CN116394445A - Re-engraving device and re-engraving method for natural sand particle morphology - Google Patents

Abstract

The invention discloses a device and method for replicating the appearance of natural sand particles, comprising a rubber sheet assembly, a beaker and a vacuum pump; the rubber sheet assembly includes a first rubber sheet, a second rubber sheet and a clamp; the first rubber sheet and The second rubber sheet is vertically overlapped and laid, and clamped by the clamp, so that the overlapping surface is sealed and in close contact; the middle part of the overlapping surface of the first rubber sheet and the second rubber sheet is provided with a topographic half cavity; two topographic half cavities A shape chamber with the same shape as the natural sand particles is formed; the rubber sheet on the top of the shape chamber is provided with an upper channel connected with the shape chamber; the top of the upper channel is connected to the vacuum pump through an upper conduit; the shape chamber The rubber sheet at the bottom is provided with a lower channel connected with the topography chamber; the bottom of the lower channel extends into the beaker filled with the engraving solution through the downcomer. The invention can accurately reproduce the morphology of natural sand particles with various particle sizes, and has the advantages of simple and convenient operation, high efficiency, high reproduction accuracy and the like.

Description

A device and method for replicating the morphology of natural sand particles

technical field

The invention relates to the fields of civil engineering and geotechnical engineering, in particular to a device and method for replicating the morphology of natural sand particles.

Background technique

There are no two sands with exactly the same particle shape in the world, which shows the complexity and difficulty of describing the shape characteristics of sand particles. The particle morphology is closely related to the physical and mechanical properties of natural sandy soil, which is of great significance for revealing the mesoscopic mechanism of the engineering properties of loose-grained rock and soil materials. The particle morphology represents the formation history of natural sand and reflects the mechanical and chemical effects of its deposition and weathering process. The morphology characteristics of sand particles formed by sedimentation mainly depend on the source of the sediment and the depositional environment; the morphology of sand particles in lacustrine or marine deposits is relatively round, and is closely related to the transportation distance, erosion intensity, and time. Decades ago, engineers realized that particle morphology would affect the engineering properties of granular materials, such as compressibility, shear strength, permeability, and thermal conductivity. It is one of the basis and included in relevant national classification standards. Figure 1 shows the stress-strain curves of natural sand particles and smooth spherical particles under the same material properties, particle size and void ratio. It can be clearly seen that under the same axial strain, the stress ratios of the two types of granular aggregates differ greatly, and the stress ratio of natural sand is higher. In addition, the stress-strain curve shapes of the two granular aggregates are also different. These are all attributed to the effect of particle morphology within the aggregate. Particle morphology will directly affect the contact properties between particles, and then change the heat and mass transfer characteristics of granular aggregates. Figure 2 is a schematic diagram of the contact between ideal spheres, and Figure 3 is a schematic diagram of the contact between natural sand particles. For an ideal sphere, there is only one contact point between two particles, while the surface of natural sand particles is uneven, and at the mesoscopic scale, there are many tiny contact points between two particles. In addition, there are micropores between the contact points of natural sand particles, and the liquid in the pores will also affect the contact heat transfer between particles. Therefore, the study of the internal relationship between particle morphology and macroscopic engineering properties of sand and soil, as well as the morphology characteristics of sand particles in different environments, can provide guidance for related geotechnical engineering practices and provide guidance for the refinement of numerical simulation techniques such as discrete elements. R&D provides basic data.

There are many existing methods for testing and evaluating the shape of sand particles, from the initial naked eye observation and caliper measurement to the current camera photography, microscope, scanning electron microscope, CT scanner, laser scanner, etc. The measurement results have also changed from two The dimension is expanded to three-dimensional scale, and the accuracy is getting higher and higher. In the process of laboratory experiments and numerical simulations, people often use some idealized artificial materials to study the influence of particle shape on the engineering properties of sand and soil, such as glass balls, rubber balls, rubber ellipsoids, rubber rods, etc. From the mesoscopic scale, the morphology of these man-made materials is very different from that of natural sand particles, making it difficult to truly describe. It should be pointed out that although the current popular 3D printing technology can easily imitate sand particles with complex shapes, due to the characteristics of the printing technology itself, it will cause layered undulations on the surface of the printed sand particles, which is different from the real sand particles. There is still a large gap. Therefore, there is an urgent need to develop a new, efficient, and convenient sand particle morphology replica device to accurately evaluate the effect of sand particle morphology on the engineering properties of aggregates.

