A magnetorheological elastomer uniform stirring device and stirring method

Abstract

The application discloses a kind of magnetorheological elastomer uniform stirring devices, including with the first fixed support of fixed connection of base and the motor of first fixed support top setting, still including two first coils, two second coils, first fixed support is away from first coil and second coil, motor is set in the direction of X axis above first fixed support, the output end of motor extends to the center of two first coils towards first coil, the output end of motor is fixedly connected with horizontally arranged mold, motor is also connected with controller and power supply by wire, power supply is connected with two first coils, two second coils, controller and motor by wire respectively.This application also designs a kind of stirring method suitable for the magnetorheological elastomer uniform stirring device of the application.The application innovatively proposes that when magnetorheological elastomer is mixed, magnetic field is used to control the movement of magnetic particles, so as to realize the uniform stirring of each material component.

Description

Technical Field

[0001] This invention relates to the field of novel smart material preparation technology, and in particular to a magnetorheological elastomer uniform stirring device and stirring method. Background Technology

[0002] In recent years, with the advancement and development of science and technology, novel intelligent composite materials, represented by magnetorheological materials, have become one of the most prominent and important fields. Magnetorheological elastomers, as a unique member of the magnetorheological materials family, possess advantages such as adjustable and controllable equivalent stiffness and fast response speed. A common preparation method for magnetorheological elastomers involves uniformly mixing micron-sized ferromagnetic particles with a polymeric elastomer (such as silicone rubber), followed by curing under an external magnetic field. During curing, the ferromagnetic particles gradually form chain-like or columnar structures within the matrix. The uniformity of these chain-like structures directly affects the magnetorheological effect of the magnetorheological elastomer. Factors influencing the uniformity of the chain-like structures include the uniformity of the mixing and the uniformity of the curing magnetic field.

[0003] Currently, in the preparation of magnetorheological elastomers, the focus is on the impact of the uniformity of the curing magnetic field on its performance, while the uniformity of mixing and stirring is also a crucial factor affecting subsequent particle chain formation. Common mixing and stirring methods are mechanical stirring based on centrifugal force, such as using a cantilever mechanical stirrer with an epoxy resin stirring rod to stir the polymer matrix and ferromagnetic particles; or using a planetary ball mill to stir the polymer matrix and ferromagnetic particles. From the perspective of stirring principles, centrifugal force-based stirring ultimately results in ferromagnetic particles being denser at the edges and sparser in the center. Although the planetary ball mill has a better stirring effect than the cantilever stirrer, it is more complex to operate and more difficult to clean, which is not conducive to the large-scale preparation of magnetorheological elastomers. Summary of the Invention

[0004] To address the problems of complex operation and cumbersome cleaning of existing planetary ball mills, which provide good mixing effects but are unsuitable for the mass production of magnetorheological elastomers, this invention proposes a magnetorheological elastomer uniform mixing device and method. In the initial stage of mixing the constituent materials, a two-dimensional uniform rotating magnetic field is generated using a Helmholtz coil. Combined with the rotation of the mold, this causes the internal ferromagnetic particles to be subjected to an effect equivalent to a three-dimensional uniform magnetic field, thereby achieving uniform mixing.

[0005] This invention is achieved through the following technical solution: It includes a first fixed bracket fixedly connected to a base and a motor disposed above the first fixed bracket. It also includes two first coils of equal size arranged parallel to each other along the X-axis, and two second coils of equal size arranged parallel to each other along the Y-axis. The first and second coils are fixedly connected to the base via the second fixed bracket. The first fixed bracket is located away from the first and second coils. The motor is disposed above the first fixed bracket along the X-axis. The output end of the motor faces the first coils and extends to the center of the two first coils. The output end of the motor is fixedly connected to a horizontally disposed mold. The two first coils and two second coils are symmetrically arranged relative to the mold. The distance between the two first coils is equal to the radius of the first coil, and the distance between the two second coils is equal to the radius of the second coil. The first and second coils do not contact each other. The motor is also connected to a controller and a power supply via wires. The power supply is connected to the two first coils, the two second coils, the controller, and the motor via wires.

