Device and method for measuring dynamic and static friction coefficients of irregular granular materials

Abstract

This invention relates to the field of interfacial friction testing technology for particulate materials, and provides a device and method for measuring the static and dynamic friction coefficients of irregular particulate materials. The method includes: obtaining static and dynamic friction forces based on the effective friction torque, the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity, and the stable time interval during which the long arc end of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity, and then obtaining the static and dynamic friction coefficients. The device and method of this invention should be able to simulate the compaction, embedding, sweeping, and restarting processes of particulate materials within a confined gap, obtaining static, dynamic, static, and dynamic friction forces, and the static and dynamic friction coefficients within the same particle placement state and the same test cycle. It also possesses multi-condition testing capabilities, including atmospheric pressure without liquid, atmospheric pressure with liquid or drilling fluid, and vacuum without liquid, thereby providing a basis for evaluating the anti-slip ability, anti-migration ability, environmental sensitivity, and wellbore reinforcement suitability of particulate materials.

Description

Technical Field

[0001] This invention relates to the field of interfacial friction testing technology for particulate materials, and is a device and method for measuring the dynamic and static friction coefficients of irregular particulate materials. Background Technology

[0002] Granular materials are widely used in engineering applications such as plugging, sealing, fissure filling, anti-slip support, underground engineering reinforcement, pipeline plugging, well plugging, geotechnical engineering, and energy engineering. When granular materials enter cracks, pore throats, slits, rough walls, or other confined spaces, their stability depends not only on particle size distribution, particle strength, morphological characteristics, and degree of compaction, but also on the frictional resistance and coefficient between particles and between particles and the wall surface.

[0003] For granular materials, their contact states exhibit significant dispersion and non-uniformity. Within confined spaces, the particle layer undergoes compaction, rearrangement, rolling, local jamming, breakage, wall embedding, and shear migration. Conventional tribometers struggle to simulate the periodic compaction, sweeping, and restarting processes of granular materials at irregular contact interfaces, thus the obtained friction coefficients fail to accurately reflect the anti-slip and anti-migration capabilities of granular materials within confined spaces. Furthermore, existing methods typically cannot simultaneously obtain the static and dynamic friction coefficients of granular materials within the same test cycle. Most methods require separate static and dynamic friction tests, or only roughly extract the initiation peak and stable friction values ​​during a single slip process. For granular materials, after a single initiation, shearing, or sweeping, the particle layer undergoes rearrangement, compaction, breakage, or local migration. If dynamic and static friction tests are conducted separately, it is difficult to maintain consistency in the initial particle placement, compaction degree, and contact boundaries, resulting in a lack of comparability between dynamic and static friction coefficients.

[0004] Furthermore, the frictional behavior of particulate materials is highly sensitive to the environmental medium. In oil and gas well engineering, wellbore reinforcement and plugging materials are typically exposed to drilling fluid, mud film, liquid-solid coupling, and pressure variations. In other engineering scenarios, particulate materials may be exposed to dry atmospheric pressure, liquid media, low pressure, vacuum, or special atmospheric conditions. Liquid media can alter the interparticle lubrication state, mud film formation, and interfacial shear resistance; vacuum or low-pressure conditions can weaken the lubrication of adsorbed films, water films, or liquid phases, making direct interparticle contact and interlocking effects more prominent. Existing friction meters and plugging evaluation equipment often struggle to simultaneously address confined contact between small-gap particles, distinguish between dynamic and static friction, and conduct comparative tests under atmospheric pressure, dry conditions, liquid media, or vacuum environments.

[0005] Existing evaluation methods for wellbore reinforcement and plugging materials in oil and gas well engineering primarily focus on pressure-bearing capacity, filtration loss, plugging rate, particle size matching, bridging effect, and seepage control. These methods can assess whether a material forms a plugging layer and the pressure differential it can withstand, but they struggle to characterize the frictional stability of particulate materials between fracture walls, pore throat walls, or weak wellbore surfaces. They also fail to distinguish the frictional differences between the static, interlocked state before activation and the continuous slip state after activation. Therefore, existing evaluation results are insufficient to fully explain when the particulate plugging layer initiates slippage, whether it continues to migrate after slippage, and the sources of differences in slippage resistance among different materials.

[0006] Patent application CN114414468A discloses a device and method for measuring the rolling friction coefficient of brittle particles. The device includes an arc-shaped stage, a platform, and a sidewall. The platform is tangentially connected to the bottom end of the arc-shaped stage. The sidewall is located on the same side of the arc-shaped stage and the platform. A bearing is mounted on the sidewall, and a rotating shaft is installed inside the bearing. The rotating shaft is located above the intersection line of the arc-shaped stage and the platform. The rotating shaft is equipped with an angle measuring mechanism for measuring the rotation angle of the particle under test and a particle stop for moving and releasing the particle along the arc surface of the arc-shaped stage. The patent application also discloses a method for measuring the rolling friction coefficient of brittle particles using a brittle particle rolling friction coefficient measuring device. While this document pertains to measuring the rolling friction coefficient of brittle particles, this application pertains to measuring the friction coefficient of irregular particulate materials. Furthermore, the friction coefficient measuring device in the document differs significantly in structure from this device.

[0007] Patent application CN119779963A discloses a friction coefficient detection device and a friction coefficient measurement method. The friction coefficient detection device includes a mounting base, a sliding platform, limiting members, a pulley assembly, a traction member, and a rotating support frame. The sliding platform is mounted on the mounting base. Two limiting members are detachably mounted on the sliding platform and are used to limit the movement of a first detection piece. The pulley assembly is located at one end of the sliding platform. The traction member has a receiving groove for accommodating a second detection piece. One end of the traction member is connected to a first load via a pull rope, which is wound around the pulley assembly. The second detection piece can slide relative to the first detection piece under the force of the first load. The rotating support frame is fixed on the mounting base and is used to support a third detection piece. One end of the pull rope is wound around the third detection piece, and the other end is connected to the first load. The pull rope cooperates with the pulley assembly, allowing the third detection piece to rotate relative to the rotating support frame under the force of the first load. The structure of the document differs significantly from that of the device in this application. Furthermore, the document is used to measure the coefficient of sliding friction and the coefficient of rotational friction, while this application is used to measure the coefficient of static friction and the coefficient of dynamic friction.

[0008] Therefore, there is an urgent need in engineering for a device and method for measuring the dynamic and static friction coefficients of small gaps in granular materials, especially for screening irregular granular materials such as oil and gas well wall strengthening materials and bridging and plugging materials. Summary of the Invention

[0009] This invention provides a device and method for measuring the static and dynamic friction coefficients of irregular particulate materials, which can effectively solve the problem that existing methods cannot simultaneously obtain the static and dynamic friction coefficients of the particulate materials within the same test cycle.

[0010] One of the technical solutions of this invention is achieved through the following measures: a device for measuring the dynamic and static friction coefficients of irregular particulate materials, comprising a housing, a drive assembly, a friction actuation and constraint assembly, and a measurement parameter module. The drive assembly includes a magnetic coupling transmission assembly and a non-coaxial motion compensation assembly. The housing contains a high-pressure vacuum chamber. The non-coaxial motion compensation assembly and the friction actuation and constraint assembly are located within the high-pressure vacuum chamber. The friction actuation and constraint assembly includes a Reuleaux triangular grinding ring and a constraint loading part. A square constraint cavity is provided in the middle of the constraint loading part, and the Reuleaux triangular grinding ring is located within the square constraint cavity. The tip and long arc-shaped end of the grinding ring can form a tip-sweeping contact state and a long arc-shaped end-sweeping contact state within the square constraint cavity. The static friction coefficient and dynamic friction coefficient are obtained by the time interval of the tip-sweeping contact and the stable time interval of the long arc-shaped end-sweeping contact, respectively. The output end of the magnetic coupling transmission assembly is connected to the input end of the non-coaxial motion compensation assembly, and the output end of the non-coaxial motion compensation assembly is connected to the Reuleaux triangle grinding ring. The measurement parameter module includes a torque acquisition module and an angle acquisition module. The torque acquisition module is located at the magnetic coupling transmission assembly, and the angle acquisition module is located at the Reuleaux triangle grinding ring.

