Magnetorheological fluid power transmission damage test method and system

Abstract

The application discloses a kind of magnetorheological fluid power transmission damage test method and system, and it is related to magnetorheological fluid test technical field.System includes transmission unit, observation unit and measurement and control unit, transmission unit includes servo motor, torque sensor, magnetorheological fluid driver and load, magnetorheological fluid driver is equipped with replaceable active disc, driven disc, excitation coil, transparent observation window and anti-centrifugal dispersion type magnetorheological fluid;Observation unit includes optical high-speed microscope, for collecting particle chain distribution evolution image and wall wear image;Measurement and control unit are used for synchronous acquisition rotation speed, torque and magnetic field intensity and control excitation current.The application can establish corresponding relationship with the wall wear characteristics obtained after experiment pause by macroscopic power parameter, particle chain microcosmic evolution parameter, can quantitatively analyze the influence of different wall surface parameters on transmission damage, provides basis for magnetorheological fluid transmission device structure optimization and life evaluation.

Description

Technical Field

[0001] This invention relates to the field of magnetorheological fluid testing technology, specifically to a method and system for testing damage in magnetorheological fluid dynamic transmission. Background Technology

[0002] Magnetorheological fluid (MRF) is an intelligent suspension composed of magnetic particles, a carrier fluid, and additives. Under the influence of an external magnetic field, the magnetic particles can form chain-like or columnar structures along the direction of the magnetic field, transforming the MRF from a low-viscosity fluid state to a solid-like state with a certain yield strength. When the magnetic field is removed, the particle chain structure disintegrates, and the MRF returns to its flow state. Therefore, MRF is widely used in clutches, brakes, vibration dampers, and intelligent power transmission devices. During MRF power transmission, there is usually relative rotation between the driving and driven discs. Under the combined action of magnetic force, shear force, centrifugal force, and gravity, the MRF particle chains undergo formation, deflection, breakage, reconstruction, and migration. The evolution of the particle chains not only affects torque transmission efficiency and transmission stability but may also cause scouring, friction, or micro-cutting effects on the walls of the driving and driven discs, leading to wall wear. Wall wear, in turn, alters the surface roughness, working clearance, and local magnetic field distribution of the transmission discs, thereby affecting the transmission accuracy, stability, and service life of MRF transmission devices.

[0003] Existing magnetorheological fluid power transmission testing devices primarily focus on macroscopic dynamic performance testing such as speed, torque, and response time. They struggle to simultaneously acquire information on the microscopic distribution and evolution of the particle chain during power transmission, and also find it difficult to establish a correlation between the particle chain motion state and wall wear characteristics. Furthermore, under high-speed conditions, magnetic particles are prone to sedimentation, agglomeration, or radial segregation, leading to unstable particle chain distribution and affecting the accuracy of damage test results. In addition, existing testing methods typically cannot perform repeatability and comparability analysis of power transmission damage under different surface roughness, materials, coatings, or textures while maintaining consistent transmission structure, operating clearance, and test conditions.

[0004] Therefore, it is necessary to provide a magnetorheological fluid power transmission damage testing method and system that can be applied to high-speed power transmission conditions, simultaneously observe the micro-evolution of particle chains, and quantitatively analyze the impact of different wall conditions on power transmission damage. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for testing power transmission damage in magnetorheological fluids, addressing the problem that existing technologies struggle to simultaneously acquire information on the microscopic evolution of particle chains and wall wear characteristics. By simultaneously acquiring dynamic parameters, particle chain evolution images, and wall wear information, quantitative analysis of power transmission damage under different wall conditions is achieved, and the stability and comparability of high-speed testing are improved.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: Firstly, the present invention proposes a magnetorheological fluid dynamic transmission damage testing system, comprising: a transmission unit, the transmission unit including a servo motor, a coupling, a torque sensor, a magnetorheological fluid actuator, and a load; the servo motor is connected to the torque sensor via the coupling; the torque sensor is connected to the active side of the magnetorheological fluid actuator; and the driven side of the magnetorheological fluid actuator is connected to the load; the magnetorheological fluid actuator includes an active disk, a driven disk, an excitation coil, a transparent observation window, a magnetorheological fluid filled in the working gap between the active disk and the driven disk, and a Hall sensor; the excitation coil is disposed on the outer periphery of the active disk and the driven disk to form an adjustable magnetic field within the working gap; both the active disk and the driven disk are detachable and replaceable structures.

[0007] The observation unit includes an optical high-speed microscope, which is aligned with the working gap and mating end face between the active disk and the driven disk through a transparent observation window. It is used to acquire images of the distribution and evolution of the magnetorheological fluid particle chain and to acquire images of the wall microstructure of the mating end face of the active disk and the driven disk after the experiment is paused.

[0008] The measurement and control unit includes a data acquisition device and a computer. The data acquisition device is used to collect data on rotational speed, torque, and magnetic field strength during the power transmission process. The computer is used to record power transmission parameters, particle chain evolution images, and wall wear images, and to perform correlation storage and computational analysis on the data and images.

[0009] As a further improvement of the present invention, the transparent observation window is set on the housing of the magnetorheological fluid actuator at a position corresponding to the mating end faces of the driving disk and the driven disk. The transparent observation window is made of quartz glass or a highly transparent and wear-resistant material, and is sealed to the housing of the magnetorheological fluid actuator by a sealing element.

