Discrete element contact parameter calibration device and method based on dynamic repose angle

Abstract

The invention discloses a discrete element contact parameter calibration device and method based on a dynamic repose angle, the device comprises a platform on which a motor and a motor control panel are fixedly arranged, the motor control panel is connected with a PC, the motor control panel is connected with the motor, and an output shaft of the motor is fixedly connected with a driving belt wheel; a first bearing seat and a second bearing seat are installed on the top face of the platform, the first bearing seat is rotationally connected with a first rotating shaft, the first rotating shaft is fixedly connected with a driven belt wheel connected with the driving belt wheel through a belt, and the two ends of the first rotating shaft are fixedly connected with driving wheels respectively. The second bearing seat is rotationally connected with a second rotating shaft; two ends of the second rotating shaft are fixedly connected with supporting wheels respectively; the cylinder is in contact with the surfaces of the driving wheel and the supporting wheel; a high-speed camera connected with a PC (Personal Computer) is fixedly arranged on the top surface of the platform, and discrete element analogue simulation software is installed in the PC. According to the invention, the dynamic angle of repose of the material in different flowing states can be measured in real time, and high-precision calibration of contact parameters among particles is facilitated through a discrete element model.

Description

Technical Field

[0001] The present invention relates to discrete element numerical simulation of bulk materials, in particular to a discrete element contact parameter calibration device and method based on dynamic repose angle. Background Art

[0002] The discrete element method (DEM) is a commonly used numerical simulation method for particle systems. By accurately constructing various mechanical models of interactions between particles and between particles and walls, it can effectively predict the motion behavior of bulk materials in static and dynamic processes at both macroscopic and microscopic levels. However, due to the wide variety of particle shapes, sizes, material properties, and external environmental conditions, the proper selection and calibration of particle contact parameters remains crucial for the accuracy of DEM simulations. The angle of repose, an important indicator for measuring particle packing and flow characteristics, has attracted widespread attention in scientific research and engineering applications. The dynamic angle of repose is not only influenced by the particle's own characteristics, such as shape, density, and surface roughness, but is also closely related to the velocity field distribution, external disturbances, and the frequency of interparticle collisions during motion. It can more fully reflect the true physical characteristics of material flow and packing processes.

[0003] However, most of the existing angle of repose measurement methods are based on the static angle of repose measurement method, which is carried out under relatively simple experimental conditions and cannot fully describe the true behavior of the particle system during movement. For the measurement of the dynamic angle of repose, it relies on high-speed camera or test bench construction, but its measurement results are often affected by the experimental environment, equipment accuracy and operation mode, and lack of quantitative evaluation of the contact mechanical behavior between particles. Moreover, under special working conditions such as fine particles or highly viscous materials, traditional measurement methods cannot achieve stable and repeatable dynamic angle of repose measurement, which greatly limits the accuracy and reliability of subsequent discrete element parameter calibration.

[0004] Based on the above needs, there is an urgent need for a special device that can comprehensively consider multiple factors in the particle movement process and accurately measure and analyze the dynamic repose angle in real time, so as to obtain the repose angle parameters of the material under different flow states, and then combine the discrete element method model to optimize the coupling relationship of the contact parameters between particles, so as to greatly improve the accuracy of numerical simulation and engineering applicability. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a discrete element contact parameter calibration device and method based on the dynamic angle of repose, which can measure the dynamic angle of repose of materials under different flow states in real time, and facilitate high-precision calibration of contact parameters between particles through discrete element models.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A discrete element contact parameter calibration device based on dynamic repose angle includes a PC, a motor control panel, a platform, and a transparent cylinder for holding bulk materials, with an opening at one end of the cylinder;

[0008] A motor and a motor control panel are fixedly installed on the platform, the motor control panel is connected to the PC, the motor control panel and the motor are connected by a wire, and the output shaft of the motor is fixedly connected to a driving pulley;

[0009] A pair of first bearing seats and a pair of second bearing seats are installed on the top surface of the platform. The first bearing seat is rotatably connected to the first rotating shaft through the bearing. The first rotating shaft is fixedly connected to the driven pulley. The driven pulley and the driving pulley are connected through a belt transmission, and driving wheels are fixedly installed at both ends of the first rotating shaft.

