A 3D printing-based particle column collapse test observation device and test method

Abstract

The present invention discloses a particle column collapse test observation device and test method based on 3D printing, the device includes a fixed frame, a movable trough bottom plate, a particle sliding trough, a liftable baffle and a lifting assembly, the baffle being liftably inserted into the particle sliding trough; it also includes an image acquisition assembly for capturing and recording images of the particle column in the particle sliding trough and its accumulation, flow and collapse process; it also includes an image analysis device for receiving and displaying the images captured by the image acquisition assembly, and analyzing the images. The present device and method have strong flexibility and applicability, and can be used to explore the effects of different independent variables on the flow and accumulation characteristics of particles in the particle column collapse, and are not limited to the characteristic variables of the particle column system, thereby improving the utilization rate of the device and facilitating multi-faceted research on the particle column collapse test; and the overall structure is simple, easy to manufacture and use, and the cost is also low, which is convenient for maintenance and updating.

Description

Technical Field

[0001] The present invention relates to the field of granular material mechanics research, and specifically to the use of 3D printing technology to characterize the multi-scale morphology of particle surfaces. The present invention is a test device and test method for controlling multi-variable particle column collapse physical tests and observing post-collapse flow and accumulation characteristics. Background Art

[0002] Landslide-debris flow is a very harmful geological disaster that poses a great threat to the production and life of nearby residents. Domestic and foreign scholars often choose to use particle column collapse model experiments to study the relevant characteristics and movement mechanism of landslide-debris flow.

[0003] Some have used cylinders to conduct collapse tests on cylindrical particle columns, studying the effects of initial aspect ratio on the flow and accumulation characteristics of particle flows. High-speed cameras were used to capture the microscopic state of the particle column collapse process, yielding relevant results. Others have used thin glass plates and swinging doors to construct a test apparatus for binary particle column collapse, investigating the effects of small particle content, initial column height, and initial arrangement on the flow characteristics of particle flows. Others have used plexiglass boxes, high-speed cameras, and pressure sensors to observe the collapse flow of particle columns and monitor the dynamic changes during the collapse process to investigate changes in particle velocity and base pressure during the column collapse. Others have used acrylic plates and electronic translation devices to conduct quasi-static collapse tests on two-component particle columns. High-speed cameras and image acquisition programs were used to track the movement trajectories of individual particles, establishing a quasi-static collapse model for particle columns. Others have used tall glass boxes and pull-out devices to simulate planar spreading landslides, investigating the influence of different layered stacking patterns and different particle gradations on the flow and accumulation characteristics of particle columns.

[0004] However, existing particle column collapse tests mostly use natural granular materials. Even after careful screening and detailed processing, the particle morphology characteristics are difficult to accurately identify and classify, making it difficult to achieve uniform morphological characteristics within a particle column system. Therefore, particle column collapse tests often use easily controllable dependent variables such as particle gradation, particle size, and particle number. The lack of particle column collapse experiments using particle morphology as an independent variable makes it impossible to study the relationship between specific particle morphological characteristics and the flow and accumulation properties of particle flows.

[0005] Furthermore, the particle column collapse test apparatus used in previous indoor experiments was mostly fixed and designed solely to control a single variable, making it difficult to adapt to changes in other variables. When studying multiple factors, the apparatus even needed to be redesigned, resulting in low overall test efficiency and a lack of economic and environmental performance. Summary of the Invention

[0006] The purpose of the present invention is to address the problems existing in the prior art and provide a collapse test observation device and test method based on 3D printed particle columns, which can control multiple variables and observe the flow and stacking characteristics of particles from multiple directions, so as to deeply explore the relationship between particle morphological characteristics and other variables and the flow and stacking characteristics of particles.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A 3D-printed particle column collapse test observation device comprises a fixed frame, one side of which is provided with a movable trough bottom plate, a particle sliding trough being provided above the trough bottom plate, and one end of the trough bottom plate and the particle sliding trough respectively extending into the fixed frame; a liftable baffle is provided on the fixed frame, and a lifting assembly connected to the baffle, wherein the baffle is liftably inserted into the particle sliding trough;

[0009] It also includes an image acquisition component, which is used to capture and record images of the particle column in the particle sliding trough and its accumulation, flow and collapse process;

[0010] It also includes an image analysis device, which is connected to the image acquisition component, receives and displays the image taken by the image acquisition component, and analyzes the image.

