation platform is the XYZ spatial position adjustment system of the observation platform. Referring to the structure of a general XY-axis moving platform, a motorized lead screw stage device is selected as the basic component to achieve independent adjustment in the X, Y, and Z axes directions. The large-range independent adjustment in the Z-axis direction provides great convenience for experimental operators to replace specimens. After the erection of the observation platform and the calibration of the spatial position are initially completed, the experiment can be started. After one experiment is completed, through the Z-axis adjustment in the XYZ spatial position adjustment system of the observation platform, the observation devices such as cameras below are moved away from the loading device to leave enough space for specimen replacement. After the specimen is replaced, the observation devices such as cameras are moved back to the original position through the Z-axis adjustment. All adjustments in this observation platform are achieved through motorized lead screw devices. Compared with manual adjustment and return of positions by humans, it has the advantage of controllable precision positions. Therefore, both positions can maintain high-precision consistency, without affecting the spatial position calibration of the camera, and can maintain the high efficiency and high precision of the experiment. And in the X-axis adjustment, by setting two sets of misaligned and facing motorized lead screw devices in a single direction, the adjustment of the same axial position of two cameras in the X-axis direction is achieved. This design innovatively adopts an interleaved nested double lead screw structure, arranging two lead screws in parallel in the same guide rail system with a 180° phase difference, and each lead screw is equipped with an independent servo motor drive, enabling two cameras to achieve completely independent motion control on the same physical track. It not only avoids the problems of excessive space occupation and large weight of the double track system, but also solves the problem that it is difficult to synchronously control the positions of two cameras with a single track and a single lead screw. Through the misaligned and facing arrangement structure, not only the precise and rapid adjustment of the camera spacing is achieved, but also the position stability and position recoverability during the long-term experiment process are effectively guaranteed. Further install a camera Z-axis fine adjustment system below the XYZ spatial position adjustment system of the observation platform. This fine adjustment system further adjusts the Z-axis position of the camera. Since the requirement for the position adjustment range is small, a smaller motorized lead screw stage device is selected. In three-dimensional DIC observation, the angle between the camera and the specimen needs to be adjusted to achieve the calibration of the spatial position. This observation platform further sets up a camera pitch angle adjustment system, and through the structure of the motor and gear, the controllable adjustment of the camera angle is achieved, providing a solution for the spatial position calibration of three-dimensional DIC.At the same time, taking into account that when the sample is broken, the high-speed flying fragments may cause damage to the camera, the present invention further designs a camera protection system. By using highly transparent materials (such as acrylic, etc.), the camera is protected. The protective material is set to a fixed shape and is connected with the camera Z-direction fine-tuning system to achieve an interference fit. After a certain number of tests, if the protective material is damaged, it can be quickly replaced, which not only ensures the safety of the camera, but also ensures the efficient conduct of the test.

[0063] Further considering the advantages of using full motor screw control in this solution, after completing the camera 3D-DIC calibration, the initial position of the camera observation system is After i trials, due to various additional factors (accidental human collision disturbance, debris splash disturbance, cumulative reset deviation), the camera position becomes At this time, the camera observation system position is offset from the initial position, and the camera observation system calibration result is invalid, resulting in the inability to implement 3D-DIC. At this time, refer to the initial position when completing the 3D-DIC calibration. The motor screw device is adjusted to reset the overall position of the camera, reproducing the 3D-DIC effect of the camera observation system and realizing the anti-disturbance and precise reset capabilities of the experimental observation platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 It is a three-dimensional diagram of a dynamic true three-axis electromagnetic Hopkinson bar system in the prior art;

[0065] Figure 2 It is a three-dimensional diagram of the dynamic true three-axis electromagnetic Hopkinson bar system of the additional observation platform of the present invention;

[0066] Figure 3a It is a three-dimensional diagram of the observation platform of the present invention;

[0067] Figure 3b It is a three-dimensional diagram of the separation and deconstruction of each system of the observation platform of the present invention;

[0068] Figure 4 It is a three-dimensional diagram of the fixed frame system of the observation platform of the present invention;

[0069] Figure 5a It is a three-dimensional schematic diagram of the connection between the fixed frame system of the observation platform of the present invention and the top wall panel;

[0070] Figure 5b This is a schematic diagram of the connection of the transverse stiffening ribs inside the fixed frame system of the observation platform of the present invention;

[0071] Figure 6 It is the XYZ spatial position adjustment system of the observation platform of the present invention;

[0072] Figure 7aIt is the 3D diagram of the Z-axis motor lead screw slider device in the XYZ spatial position adjustment system of the observation platform of the present invention;

[0073] Figure 7b It is the 3D diagram of the Y-axis motor lead screw slider device in the XYZ spatial position adjustment system of the observation platform of the present invention;

[0074] Figure 8a It is the 3D diagram of the X-axis motor lead screw slider device in the XYZ spatial position adjustment system of the observation platform of the present invention;

[0075] Figure 8b It is the 3D diagram of the X-axis motor lead screw slider device in the XYZ spatial position adjustment system of the observation platform of the present invention from another angle;

[0076] Figure 9 It is the 3D diagram of the Z-axis motor lead screw slider device with an additional Y-axis cross plate (taking one side as an example) of the present invention;

[0077] Figure 10 It is the 3D diagram of the Y-axis motor lead screw slider device with an additional X-axis cross plate (taking one side as an example) of the present invention;

[0078] Figure 11 It is the 3D diagram of the XY plane position adjustment device of the present invention;

[0079] Figure 12 It is the 3D diagram of the camera and its Z-axis fine adjustment system installed on the Y-axis adjustment device of the present invention;

[0080] Figure 13 It is the 3D diagram of the camera Z-axis fine adjustment system (taking one of them as an example) of the present invention;

[0081] Figure 14 It is the 3D diagram of the connection between the camera and the camera Z-axis fine adjustment system of the present invention;

[0082] Figure 15a It is the 3D diagram of the camera pitch angle adjustment system of the present invention;

[0083] Figure 15b It is the 3D diagram of the internal gear transmission of the camera pitch angle adjustment system of the present invention;

[0084] Figure 16 It is the 3D diagram of the connection between the camera and the camera protection system of the present invention;

[0085] Figure 17a It is the 3D diagram of the connection state of the camera protection system of the present invention;

[0086] Figure 17b It is the 3D diagram of the separation of the camera protection system of the present invention;

[0087] Figure 18It is a schematic diagram of the position of the positioning plate component in the camera positioning system of the present invention, and the figure shows an exploded view of some components;

[0088] Figure 19 It is a 3D diagram of the camera positioning system of the present invention;

[0089] Figure 20 It is a 3D diagram of the laser rangefinder of the camera positioning system of the present invention.