[0006] As a further preferred option, the power supply is a programmable power supply.

[0007] As a further preferred embodiment, the first fixed bracket, the second fixed bracket, and the mold are all made of aluminum.

[0008] The present invention also provides a stirring method applicable to the magnetorheological elastomer uniform stirring device described herein, comprising the following steps:

[0009] S1. Place the ferromagnetic particles, rubber matrix and additives in the mold, and fix the mold by the first fixing bracket;

[0010] S2. The power supply applies alternating current to the two first coils and the two second coils respectively, generating a rotating magnetic field on the XOY plane;

[0011] S3. The controller controls the motor to drive the mold to rotate around the X-axis. The ferromagnetic particles in the mold are uniformly magnetized and then move relative to each other, eventually being evenly distributed in the rubber matrix.

[0012] As a further preferred embodiment, the mass ratio of ferromagnetic particles, rubber matrix, and additives in step S1 is 20:79:1.

[0013] As a further preferred embodiment, in step S2, the power supply is applied to the two second coils with an amplitude of I. m An alternating current with a phase angle of 0° and an angular frequency of ω is applied to the two first coils with an amplitude of I. m The phase angle is Alternating current with an angular frequency of ω.

[0014] As a further preferred embodiment, in step S3, one cycle of the mold rotating 360° is T1 = kT, where k is an integer and T is the current cycle applied in the first or second coil.

[0015] As a further preferred option, k is greater than 360.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. Compared with existing centrifugal-based mechanical stirring methods, the three-dimensional magnetic field stirring method is more effective and the distribution of ferromagnetic particles is more uniform.

[0018] 2. The uniform magnetic field stirring method proposed in this invention starts from the motion analysis of ferromagnetic particles inside a magnetorheological elastomer in a magnetic field environment. By studying the influence of different magnetic field magnitudes and directions on the motion of ferromagnetic particles, it is possible to achieve uniform distribution of ferromagnetic particles in space according to specified requirements.

[0019] 3. This invention uses two pairs of Helmholtz coils to generate a two-dimensional uniform rotating magnetic field. The matrix of the magnetorheological elastomer, ferromagnetic particles and additives are mixed together and placed in a mold, which is placed inside the Helmholtz coil. By slowly rotating the mold, in conjunction with the two-dimensional uniform rotating magnetic field, an effect equivalent to a three-dimensional uniform magnetic field can be generated, thereby achieving a stirring effect on the matrix, ferromagnetic particles and additives, and ultimately achieving a uniform distribution of ferromagnetic particles in the matrix. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the stirring device in this invention.

[0021] Figure 2 This is a schematic diagram of the two pairs of Helmholtz coils in this invention.

[0022] Figure 3 This is a schematic diagram of the magnetic field of a single pair of Helmholtz coils.

[0023] Figure 4 This is a schematic diagram of the motion of ferromagnetic particles in a uniform magnetic field.

[0024] Figure 5 This is a schematic diagram illustrating the application of a three-dimensional uniform magnetic field.

[0025] Figure 6 This is a schematic diagram representing the volume element of ferromagnetic particles in space.

[0026] Figure 7 This is a cloud map showing the uniform magnetic field distribution of a three-dimensional Helmholtz coil.

[0027] The image shows:

[0028] 1. First fixed bracket; 2. Controller; 3. Power supply; 4. Wire; 5. First coil; 6. Second coil; 7. Mold; 8. Second fixed bracket; 9. Motor. Detailed Implementation

[0029] The advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments, which are given by way of example only with reference to the accompanying drawings.

[0030] Note: For ease of understanding, this invention defines the horizontal direction as the Y-axis, the vertical direction as the Z-axis, and the direction perpendicular to the paper as the X-axis.

