A magnetorheological fluid low-temperature characteristic testing system and testing method

Abstract

The present invention discloses a system and method for testing the low-temperature characteristics of magnetorheological fluid, belonging to the technical field of magnetorheological fluid. The system includes a shearing device, a low-temperature cooling device, a supporting device, a transmission mechanism, and a lifting mechanism. The shearing device forms an annular test gap between the shear column and the inner wall of the shear cylinder, and the excitation coil cooperates with the magnetic circuit structure to generate a uniform magnetic field; the low-temperature cooling device is built into the shearing device, and the transmission mechanism and the lifting mechanism respectively drive the shear column to rotate and lift. The testing method establishes a low-temperature environment, loads the magnetic field, performs shear testing, and performs multi-parameter calculations. Based on the Bingham model and the infinitesimal method, the shear yield stress formula is derived, and the coolant flow increment is calculated in combination with the heat generation power and heat dissipation power balance model to ensure constant low temperature. The present invention fills the gap in the low-temperature characteristic testing of magnetorheological fluid, and has the advantages of high test accuracy, strong environmental controllability, compact structure, and easy maintenance. It provides reliable experimental data for the application of magnetorheological fluid in low-temperature scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetorheological fluid, and in particular to a magnetorheological fluid low-temperature characteristic testing system and testing method. Background Art

[0002] Magnetorheological fluid (MRF) is a new type of intelligent material with controllable flow properties. Its unique properties lie in its exceptional fluidity: under the influence of a magnetic field, it instantly transforms from a liquid into a solid-like state, exhibiting solid-like mechanical properties. Upon removal of the magnetic field, it quickly returns to its original liquid state. This liquid-to-solid transition is characterized by rapidity, controllability, and reversibility. Shear yield stress is a key performance metric for MRF. At high temperatures, MRF is prone to expansion and even failure, leading to reduced transmission efficiency or component damage in MRF equipment. Therefore, to ensure stable operation, many MRF instruments are equipped with cooling systems to maintain a stable operating temperature. However, current rheometers generally lack low-temperature measurement capabilities for testing material rheological properties. This results in a lack of data supporting the performance parameters of MRF at low temperatures, hindering its application in these conditions. Summary of the Invention

[0003] The purpose of the present invention is to provide a system and method for testing the low-temperature characteristics of magnetorheological fluid, so as to solve the problem in the prior art of lacking a means for testing the characteristics of magnetorheological fluid in a controllable low-temperature environment.

[0004] The technical solution adopted by the present invention is as follows: In a first aspect, the present invention proposes a magnetorheological fluid low-temperature characteristic testing system, comprising:

[0005] The shearing device includes a shearing cylinder, a shearing column, an excitation coil, a magnetic circuit side wall, and a magnetic circuit bottom plate; the shearing cylinder is a cylindrical container with an open top, and a cylindrical chamber is provided in the middle of the magnetic circuit side wall, in which the shearing cylinder is embedded; the excitation coil is evenly distributed between the shearing cylinder and the cylindrical chamber; the shearing column is detachably placed in the shearing cylinder by a lifting mechanism, and an annular test gap is formed between the inner wall of the shearing cylinder and the shearing column for containing magnetorheological fluid; the shearing column can be rotated in the shearing cylinder by a transmission mechanism to perform a shear test on the magnetorheological fluid in a magnetic state; the magnetic circuit side wall is mounted on the magnetic circuit bottom plate;

[0006] The low-temperature cooling device includes a liquid inlet pipe, a liquid storage chamber, a cooling channel and a liquid discharge pipe; the liquid storage chamber is located in the side wall of the magnetic circuit below the shear cylinder, and the liquid inlet pipe is connected to the liquid storage chamber; multiple cooling channels are distributed in the wall of the shear cylinder, the bottom is connected to the liquid storage chamber, and the top is connected to the liquid discharge pipe.

[0007] As a further improvement of the present invention, the shearing device also includes an outer wall and a cover plate. The outer wall is a shell with upper and lower openings, the bottom of which is seated on the magnetic circuit bottom plate, and the magnetic circuit side wall is located inside it; the cover plate can be detachably covered on the upper opening of the outer wall.