[0090] The component names corresponding to the reference numerals in the figure are as follows: Observation platform fixed frame system 1, Observation platform XYZ spatial position adjustment system 2, Camera Z-direction fine adjustment system 3, Camera observation system 4, Camera pitch angle adjustment system 5, Camera protection system 6, Camera position determination system 7, Loading device 001, Top wall panel 100, First fixed column 101, Second fixed column 102, Third fixed column 103, Fourth fixed column 104, First transverse stiffening rib 105, Second transverse stiffening rib 106, Third transverse stiffening rib 107, Fourth transverse stiffening rib 108, Fixed column side fixing plate 109, Connecting screw between fixed column and transverse stiffening rib 110, Connecting screw between fixed column and wall top 111, Fixed column top fixing plate 112, First spatial position adjustment system Z-direction motor screw slider device 201, Second spatial position adjustment system Z-direction motor screw slider device 202, Third spatial position adjustment system Z-direction motor screw slider device 203, Fourth spatial position adjustment system Z-direction motor screw slider device 204, First spatial position adjustment system Y-direction connecting plate 205, Second spatial position adjustment system Y-direction connecting plate 206, First spatial position adjustment system Y-direction motor screw slider device 207, Second spatial position adjustment system Y-direction motor screw slider device 208, Spatial position adjustment system X-direction connecting plate 209, Spatial position adjustment system X-direction motor screw slider device 210, Spatial position adjustment system Z-direction servo motor 211, Spatial position adjustment system Z-direction transmission screw 212, Spatial position adjustment system Z-direction transmission slide 213, Spatial position adjustment system Z-direction linear slide 214, Spatial position adjustment system Z-direction linear guide 215, Spatial position adjustment system Z-direction motor screw slider device base 216, Spatial position adjustment system Y-direction servo motor 217, Spatial position adjustment system Y-direction transmission screw 218, Spatial position adjustment system Y-direction transmission slide 219, Spatial position adjustment system Y-direction linear slide 220, Spatial position adjustment system Y-direction linear guide 221, Spatial position adjustment system Y-direction motor screw slider device base 222, Spatial position adjustment system X+ direction servo motor 223, Spatial position adjustment system X+ direction transmission screw 224, Spatial position adjustment system X-direction linear guide 225 (only one guide for the X-axis, no need to distinguish directions), Spatial position adjustment system X+ direction transmission slide 226, Spatial position adjustment system X+ direction linear slide 227, Spatial position adjustment system X- direction servo motor 228, Spatial position adjustment system X- direction transmission screw 229, Spatial position adjustment system X- direction transmission slide 230, Spatial position adjustment system X- direction linear slide 231, First Z-direction fine adjustment system motor screw slider device 301, Second Z-direction fine adjustment system motor screw slider device 302, First camera connecting plate 303, Second camera connecting plate 304, Z-direction fine adjustment system servo motor 305, Z-direction fine adjustment system transmission screw 306, Z-direction fine adjustment system transmission slide 307Z-axis fine-tuning system linear slide 308, Z-axis fine-tuning system linear guide 309, base of Z-axis fine-tuning system motor screw slider device 310, first camera 401, second camera 402, first camera pitch angle adjustment device 501, second camera pitch angle adjustment device 502, pitch angle adjustment device connecting camera board 503, top plate of pitch angle adjustment device 504, support column of pitch angle adjustment device 505, gear-driven rotating column of pitch angle adjustment device 506, gear motor structure of pitch angle adjustment device 507, bottom plate of pitch angle adjustment device 508, first impact crushing protection baffle 601, second impact crushing protection baffle 602, left X-axis laser ranging positioning plate 701, right X-axis laser ranging positioning plate 702, left Y-axis laser ranging positioning plate 703, right Y-axis laser ranging positioning plate 704, left X-axis laser rangefinder 705, left Z-axis laser rangefinder 706, left Y-axis laser rangefinder 707, right Z-axis laser rangefinder 708, right X-axis laser rangefinder 709, right Y-axis laser rangefinder 710. (Regarding the description of the orientation of the positioning system here: The X, Y, and Z directions mentioned here refer to the directions in which they play a positioning role. For example, the left X-axis laser ranging positioning plate 701 means that it plays a positioning role for the distance of the left camera in the X direction.), Detailed implementation mode

[0091] The following is a more detailed description of the test usage method of the present invention. The present invention will be described in detail in combination with the accompanying drawings and specific implementation modes:

[0092] Detailed implementation mode 1: Applied to the observation platform in multi-dimensional dynamic and static combined loading.

[0093] The basic composition of each system of the observation platform and its specific functions will be described in detail. Taking the dual-axis four-direction loading as an example, the usage methods of two-dimensional dynamic observation of a single camera and three-dimensional dynamic observation of two cameras will be described respectively.

[0094] As Figure 3a and Figure 3b shown: The observation platform mainly consists of the following systems: Observation platform fixed frame system 1, Observation platform XYZ spatial position adjustment system 2, Camera Z-axis fine-tuning system 3, Camera observation system 4, Camera pitch angle adjustment system 5, Camera protection system 6, Camera position determination system 7.

[0095] As Figure 4As shown in the figure, the entire observation platform is connected to the top wall panel 100 through the first fixed column 101, the second fixed column 102, the third fixed column 103, and the fourth fixed column 104 of the observation platform fixed frame system 1. Here, the wall panel is preferably the top wall panel, and it can also be the side wall panel. Since the entire loading device 001 does not come into contact with the top wall panel 100, the vibration generated by the loading device 001 will not affect the top wall panel 100. By separating the observation platform from the loading device and its supporting plane, the stability of the observation platform is maintained.

[0096] As Figure 4 shown in the figure, additional lateral supports are connected inside the observation platform fixed frame system, and the overall flexural stiffness and stability of the observation platform are strengthened by the first lateral stiffening rib 105, the second lateral stiffening rib 106, the third lateral stiffening rib 107, and the fourth lateral stiffening rib 108.

