Study On Inductive-type Testing Instrument For Suspension Stability Of Magnetorheological Fluids

Magnetorheological Fluid is a suspension composed of ferromagnetic particles(dispersed phase),base carrier fluid(continuous phase)and special additives.Due to the large density difference between the ferromagnetic particles and the base carrier fluid,the magnetorheological fluid settles in a static state.Solving the sedimentation problem of magnetorheological fluid is a technical challenge in the field of magnetorheological technology.At present,there are no commercial instruments and evaluation standards for the evaluation of magnetorheological fluid sedimentation parameters.When ferromagnetic particles settle,the volume fraction of the particles changes in different areas of the MRF,which leads to changes in the magnetic permeability of the MRF in this area.Based on this,we established the relationship between inductance and magnetic permeability,and designed an inductive sensor to detect the change of inductance value when MRF is settling,we obtained the change of the volume fraction of ferromagnetic particles and the settling rate when MRF is settling.Aiming at this principle,we manufactured an inductive magnetorheological fluid suspension stability testing instrument.Then we not only developed and completed testing experiments,but also analyzed and compared experimental results.The results show that the designed and manufactured MRF sedimentation detection instrument can effectively evaluate the suspension stability of MRF.The specific work is as follows:(1)Mainly summarized the material foundation and engineering application of magnetorheological fluid.We analyzed the reasons of magnetorheological fluid sedimentation,and determined the composition of its sedimentation system: "four areas and three lines".In the same time,we summarized the existing ways to improve the suspension stability of MRF.We studied the current development status of detection methods and detection devices for MRF settlement characteristics at home and abroad,and analyzed the advantages and disadvantages of other detection methods and devices.Finally,we put forward the research content and significance of this article.(2)Based on the mechanism of the change of MRF permeability caused by the change of the volume fraction of ferromagnetic particles in the MRF sedimentation process,we established a correlation model between the suspension stability of the magnetorheological fluid and the change of the inductance index.Then we designed the inductive sensor,and verified the relevance of the MRF suspension stability and inductance from the theoretical calculation and simulation analysis,it can also prove the rationality of the inductive sensor design at the same time.We synthesized and compared a variety of inductance detection methods,and determined to use the AC constant current method to measure and derive theoretically.Finally,we also determined the architecture of the detector.(3)Put forward the overall design requirements of testing instruments including technical indicators such as measurement parameters,range,accuracy,instrument quality and size.We also put forward scientific testing methods and evaluation standards.We designed the mechanical system of the testing instrument,including inductive sensors,fixtures,and basic mechanical structures,which solved the stability problem of the instrument operation.In addition,we carried out the software and hardware design of the testing instrument.In hardware part,we completed the design of the inductance detection circuit,the optocoupler switch circuit,the auxiliary power circuit;and in the software part,we designed the instrument control system and human-computer interaction interface.(4)Based on the mechanical and electrical design,we not only completed the electromechanical integration design of the testing instrument,but also manufactured the test prototype and completed the debugging.Then we determined the performance evaluation method of the testing instrument.We prepared 5 sets of magnetorheological elastomer samples,and completed the calibration of the inductive sensor.In addition,we also prepared 4 sets of MRF samples,and completed the MRF sedimentation characteristic testing experiment.We obtained the sedimentation distribution curve of the MRF sample.Comparing the visual method and the capacitance method,the sedimentation trend is the same,which proves the effectiveness of this testing instrument.At the same time,we analyzed the error of the detection instrument and its source,and determined the direction of subsequent improvement work.