[0008] As a further improvement of the present invention, an annular chamber is provided in the wall thickness of the shear cylinder at the upper part of the cooling channel, and the cooling channel is connected to the drain pipe through the annular chamber.

[0009] As a further improvement of the present invention, it also includes a supporting device, which includes a supporting base plate, a supporting top plate and multiple guide pillars, the bottom ends of the guide pillars are installed on the supporting base plate, and the upper ends are fixedly connected to the supporting top plate; the magnetic circuit base plate is installed on the supporting base plate between the guide pillars.

[0010] As a further improvement of the present invention, the transmission mechanism includes a rotating motor, a motor support plate, a torque sensor and a sensor support plate; the motor support plate is located above the sensor support plate, and both are mounted on the guide column through flange bearings and can slide on the guide column; the rotating motor is mounted on the motor support plate, the torque sensor is mounted on the sensor support plate, and the rotating motor is connected to the upper end transmission shaft of the torque sensor; the lower end transmission shaft of the torque sensor is connected to the shear column through a ball bearing mounted on the cover plate.

[0011] As a further improvement of the present invention, the lifting mechanism includes a screw and a rotating handle installed on the upper end of the screw, the screw is rotatably connected to the support top plate, and the rod body is threadedly connected to the motor support plate and the sensor support plate respectively.

[0012] In a second aspect, the present invention further proposes a method for testing the low-temperature characteristics of a magnetorheological fluid. Based on the magnetorheological fluid low-temperature characteristics testing system described above, the testing method comprises the following steps:

[0013] Step 1: injecting a certain amount of magnetorheological fluid into the shear cylinder;

[0014] Step 2: Turn the rotary handle to lower the shear column into the shear cylinder, so that the magnetorheological fluid is dispersed and fills the annular test gap between the shear column and the shear cylinder;

[0015] Step 3: Start the centrifugal pump to pump the coolant into the liquid storage chamber and then into the cooling channel to cool the shear cylinder and provide a low temperature environment for the shear test of the magnetorheological fluid;

[0016] Step 4: Power the excitation coil with a programmable power supply to generate a magnetic field, and use a Tesla meter to monitor the magnetic field strength. When the magnetic field strength reaches the set value, start the rotary motor to drive the shear column to rotate, and perform a shear test on the magnetorheological fluid;

[0017] Step 5: Replace the coolant with a different low temperature value, and repeat steps 3 and 4 to perform multiple sets of magnetorheological fluid shear tests under low temperature environment;

[0018] Step 6: Calculate the shear yield stress of the magnetorheological fluid under different low temperature conditions based on the structural parameters of the shear device, the coolant temperature, and the torque;

[0019] Step 7: After the test, turn the rotary handle to lift the shear column to the initial position, remove the magnetorheological fluid and clean the test system.

[0020] As a further improvement of the present invention, in step 4, the shearing device generates heat when working. If the coolant is to maintain a constant low temperature while absorbing heat, the coolant flow rate needs to be increased on the basis of the initial flow rate. The increased flow rate is the coolant flow rate increment Q. L , calculated as follows:

[0021] The first step is to obtain the heat generation power of the shearing device: the heat source of the shearing device is the friction heat Ps generated by shearing and the electromagnetic heat Pc generated by the coil power. The friction heat Ps is affected by the torque M and the speed ω, and the electromagnetic heat is affected by the current I and the coil resistance R. m The heat generation power is as follows:

[0022] Formula 1

[0023] The second step is to obtain the heat dissipation power of the low-temperature cooling device: the shearing device conducts heat dissipation through the contact between the coolant and the shearing cylinder, and the heat dissipation power P L as follows:

[0024] Formula 2

[0025] Where c L is the specific heat capacity of the coolant, m L is the coolant mass, ΔT L is the temperature difference between the drain port and the inlet port, t is the coolant working time, ρ L is the coolant density, Q L is the coolant flow increment;

[0026] Step 3: When the heat dissipation power of the low-temperature cooling device and the heat generation power of the shearing device are equal, a balance is reached. The balance of the coolant flow increment Q can be obtained by equations 1 and 2. L :

[0027] Formula 3

[0028] As a further improvement of the present invention, in step six, the structural parameters of the shearing device include the shear column radius R a , shear cylinder inner diameter R b, shear column length L and annular test gap radius r, R a < r < R b .