Contents of the invention

The technical problem to be solved in the present invention is to provide a device and method for re-engraving the morphology of natural sand particles for the above-mentioned deficiencies in the prior art. Artificially reproduce the shape of natural sand particles with high accuracy, and provide important technical support for establishing the internal relationship between particle shape and the engineering properties of loose-grained rock and soil materials. At the same time, it can provide basic data for the update and progress of discrete element simulation technology. It has the advantages of simplicity and high engraving accuracy, and has important theoretical research value and good social and economic benefits.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

A device for replicating the morphology of natural sand particles, including a rubber sheet assembly, a beaker and a vacuum pump.

The rubber sheet assembly includes a first rubber sheet, a second rubber sheet and a clamp.

The first rubber sheet and the second rubber sheet are vertically overlapped and arranged, and are clamped by a clamp so that the overlapping surfaces are in tight contact with each other.

The middle part of the overlapped surface of the first rubber sheet and the second rubber sheet is provided with a topographic half cavity; the two topographic half cavities form a topographic chamber with the same shape as the natural sand particles.

The rubber sheet at the top of the topographic chamber is provided with an upper channel communicating with the topographical chamber; the top of the upper channel is connected with a vacuum pump through an upper conduit.

The rubber sheet at the bottom of the topography chamber is provided with a lower channel communicating with the topography chamber; the bottom of the lower channel extends into a beaker filled with a replicating solution through a downcomer.

The upper channel and the lower channel are located on the same vertical line, and their diameters are both d. If the maximum diameter of the topography chamber is D, then D≥25d, and d is not less than 0.2mm.

A conical funnel with a sealing cover is arranged on the top of the upper channel, the bottom of the upper conduit extends into the conical funnel, and the top of the upper conduit is connected with a vacuum pump.

An enlarged hole is arranged at the bottom of the lower channel, and the enlarged hole is sealed and connected with the top of the downcomer, and the bottom of the downcomer extends into the beaker filled with the engraving solution.

It also includes a rubber sheet pouring mold, which includes a rigid base, a top cover, a rigid side wall, a fixing screw and two steel needles.

The rigid base, the top cover and the rigid side wall form a sealed pouring cavity; among them, the top cover is provided with a rubber pouring port, and the rigid side wall is provided with two steel needle fixing holes, and the connection of the two steel needle fixing holes The line passes through the center of the pouring cavity.

The fixing screw is used to connect the rigid base and the top cover, and can exert a counter force on the top cover.

One ends of the two steel needles are installed on the natural sand particles, and the other ends of the two steel needles are respectively installed in corresponding steel needle fixing holes.

A method for replicating the morphology of natural sand particles, comprising the following steps.

Step 1. Install steel needles: Install a steel needle on both sides of the natural sand particles to be engraved, and the two steel needles are located on the same straight line.

Step 2. Preparation of rubber sheet: Place the natural sand particles to be engraved containing two steel needles in step 1 in the center of the pouring cavity of the film casting mold, and place the two ends of the two steel needles on the steel surface of the rigid side wall respectively. In the pin fixing hole; pour liquid rubber into the pouring cavity in stages through the rubber pouring port, cool and remove the natural sand particles to be engraved containing two steel needles, thereby preparing the first rubber sheet and the second rubber sheet; Wherein, both the first rubber sheet and the second rubber sheet have a topographic half cavity and two steel needle half holes.

Step 3. Assembling the re-engraving device: the first rubber sheet and the second rubber sheet prepared in step 2 are stacked vertically, and the sides containing the topographical half cavity are attached; then, the first rubber sheet and the second rubber sheet are fitted with a clamp. The second rubber sheet is sealed and clamped, so that the combination of the two shape half cavities forms a shape chamber that is identical to the shape of natural sand particles and sealed; the two steel needle half holes on the top of the shape chamber are enclosed to form a A steel needle with the same diameter and a sealed upper channel; the top of the upper channel is connected to the vacuum pump through the upper conduit; the two steel needles at the bottom of the topography chamber are surrounded by half-holes that are equal in diameter to the other steel needle and sealed The lower channel; extend the bottom of the lower channel through the downcomer into the beaker filled with the engraving solution.

