Magnetorheological elastomer uniform stirring device and stirring method

Abstract

The invention discloses a magnetorheological elastomer uniform stirring device which comprises a first fixing support fixedly connected with a base and a motor arranged above the first fixing support and further comprises two first coils and two second coils, the first fixing support is far away from the first coils and the second coils, the motor is arranged above the first fixing support in the X-axis direction, and the motor is arranged above the second fixing support in the X-axis direction. 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 with a horizontally-arranged mold, the motor is further connected with a controller and a power source through wires, and the power source is connected with the two first coils, the two second coils, the controller and the motor through wires. The invention further designs a stirring method suitable for the uniform stirring device for the magnetorheological elastomer. According to the invention, when all the components of the magnetorheological elastomer are mixed, a magnetic field is adopted to control the movement of magnetic particles, so that all the material components are uniformly stirred.

Description

Technical Field

[0001] The invention relates to the technical field of novel intelligent material preparation, and in particular to a magnetorheological elastomer uniform stirring device and stirring method. Background Art

[0002] In recent years, with the progress and development of science and technology, new intelligent composite materials represented by magnetorheological materials have become one of the important fields that attract attention. Magnetorheological elastomers, as a unique member of magnetorheological materials, have the advantages of adjustable and controllable equivalent stiffness and fast response speed. The common preparation method of magnetorheological elastomers is to evenly mix micron-sized ferromagnetic particles with polymer elastomers (such as silicone rubber, etc.), and then cure them under an external magnetic field. During the curing period, the ferromagnetic particles gradually form a chain or columnar structure inside the matrix, and the uniformity of the chain structure will directly affect the magnetorheological effect of the magnetorheological elastomer. The factors affecting the uniformity of the chain structure include the uniformity of mixing and stirring and the uniformity of the curing magnetic field.

[0003] At present, in the preparation process of magnetorheological elastomers, the focus is on the effect of the uniformity of the curing magnetic field on its performance, while ignoring that the uniformity of mixing and stirring is also an important factor affecting the subsequent particle chain formation. The common mixing and stirring method is a mechanical stirring method 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; another example is using a planetary ball mill to stir the polymer matrix and ferromagnetic particles. From the analysis of the stirring principle, the stirring method based on the centrifugal force principle will eventually make the ferromagnetic particles denser on both sides of the space and sparser in the middle of the space; although from the perspective of stirring effect, the stirring effect of the planetary ball mill is better than that of the cantilever stirrer, but the operation is more complicated and the cleaning is more troublesome, which is not conducive to the large-scale preparation of magnetorheological elastomers. Summary of the invention

[0004] In order to solve the problem that the planetary ball mill with good stirring effect in the above-mentioned prior art is complicated to operate and difficult to clean, which is not conducive to the mass production of magnetorheological elastomers. The present invention proposes a magnetorheological elastomer uniform stirring device and stirring method. In the initial stage of mixing the component materials, a two-dimensional uniform rotating magnetic field is generated by a Helmholtz coil, and the rotation of the mold is coordinated to make the internal ferromagnetic particles be subjected to the effect equivalent to the three-dimensional uniform magnetic field in space, thereby achieving the effect of uniform stirring.

[0005] The present invention is achieved through the following technical scheme: it includes a first fixed bracket fixedly connected to a base and a motor arranged above the first fixed bracket, and also includes two first coils of equal size and arranged in parallel along the X-axis direction, two second coils of equal size and arranged in parallel along the Y-axis direction, the first coil and the second coil are both fixedly connected to the base through the second fixed bracket, the first fixed bracket is away from the first coil and the second coil, a motor is arranged above the first fixed bracket along the X-axis direction, the output end of the motor faces the first coil and extends to the center of the two first coils, the output end of the motor is fixedly connected to a horizontally arranged mold, the two first coils and the two second coils are respectively arranged symmetrically relative to the mold, the spacing between the two first coils is equal to the radius of the first coil, the spacing between the two second coils is equal to the radius of the second coil, the first coil and the second coil are not in contact, the motor is also connected to a controller and a power supply through wires, and the power supply is respectively connected to the two first coils, the two second coils, the controller and the motor through wires.