[0029] As a further improvement of the present invention, in step six, the shear yield stress τ0 of the magnetorheological fluid is calculated as follows:

[0030] The first step is to use the Bingham model to describe the flow characteristics of magnetorheological fluid:

[0031] Formula 4

[0032] Where τ is the shear stress of the magnetorheological fluid, τ0 is the shear yield stress of the magnetorheological fluid, η0 is the zero-field viscosity of the magnetorheological fluid, is the shear rate;

[0033] The second step is to use the infinitesimal method to analyze and calculate the micro-units within the minimum unit radius. If the radial micro-unit is selected, the torque of the micro-unit is

[0034] Formula 5

[0035] Where, is the shear force of the micro unit, and the overall torque of the magnetorheological fluid can be obtained by integrating Equation 5.

[0036] Formula 6

[0037] The third step is to sort out formula 6 to obtain the shear stress and torque of the magnetorheological fluid. The relationship is:

[0038] Formula 7

[0039] Step 4: Substitute the obtained τ into Equation 4 to obtain the shear yield stress τ0 of the magnetorheological fluid; in Equation 4, the torque M is measured by the torque sensor, and the zero-field viscosity is Obtained by viscometer measurement; shear rate By speed The relationship between them is: .

[0040] Compared with the prior art, the present invention has the following technical effects:

[0041] (1) In the shearing device of the present invention, the annular test gap formed between the shear column and the inner wall of the shear cylinder can reduce the centrifugal force of the magnetorheological fluid during the shearing process and prevent it from overflowing. The shearing area is large and the adjustable torque range is wide, thereby improving the test stability and reliability. The cooling channel is embedded in the wall thickness of the shear cylinder, which can provide a direct low-temperature environment and heat dissipation conditions for the magnetorheological fluid, thereby optimizing the space design and laying a good foundation for shearing tests in low-temperature environments.

[0042] (2) The present invention establishes a heat generation and heat dissipation balance model. Considering that the shearing device will generate frictional heat and electromagnetic heat during operation, the balance model of heat generation power and heat dissipation power is established to calculate the incremental coolant flow required to maintain a constant low temperature. This achieves precise regulation of the overall coolant flow rate, ensuring that the low-temperature environment is maintained stable while absorbing heat, and provides a stable foundation for the accuracy of shear testing at low temperatures.

[0043] (3) The classical model and the microelement method are used to describe the flow characteristics of the magnetorheological fluid based on the Bingham model. The microelement method is used to analyze and calculate the micro-units within the minimum unit radius. Through integration and formula derivation, the relationship between the shear stress and torque of the magnetorheological fluid is established, and then the shear yield stress is calculated. This calculation method is based on a mature theoretical model, combined with the structural parameters of the test system and the measured data, to ensure the accuracy and reliability of the calculation results. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Figure 1 It is a schematic diagram of the three-dimensional structure of the magnetorheological fluid low-temperature characteristics testing system of the present invention;

[0046] Figure 2 yes Figure 1 The main view;

[0047] Figure 3 yes Figure 2 Schematic diagram of the structure of the medium shear device and the low-temperature cooling device;

[0048] Figure 4 is a perspective view of the shearing device;

[0049] Figure 5 It is the arrangement diagram of the excitation coil;

[0050] Figure 6 This is a simulation diagram of the magnetic field of the shearing device;

[0051] Description of reference numerals:

[0052] 1- shearing device, 11- shearing cylinder, 12- shearing column, 13- excitation coil, 14- magnetic circuit side wall, 15- magnetic circuit bottom plate, 16- outer wall, 17- cover plate;

[0053] 2- low temperature cooling device, 21- liquid inlet pipe, 22- liquid storage chamber, 23- cooling channel, 24- liquid discharge pipe;

[0054] 3-support device, 31-support bottom plate, 32-support top plate, 33-guide column, 34-Foma wheel;

[0055] 4- transmission mechanism, 41- rotating motor, 42- motor support plate, 43- torque sensor, 44- sensor support plate, 45- flange bearing, 46- connecting column, 47- ball bearing;

[0056] 5-lifting mechanism, 51-rotating handle, 52-screw rod. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by persons of ordinary skill in the art are within the scope of protection of the present invention.