[0010] The second bearing seat is rotatably connected to the second rotating shaft via a bearing, and support wheels are fixedly installed at both ends of the second rotating shaft;

[0011] The surface of the cylinder is in linear contact with the surfaces of the driving wheel and the supporting wheel;

[0012] A high-speed camera for taking pictures of the bulk material inside the cylinder is fixedly installed on the top surface of the platform. The high-speed camera is connected to a PC installed with discrete element simulation software.

[0013] Furthermore, a slide groove is provided on the platform and is directly opposite to the first bearing seat, and the second bearing seat is slidably connected to the inside of the slide groove;

[0014] The second bearing seat and the slide groove are both provided with threaded holes, and bolts pass through the threaded holes to fix the second bearing seat and the platform.

[0015] Furthermore, a circle of refractory bricks is pasted on the inner surface of the cylinder along its curved surface;

[0016] The inner diameter of the cylinder is 250 mm, the length is 500 mm, and the thickness of the refractory brick is 20 mm.

[0017] Furthermore, a speed sensor is fixedly installed on the outer wall of the cylinder, and the speed sensor is wirelessly connected to the PC.

[0018] Furthermore, an acceleration sensor is fixedly mounted on the outer wall of the cylinder, and the acceleration sensor is wirelessly connected to the PC.

[0019] Furthermore, a pressure sensor for measuring the pressure of the bulk material on the inner wall of the cylinder is installed on the inner wall of the cylinder, and the pressure sensor is wirelessly connected to the PC.

[0020] Furthermore, a Fuma wheel is fixedly installed on the bottom surface of the platform.

[0021] Furthermore, the cylinder is made of transparent acrylic glass.

[0022] A discrete element contact parameter calibration method based on dynamic repose angle includes the following steps:

[0023] Step 1: Pour the bulk material into the cylinder so that the filling degree of the cylinder is 50%;

[0024] Step 2: Set the motor speed, turn on the motor, and drive the drum to rotate. When the drum runs stably, the bulk material rises with the rotation of the drum. When the force between the particles cannot be balanced with gravity, before the particles collapse, press the stop button on the motor control panel to stop the motor. The high-speed camera records the maximum inclination angle between the accumulation slope and the horizontal plane at this time, which is the dynamic repose angle;

[0025] Step 3: Repeat step 2 5 to 10 times to obtain the dynamic angle of repose.

[0026] Step 4: Using the dynamic repose angle as the target value, the experimental process is simulated by discrete element method, the contact parameters are continuously corrected to achieve high-precision calibration, and finally the contact parameters are obtained, including the static friction coefficient, rolling friction coefficient, and viscous energy density.

[0027] Furthermore, the rotation speed of the motor is 1.78 rpm.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] First, through the PC and motor control panel, the motor speed can be adjusted in real time according to the particle type and actual application requirements on site, thereby adjusting the cylinder speed. The bulk material forms different contact stress states during the movement, which changes the running form of the bulk material inside the cylinder, thereby simulating the flow and accumulation state of the bulk material under various operating environments and operating conditions, making it easy to record the repose angle of the bulk material in different motion states through a high-speed camera, which is suitable for a variety of working conditions from fine particles to large particle systems, and provides real and reliable data support for discrete element parameter calibration; second, the acquired data is uploaded to the PC, and the contact parameters such as friction coefficient, restitution coefficient, etc. are quickly iterated and corrected through discrete element simulation software, which effectively improves the model accuracy and consistency; third, an opening is provided at one end of the cylinder to ensure that the bulk material is in different filling conditions during loading. distribution uniformity and flow stability; fourthly, the cylinder of the present invention can be reasonably designed and replaced according to the particle size, specific gravity, moisture content and other characteristics of the bulk material, and can adapt to different experimental needs; fifthly, the device proposed in the present invention has good applicability in actual projects such as particle transportation, storage and turning, and provides a basis for related industries to improve production efficiency, optimize process design and save resources; sixthly, the device of the present invention has a simple structure and is easy to operate, and can be widely used in bulk materials of different particle sizes, with significant scientific research and engineering application value; in short, the present invention can quickly and accurately obtain the dynamic repose angle of bulk materials in different motion states, and combine the discrete element method to perform high-precision calibration of key contact parameters, which greatly improves the consistency between numerical simulation and actual operation in material transportation, storage and processing, and provides reliable support for the mechanism research and process optimization of particle systems.