Step 4, copying, specifically includes the following steps:

Step 4-1. Vacuuming: Turn on the vacuum pump to form a negative pressure environment in the topography chamber.

Step 4-2, the engraving solution fills the profile chamber: the engraving solution located in the beaker will sequentially pass through the downcomer and the lower channel, enter the profile chamber, and fill the profile chamber;

Step 4-3, the engraving liquid reaches the set liquid level: the vacuum pump continues to evacuate, the engraving liquid fills the topography chamber, the height continues to rise, and enters the conical funnel through the upper channel to reach the set liquid level.

Step 4-4, pressure-holding filling: turn off the vacuum pump, set valves on the upper conduit and the lower conduit, and close the two valves at the same time, so that the topography chamber maintains a negative pressure environment within the set time T; at this time, The engraving solution located under the set liquid level is fully and completely filled into each contour gap in the topography chamber under the action of gravity; at the same time, the viscosity of the engraving solution is 2.0-2.5Pa·s, and the The diameter is not greater than 1mm, forming a capillary; due to the viscosity of the replica fluid and the effect of the capillary, the replica fluid located in the topography chamber will not flow back to the lower channel under the action of gravity.

Step 4-5, repeat step 4-1 to step 4-4 n times.

Step 5. Condensation of the engraving solution: remove the lower conduit and the upper conduit, and let the engraving device stand at room temperature, so that the engraving solution in the topography chamber condenses and hardens to form imitation natural sand particles for engraving; at this time, After the engraving solution located in the upper channel and the lower channel coagulates, two protrusions will be formed on the surface of the simulated natural sand particles.

Step 6. Form removal: remove the re-engraving device, cut off and level the two protrusions on the surface of the imitation natural sand particles, and obtain the finished imitation natural sand particles.

In step 2, the specific preparation method of the first rubber sheet and the second rubber sheet comprises the following steps:

Step 2-1. Prepare the first rubber sheet: pour liquid rubber into the pouring cavity through the rubber pouring port. When the liquid level of the liquid rubber is equal to the middle of the two steel needles, stop pouring, and place the rubber in the film pouring mold. The liquid rubber cools to form a semi-finished first rubber sheet.

Step 2-2. Coating an isolation layer: coating an isolation layer on top of the semi-finished first rubber sheet.

Step 2-3, preparing the second rubber sheet: continue to pour liquid rubber into the pouring cavity until the liquid rubber fills the pouring cavity, stop pouring, and cool the liquid rubber on the top of the isolation layer to form a semi-finished second rubber sheet.

Step 2-4, removing the natural sand particles to be reproduced containing the two steel needles, thereby preparing finished products of the first rubber sheet and the second rubber sheet.

In step 2, both the first rubber sheet and the second rubber sheet are transparent rubber.

The engraving solution includes epoxy resin and hardener, and the mass ratio of epoxy resin and hardener is in the range of 10:1 to 10:2; during the preparation of the engraving solution, a magnetic stirrer is used to mix the epoxy resin and hardener The agent is fully and evenly stirred; the heating temperature of the magnetic stirrer is 50°C to 60°C, the stirring speed is 800 rpm to 1000 rpm, and the stirring time is not less than 5 minutes.

In step 4-1, the negative pressure control speed of the vacuum pump is -2kPa/min, and the vacuum is pumped for 10 minutes to make the negative pressure in the topography chamber reach -20kPa.

The present invention has following beneficial effect:

1. Utilize common rubber materials to make the engraving device. The engraving device is easy to manufacture, and can be made with multiple particles in parallel to improve the engraving efficiency. It has good applicability and operability.

2. The sand particles in the present invention are artificially engraved by "pouring", which has the advantages of high precision and low cost compared with other existing engraving methods, and has no special requirements for operators.