[0011] This 3D-printed particle column collapse test observation device has strong flexibility and applicability. It can be used to explore the influence of different independent variables on the flow and accumulation characteristics of particles in the particle column collapse. It is not limited to the characteristic variables of the particle column system, which improves the utilization rate of the device and facilitates the multi-faceted research of the particle column collapse test. Moreover, the overall structure is simple, easy to manufacture and use, low in cost, and easy to maintain and update.

[0012] Furthermore, one side of the upper portion of the fixed frame extends outward and is provided with a slide groove structure, the baffle is installed in the slide groove structure, and the particle slide groove is arranged below the slide groove structure.

[0013] Furthermore, a covering layer with different friction coefficients is provided on the bottom plate of the trough, the particle sliding trough is an enclosed structure open at the top and bottom, and a discharge trough is provided below the tail plate at one end of the particle sliding trough away from the baffle.

[0014] Furthermore, the particle sliding groove and the baffle are respectively made of transparent materials, and the width of the baffle is smaller than the inner circumference width of the particle sliding groove.

[0015] Furthermore, the lifting assembly includes a plurality of fixed pulleys arranged on the fixed frame, a steel wire rope is wound around the fixed pulley, one end of the steel wire rope is connected to the baffle, and the other end is connected to the control rod, and the control rod is arranged on the other side of the fixed frame away from the baffle. The fixed frame is also provided with a plurality of blocking hooks for connecting the control rods.

[0016] Furthermore, the image acquisition component includes a high-speed camera supported by a tripod and multiple light sources, and the high-speed camera is arranged in a stable area in front of or above the particle sliding trough; the image analysis device is a host computer with a display screen, and the host computer is electrically connected to the high-speed camera.

[0017] A test method for a particle column collapse test observation device based on 3D printing, the test method comprising the following steps:

[0018] Prepare several particle samples;

[0019] The baffle is lifted to the highest point by the lifting assembly and kept stationary;

[0020] The trough bottom plate is arranged below the fixed frame, a covering layer is provided on the trough bottom plate, and the trough bottom plate is adjusted to be horizontal;

[0021] Placing the particle sliding trough on the covering layer, and adjusting the positions of the particle sliding trough and the covering layer so that the baffle is at a preset position on the particle sliding trough;

[0022] Controlling the lifting assembly to lower the baffle so that the baffle falls into the particle sliding trough and forms an independent trough space with the particle sliding trough; arranging the image acquisition assembly in the area in front of or above the particle sliding trough and connecting it to the image analysis device;

[0023] A group of particle samples are placed in the trough space to form a particle column, and several plumb lines are arranged on the side of the particle sliding trough facing the image acquisition component to mark it;

[0024] Turning on the image acquisition component and controlling the lifting component to lift the baffle, the particle column begins to flow and collapse. After the collapse stabilizes, stopping image acquisition and measuring test data after the particle column collapses;

[0025] Pick up the particle sample after it flows to collapse and repeat the next set of tests. After multiple sets of tests are completed, analyze the collected images to obtain the flow characteristic data and accumulation characteristic data of the particle column.

[0026] Through the collapse test observation device and method of the present invention, a particle column test group with completely identical other variables can be controlled, and the flow characteristics and stacking characteristics of the particles such as the flow velocity after the particle column collapse can be obtained in multiple directions, thereby enabling in-depth research on the relationship between different characteristics of the particles and the collapse flow and stacking characteristics of the particle column.

[0027] Furthermore, the method for preparing the particle sample is as follows:

[0028] The Cartesian coordinates of a finite number of surface points of each particle are obtained by scanning and measuring with three-dimensional laser technology, and the coordinates of the particle center of mass are obtained using data processing software. Based on this, a double mapping is performed between the particle surface and the spherical surface to obtain the spherical coordinates of each surface point;

[0029] By spherical harmonic analysis, the surface expressed by the polar radius set of the surface points of the particle is expanded, thereby obtaining a reconstructed surface function that is infinitely close to the surface shape of the particle, and calculating the surface points of the particle with different scale morphological characteristics through reconstruction;

[0030] Based on the calculated particle surface points, three-point coordinate data is taken one by one through data processing software to establish triangular facets, and a limited number of triangular facets are pieced together to form a complete particle surface, thereby generating a three-dimensional model file containing the complete particle surface data;

[0031] After adding supports to the three-dimensional model file, the particle entity is printed by selecting materials through a 3D printer, and the supports are removed to obtain a complete solid particle model, namely the particle sample.