[0011] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: Furthermore, the aforementioned magnetic coupling transmission assembly includes a main drive motor, an outer magnetic rotor, an inner magnetic rotor, and a magnetic coupling transmission shaft. The outer magnetic rotor and the inner magnetic rotor are magnetically coupled. The outer magnetic rotor is located outside the high-pressure vacuum chamber and is fixedly installed on the power output shaft of the main drive motor. The inner magnetic rotor is located inside the high-pressure vacuum chamber. The magnetic coupling transmission shaft is fixed inside the high-pressure vacuum chamber through a bearing mounting seat. The inner magnetic rotor is fixedly installed at one end of the magnetic coupling transmission shaft. A dynamic balance counterweight is provided on the bearing mounting seat.

[0012] Furthermore, the aforementioned non-coaxial motion compensation assembly includes a universal coupling, an eccentric motion support bearing, and a flexible sealing shaft. The other end of the magnetic coupling drive shaft is connected to the flexible sealing shaft via the universal coupling, and the flexible sealing shaft is connected to the Reuleaux triangular grinding ring via the eccentric motion support bearing.

[0013] Furthermore, the aforementioned housing is a split structure, comprising a left housing and a right housing. The right side of the left housing and the left side of the right housing are sealed together, forming a high-pressure vacuum cavity between the left housing and the right housing. The left housing is fixedly mounted on the left support frame via a first support base, and the right housing is fixedly mounted on the right support frame via a second support base. The right support frame is slidably mounted on the support frame.

[0014] Furthermore, a constraint loading section is provided on the right side of the high-pressure vacuum chamber inside the aforementioned right housing. A square constraint cavity is opened in the middle of the constraint loading section. A constraint plate is fixedly installed on the left side of the square constraint cavity. A Reuleaux triangular grinding ring is placed inside the square constraint cavity. A contact surface liner is provided on the inner wall of the square constraint cavity along the rotation direction of the Reuleaux triangular grinding ring. A bearing assembly is fixedly installed on the right side of the Reuleaux triangular grinding ring. A reserved hole with a diameter larger than the output end of the eccentric motion support bearing is opened on the constraint plate corresponding to the left and right sides of the bearing assembly. The output end of the eccentric motion support bearing passes through the reserved hole and is connected to the bearing assembly.

[0015] Furthermore, the aforementioned measurement parameter module also includes a thermocouple, the torque acquisition module includes a torque sensor, and the angle acquisition module includes an angle encoder. The thermocouple and angle encoder are located at the Reuleaux triangle grinding ring, and the torque sensor is located at the outer magnetic rotor or the inner magnetic rotor.

[0016] Furthermore, the aforementioned device for measuring the dynamic and static friction coefficients of irregular particulate materials also includes a vacuum system. The vacuum system includes a molecular pump, a fore-stage dry pump, a fore-stage mechanical pump, and a main pumping pipe. A signal line outlet is provided on the housing, and a fluid inlet and outlet are provided on the housing corresponding to the square constraint cavity. The fluid inlet and outlet are connected to the main pumping pipe, and the other end of the main pumping pipe is connected to the molecular pump. The pumping end of the fore-stage dry pump is connected to the outlet end of the molecular pump through a pumping pipe, and the gas supply end of the fore-stage mechanical pump is connected to the inlet end of the molecular pump through a gas supply pipe. A vacuum pressure measuring device is provided on the molecular pump, and a viewing window is provided in the high-pressure vacuum chamber.

[0017] The second technical solution of the present invention is achieved through the following measures: a measurement method using the dynamic and static friction coefficient measuring device for the irregular particulate material, comprising: Under no-load conditions, the drive assembly drives the Reuleaux triangle grinding ring to rotate to perform a no-load test. The background torque during the no-load test phase is collected, and the torque is zeroed using the background torque. After the torque is reduced to zero, the particulate material is evenly spread at the bottom of the square constraint cavity. Then, the Reuleaux triangular grinding ring is driven to rotate by the drive assembly to perform a friction test on the particulate material. The original torque and the rotation angle of the Reuleaux triangular grinding ring during the friction test are collected. The effective friction torque is obtained based on the original torque. The static friction force is obtained based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity. The dynamic friction force is obtained based on the effective friction torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity. The static friction force and dynamic friction force are combined with the equivalent normal constraint force acting on the bottom contact surface of the granular material to obtain the static friction coefficient and dynamic friction coefficient, respectively.

[0018] The following are further optimizations and / or improvements to the second technical solution of the above invention: Furthermore, obtaining the effective friction torque based on the original torque includes: Considering the existence of periodic mechanical resistance that varies with the rotation angle, let the rotation angle of the Reuleaux triangle grinding ring measured by the angle encoder be... The effective frictional torque is obtained by the following formula: In the formula, The background torque under no-load conditions. ; The original torque, ; For effective frictional torque, ; t is the turning angle, in rad; t is the test time, in s.

[0019] Furthermore, the static friction force obtained above based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity includes: establishing a static friction force expression based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity; obtaining the static friction force based on the static friction force expression; and stopping the drive and maintaining it for 3 to 5 seconds before the tip of the Reuleaux triangular grinding ring is about to sweep against the bottom of the square constraint cavity. In the formula, The static friction force is N; The time interval, s, during which the tip of the Reuleaux triangular grinding ring sweeps into contact with the bottom of the square constraint cavity; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. N represents the equivalent arm of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity.

[0020] Furthermore, the dynamic friction force obtained above, based on the effective frictional torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity, includes: Based on the effective frictional torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity, an expression for kinetic friction is established. The kinetic friction force is then obtained from this expression: In the formula, The force is kinetic friction, N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; Let be the turning angle at the time of the i-th sampling point, in rad; Let m be the equivalent force arm of the dynamic frictional force between the Reuleaux triangular grinding ring and the bottom contact area of ​​the square constraint cavity; This represents the number of sampling points.

[0021] Furthermore, the static friction coefficient and the dynamic friction coefficient mentioned above are obtained by the following formula: In the formula, The coefficient of static friction; The coefficient of kinetic friction; This represents the number of sampling points; The time interval, s, during which the tip of the Reuleaux triangular grinding ring sweeps into contact with the bottom of the square constraint cavity; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. m represents the equivalent arm of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity; The equivalent normal force corresponding to the static friction test is in N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; The equivalent normal force corresponding to the dynamic friction test is N; Let m be the equivalent force arm of the dynamic friction force of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity.

[0022] The device should be able to simulate the compaction, embedding, sweeping, and restarting processes of granular materials within a confined gap (i.e., a square confined cavity), and obtain static friction, dynamic friction, static friction coefficient, and dynamic friction coefficient under the same particle placement condition and the same test cycle. It should also have the capability to perform tests under multiple conditions, including atmospheric pressure without liquid, atmospheric pressure with liquid or drilling fluid, and vacuum without liquid, thereby providing a basis for evaluating the anti-slip ability, anti-migration ability, environmental sensitivity, and wellbore reinforcement suitability of granular materials.

[0023] Beneficial effects of this invention: 1. The device of the present invention can quickly evaluate the static and dynamic friction coefficients of granular plugging materials (granular materials) under actual formation conditions such as vacuuming and drilling fluid injection, and is suitable for initial screening and formulation comparison of plugging materials.

[0024] 2. By utilizing the geometric difference between the tip of the Reuleaux triangular grinding ring and its long arc end, a static friction initiation state and a dynamic friction slip state can be formed in the same measuring device and the same particulate material sample, thereby reducing systematic errors caused by testing with different devices.

[0025] 3. By pausing for 3 to 5 seconds before the static friction test, the particulate material is allowed to fully form a static contact and interlocking state, resulting in a clearer static friction peak and better test repeatability.

[0026] 4. The use of magnetic coupling transmission assembly and non-coaxial motion compensation assembly structure can reduce the interference of dynamic seals and shaft off-center load on friction signals.

[0027] 5. The square confined cavity and wear-resistant contact surface liner can provide a stable confined contact space, which is convenient for simulating the confined sweeping friction behavior of particulate materials in cracks, pore throats or weak surfaces of well walls.