3. By adjusting the re-engraving solution, the properties of the re-engraved particle material can be changed while maintaining a highly similar particle shape. This is of great significance for studying the engineering properties of different particles with the same shape, and can simulate particles more accurately for discrete element software. Topography provides the basis.

Description of drawings

Figure 1 shows the stress-strain curves of aggregates with different particle shapes under the same preparation conditions.

Figure 2 shows a schematic diagram of the contact interface between ideal spheres.

Figure 3 shows a schematic diagram of the contact interface between natural sand particles at the mesoscale.

Figure 4 shows a schematic diagram of the structure of natural sand particles pasted with steel needles.

Figure 5 shows a side view of the first rubber sheet and the second rubber sheet prepared by using the rubber sheet casting mold.

Fig. 6 shows a top view of preparing the first rubber sheet and the second rubber sheet by using the rubber sheet casting mold.

Fig. 7 shows a schematic structural diagram of a device for replicating the morphology of natural sand particles according to the present invention.

Including:

1. Natural sand particles; 2.1. Upper steel needle; 2.2. Lower steel needle; 3. Rigid base; 4.1. Rigid side wall 1; 4.2. Rigid side wall 2; 5. Top cover; 6.1. Fixing screw 1; 6.2. Fixing screw two; 7.1. The first rubber sheet; 7.2. The second rubber sheet; 8. Shape chamber; 9.1. Upper channel; 9.2. Lower channel; 10. Tapered funnel; ; 12.2. Fixture II; 13. Downpipe; 14. Beaker; 15. Re-engraving solution; 16. Sealing ring;

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

In the description of the present invention, it should be understood that the orientations or positional relationships indicated by the terms "left side", "right side", "upper", "lower" are based on the orientations or positional relationships shown in the accompanying drawings, and are only For the purpose of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, "first", "second" and the like do not represent components importance, and therefore should not be construed as limiting the invention. The specific dimensions used in this embodiment are only for illustrating the technical solution, and do not limit the protection scope of the present invention.

As shown in Figure 7, a device for replicating the morphology of natural sand particles includes a rubber sheet assembly, a beaker 14, a vacuum pump 18 and a rubber sheet casting mold.

The rubber sheet assembly includes a first rubber sheet 7.1, a second rubber sheet 7.2 and a clamp.

The first rubber sheet and the second rubber sheet are vertically overlapped and arranged, and are clamped by a clamp, so that the overlapping surfaces are in tight contact with each other to form a complete rubber sheet. In this embodiment, the clamp preferably includes clamp one 12.1 and clamp two 12.2.

The middle part of the coincident surface of the first rubber sheet and the second rubber sheet is provided with a shape half cavity; the two shape half cavities form a shape chamber 8 with the same shape as the natural sand particles.

The rubber sheet at the top of the profile chamber is provided with an upper channel 9.1 communicating with the profile chamber; the top of the upper channel is connected to a vacuum pump through an upper conduit 17 . Further, the rubber sheet at the top of the upper channel is preferably provided with a tapered hole, and a tapered funnel 10 is sealed in the tapered hole, the bottom of the tapered funnel is connected with the upper channel, and the top cover of the tapered funnel is provided with a sealing cover 19. A conduit hole for the upper conduit to pass through is provided on the top.

The rubber sheet at the bottom of the profile chamber is provided with a lower channel 9.2 communicating with the profile chamber; the bottom of the lower channel is preferably provided with an enlarged hole 11, and the top of the downcomer is preferably sealed and inserted in the enlarged hole by a sealing ring, and the bottom of the downcomer Stretch into the beaker filled with the engraving solution 15.

In this embodiment, the diameter of the enlarged hole is preferably 10 mm, the diameter of the top of the conical funnel is preferably 15 mm; the size of the beaker is preferably 50 ml. The lower conduit, the upper conduit, and the sealing cover are all preferably made of transparent materials.

The upper channel and the lower channel are located on the same vertical line, and their diameters are both d. If the maximum diameter of the topography chamber is D, then D≥25d, and d is not less than 0.2mm.