[0031] like Figure 1 As shown, this invention provides a magnetorheological elastomer uniform stirring device, including a first fixed support 1, a controller 2, a power supply 3, wires 4, a first coil 5, a second coil 6, a mold 7, a second fixed support 8, and a motor 9. There are two first coils 5 of equal size, arranged parallel to each other along the Y-axis; there are two second coils 6 of equal size, arranged parallel to each other along the X-axis. Both the first coils 5 and the second coils 6 are perpendicular to the horizontal plane. The first coils 5 and the second coils 6 are both fixedly connected to a base via the second fixed support 8, which can be the ground or an experimental platform, etc. The first fixed support 1 is located away from the first coils 5 and the second coils 6 and is fixedly connected to the base. The motor 9 is positioned above the first fixed support 1 along the X-axis, with its output end facing the first coils 5 and extending to the center of the two first coils 5. The output end of the motor 9 is fixedly connected to the mold 7, which is horizontally positioned. The motor 9 is used to drive the mold 7 to rotate. The two first coils 5 and the two second coils 6 are symmetrically arranged with respect to the mold 7. The distance between the two first coils 5 is equal to the radius of the first coil 5, and the distance between the two second coils 6 is equal to the radius of the second coil 6. Each of the two first coils 5 and the two second coils 6 forms a pair of Helmholtz coils. The first coils 5 and the second coils 6 do not contact each other; that is, the distance from the outer boundary of the inner coil to the center of the magnetic field, i.e., the center of the mold 7, is not less than the distance from the inner boundary of the outer coil to the center of the magnetic field. Furthermore, the regularly shaped mold 7 is strictly fixed at the center of the coils, i.e., at the origin O, ensuring that the magnetic field within the mold 7 is relatively uniform. The controller 2 is electrically connected to the motor 9 via wire 4 and is used to control the rotation of the motor 9. The power supply 3 is connected to the two first coils 5, the two second coils 6, the controller 2, and the motor 9 via wire 4. The power supply 3 is a programmable power supply used to power the controller 2 and the motor 9, and to provide the set AC current to the first coils 5 and the second coils 6. The first fixing bracket 1, the second fixing bracket 8, and the mold 7 are all made of aluminum to avoid affecting the magnetic field generated by the two pairs of Helmholtz coils.

[0032] The present invention also provides a stirring method for a magnetorheological elastomer uniform stirring device designed according to the present invention, which mainly includes the following three steps:

[0033] Step 1: Weigh the ferromagnetic particles, rubber matrix, and additives (mainly silicone oil) in a weight ratio of 20:79:1 and place them in mold 7. Fix mold 7 using the first fixing bracket 1. Connect power supply 3, first coil 5, and second coil 6 through wire 4. Figure 2 As shown. Meanwhile, the power supply 3, controller 2, and motor 9 are connected via wire 4.

[0034] like Figure 3 As shown, taking a single pair of Helmholtz coils as an example, the axes of the two Helmholtz coils A and B coincide and are along the y-axis. The midpoint of the line segment of the axis with the center of the two coils as the starting point is located at the origin. Assume the coil radius is R, the current is I, the distance from the coil center to the origin is a, and the XOY plane is the working plane, with a point p: (x0, y0, 0) located in the middle of the coil pair. Consider a small element on the left coil. Let m be the infinitesimal element symmetrically positioned on the right coil. Let n be the distance vector between the left and right coils and point p. and The line connecting the infinitesimal element and the coil forms an angle θ with the positive y-axis.

[0035] According to the Biot-Savart law, the magnetic field at point p... It is obtained by superimposing the magnetic fields generated by the two coils:

[0036]

[0037] In the formula, and These represent the spatial magnetic field strength generated by the left and right coils, respectively, with μ0 being the free permeability. The coordinates of point m on the left coil are (-a, Rcosθ, Rsinθ), and the coordinates of point n on the right coil are (a, Rcosθ, Rsinθ), where θ is the angle between the straight-line distance from point m to the y-axis and the XOY plane.

