Method for characterizing redispersibility of magnetorheological fluid material after sedimentation

Abstract

The invention discloses a characterization method for redispersibility of a magnetorheological fluid material after sedimentation, relates to the technical field of intelligent materials, and aims to solve the problems of difficulty in quantification and insufficient precision of an existing method. According to the method, the constant shear viscosity and the thixotropic ring area of fluid in three states of dispersion, sedimentation and magnetic field excitation redispersion are measured through a magneto-rheological instrument, the parameters are substituted into a specific formula to calculate the redispersion rate, and objective quantitative evaluation of the redispersion performance is achieved. The core of the method is that fluid thixotropy and sediment loosening degree are directly associated by using multi-state rheological parameter collaborative characterization, data support is provided for parameter setting in magnetorheological fluid formula optimization and engineering application, and measurement precision and reliability are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of intelligent materials, and in particular to a method for characterizing the re-dispersibility of a magnetorheological fluid material after settling. BACKGROUND

[0002] As an intelligent material, magnetorheological fluid is widely used in engineering fields such as automobile suspension and bridge damping due to its good stability and controllability. Magnetorheological fluid is usually prepared by mixing magnetic particles with an oily base. Due to the large density difference between the two, the magnetic particles in the magnetorheological fluid will settle and agglomerate. Engineering practice shows that the settled and agglomerated magnetorheological fluid will seriously affect the safety and reliability of magnetorheological devices in application. Therefore, how to characterize and evaluate the re-dispersibility of the settled magnetorheological fluid has become an important difficulty in this field.

[0003] The current industry has serious defects in verifying and evaluating the re-dispersibility of magnetorheological fluid. The mainstream methods include three categories: the first is the visual shaking method, which observes the speed of particle resuspension by manually shaking the sample tube, but this method relies on the subjective judgment of the operator and cannot quantify the dispersion efficiency, and is not sensitive to slight agglomeration; the second is the infrared penetration method (patent CN113433089A), which detects the re-dispersibility of magnetorheological fluid by measuring the amount of infrared light penetrating through the transparent container combined with the particle size distribution of the solid. This method ignores the stratification phenomenon of magnetorheological fluid during settling, and the results have large errors. The third is the solidification method of solid (US6203717B1), which extracts the solid of magnetorheological fluid, then measures the compressive strength after heat solidification treatment, and evaluates the re-dispersibility by the stress intensity of the load cell. This method cannot directly evaluate the re-dispersibility of magnetorheological fluid, but measures the re-dispersibility of magnetorheological fluid after processing and solidification, so it is difficult to evaluate the re-dispersibility of magnetorheological fluid itself. More importantly, the above methods do not establish a quantitative correlation between re-dispersibility and rheological parameters of magnetorheological fluid, resulting in lack of data support for formula optimization. SUMMARY

[0004] The purpose of the present application is to provide a method for characterizing the re-dispersibility of a magnetorheological fluid material after settling, which can improve the measurement accuracy of the re-dispersibility of magnetorheological fluid and solve the problem that the re-dispersibility of magnetorheological fluid is difficult to quantify.

[0005] To achieve the above purpose, the present application provides a method for characterizing the re-dispersibility of a magnetorheological fluid material after settling, which directly characterizes the looseness of the bottom sediment of the magnetorheological fluid and the thixotropy of the fluid through the synergistic effect of bottom sediment viscosity test and shear thixotropy ring area analysis, and objectively evaluates the re-dispersibility by using a re-dispersibility formula. The method comprises the following steps:

[0006] S1, using a magneto-rheometer to measure the constant shear viscosity value η0 and the thixotropic loop area S0 of the magnetorheological fluid in the redispersion state;

[0007] S2, the same volume of magnetorheological fluid is loaded into test tube A and test tube B, and a high-speed centrifuge is used to centrifugally settle test tube A and test tube B to obtain a sample with the supernatant and the precipitate layered;

[0008] S3, without disturbing the supernatant, a long needle tube is used to slowly extract the bottom precipitate sample along the wall of test tube A, and then a magneto-rheometer is used to measure the constant shear viscosity value η1 and the thixotropic loop area S1 of the bottom precipitate; sed sed ;

[0009] S4, test tube B is placed in an electrically excited magnetic device, and is left to stand for a certain time under a certain magnetic field; after standing, without disturbing the supernatant, a long needle tube is used to slowly extract the bottom precipitate sample along the wall of test tube B, and then a magneto-rheometer is used to measure the constant shear viscosity value η1 and the thixotropic loop area S1 of the bottom precipitate;

[0010] S5, the parameters obtained in S1-S4 are substituted into the calculation formula of the redispersion rate RD of the magnetorheological fluid:

[0011]

[0012] Preferably, in S1, S3 and S4, when the constant shear viscosity value and the thixotropic loop area of the magnetorheological fluid are measured by using the magneto-rheometer, the gap between the plates is set to 0.1 mm, the cone-plate rotor diameter is 20 mm, and the test temperature is constant at 25℃.

[0013] Preferably, in S1, S3 and S4, when the constant shear viscosity value of the magnetorheological fluid is measured by using the magneto-rheometer, the fixed shear rate is 0.25 s -1 .