As shown in Figures 5 and 6, the rubber sheet casting mold includes a rigid base 3, a top cover 5, a rigid side wall, a fixing screw and two steel needles.

The rigid base, top cover and rigid side walls form a sealed pouring cavity.

The above-mentioned top cover is covered on the top of the rigid side wall, and the detachable compression connection with the rigid base is realized through several fixed screw rods 1 6.1 and several fixed screw rods 2 6.2.

A rubber pouring port is arranged on the above-mentioned top cover.

The two steel needles are respectively an upper steel needle 2.1 and a lower steel needle 2.2.

As shown in Figure 4, an upper steel needle 2.1 is pasted on the top of the natural sand particle, and a lower steel needle 2.2 is pasted on the bottom of the natural sand particle, and the upper steel needle 2.1 and the lower steel needle 2.2 are located on the same straight line.

The particle size range of the natural sand particles is preferably 2 mm to 30 mm. The particle size of the natural river sand in this embodiment is 15.6 mm; the diameter of the steel needles is not greater than 1 mm, preferably less than 0.5 mm, preferably 0.3 mm in this embodiment. At the same time, the maximum diameter of the natural sand particles is the same as the maximum diameter D of the surface chamber, and the diameter of the steel needle is the same as the diameter d of the upper channel and the lower channel.

Place the natural sand particles with steel needles in the center of the pouring cavity, place the two ends of the two steel needles in the steel needle fixing holes of the opposite rigid side wall 1 4.1 and rigid side wall 2 4.2 respectively, and then cover The top cover is connected with the rigid base using a fixed screw rod, and a set reaction force is applied to the top cover.

Place the replica mold assembly with rubber sheet and natural sand particles at room temperature for 24 hours, then disassemble the replica mold assembly, and take out the rubber sheet, natural sand particles bonded with steel needles, and rubber sheet in sequence; Clean up the lubricating oil on the surface of natural sand particles and rubber sheets.

The geometric shapes of the first rubber sheet and the second rubber sheet are preferably cuboid, the thickness is 1/2 of the height of the cavity of the replica mold assembly, and it should be greater than 1.5 times the particle size of natural sand particles; the length and width should be greater than 15 times the natural sand particle size. sand particle size. The thickness of the first rubber sheet and the second rubber sheet in this embodiment is preferably 25mm, the length is preferably 80mm, and the width is preferably 80mm.

Furthermore, the above-mentioned rubber sheet should have sufficient plasticity, and can accurately describe the morphology and surface unevenness of the natural sand particles. Both the first rubber sheet and the second rubber sheet are further preferably transparent rubber.

A method for replicating the morphology of natural sand particles, comprising the following steps.

Step 1. Install steel needles: Install a steel needle on both sides of the natural sand particles to be engraved, and the two steel needles are located on the same straight line.

Step 2. Preparation of rubber sheet: Place the natural sand particles to be engraved containing two steel needles in step 1 in the center of the pouring cavity of the film casting mold, and place the two ends of the two steel needles on the steel surface of the rigid side wall respectively. In the pin fixing hole; pour liquid rubber into the pouring cavity in stages through the rubber pouring port, cool and remove the natural sand particles to be engraved containing two steel needles, thereby preparing the first rubber sheet and the second rubber sheet; Wherein, both the first rubber sheet and the second rubber sheet have a topographic half cavity and two steel needle half holes.

Step 3. Assemble the replica device

First, evenly spray lubricating oil on the contact surface of the rubber sheet, the shape chamber, the channel, and the inner side of the conical funnel to prevent sticking; then vertically stack the first rubber sheet and the second rubber sheet, and contain the shape half cavity Then, the first rubber sheet and the second rubber sheet are sealed and clamped with a clamp, so that the two topographic half-cavities are combined to form a topographic chamber that is identical in appearance to natural sand particles and sealed; The two steel needles on the top of the topography chamber are surrounded by half-holes to form an upper channel that is equal in diameter to one of the steel needles and sealed; the top of the upper channel is connected to the vacuum pump through the upper conduit; the two steel needles at the bottom of the topography The half-hole of the needle is enclosed to form a sealed lower channel with the same diameter as another steel needle; extend the bottom of the lower channel through the downcomer into the beaker containing the replicating solution.