[0030] The present invention provides a slide groove on the platform so that the second bearing seat can slide along it, thereby adjusting the distance between the second bearing seat and the first bearing seat, and then adjusting the spacing between the driving wheel and the supporting wheel, which is convenient for supporting and transmitting cylinders of different diameters and improving the applicability of the cylinder bearing unit.

[0031] The present invention provides an acceleration sensor and a velocity sensor to facilitate timely acquisition of the rotation status of the cylinder, thereby more accurately capturing the motion trajectory and accumulation shape of the particles during rotation or tilting, taking real-time images, and calculating the dynamic angle of repose; at the same time, by providing a pressure sensor, the interaction force between the bulk material and the inner wall of the cylinder can be measured, facilitating timely correction of the contact force model between particles and between particles and the wall.

[0032] The present invention can simulate the movement behavior of bulk materials inside a real rotary kiln by sticking a circle of refractory bricks on the inner surface of the cylinder, thereby improving the simulation accuracy and the accuracy of subsequent key contact parameter calibration.

[0033] The present invention facilitates moving the device to a desired experimental site by means of the Forma wheels arranged on the bottom surface of the platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a side structural schematic diagram of the present invention;

[0035] Figure 2 It is a front view structural schematic diagram of the present invention.

[0036] In the figure: 1. Platform; 2. Motor; 3. Driving pulley; 4. Driven pulley; 5. Belt; 6. First rotating shaft; 7. Driving wheel; 8. Cylinder; 9. Forma wheel; 10. First bearing seat; 11. Second bearing seat; 12. Support wheel. DETAILED DESCRIPTION

[0037] The specific contents of the present invention are further explained in detail below with reference to the embodiments.

[0038] like Figure 1 and Figure 2 As shown, a discrete element contact parameter calibration device based on dynamic repose angle includes a PC, a motor control panel, a platform 1 and a transparent cylinder 8 for holding bulk materials, with an opening at one end of the cylinder 8;

[0039] The platform 1 is fixedly mounted with a motor 2 and a motor control panel, the motor control panel is connected to the PC, the motor control panel and the motor are connected via a wire, and the output shaft of the motor 2 is fixedly connected to a driving pulley 3;

[0040] A pair of first bearing seats 10 are fixedly installed on the top surface of the platform 1. The first bearing seats 10 are rotatably connected to the rotating shaft 6 through the bearings. The first rotating shaft 6 is fixedly connected to the driven pulley 4. The driven pulley 4 and the driving pulley 3 are connected by a belt 5. The two ends of the first rotating shaft 6 are respectively fixedly installed with driving wheels 7.

[0041] The platform 1 is provided with a set of slide grooves that are opposite to the position of the first bearing seat 10. The two second bearing seats 11 are slidably connected to the inside of the slide grooves respectively. The second bearing seats 11 and the slide grooves are provided with threaded holes. Bolts pass through the threaded holes to fix the second bearing seats 11 and the platform 1. The second bearing seat 11 slides along the slide grooves to adjust the distance between the second bearing seat 11 and the first bearing seat 10. When the second bearing seat 11 slides to the desired position, it is fixed to the platform 1 by bolts.