[0010] As a further improvement of the present invention, the optical high-speed microscope is mounted on an independent vibration-damping bracket, which is separately set from the transmission unit to reduce the impact of vibration of the servo motor and load operation on the microscopic observation image.

[0011] As a further improvement of the present invention, the driving disk and the driven disk are interchangeable transmission disks of the same model. Different driving disks and driven disks have different wall parameters, which include at least one of surface roughness, material type, surface coating, and surface texture.

[0012] As a further improvement of the present invention, the magnetorheological fluid is an anti-centrifugal dispersion type magnetorheological fluid, which is used to suppress the sedimentation, agglomeration and radial segregation of magnetic particles during high-speed power transmission testing.

[0013] As a further improvement of the present invention, the computer is used to perform grayscale conversion, filtering, threshold segmentation, and skeleton extraction processing on the particle chain distribution evolution image to obtain the number of particle chains in the field of view, the length of the i-th particle chain, the equivalent cross-sectional area of ​​the particle chain, the equivalent volume of the particle chain, and the shear deflection angle of the particle chain relative to the magnetic field direction; and is used to perform region recognition and area conversion on the wall micro-morphology image to obtain the spatial average value of the wear mark width, wear mark area, scratch density, peeling area, and effective contact area in multiple observation fields of view.

[0014] Secondly, the present invention also proposes a method for testing the dynamic transmission damage of magnetorheological fluid, which is implemented using the aforementioned magnetorheological fluid dynamic transmission damage testing system. The method includes the following steps: Step S1, preparing an anti-centrifugal dispersion type magnetorheological fluid, and conducting pre-tests on the anti-centrifugal performance and pre-dispersion performance of the magnetorheological fluid to obtain the magnetorheological fluid particle concentration, particle size distribution, particle density or particle mass parameters, and obtaining the wear coefficient required for the wall wear model through calibration experiments.

[0015] Step S2: Fill the working gap between the active disk and the driven disk with magnetorheological fluid, start the servo motor and supply power to the excitation coil to form a magnetic field in the working gap. Under the action of the magnetic field, the magnetorheological fluid forms a particle chain and transmits the power of the active disk to the driven disk.

[0016] Step S3: During the power transmission process, the speed, torque and magnetic field strength data are collected synchronously by the data acquisition device. The distribution evolution image of the magnetorheological fluid particle chain is collected in situ by the optical high-speed microscope. Based on the particle chain distribution characteristics, the equivalent magnetic energy increment model caused by particle chain deflection is established, the equivalent electromagnetic force of the particle chain in the shear direction is calculated, and the particle chain motion state parameters are obtained.

[0017] Step S4: Replace the active disk and driven disk with different wall parameters, and repeat steps S2 and S3 to obtain the power transmission parameters, particle chain evolution parameters and particle chain motion state parameters under different wall conditions.

[0018] Step S5: After each power transmission experiment is paused, the microscopic morphology images of the mating end faces of the active and driven disks are collected using an optical high-speed microscope. Combined with the particle chain motion state parameters obtained in step S3 and the different wall working condition parameters obtained in step S4, a wall average wear depth rate model is established, the average wear depth rate of the active and driven disks is calculated, and the corresponding wall wear characteristics are recorded.

[0019] Step S6: After the test is completed, remove the magnetorheological fluid and clean the driving disk, driven disk, and magnetorheological fluid actuator.

[0020] As a further improvement of the present invention, in step S3, the equivalent electromagnetic force of the particle chain in the shear direction is obtained as follows: Step S31, extract the number of particle chains in the field of view based on the particle chain distribution evolution image acquired by the optical high-speed microscope. Length of the i-th particle chain equivalent cross-sectional area of ​​granular chain and the shear deflection angle of the particle chain relative to the direction of the magnetic field In conjunction with the magnetic field strength within the working gap, an equivalent magnetic energy increment model caused by particle chain deflection is established: Equation 1; where: Equation 2; where, This represents the equivalent magnetic energy increment caused by particle chain deflection. The number of particle chains identified within the field of view; The vacuum permeability; The equivalent relative permeability of the magnetorheological fluid; Magnetic induction intensity within the working gap The magnetic field strength obtained by conversion using calibration relationships; For the first The equivalent volume of a single particle chain; For the first The equivalent cross-sectional area of ​​a single particle chain; For the first The length of the particle chain; For the first The shear deflection angle of the particle chain relative to the direction of the magnetic field.

[0021] Step S32, Define the particle chain shear strain as: Equation 3; where, This represents the equivalent displacement of the particle chain in the shear direction. The working clearance between the driving plate and the driven plate.

[0022] Based on the partial derivative of energy with respect to displacement, the equivalent electromagnetic force of the particle chain in the shear direction is obtained: Formula 4.

[0023] In shear strain Under the small deformation approximation condition of <0.1, the equivalent electromagnetic force is expressed as: Formula 5.