Pour a sufficient amount of forging solution into the beaker, the downcomer and the enlarged hole are sealed and connected by a sealing ring, and the downcomer is inserted at least 2/3 of the height below the surface of the forging solution.

The above-mentioned engraving liquid preferably includes epoxy resin and hardener, and the mass ratio range of epoxy resin and hardener is: 10:1～10:2; In the preparation process of engraving liquid, adopt magnetic stirrer to mix epoxy resin Stir fully and evenly with the hardener; the heating temperature of the magnetic stirrer is 50°C to 60°C, the stirring speed is 800 rpm to 1000 rpm, and the stirring time is not less than 5 minutes.

Step 4, copying, specifically includes the following steps.

Step 4-1. Vacuuming: Turn on the vacuum pump to form a negative pressure environment in the topography chamber. The negative pressure control speed of the vacuum pump is preferably -2kPa/min, and the vacuuming time is preferably 10 minutes, so that the negative pressure in the topography chamber preferably reaches -20kPa.

Step 4-2. Filling the topography chamber with the replicating solution: The replicating solution in the beaker will pass through the downcomer and the downhole in turn, enter the topography chamber, and fill the topography chamber. At this time, observe the flow changes of the replicating solution in the beaker and the downcomer, and observe the change of the liquid level of the replicating solution in the conical funnel and the upcomer at the same time.

Step 4-3, the engraving liquid reaches the set liquid level: the vacuum pump continues to evacuate, the engraving liquid fills the topography chamber, the height continues to rise, and enters the conical funnel through the upper channel to reach the set liquid level.

Step 4-4, pressure-holding filling: turn off the vacuum pump, set valves on the upper conduit and the lower conduit (that is, close the upper valve 21 and the lower valve 22), and close the two valves at the same time, so that the topography chamber is set Maintain a negative pressure environment within a certain time T (preferably 5 minutes); at this time, the replica solution located under the set liquid level is fully and completely filled in each contour gap in the topography chamber under the action of gravity; with this At the same time, the viscosity of the engraving solution is 2.0-2.5Pa·s, and the diameter of the lower channel is not greater than 1mm, forming a capillary; due to the viscosity of the engraving fluid and the effect of the capillary, the engraving fluid located in the topography chamber will not be under the action of gravity. return to the lower channel. In addition, during the pressure-holding process, the micro-bubbles in the engraving solution and the bubbles in the topography chamber can be slowly and completely discharged during the intermittent pressure-holding period.

The setting of the lower channel in the above-mentioned capillary form can make the engraving liquid maintain a certain liquid level under the action of capillary tension, and prevent the incompletely hardened engraving liquid from flowing out of the topography chamber under the action of gravity, causing the chamber to fill. Incomplete, resulting in holes.

Step 4-5, repeat step 4-1 to step 4-4 n times. In this embodiment, preferably n=3.

Step 5. Condensation of the engraving solution: Remove the lower conduit and the upper conduit, and let the engraving device stand at room temperature for no less than 6 hours, so that the engraving solution in the topography chamber will condense and harden, forming a replica of imitation natural sand Particles; at this time, after the engraving solution located in the upper channel and the lower channel condenses, two protrusions will be formed on the surface of the simulated natural sand particles.

Step 6, demoulding: remove the re-engraving device, and cut off the two protrusions on the surface of the imitation natural sand particles, and preferably under the observation of a magnifying glass, use about 600 mesh fine sandpaper to polish the cut place smoothly, and clean the surface oil. The finished imitation natural sand particles are obtained.

In step 2, the specific preparation method of the first rubber sheet and the second rubber sheet includes the following steps.

Step 2-1. Prepare the first rubber sheet: pour liquid rubber into the pouring cavity through the rubber pouring port. When the liquid level of the liquid rubber is equal to the middle of the two steel needles, stop pouring, and place the rubber in the film pouring mold. The liquid rubber cools to form a semi-finished first rubber sheet.

Step 2-2. Coating an isolation layer: coating an isolation layer on top of the semi-finished first rubber sheet.

