Experimental device for visual monitoring of dynamic reconstruction of microscopic contact force chain of granular material

Abstract

The invention discloses an experimental device for dynamic reconstruction visual monitoring of a microscopic contact force chain of a granular material, which comprises a shearing shaft, the bottom of the shearing shaft is a working part, the shaft diameter is gradually reduced from top to bottom, and the bottom of the shearing shaft is matched with a through hole corresponding to a shearing box, is in contact with the granular material to be monitored and is used for generating shearing and extrusion stress. The innovation value of the method is that dynamic reconstruction and visual real-time monitoring of the microscopic contact force chain of the granular material can be realized, the problem of'black box 'which puzzles particulate matter research for a long time is solved, a key experimental means is provided for establishing a multi-scale correlation model of microscopic force chain evolution and macromechanics response and breaking through the bottleneck of the existing process technology, and the method is worthy of popularization and application. Therefore, the scientificity of key parameter setting of a simulation model and the reliability of a prediction result are remarkably improved, and a theoretical basis is provided for process optimization.

Description

Technical Field

[0001] The present invention belongs to the fields of metal powder processing, powder metallurgy, powder rolling and extrusion, and relates to a technology for visually monitoring the dynamic reconstruction of a microscopic contact force chain of granular materials, specifically an experimental device for visually monitoring the dynamic reconstruction of a microscopic contact force chain of granular materials. Background Art

[0002] Manufacturing processes such as metal powder processing, powder metallurgy, powder rolling and extrusion occupy a core position in the field of high-end equipment. Their importance is mainly reflected in breaking through the performance limits of traditional materials, realizing the integrated forming of complex structures, and promoting lightweight design innovations. They have become an indispensable technical pillar in key national fields such as aerospace, new energy equipment, precision medical equipment, and national defense and military industry.

[0003] Although metal powder processing, powder metallurgy, and powder rolling and extrusion processes have shown unique advantages in the field of high-end equipment, they still face many technical bottlenecks under the coupling of multiple scales and multiple physical fields. These bottlenecks limit the further improvement of their process performance and restrict their widespread industrial application under extreme working conditions. From the perspective of the process chain, an in-depth analysis shows that the current technology system faces challenges in three key dimensions: (1) the raw material pretreatment stage, the main problems include poor powder fluidity, poor mixing uniformity, and the segregation of powders of different densities and particle sizes; (2) the molding process stage, facing defects such as significant density gradients during the pressing process, high residual porosity, demolding damage, sintering deformation and cracking; (3) the interface engineering stage, there are key technical difficulties such as insufficient interface bonding strength and unstable surface quality.

[0004] Through systematic experimental research and theoretical analysis, it was found that the essential mechanism of these apparent process defects can be traced back to the dynamic evolution and instability of the microscopic contact force chain network structure of the particle system. Specifically, (1) the force chain mechanism of raw material processing problems: the poor fluidity of powders is due to the percolation rigid force chain network formed during static stacking, whose topological structure hinders the rearrangement movement of particles; poor mixing uniformity is due to the appearance of phase-separated force chain clusters in the multi-component system; and segregation is due to the difference in fractal dimension of the force chain network caused by particle size / density differences; (2) the force chain root of forming defects: the significant density gradient in pressing is caused by the stress arch effect, which manifests as spatial heterogeneity of the force chain network; residual pores are directly related to the fracture of the force chain, and microporous cores are formed at the fracture site; demolding damage corresponds to the elastic rebound instability of the force chain network; and sintering deformation is due to the thermodynamic non-equilibrium evolution of the force chain network; (3) the force chain nature of interface problems: insufficient interface bonding strength is due to the low force chain transmission efficiency at the rolling interface; poor surface quality is caused by the fracture or spalling of surface particles due to the concentration of shear force chains, which is directly related to the shear instability of the force chain network. It can be seen that the force chain network is the core structure of the granular material, and its dynamic evolution directly affects the compression, flow, densification and other behaviors of the material. By studying the evolution of force chains, we can establish a correlation model between microscopic force chains and macroscopic mechanical properties, deepen our understanding of the constitutive relationship of powder materials, and hopefully achieve precise control of the structural characteristics and dynamic behavior of the force chain network, in order to systematically solve the technical bottlenecks faced by processes such as metal powder processing and powder metallurgy, and promote the overall improvement of technical performance.