[0058] like Figures 1-6As shown, a system for testing the low-temperature properties of a magnetorheological fluid comprises a shearing device 1, a cryogenic cooling device 2, a supporting device 3, a transmission mechanism 4, and a lifting mechanism 5. The shearing device 1 comprises a shearing cylinder 11, a shearing post 12, an excitation coil 13, a magnetic circuit sidewall 14, a magnetic circuit bottom plate 15, an outer wall 16, and a cover plate 17. The shearing cylinder 11 is a cylindrical container with an open top, embedded within a cylindrical chamber in the center of the magnetic circuit sidewall 14. Six rectangular ring-shaped excitation coils 13 are evenly distributed between the shearing cylinder 11 and the cylindrical chamber and secured by six rectangular support blocks arranged circumferentially within the chamber. The shearing post 12 is a cylindrical structure with a connecting handle at the top. The diameter of the shearing post 12 is slightly smaller than the inner diameter of the shearing cylinder 11. The shearing post 12 is detachably positioned within the shearing cylinder 11 via the lifting mechanism 5. The height of the shearing post 12 is lower than that of the shearing cylinder 11. An annular test gap for containing the magnetorheological fluid is formed between the wall of the shearing cylinder 11 and the post 12. The shear column 12 can be rotated in the cylinder through the transmission mechanism 4 to perform a shear test on the magnetorheological fluid in the magnetic state. The shear cylinder 11, shear column 12, magnetic circuit side wall 14 and magnetic circuit bottom plate 15 are all made of electrical pure iron. The outer wall 16 is an iron-nickel alloy cavity. The bottom is placed on the magnetic circuit bottom plate 15 and wraps the magnetic circuit side wall 14. The top is sealed by a detachable cover 17 to prevent external magnetic field interference. When the excitation wire 13 turns are energized, a closed magnetic field passing through the shear cylinder 11 is formed between the excitation coil 13, the magnetic circuit side wall 14 and the magnetic circuit bottom plate 15, exerting a magnetic field on the magnetorheological fluid. Figure 6 This is a magnetic field simulation diagram (using ANSYS Maxwell software).

[0059] like Figure 3 As shown, the low-temperature cooling device 2 includes a liquid inlet pipe 21, a liquid storage chamber 22, a cooling channel 23, and a liquid drain pipe 24. The liquid storage chamber 22 is placed in the magnetic circuit side wall 14 below the shear cylinder 11, and the liquid inlet pipe 21 is connected to the liquid storage chamber 22. Multiple cooling channels 23 are evenly distributed in the wall of the shear cylinder 11, with the bottom connected to the liquid storage chamber 22 and the top connected to the liquid drain pipe 24, providing a low-temperature environment for shear testing. Specifically, an annular chamber is provided in the wall thickness of the shear cylinder 11 above the cooling channel 23. The cooling channel 23 is a straight hole or a curved channel opened in the wall thickness of the shear cylinder 11. The curved channel is spirally arranged in the wall of the shear cylinder 11 to increase the contact area between the coolant and the cylinder wall and improve the heat dissipation efficiency. The upper part of the channel is connected to the annular chamber.

[0060] Directly integrating the cooling channel 23 into the wall of the shear cylinder 11 allows the magnetorheological fluid to quickly sense low-temperature environments, paving the way for accurate shear testing. The coolant in this embodiment is an oil-based coolant, such as silicone oil, which has a freezing point of -50°C. The low temperature in this embodiment refers to temperatures below room temperature, for example, below 25°C.

[0061] When the low-temperature cooling device 2 is working, the centrifugal pump sends the coolant in the liquid storage chamber 22 into the cooling channel 23 to dissipate heat and cool the shear cylinder 11, and then discharges it from the drain pipe 24 through the annular chamber. The coolant is replenished in real time from the liquid inlet pipe 21 to circulate and cool the shear cylinder 11 and provide a low-temperature environment.