[0032] Furthermore, the image is analyzed as follows:

[0033] Among the collected continuous images, a series of continuous images from the moment before the particle column begins to collapse to the moment after the particle sample completely stops flowing are selected, and the series of continuous images are exported;

[0034] In an image analysis program, the selected series of continuous images are imported and preprocessed: denoising filtering is performed on the series of continuous images, a scale of the series of continuous images and an actual object is set, and a flow cell in the series of continuous images is selected as an analysis area;

[0035] Use PIV technology to track particle samples and calculate the flow velocity of particle samples to obtain velocity distribution and changes;

[0036] By limiting the maximum velocity and correcting the obviously abnormal velocity magnitude and direction, the flow characteristics of flow duration and velocity change are obtained; by comparing the initial and final stationary time frames, the accumulation characteristics of the collapse relative stationary angle, accumulation height and flow distance can be obtained.

[0037] Furthermore, the flow velocity is calculated as follows:

[0038] Track the particle sample in a series of consecutive images through cross-correlation analysis, and extract the displacement of the same particle sample in the previous and next images: pre-segment the image into identical grids, then perform three Fourier transforms on the previous and next frame images, and extract the displacement of the particle sample as (Δx, Δy);

[0039] When the time interval Δt between the two frames is infinitely close to 0, the calculated average speed can be regarded as the instantaneous speed at the time of shooting, that is:

[0040] ,

[0041] Where Δx represents the displacement of the particle sample in the x direction, Δy represents the displacement of the particle sample in the y direction, u represents the flow velocity of the particle sample in the x direction, and v represents the flow velocity of the particle sample in the y direction.

[0042] Compared with the prior art, the beneficial effects of the present invention are: 1. The particle column collapse test observation device based on 3D printing has strong flexibility and applicability, and can be used to explore the influence of different independent variables on the flow and accumulation characteristics of particles in the collapse of the particle column. It is not limited to the characteristic variables of the particle column system, which improves the utilization rate of the device and facilitates the multi-faceted research of the particle column collapse test; and the overall structure is simple, easy to make and use, the cost is low, and it is easy to maintain and update; 2. The trough bottom plate and the particle sliding trough are relatively flexibly and freely arranged below the fixed frame, and their relative positions can be adjusted as needed, so that the baffle can fall into the particle sliding trough from different positions to separate the volume Different trough spaces can obtain particle column systems with different stacking volumes, and can also control the aspect ratio of the particle column system; 3. The setting of the lifting component is not only a component that connects and drives the baffle to rise and fall, but also can control the lifting speed of the baffle according to the test needs; 4. Through the collapse test observation device and method of the present invention, the particle column test group with completely consistent other variables can be controlled, and the flow characteristics and stacking characteristics of the particles such as the flow velocity after the collapse of the particle column can be obtained in multiple directions, and then the relationship between different characteristics of the particles and the collapse flow and stacking characteristics of the particle column can be deeply studied; the method of observing the flow characteristics of the particles in physical experiments is supplemented, and the method of observing the stacking characteristics of the particles after collapse is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic flow chart of a particle column collapse test method based on 3D printing according to the present invention;

[0044] Figure 2 This is a schematic diagram of the three-dimensional structure of the particle column collapse test observation device based on 3D printing of the present invention;

[0045] Figure 3 Schematic diagram of the arrangement of the particle column collapse test observation device based on 3D printing of the present invention;

[0046] In the figure: 1. Fixed frame; 2. Groove bottom plate; 3. Particle sliding groove; 4. Baffle; 5. Discharge groove; 6. Fixed pulley; 7. Wire rope; 8. Control rod; 9. Groove structure; 10. Anti-movement hook; 11. High-speed camera; 12. Strong light source; 13. Laptop computer; 14. Particle sample. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. 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.