[0042] The second bearing seat 11 is rotatably connected to the second rotating shaft through a bearing, and support wheels 12 are fixedly mounted at both ends of the second rotating shaft; the surface of the cylinder 8 is in linear contact with the surfaces of the driving wheel 7 and the support wheel 12. When the motor 2 rotates, it drives the active pulley 3 to rotate, and the driven pulley 4 is driven to rotate through the belt 5, thereby driving the first rotating shaft 6 fixedly connected thereto to rotate, causing the driving wheel 7 to rotate accordingly. Under the action of friction, the roller 8 in linear contact with the surfaces of the driving wheel 7 and the support wheel 12 is driven to rotate together;

[0043] By adjusting the distance between the second bearing seat 11 and the first bearing seat 10, the distance between the driving wheel 7 and the supporting wheel 12 can be adjusted, so as to facilitate the support and transmission of cylinders 8 with different diameters;

[0044] A high-speed camera for photographing the bulk material inside the cylinder 8 is fixedly mounted on the top surface of the platform 1. The high-speed camera is located at the other end of the cylinder 8 and is connected to a PC installed with discrete element simulation software.

[0045] After the drum 8 starts to rotate, the bulk material inside the drum 8 flows. As the bulk material rises with the rotation of the drum, when the force between the particles cannot be balanced with gravity, before the particles collapse, the stop button is pressed and the motor 2 stops working. The high-speed camera records the maximum inclination angle between the accumulation slope and the horizontal plane at this time, which is the dynamic repose angle.

[0046] Preferably, a circle of refractory bricks is pasted along the inner surface of the cylinder 8 along its curved surface, and the thickness of the refractory bricks is 20 mm. Since the inner wall of the cylinder 8 is curved, directly pasting square bricks will produce gaps, causing accumulation of wet material particles and affecting equipment efficiency and experimental accuracy. To solve this problem, in this embodiment, the purchased square bricks are cut into strips to fit the curved surface, reducing gaps, and facilitating the simulation of the movement behavior of particles in a real rotary kiln.

[0047] Preferably, the inner diameter of the cylinder 8 is 250 mm and the length is 500 mm. Usually, the inner diameter of the cylinder 8 is 10 times the diameter of the particles.

[0048] Preferably, the filling degree of the bulk material in the cylinder 8 is 50%.

[0049] Preferably, a velocity sensor and an acceleration sensor are fixedly mounted on the outer wall of the cylinder 8, and both the velocity sensor and the acceleration sensor are wirelessly connected to a PC, so as to timely obtain the rotation of the cylinder 8, thereby more accurately capturing the motion trajectory and accumulation shape of the particles during rotation or tilting, so as to take real-time photos and calculate the dynamic angle of repose.

[0050] Preferably, a pressure sensor for measuring the pressure exerted by the bulk material on the inner wall of the cylinder 8 is installed on the inner wall of the cylinder 8. The pressure sensor is wirelessly connected to the PC and can measure the interaction force between the bulk material and the inner wall of the cylinder 8, so as to facilitate timely correction of the contact force model between particles and between particles and the wall.

[0051] Preferably, a Forma wheel 9 is fixedly mounted on the bottom surface of the platform 1 to facilitate moving the device to a desired experimental site.

[0052] Preferably, the cylinder 8 is made of transparent acrylic glass, so that a high-speed camera can capture clearer images.

[0053] Preferably, the rotation speed of the motor 2 is 1.78 rpm.

[0054] A discrete element contact parameter calibration method based on dynamic repose angle includes the following steps:

[0055] Step 1: Using zinc leaching slag particles as the research object, the zinc leaching slag particles are poured into the cylinder 8 so that the filling degree of the cylinder 8 is 50%;

[0056] Step 2: Set the speed of motor 2 to 1.78 rpm, turn on motor 2, and drive cylinder 8 to rotate. When cylinder 8 runs stably, the zinc leaching slag particles rise with the rotation of cylinder 8. When the force between the particles cannot be balanced with gravity, before the particles collapse, press the stop button on the motor control panel to stop motor 2. The high-speed camera records the maximum inclination angle between the accumulation slope and the horizontal plane at this time, which is the dynamic repose angle;

[0057] Step 3: Repeat the experimental process of step 2 5 to 10 times to obtain the dynamic repose angle. During the experiment, the cylinder 8 can be controlled to rotate clockwise or counterclockwise.