[0024] As a further improvement of the present invention, in step S3, the particle chain motion state parameters include the motion speed of the i-th particle chain. and local relative slip velocity The speed of the particle chain movement Displacement of the centroid of the same particle chain in consecutive frame images of particle chain distribution evolution. Time interval with adjacent frames The calculation yields the following formula: Formula 6.

[0025] For radius The particle chain at that location, based on the angular velocity of the active disk. and driven disk angular velocity Determine the local relative slip velocity And combined with the equivalent electromagnetic force in the shear direction Centrifugal force and gravity are used to check or compensate for the motion state of the particle chain; the specific formula is: Formula 7.

[0026] As a further improvement of the present invention, in step S5, a model for the average wear depth rate of the wall surface is established based on the equivalent electromagnetic force of the particle chain, centrifugal force, gravity, and relative slip velocity of the particle chain: Formula 8.

[0027] Based on the equivalent projections of the particle chain shearing direction equivalent electromagnetic force, centrifugal force, and gravitational force onto the wall contact direction, a normal equivalent force model of the particle chain on the wall is established: Equation 9; Equation 10; where, The average wear depth rate represents the change in equivalent wear volume per unit time and per unit effective contact area of ​​the wall surface. For testing time, This represents the spatial average of the effective contact area across multiple observation fields. Let t be the number of particle chains participating in wall contact. The equivalent wear coefficient, obtained through calibration, represents the equivalent wear volume generated per unit frictional work, and its dimensions are: The definition is determined, For the first The equivalent normal force exerted by each particle chain on the wall surface. Let be the sliding velocity of the particle chain relative to the wall. , , These are the non-negative projection correction factors for electromagnetic force, centrifugal force, and gravity in the wall contact direction, respectively, which can be obtained through calibration experiments. Let be the equivalent mass of the i-th particle chain. Let be the radius of the location of the i-th particle chain. Let be the local equivalent angular velocity at the location of the i-th particle chain. This is the acceleration due to gravity.

[0028] Compared with the prior art, the present invention has the following beneficial effects: 1. By setting a transparent observation window on the magnetorheological fluid actuator and using an optical high-speed microscope to observe the working gap between the active disk and the driven disk, the present invention can obtain the image of the distribution evolution of magnetorheological fluid particle chains during the power transmission process and obtain the wall wear image after the experiment is paused, thus solving the problem of the disconnect between macroscopic dynamic performance data and microscopic wear data in the existing test methods.

[0029] 2. This invention controls and collects speed, magnetic field strength, load and torque by using a servo motor, magnetic powder brake and data acquisition device respectively, so that the experimental conditions are stable and controllable, and the comparability and repeatability between different groups of test results can be improved.

[0030] 3. The present invention uses an anti-centrifugal dispersion magnetorheological fluid, which can suppress the sedimentation, agglomeration and radial segregation of magnetic particles under high speed conditions, which is beneficial to maintaining the stability of the particle chain evolution state and improving the reliability of high-speed power transmission damage testing.

[0031] 4. The driving disc and driven disc in this invention adopt the same model of replaceable structure. While keeping the main structure of the transmission device, working clearance and installation position basically unchanged, the transmission disc with different surface roughness, material, coating or texture can be replaced, so as to systematically study the influence law of different wall working conditions on power transmission damage.

[0032] 5. This invention combines the equivalent magnetic energy increment model caused by particle chain deflection, the calculation of equivalent electromagnetic force in the shear direction, the determination of particle chain motion velocity and local relative slip velocity, and the average wear depth rate model of the wall surface, so that the microscopic motion state of the particle chain can be used as the input parameter of the wall wear prediction model, thereby realizing the quantitative correlation between the magnetorheological fluid dynamic transmission process and the wall damage process.

[0033] 6. This invention, through synchronous recording, enables the particle chain evolution images and wall wear images acquired by the optical high-speed microscope to have a unified time reference with the rotational speed, torque, magnetic field strength, and excitation current data acquired by the data acquisition device. This allows for the determination of the power transmission conditions and particle chain motion states corresponding to specific wear characteristics, thereby improving the accuracy and traceability of power transmission damage analysis. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the magnetorheological fluid dynamic transmission damage testing system of the present invention.

[0035] Figure 2 This is a schematic diagram of the magnetorheological fluid actuator of the present invention.

[0036] Explanation of reference numerals in the attached drawings: 1. Servo motor; 2. Torque sensor; 3. Magnetorheological fluid actuator; 31. Driving disc; 32. Driven disc; 33. Excitation coil; 34. Magnetorheological fluid; 35. Hall sensor; 4. Magnetic powder brake; 5. High-speed optical microscope; 6. Data acquisition unit; 7. Computer; 8. Transparent observation window; 9. Coupling. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0038] like Figure 1 and Figure 2 As shown, this embodiment provides a magnetorheological fluid dynamic transmission damage testing system, including a transmission unit, an observation unit, and a measurement and control unit.

[0039] The transmission unit includes a servo motor 1, a torque sensor 2, a magnetorheological fluid actuator 3, and a load. In this embodiment, the load is a magnetic powder brake 4. The servo motor 1 is connected to the torque sensor 2 via a coupling 9, and the magnetorheological fluid actuator 3 is connected to the magnetic powder brake 4 via a coupling. The servo motor 1 provides a controllable input speed, the magnetic powder brake 4 provides an adjustable load, and the torque sensor 2 detects torque changes during power transmission.