[0028] 6. This device retains the vacuum system, fluid inlet and outlet, etc., and can be further expanded to study the frictional properties of sealing materials under vacuum, inert atmosphere, and different humidity or temperature conditions. Attached Figure Description

[0029] Appendix Figure 1 A three-dimensional view of a device for measuring the dynamic and static friction coefficients of irregular granular materials; Appendix Figure 2 Top view of the device for measuring the dynamic and static friction coefficients of irregular granular materials; Appendix Figure 3 Front view of the device for measuring the dynamic and static friction coefficients of irregular granular materials; Appendix Figure 4This is a partial sectional view of the main view of the device for measuring the dynamic and static friction coefficients of irregular granular materials. Appendix Figure 5 Right view of the device for measuring the dynamic and static friction coefficients of irregular granular materials; Appendix Figure 6 A partial right-side view of the device for measuring the dynamic and static friction coefficients of irregular granular materials; Appendix Figure 7 Front view of the drive assembly connected to the Reuleaux triangular grinding ring; Appendix Figure 8 A partial sectional view of the front view showing the connection between the drive assembly and the Reuleaux triangular grinding ring; Appendix Figure 9 A magnified stereoscopic view of the Reuleaux triangular grinding ring located on the left side of the square constraint cavity.

[0030] The codes in the attached diagram are as follows: 1 is the high-pressure vacuum chamber, 2 is the main drive motor, 3 is the outer magnetic rotor, 4 is the inner magnetic rotor, 5 is the magnetic coupling drive shaft, 6 is the bearing mounting seat, 7 is the dynamic balancing counterweight, 8 is the universal coupling, 9 is the eccentric motion support bearing, 10 is the flexible sealing shaft, 11 is the Reuleaux triangular grinding ring, 12 is the left housing, 13 is the right housing, 14 is the first support seat, 15 is the left support frame, 16 is the second support seat, 17 is the right support frame, and 18 is the support frame. The frame consists of: 19 (square constraint cavity), 20 (constraint plate), 21 (contact surface lining), 22 (bearing assembly), 23 (pre-drilled hole), 24 (molecular pump), 25 (forestage dry pump), 26 (forestage mechanical pump), 27 (main extraction pipeline), 28 (fluid inlet / outlet), 29 (extraction pipe), 30 (gas delivery pipe), 31 (vacuum pressure measuring device), 32 (constraint loading section), 33 (venting valve), 34 (vacuum gate valve), 35 (viewing window), 36 (residual gas analyzer), 37 (tip), and 38 (long arc-shaped end). Detailed Implementation

[0031] The present invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of the present invention.

[0032] In this invention, it should be noted that the terms "first," "second," etc., are used only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the support or element referred to must have a specific order and operation, and therefore should not be construed as a limitation of the invention.

[0033] For ease of description, the relative positions of the components are described based on the appendix to the instruction manual. Figure 1 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 1 The orientation of the layout is determined by the direction of the map.

[0034] The present invention will be further described below with reference to embodiments: Example 1: A device for measuring the dynamic and static friction coefficients of irregular particulate materials, comprising a housing, a drive assembly, a friction actuation and constraint assembly, and a measurement parameter module. The drive assembly includes a magnetic coupling transmission assembly and a non-coaxial motion compensation assembly. The housing contains a high-pressure vacuum chamber 1. The non-coaxial motion compensation assembly and the friction actuation and constraint assembly are located within the high-pressure vacuum chamber 1. The friction actuation and constraint assembly includes a Reuleaux triangular grinding ring 11 and a constraint loading part 32. A square constraint cavity 19 is provided in the center of the constraint loading part 32. The Reuleaux triangular grinding ring 11 is located within the square constraint cavity 19. The tip of the Reuleaux triangular grinding ring 11... Within the square constraint cavity 19, the tip-sweeping contact state and the long arc-shaped end 28 can form a tip-sweeping contact state and a long arc-shaped end-sweeping contact state, respectively. The static friction coefficient and dynamic friction coefficient are obtained through the time interval of the tip-sweeping contact and the stable time interval of the long arc-shaped end-sweeping contact, respectively. The output end of the magnetic coupling transmission assembly is connected to the input end of the non-coaxial motion compensation assembly, and the output end of the non-coaxial motion compensation assembly is connected to the Reuleaux triangular grinding ring 11. The measurement parameter module includes a torque acquisition module and an angle acquisition module. The torque acquisition module is located at the magnetic coupling transmission assembly, and the angle acquisition module is located at the Reuleaux triangular grinding ring 11.

[0035] During testing, the magnetic coupling drive assembly provides power and transmits the power to the Reuleaux triangular grinding ring 11 through the non-coaxial motion compensation assembly, driving the Reuleaux triangular grinding ring 11 to rotate within the square constraint cavity 19, thereby testing the static and dynamic friction coefficients of the particulate material.

[0036] The measuring device of this invention uses a Reuleaux triangular grinding ring 11 (hereinafter referred to as the grinding ring) as a non-circular motion actuator and a square constraint cavity 19 to construct a small-gap confined friction space, so that the particulate material is located between the grinding ring and the bottom of the square constraint cavity 19. By periodically and alternately sweeping the particulate layer (i.e., particulate material) at the bottom of the square constraint cavity 19 by the tip 37 and the long arc-shaped end 38 of the grinding ring, the static friction response and dynamic friction response of the particulate material are obtained respectively, and the static friction response and dynamic friction response are converted into static friction coefficient and dynamic friction coefficient. Among them, when the tip 37 sweeps and contacts the bottom of the square constraint cavity 19, it is used to characterize the starting friction resistance (i.e., static friction force) of the particulate layer when it transitions from a static interlocking state to a sliding state; when the long arc-shaped end 38 sweeps and contacts the bottom of the square constraint cavity 19, it is used to characterize the stable friction resistance (i.e., dynamic friction force) of the particulate layer under continuous sweeping and shear migration conditions.

[0037] This invention can simultaneously measure static friction, dynamic friction, static friction coefficient, and dynamic friction coefficient in the same particle laying state, the same confined space, and the same test cycle, reducing the errors caused by particle material relay, compaction state changes, and inconsistent contact boundaries in traditional separate tests.

[0038] This invention is also applicable to different testing environments, including normal pressure dry state, normal pressure with drilling fluid, and vacuum dry state, to compare the frictional stability of different wellbore reinforcement materials under dry state, drilling fluid lubrication / mud film effect, and low pressure environment. Therefore, this invention can provide experimental basis for the selection of oil and gas wellbore reinforcement materials, the screening of bridging and plugging material formulations, the evaluation of fracture plugging stability, and the control of weak surface slippage.

[0039] High-pressure vacuum chamber 1: Serves as the main housing space, used to accommodate structures such as the Reuleaux triangular grinding ring 11; if no vacuum is applied during use, it can be used as a closed protective chamber and a space to prevent particle scattering. Reuleaux triangular grinding ring 11: The core motion actuator; its equal-width non-circular contour, when rotating within the square constraint cavity 19, forms two contact states: a sweeping tip 37 and a sweeping long arc-shaped end 38, used to distinguish between static and dynamic friction. Square constraint cavity 19: Constructs an equal-width constraint space, restricting the movement trajectory of the Reuleaux triangular grinding ring 11, ensuring that its bottom contact state is periodic and repeatable.

[0040] Example 2: As an optimization of the above example, the magnetic coupling transmission assembly includes a main drive motor 2, an outer magnetic rotor 3, an inner magnetic rotor 4, and a magnetic coupling transmission shaft 5. The outer magnetic rotor 3 and the inner magnetic rotor 4 are magnetically coupled. The outer magnetic rotor 3 is located outside the high-pressure vacuum chamber 1 and is fixedly installed at the power output shaft of the main drive motor 2. The inner magnetic rotor 4 is located inside the high-pressure vacuum chamber 1. The magnetic coupling transmission shaft 5 is fixed inside the high-pressure vacuum chamber 1 through a bearing mounting seat 6. The inner magnetic rotor 4 is fixedly installed at one end of the magnetic coupling transmission shaft 5. A dynamic balance counterweight 7 is provided on the bearing mounting seat 6.

[0041] Main drive motor 2: Provides the power required for the rotation of the Reuleaux triangular grinding ring 11. It can achieve low-speed start-up, uniform sweeping, and restart after a pause by controlling the speed. The outer magnetic rotor 3 receives the power from the main drive motor 2 and transmits the magnetic coupling torque to the inner magnetic rotor 4 through magnetic coupling, which drives the magnetic coupling drive shaft 5 to rotate. Then, the torque is transmitted to the Reuleaux triangular grinding ring 11 through the non-coaxial motion compensation assembly, so that it makes restricted rotational movement within the square constraint cavity 19.