[0014] Preferably, in S1, S3 and S4, when the thixotropic area of the magnetorheological fluid is measured by using the magneto-rheometer, the shear rate is increased from 5 s -1 to 130 s -1 , and then decreased from 130 s -1 to 5 s -1 .

[0015] Preferably, in S2, when test tube A and test tube B are centrifugally settled by using the high-speed centrifuge, the centrifuge speed is 2000 rpm / min, and the rotation time is 5 min.

[0016] ​Preferably, in S2, the volume of the magnetorheological fluid loaded into test tube A and test tube B is 20-25 mL, and in S3 and S4, the volume of the bottom sediment taken out by using a long needle tube is 2 mL.

[0017] Preferably, in S4, the specific range of the certain magnetic field is 100 mT-500 mT.

[0018] Preferably, in S4, the specific range of the certain time length is 2 min-10 min.

[0019] Preferably, the magnetic particles in the magnetorheological fluid are carbonyl iron, and the mass ratio of the carbonyl iron to the magnetorheological fluid is 78:100.

[0020] According to the specific embodiments provided by the present application, the following technical effects are disclosed.

[0021] 1. Innovation in adopting multi-state rheology parameter collaborative characterization

[0022] Breakthrough the limitation of relying on only a single state or indirect indicators in the existing method, by measuring the constant shear viscosity and thixotropic loop area of the magnetorheological fluid in three states of redispersion, sedimentation and redispersion, directly relating the thixotropy of the fluid to the looseness of the bottom sediment, and realizing the accurate characterization of the redispersion performance.

[0023] 2. Establishment of a quantitative redispersion rate calculation model

[0024] The redispersion rate formula integrating the thixotropic loop area and shear viscosity multi-parameters is created for the first time, which converts the subjective qualitative evaluation into objective numerical results, solves the core problem that the traditional method cannot quantify the redispersion efficiency, and provides quantitative basis for performance comparison and formula optimization.

[0025] 3. Focus on accurate sampling and testing of the bottom sediment

[0026] The most compact bottom sediment after sedimentation is extracted for testing, avoiding the interference of the upper clear liquid, and at the same time, combined with the state analysis after magnetic field excitation, directly reflecting the redispersion ability of the magnetorheological fluid itself, overcoming the defects of ignoring the stratification phenomenon or relying on the performance after solidification in the existing method.

[0027] The technical solutions of the present application will be further described in detail below through the accompanying drawings and embodiments. DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any inventive labor.

[0029] Figure 1 A flowchart of an embodiment of a method for characterizing the re-dispersibility of a magnetorheological fluid material after settling. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0031] In order to make the above objectives, characteristics and advantages of the present application more apparent, comprehensible and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0032] Embodiment 1

[0033] According to the method for characterizing the re-dispersibility of a magnetorheological fluid material after settling, the re-dispersibility of a silicone oil-based magnetorheological fluid is characterized.

[0034] First, the constant shear viscosity and thixotropic loop area of the silicone oil-based magnetorheological fluid in the dispersed state are tested by using a magnetorheometer, to obtain S0 and η0.

[0035] The thixotropic loop area S0 of the dispersed state is 5800 Pa·s -1 .

[0036] The constant shear viscosity η0 of the dispersed state is 1800 mPa·s -1 .

[0037] 10 ml of the sample is placed in test tube A and settled by centrifugation by using a centrifuge. The bottom 2 mL of the precipitate is slowly drawn along the wall of the tube by using a long needle tube, and the constant shear viscosity and thixotropic loop area of the precipitate are tested, to obtain S sed and η sed .

[0038] The thixotropic loop area S sed of the precipitate after settling is 5705 Pa·s -1 .

[0039] The constant shear viscosity η sed of the precipitate after settling is 33464 mPa·s -1 .

[0040] Take another 10 ml sample in test tube B and centrifugal sedimentation by centrifuge, and then place the obtained product in an electromagnetic coil, add a magnetic field of 300 mT and stand for 35 min. Then use a long needle tube to slowly extract 2 mL of the precipitate at the bottom along the tube wall, and test the constant shear viscosity and thixotropic loop area of the precipitate to obtain S1 and η1.

[0041] The thixotropic loop area S1 of the deposit after magnetic field excitation is 5795 Pa·s -1 .

[0042] The constant shear viscosity η1 of the deposit after magnetic field excitation is 1850 mPa·s -1 .

[0043] Finally, the obtained values are introduced into formula (1) to obtain the redispersibility RD of the silicone oil-based magnetorheological fluid.

[0044] The redispersibility RD of the silicone oil-based magnetorheological fluid is 80.27%.

[0045] Example 2

[0046] According to the method for characterizing the redispersibility of a magnetorheological fluid material after sedimentation according to the present application, the redispersibility of a synthetic hydrocarbon oil-based magnetorheological fluid is characterized.

[0047] First, the constant shear viscosity and the thixotropic loop area of the synthetic hydrocarbon oil-based magnetorheological fluid in a dispersed state are tested using a magnetorheometer to obtain S0 and η0.