[0062] The support device 3 includes a support base plate 31, a support top plate 32, multiple guide posts 33, and a Formazan wheel 34. The guide posts 33 are mounted on the support base plate 31 at their bases, and the magnetic circuit base plate 15 is mounted on the support base plate 31 between the guide posts 33. The support top plate 32 is fixedly connected to the upper ends of the guide posts 33 and has a square opening in the center. The Formazan wheel 34 is mounted below the support base plate 31 and is used to move the test system.

[0063] The transmission mechanism 4 is located directly above the shear cylinder 11 and includes a rotary motor 41, a motor support plate 42, a torque sensor 43, and a sensor support plate 44. The motor support plate 42 is located above the sensor support plate 44. Both motor support plate 42 and sensor support plate 44 are mounted on the guide column 33 via flange bearings 45 and can slide on the guide column 33. The rotary motor 41 is mounted on the motor support plate 42, and the torque sensor 43 is mounted on the sensor support plate 44. The rotary motor 41 is connected to the upper drive shaft of the torque sensor 43. The lower drive shaft of the torque sensor 43 is connected to the connecting handle on the shear cylinder 12 via a ball bearing 47 mounted on the cover plate 17.

[0064] like Figure 2 As shown, the transmission mechanism 4 also includes four connecting posts 46. The upper ends of the connecting posts 46 are fixedly connected to the bottom surface of the motor support plate 42, and the lower ends are fixedly connected to the top surface of the sensor support plate 44. The connecting posts 46 are used to connect the motor support plate 42 and the sensor support plate 44 so that they can move together on the guide posts 33. When the rotary motor 41 moves upward, it can pass through the square opening in the support top plate 32.

[0065] The lifting mechanism 5 includes a screw rod 52 and a rotating handle 51 mounted on the screw rod 52. The screw rod 52 is rotatably connected to the support top plate 32 via a bearing. The rod body is threadedly connected to the motor support plate 42 and the sensor support plate 44, respectively, to drive the motor support plate 42 and the sensor support plate 44 to move up and down. In other embodiments, the lifting mechanism 5 can also be electrically operated to perform the raising and lowering operation of the transmission mechanism 4.

[0066] In addition, a temperature sensor is installed on the shear cylinder 11 for real-time monitoring of the coolant temperature in the cooling channel 23 . Temperature sensors are also installed on the liquid inlet pipe 21 and the liquid discharge pipe 24 .

[0067] The test system also includes a controller, which is a PLC controller. The controller is connected to the rotating motor 41 and is used to control the speed of the rotating motor 41. The temperature information of the coolant and the torque information from the torque sensor 43 are collected by an information acquisition card and sent to the controller.

[0068] The test system of the present invention achieves direct heat dissipation of the shearing cylinder 11 and the construction of a low-temperature test environment by integrating a shearing device 1 and a low-temperature cooling device 2. The shearing device 1 uses excitation coils 13 evenly distributed on the outer periphery of the shearing cylinder 11 in conjunction with the magnetic circuit side walls 14 to form a uniform magnetic field environment to ensure test accuracy. The low-temperature cooling device 2 can controllably cool the magnetorheological fluid and support shear yield stress testing under different low-temperature conditions. The cylindrical structural design ensures that the magnetorheological fluid has low centrifugal force and a large shearing area during the shearing process, and has the advantages of low overflow risk, a wide torque adjustment range, high test stability, and easy disassembly and cleaning.

[0069] The present invention also proposes a method for testing the low-temperature characteristics of a magnetorheological fluid. The method is based on the magnetorheological fluid low-temperature characteristics testing system described above, and the testing method includes the following steps:

[0070] Step 1: inject a certain amount of magnetorheological fluid into the shear cylinder 11.

[0071] Step 2: Turn the rotary handle 51 to lower the shear column 12 so that its bottom contacts the bottom of the shear cylinder 11, and the cover plate 17 covers the upper opening of the outer wall 16. The magnetorheological fluid is dispersed and fills the annular test gap between the shear column 12 and the wall of the shear cylinder 11, forming an annular magnetorheological fluid.