[0042] Example 3: As an optimization of the above embodiment, the non-coaxial motion compensation assembly includes a universal coupling 8, an eccentric motion support bearing 9, and a flexible sealing shaft 10. The other end of the magnetic coupling drive shaft 5 is connected to the flexible sealing shaft 10 through the universal coupling 8, and the flexible sealing shaft 10 is connected to the Reuleaux triangular grinding ring 11 through the eccentric motion support bearing 9.

[0043] Flexible sealing shaft 10: compensates for minor axial and radial offsets, reducing the off-center load on the transmission structure caused by the non-circular motion of the Reuleaux triangular grinding ring 11. Universal coupling 8: allows for a certain angular deviation, preventing jamming between the transmission structure (such as the non-coaxial motion compensation assembly) and the actuator (including the Reuleaux triangular grinding ring 11) due to geometric misalignment. Eccentric motion support bearing 9: supports the non-coaxial restricted motion of the Reuleaux triangular grinding ring 11, reducing unwanted vibration and additional friction; Dynamic balancing counterweight 7: adjusts the dynamic balance of rotating components (including the magnetically coupled transmission shaft 5), reducing the interference of periodic impacts on the torque signal.

[0044] Example 4: As an optimization of the above embodiment, the housing is a split structure, including a left housing 12 and a right housing 13. The right side of the left housing 12 and the left side of the right housing 13 are sealed together, and a high-pressure vacuum cavity 1 is formed between the left housing 12 and the right housing 13. The left housing 12 is fixedly mounted on the left support frame 15 by the first support seat 14, and the right housing 13 is fixedly mounted on the right support frame 17 by the second support seat 16. The right support frame 17 is slidably mounted on the support frame 18.

[0045] The first support 14 supports the left shell 12 and other structures, while the second support 16 supports the right shell 13, the constraint loading part 32, and other components. The right support frame 17 can slide left and right on the support frame 18 to facilitate the left and right movement of the right shell 13.

[0046] Example 5: As an optimization of the above embodiment, a constraint loading part 32 is provided on the right side of the high-pressure vacuum cavity 1 inside the right shell 13. A square constraint cavity 19 is opened in the middle of the constraint loading part 32. A constraint plate 20 is fixedly installed on the left side of the square constraint cavity 19. A Reuleaux triangular grinding ring 11 is placed in the square constraint cavity 19. A contact surface liner 21 is provided on the inner wall of the square constraint cavity 19 along the rotation direction of the Reuleaux triangular grinding ring 11. A bearing assembly 22 is fixedly installed on the right side of the Reuleaux triangular grinding ring 11. A reserved hole 23 with a diameter larger than the output end of the eccentric motion support bearing 9 is opened on the constraint plate 20 corresponding to the left and right sides of the bearing assembly 22. The output end of the eccentric motion support bearing 9 passes through the reserved hole 23 and is connected to the bearing assembly 22.

[0047] The right side of the left housing 12 and the left side of the right housing 13 can be connected together via flanges, and sealing components such as sealing rings can be installed between the flanges. These sealing components are mainly used for static sealing, and during atmospheric pressure testing, they primarily serve to prevent dust, particle escape, and structural closure and positioning. The contact surface liner 21 can be a tungsten carbide liner, which is wear-resistant and provides a stable, wear-resistant, and repeatable friction reference surface. The bearing assembly 22 supports rotation and maintains stable motion; depending on the environment, a vacuum-compatible bearing or an atmospheric pressure bearing can be selected.

[0048] Constraint plate 20: Provides or adjusts normal constraint, so that the particulate material is stably compacted and constrained in the contact area at the bottom of the square constraint cavity 19, providing a normal force basis for the calculation of the friction coefficient.

[0049] Example 6: As an optimization of the above embodiment, the measurement parameter module may further include a thermocouple, the torque acquisition module may include a torque sensor, and the angle acquisition module may include an angle encoder. The thermocouple and the angle encoder are located at the Reuleaux triangular grinding ring 11, and the torque sensor is located at the outer magnetic rotor 3 or the inner magnetic rotor 4.

[0050] Torque sensor: Measures the torque response of the Reuleaux triangular grinding ring 11 when overcoming the frictional resistance of the particulate material. Thermocouple: Records the temperature rise during the friction process, and can be used to eliminate the influence of temperature changes on the frictional behavior of the material when necessary. Angle encoder: Records the angular position of the Reuleaux triangular grinding ring 11 and establishes the correspondence between the sweep of the tip 37 and the sweep of the long arc end 38 of the Reuleaux triangular grinding ring 11 and the torque signal.

[0051] Example 7: As an optimization of the above embodiment, the device for measuring the dynamic and static friction coefficients of irregular particulate materials further includes a vacuum system. The vacuum system includes a molecular pump 24, a pre-pump dry pump 25, a pre-pump mechanical pump 26, and a main exhaust pipe 27. A signal line outlet is provided on the housing, and a fluid inlet / outlet 28 is provided on the housing corresponding to the square constraint cavity 19. The main exhaust pipe 27 is connected to the fluid inlet / outlet 28. The other end of the main exhaust pipe 27 is connected to the molecular pump 24. The exhaust end of the pre-pump dry pump 25 is connected to the exhaust end of the molecular pump 24 through an exhaust pipe 29. The gas delivery end of the pre-pump mechanical pump 26 is connected to the gas inlet end of the molecular pump 24 through a gas delivery pipe 30. A vacuum pressure measuring device 31 is provided on the molecular pump 24, and a viewing window 35 is provided on the high-pressure vacuum chamber 1.

[0052] Both gas and liquid (such as drilling fluid) enter and exit the square confinement cavity 19 through the fluid inlet / outlet 28. Gas is extracted under negative pressure, and liquid is injected under positive pressure.

[0053] The vacuum system is used for vacuum or atmosphere control, and is shut down and isolated during atmospheric pressure testing, not participating in friction testing; its presence allows this apparatus to be extended to friction studies of particulate sealing materials under vacuum or atmospheric conditions. Molecular pump 24 is used for evacuation during the high vacuum stage, backing dry pump 25 is used for initial rough evacuation, and backing mechanical pump 26 is used to transport gas or liquid.

[0054] A vent valve 33 and a switching valve (such as a vacuum gate valve 34) can be connected in series on the main extraction pipe 27. Throttling valves can be installed on both the extraction pipe 29 and the gas delivery pipe 30. The vacuum pressure measuring device 31 can be an ion gauge or a Pirani gauge for wide-range vacuum measurement. The signal line outlet can lead out the signal lines of an angle encoder and a thermocouple. A residual gas analyzer 36 can also be installed at the signal line outlet to analyze the gas composition in the high-pressure vacuum chamber 1. Sealing components such as sealing rings can be installed at the signal line outlet and the fluid inlet / outlet 28 according to conventional sealing methods to ensure airtightness. The viewing window 35 is used to observe the movement state of the Reuleaux triangular grinding ring 11, the spread state of the particulate material, and the bottom sweeping process.

[0055] During testing, particulate material (such as particulate sealing material) is placed at the bottom of the square constraint cavity 19, and the Reuleaux triangular grinding ring 11 rotates within the space of the square constraint cavity 19. Due to the uniform width geometric feature of the Reuleaux triangle, when it moves within the space of the square constraint cavity 19, it forms two typical contact states: the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19, and its long arc end 38 sweeps against the bottom of the square constraint cavity 19. When the tip 37 sweeps against the bottom of the square constraint cavity 19, the particulate material is forced to start moving from a static or near-static state, and the maximum resistance overcome at this time is defined as static friction. When the long arc end 38 sweeps against the bottom of the square constraint cavity 19, the particulate material is in a continuous sliding or rolling-slipping mixed state, and the average stable resistance at this time is defined as dynamic friction.