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

[0007] As a further preference, the first fixing bracket, the second fixing bracket and the mold are all made of aluminum.

[0008] The present invention also designs a stirring method suitable for the magnetorheological elastomer uniform stirring device of the present invention, comprising the following steps:

[0009] S1, placing ferromagnetic particles, a rubber matrix and additives in a mold, and fixing the mold by a first fixing bracket;

[0010] S2, the power supply supplies alternating current to the two first coils and the two second coils respectively, generating a rotating magnetic field in 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, and are finally evenly distributed in the rubber matrix.

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

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

[0014] As a further preference, in the step S3, a period T1=kT during which the mold rotates 360°, wherein k is an integer and T is a period of current applied to the first coil or the second coil.

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

[0016] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0019] 3. The present invention uses two pairs of Helmholtz coils to generate a two-dimensional uniform rotating magnetic field, and mixes the matrix of the magnetorheological elastomer, ferromagnetic particles and additives together and places them in a mold, and the mold is placed in the internal space of the Helmholtz coil; by slowly rotating the mold, in conjunction with the two-dimensional uniform rotating magnetic field, it can produce an effect equivalent to a three-dimensional uniform magnetic field in space, achieve a stirring effect on the matrix, ferromagnetic particles and additives, and ultimately achieve a uniform distribution of ferromagnetic particles in the matrix. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 Schematic diagram of the structure of two pairs of Helmholtz coils in the present invention.

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

[0023] Figure 4 Schematic diagram of the movement of ferromagnetic particles in a uniform magnetic field.

[0024] Figure 5 Schematic diagram of the three-dimensional uniform magnetic field application method.

[0025] Figure 6 Schematic diagram of the representative volume element of ferromagnetic particle space.

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

[0027] Indicated in the figure:

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

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

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

[0031] like Figure 1 As shown, the present invention provides a magnetorheological elastomer uniform stirring device, comprising a first fixed bracket 1, a controller 2, a power supply 3, a wire 4, a first coil 5, a second coil 6, a mold 7, a second fixed bracket 8 and a motor 9. The number of the first coils 5 is two and equal in size, and they are arranged in parallel along the Y-axis direction; the number of the second coils 6 is two and equal in size, and they are arranged in parallel along the X-axis direction. The first coil 5 and the second coil 6 are both perpendicular to the horizontal plane. The first coil 5 and the second coil 6 are fixedly connected to the base through the second fixed bracket 8, and the base can be the ground or a laboratory table. The first fixed bracket 1 is away from the first coil 5 and the second coil 6 and is fixedly connected to the base. A motor 9 is arranged above the first fixed bracket 1 along the X-axis direction, and the output end of the motor 9 faces the first coil 5 and extends to the center of the two first coils 5. The output end of the motor 9 is fixedly connected to the mold 7, and the mold 7 is arranged horizontally. The motor 9 is used to drive the mold 7 to rotate. The two first coils 5 are symmetrically arranged relative to the mold 7, and the two second coils 6 are symmetrically arranged relative to the mold 7. The spacing between the two first coils 5 is equal to the radius of the first coil 5, and the spacing between the two second coils 6 is equal to the radius of the second coil 6. The two first coils 5 and the two second coils 6 each form a pair of Helmholtz coils. The first coil 5 and the second coil 6 do not contact, that is, the distance from the outer boundary of the coil in the inner circle to the center of the magnetic field, that is, the center of the mold 7 is not less than the distance from the inner boundary of the coil in the outer circle to the center of the magnetic field. In addition, the mold 7 with a regular shape is strictly fixed at the center of the coil, that is, at the position of the origin 0, to ensure that the magnetic field in the mold 7 is relatively uniform. The controller 2 is electrically connected to the motor 9 through the wire 4 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 through the wire 4, respectively. The power supply 3 is a program-controlled power supply, which is used to power the controller 2 and the motor 9, and provide the first coil 5 and the second coil 6 with a set alternating current. The first fixed bracket 1, the second fixed 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 suitable for the present invention, which mainly comprises the following three steps:

