A device and method for measuring rolling friction coefficient of brittle particles

Abstract

The present invention discloses a device for measuring the rolling friction coefficient of brittle particles, comprising an arc-shaped table, a platform and a side wall, wherein the platform is tangent to the bottom end of the arc-shaped table, the side wall is arranged on the same side of the arc-shaped table and the platform, a bearing is installed on the side wall, a rotating shaft is installed in the bearing, the rotating shaft is located above the intersection line between the arc-shaped table and the platform, and an angle measuring mechanism for measuring the rotation angle of the particles to be measured and a particle stopper for moving and releasing the particles to be measured along the arc surface of the arc-shaped table are respectively arranged on the rotating shaft; a method for measuring the rolling friction coefficient of brittle particles is also disclosed, which is to use a device for measuring the rolling friction coefficient of brittle particles for measurement. The device of the present invention replaces the vertical high platform originally having a height difference with a platform, and the particles to be measured do not need to be thrown out, which reduces the risk of brittle particles being broken, can obtain sufficient measurement data, and improves the accuracy during measurement.

Description

Technical Field

[0001] The invention belongs to the field of rolling friction coefficient measurement, and in particular relates to a device and a method for measuring the rolling friction coefficient of brittle particles. Background Art

[0002] Granular media is a common material configuration in human production and life. Its discrete characteristics cause it to exhibit some unique properties different from general solids, liquids, and gases. However, people's understanding of granular materials is far from mature. Today, the discrete element method has been proven to be a reliable and effective tool to characterize the properties of granular bulk materials. The micromechanical properties of particles affect the macroscopic properties of particle flow. Therefore, it is particularly important to calibrate the contact parameters input into EDEM through precise experiments, which has an indispensable influence on the precise expression of the macroscopic parameters of materials and their equipment in subsequent research on earthmoving machinery.

[0003] The rolling friction coefficient is an important contact parameter in EDEM simulation, which directly affects the accuracy and results of the simulation. The selection of rolling friction is of great significance to the detection and evaluation of material piles. There is currently no definite measuring device and measuring method for the determination of the rolling friction coefficient. Most of them are calibrated by virtual measurement. The rolling friction coefficient deduced by the virtual measurement and control variable method has a large error due to the continuous changes of various parameters. We have found a device for measuring the rolling friction coefficient disclosed in patent No. 201621411240.1. The device includes a vertical platform, an arc-shaped inclined platform, and a stone slab. The vertical platform is a square body with four vertical sides. The top of the vertical platform is provided with an arc-shaped inclined platform; the bottom end of the arc-shaped inclined platform is connected to a side of the vertical platform, and the bottom of this side is provided with a horizontal stone slab; the stone slab is covered with wet paper towels. The utility model sets a clamping device on the arc-shaped inclined platform, which is convenient for measuring the angle and height of the initial rolling position of the experimental ball, making the measurement data more accurate; the arc-shaped inclined platform is set on a vertical high platform, so that a height difference is formed between the bottom end of the arc-shaped inclined platform and the stone slab, which is convenient for calculating the kinetic energy of the horizontal throwing of the experimental ball. The device is used to measure hard particles (such as stone particles) without any problem, but when measuring brittle particles (such as soil particles), the particles are easily broken after being thrown, and sufficient measurement data cannot be obtained, which affects the accuracy of the measurement. Summary of the invention

[0004] The purpose of the present invention is to solve the above technical problems and provide a device and method for measuring the rolling friction coefficient of brittle particles. The device of the present invention reduces the throwing setting, reduces the risk of brittle particles breaking, and then can improve the accuracy of measurement.

[0005] To achieve the above-mentioned purpose, the technical solution of the present invention is:

[0006] A device for measuring the rolling friction coefficient of brittle particles comprises an arc table, a platform and a side wall, wherein the platform is tangentially connected to the bottom end of the arc table, the side wall is arranged on the same side of the arc table and the platform, a bearing is installed on the side wall, a rotating shaft is installed in the bearing, the rotating shaft is located above the intersection line of the arc table and the platform, and an angle measuring mechanism for measuring the rotation angle of the measured particle and a particle stopper for moving and releasing the measured particle along the arc surface of the arc table are respectively arranged on the rotating shaft.

[0007] As a further technical solution, the above-mentioned particle baffle includes a lifting rod and a particle baffle plate. The lifting rod is movable through the upper and lower surfaces of the rotating shaft. A limiting rod is provided at the upper end of the lifting rod, so that the lifting rod is stuck on the upper surface of the rotating shaft and rotates coaxially with the rotating shaft; a limiting seat is provided on the upper surface of the rotating shaft for placing the limiting rod; the particle baffle plate is arranged at the lower end of the lifting rod. When the lifting rod is stuck on the upper surface of the rotating shaft, the distance between the particle baffle plate and the arc surface is smaller than the diameter of the particle to be measured.