[0048] In the description of the present invention, it should be noted that the terms "middle", "upper", "lower", "left", "right", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the present invention. Example 1

[0049] like Figure 1 and Figure 2 As shown, a particle column collapse test observation device based on 3D printing includes a fixed frame 1, a movable trough bottom plate 2 is provided on one side of the fixed frame 1, a particle sliding trough 3 is provided above the trough bottom plate 2, and one end of the trough bottom plate 2 and the particle sliding trough 3 respectively extends into the fixed frame 1; a liftable baffle 4 is provided on the fixed frame 1, and a lifting assembly connected to the baffle 4, and the baffle 4 is liftably inserted into the particle sliding trough 3;

[0050] It also includes an image acquisition component, which is used to capture and record images of the particle column in the particle sliding trough and its accumulation, flow and collapse process;

[0051] It also includes an image analysis device, which is connected to the image acquisition component, receives and displays the image taken by the image acquisition component, and analyzes the image.

[0052] This 3D-printed particle column collapse test observation device has strong flexibility and applicability. It can be used to explore the influence of different independent variables on the flow and accumulation characteristics of particles in the particle column collapse. It is not limited to the characteristic variables of the particle column system, which improves the utilization rate of the device and facilitates the multi-faceted research of the particle column collapse test. Moreover, the overall structure is simple, easy to manufacture and use, low in cost, and easy to maintain and update.

[0053] The fixed frame 1 is mainly used to install the baffle 4 and control the lifting assembly of the baffle 4. The trough bottom plate 2 and the particle sliding trough 3 are relatively flexibly and freely arranged below the fixed frame 1. Their relative positions can be adjusted as needed, allowing the baffle 4 to fall into the particle sliding trough 3 from different positions, separating trough spaces of different volumes, thereby obtaining particle column systems with different stacking volumes. The position adjustment of the particle sliding trough 3 and the baffle 4 is reflected in the control of the aspect ratio of the particle column system.

[0054] The lifting assembly is not only a component for connecting and driving the baffle to rise and fall, but also can control the lifting speed of the baffle according to test needs, so as to observe the flow and collapse characteristics of the particle column at different evacuation speeds of the baffle.

[0055] Furthermore, an upper side of the fixed frame 1 extends outward and is provided with a slide groove structure 9 , the baffle 4 is installed in the slide groove structure 9 , and the particle slide groove 3 is arranged below the slide groove structure 9 .

[0056] The fixed frame 1 is composed of multiple horizontal bars, longitudinal bars and vertical bars, and has two layers, the upper layer is longer than the lower layer, so that the chute structure can be set on the side of the upper layer, and the chute bottom plate and the particle sliding chute can be placed below.

[0057] The slide groove structure is a vertical slide groove on the side wall, and the baffle can be slidably arranged in it and can move up and down along it under the traction of the lifting assembly.

[0058] Furthermore, a covering layer with different friction coefficients is provided on the bottom plate 2 of the trough, and the covering layer is a gasket coated or pasted on the bottom plate of the trough; the covering layer can be replaced to change the friction coefficient faced by the particle sample, and the covering layer can also form a sealing structure with the bottom of the particle sliding trough to prevent the particle column from flowing out from the gap between the two during the flow collapse process.

[0059] The particle sliding trough 3 is an enclosed structure open at the top and bottom, that is, it has no bottom plate and top plate structure; a discharge trough 5 is provided below the tail plate of the particle sliding trough 3 at one end away from the baffle, and the discharge trough is away from the position where the particle column collapses. Its purpose is to facilitate the sliding out of subsequent particle samples. The height of the discharge trough is about 5 cm.

[0060] Furthermore, the particle sliding groove 3 and the baffle 4 are made of transparent materials, such as organic glass plates. The width of the baffle is slightly smaller than the inner circumference width of the particle sliding groove, so that it can be just accommodated in the particle sliding groove without affecting its up and down movement.

[0061] The inner dimensions of the particle sliding trough 3 are 150.0 cm (length) × 30.0 cm (width) × 65.0 cm (height), the dimensions of the trough bottom plate 2 are 200.0 cm (length) × 50.0 cm (width) × 1.0 cm (thickness), and the dimensions of the rigid baffle 4 are 70.0 cm (length) × 29.8 cm (width) × 2.0 cm (thickness).

[0062] Furthermore, the lifting assembly includes a plurality of fixed pulleys 6 arranged on the fixed frame 1, a steel wire rope 7 is wound around the fixed pulley 6, one end of the steel wire rope 7 is connected to the baffle 4, and the other end is connected to the control rod 8, and the control rod 8 is arranged on the other side of the fixed frame 1 away from the baffle 4. The fixed frame 1 is also provided with a plurality of blocking hooks 10 for connecting the control rod 8.