[0040] The magnetorheological fluid actuator 3 includes a driving disk 31, a driven disk 32, an excitation coil 33, a magnetorheological fluid 34, a Hall sensor 35, and a transparent observation window 8. A working gap is formed between the driving disk 31 and the driven disk 32, and the magnetorheological fluid 34 fills the working gap. The excitation coil 33 is disposed on the outer periphery of the driving disk 31 and the driven disk 32 to generate a magnetic field within the working gap. The Hall sensor 35 detects the magnetic induction intensity within the working gap, and the computer 7 calculates the magnetic field strength within the working gap according to a calibration relationship.

[0041] Both the driving disc 31 and the driven disc 32 adopt a detachable and replaceable structure. Specifically, the driving disc 31 and the driven disc 32 can be installed on the corresponding rotating shaft or disc base via threaded connection, locating pin connection, or clamping connection, respectively. When it is necessary to test different wall surface conditions, the current driving disc 31 and driven disc 32 can be removed and replaced with the same model of transmission discs with different surface roughness, materials, surface coatings, or surface textures. Since the external dimensions and installation references of different transmission discs are consistent, the same working clearance and transmission structure can be maintained after replacement, thereby improving the comparability of different groups of experimental results.

[0042] A transparent observation window 8 is mounted on the housing of the magnetorheological fluid actuator 3 and corresponds to the mating end faces of the driving disk 31 and the driven disk 32. The transparent observation window 8 can be made of quartz glass or other highly transparent, wear-resistant materials and is sealed to the housing via a sealing ring to prevent leakage of the magnetorheological fluid 34. Through the transparent observation window 8, the optical high-speed microscope 5 can observe the distribution of magnetorheological fluid particle chains between the driving disk 31 and the driven disk 32 during power transmission, and can observe the wear morphology of the walls of the driving disk 31 and the driven disk 32 after the power transmission experiment has been paused.

[0043] The observation unit includes an optical high-speed microscope 5. The optical high-speed microscope 5 is positioned outside the transparent observation window 8 and aligned with the working gap and mating end faces of the active disk 31 and the driven disk 32. Preferably, the optical high-speed microscope 5 is mounted on an independent vibration-damping bracket, which is separate from the transmission unit to reduce the impact of vibrations from the servo motor 1, magnetorheological fluid actuator 3, and magnetic powder brake 4 on image acquisition quality. Images acquired by the optical high-speed microscope 5 are transmitted to a computer 7 for subsequent particle chain identification, shear angle extraction, and for extracting the spatial average of the effective contact area within multiple observation fields and analyzing wall wear from wall microstructure images acquired after the experiment has paused.

[0044] The measurement and control unit includes a data acquisition unit 6 and a computer 7. The data acquisition unit 6 is used to collect data on rotational speed, torque, excitation current, and magnetic induction intensity within the working gap. The computer 7 is connected to both the optical high-speed microscope 5 and the data acquisition unit 6, and is used to synchronously record power transmission parameters and particle chain evolution images. It also associates, stores, and analyzes the wall microstructure images collected after the experiment is paused with the corresponding power transmission parameters and particle chain evolution parameters. The excitation current and load torque can be adjusted by corresponding controllers.

[0045] In this embodiment, the magnetorheological fluid 34 is an anti-centrifugal dispersion type magnetorheological fluid. The anti-centrifugal dispersion type magnetorheological fluid 34 includes magnetic particles, a base fluid, and a dispersion stabilizing additive. The magnetic particles can be carbonyl iron powder, iron-cobalt alloy particles, or other soft magnetic particles. The base fluid can be silicone oil, mineral oil, synthetic oil, or a water-based base fluid. The dispersion stabilizing additive can include at least one of surfactants, thixotropic agents, thickeners, anti-settling agents, or density regulators. The dispersion stabilizing additive improves the suspension stability between the magnetic particles and the base fluid, thereby suppressing sedimentation, agglomeration, and radial segregation of the magnetic particles under high-speed rotation conditions. Pre-testing of anti-centrifugal performance can include static sedimentation testing and centrifugation testing. After centrifugation, if the volume fraction difference between the upper and lower layers of the magnetorheological fluid is less than a preset threshold, or if no obvious stratification, hard sedimentation, or irreversible agglomeration occurs after centrifugation, the magnetorheological fluid is determined to meet the anti-centrifugal dispersion requirements of this testing system.

[0046] The magnetorheological fluid 34 can suppress the sedimentation, agglomeration and radial segregation of magnetic particles under high-speed rotation conditions, making the particle chain distribution more stable and improving the reliability of high-speed power transmission damage testing.

[0047] This embodiment also provides a method for testing damage in magnetorheological fluid dynamic transmission, including the following steps.