Step 2-3, preparing the second rubber sheet: continue to pour liquid rubber into the pouring cavity until the liquid rubber fills the pouring cavity, stop pouring, and cool the liquid rubber on the top of the isolation layer to form a semi-finished second rubber sheet.

Step 2-4, removing the natural sand particles to be reproduced containing the two steel needles, thereby preparing finished products of the first rubber sheet and the second rubber sheet.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be carried out to the technical solutions of the present invention. These equivalent transformations All belong to the protection scope of the present invention.

Claims (10)

1. A device for replicating natural sand particle morphology, characterized in that: it includes a rubber sheet assembly, a beaker and a vacuum pump; The rubber sheet assembly includes a first rubber sheet, a second rubber sheet and a clamp; The first rubber sheet and the second rubber sheet are vertically overlapped and arranged, and are clamped by a clamp, so that the overlapping surfaces are sealed and tightly contacted; The middle part of the overlapping surface of the first rubber sheet and the second rubber sheet is provided with a shape half cavity; the two shape half cavities form a shape chamber with the same shape as the natural sand particle; The rubber sheet at the top of the topographic chamber is provided with an upper channel connected with the topographic chamber; the top of the upper channel is connected to the vacuum pump through the upper conduit; The rubber sheet at the bottom of the topography chamber is provided with a lower channel communicating with the topography chamber; the bottom of the lower channel extends into a beaker filled with a replicating solution through a downcomer. 2. the engraving device of natural sand grain shape according to claim 1, it is characterized in that: upper channel and lower channel are positioned on same vertical line, and diameter is d, the maximum diameter of setting profile chamber is D, then D≥25d, and d is not less than 0.2mm. 3. The device for replicating the appearance of natural sand particles according to claim 1, characterized in that: the top of the upper channel is provided with a conical funnel with a sealing cover, the bottom of the upper conduit extends into the conical funnel, and the top of the upper conduit Connected to a vacuum pump. 4. The device for replicating the appearance of natural sand particles according to claim 1, characterized in that: the bottom of the lower tunnel is provided with an enlarged hole, the enlarged hole is sealed and connected with the top of the downcomer, and the bottom of the downcomer extends into a container for replicating. solution in a beaker. 5. the engraving device of natural sand particle appearance according to claim 1, is characterized in that: also comprise rubber sheet casting mold, rubber sheet casting mold comprises rigid base, top cover, rigid side wall, fixed screw rod and two steel needle; The rigid base, the top cover and the rigid side wall form a sealed pouring cavity; among them, the top cover is provided with a rubber pouring port, and the rigid side wall is provided with two steel needle fixing holes, and the connection of the two steel needle fixing holes The line passes through the center of the pouring cavity; The fixing screw is used to connect the rigid base and the top cover, and can exert a reaction force on the top cover; One ends of the two steel needles are installed on the natural sand particles, and the other ends of the two steel needles are respectively installed in corresponding steel needle fixing holes. 6. A method for re-engraving the morphology of natural sand particles, characterized in that: comprising the steps: Step 1. Install steel needles: Install a steel needle on both sides of the natural sand particles to be engraved, and the two steel needles are located on the same straight line; Step 2. Preparation of rubber sheet: Place the natural sand particles to be engraved containing two steel needles in step 1 in the center of the pouring cavity of the film casting mold, and place the two ends of the two steel needles on the steel surface of the rigid side wall respectively. In the pin fixing hole; pour liquid rubber into the pouring cavity in stages through the rubber pouring port, cool and remove the natural sand particles to be engraved containing two steel needles, thereby preparing the first rubber sheet and the second rubber sheet; Wherein, both the first rubber sheet and the second rubber sheet have a shape half cavity and two steel needle half holes; Step 3. Assembling the re-engraving device: the first rubber sheet and the second rubber sheet prepared in step 2 are stacked vertically, and the sides containing the topographical half cavity are attached; then, the first rubber sheet and the second rubber sheet are fitted with a clamp. The second rubber sheet is sealed and clamped, so that the combination of the two shape half cavities forms a shape