[0056] Example 8: A measurement method using the aforementioned irregular particulate material dynamic and static friction coefficient measuring device, comprising: Under no-load conditions, the drive assembly drives the Reuleaux triangle grinding ring 11 to rotate to perform a no-load test, and the background torque during the no-load test phase is collected. The torque is then zeroed using the background torque. After the torque is reduced to zero, the particulate material is evenly spread at the bottom of the square constraint cavity 19. Then, the Reuleaux triangular grinding ring 11 is driven to rotate by the drive assembly to perform a friction test on the particulate material. The original torque and the rotation angle of the Reuleaux triangular grinding ring 11 during the friction test are collected. The effective friction torque is obtained based on the original torque. The static friction force is obtained based on the effective frictional torque and the time interval during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps into the bottom of the square constraint cavity 19. The dynamic friction force is obtained based on the effective frictional torque and the stable time interval of the long arc end 38 of the Reuleaux triangular grinding ring 11 sweeping against the bottom of the square constraint cavity 19. The static friction force and dynamic friction force are combined with the equivalent normal constraint force acting on the bottom contact surface of the granular material to obtain the static friction coefficient and dynamic friction coefficient, respectively.

[0057] The friction test includes a static friction test stage and a dynamic friction test stage. In the static friction test stage, the tip 37 of the Reuleaux triangular grinding ring 11 sweeps and contacts the bottom of the square constraint cavity 19. In the dynamic friction test stage, the long arc end 38 of the Reuleaux triangular grinding ring 11 sweeps and contacts the bottom of the square constraint cavity 19.

[0058] Example 9: As an optimization of Example 8 above, the effective friction torque is obtained based on the original torque, including: Considering the existence of periodic mechanical resistance that varies with the rotation angle, let the rotation angle of the Reuleaux triangular grinding ring 11 measured by the angle encoder be... The effective frictional torque is obtained by the following formula: In the formula, The background torque under no-load conditions. ; The original torque, ; For effective frictional torque, ; The turning angle is rad; t is the test time, s; When the no-load background torque fluctuation is small, its average value can be taken as the background torque value for torque to return to zero: In the formula, This represents the average background torque under no-load conditions. ; Let the unloaded background torque be at the i-th sampling point time. ; t represents the number of sampling points during the no-load testing phase. i Let be the time of the i-th sampling point, s.

[0059] When the torque sensor outputs the effective frictional torque as At that time, based on the equivalent force arm between the bottom contact area of ​​the Reuleaux triangular grinding ring 11 and the square constraint cavity 19, the effective frictional torque signal is converted into the equivalent frictional force: In the formula, F(t) The equivalent frictional force is N; The effective friction torque after deducting the background torque under no-load conditions. ; R e The equivalent arm of the Reuleaux triangular grinding ring 11 relative to the bottom contact area of ​​the square constraint cavity 19 is m; The normal contact force at the k-th contact point at the bottom is N; Let m be the instantaneous rotation center of the Reuleaux triangle grinding ring, and m be the number of contact points.

[0060] in, The instantaneous rotation center of the Reuleaux triangle grinding ring, This represents the position of the kth contact point at the bottom. This is the instantaneous rotational center position of the Reuleaux triangle grinding ring. The equivalent force arm R... e It can be calculated using the above formula, or it can be obtained through calibration using a standard friction sample.

[0061] Example 10: As an optimization of Example 8 above, the static friction force is obtained based on the effective friction torque and the time interval during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19. This includes: establishing a static friction force expression based on the effective friction torque and the time interval during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19; obtaining the static friction force based on the static friction force expression; and stopping the drive and maintaining it for 3 to 5 seconds just before the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19. In this invention, the Reuleaux triangular grinding ring 11 undergoes a uniformly confined motion within the square constraint cavity 19. Since the geometric center, instantaneous rotation center, and equivalent point of action of the bottom contact area of ​​the Reuleaux triangle do not always coincide, the Reuleaux triangular grinding ring 11 experiences periodic eccentric pressing, lateral squeezing, and bottom sweeping actions during rotation. Therefore, the normal constraint force on the particulate material (such as particulate sealing material) is not solely determined by the weight of the measuring device or the applied load, but is jointly determined by the preload, the eccentric motion of the Reuleaux triangle, the reaction force of the square constraint cavity, and the compressive deformation of the particulate layer.

[0062] Suppose that the rotation angle of the Reuleaux triangular grinding ring 11 measured by the angle encoder is... The equivalent normal force on the granular material at the bottom of the square confined cavity 19 can be expressed as: In the formula, The equivalent normal force is N; The basic normal force generated by externally loaded structures or initial assembly preload, in N; The lateral constraint reaction force, N, can be directly measured by a sensor (such as a tension / compression force sensor); The geometric transfer coefficient for the transformation of lateral constraint reaction force into bottom normal force is related to the instantaneous attitude, contact point position, and contact normal direction of the Reuleaux triangular grinding ring 11 within the square constraint cavity 19 space, and can be determined through geometric relationships or experimental calibration. Specifically, when there is a main lateral contact point between the grinding ring and the square constraint cavity 19, for: in, The instantaneous center coordinates of Reuleaux triangle grinding ring 11 are given. The coordinates of the main lateral contact points are... The coordinates are the pressure center coordinates of the bottom contact area.

[0063] During the static friction test, just before the tip 37 of the Reuleaux triangular grinding ring 11 is about to sweep against the particulate material at the bottom of the square constraint cavity 19, the Reuleaux triangular grinding ring 11 is briefly paused for 3 to 5 seconds. This allows the particulate material and the contact surface liner 21 to re-establish a relatively static contact state, and causes a certain degree of compaction, interlocking, and structural recovery between the particulate materials. After the pause, the Reuleaux triangular grinding ring 11 is restarted. The peak value of the starting resistance generated when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19 can be taken as the static friction force. Let the time interval for the tip 37 of the Reuleaux triangular grinding ring 11 to sweep against the bottom of the square constraint cavity 19 be... Then static friction It can be represented as: Substituting further into the torque inverse calculation relationship, we can obtain: In the formula, The static friction force is N; The time interval, s, during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps into contact with the bottom of the square constraint cavity 19; The original torque, ; R e N represents the equivalent arm of the Reuleaux triangular grinding ring 11 relative to the bottom contact area of ​​the square constraint cavity 19; This represents the average background torque under no-load conditions. ; If the angle is synchronously zeroed out, the expression for static friction is obtained: In the formula, The static friction force is N; The time interval, s, during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps into contact with the bottom of the square constraint cavity 19; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. The equivalent arm, m, is used for testing the static friction force of the Reuleaux triangular grinding ring 11 relative to the bottom contact area of ​​the square constraint cavity 19.

[0064] Example 11: As an optimization of Example 8 above, the dynamic friction force is obtained based on the effective frictional torque and the stable time interval during which the long arc end 38 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19, including: Based on the effective frictional torque and the stable time interval of the long arc end 38 of the Reuleaux triangular grinding ring 11 sweeping into the bottom of the square constraint cavity 19, an expression for dynamic friction force is established, and the dynamic friction force is obtained from the expression for dynamic friction force. During the dynamic friction test, when the long arc-shaped end 38 of the Reuleaux triangular grinding ring 11 sweeps into contact with the granular material at the bottom of the square constraint cavity 19, the contact area is relatively long, and the granular material is mainly in a combined state of continuous shearing, sliding, and rolling. To avoid the unsteady-state effects at the start and end of the test, the stable time interval during the process of the long arc-shaped end 38 sweeping into contact with the bottom of the square constraint cavity 19 can be selected as the dynamic friction analysis interval. Let this stable time interval be... Then the kinetic friction force can be taken as the average value of the equivalent friction force within the stable time interval: The force is kinetic friction, N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; F(t i ) Let N be the equivalent frictional force at the i-th sampling point. Substituting the torque back-calculation relationship and the angle synchronous zeroing method, we can obtain the expression for the kinetic friction force: In the formula, The force is kinetic friction, N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; Let be the turning angle at the time of the i-th sampling point, in rad; The equivalent force of the dynamic frictional force of the Reuleaux triangular grinding ring 11 relative to the bottom contact area of ​​the square constraint cavity 19 is m; This represents the number of sampling points.

[0065] Example 12: As an optimization of Example 8 above, the static friction coefficient and dynamic friction coefficient are obtained by the following formula: In the formula, The coefficient of static friction; The coefficient of kinetic friction; This represents the number of sampling points; The time interval, s, during which the tip 37 of the Reuleaux triangular grinding ring 11 sweeps into contact with the bottom of the square constraint cavity 19; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. The equivalent force arm for static friction testing of the Reuleaux triangular grinding ring 11 relative to the bottom contact area of ​​the square constraint cavity 19 is m; The equivalent normal force corresponding to the static friction test is in N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; The equivalent normal force, N, corresponds to the dynamic friction test.