[0048] Step S1: Prepare the magnetorheological fluid 34 and conduct preliminary tests on its anti-centrifugal and pre-dispersion properties. Specifically, mix magnetic particles, carrier liquid, and additives in a set ratio, and prepare an anti-centrifugal dispersion magnetorheological fluid after stirring, ultrasonic dispersion, or mechanical dispersion. Then, observe the magnetorheological fluid 34 under static conditions and conduct a pre-centrifugal test to determine whether the magnetic particles show significant sedimentation, agglomeration, or stratification, and record the particle concentration, particle size distribution, particle density, or particle mass parameters. Further, obtain the wear coefficient required for the average wall wear depth rate model through calibration experiments. And correction factors for electromagnetic force, centrifugal force, and gravity in the direction of action on the wall. , and The particle parameters, wear coefficient, and correction coefficient obtained in this step serve as the basic input parameters for subsequent calculations of the equivalent electromagnetic force of the particle chain and the average wear depth rate of the wall.

[0049] Step S2: Fill the working gap between the active disk 31 and the driven disk 32 with magnetorheological fluid 34, start the servo motor 1 and supply power to the excitation coil 33.

[0050] Specifically, the servo motor 1 drives the active disk 31 to rotate, energizing the excitation coil 33 and creating a magnetic field between the active disk 31 and the driven disk 32. Magnetic particles in the magnetorheological fluid 34 form a particle chain under the influence of the magnetic field. This particle chain undergoes shearing action between the active disk 31 and the driven disk 32, transmitting power from the active disk 31 to the driven disk 32. The magnetic powder brake 4 applies a load to the driven disk 32 to simulate the actual power transmission resistance.

[0051] Step S3: Synchronously acquire power transmission parameters and particle chain evolution images, and calculate particle chain motion state parameters.

[0052] Specifically, during the power transmission process, the data acquisition unit 6 synchronously acquires the speed of the servo motor 1, the torque output by the torque sensor 2, and the magnetic induction intensity detected by the Hall sensor 35 within the working gap. The computer 7 calculates the magnetic field strength within the working gap based on the calibration relationship. The optical high-speed microscope 5 images the working gap between the active disk 31 and the driven disk 32 through the transparent observation window 8, acquiring images of the distribution and evolution of the magnetorheological fluid particle chain in real time.

[0053] Computer 7 performs grayscale conversion, filtering, threshold segmentation, and skeleton extraction on the particle chain image, identifies the center line of a single particle chain, and counts the number of particle chains within the field of view. The length of the i-th particle chain equivalent cross-sectional area of ​​granular chain and the shear deflection angle of the particle chain relative to the direction of the magnetic field Among them, the length of the particle chain The equivalent cross-sectional area of ​​the particle chain is obtained by converting the pixel length of the particle chain centerline through microscopic calibration. The equivalent volume of the particle chain can be determined based on the width of the particle chain image, particle size, or a preset equivalent cross-sectional model. according to Calculated.

[0054] In this embodiment, the shear strain of the i-th particle chain It can be defined as the equivalent displacement of the particle chain in the shear direction. During work breaks The ratio of , and can be approximately expressed as under small deformation conditions. By combining the model of the equivalent magnetic energy increment caused by particle chain deflection with the partial derivative of energy with respect to displacement, the equivalent electromagnetic force of the particle chain in the shear direction can be obtained. .

[0055] The specific calculation methods for particle chain motion velocity and local relative slip velocity are as follows.

[0056] Step S31: Extract the number of particle chains within the field of view based on the particle chain distribution evolution image acquired by the optical high-speed microscope. Length of the i-th particle chain equivalent cross-sectional area of ​​granular chain and the shear deflection angle of the particle chain relative to the direction of the magnetic field In conjunction with the magnetic field strength within the working gap, an equivalent magnetic energy increment model caused by particle chain deflection is established: Equation 1; where: Equation 2; where, This represents the equivalent magnetic energy increment caused by particle chain deflection. The number of particle chains identified within the field of view; The vacuum permeability; The equivalent relative permeability of the magnetorheological fluid can be determined by testing the magnetization curve of the magnetorheological fluid sample. Magnetic induction intensity within the working gap The magnetic field strength obtained by conversion using calibration relationships For the first The equivalent volume of a single particle chain; For the first The equivalent cross-sectional area of ​​a single particle chain; For the first The length of the particle chain; For the first The shear deflection angle of the particle chain relative to the direction of the magnetic field.

[0057] Step S32, Define the particle chain shear strain as: Equation 3; where, This represents the equivalent displacement of the particle chain in the shear direction. The working clearance between the driving plate and the driven plate.

[0058] Based on the partial derivative of energy with respect to displacement, the equivalent electromagnetic force of the particle chain in the shear direction is obtained: Formula 4.

[0059] In shear strain Under the small deformation approximation condition of <0.1, the equivalent electromagnetic force is expressed as: Formula 5.

[0060] After obtaining the electromagnetic force Fe in the shear direction, and combining the relative rotational speed between the active disk 31 and the driven disk 32, the centrifugal force and gravity acting on the particles, the particle chain velocity obtained from continuous frame images is analyzed. To conduct verification or compensation.

[0061] Particle chain speed This can be obtained through recognition from consecutive frame images. Specifically, computer 7 identifies the same centroid position of the particle chain in two adjacent frames of particle chain evolution images and calculates the displacement of the centroid of the particle chain along the shear direction or radial direction. And based on the time interval between two adjacent frames. Calculate the velocity of the particle chain: Formula 6.