[0008] As a further technical solution, the above-mentioned angle measuring mechanism includes an angle plate and an angle indicating needle, wherein the angle plate is installed on the side wall with the bearing as the center of the circle; one end of the angle indicating needle is fixed on the rotating shaft and rotates coaxially with the rotating shaft; the other end of the angle indicating needle points to the angle number on the angle plate.

[0009] As a further technical solution, when the lifting rod is naturally placed vertically, the angle indicating needle points to 0° on the angle plate.

[0010] As a further technical solution, the angle of the above-mentioned arc surface is not greater than 90°.

[0011] A method for measuring the rolling friction coefficient of brittle particles is to use a brittle particle rolling friction coefficient measuring device as described above for measurement, place the particle to be measured on an arc table so that it rolls down to the platform without initial velocity until it stops, measure the rolling friction resistance work Q1 of the particle to be measured on the arc table, the linear friction resistance work Q2 on the platform and the gravity work Q of the particle to be measured during this process, and use the law of conservation of energy Q=Q1+Q2 to calculate the rolling friction coefficient μ of the particle to be measured.

[0012] As a further technical solution, the method for measuring the rolling friction resistance work Q1 described above is:

[0013] (1) Record the angle θ between the starting position of the particle to be tested and the vertical plane;

[0014] (2) When the particle to be tested rolls down at a small angle β, the positive pressure of the particle to be tested on the arc table remains unchanged because the angle is very small. The friction force in this process is

[0015] f=μmg cos(θ-β) ①

[0016] (3) Relative rolling distance of the particles to be measured:

[0017]

[0018] (4) The work done by rolling friction in this process is

[0019] ΔQ1=f·L1

[0020] Right now

[0021] It can be seen from this that the work done by the rolling friction resistance Q1 on the arc table is the integral of β in [0, θ], that is,

[0022]

[0023] in,

[0024] R: radius of the arc table;

[0025] μ: rolling friction coefficient;

[0026] m: weight of the particle to be measured;

[0027] g: acceleration due to gravity.

[0028] As a further technical solution, the friction resistance work Q2 mentioned above is calculated according to formula ⑤:

[0029] Q2=μmgL ⑤

[0030] in,

[0031] μ: rolling friction coefficient;

[0032] m: weight of the particle to be measured;

[0033] g: acceleration due to gravity;

[0034] L: The rolling distance of the particle to be tested on the platform.

[0035] As a further technical solution, the gravitational work Q of the particles to be measured is calculated according to formula ⑥:

[0036] Q=mgH=mgR(1-cosθ) ⑥

[0037] in,

[0038] m: weight of the particle to be measured;

[0039] g: acceleration due to gravity;

[0040] H: vertical height between the particle to be tested and the platform;

[0041] R: radius of the arc table;

[0042] θ: The angle between the starting position of the particle to be measured and the vertical plane.

[0043] As a further technical solution, the rolling friction coefficient μ mentioned above can be obtained by the equation:

[0044]

[0045] Further deduction yields:

[0046] mgR(1-cosθ)=Rμmg(1-cosθ)+μmgL,

[0047] Then, μ = R (1-cosθ) / [R (1-cosθ) + L] is calculated;

[0048] R: radius of the arc table;

[0049] θ: the angle between the starting position of the particle to be measured and the vertical plane;

[0050] L: rolling distance of the particle to be tested on the platform;

[0051] The measurement units of R and L are consistent.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The device of the present invention replaces the original vertical platform with a height difference with a platform, and the particles to be measured do not need to be thrown out, which reduces the risk of brittle particles being broken, can obtain sufficient measurement data, and improves the accuracy of measurement; and the present invention can be used to measure hard particles and brittle particles (such as soil particles), and has a wider range of applications.

[0054] 2. The present invention is designed to have a particle stopper that rotates synchronously with the angle measuring mechanism. When the lifting rod rotates with the rotating shaft as the center to drive the particle to be measured to move along the arc surface of the arc table, the angle indicator needle rotates synchronously with the rotating shaft, and the angle θ between the starting position of the particle to be measured and the vertical plane can be directly read; when the particle to be measured reaches the set angle, the lifting rod is lifted upward to enable the particle to be measured to roll along the arc surface toward the platform without initial velocity, thereby achieving synchronous rolling and angle measurement, reducing the tedious operation of the experimenter to measure the angle separately, and the particle to be measured and the angle indicator needle move synchronously, so the measurement is more accurate.

