Researches On Electrorheological Effect And Rheo-optical Characteristics

The change of structure and rheologic properties in a dispersing system of solid-liquid under an external electric field is called as electrorheological (ER) effect. Electrorheological fluids( ER fluids) is a composite suspension of polarizable solid particles with a radium of u m dispersed in an unpolarizable continuous medium. ER fluids, as a kind of smart material, possibly be revolutionary in several areas of industry and technology due to their attractive features of rapid(within ms order),reversible and dramatic changes in rheologic properties upon applied electric field of kilo-voltage per millimeter order. In this dissertation, on the basis of researches on the mechanisms of electrorheological effect and the change in microstructure of composite dispersion under the applied electric field. The theoretical analysis to rheo-optic characteristics of an electrorheological fluid under an electric field is first conducted systematically. The light-controlling properties of an electrorheological fluid is evaluated and an intelligent structure of electrorheological fluids-based smart windows (ERFSW) is proposed and designed at the first time. And thus give an developing application of electrorheological fluids in smart windows. Some helpful and new results were obtained as follows.1 .Upon brief reviewing current mathematical and physical models and mechanisms for electrorheological effect, the theoretical analysis of the dielectric relaxation of electrorheological fluids and the frequency-inducing characteristics for electrorheological effect are conducted. Based on statistical thermodynamic analysis and osmotic pressure calculating of an electrorheological fluid complex system, phenomenological theory is adopted to evaluated phase reparation characteristics. Thus critical factors corresponding to experimental results are introduced. For the first time, the oriented percolation model is applied to analyzed the critical particle concentration of 0.37 and which is characterized an electrorheological fluid and independent to the external electric field. At Last, expert system design configuration is proposed on variable function.2.The characteristics of microstructure variation induced by different space electric fields are investigated experimentally. Electrorheological fluids based on metal and silica particles dispersed in silicone oil respectively are observed by means of an optic microscope. The fractal theory is adopted to characterize phase separation ofelectrorheological fluids and the fractal dimension (Df) of an electrorheological fluid of 10% particles in silicone oil is determined as 1.78. Thus it is testified that particle chains developing process is due to electric field induced diffusion limited aggregation (EDLA) and the fractal dimension is independent to the strength of electric field but the fractal dimension of particle aggregates of Electrorhelogical fluid is up to 1.8 as characterized by diffusion limited aggregation (DLA) with the increase of particle volume concentration.3.On the basis of induced fibrillation theory, a mathematical model is developed to conduct a computer two-dimensional simulation under the consideration of short range repel and hydrokinetic obstruction. Another three-dimensional simulation model is based on the Coulomb law An ordering parameter is used to characterize the formation of particle chains. The results indicated that in the course of particles chains formation, low or high dimensions of the particle chains are decisive factors of the structure and the stability of an electrorheological fluid, respectively.4. The rheo-optic characteristics of composite suspension are due to its phase separation induced by an electric field. Light-scattering properties are in-depth analyzed and it is supposed that using an electrorheological fluid to constitute a network in an application to three-dimensional photonic crystal scattering gratings. The electric field induced birefringence and dichroism are accessed and dependence of change in mi...