[0062] For radius The local relative slip velocity of the particle chain at that location is calculated based on the difference in angular velocity between the driving disk 31 and the driven disk 32. Equation 7; where, Let be the velocity of the i-th particle chain. Let be the displacement of the i-th particle chain or its centroid in two adjacent frames. The time interval between adjacent frames. Let be the local relative slip velocity of the i-th particle chain relative to the wall. Let be the radius of the location of the particle chain. For active disk angular velocity, The angular velocity of the driven disk.

[0063] Step S4: Replace the active disk 31 and driven disk 32 with different wall parameters, and repeat steps S2 and S3 to complete multiple sets of power transmission experiments.

[0064] Specifically, the main structure, working clearance, speed control method, magnetic field control method, and load conditions of the magnetorheological fluid actuator 3 are kept consistent, and only the wall parameters of the driving disk 31 and the driven disk 32 are changed. The wall parameters include surface roughness, disk material, surface coating, or surface texture. After each set of driving disk 31 and driven disk 32 is replaced, steps S2 and S3 are repeated to obtain the speed, torque, magnetic field strength, particle chain evolution image, and particle chain motion state parameters under the wall surface conditions.

[0065] In tests under different wall conditions, a single-variable comparison method is preferred. That is, in each experimental group, only one wall parameter of the driving disk 31 and the driven disk 32 is changed, such as only changing the surface roughness, only changing the disk material, only changing the surface coating, or only changing the surface texture, while keeping the type of magnetorheological fluid, filling volume, working clearance, input speed, excitation current, magnetic field strength, load torque, test time, and ambient temperature consistent. This single-variable control reduces the interference of other operating conditions on the test results, making the correspondence between different wall parameters and power transmission damage clearer.

[0066] Step S4 establishes the correspondence between different wall conditions and power transmission performance and particle chain distribution, providing a comparative basis for subsequent wear characteristic analysis.

[0067] The different wall conditions include different surface roughness, different disk materials, different surface coatings or different surface textures. For each set of wall conditions, rotational speed, torque, magnetic field strength, particle chain evolution image and wall wear image are obtained simultaneously to establish the correspondence between wall conditions, particle chain motion state and wear characteristics.

[0068] Step S5: Acquire microscopic images of the wall surface, establish a model of the average wear depth rate of the wall surface, and calculate the average wear depth rate of the driving disk 31 and the driven disk 32. .

[0069] Specifically, after each power transmission experiment is paused, the optical high-speed microscope 5 images the mating end faces of the active disk 31 and the driven disk 32 through the transparent observation window 8, obtaining a microscopic image of the wall surface. The computer 7 processes the microscopic image of the wall surface, extracting wear features such as wear track width, wear track area, scratch density, local spalling area, and effective contact area of ​​the wall surface. The image acquisition time of the wall surface microscopic image acquired after the experiment is paused is recorded, and this image is correlated with the start time, pause time, test period, cumulative running time, cumulative revolutions, wall parameters, and particle chain motion state parameters obtained in step S3.

[0070] The method for calculating wall wear characteristics is as follows: Based on the equivalent electromagnetic force of the particle chain, centrifugal force, gravity, and relative particle slip velocity, a model for the average wear depth rate of the wall is established. Formula 8.

[0071] Based on the equivalent projections of the particle chain shearing direction equivalent electromagnetic force, centrifugal force, and gravitational force onto the wall contact direction, a normal equivalent force model of the particle chain on the wall is established: Equation 9; Equation 10; where, The average wear depth rate represents the change in equivalent wear volume per unit time and per unit effective contact area of ​​the wall surface. For testing time, This represents the spatial average of the effective contact area across multiple observation fields. Let t be the number of particle chains participating in wall contact. The equivalent wear coefficient, obtained through calibration, represents the equivalent wear volume generated per unit frictional work, and its dimensions are: The definition is determined; when When taking the average wear depth rate, The dimensions are , equivalent to , For the first The equivalent normal force exerted by each particle chain on the wall surface. Let be the sliding velocity of the particle chain relative to the wall. , , These are the non-negative projection correction factors for electromagnetic force, centrifugal force, and gravity in the wall contact direction, respectively, which can be obtained through calibration experiments. Let be the equivalent mass of the i-th particle chain. Let be the radius of the location of the i-th particle chain. Let be the local equivalent angular velocity at the location of the i-th particle chain. This is the acceleration due to gravity.

[0072] in, It can be calculated or estimated based on particle size, particle density, and equivalent volume of the particle chain. The model is obtained from the equivalent magnetic energy increment model and the equivalent electromagnetic force model in the shear direction caused by the particle chain deflection in step S3. It is obtained from the displacement of the particle chain image and the relative angular velocity of the active and driven disks in step S3; Obtained by image recognition and area extraction of the wall microstructure; , , and The results were obtained through calibration experiments. Therefore, the calculation of the average wall wear depth rate in step S5 establishes a clear data connection with the equivalent magnetic energy increment caused by particle chain deflection, the equivalent electromagnetic force in the shear direction, the particle chain velocity, the local relative slip velocity, and the wall microstructure characteristics.