[0097] As Figure 5a shown in the figure, taking the second fixed column 102 as an example, a fixed column lateral fixing plate 109 is arranged on the side of the second fixed column 102, and the connection between the fixed column and the lateral stiffening rib is realized through the fixed column and lateral stiffening rib connection screw 110.

[0098] As Figure 5b shown in the figure, the second fixed column 102 is connected to the top wall panel 100 through a number of fixed column and wall top connection screws 111 and a fixed column top fixing plate 112.

[0099] As Figure 6 shown: In the XYZ spatial position adjustment system 2 of the observation platform, all-motor screw control is used to achieve high-precision position adjustment, ensure the consistency and controllability of the position, and thus improve the test efficiency and success rate. In the XYZ spatial position adjustment system 2 of the observation platform, the devices for realizing the adjustment in the Z-axis direction include: the first spatial position adjustment system Z-direction motor screw slider device 201, the second spatial position adjustment system Z-direction motor screw slider device 202, the third spatial position adjustment system Z-direction motor screw slider device 203, and the fourth spatial position adjustment system Z-direction motor screw slider device 204.

[0100] As Figure 7aAs shown, the above four Z-axis motor screw slider devices are all standard motor screw structures. Taking the Z-axis motor screw slider device 201 of the first spatial position adjustment system as an example to illustrate its detailed structure and function, start the Z-axis servo motor 211 of the spatial position adjustment system. The Z-axis servo motor 211 of the spatial position adjustment system drives the Z-axis transmission screw 212 of the spatial position adjustment system to rotate. The Z-axis transmission screw 212 of the spatial position adjustment system drives the Z-axis transmission slide 213 of the spatial position adjustment system to move in the Z-axis direction. The Z-axis linear slide 214 of the spatial position adjustment system is an auxiliary sliding mechanism to reduce the load of the Z-axis transmission slide 213 of the spatial position adjustment system, realizing controllable and high-precision adjustment in the Z-axis direction. Connect the Z-axis transmission slide 213 and the Z-axis linear slide 214 of the spatial position adjustment system to the Y-axis connecting plate 205 of the first spatial position adjustment system. Similarly, all the Z-axis transmission slides and linear slides are respectively connected to the Y-axis connecting plate 205 of the first spatial position adjustment system and the Y-axis connecting plate 206 of the second spatial position adjustment system. In this way, the observation platform can achieve synchronous adjustment in the Z-axis direction.

[0101] Through the Z-axis motor screw slider device 201 of the first spatial position adjustment system, the Z-axis motor screw slider device 202 of the second spatial position adjustment system, the Z-axis motor screw slider device 203 of the third spatial position adjustment system, and the Z-axis motor screw slider device 204 of the fourth spatial position adjustment system, synchronously control the consistency of the motor drive slider in the Z-axis displacement, maintaining the horizontality of the observation platform, that is, each Z-axis transmission slide is at the same height, thereby ensuring that the observation platform is in the same horizontal plane in space.

[0102] Another example Figure 6 As shown, the device for realizing the Y-axis direction adjustment includes: the Y-axis motor screw slider device 207 of the first spatial position adjustment system and the Y-axis motor screw slider device 208 of the second spatial position adjustment system. The above two Y-axis motor screw slider devices are all standard motor screw structures and are the same structural devices as the above Z-axis motor screw slider devices. Taking the Y-axis motor screw slider device 207 of the first spatial position adjustment system as an example to illustrate its detailed structure and function, as Figure 7b shown, start the Y-axis servo motor 217 of the spatial position adjustment system. The Y-axis servo motor 217 of the spatial position adjustment system drives the Y-axis transmission screw 218 of the spatial position adjustment system to rotate. The Y-axis transmission screw 218 of the spatial position adjustment system drives the Y-axis transmission slide 219 of the spatial position adjustment system to move in the Y-axis direction. The Y-axis linear slide 220 of the spatial position adjustment system is an auxiliary sliding mechanism to reduce the load of the Y-axis transmission slide 219 of the spatial position adjustment system, realizing controllable and high-precision adjustment in the Y-axis direction.

[0103] By synchronously controlling the consistency of the displacement of the motor-driven slider in the Y-axis direction through the Y-axis motor screw slider device 207 of the first spatial position adjustment system and the Y-axis motor screw slider device 208 of the second spatial position adjustment system, highly precise and controllable adjustment of the Y-axis position of the observation platform can be achieved. Further, connecting the X-axis adjustment system to the X-axis connecting plate 209 of the spatial position adjustment system enables precise adjustment of the X-axis on the basis of achieving controllable adjustment of the Y-axis.

[0104] As Figure 6 shown, the device for realizing the adjustment in the X-axis direction is only: the X-axis motor screw slider device 210 of the spatial position adjustment system. This X-axis motor screw slider device is a non-standard motor screw device. Two sets of motor screw devices are arranged in a staggered manner within a single device. Their structural compositions and functions are the same, and both are driven by a motor to drive the transmission screw to achieve movement.