[0072] Step 3: Start the centrifugal pump to pump the coolant into the liquid storage chamber and into the cooling channel 23 to cool the shear cylinder 11 and provide a low-temperature environment for the shear test of the magnetorheological fluid. The centrifugal pump is connected to a controller, which controls the coolant pumping flow rate.

[0073] Step 4: A programmable power supply powers the excitation coil 13 to generate a magnetic field. A Tesla meter monitors the magnetic field strength. When the magnetic field strength reaches the set value, the rotary motor 41 is activated to rotate the shear rod 12, performing a shear test on the MR fluid. The torque and speed are collected by the torque sensor 43 and uploaded to the controller. The Tesla meter is a handheld device. The measurement position is set near the MR fluid within the annular test gap. Four measurement points are evenly distributed around the circumference of the gap to observe the magnitude and uniformity of the magnetic field.

[0074] In this step, since the shearing device 1 generates heat when working, if the coolant is to maintain a constant low temperature while absorbing heat, the coolant flow rate must be increased on the basis of the initial flow rate. The increased flow rate is the coolant flow increment Q. L, calculated as follows:

[0075] The first step is to obtain the heat generation power of the shearing device 1: the heat source of the shearing device is the friction heat Ps generated by shearing and the electromagnetic heat Pc generated by the coil energization. The friction heat Ps is affected by the torque M and the speed ω, and the electromagnetic heat is affected by the current I and the coil resistance R. m The heat generation power is as follows:

[0076] Formula 1

[0077] Step 2: Obtain the heat dissipation power of the low-temperature cooling device 2: The shearing device 1 conducts heat dissipation through contact between the coolant and the shearing cylinder. The heat dissipation power PL is as follows:

[0078] Formula 2

[0079] Where c L is the specific heat capacity of the coolant, m L is the coolant mass, ΔT L is the temperature difference between the drain port and the inlet port, t is the coolant working time, ρ L is the coolant density, Q L is the coolant flow increment;

[0080] Step 3: When the heat dissipation power of the low-temperature cooling device and the heat generation power of the shearing device are equal, a balance is reached. The increase in coolant flow rate QL after the balance can be obtained from Equation 1 and Equation 2:

[0081] Formula 3

[0082] By obtaining the coolant flow increment Q L , it can accurately adjust the overall flow of coolant, while taking away heat, ensuring the constancy of the low-temperature environment, providing a stable foundation for the accuracy of shear testing at low temperatures.

[0083] Step 5: Replace the coolant with a different low-temperature value, and repeat steps 3 and 4 to perform multiple sets of magnetorheological fluid shear tests under low-temperature environments.

[0084] Step 6: Based on the structural parameters of the shear device, coolant temperature and torque, calculate the shear yield stress of the magnetorheological fluid under different low temperature conditions. The structural parameters of this test system include the shear column radius R a , shear cylinder inner diameter R b , shear column length L, shear gap radius r, R a <r< R b .

[0085] In the present invention, the shear yield stress τ0 of the magnetorheological fluid is calculated as follows:

[0086] The first step is to use the Bingham model to describe the flow characteristics of magnetorheological fluid:

[0087] Formula 4

[0088] Where τ is the shear stress of the magnetorheological fluid, τ0 is the shear yield stress of the magnetorheological fluid, η0 is the zero-field viscosity of the magnetorheological fluid, is the shear rate;

[0089] The second step is to use the infinitesimal method to analyze and calculate the micro-units within the minimum unit radius. If the radial micro-unit is selected, the torque of the micro-unit is

[0090] Formula 5

[0091] Where dFτ is the shear force of the micro unit. By integrating Equation 5, we can get the overall torque M of the magnetorheological fluid:

[0092] Formula 6

[0093] The third step is to rearrange formula (6) to obtain the relationship between the shear stress and torque M of the magnetorheological fluid:

[0094] Formula 7

[0095] Step 4: Substitute the obtained τ into Equation 4 to obtain the shear yield stress τ0 of the magnetorheological fluid;

[0096] In formula 4, the torque M is measured by the torque sensor, and the shear rate Obtained by speed conversion,

[0097] The zero-field viscosity η0 is obtained by measuring the viscometer. and The conversion relationship is:

[0098] .