[0073] The spatial average of the effective contact area across multiple observation fields can be obtained by calibrating, thresholding, and identifying regions in the microscopic morphology image of the wall surface. Specifically, computer 7 identifies areas of wear, scratches, flaking, or bright spots from particle contact, and converts the pixel area of ​​the identified areas into the actual area according to the microscopic calibration ratio. When it is necessary to test the spatial average of the effective contact area across multiple observation fields, computer 7 can perform a time-averaged average of the instantaneous wear rate at multiple sampling moments within the test period, or a spatial average of the wear rate across multiple observation fields, thereby obtaining the average wear depth rate of the active disk 31 and the driven disk 32 under the corresponding wall surface conditions. .

[0074] Step S6: After the test, remove the magnetorheological fluid 34 and clean the active disk 31, driven disk 32, and magnetorheological fluid actuator 3. Specifically, after the test, stop the servo motor 1, release the load of the magnetic powder brake 4, and after the magnetorheological fluid actuator 3 stops running, remove the magnetorheological fluid 34 and clean the active disk 31, driven disk 32, transparent observation window 8, and working gap to facilitate subsequent repeated experiments or changes to other test conditions.

[0075] Through the above embodiments, this invention enables the acquisition of macroscopic dynamic parameters, observation of microscopic evolution of particle chains, and quantitative analysis of wall wear during the power transmission process of magnetorheological fluids. Compared with traditional devices that only perform torque and speed tests, this invention can not only evaluate the transmission performance of magnetorheological fluids but also further reveal the interaction between particle chain motion and wall wear under different wall conditions, thereby providing experimental basis for the structural optimization, material selection, and surface treatment design of magnetorheological fluid transmission devices.

[0076] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes that can be made by those skilled in the art within the scope of their knowledge without departing from the spirit of the present invention are within the protection scope of the claims of the present invention.

Claims

1. A magnetorheological fluid dynamic transmission damage testing system, characterized in that, include: The transmission unit includes a servo motor, a coupling, a torque sensor, a magnetorheological fluid actuator, and a load. The servo motor is connected to the torque sensor via the coupling. The torque sensor is connected to the active side of the magnetorheological fluid actuator, and the driven side of the magnetorheological fluid actuator is connected to the load. The magnetorheological fluid actuator includes an active disk, a driven disk, an excitation coil, a transparent observation window, magnetorheological fluid filling the working gap between the active disk and the driven disk, and a Hall sensor. The excitation coil is disposed on the outer periphery of the active disk and the driven disk to form an adjustable magnetic field within the working gap. Both the active disk and the driven disk are detachable and replaceable. The observation unit includes an optical high-speed microscope, which is aligned with the working gap and mating end face between the active disk and the driven disk through a transparent observation window. It is used to acquire images of the distribution and evolution of the magnetorheological fluid particle chain and to acquire images of the wall microstructure of the mating end face of the active disk and the driven disk after the experiment is paused. The measurement and control unit includes a data acquisition device and a computer. The data acquisition device is used to collect data on rotational speed, torque, and magnetic field strength during the power transmission process. The computer is used to record power transmission parameters, particle chain evolution images, and wall wear images, and to perform correlation storage and computational analysis on the data and images.

2. The magnetorheological fluid dynamic transmission damage testing system according to claim 1, characterized in that, The transparent observation window is located on the housing of the magnetorheological fluid actuator, corresponding to the mating end faces of the driving and driven disks. The transparent observation window is made of quartz glass or a highly transparent and wear-resistant material, and is sealed to the housing of the magnetorheological fluid actuator through a sealing element.

3. The magnetorheological fluid dynamic transmission damage testing system according to claim 1, characterized in that, The optical high-speed microscope is mounted on an independent vibration-damping bracket, which is separate from the transmission unit, to reduce the impact of vibrations from the servo motor and load operation on the microscopic observation images.

4. The magnetorheological fluid dynamic transmission damage testing system according to claim 1, characterized in that, The driving disc and the driven disc are interchangeable transmission discs of the same model. Different driving discs and driven discs have different wall parameters, which include at least one of surface roughness, material type, surface coating, and surface texture.

5. The magnetorheological fluid dynamic transmission damage testing system according to claim 1, characterized in that, The magnetorheological fluid is an anti-centrifugal dispersion type magnetorheological fluid, used to suppress the sedimentation, agglomeration and radial segregation of magnetic particles during high-speed power transmission testing.

6. The magnetorheological fluid dynamic transmission damage testing system according to claim 1, characterized in that, The computer is used to perform grayscale conversion, filtering, threshold segmentation, and skeleton extraction on the particle chain distribution evolution image to obtain the number of particle chains in the field of view, the length of the i-th particle chain, the equivalent cross-sectional area of ​​the particle chain, the equivalent volume of the particle chain, and the shear deflection angle of the particle chain relative to the magnetic field direction; and is used to perform region identification and area conversion on the wall micro-morphology image to obtain the spatial average value of the wear mark width, wear mark area, scratch density, peeling area, and effective contact area in multiple observation fields of view.