[0038] To simplify the calculation, the x0 and y0 terms containing the coordinates of point p are substituted:

[0039]

[0040] In the formula, ε1, ε2, η, u1 and u2 are all intermediate variables and have no actual physical meaning.

[0041] Magnetic flux density at point p for

[0042]

[0043] In the formula

[0044]

[0045] Under the external magnetic field generated by a Helmholtz coil, ferromagnetic particles move within the matrix due to electromagnetic forces, such as... Figure 4 As shown, ferromagnetic particles will aggregate into multiple chain-like structures along the direction of the applied magnetic field. If the spacing between particles is too large before aggregation, the electromagnetic force generated by the applied magnetic field will cause the particles to move closer together, shortening the spacing between particles; if the spacing between particles is too small before aggregation, the repulsive force between particles will ensure that the particles maintain a certain distance.

[0046] Step 2, the stirring method of the present invention requires the use of, for example Figure 5 The spatial three-dimensional magnetic field shown is as follows: first, a uniform rotating magnetic field is generated on the XOY surface, and then the magnetic field on the XOY surface is rotated in space.

[0047] Power supply 3 supplies an amplitude of I to the two second coils 6. m An alternating current with a phase angle of 0° and an angular frequency of ω is applied to the two first coils 5 with an amplitude of I. m The phase angle is An alternating current with an angular frequency of ω corresponds to the current I in the first coil 5 and the second coil 6. X and I Y They can be represented as follows:

[0048]

[0049] The axes of the magnetic induction intensity generated by the two pairs of coils are spatially separated. The amplitude of the magnetic induction intensity of each coil varies with time according to a cosine law. The magnetic induction intensity of the first coil 5 and the second coil 6 are respectively represented by... and The formula is as follows:

[0050]

[0051] In the formula, B mx and B my They are respectively the input amplitude I m The magnetic induction intensity produced by two pairs of coils under coil current, and the magnetic induction intensity of the combined magnetic field of the two pairs of coils. for

[0052]

[0053] To generate a 360° rotating magnetic field in the XOY plane, the first coil 5 and the second coil 6 need to work together to apply an amplitude of I in the X-axis and Y-axis directions, respectively. m (The current must not exceed the maximum allowable current of the coil), frequency f is 1Hz, AC current with an initial phase angle difference of 90°, one cycle time As time changes, this can generate a rotating magnetic field in any direction within the XOY plane, as shown in equation (6), where the magnetic induction intensity amplitude... μ is the relative permeability of the magnetorheological elastic body, and R is the relative permeability of the magnetorheological elastic x and R y These are the radii of the second and first coils, respectively.

[0054] Step 3, to achieve Figure 5 The spatial magnetic field requires the motor 9 to slowly rotate the mold 7 around the X-axis. The power supply 3 simultaneously powers the controller 2 and the motor 9. The controller 2 outputs a control signal to the motor 9, enabling it to slowly rotate around the X-axis. A 360° rotation of the mold 7 constitutes one cycle, denoted by T1, satisfying T1 = kT. This means the cycle of the mold 7 rotating 360° is k times the period of the applied current in the coil, where k is an integer. A larger k value results in slower rotation of the mold 7, and a smaller k value results in faster rotation. To minimize the influence of centrifugal force during mold 7 rotation, the k value should be as large as possible, preferably exceeding 360, meaning the rotation speed of the mold 7 should be as low as possible. The two-dimensional rotating magnetic field on the XOY plane, combined with the slow rotation of the mold 7, allows the internal ferromagnetic particles to experience an effect equivalent to a three-dimensional uniform magnetic field in space.