[0005] At present, the research on the network structure characteristics and evolution of microscopic contact force chains of granular materials is mainly carried out through simulation methods. The experimental aspects are mainly focused on the study of the structural characteristics of the force chains of static granular systems, while the experimental research on the dynamic reconstruction of force chains is almost blank. This is mainly due to the fundamental limitations of the technology and the lack of theoretical methods. Specifically: (1) In terms of imaging technology, the scanning frequency of industrial CT is low and it is impossible to capture the moment when the force chain breaks / reorganizes. In addition, high-speed photography cannot penetrate the three-dimensional particle layer, and the cost of synchrotron radiation light source is extremely high. (2) In terms of force measurement technology, the photoelastic method is limited by the transparency of the particles, and the pressure-sensitive film can only measure the boundary force, but cannot measure the contact force between particles. (3) In terms of theoretical methods, the lack of dynamic constitutive theory and theoretical guidance on cross-scale correlation fracture has limited the breakthrough of process bottlenecks such as metal powder processing and powder metallurgy. Based on the above research status and difficulties, relying on the support of national key projects, the experimental device of the present invention is designed by combining simulation and experiment to explore the key scientific issues in the theory of particle systems. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art; to this end, the present invention proposes an experimental device for visual monitoring of the dynamic reconstruction of microscopic contact force chains of granular materials, which is used to solve the technical problem that there is almost no experimental research on the dynamic reconstruction of force chains. The present invention is based on the principle of photoelasticity experiment, and through the cooperation of a rotational shear system and an optical imaging system, it captures the force chain structural characteristics of the particle system and the dynamic evolution law of the fracture-reconstruction of the force chain structure under shear action, thereby solving the above-mentioned problems.

[0007] To achieve the above objectives, the first aspect of the present invention provides an experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials, comprising a shear shaft, the bottom of which is a working portion and the shaft diameter gradually decreases from top to bottom, the bottom of the shear shaft cooperates with the through hole corresponding to the shear box and contacts the granular material to be monitored, for generating shear and compression stresses; A shear box is disposed below the shear shaft. The upper end of the shear box is open and the bottom is transparent. It is used to place the granular material to be monitored. A through hole is provided at the bottom of the shear box corresponding to the shear shaft, and the shear box is configured to be movable up and down. By adjusting the position of the shear box relative to the axis of the shear shaft, the extrusion stress on the granular material to be monitored in the shear box can be dynamically controlled. An optical imaging unit is configured along the axis of the shear axis, with the shear box located in the middle of the optical imaging unit. The optical axis of the optical imaging unit is parallel to the axis of the shear axis. The optical imaging unit includes a high-speed camera, a light source, and an optical path assembly. The optical path assembly includes multiple optical elements, and any optical element in the optical path assembly is configured to be able to translate or rotate along the optical axis. The driving unit is used to drive the shear shaft. The driving unit is configured to be movable along the axial direction of the shear shaft to ensure parallelism between the transmission plane of the driving unit and the shear shaft and the cross section of the shear shaft.

[0008] Furthermore, any optical element in the optical path assembly is installed via a pin fixture, and the angle adjustment mechanism between the optical element and the pin fixture adopts a threaded coupling design.

[0009] Furthermore, the optical element in the angle adjustment mechanism is axially compressed and fixed by an upper end face adjusting bolt, and the angle locking state is maintained by means of the static friction effect of the bolt-pin interface; when the rotation angle is adjusted, the bolt pre-tightening force is gradually released through a controllable torque wrench, so that the optical element rotates slightly around the rotation center of the pin.

[0010] An experimental method for an experimental device for dynamic reconstruction and visualization monitoring of microscopic contact force chains of granular materials, wherein the experimental method is applied to the above-mentioned experimental device; The method comprises placing the granular material to be monitored in a shear box and laying it flat, with the bottom of the shear shaft being matched with the corresponding through hole of the shear box and in contact with the granular material to be monitored; Adjust the translational motion of the optical element along the optical axis (vertical direction) and the rotational motion in the horizontal plane to perform multi-degree-of-freedom coordinated adjustment to achieve optical path polarization control; Adjust the position of the shear box relative to the axial direction of the shear axis to dynamically control the extrusion stress of the granular material to be monitored in the shear box; Adjust the speed of the shear shaft to change the extrusion stress; The light generated by the square light source passes through the optical element below the shear box, the shear box and the granular material to be monitored, the optical element above the shear box, and is finally captured by the high-speed camera; Based on the principle of photoelasticity experiment, a high-speed camera is used to capture the force chain structural characteristics of the monitored granular material in the shear box, as well as the dynamic evolution of the force chain structure fracture and reconstruction under shear action.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1) Realize the visual real-time monitoring of the force chain structural characteristics and fracture and reconstruction dynamic evolution of granular materials under continuous shearing; 2) Adopt innovative modular coupling design concept to achieve collaborative optimization of multifunctional systems.

