Magnetorheological fluid low-temperature characteristic test system and test method

Abstract

The invention discloses a system and a method for testing low-temperature characteristics of magnetorheological fluid, and belongs to the technical field of magnetorheological fluid. The system comprises a shearing device, a low-temperature cooling device, a supporting device, a transmission mechanism and a lifting mechanism, the shearing device and the inner wall of a shearing cylinder form an annular test gap through a shearing column, and a magnet exciting coil cooperates with a magnetic circuit structure to generate a uniform magnetic field; the low-temperature cooling device is arranged in the shearing device, and the transmission mechanism and the lifting mechanism respectively drive the shearing column to rotate and lift. The test method comprises the steps of low-temperature environment establishment, magnetic field loading, shear test and multi-parameter calculation, derivation of a shear yield stress formula based on a Bingham model and an infinitesimal method, calculation of coolant flow increment in combination with a heat production power and heat dissipation power balance model, and guarantee of low temperature constancy. The magnetorheological fluid low-temperature characteristic testing device fills the blank of magnetorheological fluid low-temperature characteristic testing, has the advantages of being high in testing precision, high in environment controllability, compact in structure, easy to maintain and the like, and provides reliable experimental data for application of magnetorheological fluid in a low-temperature scene.

Description

Technical Field

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

[0002] Magnetorheological fluid is a new type of intelligent material with controllable fluidity. Its particularity lies in its special fluidity: under the action of a magnetic field, the originally liquid magnetorheological fluid instantaneously transforms into a solid-like state, showing the mechanical properties of a solid-like material; at the moment when the magnetic field is removed, it can quickly return to its original liquid state. This transformation from liquid to solid has the characteristics of rapid change, controllable degree, and reversible process. Shear yield stress is an important index to measure the performance of magnetorheological fluid. In a high-temperature environment, magnetorheological fluid is prone to expansion and even failure, which will lead to a decrease in the transmission efficiency of magnetorheological devices or damage to components. Therefore, to ensure the stable operation of the equipment, many magnetorheometers are equipped with a heat dissipation system to control the working temperature within a reasonable range. However, currently on the market, rheometers generally cannot provide a low-temperature measurement environment when testing the rheological characteristics of materials, which makes the performance parameters of magnetorheological fluid under low-temperature conditions lack data support, thereby restricting its application expansion under low-temperature working conditions. Summary of the Invention

[0003] The purpose of the present invention is to propose a magnetorheological fluid low-temperature characteristic test system and a test method to solve the problem in the prior art of lacking test means for the characteristics of magnetorheological fluid under a controllable low-temperature environment.

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

[0005] A shearing device, including a shearing cylinder, a shearing column, an exciting coil, a magnetic circuit side wall, and a magnetic circuit bottom plate; the shearing cylinder is a columnar container with an open upper part, a columnar chamber is provided in the middle of the magnetic circuit side wall, and the shearing cylinder is embedded therein; the exciting coils are evenly distributed between the shearing cylinder and the columnar chamber; the shearing column is detachably placed in the shearing cylinder through 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 rotate in the shearing cylinder through a transmission mechanism to perform shearing tests on the magnetorheological fluid in the magnetized state; the magnetic circuit side wall is installed on the magnetic circuit bottom plate;

[0006] A low-temperature cooling device, including an inlet pipe, a liquid storage chamber, cooling channels, and a drain pipe; the liquid storage chamber is located in the magnetic circuit side wall below the shearing cylinder, and the inlet pipe is connected to the liquid storage chamber; a plurality of cooling channels are evenly distributed in the wall of the shearing cylinder, connected to the liquid storage chamber at the bottom and connected to the drain pipe at the upper part.

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

[0008] As a further improvement of the present invention, an annular chamber is provided inside the wall thickness of the shearing 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, a support device is further included. The support device includes a support bottom plate, a support top plate, and multiple guide columns. The bottom ends of the guide columns are installed on the support bottom plate, and the upper ends are fixedly connected to the support top plate. The magnetic circuit bottom plate is installed on the support bottom plate between the guide columns.