chamber that is identical to the shape of natural sand particles and sealed; the two steel needle half holes on the top of the shape chamber are enclosed to form a A steel needle with the same diameter and a sealed upper channel; the top of the upper channel is connected to the vacuum pump through the upper conduit; the two steel needles at the bottom of the topography chamber are surrounded by half-holes that are equal in diameter to the other steel needle and sealed The lower channel; extend the bottom of the lower channel through the downcomer into the beaker filled with the engraving solution; Step 4, copying, specifically includes the following steps: Step 4-1. Vacuuming: Turn on the vacuum pump to form a negative pressure environment in the topography chamber; Step 4-2, the engraving solution fills the profile chamber: the engraving solution located in the beaker will sequentially pass through the downcomer and the lower channel, enter the profile chamber, and fill the profile chamber; Step 4-3, the engraving liquid reaches the set liquid level: the vacuum pump continues to evacuate, the engraving liquid is filled with the profile chamber, the height continues to rise, and enters the conical funnel through the upper channel, so as to reach the set liquid level; Step 4-4, pressure-holding filling: turn off the vacuum pump, set valves on the upper conduit and the lower conduit, and close the two valves at the same time, so that the topography chamber maintains a negative pressure environment within the set time T; at this time, The engraving solution located under the set liquid level is fully and completely filled into each contour gap in the topography chamber under the action of gravity; at the same time, the viscosity of the engraving solution is 2.0-2.5Pa·s, and the The diameter is not greater than 1mm, forming a capillary; due to the viscosity of the replica fluid and the effect of the capillary, the replica fluid located in the topography chamber will not flow back to the lower channel under the action of gravity; Step 4-5, repeat step 4-1 to step 4-4 n times; Step 5. Condensation of the engraving solution: remove the lower conduit and the upper conduit, and let the engraving device stand at room temperature, so that the engraving solution in the topography chamber condenses and hardens to form imitation natural sand particles for engraving; at this time, After the engraving solution located in the upper channel and the lower channel condenses, two protrusions will be formed on the surface of the imitation natural sand particles; Step 6. Form removal: remove the re-engraving device, cut off and level the two protrusions on the surface of the imitation natural sand particles, and obtain the finished imitation natural sand particles. 7. the engraving method of natural sand particle appearance according to claim 6 is characterized in that: in step 2, the specific preparation method of the first rubber sheet and the second rubber sheet comprises the steps: Step 2-1. Prepare the first rubber sheet: pour liquid rubber into the pouring cavity through the rubber pouring port. When the liquid level of the liquid rubber is equal to the middle of the two steel needles, stop pouring, and place the rubber in the film pouring mold. The liquid rubber is cooled to form the first rubber sheet of the semi-finished product; Step 2-2, coating the isolation layer: coating the isolation layer on the top of the semi-finished first rubber sheet; Step 2-3, preparing the second rubber sheet: continue pouring liquid rubber into the pouring cavity until the liquid rubber fills the pouring cavity, stop pouring, and cool the liquid rubber at the top of the isolation layer to form a semi-finished second rubber sheet; Step 2-4, removing the natural sand particles to be reproduced containing the two steel needles, thereby preparing finished products of the first rubber sheet and the second rubber sheet. 8. The method for replicating the morphology of natural sand particles according to claim 6 or 7, characterized in that: in step 2, both the first rubber sheet and the second rubber sheet are transparent rubber. 9. The replica method of natural sand particle morphology according to claim 6, characterized in that: the replica solution comprises epoxy resin and hardener, and the mass ratio range of epoxy resin and hardener is: 10:1 ~10:2; During the preparation of the engraving solution, use a magnetic stirrer to fully and evenly stir the epoxy resin and hardener; the heating temperature of the magnetic stirrer is 50 ° C ~ 60 ° C, and the stirring speed is 800 rpm ~ 1000 rpm rpm, and the stirring time is not less than 5 minutes. 10. The method for replicating the morphology of natural sand particles according to claim 6, characterized in that: in step 4-1, the negative pressure control speed of the vacuum pump is -2kPa/min, and the vacuum is pumped for 10 minutes to make the morphology cavity The negative pressure value in the room reaches -20kPa.

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