[0012] 3) Using an optical imaging system based on kinematic mounting principles, each optical element is equipped with a coarse and fine adjustment mechanism to support real-time polarization state calibration during the experiment; 4) For the rotary shear system, the relative position of the shear box and the shear axis can be adjusted through the displacement platform, which can dynamically control the extrusion stress on the elastic-plastic particles in the shear box, breaking the fixed boundary restrictions of the traditional shear box and achieving independent control of the shear-extrusion composite load; 5) The innovative value of this invention lies in its ability to dynamically reconstruct and visualize the microscopic contact force chain of granular materials in real time, resolving the "black box" problem that has long plagued granular material research. This provides a key experimental approach for establishing a multi-scale correlation model between the evolution of microscopic force chains and macroscopic mechanical responses, thereby breaking through existing process technology bottlenecks. This significantly improves the scientific nature of key parameter settings in simulation models and the reliability of prediction results, thus providing a theoretical basis for process optimization. This technological breakthrough will not only effectively improve product quality but will also drive metal powder processing technology forward in the direction of high precision, high performance, and high stability, ultimately providing solid technical support for the field of high-end equipment manufacturing. 6) The cost of the solution adopted by the present invention is lower than that of the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 Schematic diagram of the present invention.

[0015] Figure 2 This is a schematic diagram from another angle of the present invention.

[0016] Figure 3 It is an enlarged schematic diagram of the shear axis position of the present invention.

[0017] Figure 4 Schematic diagram of the connection between the pin fixture of the present invention and the optical element.

[0018] Figure 5 This is a schematic diagram of installing side panels in a rectangular trough according to the present invention.

[0019] Figure 6 It is a schematic diagram of the connection between the side panels and the clamping blocks in the present invention.

[0020] In the figure: base plate 1, rectangular groove mounting side plate 2, fixed beam 3, high-speed camera 4, plane polarizer 5, 1 / 4 wave plate 6, shear shaft 7, transparent base plate 8, annular side wall 9, mounting side plate 10, displacement platform A11, square light source 12, rectangular mounting platform 13, displacement platform B14, motor 15, transmission belt 16, mounting back plate 17, shear shaft mounting bracket 18, pin fixture 19, slot 20, slider 21, block 22. DETAILED DESCRIPTION

[0021] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Example 1, please refer to Figure 1-4FIG. 1 , an embodiment of the first aspect of the present invention provides an experimental device for dynamic reconstruction and visualization monitoring of microscopic contact force chains of granular materials, comprising a rotating shear system, wherein a set of 1 / 4 wave plates 6, a plane polarizer 5, and a high-speed camera 4 are sequentially arranged upwardly on the rotating shear system, and another set of 1 / 4 wave plates 6, a plane polarizer 5, and a square light source 12 are sequentially arranged downwardly on the rotating shear system; the rotating shear system, the high-speed camera 4, the 1 / 4 wave plate 6, the plane polarizer 5, and the square light source 12 are coaxially arranged; Based on the principle of kinematic constraints, the optical components (plane polarizer 5 and quarter-wave plate 6) are fixed to the bearing surface of the displacement platform using pin fixtures. The spatial arrangement of the quarter-wave plate 6 and plane polarizer 5 strictly follows the polarization interference sequence from top to bottom: first-stage plane polarizer → first quarter-wave plate → second quarter-wave plate → secondary plane polarizer.

[0023] The two groups of 1 / 4 wave plates 6 and plane polarizers 5 are respectively connected to adjustable brackets on both sides through a displacement platform A11. The adjustable brackets are connected to the base plate 1. The tops of the adjustable brackets on both sides are also fixedly connected to fixed beams 3. A light transmission hole is opened in the middle of the fixed beam 3 and a high-speed camera 4 is fixedly connected at this position. The lens of the high-speed camera 4 faces the light transmission hole. The square light source 12 is fixedly mounted on the base plate 1.

[0024] The rotary shearing system includes a shearing box (transparent bottom plate 8, annular side wall 9), a shearing shaft 7, a transmission belt 16 and a shearing shaft mounting bracket 18. The shearing shaft 7 is vertically arranged in the shearing box, and the middle part of the shearing shaft 7 is rotatably connected to the mounting hole opened on the shearing shaft mounting bracket 18 through an angular contact bearing; the shearing shaft 7 adopts a gradient diameter configuration design that gradually shrinks from top to bottom, and the rotation of the shearing shaft 7 realizes directional shearing drive of the elastic-plastic two-dimensional particle system in the shearing box.