[0063] In this embodiment, the two fixed pulleys 6 are arranged on both sides of the top of the fixed frame, and the wire rope 7 is passed around the fixed pulleys, one end of which is connected to the control rod 8 and the other end is connected to the baffle 4. The baffle 4 can be raised or lowered by moving the control rod 8 up and down. The control rod can be manually controlled or driven by a motor.

[0064] The blocking hook 10 is placed at the lifting position of the control rod to prevent the control rod from continuing to rise or fall, thereby preventing the baffle from falling and breaking the bottom plate of the tank due to insufficient power, or preventing the baffle from impacting the fixed steel frame due to excessive power.

[0065] In this embodiment, the control rod 8 is a horizontal rod, and the blocking hooks 10 are arranged in three pairs at the top, middle and bottom. When the control rod is blocked by the middle pair of blocking hooks, the baffle is raised to the notch of the particle sliding groove. When the control rod is blocked by the upper pair of blocking hooks, the baffle falls into the particle sliding groove and just abuts the covering layer below. When the control rod is blocked by the lower pair of blocking hooks, the baffle is raised to the highest position and will not hit the limit above the fixed frame.

[0066] Furthermore, the image acquisition component includes a high-speed camera 11 supported by a tripod and multiple 100W strong light sources 12. The high-speed camera 11 is set in a stable area in front of or above the particle sliding trough 3, and can be fixed in time after adjusting the image acquisition area and angle according to the display of the host computer; the strong light sources 12 are selected and placed according to the shooting range and effect to illuminate the static accumulation area of ​​the particle sample 14 in the particle sliding trough 3; the image analysis equipment is a host computer with a display screen, such as a laptop computer 13. The laptop computer 13 is connected to the high-speed camera 11 through a data transmission line, and is also connected to the strong light source through a cable to receive and display the shooting image of the high-speed camera in real time, and also facilitate the adjustment and file storage of the strong light source 12 and the high-speed camera 11. Example 2

[0067] This embodiment takes a particle sample with a maximum spherical harmonic order of 8 (having a local roundness morphology feature) as an example for preparation and testing, and describes in detail the entire test process and the specific operation process of the device.

[0068] First, prepare a number of particle samples. The method for preparing the particle samples is as follows:

[0069] Step 1: Based on the particle surface point data obtained by 3D scanning, the maximum spherical harmonic series N = 8 and 15 are taken, and the spherical harmonic function of each particle is calculated using MATLAB software. This generates a 3D particle model with local roundness morphological characteristics and stores it in an STL file;

[0070] Step 2: Add support components to each 3D particle model and combine them together to generate the final 3D particle model with support stl file, import the stl file into the 3D printer and print it in multiple copies; in this embodiment, due to the number of samples and the requirements of the experimental parallel group setting, four copies are printed;

[0071] Step 3: Remove the supports from the printed particle entities by cutting and divide them into 4 groups of particle samples with the same quantity and shape. At this point, the sample preparation is completed.

[0072] More specifically, a Cartesian coordinate set P = {P1(x1, y1, z1), P2(x2, y2, z2), ..., P k (x k ,y k ,z k )}, use data processing software to obtain the particle center of mass coordinates P0 (x0, y0, z0), and use this to perform double mapping between the particle surface and the spherical surface to obtain the spherical coordinates P (r, θ, φ) of each surface point.

[0073] By spherical harmonic analysis, the surface expressed by the polar radius set of the particle surface points is expanded by spherical harmonics, thereby obtaining a reconstructed surface function R={R1(θ1,φ1), R2(θ2,φ2),…, R k (θ k ,φ k )}, the particle surface points with different scale morphological characteristics are calculated by reconstruction; for the same particle measurement data, the particle surface with different scale morphological characteristics can be reconstructed by taking different maximum spherical harmonic series N.

[0074] The entire reconstruction process is carried out according to the following formula:

[0075] ,

[0076] ,

[0077] ,

[0078] ,

[0079] Where r(θ, φ) is the polar radius of the particle surface point measured and calculated, and R(θ, φ) is the polar radius of the reconstructed particle surface point, where θ∈(0, π) and φ∈(0, 2π) are the zenith angle and azimuth angle in the spherical coordinate system, respectively. are the spherical harmonic coefficients, is a spherical harmonic function, where n∈[0,N], m∈[-n,n], are the associated Legendre functions The degree and order of , N is the maximum spherical harmonic series, both are integers.