[0105] As Figure 8a and Figure 8bAs shown in the figure, in the spatial position adjustment system, the X+-direction servo motor 223 drives the X+-direction transmission lead screw 224 of the spatial position adjustment system to rotate, and the X+-direction transmission lead screw 224 of the spatial position adjustment system drives the X+-direction transmission slide 226 to move in the X+-axis direction. Similarly, the X--direction servo motor 228 drives the X--direction transmission lead screw 229 of the spatial position adjustment system to rotate, and the X--direction transmission lead screw 229 of the spatial position adjustment system drives the X--direction transmission slide 230 to move in the X--axis direction. The above constructs a dislocation structure in which two parallel lead screws with a distance difference and a slider assembly work together within the same guide rail. Its core principle is to simultaneously set the X+-direction transmission lead screw 224 and the X--direction transmission lead screw 229 of the spatial position adjustment system within the X-direction linear guide 225 of the spatial position adjustment system. The two lead screws are parallel but dislocated. The X+-direction transmission lead screw 224 and the X--direction transmission lead screw 229 of the spatial position adjustment system are respectively driven by the X+-direction servo motor 223 and the X--direction servo motor 228 of the spatial position adjustment system. Cooperating with the X+-direction transmission slide 226, the X+-direction linear slide 227, the X--direction transmission slide 230, and the X--direction linear slide 231 of the spatial position adjustment system, the controllable and precise relative movement of two objects on the same guide rail can be realized. The dislocation design of the two sets of devices enables the observation platform to achieve high-precision relative position adjustment in the X-axis direction. Since the layout directions are opposite, the two camera devices are respectively installed on the X+-direction transmission slide 226 and the X--direction transmission slide 230 of the spatial position adjustment system. It can not only realize the adjustment of the X-axis position of a single camera, meet the requirements of X-axis position control in the two-dimensional dynamic observation of a single camera, but also realize the precise control between the positions of the two cameras, providing a reliable solution for the position adjustment of camera calibration in 3D-DIC based on dual-camera three-dimensional dynamic observation (precise and controllable relative adjustment of two cameras on the same axis). The servo motor drives the transmission lead screw to drive the slide to move along the X-axis direction. At the same time, the linear slide serves as an auxiliary mechanism to reduce the load of the slide and ensure the smoothness and accuracy of the sliding process. The design of this dislocation layout takes into account both structural compactness and functional diversity, providing a reliable solution for realizing complex single-axis opposite relative adjustment.

[0106] The camera Z-axis fine-tuning system 3 can finely adjust the position of the camera observation system 4 in the Z-axis direction. When only performing two-dimensional dynamic observation of a single camera, the camera Z-axis fine-tuning system 3 can achieve high-precision controllable adjustment of the field of view size by finely adjusting the position of the camera in the Z-axis direction, ensuring that the observation object is at the center of the field of view and of appropriate size. When further performing three-dimensional dynamic observation of two cameras, during the calibration of the 3D-DIC camera, the relative adjustment of the Z-axis positions between the two cameras can be achieved through this camera Z-axis fine-tuning system 3 to assist in quickly completing the calibration.

[0107] As Figure 9 shown, it shows the connection method of the Z-axis adjustment and the Y-axis adjustment.

[0108] As Figure 10 shown, it shows the connection method of the X-axis adjustment and the Y-axis adjustment.

[0109] As Figure 11 shown, it shows the movement mode of the observation platform in the Y-axis direction. By the cooperation of the front and rear two motors to drive the connecting plate, the movement of the Y-axis is achieved.

[0110] As Figure 12 shown, the camera Z-axis fine-tuning system 3 includes a first Z-axis fine-tuning system motor screw slider device 301 and a second Z-axis fine-tuning system motor screw slider device 302. The above two Z-axis fine-tuning motor screw slider devices are both standard motor screw structures, which are the same structural devices as the above X-axis and Y-axis motor screw slider devices, only different in size.

[0111] As Figure 13 shown, taking the first Z-axis fine-tuning system motor screw slider device 301 as an example to illustrate its detailed structure and function. Start the Z-axis fine-tuning system servo motor 305. The Z-axis fine-tuning system servo motor 305 drives the Z-axis fine-tuning system transmission screw 306 to rotate. The Z-axis fine-tuning system transmission screw 306 drives the Z-axis fine-tuning system transmission slide 307 to move in the Z-axis direction. The Z-axis fine-tuning linear slide 308 is an auxiliary sliding mechanism to reduce the load of the Z-axis fine-tuning system transmission slide 307, achieving controllable high-precision adjustment in the Z-axis direction.

[0112] Again, as Figure 12 shown, by connecting the first camera 401 and the second camera 402 to the first Z-axis fine-tuning system motor screw slider device 301 and the second Z-axis fine-tuning system motor screw slider device 302 respectively through the first camera connecting plate 303 and the second camera connecting plate 304, the precise control of the Z-axis positions of the two cameras can be achieved. Through two independent motor screws, the precise control of the relative positions between the two cameras is ensured.

[0113] Considering the need to adjust the angle of the camera observation system 4 during the observation, the observation platform further invented and designed a camera pitch angle adjustment system 5, which can realize the adjustment of the observation angle of the camera observation system 4 relative to the specimen (the formation of an observation angle between the camera observation systems 4 is mainly to achieve 3D-DIC).

[0114] As Figure 12 and Figure 14 shown, the camera pitch angle adjustment system 5 includes a first camera pitch angle adjustment device 501 and a second camera pitch angle adjustment device 502. The above two devices achieve the adjustment of the camera pitch angle through the motor gear drive method, and both devices have the same structure.

[0115] As Figure 15a , Figure 15b and Figure 16 shown, taking the first camera pitch angle adjustment device 501 as an example to illustrate its detailed structure and function, the first camera pitch angle adjustment device 501 is connected to the first camera connection plate 303 through the pitch angle adjustment device lower top plate 508, and is connected to the pitch angle adjustment device upper top plate 504 and the pitch angle adjustment device lower top plate 508 through the pitch angle adjustment device support column 505. The pitch angle adjustment device gear motor structure 507 is fixed on the pitch angle adjustment device lower top plate 508. When the pitch angle adjustment device gear motor structure 507 is started, through the gear drive method, the pitch angle adjustment device gear transmission rotating column 506 rotates, driving the pitch angle adjustment device connection camera plate 503 to rotate. The first camera 401 is fixed on the pitch angle adjustment device connection camera plate 503, thereby realizing the angle adjustment of the first camera 401. Since the first camera pitch angle adjustment device 501 and the second camera pitch angle adjustment device 502 are independent, the first camera 401 and the second camera 402 can achieve relative angle adjustment.

[0116] Since in the dynamic impact test, the broken fragments of the specimen usually fly around in all directions. The broken test blocks have sharp edges and corners and a relatively fast flying speed, posing a potential threat to the camera lens and sensor. Therefore, appropriate protective measures need to be taken during the test to ensure the safety of the equipment. In view of this, a camera protection system 6 is further designed in the observation platform to protect the camera.

[0117] As Figure 12As shown, the camera protection system 6 includes a first impact-breaking protection baffle 601 and a second impact-breaking protection baffle 602. To ensure the safety of the camera while having a high imaging quality, the material of the impact-breaking protection baffle generally uses a transparent material with a certain strength (such as laminated glass, acrylic, etc.). In repeated tests, the impact-breaking protection baffle is impacted multiple times, and there are problems such as damage affecting the imaging quality and even destruction. Therefore, for convenient and quick replacement, the impact-breaking protection baffle is designed with a tail boss shape, and a groove is provided on the camera connecting plate to achieve quick disassembly and replacement.