[0066] The testing procedure using the device and method for measuring the dynamic and static friction coefficients of irregular granular materials described in this invention is as follows: Test Procedure 1: Friction Coefficient Test of Particulate Materials under Normal Pressure, Without Drilling Fluid Step 1: Device Inspection and No-Load Calibration: Turn off the molecular pump 24, fore-stage dry pump 25, fore-stage mechanical pump 26, and fluid inlet / outlet 28 to bring the high-pressure vacuum chamber 1 to atmospheric pressure. Check that the square confinement chamber 19, contact surface liner 21, Reuleaux triangular grinding ring 11, torque sensor, and angle encoder are securely installed. Start the main drive motor 2 and run it at low speed, recording the no-load torque curve to subtract the background resistance of the magnetic coupling transmission assembly, etc.

[0067] Step 2: Contact Surface Cleaning: Remove the constraint plate 20, clean the bottom of the square constraint cavity 19 and the contact surface lining 21, ensuring there are no residual particles, oil stains, or obvious wear marks. If necessary, perform pre-run-in with standard particle material, then clean again and record the condition of the contact surface.

[0068] Step 3: Add granular plugging material: Weigh a certain mass of the granular plugging material to be tested (granular material) and evenly spread it in the bottom contact area of ​​the square constraint cavity 19. The spreading thickness should be consistent, and record the particle size distribution, material mass, spreading area, and initial compaction method. This procedure does not involve pumping drilling fluid; the granular material is tested in a dry state or a specified moist state.

[0069] Step 4: Apply normal constraint: Reset the constraint plate 20 and apply a stable normal constraint to the particulate material through the constraint plate 20, so that the particulate material forms repeatable contact with the Reuleaux triangular grinding ring 11 and the bottom contact surface liner 21. Record the normal constraint force or the corresponding calibration value.

[0070] Step 5: Pre-static friction test pause: Control the Reuleaux triangular grinding ring 11 to rotate to the position where the tip 37 is about to sweep and contact the bottom of the square constraint cavity 19, stop the drive and hold for 3 to 5 seconds to allow the particulate material to fully settle, interlock, and contact under normal constraint. After the pause, restart the main drive motor 2 at the set low speed and collect the peak torque when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps and contacts the bottom of the square constraint cavity 19. After deducting the no-load torque, calculate the torque based on the equivalent force arm R. e The effective torque is converted into equivalent frictional force, and the maximum starting resistance at the moment when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps into contact with the bottom is taken as the static friction force F. s .

[0071] Step 6: Dynamic Friction Test: Continue to drive the Reuleaux triangular grinding ring 11 to rotate, so that the long arc end 38 of the Reuleaux triangular grinding ring 11 sweeps against the bottom contact area of ​​the square constraint cavity 19. Record the stabilization time interval for this stage. According to the equivalent arm R e After deducting the no-load torque, it is converted into dynamic friction force F. d To improve accuracy, the average of the stable time intervals corresponding to multiple long arc-shaped end sweeps can be calculated.

[0072] Step 7: Repeated Cyclic Testing and Data Filtering: Perform 3 to 5 consecutive tests in the sequence of "pause-tip start-arc sweep". Eliminate abnormal peak values ​​that are obviously caused by stuck particles, abnormal particle accumulation, or mechanical impact, and calculate the static friction force, dynamic friction force, and their coefficients.

[0073] Step 8: Friction Coefficient Calculation and Result Output: Using F s F d It calculates the static and dynamic friction coefficients and can output results such as torque-time curves, torque-angle curves, peak static friction, average dynamic friction force, friction coefficient, test speed, dwell time, particle mass, and normal load.

[0074] Step 2: Friction coefficient test of drilling fluid and granular plugging material under normal pressure. Step 1: Device Inspection and No-Load Calibration: Turn off the molecular pump 24, dry pump, and vacuum extraction pipe 29 to bring the device to atmospheric pressure. Check that the square constraint cavity 19, contact surface liner 21, Reuleaux triangular grinding ring 11, constraint plate 20, torque sensor, angle encoder, and drilling fluid inlet or storage structure are securely installed. Start the main drive motor 2 and run it at low speed, recording the no-load torque under atmospheric pressure no-load conditions. If the no-load torque changes periodically with the rotation angle, the angle signal can be recorded simultaneously to establish a no-load background torque function. In the formula, This represents the average background torque under no-load conditions. ; Let the unloaded background torque be at the i-th sampling point time. ; t represents the number of sampling points during the no-load testing phase. i Let be the time of the i-th sampling point, s.

[0075] Step 2: Unifying Contact Surface Cleaning and Wetting Status: Open the constraint plate 20 and clean the bottom of the square constraint cavity 19, the contact surface liner 21, and the surface of the Reuleaux triangular grinding ring 11, ensuring no residual particles, deposited mud film, oil stains, or obvious wear marks. If necessary, use standard particle materials and standard drilling fluid for pre-run-in to reduce differences in initial surface conditions. After pre-run-in, clean the contact surfaces again and record the contact surface material, roughness, wear status, and presence of residual mud film. For tests comparing different drilling fluid systems, the initial wetting status of the contact surfaces should be kept consistent before each test.

[0076] Step 3: Prepare and add drilling fluid: Prepare drilling fluid according to the set formula, and record parameters such as drilling fluid density, viscosity, filtration loss, solids content, sand content, lubricant content, pH value, and temperature. Reset the constraint plate 20, and add a certain volume of drilling fluid to the bottom contact area of ​​the square constraint cavity 19, so that a repeatable liquid-phase lubrication or mud film contact environment is formed between the contact surface liner 21, the granular plugging material, and the Reuleaux triangular grinding ring 11. The amount of drilling fluid added should be sufficient to cover the particle layer or form a set liquid film thickness, but should not be excessive to avoid significant floating, migration, or uncontrolled accumulation of the granular material.

[0077] Step 4: Add granular plugging material: Weigh a certain mass of the granular plugging material to be tested and add it evenly to the bottom contact area of ​​the square confinement cavity 19 containing drilling fluid. During the addition process, local agglomeration and large particle accumulation should be avoided as much as possible. Gradual spreading, gentle stirring, or pre-mixing can be used to ensure a relatively uniform distribution of the granular material in the drilling fluid. Record the particle size distribution, material mass, spread area, addition order, drilling fluid volume, and the mass ratio or volume ratio of the granular material to the drilling fluid.

[0078] Step 5: Static Wetting and Initial Compaction: After adding the granular plugging material and drilling fluid, allow the device to stand for a certain period of time to ensure the granular material and drilling fluid are fully wetted, and to allow the drilling fluid to form a stable liquid film or mud film between the contact surface liner 21 and the granular material. The granular material, drilling fluid, Reuleaux triangular grinding ring 11, and the bottom contact surface liner 21 of the square constraint cavity 19 form a repeatable contact. Record the normal constraint force and its calibration function.

[0079] Step 6: Static Friction Test: Control the Reuleaux triangular grinding ring 11 to rotate until its tip 37 is about to sweep against the bottom of the square constraint cavity 19. Stop the drive and hold for 3 to 5 seconds to allow the particulate material to form a stable static contact state under the drilling fluid environment and normal constraint. This pause process can promote the stabilization of particle embedding, mud film bearing, and liquid film distribution. After the pause, restart the main drive motor 2 at a set low speed and collect the peak torque when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps against the bottom of the square constraint cavity 19. After deducting the no-load torque, convert the effective torque into equivalent friction force according to the equivalent force arm, and take the maximum starting resistance at the moment the tip 37 sweeps against the bottom as the static friction force under the drilling fluid environment.

[0080] Step 7: Dynamic Friction Test: Continue driving the Reuleaux triangular grinding ring 11 to rotate, causing its long arc end 38 to sweep against the bottom contact area of ​​the square constraint cavity 19. Collect the stable time interval for this stage. Since drilling fluid alters interparticle friction, contact surface lubrication, and mud film shear resistance, the dynamic friction stage should exclude unsteady disturbances during entry and exit from the contact area. Calculate the stable time interval corresponding to the long arc end 38 of the Reuleaux triangular grinding ring 11. After deducting the no-load torque, convert the torque into dynamic friction force based on the equivalent force arm. To improve accuracy, average the stable time intervals corresponding to multiple long arc sweeps.