[0033] Step 1, weigh the ferromagnetic particles, the rubber matrix and the additive (mainly silicone oil) in a weight ratio of 20:79:1 and place them in a mold 7, fix the mold 7 by a first fixing bracket 1, connect the power supply 3, the first coil 5 and the second coil 6 by a wire 4, as shown in FIG. Figure 2 At the same time, the power supply 3, the controller 2, and the motor 9 are connected through the 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 direction, and the midpoint of the axis line segment starting from the center of the two coils is at the origin of the coordinate system. Assume that the radius of the coil is R, the current is I, the distance from the center of the coil to the origin is a, and the XOY plane is the working plane, with a point p: (x0, y0, 0) on it in the middle of the coil pair. Take a microelement on the left coil Let m be the infinitesimal element at the symmetrical position on the right coil. Let n be the distance vectors of the left and right coils to point p. and The line connecting the infinitesimal element and the coil makes an angle θ with the positive direction of the y-axis.

[0035] According to the Biot-Savart law, the magnetic field at point p is The magnetic fields generated by the two coils are superimposed to obtain:

[0036]

[0037] In the formula, and Represents the spatial magnetic field strength generated by the left and right coils respectively, μ0 is the vacuum magnetic 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), and 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, replace the x0 and y0 items containing the coordinates of point p:

[0039]

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

[0041] The magnetic induction intensity at point p for

[0042]

[0043] In the formula

[0044]

[0045] In the external magnetic field generated by the Helmholtz coil, the ferromagnetic particles move in the matrix due to the electromagnetic force, such as Figure 4 As shown. Ferromagnetic particles will aggregate into multiple chain structures along the direction of the external magnetic field. If the distance between particles is too large before aggregation, the electromagnetic force generated by the external magnetic field will force the particles to approach and shorten the distance between particles. If the distance 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 needs to be adopted as follows Figure 5 The three-dimensional magnetic field in space is shown as follows: first, a uniform rotating magnetic field in the XOY plane is generated, and secondly, the magnetic field in the XOY plane is allowed to rotate in space.

[0047] The power supply 3 supplies a current with 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 supplied to the two first coils 5 with an amplitude of I m , the phase angle is The alternating current with an angular frequency of ω, the current I corresponding to the first coil 5 and the second coil 6 X and I Y Can be expressed as

[0048]

[0049] The axis positions of the magnetic induction intensity of the two pairs of coils are different in space. The amplitude of the magnetic induction intensity of each coil changes with time according to the cosine law. The magnetic induction intensity of the first coil 5 and the second coil 6 are respectively expressed as and The formula is as follows:

[0050]

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

[0052]

[0053] Corresponding to the specific current application situation, in order to generate a 360° rotating magnetic field on the XOY plane, the first coil 5 and the second coil 6 need to cooperate with each other to apply a current with an amplitude of I in the X-axis direction and the Y-axis direction respectively. m (cannot exceed the maximum current allowed by the coil), the frequency f is 1Hz, the initial phase angle is 90° different, and the cycle time is As time changes, a rotating magnetic field can be generated in any direction in the XOY plane, as shown in equation (6), where the magnetic induction intensity amplitude is μ is the relative magnetic permeability of the magnetorheological elastomer, R x and R y are the second and first coil radii respectively.