[0099] Step 7: After the test is completed, the rotary handle 51 is rotated to lift the shear column 12 to the initial position, the magnetorheological fluid is removed and the test system is cleaned.

[0100] The testing method of the present invention lays the foundation for accurate testing by providing a constant low-temperature environment; based on the shear yield stress formula, the yield strength characteristics of the magnetorheological fluid under different low-temperature conditions can be easily obtained.

[0101] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Various changes that can be made within the scope of knowledge possessed by technicians in the relevant technical field without departing from the spirit of the present invention are all within the scope of protection of the claims of the present invention.

Claims

1. A method for testing the low-temperature characteristics of a magnetorheological fluid, based on a system for testing the low-temperature characteristics of a magnetorheological fluid, wherein the shear device (1) of the test system comprises a shear cylinder (11), a shear column (12), an excitation coil (13), a magnetic circuit side wall (14) and a magnetic circuit bottom plate (15); the shear cylinder (11) is a cylindrical container with an open top, a cylindrical chamber is provided in the middle of the magnetic circuit side wall (14), and the shear cylinder (11) is embedded therein; the excitation coil (13) is evenly distributed between the shear cylinder (11) and the cylindrical chamber; the shear column (12) is detachably placed in the shear cylinder (11) by a lifting mechanism (5), and an annular test gap is formed between the inner cylinder wall of the shear cylinder (11) and the shear column (12) , used for containing magnetorheological fluid; the shear column (12) can rotate in the shear cylinder (11) through the transmission mechanism (4) to perform shear testing on the magnetorheological fluid in the magnetic state; the magnetic circuit side wall (14) is installed on the magnetic circuit bottom plate (15); the low-temperature cooling device (2) includes a liquid inlet pipe (21), a liquid storage chamber (22), a cooling channel (23) and a liquid discharge pipe (24); the liquid storage chamber (22) is located in the magnetic circuit side wall (14) below the shear cylinder (11), and the liquid inlet pipe (21) is connected to the liquid storage chamber (22); a plurality of cooling channels (23) are evenly distributed in the wall of the shear cylinder (11), the bottom is connected to the liquid storage chamber (22), and the upper part is connected to the liquid discharge pipe (24); it is characterized in that, The test method comprises the following steps: Step 1: injecting a certain amount of magnetorheological fluid into the shearing cylinder (11); Step 2: Turn the rotary handle (51) to lower the shear column (12) into the shear cylinder (11), so that the magnetorheological fluid is dispersed and fills the annular test gap between the shear column (12) and the shear cylinder (11); Step 3: Start the centrifugal pump to pump the coolant into the liquid storage chamber (22) and then into the cooling channel (23), cooling the shear cylinder (11) to provide a low temperature environment for the shear test of the magnetorheological fluid; Step 4: Power the excitation coil (13) with a programmable power supply to generate a magnetic field, and monitor the magnetic field strength with a Tesla meter. When the magnetic field strength reaches a set value, start the rotary motor (41) to drive the shear column (12) to rotate, and perform a shear test on the magnetorheological fluid; Step 5: Replace the coolant with a different low temperature value, and repeat steps 3 and 4 to perform multiple sets of magnetorheological fluid shear tests under low temperature environment; Step 6: Calculate the shear yield stress of the magnetorheological fluid under different low temperature conditions based on the structural parameters of the shearing device (1), the coolant temperature and the torque; Step 7: After the test is completed, the rotary handle (51) is turned to lift the shear column (12) to the initial position, the magnetorheological fluid is taken out and the test system is cleaned.

2. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 1, characterized in that: In step 4, the shearing device generates heat when working. If the coolant is to maintain a constant low temperature while absorbing heat, the coolant flow rate must be increased on the basis of the initial flow rate. The increased flow rate is the coolant flow increment Q. L， Calculated as follows: The first step is to obtain the heat generation power of the shearing device: the heat sources of the shearing device are the friction heat Ps generated by shearing and the electromagnetic heat Pc generated by the coil being energized. The friction heat Ps is affected by the torque M and the speed ω, and the electromagnetic heat is affected by the current I and the coil resistance Rm. The heat generation power is as follows: The second step is to obtain the heat dissipation power of the low-temperature cooling device: the shearing device conducts heat dissipation through the contact between the coolant and the shearing cylinder, and the heat dissipation power P L as follows: Where c L is the specific heat capacity of the coolant, m L is the coolant mass, ΔT L is the temperature difference between the drain port and the inlet port, t is the coolant working time, ρ L is the coolant density, Q L is the coolant flow increment; Step 3: When the heat dissipation power of the low-temperature cooling device and the heat generation power of the shearing device are equal, a balance is reached. The balance of the coolant flow increment Q can be obtained by equations 1 and 2. L :

3. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 1, characterized in that: In step 6, the structural parameters of the shearing device include the shear column radius R a , shear cylinder inner diameter R b , shear column length L and annular test gap radius r, R a <r<R b .

4. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 3, characterized in that: In step 6, the shear yield stress τ0 of the magnetorheological fluid is calculated as follows: The first step is to use the Bingham model to describe the flow characteristics of magnetorheological fluid: Where τ is the shear stress of the magnetorheological fluid, τ0 is the shear yield stress of the magnetorheological fluid, η0 is the zero-field viscosity of the magnetorheological fluid, is the shear rate; The second step is to use the infinitesimal method to analyze and calculate the micro-units within the minimum unit radius. If the radial micro-unit is selected, the torque of the micro-unit is dM = rdFτ = rτ2πrdr = 2πτr 2 dr Equation 5 Where dFτ is the shear force of the micro unit. By integrating Equation 5, we can get the overall torque M of the magnetorheological fluid. In the third step, the relationship between the shear stress and torque M of the magnetorheological fluid can be obtained by rearranging formula 6: Step 4: Substitute the obtained τ into Equation 4 to obtain the shear yield stress τ0 of the magnetorheological fluid; in Equation 4, the torque M is measured by the torque sensor, and the zero-field viscosity η0 is measured by the viscometer; the shear rate Obtained by the speed ω conversion, the relationship between them is:

5. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 1, characterized in that: The shearing device also includes an outer wall (16) and a cover plate (17). The outer wall (16) is a shell with upper and lower openings, the bottom of which is seated on the magnetic circuit bottom plate (15), and the magnetic circuit side wall (14) is located inside the outer wall (16). The cover plate (17) can be detachably covered on the upper opening of the outer wall (16).

6. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 1, characterized in that: An annular chamber is provided in the wall thickness of the shearing cylinder (11) above the cooling channel (23), and the cooling channel (23) is connected to the drain pipe (24) through the annular chamber.

7. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 1, characterized in that: The invention also includes a supporting device (3), wherein the supporting device (3) includes a supporting base plate (31), a supporting top plate (32) and a plurality of guide pillars (33), wherein the bottom ends of the guide pillars (33) are mounted on the supporting base plate (31) and the upper ends are fixedly connected to the supporting top plate (32); and the magnetic circuit base plate (15) is mounted on the supporting base plate (31) between the guide pillars (33).

8. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 7, characterized in that: The transmission mechanism (4) comprises a rotating motor (41), a motor support plate (42), a torque sensor (43) and a sensor support plate (44); the motor support plate (42) is located above the sensor support plate (44); both are sleeved on the guide column (33) through a flange bearing (45) and can slide on the guide column (33); the rotating motor (41) is mounted on the motor support plate (42), the torque sensor (43) is mounted on the sensor support plate (44), and the rotating motor (41) is connected to the upper end transmission shaft of the torque sensor (43); the lower end transmission shaft of the torque sensor (43) is connected to the shear column (12) through a ball bearing (47) mounted on the cover plate (17).

9. The method for testing the low-temperature characteristics of magnetorheological fluid according to claim 8, characterized in that: The lifting mechanism (5) comprises a screw rod (52) and a rotating handle (51) mounted on the upper end of the screw rod (52); the screw rod (52) is rotatably connected to the support top plate (32); and the rod body is respectively threadedly connected to the motor support plate (42) and the sensor support plate (44).

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