[0010] As a further improvement of the present invention, the transmission mechanism includes a rotary 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 sleeved on the guide columns through flange bearings and can slide on the guide columns. The rotary motor is installed on the motor support plate, the torque sensor is installed on the sensor support plate, and the rotary 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 shearing column through a ball bearing installed on the cover plate.

[0011] As a further improvement of the present invention, the lifting mechanism includes a lead screw and a rotary handle installed at the upper end of the lead screw. The lead 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 the second aspect, the present invention also proposes a method for testing the low-temperature characteristics of a magnetorheological fluid. Based on the above-mentioned magnetorheological fluid low-temperature characteristic testing system, the testing method includes the following steps:

[0013] Step 1: Inject a fixed amount of magnetorheological fluid into the shearing cylinder.

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

[0015] Step 3: Start the centrifugal pump, pump the coolant into the liquid storage chamber and then into the cooling channel to cool the shearing cylinder, providing a low-temperature environment for the shearing test of the magnetorheological fluid.

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

[0017] Step 5: Replace the coolant with different low-temperature values, and repeat Steps 3 and 4 to conduct multiple groups of shear tests on the magnetorheological fluid under low-temperature environments;

[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, rotate the rotating handle to lift the shear column to the initial position, take out the magnetorheological fluid, and clean the test system.

[0020] As a further improvement of the present invention, in Step 4, heat is generated when the shear device works. If the coolant is required 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 , and it is calculated according to the following method:

[0021] First step: Obtain the heat generation power of the shear device: The heat source of the shear device is the frictional heat Ps generated by shearing and the electromagnetic heat Pc generated by the energization of the coil. The frictional heat Ps is affected by the torque M and the rotational speed ω, and the electromagnetic heat is affected by the current I and the coil resistance R m , and the heat generation power is as follows:

[0022] Equation 1

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

[0024] Equation 2

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

[0026] Third step: When the heat dissipation power of the low-temperature cooling device is equal to the heat generation power of the shear device, balance is achieved. From Equation 1 and Equation 2, the coolant flow rate increment Q L after balance can be obtained:

[0027] . Equation 3

[0028] As a further improvement of the present invention, in Step 6, the structural parameters of the shear device include the shear column radius R a , the inner diameter R b, the shear column length L and the radius r of the annular test gap, R a < r < R b .

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

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

[0031] Equation 4

[0032] In the formula, 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 microelement method to analyze and calculate the microelement within the radius of the extremely small unit. If a radial microelement is selected, the torque of the microelement is

[0034] Equation 5

[0035] In the formula, is the shear force of the microelement. Integrating Equation 5, the overall torque of the magnetorheological fluid can be obtained

[0036] Equation 6

[0037] The third step is to organize Equation 6 to obtain the relationship between the shear stress and torque of:

[0038] ; Equation 7

[0039] The fourth step is to substitute the obtained τ into Equation 4 to find the shear yield stress τ0 of the magnetorheological fluid; the torque M in Equation 4 is measured by a torque sensor, and the zero-field viscosity is measured by a viscometer; the shear rate is obtained by converting the rotational speed , and their relationship 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 column body of the shearing column and the inner wall of the shearing cylinder enables the magnetorheological fluid to have a small centrifugal force and is not easily spilled during the shearing process. Moreover, the shearing area is large, the adjustable torque range is wide, which improves the test stability and reliability. The cooling channel is embedded in the wall thickness of the shearing cylinder, which can provide a direct low-temperature environment and heat dissipation conditions for the magnetorheological fluid, optimizing the space design and laying a good foundation for the shearing test under low-temperature environment.

[0042] (2) The present invention establishes a heat generation and heat dissipation balance model. Considering that the shearing device generates frictional heat and electromagnetic heat during operation, by establishing a balance model of heat generation power and heat dissipation power, the increment of coolant flow rate required to maintain a constant low temperature is calculated, realizing the precise adjustment of the total coolant flow rate, ensuring the stability of the low-temperature environment while absorbing heat, and providing a stable basis for the accuracy of the shearing test under low temperature.