[0081] Step 8: Cyclic Repetition and Liquid Phase State Monitoring: Conduct 3 to 5 consecutive tests in the sequence of "pause—tip start—arc surface sweep." During the test, observe whether the particulate material exhibits obvious sedimentation, agglomeration, drift, mud film peeling, or localized accumulation. If the drilling fluid experiences significant water loss, thickening, particle deposition, or changes in liquid film thickness, record this phenomenon and remove abnormal peak values ​​caused by particle jamming, abnormal particle accumulation, liquid film rupture, or mechanical impact during data processing. Calculate the static friction force, dynamic friction force, and their coefficients for each cycle.

[0082] Step 9: Friction Coefficient Calculation and Result Output: Calculate the static and dynamic friction coefficients of the granular plugging material under drilling fluid conditions based on static friction, dynamic friction, and normal constraint force. Output the following results: torque-time curve, torque-angle curve, peak static friction force, average dynamic friction force, static friction coefficient, dynamic friction coefficient, drilling fluid type, drilling fluid performance parameters, granular material mass, particle size distribution, liquid-solid ratio, test rotation speed, dwell time, normal load, and test temperature.

[0083] Step 3: Vacuuming, no drilling fluid added, friction coefficient test of granular plugging material Step 1: Device Inspection and No-Load Calibration: Check that the high-pressure vacuum chamber 1, first support base 14, second support base 16, constraint loading part 32, contact surface liner 21, Reuleaux triangular grinding ring 11, magnetic coupling transmission assembly, torque sensor, and angle encoder are securely installed. Confirm that the molecular pump 24, fore-stage dry pump 25, main pumping line 27, ion gauge, and Pirani gauge are functioning correctly. Without adding granular sealing material, first drive the main drive motor 2 at low speed under normal pressure or a predetermined vacuum state and record the no-load torque.

[0084] Step 2: Contact Surface Cleaning and Drying: Open the constraint plate 20 and clean the bottom of the square constraint cavity 19, the contact surface liner 21, and the surface of the Reuleaux triangular grinding ring 11, ensuring there are no residual particles, oil stains, moisture, or obvious wear marks. If necessary, use anhydrous cleaning agents, dry gas purging, or low-temperature drying to remove residual moisture from the contact surfaces. For vacuum friction testing, avoid allowing ordinary lubricating oil, drilling fluid residues, or volatile contaminants to enter the test area to prevent them from evaporating during the vacuum process and affecting the friction test results.

[0085] Step 3: Add granular plugging material: Weigh a certain mass of the granular plugging material to be tested and evenly spread it in the bottom contact area of ​​the square constraint cavity 19. Record the particle size distribution, material mass, spread thickness, spread area, and initial compaction method of the granular material. This procedure does not add drilling fluid, and the granular material is tested in a dry state or at a pre-specified moisture content. If it is necessary to study the effect of moisture content, the granular material should be weighed, dried, or conditioned before testing, and the initial moisture content should be recorded.

[0086] Step 4: Apply initial normal constraint and seal the high-pressure vacuum chamber 1: Apply initial normal constraint to the particulate material using the constraint plate 20 (in fact, resetting the constraint plate 20 is equivalent to applying the constraint), so that the particulate material forms stable contact with the Reuleaux triangular grinding ring 11 and the bottom of the square constraint cavity 19. Record the initial normal constraint force or the corresponding calibration value. Then install the constraint plate 20, fix the left housing 12 and right housing 13 together, check the sealing status of the sealing assembly and the electrical signal lead-out point, and confirm that the signals from the torque sensor and angle encoder can be transmitted normally.

[0087] Step 5: Vacuuming and Environmental Stabilization: Start the fore-stage dry pump 25 and molecular pump 24 sequentially to evacuate the high-pressure vacuum chamber 1 through the main evacuation line 27, and monitor the chamber vacuum level using a Pirani gauge and an ion gauge. During the vacuuming process, avoid disturbing the particulate material with rapid airflow; this can be achieved by gradually opening the throttle valve to reduce airflow impact. After the high-pressure vacuum chamber 1 reaches the set vacuum level and stabilizes for a period of time, record the vacuum level, stabilization time, chamber temperature, and residual gas state. If a residual gas analyzer 36 is configured, the main residual gas components within the high-pressure vacuum chamber 1 can be recorded. This procedure does not pump drilling fluid; it only tests the dry-state frictional characteristics of the particulate plugging material under vacuum or low-pressure atmosphere conditions.

[0088] Step 6: Verification of No-Load Torque or Background Torque under Vacuum Conditions: After reaching the set vacuum level, a short period of low-speed idle rotation can be performed for verification, recording the rotation angle and no-load torque under vacuum conditions. Since the vacuum environment may alter the resistance state of bearings, sealing components, magnetic coupling transmission assemblies, etc., the no-load torque under vacuum conditions should be used for subtraction during formal testing. If the vacuum no-load verification cannot be completed without disturbing the particle layer, the pre-test vacuum no-load calibration curve or standard sample calibration curve should be used as the basis for background correction.

[0089] Step 7: Static Friction Test: Control the Reuleaux triangular grinding ring 11 to rotate to the position where its tip 37 is about to sweep and contact the bottom of the square constraint cavity 19. Stop the drive and hold for 3 to 5 seconds to allow the particulate material to be fully stationary, interlocked, and in contact under vacuum and normal constraint. Under vacuum, the adsorption film and liquid lubrication on the surface of the particulate material are weakened, and the direct contact and interlocking effect between particles may be enhanced. Therefore, the pause time and normal constraint conditions should be kept consistent to ensure comparability between different tests. After the pause, restart the main drive motor 2 at a set low speed and collect the peak torque when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps and contacts the bottom of the square constraint cavity 19. After deducting the vacuum no-load torque, convert it into equivalent friction force according to the equivalent force arm related to the rotation angle, and take the maximum starting resistance at the moment when the tip 37 of the Reuleaux triangular grinding ring 11 sweeps and contacts the bottom of the square constraint cavity 19 as the static friction force F under vacuum conditions. s .

[0090] Step 8: Dynamic friction test: Continue driving the Reuleaux triangular grinding ring 11 to rotate, causing its long arc-shaped end 38 to sweep and contact the bottom contact area. Collect the torque signal during the stable sweeping phase of the long arc-shaped end 38, eliminating unsteady disturbances caused by entering or exiting the contact area, and localized particle jamming. Subtract the no-load torque under vacuum conditions, and convert the torque into dynamic friction force F based on the equivalent force arm related to the rotation angle. d To improve accuracy, the average can be calculated by selecting multiple stable time intervals corresponding to the 38 sweeps at the long arc ends.

[0091] Step 9: Cyclic Repetition and Vacuum Stability Monitoring: Perform 3 to 5 consecutive tests following the sequence of "pause—tip start—arc surface sweep." During the test, continuously record the vacuum level, high-pressure vacuum chamber 1 temperature, torque signal, and rotation angle signal, observing for vacuum fluctuations, particle scattering, abnormal particle jamming, frictional heat accumulation, or mechanical impact. If the vacuum level changes significantly during the test, record the time of change and assess its impact on the friction test results. Discard any abnormal peak values ​​clearly caused by abnormal particle accumulation, particle jamming, or mechanical impact, and calculate the static friction force, dynamic friction force, and their coefficients.

[0092] Step 10: Venting, Sampling, and Result Output: After the test, stop the main drive motor 2, close the high vacuum gate valve 34 and molecular pump 24, and slowly open the venting valve 33 to restore the cavity to normal pressure, avoiding rapid venting that could disturb the particulate material. Separate the left shell 12 from the right shell 13, and observe and record the wear, breakage, agglomeration, compaction marks, and contact surface wear marks of the particulate material. Calculate the static and dynamic friction coefficients of the particulate sealing material based on the static friction, dynamic friction, and other parameters obtained under vacuum conditions. Output the torque-time curve, torque-angle curve, vacuum-time curve, static friction peak value, dynamic friction average value, static friction coefficient, dynamic friction coefficient, particulate material mass, particle size distribution, layup thickness, test speed, pause time, normal load, vacuum degree, and high-pressure vacuum chamber temperature.