[0054] Step 3: To achieve Figure 5 In order to reduce the influence of centrifugal force when the mold 7 rotates, the k value should be as large as possible, preferably more than 360, that is, the speed of the mold 7 rotation should be as small as possible. The two-dimensional rotating magnetic field of the XOY plane cooperates with the slow rotation of the mold 7, so that the internal ferromagnetic particles can be subjected to the same effect as the three-dimensional uniform magnetic field in space.

[0055] In step 3, under the action of a uniform magnetic field in space, the ferromagnetic particles will first be magnetized, and the magnetized particles will move (following the principle that particles of the same magnetism attract each other and particles of different magnetism repel each other), such as Figure 6 As shown. Ferromagnetic particles of different shapes (usually spheres) can be regarded as representative volume elements completely surrounded by a cube, and the particle motion range is its own representative volume element. A magnetorheological elastomer can be regarded as a collection of countless regular representative volume elements in space. Under the action of a uniform magnetic field in space, the ferromagnetic particles will eventually be distributed according to the regular representative volume elements, that is, evenly distributed inside the magnetorheological elastomer.

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

[0057] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A magnetorheological elastomer uniform stirring device, comprising a first fixed bracket (1) fixedly connected to a base and a motor (9) arranged above the first fixed bracket (1), characterized in that: The invention also comprises two first coils (6) of equal size and arranged in parallel along the X-axis direction, and two second coils (5) of equal size and arranged in parallel along the Y-axis direction. The first coil (5) and the second coil (6) are both fixedly connected to the base through a second fixed bracket (8). The first fixed bracket (1) is far away from the first coil (5) and the second coil (6). A motor (9) is arranged above the first fixed bracket (1) along the X-axis direction. The output end of the motor (9) faces the first coil (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 A mold (7) is provided, the two first coils (5) and the two second coils (6) are symmetrically arranged relative to the mold (7), the spacing between the two first coils (5) is equal to the radius of the first coil (5), the spacing between the two second coils (6) is equal to the radius of the second coil (6), the first coil (5) and the second coil (6) are not in contact, the motor (9) is also connected to the controller (2) and the power supply (3) through the wire (4), and the power supply (3) is respectively connected to the two first coils (5), the two second coils (6), the controller (2) and the motor (9) through the wire (4).

2. A magnetorheological elastomer uniform stirring device according to claim 1, characterized in that: The power supply (3) is a program-controlled power supply.

3. A magnetorheological elastomer uniform stirring device according to claim 2, characterized in that: The first fixing bracket (1), the second fixing bracket (8) and the mould (7) are all made of aluminium.

4. A stirring method applicable to a magnetorheological elastomer uniform stirring device according to any one of claims 1 to 3, characterized in that: The following steps are included: S1, placing ferromagnetic particles, a rubber matrix and additives in a mold (7), and fixing the mold (7) by a first fixing bracket (1); S2, the power source (3) supplies alternating current to the two first coils (5) and the two second coils (6) respectively, so as to generate a rotating magnetic field in the XOY plane; S3, the controller (2) controls the motor (9) to drive the mold (7) to rotate around the X-axis, and the ferromagnetic particles in the mold (7) are uniformly magnetized and then move relative to each other, and are finally uniformly distributed in the rubber matrix.

5. A method for uniformly stirring a magnetorheological elastomer according to claim 4, characterized in that: In the step S1, the mass ratio of the ferromagnetic particles, the rubber matrix and the additive is 20:79:

1.

6. A method for uniformly stirring a magnetorheological elastomer according to claim 4, characterized in that: In step S2, the power source (3) supplies a current with 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 supplied to the two first coils (5) with an amplitude of I m , the phase angle is Alternating current with angular frequency ω.

7. A method for uniformly stirring a magnetorheological elastomer according to claim 4, characterized in that: In the step S3, the mold (7) rotates 360° for a period T1=kT, where k is an integer and T is the period of current applied to the first coil (5) or the second coil (6).

8. A method for uniformly stirring a magnetorheological elastomer according to claim 7, characterized in that: The k is greater than 360.

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