[0055] 3. In the measurement method developed on the device of the present invention, the rolling friction coefficient μ is only related to the radius R of the arc platform, the angle θ between the starting position of the particle to be measured and the vertical plane, and the rolling distance L of the particle to be measured on the platform, wherein R and θ are fixed values, and L is a test value, which can be easily obtained through measurement. Therefore, compared with the original high-platform test method, the present invention reduces the statistics of the movement time t of the measured particles, reduces human errors, and makes the statistical results more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a structural schematic diagram of a device for measuring rolling friction coefficient of brittle particles of the present invention;

[0057] Figure 2 This is a schematic diagram of measurement data of the present invention.

[0058] Figure numerals: 1-arc table, 2-platform, 3-side wall, 4-bearing, 5-rotating shaft, 6-lifting rod, 7-particle baffle, 8-limiting rod, 9-limiting seat, 10-angle plate, 11-angle indicating needle, 12-particle to be measured. DETAILED DESCRIPTION

[0059] The present invention is further described in detail below in conjunction with examples, but the implementation mode of the present invention is not limited to the scope represented by the examples.

[0060] Embodiment 1:

[0061] like Figure 1As shown, a device for measuring the rolling friction coefficient of brittle particles includes an arc table 1, the arc surface angle of the arc table 1 is 90°, a platform 2 and a side wall 3, the platform 2 is tangentially connected to the bottom end of the arc table 1, the side wall 3 is arranged on the same side of the arc table 1 and the platform 2, a bearing 4 is installed on the side wall 3, a rotating shaft 5 is installed in the bearing 4, the rotating shaft 5 is located above the intersection line of the arc table 1 and the platform 2, and an angle measuring mechanism for measuring the rotation angle of the particle to be measured and a particle stopper for moving and releasing the particle 12 to be measured along the arc surface of the arc table 1 are respectively provided on the rotating shaft 5. The particle blocking member includes a lifting rod 6 and a particle baffle 7; the lifting rod 6 is movable through the upper and lower surfaces of the rotating shaft 5 and can be freely moved up and down; a limiting rod 8 is provided at the upper end of the lifting rod 6, which then limits the lifting rod 6 to the upper surface of the rotating shaft 5 and rotates coaxially with the rotating shaft 5; a limiting seat 9 is provided on the upper surface of the rotating shaft 5 for placing the limiting rod 8, and the limiting seat 9 is a V-shaped structure fixed on the upper surface of the rotating shaft 5, and the limiting rod 8 is placed between the V-shaped structures to achieve front and rear limiting; the particle baffle 7 is arranged at the lower end of the lifting rod 6, and the particle baffle 7 is a strip plate structure, which forms an "L" shape with the lifting rod 6 and can rotate with the lifting rod 6; when the lifting rod 6 is stuck on the upper surface of the rotating shaft 5, the distance between the particle baffle 7 and the arc surface is less than the diameter of the particle 12 to be measured, so that the particle 12 to be measured can be blocked, and then the particle 12 to be measured can be pushed by the particle baffle 7 to the set height of the arc surface.

[0062] An angle measuring mechanism is provided on the side wall 3, and the angle measuring mechanism includes an angle plate 10 and an angle indicating needle 11. The angle plate 10 is installed on the side wall 3 with the bearing 4 as the center of the circle. The angle plate 10 is a fan-shaped structure and is located at the lower right corner of the bearing 4. One end of the angle indicating needle 11 is fixed on the rotating shaft 5 and rotates coaxially with the rotating shaft 5; the other end of the angle indicating needle 11 points to the angle number on the angle plate 10. In this embodiment, the lifting rod 6 and the angle indicating needle 11 are at an angle of 90°. When the lifting rod 6 is naturally placed vertically, the angle indicating needle 11 points horizontally to 0° on the angle plate 10. When the lifting rod 6 starts to rotate, the reading after the angle indicating needle 11 rotates synchronously is the rotation angle of the lifting rod 6, and is also the angle θ between the starting position of the particle 12 to be measured and the vertical plane.

[0063] The device of the present invention operates as follows:

[0064] 1. In the initial state, the lifting rod 6 is suspended on the rotating shaft 5 through the limiting rod 8 and is naturally placed vertically. At this time, the angle indicator needle 11 horizontally points to 0° on the angle plate 10.