[0043] (3) Using the classical model and the microelement method, based on the Bingham model to describe the flow characteristics of the magnetorheological fluid, the microelement method is used to analyze and calculate the microelement within the radius of the extremely small unit. 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 obtained. This calculation method is based on a mature theoretical model, combined with the structural parameters and measured data of the test system, ensuring the accuracy and reliability of the calculation results. Description of the Drawings

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

[0045] Figure 1 is a three-dimensional structural schematic diagram of the magnetorheological fluid low-temperature characteristic test system of the present invention;

[0046] Figure 2 is Figure 1 the front view of

[0047] Figure 3 is Figure 2 the structural schematic diagram of the shearing device and the low-temperature cooling device in

[0048] Figure 4 is the three-dimensional view of the shearing device;

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

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

[0051] Description of the 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 post, 34 - Furniture 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 - Lead screw. Detailed implementation manners

[0057] 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 described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0058] Such as Figures 1-6As shown in the figure, a test system for the low-temperature characteristics of magnetorheological fluid includes a shearing device 1, a low-temperature cooling device 2, a supporting device 3, a transmission mechanism 4, and a lifting mechanism 5. Among them, the shearing device 1 is composed of a shearing cylinder 11, a shearing column 12, an exciting coil 13, a magnetic circuit side wall 14, a magnetic circuit bottom plate 15, an outer wall 16, and a cover plate 17. The shearing cylinder 11 is a columnar container with an open upper part, embedded in the columnar chamber in the middle of the magnetic circuit side wall 14. Six rectangular ring-shaped exciting coils 13 are evenly distributed between the shearing cylinder 11 and the columnar chamber, and are fixed by six rectangular support blocks arranged circumferentially in the chamber. The shearing column 12 is a cylindrical structure with a connecting handle at the upper part. The diameter of the column body of the shearing column 12 is slightly smaller than the inner diameter of the shearing cylinder 11, and it can be detachably placed in the shearing cylinder 11 through the lifting mechanism 5. The height of the column body of the shearing column 12 is lower than the height of the shearing cylinder 11. An annular test gap for containing magnetorheological fluid is formed between the cylinder wall of the shearing cylinder 11 and the column body of the shearing column 12. The shearing column 12 can rotate in the cylinder through the transmission mechanism 4 to perform a shearing test on the magnetorheological fluid in the magnetized state. The shearing cylinder 11, the shearing column 12, the magnetic circuit side wall 14, and the magnetic circuit bottom plate 15 are all made of electrolytic iron. The outer wall 16 is an iron-nickel alloy cavity, placed on the magnetic circuit bottom plate 15 at the bottom and wrapping the magnetic circuit side wall 14, and its top is sealed by a separable cover plate 17 to prevent external magnetic field interference. When the exciting coil 13 is energized, a closed magnetic field passing through the shearing cylinder 11 is formed between the exciting coil 13, the magnetic circuit side wall 14, and the magnetic circuit bottom plate 15, applying a magnetic field to the magnetorheological fluid. Figure 6 It is a magnetic field simulation diagram (using ANSYS Maxwell software).

[0059] As Figure 3 shown in the figure, 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 placed in the magnetic circuit side wall 14 below the shearing 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 cylinder wall of the shearing cylinder 11, connected to the liquid storage chamber 22 at the bottom and to the liquid discharge pipe 24 at the upper part, providing a low-temperature environment for the shearing test. Specifically, an annular chamber is provided in the wall thickness of the shearing cylinder 11 above the cooling channel 23. The cooling channel 23 is a straight hole or a curved hole opened in the wall thickness of the shearing cylinder 11. The curved holes are arranged in a spiral pattern in the cylinder wall of the shearing cylinder 11 to increase the contact area between the coolant and the cylinder wall and improve the heat dissipation efficiency. The upper parts of the channels all lead to the annular chamber.

[0060] Directly arranging the cooling channel 23 in the wall thickness of the shearing cylinder 11 can enable the magnetorheological fluid to quickly sense the low-temperature environment, laying a foundation for accurately carrying out the shearing test. The coolant in this embodiment is an oil-based coolant, such as silicone oil, whose freezing point can reach -50 degrees Celsius. The low temperature mentioned in this embodiment refers to a temperature lower than room temperature, for example, an environment lower than 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 shearing cylinder 11, and then discharges it from the drain pipe 24 through the annular chamber. The coolant is replenished in real time from the inlet pipe 21 to circulate and cool the shearing cylinder 11 and provide a low-temperature environment.