[0058] Step 4: Taking the dynamic repose angle as the target value, the contact parameters are continuously corrected through discrete element simulation to achieve high-precision calibration. The final contact parameters are: static friction coefficient 0.74, rolling friction coefficient 0.66, and viscous energy density 8588.45 j / m 3 .

Claims

1. A discrete element contact parameter calibration device based on dynamic repose angle, characterized in that: It comprises a PC, a motor control panel, a platform (1) and a transparent cylinder (8) for holding bulk materials, wherein one end of the cylinder (8) is provided with an opening; A motor (2) and a motor control panel are fixedly mounted on the platform (1), the motor control panel is connected to a PC, the motor control panel and the motor are connected via a wire, and the output shaft of the motor (2) is fixedly connected to a driving pulley (3); A pair of first bearing seats (10) and a pair of second bearing seats (11) are installed on the top surface of the platform (1); the first bearing seat (10) is rotatably connected to a first rotating shaft (6) through a bearing; the first rotating shaft (6) is fixedly connected to a driven pulley (4); the driven pulley (4) and the driving pulley (3) are connected through a belt (5); and driving wheels (7) are fixedly installed at both ends of the first rotating shaft (6); The second bearing seat (11) is rotatably connected to a second rotating shaft via a bearing, and support wheels (12) are fixedly mounted on both ends of the second rotating shaft. The surface of the cylinder (8) is in linear contact with the surfaces of the driving wheel (7) and the supporting wheel (12); A high-speed camera for photographing the bulk material inside the cylinder (8) is fixedly installed on the top surface of the platform (1). The high-speed camera is connected to a PC, and the PC is installed with discrete element simulation software.

2. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1, characterized in that: The platform (1) is provided with a slide groove facing the first bearing seat (10), and the second bearing seat (11) is slidably connected to the inside of the slide groove. The second bearing seat (11) and the slide groove are both provided with threaded holes, and bolts pass through the threaded holes to fix the second bearing seat (11) and the platform (1).

3. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: The inner surface of the cylinder (8) is pasted with a circle of refractory bricks along its arc surface; The inner diameter of the cylinder (8) is 250 mm, the length is 500 mm, and the thickness of the refractory brick is 20 mm.

4. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: A speed sensor is fixedly mounted on the outer wall of the cylinder (8), and the speed sensor is wirelessly connected to the PC.

5. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: An acceleration sensor is fixedly mounted on the outer wall of the cylinder (8), and the acceleration sensor is wirelessly connected to a PC.

6. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: A pressure sensor for measuring the pressure of the bulk material acting on the inner wall of the cylinder (8) is installed on the inner wall of the cylinder (8), and the pressure sensor is wirelessly connected to the PC.

7. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: A Fuma wheel (9) is fixedly mounted on the bottom surface of the platform (1).

8. The discrete element contact parameter calibration device based on dynamic repose angle according to claim 1 or 2, characterized in that: The cylinder (8) is made of transparent acrylic glass.

9. A method for calibrating discrete element contact parameters based on dynamic repose angle of the device as claimed in claim 1, characterized in that: The steps include: Step 1: Pour the bulk material into the cylinder (8) to make the filling degree of the cylinder (8) 50%; Step 2, set the speed of the motor (2), turn on the motor (2), drive the cylinder (8) to rotate, wait for the cylinder (8) to run stably, the bulk material rises with the rotation of the cylinder (8), when the force between the particles cannot be balanced with the gravity, before the particles collapse, press the stop button on the motor control panel, the motor (2) stops rotating, and the high-speed camera records the maximum inclination angle between the accumulation slope and the horizontal plane at this time, which is the dynamic repose angle; Step 3: Repeat step 2 5 to 10 times to obtain the dynamic angle of repose. Step 4: Using the dynamic repose angle as the target value, the experimental process is simulated by discrete element method, the contact parameters are continuously corrected to achieve high-precision calibration, and finally the contact parameters are obtained, including the static friction coefficient, rolling friction coefficient, and viscous energy density.

10. The discrete element contact parameter calibration method based on dynamic repose angle according to claim 9, characterized in that: The rotation speed of the motor (2) is 1.78 rpm.

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