7. A method for testing damage to magnetorheological fluid dynamic transmission, implemented using the magnetorheological fluid dynamic transmission damage testing system according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Prepare a centrifugally resistant magnetorheological fluid and conduct pre-tests on the centrifugally resistant and pre-dispersion properties of the magnetorheological fluid to obtain the particle concentration, particle size distribution, particle density or particle mass parameters of the magnetorheological fluid, and obtain the wear coefficient required for the wall wear model through calibration experiments. Step S2: Fill the working gap between the active disk and the driven disk with magnetorheological fluid, start the servo motor and supply power to the excitation coil to form a magnetic field in the working gap. Under the action of the magnetic field, the magnetorheological fluid forms a particle chain and transmits the power of the active disk to the driven disk. Step S3: During the power transmission process, the speed, torque and magnetic field strength data are collected synchronously by the data acquisition device. The distribution evolution image of the magnetorheological fluid particle chain is collected in situ by the optical high-speed microscope. Based on the particle chain distribution characteristics, the equivalent magnetic energy increment model caused by particle chain deflection is established, the equivalent electromagnetic force of the particle chain in the shear direction is calculated, and the particle chain motion state parameters are obtained. Step S4: Replace the active disk and driven disk with different wall parameters, and repeat steps S2 and S3 to obtain the power transmission parameters, particle chain evolution parameters and particle chain motion state parameters under different wall conditions. Step S5: After each power transmission experiment is paused, the microscopic morphology images of the mating end faces of the active and driven disks are collected using an optical high-speed microscope. Combined with the particle chain motion state parameters obtained in step S3 and the different wall working condition parameters obtained in step S4, a wall average wear depth rate model is established, the average wear depth rate of the active and driven disks is calculated, and the corresponding wall wear characteristics are recorded. Step S6: After the test is completed, remove the magnetorheological fluid and clean the driving disk, driven disk, and magnetorheological fluid actuator.

8. The method for testing damage through dynamic transmission of magnetorheological fluid according to claim 7, characterized in that, In step S3, the equivalent electromagnetic force of the particle chain in the shear direction is obtained as follows: Step S31: Based on the particle chain distribution evolution image acquired by the optical high-speed microscope, extract the number of particle chains identified within the field of view. Length of the i-th particle chain equivalent cross-sectional area of ​​particle chain and the shear deflection angle of the particle chain relative to the direction of the magnetic field In conjunction with the magnetic field strength within the working gap, an equivalent magnetic energy increment model caused by particle chain deflection is established: Formula 1; in: Formula 2; In the formula, This represents the equivalent magnetic energy increment caused by particle chain deflection. The number of particle chains identified within the field of view; Permeability of free space; The equivalent relative permeability of the magnetorheological fluid; Magnetic induction intensity within the working gap The magnetic field strength obtained by conversion using calibration relationships; For the first The equivalent volume of a single particle chain; For the first The equivalent cross-sectional area of ​​a single particle chain; For the first The length of the particle chain; For the first The shear deflection angle of the particle chain relative to the direction of the magnetic field; Step S32, Define the particle chain shear strain as: Formula 3; in, This represents the equivalent displacement of the particle chain in the shear direction. The working gap between the driving and driven disks is given; based on the partial derivative of energy with respect to displacement, the equivalent electromagnetic force of the particle chain in the shear direction is obtained: Equation 4; In shear strain Under the approximate condition of small deformation <0.1, the equivalent electromagnetic force is expressed as: Formula 5.

9. The method for testing damage in magnetorheological fluid dynamic transmission according to claim 8, characterized in that, In step S3, the particle chain motion state parameters include the motion velocity of the i-th particle chain. and local relative slip velocity The speed of the particle chain movement Displacement of the centroid of the same particle chain in consecutive frame images of particle chain distribution evolution. Time interval with adjacent frames The calculation yields the following formula: Formula 6; For radius The particle chain at that location, based on the angular velocity of the active disk. and driven disk angular velocity Determine the local relative slip velocity And combined with the equivalent electromagnetic force in the shear direction Centrifugal force and gravity are used to check or compensate for the motion state of the particle chain; the specific formula is: Formula 7.

10. The method for testing damage through dynamic transmission of magnetorheological fluid according to claim 9, characterized in that, In step S5, a model for the average wear depth rate of the wall surface is established based on the equivalent electromagnetic force of the particle chain, centrifugal force, gravity, and relative slip velocity of the particle chain. Formula 8; Based on the equivalent projections of the particle chain shearing direction equivalent electromagnetic force, centrifugal force, and gravitational force onto the wall contact direction, a normal equivalent force model of the particle chain on the wall is established: Equation 9; Formula 10; In the formula, The average wear depth rate represents the change in equivalent wear volume per unit time and per unit effective contact area of ​​the wall surface. For testing time, This represents the spatial average of the effective contact area across multiple observation fields. Let t be the number of particle chains participating in wall contact. The equivalent wear coefficient, obtained through calibration, represents the equivalent wear volume generated per unit frictional work, and its dimensions are: The definition is determined, For the first The equivalent normal force exerted by each particle chain on the wall surface. Let be the sliding velocity of the particle chain relative to the wall. , , These are the non-negative projection correction factors for electromagnetic force, centrifugal force, and gravity in the wall contact direction, respectively, which can be obtained through calibration experiments. Let be the equivalent mass of the i-th particle chain. Let be the radius of the location of the i-th particle chain. Let be the local equivalent angular velocity at the location of the i-th particle chain. This is the acceleration due to gravity.

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