[0080] Based on the calculated particle surface points, data processing software sequentially extracts three-point coordinate data to create triangular facets. A finite number of these facets are then assembled into a complete particle surface, generating a 3D model file containing the complete particle surface data. After adding supports to the 3D model file, the particle solid is printed using a 3D printer with a selected material. After removing the supports, a complete solid particle model, i.e., the particle specimen, is obtained. Printing accuracy depends on the particle size and the size of the triangular facets that represent the primary morphology. The printing material is determined by the experimental simulation parameters.

[0081] The above method uses the particle morphology characteristics as controllable independent variables to prepare particle samples, so as to facilitate the development of physical experiments to explore the relationship between the particle surface morphology and its mechanical properties, and promote the research and development of the basic theory of granular material mechanics.

[0082] A test method for a particle column collapse test observation device based on 3D printing, combined with Figure 3As shown, the test method includes the following steps:

[0083] (1) Lift the baffle 4 to the highest point through the lifting assembly and keep it stationary to prevent it from falling;

[0084] (2) Place the trough bottom plate 2 below the fixed frame 1, apply a covering layer that meets the test design on the trough bottom plate 2, place a level meter on it for observation, and adjust the trough bottom plate 2 to a horizontal level by inserting a pad under the trough bottom plate 2;

[0085] (3) placing the particle sliding trough 3 on the covering layer, ensuring that the covering layer can completely cover the bottom of the particle sliding trough 3, and adjusting the positions of the particle sliding trough 3 and the covering layer so that the baffle 4 is at a preset position on the particle sliding trough 3, and the baffle can be raised and lowered smoothly and quickly;

[0086] (4) Control the lifting assembly to lower the baffle 4, allowing the baffle 4 to fall into the particle sliding trough 3 and form an independent trough space with the particle sliding trough 3; arrange the image acquisition assembly in the front or upper area of ​​the particle sliding trough 3 and connect the image analysis equipment;

[0087] (5) Take a group of particle samples 14 of N=8 and slowly place them into the tank space to form a particle column.

[0088] (6) Place several plumb lines on the side of the particle sliding trough 3 facing the image acquisition component and mark them to facilitate subsequent high-speed camera adjustment and image analysis;

[0089] Turn on two strong light sources 12, one aligned roughly in the middle of the baffle and the other roughly 75 cm from the middle of the particle chute. Set up the high-speed camera 11. In this example, a Vic-2D 5M image acquisition device is used. The high-speed camera 11 is connected to a laptop computer 13 via a data transmission line. Run the VicSnap control software that is compatible with the high-speed camera on the laptop computer 13 to view the current image. Based on the current image, adjust the lens and position of the high-speed camera 11, as well as the position and angle of the light source, until the shooting angle is perpendicular to the front of the particle chute 3 and the entire particle chute 3 and the particle column within the chute are clearly visible (ensuring that the particle chute is horizontally and vertically aligned in the image).

[0090] (7) Turning on the image acquisition component and controlling the lifting component to lift the baffle, the particle column begins to flow and collapse;

[0091] (8) After the collapse is stable, stop image acquisition and measure other test data required after the particle column collapse;

[0092] (9) Pick up the particle sample after it flows to collapse, repeat the operations of lowering the baffle, placing the particle sample, debugging the high-speed camera, collapse test, recording data, etc., complete 2-3 tests and proceed to the next set of tests;

[0093] (10) After completing the experiment on the particle group of N = 8, repeat the experiment using particles of N = 15 to obtain the experimental data and perform image analysis.

[0094] After completing multiple groups of experiments, the collected images are analyzed to obtain the flow characteristic data and accumulation characteristic data of the particle column.

[0095] Furthermore, the image is analyzed as follows:

[0096] (1) From the collected continuous images, a series of continuous images from the moment before the particle column begins to collapse to the moment after the particle sample completely stops flowing are selected, and the series of continuous images are exported.

[0097] (2) In the MATLAB-PIVLab image analysis program, the selected series of continuous images are imported and preprocessed: denoising filtering is performed on the series of continuous images, the scale of the series of continuous images and the actual object is set, and the flow channel in the series of continuous images is selected as the analysis area.