[0065] 2. Place the particles 12 to be tested behind the particle baffle 7;

[0066] 3. Rotate the lifting rod 6, and the particle baffle 7 rotates synchronously to push the particle 12 to be measured onto the arc surface of the arc table 1. At this time, the reading of the angle indicator needle 11 is synchronously read, that is, the angle θ between the starting position of the particle 12 to be measured and the vertical plane;

[0067] 4. Lift the lifting rod 6 upward, the particle baffle 7 is moved away, and the particles 12 to be tested roll along the arc surface of the arc table 1 onto the platform 2 until they stop.

[0068] 5. Measure the rolling distance L of the particle 12 to be tested on the platform 2 and then perform calculation.

[0069] Embodiment 2:

[0070] A method for measuring the rolling friction coefficient of brittle particles is to use a brittle particle rolling friction coefficient measuring device as described in Example 1 above to perform measurement, place the particle 12 to be measured on an arc table 1 so that it rolls downward to a platform 2 without initial velocity until it stops, measure the rolling friction resistance work Q1 of the particle 12 to be measured on the arc table 1, the linear friction resistance work Q2 on the platform 2, and the gravitational work Q of the particle 12 to be measured during this process, and use the law of conservation of energy Q=Q1+Q2 to calculate the rolling friction coefficient μ of the particle 12 to be measured.

[0071] The measurement method of rolling friction resistance work Q1 is:

[0072] (1) Recording the angle θ between the starting position of the particle 12 to be tested and the vertical plane;

[0073] (2) When the particle 12 to be tested rolls down at a small angle β, since the angle is very small, the positive pressure of the particle 12 to be tested on the arc table 1 remains unchanged. The friction force in this process is

[0074] f=μmgcos(θ-β) ①

[0075] (3) Relative rolling distance of the particle 12 to be measured:

[0076]

[0077] (4) The work done by rolling friction in this process is

[0078] ΔQ1=f·L1

[0079] Right now

[0080] It can be seen that the work done by the rolling friction resistance Q1 on the arc table 1 is the integral of β in [0, θ], that is,

[0081]

[0082] in,

[0083] R: radius of the arc stage 1;

[0084] μ: rolling friction coefficient;

[0085] m: weight of the particle 12 to be measured;

[0086] g: acceleration due to gravity.

[0087] The friction resistance work Q2 is calculated according to formula ⑤:

[0088] Q2=μmgL ⑤

[0089] in,

[0090] μ: rolling friction coefficient;

[0091] m: weight of the particle 12 to be measured;

[0092] g: acceleration due to gravity;

[0093] L: rolling distance of the particle 12 to be tested on the platform 2.

[0094] The gravitational work Q of the particle 12 to be measured is calculated according to formula ⑥:

[0095] Q=mgH=mgR(1-cosθ) ⑥

[0096] in,

[0097] m: weight of the particle 12 to be measured;

[0098] g: acceleration due to gravity;

[0099] H: vertical height between the particle 12 to be tested and the platform 2;

[0100] R: radius of the arc stage 1;

[0101] θ: the angle between the starting position of the particle 12 to be measured and the vertical plane.

[0102] As a further technical solution, the above rolling friction coefficient μ is obtained according to Q=Q1+Q2:

[0103]

[0104] Further deduction yields:

[0105] mgR(1-cosθ)=Rμmg(1-cosθ)+μmgL,

[0106] Then, μ = R (1-cosθ) / [R (1-cosθ) + L] is calculated;

[0107] R: radius of the arc platform 1;

[0108] θ: the angle between the starting position of the particle 12 to be tested and the vertical plane;

[0109] L: rolling distance of the particle 12 to be tested on the platform 2;

[0110] The measurement units of R and L are the same.

[0111] The particle 12 to be measured is a soil particle, the angle θ between the starting position of the particle 12 to be measured and the vertical plane is 15°, and the radius R of the arc platform 1 is 390 mm.

[0112] Test surface: The contact surface between the arc platform 1 and the platform 2 is steel; the final rolling distance L (unit: mm) of the soil particles on the platform 2 is shown in Table 1:

[0113] Table 1

[0114] Number of tests Soil particles Number of tests Soil particles Number of tests Soil particles 1 390 13 422 25 376 2 386 14 387 26 362 3 445 15 436 27 384 4 392 16 385 28 406 5 354 17 374 29 439 6 409 18 398 30 413 7 388 19 398 31 401 8 344 20 415 32 325 9 364 21 404 33 364 10 407 22 397 34 354 11 378 23 424 35 383 12 335 24 452 36 391

[0115] According to the data analysis, the average value of L was finally determined to be 391.2. The rolling friction coefficient was solved according to the formula μ = R (1-cosθ) / [R (1-cosθ) + L], where R = 390 and θ = 15°. The rolling friction coefficient of soil particles-steel surface was 0.033.