[0118] As Figure 17a and Figure 17b , taking the connection between the first camera connecting plate 303 and the first impact-breaking protection baffle 601 as an example for the specific connection method, a groove is provided below the first camera connecting plate 303 to cooperate with one end of the first impact-breaking protection baffle 601 to achieve quick disassembly and assembly.

[0119] Specific Embodiment 2: Method for Evaluating and Resetting the Position Stability of the Camera Observation System

[0120] As Figure 18 , Figure 19 , Figure 20 shown, it is a method for using an observation platform applied to multi-dimensional dynamic and static combined loading, especially relating to a method for evaluating and resetting the position stability of a camera observation system.

[0121] Step 1: Determine the initial position of the camera. Measure the initial three-dimensional coordinates of the camera through a laser rangefinder to establish a reference position.

[0122] After completing the three-dimensional calibration, according to the camera position measurement system 7, measure the position information of the camera. The measurement and positioning logic is as follows: First, measure the distance from the rangefinder to the positioning plate. Since the position of the camera relative to the rangefinder is unchanged, the distance measured by the rangefinder can be used as the coordinates of this camera.

[0123] Step 2: Calculate the position offset after perturbation, quantify the offset of the camera after being perturbed, and determine whether resetting is required.

[0124] Quantify the initial position information of the camera as: The specific measurement method is as follows: For the left ultra-high-speed camera, use the left X-direction laser rangefinder 705 to measure the distance between the left X-direction laser rangefinder 705 and the left X-direction laser ranging positioning plate 701, and define this distance as the position x of the left ultra-high-speed camera on the X-axis 0l , use the left Y-direction laser rangefinder 707 to measure the distance between the left Y-direction laser rangefinder 707 and the left Y-direction laser ranging positioning plate 703, and define this distance as the position y of the left ultra-high-speed camera on the Y-axis 0l, use the left Z - direction laser rangefinder 706 to measure the distance between the left Z - direction laser rangefinder 706 and the top wall panel 100, and define this distance as the position z of the left ultra - high - speed camera on the Z - axis 0l ;

[0125] For the right ultra - high - speed camera, use the right X - direction laser rangefinder 709 to measure the distance between the right X - direction laser rangefinder 709 and the right X - direction laser ranging positioning plate 702, and define this distance as the position x of the right ultra - high - speed camera on the X - axis 0r , use the right Y - direction laser rangefinder 710 to measure the distance between the right Y - direction laser rangefinder 710 and the right Y - direction laser ranging positioning plate 704, and define this distance as the position y of the right ultra - high - speed camera on the Y - axis 0r , use the right Z - direction laser rangefinder 708 to measure the distance between the right Z - direction laser rangefinder 708 and the top wall panel 100, and define the right Z - direction laser rangefinder 708 as the position z of the right ultra - high - speed camera on the Z - axis 0r . After i tests, record the first test after calibration as the first time. Here, i times refers to the number of tests where the calibration result fails due to multiple cumulative disturbances. Due to the randomness of the disturbances, it is not possible to directly determine how many times. Due to the action of various additional factors (accidental human collision disturbances, debris splashing disturbances, cumulative reset deviations), referring to the method for measuring the initial position of the camera, measure the position information of the camera after being disturbed, and the camera position becomes The offset formula of the camera position relative to the initial position at this time is When the 3D - DIC calibration result fails after multiple disturbances, according to the positions of the two cameras when the calibration was initially completed Reset it to ensure the calibration effect of 3D - DIC and solve the problem of repeated calibration and positioning.

[0126] At the same time, define the position stability index formula: S(i)=(Δx(i)) 2 +(Δy(i)) 2 +(Δz(i)) 2 . The smaller the value of S(i), the more stable the position of the camera observation system. It is recommended that S(i) be no more than 10 mm in the experiment 2 , when S(i) is close to the critical value, perform a reset adjustment referring to the position when the calibration was completed. This position stability evaluation and reset method can quantitatively evaluate the guarantee effect of the observation platform on the position stability of the camera observation system, reflecting the advantage of this solution in overcoming the influence of external disturbances.

[0127] Specific implementation method 3: Application case illustration, dynamic Poisson's ratio and energy evolution analysis

[0128] Combined with this method, the measurement of dynamic mechanical parameters of rock specimens under one - dimensional and two - dimensional dynamic loading can be realized.

[0129] The real-time evolution of the dynamic Poisson's ratio and the evolution of the specimen deformation energy are the keys to revealing the essence of dynamic damage in rock-like materials. The dynamic Poisson's ratio directly reflects the initiation threshold of microcracks inside the material through the transverse-axial strain relationship (the sudden increase point of the Poisson's ratio corresponds to the critical state of crack nucleation, representing the phase transition point from volume strain energy dominance to shear strain energy dominance). At the same time, the dynamic Poisson's ratio, as a key mechanical parameter characterizing the coupling effect between transverse deformation and axial deformation during the dynamic deformation process of the material, is the core index for evaluating the dynamic constitutive relationship, energy dissipation characteristics, and damage evolution law of rock masses. Currently, there is no method for observing the dynamic Poisson's ratio of rock-like solid materials under two-dimensional dynamic loading. The energy evolution process quantitatively characterizes the conversion path of external mechanical work into elastic stored energy, plastic dissipated energy, and crack surface energy. Based on the dynamic true triaxial Hopkinson bar test system and the observation platform of the present invention, a real-time evolution measurement method for the Poisson's ratio of rock-like materials in one-dimensional and two-dimensional dynamic stress fields can be constructed. By using the abnormal fluctuation of the Poisson's ratio to identify the crack initiation phase transition point, exploring the law of specimen dynamic deformation energy evolution, and elaborating the relationship between the peak value of specimen dynamic deformation energy, deformation turning point, and dynamic disturbance characteristics, the specific method is as follows: [[ID=③]]

[0130] [[ID=④]]Step 1 Specimen preparation:[[ID=⑤]] [[ID=⑥]]