[0098] (3) Use PIV technology to track the particle sample and calculate the flow velocity of the particle sample to obtain the velocity distribution and change.

[0099] (4) By limiting the maximum velocity and direction and correcting the obviously abnormal velocity magnitude and direction, the flow characteristics of flow duration and velocity change are obtained; by comparing the initial and final static time frames, the accumulation characteristics of the collapse relative static angle, accumulation height and flow distance can be obtained.

[0100] Furthermore, the flow velocity is calculated as follows:

[0101] Cross-correlation analysis is used to track particle samples in a series of continuous images, and the displacement of the same particle sample in the previous and next images is extracted. The images are pre-divided into identical grids. The size of the grid should be determined according to the size and movement of the particle sample to be analyzed. This is to prevent a grid that is too large from covering both the old and new positions of the particle, resulting in a displacement of 0. It is also to prevent a grid that is too small from not covering a particle, which would greatly increase the amount of analysis. The previous and next frame images are then subjected to three Fourier transforms, as shown in the following formula:

[0102] ,

[0103] ,

[0104] ,

[0105] in, , , The two frames before and after and The Fourier transform of There will be a unique maximum value at (x+Δx, y+Δy), that is, the front and back positions of the same particle are tracked, and the displacement of the particle sample is extracted as (Δx, Δy);

[0106] When the time interval Δt between the two frames is infinitely close to 0, the calculated average speed can be regarded as the instantaneous speed at the time of shooting, that is:

[0107] ,

[0108] Where Δx represents the displacement of the particle sample in the x direction, Δy represents the displacement of the particle sample in the y direction, u represents the flow velocity of the particle sample in the x direction, and v represents the flow velocity of the particle sample in the y direction.

[0109] The collapse test observation device and method of the present invention can control a particle column test set with completely identical other variables, providing comprehensive insights into the flow and accumulation characteristics of particles after column collapse, such as flow velocity. This allows for in-depth research into the relationship between different particle characteristics and the flow and accumulation characteristics of collapsed particle columns. This approach complements the methods used in physical experiments to observe particle flow characteristics and improves the methods used to observe the accumulation characteristics of particles after collapse.

[0110] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A 3D printing-based particle column collapse test observation device, characterized in that: The invention comprises a fixed frame, a movable trough bottom plate is provided on one side of the fixed frame, a particle sliding trough is provided above the trough bottom plate, and one end of the trough bottom plate and the particle sliding trough respectively extends into the fixed frame; a liftable baffle is provided on the fixed frame, and a lifting assembly connected to the baffle, and the baffle is liftably inserted into the particle sliding trough; the baffle and the particle sliding trough form an independent trough space, and a particle sample is placed in the trough space to form a particle column; It also includes an image acquisition component, which is used to capture and record images of the particle column in the particle sliding trough and its accumulation, flow and collapse process; Also included is an image analysis device, which is connected to the image acquisition component, receives and displays the image captured by the image acquisition component, and analyzes the image; The method for preparing the particle sample is as follows: The Cartesian coordinates of a finite number of surface points of each particle are obtained by scanning and measuring with three-dimensional laser technology, and the coordinates of the particle center of mass are obtained using data processing software. Based on this, a double mapping is performed between the particle surface and the spherical surface to obtain the spherical coordinates of each surface point; By spherical harmonic analysis, the surface expressed by the polar radius set of the surface points of the particle is expanded, thereby obtaining a reconstructed surface function that is infinitely close to the surface shape of the particle, and calculating the surface points of the particle with different scale morphological characteristics through reconstruction; Based on the calculated particle surface points, three-point coordinate data is taken one by one through data processing software to establish triangular facets, and a limited number of triangular facets are pieced together to form a complete particle surface, thereby generating a three-dimensional model file containing the complete particle surface data; After adding supports to the three-dimensional model file, the particle entity is printed by selecting materials through a 3D printer, and the supports are removed to obtain a complete solid particle model, namely the particle sample.

2. The 3D printing-based particle column collapse test observation device according to claim 1, characterized in that: An upper side of the fixed frame extends outward and is provided with a slide groove structure, the baffle is installed in the slide groove structure, and the particle slide groove is arranged below the slide groove structure.

