Study On The Flow-modified Permittivity In The Response Of Electrorheological Fluids

Electrorheological fluids is an intelligent material, its mechanical performance (such as viscosity, shearing strength and so on) can be regulated continuously by the applied field. The electrorheological apparatus have been used in various fields such as the automation, automobile manufacture, mechanical transmission, robot and so on.The research on the mechanism of electrorheological effect is the core content of the basic study of electrorheological technology. Both the electrostatic polarization model and the interface polarization model emphasize that the electrorheological effect is caused by the mismatch of the two components of electrorheological fluids. It relates with the dielectric constant of the electrorheological fluids no matter what it is dielectric mismatch or conductive mismatch. But both of the two models are static states, no considering the dynamic transmission process of the electrorheological fluids in shear field or pressure gradient field. The investigation indicate that the particles or the congregating which built up by particles will reorient the new direction under strong field such as electric field, shear field or pressure gradient field and so on, and this process can alter the dielectric constant, the coefficient of dielectric loss and the relaxation frequency of electrorheological fluids, this is called flow-modified permittivity (that is FMP effect). Owing to the limit polarization speed of particles, the FMP effect plays an important role on the influence to the electrorheological effect. This paper carries through some aspect work about FMP effect as follows:First of all, this article detailedly expatiates the FMP theory, studies the influence of FMP effect to the local electric field of two particles in shear field, we obtain the result that the action of FMP effect is great when it is in small dielectric mismatch situation, it may be neglected in big dielectric mismatch situation by using the Matlab software, and the relationship between FMP effect and the local electric field is not a simple function.Secondly, this article studies the kinetic influence of electrorheological particles caused by FMP effect in poiseuille flow field, and finds that the action of FMP effect is not prominence, but it indeed does great contributions to the location of the particles.In addition, this article carries through the electrorheological power transmission experiment about FMP effect, the experiment uses the parallel-plate and the annular structure electrorheological elements, according to the results of experiments and theoretical analysis, we obtain that the chain-net structure will capture the particles from the upstream in the response of the dynamic transmission process, and during the process, the FMP effect and the capture effect both give contributions to the dielectric constant of the particles, and it expresses the changes of the mechanical performance on macroscopic. We get the control equation about the coupling dynamics process of FMP effect and capture effect for the first time, and propose the idea about getting information of the particles becoming chains by FMP effect.In the end, this article gives the results of dynamic simulation about FMP effect in the response of electrorheological fluids in poiseuille flow field between two parallel plates on the base of the modified polarization model by FMP, uses the molecule dynamics method and finds that the structure of electrorheological fluids will alter to some small extent by FMP effect, the time in which will alter too,also the mechanical performance suffer the influence, and testify the possibility that the particles which enters the screen just now or the isolation particles in the screen are captured by the electrorheological congregating. Through comparing the relation curves of shear strength and pressure gradient under the different dielectric relaxation time, we find that the electrorheological effect connects the relaxation time of particle intimately, and there must be an optimal dielectric relaxation rate.The innovation of this article is proposing the FMP effect and capture effect coupling process basing on this"the structure - strength"the dynamic coupling of electrorheological fluids. And the meaning of this research will develop the electrorheological mechanism into the kinetic field, it has the guiding significance to the design of electrorheological components and the active action for impelling the developing of electrorheological technology.