[0131] [[ID=⑦]](1) According to the loading requirements of the dynamic true triaxial electromagnetic Hopkinson bar test system, the specimen is processed into a standard cube configuration of 51mm×51mm×51mm. This specimen size can avoid stress concentration and local failure of the specimen.[[ID=⑧]] [[ID=⑨]]

[0132] [[ID=⑩]](2) Speckle field production: Thoroughly clean the specimen observation surface with anhydrous ethanol to remove surface oil stains and particulate impurities, forming a flat base. Subsequently, evenly spray a white primer on the observation surface. The thickness of the primer should not be too thick to avoid deformation distortion (<0.5mm). Wait for it to naturally cure for 24 hours in a constant temperature and dry environment at 25°C. Next, use methods such as speckle printing, speckle sticking, or spraying speckles through a spray gun to prepare a speckle field with high contrast and random distribution.[[ID=⑪]] [[ID=⑫]]

[0133] [[ID=⑬]]Step 2 Specimen installation and loading system preparation:[[ID=⑭]] [[ID=⑮]]

[0134] [[ID=⑯]]Install the sample at the loading position of the test system. According to the experimental needs and the observation ability of the observation platform, one-dimensional dynamic loading and two-dimensional dynamic loading can be selected. In one-dimensional dynamic loading, adjust the two incident bars of the target loading axis to be coaxial with the specimen to ensure uniaxial two-way synchronous loading in the loading axis direction; in two-dimensional dynamic loading, adjust the four incident bars of the two target loading axes to be coaxial with the two axes of the specimen respectively to ensure biaxial four-way synchronous loading. The strain gauges pasted on the bars can collect stress wave signals, and through the stress wave calculation principle, the dynamic stress-strain data of the specimen along the loading direction can be calculated.[[ID=⑰]]

[0135] Step 3 Observation Platform Debugging, Camera Calibration, and Explanation of Observation Results:

[0136] Based on the modular observation platform of the present invention, first select two ultra-high-speed cameras with the same parameters (it is recommended to use the same model of fixed-focus lens to ensure the consistency of the focal length). Relying on the high-rigidity frame and three-dimensional adjustment mechanism of the platform, adjust the spatial positions of the two cameras through the above method so that their optical axes are symmetrically distributed on both sides of the central normal of the measured surface, and adjust the observation angle according to the feedback of the camera imaging software to ensure that the measured area is completely covered by the central imaging area of the double-camera target surface and the image is clear. The camera parameter settings need to meet the following requirements: the synchronous trigger error is less than 1 μs, and the camera shooting speed is ≥100000 frames per second. Before the loading test, perform three-dimensional digital image correlation (3D-DIC) calibration. Based on the high stability and excellent anti-disturbance ability of this observation platform, after the calibration is completed, the test can be carried out efficiently and stably, meeting the requirements of high-precision dynamic mechanics testing.

[0137] In one-dimensional dynamic loading, based on the three-dimensional DIC observation of this observation platform, the displacement and strain along the loading axis can be observed, and at the same time, the displacement and strain in the axial direction orthogonal to the loading axis can also be observed. Assuming that the X-axis is used as the loading axis, the displacement and strain along the X-axis in one-dimensional dynamic loading are respectively denoted as and The stress along the loading axis can be calculated by the stress wave theory The orthogonal axes are the Y-axis and the Z-axis, and the corresponding displacement and strain can be denoted as and and Furthermore, combined with the dynamic true triaxial electromagnetic Hopkinson bar test system, the out-of-plane displacement of the specimen surface in two-dimensional dynamic loading can be observed for the first time, so as to calculate the strain in the out-of-plane direction of the specimen. In two-dimensional loading, the X-axis and the Y-axis are used as the loading axes, and the displacement and strain along the X-axis and the Y-axis in two-dimensional dynamic loading are respectively denoted as and and The stress along the loading axis can be calculated by the stress wave theory and The orthogonal axis is the Z-axis, and the corresponding displacement and strain can be denoted as and

[0138] Step 4 Explanation of the Calculation Method:

[0139] (1) According to the observation results obtained above, the dynamic Poisson's ratios of rock-like solid materials under one-dimensional loading and two-dimensional loading can be calculated respectively:

[0140] Referring to the definition of the static Poisson's ratio, the one-dimensional dynamic Poisson's ratio:

[0141] Based on the observation results of this observation method, the dynamic Poisson's ratio of two-dimensional dynamic loading can be obtained:

[0142]

[0143] Based on the data obtained from the above observation method, the present invention constructs a dynamic Poisson's ratio formula applicable to the two-dimensional dynamic loading scenario, providing a key method for in-depth analysis of the mechanical behavior of materials and filling the gap in the accurate calculation of the dynamic Poisson's ratio of rock-like materials under two-dimensional dynamic loading.

[0144] (2) Calculation of the evolution of the specimen deformation energy:

[0145] Before the crack appears, the specimen is considered an elastic body, and the elastic deformation energy E under different-dimensional loading e can be calculated respectively according to the following formulas:

[0146] Elastic deformation energy of the specimen under one-dimensional dynamic loading:

[0147]

[0148] The elastic deformation energy can be decomposed into volumetric deformation energy and shape deformation energy:

[0149] The volumetric deformation energy is:

[0150] The shape change energy is:

[0151] The energy ratio R 1 is defined as the ratio of the volumetric deformation energy to the shape change energy:

[0152] Elastic deformation energy of the specimen under two-dimensional dynamic loading:

[0153] The elastic deformation energy can be decomposed into volumetric deformation energy and shape deformation energy,

[0154] The volumetric deformation energy is:

[0155] The shape change energy is:

[0156]

[0157] The energy ratio R 2 is defined as the ratio of the volumetric deformation energy to the shape change energy:

[0158]

[0159] Through R i the energy distribution of the specimen during the dynamic deformation process can be calculated in real time. If R is measuredi Mutation (such as from R i > 1 to R i < 1), indicating that the material changes from volume deformation-dominated (energy storage stage) to shape distortion-dominated (damage dissipation stage). At this time, it corresponds to the critical state of crack nucleation. Denote this time as the deformation turning point, and the elastic deformation energy is the peak value of the elastic deformation energy

[0160] Reliable data obtained by observation methods is the basis for constructing the calculation system of the specimen deformation energy evolution. For one-dimensional and two-dimensional loading, accurate displacement, strain, and stress data are obtained with the help of an observation platform, and the corresponding calculation methods for elastic deformation energy are given. The elastic deformation energy is decomposed, and the energy ratio is defined. The change of this ratio is used to judge the transformation of the material deformation state, providing a quantitative analysis method for studying the dynamic deformation of rock-like materials.