[0062] The support device 3 includes a support bottom plate 31, a support top plate 32, a plurality of guide columns 33 and Fuma wheels 34. The bottom of the guide column 33 is installed on the support bottom plate 31, and the magnetic circuit bottom plate 15 is installed on the support bottom plate 31 between the plurality of guide columns 33. The support top plate 32 is fixedly connected to the upper end of the guide column 33, and a square opening is formed in the middle of the support top plate 32. The Fuma wheels 34 are installed below the support bottom plate 31 and are used to move the test system.

[0063] The transmission mechanism 4 is located directly above the shearing cylinder 11 and includes 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, and 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 installed on the motor support plate 42, and the torque sensor 43 is installed on the sensor support plate 44. 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 connecting handle on the shearing column 12 through a ball bearing 47 installed on the cover plate 17.

[0064] As Figure 2 shown, the transmission mechanism 4 further includes four connecting columns 46. The upper ends of the connecting columns 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 columns 46 are used to connect the motor support plate 42 and the sensor support plate 44 together to move together on the guide column 33. When the rotating motor 41 moves upward, it can pass through the square opening on the support top plate 32.

[0065] The lifting mechanism 5 includes a lead screw 52 and a rotating handle 51 installed on the lead screw 52. The lead screw 52 is rotationally connected to the support top plate 32 through a bearing, and 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 perform the lifting operation of the transmission mechanism 4 in an electric manner.

[0066] In addition, a temperature sensor is installed on the shearing cylinder 11 to monitor the temperature of the coolant in the cooling channel 23 in real time, and temperature sensors are also installed on the inlet pipe 21 and the drain pipe 24.

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

[0068] The test system of the present invention realizes direct heat dissipation of the shear cylinder 11 and construction of a low-temperature test environment by integrating the shear device 1 and the low-temperature cooling device 2. The shear device 1 uses the excitation coils 13 uniformly distributed on the outer periphery of the shear cylinder 11 to cooperate with the magnetic circuit side wall 14 to form a uniform magnetic field environment, ensuring the test accuracy. The low-temperature cooling device 2 can controllably cool the magnetorheological fluid and support the shear yield stress test under different low-temperature conditions. The barrel structure design makes the magnetorheological fluid have small centrifugal force and large shear area during the shearing process, and has the advantages of low overflow risk, wide torque adjustment range, high test stability, and convenient disassembly, cleaning, etc.

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

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

[0071] Step 2: Rotate the rotary handle 51 to lower the shear column 12 until 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 disperses and fills the annular test gap between the column body of the shear column 12 and the cylinder wall of the shear cylinder 11 to form an annular magnetorheological fluid.

[0072] Step 3: Start the centrifugal pump to pump the coolant into the liquid storage chamber and enter 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 the controller, and the pump-in flow rate of the coolant is controlled by the controller.

[0073] Step 4: Supply power to the excitation coil 13 through the programmable power supply to generate a magnetic field, and monitor the magnetic field intensity with a teslameter. When the magnetic field intensity reaches the set value, start the rotary motor 41 to drive the shear column 12 to rotate, perform a shear test on the magnetorheological fluid, collect the torque and rotational speed through the torque sensor 43 and upload them to the controller. The teslameter is a handheld device, and the measurement position is set in the area near the magnetorheological fluid in the annular test gap. Four measurement points are selected evenly along the circumference at the top of the annular test gap to observe the magnitude and uniformity of the magnetic field.

[0074] In this step, since heat will be generated when the shear device 1 works, 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, and the increased flow rate is the coolant flow rate increment Q L, is calculated by the following method:

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

[0076] Equation 1

[0077] Second step, obtain the heat dissipation power of the low-temperature cooling device 2: The shearing device 1 conducts heat dissipation through the coolant in contact with the shearing cylinder. The heat dissipation power PL is as follows:

[0078] Equation 2

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

[0080] Third step, when the heat dissipation power of the low-temperature cooling device is equal to the heat generation power of the shearing device, it reaches equilibrium. From Equation 1 and Equation 2, the coolant flow rate increment QL increased after equilibrium can be obtained:

[0081] . Equation 3

[0082] By obtaining the coolant flow rate increment Q L , the overall coolant flow rate can be accurately adjusted. While taking away the heat, it ensures the constancy of the low-temperature environment and provides a stable basis for the accuracy of the shearing test at low temperatures.