[0116] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "head", "tail", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience 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 operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present invention. It should also be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection; it can be a detachable connection; it can also be a point connection; it can be a direct connection; it can be an indirect connection through an intermediate medium, so that the internals of the two elements can be connected. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The device connection methods not fully described in the present invention are all understood as conventional connection methods in the field.

[0117] The above embodiments are only specific examples for further describing the purpose, technical solutions and beneficial effects of the present invention, and the present invention is not limited thereto. Any modification, equivalent replacement, improvement, etc. made within the scope disclosed by the present invention are included in the protection scope of the present invention.

Claims

1. A device for measuring the rolling friction coefficient of brittle particles, comprising an arc table, characterized in that: It also includes a platform and a side wall, wherein the platform is tangentially connected to the bottom end of the arc platform, the side wall is arranged on the same side of the arc platform and the platform, a bearing is installed on the side wall, a rotating shaft is installed in the bearing, the rotating shaft is located above the intersection line of the arc platform and the platform, and an angle measuring mechanism for measuring the rotation angle of the particles to be measured and a particle stopper for moving and releasing the particles to be measured along the arc surface of the arc platform are respectively arranged on the rotating shaft; The particle blocking member comprises a lifting rod and a particle blocking plate. The lifting rod movably passes through the upper and lower surfaces of the rotating shaft. A limiting rod is provided at the upper end of the lifting rod, so that the lifting rod is clamped on the upper surface of the rotating shaft and rotates coaxially with the rotating shaft. A limiting seat is provided on the upper surface of the rotating shaft for placing the limiting rod. The particle blocking plate is provided at the lower end of the lifting rod. When the lifting rod is clamped on the upper surface of the rotating shaft, the distance between the particle blocking plate and the arc surface is smaller than the diameter of the particle to be measured. The angle of the arc surface is no greater than 90°.

2. The device for measuring rolling friction coefficient of brittle particles according to claim 1, characterized in that: The angle measuring mechanism includes an angle plate and an angle indicating needle. The angle plate is installed on the side wall with the bearing as the center of the circle. One end of the angle indicating needle is fixed on the rotating shaft and rotates coaxially with the rotating shaft. The other end of the angle indicating needle points to the angle number on the angle plate.

3. The device for measuring rolling friction coefficient of brittle particles according to claim 2, characterized in that: When the lifting rod is naturally placed vertically, the angle indicator needle points to 0° on the angle plate.

4. A method for measuring the rolling friction coefficient of brittle particles, characterized in that: The measurement is performed using a brittle particle rolling friction coefficient measuring device as described in claim 2 or 3, the particle to be measured is placed on an arc table so that it rolls down to the platform without initial velocity until it stops, and the rolling friction resistance work Q1 of the particle to be measured on the arc table, the linear friction resistance work Q2 on the platform, and the gravity work Q of the particle to be measured are measured during this process, and the rolling friction coefficient μ of the particle to be measured is calculated using the energy conservation law Q=Q1+Q2; The measuring method of the rolling friction resistance work Q1 is: (1) Record the angle θ between the starting position of the particle to be tested and the vertical plane; (2) When the particle to be tested rolls down at a small angle β, since the angle is very small, the positive pressure of the particle to be tested on the arc table remains unchanged. The friction force in this process is: f=μmgcos(θ-β) ① (3) Relative rolling distance of the particles to be measured: (4) The work done by rolling friction in this process is: ΔQ1=f·L1 Right now It can be seen from this that the work done by the rolling friction resistance Q1 on the arc table is the integral of β in [0, θ], that is: in, R: radius of the arc table; μ: rolling friction coefficient; m: weight of the particle to be measured; g: acceleration due to gravity; The friction resistance work Q2 is calculated according to formula ⑤: Q2=μmgL ⑤ in, μ: rolling friction coefficient; m: weight of the particle to be measured; g: acceleration due to gravity; L: rolling distance of the particle to be tested on the platform; The gravitational work Q of the particles to be measured is calculated according to formula ⑥: Q=mgH=mgR(1-cosθ) ⑥ in, m: weight of the particle to be measured; g: acceleration due to gravity; H: vertical height between the particle to be tested and the platform; R: radius of the arc table; θ: the angle between the starting position of the particle to be measured and the vertical plane; The rolling friction coefficient μ is obtained according to Q=Q1+Q2: Further deduction yields: mgR(1-cosθ)=Rμmg(1-cosθ)+μmgL, Then, μ = R (1-cosθ) / [R (1-cosθ) + L] is calculated; R: radius of the arc table; θ: the angle between the starting position of the particle to be measured and the vertical plane; L: rolling distance of the particle to be tested on the platform; The measurement units of R and L are consistent.

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