[0025] The shear box includes a transparent bottom plate 8 and an annular side wall 9, and the lower end of the annular side wall 9 is fixedly connected to the transparent bottom plate 8; a through hole is opened on the transparent bottom plate 8 at the position corresponding to the shear axis 7, and the lower end of the shear axis 7 is set through the through hole, and the shear axis 7 is a hollow shaft. The annular side wall 9 is connected to the mounting back plate 17 through the displacement platform A11, so as to realize the up and down adjustment of the shear box, and cooperate with the shear axis with a gradient diameter configuration design to realize the controllable loading of the extrusion stress, and the position of the shear box and the shear axis is relatively adjustable, so as to dynamically regulate the extrusion stress of the elastic-plastic particles in the shear box. The annular side wall 9 forms an adjustable rigid connection with the displacement platform A11, and the transparent bottom plate 8 is glued to the precisely machined step surface of the annular side wall 9 to ensure the isotropy of the interface mechanical transmission.

[0026] The shear shaft mounting bracket 18 is fixedly connected to the mounting back plate 17 , and both ends of the mounting back plate 17 are fixedly connected to the adjustable brackets on both sides; the shear box is also connected to the mounting back plate 17 through the corresponding displacement platform A11 .

[0027] The shear shaft 7 is also provided with a belt groove on its surface. The shear shaft 7 is connected to a fixed pulley on the output shaft of a motor 15 via a transmission belt 16. The motor 15 is rigidly connected to a rectangular mounting platform 13 via a displacement platform B14, which is in turn fixedly connected to the base plate 1. The adjustment mechanism of the motor 15 enables alignment adjustment of the transmission system comprising the shear shaft 7, transmission belt 16, and motor 15, enabling precise vertical adjustment of the motor's position, thereby ensuring parallelism between the transmission plane of the transmission belt 16 and a horizontal reference plane.

[0028] The mounting back plate 17 is provided with a slot for the transmission belt 16 to pass through.

[0029] The transmission system, shear shaft and shear box constitute a stress loading control system. The stress loading control system adopts a modular mechanical coupling design. The mounting back plate 17 is rigidly connected to the rectangular groove mounting side plate 2 through bolts, and a high-precision displacement platform B14 is installed on the working surface.

[0030] like Figure 4 , a pin structure is formed on one side of the bracket of the plane polarizer 5 or 1 / 4 wave plate 6, and a through hole for the adjustment bolt to pass through is provided at the axial center position of the pin structure, which is fixedly connected to the opening of the pin fixture 19 by the adjusting bolt, and a C-shaped slot is provided on the pin fixture 19 and the C-shaped slot is used to connect the plane polarizer 5 or 1 / 4 wave plate 6 bracket, the pin fixture 19 is fixedly connected to the displacement platform A11, the axis of the adjustment bolt connected at the opening of the pin fixture 19 is vertically arranged, and a through hole for the adjustment bolt to pass through is correspondingly provided through one end of the pin fixture 19, and a threaded hole threadedly connected to the adjustment bolt is correspondingly provided at the other end of the pin fixture 19; one end of the adjusting bolt passes through the through hole and the corresponding through hole on the bracket of the plane polarizer 5 or 1 / 4 wave plate 6 and is threadedly connected to the threaded hole, and by rotating the bolt, the two ends of the pin fixture 19 clamp the bracket of the plane polarizer 5 or 1 / 4 wave plate 6 to achieve positioning, so as to facilitate the position adjustment of the plane polarizer 5 or 1 / 4 wave plate 6.

[0031] In addition, the way in which the displacement platform A11 cooperates with the pin fixture 19 can enable the optical elements (plane polarizer 5, 1 / 4 wave plate 6) to perform translational motion along the optical axis direction (vertical direction) and rotational motion in the horizontal plane, thereby realizing multi-degree-of-freedom coordinated adjustment of the optical imaging system, thereby improving the flexibility of optical path polarization control and experimental repeatability.