[0083] Step five, replace the coolant with different low-temperature values, and repeat Step three and Step four to conduct multiple groups of magnetorheological fluid shearing tests under low-temperature environments.

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

[0085] In the present invention, the calculation method of the shear yield stress τ0 of the magnetorheological fluid is:

[0086] Step 1: Use the Bingham model to describe the flow characteristics of the magnetorheological fluid:

[0087] Equation 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] Step 2: Use the microelement method to analyze and calculate the microelement within the radius of the extremely small unit. If a radial microelement is selected, the torque of the microelement is

[0090] Equation 5

[0091] Where dFτ is the shear force of the microelement. Integrating Equation 5 gives the overall torque M of the magnetorheological fluid

[0092] Equation 6

[0093] Step 3: Rearranging Equation (6) gives the relationship between the shear stress of the magnetorheological fluid and the torque M as:

[0094] . Equation 7

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

[0096] In Equation 4, the torque M is measured by a torque sensor, and the shear rate is obtained by conversion from the rotational speed,

[0097] The zero-field viscosity η0 is measured by a viscometer. Among them, the shear rate and The conversion relationship is:

[0098] .

[0099] Step 7: After the test, rotate the rotary handle 51 to lift the shear column 12 to the initial position, take out the magnetorheological fluid, and clean the test system.

[0100] The test method of the present invention lays a 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 conveniently obtained.

[0101] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. All various changes that can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art to which the present invention pertains are within the scope of protection of the claims of the present invention.

Claims

1. A test system for the low-temperature characteristics of magnetorheological fluid, characterized in that, Comprising: A shearing device (1), including a shearing cylinder (11), a shearing column (12), an exciting coil (13), a magnetic circuit side wall (14) and a magnetic circuit bottom plate (15); the shearing cylinder (11) is a columnar container with an open upper part, a columnar chamber is provided in the middle of the magnetic circuit side wall (14), and the shearing cylinder (11) is embedded therein; the exciting coils (13) are evenly distributed between the shearing cylinder (11) and the columnar chamber; the shearing column (12) is detachably placed in the shearing cylinder (11) through a lifting mechanism (5), and an annular test gap is formed between the inner wall of the shearing cylinder (11) and the shearing column (12) for containing magnetorheological fluid; the shearing column (12) can rotate in the shearing cylinder (11) through a transmission mechanism (4) to perform a shearing test on the magnetorheological fluid in the magnetized state; the magnetic circuit side wall (14) is installed on the magnetic circuit bottom plate (15); A low-temperature cooling device (2), including 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 shearing 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 shearing cylinder (11), the bottom is connected to the liquid storage chamber (22), and the upper part is connected to the liquid discharge pipe (24).

2. The magnetorheological fluid low-temperature characteristic testing system according to claim 1, characterized in that The shearing device further includes an outer wall (16) and a cover plate (17), the outer wall (16) is a shell with open upper and lower parts, the bottom is seated on the magnetic circuit bottom plate (15), and the magnetic circuit side wall (14) is located inside it; the cover plate (17) is detachably covered on the upper opening of the outer wall (16).

3. The magnetorheological fluid low-temperature characteristic test system 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 liquid discharge pipe (24) through the annular chamber.

4. The magnetorheological fluid low-temperature characteristic testing system according to claim 1, wherein It further includes a support device (3), the support device (3) includes a support bottom plate (31), a support top plate (32) and a plurality of guide columns (33), the bottom ends of the guide columns (33) are installed on the support bottom plate (31), and the upper ends are fixedly connected to the support top plate (32); the magnetic circuit bottom plate (15) is installed on the support bottom plate (31) between the guide columns (33).