[0161] (3) Further establish the relationship between the peak value of the specimen's elastic deformation energy, the deformation turning point, and the characteristics of dynamic disturbance: For dynamic loading, the pulse width T and amplitude A of the loading are two important factors (in rock-like solid materials, it is default to use a sine wave for loading, so the influence of the waveform does not need to be considered). For one-dimensional dynamic loading, the relationship between the deformation turning point, the peak value of the elastic deformation energy, and the pulse width and amplitude of the loading can be discussed, and try to establish the following functional relationship:

[0162]

[0163] For two-dimensional dynamic loading, on the basis of discussing the relationship between the deformation turning point, the peak value of the elastic deformation energy, and the pulse width and amplitude of the loading, further consider the amplitude ratio between the two loads on the influence of the above two parameters, and try to establish the following functional relationship:

[0164] In one-dimensional and two-dimensional dynamic loading, considering the characteristics of the loading pulse width, amplitude, etc. of the dynamic load, combined with the calculation method of the specimen deformation energy evolution, relevant functional relationships are established. This provides a new perspective for understanding the mechanical behavior of rock-like materials under dynamic loading and helps the dynamic mechanics research of rock-like materials.

[0165] Note: The calculation of the stress along the loading axis by the stress wave theory belongs to the mature calculation in this technical field, so it is not described in detail in this article.

[0166] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. Method of using an observation platform with multi-dimensional static and dynamic combined loading, wherein the observation platform with multi-dimensional static and dynamic combined loading comprises: Observation platform fixed frame system (1), observation platform XYZ spatial position adjustment system (2), camera Z-direction fine adjustment system (3), camera observation system (4), camera pitch angle adjustment system (5), camera protection system (6) and camera position determination system (7); The entire observation platform is connected to the top wall panel or the side wall panel through the observation platform fixed frame system (1); The camera Z-direction fine adjustment system (3) finely adjusts the position of the camera observation system (4) in the Z-axis direction, and through this camera Z-direction fine adjustment system (3) during the calibration of the 3D-DIC camera, realizes the relative adjustment of the Z-axis position between two cameras to assist in quickly completing the calibration; The camera pitch angle adjustment system (5) is used to realize the adjustment of the observation angle of the camera observation system (4) relative to the specimen; The camera protection system (6) is fixed through the camera connection plate to protect the camera observation system (4); Determine the position information of the camera according to the camera position determination system (7); The usage method of the observation platform for multi-dimensional dynamic and static combined loading is specifically the method for evaluating and resetting the position stability of the camera observation system, and is characterized in that it includes the following steps: Step 1: Determine the initial position of the camera. Determine the initial three-dimensional coordinates of the camera through a laser rangefinder to establish a reference position; After completing the three-dimensional calibration, determine the position information of the camera according to the camera position determination system (7). The measurement and positioning logic is: First, measure the distance from the rangefinder to the positioning plate; Step 2: Calculate the position offset after perturbation, quantify the offset of the camera after being perturbed, and judge whether reset is required; The initial position information of the quantization camera is as follows: The specific measurement method is as follows: For the left ultra-high-speed camera, use the left X-direction laser rangefinder (705) to measure the distance between the left X-direction laser rangefinder (705) and the left X-direction laser ranging positioning plate (701), and define this distance as the position x of the left ultra-high-speed camera on the X-axis 0l , use the left Y-direction laser rangefinder (707) to measure the distance between the left Y-direction laser rangefinder (707) and the left Y-direction laser ranging positioning plate (703), and define this distance as the position y of the left ultra-high-speed camera on the Y-axis 0l , use the left Z-direction laser rangefinder (706) to measure the distance between the left Z-direction laser rangefinder (706) and the top wall panel (100), and define this distance as the position z of the left ultra-high-speed camera on the Z-axis 0l ; For the right high-speed camera, use the right X-direction laser rangefinder (709) to measure the distance between the right X-direction laser rangefinder (709) and the right X-direction laser ranging and positioning plate (702), and define this distance as the position x of the right high-speed camera on the X-axis 0r , use the right Y-direction laser rangefinder (710) to measure the distance between the right Y-direction laser rangefinder (710) and the right Y-direction laser ranging and positioning plate (704), and define this distance as the position y of the right high-speed camera on the Y-axis 0r , use the right Z-direction laser rangefinder (708) to measure the distance between the right Z-direction laser rangefinder (708) and the top wall panel (100), and define the right Z-direction laser rangefinder (708) as the position z of the right high-speed camera on the Z-axis 0r ; After i tests, record the first test after calibration as the first time. Here, i refers to the number of tests in which the calibration result fails due to multiple cumulative disturbances; due to the action of various additional factors, refer to the method for measuring the initial position of the reference camera to measure the position information of the camera after being disturbed, and the position of the camera becomes The formula for the offset of the camera position relative to the initial position at this time is When the 3D-DIC calibration result fails after multiple disturbances, according to the positions of the two cameras when the calibration is initially completed Reset it; Meanwhile, define the formula for the position stability index: S(i) = (Δx(i)) 2 +(Δy(i)) 2 +(Δz(i)) 2 , when S(i) is close to the critical value, reset and adjust with reference to the position at the time of calibration completion.

2. The method for using the observation platform with multi-dimensional dynamic and static combined loading according to claim 1, characterized in that: The smaller the value of S(i), the more stable the position of the camera observation system. During the test, S(i) is not greater than 10 mm 2 .

3. The method for using the observation platform with multi-dimensional dynamic and static combined loading according to claim 1, characterized in that: The camera protection system (6) uses a transparent material with a certain strength. The impact-breaking protection baffle of the camera protection system (6) is designed in the shape of a tail boss, and a groove is provided on the camera connection plate.

