Study On The Acoustic Propagation Mechanism And Characteristics Of Electrorheological Fluid

The electrorheological fluid, among the complex fluids, is a kind of smart or intelligent materials. At the presence of an external electric field, the dispersed particles in ER suspensions can form orderly microstructures to a certain extent, resulting in the drastic changes of many physical properties of the materials. So in the dissertation, the electrorheological fluid as the water acoustical material is proposed. Then put the emphasis on the study about the theoretical model, the numerical calculation and experiment. Combined with practice, several acoustical structure is designed, and the characteristic of acoustic wave in its is researched. The main works in the dissertation are list as following:The electrorheological fluid as the water acoustical material is proposed. Base on the Biot theory, the model of the acoustic wave's propagation is established. To get the result uniformed with experiment, some Biot parameters are modified. The speed of acoustic wave and the loss factor in different electric field are calculated based on the acoustic model. From the result, we can find the influence of different Biot parameters. The theoretical results and experimental results show that the acoustic model based on Biot theory is right.Research the propagation of acoustic wave in layered media and the layered media composing the electrorheological fluid is proposed. For calculating the reflect coefficient, the FEM model based on Biot theory is build. Acoustical insulation analysis and calculation is done through the Matlab. Several acoustic structures are designed. The calculation results show that the arrangement ways of electrorheological fluid is important factor of the acoustical structure. Comparing the double sandwich with the three layered sandwich, the characteristic of sound insulation of the three layered sandwich in middle and high frequency is better, but in the low frequency, the double sandwich is better.The electrorheological fluid is proposed as a gradient acoustic media. On the electric field, the impedance of electrorheological fluid is changeable, the ER fluid have the potential to be active acoustic impedance matching materials, which could especially useful for the matching acoustic impedance between a solid transducer and fluids. In the dissertation, the model of acoustic wave propagation in an inhomogeneous layer is established which based on wave equations. Further we got the transmission matrix of this inhomogeneous layer and derive the energy reflection coefficients for it. Based on this mathematic model, we calculate the reflection coefficients for inhomogeneous layer with different impedance profile, and then the better impedance profile is got.According to the characteristic of electrorheological fluid, fuzzy control method is proposed. Combined with the impedance match method, a new control strategy is applied to the control system. Then puts emphasis on the study about the input/output variable, the control rules and the logical reasoning of controller. At last, the experiment is carried out. The results denoted that the active sound absorption method is feasible.Based on the theory research, a test system is designed which can test the reflection coefficient of electrorheological fluid. From the experiment result, we can know that under the different field, the reflection coefficient and impedance present drastic changes, and the result of the theoretical analysis are proved at the same time.