[0093] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A device for measuring the dynamic and static friction coefficients of irregular granular materials, characterized in that, The system includes a housing, a drive assembly, a friction actuator and constraint assembly, and a measurement parameter module. The drive assembly includes a magnetic coupling transmission assembly and a non-coaxial motion compensation assembly. The housing contains a high-pressure vacuum chamber, where the non-coaxial motion compensation assembly and the friction actuator and constraint assembly are located. The friction actuator and constraint assembly includes a Reuleaux triangular grinding ring and a constraint loading section. A square constraint cavity is provided in the middle of the constraint loading section, and the Reuleaux triangular grinding ring is located in the square constraint cavity. The tip and long arc-shaped end of the Reuleaux triangular grinding ring can form a tip sweeping contact state and a long arc-shaped end sweeping contact state within the square constraint cavity. The static friction coefficient and dynamic friction coefficient are obtained by the time interval of the tip sweeping contact and the stable time interval of the long arc-shaped end sweeping contact, respectively. The output end of the magnetic coupling transmission assembly is connected to the input end of the non-coaxial motion compensation assembly, and the output end of the non-coaxial motion compensation assembly is connected to the Reuleaux triangular grinding ring. The measurement parameter module includes a torque acquisition module and a rotation angle acquisition module. The torque acquisition module is located at the magnetic coupling transmission assembly, and the rotation angle acquisition module is located at the Reuleaux triangular grinding ring.

2. The device for measuring the dynamic and static friction coefficients of irregular granular materials according to claim 1, characterized in that, The magnetic coupling drive assembly includes a main drive motor, an outer magnetic rotor, an inner magnetic rotor, and a magnetic coupling drive shaft. The outer magnetic rotor and the inner magnetic rotor are magnetically coupled. The outer magnetic rotor is located outside the high-pressure vacuum chamber and is fixedly installed on the power output shaft of the main drive motor. The inner magnetic rotor is located inside the high-pressure vacuum chamber. The magnetic coupling drive shaft is fixed inside the high-pressure vacuum chamber through a bearing mounting seat. The inner magnetic rotor is fixedly installed at one end of the magnetic coupling drive shaft. A dynamic balance counterweight is provided on the bearing mounting seat.

3. The device for measuring the dynamic and static friction coefficients of irregular granular materials according to claim 2, characterized in that, The non-coaxial motion compensation assembly includes a universal coupling, an eccentric motion support bearing, and a flexible sealing shaft. The other end of the magnetic coupling drive shaft is connected to the flexible sealing shaft through the universal coupling, and the flexible sealing shaft is connected to the Reuleaux triangular grinding ring through the eccentric motion support bearing.

4. The device for measuring the dynamic and static friction coefficients of irregular particulate materials according to claim 1, 2, or 3, characterized in that, The housing has a split structure, consisting of a left housing and a right housing. The right side of the left housing and the left side of the right housing are sealed together, forming a high-pressure vacuum cavity between them. The left housing is fixedly mounted on a left support frame via a first support base, and the right housing is fixedly mounted on a right support frame via a second support base. The right support frame is slidably mounted on a support frame. A constraint loading part is provided on the right side of the high-pressure vacuum cavity inside the right housing. A square constraint cavity is opened in the middle of the constraint loading part. A constraint plate is fixedly installed on the left side of the square constraint cavity. A Reuleaux triangular grinding ring is placed inside the square constraint cavity. A contact surface liner is provided on the inner wall of the square constraint cavity along the rotation direction of the Reuleaux triangular grinding ring. A bearing assembly is fixedly installed on the right side of the Reuleaux triangular grinding ring. A reserved hole with a diameter larger than the output end of the eccentric motion support bearing is opened on the constraint plate corresponding to the left and right sides of the bearing assembly. The output end of the eccentric motion support bearing passes through the reserved hole and connects to the bearing assembly.

5. The device for measuring the dynamic and static friction coefficients of irregular granular materials according to claim 4, characterized in that, It also includes a vacuum system, which includes a molecular pump, a forepump, a forepump mechanical pump, and a main pumping pipe. The housing has a signal line outlet, and the housing corresponding to the square confinement cavity has a fluid inlet and outlet. The fluid inlet and outlet are connected to the main pumping pipe, and the other end of the main pumping pipe is connected to the molecular pump. The pumping end of the forepump and the outlet of the molecular pump are connected through a pumping pipe, and the gas delivery end of the forepump and the gas inlet of the molecular pump are connected through a gas delivery pipe. The molecular pump is equipped with a vacuum pressure measuring device, and the high-pressure vacuum chamber is equipped with a viewing window. Or / and, the measurement parameter module also includes a thermocouple, the torque acquisition module includes a torque sensor, the angle acquisition module includes an angle encoder, the thermocouple and the angle encoder are set at the Reuleaux triangle grinding ring, and the torque sensor is set at the outer magnetic rotor or the inner magnetic rotor.

6. A method for measuring the dynamic and static friction coefficients of irregular particulate materials according to any one of claims 1 to 5, characterized in that, The measurement method using the aforementioned irregular particulate material dynamic and static friction coefficient measuring device includes: Under no-load conditions, the drive assembly drives the Reuleaux triangle grinding ring to rotate to perform a no-load test. The background torque during the no-load test phase is collected, and the torque is zeroed using the background torque. After the torque is reduced to zero, the particulate material is evenly spread at the bottom of the square constraint cavity. Then, the Reuleaux triangular grinding ring is driven to rotate by the drive assembly to perform a friction test on the particulate material. The original torque and the rotation angle of the Reuleaux triangular grinding ring during the friction test are collected. The effective friction torque is obtained based on the original torque. The static friction force is obtained based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity. The dynamic friction force is obtained based on the effective friction torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity. The static friction force and dynamic friction force are combined with the equivalent normal constraint force acting on the bottom contact surface of the granular material to obtain the static friction coefficient and dynamic friction coefficient, respectively.

7. The method according to claim 6, characterized in that, The effective friction torque is obtained based on the original torque, including: Suppose that the angle encoder measures the rotation angle of the Reuleaux triangle grinding ring as... The effective frictional torque is obtained by the following formula: In the formula, The background torque under no-load conditions. ; The original torque, ; For effective frictional torque, ; t is the turning angle, in rad; t is the test time, in s.

8. The method according to claim 6 or 7, characterized in that, The static friction force is obtained based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity. This includes: establishing a static friction force expression based on the effective frictional torque and the time interval during which the tip of the Reuleaux triangular grinding ring sweeps against the bottom of the square constraint cavity; obtaining the static friction force based on this expression; and stopping the drive and maintaining this position for 3 to 5 seconds just before the tip of the Reuleaux triangular grinding ring is about to sweep against the bottom of the square constraint cavity. In the formula, The static friction force is N; The time interval, s, during which the tip of the Reuleaux triangular grinding ring sweeps into contact with the bottom of the square constraint cavity; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. N represents the equivalent arm of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity.

9. The method according to claim 8, characterized in that, The dynamic friction force is obtained based on the effective frictional torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity, including: Based on the effective frictional torque and the stable time interval of the long arc end of the Reuleaux triangular grinding ring sweeping against the bottom of the square constraint cavity, an expression for kinetic friction is established. The kinetic friction force is then obtained from this expression: In the formula, The force is kinetic friction, N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; Let be the turning angle at the time of the i-th sampling point, in rad; Let m be the equivalent force arm of the dynamic frictional force between the Reuleaux triangular grinding ring and the bottom contact area of ​​the square constraint cavity; This represents the number of sampling points.

10. The method according to claim 9, characterized in that, The static friction coefficient and the dynamic friction coefficient are obtained by the following formula: In the formula, The coefficient of static friction; The coefficient of kinetic friction; This represents the number of sampling points; The time interval, s, during which the tip of the Reuleaux triangular grinding ring sweeps into contact with the bottom of the square constraint cavity; The background torque under no-load conditions. ; The original torque, ; The turning angle is measured in rad. m represents the equivalent arm of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity; The equivalent normal force corresponding to the static friction test is in N; For a stable time interval, s; t i Let be the time of the i-th sampling point, in seconds; Let the idle background torque be the value at the i-th sampling point. ; The original torque at the time of the i-th sampling point. ; The equivalent normal force corresponding to the dynamic friction test is N; Let m be the equivalent force arm of the dynamic friction force of the Reuleaux triangular grinding ring relative to the bottom contact area of ​​the square constraint cavity.

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