Study On The Acoustic And Vibration Properties Of Electrorheological Fluids

The electrorheological (ER) 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 microstrucrures to a certain extent, resulting in the drastic changes of many physical properties of the materials. In this work, a flexible sandwiched ER composite layer is designed and fabricated and the sound transmission behaviors of the ER layer have been investigated carefully. The materials employed for ER outer layers are thin plastic film with conductive glue coating and conductive rubber, respectively. The ER materials used in experiments are corn starch/ silicone oil system and acrylamide coated Cr-doped TiO₂ particle/ silicone oil system, respectively. The electrode style is the upper-lower layer face electrode (corresponding to the direction of electric field parallel to the transmitted sound) and the single sided grating electrode (corresponding to the direction of electric field vertical to the transmitted sound). The influence of the layer face size to the sound transmission is also studied. The vibration-radiation model for the ER layer is set up to analyze the corresponding relation of the resonance effect in ER layer surface and the hump effect in the sound transmission spectrum. The origin of the tunability of transmitted sound with respect to electric field is qualitatively addressed. Besides, based on the idea of intelligent materials and systems, the ER fluid is employed to act as actuator for vibration control and the piezoelectric ceramic is used as vibration responder and exciter for the solidification of ER fluids. There are two generation self-coupled ER dampers fabricated and investigated experimentally and theoretically. The main results are list as following:1. For the ER layer of starch ER fluid and plastic film electrode: about within 80-150Hz, the transmitted sound pressure level (SPL) increases with electric field. A resonance hump occurs in the SPL spectrum. The height of hump also increases with electric field. At volume fraction of 31%, the frequency of the hump apex move toward the high frequency direction. Within the frequency range with tunable SPL, the phase of the transmitted sound increases with electric field. With the volume fraction increases from 16% to 31%, the frequency band with SPL tunability makes a high frequency shift, moving from 75-140Hz to 0-170Hz, and the tunability of SPL is also increases.