5. The magnetorheological fluid low-temperature characteristic testing system according to claim 4, wherein, The transmission mechanism (4) includes 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), and both are sleeved on the guide columns (33) through flange bearings (45) and can slide on the guide columns (33); the rotating motor (41) is installed on the motor support plate (42), the torque sensor (43) is installed 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 shearing column (12) through a ball bearing (47) installed on the cover plate (17).

6. The magnetorheological fluid low-temperature characteristic test system according to claim 5, wherein The lifting mechanism (5) includes a lead screw (52) and a rotating handle (51) installed at the upper end of the lead screw (52). The lead screw (52) is rotatably connected to the support top plate (32), and the rod body is threadedly connected to the motor support plate (42) and the sensor support plate (44) respectively.

7. A method for testing the low-temperature characteristics of a magnetorheological fluid, based on the magnetorheological fluid low-temperature characteristic testing system according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: Inject a certain amount of magnetorheological fluid into the shear cylinder (11). Step 2: Rotate the rotating 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, pump the coolant into the liquid storage chamber (22) and then 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. Step 4: Supply power to the excitation coil (13) through a programmable power supply to generate a magnetic field, monitor the magnetic field intensity with a Tesla meter. When the magnetic field intensity reaches the set value, start the rotating 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 different low-temperature values, and repeat Step 3 and Step 4 to conduct multiple groups of shear tests of the magnetorheological fluid under low-temperature environments. 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 (1), the coolant temperature, and the torque. Step 7: After the test is completed, rotate the rotating handle (51) to lift the shear column (12) to the initial position, take out the magnetorheological fluid and clean the test system.

8. The method for testing the low-temperature characteristics of a magnetorheological fluid according to claim 7, characterized in that, In Step 4, heat is generated when the cutting device is working. If the coolant is required 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, and the increased flow rate is the coolant flow rate increment Q L， Calculate according to the following method: First step: Obtain the heat generation power of the shear device: The heat sources of the shear device are the frictional heat Ps generated by shear and the electromagnetic heat Pc generated by the energization of the coil. The frictional heat Ps is affected by the torque M and the rotational speed ω, and the electromagnetic heat is affected by the current I and the coil resistance Rm. The heat generation power is as follows: Formula 1 Step 2: 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 is as follows: Formula 2 where c L is the specific heat capacity of the coolant, m L is the mass of the coolant, ΔT L is the temperature difference between the liquid discharge port and the liquid inlet port, t is the working time of the coolant, ρ L is the density of the coolant, Q L is the coolant flow rate increment; Step 3: When the heat dissipation power of the low-temperature cooling device is equal to the heat generation power of the shearing device, equilibrium is reached, and the coolant flow rate increment Q after equilibrium can be obtained from Equation 1 and Equation 2 L : Formula 3.

9. The method for testing the low-temperature characteristics of the magnetorheological fluid according to claim 7, wherein In Step Six, the structural parameters of the shearing device include the radius R of the shearing column a , the inner diameter R of the shearing cylinder b , the length L of the shearing column, and the radius r of the annular test gap, where R a < r < R b .

10. The method for testing the low-temperature characteristics of a magnetorheological fluid according to claim 9, characterized in that, In Step 6, the calculation method of the shear yield stress τ0 of the magnetorheological fluid is: First step: Use the Bingham model to describe the flow characteristics of the magnetorheological fluid: Formula 4 where τ is the shear stress of the magnetorheological fluid, τ0 is the shear yield stress of the magnetorheological fluid, and η0 is the zero-field viscosity of the magnetorheological fluid, is the shear rate; Second step: Adopt the microelement method to analyze and calculate the microelement within the minimum unit radius. If a radial microelement is selected, the torque of the microelement is Formula 5 In the formula, is the shear force of the micro unit. Integrating Equation 5 gives the overall torque of the magnetorheological fluid , Formula 6 Step 3: By arranging Equation 6, the relationship between the shear stress and torque of the magnetorheological fluid can be obtained as follows: is: ; Formula 7 Step 4: Substitute the obtained τ into Equation 4 to calculate the shear yield stress τ0 of the magnetorheological fluid; in Equation 4, the torque M is measured by a torque sensor, and the zero-field viscosity is measured by a viscometer; the shear rate is obtained by converting the rotational speed , and the relationship between them is as follows: .

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