[0055] In step 3, under the influence of a uniform magnetic field, the ferromagnetic particles will first be magnetized. The magnetized particles will then move (following the principle that like magnetic particles attract each other and unlike magnetic particles repel each other), such as... Figure 6 As shown, ferromagnetic particles of different morphologies (generally spheres) can all be considered as representative volume elements completely surrounded by a cube, and the range of particle movement is its own representative volume element. Magnetorheological elastic bodies can be regarded as a collection of countless regular representative volume elements in space. Under the action of a uniform magnetic field in space, ferromagnetic particles will eventually be distributed according to regular representative volume elements, that is, uniformly distributed inside the magnetorheological elastic body.

[0056] Example 1, such as Figure 7 As shown, Figure 7 To establish a simulation model of a three-dimensional spatial magnetic field in COMSOL, the cross-sectional area of ​​the Helmholtz coil is set to 1 mm². 2 The conductivity is 6×10 7S / m, number of turns is 200. An AC current with an amplitude of 10A and a frequency of 1Hz is applied to the second coil 6, with an initial phase of 0°; an AC current with an amplitude of 10A and a frequency of 1Hz is applied to the first coil 5, with an initial phase of 90°. When the mold 7 has not yet rotated, the spatial magnetic field distribution cloud map generated by the Helmholtz coil shows that the uniformity of the magnetic field distribution on the XOY surface is good in this embodiment.

[0057] In addition to the above embodiments, the present invention may have other implementation methods. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A stirring method for a magnetorheological elastomer uniform stirring device, the stirring device comprising a first fixed support (1) fixedly connected to a base and a motor (9) disposed above the first fixed support (1), characterized in that: It also includes two first coils (5) of equal size and parallel to each other along the X-axis, and two second coils (6) of equal size and parallel to each other along the Y-axis. The first coils (5) and the second coils (6) are both fixedly connected to the base by a second fixed bracket (8). The first fixed bracket (1) is away from the first coils (5) and the second coils (6). A motor (9) is arranged above the first fixed bracket (1) along the X-axis. The output end of the motor (9) faces the first coils (5) and extends to the center of the two first coils (5). The output end of the motor (9) is fixedly connected to a horizontal... The mold (7) is set up, and the two first coils (5) and the two second coils (6) are symmetrically arranged with respect to the mold (7). The distance between the two first coils (5) is equal to the radius of the first coil (5), and the distance between the two second coils (6) is equal to the radius of the second coil (6). The first coils (5) and the second coils (6) do not contact each other. The motor (9) is also connected to the controller (2) and the power supply (3) through the wire (4). The power supply (3) is connected to the two first coils (5), the two second coils (6), the controller (2) and the motor (9) through the wire (4). The stirring method includes the following steps: S1. Place the ferromagnetic particles, rubber matrix and additives in the mold (7) and fix the mold (7) by the first fixing bracket (1); S2, the power supply (3) supplies alternating current to the two first coils (5) and the two second coils (6) respectively, generating a rotating magnetic field on the XOY surface; S3. The controller (2) controls the motor (9) to drive the mold (7) to rotate around the X-axis. The ferromagnetic particles in the mold (7) are uniformly magnetized and then move relative to each other, eventually being uniformly distributed in the rubber matrix.

2. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 1, characterized in that: The power supply (3) is a programmable power supply.

3. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 2, characterized in that: The first fixed bracket (1), the second fixed bracket (8) and the mold (7) are all made of aluminum.

4. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 1, characterized in that: In step S1, the mass ratio of ferromagnetic particles, rubber matrix, and additives is 20:79:

1.

5. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 1, characterized in that: In step S2, the power supply (3) supplies an amplitude of [value missing] to the two second coils (6). The phase angle is 0° and the angular frequency is An alternating current with an amplitude of [value missing] is passed into the two first coils (5). The phase angle is angular frequency is Alternating current.

6. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 1, characterized in that: In step S3, one cycle of the mold (7) rotating 360° is T1=kT, where k is an integer and T is the current cycle applied in the first coil (5) or the second coil (6).

7. The stirring method of the magnetorheological elastomer uniform stirring device according to claim 6, characterized in that: The value of k is greater than 360.

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