4. A method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional dynamic and static combined loading, wherein the observation platform with multi-dimensional dynamic and static combined loading includes: Observation platform fixed frame system (1), observation platform XYZ spatial position adjustment system (2), camera Z-direction fine adjustment system (3), camera observation system (4), camera pitch angle adjustment system (5), camera protection system (6) and camera position determination system (7); The entire observation platform is connected to the top wall panel or the side wall panel through the observation platform fixed frame system (1); The camera Z-direction fine adjustment system (3) finely adjusts the position of the camera observation system (4) in the Z-axis direction, and through this camera Z-direction fine adjustment system (3) during the calibration of the 3D-DIC camera, realizes the relative adjustment of the Z-axis position between two cameras to assist in quickly completing the calibration; The camera pitch angle adjustment system (5) is used to realize the adjustment of the observation angle of the camera observation system (4) relative to the specimen; The camera protection system (6) is fixed through the camera connection plate to protect the camera observation system (4); Determine the position information of the camera according to the camera position determination system (7); It is characterized in that: measuring the dynamic mechanical parameters of the specimen under dynamic loading includes the following steps: Step 1, specimen preparation; Step 2, specimen installation and loading system preparation; Step 3, observation platform debugging, camera calibration and observation; For the observation platform based on multi-dimensional dynamic and static combined loading, first select two cameras with the same parameters. Relying on the framework of the platform and the three-dimensional adjustment mechanism, adjust the spatial positions of the two cameras so that their optical axes are symmetrically distributed on both sides of the central normal of the surface to be measured, and adjust the observation angle according to the feedback of the camera imaging software to ensure that the area to be measured is completely covered by the central imaging area of the double-camera target surface and the image is clear; Set the camera parameters; In one-dimensional dynamic loading, the 3D-DIC observation based on this observation platform can observe the displacement and strain along the loading axis, and can also observe the displacement and strain in the axial direction orthogonal to the loading axis. Assuming that the X-axis is used as the loading axis, the displacement and strain along the X-axis in one-dimensional dynamic loading are respectively denoted as and The stress along the loading axis is calculated by the stress wave theory The orthogonal axes are the Y-axis and the Z-axis. The corresponding displacements and strains are denoted as and and Furthermore, combined with the dynamic true triaxial electromagnetic Hopkinson bar test system for the first time, the out-of-plane displacement on the surface of the specimen in two-dimensional dynamic loading is observed, so as to calculate the strain in the out-of-plane direction of the specimen. In two-dimensional loading, the X-axis and the Y-axis are used as the loading axes. The displacements and strains along the X-axis and the Y-axis in two-dimensional dynamic loading are respectively denoted as and and The stress along the loading axis is calculated by the stress wave theory and The orthogonal axis is the Z-axis. The corresponding displacements and strains are denoted as and Step 4, measurement of dynamic mechanical parameters: When the dynamic mechanical parameter is the dynamic Poisson's ratio, the calculation method is as follows: According to the above-obtained observation results, calculate the dynamic Poisson's ratios of the specimen under one-dimensional loading and two-dimensional loading respectively: Referring to the definition of the static Poisson's ratio, the one-dimensional dynamic Poisson's ratio is: According to the observation results of this observation method, obtain the dynamic Poisson's ratio of two-dimensional dynamic loading:

5. The method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional dynamic and static combined loading according to claim 4, characterized in that: Step 4, Measurement of dynamic mechanical parameters: When the dynamic mechanical parameter is the elastic deformation energy of the specimen, the calculation method is as follows: For the evolution calculation of the specimen deformation energy, it is considered that the specimen is an elastic body before the crack appears. The elastic deformation energy E under different dimensional loadings e is calculated respectively according to the following formulas: Elastic deformation energy of the specimen under one-dimensional dynamic loading: Decompose the elastic deformation energy into volumetric deformation energy and shape deformation energy: The volumetric strain energy is as follows: The shape change can be: Energy ratio R 1 It is defined as the ratio of the volumetric strain energy to the shape change energy: Elastic deformation energy of the specimen under two-dimensional dynamic loading: Decompose the elastic deformation energy into volumetric deformation energy and shape deformation energy, The volumetric strain energy is: The shape change can be as follows: Energy ratio R 2 It is defined as the ratio of the volumetric strain energy to the shape change energy: Through R i Calculate the energy distribution of the specimen during dynamic deformation in real time. If R is measured i Mutation: such as from R i > 1 to R i < 1, indicating that the material changes from volume deformation dominance to shape distortion dominance. At this time, it corresponds to the critical state of crack nucleation. Denote this as the deformation turning point, and the elastic deformation energy is the peak value of the elastic deformation energy 6. The method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional dynamic and static combined loading according to claim 5, characterized in that: Further establish the relationship between the peak value of the elastic deformation energy of the specimen, the deformation turning point and the characteristics of dynamic disturbance: For dynamic loading, the pulse width T and amplitude A of the loading are two important factors. Discuss the relationship between the deformation turning point, the peak value of the elastic deformation energy and the pulse width and amplitude of the loading for one-dimensional dynamic loading, and establish the following functional relationship: On the basis of discussing the relationship between the deformation turning point, the peak value of the elastic deformation energy and the pulse width and amplitude of the loading for two-dimensional dynamic loading, further consider the amplitude ratio between the two loads The influence of the above two parameters, where the two parameters refer to: the deformation turning point under two-dimensional dynamic loading and the peak value of the elastic deformation energy Establish the following functional relationship:

7. The method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional dynamic and static combined loading according to claim 4, characterized in that In the specimen preparation steps: (1) According to the loading requirements of the dynamic true triaxial electromagnetic Hopkinson bar test system, the specimen is processed into a standard cube configuration of 51mm×51mm×51mm; (2) Speckle field production: Thoroughly clean the observation surface of the specimen with anhydrous ethanol to remove surface oil stains and particulate impurities to form a flat base; then evenly spray a white primer on the observation surface with a primer thickness <0.5mm, and wait for it to naturally cure for several hours in a constant temperature and dry environment, and then prepare the speckle field in the next step.

8. The method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional static and dynamic combined loading according to claim 4, characterized in that: Adjust the spatial positions of the two cameras so that their optical axes are symmetrically distributed on both sides of the central normal of the surface to be measured.

9. The method for measuring the dynamic mechanical parameters of a specimen using an observation platform with multi-dimensional dynamic and static combined loading according to claim 4, characterized in that: Set the camera parameters, which need to meet the following requirements: the synchronous trigger error is less than 1μs, and the camera shooting speed ≥ 100000 frames / second.

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