3. The 3D printing-based particle column collapse test observation device according to claim 1, characterized in that: The bottom plate of the trough is provided with covering layers with different friction coefficients. The particle sliding trough is an enclosed structure open at the top and bottom. A discharge trough is provided below the tail plate at one end of the particle sliding trough away from the baffle.

4. The 3D printing-based particle column collapse test observation device according to claim 1, characterized in that: The particle sliding groove and the baffle are respectively made of transparent materials, and the width of the baffle is smaller than the inner circumference width of the particle sliding groove.

5. The 3D printing-based particle column collapse test observation device according to claim 1, characterized in that: The lifting assembly includes a plurality of fixed pulleys arranged on the fixed frame, a steel wire rope is wound around the fixed pulley, one end of the steel wire rope is connected to the baffle, and the other end is connected to the control rod, and the control rod is arranged on the other side of the fixed frame away from the baffle. The fixed frame is also provided with a plurality of blocking hooks for connecting the control rods.

6. The 3D printing-based particle column collapse test observation device according to claim 1, characterized in that: The image acquisition component includes a high-speed camera supported by a tripod and multiple light sources. The high-speed camera is set in a stable area in front of or above the particle sliding trough; the image analysis device is a host computer with a display screen, and the host computer is electrically connected to the high-speed camera.

7. A test method using the 3D printing-based particle column collapse test observation device according to any one of claims 1 to 6, characterized in that: The test method comprises the following steps: Prepare several particle samples; The baffle is lifted to the highest point by the lifting assembly and kept stationary; The trough bottom plate is arranged below the fixed frame, a covering layer is provided on the trough bottom plate, and the trough bottom plate is adjusted to be horizontal; Placing the particle sliding trough on the covering layer, and adjusting the positions of the particle sliding trough and the covering layer so that the baffle is at a preset position on the particle sliding trough; Controlling the lifting assembly to lower the baffle so that the baffle falls into the particle sliding trough and forms an independent trough space with the particle sliding trough; arranging the image acquisition assembly in the area in front of or above the particle sliding trough and connecting it to the image analysis device; A group of particle samples are placed in the trough space to form a particle column, and several plumb lines are arranged on the side of the particle sliding trough facing the image acquisition component to mark it; Turning on the image acquisition component and controlling the lifting component to lift the baffle, the particle column begins to flow and collapse. After the collapse stabilizes, stopping image acquisition and measuring test data after the particle column collapses; Pick up the particle sample after it flows to collapse and repeat the next set of tests. After multiple sets of tests are completed, analyze the collected images to obtain the flow characteristic data and accumulation characteristic data of the particle column.

8. The test method of the particle column collapse test observation device based on 3D printing according to claim 7, characterized in that: The method for analyzing the image is as follows: Among the collected continuous images, a series of continuous images from the moment before the particle column begins to collapse to the moment after the particle sample completely stops flowing are selected, and the series of continuous images are exported; In an image analysis program, the selected series of continuous images are imported and preprocessed: denoising filtering is performed on the series of continuous images, a scale of the series of continuous images and an actual object is set, and a flow cell in the series of continuous images is selected as an analysis area; Use PIV technology to track particle samples and calculate the flow velocity of particle samples to obtain velocity distribution and changes; By limiting the maximum velocity and correcting the obviously abnormal velocity magnitude and direction, the flow characteristics of flow duration and velocity change are obtained; by comparing the initial and final stationary time frames, the accumulation characteristics of the collapse relative stationary angle, accumulation height and flow distance are obtained.

9. The test method of the particle column collapse test observation device based on 3D printing according to claim 8, characterized in that: The flow velocity is calculated as follows: Track the particle sample in a series of consecutive images through cross-correlation analysis, and extract the displacement of the same particle sample in the previous and next images: pre-segment the image into identical grids, then perform three Fourier transforms on the previous and next frame images, and extract the displacement of the particle sample as (Δx, Δy); When the time interval ∆t between the two frames is infinitely close to 0, the calculated average speed is regarded as the instantaneous speed at the time of shooting, that is: ， Where x represents the horizontal displacement direction of the particle sample, y represents the vertical displacement direction of the particle sample, Δx represents the displacement of the particle sample in the x direction, Δy represents the displacement of the particle sample in the y direction, u represents the flow velocity of the particle sample in the x direction, and v represents the flow velocity of the particle sample in the y direction.

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