[0048] The thixotropic loop area S0 in the dispersed state is 8010 Pa·s -1 .

[0049] The constant shear viscosity η0 in the dispersed state is 1203 mPa·s -1 .

[0050] Take 10 ml sample in test tube A and centrifugal sedimentation by centrifuge, and then use a long needle tube to slowly extract 2 mL of the precipitate at the bottom along the tube wall, and test the constant shear viscosity and thixotropic loop area of the precipitate to obtain S sed and η sed .

[0051] The thixotropic loop area S sed of the deposit after sedimentation is 3520 Pa·s -1 .

[0052] The constant shear viscosity η sed of the deposit after sedimentation is 45112 mPa·s -1 .

[0053] Take another 10ml sample in test tube B, centrifugal sedimentation by centrifuge, the resulting material is placed in the electromagnetic coil, add magnetic 300mT and stand for 35min, then use long needle tube along the tube wall slowly extracted 2mL precipitate at the bottom, test its constant shear viscosity and thixotropic loop area, get S1 and η1.

[0054] Thixotropic loop area of the deposit after magnetic field excitation S1 = 7606Pa·s -1

[0055] Constant shear viscosity of the deposit after magnetic field excitation η1 = 1500mPa·s -1

[0056] Finally, the resulting numerical value is introduced into formula (1), to get the re-dispersion efficiency of synthetic hydrocarbon oil-based magnetorheological fluid.

[0057] The re-dispersion efficiency of silicone oil-based magnetorheological fluid RD = 72.95%.

[0058] The remaining technical features in the above examples can be flexibly selected by those skilled in the art according to actual conditions to meet different specific actual needs. The changes and variations made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the protection scope of the appended claims of the present application. In the above description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it is apparent to those skilled in the art that the present application can be implemented without necessarily adopting these specific details. In other examples, well-known technologies, such as specific construction details, operating conditions and other technical conditions, are not specifically described in order not to obscure the present application.

Claims

1. A method of characterizing the post-settling redispersibility of a magnetorheological fluid material, the method comprising: The loose degree of the bottom sediment of the magnetorheological fluid and the thixotropy of the fluid are directly characterized by the synergy of the bottom sediment viscosity test and the shear thixotropic loop area analysis, the objective evaluation of the redispersion is realized by using the redispersion rate formula calculation, and the specific steps include the following steps: S1, using the magnetorheological instrument to measure the constant shear viscosity value η0 and the thixotropic loop area S0 of the magnetorheological fluid in the redispersion state; S2, the same volume of the magnetorheological fluid is filled into test tubes A and B, and the test tubes A and B are centrifuged to obtain a sample with the upper clear liquid and the bottom sediment; S3, using a long needle tube to slowly extract the bottom precipitate sample along the tube wall of test tube A without disturbing the supernatant; then using a magneto-rheometer to measure the constant shear viscosity value η of the bottom precipitate sed and thixotropic ring area S sed ; S4, the test tube B is placed in the electrically excited magnetic device, and is statically placed under a certain magnetic field for a certain time; after the static placement, the bottom sediment sample is slowly extracted along the wall of the test tube B by using a long needle tube without disturbing the upper clear liquid; then the constant shear viscosity value η1 and the thixotropic loop area S1 of the bottom sediment are measured by using the magnetorheological instrument; S5, the parameters obtained in S1-S4 are substituted into the calculation formula of the redispersion rate RD of the magnetorheological fluid:

2. The method of claim 1, wherein the method is characterized by: In S1, S3 and S4, when the constant shear viscosity value and the thixotropic loop area of the magnetorheological fluid are measured by using the magnetorheological instrument, the gap between the plates is set to 0.1 mm, the cone-plate rotor diameter is 20 mm, and the test temperature is constant at 25℃.

3. The method of claim 1, wherein the method is characterized by: In S1, S3 and S4, when measuring the constant shear viscosity value of the magnetorheological fluid using the magnetorheometer, the fixed shear rate is 0.25 s -1 .

4. The method of claim 1, wherein the method is characterized by: In S1, S3 and S4, when measuring the thixotropic area of the magneto-rheological fluid using the magneto-rheological instrument, the shear rate is increased from 5 s -1 to 130 s -1 , and then decreased from 130 s -1 to 5 s -1 .

5. The method of claim 1, wherein: In S2, when the test tubes A and B are centrifuged by using the high-speed centrifuge, the centrifuge speed is 2000 rpm / min, and the rotation time is 5 min.

6. The method of claim 1, wherein the method is characterized by: In S2, the volume of the magnetorheological fluid filled into the test tubes A and B is 10-25 mL, and in S3 and S4, the volume of the bottom sediment extracted by using the long needle tube is 2 mL.

7. The method of claim 1, wherein the method is characterized by: In S4, the specific range of the certain magnetic field is 100 mT-500 mT.

8. The method of claim 1, wherein the method is characterized by: In S4, the specific range of the certain time is 2 min-10 min.

9. The method of claim 1, wherein the method is characterized by: The magnetic particles in the magnetorheological fluid are carbonyl iron, and the mass ratio of the magnetorheological fluid is 78:100.

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