[0032] The angle adjustment mechanism between the above-mentioned optical elements (plane polarizer 5, 1 / 4 wave plate 6) and the pin fixture adopts a threaded coupling design. Each optical element is axially compressed and fixed by adjusting bolts, and the angle locking state is maintained by the static friction effect of the contact interface between the pin fixture 19 and the pin structure. When adjusting the rotation angle, the bolt pre-tightening force is gradually released by a controllable torque wrench, so that the optical element rotates slightly around the rotation center of the pin. This mechanism meets the real-time calibration requirements of the polarization orientation of the optical element during dynamic experiments, ensuring the long-term stability of the polarization optical path system.

[0033] The adjustable bracket includes a rectangular groove mounting side vertical plate 2 and a mounting side plate 10. Each adjustable bracket includes two rectangular groove mounting side vertical plates 2. Multiple mounting side plates 10 are connected between the two rectangular groove mounting side vertical plates 2. The mounting side plates 10 are used to connect the bracket of the plane polarizer 5 or the 1 / 4 wave plate 6.

[0034] like Figure 5 A plurality of slots 20 are equidistantly provided on one side of the rectangular groove mounting side vertical plate 2. The lower end of the rectangular groove mounting side vertical plate 2 is integrally formed into a slider 21 and slidably connected to the base plate 1. At the same time, the base plate 1 and the slider 21 are connected by bolts. Specifically, the bolts pass through the base plate 1 and are threadedly connected to the slider 21 to achieve fixation.

[0035] like Figure 6 One side of the mounting side plate 10 is fixedly connected to two clamping blocks 22 .

[0036] The block 22 of the mounting side panel 10 engages the slot 20, and the block 22 and slot 20 can be reinforced with screws. This connection between the block 22 and slot 20 allows for coarse adjustment of the mounting side panel 10 position, and further allows for coarse adjustment of the position of the optical element attached to the mounting side panel 10. Fine adjustment is achieved via the displacement platform, also achieving a modular connection.

[0037] Similarly, the same modular design can be adopted between the mounting back plate 17 and the rectangular groove mounting side vertical plate 2.

[0038] Example 2, an experimental method for an experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials, wherein the method is applied to the experimental device; The method comprises placing the granular material to be monitored in a shear box and laying it flat, with the bottom of the shear shaft being matched with the corresponding through hole of the shear box and in contact with the granular material to be monitored; Adjust the translational motion of the optical element along the optical axis (vertical direction) and the rotational motion in the horizontal plane to perform multi-degree-of-freedom coordinated adjustment to achieve optical path polarization control; Adjust the position of the shear box relative to the axial direction of the shear axis to dynamically control the extrusion stress of the granular material to be monitored in the shear box; Adjust the speed of the shear shaft to change the extrusion stress; The light generated by the square light source passes through the optical element below the shear box, the shear box and the granular material to be monitored, the optical element above the shear box, and is finally captured by the high-speed camera; Based on the principle of photoelasticity experiment, a high-speed camera is used to capture the force chain structure characteristics of the monitored granular material in the shear box, as well as the dynamic evolution of the force chain structure fracture and reconstruction under shear action; The method further comprises controlling the shearing speed by changing the rotation speed of the motor driving the shearing shaft 7 .

[0039] The method further includes realizing different filling schemes by filling elastoplastic particles with different characteristic parameters, such as particle size, particle size distribution, friction coefficient and other parameters of the filling particles.

[0040] The above embodiments are only used to illustrate the technical method of the present invention and are not intended to limit the present invention. 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 method of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical method of the present invention.

Claims

1. An experimental device for dynamic reconstruction and visualization monitoring of microscopic contact force chains of granular materials, characterized by: include: The shear shaft has a working part at the bottom and a shaft diameter that gradually decreases from top to bottom. The bottom of the shear shaft is matched with the through hole corresponding to the shear box and contacts the granular material to be monitored to generate shear and extrusion stress; A shear box is disposed below the shear shaft. The upper end of the shear box is open and the bottom is transparent. It is used to place the granular material to be monitored. A through hole is provided at the bottom of the shear box corresponding to the shear shaft, and the shear box is configured to be movable up and down. By adjusting the position of the shear box relative to the axis of the shear shaft, the extrusion stress on the granular material to be monitored in the shear box can be dynamically controlled. An optical imaging unit is configured along the axis of the shear axis, with the shear box located in the middle of the optical imaging unit. The optical axis of the optical imaging unit is parallel to the axis of the shear axis. The optical imaging unit includes a high-speed camera, a light source, and an optical path assembly. The optical path assembly includes multiple optical elements, and any optical element in the optical path assembly is configured to be able to translate or rotate along the optical axis. The driving unit is used to drive the shear shaft. The driving unit is configured to be movable along the axial direction of the shear shaft to ensure parallelism between the transmission plane of the driving unit and the shear shaft and the cross section of the shear shaft.

2. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 1 is characterized in that: Any optical element in the optical path assembly is installed via a pin fixture, and the angle adjustment mechanism between the optical element and the pin fixture adopts a threaded coupling design.

3. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 2 is characterized in that: The optical element in the angle adjustment mechanism is axially compressed and fixed by an upper end surface adjusting bolt, and the angle locking state is maintained by means of the static friction effect of the bolt-pin interface; when adjusting the rotation angle, the bolt pre-tightening force is gradually released by a controllable torque wrench, so that the optical element rotates slightly around the rotation center of the pin.

4. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 1 is characterized in that: Optical elements and a high-speed camera are sequentially arranged above the shear axis; optical elements and a square light source are sequentially arranged below the shear box. The optical elements are connected to adjustable brackets on both sides through a displacement platform A, and the adjustable brackets are connected to the bottom plate.

5. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 1 or 4, characterized in that: The middle part of the shear shaft is rotatably connected to the mounting hole on the shear shaft mounting bracket through an angular contact bearing; a belt groove is also provided on the surface of the shear shaft, and the shear shaft is connected to the fixed pulley on the motor output shaft through a transmission belt; The shear box includes a transparent bottom plate and an annular side wall, the lower end of the annular side wall is fixedly connected to the transparent bottom plate; a through hole is opened on the transparent bottom plate at a position corresponding to the shear axis, and the lower end of the shear axis is arranged through the through hole, and the shear axis is a hollow shaft; The shear shaft mounting bracket is fixedly connected to the mounting back plate, and both ends of the mounting back plate are fixedly connected to the adjustable brackets on both sides. The motor is rigidly connected to the rectangular mounting platform through the displacement platform B, and the rectangular mounting platform is fixedly connected to the base plate.

6. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 2 or 3, characterized in that: The optical element includes a plane polarizer and a quarter wave plate. One side of the bracket of the plane polarizer and the quarter wave plate is formed with a pin structure, and the pin structure is rotatably connected to the pin fixture.

7. The experimental device for dynamic reconstruction and visual monitoring of microscopic contact force chains of granular materials according to claim 5, characterized in that: The adjustable bracket includes a rectangular groove mounting side vertical plate and a mounting side plate, each adjustable bracket includes two rectangular groove mounting side vertical plates, and a plurality of mounting side plates are connected between the two rectangular groove mounting side vertical plates; A plurality of slots are provided at equal distances on one side of the rectangular slot mounting side vertical plate. The lower end of the rectangular slot mounting side vertical plate is integrally formed into a slider and slidably connected to the bottom plate. The slider is fixedly connected to the bottom plate by bolts to achieve a fixed connection between the rectangular slot mounting side vertical plate and the bottom plate. One side of the mounting side plate is fixedly connected to two clamping blocks; Install the card block of the side panel into the card slot.

8. An experimental method for an experimental device for dynamic reconstruction and visualization monitoring of microscopic contact force chains of granular materials, characterized in that: The experimental method is applied to the above experimental device; The method comprises placing the granular material to be monitored in a shear box and laying it flat, with the bottom of the shear shaft being matched with the corresponding through hole of the shear box and in contact with the granular material to be monitored; Adjust the translational motion of the optical element along the optical axis and the rotational motion in the horizontal plane to perform multi-degree-of-freedom coordinated adjustment to achieve optical path polarization control; Adjust the position of the shear box relative to the axial direction of the shear axis to dynamically control the extrusion stress of the granular material to be monitored in the shear box; Adjust the speed of the shear shaft to change the extrusion stress; The light generated by the square light source passes through the optical element below the shear box, the shear box and the granular material to be monitored, the optical element above the shear box, and is finally captured by the high-speed camera; Based on the principle of photoelasticity experiment, a high-speed camera is used to capture the force chain structural characteristics of the monitored granular material in the shear box, as well as the dynamic evolution of the force chain structure fracture and reconstruction under shear action.

9. The experimental method of the experimental device for dynamic reconstruction and visualization monitoring of microscopic contact force chains of granular materials according to claim 8, characterized in that: The method further comprises realizing different filling schemes by filling elastoplastic particles with different characteristic parameters.

10. Application of an experimental device for visual monitoring of dynamic reconstruction of microscopic contact force chains of granular materials to capture the structural characteristics of the force chains of granular systems and the dynamic evolution of the force chain structure from fracture to reconstruction under shear.

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